diff --git a/docs/manifest-format.txt b/docs/manifest-format.txt
index da0e69f..211344ee 100644
--- a/docs/manifest-format.txt
+++ b/docs/manifest-format.txt
@@ -22,6 +22,7 @@
   <!DOCTYPE manifest [
     <!ELEMENT manifest (remote*,
                         default?,
+                        manifest-server?,
                         remove-project*,
                         project*)>
   
@@ -33,6 +34,9 @@
     <!ELEMENT default (EMPTY)>
     <!ATTLIST default remote   IDREF #IMPLIED>
     <!ATTLIST default revision CDATA #IMPLIED>
+
+    <!ELEMENT manifest-server (EMPTY)>
+    <!ATTLIST url              CDATA #REQUIRED>
   
     <!ELEMENT project (EMPTY)>
     <!ATTLIST project name     CDATA #REQUIRED>
@@ -89,6 +93,27 @@
 revision attribute will use this revision.
 
 
+Element manifest-server
+-----------------------
+
+At most one manifest-server may be specified. The url attribute
+is used to specify the URL of a manifest server, which is an
+XML RPC service that will return a manifest in which each project
+is pegged to a known good revision for the current branch and
+target.
+
+The manifest server should implement:
+
+  GetApprovedManifest(branch, target)
+
+The target to use is defined by environment variables TARGET_PRODUCT
+and TARGET_BUILD_VARIANT. These variables are used to create a string
+of the form $TARGET_PRODUCT-$TARGET_BUILD_VARIANT, e.g. passion-userdebug.
+If one of those variables or both are not present, the program will call
+GetApprovedManifest without the target paramater and the manifest server
+should choose a reasonable default target.
+
+
 Element project
 ---------------
 
diff --git a/manifest_xml.py b/manifest_xml.py
index 7d02f9d..d0c9deb 100644
--- a/manifest_xml.py
+++ b/manifest_xml.py
@@ -65,8 +65,8 @@
 
     self._Unload()
 
-  def Link(self, name):
-    """Update the repo metadata to use a different manifest.
+  def Override(self, name):
+    """Use a different manifest, just for the current instantiation.
     """
     path = os.path.join(self.manifestProject.worktree, name)
     if not os.path.isfile(path):
@@ -80,6 +80,11 @@
     finally:
       self.manifestFile = old
 
+  def Link(self, name):
+    """Update the repo metadata to use a different manifest.
+    """
+    self.Override(name)
+
     try:
       if os.path.exists(self.manifestFile):
         os.remove(self.manifestFile)
@@ -123,6 +128,12 @@
       root.appendChild(e)
       root.appendChild(doc.createTextNode(''))
 
+    if self._manifest_server:
+      e = doc.createElement('manifest-server')
+      e.setAttribute('url', self._manifest_server)
+      root.appendChild(e)
+      root.appendChild(doc.createTextNode(''))
+
     sort_projects = list(self.projects.keys())
     sort_projects.sort()
 
@@ -169,6 +180,11 @@
     return self._default
 
   @property
+  def manifest_server(self):
+    self._Load()
+    return self._manifest_server
+
+  @property
   def IsMirror(self):
     return self.manifestProject.config.GetBoolean('repo.mirror')
 
@@ -178,6 +194,7 @@
     self._remotes = {}
     self._default = None
     self.branch = None
+    self._manifest_server = None
 
   def _Load(self):
     if not self._loaded:
@@ -247,6 +264,15 @@
       self._default = _Default()
 
     for node in config.childNodes:
+      if node.nodeName == 'manifest-server':
+        url = self._reqatt(node, 'url')
+        if self._manifest_server is not None:
+            raise ManifestParseError, \
+                'duplicate manifest-server in %s' % \
+                (self.manifestFile)
+        self._manifest_server = url
+
+    for node in config.childNodes:
       if node.nodeName == 'project':
         project = self._ParseProject(node)
         if self._projects.get(project.name):
@@ -315,7 +341,7 @@
   def _ParseProject(self, node):
     """
     reads a <project> element from the manifest file
-    """ 
+    """
     name = self._reqatt(node, 'name')
 
     remote = self._get_remote(node)
diff --git a/subcmds/sync.py b/subcmds/sync.py
index ceb81ea..deff171 100644
--- a/subcmds/sync.py
+++ b/subcmds/sync.py
@@ -17,9 +17,11 @@
 import os
 import re
 import shutil
+import socket
 import subprocess
 import sys
 import time
+import xmlrpclib
 
 from git_command import GIT
 from project import HEAD
@@ -57,6 +59,10 @@
 if the project is currently on a topic branch, but the manifest
 revision is temporarily needed.
 
+The -s/--smart-sync option can be used to sync to a known good
+build as specified by the manifest-server element in the current
+manifest.
+
 SSH Connections
 ---------------
 
@@ -97,6 +103,9 @@
     p.add_option('-d','--detach',
                  dest='detach_head', action='store_true',
                  help='detach projects back to manifest revision')
+    p.add_option('-s', '--smart-sync',
+                 dest='smart_sync', action='store_true',
+                 help='smart sync using manifest from a known good build')
 
     g = p.add_option_group('repo Version options')
     g.add_option('--no-repo-verify',
@@ -182,6 +191,49 @@
       print >>sys.stderr, 'error: cannot combine -n and -l'
       sys.exit(1)
 
+    if opt.smart_sync:
+      if not self.manifest.manifest_server:
+        print >>sys.stderr, \
+            'error: cannot smart sync: no manifest server defined in manifest'
+        sys.exit(1)
+      try:
+        server = xmlrpclib.Server(self.manifest.manifest_server)
+        p = self.manifest.manifestProject
+        b = p.GetBranch(p.CurrentBranch)
+        branch = b.merge
+
+        env = dict(os.environ)
+        if (env.has_key('TARGET_PRODUCT') and
+            env.has_key('TARGET_BUILD_VARIANT')):
+          target = '%s-%s' % (env['TARGET_PRODUCT'],
+                              env['TARGET_BUILD_VARIANT'])
+          [success, manifest_str] = server.GetApprovedManifest(branch, target)
+        else:
+          [success, manifest_str] = server.GetApprovedManifest(branch)
+
+        if success:
+          manifest_name = "smart_sync_override.xml"
+          manifest_path = os.path.join(self.manifest.manifestProject.worktree,
+                                       manifest_name)
+          try:
+            f = open(manifest_path, 'w')
+            try:
+              f.write(manifest_str)
+              self.manifest.Override(manifest_name)
+            finally:
+              f.close()
+          except IOError:
+            print >>sys.stderr, 'error: cannot write manifest to %s' % \
+                manifest_path
+            sys.exit(1)
+        else:
+          print >>sys.stderr, 'error: %s' % manifest_str
+          sys.exit(1)
+      except socket.error:
+        print >>sys.stderr, 'error: cannot connect to manifest server %s' % (
+            self.manifest.manifest_server)
+        sys.exit(1)
+
     rp = self.manifest.repoProject
     rp.PreSync()