diff --git a/.bazelversion b/.bazelversion
index 47b322c..1545d96 100644
--- a/.bazelversion
+++ b/.bazelversion
@@ -1 +1 @@
-3.4.1
+3.5.0
diff --git a/Documentation/config-gerrit.txt b/Documentation/config-gerrit.txt
index d96ae46..6b89d67 100644
--- a/Documentation/config-gerrit.txt
+++ b/Documentation/config-gerrit.txt
@@ -2828,7 +2828,8 @@
 +
 Enable (or disable) the `'$site_path'/logs/httpd_log` request log.
 If enabled, an NCSA combined log format request log file is written
-out by the internal HTTP daemon.
+out by the internal HTTP daemon. The httpd log format is documented
+link:logs.html#_httpd_log[here].
 +
 `log4j.appender` with the name `httpd_log` can be configured to overwrite
 programmatic configuration.
@@ -4881,6 +4882,21 @@
 +
 By default, 30s.
 
+[[sshd.gracefulStopTimeout]]sshd.gracefulStopTimeout::
++
+Set a graceful stop time. If set, Gerrit ensures that all open SSH
+sessions are preserved for a maximum period of time, before forcing the
+shutdown of the SSH daemon. During this period, no new requests
+will be accepted. This option is meant to be used in setups performing
+rolling restarts.
++
+Values should use common unit suffixes to express their setting:
++
+* s, sec, second, seconds
+* m, min, minute, minutes
++
+By default, 0 seconds (immediate shutdown).
+
 [[sshd.maxConnectionsPerUser]]sshd.maxConnectionsPerUser::
 +
 Maximum number of concurrent SSH sessions that a user account
@@ -5006,6 +5022,7 @@
 +
 Enable (or disable) the `'$site_path'/logs/sshd_log` request log.
 If enabled, a request log file is written out by the SSH daemon.
+The sshd log format is documented link:logs.html#_sshd_log[here].
 +
 `log4j.appender` with the name `sshd_log` can be configured to overwrite
 programmatic configuration.
diff --git a/Documentation/config-reverseproxy.txt b/Documentation/config-reverseproxy.txt
index eff777b..3a9bcc7 100644
--- a/Documentation/config-reverseproxy.txt
+++ b/Documentation/config-reverseproxy.txt
@@ -21,6 +21,13 @@
   	listenUrl = proxy-http://127.0.0.1:8081/r/
 ----
 
+== Reverse proxy and client IPs
+
+When behind a reverse proxy the http_log will log the IP of the reverse proxy
+as client.ip. To log the correct client IP you must provide the
+'X-Forwarded-For' header from the reverse proxy.
+See the nginx configuration example below.
+
 
 == Apache 2 Configuration
 
diff --git a/Documentation/dev-bazel.txt b/Documentation/dev-bazel.txt
index 01cd494..ee2f4a1 100644
--- a/Documentation/dev-bazel.txt
+++ b/Documentation/dev-bazel.txt
@@ -90,12 +90,12 @@
 
 ```
 $ cat << EOF > ~/.bazelrc
-> build --define=ABSOLUTE_JAVABASE=<path-to-java-13>
-> build --javabase=@bazel_tools//tools/jdk:absolute_javabase
-> build --host_javabase=@bazel_tools//tools/jdk:absolute_javabase
-> build --host_java_toolchain=@bazel_tools//tools/jdk:toolchain_vanilla
-> build --java_toolchain=@bazel_tools//tools/jdk:toolchain_vanilla
-> EOF
+build --define=ABSOLUTE_JAVABASE=<path-to-java-13>
+build --javabase=@bazel_tools//tools/jdk:absolute_javabase
+build --host_javabase=@bazel_tools//tools/jdk:absolute_javabase
+build --host_java_toolchain=@bazel_tools//tools/jdk:toolchain_vanilla
+build --java_toolchain=@bazel_tools//tools/jdk:toolchain_vanilla
+EOF
 ```
 
 Now, invoking Bazel with just `bazel build :release` would include
diff --git a/Documentation/dev-e2e-tests.txt b/Documentation/dev-e2e-tests.txt
index 78b2c15..c5b3bfc 100644
--- a/Documentation/dev-e2e-tests.txt
+++ b/Documentation/dev-e2e-tests.txt
@@ -27,14 +27,33 @@
 leveraged to run tests at the Git protocol level.
 
 Gatling is written in Scala, but the abstraction provided by the Gatling DSL makes the scenarios
-implementation easy even without any Scala knowledge. The
-link:https://gitenterprise.me/2019/12/20/stress-your-gerrit-with-gatling/[Stress your Gerrit with Gatling,role=external,window=_blank]
-blog post has more introductory information.
+implementation easy even without any Scala knowledge. The online `End-to-end tests`
+link:https://www.gerritcodereview.com/presentations.html#list-of-presentations[presentation,role=external,window=_blank]
+links posted on the homepage have more introductory information.
+
+== IDE: IntelliJ
 
 Examples of scenarios can be found in the `e2e-tests` directory. The files in that directory should
 be formatted using the mainstream
 link:https://plugins.jetbrains.com/plugin/1347-scala[Scala plugin for IntelliJ,role=external,window=_blank].
 The latter is not mandatory but preferred for `sbt` and Scala IDE purposes in this project.
+So, Eclipse can also be used alongside as a development IDE; this is described below.
+
+=== Eclipse
+
+1. Install the link:http://scala-ide.org/docs/user/gettingstarted.html[Scala plugin for Eclipse,role=external,window=_blank].
+1. Run `sbt eclipse` from the `e2e-tests` root directory.
+1. Import the resulting `e2e-tests` eclipse file inside the Gerrit project, in Eclipse.
+1. You should see errors in Eclipse telling you there are missing packages.
+1. This is due to the sbt-eclipse plugin not properly linking the Gerrit Gatling e2e tests with
+   Gatling Git plugin.
+1. You then have to right-click on the root directory and choose the build path->link source option.
+1. Then you have to browse to `.sbt/1.0/staging`, find the folder where gatling-git is contained,
+   and choose that.
+1. That last step should link the gatling-git plugin to the project; e2e tests should not show
+   errors anymore.
+1. You may get errors in the gatling-git directory; these should not affect Gerrit Gatling
+   development and can be ignored.
 
 == How to build the tests
 
@@ -163,10 +182,11 @@
 Plugin or otherwise non-core scenarios may do so just as well. The core java package
 `com.google.gerrit.scenarios` from the example above has to be replaced with the one under which
 those scenario classes are. Such extending scenarios can also add extension-specific properties.
-Early examples of this can be found in the Gerrit
-`link:https://gerrit.googlesource.com/plugins/high-availability[high-availability,role=external,window=_blank]`
-and `link:https://gerrit.googlesource.com/plugins/multi-site[multi-site,role=external,window=_blank]`
-plugins test code.
+Examples of this can be found in these Gerrit plugins test code:
+
+* `link:https://gerrit.googlesource.com/plugins/high-availability[high-availability,role=external,window=_blank]`
+* `link:https://gerrit.googlesource.com/plugins/multi-site[multi-site,role=external,window=_blank]`
+* `link:https://gerrit.googlesource.com/plugins/rename-project[rename-project,role=external,window=_blank]`
 
 Further above, the `_PROJECT` keyword is prefixed with an underscore, which means that its value
 gets automatically generated by the scenario. Any property setting for it is therefore not
diff --git a/Documentation/dev-eclipse.txt b/Documentation/dev-eclipse.txt
index 9596a55..742cf42 100644
--- a/Documentation/dev-eclipse.txt
+++ b/Documentation/dev-eclipse.txt
@@ -41,6 +41,37 @@
 Filters on a folder, they will be overwritten the next time you run
 `tools/eclipse/project.py`.
 
+=== Eclipse project on MacOS
+
+By default, bazel uses `/private/var/tmp` as the
+link:https://docs.bazel.build/versions/master/output_directories.html[outputRoot on MacOS].
+This means that the eclipse project will reference libraries stored under that directory.
+However, MacOS runs periodic cleanup task which deletes the content under `/private/var/tmp`
+which wasn't accessed or modified for some days, by default 3 days. This can lead to a broken
+Eclipse project as referenced libraries get deleted.
+
+There are two possibilities to mitigate this issue.
+
+==== Change the location of the bazel output directory
+On Linux, the output directory defaults to `$HOME/.cache/bazel` and the same can be configured
+on Mac too. Edit, or create, the `$HOME/.bazelrc` file and add the following line:
+----
+startup --output_user_root=/Users/johndoe/.cache/bazel
+----
+
+==== Increase the treshold for the cleanup of temporary files
+The default treshold for the cleanup can be overriden by creating a configuration file under
+`/etc/periodic.conf` and setting a larger value for the `daily_clean_tmps_days`.
+
+An example `/etc/periodic.conf` file:
+
+----
+# This file overrides the settings from /etc/defaults/periodic.conf
+daily_clean_tmps_days="45"                              # If not accessed for
+----
+
+For more details about the proposed workaround see link:https://superuser.com/a/187105[this post]
+
 === Eclipse project with custom plugins ===
 
 To add custom plugins to the eclipse project add them to `tools/bzl/plugins.bzl`
diff --git a/Documentation/images/inline-edit-create-change-project-screen-dialog.png b/Documentation/images/inline-edit-create-change-project-screen-dialog.png
deleted file mode 100644
index ea5daa9..0000000
--- a/Documentation/images/inline-edit-create-change-project-screen-dialog.png
+++ /dev/null
Binary files differ
diff --git a/Documentation/images/inline-edit-create-change-project-screen.png b/Documentation/images/inline-edit-create-change-project-screen.png
deleted file mode 100644
index e9c7033..0000000
--- a/Documentation/images/inline-edit-create-change-project-screen.png
+++ /dev/null
Binary files differ
diff --git a/Documentation/images/inline-edit-create-follow-up-change.png b/Documentation/images/inline-edit-create-follow-up-change.png
deleted file mode 100644
index 3e81eee..0000000
--- a/Documentation/images/inline-edit-create-follow-up-change.png
+++ /dev/null
Binary files differ
diff --git a/Documentation/images/inline-edit-edit-in-diff-screen-patch-list.png b/Documentation/images/inline-edit-edit-in-diff-screen-patch-list.png
deleted file mode 100644
index bdbc59d..0000000
--- a/Documentation/images/inline-edit-edit-in-diff-screen-patch-list.png
+++ /dev/null
Binary files differ
diff --git a/Documentation/images/inline-edit-edit-in-patch-list.png b/Documentation/images/inline-edit-edit-in-patch-list.png
deleted file mode 100644
index 9a31e02..0000000
--- a/Documentation/images/inline-edit-edit-in-patch-list.png
+++ /dev/null
Binary files differ
diff --git a/Documentation/index.txt b/Documentation/index.txt
index 4fb977a..8f36ecc 100644
--- a/Documentation/index.txt
+++ b/Documentation/index.txt
@@ -69,6 +69,7 @@
 . link:cmd-index.html[Command Line Tools]
 . link:config-plugins.html#replication[Replication]
 . link:config-plugins.html[Plugins]
+. link:logs.html[Log Files]
 . link:metrics.html[Metrics]
 . link:config-reverseproxy.html[Reverse Proxy]
 . link:config-auto-site-initialization.html[Automatic Site Initialization on Startup]
diff --git a/Documentation/logs.txt b/Documentation/logs.txt
new file mode 100644
index 0000000..43a8e62
--- /dev/null
+++ b/Documentation/logs.txt
@@ -0,0 +1,174 @@
+= Gerrit Code Review - Logs
+
+Gerrit writes log files in the `$site_path/logs/` folder tracking requests,
+background and plugin activity and errors. By default logs are written in
+link:config-gerrit.html#log.textLogging[text format], optionally in
+link:config-gerrit.html#log.jsonLogging[JSON format].
+By default log files are link:config-gerrit.html#log.compress[compressed]
+at server startup and then daily at 11pm and
+link:config-gerrit.html#log.rotate[rotated] every midnight.
+
+== Logs
+
+The following logs can be written.
+
+=== HTTPD Log
+
+The httpd log tracks HTTP requests processed by Gerrit's http daemon
+and is written to `$site_path/logs/httpd_log`. Enabled or disabled via the
+link:config-gerrit.html#httpd.requestLog[httpd.requestLog] option.
+
+Format is an enhanced
+link:https://httpd.apache.org/docs/2.4/logs.html#combined[NCSA combined log],
+if a log field is not present, a "-" is substituted:
+
+* `host`: The IP address of the HTTP client that made the HTTP resource request.
+  If you are using a reverse proxy it depends on the proxy configuration if the
+  proxy IP address or the client IP address is logged.
+* `[thread name]`: name of the Java thread executing the request.
+* `remote logname`:  the identifier used to
+  link: https://tools.ietf.org/html/rfc1413[identify the client making the HTTP request],
+  Gerrit always logs a dash `-`.
+* `username`: the username used by the client for authentication. "-" for
+  anonymous requests.
+* `[date:time]`: The date and time stamp of the HTTP request.
+  The time that the request was received. The format is until Gerrit 3.1
+  `[dd/MMM/yyyy:HH:mm:ss.SSS ZZZZ]`. For Gerrit 3.2 or newer
+  link:https://www.w3.org/TR/NOTE-datetime[ISO 8601 format] `[yyyy-MM-dd'T'HH:mm:ss,SSSZ]`
+  is used for all timestamps.
+* `request`: The request line from the client is given in double quotes.
+** the HTTP method used by the client.
+** the resource the client requested.
+** the protocol/version used by the client.
+* `statuscode`: the link:https://tools.ietf.org/html/rfc2616#section-10[HTTP status code]
+  that the server sent back to the client.
+* `response size`: the number of bytes of data transferred as part of the HTTP
+  response, not including the HTTP header.
+* `latency`: response time in milliseconds.
+* `referer`: the `Referer` HTTP request header. This gives the site that
+  the client reports having been referred from.
+* `client agent`: the client agent which sent the request.
+
+Example:
+```
+12.34.56.78 [HTTP-4136374] - johndoe [28/Aug/2020:10:02:20 +0200] "GET /a/plugins/metrics-reporter-prometheus/metrics HTTP/1.1" 200 1247498 1900 - "Prometheus/2.13.1"
+```
+
+=== SSHD Log
+
+The sshd log tracks ssh requests processed by Gerrit's ssh daemon
+and is written to `$site_path/logs/sshd_log`. Enabled or disabled
+via option link:config-gerrit.html#sshd.requestLog[sshd.requestLog].
+
+Log format:
+
+* `[date time]`: The time that the request was received.
+  The format is until Gerrit 3.1 `[yyyy-mm-dd HH:mm:ss.SSS ZZZZ]`.
+  For Gerrit 3.2 or newer
+  link:https://www.w3.org/TR/NOTE-datetime[ISO 8601 format] `[yyyy-MM-dd'T'HH:mm:ss,SSSZ]`
+  is used for all timestamps.
+* `sessionid`: hexadecimal session identifier, all requests of the
+  same connection share the same sessionid. Gerrit does not support multiplexing multiple
+  sessions on the same connection. Grep the log file using the sessionid as filter to
+  get all requests from that session.
+* `[thread name]`: name of the Java thread executing the request.
+* `username`: the username used by the client for authentication.
+* `a/accountid`: identifier of the Gerrit account which is logged on.
+* `operation`: the operation being executed via ssh.
+** `LOGIN FROM <host>`: login and start new SSH session from the given host.
+** `AUTH FAILURE FROM <host> <message>`: failed authentication from given host and cause of failure.
+** `LOGOUT`: logout and terminate SSH session.
+** `git-upload-pack.<projectname>`: git fetch or clone command for given project.
+** `git-receive-pack.<projectname>`: git push command for given project.
+** Gerrit ssh commands which may be logged in this field are documented
+   link:cmd-index.html#_server[here].
+* `wait`: command wait time, time in milliseconds the command waited for an execution thread.
+* `exec`: command execution time, time in milliseconds to execute the command.
+* `status`: status code. 0 means success, any other value is an error.
+
+The `git-upload-pack` command provides the following additional fields after the `exec`
+and before the `status` field. All times are in milliseconds. Fields are -1 if not available
+when the upload-pack request returns an empty result since the client's repository was up to date:
+
+* `time negotiating`: time for negotiating which objects need to be transferred.
+* `time searching for reuse`: time jgit searched for deltas which can be reused.
+  That is the time spent matching existing representations against objects that
+  will be transmitted, or that the client can be assumed to already have.
+* `time searching for sizes`: time jgit was searching for sizes of all objects that
+  will enter the delta compression search window. The sizes need to
+  be known to better match similar objects together and improve
+  delta compression ratios.
+* `time counting`: time jgit spent enumerating the objects that need to
+  be included in the output. This time includes any restarts that
+  occur when a cached pack is selected for reuse.
+* `time compressing`: time jgit was compressing objects.  This is observed
+  wall-clock time and does not accurately track CPU time used when
+  multiple threads were used to perform the delta compression.
+* `time writing`: time jgit needed to write packfile, from start of
+  header until end of trailer. The transfer speed can be
+  approximated by dividing `total bytes` by this value.
+* `total time in UploadPack`: total time jgit spent in upload-pack.
+* `bitmap index misses`: number of misses when trying to use bitmap index,
+  -1 means no bitmap index available. This is the count of objects that
+  needed to be discovered through an object walk because they were not found
+  in bitmap indices.
+* `total deltas`: total number of deltas transferred. This may be lower than the actual
+  number of deltas if a cached pack was reused.
+* `total objects`: total number of objects transferred. This total includes
+  the value of `total deltas`.
+* `total bytes`: total number of bytes transferred. This size includes the pack
+  header, trailer, thin pack, and reused cached packs.
+* `client agent`: the client agent and version which sent the request.
+
+Example: a CI system established a SSH connection, sent an upload-pack command (git fetch) and closed the connection:
+```
+[2020-08-28 11:00:01,391 +0200] 8a154cae [sshd-SshServer[570fc452]-nio2-thread-299] voter a/1000023 LOGIN FROM 12.34.56.78
+[2020-08-28 11:00:01,556 +0200] 8a154cae [SSH git-upload-pack /AP/ajs/jpaas-msg-svc.git (voter)] voter a/1000056 git-upload-pack./demo/project.git 0ms 115ms 92ms 1ms 0ms 6ms 0ms 0ms 7ms 3 10 26 2615 0 git/2.26.2
+[2020-08-28 11:00:01,583 +0200] 8a154cae [sshd-SshServer[570fc452]-nio2-thread-168] voter a/1000023 LOGOUT
+```
+
+=== Error Log
+
+The error log tracks errors and stack traces and is written to
+`$site_path/logs/error_log`.
+
+Log format:
+
+* `[date time]`: The time that the request was received.
+  The format is until Gerrit 3.1 `[yyyy-mm-dd HH:mm:ss.SSS ZZZZ]`.
+  For Gerrit 3.2 or newer
+  link:https://www.w3.org/TR/NOTE-datetime[ISO 8601 format] `[yyyy-MM-dd'T'HH:mm:ss,SSSZ]`
+  is used for all timestamps.
+* `[thread name]`: : name of the Java thread executing the request.
+* `level`: log level (ERROR, WARN, INFO, DEBUG).
+* `logger`: name of the logger.
+* `message`: log message.
+* `stacktrace`: Java stacktrace when an execption was caught, usually spans multiple lines.
+
+=== GC Log
+
+The gc log tracks git garbage collection running in a background thread
+if enabled and is written to `$site_path/logs/gc_log`.
+
+Log format:
+
+* `[date time]`: The time that the request was received.
+  The format is until Gerrit 3.1 `[yyyy-mm-dd HH:mm:ss.SSS ZZZZ]`.
+  For Gerrit 3.2 or newer
+  link:https://www.w3.org/TR/NOTE-datetime[ISO 8601 format] `[yyyy-MM-dd'T'HH:mm:ss,SSSZ]`
+  is used for all timestamps.
+* `level`: log level (ERROR, WARN, INFO, DEBUG).
+* `message`: log message.
+
+=== Plugin Logs
+
+Some plugins write their own log file.
+E.g. the replication plugin writes its log to `$site_path/logs/replication_log`.
+Refer to each plugin's documentation for more details on their logs.
+
+GERRIT
+------
+Part of link:index.html[Gerrit Code Review]
+
+SEARCHBOX
+---------
diff --git a/Documentation/rest-api-changes.txt b/Documentation/rest-api-changes.txt
index 4227655..e09d936 100644
--- a/Documentation/rest-api-changes.txt
+++ b/Documentation/rest-api-changes.txt
@@ -5026,6 +5026,137 @@
   }
 ----
 
+[[get-ported-comments]]
+=== Get Ported Comments
+--
+'GET /changes/link:#change-id[\{change-id\}]/revisions/link:#revision-id[\{revision-id\}]/ported_comments'
+--
+
+Ports comments of other revisions to the requested revision.
+
+Only comments added on earlier patchsets are ported. That set of comments is filtered even further
+due to some additional rules. Callers of this endpoint shouldn't rely on the exact logic of which
+comments are ported as that logic might change in the future. Instead, callers must be able to
+handle any smaller/larger set of comments returned by this endpoint.
+
+Typically, a comment thread is returned fully or excluded fully. However, draft comments and
+robot comments are ignored and not returned via this endpoint. Hence, it's possible to get ported
+comments from this endpoint which are a reply to a non-ported robot comment. Callers must be
+able to deal with this situation.
+
+The returned comments are organized in a map of file path to link:#comment-info[CommentInfo] entries
+in the same fashion as for the link:#list-comments[List Revision Comments] endpoint.
+The map is filled with the original comment attributes except for these attributes: `path`, `line`,
+and `range` point to the computed position in the target revision. If the exactly correct position
+can't be determined, those fields will be filled with the next best position. That can also mean
+not filling the `line` or `range` attribute anymore and thus converting the comment to a file
+comment (or even moving the comment to a different file or the patchset level). Callers of this
+endpoint must be able to deal with this and not rely on the original comment position.
+
+It's possible that this endpoint returns different link:#comment-info[CommentInfo] entries with
+the same comment UUID. This is not a bug but a feature. If a comment appears on a file which Gerrit
+recognizes as copied between patchsets, the ported version of this comment consists of two ported
+instances having the same UUID but different `file`/`line`/`range` positions. Callers must be able
+to handle this situation.
+
+Repeated calls of this endpoint might produce different results. Internal errors during the
+position computation are mapped to fallback locations for affected comments. Those errors might
+have vanished on later calls, upon which this endpoint returns the actually mapped position. In
+addition, comments can be deleted and draft comments can be published, upon which the set of ported
+comments may change.
+
+.Request
+----
+  GET /changes/myProject~master~I8473b95934b5732ac55d26311a706c9c2bde9940/revisions/4/ported_comments/ HTTP/1.0
+----
+
+.Response
+----
+  HTTP/1.1 200 OK
+  Content-Disposition: attachment
+  Content-Type: application/json; charset=UTF-8
+
+  )]}'
+  {
+    "gerrit-server/src/main/java/com/google/gerrit/server/project/RefControl.java": [
+      {
+        "id": "TvcXrmjM",
+        "patch_set": 2,
+        "line": 23,
+        "message": "[nit] trailing whitespace",
+        "updated": "2013-02-26 15:40:43.986000000",
+        "author": {
+          "_account_id": 1000096,
+          "name": "John Doe",
+          "email": "john.doe@example.com"
+        },
+        "unresolved": true
+      },
+      {
+        "id": "TveXwFiA",
+        "patch_set": 2,
+        "line": 23,
+        "in_reply_to": "TvcXrmjM",
+        "message": "Done",
+        "updated": "2013-02-26 15:40:45.328000000",
+        "author": {
+          "_account_id": 1000097,
+          "name": "Jane Roe",
+          "email": "jane.roe@example.com"
+        },
+        "unresolved": true
+      }
+    ]
+  }
+----
+
+[[get-ported-drafts]]
+=== Get Ported Drafts
+--
+'GET /changes/link:#change-id[\{change-id\}]/revisions/link:#revision-id[\{revision-id\}]/ported_drafts'
+--
+
+Ports draft comments of other revisions to the requested revision.
+
+This endpoint behaves similarly to the link:#get-ported-comments[Get Ported Comments] endpoint.
+With this endpoint, only draft comments of the calling user are ported, though. If a draft comment
+is a reply to a published comment, only the ported draft comment is returned.
+
+Depending on the filtering rules, it's possible that this endpoint returns a draft comment which is
+a reply to a comment thread which is not returned by the
+link:#get-ported-comments[Get Ported Comments] endpoint. That's intended behavior. Callers must be
+able to handle this situation. The same holds for drafts which are a reply to a robot comment.
+
+Different than the link:#get-ported-comments[Get Ported Comments] endpoint, the `author` of the
+returned comments is not filled for this endpoint as only comments of the calling user are returned.
+
+.Request
+----
+  GET /changes/myProject~master~I8473b95934b5732ac55d26311a706c9c2bde9940/revisions/674ac754f91e64a0efb8087e59a176484bd534d1/ported_drafts/ HTTP/1.0
+----
+
+.Response
+----
+  HTTP/1.1 200 OK
+  Content-Disposition: attachment
+  Content-Type: application/json; charset=UTF-8
+
+  )]}'
+  {
+    "gerrit-server/src/main/java/com/google/gerrit/server/project/RefControl.java": [
+      {
+        "id": "TveXwFiA",
+        "patch_set": 2,
+        "line": 23,
+        "in_reply_to": "TvcXrmjM",
+        "message": "Done",
+        "updated": "2013-02-26 15:40:45.328000000",
+        "unresolved": true
+      }
+    ]
+  }
+----
+
 [[apply-fix]]
 === Apply Fix
 --
diff --git a/WORKSPACE b/WORKSPACE
index 6be35cf..4c2fe35 100644
--- a/WORKSPACE
+++ b/WORKSPACE
@@ -219,15 +219,15 @@
     sha1 = GUAVA_BIN_SHA1,
 )
 
-CAFFEINE_VERS = "2.8.0"
+CAFFEINE_VERS = "2.8.5"
 
 maven_jar(
     name = "caffeine",
     artifact = "com.github.ben-manes.caffeine:caffeine:" + CAFFEINE_VERS,
-    sha1 = "6000774d7f8412ced005a704188ced78beeed2bb",
+    sha1 = "f0eafef6e1529a44e36549cd9d1fc06d3a57f384",
 )
 
-CAFFEINE_GUAVA_SHA256 = "3a66ee3ec70971dee0bae6e56bda7b8742bc4bedd7489161bfbbaaf7137d89e1"
+CAFFEINE_GUAVA_SHA256 = "a7ce6d29c40bccd688815a6734070c55b20cd326351a06886a6144005aa32299"
 
 # TODO(davido): Rename guava.jar to caffeine-guava.jar on fetch to prevent potential
 # naming collision between caffeine guava adapter and guava library itself.
@@ -758,8 +758,8 @@
 # Keep this version of Soy synchronized with the version used in Gitiles.
 maven_jar(
     name = "soy",
-    artifact = "com.google.template:soy:2019-10-08",
-    sha1 = "4518bf8bac2dbbed684849bc209c39c4cb546237",
+    artifact = "com.google.template:soy:2020-08-24",
+    sha1 = "e774bf5cc95923d2685292883fe219e231346e50",
 )
 
 maven_jar(
diff --git a/e2e-tests/build.sbt b/e2e-tests/build.sbt
index a322970..294212c 100644
--- a/e2e-tests/build.sbt
+++ b/e2e-tests/build.sbt
@@ -2,7 +2,6 @@
 
 enablePlugins(GatlingPlugin)
 
-lazy val gatlingGitExtension = RootProject(uri("git://github.com/GerritForge/gatling-git.git"))
 lazy val root = (project in file("."))
     .settings(
       inThisBuild(List(
@@ -12,8 +11,8 @@
       )),
       name := "gerrit",
       libraryDependencies ++=
-          gatling ++
+          gatling ++ gatlingGit ++
               Seq("io.gatling" % "gatling-core" % GatlingVersion) ++
               Seq("io.gatling" % "gatling-app" % GatlingVersion),
       scalacOptions += "-language:postfixOps"
-    ) dependsOn gatlingGitExtension
+    )
diff --git a/e2e-tests/project/Dependencies.scala b/e2e-tests/project/Dependencies.scala
index 63328f9..56ef740 100644
--- a/e2e-tests/project/Dependencies.scala
+++ b/e2e-tests/project/Dependencies.scala
@@ -2,9 +2,17 @@
 
 object Dependencies {
   val GatlingVersion = "3.2.0"
+  val GatlingGitVersion = "1.0.12"
 
   lazy val gatling = Seq(
     "io.gatling.highcharts" % "gatling-charts-highcharts",
     "io.gatling" % "gatling-test-framework",
   ).map(_ % GatlingVersion % Test)
+
+  lazy val gatlingGit = Seq(
+    "com.gerritforge" %% "gatling-git" % GatlingGitVersion excludeAll(
+      ExclusionRule(organization = "io.gatling"),
+      ExclusionRule(organization = "io.gatling.highcharts")
+    )
+  )
 }
diff --git a/e2e-tests/project/plugins.sbt b/e2e-tests/project/plugins.sbt
index 36cd201..9ed0f89 100644
--- a/e2e-tests/project/plugins.sbt
+++ b/e2e-tests/project/plugins.sbt
@@ -1 +1,2 @@
 addSbtPlugin("io.gatling" % "gatling-sbt" % "3.0.0")
+addSbtPlugin("com.typesafe.sbteclipse" % "sbteclipse-plugin" % "5.2.4")
diff --git a/e2e-tests/src/test/resources/data/com/google/gerrit/scenarios/CreateProject-body.json b/e2e-tests/src/test/resources/data/com/google/gerrit/scenarios/CreateProject-body.json
index bcf4708..282ac99 100644
--- a/e2e-tests/src/test/resources/data/com/google/gerrit/scenarios/CreateProject-body.json
+++ b/e2e-tests/src/test/resources/data/com/google/gerrit/scenarios/CreateProject-body.json
@@ -1,3 +1,4 @@
 {
-  "create_empty_commit": "true"
+  "create_empty_commit": "true",
+  "parent": "${parent}"
 }
diff --git a/e2e-tests/src/test/resources/data/com/google/gerrit/scenarios/CreateProject.json b/e2e-tests/src/test/resources/data/com/google/gerrit/scenarios/CreateProject.json
index cd90739..c141bb8 100644
--- a/e2e-tests/src/test/resources/data/com/google/gerrit/scenarios/CreateProject.json
+++ b/e2e-tests/src/test/resources/data/com/google/gerrit/scenarios/CreateProject.json
@@ -1,5 +1,6 @@
 [
   {
-    "url": "HTTP_SCHEME://HOSTNAME:HTTP_PORT/a/projects/PROJECT"
+    "url": "HTTP_SCHEME://HOSTNAME:HTTP_PORT/a/projects/PROJECT",
+    "parent": "PARENT"
   }
 ]
diff --git a/e2e-tests/src/test/scala/com/google/gerrit/scenarios/CreateProject.scala b/e2e-tests/src/test/scala/com/google/gerrit/scenarios/CreateProject.scala
index d631292..f2b3d12 100644
--- a/e2e-tests/src/test/scala/com/google/gerrit/scenarios/CreateProject.scala
+++ b/e2e-tests/src/test/scala/com/google/gerrit/scenarios/CreateProject.scala
@@ -28,7 +28,7 @@
 
   val test: ScenarioBuilder = scenario(unique)
       .feed(data)
-      .exec(httpRequest.body(RawFileBody(body)).asJson)
+      .exec(httpRequest.body(ElFileBody(body)).asJson)
 
   setUp(
     test.inject(
diff --git a/e2e-tests/src/test/scala/com/google/gerrit/scenarios/GerritSimulation.scala b/e2e-tests/src/test/scala/com/google/gerrit/scenarios/GerritSimulation.scala
index 4832392..679320d 100644
--- a/e2e-tests/src/test/scala/com/google/gerrit/scenarios/GerritSimulation.scala
+++ b/e2e-tests/src/test/scala/com/google/gerrit/scenarios/GerritSimulation.scala
@@ -67,6 +67,8 @@
     case ("number", number) =>
       val precedes = replaceKeyWith("_number", 0, number.toString)
       replaceProperty("number", 1, precedes)
+    case ("parent", parent) =>
+      replaceProperty("parent", "All-Projects", parent.toString)
     case ("project", project) =>
       var precedes = replaceKeyWith("_project", name, project.toString)
       precedes = replaceOverride(precedes)
diff --git a/java/com/google/gerrit/acceptance/GerritServer.java b/java/com/google/gerrit/acceptance/GerritServer.java
index 50d11a1..5942c0f 100644
--- a/java/com/google/gerrit/acceptance/GerritServer.java
+++ b/java/com/google/gerrit/acceptance/GerritServer.java
@@ -35,6 +35,7 @@
 import com.google.gerrit.acceptance.testsuite.change.PerCommentOperationsImpl;
 import com.google.gerrit.acceptance.testsuite.change.PerDraftCommentOperationsImpl;
 import com.google.gerrit.acceptance.testsuite.change.PerPatchsetOperationsImpl;
+import com.google.gerrit.acceptance.testsuite.change.PerRobotCommentOperationsImpl;
 import com.google.gerrit.acceptance.testsuite.group.GroupOperations;
 import com.google.gerrit.acceptance.testsuite.group.GroupOperationsImpl;
 import com.google.gerrit.acceptance.testsuite.project.ProjectOperations;
@@ -518,6 +519,7 @@
             factory(PerPatchsetOperationsImpl.Factory.class);
             factory(PerCommentOperationsImpl.Factory.class);
             factory(PerDraftCommentOperationsImpl.Factory.class);
+            factory(PerRobotCommentOperationsImpl.Factory.class);
             factory(PushOneCommit.Factory.class);
             install(InProcessProtocol.module());
             install(new NoSshModule());
diff --git a/java/com/google/gerrit/acceptance/testsuite/change/ChangeOperations.java b/java/com/google/gerrit/acceptance/testsuite/change/ChangeOperations.java
index aa0391d..c4e4192 100644
--- a/java/com/google/gerrit/acceptance/testsuite/change/ChangeOperations.java
+++ b/java/com/google/gerrit/acceptance/testsuite/change/ChangeOperations.java
@@ -127,5 +127,13 @@
      * @return an aggregation of operations on a specific draft comment
      */
     PerDraftCommentOperations draftComment(String commentUuid);
+
+    /**
+     * Starts the fluent chain for querying or modifying a robot comment. Please see the methods of
+     * {@link PerRobotCommentOperations} for details on possible operations.
+     *
+     * @return an aggregation of operations on a specific robot comment
+     */
+    PerRobotCommentOperations robotComment(String commentUuid);
   }
 }
diff --git a/java/com/google/gerrit/acceptance/testsuite/change/ChangeOperationsImpl.java b/java/com/google/gerrit/acceptance/testsuite/change/ChangeOperationsImpl.java
index f04de17..3b15b57 100644
--- a/java/com/google/gerrit/acceptance/testsuite/change/ChangeOperationsImpl.java
+++ b/java/com/google/gerrit/acceptance/testsuite/change/ChangeOperationsImpl.java
@@ -87,6 +87,7 @@
   private final PerPatchsetOperationsImpl.Factory perPatchsetOperationsFactory;
   private final PerCommentOperationsImpl.Factory perCommentOperationsFactory;
   private final PerDraftCommentOperationsImpl.Factory perDraftCommentOperationsFactory;
+  private final PerRobotCommentOperationsImpl.Factory perRobotCommentOperationsFactory;
 
   @Inject
   public ChangeOperationsImpl(
@@ -102,7 +103,8 @@
       ChangeFinder changeFinder,
       PerPatchsetOperationsImpl.Factory perPatchsetOperationsFactory,
       PerCommentOperationsImpl.Factory perCommentOperationsFactory,
-      PerDraftCommentOperationsImpl.Factory perDraftCommentOperationsFactory) {
+      PerDraftCommentOperationsImpl.Factory perDraftCommentOperationsFactory,
+      PerRobotCommentOperationsImpl.Factory perRobotCommentOperationsFactory) {
     this.seq = seq;
     this.changeInserterFactory = changeInserterFactory;
     this.patchsetInserterFactory = patchsetInserterFactory;
@@ -116,6 +118,7 @@
     this.perPatchsetOperationsFactory = perPatchsetOperationsFactory;
     this.perCommentOperationsFactory = perCommentOperationsFactory;
     this.perDraftCommentOperationsFactory = perDraftCommentOperationsFactory;
+    this.perRobotCommentOperationsFactory = perRobotCommentOperationsFactory;
   }
 
   @Override
@@ -555,5 +558,11 @@
       ChangeNotes changeNotes = getChangeNotes();
       return perDraftCommentOperationsFactory.create(changeNotes, commentUuid);
     }
+
+    @Override
+    public PerRobotCommentOperations robotComment(String commentUuid) {
+      ChangeNotes changeNotes = getChangeNotes();
+      return perRobotCommentOperationsFactory.create(changeNotes, commentUuid);
+    }
   }
 }
diff --git a/java/com/google/gerrit/acceptance/testsuite/change/CommentSide.java b/java/com/google/gerrit/acceptance/testsuite/change/CommentSide.java
new file mode 100644
index 0000000..b7e720b
--- /dev/null
+++ b/java/com/google/gerrit/acceptance/testsuite/change/CommentSide.java
@@ -0,0 +1,36 @@
+// Copyright (C) 2020 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.acceptance.testsuite.change;
+
+/**
+ * Marks the commit that contains the comment (also known as side). Used by {@link
+ * TestCommentCreation} and {@link TestRobotCommentCreation}.
+ */
+enum CommentSide {
+  PATCHSET_COMMIT(1),
+  AUTO_MERGE_COMMIT(0),
+  PARENT_COMMIT(-1),
+  SECOND_PARENT_COMMIT(-2);
+
+  private final short numericSide;
+
+  CommentSide(int numericSide) {
+    this.numericSide = (short) numericSide;
+  }
+
+  public short getNumericSide() {
+    return numericSide;
+  }
+}
diff --git a/java/com/google/gerrit/acceptance/testsuite/change/FileBuilder.java b/java/com/google/gerrit/acceptance/testsuite/change/FileBuilder.java
new file mode 100644
index 0000000..c8514a7
--- /dev/null
+++ b/java/com/google/gerrit/acceptance/testsuite/change/FileBuilder.java
@@ -0,0 +1,33 @@
+// Copyright (C) 2020 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.acceptance.testsuite.change;
+
+import java.util.function.Function;
+
+/**
+ * Builder for the file specification of line/range comments. Used by {@link TestCommentCreation}
+ * and {@link TestRobotCommentCreation}.
+ */
+public class FileBuilder<T> {
+  private final Function<String, T> nextStepProvider;
+
+  public FileBuilder(Function<String, T> nextStepProvider) {
+    this.nextStepProvider = nextStepProvider;
+  }
+  /** File on which the comment should be added. */
+  public T ofFile(String file) {
+    return nextStepProvider.apply(file);
+  }
+}
diff --git a/java/com/google/gerrit/acceptance/testsuite/change/PerCommentOperationsImpl.java b/java/com/google/gerrit/acceptance/testsuite/change/PerCommentOperationsImpl.java
index 5f046ca..0218731 100644
--- a/java/com/google/gerrit/acceptance/testsuite/change/PerCommentOperationsImpl.java
+++ b/java/com/google/gerrit/acceptance/testsuite/change/PerCommentOperationsImpl.java
@@ -56,6 +56,11 @@
   }
 
   static TestHumanComment toTestComment(HumanComment comment) {
-    return TestHumanComment.builder().uuid(comment.key.uuid).parentUuid(comment.parentUuid).build();
+    return TestHumanComment.builder()
+        .uuid(comment.key.uuid)
+        .parentUuid(comment.parentUuid)
+        .tag(comment.tag)
+        .unresolved(comment.unresolved)
+        .build();
   }
 }
diff --git a/java/com/google/gerrit/acceptance/testsuite/change/PerPatchsetOperations.java b/java/com/google/gerrit/acceptance/testsuite/change/PerPatchsetOperations.java
index 33d2d43..f4c70bd 100644
--- a/java/com/google/gerrit/acceptance/testsuite/change/PerPatchsetOperations.java
+++ b/java/com/google/gerrit/acceptance/testsuite/change/PerPatchsetOperations.java
@@ -67,4 +67,25 @@
    * @return builder to create a new comment
    */
   TestCommentCreation.Builder newDraftComment();
+
+  /**
+   * Starts the fluent chain to create a new robot comment. The returned builder can be used to
+   * specify the attributes of the robot comment. To create the robot comment for real, {@link
+   * TestRobotCommentCreation.Builder#create()} must be called.
+   *
+   * <p>Example:
+   *
+   * <pre>
+   * String createdRobotCommentUuid = changeOperations
+   *     .change(changeId)
+   *     .currentPatchset()
+   *     .newRobotComment()
+   *     .onLine(2)
+   *     .ofFile("file1")
+   *     .create();
+   * </pre>
+   *
+   * @return builder to create a new comment
+   */
+  TestRobotCommentCreation.Builder newRobotComment();
 }
diff --git a/java/com/google/gerrit/acceptance/testsuite/change/PerPatchsetOperationsImpl.java b/java/com/google/gerrit/acceptance/testsuite/change/PerPatchsetOperationsImpl.java
index d39f1e1..465c419 100644
--- a/java/com/google/gerrit/acceptance/testsuite/change/PerPatchsetOperationsImpl.java
+++ b/java/com/google/gerrit/acceptance/testsuite/change/PerPatchsetOperationsImpl.java
@@ -16,13 +16,13 @@
 
 import static com.google.gerrit.server.CommentsUtil.setCommentCommitId;
 
-import com.google.gerrit.acceptance.testsuite.change.TestCommentCreation.CommentSide;
 import com.google.gerrit.entities.Account;
 import com.google.gerrit.entities.Comment.Status;
 import com.google.gerrit.entities.HumanComment;
 import com.google.gerrit.entities.Patch;
 import com.google.gerrit.entities.PatchSet;
 import com.google.gerrit.entities.Project;
+import com.google.gerrit.entities.RobotComment;
 import com.google.gerrit.extensions.client.Comment;
 import com.google.gerrit.extensions.client.Comment.Range;
 import com.google.gerrit.extensions.restapi.RestApiException;
@@ -101,6 +101,11 @@
     return TestCommentCreation.builder(this::createComment, Status.DRAFT);
   }
 
+  @Override
+  public TestRobotCommentCreation.Builder newRobotComment() {
+    return TestRobotCommentCreation.builder(this::createRobotComment);
+  }
+
   private String createComment(TestCommentCreation commentCreation)
       throws IOException, RestApiException, UpdateException {
     Project.NameKey project = changeNotes.getProjectName();
@@ -126,6 +131,20 @@
     return userFactory.create(authorId);
   }
 
+  private IdentifiedUser getAuthor(TestRobotCommentCreation robotCommentCreation) {
+    Account.Id authorId = robotCommentCreation.author().orElse(changeNotes.getChange().getOwner());
+    return userFactory.create(authorId);
+  }
+
+  private static Comment.Range toCommentRange(TestRange range) {
+    Comment.Range commentRange = new Range();
+    commentRange.startLine = range.start().line();
+    commentRange.startCharacter = range.start().charOffset();
+    commentRange.endLine = range.end().line();
+    commentRange.endCharacter = range.end().charOffset();
+    return commentRange;
+  }
+
   private class CommentAdditionOp implements BatchUpdateOp {
     private String createdCommentUuid;
     private final TestCommentCreation commentCreation;
@@ -154,11 +173,13 @@
       short side = commentCreation.side().orElse(CommentSide.PATCHSET_COMMIT).getNumericSide();
       Boolean unresolved = commentCreation.unresolved().orElse(null);
       String parentUuid = commentCreation.parentUuid().orElse(null);
+      Timestamp createdOn =
+          commentCreation.createdOn().map(Timestamp::from).orElse(context.getWhen());
       HumanComment newComment =
           commentsUtil.newHumanComment(
               context.getNotes(),
               context.getUser(),
-              context.getWhen(),
+              createdOn,
               filePath,
               patchsetId,
               side,
@@ -173,7 +194,7 @@
       // Specification of range trumps explicit line specification.
       commentCreation
           .range()
-          .map(this::toCommentRange)
+          .map(PerPatchsetOperationsImpl::toCommentRange)
           .ifPresent(range -> newComment.setLineNbrAndRange(null, range));
 
       setCommentCommitId(
@@ -183,14 +204,89 @@
           changeNotes.getPatchSets().get(patchsetId));
       return newComment;
     }
+  }
 
-    private Comment.Range toCommentRange(TestRange range) {
-      Comment.Range commentRange = new Range();
-      commentRange.startLine = range.start().line();
-      commentRange.startCharacter = range.start().charOffset();
-      commentRange.endLine = range.end().line();
-      commentRange.endCharacter = range.end().charOffset();
-      return commentRange;
+  private String createRobotComment(TestRobotCommentCreation robotCommentCreation)
+      throws IOException, RestApiException, UpdateException {
+    Project.NameKey project = changeNotes.getProjectName();
+
+    try (Repository repository = repositoryManager.openRepository(project);
+        ObjectInserter objectInserter = repository.newObjectInserter();
+        RevWalk revWalk = new RevWalk(objectInserter.newReader())) {
+      Timestamp now = TimeUtil.nowTs();
+
+      IdentifiedUser author = getAuthor(robotCommentCreation);
+      RobotCommentAdditionOp robotCommentAdditionOp =
+          new RobotCommentAdditionOp(robotCommentCreation);
+      try (BatchUpdate batchUpdate = batchUpdateFactory.create(project, author, now)) {
+        batchUpdate.setRepository(repository, revWalk, objectInserter);
+        batchUpdate.addOp(changeNotes.getChangeId(), robotCommentAdditionOp);
+        batchUpdate.execute();
+      }
+      return robotCommentAdditionOp.createdRobotCommentUuid;
+    }
+  }
+
+  private class RobotCommentAdditionOp implements BatchUpdateOp {
+    private String createdRobotCommentUuid;
+    private final TestRobotCommentCreation robotCommentCreation;
+
+    public RobotCommentAdditionOp(TestRobotCommentCreation robotCommentCreation) {
+      this.robotCommentCreation = robotCommentCreation;
+    }
+
+    @Override
+    public boolean updateChange(ChangeContext context) throws Exception {
+      RobotComment robotComment = toNewRobotComment(context, robotCommentCreation);
+      ChangeUpdate changeUpdate = context.getUpdate(patchsetId);
+      changeUpdate.putRobotComment(robotComment);
+      // For robot comments, only the tag set on the ChangeUpdate (and not on the RobotComment)
+      // matters.
+      robotCommentCreation.tag().ifPresent(changeUpdate::setTag);
+      createdRobotCommentUuid = robotComment.key.uuid;
+      return true;
+    }
+
+    private RobotComment toNewRobotComment(
+        ChangeContext context, TestRobotCommentCreation robotCommentCreation)
+        throws PatchListNotAvailableException {
+      String message = robotCommentCreation.message().orElse("The text of a test robot comment.");
+
+      String filePath = robotCommentCreation.file().orElse(Patch.PATCHSET_LEVEL);
+      short side = robotCommentCreation.side().orElse(CommentSide.PATCHSET_COMMIT).getNumericSide();
+      String robotId = robotCommentCreation.robotId().orElse("robot");
+      String robotRunId = robotCommentCreation.robotId().orElse("1");
+      RobotComment newRobotComment =
+          commentsUtil.newRobotComment(
+              context, filePath, patchsetId, side, message, robotId, robotRunId);
+
+      // TODO(paiking): This should not be needed, as the tag only matters in ChangeUpdate.
+      robotCommentCreation.tag().ifPresent(tag -> newRobotComment.tag = tag);
+
+      robotCommentCreation.line().ifPresent(line -> newRobotComment.setLineNbrAndRange(line, null));
+      // Specification of range trumps explicit line specification.
+      robotCommentCreation
+          .range()
+          .map(PerPatchsetOperationsImpl::toCommentRange)
+          .ifPresent(range -> newRobotComment.setLineNbrAndRange(null, range));
+
+      robotCommentCreation
+          .unresolved()
+          .ifPresent(unresolved -> newRobotComment.unresolved = unresolved);
+      robotCommentCreation
+          .parentUuid()
+          .ifPresent(parentUuid -> newRobotComment.parentUuid = parentUuid);
+      robotCommentCreation.url().ifPresent(url -> newRobotComment.url = url);
+      if (!robotCommentCreation.properties().isEmpty()) {
+        newRobotComment.properties = robotCommentCreation.properties();
+      }
+
+      setCommentCommitId(
+          newRobotComment,
+          patchListCache,
+          context.getChange(),
+          changeNotes.getPatchSets().get(patchsetId));
+      return newRobotComment;
     }
   }
 }
diff --git a/java/com/google/gerrit/acceptance/testsuite/change/PerRobotCommentOperations.java b/java/com/google/gerrit/acceptance/testsuite/change/PerRobotCommentOperations.java
new file mode 100644
index 0000000..c9718aa
--- /dev/null
+++ b/java/com/google/gerrit/acceptance/testsuite/change/PerRobotCommentOperations.java
@@ -0,0 +1,29 @@
+// Copyright (C) 2020 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.acceptance.testsuite.change;
+
+/** An aggregation of methods on a specific, robot comment. */
+public interface PerRobotCommentOperations {
+
+  /**
+   * Retrieves the robot comment.
+   *
+   * <p><strong>Note:</strong> This call will fail with an exception if the requested comment
+   * doesn't exist or if it is a comment of another type.
+   *
+   * @return the corresponding {@code TestRobotComment}
+   */
+  TestRobotComment get();
+}
diff --git a/java/com/google/gerrit/acceptance/testsuite/change/PerRobotCommentOperationsImpl.java b/java/com/google/gerrit/acceptance/testsuite/change/PerRobotCommentOperationsImpl.java
new file mode 100644
index 0000000..075c451
--- /dev/null
+++ b/java/com/google/gerrit/acceptance/testsuite/change/PerRobotCommentOperationsImpl.java
@@ -0,0 +1,64 @@
+// Copyright (C) 2020 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.acceptance.testsuite.change;
+
+import static com.google.common.collect.MoreCollectors.onlyElement;
+
+import com.google.gerrit.entities.RobotComment;
+import com.google.gerrit.server.CommentsUtil;
+import com.google.gerrit.server.notedb.ChangeNotes;
+import com.google.inject.Inject;
+import com.google.inject.assistedinject.Assisted;
+
+/**
+ * The implementation of {@link PerRobotCommentOperations}.
+ *
+ * <p>There is only one implementation of {@link PerRobotCommentOperations}. Nevertheless, we keep
+ * the separation between interface and implementation to enhance clarity.
+ */
+public class PerRobotCommentOperationsImpl implements PerRobotCommentOperations {
+  private final CommentsUtil commentsUtil;
+
+  private final ChangeNotes changeNotes;
+  private final String commentUuid;
+
+  public interface Factory {
+    PerRobotCommentOperationsImpl create(ChangeNotes changeNotes, String commentUuid);
+  }
+
+  @Inject
+  public PerRobotCommentOperationsImpl(
+      CommentsUtil commentsUtil, @Assisted ChangeNotes changeNotes, @Assisted String commentUuid) {
+    this.commentsUtil = commentsUtil;
+    this.changeNotes = changeNotes;
+    this.commentUuid = commentUuid;
+  }
+
+  @Override
+  public TestRobotComment get() {
+    RobotComment comment =
+        commentsUtil.robotCommentsByChange(changeNotes).stream()
+            .filter(foundComment -> foundComment.key.uuid.equals(commentUuid))
+            .collect(onlyElement());
+    return toTestRobotComment(comment);
+  }
+
+  static TestRobotComment toTestRobotComment(RobotComment robotComment) {
+    return TestRobotComment.builder()
+        .uuid(robotComment.key.uuid)
+        .parentUuid(robotComment.parentUuid)
+        .build();
+  }
+}
diff --git a/java/com/google/gerrit/acceptance/testsuite/change/PositionBuilder.java b/java/com/google/gerrit/acceptance/testsuite/change/PositionBuilder.java
new file mode 100644
index 0000000..b061c81
--- /dev/null
+++ b/java/com/google/gerrit/acceptance/testsuite/change/PositionBuilder.java
@@ -0,0 +1,34 @@
+// Copyright (C) 2020 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.acceptance.testsuite.change;
+
+import java.util.function.IntFunction;
+
+/**
+ * Builder to simplify a position specification. Used by {@link TestCommentCreation} and {@link
+ * TestRobotCommentCreation}.
+ */
+public class PositionBuilder<T> {
+  private final IntFunction<T> nextStepProvider;
+
+  public PositionBuilder(IntFunction<T> nextStepProvider) {
+    this.nextStepProvider = nextStepProvider;
+  }
+
+  /** Character offset within the line. A value of 0 indicates the beginning of the line. */
+  public T charOffset(int characterOffset) {
+    return nextStepProvider.apply(characterOffset);
+  }
+}
diff --git a/java/com/google/gerrit/acceptance/testsuite/change/StartAwarePositionBuilder.java b/java/com/google/gerrit/acceptance/testsuite/change/StartAwarePositionBuilder.java
new file mode 100644
index 0000000..c9a0eff
--- /dev/null
+++ b/java/com/google/gerrit/acceptance/testsuite/change/StartAwarePositionBuilder.java
@@ -0,0 +1,49 @@
+// Copyright (C) 2020 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.acceptance.testsuite.change;
+
+import java.util.function.Consumer;
+import java.util.function.Function;
+
+/**
+ * Builder for the end position of a range. Used by {@link TestCommentCreation} and {@link
+ * TestRobotCommentCreation}.
+ */
+public class StartAwarePositionBuilder<T> {
+  private final TestRange.Builder testRangeBuilder;
+  private final Consumer<TestRange> rangeConsumer;
+  private final Function<String, T> fileFunction;
+
+  public StartAwarePositionBuilder(
+      TestRange.Builder testRangeBuilder,
+      Consumer<TestRange> rangeConsumer,
+      Function<String, T> fileFunction) {
+    this.testRangeBuilder = testRangeBuilder;
+    this.rangeConsumer = rangeConsumer;
+    this.fileFunction = fileFunction;
+  }
+
+  /** Line of the end position of the range. */
+  public PositionBuilder<FileBuilder<T>> toLine(int endLine) {
+    return new PositionBuilder<>(
+        endCharOffset -> {
+          TestRange.Position end =
+              TestRange.Position.builder().line(endLine).charOffset(endCharOffset).build();
+          TestRange range = testRangeBuilder.setEnd(end).build();
+          rangeConsumer.accept(range);
+          return new FileBuilder<T>(fileFunction);
+        });
+  }
+}
diff --git a/java/com/google/gerrit/acceptance/testsuite/change/TestCommentCreation.java b/java/com/google/gerrit/acceptance/testsuite/change/TestCommentCreation.java
index d1d1567..2031bde 100644
--- a/java/com/google/gerrit/acceptance/testsuite/change/TestCommentCreation.java
+++ b/java/com/google/gerrit/acceptance/testsuite/change/TestCommentCreation.java
@@ -21,11 +21,16 @@
 import com.google.gerrit.entities.Account;
 import com.google.gerrit.entities.Comment;
 import com.google.gerrit.entities.Patch;
+import java.time.Instant;
+import java.time.LocalDateTime;
+import java.time.ZoneOffset;
 import java.util.Optional;
-import java.util.function.Function;
-import java.util.function.IntFunction;
 
-/** Attributes of the comment. If not provided, arbitrary values will be used. */
+/**
+ * Attributes of the human comment. If not provided, arbitrary values will be used. This class is
+ * very similar to {@link TestRobotCommentCreation} to allow separation between robot and human
+ * comments.
+ */
 @AutoValue
 public abstract class TestCommentCreation {
 
@@ -47,11 +52,13 @@
 
   public abstract Optional<Account.Id> author();
 
+  public abstract Optional<Instant> createdOn();
+
   abstract Comment.Status status();
 
   abstract ThrowingFunction<TestCommentCreation, String> commentCreator();
 
-  public static TestCommentCreation.Builder builder(
+  public static Builder builder(
       ThrowingFunction<TestCommentCreation, String> commentCreator, Comment.Status commentStatus) {
     return new AutoValue_TestCommentCreation.Builder()
         .commentCreator(commentCreator)
@@ -82,8 +89,8 @@
      * Starts the fluent change to create a line comment. The line comment will be at the indicated
      * line. Lines start with 1.
      */
-    public FileBuilder onLine(int line) {
-      return new FileBuilder(file -> file(file).line(line).range(null));
+    public FileBuilder<Builder> onLine(int line) {
+      return new FileBuilder<>(file -> file(file).line(line).range(null));
     }
 
     /**
@@ -91,12 +98,12 @@
      * Lines start at 1. The start position (line, charOffset) is inclusive, the end position (line,
      * charOffset) is exclusive.
      */
-    public PositionBuilder<StartAwarePositionBuilder> fromLine(int startLine) {
+    public PositionBuilder<StartAwarePositionBuilder<Builder>> fromLine(int startLine) {
       return new PositionBuilder<>(
           startCharOffset -> {
             Position start = Position.builder().line(startLine).charOffset(startCharOffset).build();
             TestRange.Builder testRangeBuilder = TestRange.builder().setStart(start);
-            return new StartAwarePositionBuilder(this, testRangeBuilder);
+            return new StartAwarePositionBuilder<>(testRangeBuilder, this::range, this::file);
           });
     }
 
@@ -173,14 +180,29 @@
     public abstract Builder author(Account.Id accountId);
 
     /**
+     * Creation time of the comment. Like {@link #createdOn(Instant)} but with an arbitrary, fixed
+     * time zone (-> deterministic test execution).
+     */
+    public Builder createdOn(LocalDateTime createdOn) {
+      // We don't care about the exact time zone in most tests, just that it's fixed so that tests
+      // are deterministic.
+      return createdOn(createdOn.atZone(ZoneOffset.UTC).toInstant());
+    }
+
+    /**
+     * Creation time of the comment. This may also lie in the past or future. Comments stored in
+     * NoteDb support only second precision.
+     */
+    public abstract Builder createdOn(Instant createdOn);
+
+    /**
      * Status of the comment. Hidden in the API surface. Use {@link
      * PerPatchsetOperations#newComment()} or {@link PerPatchsetOperations#newDraftComment()}
      * depending on which type of comment you want to create.
      */
     abstract Builder status(Comment.Status value);
 
-    abstract TestCommentCreation.Builder commentCreator(
-        ThrowingFunction<TestCommentCreation, String> commentCreator);
+    abstract Builder commentCreator(ThrowingFunction<TestCommentCreation, String> commentCreator);
 
     abstract TestCommentCreation autoBuild();
 
@@ -194,72 +216,4 @@
       return commentCreation.commentCreator().applyAndThrowSilently(commentCreation);
     }
   }
-
-  /** Builder for the file specification of line/range comments. */
-  public static class FileBuilder {
-    private final Function<String, Builder> nextStepProvider;
-
-    private FileBuilder(Function<String, Builder> nextStepProvider) {
-      this.nextStepProvider = nextStepProvider;
-    }
-
-    /** File on which the comment should be added. */
-    public Builder ofFile(String file) {
-      return nextStepProvider.apply(file);
-    }
-  }
-
-  /** Builder to simplify a position specification. */
-  public static class PositionBuilder<T> {
-    private final IntFunction<T> nextStepProvider;
-
-    private PositionBuilder(IntFunction<T> nextStepProvider) {
-      this.nextStepProvider = nextStepProvider;
-    }
-
-    /** Character offset within the line. A value of 0 indicates the beginning of the line. */
-    public T charOffset(int characterOffset) {
-      return nextStepProvider.apply(characterOffset);
-    }
-  }
-
-  /** Builder for the end position of a range. */
-  public static class StartAwarePositionBuilder {
-    private final TestCommentCreation.Builder testCommentCreationBuilder;
-    private final TestRange.Builder testRangeBuilder;
-
-    private StartAwarePositionBuilder(
-        Builder testCommentCreationBuilder, TestRange.Builder testRangeBuilder) {
-      this.testCommentCreationBuilder = testCommentCreationBuilder;
-      this.testRangeBuilder = testRangeBuilder;
-    }
-
-    /** Line of the end position of the range. */
-    public PositionBuilder<FileBuilder> toLine(int endLine) {
-      return new PositionBuilder<>(
-          endCharOffset -> {
-            Position end = Position.builder().line(endLine).charOffset(endCharOffset).build();
-            TestRange range = testRangeBuilder.setEnd(end).build();
-            testCommentCreationBuilder.range(range);
-            return new FileBuilder(testCommentCreationBuilder::file);
-          });
-    }
-  }
-
-  enum CommentSide {
-    PATCHSET_COMMIT(1),
-    AUTO_MERGE_COMMIT(0),
-    PARENT_COMMIT(-1),
-    SECOND_PARENT_COMMIT(-2);
-
-    private final short numericSide;
-
-    CommentSide(int numericSide) {
-      this.numericSide = (short) numericSide;
-    }
-
-    public short getNumericSide() {
-      return numericSide;
-    }
-  }
 }
diff --git a/java/com/google/gerrit/acceptance/testsuite/change/TestHumanComment.java b/java/com/google/gerrit/acceptance/testsuite/change/TestHumanComment.java
index 9bb026f..3a7f2ae 100644
--- a/java/com/google/gerrit/acceptance/testsuite/change/TestHumanComment.java
+++ b/java/com/google/gerrit/acceptance/testsuite/change/TestHumanComment.java
@@ -28,6 +28,12 @@
   /** UUID of another comment to which this comment is a reply. */
   public abstract Optional<String> parentUuid();
 
+  /** Tag of a comment. */
+  public abstract Optional<String> tag();
+
+  /** Unresolved state of a comment. */
+  public abstract boolean unresolved();
+
   static Builder builder() {
     return new AutoValue_TestHumanComment.Builder();
   }
@@ -38,6 +44,10 @@
 
     abstract Builder parentUuid(@Nullable String parentUuid);
 
+    abstract Builder tag(@Nullable String tag);
+
+    abstract Builder unresolved(boolean unresolved);
+
     abstract TestHumanComment build();
   }
 }
diff --git a/java/com/google/gerrit/acceptance/testsuite/change/TestRobotComment.java b/java/com/google/gerrit/acceptance/testsuite/change/TestRobotComment.java
new file mode 100644
index 0000000..76fb52f
--- /dev/null
+++ b/java/com/google/gerrit/acceptance/testsuite/change/TestRobotComment.java
@@ -0,0 +1,43 @@
+// Copyright (C) 2020 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.acceptance.testsuite.change;
+
+import com.google.auto.value.AutoValue;
+import com.google.gerrit.common.Nullable;
+import java.util.Optional;
+
+/** Representation of a robot comment used for testing purposes. */
+@AutoValue
+public abstract class TestRobotComment {
+
+  /** The UUID of the comment. Should be unique. */
+  public abstract String uuid();
+
+  /** UUID of another comment to which this comment is a reply. */
+  public abstract Optional<String> parentUuid();
+
+  static Builder builder() {
+    return new AutoValue_TestRobotComment.Builder();
+  }
+
+  @AutoValue.Builder
+  abstract static class Builder {
+    abstract Builder uuid(String uuid);
+
+    abstract Builder parentUuid(@Nullable String parentUuid);
+
+    abstract TestRobotComment build();
+  }
+}
diff --git a/java/com/google/gerrit/acceptance/testsuite/change/TestRobotCommentCreation.java b/java/com/google/gerrit/acceptance/testsuite/change/TestRobotCommentCreation.java
new file mode 100644
index 0000000..809190d
--- /dev/null
+++ b/java/com/google/gerrit/acceptance/testsuite/change/TestRobotCommentCreation.java
@@ -0,0 +1,214 @@
+// Copyright (C) 2020 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.acceptance.testsuite.change;
+
+import com.google.auto.value.AutoValue;
+import com.google.common.collect.ImmutableMap;
+import com.google.gerrit.acceptance.testsuite.ThrowingFunction;
+import com.google.gerrit.acceptance.testsuite.change.TestRange.Position;
+import com.google.gerrit.common.Nullable;
+import com.google.gerrit.entities.Account;
+import com.google.gerrit.entities.Patch;
+import java.util.Map;
+import java.util.Optional;
+
+/**
+ * Attributes of the robot comment. If not provided, arbitrary values will be used. This class is
+ * very similar to {@link TestCommentCreation} to allow separation between robot and human comments.
+ */
+@AutoValue
+public abstract class TestRobotCommentCreation {
+
+  public abstract Optional<String> message();
+
+  public abstract Optional<String> file();
+
+  public abstract Optional<Integer> line();
+
+  public abstract Optional<TestRange> range();
+
+  public abstract Optional<CommentSide> side();
+
+  public abstract Optional<Boolean> unresolved();
+
+  public abstract Optional<String> parentUuid();
+
+  public abstract Optional<String> tag();
+
+  public abstract Optional<Account.Id> author();
+
+  public abstract Optional<String> robotId();
+
+  public abstract Optional<String> robotRunId();
+
+  public abstract Optional<String> url();
+
+  public abstract ImmutableMap<String, String> properties();
+
+  abstract ThrowingFunction<TestRobotCommentCreation, String> commentCreator();
+
+  public static Builder builder(ThrowingFunction<TestRobotCommentCreation, String> commentCreator) {
+    return new AutoValue_TestRobotCommentCreation.Builder().commentCreator(commentCreator);
+  }
+
+  @AutoValue.Builder
+  public abstract static class Builder {
+
+    public Builder noMessage() {
+      return message("");
+    }
+
+    /** Message text of the comment. */
+    public abstract Builder message(String message);
+
+    /** Indicates a patchset-level comment. */
+    public Builder onPatchsetLevel() {
+      return file(Patch.PATCHSET_LEVEL);
+    }
+
+    /** Indicates a file comment. The comment will be on the specified file. */
+    public Builder onFileLevelOf(String filePath) {
+      return file(filePath).line(null).range(null);
+    }
+
+    /**
+     * Starts the fluent change to create a line comment. The line comment will be at the indicated
+     * line. Lines start with 1.
+     */
+    public FileBuilder<Builder> onLine(int line) {
+      return new FileBuilder<>(file -> file(file).line(line).range(null));
+    }
+
+    /**
+     * Starts the fluent chain to create a range comment. The range begins at the specified line.
+     * Lines start at 1. The start position (line, charOffset) is inclusive, the end position (line,
+     * charOffset) is exclusive.
+     */
+    public PositionBuilder<StartAwarePositionBuilder<Builder>> fromLine(int startLine) {
+      return new PositionBuilder<>(
+          startCharOffset -> {
+            Position start = Position.builder().line(startLine).charOffset(startCharOffset).build();
+            TestRange.Builder testRangeBuilder = TestRange.builder().setStart(start);
+            return new StartAwarePositionBuilder<>(testRangeBuilder, this::range, this::file);
+          });
+    }
+
+    /** File on which the comment should be added. */
+    abstract Builder file(String filePath);
+
+    /** Line on which the comment should be added. */
+    abstract Builder line(@Nullable Integer line);
+
+    /** Range on which the comment should be added. */
+    abstract Builder range(@Nullable TestRange range);
+
+    /**
+     * Indicates that the comment refers to a file, line, range, ... in the commit of the patchset.
+     *
+     * <p>On the UI, such comments are shown on the right side of a diff view when a diff against
+     * base is selected. See {@link #onParentCommit()} for comments shown on the left side.
+     */
+    public Builder onPatchsetCommit() {
+      return side(CommentSide.PATCHSET_COMMIT);
+    }
+
+    /**
+     * Indicates that the comment refers to a file, line, range, ... in the parent commit of the
+     * patchset.
+     *
+     * <p>On the UI, such comments are shown on the left side of a diff view when a diff against
+     * base is selected. See {@link #onPatchsetCommit()} for comments shown on the right side.
+     *
+     * <p>For merge commits, this indicates the first parent commit.
+     */
+    public Builder onParentCommit() {
+      return side(CommentSide.PARENT_COMMIT);
+    }
+
+    /** Like {@link #onParentCommit()} but for the second parent of a merge commit. */
+    public Builder onSecondParentCommit() {
+      return side(CommentSide.SECOND_PARENT_COMMIT);
+    }
+
+    /**
+     * Like {@link #onParentCommit()} but for the AutoMerge commit created from the parents of a
+     * merge commit.
+     */
+    public Builder onAutoMergeCommit() {
+      return side(CommentSide.AUTO_MERGE_COMMIT);
+    }
+
+    abstract Builder side(CommentSide side);
+
+    /** Indicates a resolved comment. */
+    public Builder resolved() {
+      return unresolved(false);
+    }
+
+    /** Indicates an unresolved comment. */
+    public Builder unresolved() {
+      return unresolved(true);
+    }
+
+    abstract Builder unresolved(boolean unresolved);
+
+    /**
+     * UUID of another comment to which this comment is a reply. This comment must have similar
+     * attributes (e.g. file, line, side) as the parent comment. The parent comment must be a
+     * published comment.
+     */
+    public abstract Builder parentUuid(String parentUuid);
+
+    /** Tag to attach to the comment. */
+    public abstract Builder tag(String value);
+
+    /** Author of the comment. Must be an existing user account. */
+    public abstract Builder author(Account.Id accountId);
+
+    /** Id of the robot that created the comment. */
+    public abstract Builder robotId(String robotId);
+
+    /** An ID of the run of the robot that created the comment. */
+    public abstract Builder robotRunId(String robotRunId);
+
+    /** Url for more information for the robot comment. */
+    public abstract Builder url(String url);
+
+    /** Robot specific properties as map that maps arbitrary keys to values. */
+    public abstract Builder properties(Map<String, String> properties);
+
+    abstract ImmutableMap.Builder<String, String> propertiesBuilder();
+
+    public Builder addProperty(String key, String value) {
+      propertiesBuilder().put(key, value);
+      return this;
+    }
+
+    abstract Builder commentCreator(
+        ThrowingFunction<TestRobotCommentCreation, String> commentCreator);
+
+    abstract TestRobotCommentCreation autoBuild();
+
+    /**
+     * Creates the robot comment.
+     *
+     * @return the UUID of the created robot comment
+     */
+    public String create() {
+      TestRobotCommentCreation commentCreation = autoBuild();
+      return commentCreation.commentCreator().applyAndThrowSilently(commentCreation);
+    }
+  }
+}
diff --git a/java/com/google/gerrit/extensions/common/testing/RobotCommentInfoSubject.java b/java/com/google/gerrit/extensions/common/testing/RobotCommentInfoSubject.java
index dd226ed..5176145 100644
--- a/java/com/google/gerrit/extensions/common/testing/RobotCommentInfoSubject.java
+++ b/java/com/google/gerrit/extensions/common/testing/RobotCommentInfoSubject.java
@@ -18,6 +18,7 @@
 import static com.google.gerrit.truth.ListSubject.elements;
 
 import com.google.common.truth.FailureMetadata;
+import com.google.common.truth.MapSubject;
 import com.google.common.truth.StringSubject;
 import com.google.common.truth.Subject;
 import com.google.gerrit.extensions.common.FixSuggestionInfo;
@@ -59,6 +60,26 @@
     return check("path").that(robotCommentInfo.path);
   }
 
+  public StringSubject robotId() {
+    isNotNull();
+    return check("robotId").that(robotCommentInfo.robotId);
+  }
+
+  public StringSubject robotRunId() {
+    isNotNull();
+    return check("robotRunId").that(robotCommentInfo.robotRunId);
+  }
+
+  public StringSubject url() {
+    isNotNull();
+    return check("url").that(robotCommentInfo.url);
+  }
+
+  public MapSubject properties() {
+    isNotNull();
+    return check("property").that(robotCommentInfo.properties);
+  }
+
   public FixSuggestionInfoSubject onlyFixSuggestion() {
     return fixSuggestions().onlyElement();
   }
diff --git a/java/com/google/gerrit/server/CommentsUtil.java b/java/com/google/gerrit/server/CommentsUtil.java
index 30913f7..4d5778a 100644
--- a/java/com/google/gerrit/server/CommentsUtil.java
+++ b/java/com/google/gerrit/server/CommentsUtil.java
@@ -21,7 +21,6 @@
 import static java.util.stream.Collectors.toList;
 
 import com.google.common.collect.ComparisonChain;
-import com.google.common.collect.ImmutableSet;
 import com.google.common.collect.Lists;
 import com.google.common.collect.Ordering;
 import com.google.gerrit.common.Nullable;
@@ -51,12 +50,8 @@
 import java.sql.Timestamp;
 import java.util.ArrayList;
 import java.util.Collection;
-import java.util.HashSet;
 import java.util.List;
-import java.util.Map;
 import java.util.Optional;
-import java.util.Set;
-import java.util.stream.Collectors;
 import org.eclipse.jgit.lib.ObjectId;
 import org.eclipse.jgit.lib.Ref;
 import org.eclipse.jgit.lib.Repository;
@@ -189,6 +184,12 @@
         .findFirst();
   }
 
+  public Optional<HumanComment> getPublishedHumanComment(ChangeNotes notes, String uuid) {
+    return publishedHumanCommentsByChange(notes).stream()
+        .filter(c -> c.key.uuid.equals(uuid))
+        .findFirst();
+  }
+
   public Optional<HumanComment> getDraft(ChangeNotes notes, IdentifiedUser user, Comment.Key key) {
     return draftByChangeAuthor(notes, user.getAccountId()).stream()
         .filter(c -> key.equals(c.key))
@@ -205,6 +206,10 @@
     return sort(Lists.newArrayList(notes.getRobotComments().values()));
   }
 
+  public Optional<RobotComment> getRobotComment(ChangeNotes notes, String uuid) {
+    return robotCommentsByChange(notes).stream().filter(c -> c.key.uuid.equals(uuid)).findFirst();
+  }
+
   public List<HumanComment> draftByChange(ChangeNotes notes) {
     List<HumanComment> comments = new ArrayList<>();
     for (Ref ref : getDraftRefs(notes.getChangeId())) {
@@ -344,43 +349,6 @@
     update.deleteCommentByRewritingHistory(commentKey.uuid, newMessage);
   }
 
-  /**
-   * Gets all of the {@link HumanComment} in the comment threads that received a reply.
-   *
-   * @param changeNotes notes of this change.
-   * @param newComments set of all the new comments added on the change by the current user.
-   * @return set of all comments in the comments thread that received a reply.
-   */
-  public Set<HumanComment> getAllHumanCommentsInCommentThreads(
-      ChangeNotes changeNotes, ImmutableSet<HumanComment> newComments) {
-    Map<String, HumanComment> uuidToComment =
-        publishedHumanCommentsByChange(changeNotes).stream()
-            .collect(Collectors.toMap(c -> c.key.uuid, c -> c));
-
-    // Copy the set so that it won't be mutated.
-    List<HumanComment> toTraverse = new ArrayList<>(newComments);
-    Set<String> seen = new HashSet<>();
-    Set<HumanComment> allCommentsInCommentThreads = new HashSet<>();
-    while (!toTraverse.isEmpty()) {
-      HumanComment current = toTraverse.remove(0);
-      allCommentsInCommentThreads.add(current);
-
-      if (current.parentUuid != null) {
-        HumanComment parent = uuidToComment.get(current.parentUuid);
-        if (parent == null) {
-          // If we can't find the parent within the human comments, the parent must be a robot
-          // comment and can be ignored.
-          continue;
-        }
-        if (!seen.contains(current.parentUuid)) {
-          toTraverse.add(parent);
-          seen.add(current.parentUuid);
-        }
-      }
-    }
-    return allCommentsInCommentThreads;
-  }
-
   private static List<HumanComment> commentsOnFile(
       Collection<HumanComment> allComments, String file) {
     List<HumanComment> result = new ArrayList<>(allComments.size());
diff --git a/java/com/google/gerrit/server/change/CommentThread.java b/java/com/google/gerrit/server/change/CommentThread.java
new file mode 100644
index 0000000..7b729d2
--- /dev/null
+++ b/java/com/google/gerrit/server/change/CommentThread.java
@@ -0,0 +1,69 @@
+// Copyright (C) 2020 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.server.change;
+
+import com.google.auto.value.AutoValue;
+import com.google.common.base.Preconditions;
+import com.google.common.collect.ImmutableList;
+import com.google.common.collect.Iterables;
+import com.google.gerrit.entities.Comment;
+import java.util.List;
+
+/**
+ * Representation of a comment thread.
+ *
+ * <p>A comment thread consists of at least one comment.
+ *
+ * @param <T> type of comments in the thread. Can also be {@link Comment} if the thread mixes
+ *     comments of different types.
+ */
+@AutoValue
+public abstract class CommentThread<T extends Comment> {
+
+  /** Comments in the thread in exactly the order they appear in the thread. */
+  public abstract ImmutableList<T> comments();
+
+  /** Whether the whole thread is considered as unresolved. */
+  public boolean unresolved() {
+    return Iterables.getLast(comments()).unresolved;
+  }
+
+  public static <T extends Comment> Builder<T> builder() {
+    return new AutoValue_CommentThread.Builder<>();
+  }
+
+  @AutoValue.Builder
+  public abstract static class Builder<T extends Comment> {
+
+    public abstract Builder<T> comments(List<T> value);
+
+    public Builder<T> addComment(T comment) {
+      commentsBuilder().add(comment);
+      return this;
+    }
+
+    abstract ImmutableList.Builder<T> commentsBuilder();
+
+    abstract ImmutableList<T> comments();
+
+    abstract CommentThread<T> autoBuild();
+
+    public CommentThread<T> build() {
+      Preconditions.checkState(
+          !comments().isEmpty(), "A comment thread must contain at least one comment.");
+      return autoBuild();
+    }
+  }
+}
diff --git a/java/com/google/gerrit/server/change/CommentThreads.java b/java/com/google/gerrit/server/change/CommentThreads.java
new file mode 100644
index 0000000..b948737
--- /dev/null
+++ b/java/com/google/gerrit/server/change/CommentThreads.java
@@ -0,0 +1,137 @@
+// Copyright (C) 2020 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.server.change;
+
+import static com.google.common.collect.ImmutableSet.toImmutableSet;
+import static java.util.stream.Collectors.groupingBy;
+
+import com.google.common.collect.ImmutableMap;
+import com.google.common.collect.ImmutableSet;
+import com.google.common.collect.Streams;
+import com.google.gerrit.entities.Comment;
+import java.util.Comparator;
+import java.util.Map;
+import java.util.PriorityQueue;
+import java.util.Queue;
+import java.util.function.Function;
+
+/**
+ * Identifier of comment threads.
+ *
+ * <p>Comments are ordered into threads according to their parent relationship indicated via {@link
+ * Comment#parentUuid}. It's possible that two comments refer to the same parent, which especially
+ * happens when two persons reply in parallel. If such branches exist, we merge them into a flat
+ * list taking the comment creation date ({@link Comment#writtenOn} into account (but still
+ * preserving the general parent order). Remaining ties are resolved by using the natural order of
+ * the comment UUID, which is unique.
+ *
+ * @param <T> type of comments in the threads. Can also be {@link Comment} if the threads mix
+ *     comments of different types.
+ */
+public class CommentThreads<T extends Comment> {
+
+  private final ImmutableMap<String, T> commentPerUuid;
+  private final Map<String, ImmutableSet<T>> childrenPerParent;
+
+  public CommentThreads(
+      ImmutableMap<String, T> commentPerUuid, Map<String, ImmutableSet<T>> childrenPerParent) {
+    this.commentPerUuid = commentPerUuid;
+    this.childrenPerParent = childrenPerParent;
+  }
+
+  public static <T extends Comment> CommentThreads<T> forComments(Iterable<T> comments) {
+    ImmutableMap<String, T> commentPerUuid =
+        Streams.stream(comments)
+            .distinct()
+            .collect(ImmutableMap.toImmutableMap(comment -> comment.key.uuid, Function.identity()));
+
+    Map<String, ImmutableSet<T>> childrenPerParent =
+        commentPerUuid.values().stream()
+            .filter(comment -> comment.parentUuid != null)
+            .collect(groupingBy(comment -> comment.parentUuid, toImmutableSet()));
+    return new CommentThreads<>(commentPerUuid, childrenPerParent);
+  }
+
+  /**
+   * Returns all comments organized into threads.
+   *
+   * <p>Comments appear only once.
+   */
+  public ImmutableSet<CommentThread<T>> getThreads() {
+    ImmutableSet<T> roots =
+        commentPerUuid.values().stream().filter(this::isRoot).collect(toImmutableSet());
+
+    return buildThreadsOf(roots);
+  }
+
+  /**
+   * Returns only the comment threads to which the specified comments are a reply.
+   *
+   * <p>If the specified child comments are part of the comments originally provided to {@link
+   * CommentThreads#forComments(Iterable)}, they will also appear in the returned comment threads.
+   * They don't need to be part of the originally provided comments, though, but should refer to one
+   * of these comments via their {@link Comment#parentUuid}. Child comments not referring to any
+   * known comments will be ignored.
+   *
+   * @param childComments comments for which the matching threads should be determined
+   * @return threads to which the provided child comments are a reply
+   */
+  public ImmutableSet<CommentThread<T>> getThreadsForChildren(Iterable<? extends T> childComments) {
+    ImmutableSet<T> relevantRoots =
+        Streams.stream(childComments)
+            .map(this::findRoot)
+            .filter(root -> commentPerUuid.containsKey(root.key.uuid))
+            .collect(toImmutableSet());
+    return buildThreadsOf(relevantRoots);
+  }
+
+  private T findRoot(T comment) {
+    T current = comment;
+    while (!isRoot(current)) {
+      current = commentPerUuid.get(current.parentUuid);
+    }
+    return current;
+  }
+
+  private boolean isRoot(T current) {
+    return current.parentUuid == null || !commentPerUuid.containsKey(current.parentUuid);
+  }
+
+  private ImmutableSet<CommentThread<T>> buildThreadsOf(ImmutableSet<T> roots) {
+    return roots.stream()
+        .map(root -> buildCommentThread(root, childrenPerParent))
+        .collect(toImmutableSet());
+  }
+
+  private static <T extends Comment> CommentThread<T> buildCommentThread(
+      T root, Map<String, ImmutableSet<T>> childrenPerParent) {
+    CommentThread.Builder<T> commentThread = CommentThread.builder();
+    // Expand comments gradually from the root. If there is more than one child per level, place the
+    // earlier-created child earlier in the thread. Break ties with the UUID to be deterministic.
+    Queue<T> unvisited =
+        new PriorityQueue<>(
+            Comparator.comparing((T comment) -> comment.writtenOn)
+                .thenComparing(comment -> comment.key.uuid));
+    unvisited.add(root);
+    while (!unvisited.isEmpty()) {
+      T nextComment = unvisited.remove();
+      commentThread.addComment(nextComment);
+      ImmutableSet<T> children =
+          childrenPerParent.getOrDefault(nextComment.key.uuid, ImmutableSet.of());
+      unvisited.addAll(children);
+    }
+    return commentThread.build();
+  }
+}
diff --git a/java/com/google/gerrit/server/change/DraftCommentResource.java b/java/com/google/gerrit/server/change/DraftCommentResource.java
index e0648cf..19a495d 100644
--- a/java/com/google/gerrit/server/change/DraftCommentResource.java
+++ b/java/com/google/gerrit/server/change/DraftCommentResource.java
@@ -20,6 +20,7 @@
 import com.google.gerrit.extensions.restapi.RestResource;
 import com.google.gerrit.extensions.restapi.RestView;
 import com.google.gerrit.server.CurrentUser;
+import com.google.gerrit.server.notedb.ChangeNotes;
 import com.google.inject.TypeLiteral;
 
 public class DraftCommentResource implements RestResource {
@@ -50,6 +51,10 @@
     return comment;
   }
 
+  public ChangeNotes getNotes() {
+    return rev.getNotes();
+  }
+
   public String getId() {
     return comment.key.uuid;
   }
diff --git a/java/com/google/gerrit/server/query/change/ChangeData.java b/java/com/google/gerrit/server/query/change/ChangeData.java
index 7f7df8c..8301576 100644
--- a/java/com/google/gerrit/server/query/change/ChangeData.java
+++ b/java/com/google/gerrit/server/query/change/ChangeData.java
@@ -60,6 +60,8 @@
 import com.google.gerrit.server.ReviewerStatusUpdate;
 import com.google.gerrit.server.StarredChangesUtil;
 import com.google.gerrit.server.StarredChangesUtil.StarRef;
+import com.google.gerrit.server.change.CommentThread;
+import com.google.gerrit.server.change.CommentThreads;
 import com.google.gerrit.server.change.MergeabilityCache;
 import com.google.gerrit.server.change.PureRevert;
 import com.google.gerrit.server.config.AllUsersName;
@@ -790,47 +792,15 @@
       List<Comment> comments =
           Stream.concat(publishedComments().stream(), robotComments().stream()).collect(toList());
 
-      // Build a map of uuid to list of direct descendants.
-      Map<String, List<Comment>> forest = new HashMap<>();
-      for (Comment comment : comments) {
-        List<Comment> siblings = forest.get(comment.parentUuid);
-        if (siblings == null) {
-          siblings = new ArrayList<>();
-          forest.put(comment.parentUuid, siblings);
-        }
-        siblings.add(comment);
-      }
-
-      // Find latest comment in each thread and apply to unresolved counter.
-      int unresolved = 0;
-      if (forest.containsKey(null)) {
-        for (Comment root : forest.get(null)) {
-          if (getLatestComment(forest, root).unresolved) {
-            unresolved++;
-          }
-        }
-      }
-      unresolvedCommentCount = unresolved;
+      ImmutableSet<CommentThread<Comment>> commentThreads =
+          CommentThreads.forComments(comments).getThreads();
+      unresolvedCommentCount =
+          (int) commentThreads.stream().filter(CommentThread::unresolved).count();
     }
 
     return unresolvedCommentCount;
   }
 
-  protected Comment getLatestComment(Map<String, List<Comment>> forest, Comment root) {
-    List<Comment> children = forest.get(root.key.uuid);
-    if (children == null) {
-      return root;
-    }
-    Comment latest = null;
-    for (Comment comment : children) {
-      Comment branchLatest = getLatestComment(forest, comment);
-      if (latest == null || branchLatest.writtenOn.after(latest.writtenOn)) {
-        latest = branchLatest;
-      }
-    }
-    return latest;
-  }
-
   public void setUnresolvedCommentCount(Integer count) {
     this.unresolvedCommentCount = count;
   }
diff --git a/java/com/google/gerrit/server/restapi/change/CommentPorter.java b/java/com/google/gerrit/server/restapi/change/CommentPorter.java
index 3effa8c..05241e2 100644
--- a/java/com/google/gerrit/server/restapi/change/CommentPorter.java
+++ b/java/com/google/gerrit/server/restapi/change/CommentPorter.java
@@ -29,6 +29,8 @@
 import com.google.gerrit.entities.Project;
 import com.google.gerrit.extensions.client.DiffPreferencesInfo.Whitespace;
 import com.google.gerrit.server.CommentsUtil;
+import com.google.gerrit.server.change.CommentThread;
+import com.google.gerrit.server.change.CommentThreads;
 import com.google.gerrit.server.notedb.ChangeNotes;
 import com.google.gerrit.server.patch.DiffMappings;
 import com.google.gerrit.server.patch.GitPositionTransformer;
@@ -43,6 +45,7 @@
 import com.google.gerrit.server.patch.PatchListNotAvailableException;
 import com.google.inject.Inject;
 import com.google.inject.Singleton;
+import java.util.Collection;
 import java.util.List;
 import java.util.Map;
 import java.util.Map.Entry;
@@ -102,8 +105,18 @@
 
   private ImmutableList<HumanComment> filterToRelevant(
       List<HumanComment> allComments, PatchSet targetPatchset) {
-    return allComments.stream()
-        .filter(comment -> comment.key.patchSetId < targetPatchset.number())
+    ImmutableList<HumanComment> previousPatchsetsComments =
+        allComments.stream()
+            .filter(comment -> comment.key.patchSetId < targetPatchset.number())
+            .collect(toImmutableList());
+
+    ImmutableSet<CommentThread<HumanComment>> commentThreads =
+        CommentThreads.forComments(previousPatchsetsComments).getThreads();
+
+    return commentThreads.stream()
+        .filter(CommentThread::unresolved)
+        .map(CommentThread::comments)
+        .flatMap(Collection::stream)
         .collect(toImmutableList());
   }
 
diff --git a/java/com/google/gerrit/server/restapi/change/CreateDraftComment.java b/java/com/google/gerrit/server/restapi/change/CreateDraftComment.java
index b749e6a..399da8f 100644
--- a/java/com/google/gerrit/server/restapi/change/CreateDraftComment.java
+++ b/java/com/google/gerrit/server/restapi/change/CreateDraftComment.java
@@ -81,6 +81,11 @@
       throw new BadRequestException("line must be >= 0");
     } else if (in.line != null && in.range != null && in.line != in.range.endLine) {
       throw new BadRequestException("range endLine must be on the same line as the comment");
+    } else if (in.inReplyTo != null
+        && !commentsUtil.getPublishedHumanComment(rsrc.getNotes(), in.inReplyTo).isPresent()
+        && !commentsUtil.getRobotComment(rsrc.getNotes(), in.inReplyTo).isPresent()) {
+      throw new BadRequestException(
+          String.format("Invalid inReplyTo, comment %s not found", in.inReplyTo));
     }
 
     try (BatchUpdate bu =
diff --git a/java/com/google/gerrit/server/restapi/change/PostReview.java b/java/com/google/gerrit/server/restapi/change/PostReview.java
index 9064dc8..32c1656 100644
--- a/java/com/google/gerrit/server/restapi/change/PostReview.java
+++ b/java/com/google/gerrit/server/restapi/change/PostReview.java
@@ -616,6 +616,7 @@
         ensureCommentNotOnMagicFilesOfAutoMerge(path, comment);
         ensureRangeIsValid(path, comment.range);
         ensureValidPatchsetLevelComment(path, comment);
+        ensureValidInReplyTo(revision.getNotes(), comment.inReplyTo);
       }
     }
   }
@@ -662,6 +663,16 @@
     }
   }
 
+  private void ensureValidInReplyTo(ChangeNotes changeNotes, String inReplyTo)
+      throws BadRequestException {
+    if (inReplyTo != null
+        && !commentsUtil.getPublishedHumanComment(changeNotes, inReplyTo).isPresent()
+        && !commentsUtil.getRobotComment(changeNotes, inReplyTo).isPresent()) {
+      throw new BadRequestException(
+          String.format("Invalid inReplyTo, comment %s not found", inReplyTo));
+    }
+  }
+
   private void checkRobotComments(
       RevisionResource revision, Map<String, List<RobotCommentInput>> in)
       throws BadRequestException, PatchListNotAvailableException {
diff --git a/java/com/google/gerrit/server/restapi/change/PutDraftComment.java b/java/com/google/gerrit/server/restapi/change/PutDraftComment.java
index f327f16..39de43d 100644
--- a/java/com/google/gerrit/server/restapi/change/PutDraftComment.java
+++ b/java/com/google/gerrit/server/restapi/change/PutDraftComment.java
@@ -86,8 +86,12 @@
       throw new BadRequestException("patchset-level comments can't have side, range, or line");
     } else if (in.line != null && in.range != null && in.line != in.range.endLine) {
       throw new BadRequestException("range endLine must be on the same line as the comment");
+    } else if (in.inReplyTo != null
+        && !commentsUtil.getPublishedHumanComment(rsrc.getNotes(), in.inReplyTo).isPresent()
+        && !commentsUtil.getRobotComment(rsrc.getNotes(), in.inReplyTo).isPresent()) {
+      throw new BadRequestException(
+          String.format("Invalid inReplyTo, comment %s not found", in.inReplyTo));
     }
-
     try (BatchUpdate bu =
         updateFactory.create(rsrc.getChange().getProject(), rsrc.getUser(), TimeUtil.nowTs())) {
       Op op = new Op(rsrc.getComment().key, in);
diff --git a/java/com/google/gerrit/server/restapi/change/ReplyAttentionSetUpdates.java b/java/com/google/gerrit/server/restapi/change/ReplyAttentionSetUpdates.java
index 1f6574f..c523036 100644
--- a/java/com/google/gerrit/server/restapi/change/ReplyAttentionSetUpdates.java
+++ b/java/com/google/gerrit/server/restapi/change/ReplyAttentionSetUpdates.java
@@ -17,6 +17,8 @@
 import static com.google.common.collect.ImmutableSet.toImmutableSet;
 
 import com.google.common.collect.ImmutableSet;
+import com.google.common.collect.Sets;
+import com.google.common.collect.Sets.SetView;
 import com.google.gerrit.entities.Account;
 import com.google.gerrit.entities.HumanComment;
 import com.google.gerrit.entities.PatchSet;
@@ -32,6 +34,8 @@
 import com.google.gerrit.server.account.ServiceUserClassifier;
 import com.google.gerrit.server.change.AddToAttentionSetOp;
 import com.google.gerrit.server.change.AttentionSetUnchangedOp;
+import com.google.gerrit.server.change.CommentThread;
+import com.google.gerrit.server.change.CommentThreads;
 import com.google.gerrit.server.change.RemoveFromAttentionSetOp;
 import com.google.gerrit.server.notedb.ChangeNotes;
 import com.google.gerrit.server.notedb.ChangeUpdate;
@@ -44,6 +48,7 @@
 import com.google.inject.Inject;
 import java.io.IOException;
 import java.util.ArrayList;
+import java.util.Collection;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Set;
@@ -208,19 +213,22 @@
   /** Adds all authors of all comment threads that received a reply during this update */
   private void addAllAuthorsOfCommentThreads(
       BatchUpdate bu, ChangeNotes changeNotes, ImmutableSet<HumanComment> allNewComments) {
-    Set<HumanComment> allCommentsInCommentThreads =
-        commentsUtil.getAllHumanCommentsInCommentThreads(changeNotes, allNewComments);
-    // Copy the set to make it mutable, so that we can delete users that were already added.
-    Set<Account.Id> possibleUsersToAdd =
-        new HashSet<>(approvalsUtil.getReviewers(changeNotes).all());
+    List<HumanComment> publishedComments = commentsUtil.publishedHumanCommentsByChange(changeNotes);
+    ImmutableSet<CommentThread<HumanComment>> repliedToCommentThreads =
+        CommentThreads.forComments(publishedComments).getThreadsForChildren(allNewComments);
 
-    for (HumanComment comment : allCommentsInCommentThreads) {
-      Account.Id author = comment.author.getId();
-      if (possibleUsersToAdd.contains(author)) {
-        addToAttentionSet(
-            bu, changeNotes, author, "Someone else replied on a comment you posted", false);
-        possibleUsersToAdd.remove(author);
-      }
+    ImmutableSet<Account.Id> repliedToUsers =
+        repliedToCommentThreads.stream()
+            .map(CommentThread::comments)
+            .flatMap(Collection::stream)
+            .map(comment -> comment.author.getId())
+            .collect(toImmutableSet());
+    ImmutableSet<Account.Id> possibleUsersToAdd = approvalsUtil.getReviewers(changeNotes).all();
+    SetView<Account.Id> usersToAdd = Sets.intersection(possibleUsersToAdd, repliedToUsers);
+
+    for (Account.Id user : usersToAdd) {
+      addToAttentionSet(
+          bu, changeNotes, user, "Someone else replied on a comment you posted", false);
     }
   }
 
diff --git a/java/com/google/gerrit/sshd/SshDaemon.java b/java/com/google/gerrit/sshd/SshDaemon.java
index 5145c13..c43bf91 100644
--- a/java/com/google/gerrit/sshd/SshDaemon.java
+++ b/java/com/google/gerrit/sshd/SshDaemon.java
@@ -62,7 +62,9 @@
 import java.util.Iterator;
 import java.util.List;
 import java.util.Set;
+import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.ExecutorService;
+import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicInteger;
 import org.apache.mina.transport.socket.SocketSessionConfig;
 import org.apache.sshd.common.BaseBuilder;
@@ -72,6 +74,8 @@
 import org.apache.sshd.common.compression.BuiltinCompressions;
 import org.apache.sshd.common.compression.Compression;
 import org.apache.sshd.common.forward.DefaultForwarderFactory;
+import org.apache.sshd.common.future.CloseFuture;
+import org.apache.sshd.common.future.SshFutureListener;
 import org.apache.sshd.common.io.AbstractIoServiceFactory;
 import org.apache.sshd.common.io.IoAcceptor;
 import org.apache.sshd.common.io.IoServiceFactory;
@@ -142,6 +146,7 @@
   private final List<HostKey> hostKeys;
   private volatile IoAcceptor daemonAcceptor;
   private final Config cfg;
+  private final long gracefulStopTimeout;
 
   @Inject
   SshDaemon(
@@ -212,6 +217,8 @@
     SshSessionBackend backend = cfg.getEnum("sshd", null, "backend", SshSessionBackend.NIO2);
     boolean channelIdTracking = cfg.getBoolean("sshd", "enableChannelIdTracking", true);
 
+    gracefulStopTimeout = cfg.getTimeUnit("sshd", null, "gracefulStopTimeout", 0, TimeUnit.SECONDS);
+
     System.setProperty(
         IoServiceFactoryFactory.class.getName(),
         backend == SshSessionBackend.MINA
@@ -341,6 +348,12 @@
   public synchronized void stop() {
     if (daemonAcceptor != null) {
       try {
+        if (gracefulStopTimeout > 0) {
+          logger.atInfo().log(
+              "Stopping SSHD sessions gracefully with %d seconds timeout.", gracefulStopTimeout);
+          daemonAcceptor.unbind(daemonAcceptor.getBoundAddresses());
+          waitForSessionClose();
+        }
         daemonAcceptor.close(true).await();
         shutdownExecutors();
         logger.atInfo().log("Stopped Gerrit SSHD");
@@ -352,6 +365,30 @@
     }
   }
 
+  private void waitForSessionClose() {
+    Collection<IoSession> ioSessions = daemonAcceptor.getManagedSessions().values();
+    CountDownLatch allSessionsClosed = new CountDownLatch(ioSessions.size());
+    for (IoSession io : ioSessions) {
+      logger.atFine().log("Waiting for session %s to stop.", io.getId());
+      io.addCloseFutureListener(
+          new SshFutureListener<CloseFuture>() {
+            @Override
+            public void operationComplete(CloseFuture future) {
+              allSessionsClosed.countDown();
+            }
+          });
+    }
+    try {
+      if (!allSessionsClosed.await(gracefulStopTimeout, TimeUnit.SECONDS)) {
+        logger.atWarning().log(
+            "Timeout waiting for SSH session to close. SSHD will be shut down immediately.");
+      }
+    } catch (InterruptedException e) {
+      logger.atWarning().withCause(e).log(
+          "Interrupted waiting for SSH-sessions to close. SSHD will be shut down immediately.");
+    }
+  }
+
   private void shutdownExecutors() {
     if (executor != null) {
       executor.shutdownNow();
diff --git a/java/com/google/gerrit/testing/TestCommentHelper.java b/java/com/google/gerrit/testing/TestCommentHelper.java
index 889bc18..76a5521 100644
--- a/java/com/google/gerrit/testing/TestCommentHelper.java
+++ b/java/com/google/gerrit/testing/TestCommentHelper.java
@@ -17,6 +17,7 @@
 import static java.util.stream.Collectors.toList;
 
 import com.google.common.collect.ImmutableList;
+import com.google.gerrit.entities.Change;
 import com.google.gerrit.extensions.api.GerritApi;
 import com.google.gerrit.extensions.api.changes.DraftInput;
 import com.google.gerrit.extensions.api.changes.ReviewInput;
@@ -148,13 +149,30 @@
     addRobotComment(targetChangeId, robotCommentInput, "robot comment test");
   }
 
+  public void addRobotComment(Change.Id targetChangeId, RobotCommentInput robotCommentInput)
+      throws Exception {
+    addRobotComment(targetChangeId, robotCommentInput, "robot comment test");
+  }
+
   public void addRobotComment(
       String targetChangeId, RobotCommentInput robotCommentInput, String message) throws Exception {
+    ReviewInput reviewInput = createReviewInput(robotCommentInput, message);
+    gApi.changes().id(targetChangeId).current().review(reviewInput);
+  }
+
+  public void addRobotComment(
+      Change.Id targetChangeId, RobotCommentInput robotCommentInput, String message)
+      throws Exception {
+    ReviewInput reviewInput = createReviewInput(robotCommentInput, message);
+    gApi.changes().id(targetChangeId.get()).current().review(reviewInput);
+  }
+
+  private ReviewInput createReviewInput(RobotCommentInput robotCommentInput, String message) {
     ReviewInput reviewInput = new ReviewInput();
     reviewInput.robotComments =
         Collections.singletonMap(robotCommentInput.path, ImmutableList.of(robotCommentInput));
     reviewInput.message = message;
     reviewInput.tag = ChangeMessagesUtil.AUTOGENERATED_TAG_PREFIX;
-    gApi.changes().id(targetChangeId).current().review(reviewInput);
+    return reviewInput;
   }
 }
diff --git a/javatests/com/google/gerrit/acceptance/api/revision/PortedCommentsIT.java b/javatests/com/google/gerrit/acceptance/api/revision/PortedCommentsIT.java
index 702602b..a6301f9 100644
--- a/javatests/com/google/gerrit/acceptance/api/revision/PortedCommentsIT.java
+++ b/javatests/com/google/gerrit/acceptance/api/revision/PortedCommentsIT.java
@@ -27,6 +27,7 @@
 import com.google.gerrit.acceptance.AbstractDaemonTest;
 import com.google.gerrit.acceptance.testsuite.account.AccountOperations;
 import com.google.gerrit.acceptance.testsuite.change.ChangeOperations;
+import com.google.gerrit.acceptance.testsuite.change.TestCommentCreation;
 import com.google.gerrit.acceptance.testsuite.change.TestPatchset;
 import com.google.gerrit.acceptance.testsuite.request.RequestScopeOperations;
 import com.google.gerrit.entities.Account;
@@ -37,10 +38,10 @@
 import com.google.gerrit.extensions.restapi.RestApiException;
 import com.google.gerrit.truth.NullAwareCorrespondence;
 import com.google.inject.Inject;
+import java.time.LocalDateTime;
 import java.util.Collection;
 import java.util.List;
 import java.util.Map;
-import org.junit.Ignore;
 import org.junit.Test;
 
 public class PortedCommentsIT extends AbstractDaemonTest {
@@ -57,9 +58,9 @@
     PatchSet.Id patchset2Id = changeOps.change(changeId).newPatchset().create();
     PatchSet.Id patchset3Id = changeOps.change(changeId).newPatchset().create();
     // Add comments.
-    String comment1Uuid = changeOps.change(changeId).patchset(patchset1Id).newComment().create();
-    changeOps.change(changeId).patchset(patchset2Id).newComment().create();
-    changeOps.change(changeId).patchset(patchset3Id).newComment().create();
+    String comment1Uuid = newComment(patchset1Id).create();
+    newComment(patchset2Id).create();
+    newComment(patchset3Id).create();
 
     List<CommentInfo> portedComments = flatten(getPortedComments(patchset2Id));
 
@@ -75,8 +76,8 @@
     PatchSet.Id patchset3Id = changeOps.change(changeId).newPatchset().create();
     PatchSet.Id patchset4Id = changeOps.change(changeId).newPatchset().create();
     // Add comments.
-    String comment1Uuid = changeOps.change(changeId).patchset(patchset1Id).newComment().create();
-    String comment3Uuid = changeOps.change(changeId).patchset(patchset3Id).newComment().create();
+    String comment1Uuid = newComment(patchset1Id).create();
+    String comment3Uuid = newComment(patchset3Id).create();
 
     List<CommentInfo> portedComments = flatten(getPortedComments(patchset4Id));
 
@@ -92,8 +93,8 @@
     PatchSet.Id patchset1Id = changeOps.change(changeId).currentPatchset().get().patchsetId();
     PatchSet.Id patchset2Id = changeOps.change(changeId).newPatchset().create();
     // Add comments.
-    String comment1Uuid = changeOps.change(changeId).patchset(patchset1Id).newComment().create();
-    String comment2Uuid = changeOps.change(changeId).patchset(patchset1Id).newComment().create();
+    String comment1Uuid = newComment(patchset1Id).create();
+    String comment2Uuid = newComment(patchset1Id).create();
 
     List<CommentInfo> portedComments = flatten(getPortedComments(patchset2Id));
 
@@ -109,21 +110,9 @@
     PatchSet.Id patchset1Id = changeOps.change(changeId).currentPatchset().get().patchsetId();
     PatchSet.Id patchset2Id = changeOps.change(changeId).newPatchset().create();
     // Add comments.
-    String rootCommentUuid = changeOps.change(changeId).patchset(patchset1Id).newComment().create();
-    String child1CommentUuid =
-        changeOps
-            .change(changeId)
-            .patchset(patchset1Id)
-            .newComment()
-            .parentUuid(rootCommentUuid)
-            .create();
-    String child2CommentUuid =
-        changeOps
-            .change(changeId)
-            .patchset(patchset1Id)
-            .newComment()
-            .parentUuid(child1CommentUuid)
-            .create();
+    String rootCommentUuid = newComment(patchset1Id).create();
+    String child1CommentUuid = newComment(patchset1Id).parentUuid(rootCommentUuid).create();
+    String child2CommentUuid = newComment(patchset1Id).parentUuid(child1CommentUuid).create();
 
     List<CommentInfo> portedComments = flatten(getPortedComments(patchset2Id));
 
@@ -133,17 +122,14 @@
   }
 
   @Test
-  // TODO(aliceks): Filter out unresolved comment threads.
-  @Ignore
-  public void onlyUnresolvedCommentsArePorted() throws Exception {
+  public void onlyUnresolvedPublishedCommentsArePorted() throws Exception {
     // Set up change and patchsets.
     Change.Id changeId = changeOps.newChange().create();
     PatchSet.Id patchset1Id = changeOps.change(changeId).currentPatchset().get().patchsetId();
     PatchSet.Id patchset2Id = changeOps.change(changeId).newPatchset().create();
     // Add comments.
-    changeOps.change(changeId).patchset(patchset1Id).newComment().resolved().create();
-    String comment2Uuid =
-        changeOps.change(changeId).patchset(patchset1Id).newComment().unresolved().create();
+    newComment(patchset1Id).resolved().create();
+    String comment2Uuid = newComment(patchset1Id).unresolved().create();
 
     List<CommentInfo> portedComments = flatten(getPortedComments(patchset2Id));
 
@@ -151,33 +137,34 @@
   }
 
   @Test
-  // TODO(aliceks): Filter out unresolved comment threads.
-  @Ignore
+  public void onlyUnresolvedDraftCommentsArePorted() throws Exception {
+    Account.Id accountId = accountOps.newAccount().create();
+    // Set up change and patchsets.
+    Change.Id changeId = changeOps.newChange().create();
+    PatchSet.Id patchset1Id = changeOps.change(changeId).currentPatchset().get().patchsetId();
+    PatchSet.Id patchset2Id = changeOps.change(changeId).newPatchset().create();
+    // Add comments.
+    newDraftComment(patchset1Id).author(accountId).resolved().create();
+    String comment2Uuid = newDraftComment(patchset1Id).author(accountId).unresolved().create();
+
+    List<CommentInfo> portedComments =
+        flatten(getPortedDraftCommentsOfUser(patchset2Id, accountId));
+
+    assertThat(portedComments).comparingElementsUsing(hasUuid()).containsExactly(comment2Uuid);
+  }
+
+  @Test
   public void unresolvedStateOfLastCommentInThreadMatters() throws Exception {
     // Set up change and patchsets.
     Change.Id changeId = changeOps.newChange().create();
     PatchSet.Id patchset1Id = changeOps.change(changeId).currentPatchset().get().patchsetId();
     PatchSet.Id patchset2Id = changeOps.change(changeId).newPatchset().create();
     // Add comments.
-    String rootComment1Uuid =
-        changeOps.change(changeId).patchset(patchset1Id).newComment().resolved().create();
+    String rootComment1Uuid = newComment(patchset1Id).resolved().create();
     String childComment1Uuid =
-        changeOps
-            .change(changeId)
-            .patchset(patchset1Id)
-            .newComment()
-            .parentUuid(rootComment1Uuid)
-            .unresolved()
-            .create();
-    String rootComment2Uuid =
-        changeOps.change(changeId).patchset(patchset1Id).newComment().unresolved().create();
-    changeOps
-        .change(changeId)
-        .patchset(patchset1Id)
-        .newComment()
-        .parentUuid(rootComment2Uuid)
-        .resolved()
-        .create();
+        newComment(patchset1Id).parentUuid(rootComment1Uuid).unresolved().create();
+    String rootComment2Uuid = newComment(patchset1Id).unresolved().create();
+    newComment(patchset1Id).parentUuid(rootComment2Uuid).resolved().create();
 
     List<CommentInfo> portedComments = flatten(getPortedComments(patchset2Id));
 
@@ -192,24 +179,21 @@
     Change.Id changeId = changeOps.newChange().create();
     PatchSet.Id patchset1Id = changeOps.change(changeId).currentPatchset().get().patchsetId();
     PatchSet.Id patchset2Id = changeOps.change(changeId).newPatchset().create();
-    // Add comments.
-    String rootCommentUuid =
-        changeOps.change(changeId).patchset(patchset1Id).newComment().resolved().create();
+    // Add comments. Comments should be more than 1 second apart as NoteDb only supports second
+    // precision.
+    LocalDateTime now = LocalDateTime.now();
+    String rootCommentUuid = newComment(patchset1Id).resolved().createdOn(now).create();
     String childComment1Uuid =
-        changeOps
-            .change(changeId)
-            .patchset(patchset1Id)
-            .newComment()
+        newComment(patchset1Id)
             .parentUuid(rootCommentUuid)
             .resolved()
+            .createdOn(now.plusSeconds(5))
             .create();
     String childComment2Uuid =
-        changeOps
-            .change(changeId)
-            .patchset(patchset1Id)
-            .newComment()
+        newComment(patchset1Id)
             .parentUuid(rootCommentUuid)
             .unresolved()
+            .createdOn(now.plusSeconds(10))
             .create();
 
     List<CommentInfo> portedComments = flatten(getPortedComments(patchset2Id));
@@ -220,6 +204,30 @@
   }
 
   @Test
+  public void unresolvedStateOfDraftCommentsIsIgnoredForPublishedComments() throws Exception {
+    Account.Id accountId = accountOps.newAccount().create();
+    // Set up change and patchsets.
+    Change.Id changeId = changeOps.newChange().create();
+    PatchSet.Id patchset1Id = changeOps.change(changeId).currentPatchset().get().patchsetId();
+    PatchSet.Id patchset2Id = changeOps.change(changeId).newPatchset().create();
+    // Add comments.
+    String rootComment1Uuid = newComment(patchset1Id).resolved().create();
+    newDraftComment(patchset1Id)
+        .author(accountId)
+        .parentUuid(rootComment1Uuid)
+        .unresolved()
+        .create();
+    String rootComment2Uuid = newComment(patchset1Id).unresolved().create();
+    newDraftComment(patchset1Id).author(accountId).parentUuid(rootComment2Uuid).resolved().create();
+
+    // Draft comments are only visible to their author.
+    requestScopeOps.setApiUser(accountId);
+    List<CommentInfo> portedComments = flatten(getPortedComments(patchset2Id));
+
+    assertThat(portedComments).comparingElementsUsing(hasUuid()).containsExactly(rootComment2Uuid);
+  }
+
+  @Test
   public void draftCommentsAreNotPortedViaApiForPublishedComments() throws Exception {
     Account.Id accountId = accountOps.newAccount().create();
     // Set up change and patchsets.
@@ -227,7 +235,7 @@
     PatchSet.Id patchset1Id = changeOps.change(changeId).currentPatchset().get().patchsetId();
     PatchSet.Id patchset2Id = changeOps.change(changeId).newPatchset().create();
     // Add draft comment.
-    changeOps.change(changeId).patchset(patchset1Id).newDraftComment().author(accountId).create();
+    newDraftComment(patchset1Id).author(accountId).create();
 
     // Draft comments are only visible to their author.
     requestScopeOps.setApiUser(accountId);
@@ -244,7 +252,7 @@
     PatchSet.Id patchset1Id = changeOps.change(changeId).currentPatchset().get().patchsetId();
     PatchSet.Id patchset2Id = changeOps.change(changeId).newPatchset().create();
     // Add comment.
-    changeOps.change(changeId).patchset(patchset1Id).newComment().author(accountId).create();
+    newComment(patchset1Id).author(accountId).create();
 
     List<CommentInfo> portedComments =
         flatten(getPortedDraftCommentsOfUser(patchset2Id, accountId));
@@ -260,7 +268,7 @@
     PatchSet.Id patchset1Id = changeOps.change(changeId).currentPatchset().get().patchsetId();
     PatchSet.Id patchset2Id = changeOps.change(changeId).newPatchset().create();
     // Add draft comment.
-    changeOps.change(changeId).patchset(patchset1Id).newComment().author(accountId).create();
+    newComment(patchset1Id).author(accountId).create();
 
     List<CommentInfo> portedComments =
         flatten(getPortedDraftCommentsOfUser(patchset2Id, accountId));
@@ -277,7 +285,7 @@
     PatchSet.Id patchset1Id = changeOps.change(changeId).currentPatchset().get().patchsetId();
     PatchSet.Id patchset2Id = changeOps.change(changeId).newPatchset().create();
     // Add draft comment.
-    changeOps.change(changeId).patchset(patchset1Id).newComment().author(otherUserId).create();
+    newComment(patchset1Id).author(otherUserId).create();
 
     List<CommentInfo> portedComments = flatten(getPortedDraftCommentsOfUser(patchset2Id, userId));
 
@@ -292,10 +300,7 @@
     PatchSet.Id patchset2Id = changeOps.change(changeId).newPatchset().create();
     // Add comments.
     String rangeCommentUuid =
-        changeOps
-            .change(changeId)
-            .patchset(patchset1Id)
-            .newComment()
+        newComment(patchset1Id)
             .message("Range comment")
             .fromLine(1)
             .charOffset(2)
@@ -304,30 +309,11 @@
             .ofFile("myFile")
             .create();
     String lineCommentUuid =
-        changeOps
-            .change(changeId)
-            .patchset(patchset1Id)
-            .newComment()
-            .message("Line comment")
-            .onLine(1)
-            .ofFile("myFile")
-            .create();
+        newComment(patchset1Id).message("Line comment").onLine(1).ofFile("myFile").create();
     String fileCommentUuid =
-        changeOps
-            .change(changeId)
-            .patchset(patchset1Id)
-            .newComment()
-            .message("File comment")
-            .onFileLevelOf("myFile")
-            .create();
+        newComment(patchset1Id).message("File comment").onFileLevelOf("myFile").create();
     String patchsetLevelCommentUuid =
-        changeOps
-            .change(changeId)
-            .patchset(patchset1Id)
-            .newComment()
-            .message("Patchset-level comment")
-            .onPatchsetLevel()
-            .create();
+        newComment(patchset1Id).message("Patchset-level comment").onPatchsetLevel().create();
 
     List<CommentInfo> portedComments = flatten(getPortedComments(patchset2Id));
 
@@ -344,8 +330,7 @@
     PatchSet.Id patchset1Id = changeOps.change(changeId).currentPatchset().get().patchsetId();
     PatchSet.Id patchset2Id = changeOps.change(changeId).newPatchset().create();
     // Add comments.
-    String commentUuid =
-        changeOps.change(changeId).patchset(patchset1Id).newComment().onParentCommit().create();
+    String commentUuid = newComment(patchset1Id).onParentCommit().create();
 
     List<CommentInfo> portedComments = flatten(getPortedComments(patchset2Id));
 
@@ -359,7 +344,7 @@
     PatchSet.Id patchset1Id = changeOps.change(changeId).currentPatchset().get().patchsetId();
     PatchSet.Id patchset2Id = changeOps.change(changeId).newPatchset().create();
     // Add comment.
-    String commentUuid = changeOps.change(changeId).patchset(patchset1Id).newComment().create();
+    String commentUuid = newComment(patchset1Id).create();
 
     List<CommentInfo> portedComments = flatten(getPortedComments(patchset2Id));
 
@@ -373,7 +358,7 @@
     PatchSet.Id patchset1Id = changeOps.change(changeId).currentPatchset().get().patchsetId();
     PatchSet.Id patchset2Id = changeOps.change(changeId).newPatchset().create();
     // Add comment.
-    String commentUuid = changeOps.change(changeId).patchset(patchset1Id).newComment().create();
+    String commentUuid = newComment(patchset1Id).create();
 
     CommentInfo portedComment = getPortedComment(patchset2Id, commentUuid);
 
@@ -388,13 +373,7 @@
     PatchSet.Id patchset1Id = changeOps.change(changeId).currentPatchset().get().patchsetId();
     PatchSet.Id patchset2Id = changeOps.change(changeId).newPatchset().create();
     // Add comment.
-    String commentUuid =
-        changeOps
-            .change(changeId)
-            .patchset(patchset1Id)
-            .newDraftComment()
-            .author(authorId)
-            .create();
+    String commentUuid = newDraftComment(patchset1Id).author(authorId).create();
 
     Map<String, List<CommentInfo>> portedComments =
         getPortedDraftCommentsOfUser(patchset2Id, authorId);
@@ -413,8 +392,7 @@
     TestPatchset patchset1 = changeOps.change(changeId).currentPatchset().get();
     PatchSet.Id patchset2Id = changeOps.change(changeId).newPatchset().create();
     // Add comment.
-    String commentUuid =
-        changeOps.change(changeId).patchset(patchset1.patchsetId()).newComment().create();
+    String commentUuid = newComment(patchset1.patchsetId()).create();
 
     CommentInfo portedComment = getPortedComment(patchset2Id, commentUuid);
 
@@ -428,13 +406,7 @@
     TestPatchset patchset1 = changeOps.change(changeId).currentPatchset().get();
     PatchSet.Id patchset2Id = changeOps.change(changeId).newPatchset().create();
     // Add comment.
-    String commentUuid =
-        changeOps
-            .change(changeId)
-            .patchset(patchset1.patchsetId())
-            .newComment()
-            .message("My comment text")
-            .create();
+    String commentUuid = newComment(patchset1.patchsetId()).message("My comment text").create();
 
     CommentInfo portedComment = getPortedComment(patchset2Id, commentUuid);
 
@@ -448,15 +420,9 @@
     TestPatchset patchset1 = changeOps.change(changeId).currentPatchset().get();
     PatchSet.Id patchset2Id = changeOps.change(changeId).newPatchset().create();
     // Add comments.
-    String rootCommentUuid =
-        changeOps.change(changeId).patchset(patchset1.patchsetId()).newComment().create();
+    String rootCommentUuid = newComment(patchset1.patchsetId()).create();
     String childCommentUuid =
-        changeOps
-            .change(changeId)
-            .patchset(patchset1.patchsetId())
-            .newComment()
-            .parentUuid(rootCommentUuid)
-            .create();
+        newComment(patchset1.patchsetId()).parentUuid(rootCommentUuid).create();
 
     CommentInfo portedComment = getPortedComment(patchset2Id, childCommentUuid);
 
@@ -471,8 +437,7 @@
     PatchSet.Id patchset1Id = changeOps.change(changeId).currentPatchset().get().patchsetId();
     PatchSet.Id patchset2Id = changeOps.change(changeId).newPatchset().create();
     // Add comment.
-    String commentUuid =
-        changeOps.change(changeId).patchset(patchset1Id).newComment().author(authorId).create();
+    String commentUuid = newComment(patchset1Id).author(authorId).create();
 
     CommentInfo portedComment = getPortedComment(patchset2Id, commentUuid);
 
@@ -487,13 +452,7 @@
     PatchSet.Id patchset1Id = changeOps.change(changeId).currentPatchset().get().patchsetId();
     PatchSet.Id patchset2Id = changeOps.change(changeId).newPatchset().create();
     // Add comment.
-    String commentUuid =
-        changeOps
-            .change(changeId)
-            .patchset(patchset1Id)
-            .newDraftComment()
-            .author(authorId)
-            .create();
+    String commentUuid = newDraftComment(patchset1Id).author(authorId).create();
 
     Map<String, List<CommentInfo>> portedComments =
         getPortedDraftCommentsOfUser(patchset2Id, authorId);
@@ -510,13 +469,7 @@
     TestPatchset patchset1 = changeOps.change(changeId).currentPatchset().get();
     PatchSet.Id patchset2Id = changeOps.change(changeId).newPatchset().create();
     // Add comment.
-    String commentUuid =
-        changeOps
-            .change(changeId)
-            .patchset(patchset1.patchsetId())
-            .newComment()
-            .tag("My comment tag")
-            .create();
+    String commentUuid = newComment(patchset1.patchsetId()).tag("My comment tag").create();
 
     CommentInfo portedComment = getPortedComment(patchset2Id, commentUuid);
 
@@ -530,7 +483,7 @@
     PatchSet.Id patchset1Id = changeOps.change(changeId).currentPatchset().get().patchsetId();
     PatchSet.Id patchset2Id = changeOps.change(changeId).newPatchset().create();
     // Add comment.
-    String commentUuid = changeOps.change(changeId).patchset(patchset1Id).newComment().create();
+    String commentUuid = newComment(patchset1Id).create();
 
     CommentInfo portedComment = getPortedComment(patchset2Id, commentUuid);
 
@@ -544,7 +497,7 @@
     PatchSet.Id patchset1Id = changeOps.change(changeId).currentPatchset().get().patchsetId();
     PatchSet.Id patchset2Id = changeOps.change(changeId).newPatchset().create();
     // Add comment.
-    String commentUuid = changeOps.change(changeId).patchset(patchset1Id).newComment().create();
+    String commentUuid = newComment(patchset1Id).create();
 
     CommentInfo portedComment = getPortedComment(patchset2Id, commentUuid);
 
@@ -561,13 +514,7 @@
     PatchSet.Id patchset1Id = changeOps.change(changeId).currentPatchset().get().patchsetId();
     PatchSet.Id patchset2Id = changeOps.change(changeId).newPatchset().create();
     // Add comment.
-    String commentUuid =
-        changeOps
-            .change(changeId)
-            .patchset(patchset1Id)
-            .newComment()
-            .onFileLevelOf("myFile")
-            .create();
+    String commentUuid = newComment(patchset1Id).onFileLevelOf("myFile").create();
 
     Map<String, List<CommentInfo>> portedComments = getPortedComments(patchset2Id);
 
@@ -591,10 +538,7 @@
             .create();
     // Add comment.
     String commentUuid =
-        changeOps
-            .change(changeId)
-            .patchset(patchset1Id)
-            .newComment()
+        newComment(patchset1Id)
             .fromLine(3)
             .charOffset(2)
             .toLine(4)
@@ -625,10 +569,7 @@
             .create();
     // Add comment.
     String commentUuid =
-        changeOps
-            .change(changeId)
-            .patchset(patchset1Id)
-            .newComment()
+        newComment(patchset1Id)
             .fromLine(3)
             .charOffset(2)
             .toLine(4)
@@ -654,10 +595,7 @@
         changeOps.change(changeId).newPatchset().file("myFile").renameTo("newFileName").create();
     // Add comment.
     String commentUuid =
-        changeOps
-            .change(changeId)
-            .patchset(patchset1Id)
-            .newComment()
+        newComment(patchset1Id)
             .fromLine(3)
             .charOffset(2)
             .toLine(4)
@@ -692,10 +630,7 @@
             .create();
     // Add comment.
     String commentUuid =
-        changeOps
-            .change(changeId)
-            .patchset(patchset1Id)
-            .newComment()
+        newComment(patchset1Id)
             .fromLine(3)
             .charOffset(2)
             .toLine(4)
@@ -735,10 +670,7 @@
             .create();
     // Add comment.
     String commentUuid =
-        changeOps
-            .change(changeId)
-            .patchset(patchset1Id)
-            .newComment()
+        newComment(patchset1Id)
             .fromLine(3)
             .charOffset(2)
             .toLine(4)
@@ -778,10 +710,7 @@
             .create();
     // Add comment.
     String commentUuid =
-        changeOps
-            .change(changeId)
-            .patchset(patchset1Id)
-            .newComment()
+        newComment(patchset1Id)
             .fromLine(3)
             .charOffset(2)
             .toLine(4)
@@ -810,10 +739,7 @@
             .create();
     // Add comment.
     String commentUuid =
-        changeOps
-            .change(changeId)
-            .patchset(patchset1Id)
-            .newComment()
+        newComment(patchset1Id)
             .fromLine(2)
             .charOffset(2)
             .toLine(3)
@@ -844,10 +770,7 @@
             .create();
     // Add comment.
     String commentUuid =
-        changeOps
-            .change(changeId)
-            .patchset(patchset1Id)
-            .newComment()
+        newComment(patchset1Id)
             .fromLine(1)
             .charOffset(2)
             .toLine(2)
@@ -878,10 +801,7 @@
             .create();
     // Add comment.
     String commentUuid =
-        changeOps
-            .change(changeId)
-            .patchset(patchset1Id)
-            .newComment()
+        newComment(patchset1Id)
             .fromLine(1)
             .charOffset(2)
             .toLine(3)
@@ -912,10 +832,7 @@
             .create();
     // Add comment.
     String commentUuid =
-        changeOps
-            .change(changeId)
-            .patchset(patchset1Id)
-            .newComment()
+        newComment(patchset1Id)
             .fromLine(1)
             .charOffset(2)
             .toLine(3)
@@ -944,10 +861,7 @@
             .create();
     // Add comment.
     String commentUuid =
-        changeOps
-            .change(changeId)
-            .patchset(patchset1Id)
-            .newComment()
+        newComment(patchset1Id)
             .fromLine(3)
             .charOffset(2)
             .toLine(3)
@@ -977,10 +891,7 @@
             .create();
     // Add comment.
     String commentUuid =
-        changeOps
-            .change(changeId)
-            .patchset(patchset1Id)
-            .newComment()
+        newComment(patchset1Id)
             .fromLine(2)
             .charOffset(2)
             .toLine(4)
@@ -1009,10 +920,7 @@
             .create();
     // Add comment.
     String commentUuid =
-        changeOps
-            .change(changeId)
-            .patchset(patchset1Id)
-            .newComment()
+        newComment(patchset1Id)
             .fromLine(3)
             .charOffset(2)
             .toLine(4)
@@ -1049,10 +957,7 @@
             .create();
     // Add comment.
     String commentUuid =
-        changeOps
-            .change(changeId)
-            .patchset(patchset1Id)
-            .newComment()
+        newComment(patchset1Id)
             .fromLine(2)
             .charOffset(2)
             .toLine(4)
@@ -1076,10 +981,7 @@
         changeOps.change(changeId).newPatchset().file("myFile").delete().create();
     // Add comment.
     String commentUuid =
-        changeOps
-            .change(changeId)
-            .patchset(patchset1Id)
-            .newComment()
+        newComment(patchset1Id)
             .fromLine(3)
             .charOffset(2)
             .toLine(4)
@@ -1108,14 +1010,7 @@
             .content("Line 1\nLine 1.1\nLine 1.2\nLine 2\nLine 3\nLine 4\n")
             .create();
     // Add comment.
-    String commentUuid =
-        changeOps
-            .change(changeId)
-            .patchset(patchset1Id)
-            .newComment()
-            .onLine(3)
-            .ofFile("myFile")
-            .create();
+    String commentUuid = newComment(patchset1Id).onLine(3).ofFile("myFile").create();
 
     CommentInfo portedComment = getPortedComment(patchset2Id, commentUuid);
 
@@ -1136,14 +1031,7 @@
             .content("Line 2\nLine 3\nLine 4\n")
             .create();
     // Add comment.
-    String commentUuid =
-        changeOps
-            .change(changeId)
-            .patchset(patchset1Id)
-            .newComment()
-            .onLine(3)
-            .ofFile("myFile")
-            .create();
+    String commentUuid = newComment(patchset1Id).onLine(3).ofFile("myFile").create();
 
     CommentInfo portedComment = getPortedComment(patchset2Id, commentUuid);
 
@@ -1159,14 +1047,7 @@
     PatchSet.Id patchset2Id =
         changeOps.change(changeId).newPatchset().file("myFile").renameTo("newFileName").create();
     // Add comment.
-    String commentUuid =
-        changeOps
-            .change(changeId)
-            .patchset(patchset1Id)
-            .newComment()
-            .onLine(3)
-            .ofFile("myFile")
-            .create();
+    String commentUuid = newComment(patchset1Id).onLine(3).ofFile("myFile").create();
 
     Map<String, List<CommentInfo>> portedComments = getPortedComments(patchset2Id);
 
@@ -1190,14 +1071,7 @@
     PatchSet.Id patchset3Id =
         changeOps.change(changeId).newPatchset().file("myFile").renameTo("newFileName").create();
     // Add comment.
-    String commentUuid =
-        changeOps
-            .change(changeId)
-            .patchset(patchset1Id)
-            .newComment()
-            .onLine(3)
-            .ofFile("myFile")
-            .create();
+    String commentUuid = newComment(patchset1Id).onLine(3).ofFile("myFile").create();
 
     Map<String, List<CommentInfo>> portedComments = getPortedComments(patchset3Id);
 
@@ -1227,14 +1101,7 @@
             .content("Line 1\nLine 1.1\nLine 1.2\nLine 2\nLine 3\nLine 4\n")
             .create();
     // Add comment.
-    String commentUuid =
-        changeOps
-            .change(changeId)
-            .patchset(patchset1Id)
-            .newComment()
-            .onLine(3)
-            .ofFile("myFile")
-            .create();
+    String commentUuid = newComment(patchset1Id).onLine(3).ofFile("myFile").create();
 
     Map<String, List<CommentInfo>> portedComments = getPortedComments(patchset2Id);
 
@@ -1261,14 +1128,7 @@
             .content("Line 1\nLine two\nLine three\nLine 4\n")
             .create();
     // Add comment.
-    String commentUuid =
-        changeOps
-            .change(changeId)
-            .patchset(patchset1Id)
-            .newComment()
-            .onLine(2)
-            .ofFile("myFile")
-            .create();
+    String commentUuid = newComment(patchset1Id).onLine(2).ofFile("myFile").create();
 
     Map<String, List<CommentInfo>> portedComments = getPortedComments(patchset2Id);
 
@@ -1291,14 +1151,7 @@
             .content("Line 1\nLine 2\nLine three\nLine 4\n")
             .create();
     // Add comment.
-    String commentUuid =
-        changeOps
-            .change(changeId)
-            .patchset(patchset1Id)
-            .newComment()
-            .onLine(2)
-            .ofFile("myFile")
-            .create();
+    String commentUuid = newComment(patchset1Id).onLine(2).ofFile("myFile").create();
 
     CommentInfo portedComment = getPortedComment(patchset2Id, commentUuid);
 
@@ -1319,14 +1172,7 @@
             .content("Line 1\nLine 2\nSome completely\ndifferent\ncontent\n")
             .create();
     // Add comment.
-    String commentUuid =
-        changeOps
-            .change(changeId)
-            .patchset(patchset1Id)
-            .newComment()
-            .onLine(3)
-            .ofFile("myFile")
-            .create();
+    String commentUuid = newComment(patchset1Id).onLine(3).ofFile("myFile").create();
 
     CommentInfo portedComment = getPortedComment(patchset2Id, commentUuid);
 
@@ -1347,14 +1193,7 @@
             .content("Line 1\nLine 2\nSome completely\ndifferent\ncontent\n")
             .create();
     // Add comment.
-    String commentUuid =
-        changeOps
-            .change(changeId)
-            .patchset(patchset1Id)
-            .newComment()
-            .onLine(4)
-            .ofFile("myFile")
-            .create();
+    String commentUuid = newComment(patchset1Id).onLine(4).ofFile("myFile").create();
 
     CommentInfo portedComment = getPortedComment(patchset2Id, commentUuid);
 
@@ -1375,14 +1214,7 @@
             .content("Line 1\nLine 2\nLine three\nLine 4\n")
             .create();
     // Add comment.
-    String commentUuid =
-        changeOps
-            .change(changeId)
-            .patchset(patchset1Id)
-            .newComment()
-            .onLine(4)
-            .ofFile("myFile")
-            .create();
+    String commentUuid = newComment(patchset1Id).onLine(4).ofFile("myFile").create();
 
     CommentInfo portedComment = getPortedComment(patchset2Id, commentUuid);
 
@@ -1398,14 +1230,7 @@
     PatchSet.Id patchset2Id =
         changeOps.change(changeId).newPatchset().file("myFile").delete().create();
     // Add comment.
-    String commentUuid =
-        changeOps
-            .change(changeId)
-            .patchset(patchset1Id)
-            .newComment()
-            .onLine(3)
-            .ofFile("myFile")
-            .create();
+    String commentUuid = newComment(patchset1Id).onLine(3).ofFile("myFile").create();
 
     Map<String, List<CommentInfo>> portedComments = getPortedComments(patchset2Id);
     assertThatMap(portedComments).keys().containsExactly(Patch.PATCHSET_LEVEL);
@@ -1428,13 +1253,7 @@
             .content("Line 1\nLine 1.1\nLine 1.2\nLine 2\nLine 3\nLine 4\n")
             .create();
     // Add comment.
-    String commentUuid =
-        changeOps
-            .change(changeId)
-            .patchset(patchset1Id)
-            .newComment()
-            .onFileLevelOf("myFile")
-            .create();
+    String commentUuid = newComment(patchset1Id).onFileLevelOf("myFile").create();
 
     CommentInfo portedComment = getPortedComment(patchset2Id, commentUuid);
 
@@ -1450,13 +1269,7 @@
     PatchSet.Id patchset2Id =
         changeOps.change(changeId).newPatchset().file("myFile").renameTo("newFileName").create();
     // Add comment.
-    String commentUuid =
-        changeOps
-            .change(changeId)
-            .patchset(patchset1Id)
-            .newComment()
-            .onFileLevelOf("myFile")
-            .create();
+    String commentUuid = newComment(patchset1Id).onFileLevelOf("myFile").create();
 
     Map<String, List<CommentInfo>> portedComments = getPortedComments(patchset2Id);
 
@@ -1481,7 +1294,7 @@
             .content("Line 1\nLine 2\nLine 3\nLine 4\n")
             .create();
     // Add comment.
-    changeOps.change(changeId).patchset(patchset1Id).newComment().onFileLevelOf("myFile").create();
+    newComment(patchset1Id).onFileLevelOf("myFile").create();
 
     Map<String, List<CommentInfo>> portedComments = getPortedComments(patchset2Id);
 
@@ -1499,13 +1312,7 @@
     PatchSet.Id patchset2Id =
         changeOps.change(changeId).newPatchset().file("myFile").delete().create();
     // Add comment.
-    String commentUuid =
-        changeOps
-            .change(changeId)
-            .patchset(patchset1Id)
-            .newComment()
-            .onFileLevelOf("myFile")
-            .create();
+    String commentUuid = newComment(patchset1Id).onFileLevelOf("myFile").create();
 
     Map<String, List<CommentInfo>> portedComments = getPortedComments(patchset2Id);
     assertThatMap(portedComments).keys().containsExactly(Patch.PATCHSET_LEVEL);
@@ -1528,7 +1335,7 @@
             .content("Line 1\nLine 1.1\nLine 1.2\nLine 2\nLine 3\nLine 4\n")
             .create();
     // Add comment.
-    changeOps.change(changeId).patchset(patchset1Id).newComment().onPatchsetLevel().create();
+    newComment(patchset1Id).onPatchsetLevel().create();
 
     Map<String, List<CommentInfo>> portedComments = getPortedComments(patchset2Id);
 
@@ -1544,7 +1351,7 @@
     PatchSet.Id patchset2Id =
         changeOps.change(changeId).newPatchset().file("myFile").renameTo("newFileName").create();
     // Add comment.
-    changeOps.change(changeId).patchset(patchset1Id).newComment().onPatchsetLevel().create();
+    newComment(patchset1Id).onPatchsetLevel().create();
 
     Map<String, List<CommentInfo>> portedComments = getPortedComments(patchset2Id);
 
@@ -1565,10 +1372,7 @@
             .create();
     // Add comment.
     String commentUuid =
-        changeOps
-            .change(changeId)
-            .patchset(patchset1Id)
-            .newComment()
+        newComment(patchset1Id)
             // The /COMMIT_MSG file has a header of 6 lines, so the summary line is in line 7.
             // Place comment on 'Text 2' which is line 10.
             .onLine(10)
@@ -1605,14 +1409,7 @@
         changeOps.change(childChangeId).newPatchset().parent().patchset(parentPatchset2Id).create();
     // Add comment.
     String commentUuid =
-        changeOps
-            .change(childChangeId)
-            .patchset(childPatchset1Id)
-            .newComment()
-            .onParentCommit()
-            .onLine(1)
-            .ofFile("myFile")
-            .create();
+        newComment(childPatchset1Id).onParentCommit().onLine(1).ofFile("myFile").create();
 
     CommentInfo portedComment = getPortedComment(childPatchset2Id, commentUuid);
 
@@ -1654,14 +1451,7 @@
             .create();
     // Add comment.
     String commentUuid =
-        changeOps
-            .change(childChangeId)
-            .patchset(childPatchset1Id)
-            .newComment()
-            .onParentCommit()
-            .onLine(1)
-            .ofFile("file1")
-            .create();
+        newComment(childPatchset1Id).onParentCommit().onLine(1).ofFile("file1").create();
 
     CommentInfo portedComment = getPortedComment(childPatchset2Id, commentUuid);
 
@@ -1703,14 +1493,7 @@
             .create();
     // Add comment.
     String commentUuid =
-        changeOps
-            .change(childChangeId)
-            .patchset(childPatchset1Id)
-            .newComment()
-            .onSecondParentCommit()
-            .onLine(1)
-            .ofFile("file2")
-            .create();
+        newComment(childPatchset1Id).onSecondParentCommit().onLine(1).ofFile("file2").create();
 
     CommentInfo portedComment = getPortedComment(childPatchset2Id, commentUuid);
 
@@ -1758,14 +1541,7 @@
             .create();
     // Add comment.
     String commentUuid =
-        changeOps
-            .change(childChangeId)
-            .patchset(childPatchset1Id)
-            .newComment()
-            .onAutoMergeCommit()
-            .onLine(1)
-            .ofFile("file1")
-            .create();
+        newComment(childPatchset1Id).onAutoMergeCommit().onLine(1).ofFile("file1").create();
 
     CommentInfo portedComment = getPortedComment(childPatchset2Id, commentUuid);
 
@@ -1776,6 +1552,22 @@
     assertThat(portedComment).line().isGreaterThan(2);
   }
 
+  private TestCommentCreation.Builder newComment(PatchSet.Id patchsetId) {
+    // Create unresolved comments by default as only those are ported. Tests get override the
+    // unresolved state by explicitly setting it.
+    return changeOps.change(patchsetId.changeId()).patchset(patchsetId).newComment().unresolved();
+  }
+
+  private TestCommentCreation.Builder newDraftComment(PatchSet.Id patchsetId) {
+    // Create unresolved comments by default as only those are ported. Tests get override the
+    // unresolved state by explicitly setting it.
+    return changeOps
+        .change(patchsetId.changeId())
+        .patchset(patchsetId)
+        .newDraftComment()
+        .unresolved();
+  }
+
   private CommentInfo getPortedComment(PatchSet.Id patchsetId, String commentUuid)
       throws RestApiException {
     Map<String, List<CommentInfo>> portedComments = getPortedComments(patchsetId);
diff --git a/javatests/com/google/gerrit/acceptance/api/revision/RobotCommentsIT.java b/javatests/com/google/gerrit/acceptance/api/revision/RobotCommentsIT.java
index 27b866b..1ad952c 100644
--- a/javatests/com/google/gerrit/acceptance/api/revision/RobotCommentsIT.java
+++ b/javatests/com/google/gerrit/acceptance/api/revision/RobotCommentsIT.java
@@ -14,9 +14,11 @@
 
 package com.google.gerrit.acceptance.api.revision;
 
+import static com.google.common.collect.ImmutableSet.toImmutableSet;
 import static com.google.common.collect.MoreCollectors.onlyElement;
 import static com.google.common.truth.Truth.assertThat;
 import static com.google.gerrit.acceptance.PushOneCommit.SUBJECT;
+import static com.google.gerrit.entities.Patch.COMMIT_MSG;
 import static com.google.gerrit.entities.Patch.PATCHSET_LEVEL;
 import static com.google.gerrit.extensions.client.ListChangesOption.MESSAGES;
 import static com.google.gerrit.extensions.common.testing.DiffInfoSubject.assertThat;
@@ -32,8 +34,11 @@
 import com.google.gerrit.acceptance.PushOneCommit;
 import com.google.gerrit.acceptance.UseClockStep;
 import com.google.gerrit.acceptance.config.GerritConfig;
+import com.google.gerrit.acceptance.testsuite.change.ChangeOperations;
+import com.google.gerrit.entities.Change;
 import com.google.gerrit.entities.Patch;
 import com.google.gerrit.extensions.api.changes.PublishChangeEditInput;
+import com.google.gerrit.extensions.api.changes.ReviewInput;
 import com.google.gerrit.extensions.api.changes.ReviewInput.RobotCommentInput;
 import com.google.gerrit.extensions.client.Comment;
 import com.google.gerrit.extensions.client.Side;
@@ -67,6 +72,7 @@
 
 public class RobotCommentsIT extends AbstractDaemonTest {
   @Inject private TestCommentHelper testCommentHelper;
+  @Inject private ChangeOperations changeOperations;
 
   private static final String PLAIN_TEXT_CONTENT_TYPE = "text/plain";
   private static final String GERRIT_COMMIT_MESSAGE_TYPE = "text/x-gerrit-commit-message";
@@ -320,6 +326,58 @@
   }
 
   @Test
+  public void robotCommentInvalidInReplyTo() throws Exception {
+    Change.Id changeId = changeOperations.newChange().create();
+    RobotCommentInput input = TestCommentHelper.createRobotCommentInput(PATCHSET_LEVEL);
+    input.inReplyTo = "invalid";
+    BadRequestException ex =
+        assertThrows(
+            BadRequestException.class, () -> testCommentHelper.addRobotComment(changeId, input));
+    assertThat(ex.getMessage()).contains("inReplyTo");
+  }
+
+  @Test
+  public void canCreateRobotCommentWithRobotCommentAsParent() throws Exception {
+    Change.Id changeId = changeOperations.newChange().create();
+    String parentRobotCommentUuid =
+        changeOperations.change(changeId).currentPatchset().newRobotComment().create();
+
+    ReviewInput.RobotCommentInput robotCommentInput =
+        TestCommentHelper.createRobotCommentInputWithMandatoryFields(COMMIT_MSG);
+    robotCommentInput.message = "comment reply";
+    robotCommentInput.inReplyTo = parentRobotCommentUuid;
+    testCommentHelper.addRobotComment(changeId, robotCommentInput);
+
+    RobotCommentInfo resultComment =
+        Iterables.getOnlyElement(
+            gApi.changes().id(changeId.get()).current().robotCommentsAsList().stream()
+                .filter(c -> c.message.equals("comment reply"))
+                .collect(toImmutableSet()));
+    assertThat(resultComment.inReplyTo).isEqualTo(parentRobotCommentUuid);
+  }
+
+  @Test
+  public void canCreateRobotCommentWithHumanCommentAsParent() throws Exception {
+    Change.Id changeId = changeOperations.newChange().create();
+    String changeIdString = changeOperations.change(changeId).get().changeId();
+    String parentCommentUuid =
+        changeOperations.change(changeId).currentPatchset().newComment().create();
+
+    ReviewInput.RobotCommentInput robotCommentInput =
+        TestCommentHelper.createRobotCommentInputWithMandatoryFields(COMMIT_MSG);
+    robotCommentInput.message = "comment reply";
+    robotCommentInput.inReplyTo = parentCommentUuid;
+    testCommentHelper.addRobotComment(changeIdString, robotCommentInput);
+
+    RobotCommentInfo resultComment =
+        Iterables.getOnlyElement(
+            gApi.changes().id(changeIdString).current().robotCommentsAsList().stream()
+                .filter(c -> c.message.equals("comment reply"))
+                .collect(toImmutableSet()));
+    assertThat(resultComment.inReplyTo).isEqualTo(parentCommentUuid);
+  }
+
+  @Test
   public void hugeRobotCommentIsRejected() {
     int defaultSizeLimit = 1 << 20;
     fixReplacementInfo.replacement = getStringFor(defaultSizeLimit + 1);
diff --git a/javatests/com/google/gerrit/acceptance/rest/change/AttentionSetIT.java b/javatests/com/google/gerrit/acceptance/rest/change/AttentionSetIT.java
index b156d1b..ed4c33a 100644
--- a/javatests/com/google/gerrit/acceptance/rest/change/AttentionSetIT.java
+++ b/javatests/com/google/gerrit/acceptance/rest/change/AttentionSetIT.java
@@ -22,14 +22,19 @@
 import com.google.common.collect.ImmutableMap;
 import com.google.common.collect.ImmutableSet;
 import com.google.common.collect.Iterables;
+import com.google.common.truth.Correspondence;
 import com.google.gerrit.acceptance.AbstractDaemonTest;
 import com.google.gerrit.acceptance.NoHttpd;
 import com.google.gerrit.acceptance.PushOneCommit;
 import com.google.gerrit.acceptance.TestAccount;
 import com.google.gerrit.acceptance.UseClockStep;
+import com.google.gerrit.acceptance.testsuite.account.AccountOperations;
+import com.google.gerrit.acceptance.testsuite.change.ChangeOperations;
 import com.google.gerrit.acceptance.testsuite.request.RequestScopeOperations;
 import com.google.gerrit.common.Nullable;
+import com.google.gerrit.entities.Account;
 import com.google.gerrit.entities.AttentionSetUpdate;
+import com.google.gerrit.entities.Change;
 import com.google.gerrit.entities.Patch;
 import com.google.gerrit.extensions.api.changes.AddReviewerInput;
 import com.google.gerrit.extensions.api.changes.AttentionSetInput;
@@ -39,12 +44,17 @@
 import com.google.gerrit.extensions.client.ReviewerState;
 import com.google.gerrit.extensions.client.Side;
 import com.google.gerrit.extensions.restapi.BadRequestException;
+import com.google.gerrit.server.query.change.ChangeData;
+import com.google.gerrit.server.query.change.InternalChangeQuery;
 import com.google.gerrit.server.util.time.TimeUtil;
 import com.google.gerrit.testing.FakeEmailSender;
 import com.google.gerrit.testing.TestCommentHelper;
+import com.google.gerrit.truth.NullAwareCorrespondence;
 import com.google.inject.Inject;
+import com.google.inject.Provider;
 import java.time.Duration;
 import java.time.Instant;
+import java.util.ArrayList;
 import java.util.List;
 import java.util.concurrent.TimeUnit;
 import java.util.function.LongSupplier;
@@ -56,9 +66,13 @@
 @UseClockStep(clockStepUnit = TimeUnit.MINUTES)
 public class AttentionSetIT extends AbstractDaemonTest {
 
+  @Inject private ChangeOperations changeOperations;
+  @Inject private AccountOperations accountOperations;
   @Inject private RequestScopeOperations requestScopeOperations;
+
   @Inject private FakeEmailSender email;
   @Inject private TestCommentHelper testCommentHelper;
+  @Inject private Provider<InternalChangeQuery> changeQueryProvider;
 
   /** Simulates a fake clock. Uses second granularity. */
   private static class FakeClock implements LongSupplier {
@@ -165,7 +179,8 @@
     assertThat(emailBody)
         .contains(
             user.fullName()
-                + " removed themselves from the attention set of this change.\n The reason is: removed.");
+                + " removed themselves from the attention set of this change.\n"
+                + " The reason is: removed.");
   }
 
   @Test
@@ -611,7 +626,8 @@
 
     assertThat(exception.getMessage())
         .isEqualTo(
-            "user can not be added/removed twice, and can not be added and removed at the same time");
+            "user can not be added/removed twice, and can not be added and removed at the same"
+                + " time");
   }
 
   @Test
@@ -627,7 +643,8 @@
 
     assertThat(exception.getMessage())
         .isEqualTo(
-            "user can not be added/removed twice, and can not be added and removed at the same time");
+            "user can not be added/removed twice, and can not be added and removed at the same"
+                + " time");
   }
 
   @Test
@@ -663,7 +680,8 @@
 
     assertThat(exception.getMessage())
         .isEqualTo(
-            "user can not be added/removed twice, and can not be added and removed at the same time");
+            "user can not be added/removed twice, and can not be added and removed at the same"
+                + " time");
   }
 
   @Test
@@ -958,6 +976,64 @@
   }
 
   @Test
+  public void reviewAddsAllUsersInCommentThreadEvenOfDifferentChildBranch() throws Exception {
+    Account.Id changeOwner = accountOperations.newAccount().create();
+    Change.Id changeId = changeOperations.newChange().owner(changeOwner).create();
+    Account.Id user1 = accountOperations.newAccount().create();
+    Account.Id user2 = accountOperations.newAccount().create();
+    Account.Id user3 = accountOperations.newAccount().create();
+    Account.Id user4 = accountOperations.newAccount().create();
+    // Add users as reviewers.
+    gApi.changes().id(changeId.get()).addReviewer(user1.toString());
+    gApi.changes().id(changeId.get()).addReviewer(user2.toString());
+    gApi.changes().id(changeId.get()).addReviewer(user3.toString());
+    gApi.changes().id(changeId.get()).addReviewer(user4.toString());
+    // Add a comment thread with branches. Such threads occur if people reply in parallel without
+    // having seen/loaded the reply of another person.
+    String root =
+        changeOperations.change(changeId).currentPatchset().newComment().author(user1).create();
+    String sibling1 =
+        changeOperations
+            .change(changeId)
+            .currentPatchset()
+            .newComment()
+            .author(user2)
+            .parentUuid(root)
+            .create();
+    String sibling2 =
+        changeOperations
+            .change(changeId)
+            .currentPatchset()
+            .newComment()
+            .author(user3)
+            .parentUuid(root)
+            .create();
+    changeOperations
+        .change(changeId)
+        .currentPatchset()
+        .newComment()
+        .author(user4)
+        .parentUuid(sibling2)
+        .create();
+    // Clear the attention set. Necessary as we used Gerrit APIs above which affect the attention
+    // set.
+    AttentionSetInput clearAttention = new AttentionSetInput("clear attention set");
+    gApi.changes().id(changeId.get()).attention(user1.toString()).remove(clearAttention);
+    gApi.changes().id(changeId.get()).attention(user2.toString()).remove(clearAttention);
+    gApi.changes().id(changeId.get()).attention(user3.toString()).remove(clearAttention);
+    gApi.changes().id(changeId.get()).attention(user4.toString()).remove(clearAttention);
+
+    requestScopeOperations.setApiUser(changeOwner);
+    // Simulate that this reply is a child of sibling1 and thus parallel to sibling2 and its child.
+    gApi.changes().id(changeId.get()).current().review(reviewInReplyToComment(sibling1));
+
+    List<AttentionSetUpdate> attentionSetUpdates = getAttentionSetUpdates(changeId);
+    assertThat(attentionSetUpdates)
+        .comparingElementsUsing(hasAccount())
+        .containsExactly(user1, user2, user3, user4);
+  }
+
+  @Test
   public void reviewAddsAllUsersInCommentThreadWhenPostedAsDraft() throws Exception {
     PushOneCommit.Result r = createChange();
     requestScopeOperations.setApiUser(user.id());
@@ -1281,11 +1357,20 @@
 
   private List<AttentionSetUpdate> getAttentionSetUpdatesForUser(
       PushOneCommit.Result r, TestAccount account) {
-    return r.getChange().attentionSet().stream()
-        .filter(a -> a.account().get() == account.id().get())
+    return getAttentionSetUpdates(r.getChange().getId()).stream()
+        .filter(a -> a.account().equals(account.id()))
         .collect(Collectors.toList());
   }
 
+  private List<AttentionSetUpdate> getAttentionSetUpdates(Change.Id changeId) {
+    List<ChangeData> changeData = changeQueryProvider.get().byLegacyChangeId(changeId);
+    if (changeData.size() != 1) {
+      throw new IllegalStateException(
+          String.format("Not exactly one change found for ID %s.", changeId));
+    }
+    return new ArrayList<>(Iterables.getOnlyElement(changeData).attentionSet());
+  }
+
   private ReviewInput reviewWithComment() {
     return reviewInReplyToComment(null);
   }
@@ -1301,4 +1386,8 @@
     reviewInput.comments = ImmutableMap.of(Patch.COMMIT_MSG, ImmutableList.of(comment));
     return reviewInput;
   }
+
+  private Correspondence<AttentionSetUpdate, Account.Id> hasAccount() {
+    return NullAwareCorrespondence.transforming(AttentionSetUpdate::account, "hasAccount");
+  }
 }
diff --git a/javatests/com/google/gerrit/acceptance/server/change/CommentsIT.java b/javatests/com/google/gerrit/acceptance/server/change/CommentsIT.java
index 88705e1..4f61d79 100644
--- a/javatests/com/google/gerrit/acceptance/server/change/CommentsIT.java
+++ b/javatests/com/google/gerrit/acceptance/server/change/CommentsIT.java
@@ -14,10 +14,12 @@
 
 package com.google.gerrit.acceptance.server.change;
 
+import static com.google.common.collect.ImmutableSet.toImmutableSet;
 import static com.google.common.truth.Truth.assertThat;
 import static com.google.common.truth.Truth8.assertThat;
 import static com.google.gerrit.acceptance.PushOneCommit.FILE_NAME;
 import static com.google.gerrit.acceptance.PushOneCommit.SUBJECT;
+import static com.google.gerrit.entities.Patch.COMMIT_MSG;
 import static com.google.gerrit.entities.Patch.PATCHSET_LEVEL;
 import static com.google.gerrit.testing.GerritJUnit.assertThrows;
 import static com.google.gerrit.truth.MapSubject.assertThatMap;
@@ -51,13 +53,11 @@
 import com.google.gerrit.extensions.client.Side;
 import com.google.gerrit.extensions.common.ChangeInfo;
 import com.google.gerrit.extensions.common.CommentInfo;
-import com.google.gerrit.extensions.common.RobotCommentInfo;
 import com.google.gerrit.extensions.restapi.AuthException;
 import com.google.gerrit.extensions.restapi.BadRequestException;
 import com.google.gerrit.extensions.restapi.IdString;
 import com.google.gerrit.extensions.restapi.ResourceNotFoundException;
 import com.google.gerrit.extensions.restapi.TopLevelResource;
-import com.google.gerrit.server.CommentsUtil;
 import com.google.gerrit.server.change.ChangeResource;
 import com.google.gerrit.server.change.RevisionResource;
 import com.google.gerrit.server.notedb.ChangeNoteUtil;
@@ -66,7 +66,6 @@
 import com.google.gerrit.server.restapi.change.PostReview;
 import com.google.gerrit.testing.FakeEmailSender;
 import com.google.gerrit.testing.FakeEmailSender.Message;
-import com.google.gerrit.testing.TestCommentHelper;
 import com.google.inject.Inject;
 import com.google.inject.Provider;
 import java.sql.Timestamp;
@@ -98,8 +97,6 @@
   @Inject private ChangeOperations changeOperations;
   @Inject private AccountOperations accountOperations;
   @Inject private RequestScopeOperations requestScopeOperations;
-  @Inject private CommentsUtil commentsUtil;
-  @Inject private TestCommentHelper testCommentHelper;
 
   private final Integer[] lines = {0, 1};
 
@@ -658,6 +655,34 @@
   }
 
   @Test
+  public void putDraft_humanInReplyTo() throws Exception {
+    Change.Id changeId = changeOperations.newChange().create();
+    String parentCommentUuid =
+        changeOperations.change(changeId).currentPatchset().newComment().create();
+
+    DraftInput draft = newDraft(COMMIT_MSG, Side.REVISION, 0, "foo");
+    draft.inReplyTo = parentCommentUuid;
+    String createdDraftUuid = addDraft(changeId, draft).id;
+    TestHumanComment actual =
+        changeOperations.change(changeId).draftComment(createdDraftUuid).get();
+    assertThat(actual.parentUuid()).hasValue(parentCommentUuid);
+  }
+
+  @Test
+  public void putDraft_robotInReplyTo() throws Exception {
+    Change.Id changeId = changeOperations.newChange().create();
+    String parentRobotCommentUuid =
+        changeOperations.change(changeId).currentPatchset().newRobotComment().create();
+
+    DraftInput draft = newDraft(COMMIT_MSG, Side.REVISION, 0, "foo");
+    draft.inReplyTo = parentRobotCommentUuid;
+    String createdDraftUuid = addDraft(changeId, draft).id;
+    TestHumanComment actual =
+        changeOperations.change(changeId).draftComment(createdDraftUuid).get();
+    assertThat(actual.parentUuid()).hasValue(parentRobotCommentUuid);
+  }
+
+  @Test
   public void putDraft_idMismatch() throws Exception {
     String file = "file";
     PushOneCommit.Result r = createChange();
@@ -702,6 +727,16 @@
   }
 
   @Test
+  public void putDraft_invalidInReplyTo() throws Exception {
+    Change.Id changeId = changeOperations.newChange().create();
+    DraftInput draft = newDraft(COMMIT_MSG, Side.REVISION, 0, "foo");
+    draft.inReplyTo = "invalid";
+    BadRequestException exception =
+        assertThrows(BadRequestException.class, () -> addDraft(changeId, draft));
+    assertThat(exception.getMessage()).contains(String.format("%s not found", draft.inReplyTo));
+  }
+
+  @Test
   public void putDraft_updatePath() throws Exception {
     PushOneCommit.Result r = createChange();
     String changeId = r.getChangeId();
@@ -715,22 +750,62 @@
   }
 
   @Test
-  public void putDraft_updateInReplyToAndTag() throws Exception {
-    PushOneCommit.Result r = createChange();
-    String changeId = r.getChangeId();
-    String revId = r.getCommit().getName();
-    DraftInput draftInput1 = newDraft(FILE_NAME, Side.REVISION, 0, "foo");
-    CommentInfo commentInfo = addDraft(changeId, revId, draftInput1);
-    DraftInput draftInput2 = newDraft(FILE_NAME, Side.REVISION, 0, "bar");
-    String inReplyTo = "in_reply_to";
+  public void putDraft_updateInvalidInReplyTo() throws Exception {
+    Change.Id changeId = changeOperations.newChange().create();
+    DraftInput originalDraftInput = newDraft(FILE_NAME, Side.REVISION, 0, "foo");
+    CommentInfo originalDraft = addDraft(changeId, originalDraftInput);
+
+    DraftInput updatedDraftInput = newDraft(FILE_NAME, Side.REVISION, 0, "bar");
+    updatedDraftInput.inReplyTo = "invalid";
+    BadRequestException exception =
+        assertThrows(
+            BadRequestException.class,
+            () -> updateDraft(changeId, updatedDraftInput, originalDraft.id));
+    assertThat(exception.getMessage()).contains(String.format("Invalid inReplyTo"));
+  }
+
+  @Test
+  public void putDraft_updateHumanInReplyTo() throws Exception {
+    Change.Id changeId = changeOperations.newChange().create();
+    String parentCommentUuid =
+        changeOperations.change(changeId).currentPatchset().newComment().create();
+    DraftInput originalDraftInput = newDraft(FILE_NAME, Side.REVISION, 0, "foo");
+    CommentInfo originalDraft = addDraft(changeId, originalDraftInput);
+
+    DraftInput updateDraftInput = newDraft(FILE_NAME, Side.REVISION, 0, "bar");
+    updateDraftInput.inReplyTo = parentCommentUuid;
+    updateDraft(changeId, updateDraftInput, originalDraft.id);
+    assertThat(changeOperations.change(changeId).draftComment(originalDraft.id).get().parentUuid())
+        .hasValue(parentCommentUuid);
+  }
+
+  @Test
+  public void putDraft_updateRobotInReplyTo() throws Exception {
+    Change.Id changeId = changeOperations.newChange().create();
+    String parentRobotCommentUuid =
+        changeOperations.change(changeId).currentPatchset().newRobotComment().create();
+    DraftInput originalDraftInput = newDraft(FILE_NAME, Side.REVISION, 0, "foo");
+    CommentInfo originalDraft = addDraft(changeId, originalDraftInput);
+
+    DraftInput updateDraftInput = newDraft(FILE_NAME, Side.REVISION, 0, "bar");
+    updateDraftInput.inReplyTo = parentRobotCommentUuid;
+    updateDraft(changeId, updateDraftInput, originalDraft.id);
+    assertThat(changeOperations.change(changeId).draftComment(originalDraft.id).get().parentUuid())
+        .hasValue(parentRobotCommentUuid);
+  }
+
+  @Test
+  public void putDraft_updateTag() throws Exception {
+    Change.Id changeId = changeOperations.newChange().create();
+    DraftInput originalDraftInput = newDraft(FILE_NAME, Side.REVISION, 0, "foo");
+    CommentInfo originalDraft = addDraft(changeId, originalDraftInput);
+
+    DraftInput updateDraftInput = newDraft(FILE_NAME, Side.REVISION, 0, "bar");
     String tag = "täg";
-    draftInput2.inReplyTo = inReplyTo;
-    draftInput2.tag = tag;
-    updateDraft(changeId, revId, draftInput2, commentInfo.id);
-    com.google.gerrit.entities.Comment comment =
-        Iterables.getOnlyElement(commentsUtil.draftByChange(r.getChange().notes()));
-    assertThat(comment.parentUuid).isEqualTo(inReplyTo);
-    assertThat(comment.tag).isEqualTo(tag);
+    updateDraftInput.tag = tag;
+    updateDraft(changeId, updateDraftInput, originalDraft.id);
+    assertThat(changeOperations.change(changeId).draftComment(originalDraft.id).get().tag())
+        .hasValue(tag);
   }
 
   @Test
@@ -1474,26 +1549,73 @@
 
   @Test
   public void canCreateHumanCommentWithRobotCommentAsParentAndUnsetUnresolved() throws Exception {
-    PushOneCommit.Result result = createChange();
-    String changeId = result.getChangeId();
-    String ps1 = result.getCommit().name();
+    Change.Id changeId = changeOperations.newChange().create();
+    String parentRobotCommentUuid =
+        changeOperations.change(changeId).currentPatchset().newRobotComment().create();
 
-    testCommentHelper.addRobotComment(
-        result.getChangeId(),
-        TestCommentHelper.createRobotCommentInputWithMandatoryFields(FILE_NAME));
-    RobotCommentInfo robotCommentInfo =
-        Iterables.getOnlyElement(gApi.changes().id(changeId).current().robotCommentsAsList());
+    CommentInput createdCommentInput = newComment(COMMIT_MSG, "comment reply");
+    createdCommentInput.inReplyTo = parentRobotCommentUuid;
+    createdCommentInput.unresolved = null;
+    addComments(changeId, createdCommentInput);
 
-    CommentInput comment = newComment(FILE_NAME, "comment 1 reply");
-    comment.inReplyTo = robotCommentInfo.id;
-    comment.unresolved = null;
-    addComments(changeId, ps1, comment);
+    CommentInfo resultNewComment =
+        Iterables.getOnlyElement(
+            getPublishedCommentsAsList(changeId).stream()
+                .filter(c -> c.message.equals("comment reply"))
+                .collect(toImmutableSet()));
 
-    CommentInfo resultComment = Iterables.getOnlyElement(getPublishedCommentsAsList(changeId));
-    assertThat(resultComment.inReplyTo).isEqualTo(robotCommentInfo.id);
+    assertThat(resultNewComment.inReplyTo).isEqualTo(parentRobotCommentUuid);
 
     // Default unresolved is false.
-    assertThat(resultComment.unresolved).isFalse();
+    assertThat(resultNewComment.unresolved).isFalse();
+  }
+
+  @Test
+  public void canCreateHumanCommentWithHumanCommentAsParent() throws Exception {
+    Change.Id changeId = changeOperations.newChange().create();
+    String parentCommentUuid =
+        changeOperations.change(changeId).currentPatchset().newComment().create();
+
+    CommentInput createdCommentInput = newComment(COMMIT_MSG, "comment reply");
+    createdCommentInput.inReplyTo = parentCommentUuid;
+    addComments(changeId, createdCommentInput);
+
+    CommentInfo resultNewComment =
+        Iterables.getOnlyElement(
+            getPublishedCommentsAsList(changeId).stream()
+                .filter(c -> c.message.equals("comment reply"))
+                .collect(toImmutableSet()));
+    assertThat(resultNewComment.inReplyTo).isEqualTo(parentCommentUuid);
+  }
+
+  @Test
+  public void canCreateHumanCommentWithRobotCommentAsParent() throws Exception {
+    Change.Id changeId = changeOperations.newChange().create();
+    String parentRobotCommentUuid =
+        changeOperations.change(changeId).currentPatchset().newRobotComment().create();
+
+    CommentInput createdCommentInput = newComment(COMMIT_MSG, "comment reply");
+    createdCommentInput.inReplyTo = parentRobotCommentUuid;
+    addComments(changeId, createdCommentInput);
+
+    CommentInfo resultNewComment =
+        Iterables.getOnlyElement(
+            getPublishedCommentsAsList(changeId).stream()
+                .filter(c -> c.message.equals("comment reply"))
+                .collect(toImmutableSet()));
+    assertThat(resultNewComment.inReplyTo).isEqualTo(parentRobotCommentUuid);
+  }
+
+  @Test
+  public void cannotCreateCommentWithInvalidInReplyTo() throws Exception {
+    Change.Id changeId = changeOperations.newChange().create();
+
+    CommentInput comment = newComment(COMMIT_MSG, "comment 1 reply");
+    comment.inReplyTo = "invalid";
+
+    BadRequestException exception =
+        assertThrows(BadRequestException.class, () -> addComments(changeId, comment));
+    assertThat(exception.getMessage()).contains(String.format("%s not found", comment.inReplyTo));
   }
 
   private List<CommentInfo> getRevisionComments(String changeId, String revId) throws Exception {
@@ -1510,6 +1632,12 @@
     return comment;
   }
 
+  private void addComments(Change.Id changeId, CommentInput... commentInputs) throws Exception {
+    ReviewInput input = new ReviewInput();
+    input.comments = Arrays.stream(commentInputs).collect(groupingBy(c -> c.path));
+    gApi.changes().id(changeId.get()).current().review(input);
+  }
+
   private void addComments(String changeId, String revision, CommentInput... commentInputs)
       throws Exception {
     ReviewInput input = new ReviewInput();
@@ -1610,11 +1738,19 @@
     return gApi.changes().id(changeId).revision(revId).createDraft(in).get();
   }
 
+  private CommentInfo addDraft(Change.Id changeId, DraftInput in) throws Exception {
+    return gApi.changes().id(changeId.get()).current().createDraft(in).get();
+  }
+
   private void updateDraft(String changeId, String revId, DraftInput in, String uuid)
       throws Exception {
     gApi.changes().id(changeId).revision(revId).draft(uuid).update(in);
   }
 
+  private void updateDraft(Change.Id changeId, DraftInput in, String uuid) throws Exception {
+    gApi.changes().id(changeId.get()).current().draft(uuid).update(in);
+  }
+
   private void deleteDraft(String changeId, String revId, String uuid) throws Exception {
     gApi.changes().id(changeId).revision(revId).draft(uuid).delete();
   }
@@ -1633,6 +1769,10 @@
     return gApi.changes().id(changeId).commentsAsList();
   }
 
+  private List<CommentInfo> getPublishedCommentsAsList(Change.Id changeId) throws Exception {
+    return gApi.changes().id(changeId.get()).commentsAsList();
+  }
+
   private Map<String, List<CommentInfo>> getDraftComments(String changeId, String revId)
       throws Exception {
     return gApi.changes().id(changeId).revision(revId).drafts();
diff --git a/javatests/com/google/gerrit/acceptance/testsuite/change/ChangeOperationsImplTest.java b/javatests/com/google/gerrit/acceptance/testsuite/change/ChangeOperationsImplTest.java
index 975d7ec..0bd6554 100644
--- a/javatests/com/google/gerrit/acceptance/testsuite/change/ChangeOperationsImplTest.java
+++ b/javatests/com/google/gerrit/acceptance/testsuite/change/ChangeOperationsImplTest.java
@@ -1175,6 +1175,39 @@
   }
 
   @Test
+  public void tagOfPublishedCommentCanBeRetrieved() {
+    Change.Id changeId = changeOperations.newChange().create();
+    String childCommentUuid =
+        changeOperations.change(changeId).currentPatchset().newComment().tag("tag").create();
+
+    TestHumanComment comment = changeOperations.change(changeId).comment(childCommentUuid).get();
+
+    assertThat(comment.tag()).value().isEqualTo("tag");
+  }
+
+  @Test
+  public void unresolvedOfUnresolvedPublishedCommentCanBeRetrieved() {
+    Change.Id changeId = changeOperations.newChange().create();
+    String childCommentUuid =
+        changeOperations.change(changeId).currentPatchset().newComment().unresolved().create();
+
+    TestHumanComment comment = changeOperations.change(changeId).comment(childCommentUuid).get();
+
+    assertThat(comment.unresolved()).isTrue();
+  }
+
+  @Test
+  public void unresolvedOfResolvedPublishedCommentCanBeRetrieved() {
+    Change.Id changeId = changeOperations.newChange().create();
+    String childCommentUuid =
+        changeOperations.change(changeId).currentPatchset().newComment().resolved().create();
+
+    TestHumanComment comment = changeOperations.change(changeId).comment(childCommentUuid).get();
+
+    assertThat(comment.unresolved()).isFalse();
+  }
+
+  @Test
   public void draftCommentCanBeRetrieved() {
     Change.Id changeId = changeOperations.newChange().create();
     String commentUuid = changeOperations.change(changeId).currentPatchset().newComment().create();
@@ -1212,6 +1245,36 @@
     assertThat(comment.parentUuid()).value().isEqualTo(parentCommentUuid);
   }
 
+  @Test
+  public void robotCommentCanBeRetrieved() {
+    Change.Id changeId = changeOperations.newChange().create();
+    String commentUuid =
+        changeOperations.change(changeId).currentPatchset().newRobotComment().create();
+
+    TestRobotComment comment = changeOperations.change(changeId).robotComment(commentUuid).get();
+
+    assertThat(comment.uuid()).isEqualTo(commentUuid);
+  }
+
+  @Test
+  public void parentUuidOfRobotCommentCanBeRetrieved() {
+    Change.Id changeId = changeOperations.newChange().create();
+    String parentCommentUuid =
+        changeOperations.change(changeId).currentPatchset().newRobotComment().create();
+    String childCommentUuid =
+        changeOperations
+            .change(changeId)
+            .currentPatchset()
+            .newRobotComment()
+            .parentUuid(parentCommentUuid)
+            .create();
+
+    TestRobotComment comment =
+        changeOperations.change(changeId).robotComment(childCommentUuid).get();
+
+    assertThat(comment.parentUuid()).value().isEqualTo(parentCommentUuid);
+  }
+
   private ChangeInfo getChangeFromServer(Change.Id changeId) throws RestApiException {
     return gApi.changes().id(changeId.get()).get();
   }
diff --git a/javatests/com/google/gerrit/acceptance/testsuite/change/PatchsetOperationsImplTest.java b/javatests/com/google/gerrit/acceptance/testsuite/change/PatchsetOperationsImplTest.java
index cf687aa..c29cf99 100644
--- a/javatests/com/google/gerrit/acceptance/testsuite/change/PatchsetOperationsImplTest.java
+++ b/javatests/com/google/gerrit/acceptance/testsuite/change/PatchsetOperationsImplTest.java
@@ -14,8 +14,11 @@
 
 package com.google.gerrit.acceptance.testsuite.change;
 
+import static com.google.common.truth.Truth.assertThat;
 import static com.google.gerrit.extensions.common.testing.CommentInfoSubject.assertThat;
 import static com.google.gerrit.extensions.common.testing.CommentInfoSubject.assertThatList;
+import static com.google.gerrit.extensions.common.testing.RobotCommentInfoSubject.assertThat;
+import static com.google.gerrit.extensions.common.testing.RobotCommentInfoSubject.assertThatList;
 
 import com.google.common.truth.Correspondence;
 import com.google.gerrit.acceptance.AbstractDaemonTest;
@@ -27,9 +30,16 @@
 import com.google.gerrit.entities.PatchSet;
 import com.google.gerrit.extensions.client.Side;
 import com.google.gerrit.extensions.common.CommentInfo;
+import com.google.gerrit.extensions.common.RobotCommentInfo;
 import com.google.gerrit.extensions.restapi.RestApiException;
 import com.google.gerrit.truth.NullAwareCorrespondence;
 import com.google.inject.Inject;
+import java.sql.Timestamp;
+import java.time.Duration;
+import java.time.Instant;
+import java.time.LocalDateTime;
+import java.time.Month;
+import java.time.ZoneOffset;
 import java.util.List;
 import org.junit.Test;
 
@@ -44,7 +54,6 @@
     Change.Id changeId = changeOperations.newChange().create();
 
     String commentUuid = changeOperations.change(changeId).currentPatchset().newComment().create();
-
     List<CommentInfo> comments = getCommentsFromServer(changeId);
     assertThatList(comments).comparingElementsUsing(hasUuid()).containsExactly(commentUuid);
   }
@@ -313,6 +322,59 @@
   }
 
   @Test
+  public void commentIsCreatedWithSpecifiedCreationTime() throws Exception {
+    Change.Id changeId = changeOperations.newChange().create();
+
+    // Don't use nanos. NoteDb supports only second precision.
+    Instant creationTime =
+        LocalDateTime.of(2020, Month.SEPTEMBER, 15, 12, 10, 43).atZone(ZoneOffset.UTC).toInstant();
+    String commentUuid =
+        changeOperations
+            .change(changeId)
+            .currentPatchset()
+            .newComment()
+            .createdOn(creationTime)
+            .create();
+
+    Timestamp creationTimestamp = Timestamp.from(creationTime);
+    CommentInfo comment = getCommentFromServer(changeId, commentUuid);
+    assertThat(comment).updated().isEqualTo(creationTimestamp);
+  }
+
+  @Test
+  public void zoneOfCreationDateCanBeOmitted() throws Exception {
+    Change.Id changeId = changeOperations.newChange().create();
+
+    // As we don't care about the exact time zone internally used as a default, do a relative test
+    // so that we don't need to assert on exact instants in time. For a relative test, we need two
+    // comments whose creation date should be exactly the specified amount apart.
+    // Don't use nanos or millis. NoteDb supports only second precision.
+    LocalDateTime creationTime1 = LocalDateTime.of(2020, Month.SEPTEMBER, 15, 12, 10, 43);
+    LocalDateTime creationTime2 = creationTime1.plusMinutes(10);
+    String commentUuid1 =
+        changeOperations
+            .change(changeId)
+            .currentPatchset()
+            .newComment()
+            .createdOn(creationTime1)
+            .create();
+    String commentUuid2 =
+        changeOperations
+            .change(changeId)
+            .currentPatchset()
+            .newComment()
+            .createdOn(creationTime2)
+            .create();
+
+    CommentInfo comment1 = getCommentFromServer(changeId, commentUuid1);
+    Instant comment1Creation = comment1.updated.toInstant();
+    CommentInfo comment2 = getCommentFromServer(changeId, commentUuid2);
+    Instant comment2Creation = comment2.updated.toInstant();
+    Duration commentCreationDifference = Duration.between(comment1Creation, comment2Creation);
+    assertThat(commentCreationDifference).isEqualTo(Duration.ofMinutes(10));
+  }
+
+  @Test
   public void draftCommentCanBeCreatedWithoutSpecifyingAnyParameters() throws Exception {
     Change.Id changeId = changeOperations.newChange().create();
 
@@ -624,6 +686,59 @@
   }
 
   @Test
+  public void draftCommentIsCreatedWithSpecifiedCreationTime() throws Exception {
+    Change.Id changeId = changeOperations.newChange().create();
+
+    // Don't use nanos. NoteDb supports only second precision.
+    Instant creationTime =
+        LocalDateTime.of(2020, Month.SEPTEMBER, 15, 12, 10, 43).atZone(ZoneOffset.UTC).toInstant();
+    String commentUuid =
+        changeOperations
+            .change(changeId)
+            .currentPatchset()
+            .newDraftComment()
+            .createdOn(creationTime)
+            .create();
+
+    Timestamp creationTimestamp = Timestamp.from(creationTime);
+    CommentInfo comment = getDraftCommentFromServer(changeId, commentUuid);
+    assertThat(comment).updated().isEqualTo(creationTimestamp);
+  }
+
+  @Test
+  public void zoneOfCreationDateOfDraftCommentCanBeOmitted() throws Exception {
+    Change.Id changeId = changeOperations.newChange().create();
+
+    // As we don't care about the exact time zone internally used as a default, do a relative test
+    // so that we don't need to assert on exact instants in time. For a relative test, we need two
+    // comments whose creation date should be exactly the specified amount apart.
+    // Don't use nanos or millis. NoteDb supports only second precision.
+    LocalDateTime creationTime1 = LocalDateTime.of(2020, Month.SEPTEMBER, 15, 12, 10, 43);
+    LocalDateTime creationTime2 = creationTime1.plusMinutes(10);
+    String commentUuid1 =
+        changeOperations
+            .change(changeId)
+            .currentPatchset()
+            .newDraftComment()
+            .createdOn(creationTime1)
+            .create();
+    String commentUuid2 =
+        changeOperations
+            .change(changeId)
+            .currentPatchset()
+            .newDraftComment()
+            .createdOn(creationTime2)
+            .create();
+
+    CommentInfo comment1 = getDraftCommentFromServer(changeId, commentUuid1);
+    Instant comment1Creation = comment1.updated.toInstant();
+    CommentInfo comment2 = getDraftCommentFromServer(changeId, commentUuid2);
+    Instant comment2Creation = comment2.updated.toInstant();
+    Duration commentCreationDifference = Duration.between(comment1Creation, comment2Creation);
+    assertThat(commentCreationDifference).isEqualTo(Duration.ofMinutes(10));
+  }
+
+  @Test
   public void noDraftCommentsAreCreatedOnCreationOfPublishedComment() throws Exception {
     Change.Id changeId = changeOperations.newChange().create();
 
@@ -643,10 +758,393 @@
     assertThatList(comments).isEmpty();
   }
 
+  @Test
+  public void robotCommentCanBeCreatedWithoutSpecifyingAnyParameters() throws Exception {
+    Change.Id changeId = changeOperations.newChange().create();
+
+    String commentUuid =
+        changeOperations.change(changeId).currentPatchset().newRobotComment().create();
+    List<RobotCommentInfo> robotComments = getRobotCommentsFromServerFromCurrentPatchset(changeId);
+    assertThatList(robotComments).comparingElementsUsing(hasUuid()).containsExactly(commentUuid);
+  }
+
+  @Test
+  public void robotCommentCanBeCreatedOnOlderPatchset() throws Exception {
+    Change.Id changeId = changeOperations.newChange().create();
+    PatchSet.Id previousPatchsetId =
+        changeOperations.change(changeId).currentPatchset().get().patchsetId();
+    changeOperations.change(changeId).newPatchset().create();
+
+    String commentUuid =
+        changeOperations.change(changeId).patchset(previousPatchsetId).newRobotComment().create();
+
+    CommentInfo comment = getRobotCommentFromServer(previousPatchsetId, commentUuid);
+    assertThat(comment).uuid().isEqualTo(commentUuid);
+  }
+
+  @Test
+  public void robotCommentIsCreatedWithSpecifiedMessage() throws Exception {
+    Change.Id changeId = changeOperations.newChange().create();
+
+    String commentUuid =
+        changeOperations
+            .change(changeId)
+            .currentPatchset()
+            .newRobotComment()
+            .message("Test comment message")
+            .create();
+
+    CommentInfo comment = getRobotCommentFromServerInCurrentPatchset(changeId, commentUuid);
+    assertThat(comment).message().isEqualTo("Test comment message");
+  }
+
+  @Test
+  public void robotCommentCanBeCreatedWithEmptyMessage() throws Exception {
+    Change.Id changeId = changeOperations.newChange().create();
+
+    String commentUuid =
+        changeOperations.change(changeId).currentPatchset().newRobotComment().noMessage().create();
+
+    CommentInfo comment = getRobotCommentFromServerInCurrentPatchset(changeId, commentUuid);
+    assertThat(comment).message().isNull();
+  }
+
+  @Test
+  public void patchsetLevelRobotCommentCanBeCreated() throws Exception {
+    Change.Id changeId = changeOperations.newChange().create();
+
+    String commentUuid =
+        changeOperations
+            .change(changeId)
+            .currentPatchset()
+            .newRobotComment()
+            .onPatchsetLevel()
+            .create();
+
+    CommentInfo comment = getRobotCommentFromServerInCurrentPatchset(changeId, commentUuid);
+    assertThat(comment).path().isEqualTo(Patch.PATCHSET_LEVEL);
+  }
+
+  @Test
+  public void fileRobotCommentCanBeCreated() throws Exception {
+    Change.Id changeId = changeOperations.newChange().file("file1").content("Line 1").create();
+
+    String commentUuid =
+        changeOperations
+            .change(changeId)
+            .currentPatchset()
+            .newRobotComment()
+            .onFileLevelOf("file1")
+            .create();
+
+    CommentInfo comment = getRobotCommentFromServerInCurrentPatchset(changeId, commentUuid);
+    assertThat(comment).path().isEqualTo("file1");
+    assertThat(comment).line().isNull();
+    assertThat(comment).range().isNull();
+  }
+
+  @Test
+  public void lineRobotCommentCanBeCreated() throws Exception {
+    Change.Id changeId =
+        changeOperations
+            .newChange()
+            .file("file1")
+            .content("Line 1\nLine 2\nLine 3\nLine 4\n")
+            .create();
+
+    String commentUuid =
+        changeOperations
+            .change(changeId)
+            .currentPatchset()
+            .newRobotComment()
+            .onLine(3)
+            .ofFile("file1")
+            .create();
+
+    CommentInfo comment = getRobotCommentFromServerInCurrentPatchset(changeId, commentUuid);
+    assertThat(comment).line().isEqualTo(3);
+    assertThat(comment).range().isNull();
+  }
+
+  @Test
+  public void rangeRobotCommentCanBeCreated() throws Exception {
+    Change.Id changeId =
+        changeOperations
+            .newChange()
+            .file("file1")
+            .content("Line 1\nLine 2\nLine 3\nLine 4\n")
+            .create();
+
+    String commentUuid =
+        changeOperations
+            .change(changeId)
+            .currentPatchset()
+            .newRobotComment()
+            .fromLine(2)
+            .charOffset(4)
+            .toLine(3)
+            .charOffset(5)
+            .ofFile("file1")
+            .create();
+
+    CommentInfo comment = getRobotCommentFromServerInCurrentPatchset(changeId, commentUuid);
+    assertThat(comment).range().startLine().isEqualTo(2);
+    assertThat(comment).range().startCharacter().isEqualTo(4);
+    assertThat(comment).range().endLine().isEqualTo(3);
+    assertThat(comment).range().endCharacter().isEqualTo(5);
+    // Line is automatically filled from specified range. It's the end line.
+    assertThat(comment).line().isEqualTo(3);
+  }
+
+  @Test
+  public void robotCommentCanBeCreatedOnPatchsetCommit() throws Exception {
+    Change.Id changeId = changeOperations.newChange().create();
+
+    String commentUuid =
+        changeOperations
+            .change(changeId)
+            .currentPatchset()
+            .newRobotComment()
+            .onPatchsetCommit()
+            .create();
+
+    CommentInfo comment = getRobotCommentFromServerInCurrentPatchset(changeId, commentUuid);
+    // Null is often used instead of Side.REVISION as Side.REVISION is the default.
+    assertThat(comment).side().isAnyOf(Side.REVISION, null);
+    assertThat(comment).parent().isNull();
+  }
+
+  @Test
+  public void robotCommentCanBeCreatedOnParentCommit() throws Exception {
+    Change.Id changeId = changeOperations.newChange().create();
+
+    String commentUuid =
+        changeOperations
+            .change(changeId)
+            .currentPatchset()
+            .newRobotComment()
+            .onParentCommit()
+            .create();
+
+    CommentInfo comment = getRobotCommentFromServerInCurrentPatchset(changeId, commentUuid);
+    assertThat(comment).side().isEqualTo(Side.PARENT);
+    assertThat(comment).parent().isEqualTo(1);
+  }
+
+  @Test
+  public void robotCommentCanBeCreatedOnSecondParentCommit() throws Exception {
+    Change.Id parent1ChangeId = changeOperations.newChange().create();
+    Change.Id parent2ChangeId = changeOperations.newChange().create();
+    Change.Id changeId =
+        changeOperations
+            .newChange()
+            .mergeOf()
+            .change(parent1ChangeId)
+            .and()
+            .change(parent2ChangeId)
+            .create();
+
+    String commentUuid =
+        changeOperations
+            .change(changeId)
+            .currentPatchset()
+            .newRobotComment()
+            .onSecondParentCommit()
+            .create();
+
+    CommentInfo comment = getRobotCommentFromServerInCurrentPatchset(changeId, commentUuid);
+    assertThat(comment).side().isEqualTo(Side.PARENT);
+    assertThat(comment).parent().isEqualTo(2);
+  }
+
+  @Test
+  public void robotCommentCanBeCreatedOnNonExistingSecondParentCommit() throws Exception {
+    Change.Id parentChangeId = changeOperations.newChange().create();
+    Change.Id changeId = changeOperations.newChange().childOf().change(parentChangeId).create();
+
+    String commentUuid =
+        changeOperations
+            .change(changeId)
+            .currentPatchset()
+            .newRobotComment()
+            .onSecondParentCommit()
+            .create();
+
+    // We want to be able to create such invalid robot comments for testing purposes (e.g. testing
+    // error handling or resilience of an endpoint) and hence we need to allow such invalid robot
+    // comments in the test API.
+    CommentInfo comment = getRobotCommentFromServerInCurrentPatchset(changeId, commentUuid);
+    assertThat(comment).side().isEqualTo(Side.PARENT);
+    assertThat(comment).parent().isEqualTo(2);
+  }
+
+  @Test
+  public void robotCommentCanBeCreatedOnAutoMergeCommit() throws Exception {
+    Change.Id parent1ChangeId = changeOperations.newChange().create();
+    Change.Id parent2ChangeId = changeOperations.newChange().create();
+    Change.Id changeId =
+        changeOperations
+            .newChange()
+            .mergeOf()
+            .change(parent1ChangeId)
+            .and()
+            .change(parent2ChangeId)
+            .create();
+
+    String commentUuid =
+        changeOperations
+            .change(changeId)
+            .currentPatchset()
+            .newRobotComment()
+            .onAutoMergeCommit()
+            .create();
+
+    CommentInfo comment = getRobotCommentFromServerInCurrentPatchset(changeId, commentUuid);
+    assertThat(comment).side().isEqualTo(Side.PARENT);
+    assertThat(comment).parent().isNull();
+  }
+
+  @Test
+  public void robotCommentCanBeCreatedAsResolved() throws Exception {
+    Change.Id changeId = changeOperations.newChange().create();
+
+    String commentUuid =
+        changeOperations.change(changeId).currentPatchset().newRobotComment().resolved().create();
+
+    CommentInfo comment = getRobotCommentFromServerInCurrentPatchset(changeId, commentUuid);
+    assertThat(comment).unresolved().isFalse();
+  }
+
+  @Test
+  public void robotCommentCanBeCreatedAsUnresolved() throws Exception {
+    Change.Id changeId = changeOperations.newChange().create();
+
+    String commentUuid =
+        changeOperations.change(changeId).currentPatchset().newRobotComment().unresolved().create();
+
+    CommentInfo comment = getRobotCommentFromServerInCurrentPatchset(changeId, commentUuid);
+    assertThat(comment).unresolved().isTrue();
+  }
+
+  @Test
+  public void replyToRobotCommentCanBeCreated() throws Exception {
+    Change.Id changeId = changeOperations.newChange().create();
+    String parentCommentUuid =
+        changeOperations.change(changeId).currentPatchset().newRobotComment().create();
+
+    String commentUuid =
+        changeOperations
+            .change(changeId)
+            .currentPatchset()
+            .newRobotComment()
+            .parentUuid(parentCommentUuid)
+            .create();
+
+    CommentInfo comment = getRobotCommentFromServerInCurrentPatchset(changeId, commentUuid);
+    assertThat(comment).inReplyTo().isEqualTo(parentCommentUuid);
+  }
+
+  @Test
+  public void tagCanBeAttachedToARobotComment() throws Exception {
+    Change.Id changeId = changeOperations.newChange().create();
+
+    String commentUuid =
+        changeOperations
+            .change(changeId)
+            .currentPatchset()
+            .newRobotComment()
+            .tag("my special tag")
+            .create();
+
+    CommentInfo comment = getRobotCommentFromServerInCurrentPatchset(changeId, commentUuid);
+    assertThat(comment).tag().isEqualTo("my special tag");
+  }
+
+  @Test
+  public void robotCommentIsCreatedWithSpecifiedAuthor() throws Exception {
+    Change.Id changeId = changeOperations.newChange().create();
+    Account.Id accountId = accountOperations.newAccount().create();
+
+    String commentUuid =
+        changeOperations
+            .change(changeId)
+            .currentPatchset()
+            .newRobotComment()
+            .author(accountId)
+            .create();
+
+    CommentInfo comment = getRobotCommentFromServerInCurrentPatchset(changeId, commentUuid);
+    assertThat(comment).author().id().isEqualTo(accountId.get());
+  }
+
+  @Test
+  public void robotCommentIsCreatedWithRobotId() throws Exception {
+    Change.Id changeId = changeOperations.newChange().create();
+
+    String commentUuid =
+        changeOperations
+            .change(changeId)
+            .currentPatchset()
+            .newRobotComment()
+            .robotId("robot-id")
+            .create();
+
+    RobotCommentInfo comment = getRobotCommentFromServerInCurrentPatchset(changeId, commentUuid);
+    assertThat(comment).robotId().isEqualTo("robot-id");
+  }
+
+  @Test
+  public void robotCommentIsCreatedWithRobotRunId() throws Exception {
+    Change.Id changeId = changeOperations.newChange().create();
+
+    String commentUuid =
+        changeOperations
+            .change(changeId)
+            .currentPatchset()
+            .newRobotComment()
+            .robotId("robot-run-id")
+            .create();
+
+    RobotCommentInfo comment = getRobotCommentFromServerInCurrentPatchset(changeId, commentUuid);
+    assertThat(comment).robotId().isEqualTo("robot-run-id");
+  }
+
+  @Test
+  public void robotCommentIsCreatedWithUrl() throws Exception {
+    Change.Id changeId = changeOperations.newChange().create();
+
+    String commentUuid =
+        changeOperations.change(changeId).currentPatchset().newRobotComment().url("url").create();
+
+    RobotCommentInfo comment = getRobotCommentFromServerInCurrentPatchset(changeId, commentUuid);
+    assertThat(comment).url().isEqualTo("url");
+  }
+
+  @Test
+  public void robotCommentIsCreatedWithProperty() throws Exception {
+    Change.Id changeId = changeOperations.newChange().create();
+
+    String commentUuid =
+        changeOperations
+            .change(changeId)
+            .currentPatchset()
+            .newRobotComment()
+            .addProperty("key", "value")
+            .create();
+
+    RobotCommentInfo comment = getRobotCommentFromServerInCurrentPatchset(changeId, commentUuid);
+    assertThat(comment).properties().containsExactly("key", "value");
+  }
+
   private List<CommentInfo> getCommentsFromServer(Change.Id changeId) throws RestApiException {
     return gApi.changes().id(changeId.get()).commentsAsList();
   }
 
+  private List<RobotCommentInfo> getRobotCommentsFromServerFromCurrentPatchset(Change.Id changeId)
+      throws RestApiException {
+    return gApi.changes().id(changeId.get()).current().robotCommentsAsList();
+  }
+
   private List<CommentInfo> getDraftCommentsFromServer(Change.Id changeId) throws RestApiException {
     return gApi.changes().id(changeId.get()).draftsAsList();
   }
@@ -662,6 +1160,33 @@
                     String.format("Comment %s not found on change %d", uuid, changeId.get())));
   }
 
+  private RobotCommentInfo getRobotCommentFromServerInCurrentPatchset(
+      Change.Id changeId, String uuid) throws RestApiException {
+    return gApi.changes().id(changeId.get()).current().robotCommentsAsList().stream()
+        .filter(comment -> comment.id.equals(uuid))
+        .findAny()
+        .orElseThrow(
+            () ->
+                new IllegalStateException(
+                    String.format(
+                        "Robot Comment %s not found on change %d on the latest patchset",
+                        uuid, changeId.get())));
+  }
+
+  private RobotCommentInfo getRobotCommentFromServer(PatchSet.Id patchsetId, String uuid)
+      throws RestApiException {
+    return gApi.changes().id(patchsetId.changeId().toString())
+        .revision(patchsetId.getId().toString()).robotCommentsAsList().stream()
+        .filter(comment -> comment.id.equals(uuid))
+        .findAny()
+        .orElseThrow(
+            () ->
+                new IllegalStateException(
+                    String.format(
+                        "Robot Comment %s not found on change %d on patchset %d",
+                        uuid, patchsetId.changeId().get(), patchsetId.get())));
+  }
+
   private CommentInfo getDraftCommentFromServer(Change.Id changeId, String uuid)
       throws RestApiException {
     return gApi.changes().id(changeId.get()).draftsAsList().stream()
diff --git a/javatests/com/google/gerrit/elasticsearch/ElasticContainer.java b/javatests/com/google/gerrit/elasticsearch/ElasticContainer.java
index 60bf64c..1a43269 100644
--- a/javatests/com/google/gerrit/elasticsearch/ElasticContainer.java
+++ b/javatests/com/google/gerrit/elasticsearch/ElasticContainer.java
@@ -41,7 +41,7 @@
       case V6_7:
         return "blacktop/elasticsearch:6.7.2";
       case V6_8:
-        return "blacktop/elasticsearch:6.8.11";
+        return "blacktop/elasticsearch:6.8.12";
       case V7_0:
         return "blacktop/elasticsearch:7.0.1";
       case V7_1:
diff --git a/javatests/com/google/gerrit/elasticsearch/ElasticVersionTest.java b/javatests/com/google/gerrit/elasticsearch/ElasticVersionTest.java
index 9296a6b..b9d5313 100644
--- a/javatests/com/google/gerrit/elasticsearch/ElasticVersionTest.java
+++ b/javatests/com/google/gerrit/elasticsearch/ElasticVersionTest.java
@@ -72,15 +72,15 @@
   public void atLeastMinorVersion() throws Exception {
     assertThat(ElasticVersion.V6_7.isAtLeastMinorVersion(ElasticVersion.V6_7)).isTrue();
     assertThat(ElasticVersion.V6_8.isAtLeastMinorVersion(ElasticVersion.V6_8)).isTrue();
-    assertThat(ElasticVersion.V7_0.isAtLeastMinorVersion(ElasticVersion.V6_7)).isFalse();
-    assertThat(ElasticVersion.V7_1.isAtLeastMinorVersion(ElasticVersion.V6_7)).isFalse();
-    assertThat(ElasticVersion.V7_2.isAtLeastMinorVersion(ElasticVersion.V6_7)).isFalse();
-    assertThat(ElasticVersion.V7_3.isAtLeastMinorVersion(ElasticVersion.V6_7)).isFalse();
-    assertThat(ElasticVersion.V7_4.isAtLeastMinorVersion(ElasticVersion.V6_7)).isFalse();
-    assertThat(ElasticVersion.V7_5.isAtLeastMinorVersion(ElasticVersion.V6_7)).isFalse();
-    assertThat(ElasticVersion.V7_6.isAtLeastMinorVersion(ElasticVersion.V6_7)).isFalse();
-    assertThat(ElasticVersion.V7_7.isAtLeastMinorVersion(ElasticVersion.V6_7)).isFalse();
-    assertThat(ElasticVersion.V7_8.isAtLeastMinorVersion(ElasticVersion.V6_7)).isFalse();
+    assertThat(ElasticVersion.V7_0.isAtLeastMinorVersion(ElasticVersion.V6_8)).isFalse();
+    assertThat(ElasticVersion.V7_1.isAtLeastMinorVersion(ElasticVersion.V6_8)).isFalse();
+    assertThat(ElasticVersion.V7_2.isAtLeastMinorVersion(ElasticVersion.V6_8)).isFalse();
+    assertThat(ElasticVersion.V7_3.isAtLeastMinorVersion(ElasticVersion.V6_8)).isFalse();
+    assertThat(ElasticVersion.V7_4.isAtLeastMinorVersion(ElasticVersion.V6_8)).isFalse();
+    assertThat(ElasticVersion.V7_5.isAtLeastMinorVersion(ElasticVersion.V6_8)).isFalse();
+    assertThat(ElasticVersion.V7_6.isAtLeastMinorVersion(ElasticVersion.V6_8)).isFalse();
+    assertThat(ElasticVersion.V7_7.isAtLeastMinorVersion(ElasticVersion.V6_8)).isFalse();
+    assertThat(ElasticVersion.V7_8.isAtLeastMinorVersion(ElasticVersion.V6_8)).isFalse();
   }
 
   @Test
diff --git a/javatests/com/google/gerrit/server/change/CommentThreadTest.java b/javatests/com/google/gerrit/server/change/CommentThreadTest.java
new file mode 100644
index 0000000..dc46e48
--- /dev/null
+++ b/javatests/com/google/gerrit/server/change/CommentThreadTest.java
@@ -0,0 +1,80 @@
+// Copyright (C) 2020 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.server.change;
+
+import static com.google.common.truth.Truth.assertThat;
+import static com.google.gerrit.testing.GerritJUnit.assertThrows;
+
+import com.google.gerrit.entities.Account;
+import com.google.gerrit.entities.Comment;
+import com.google.gerrit.entities.Comment.Key;
+import com.google.gerrit.entities.HumanComment;
+import java.sql.Timestamp;
+import org.junit.Test;
+
+public class CommentThreadTest {
+
+  @Test
+  public void threadMustContainAtLeastOneComment() {
+    assertThrows(IllegalStateException.class, () -> CommentThread.builder().build());
+  }
+
+  @Test
+  public void threadCanBeUnresolved() {
+    HumanComment root = unresolved(createComment("root"));
+    CommentThread<Comment> commentThread = CommentThread.builder().addComment(root).build();
+
+    assertThat(commentThread.unresolved()).isTrue();
+  }
+
+  @Test
+  public void threadCanBeResolved() {
+    HumanComment root = resolved(createComment("root"));
+    CommentThread<Comment> commentThread = CommentThread.builder().addComment(root).build();
+
+    assertThat(commentThread.unresolved()).isFalse();
+  }
+
+  @Test
+  public void lastCommentInThreadDeterminesUnresolvedStatus() {
+    HumanComment root = resolved(createComment("root"));
+    HumanComment child = unresolved(createComment("child"));
+    CommentThread<Comment> commentThread =
+        CommentThread.builder().addComment(root).addComment(child).build();
+
+    assertThat(commentThread.unresolved()).isTrue();
+  }
+
+  private static HumanComment createComment(String commentUuid) {
+    return new HumanComment(
+        new Key(commentUuid, "myFile", 1),
+        Account.id(100),
+        new Timestamp(1234),
+        (short) 1,
+        "Comment text",
+        "serverId",
+        true);
+  }
+
+  private static HumanComment resolved(HumanComment comment) {
+    comment.unresolved = false;
+    return comment;
+  }
+
+  private static HumanComment unresolved(HumanComment comment) {
+    comment.unresolved = true;
+    return comment;
+  }
+}
diff --git a/javatests/com/google/gerrit/server/change/CommentThreadsTest.java b/javatests/com/google/gerrit/server/change/CommentThreadsTest.java
new file mode 100644
index 0000000..56566d3
--- /dev/null
+++ b/javatests/com/google/gerrit/server/change/CommentThreadsTest.java
@@ -0,0 +1,285 @@
+// Copyright (C) 2020 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.server.change;
+
+import static com.google.common.truth.Truth.assertThat;
+
+import com.google.common.collect.ImmutableList;
+import com.google.common.collect.ImmutableSet;
+import com.google.gerrit.entities.Account;
+import com.google.gerrit.entities.Comment.Key;
+import com.google.gerrit.entities.HumanComment;
+import java.sql.Timestamp;
+import org.junit.Test;
+
+public class CommentThreadsTest {
+
+  @Test
+  public void threadsAreEmptyWhenNoCommentsAreProvided() {
+    ImmutableList<HumanComment> comments = ImmutableList.of();
+    ImmutableSet<CommentThread<HumanComment>> commentThreads =
+        CommentThreads.forComments(comments).getThreads();
+
+    ImmutableSet<CommentThread<HumanComment>> expectedThreads = ImmutableSet.of();
+    assertThat(commentThreads).isEqualTo(expectedThreads);
+  }
+
+  @Test
+  public void threadsCanBeCreatedFromSingleRoot() {
+    HumanComment root = createComment("root");
+
+    ImmutableList<HumanComment> comments = ImmutableList.of(root);
+    ImmutableSet<CommentThread<HumanComment>> commentThreads =
+        CommentThreads.forComments(comments).getThreads();
+
+    ImmutableSet<CommentThread<HumanComment>> expectedThreads = ImmutableSet.of(toThread(root));
+    assertThat(commentThreads).isEqualTo(expectedThreads);
+  }
+
+  @Test
+  public void threadsCanBeCreatedFromUnorderedComments() {
+    HumanComment root = createComment("root");
+    HumanComment child1 = asReply(createComment("child1"), "root");
+    HumanComment child2 = asReply(createComment("child2"), "child1");
+    HumanComment child3 = asReply(createComment("child3"), "child2");
+
+    ImmutableList<HumanComment> comments = ImmutableList.of(child2, child1, root, child3);
+    ImmutableSet<CommentThread<HumanComment>> commentThreads =
+        CommentThreads.forComments(comments).getThreads();
+
+    ImmutableSet<CommentThread<HumanComment>> expectedThreads =
+        ImmutableSet.of(toThread(root, child1, child2, child3));
+    assertThat(commentThreads).isEqualTo(expectedThreads);
+  }
+
+  @Test
+  public void childWithNotAvailableParentIsAssumedToBeRoot() {
+    HumanComment child1 = asReply(createComment("child1"), "root");
+
+    ImmutableList<HumanComment> comments = ImmutableList.of(child1);
+    ImmutableSet<CommentThread<HumanComment>> commentThreads =
+        CommentThreads.forComments(comments).getThreads();
+
+    ImmutableSet<CommentThread<HumanComment>> expectedThreads = ImmutableSet.of(toThread(child1));
+    assertThat(commentThreads).isEqualTo(expectedThreads);
+  }
+
+  @Test
+  public void threadsIgnoreDuplicateRoots() {
+    HumanComment root = createComment("root");
+    HumanComment child1 = asReply(createComment("child1"), "root");
+
+    ImmutableList<HumanComment> comments = ImmutableList.of(root, root, child1);
+    ImmutableSet<CommentThread<HumanComment>> commentThreads =
+        CommentThreads.forComments(comments).getThreads();
+
+    ImmutableSet<CommentThread<HumanComment>> expectedThreads =
+        ImmutableSet.of(toThread(root, child1));
+    assertThat(commentThreads).isEqualTo(expectedThreads);
+  }
+
+  @Test
+  public void threadsIgnoreDuplicateChildren() {
+    HumanComment root = createComment("root");
+    HumanComment child1 = asReply(createComment("child1"), "root");
+
+    ImmutableList<HumanComment> comments = ImmutableList.of(root, child1, child1);
+    ImmutableSet<CommentThread<HumanComment>> commentThreads =
+        CommentThreads.forComments(comments).getThreads();
+
+    ImmutableSet<CommentThread<HumanComment>> expectedThreads =
+        ImmutableSet.of(toThread(root, child1));
+    assertThat(commentThreads).isEqualTo(expectedThreads);
+  }
+
+  @Test
+  public void commentsAreOrderedIntoCorrectThreads() {
+    HumanComment thread1Root = createComment("thread1Root");
+    HumanComment thread1Child1 = asReply(createComment("thread1Child1"), "thread1Root");
+    HumanComment thread1Child2 = asReply(createComment("thread1Child2"), "thread1Child1");
+    HumanComment thread2Root = createComment("thread2Root");
+    HumanComment thread2Child1 = asReply(createComment("thread2Child1"), "thread2Root");
+
+    ImmutableList<HumanComment> comments =
+        ImmutableList.of(thread2Root, thread1Child2, thread1Child1, thread1Root, thread2Child1);
+    ImmutableSet<CommentThread<HumanComment>> commentThreads =
+        CommentThreads.forComments(comments).getThreads();
+
+    ImmutableSet<CommentThread<HumanComment>> expectedThreads =
+        ImmutableSet.of(
+            toThread(thread1Root, thread1Child1, thread1Child2),
+            toThread(thread2Root, thread2Child1));
+    assertThat(commentThreads).isEqualTo(expectedThreads);
+  }
+
+  @Test
+  public void branchedThreadsAreFlattenedAccordingToDate() {
+    HumanComment root = writtenOn(createComment("root"), new Timestamp(1));
+    HumanComment sibling1 = writtenOn(asReply(createComment("sibling1"), "root"), new Timestamp(2));
+    HumanComment sibling2 = writtenOn(asReply(createComment("sibling2"), "root"), new Timestamp(3));
+    HumanComment sibling1Child =
+        writtenOn(asReply(createComment("sibling1Child"), "sibling1"), new Timestamp(4));
+    HumanComment sibling2Child =
+        writtenOn(asReply(createComment("sibling2Child"), "sibling2"), new Timestamp(5));
+
+    ImmutableList<HumanComment> comments =
+        ImmutableList.of(sibling2, sibling2Child, sibling1, sibling1Child, root);
+    ImmutableSet<CommentThread<HumanComment>> commentThreads =
+        CommentThreads.forComments(comments).getThreads();
+
+    ImmutableSet<CommentThread<HumanComment>> expectedThreads =
+        ImmutableSet.of(toThread(root, sibling1, sibling2, sibling1Child, sibling2Child));
+    assertThat(commentThreads).isEqualTo(expectedThreads);
+  }
+
+  @Test
+  public void threadsConsiderParentRelationshipStrongerThanDate() {
+    HumanComment root = writtenOn(createComment("root"), new Timestamp(3));
+    HumanComment child1 = writtenOn(asReply(createComment("child1"), "root"), new Timestamp(2));
+    HumanComment child2 = writtenOn(asReply(createComment("child2"), "child1"), new Timestamp(1));
+
+    ImmutableList<HumanComment> comments = ImmutableList.of(child2, child1, root);
+    ImmutableSet<CommentThread<HumanComment>> commentThreads =
+        CommentThreads.forComments(comments).getThreads();
+
+    ImmutableSet<CommentThread<HumanComment>> expectedThreads =
+        ImmutableSet.of(toThread(root, child1, child2));
+    assertThat(commentThreads).isEqualTo(expectedThreads);
+  }
+
+  @Test
+  public void threadsFallBackToUuidOrderIfParentAndDateAreTheSame() {
+    HumanComment root = writtenOn(createComment("root"), new Timestamp(1));
+    HumanComment sibling1 = writtenOn(asReply(createComment("sibling1"), "root"), new Timestamp(2));
+    HumanComment sibling2 = writtenOn(asReply(createComment("sibling2"), "root"), new Timestamp(2));
+
+    ImmutableList<HumanComment> comments = ImmutableList.of(sibling2, sibling1, root);
+    ImmutableSet<CommentThread<HumanComment>> commentThreads =
+        CommentThreads.forComments(comments).getThreads();
+
+    ImmutableSet<CommentThread<HumanComment>> expectedThreads =
+        ImmutableSet.of(toThread(root, sibling1, sibling2));
+    assertThat(commentThreads).isEqualTo(expectedThreads);
+  }
+
+  @Test
+  public void specificThreadsCanBeRequestedByTheirReply() {
+    HumanComment thread1Root = createComment("thread1Root");
+    HumanComment thread2Root = createComment("thread2Root");
+
+    HumanComment thread1Reply = asReply(createComment("thread1Reply"), "thread1Root");
+
+    ImmutableList<HumanComment> comments = ImmutableList.of(thread1Root, thread2Root, thread1Reply);
+    ImmutableSet<CommentThread<HumanComment>> commentThreads =
+        CommentThreads.forComments(comments).getThreadsForChildren(ImmutableList.of(thread1Reply));
+
+    ImmutableSet<CommentThread<HumanComment>> expectedThreads =
+        ImmutableSet.of(toThread(thread1Root, thread1Reply));
+    assertThat(commentThreads).isEqualTo(expectedThreads);
+  }
+
+  @Test
+  public void requestedThreadsDoNotNeedToContainReply() {
+    HumanComment thread1Root = createComment("thread1Root");
+    HumanComment thread2Root = createComment("thread2Root");
+
+    HumanComment thread1Reply = asReply(createComment("thread1Reply"), "thread1Root");
+
+    ImmutableList<HumanComment> comments = ImmutableList.of(thread1Root, thread2Root);
+    ImmutableSet<CommentThread<HumanComment>> commentThreads =
+        CommentThreads.forComments(comments).getThreadsForChildren(ImmutableList.of(thread1Reply));
+
+    ImmutableSet<CommentThread<HumanComment>> expectedThreads =
+        ImmutableSet.of(toThread(thread1Root));
+    assertThat(commentThreads).isEqualTo(expectedThreads);
+  }
+
+  @Test
+  public void completeThreadCanBeRequestedByReplyToRootComment() {
+    HumanComment root = createComment("root");
+    HumanComment child = asReply(createComment("child"), "root");
+
+    HumanComment reply = asReply(createComment("reply"), "root");
+
+    ImmutableList<HumanComment> comments = ImmutableList.of(root, child);
+    ImmutableSet<CommentThread<HumanComment>> commentThreads =
+        CommentThreads.forComments(comments).getThreadsForChildren(ImmutableList.of(reply));
+
+    ImmutableSet<CommentThread<HumanComment>> expectedThreads =
+        ImmutableSet.of(toThread(root, child));
+    assertThat(commentThreads).isEqualTo(expectedThreads);
+  }
+
+  @Test
+  public void completeThreadWithBranchesCanBeRequestedByReplyToIntermediateComment() {
+    HumanComment root = writtenOn(createComment("root"), new Timestamp(1));
+    HumanComment sibling1 = writtenOn(asReply(createComment("sibling1"), "root"), new Timestamp(2));
+    HumanComment sibling2 = writtenOn(asReply(createComment("sibling2"), "root"), new Timestamp(3));
+    HumanComment sibling1Child =
+        writtenOn(asReply(createComment("sibling1Child"), "sibling1"), new Timestamp(4));
+    HumanComment sibling2Child =
+        writtenOn(asReply(createComment("sibling2Child"), "sibling2"), new Timestamp(5));
+
+    HumanComment reply = asReply(createComment("sibling1"), "root");
+
+    ImmutableList<HumanComment> comments =
+        ImmutableList.of(root, sibling1, sibling2, sibling1Child, sibling2Child);
+    ImmutableSet<CommentThread<HumanComment>> commentThreads =
+        CommentThreads.forComments(comments).getThreadsForChildren(ImmutableList.of(reply));
+
+    ImmutableSet<CommentThread<HumanComment>> expectedThreads =
+        ImmutableSet.of(toThread(root, sibling1, sibling2, sibling1Child, sibling2Child));
+    assertThat(commentThreads).isEqualTo(expectedThreads);
+  }
+
+  @Test
+  public void requestedThreadsAreEmptyIfReplyDoesNotReferToAThread() {
+    HumanComment root = createComment("root");
+
+    HumanComment reply = asReply(createComment("reply"), "invalid");
+
+    ImmutableList<HumanComment> comments = ImmutableList.of(root);
+    ImmutableSet<CommentThread<HumanComment>> commentThreads =
+        CommentThreads.forComments(comments).getThreadsForChildren(ImmutableList.of(reply));
+
+    ImmutableSet<CommentThread<HumanComment>> expectedThreads = ImmutableSet.of();
+    assertThat(commentThreads).isEqualTo(expectedThreads);
+  }
+
+  private static HumanComment createComment(String commentUuid) {
+    return new HumanComment(
+        new Key(commentUuid, "myFile", 1),
+        Account.id(100),
+        new Timestamp(1234),
+        (short) 1,
+        "Comment text",
+        "serverId",
+        true);
+  }
+
+  private static HumanComment asReply(HumanComment comment, String parentUuid) {
+    comment.parentUuid = parentUuid;
+    return comment;
+  }
+
+  private static HumanComment writtenOn(HumanComment comment, Timestamp writtenOn) {
+    comment.writtenOn = writtenOn;
+    return comment;
+  }
+
+  private static CommentThread<HumanComment> toThread(HumanComment... comments) {
+    return CommentThread.<HumanComment>builder().comments(ImmutableList.copyOf(comments)).build();
+  }
+}
diff --git a/javatests/com/google/gerrit/server/restapi/change/CommentPorterTest.java b/javatests/com/google/gerrit/server/restapi/change/CommentPorterTest.java
index cb29315..9c30fc9 100644
--- a/javatests/com/google/gerrit/server/restapi/change/CommentPorterTest.java
+++ b/javatests/com/google/gerrit/server/restapi/change/CommentPorterTest.java
@@ -57,6 +57,8 @@
 
   @Mock private PatchListCache patchListCache;
 
+  private int uuidCounter = 0;
+
   @Test
   public void commentsAreNotDroppedWhenDiffNotAvailable() throws Exception {
     Project.NameKey project = Project.nameKey("myProject");
@@ -206,7 +208,7 @@
 
   private HumanComment createComment(PatchSet.Id patchsetId, String filePath) {
     return new HumanComment(
-        new Comment.Key("commentUuid", filePath, patchsetId.get()),
+        new Comment.Key(getUniqueUuid(), filePath, patchsetId.get()),
         Account.id(100),
         new Timestamp(1234),
         (short) 1,
@@ -215,6 +217,10 @@
         true);
   }
 
+  private String getUniqueUuid() {
+    return "commentUuid" + uuidCounter++;
+  }
+
   private Correspondence<HumanComment, String> hasFilePath() {
     return NullAwareCorrespondence.transforming(comment -> comment.key.filename, "hasFilePath");
   }
diff --git a/plugins/delete-project b/plugins/delete-project
index 516fbd8..2dc456a 160000
--- a/plugins/delete-project
+++ b/plugins/delete-project
@@ -1 +1 @@
-Subproject commit 516fbd8aebfcc49b278b0eb985add293d753bb3f
+Subproject commit 2dc456a6891f1bc55a9d637cf2553f27ceae6c49
diff --git a/polygerrit-ui/app/elements/change/gr-confirm-revert-dialog/gr-confirm-revert-dialog.js b/polygerrit-ui/app/elements/change/gr-confirm-revert-dialog/gr-confirm-revert-dialog.js
deleted file mode 100644
index 9489b94..0000000
--- a/polygerrit-ui/app/elements/change/gr-confirm-revert-dialog/gr-confirm-revert-dialog.js
+++ /dev/null
@@ -1,211 +0,0 @@
-/**
- * @license
- * Copyright (C) 2016 The Android Open Source Project
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-import '../../shared/gr-dialog/gr-dialog.js';
-import '../../../styles/shared-styles.js';
-import '../../plugins/gr-endpoint-decorator/gr-endpoint-decorator.js';
-import '../../shared/gr-js-api-interface/gr-js-api-interface.js';
-import {GestureEventListeners} from '@polymer/polymer/lib/mixins/gesture-event-listeners.js';
-import {LegacyElementMixin} from '@polymer/polymer/lib/legacy/legacy-element-mixin.js';
-import {PolymerElement} from '@polymer/polymer/polymer-element.js';
-import {htmlTemplate} from './gr-confirm-revert-dialog_html.js';
-
-const ERR_COMMIT_NOT_FOUND =
-    'Unable to find the commit hash of this change.';
-const CHANGE_SUBJECT_LIMIT = 50;
-
-// TODO(dhruvsri): clean up repeated definitions after moving to js modules
-const REVERT_TYPES = {
-  REVERT_SINGLE_CHANGE: 1,
-  REVERT_SUBMISSION: 2,
-};
-
-/**
- * @extends PolymerElement
- */
-class GrConfirmRevertDialog extends GestureEventListeners(
-    LegacyElementMixin(PolymerElement)) {
-  static get template() { return htmlTemplate; }
-
-  static get is() { return 'gr-confirm-revert-dialog'; }
-  /**
-   * Fired when the confirm button is pressed.
-   *
-   * @event confirm
-   */
-
-  /**
-   * Fired when the cancel button is pressed.
-   *
-   * @event cancel
-   */
-
-  static get properties() {
-    return {
-      /* The revert message updated by the user
-      The default value is set by the dialog */
-      _message: String,
-      _revertType: {
-        type: Number,
-        value: REVERT_TYPES.REVERT_SINGLE_CHANGE,
-      },
-      _showRevertSubmission: {
-        type: Boolean,
-        value: false,
-      },
-      _changesCount: Number,
-      _showErrorMessage: {
-        type: Boolean,
-        value: false,
-      },
-      /* store the default revert messages per revert type so that we can
-      check if user has edited the revert message or not
-      Set when populate() is called */
-      _originalRevertMessages: {
-        type: Array,
-        value() { return []; },
-      },
-      // Store the actual messages that the user has edited
-      _revertMessages: {
-        type: Array,
-        value() { return []; },
-      },
-    };
-  }
-
-  _computeIfSingleRevert(revertType) {
-    return revertType === REVERT_TYPES.REVERT_SINGLE_CHANGE;
-  }
-
-  _computeIfRevertSubmission(revertType) {
-    return revertType === REVERT_TYPES.REVERT_SUBMISSION;
-  }
-
-  _modifyRevertMsg(change, commitMessage, message) {
-    return this.$.jsAPI.modifyRevertMsg(change,
-        message, commitMessage);
-  }
-
-  populate(change, commitMessage, changes) {
-    this._changesCount = changes.length;
-    // The option to revert a single change is always available
-    this._populateRevertSingleChangeMessage(
-        change, commitMessage, change.current_revision);
-    this._populateRevertSubmissionMessage(change, changes, commitMessage);
-  }
-
-  _populateRevertSingleChangeMessage(change, commitMessage, commitHash) {
-    // Figure out what the revert title should be.
-    const originalTitle = (commitMessage || '').split('\n')[0];
-    const revertTitle = `Revert "${originalTitle}"`;
-    if (!commitHash) {
-      this.dispatchEvent(new CustomEvent('show-alert', {
-        detail: {message: ERR_COMMIT_NOT_FOUND},
-        composed: true, bubbles: true,
-      }));
-      return;
-    }
-    const revertCommitText = `This reverts commit ${commitHash}.`;
-
-    this._message = `${revertTitle}\n\n${revertCommitText}\n\n` +
-        `Reason for revert: <INSERT REASONING HERE>\n`;
-    // This is to give plugins a chance to update message
-    this._message = this._modifyRevertMsg(change, commitMessage,
-        this._message);
-    this._revertType = REVERT_TYPES.REVERT_SINGLE_CHANGE;
-    this._showRevertSubmission = false;
-    this._revertMessages[this._revertType] = this._message;
-    this._originalRevertMessages[this._revertType] = this._message;
-  }
-
-  _getTrimmedChangeSubject(subject) {
-    if (!subject) return '';
-    if (subject.length < CHANGE_SUBJECT_LIMIT) return subject;
-    return subject.substring(0, CHANGE_SUBJECT_LIMIT) + '...';
-  }
-
-  _modifyRevertSubmissionMsg(change, msg, commitMessage) {
-    return this.$.jsAPI.modifyRevertSubmissionMsg(change, msg,
-        commitMessage);
-  }
-
-  _populateRevertSubmissionMessage(change, changes, commitMessage) {
-    // Follow the same convention of the revert
-    const commitHash = change.current_revision;
-    if (!commitHash) {
-      this.dispatchEvent(new CustomEvent('show-alert', {
-        detail: {message: ERR_COMMIT_NOT_FOUND},
-        composed: true, bubbles: true,
-      }));
-      return;
-    }
-    if (!changes || changes.length <= 1) return;
-    const submissionId = change.submission_id;
-    const revertTitle = 'Revert submission ' + submissionId;
-    this._message = revertTitle + '\n\n' + 'Reason for revert: <INSERT ' +
-      'REASONING HERE>\n';
-    this._message += 'Reverted Changes:\n';
-    changes.forEach(change => {
-      this._message += change.change_id.substring(0, 10) + ':'
-        + this._getTrimmedChangeSubject(change.subject) + '\n';
-    });
-    this._message = this._modifyRevertSubmissionMsg(change, this._message,
-        commitMessage);
-    this._revertType = REVERT_TYPES.REVERT_SUBMISSION;
-    this._revertMessages[this._revertType] = this._message;
-    this._originalRevertMessages[this._revertType] = this._message;
-    this._showRevertSubmission = true;
-  }
-
-  _handleRevertSingleChangeClicked() {
-    this._showErrorMessage = false;
-    this._revertMessages[REVERT_TYPES.REVERT_SUBMISSION] = this._message;
-    this._message = this._revertMessages[REVERT_TYPES.REVERT_SINGLE_CHANGE];
-    this._revertType = REVERT_TYPES.REVERT_SINGLE_CHANGE;
-  }
-
-  _handleRevertSubmissionClicked() {
-    this._showErrorMessage = false;
-    this._revertType = REVERT_TYPES.REVERT_SUBMISSION;
-    this._revertMessages[REVERT_TYPES.REVERT_SINGLE_CHANGE] = this._message;
-    this._message = this._revertMessages[REVERT_TYPES.REVERT_SUBMISSION];
-  }
-
-  _handleConfirmTap(e) {
-    e.preventDefault();
-    e.stopPropagation();
-    if (this._message === this._originalRevertMessages[this._revertType]) {
-      this._showErrorMessage = true;
-      return;
-    }
-    this.dispatchEvent(new CustomEvent('confirm', {
-      detail: {revertType: this._revertType,
-        message: this._message},
-      composed: true, bubbles: false,
-    }));
-  }
-
-  _handleCancelTap(e) {
-    e.preventDefault();
-    e.stopPropagation();
-    this.dispatchEvent(new CustomEvent('cancel', {
-      detail: {revertType: this._revertType},
-      composed: true, bubbles: false,
-    }));
-  }
-}
-
-customElements.define(GrConfirmRevertDialog.is, GrConfirmRevertDialog);
diff --git a/polygerrit-ui/app/elements/change/gr-confirm-revert-dialog/gr-confirm-revert-dialog.ts b/polygerrit-ui/app/elements/change/gr-confirm-revert-dialog/gr-confirm-revert-dialog.ts
new file mode 100644
index 0000000..beaf0f8
--- /dev/null
+++ b/polygerrit-ui/app/elements/change/gr-confirm-revert-dialog/gr-confirm-revert-dialog.ts
@@ -0,0 +1,248 @@
+/**
+ * @license
+ * Copyright (C) 2016 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+import '../../shared/gr-dialog/gr-dialog';
+import '../../../styles/shared-styles';
+import '../../plugins/gr-endpoint-decorator/gr-endpoint-decorator';
+import '../../shared/gr-js-api-interface/gr-js-api-interface';
+import {GestureEventListeners} from '@polymer/polymer/lib/mixins/gesture-event-listeners';
+import {LegacyElementMixin} from '@polymer/polymer/lib/legacy/legacy-element-mixin';
+import {PolymerElement} from '@polymer/polymer/polymer-element';
+import {htmlTemplate} from './gr-confirm-revert-dialog_html';
+import {customElement, property} from '@polymer/decorators';
+import {JsApiService} from '../../shared/gr-js-api-interface/gr-js-api-types';
+import {ChangeInfo, CommitId} from '../../../types/common';
+
+const ERR_COMMIT_NOT_FOUND = 'Unable to find the commit hash of this change.';
+const CHANGE_SUBJECT_LIMIT = 50;
+
+// TODO(dhruvsri): clean up repeated definitions after moving to js modules
+const REVERT_TYPES = {
+  REVERT_SINGLE_CHANGE: 1,
+  REVERT_SUBMISSION: 2,
+};
+
+export interface GrConfirmRevertDialog {
+  $: {
+    jsAPI: JsApiService & Element;
+  };
+}
+@customElement('gr-confirm-revert-dialog')
+export class GrConfirmRevertDialog extends GestureEventListeners(
+  LegacyElementMixin(PolymerElement)
+) {
+  static get template() {
+    return htmlTemplate;
+  }
+
+  /**
+   * Fired when the confirm button is pressed.
+   *
+   * @event confirm
+   */
+
+  /**
+   * Fired when the cancel button is pressed.
+   *
+   * @event cancel
+   */
+
+  /* The revert message updated by the user
+      The default value is set by the dialog */
+  @property({type: String})
+  _message?: string;
+
+  @property({type: Number})
+  _revertType = REVERT_TYPES.REVERT_SINGLE_CHANGE;
+
+  @property({type: Boolean})
+  _showRevertSubmission = false;
+
+  @property({type: Number})
+  _changesCount?: number;
+
+  @property({type: Boolean})
+  _showErrorMessage = false;
+
+  /* store the default revert messages per revert type so that we can
+  check if user has edited the revert message or not
+  Set when populate() is called */
+  @property({type: Array})
+  _originalRevertMessages: string[] = [];
+
+  // Store the actual messages that the user has edited
+  @property({type: Array})
+  _revertMessages: string[] = [];
+
+  _computeIfSingleRevert(revertType: number) {
+    return revertType === REVERT_TYPES.REVERT_SINGLE_CHANGE;
+  }
+
+  _computeIfRevertSubmission(revertType: number) {
+    return revertType === REVERT_TYPES.REVERT_SUBMISSION;
+  }
+
+  _modifyRevertMsg(change: ChangeInfo, commitMessage: string, message: string) {
+    return this.$.jsAPI.modifyRevertMsg(change, message, commitMessage);
+  }
+
+  populate(change: ChangeInfo, commitMessage: string, changes: ChangeInfo[]) {
+    this._changesCount = changes.length;
+    // The option to revert a single change is always available
+    this._populateRevertSingleChangeMessage(
+      change,
+      commitMessage,
+      change.current_revision
+    );
+    this._populateRevertSubmissionMessage(change, changes, commitMessage);
+  }
+
+  _populateRevertSingleChangeMessage(
+    change: ChangeInfo,
+    commitMessage: string,
+    commitHash?: CommitId
+  ) {
+    // Figure out what the revert title should be.
+    const originalTitle = (commitMessage || '').split('\n')[0];
+    const revertTitle = `Revert "${originalTitle}"`;
+    if (!commitHash) {
+      this.dispatchEvent(
+        new CustomEvent('show-alert', {
+          detail: {message: ERR_COMMIT_NOT_FOUND},
+          composed: true,
+          bubbles: true,
+        })
+      );
+      return;
+    }
+    const revertCommitText = `This reverts commit ${commitHash}.`;
+
+    const message =
+      `${revertTitle}\n\n${revertCommitText}\n\n` +
+      'Reason for revert: <INSERT REASONING HERE>\n';
+    // This is to give plugins a chance to update message
+    this._message = this._modifyRevertMsg(change, commitMessage, message);
+    this._revertType = REVERT_TYPES.REVERT_SINGLE_CHANGE;
+    this._showRevertSubmission = false;
+    this._revertMessages[this._revertType] = this._message;
+    this._originalRevertMessages[this._revertType] = this._message;
+  }
+
+  _getTrimmedChangeSubject(subject: string) {
+    if (!subject) return '';
+    if (subject.length < CHANGE_SUBJECT_LIMIT) return subject;
+    return subject.substring(0, CHANGE_SUBJECT_LIMIT) + '...';
+  }
+
+  _modifyRevertSubmissionMsg(
+    change: ChangeInfo,
+    msg: string,
+    commitMessage: string
+  ) {
+    return this.$.jsAPI.modifyRevertSubmissionMsg(change, msg, commitMessage);
+  }
+
+  _populateRevertSubmissionMessage(
+    change: ChangeInfo,
+    changes: ChangeInfo[],
+    commitMessage: string
+  ) {
+    // Follow the same convention of the revert
+    const commitHash = change.current_revision;
+    if (!commitHash) {
+      this.dispatchEvent(
+        new CustomEvent('show-alert', {
+          detail: {message: ERR_COMMIT_NOT_FOUND},
+          composed: true,
+          bubbles: true,
+        })
+      );
+      return;
+    }
+    if (!changes || changes.length <= 1) return;
+    const revertTitle = `Revert submission ${change.submission_id}`;
+    let message =
+      revertTitle +
+      '\n\n' +
+      'Reason for revert: <INSERT ' +
+      'REASONING HERE>\n';
+    message += 'Reverted Changes:\n';
+    changes.forEach(change => {
+      message +=
+        `${change.change_id.substring(0, 10)}:` +
+        `${this._getTrimmedChangeSubject(change.subject)}\n`;
+    });
+    this._message = this._modifyRevertSubmissionMsg(
+      change,
+      message,
+      commitMessage
+    );
+    this._revertType = REVERT_TYPES.REVERT_SUBMISSION;
+    this._revertMessages[this._revertType] = this._message;
+    this._originalRevertMessages[this._revertType] = this._message;
+    this._showRevertSubmission = true;
+  }
+
+  _handleRevertSingleChangeClicked() {
+    this._showErrorMessage = false;
+    if (this._message)
+      this._revertMessages[REVERT_TYPES.REVERT_SUBMISSION] = this._message;
+    this._message = this._revertMessages[REVERT_TYPES.REVERT_SINGLE_CHANGE];
+    this._revertType = REVERT_TYPES.REVERT_SINGLE_CHANGE;
+  }
+
+  _handleRevertSubmissionClicked() {
+    this._showErrorMessage = false;
+    this._revertType = REVERT_TYPES.REVERT_SUBMISSION;
+    if (this._message)
+      this._revertMessages[REVERT_TYPES.REVERT_SINGLE_CHANGE] = this._message;
+    this._message = this._revertMessages[REVERT_TYPES.REVERT_SUBMISSION];
+  }
+
+  _handleConfirmTap(e: MouseEvent) {
+    e.preventDefault();
+    e.stopPropagation();
+    if (this._message === this._originalRevertMessages[this._revertType]) {
+      this._showErrorMessage = true;
+      return;
+    }
+    this.dispatchEvent(
+      new CustomEvent('confirm', {
+        detail: {revertType: this._revertType, message: this._message},
+        composed: true,
+        bubbles: false,
+      })
+    );
+  }
+
+  _handleCancelTap(e: MouseEvent) {
+    e.preventDefault();
+    e.stopPropagation();
+    this.dispatchEvent(
+      new CustomEvent('cancel', {
+        detail: {revertType: this._revertType},
+        composed: true,
+        bubbles: false,
+      })
+    );
+  }
+}
+
+declare global {
+  interface HTMLElementTagNameMap {
+    'gr-confirm-revert-dialog': GrConfirmRevertDialog;
+  }
+}
diff --git a/polygerrit-ui/app/elements/change/gr-confirm-submit-dialog/gr-confirm-submit-dialog.js b/polygerrit-ui/app/elements/change/gr-confirm-submit-dialog/gr-confirm-submit-dialog.js
deleted file mode 100644
index 42afcc2..0000000
--- a/polygerrit-ui/app/elements/change/gr-confirm-submit-dialog/gr-confirm-submit-dialog.js
+++ /dev/null
@@ -1,92 +0,0 @@
-/**
- * @license
- * Copyright (C) 2018 The Android Open Source Project
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-import '@polymer/iron-icon/iron-icon.js';
-import '../../shared/gr-icons/gr-icons.js';
-import '../../shared/gr-dialog/gr-dialog.js';
-import '../../shared/gr-rest-api-interface/gr-rest-api-interface.js';
-import '../../plugins/gr-endpoint-decorator/gr-endpoint-decorator.js';
-import '../../plugins/gr-endpoint-param/gr-endpoint-param.js';
-import '../../../styles/shared-styles.js';
-import {GestureEventListeners} from '@polymer/polymer/lib/mixins/gesture-event-listeners.js';
-import {LegacyElementMixin} from '@polymer/polymer/lib/legacy/legacy-element-mixin.js';
-import {PolymerElement} from '@polymer/polymer/polymer-element.js';
-import {htmlTemplate} from './gr-confirm-submit-dialog_html.js';
-
-/** @extends PolymerElement */
-class GrConfirmSubmitDialog extends GestureEventListeners(
-    LegacyElementMixin(
-        PolymerElement)) {
-  static get template() { return htmlTemplate; }
-
-  static get is() { return 'gr-confirm-submit-dialog'; }
-  /**
-   * Fired when the confirm button is pressed.
-   *
-   * @event confirm
-   */
-
-  /**
-   * Fired when the cancel button is pressed.
-   *
-   * @event cancel
-   */
-
-  static get properties() {
-    return {
-      /**
-       * @type {Gerrit.Change}
-       */
-      change: Object,
-
-      /**
-       * @type {{
-       *    label: string,
-       *  }}
-       */
-      action: Object,
-    };
-  }
-
-  resetFocus(e) {
-    this.$.dialog.resetFocus();
-  }
-
-  _computeHasChangeEdit(change) {
-    return !!change.revisions &&
-        Object.values(change.revisions).some(rev => rev._number == 'edit');
-  }
-
-  _computeUnresolvedCommentsWarning(change) {
-    const unresolvedCount = change.unresolved_comment_count;
-    const plural = unresolvedCount > 1 ? 's' : '';
-    return `Heads Up! ${unresolvedCount} unresolved comment${plural}.`;
-  }
-
-  _handleConfirmTap(e) {
-    e.preventDefault();
-    e.stopPropagation();
-    this.dispatchEvent(new CustomEvent('confirm', {bubbles: false}));
-  }
-
-  _handleCancelTap(e) {
-    e.preventDefault();
-    e.stopPropagation();
-    this.dispatchEvent(new CustomEvent('cancel', {bubbles: false}));
-  }
-}
-
-customElements.define(GrConfirmSubmitDialog.is, GrConfirmSubmitDialog);
diff --git a/polygerrit-ui/app/elements/change/gr-confirm-submit-dialog/gr-confirm-submit-dialog.ts b/polygerrit-ui/app/elements/change/gr-confirm-submit-dialog/gr-confirm-submit-dialog.ts
new file mode 100644
index 0000000..666f95d
--- /dev/null
+++ b/polygerrit-ui/app/elements/change/gr-confirm-submit-dialog/gr-confirm-submit-dialog.ts
@@ -0,0 +1,98 @@
+/**
+ * @license
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+import '@polymer/iron-icon/iron-icon';
+import '../../shared/gr-icons/gr-icons';
+import '../../shared/gr-dialog/gr-dialog';
+import '../../shared/gr-rest-api-interface/gr-rest-api-interface';
+import '../../plugins/gr-endpoint-decorator/gr-endpoint-decorator';
+import '../../plugins/gr-endpoint-param/gr-endpoint-param';
+import '../../../styles/shared-styles';
+import {GestureEventListeners} from '@polymer/polymer/lib/mixins/gesture-event-listeners';
+import {LegacyElementMixin} from '@polymer/polymer/lib/legacy/legacy-element-mixin';
+import {PolymerElement} from '@polymer/polymer/polymer-element';
+import {htmlTemplate} from './gr-confirm-submit-dialog_html';
+import {customElement, property} from '@polymer/decorators';
+import {ChangeInfo, ActionInfo} from '../../../types/common';
+import {GrDialog} from '../../shared/gr-dialog/gr-dialog';
+
+export interface GrConfirmSubmitDialog {
+  $: {
+    dialog: GrDialog;
+  };
+}
+@customElement('gr-confirm-submit-dialog')
+export class GrConfirmSubmitDialog extends GestureEventListeners(
+  LegacyElementMixin(PolymerElement)
+) {
+  static get template() {
+    return htmlTemplate;
+  }
+
+  /**
+   * Fired when the confirm button is pressed.
+   *
+   * @event confirm
+   */
+
+  /**
+   * Fired when the cancel button is pressed.
+   *
+   * @event cancel
+   */
+
+  @property({type: Object})
+  change?: ChangeInfo;
+
+  @property({type: Object})
+  action?: ActionInfo;
+
+  resetFocus() {
+    this.$.dialog.resetFocus();
+  }
+
+  _computeHasChangeEdit(change?: ChangeInfo) {
+    return (
+      !!change &&
+      !!change.revisions &&
+      Object.values(change.revisions).some(rev => rev._number === 'edit')
+    );
+  }
+
+  _computeUnresolvedCommentsWarning(change: ChangeInfo) {
+    const unresolvedCount = change.unresolved_comment_count;
+    const plural = unresolvedCount && unresolvedCount > 1 ? 's' : '';
+    return `Heads Up! ${unresolvedCount} unresolved comment${plural}.`;
+  }
+
+  _handleConfirmTap(e: MouseEvent) {
+    e.preventDefault();
+    e.stopPropagation();
+    this.dispatchEvent(new CustomEvent('confirm', {bubbles: false}));
+  }
+
+  _handleCancelTap(e: MouseEvent) {
+    e.preventDefault();
+    e.stopPropagation();
+    this.dispatchEvent(new CustomEvent('cancel', {bubbles: false}));
+  }
+}
+
+declare global {
+  interface HTMLElementTagNameMap {
+    'gr-confirm-submit-dialog': GrConfirmSubmitDialog;
+  }
+}
diff --git a/polygerrit-ui/app/elements/change/gr-reply-dialog/gr-reply-dialog.js b/polygerrit-ui/app/elements/change/gr-reply-dialog/gr-reply-dialog.js
index 6ecdabb..630681c 100644
--- a/polygerrit-ui/app/elements/change/gr-reply-dialog/gr-reply-dialog.js
+++ b/polygerrit-ui/app/elements/change/gr-reply-dialog/gr-reply-dialog.js
@@ -540,7 +540,7 @@
     if (reviewer.account) {
       reviewerId = reviewer.account._account_id || reviewer.account.email;
     } else if (reviewer.group) {
-      reviewerId = reviewer.group.id;
+      reviewerId = decodeURIComponent(reviewer.group.id);
       confirmed = reviewer.group.confirmed;
     }
     return {reviewer: reviewerId, confirmed};
diff --git a/polygerrit-ui/app/elements/change/gr-reviewer-list/gr-reviewer-list.js b/polygerrit-ui/app/elements/change/gr-reviewer-list/gr-reviewer-list.js
deleted file mode 100644
index 174bbbb..0000000
--- a/polygerrit-ui/app/elements/change/gr-reviewer-list/gr-reviewer-list.js
+++ /dev/null
@@ -1,303 +0,0 @@
-/**
- * @license
- * Copyright (C) 2015 The Android Open Source Project
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-import '../../shared/gr-account-chip/gr-account-chip.js';
-import '../../shared/gr-button/gr-button.js';
-import '../../shared/gr-rest-api-interface/gr-rest-api-interface.js';
-import '../../../styles/shared-styles.js';
-import {dom} from '@polymer/polymer/lib/legacy/polymer.dom.js';
-import {GestureEventListeners} from '@polymer/polymer/lib/mixins/gesture-event-listeners.js';
-import {LegacyElementMixin} from '@polymer/polymer/lib/legacy/legacy-element-mixin.js';
-import {PolymerElement} from '@polymer/polymer/polymer-element.js';
-import {htmlTemplate} from './gr-reviewer-list_html.js';
-import {
-  hasAttention,
-  isServiceUser,
-} from '../../../utils/account-util.js';
-
-/**
- * @extends PolymerElement
- */
-class GrReviewerList extends GestureEventListeners(
-    LegacyElementMixin(PolymerElement)) {
-  static get template() { return htmlTemplate; }
-
-  static get is() { return 'gr-reviewer-list'; }
-  /**
-   * Fired when the "Add reviewer..." button is tapped.
-   *
-   * @event show-reply-dialog
-   */
-
-  static get properties() {
-    return {
-      change: Object,
-      serverConfig: Object,
-      disabled: {
-        type: Boolean,
-        value: false,
-        reflectToAttribute: true,
-      },
-      mutable: {
-        type: Boolean,
-        value: false,
-      },
-      reviewersOnly: {
-        type: Boolean,
-        value: false,
-      },
-      ccsOnly: {
-        type: Boolean,
-        value: false,
-      },
-
-      _displayedReviewers: {
-        type: Array,
-        value() { return []; },
-      },
-      _reviewers: {
-        type: Array,
-        value() { return []; },
-      },
-      _showInput: {
-        type: Boolean,
-        value: false,
-      },
-      _addLabel: {
-        type: String,
-        computed: '_computeAddLabel(ccsOnly)',
-      },
-      _hiddenReviewerCount: {
-        type: Number,
-        computed: '_computeHiddenCount(_reviewers, _displayedReviewers)',
-      },
-
-      // Used for testing.
-      _lastAutocompleteRequest: Object,
-      _xhrPromise: Object,
-    };
-  }
-
-  static get observers() {
-    return [
-      '_reviewersChanged(change.reviewers.*, change.owner, serverConfig)',
-    ];
-  }
-
-  /**
-   * Converts change.permitted_labels to an array of hashes of label keys to
-   * numeric scores.
-   * Example:
-   * [{
-   *   'Code-Review': ['-1', ' 0', '+1']
-   * }]
-   * will be converted to
-   * [{
-   *   label: 'Code-Review',
-   *   scores: [-1, 0, 1]
-   * }]
-   */
-  _permittedLabelsToNumericScores(labels) {
-    if (!labels) return [];
-    return Object.keys(labels).map(label => {
-      return {
-        label,
-        scores: labels[label].map(v => parseInt(v, 10)),
-      };
-    });
-  }
-
-  /**
-   * Returns hash of labels to max permitted score.
-   *
-   * @param {!Object} change
-   * @returns {!Object} labels to max permitted scores hash
-   */
-  _getMaxPermittedScores(change) {
-    return this._permittedLabelsToNumericScores(change.permitted_labels)
-        .map(({label, scores}) => {
-          return {
-            [label]: scores
-                .map(v => parseInt(v, 10))
-                .reduce((a, b) => Math.max(a, b))};
-        })
-        .reduce((acc, i) => Object.assign(acc, i), {});
-  }
-
-  /**
-   * Returns max permitted score for reviewer.
-   *
-   * @param {!Object} reviewer
-   * @param {!Object} change
-   * @param {string} label
-   * @return {number}
-   */
-  _getReviewerPermittedScore(reviewer, change, label) {
-    // Note (issue 7874): sometimes the "all" list is not included in change
-    // detail responses, even when DETAILED_LABELS is included in options.
-    if (!change.labels[label].all) { return NaN; }
-    const detailed = change.labels[label].all.filter(
-        ({_account_id}) => reviewer._account_id === _account_id).pop();
-    if (!detailed) {
-      return NaN;
-    }
-    if (detailed.hasOwnProperty('permitted_voting_range')) {
-      return detailed.permitted_voting_range.max;
-    } else if (detailed.hasOwnProperty('value')) {
-      // If preset, user can vote on the label.
-      return 0;
-    }
-    return NaN;
-  }
-
-  _computeVoteableText(reviewer, change) {
-    if (!change || !change.labels) { return ''; }
-    const maxScores = [];
-    const maxPermitted = this._getMaxPermittedScores(change);
-    for (const label of Object.keys(change.labels)) {
-      const maxScore =
-            this._getReviewerPermittedScore(reviewer, change, label);
-      if (isNaN(maxScore) || maxScore < 0) { continue; }
-      if (maxScore > 0 && maxScore === maxPermitted[label]) {
-        maxScores.push(`${label}: +${maxScore}`);
-      } else {
-        maxScores.push(`${label}`);
-      }
-    }
-    return maxScores.join(', ');
-  }
-
-  _reviewersChanged(changeRecord, owner, serverConfig) {
-    // Polymer 2: check for undefined
-    if ([changeRecord, owner, serverConfig].includes(undefined)) {
-      return;
-    }
-
-    let result = [];
-    const reviewers = changeRecord.base;
-    for (const key in reviewers) {
-      if (this.reviewersOnly && key !== 'REVIEWER') {
-        continue;
-      }
-      if (this.ccsOnly && key !== 'CC') {
-        continue;
-      }
-      if (key === 'REVIEWER' || key === 'CC') {
-        result = result.concat(reviewers[key]);
-      }
-    }
-    this._reviewers = result
-        .filter(reviewer => reviewer._account_id != owner._account_id)
-        // Sort order:
-        // 1. Human users in the attention set.
-        // 2. Other human users.
-        // 3. Service users.
-        .sort((r1, r2) => {
-          const a1 = hasAttention(serverConfig, r1, this.change) ? 1 : 0;
-          const a2 = hasAttention(serverConfig, r2, this.change) ? 1 : 0;
-          const s1 = isServiceUser(r1) ? -2 : 0;
-          const s2 = isServiceUser(r2) ? -2 : 0;
-          return a2 - a1 + s2 - s1;
-        });
-
-    if (this._reviewers.length > 8) {
-      this._displayedReviewers = this._reviewers.slice(0, 6);
-    } else {
-      this._displayedReviewers = this._reviewers;
-    }
-  }
-
-  _computeHiddenCount(reviewers, displayedReviewers) {
-    // Polymer 2: check for undefined
-    if ([reviewers, displayedReviewers].includes(undefined)) {
-      return undefined;
-    }
-
-    return reviewers.length - displayedReviewers.length;
-  }
-
-  _computeCanRemoveReviewer(reviewer, mutable) {
-    if (!mutable) { return false; }
-
-    let current;
-    for (let i = 0; i < this.change.removable_reviewers.length; i++) {
-      current = this.change.removable_reviewers[i];
-      if (current._account_id === reviewer._account_id ||
-          (!reviewer._account_id && current.email === reviewer.email)) {
-        return true;
-      }
-    }
-    return false;
-  }
-
-  _handleRemove(e) {
-    e.preventDefault();
-    const target = dom(e).rootTarget;
-    if (!target.account) { return; }
-    const accountID = target.account._account_id || target.account.email;
-    this.disabled = true;
-    this._xhrPromise = this._removeReviewer(accountID).then(response => {
-      this.disabled = false;
-      if (!response.ok) { return response; }
-
-      const reviewers = this.change.reviewers;
-
-      for (const type of ['REVIEWER', 'CC']) {
-        reviewers[type] = reviewers[type] || [];
-        for (let i = 0; i < reviewers[type].length; i++) {
-          if (reviewers[type][i]._account_id == accountID ||
-          reviewers[type][i].email == accountID) {
-            this.splice('change.reviewers.' + type, i, 1);
-            break;
-          }
-        }
-      }
-    })
-        .catch(err => {
-          this.disabled = false;
-          throw err;
-        });
-  }
-
-  _handleAddTap(e) {
-    e.preventDefault();
-    const value = {};
-    if (this.reviewersOnly) {
-      value.reviewersOnly = true;
-    }
-    if (this.ccsOnly) {
-      value.ccsOnly = true;
-    }
-    this.dispatchEvent(new CustomEvent('show-reply-dialog', {
-      detail: {value},
-      composed: true, bubbles: true,
-    }));
-  }
-
-  _handleViewAll(e) {
-    this._displayedReviewers = this._reviewers;
-  }
-
-  _removeReviewer(id) {
-    return this.$.restAPI.removeChangeReviewer(this.change._number, id);
-  }
-
-  _computeAddLabel(ccsOnly) {
-    return ccsOnly ? 'Add CC' : 'Add reviewer';
-  }
-}
-
-customElements.define(GrReviewerList.is, GrReviewerList);
diff --git a/polygerrit-ui/app/elements/change/gr-reviewer-list/gr-reviewer-list.ts b/polygerrit-ui/app/elements/change/gr-reviewer-list/gr-reviewer-list.ts
new file mode 100644
index 0000000..70e7ba7
--- /dev/null
+++ b/polygerrit-ui/app/elements/change/gr-reviewer-list/gr-reviewer-list.ts
@@ -0,0 +1,339 @@
+/**
+ * @license
+ * Copyright (C) 2015 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+import '../../shared/gr-account-chip/gr-account-chip';
+import '../../shared/gr-button/gr-button';
+import '../../shared/gr-rest-api-interface/gr-rest-api-interface';
+import '../../../styles/shared-styles';
+import {dom, EventApi} from '@polymer/polymer/lib/legacy/polymer.dom';
+import {GestureEventListeners} from '@polymer/polymer/lib/mixins/gesture-event-listeners';
+import {LegacyElementMixin} from '@polymer/polymer/lib/legacy/legacy-element-mixin';
+import {PolymerElement} from '@polymer/polymer/polymer-element';
+import {htmlTemplate} from './gr-reviewer-list_html';
+import {hasAttention, isServiceUser} from '../../../utils/account-util';
+import {customElement, property, computed, observe} from '@polymer/decorators';
+import {
+  ChangeInfo,
+  ServerInfo,
+  LabelNameToValueMap,
+  AccountInfo,
+  ApprovalInfo,
+  Reviewers,
+  AccountId,
+  DetailedLabelInfo,
+} from '../../../types/common';
+import {PolymerDeepPropertyChange} from '@polymer/polymer/interfaces';
+import {GrAccountChip} from '../../shared/gr-account-chip/gr-account-chip';
+import {RestApiService} from '../../../services/services/gr-rest-api/gr-rest-api';
+import {hasOwnProperty} from '../../../utils/common-util';
+
+export interface GrReviewerList {
+  $: {
+    restAPI: RestApiService & Element;
+  };
+}
+
+@customElement('gr-reviewer-list')
+export class GrReviewerList extends GestureEventListeners(
+  LegacyElementMixin(PolymerElement)
+) {
+  static get template() {
+    return htmlTemplate;
+  }
+
+  /**
+   * Fired when the "Add reviewer..." button is tapped.
+   *
+   * @event show-reply-dialog
+   */
+
+  @property({type: Object})
+  change?: ChangeInfo;
+
+  @property({type: Object})
+  serverConfig?: ServerInfo;
+
+  @property({type: Boolean, reflectToAttribute: true})
+  disabled = false;
+
+  @property({type: Boolean})
+  mutable = false;
+
+  @property({type: Boolean})
+  reviewersOnly = false;
+
+  @property({type: Boolean})
+  ccsOnly = false;
+
+  @property({type: Array})
+  _displayedReviewers: AccountInfo[] = [];
+
+  @property({type: Array})
+  _reviewers: AccountInfo[] = [];
+
+  @property({type: Boolean})
+  _showInput = false;
+
+  @property({type: Object})
+  _xhrPromise?: Promise<Response | undefined>;
+
+  @computed('ccsOnly')
+  get _addLabel() {
+    return this.ccsOnly ? 'Add CC' : 'Add reviewer';
+  }
+
+  @computed('_reviewers', '_displayedReviewers')
+  get _hiddenReviewerCount() {
+    // Polymer 2: check for undefined
+    if (
+      this._reviewers === undefined ||
+      this._displayedReviewers === undefined
+    ) {
+      return undefined;
+    }
+    return this._reviewers.length - this._displayedReviewers.length;
+  }
+
+  /**
+   * Converts change.permitted_labels to an array of hashes of label keys to
+   * numeric scores.
+   * Example:
+   * [{
+   *   'Code-Review': ['-1', ' 0', '+1']
+   * }]
+   * will be converted to
+   * [{
+   *   label: 'Code-Review',
+   *   scores: [-1, 0, 1]
+   * }]
+   */
+  _permittedLabelsToNumericScores(labels: LabelNameToValueMap | undefined) {
+    if (!labels) return [];
+    return Object.keys(labels).map(label => {
+      return {
+        label,
+        scores: labels[label].map(v => parseInt(v, 10)),
+      };
+    });
+  }
+
+  /**
+   * Returns hash of labels to max permitted score.
+   *
+   * @returns labels to max permitted scores hash
+   */
+  _getMaxPermittedScores(change: ChangeInfo) {
+    return this._permittedLabelsToNumericScores(change.permitted_labels)
+      .map(({label, scores}) => {
+        return {
+          [label]: scores.reduce((a, b) => Math.max(a, b)),
+        };
+      })
+      .reduce((acc, i) => Object.assign(acc, i), {});
+  }
+
+  /**
+   * Returns max permitted score for reviewer.
+   */
+  _getReviewerPermittedScore(
+    reviewer: AccountInfo,
+    change: ChangeInfo,
+    label: string
+  ) {
+    // Note (issue 7874): sometimes the "all" list is not included in change
+    // detail responses, even when DETAILED_LABELS is included in options.
+    if (!change.labels) {
+      return NaN;
+    }
+    const detailedLabel = change.labels[label] as DetailedLabelInfo;
+    if (!detailedLabel.all) {
+      return NaN;
+    }
+    const detailed = detailedLabel.all
+      .filter(
+        (approval: ApprovalInfo) =>
+          reviewer._account_id === approval._account_id
+      )
+      .pop();
+    if (!detailed) {
+      return NaN;
+    }
+    if (hasOwnProperty(detailed, 'permitted_voting_range')) {
+      if (!detailed.permitted_voting_range) return NaN;
+      return detailed.permitted_voting_range.max;
+    } else if (hasOwnProperty(detailed, 'value')) {
+      // If preset, user can vote on the label.
+      return 0;
+    }
+    return NaN;
+  }
+
+  _computeVoteableText(reviewer: AccountInfo, change: ChangeInfo) {
+    if (!change || !change.labels) {
+      return '';
+    }
+    const maxScores = [];
+    const maxPermitted = this._getMaxPermittedScores(change);
+    for (const label of Object.keys(change.labels)) {
+      const maxScore = this._getReviewerPermittedScore(reviewer, change, label);
+      if (isNaN(maxScore) || maxScore < 0) {
+        continue;
+      }
+      if (maxScore > 0 && maxScore === maxPermitted[label]) {
+        maxScores.push(`${label}: +${maxScore}`);
+      } else {
+        maxScores.push(`${label}`);
+      }
+    }
+    return maxScores.join(', ');
+  }
+
+  @observe('change.reviewers.*', 'change.owner', 'serverConfig')
+  _reviewersChanged(
+    changeRecord: PolymerDeepPropertyChange<Reviewers, Reviewers>,
+    owner: AccountInfo,
+    serverConfig: ServerInfo
+  ) {
+    // Polymer 2: check for undefined
+    if (
+      changeRecord === undefined ||
+      owner === undefined ||
+      serverConfig === undefined ||
+      this.change === undefined
+    ) {
+      return;
+    }
+    let result: AccountInfo[] = [];
+    const reviewers = changeRecord.base;
+    for (const key in reviewers) {
+      if (this.reviewersOnly && key !== 'REVIEWER') {
+        continue;
+      }
+      if (this.ccsOnly && key !== 'CC') {
+        continue;
+      }
+      if (key === 'REVIEWER' || key === 'CC') {
+        result = result.concat(reviewers[key]!);
+      }
+    }
+    this._reviewers = result
+      .filter(reviewer => reviewer._account_id !== owner._account_id)
+      // Sort order:
+      // 1. Human users in the attention set.
+      // 2. Other human users.
+      // 3. Service users.
+      .sort((r1, r2) => {
+        const a1 = hasAttention(serverConfig, r1, this.change!) ? 1 : 0;
+        const a2 = hasAttention(serverConfig, r2, this.change!) ? 1 : 0;
+        const s1 = isServiceUser(r1) ? -2 : 0;
+        const s2 = isServiceUser(r2) ? -2 : 0;
+        return a2 - a1 + s2 - s1;
+      });
+
+    if (this._reviewers.length > 8) {
+      this._displayedReviewers = this._reviewers.slice(0, 6);
+    } else {
+      this._displayedReviewers = this._reviewers;
+    }
+  }
+
+  _computeCanRemoveReviewer(reviewer: AccountInfo, mutable: boolean) {
+    if (
+      !mutable ||
+      this.change === undefined ||
+      this.change.removable_reviewers === undefined
+    ) {
+      return false;
+    }
+
+    let current;
+    for (let i = 0; i < this.change.removable_reviewers.length; i++) {
+      current = this.change.removable_reviewers[i];
+      if (
+        current._account_id === reviewer._account_id ||
+        (!reviewer._account_id && current.email === reviewer.email)
+      ) {
+        return true;
+      }
+    }
+    return false;
+  }
+
+  _handleRemove(e: Event) {
+    e.preventDefault();
+    const target = (dom(e) as EventApi).rootTarget as GrAccountChip;
+    if (!target.account || !this.change) {
+      return;
+    }
+    const accountID = target.account._account_id;
+    this.disabled = true;
+    if (!accountID) return;
+    this._xhrPromise = this._removeReviewer(accountID)
+      .then((response: Response | undefined) => {
+        this.disabled = false;
+        if (!response || !response.ok) {
+          return response;
+        }
+        if (!this.change || !this.change.reviewers) return;
+        const reviewers: {[type: string]: AccountInfo[] | undefined} = this
+          .change!.reviewers;
+        for (const type of ['REVIEWER', 'CC']) {
+          reviewers[type] = reviewers[type] || [];
+          for (let i = 0; i < reviewers[type]!.length; i++) {
+            if (reviewers[type]![i]._account_id === accountID) {
+              this.splice('change.reviewers.' + type, i, 1);
+              break;
+            }
+          }
+        }
+        return;
+      })
+      .catch((err: Error) => {
+        this.disabled = false;
+        throw err;
+      });
+  }
+
+  _handleAddTap(e: Event) {
+    e.preventDefault();
+    const value = {
+      reviewersOnly: false,
+      ccsOnly: false,
+    };
+    if (this.reviewersOnly) {
+      value.reviewersOnly = true;
+    }
+    if (this.ccsOnly) {
+      value.ccsOnly = true;
+    }
+    this.dispatchEvent(
+      new CustomEvent('show-reply-dialog', {
+        detail: {value},
+        composed: true,
+        bubbles: true,
+      })
+    );
+  }
+
+  _handleViewAll() {
+    this._displayedReviewers = this._reviewers;
+  }
+
+  _removeReviewer(id: AccountId): Promise<Response | undefined> {
+    if (!this.change) return Promise.resolve(undefined);
+    return this.$.restAPI.removeChangeReviewer(this.change._number, id);
+  }
+}
diff --git a/polygerrit-ui/app/elements/change/gr-reviewer-list/gr-reviewer-list_test.js b/polygerrit-ui/app/elements/change/gr-reviewer-list/gr-reviewer-list_test.js
index 521945f..834cc43 100644
--- a/polygerrit-ui/app/elements/change/gr-reviewer-list/gr-reviewer-list_test.js
+++ b/polygerrit-ui/app/elements/change/gr-reviewer-list/gr-reviewer-list_test.js
@@ -163,21 +163,24 @@
     element.reviewersOnly = false;
     element._handleAddTap(e);
     assert.equal(fireStub.lastCall.args[0].type, 'show-reply-dialog');
-    assert.deepEqual(fireStub.lastCall.args[0].detail, {value: {}});
+    assert.deepEqual(fireStub.lastCall.args[0].detail, {value: {
+      reviewersOnly: false,
+      ccsOnly: false,
+    }});
 
     element.reviewersOnly = true;
     element._handleAddTap(e);
     assert.equal(fireStub.lastCall.args[0].type, 'show-reply-dialog');
     assert.deepEqual(
         fireStub.lastCall.args[0].detail,
-        {value: {reviewersOnly: true}});
+        {value: {reviewersOnly: true, ccsOnly: false}});
 
     element.ccsOnly = true;
     element.reviewersOnly = false;
     element._handleAddTap(e);
     assert.equal(fireStub.lastCall.args[0].type, 'show-reply-dialog');
     assert.deepEqual(fireStub.lastCall.args[0].detail,
-        {value: {ccsOnly: true}});
+        {value: {ccsOnly: true, reviewersOnly: false}});
   });
 
   test('dont show all reviewers button with 4 reviewers', () => {
diff --git a/polygerrit-ui/app/elements/core/gr-router/gr-router.ts b/polygerrit-ui/app/elements/core/gr-router/gr-router.ts
index 6f1bc60..aa2e4ce 100644
--- a/polygerrit-ui/app/elements/core/gr-router/gr-router.ts
+++ b/polygerrit-ui/app/elements/core/gr-router/gr-router.ts
@@ -72,6 +72,7 @@
   DASHBOARD: /^\/dashboard\/(.+)$/,
   CUSTOM_DASHBOARD: /^\/dashboard\/?$/,
   PROJECT_DASHBOARD: /^\/p\/(.+)\/\+\/dashboard\/(.+)/,
+  LEGACY_PROJECT_DASHBOARD: /^\/projects\/(.+),dashboards\/(.+)/,
 
   AGREEMENTS: /^\/settings\/agreements\/?/,
   NEW_AGREEMENTS: /^\/settings\/new-agreement\/?/,
@@ -880,6 +881,11 @@
       '_handleProjectDashboardRoute'
     );
 
+    this._mapRoute(
+      RoutePattern.LEGACY_PROJECT_DASHBOARD,
+      '_handleLegacyProjectDashboardRoute'
+    );
+
     this._mapRoute(RoutePattern.GROUP_INFO, '_handleGroupInfoRoute', true);
 
     this._mapRoute(
@@ -1255,6 +1261,10 @@
     this.reporting.setRepoName(project);
   }
 
+  _handleLegacyProjectDashboardRoute(data: PageContextWithQueryMap) {
+    this._redirect('/p/' + data.params[0] + '/+/dashboard/' + data.params[1]);
+  }
+
   _handleGroupInfoRoute(data: PageContextWithQueryMap) {
     this._redirect('/admin/groups/' + encodeURIComponent(data.params[0]));
   }
diff --git a/polygerrit-ui/app/elements/core/gr-router/gr-router_test.js b/polygerrit-ui/app/elements/core/gr-router/gr-router_test.js
index 5ee58c9..927434b 100644
--- a/polygerrit-ui/app/elements/core/gr-router/gr-router_test.js
+++ b/polygerrit-ui/app/elements/core/gr-router/gr-router_test.js
@@ -197,6 +197,7 @@
       '_handleImproperlyEncodedPlusRoute',
       '_handlePassThroughRoute',
       '_handleProjectDashboardRoute',
+      '_handleLegacyProjectDashboardRoute',
       '_handleProjectsOldRoute',
       '_handleRepoAccessRoute',
       '_handleRepoDashboardsRoute',
@@ -617,6 +618,14 @@
       handlePassThroughRoute = sinon.stub(element, '_handlePassThroughRoute');
     });
 
+    test('_handleLegacyProjectDashboardRoute', () => {
+      const params = {0: 'gerrit/project', 1: 'dashboard:main'};
+      element._handleLegacyProjectDashboardRoute({params});
+      assert.isTrue(redirectStub.calledOnce);
+      assert.equal(redirectStub.lastCall.args[0],
+          '/p/gerrit/project/+/dashboard/dashboard:main');
+    });
+
     test('_handleAgreementsRoute', () => {
       const data = {params: {}};
       element._handleAgreementsRoute(data);
diff --git a/polygerrit-ui/app/elements/diff/gr-diff/gr-diff.ts b/polygerrit-ui/app/elements/diff/gr-diff/gr-diff.ts
index 2502e45..8ac47a2 100644
--- a/polygerrit-ui/app/elements/diff/gr-diff/gr-diff.ts
+++ b/polygerrit-ui/app/elements/diff/gr-diff/gr-diff.ts
@@ -347,7 +347,7 @@
     // document.getSelection() cannot reference the actual DOM elements making
     // up the diff, because they are in the shadow DOM of the gr-diff element.
     // This takes the shadow DOM selection if one exists.
-    return this.root instanceof ShadowRoot
+    return this.root instanceof ShadowRoot && this.root.getSelection
       ? this.root.getSelection()
       : document.getSelection();
   }
@@ -561,7 +561,13 @@
       );
       return;
     }
-    this._createComment(el, lineNum);
+
+    // TODO(TS): existing logic always pass undefined lineNum
+    // for file level comment, the drafts API will reject the
+    // request if file level draft contains the `line: 'FILE'` field
+    // probably should do this inside of the _createComment, this
+    // is just to keep existing behavior.
+    this._createComment(el, lineNum === FILE ? undefined : lineNum);
   }
 
   createRangeComment() {
@@ -644,7 +650,7 @@
 
   _createComment(
     lineEl: Element,
-    lineNum: LineNumber,
+    lineNum?: LineNumber,
     side?: Side,
     range?: CommentRange
   ) {
diff --git a/polygerrit-ui/app/elements/settings/gr-account-info/gr-account-info.ts b/polygerrit-ui/app/elements/settings/gr-account-info/gr-account-info.ts
index e4cf3a1..d970b0a 100644
--- a/polygerrit-ui/app/elements/settings/gr-account-info/gr-account-info.ts
+++ b/polygerrit-ui/app/elements/settings/gr-account-info/gr-account-info.ts
@@ -164,25 +164,30 @@
   }
 
   _maybeSetName() {
+    // Note that we are intentionally not acting on this._account.name being the
+    // empty string (which is falsy).
     return this._hasNameChange && this.nameMutable && this._account?.name
       ? this.$.restAPI.setAccountName(this._account.name)
       : Promise.resolve();
   }
 
   _maybeSetUsername() {
+    // Note that we are intentionally not acting on this._username being the
+    // empty string (which is falsy).
     return this._hasUsernameChange && this.usernameMutable && this._username
       ? this.$.restAPI.setAccountUsername(this._username)
       : Promise.resolve();
   }
 
   _maybeSetDisplayName() {
-    return this._hasDisplayNameChange && this._account?.display_name
+    return this._hasDisplayNameChange &&
+      this._account?.display_name !== undefined
       ? this.$.restAPI.setAccountDisplayName(this._account.display_name)
       : Promise.resolve();
   }
 
   _maybeSetStatus() {
-    return this._hasStatusChange && this._account?.status
+    return this._hasStatusChange && this._account?.status !== undefined
       ? this.$.restAPI.setAccountStatus(this._account.status)
       : Promise.resolve();
   }
diff --git a/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-js-api-types.ts b/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-js-api-types.ts
index 7455cad..0a5dbc9 100644
--- a/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-js-api-types.ts
+++ b/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-js-api-types.ts
@@ -39,5 +39,10 @@
     origMsg: string
   ): string;
   handleEvent(eventName: EventType, detail: any): void;
+  modifyRevertMsg(
+    change: ChangeInfo,
+    revertMsg: string,
+    origMsg: string
+  ): string;
   // TODO(TS): Add more methods when needed for the TS conversion.
 }
diff --git a/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-reporting-js-api.ts b/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-reporting-js-api.ts
index ddf4c21..0bf6676 100644
--- a/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-reporting-js-api.ts
+++ b/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-reporting-js-api.ts
@@ -37,4 +37,11 @@
       details
     );
   }
+
+  reportLifeCycle(eventName: string, details?: EventDetails) {
+    return this.reporting.reportLifeCycle(
+      `${this.plugin.getPluginName()}-${eventName}`,
+      details
+    );
+  }
 }
diff --git a/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-reporting-js-api_test.js b/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-reporting-js-api_test.js
index e05dff3..1229641 100644
--- a/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-reporting-js-api_test.js
+++ b/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-reporting-js-api_test.js
@@ -57,5 +57,19 @@
           {}
       );
     });
+
+    test('redirect reportLifeCycle call to reportingService', () => {
+      sinon.spy(appContext.reportingService, 'reportLifeCycle');
+      reporting.reportLifeCycle('test', {});
+      assert.isTrue(appContext.reportingService.reportLifeCycle.called);
+      assert.equal(
+          appContext.reportingService.reportLifeCycle.lastCall.args[0],
+          'testplugin-test'
+      );
+      assert.deepEqual(
+          appContext.reportingService.reportLifeCycle.lastCall.args[1],
+          {}
+      );
+    });
   });
 });
\ No newline at end of file
diff --git a/polygerrit-ui/app/services/services/gr-rest-api/gr-rest-api.ts b/polygerrit-ui/app/services/services/gr-rest-api/gr-rest-api.ts
index 90112b9..e3c2ce8 100644
--- a/polygerrit-ui/app/services/services/gr-rest-api/gr-rest-api.ts
+++ b/polygerrit-ui/app/services/services/gr-rest-api/gr-rest-api.ts
@@ -605,4 +605,8 @@
     changeNum: ChangeNum,
     messageId: ChangeMessageId
   ): Promise<Response>;
+  removeChangeReviewer(
+    changeNum: ChangeNum,
+    reviewerID: AccountId | GroupId
+  ): Promise<Response | undefined>;
 }
diff --git a/polygerrit-ui/app/types/common.ts b/polygerrit-ui/app/types/common.ts
index e131b4f..0c4bc8b 100644
--- a/polygerrit-ui/app/types/common.ts
+++ b/polygerrit-ui/app/types/common.ts
@@ -142,6 +142,10 @@
  */
 export type LabelInfo = QuickLabelInfo | DetailedLabelInfo;
 
+export type Reviewers = {
+  REVIEWER?: AccountInfo[];
+  CC?: AccountInfo[];
+};
 interface LabelCommonInfo {
   optional?: boolean; // not set if false
 }
@@ -211,10 +215,7 @@
   labels?: LabelNameToInfoMap;
   permitted_labels?: LabelNameToValueMap;
   removable_reviewers?: AccountInfo[];
-  reviewers?: {
-    REVIEWER?: AccountInfo[];
-    CC?: AccountInfo[];
-  };
+  reviewers?: Reviewers;
   pending_reviewers?: AccountInfo[];
   reviewer_updates?: ReviewerUpdateInfo[];
   messages?: ChangeMessageInfo[];