diff --git a/MODULE.bazel b/MODULE.bazel
index f98cf57..ac7d934 100644
--- a/MODULE.bazel
+++ b/MODULE.bazel
@@ -5,8 +5,8 @@
 bazel_dep(name = "rbe_autoconfig")
 git_override(
     module_name = "rbe_autoconfig",
-    remote = "https://github.com/davido/rbe_autoconfig.git",
     commit = "71f39817c028949bd6d25f1806502bcd33028d14",
+    remote = "https://github.com/davido/rbe_autoconfig.git",
 )
 
 register_toolchains("//tools:error_prone_warnings_toolchain_java17_definition")
@@ -23,7 +23,7 @@
 
 BOUNCYCASTLE_VERSION = "1.83"
 
-BYTE_BUDDY_VERSION = "1.18.2"
+BYTE_BUDDY_VERSION = "1.18.4"
 
 JETTY_VERSION = "12.1.5"
 
@@ -62,7 +62,7 @@
         "org.apache.httpcomponents:httpcore:4.4.16",
         "org.apache.sshd:sshd-osgi:" + SSHD_VERSION,
         "org.apache.sshd:sshd-sftp:" + SSHD_VERSION,
-        "org.assertj:assertj-core:3.27.6",
+        "org.assertj:assertj-core:3.27.7",
         "org.bouncycastle:bcpg-jdk18on:" + BOUNCYCASTLE_VERSION,
         "org.bouncycastle:bcpkix-jdk18on:" + BOUNCYCASTLE_VERSION,
         "org.bouncycastle:bcprov-jdk18on:" + BOUNCYCASTLE_VERSION,
diff --git a/org.eclipse.jgit.packaging/org.eclipse.jgit.target/jgit-4.34.target b/org.eclipse.jgit.packaging/org.eclipse.jgit.target/jgit-4.34.target
index 957e6aa..2b01f35 100644
--- a/org.eclipse.jgit.packaging/org.eclipse.jgit.target/jgit-4.34.target
+++ b/org.eclipse.jgit.packaging/org.eclipse.jgit.target/jgit-4.34.target
@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="UTF-8" standalone="no"?>
 <?pde?>
 <!-- generated with https://github.com/eclipse-cbi/targetplatform-dsl -->
-<target name="jgit-4.34" sequenceNumber="1765895853">
+<target name="jgit-4.34" sequenceNumber="1769375519">
   <locations>
     <location includeMode="slicer" includeAllPlatforms="false" includeSource="true" includeConfigurePhase="true" type="InstallableUnit">
       <unit id="com.jcraft.jsch" version="0.1.55.v20230916-1400"/>
@@ -195,13 +195,13 @@
         <dependency>
           <groupId>net.bytebuddy</groupId>
           <artifactId>byte-buddy</artifactId>
-          <version>1.18.2</version>
+          <version>1.18.4</version>
           <type>jar</type>
         </dependency>
         <dependency>
           <groupId>net.bytebuddy</groupId>
           <artifactId>byte-buddy-agent</artifactId>
-          <version>1.18.2</version>
+          <version>1.18.4</version>
           <type>jar</type>
         </dependency>
       </dependencies>
@@ -239,7 +239,7 @@
         <dependency>
           <groupId>org.assertj</groupId>
           <artifactId>assertj-core</artifactId>
-          <version>3.27.6</version>
+          <version>3.27.7</version>
           <type>jar</type>
         </dependency>
       </dependencies>
diff --git a/org.eclipse.jgit.packaging/org.eclipse.jgit.target/jgit-4.35.target b/org.eclipse.jgit.packaging/org.eclipse.jgit.target/jgit-4.35.target
index d503246..b838cfc 100644
--- a/org.eclipse.jgit.packaging/org.eclipse.jgit.target/jgit-4.35.target
+++ b/org.eclipse.jgit.packaging/org.eclipse.jgit.target/jgit-4.35.target
@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="UTF-8" standalone="no"?>
 <?pde?>
 <!-- generated with https://github.com/eclipse-cbi/targetplatform-dsl -->
-<target name="jgit-4.35" sequenceNumber="1765895853">
+<target name="jgit-4.35" sequenceNumber="1769375519">
   <locations>
     <location includeMode="slicer" includeAllPlatforms="false" includeSource="true" includeConfigurePhase="true" type="InstallableUnit">
       <unit id="com.jcraft.jsch" version="0.1.55.v20230916-1400"/>
@@ -195,13 +195,13 @@
         <dependency>
           <groupId>net.bytebuddy</groupId>
           <artifactId>byte-buddy</artifactId>
-          <version>1.18.2</version>
+          <version>1.18.4</version>
           <type>jar</type>
         </dependency>
         <dependency>
           <groupId>net.bytebuddy</groupId>
           <artifactId>byte-buddy-agent</artifactId>
-          <version>1.18.2</version>
+          <version>1.18.4</version>
           <type>jar</type>
         </dependency>
       </dependencies>
@@ -239,7 +239,7 @@
         <dependency>
           <groupId>org.assertj</groupId>
           <artifactId>assertj-core</artifactId>
-          <version>3.27.6</version>
+          <version>3.27.7</version>
           <type>jar</type>
         </dependency>
       </dependencies>
diff --git a/org.eclipse.jgit.packaging/org.eclipse.jgit.target/jgit-4.36.target b/org.eclipse.jgit.packaging/org.eclipse.jgit.target/jgit-4.36.target
index ce5da93..278511b 100644
--- a/org.eclipse.jgit.packaging/org.eclipse.jgit.target/jgit-4.36.target
+++ b/org.eclipse.jgit.packaging/org.eclipse.jgit.target/jgit-4.36.target
@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="UTF-8" standalone="no"?>
 <?pde?>
 <!-- generated with https://github.com/eclipse-cbi/targetplatform-dsl -->
-<target name="jgit-4.36" sequenceNumber="1765895853">
+<target name="jgit-4.36" sequenceNumber="1769375519">
   <locations>
     <location includeMode="slicer" includeAllPlatforms="false" includeSource="true" includeConfigurePhase="true" type="InstallableUnit">
       <unit id="com.jcraft.jsch" version="0.1.55.v20230916-1400"/>
@@ -195,13 +195,13 @@
         <dependency>
           <groupId>net.bytebuddy</groupId>
           <artifactId>byte-buddy</artifactId>
-          <version>1.18.2</version>
+          <version>1.18.4</version>
           <type>jar</type>
         </dependency>
         <dependency>
           <groupId>net.bytebuddy</groupId>
           <artifactId>byte-buddy-agent</artifactId>
-          <version>1.18.2</version>
+          <version>1.18.4</version>
           <type>jar</type>
         </dependency>
       </dependencies>
@@ -239,7 +239,7 @@
         <dependency>
           <groupId>org.assertj</groupId>
           <artifactId>assertj-core</artifactId>
-          <version>3.27.6</version>
+          <version>3.27.7</version>
           <type>jar</type>
         </dependency>
       </dependencies>
diff --git a/org.eclipse.jgit.packaging/org.eclipse.jgit.target/jgit-4.37.target b/org.eclipse.jgit.packaging/org.eclipse.jgit.target/jgit-4.37.target
index ddfd6a1..3df478a 100644
--- a/org.eclipse.jgit.packaging/org.eclipse.jgit.target/jgit-4.37.target
+++ b/org.eclipse.jgit.packaging/org.eclipse.jgit.target/jgit-4.37.target
@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="UTF-8" standalone="no"?>
 <?pde?>
 <!-- generated with https://github.com/eclipse-cbi/targetplatform-dsl -->
-<target name="jgit-4.37" sequenceNumber="1765895853">
+<target name="jgit-4.37" sequenceNumber="1769375519">
   <locations>
     <location includeMode="slicer" includeAllPlatforms="false" includeSource="true" includeConfigurePhase="true" type="InstallableUnit">
       <unit id="com.jcraft.jsch" version="0.1.55.v20230916-1400"/>
@@ -195,13 +195,13 @@
         <dependency>
           <groupId>net.bytebuddy</groupId>
           <artifactId>byte-buddy</artifactId>
-          <version>1.18.2</version>
+          <version>1.18.4</version>
           <type>jar</type>
         </dependency>
         <dependency>
           <groupId>net.bytebuddy</groupId>
           <artifactId>byte-buddy-agent</artifactId>
-          <version>1.18.2</version>
+          <version>1.18.4</version>
           <type>jar</type>
         </dependency>
       </dependencies>
@@ -239,7 +239,7 @@
         <dependency>
           <groupId>org.assertj</groupId>
           <artifactId>assertj-core</artifactId>
-          <version>3.27.6</version>
+          <version>3.27.7</version>
           <type>jar</type>
         </dependency>
       </dependencies>
diff --git a/org.eclipse.jgit.packaging/org.eclipse.jgit.target/jgit-4.38.target b/org.eclipse.jgit.packaging/org.eclipse.jgit.target/jgit-4.38.target
index 8d89bf2..3fb1dbe 100644
--- a/org.eclipse.jgit.packaging/org.eclipse.jgit.target/jgit-4.38.target
+++ b/org.eclipse.jgit.packaging/org.eclipse.jgit.target/jgit-4.38.target
@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="UTF-8" standalone="no"?>
 <?pde?>
 <!-- generated with https://github.com/eclipse-cbi/targetplatform-dsl -->
-<target name="jgit-4.38" sequenceNumber="1766134741">
+<target name="jgit-4.38" sequenceNumber="1769375519">
   <locations>
     <location includeMode="slicer" includeAllPlatforms="false" includeSource="true" includeConfigurePhase="true" type="InstallableUnit">
       <unit id="com.jcraft.jsch" version="0.1.55.v20230916-1400"/>
@@ -195,13 +195,13 @@
         <dependency>
           <groupId>net.bytebuddy</groupId>
           <artifactId>byte-buddy</artifactId>
-          <version>1.18.2</version>
+          <version>1.18.4</version>
           <type>jar</type>
         </dependency>
         <dependency>
           <groupId>net.bytebuddy</groupId>
           <artifactId>byte-buddy-agent</artifactId>
-          <version>1.18.2</version>
+          <version>1.18.4</version>
           <type>jar</type>
         </dependency>
       </dependencies>
@@ -239,7 +239,7 @@
         <dependency>
           <groupId>org.assertj</groupId>
           <artifactId>assertj-core</artifactId>
-          <version>3.27.6</version>
+          <version>3.27.7</version>
           <type>jar</type>
         </dependency>
       </dependencies>
diff --git a/org.eclipse.jgit.packaging/org.eclipse.jgit.target/jgit-4.39.target b/org.eclipse.jgit.packaging/org.eclipse.jgit.target/jgit-4.39.target
index e21a5b9..7742ddb 100644
--- a/org.eclipse.jgit.packaging/org.eclipse.jgit.target/jgit-4.39.target
+++ b/org.eclipse.jgit.packaging/org.eclipse.jgit.target/jgit-4.39.target
@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="UTF-8" standalone="no"?>
 <?pde?>
 <!-- generated with https://github.com/eclipse-cbi/targetplatform-dsl -->
-<target name="jgit-4.39" sequenceNumber="1766135179">
+<target name="jgit-4.39" sequenceNumber="1769375519">
   <locations>
     <location includeMode="slicer" includeAllPlatforms="false" includeSource="true" includeConfigurePhase="true" type="InstallableUnit">
       <unit id="com.jcraft.jsch" version="0.1.55.v20230916-1400"/>
@@ -19,11 +19,11 @@
       <unit id="org.hamcrest.source" version="3.0.0"/>
       <unit id="org.junit" version="4.13.2.v20240929-1000"/>
       <unit id="org.junit.source" version="4.13.2.v20240929-1000"/>
-      <unit id="org.objectweb.asm" version="9.9.0"/>
-      <unit id="org.objectweb.asm.commons" version="9.9.0"/>
-      <unit id="org.objectweb.asm.util" version="9.9.0"/>
-      <unit id="org.objectweb.asm.tree" version="9.9.0"/>
-      <unit id="org.objectweb.asm.tree.analysis" version="9.9.0"/>
+      <unit id="org.objectweb.asm" version="9.9.1"/>
+      <unit id="org.objectweb.asm.commons" version="9.9.1"/>
+      <unit id="org.objectweb.asm.util" version="9.9.1"/>
+      <unit id="org.objectweb.asm.tree" version="9.9.1"/>
+      <unit id="org.objectweb.asm.tree.analysis" version="9.9.1"/>
       <unit id="org.objenesis" version="3.4.0"/>
       <unit id="org.objenesis.source" version="3.4.0"/>
       <unit id="org.osgi.service.cm" version="1.6.1.202109301733"/>
@@ -195,13 +195,13 @@
         <dependency>
           <groupId>net.bytebuddy</groupId>
           <artifactId>byte-buddy</artifactId>
-          <version>1.18.2</version>
+          <version>1.18.4</version>
           <type>jar</type>
         </dependency>
         <dependency>
           <groupId>net.bytebuddy</groupId>
           <artifactId>byte-buddy-agent</artifactId>
-          <version>1.18.2</version>
+          <version>1.18.4</version>
           <type>jar</type>
         </dependency>
       </dependencies>
@@ -239,7 +239,7 @@
         <dependency>
           <groupId>org.assertj</groupId>
           <artifactId>assertj-core</artifactId>
-          <version>3.27.6</version>
+          <version>3.27.7</version>
           <type>jar</type>
         </dependency>
       </dependencies>
diff --git a/org.eclipse.jgit.packaging/org.eclipse.jgit.target/maven/dependencies.tpd b/org.eclipse.jgit.packaging/org.eclipse.jgit.target/maven/dependencies.tpd
index 55f40d1..5368a95 100644
--- a/org.eclipse.jgit.packaging/org.eclipse.jgit.target/maven/dependencies.tpd
+++ b/org.eclipse.jgit.packaging/org.eclipse.jgit.target/maven/dependencies.tpd
@@ -56,7 +56,7 @@
 	dependency {
 		groupId = "org.assertj"
 		artifactId = "assertj-core"
-		version = "3.27.6"
+		version = "3.27.7"
 	}
 }
 
@@ -97,12 +97,12 @@
 	dependency {
 		groupId = "net.bytebuddy"
 		artifactId = "byte-buddy"
-		version = "1.18.2"
+		version = "1.18.4"
 	}
 	dependency {
 		groupId = "net.bytebuddy"
 		artifactId = "byte-buddy-agent"
-		version = "1.18.2"
+		version = "1.18.4"
 	}
 }
 
diff --git a/org.eclipse.jgit.packaging/org.eclipse.jgit.target/orbit/orbit-4.39.tpd b/org.eclipse.jgit.packaging/org.eclipse.jgit.target/orbit/orbit-4.39.tpd
index 299d7d0..48725ca 100644
--- a/org.eclipse.jgit.packaging/org.eclipse.jgit.target/orbit/orbit-4.39.tpd
+++ b/org.eclipse.jgit.packaging/org.eclipse.jgit.target/orbit/orbit-4.39.tpd
@@ -17,11 +17,11 @@
 	org.hamcrest.source [3.0.0,3.0.0]
 	org.junit [4.13.2.v20240929-1000,4.13.2.v20240929-1000]
 	org.junit.source [4.13.2.v20240929-1000,4.13.2.v20240929-1000]
-	org.objectweb.asm [9.9.0,9.9.0]
-	org.objectweb.asm.commons [9.9.0,9.9.0]
-	org.objectweb.asm.util [9.9.0,9.9.0]
-	org.objectweb.asm.tree [9.9.0,9.9.0]
-	org.objectweb.asm.tree.analysis [9.9.0,9.9.0]
+	org.objectweb.asm [9.9.1,9.9.1]
+	org.objectweb.asm.commons [9.9.1,9.9.1]
+	org.objectweb.asm.util [9.9.1,9.9.1]
+	org.objectweb.asm.tree [9.9.1,9.9.1]
+	org.objectweb.asm.tree.analysis [9.9.1,9.9.1]
 	org.objenesis [3.4,3.4]
 	org.objenesis.source [3.4,3.4]
 	org.osgi.service.cm [1.6.1.202109301733,1.6.1.202109301733]
diff --git a/org.eclipse.jgit.test/src/org/eclipse/jgit/internal/storage/dfs/MidxTestUtils.java b/org.eclipse.jgit.test/src/org/eclipse/jgit/internal/storage/dfs/MidxTestUtils.java
new file mode 100644
index 0000000..b34b822
--- /dev/null
+++ b/org.eclipse.jgit.test/src/org/eclipse/jgit/internal/storage/dfs/MidxTestUtils.java
@@ -0,0 +1,147 @@
+/*
+ * Copyright (C) 2025, Google LLC.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Distribution License v. 1.0 which is available at
+ * https://www.eclipse.org/org/documents/edl-v10.php.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+package org.eclipse.jgit.internal.storage.dfs;
+
+import static java.nio.charset.StandardCharsets.UTF_8;
+import static org.eclipse.jgit.lib.Constants.OBJ_BLOB;
+import static org.junit.Assert.assertEquals;
+
+import java.io.IOException;
+import java.util.Arrays;
+import java.util.List;
+import java.util.zip.Deflater;
+
+import org.eclipse.jgit.annotations.Nullable;
+import org.eclipse.jgit.lib.NullProgressMonitor;
+import org.eclipse.jgit.lib.ObjectId;
+
+/**
+ * Helpers to write multipack indexes
+ */
+public class MidxTestUtils {
+	private MidxTestUtils() {
+	}
+
+	/**
+	 * Write a single pack into the repo with the blob as contents
+	 *
+	 * @param db
+	 *            repository
+	 * @param blob
+	 *            blob to write into the pack
+	 * @return object id of the blob written in the pack
+	 * @throws IOException
+	 *             a problem writing in the repo
+	 */
+	static ObjectId writePackWithBlob(DfsRepository db, String blob)
+			throws IOException {
+		return writePackWithBlobs(db, blob)[0];
+	}
+
+	/**
+	 * Write multiple blobs into a single pack in the repo
+	 *
+	 * @param db
+	 *            repository
+	 * @param blobs
+	 *            blobs to write into the pack
+	 * @return object ids of the blobs written in the pack, in the same order as
+	 *         the input parameters
+	 * @throws IOException
+	 *             a problem writing in the repo
+	 */
+	static ObjectId[] writePackWithBlobs(DfsRepository db, String... blobs)
+			throws IOException {
+		ObjectId[] oids = new ObjectId[blobs.length];
+
+		DfsInserter ins = (DfsInserter) db.newObjectInserter();
+		ins.setCompressionLevel(Deflater.NO_COMPRESSION);
+		for (int i = 0; i < blobs.length; i++) {
+			oids[i] = ins.insert(OBJ_BLOB, blobs[i].getBytes(UTF_8));
+		}
+		ins.flush();
+		return oids;
+	}
+
+	/**
+	 * Write a midx covering the only pack in the repo
+	 *
+	 * @param db
+	 *            a repository with a single pack
+	 * @return a midx covering that single pack
+	 * @throws IOException
+	 *             a problem writing in the repo
+	 */
+	static DfsPackFileMidx writeSinglePackMidx(DfsRepository db)
+			throws IOException {
+		DfsPackFile[] packs = db.getObjectDatabase().getPacks();
+		assertEquals("More than one pack in db", 1, packs.length);
+		return writeSinglePackMidx(db, packs[0]);
+	}
+
+	/**
+	 * Write a midx covering a single pack
+	 *
+	 * @param db
+	 *            a repository to write the midx covering the pack
+	 * @param pack
+	 *            a pack in the repository that will be covered by a new midx
+	 * @return a midx covering that single pack
+	 * @throws IOException
+	 *             a problem writing in the repo
+	 */
+	static DfsPackFileMidx writeSinglePackMidx(DfsRepository db,
+			DfsPackFile pack) throws IOException {
+		return writeMultipackIndex(db, new DfsPackFile[] { pack }, null);
+	}
+
+	/**
+	 * Write a midx covering a single pack
+	 *
+	 * @param db
+	 *            a repository to write the midx covering the pack
+	 * @param pack
+	 *            a pack in the repository that will be covered by a new midx
+	 * @param base
+	 *            base of this midx (can be null)
+	 * @return a midx covering that single pack
+	 * @throws IOException
+	 *             a problem writing in the repo
+	 */
+	static DfsPackFileMidx writeSinglePackMidx(DfsRepository db,
+			DfsPackFile pack, @Nullable DfsPackFileMidx base)
+			throws IOException {
+		return writeMultipackIndex(db, new DfsPackFile[] { pack }, base);
+	}
+
+	/**
+	 * Write a midx in the repository
+	 *
+	 * @param db
+	 *            the repository
+	 * @param packs
+	 *            packs to be covered by this midx
+	 * @param base
+	 *            base of the newly created midx
+	 * @return the new midx instance
+	 * @throws IOException
+	 *             a problem writing in the repo
+	 */
+	static DfsPackFileMidx writeMultipackIndex(DfsRepository db,
+			DfsPackFile[] packs, DfsPackFileMidx base) throws IOException {
+		DfsPackDescription desc = DfsMidxWriter.writeMidx(
+				NullProgressMonitor.INSTANCE, db.getObjectDatabase(),
+				Arrays.asList(packs),
+				base != null ? base.getPackDescription() : null);
+		db.getObjectDatabase().commitPack(List.of(desc), null);
+		return DfsPackFileMidx.create(DfsBlockCache.getInstance(), desc,
+				Arrays.asList(packs), base);
+	}
+}
diff --git a/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/dfs/DfsPackFileMidxIndexTest.java b/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/dfs/DfsPackFileMidxIndexTest.java
new file mode 100644
index 0000000..8574688
--- /dev/null
+++ b/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/dfs/DfsPackFileMidxIndexTest.java
@@ -0,0 +1,241 @@
+/*
+ * Copyright (C) 2025, Google LLC.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Distribution License v. 1.0 which is available at
+ * https://www.eclipse.org/org/documents/edl-v10.php.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+package org.eclipse.jgit.internal.storage.dfs;
+
+import static org.eclipse.jgit.internal.storage.dfs.MidxTestUtils.writeMultipackIndex;
+import static org.eclipse.jgit.internal.storage.dfs.MidxTestUtils.writePackWithBlobs;
+import static org.eclipse.jgit.internal.storage.dfs.MidxTestUtils.writeSinglePackMidx;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNotEquals;
+import static org.junit.Assert.assertTrue;
+
+import java.io.IOException;
+import java.util.Arrays;
+import java.util.Comparator;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+
+import org.eclipse.jgit.internal.storage.file.PackIndex;
+import org.eclipse.jgit.internal.storage.file.PackReverseIndex;
+import org.eclipse.jgit.lib.AbbreviatedObjectId;
+import org.eclipse.jgit.lib.ObjectId;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.Parameterized;
+import org.junit.runners.Parameterized.Parameters;
+
+@RunWith(Parameterized.class)
+public class DfsPackFileMidxIndexTest {
+
+	private static final ObjectId NOT_IN_PACK = ObjectId
+			.fromString("3f306cb3fcd5116919fecad615524bd6e6ea4ba7");
+
+	private static final List<String> BLOBS = List.of("blob one", "blob two",
+			"blob three", "blob four", "blob five", "blob six");
+
+	@Parameters(name = "{0}")
+	public static Iterable<TestInput> data() throws IOException {
+		return List.of(setupOneMidxOverOnePack(), setupOneMidxOverNPacks(),
+				setupMidxChainEachOverNPacks(),
+				setupMidxChainSingleAndNPacks());
+	}
+
+	private record TestInput(String testDesc, DfsRepository db,
+			DfsPackFileMidx midx, ObjectId[] oids) {
+		@Override
+		public String toString() {
+			return testDesc;
+		}
+
+	}
+
+	private TestInput ti;
+
+	public DfsPackFileMidxIndexTest(TestInput ti) {
+		this.ti = ti;
+	}
+
+	@Test
+	public void getPackIndex_getObjectCount() {
+		try (DfsReader ctx = ti.db().getObjectDatabase().newReader()) {
+			assertEquals(ti.oids().length,
+					ti.midx().getPackIndex(ctx).getObjectCount());
+		}
+	}
+
+	@Test
+	public void getPackIndex_position_findPosition_getObjectId() {
+		try (DfsReader ctx = ti.db.getObjectDatabase().newReader()) {
+			PackIndex idx = ti.midx().getPackIndex(ctx);
+			for (int i = 0; i < ti.oids().length; i++) {
+				ObjectId expected = ti.oids()[i];
+				int position = idx.findPosition(expected);
+				assertNotEquals(-1, position);
+				ObjectId actual = idx.getObjectId(position);
+				assertEquals(expected, actual);
+			}
+			assertEquals(-1, idx.findPosition(NOT_IN_PACK));
+		}
+	}
+
+	@Test
+	public void getPackIndex_offset_findOffset_getOffset() {
+		try (DfsReader ctx = ti.db.getObjectDatabase().newReader()) {
+			PackIndex idx = ti.midx().getPackIndex(ctx);
+			for (int i = 0; i < ti.oids().length; i++) {
+				ObjectId oid = ti.oids()[i];
+				int oidPosition = idx.findPosition(oid);
+
+				long offsetById = idx.findOffset(oid);
+				long offsetByPos = idx.getOffset(oidPosition);
+				assertEquals(offsetById, offsetByPos);
+			}
+			assertEquals(-1, idx.findOffset(NOT_IN_PACK));
+		}
+	}
+
+	@Test
+	public void getPackIndex_objects_contains_hasObjects() {
+		try (DfsReader ctx = ti.db.getObjectDatabase().newReader()) {
+			PackIndex idx = ti.midx().getPackIndex(ctx);
+			for (int i = 0; i < ti.oids().length; i++) {
+				ObjectId oid = ti.oids()[i];
+				assertTrue(idx.contains(oid));
+				assertTrue(idx.hasObject(oid));
+			}
+			assertFalse(idx.contains(NOT_IN_PACK));
+			assertFalse(idx.hasObject(NOT_IN_PACK));
+		}
+	}
+
+	@Test
+	public void getPackIndex_resolve() throws IOException {
+		try (DfsReader ctx = ti.db.getObjectDatabase().newReader()) {
+			PackIndex idx = ti.midx().getPackIndex(ctx);
+			Set<ObjectId> matches = new HashSet<>();
+			// Sha1 of "blob two" = ae4116e0972d85cd751b458fea94ca9eb84dd692
+			idx.resolve(matches, AbbreviatedObjectId.fromString("ae411"), 100);
+			assertEquals(1, matches.size());
+		}
+	}
+
+	@Test
+	public void getReverseIndex_findObject() throws IOException {
+		try (DfsReader ctx = ti.db.getObjectDatabase().newReader()) {
+			PackIndex idx = ti.midx().getPackIndex(ctx);
+			PackReverseIndex ridx = ti.midx().getReverseIdx(ctx);
+			for (ObjectId oid : ti.oids()) {
+				long offset = idx.findOffset(oid);
+				assertEquals(oid, ridx.findObject(offset));
+			}
+		}
+	}
+
+	@Test
+	public void getReverseIndex_findObjectByPosition() throws IOException {
+		try (DfsReader ctx = ti.db.getObjectDatabase().newReader()) {
+			PackIndex idx = ti.midx().getPackIndex(ctx);
+			ObjectId[] offsetOrder = ti.oids().clone();
+			Arrays.sort(offsetOrder, Comparator.comparingLong(idx::findOffset));
+
+			PackReverseIndex ridx = ti.midx().getReverseIdx(ctx);
+			for (int i = 0; i < offsetOrder.length; i++) {
+				assertEquals(offsetOrder[i], ridx.findObjectByPosition(i));
+			}
+		}
+	}
+
+	@Test
+	public void getReverseIndex_findPosition() throws IOException {
+		try (DfsReader ctx = ti.db.getObjectDatabase().newReader()) {
+			PackIndex idx = ti.midx().getPackIndex(ctx);
+			ObjectId[] offsetOrder = ti.oids().clone();
+			Arrays.sort(offsetOrder, Comparator.comparingLong(idx::findOffset));
+
+			PackReverseIndex ridx = ti.midx().getReverseIdx(ctx);
+			for (int i = 0; i < offsetOrder.length; i++) {
+				long offset = idx.findOffset(offsetOrder[i]);
+				int position = ridx.findPosition(offset);
+				assertEquals(i, position);
+			}
+		}
+	}
+	static TestInput setupOneMidxOverOnePack() throws IOException {
+		InMemoryRepository db = new InMemoryRepository(
+				new DfsRepositoryDescription("one_midx_one_pack"));
+		ObjectId[] objectIds = writePackWithBlobs(db,
+				BLOBS.toArray(String[]::new));
+		DfsPackFileMidx midx1 = writeSinglePackMidx(db);
+		return new TestInput("one midx - one pack", db, midx1, objectIds);
+	}
+
+	static TestInput setupOneMidxOverNPacks() throws IOException {
+		InMemoryRepository db = new InMemoryRepository(
+				new DfsRepositoryDescription("one_midx_n_packs"));
+
+		ObjectId[] objectIds = BLOBS.stream().map(s -> {
+			try {
+				return MidxTestUtils.writePackWithBlob(db, s);
+			} catch (IOException e) {
+				throw new RuntimeException(e);
+			}
+		}).toArray(ObjectId[]::new);
+		DfsPackFileMidx midx1 = writeMultipackIndex(db,
+				db.getObjectDatabase().getPacks(), null);
+		return new TestInput("one midx - n packs", db, midx1, objectIds);
+	}
+
+	static TestInput setupMidxChainEachOverNPacks() throws IOException {
+		InMemoryRepository db = new InMemoryRepository(
+				new DfsRepositoryDescription("two_midx_3_packs_each"));
+
+		ObjectId[] objectIds = BLOBS.stream().map(s -> {
+			try {
+				return MidxTestUtils.writePackWithBlob(db, s);
+			} catch (IOException e) {
+				throw new RuntimeException(e);
+			}
+		}).toArray(ObjectId[]::new);
+		DfsPackFile[] packs = db.getObjectDatabase().getPacks();
+		// If the amount of blobs (i.e. packs), adjust the ranges covered by
+		// midx.
+		assertEquals(6, BLOBS.size());
+		DfsPackFileMidx midxBase = MidxTestUtils.writeMultipackIndex(db,
+				Arrays.copyOfRange(packs, 3, 6), null);
+		DfsPackFileMidx midxTip = MidxTestUtils.writeMultipackIndex(db,
+				Arrays.copyOfRange(packs, 0, 3), midxBase);
+		return new TestInput("two midx - 3 packs each", db, midxTip, objectIds);
+	}
+
+	static TestInput setupMidxChainSingleAndNPacks() throws IOException {
+		InMemoryRepository db = new InMemoryRepository(
+				new DfsRepositoryDescription("two_midx_3_packs_each"));
+
+		ObjectId[] objectIds = BLOBS.stream().map(s -> {
+			try {
+				return MidxTestUtils.writePackWithBlob(db, s);
+			} catch (IOException e) {
+				throw new RuntimeException(e);
+			}
+		}).toArray(ObjectId[]::new);
+		DfsPackFile[] packs = db.getObjectDatabase().getPacks();
+		// If the amount of blobs (i.e. packs), adjust the ranges covered by
+		// midx.
+		assertEquals(6, BLOBS.size());
+		DfsPackFileMidx midxBase = MidxTestUtils.writeMultipackIndex(db,
+				Arrays.copyOfRange(packs, 1, 6), null);
+		DfsPackFileMidx midxTip = MidxTestUtils.writeMultipackIndex(db,
+				Arrays.copyOfRange(packs, 0, 1), midxBase);
+		return new TestInput("two midx - 1 pack, 5 packs", db, midxTip,
+				objectIds);
+	}
+}
diff --git a/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/dfs/DfsPackFileMidxNPacksTest.java b/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/dfs/DfsPackFileMidxNPacksTest.java
index 758ac1f..706bc91 100644
--- a/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/dfs/DfsPackFileMidxNPacksTest.java
+++ b/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/dfs/DfsPackFileMidxNPacksTest.java
@@ -18,6 +18,7 @@
 import static org.junit.Assert.assertArrayEquals;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNotEquals;
 import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.assertNull;
 import static org.junit.Assert.assertThrows;
@@ -27,11 +28,8 @@
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
 import java.util.Arrays;
-import java.util.HashMap;
 import java.util.HashSet;
-import java.util.LinkedHashMap;
 import java.util.List;
-import java.util.Map;
 import java.util.Set;
 import java.util.zip.Deflater;
 
@@ -40,11 +38,8 @@
 import org.eclipse.jgit.internal.storage.dfs.DfsPackFileMidx.VOffsetCalculator;
 import org.eclipse.jgit.internal.storage.dfs.DfsPackFileMidxNPacks.VOffsetCalculatorNPacks;
 import org.eclipse.jgit.internal.storage.file.PackBitmapIndex;
-import org.eclipse.jgit.internal.storage.file.PackIndex;
 import org.eclipse.jgit.internal.storage.midx.MultiPackIndex.PackOffset;
-import org.eclipse.jgit.internal.storage.midx.MultiPackIndexWriter;
 import org.eclipse.jgit.internal.storage.pack.ObjectToPack;
-import org.eclipse.jgit.internal.storage.pack.PackExt;
 import org.eclipse.jgit.internal.storage.pack.PackOutputStream;
 import org.eclipse.jgit.internal.storage.pack.PackWriter;
 import org.eclipse.jgit.junit.JGitTestUtil;
@@ -101,11 +96,11 @@ public void midx_findIdxPosition_withBase() throws IOException {
 		DfsPackFile[] packs = db.getObjectDatabase().getPacks();
 
 		// Packs are in reverse insertion order
-		DfsPackFileMidx midxBase = writeMultipackIndex(
+		DfsPackFileMidx midxBase = MidxTestUtils.writeMultipackIndex(db,
 				Arrays.copyOfRange(packs, 4, 6), null);
-		DfsPackFileMidx midxMid = writeMultipackIndex(
+		DfsPackFileMidx midxMid = MidxTestUtils.writeMultipackIndex(db,
 				Arrays.copyOfRange(packs, 2, 4), midxBase);
-		DfsPackFileMidx midxTip = writeMultipackIndex(
+		DfsPackFileMidx midxTip = MidxTestUtils.writeMultipackIndex(db,
 				Arrays.copyOfRange(packs, 0, 2), midxMid);
 
 		try (DfsReader ctx = db.getObjectDatabase().newReader()) {
@@ -120,6 +115,49 @@ public void midx_findIdxPosition_withBase() throws IOException {
 	}
 
 	@Test
+	public void midx_getObjectAt() throws IOException {
+		ObjectId o1 = writePackWithBlob("something".getBytes(UTF_8));
+		ObjectId o2 = writePackWithBlob("something else".getBytes(UTF_8));
+		ObjectId o3 = writePackWithBlob("and more".getBytes(UTF_8));
+		DfsPackFileMidx midx = writeMultipackIndex();
+
+		try (DfsReader ctx = db.getObjectDatabase().newReader()) {
+			assertEquals(o1, midx.getObjectAt(ctx, 2));
+			assertEquals(o2, midx.getObjectAt(ctx, 0));
+			assertEquals(o3, midx.getObjectAt(ctx, 1));
+		}
+	}
+
+	@Test
+	public void midx_getObjectAt_withBase() throws IOException {
+		ObjectId o1 = writePackWithBlob("o1".getBytes(UTF_8));
+		ObjectId o2 = writePackWithBlob("o2".getBytes(UTF_8));
+		ObjectId o3 = writePackWithBlob("o3".getBytes(UTF_8));
+		ObjectId o4 = writePackWithBlob("o4".getBytes(UTF_8));
+		ObjectId o5 = writePackWithBlob("o5".getBytes(UTF_8));
+		ObjectId o6 = writePackWithBlob("o6".getBytes(UTF_8));
+		DfsPackFile[] packs = db.getObjectDatabase().getPacks();
+
+		// Packs are in reverse insertion order
+		DfsPackFileMidx midxBase = MidxTestUtils.writeMultipackIndex(db,
+				Arrays.copyOfRange(packs, 4, 6), null);
+		DfsPackFileMidx midxMid = MidxTestUtils.writeMultipackIndex(db,
+				Arrays.copyOfRange(packs, 2, 4), midxBase);
+		DfsPackFileMidx midxTip = MidxTestUtils.writeMultipackIndex(db,
+				Arrays.copyOfRange(packs, 0, 2), midxMid);
+
+		try (DfsReader ctx = db.getObjectDatabase().newReader()) {
+			assertEquals(o1, midxTip.getObjectAt(ctx, 0));
+			assertEquals(o2, midxTip.getObjectAt(ctx, 1));
+			assertEquals(o3, midxTip.getObjectAt(ctx, 2));
+			assertEquals(o4, midxTip.getObjectAt(ctx, 3));
+			// In sha1 order
+			assertEquals(o5, midxTip.getObjectAt(ctx, 5));
+			assertEquals(o6, midxTip.getObjectAt(ctx, 4));
+		}
+	}
+
+	@Test
 	public void midx_hasObject() throws IOException {
 		ObjectId o1 = writePackWithRandomBlob(100);
 		ObjectId o2 = writePackWithRandomBlob(200);
@@ -146,9 +184,9 @@ public void midx_hasObject_withBase() throws IOException {
 		DfsPackFile[] packs = db.getObjectDatabase().getPacks();
 
 		// Packs are in reverse insertion order
-		DfsPackFileMidx midxBase = writeMultipackIndex(
+		DfsPackFileMidx midxBase = MidxTestUtils.writeMultipackIndex(db,
 				Arrays.copyOfRange(packs, 3, 6), null);
-		DfsPackFileMidx midxTip = writeMultipackIndex(
+		DfsPackFileMidx midxTip = MidxTestUtils.writeMultipackIndex(db,
 				Arrays.copyOfRange(packs, 0, 3), midxBase);
 
 		try (DfsReader ctx = db.getObjectDatabase().newReader()) {
@@ -210,9 +248,9 @@ public void midx_get_withBase() throws IOException {
 
 		DfsPackFile[] packs = db.getObjectDatabase().getPacks();
 		// Packs are in reverse insertion order
-		DfsPackFileMidx midxBase = writeMultipackIndex(
+		DfsPackFileMidx midxBase = MidxTestUtils.writeMultipackIndex(db,
 				Arrays.copyOfRange(packs, 3, 6), null);
-		DfsPackFileMidx midxTip = writeMultipackIndex(
+		DfsPackFileMidx midxTip = MidxTestUtils.writeMultipackIndex(db,
 				Arrays.copyOfRange(packs, 0, 3), midxBase);
 
 		try (DfsReader ctx = db.getObjectDatabase().newReader()) {
@@ -277,9 +315,9 @@ public void midx_load_withBase() throws IOException {
 
 		DfsPackFile[] packs = db.getObjectDatabase().getPacks();
 		// Packs are in reverse insertion order
-		DfsPackFileMidx midxBase = writeMultipackIndex(
+		DfsPackFileMidx midxBase = MidxTestUtils.writeMultipackIndex(db,
 				Arrays.copyOfRange(packs, 3, 6), null);
-		DfsPackFileMidx midxTip = writeMultipackIndex(
+		DfsPackFileMidx midxTip = MidxTestUtils.writeMultipackIndex(db,
 				Arrays.copyOfRange(packs, 0, 3), midxBase);
 
 		try (DfsReader ctx = db.getObjectDatabase().newReader()) {
@@ -376,9 +414,9 @@ public void midx_resolve_withBase() throws Exception {
 
 		DfsPackFile[] packs = db.getObjectDatabase().getPacks();
 		// Packs are in reverse insertion order
-		DfsPackFileMidx midxBase = writeMultipackIndex(
+		DfsPackFileMidx midxBase = MidxTestUtils.writeMultipackIndex(db,
 				Arrays.copyOfRange(packs, 3, 6), null);
-		DfsPackFileMidx midxTip = writeMultipackIndex(
+		DfsPackFileMidx midxTip = MidxTestUtils.writeMultipackIndex(db,
 				Arrays.copyOfRange(packs, 0, 3), midxBase);
 
 		try (DfsReader ctx = db.getObjectDatabase().newReader()) {
@@ -446,9 +484,9 @@ public void midx_findAllFromPack_withBase() throws Exception {
 
 		DfsPackFile[] packs = db.getObjectDatabase().getPacks();
 		// Packs are in reverse insertion order (o6 -> o1)
-		DfsPackFileMidx midxBase = writeMultipackIndex(
+		DfsPackFileMidx midxBase = MidxTestUtils.writeMultipackIndex(db,
 				Arrays.copyOfRange(packs, 3, 6), null);
-		DfsPackFileMidx midxTip = writeMultipackIndex(
+		DfsPackFileMidx midxTip = MidxTestUtils.writeMultipackIndex(db,
 				Arrays.copyOfRange(packs, 0, 3), midxBase);
 
 		List<ObjectToPack> otps = List.of(new DfsObjectToPack(o1, OBJ_BLOB),
@@ -524,9 +562,9 @@ public void midx_copyPackAsIs_withBase() throws Exception {
 				.map(size -> size - 12 - 20) // remove header + CRC
 				.sum();
 
-		DfsPackFileMidx midxBase = writeMultipackIndex(
+		DfsPackFileMidx midxBase = MidxTestUtils.writeMultipackIndex(db,
 				Arrays.copyOfRange(packs, 3, 6), null);
-		DfsPackFileMidx midxTip = writeMultipackIndex(
+		DfsPackFileMidx midxTip = MidxTestUtils.writeMultipackIndex(db,
 				Arrays.copyOfRange(packs, 0, 3), midxBase);
 
 		try (DfsReader ctx = db.getObjectDatabase().newReader();
@@ -561,9 +599,9 @@ public void midx_copyAsIs_withBase() throws Exception {
 
 		DfsPackFile[] packs = db.getObjectDatabase().getPacks();
 		// Packs are in reverse insertion order
-		DfsPackFileMidx midxBase = writeMultipackIndex(
+		DfsPackFileMidx midxBase = MidxTestUtils.writeMultipackIndex(db,
 				Arrays.copyOfRange(packs, 3, 6), null);
-		DfsPackFileMidx midxTip = writeMultipackIndex(
+		DfsPackFileMidx midxTip = MidxTestUtils.writeMultipackIndex(db,
 				Arrays.copyOfRange(packs, 0, 3), midxBase);
 
 		assertEquals(213, copyAsIs(midxTip, baseObject).length);
@@ -633,9 +671,9 @@ public void midx_getObjectType_withBase() throws Exception {
 
 		DfsPackFile[] packs = db.getObjectDatabase().getPacks();
 		// Packs are in reverse insertion order
-		DfsPackFileMidx midxBase = writeMultipackIndex(
+		DfsPackFileMidx midxBase = MidxTestUtils.writeMultipackIndex(db,
 				Arrays.copyOfRange(packs, 4, 7), null);
-		DfsPackFileMidx midxTip = writeMultipackIndex(
+		DfsPackFileMidx midxTip = MidxTestUtils.writeMultipackIndex(db,
 				Arrays.copyOfRange(packs, 0, 4), midxBase);
 
 		try (RevWalk rw = new RevWalk(db);
@@ -692,9 +730,9 @@ public void midx_getObjectSize_byId_withBase() throws Exception {
 
 		DfsPackFile[] packs = db.getObjectDatabase().getPacks();
 		// Packs are in reverse insertion order
-		DfsPackFileMidx midxBase = writeMultipackIndex(
+		DfsPackFileMidx midxBase = MidxTestUtils.writeMultipackIndex(db,
 				Arrays.copyOfRange(packs, 3, 5), null);
-		DfsPackFileMidx midxTip = writeMultipackIndex(
+		DfsPackFileMidx midxTip = MidxTestUtils.writeMultipackIndex(db,
 				Arrays.copyOfRange(packs, 0, 3), midxBase);
 
 		try (RevWalk rw = new RevWalk(db);
@@ -744,9 +782,9 @@ public void midx_getObjectSize_byOffset_withBase() throws Exception {
 
 		DfsPackFile[] packs = db.getObjectDatabase().getPacks();
 		// Packs are in reverse insertion order
-		DfsPackFileMidx midxBase = writeMultipackIndex(
+		DfsPackFileMidx midxBase = MidxTestUtils.writeMultipackIndex(db,
 				Arrays.copyOfRange(packs, 3, 5), null);
-		DfsPackFileMidx midxTip = writeMultipackIndex(
+		DfsPackFileMidx midxTip = MidxTestUtils.writeMultipackIndex(db,
 				Arrays.copyOfRange(packs, 0, 3), midxBase);
 
 		try (RevWalk rw = new RevWalk(db);
@@ -815,9 +853,9 @@ public void midx_fillRepresentation_withBase() throws Exception {
 
 		DfsPackFile[] packs = db.getObjectDatabase().getPacks();
 		assertEquals(6, packs.length);
-		DfsPackFileMidx midxBase = writeMultipackIndex(
+		DfsPackFileMidx midxBase = MidxTestUtils.writeMultipackIndex(db,
 				Arrays.copyOfRange(packs, 3, 6), null);
-		DfsPackFileMidx midxTip = writeMultipackIndex(
+		DfsPackFileMidx midxTip = MidxTestUtils.writeMultipackIndex(db,
 				Arrays.copyOfRange(packs, 0, 3), midxBase);
 
 		try (DfsReader ctx = db.getObjectDatabase().newReader()) {
@@ -872,7 +910,8 @@ public void midx_getAllCoveredPacks() throws Exception {
 
 		DfsPackFile[] packs = db.getObjectDatabase().getPacks();
 		assertEquals(4, packs.length);
-		DfsPackFileMidx midx = writeMultipackIndex(packs, null);
+		DfsPackFileMidx midx = MidxTestUtils.writeMultipackIndex(db, packs,
+				null);
 
 		assertEquals(4, midx.getAllCoveredPacks().size());
 		List<DfsPackDescription> expected = Arrays.stream(packs)
@@ -892,11 +931,11 @@ public void midx_getAllCoveredPacks_withBase() throws Exception {
 
 		DfsPackFile[] packs = db.getObjectDatabase().getPacks();
 		assertEquals(6, packs.length);
-		DfsPackFileMidx midxBase = writeMultipackIndex(
+		DfsPackFileMidx midxBase = MidxTestUtils.writeMultipackIndex(db,
 				Arrays.copyOfRange(packs, 4, 6), null);
-		DfsPackFileMidx midxMiddle = writeMultipackIndex(
+		DfsPackFileMidx midxMiddle = MidxTestUtils.writeMultipackIndex(db,
 				Arrays.copyOfRange(packs, 2, 4), midxBase);
-		DfsPackFileMidx midxTip = writeMultipackIndex(
+		DfsPackFileMidx midxTip = MidxTestUtils.writeMultipackIndex(db,
 				Arrays.copyOfRange(packs, 0, 2), midxMiddle);
 
 		assertEquals(6, midxTip.getAllCoveredPacks().size());
@@ -917,9 +956,9 @@ public void midx_getCoveredPacks_withBase_onlyTopMidx() throws Exception {
 
 		DfsPackFile[] packs = db.getObjectDatabase().getPacks();
 		assertEquals(6, packs.length);
-		DfsPackFileMidx midxBase = writeMultipackIndex(
+		DfsPackFileMidx midxBase = MidxTestUtils.writeMultipackIndex(db,
 				Arrays.copyOfRange(packs, 3, 6), null);
-		DfsPackFileMidx midxTip = writeMultipackIndex(
+		DfsPackFileMidx midxTip = MidxTestUtils.writeMultipackIndex(db,
 				Arrays.copyOfRange(packs, 0, 3), midxBase);
 
 		assertEquals(3, midxTip.getCoveredPacks().size());
@@ -977,6 +1016,24 @@ public void packwriter_via_midx() throws Exception {
 	}
 
 	@Test
+	public void getChecksum() throws Exception {
+		MidxTestUtils.writePackWithBlob(db, "something");
+		MidxTestUtils.writePackWithBlob(db, "something else");
+		MidxTestUtils.writePackWithBlob(db, "and more");
+		DfsPackFileMidx midx = writeMultipackIndex();
+
+		try (DfsReader ctx = db.getObjectDatabase().newReader()) {
+			byte[] checksum = midx.getChecksum(ctx);
+			assertNotNull(checksum);
+			assertEquals(20, checksum.length);
+			assertNotEquals('M', checksum[0]);
+			assertNotEquals('I', checksum[1]);
+			assertNotEquals('D', checksum[2]);
+			assertNotEquals('X', checksum[3]);
+		}
+	}
+
+	@Test
 	public void voffsetcalculator_encode() {
 		DfsPackFile one = createDfsPackFile(800);
 		DfsPackFile two = createDfsPackFile(1200);
@@ -1154,7 +1211,8 @@ private static DfsPackFile createDfsPackFile(int size) {
 	}
 
 	private DfsPackFileMidx writeMultipackIndex() throws IOException {
-		return writeMultipackIndex(db.getObjectDatabase().getPacks(), null);
+		DfsPackFile[] packs = db.getObjectDatabase().getPacks();
+		return MidxTestUtils.writeMultipackIndex(db, packs, null);
 	}
 
 	private void gcWithBitmaps() throws IOException {
@@ -1162,35 +1220,6 @@ private void gcWithBitmaps() throws IOException {
 		garbageCollector.pack(NullProgressMonitor.INSTANCE);
 	}
 
-	private DfsPackFileMidx writeMultipackIndex(DfsPackFile[] packs,
-			DfsPackFileMidx base) throws IOException {
-		LinkedHashMap<String, PackIndex> forMidx = new LinkedHashMap<>(
-				packs.length);
-		Map<String, DfsPackDescription> descByName = new HashMap<>(
-				packs.length);
-		try (DfsReader ctx = db.getObjectDatabase().newReader()) {
-			for (DfsPackFile pack : packs) {
-				forMidx.put(pack.getPackDescription().getPackName(),
-						pack.getPackIndex(ctx));
-				descByName.put(pack.getPackDescription().getPackName(),
-						pack.getPackDescription());
-			}
-		}
-		MultiPackIndexWriter w = new MultiPackIndexWriter();
-		DfsPackDescription desc = db.getObjectDatabase().newPack(GC);
-		try (DfsOutputStream out = db.getObjectDatabase().writeFile(desc,
-				PackExt.MULTI_PACK_INDEX)) {
-			MultiPackIndexWriter.Result midxStats = w
-					.write(NullProgressMonitor.INSTANCE, out, forMidx);
-			desc.setCoveredPacks(midxStats.packNames().stream()
-					.map(descByName::get).toList());
-			desc.addFileExt(PackExt.MULTI_PACK_INDEX);
-		}
-		db.getObjectDatabase().commitPack(List.of(desc), null);
-		return DfsPackFileMidx.create(DfsBlockCache.getInstance(), desc,
-				Arrays.asList(packs), base);
-	}
-
 	private RevCommit writePackWithCommit() throws Exception {
 		try (TestRepository<InMemoryRepository> repository = new TestRepository<>(
 				db)) {
diff --git a/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/dfs/DfsPackFileMidxSingleTest.java b/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/dfs/DfsPackFileMidxSingleTest.java
index 9f698db..aa2ddca 100644
--- a/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/dfs/DfsPackFileMidxSingleTest.java
+++ b/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/dfs/DfsPackFileMidxSingleTest.java
@@ -11,6 +11,8 @@
 
 import static java.nio.charset.StandardCharsets.UTF_8;
 import static org.eclipse.jgit.internal.storage.dfs.DfsObjDatabase.PackSource.GC;
+import static org.eclipse.jgit.internal.storage.dfs.MidxTestUtils.writePackWithBlobs;
+import static org.eclipse.jgit.internal.storage.dfs.MidxTestUtils.writeSinglePackMidx;
 import static org.eclipse.jgit.internal.storage.pack.PackExt.PACK;
 import static org.eclipse.jgit.lib.Constants.OBJ_BLOB;
 import static org.eclipse.jgit.lib.Constants.OBJ_COMMIT;
@@ -18,6 +20,7 @@
 import static org.junit.Assert.assertArrayEquals;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNotEquals;
 import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.assertNull;
 import static org.junit.Assert.assertThrows;
@@ -27,23 +30,16 @@
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
 import java.util.Arrays;
-import java.util.HashMap;
 import java.util.HashSet;
-import java.util.LinkedHashMap;
 import java.util.List;
-import java.util.Map;
 import java.util.Set;
-import java.util.zip.Deflater;
 
 import org.eclipse.jgit.annotations.Nullable;
 import org.eclipse.jgit.internal.storage.dfs.DfsPackFileMidx.DfsPackOffset;
 import org.eclipse.jgit.internal.storage.dfs.DfsPackFileMidxSingle.SingleVOffsetCalculator;
 import org.eclipse.jgit.internal.storage.file.PackBitmapIndex;
-import org.eclipse.jgit.internal.storage.file.PackIndex;
 import org.eclipse.jgit.internal.storage.midx.MultiPackIndex.PackOffset;
-import org.eclipse.jgit.internal.storage.midx.MultiPackIndexWriter;
 import org.eclipse.jgit.internal.storage.pack.ObjectToPack;
-import org.eclipse.jgit.internal.storage.pack.PackExt;
 import org.eclipse.jgit.internal.storage.pack.PackOutputStream;
 import org.eclipse.jgit.internal.storage.pack.PackWriter;
 import org.eclipse.jgit.junit.JGitTestUtil;
@@ -76,10 +72,10 @@ public void setUp() {
 
 	@Test
 	public void findIdxPosition() throws IOException {
-		ObjectId[] oids = writePackWithBlobs("something", "something else",
-				"and more");
+		ObjectId[] oids = writePackWithBlobs(db, "something",
+				"something else", "and more");
 		// oids = [a4..., 33..., 64...]
-		DfsPackFileMidx midx = writeSinglePackMidx();
+		DfsPackFileMidx midx = writeSinglePackMidx(db);
 
 		try (DfsReader ctx = db.getObjectDatabase().newReader()) {
 			assertEquals(2, midx.findIdxPosition(ctx, oids[0]));
@@ -91,19 +87,20 @@ public void findIdxPosition() throws IOException {
 
 	@Test
 	public void findIdxPosition_withBase() throws IOException {
-		ObjectId o1 = writePackWithBlob("o1".getBytes(UTF_8)); // 38
-		ObjectId o2 = writePackWithBlob("o2".getBytes(UTF_8)); // 4a
-		ObjectId o3 = writePackWithBlob("o3".getBytes(UTF_8)); // 45
-		ObjectId o4 = writePackWithBlob("o4".getBytes(UTF_8)); // 4b
-		ObjectId o5 = writePackWithBlob("o5".getBytes(UTF_8)); // 68
-		ObjectId o6 = writePackWithBlob("o6".getBytes(UTF_8)); // 4d
+		ObjectId o1 = MidxTestUtils.writePackWithBlob(db, "o1"); // 38
+		ObjectId o2 = MidxTestUtils.writePackWithBlob(db, "o2"); // 4a
+		ObjectId o3 = MidxTestUtils.writePackWithBlob(db, "o3"); // 45
+		ObjectId o4 = MidxTestUtils.writePackWithBlob(db, "o4"); // 4b
+		ObjectId o5 = MidxTestUtils.writePackWithBlob(db, "o5"); // 68
+		ObjectId o6 = MidxTestUtils.writePackWithBlob(db, "o6"); // 4d
 		DfsPackFile[] packs = db.getObjectDatabase().getPacks();
 
 		// Packs are in reverse insertion order
-		DfsPackFileMidx midxBase = writeMultipackIndex(
+		DfsPackFileMidx midxBase = MidxTestUtils.writeMultipackIndex(db,
 				Arrays.copyOfRange(packs, 3, 6), null);
-		DfsPackFileMidx midxMid = writeSinglePackMidx(packs[2], midxBase);
-		DfsPackFileMidx midxTip = writeMultipackIndex(
+		DfsPackFileMidx midxMid = writeSinglePackMidx(db,
+				packs[2], midxBase);
+		DfsPackFileMidx midxTip = MidxTestUtils.writeMultipackIndex(db,
 				Arrays.copyOfRange(packs, 0, 2), midxMid);
 
 		try (DfsReader ctx = db.getObjectDatabase().newReader()) {
@@ -117,9 +114,53 @@ public void findIdxPosition_withBase() throws IOException {
 	}
 
 	@Test
+	public void getObjectAt() throws IOException {
+		ObjectId[] oids = writePackWithBlobs(db, "something",
+				"something else", "and more");
+		// oids = [a4..., 33..., 64...]
+		DfsPackFileMidx midx = writeSinglePackMidx(db);
+
+		try (DfsReader ctx = db.getObjectDatabase().newReader()) {
+			assertEquals(oids[0], midx.getObjectAt(ctx, 2));
+			assertEquals(oids[1], midx.getObjectAt(ctx, 0));
+			assertEquals(oids[2], midx.getObjectAt(ctx, 1));
+		}
+	}
+
+	@Test
+	public void getObjectAt_withBase() throws IOException {
+		ObjectId o1 = MidxTestUtils.writePackWithBlob(db, "o1");
+		ObjectId o2 = MidxTestUtils.writePackWithBlob(db, "o2");
+		ObjectId o3 = MidxTestUtils.writePackWithBlob(db, "o3");
+		ObjectId o4 = MidxTestUtils.writePackWithBlob(db, "o4");
+		ObjectId o5 = MidxTestUtils.writePackWithBlob(db, "o5");
+		ObjectId o6 = MidxTestUtils.writePackWithBlob(db, "o6");
+		DfsPackFile[] packs = db.getObjectDatabase().getPacks();
+
+		// Packs are in reverse insertion order
+		DfsPackFileMidx midxBase = MidxTestUtils.writeMultipackIndex(db,
+				Arrays.copyOfRange(packs, 3, 6), null);
+		DfsPackFileMidx midxMid = writeSinglePackMidx(db,
+				packs[2], midxBase);
+		DfsPackFileMidx midxTip = MidxTestUtils.writeMultipackIndex(db,
+				Arrays.copyOfRange(packs, 0, 2), midxMid);
+
+		try (DfsReader ctx = db.getObjectDatabase().newReader()) {
+			assertEquals(o1, midxTip.getObjectAt(ctx, 0));
+			assertEquals(o3, midxTip.getObjectAt(ctx, 1));
+			assertEquals(o2, midxTip.getObjectAt(ctx, 2));
+			assertEquals(o4, midxTip.getObjectAt(ctx, 3));
+			// In sha1 order
+			assertEquals(o6, midxTip.getObjectAt(ctx, 4));
+			assertEquals(o5, midxTip.getObjectAt(ctx, 5));
+		}
+	}
+
+	@Test
 	public void hasObject() throws IOException {
-		ObjectId[] oids = writePackWithBlobs("aaaa", "bbbb", "cccc");
-		DfsPackFile midx = writeSinglePackMidx();
+		ObjectId[] oids = writePackWithBlobs(db, "aaaa", "bbbb",
+				"cccc");
+		DfsPackFile midx = writeSinglePackMidx(db);
 
 		// DfsPackFile midx = readDfsPackFileMidx();
 		try (DfsReader ctx = db.getObjectDatabase().newReader()) {
@@ -141,9 +182,10 @@ public void hasObject_withBase() throws IOException {
 		DfsPackFile[] packs = db.getObjectDatabase().getPacks();
 
 		// Packs are in reverse insertion order
-		DfsPackFileMidx midxBase = writeMultipackIndex(
+		DfsPackFileMidx midxBase = MidxTestUtils.writeMultipackIndex(db,
 				Arrays.copyOfRange(packs, 1, 6), null);
-		DfsPackFileMidx midxTip = writeSinglePackMidx(packs[0], midxBase);
+		DfsPackFileMidx midxTip = writeSinglePackMidx(db,
+				packs[0], midxBase);
 
 		try (DfsReader ctx = db.getObjectDatabase().newReader()) {
 			assertTrue(midxBase.hasObject(ctx, o1));
@@ -172,8 +214,9 @@ public void get() throws IOException {
 		byte[] contentTwo = "TWO".getBytes(UTF_8);
 		byte[] contentThree = "THREE".getBytes(UTF_8);
 
-		ObjectId[] oids = writePackWithBlobs("ONE", "TWO", "THREE");
-		DfsPackFile midx = writeSinglePackMidx();
+		ObjectId[] oids = writePackWithBlobs(db, "ONE", "TWO",
+				"THREE");
+		DfsPackFile midx = writeSinglePackMidx(db);
 
 		try (DfsReader ctx = db.getObjectDatabase().newReader()) {
 			ObjectLoader objectLoader = midx.get(ctx, oids[0]);
@@ -204,9 +247,10 @@ public void get_withBase() throws IOException {
 
 		DfsPackFile[] packs = db.getObjectDatabase().getPacks();
 		// Packs are in reverse insertion order
-		DfsPackFileMidx midxBase = writeMultipackIndex(
+		DfsPackFileMidx midxBase = MidxTestUtils.writeMultipackIndex(db,
 				Arrays.copyOfRange(packs, 1, 6), null);
-		DfsPackFileMidx midxTip = writeSinglePackMidx(packs[0], midxBase);
+		DfsPackFileMidx midxTip = writeSinglePackMidx(db,
+				packs[0], midxBase);
 
 		try (DfsReader ctx = db.getObjectDatabase().newReader()) {
 			ObjectLoader objectLoader = midxTip.get(ctx, o1);
@@ -232,8 +276,9 @@ public void load() throws IOException {
 		byte[] contentTwo = "TWO".getBytes(UTF_8);
 		byte[] contentThree = "THREE".getBytes(UTF_8);
 
-		ObjectId[] oids = writePackWithBlobs("ONE", "TWO", "THREE");
-		DfsPackFile midx = writeSinglePackMidx();
+		ObjectId[] oids = writePackWithBlobs(db, "ONE", "TWO",
+				"THREE");
+		DfsPackFile midx = writeSinglePackMidx(db);
 
 		try (DfsReader ctx = db.getObjectDatabase().newReader()) {
 			ObjectLoader objectLoader = midx.load(ctx,
@@ -268,9 +313,10 @@ public void load_withBase() throws IOException {
 
 		DfsPackFile[] packs = db.getObjectDatabase().getPacks();
 		// Packs are in reverse insertion order
-		DfsPackFileMidx midxBase = writeMultipackIndex(
+		DfsPackFileMidx midxBase = MidxTestUtils.writeMultipackIndex(db,
 				Arrays.copyOfRange(packs, 1, 6), null);
-		DfsPackFileMidx midxTip = writeSinglePackMidx(packs[0], midxBase);
+		DfsPackFileMidx midxTip = writeSinglePackMidx(db,
+				packs[0], midxBase);
 
 		try (DfsReader ctx = db.getObjectDatabase().newReader()) {
 			ObjectLoader objectLoader = midxTip.load(ctx,
@@ -293,8 +339,9 @@ public void load_withBase() throws IOException {
 
 	@Test
 	public void findOffset() throws IOException {
-		ObjectId[] oids = writePackWithBlobs("ONE", "TWO", "THREE");
-		DfsPackFileMidx midx = writeSinglePackMidx();
+		ObjectId[] oids = writePackWithBlobs(db, "ONE", "TWO",
+				"THREE");
+		DfsPackFileMidx midx = writeSinglePackMidx(db);
 		DfsPackFile realPack = findPack(oids[0]);
 
 		try (DfsReader ctx = db.getObjectDatabase().newReader()) {
@@ -328,9 +375,10 @@ public void findOffset_withBase() throws IOException {
 
 		DfsPackFile[] packs = db.getObjectDatabase().getPacks();
 		// Packs are in reverse insertion order
-		DfsPackFileMidx midxBase = writeMultipackIndex(
+		DfsPackFileMidx midxBase = MidxTestUtils.writeMultipackIndex(db,
 				Arrays.copyOfRange(packs, 1, 6), null);
-		DfsPackFileMidx midxTip = writeSinglePackMidx(packs[0], midxBase);
+		DfsPackFileMidx midxTip = writeSinglePackMidx(db,
+				packs[0], midxBase);
 		DfsPackFile coveredPack = findPack(o6);
 
 		try (DfsReader ctx = db.getObjectDatabase().newReader()) {
@@ -363,8 +411,9 @@ public void findOffset_withBase() throws IOException {
 	@Test
 	public void resolve() throws Exception {
 		// These oids do NOT have same prefix
-		ObjectId[] oids = writePackWithBlobs("AAAAAA", "BBBBBB", "CCCCCCC");
-		DfsPackFile midx = writeSinglePackMidx();
+		ObjectId[] oids = writePackWithBlobs(db, "AAAAAA",
+				"BBBBBB", "CCCCCCC");
+		DfsPackFile midx = writeSinglePackMidx(db);
 
 		try (DfsReader ctx = db.getObjectDatabase().newReader()) {
 			Set<ObjectId> matches = new HashSet<>();
@@ -392,9 +441,10 @@ public void resolve_withBase() throws Exception {
 
 		DfsPackFile[] packs = db.getObjectDatabase().getPacks();
 		// Packs are in reverse insertion order
-		DfsPackFileMidx midxBase = writeMultipackIndex(
+		DfsPackFileMidx midxBase = MidxTestUtils.writeMultipackIndex(db,
 				Arrays.copyOfRange(packs, 1, 6), null);
-		DfsPackFileMidx midxTip = writeSinglePackMidx(packs[0], midxBase);
+		DfsPackFileMidx midxTip = writeSinglePackMidx(db,
+				packs[0], midxBase);
 
 		try (DfsReader ctx = db.getObjectDatabase().newReader()) {
 			Set<ObjectId> matches = new HashSet<>();
@@ -423,8 +473,8 @@ public void resolve_withBase() throws Exception {
 
 	@Test
 	public void findAllFromPack() throws Exception {
-		ObjectId[] objectIds = writePackWithBlobs("aaaaaaaa", "bbbbbbbbb",
-				"cccccccccc");
+		ObjectId[] objectIds = writePackWithBlobs(db, "aaaaaaaa",
+				"bbbbbbbbb", "cccccccccc");
 		DfsPackFile midx = writeMultipackIndex();
 
 		List<ObjectToPack> otps = List.of(
@@ -463,9 +513,10 @@ public void findAllFromPack_withBase() throws Exception {
 
 		DfsPackFile[] packs = db.getObjectDatabase().getPacks();
 		// Packs are in reverse insertion order (o6 -> o1)
-		DfsPackFileMidx midxBase = writeMultipackIndex(
+		DfsPackFileMidx midxBase = MidxTestUtils.writeMultipackIndex(db,
 				Arrays.copyOfRange(packs, 1, 6), null);
-		DfsPackFileMidx midxTip = writeSinglePackMidx(packs[0], midxBase);
+		DfsPackFileMidx midxTip = writeSinglePackMidx(db,
+				packs[0], midxBase);
 
 		List<ObjectToPack> otps = List.of(new DfsObjectToPack(o1, OBJ_BLOB),
 				new DfsObjectToPack(o4, OBJ_BLOB),
@@ -504,9 +555,9 @@ public void findAllFromPack_withBase() throws Exception {
 
 	@Test
 	public void copyPackAsIs() throws Exception {
-		ObjectId[] objectIds = writePackWithBlobs("aaaaaa", "bbbbbbbb",
-				"ccccccccc");
-		DfsPackFileMidx midx = writeSinglePackMidx();
+		ObjectId[] objectIds = writePackWithBlobs(db, "aaaaaa",
+				"bbbbbbbb", "ccccccccc");
+		DfsPackFileMidx midx = writeSinglePackMidx(db);
 		DfsPackFile pack = findPack(objectIds[0]);
 		assertArrayEquals(copyPackAsIs(pack), copyPackAsIs(midx));
 	}
@@ -526,9 +577,10 @@ public void copyPackAsIs_withBase() throws Exception {
 				.map(size -> size - 12 - 20) // remove header + CRC
 				.sum();
 
-		DfsPackFileMidx midxBase = writeMultipackIndex(
+		DfsPackFileMidx midxBase = MidxTestUtils.writeMultipackIndex(db,
 				Arrays.copyOfRange(packs, 1, 6), null);
-		DfsPackFileMidx midxTip = writeSinglePackMidx(packs[0], midxBase);
+		DfsPackFileMidx midxTip = writeSinglePackMidx(db,
+				packs[0], midxBase);
 
 		try (DfsReader ctx = db.getObjectDatabase().newReader();
 				PackWriter pw = new PackWriter(new PackConfig(), ctx);
@@ -556,7 +608,7 @@ public void copyPackAsIs_withBase() throws Exception {
 	@Test
 	public void copyAsIs() throws Exception {
 		ObjectId blob = writePackWithRandomBlob(200);
-		DfsPackFileMidx midx = writeSinglePackMidx();
+		DfsPackFileMidx midx = writeSinglePackMidx(db);
 
 		assertEquals(213, copyAsIs(midx, blob).length);
 	}
@@ -567,14 +619,15 @@ public void copyAsIs_withBase() throws Exception {
 		ObjectId baseObject = writePackWithRandomBlob(200);
 		writePackWithRandomBlob(150);
 		writePackWithRandomBlob(400);
-		writePackWithBlob("woohooABCxxxxx11111".getBytes(UTF_8));
+		MidxTestUtils.writePackWithBlob(db, "woohooABCxxxxx11111");
 		ObjectId tipObject = writePackWithRandomBlob(600);
 
 		DfsPackFile[] packs = db.getObjectDatabase().getPacks();
 		// Packs are in reverse insertion order
-		DfsPackFileMidx midxBase = writeMultipackIndex(
+		DfsPackFileMidx midxBase = MidxTestUtils.writeMultipackIndex(db,
 				Arrays.copyOfRange(packs, 1, 6), null);
-		DfsPackFileMidx midxTip = writeSinglePackMidx(packs[0], midxBase);
+		DfsPackFileMidx midxTip = writeSinglePackMidx(db,
+				packs[0], midxBase);
 
 		assertEquals(213, copyAsIs(midxTip, baseObject).length);
 
@@ -613,7 +666,7 @@ public void getDeltaHeader() {
 	public void getObjectType() throws Exception {
 		CommitObjects commitObjects = writePackWithOneCommit();
 		gcWithBitmaps();
-		DfsPackFile midx = writeSinglePackMidx();
+		DfsPackFile midx = writeSinglePackMidx(db);
 
 		try (DfsReader ctx = db.getObjectDatabase().newReader()) {
 			long commitPos = midx.findOffset(ctx, commitObjects.commit());
@@ -642,9 +695,10 @@ public void getObjectType_withBase() throws Exception {
 
 		DfsPackFile[] packs = db.getObjectDatabase().getPacks();
 		// Packs are in reverse insertion order
-		DfsPackFileMidx midxBase = writeMultipackIndex(
+		DfsPackFileMidx midxBase = MidxTestUtils.writeMultipackIndex(db,
 				Arrays.copyOfRange(packs, 1, 7), null);
-		DfsPackFileMidx midxTip = writeSinglePackMidx(packs[0], midxBase);
+		DfsPackFileMidx midxTip = writeSinglePackMidx(db,
+				packs[0], midxBase);
 
 		try (DfsReader ctx = db.getObjectDatabase().newReader()) {
 			long commitPos = midxTip.findOffset(ctx, objs.commit());
@@ -668,7 +722,7 @@ public void getObjectType_withBase() throws Exception {
 	public void getObjectSize_byId() throws Exception {
 		CommitObjects objs = writePackWithOneCommit();
 		gcWithBitmaps();
-		DfsPackFile midx = writeSinglePackMidx();
+		DfsPackFile midx = writeSinglePackMidx(db);
 
 		try (DfsReader ctx = db.getObjectDatabase().newReader()) {
 			assertEquals(168, midx.getObjectSize(ctx, objs.commit()));
@@ -689,9 +743,10 @@ public void getObjectSize_byId_withBase() throws Exception {
 
 		DfsPackFile[] packs = db.getObjectDatabase().getPacks();
 		// Packs are in reverse insertion order
-		DfsPackFileMidx midxBase = writeMultipackIndex(
+		DfsPackFileMidx midxBase = MidxTestUtils.writeMultipackIndex(db,
 				Arrays.copyOfRange(packs, 1, 5), null);
-		DfsPackFileMidx midxTip = writeSinglePackMidx(packs[0], midxBase);
+		DfsPackFileMidx midxTip = writeSinglePackMidx(db,
+				packs[0], midxBase);
 
 		try (RevWalk rw = new RevWalk(db);
 				DfsReader ctx = db.getObjectDatabase().newReader()) {
@@ -711,7 +766,7 @@ public void getObjectSize_byId_withBase() throws Exception {
 	public void getObjectSize_byOffset() throws Exception {
 		ObjectId commit = writePackWithCommit();
 		gcWithBitmaps();
-		DfsPackFile midx = writeSinglePackMidx();
+		DfsPackFile midx = writeSinglePackMidx(db);
 
 		try (RevWalk rw = new RevWalk(db);
 				DfsReader ctx = db.getObjectDatabase().newReader()) {
@@ -737,9 +792,10 @@ public void getObjectSize_byOffset_withBase() throws Exception {
 
 		DfsPackFile[] packs = db.getObjectDatabase().getPacks();
 		// Packs are in reverse insertion order
-		DfsPackFileMidx midxBase = writeMultipackIndex(
+		DfsPackFileMidx midxBase = MidxTestUtils.writeMultipackIndex(db,
 				Arrays.copyOfRange(packs, 1, 5), null);
-		DfsPackFileMidx midxTip = writeSinglePackMidx(packs[0], midxBase);
+		DfsPackFileMidx midxTip = writeSinglePackMidx(db,
+				packs[0], midxBase);
 
 		try (RevWalk rw = new RevWalk(db);
 				DfsReader ctx = db.getObjectDatabase().newReader()) {
@@ -764,7 +820,7 @@ public void getObjectSize_byOffset_withBase() throws Exception {
 	@Test
 	public void objectSizeIndex_disabled() throws Exception {
 		writePackWithRandomBlob(200);
-		DfsPackFile midx = writeSinglePackMidx();
+		DfsPackFile midx = writeSinglePackMidx(db);
 
 		try (DfsReader ctx = db.getObjectDatabase().newReader()) {
 			assertFalse(midx.hasObjectSizeIndex(ctx));
@@ -775,7 +831,7 @@ public void objectSizeIndex_disabled() throws Exception {
 	public void fillRepresentation() throws Exception {
 		RevCommit commit = writePackWithCommit();
 		gcWithBitmaps();
-		DfsPackFile midx = writeSinglePackMidx();
+		DfsPackFile midx = writeSinglePackMidx(db);
 
 		DfsObjectRepresentation rep = fillRepresentation(midx, commit,
 				OBJ_COMMIT);
@@ -806,9 +862,10 @@ public void fillRepresentation_withBase() throws Exception {
 
 		DfsPackFile[] packs = db.getObjectDatabase().getPacks();
 		assertEquals(6, packs.length);
-		DfsPackFileMidx midxBase = writeMultipackIndex(
+		DfsPackFileMidx midxBase = MidxTestUtils.writeMultipackIndex(db,
 				Arrays.copyOfRange(packs, 1, 6), null);
-		DfsPackFileMidx midxTip = writeSinglePackMidx(packs[0], midxBase);
+		DfsPackFileMidx midxTip = writeSinglePackMidx(db,
+				packs[0], midxBase);
 
 		try (DfsReader ctx = db.getObjectDatabase().newReader()) {
 			// Commit in tip midx
@@ -841,7 +898,7 @@ public void getBitmapIndex() throws Exception {
 		RevCommit c2 = writePackWithCommit();
 		gcWithBitmaps();
 
-		DfsPackFileMidx midx = writeSinglePackMidx();
+		DfsPackFileMidx midx = writeSinglePackMidx(db);
 		try (DfsReader ctx = db.getObjectDatabase().newReader()) {
 			PackBitmapIndex bitmapIndex = midx.getBitmapIndex(ctx);
 			assertNotNull(bitmapIndex);
@@ -853,9 +910,9 @@ public void getBitmapIndex() throws Exception {
 
 	@Test
 	public void getAllCoveredPacks() throws Exception {
-		ObjectId[] objectIds = writePackWithBlobs("aaaaaaaa", "bbbbbbb",
-				"ccccccc");
-		DfsPackFileMidx midx = writeSinglePackMidx();
+		ObjectId[] objectIds = writePackWithBlobs(db, "aaaaaaaa",
+				"bbbbbbb", "ccccccc");
+		DfsPackFileMidx midx = writeSinglePackMidx(db);
 		DfsPackFile realPack = findPack(objectIds[0]);
 
 		assertEquals(1, midx.getAllCoveredPacks().size());
@@ -872,9 +929,10 @@ public void getAllCoveredPacks_withBase() throws Exception {
 
 		DfsPackFile[] packs = db.getObjectDatabase().getPacks();
 		assertEquals(5, packs.length);
-		DfsPackFileMidx midxBase = writeMultipackIndex(
+		DfsPackFileMidx midxBase = MidxTestUtils.writeMultipackIndex(db,
 				Arrays.copyOfRange(packs, 1, 5), null);
-		DfsPackFileMidx midxTip = writeSinglePackMidx(packs[0], midxBase);
+		DfsPackFileMidx midxTip = writeSinglePackMidx(db,
+				packs[0], midxBase);
 
 		assertEquals(5, midxTip.getAllCoveredPacks().size());
 		List<DfsPackDescription> expected = Arrays.stream(packs)
@@ -893,9 +951,10 @@ public void getCoveredPacks_withBase_onlyTopMidx() throws Exception {
 
 		DfsPackFile[] packs = db.getObjectDatabase().getPacks();
 		assertEquals(5, packs.length);
-		DfsPackFileMidx midxBase = writeMultipackIndex(
+		DfsPackFileMidx midxBase = MidxTestUtils.writeMultipackIndex(db,
 				Arrays.copyOfRange(packs, 1, 5), null);
-		DfsPackFileMidx midxTip = writeSinglePackMidx(packs[0], midxBase);
+		DfsPackFileMidx midxTip = writeSinglePackMidx(db,
+				packs[0], midxBase);
 
 		assertEquals(1, midxTip.getCoveredPacks().size());
 		assertEquals(packs[0].getPackDescription(),
@@ -905,7 +964,8 @@ public void getCoveredPacks_withBase_onlyTopMidx() throws Exception {
 	@Test
 	public void corrupt() throws Exception {
 		RevCommit commit = writePackWithCommit();
-		DfsPackFileMidx midx = writeSinglePackMidx(findPack(commit));
+		DfsPackFile pack = findPack(commit);
+		DfsPackFileMidx midx = writeSinglePackMidx(db, pack);
 		try (DfsReader ctx = db.getObjectDatabase().newReader()) {
 			assertFalse(midx.isCorrupt(midx.findOffset(ctx, commit)));
 		}
@@ -913,13 +973,13 @@ public void corrupt() throws Exception {
 
 	@Test
 	public void packwriter_via_midx() throws Exception {
-		ObjectId[] oids = writePackWithBlobs("xxxxxxxyyyy", "booooohooooo",
-				"baaaaahaaaaaa");
+		ObjectId[] oids = writePackWithBlobs(db, "xxxxxxxyyyy",
+				"booooohooooo", "baaaaahaaaaaa");
 		ObjectId blob = oids[0];
 		ObjectId blobTwo = oids[1];
 		ObjectId notPacked = oids[2];
 
-		writeSinglePackMidx();
+		writeSinglePackMidx(db);
 
 		db.getObjectDatabase().setUseMultipackIndex(true);
 		byte[] writtenPack;
@@ -951,6 +1011,26 @@ public void packwriter_via_midx() throws Exception {
 	}
 
 	@Test
+	public void getChecksum() throws Exception {
+		writePackWithBlobs(db, "something", "something else", "and more");
+		DfsPackFileMidx midx = writeSinglePackMidx(db);
+		try (DfsReader ctx = db.getObjectDatabase().newReader()) {
+			// The checksum includes packnames and can
+			// change between runs (e.g. running this test alone, or locally vs
+			// jenkins).
+			// Check at least that we don't get an empty checksum or the first
+			// bytes of the midx.
+			byte[] checksum = midx.getChecksum(ctx);
+			assertNotNull(checksum);
+			assertEquals(20, checksum.length);
+			assertNotEquals('M', checksum[0]);
+			assertNotEquals('I', checksum[1]);
+			assertNotEquals('D', checksum[2]);
+			assertNotEquals('X', checksum[3]);
+		}
+	}
+
+	@Test
 	public void voffsetcalculator_encode() {
 		DfsPackFile pack = createDfsPackFile(900);
 		SingleVOffsetCalculator calc = new SingleVOffsetCalculator(pack, null);
@@ -1061,23 +1141,8 @@ private static DfsPackFile createDfsPackFile(int size) {
 	}
 
 	private DfsPackFileMidx writeMultipackIndex() throws IOException {
-		return writeMultipackIndex(db.getObjectDatabase().getPacks(), null);
-	}
-
-	private DfsPackFileMidx writeSinglePackMidx() throws IOException {
 		DfsPackFile[] packs = db.getObjectDatabase().getPacks();
-		assertEquals("More than one pack in db", 1, packs.length);
-		return writeSinglePackMidx(packs[0]);
-	}
-
-	private DfsPackFileMidx writeSinglePackMidx(DfsPackFile pack)
-			throws IOException {
-		return writeMultipackIndex(new DfsPackFile[] { pack }, null);
-	}
-
-	private DfsPackFileMidx writeSinglePackMidx(DfsPackFile pack,
-			DfsPackFileMidx base) throws IOException {
-		return writeMultipackIndex(new DfsPackFile[] { pack }, base);
+		return MidxTestUtils.writeMultipackIndex(db, packs, null);
 	}
 
 	private void gcWithBitmaps() throws IOException {
@@ -1085,35 +1150,6 @@ private void gcWithBitmaps() throws IOException {
 		garbageCollector.pack(NullProgressMonitor.INSTANCE);
 	}
 
-	private DfsPackFileMidx writeMultipackIndex(DfsPackFile[] packs,
-			DfsPackFileMidx base) throws IOException {
-		LinkedHashMap<String, PackIndex> forMidx = new LinkedHashMap<>(
-				packs.length);
-		Map<String, DfsPackDescription> descByName = new HashMap<>(
-				packs.length);
-		try (DfsReader ctx = db.getObjectDatabase().newReader()) {
-			for (DfsPackFile pack : packs) {
-				forMidx.put(pack.getPackDescription().getPackName(),
-						pack.getPackIndex(ctx));
-				descByName.put(pack.getPackDescription().getPackName(),
-						pack.getPackDescription());
-			}
-		}
-		MultiPackIndexWriter w = new MultiPackIndexWriter();
-		DfsPackDescription desc = db.getObjectDatabase().newPack(GC);
-		try (DfsOutputStream out = db.getObjectDatabase().writeFile(desc,
-				PackExt.MULTI_PACK_INDEX)) {
-			MultiPackIndexWriter.Result midxStats = w
-					.write(NullProgressMonitor.INSTANCE, out, forMidx);
-			desc.setCoveredPacks(midxStats.packNames().stream()
-					.map(descByName::get).toList());
-			desc.addFileExt(PackExt.MULTI_PACK_INDEX);
-		}
-		db.getObjectDatabase().commitPack(List.of(desc), null);
-		return DfsPackFileMidx.create(DfsBlockCache.getInstance(), desc,
-				Arrays.asList(packs), base);
-	}
-
 	private RevCommit writePackWithCommit() throws Exception {
 		try (TestRepository<InMemoryRepository> repository = new TestRepository<>(
 				db)) {
@@ -1153,18 +1189,6 @@ private ObjectId writePackWithBlob(byte[] data) throws IOException {
 		return blobId;
 	}
 
-	private ObjectId[] writePackWithBlobs(String... blobs) throws IOException {
-		ObjectId[] oids = new ObjectId[blobs.length];
-
-		DfsInserter ins = (DfsInserter) db.newObjectInserter();
-		ins.setCompressionLevel(Deflater.NO_COMPRESSION);
-		for (int i = 0; i < blobs.length; i++) {
-			oids[i] = ins.insert(OBJ_BLOB, blobs[i].getBytes(UTF_8));
-		}
-		ins.flush();
-		return oids;
-	}
-
 	private DfsPackFile findPack(ObjectId oid) throws IOException {
 		DfsPackFile[] packs = db.getObjectDatabase().getPacks();
 		try (DfsReader ctx = db.getObjectDatabase().newReader()) {
diff --git a/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/file/PackBitmapIndexBuilderTest.java b/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/file/PackBitmapIndexBuilderTest.java
new file mode 100644
index 0000000..10d9c2e
--- /dev/null
+++ b/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/file/PackBitmapIndexBuilderTest.java
@@ -0,0 +1,318 @@
+/*
+ * Copyright (C) 2026, Google LLC.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Distribution License v. 1.0 which is available at
+ * https://www.eclipse.org/org/documents/edl-v10.php.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+package org.eclipse.jgit.internal.storage.file;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertTrue;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+
+import org.eclipse.jgit.internal.storage.pack.BitmapCommit;
+import org.eclipse.jgit.internal.storage.pack.ObjectToPack;
+import org.eclipse.jgit.lib.BitmapIndex;
+import org.eclipse.jgit.lib.Constants;
+import org.eclipse.jgit.lib.ObjectId;
+import org.eclipse.jgit.lib.ObjectIdOwnerMap;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.Parameterized;
+
+import com.googlecode.javaewah.EWAHCompressedBitmap;
+
+@RunWith(Parameterized.class)
+public class PackBitmapIndexBuilderTest {
+
+	/**
+	 * Numbers are oids
+	 *
+	 * <pre>
+	 *     tip
+	 *     10 (commit) -> 9 (tree) -> 8 (blob)
+	 *      |
+	 *      7 (commit) -> 6 (tree) -> 5,4  (blobs)
+	 *      |
+	 *      3 (commit) -> 2 (tree) ->  1 (blob)
+	 * </pre>
+	 */
+	private static final List<ObjectToPack> opts = List.of(
+			otp(10, 400, Constants.OBJ_COMMIT), otp(9, 900, Constants.OBJ_TREE),
+			otp(8, 280, Constants.OBJ_BLOB), otp(7, 200, Constants.OBJ_COMMIT),
+			otp(6, 410, Constants.OBJ_TREE), otp(5, 500, Constants.OBJ_BLOB),
+			otp(4, 450, Constants.OBJ_BLOB), otp(3, 470, Constants.OBJ_COMMIT),
+			otp(2, 700, Constants.OBJ_TREE), otp(1, 240, Constants.OBJ_BLOB));
+
+	public enum TestSetup {
+		SINGLE_BUILDER
+	}
+
+	@Parameterized.Parameters(name = "{0}")
+	public static Iterable<TestSetup> data() {
+		return Arrays.stream(TestSetup.values()).toList();
+	}
+
+	private final TestSetup currentSetup;
+
+	public PackBitmapIndexBuilderTest(TestSetup ts) {
+		this.currentSetup = ts;
+	}
+
+	@Test
+	public void getObjectSet() {
+		ObjectIdOwnerMap<ObjectIdOwnerMap.Entry> objectSet = createBuilder()
+				.getObjectSet();
+		for (int i = 1; i <= 10; i++) {
+			assertTrue(objectSet.contains(oid(i)));
+		}
+	}
+
+	@Test
+	public void addBitmap_getBitmap() {
+		EWAHCompressedBitmap added = EWAHCompressedBitmap.bitmapOf(1, 3, 5);
+		PackBitmapIndexBuilder pbi = createBuilder();
+		pbi.addBitmap(oid(11), added, 10);
+
+		EWAHCompressedBitmap retrieved = pbi.getBitmap(oid(11));
+		assertEquals(added, retrieved);
+	}
+
+	@Test
+	public void ofObjectType() {
+		PackBitmapIndexBuilder pbi = createBuilder();
+		BitmapIndexImpl bii = new BitmapIndexImpl(pbi);
+		BitmapIndex.BitmapBuilder bb = bii.newBitmapBuilder();
+		bb.addObject(oid(10), Constants.OBJ_COMMIT);
+		bb.addObject(oid(9), Constants.OBJ_TREE);
+		bb.addObject(oid(8), Constants.OBJ_BLOB);
+		BitmapIndex.Bitmap b = bb.build();
+
+		EWAHCompressedBitmap commits = pbi.ofObjectType(b.retrieveCompressed(),
+				Constants.OBJ_COMMIT);
+		assertInBitmap(pbi, commits, 10);
+		assertNotInBitmap(pbi, commits, 9);
+		assertNotInBitmap(pbi, commits, 8);
+
+		EWAHCompressedBitmap trees = pbi.ofObjectType(b.retrieveCompressed(),
+				Constants.OBJ_TREE);
+		assertNotInBitmap(pbi, trees, 10);
+		assertInBitmap(pbi, trees, 9);
+		assertNotInBitmap(pbi, trees, 8);
+
+		EWAHCompressedBitmap blobs = pbi.ofObjectType(b.retrieveCompressed(),
+				Constants.OBJ_BLOB);
+		assertNotInBitmap(pbi, blobs, 10);
+		assertNotInBitmap(pbi, blobs, 9);
+		assertInBitmap(pbi, blobs, 8);
+	}
+
+	@Test
+	public void findPosition() {
+		PackBitmapIndexBuilder pbi = createBuilder();
+		// All valid, non-repeating positions
+		Set<Integer> seen = new HashSet<>();
+		for (int oidAsInt = 1; oidAsInt <= 10; oidAsInt++) {
+			int p = pbi.findPosition(oid(oidAsInt));
+			assertTrue(p >= 0);
+			assertTrue(p < 10);
+			assertFalse(seen.contains(p));
+			seen.add(p);
+		}
+	}
+
+	@Test
+	public void getObject() {
+		PackBitmapIndexBuilder pbi = createBuilder();
+		for (int oidAsInt = 1; oidAsInt <= 10; oidAsInt++) {
+			ObjectId expected = oid(oidAsInt);
+			int p = pbi.findPosition(expected);
+			ObjectId actual = pbi.getObject(p);
+			assertEquals(expected, actual);
+		}
+	}
+
+	@Test
+	public void commits() {
+		PackBitmapIndexBuilder pbi = createBuilder();
+		EWAHCompressedBitmap commits = pbi.getCommits();
+		assertInBitmap(pbi, commits, 10);
+		assertInBitmap(pbi, commits, 7);
+		assertInBitmap(pbi, commits, 3);
+
+		assertNotInBitmap(pbi, commits, 9);
+		assertNotInBitmap(pbi, commits, 8);
+	}
+
+	@Test
+	public void trees() {
+		PackBitmapIndexBuilder pbi = createBuilder();
+		EWAHCompressedBitmap trees = pbi.getTrees();
+		assertInBitmap(pbi, trees, 9);
+		assertInBitmap(pbi, trees, 6);
+		assertInBitmap(pbi, trees, 2);
+
+		assertNotInBitmap(pbi, trees, 10);
+		assertNotInBitmap(pbi, trees, 8);
+	}
+
+	@Test
+	public void blobs() {
+		PackBitmapIndexBuilder pbi = createBuilder();
+		EWAHCompressedBitmap blobs = pbi.getBlobs();
+		assertInBitmap(pbi, blobs, 8);
+		assertInBitmap(pbi, blobs, 5);
+		assertInBitmap(pbi, blobs, 4);
+		assertInBitmap(pbi, blobs, 1);
+
+		assertNotInBitmap(pbi, blobs, 10);
+		assertNotInBitmap(pbi, blobs, 9);
+	}
+
+	@Test
+	public void getBitmapCount() {
+		// The builder only counts bitmaps "in progress" (in xor queue or ready
+		// to write)
+		assertEquals(0, createBuilder().getBitmapCount());
+	}
+
+	@Test
+	public void getBitmapCount_newBitmaps() {
+
+	}
+
+	@Test
+	public void reachableObjects_setInBitmap() {
+		PackBitmapIndexBuilder builder = createBuilder();
+		EWAHCompressedBitmap bitmapTen = builder.getBitmap(oid(10));
+		assertNotNull(bitmapTen);
+		for (int oidAsInt = 10; oidAsInt > 0; oidAsInt--) {
+			assertInBitmap(builder, bitmapTen, oidAsInt);
+		}
+
+		EWAHCompressedBitmap bitmapSeven = builder.getBitmap(oid(7));
+		assertNotNull(bitmapSeven);
+		assertNotInBitmap(builder, bitmapSeven, 10);
+		assertNotInBitmap(builder, bitmapSeven, 9);
+		assertNotInBitmap(builder, bitmapSeven, 8);
+		for (int i = 7; i > 0; i--) {
+			assertInBitmap(builder, bitmapSeven, i);
+		}
+	}
+
+	@Test
+	public void processBitmapForWrite() {
+		// processBitmapForWrite keeps the bitmaps in the builder instead of in
+		// the superclass, to calculate the XORs
+		PackBitmapIndexBuilder builder = createBuilder();
+		BitmapIndex bb = new BitmapIndexImpl(builder);
+		BitmapIndex.BitmapBuilder oneBitmap = bb.newBitmapBuilder();
+		oneBitmap.addObject(oid(10), Constants.OBJ_COMMIT);
+		oneBitmap.addObject(oid(9), Constants.OBJ_TREE);
+		oneBitmap.addObject(oid(8), Constants.OBJ_BLOB);
+		oneBitmap.addObject(oid(7), Constants.OBJ_COMMIT);
+		oneBitmap.addObject(oid(6), Constants.OBJ_TREE);
+		oneBitmap.addObject(oid(5), Constants.OBJ_BLOB);
+
+		BitmapIndex.BitmapBuilder anotherBitmap = bb.newBitmapBuilder();
+		anotherBitmap.addObject(oid(7), Constants.OBJ_COMMIT);
+		anotherBitmap.addObject(oid(6), Constants.OBJ_TREE);
+		anotherBitmap.addObject(oid(5), Constants.OBJ_BLOB);
+
+		builder.processBitmapForWrite(
+				new BitmapCommit(oid(10), false, 0, false), oneBitmap, 0);
+		builder.processBitmapForWrite(new BitmapCommit(oid(7), false, 0, false),
+				oneBitmap, 0);
+		assertEquals(2, builder.getBitmapCount());
+
+		List<PackBitmapIndexBuilder.StoredEntry> ses = builder
+				.getCompressedBitmaps();
+		assertEquals(2, ses.size());
+		assertEquals(oid(7), ses.get(0).getObjectId());
+		assertEquals(6, ses.get(0).getIdxPosition());
+
+		assertEquals(oid(10), ses.get(1).getObjectId());
+		assertEquals(9, ses.get(1).getIdxPosition());
+	}
+
+	@Test
+	public void getObjectCount() {
+		assertEquals(10, createBuilder().getObjectCount());
+	}
+
+	private static void assertInBitmap(PackBitmapIndexBuilder builder,
+			EWAHCompressedBitmap bitmap, int oidAsInt) {
+		ObjectId oid = oid(oidAsInt);
+		int pos = builder.findPosition(oid);
+		assertTrue(pos >= 0);
+		assertTrue(bitmap.get(pos));
+	}
+
+	private static void assertNotInBitmap(PackBitmapIndexBuilder builder,
+			EWAHCompressedBitmap bitmap, int oidAsInt) {
+		ObjectId oid = oid(oidAsInt);
+		int pos = builder.findPosition(oid);
+		assertTrue(pos >= 0);
+		assertFalse(bitmap.get(pos));
+	}
+
+	private PackBitmapIndexBuilder createBuilder() {
+		ArrayList<ObjectToPack> objectsToPack = new ArrayList<>(opts);
+		Collections.reverse(objectsToPack);
+		return switch (currentSetup) {
+		case SINGLE_BUILDER -> setupSinglePackBitmapIndex(objectsToPack);
+		};
+	}
+
+	static PackBitmapIndexBuilder setupSinglePackBitmapIndex(
+			List<ObjectToPack> objectsToPack) {
+		PackBitmapIndexBuilder b = new PackBitmapIndexBuilder(objectsToPack);
+
+		BitmapIndex bi = new BitmapIndexImpl(b);
+		// Base commit (3, 2, 1)
+		BitmapIndex.BitmapBuilder bitmapOne = bi.newBitmapBuilder();
+		bitmapOne.addObject(oid(3), Constants.OBJ_COMMIT);
+		bitmapOne.addObject(oid(2), Constants.OBJ_TREE);
+		bitmapOne.addObject(oid(1), Constants.OBJ_BLOB);
+		b.addBitmap(oid(3), bitmapOne.build(), 0);
+
+		// Middle commit (7, 6, 5, 4) with base commit as parent
+		BitmapIndex.BitmapBuilder middleBitmap = bi.newBitmapBuilder();
+		middleBitmap.addObject(oid(7), Constants.OBJ_COMMIT);
+		middleBitmap.addObject(oid(6), Constants.OBJ_TREE);
+		middleBitmap.addObject(oid(5), Constants.OBJ_BLOB);
+		middleBitmap.addObject(oid(4), Constants.OBJ_BLOB);
+		middleBitmap.or(bitmapOne);
+		b.addBitmap(oid(7), middleBitmap, 0);
+
+		BitmapIndex.BitmapBuilder tipBitmap = bi.newBitmapBuilder();
+		tipBitmap.addObject(oid(10), Constants.OBJ_COMMIT);
+		tipBitmap.addObject(oid(9), Constants.OBJ_TREE);
+		tipBitmap.addObject(oid(8), Constants.OBJ_BLOB);
+		tipBitmap.or(middleBitmap);
+		b.addBitmap(oid(10), tipBitmap, 0);
+
+		return b;
+	}
+
+	private static ObjectToPack otp(int oid, long offset, int type) {
+		ObjectToPack otp = new ObjectToPack(oid(oid), type);
+		otp.setOffset(offset);
+		return otp;
+	}
+
+	private static ObjectId oid(int n) {
+		return ObjectId.fromRaw(new int[] { 0, 0, 0, 0, n });
+	}
+}
diff --git a/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/midx/MultiPackIndexTest.java b/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/midx/MultiPackIndexTest.java
index 6436e31..3a90e21 100644
--- a/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/midx/MultiPackIndexTest.java
+++ b/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/midx/MultiPackIndexTest.java
@@ -126,6 +126,7 @@ public void basicMidx() throws IOException {
 				1502);
 
 		assertNull(midx.find(ObjectId.zeroId()));
+		assertNotNull(midx.getChecksum());
 	}
 
 	@Test
@@ -387,24 +388,24 @@ public void jgit_findPosition() throws IOException {
 		MultiPackIndex midx = MultiPackIndexLoader
 				.read(new ByteArrayInputStream(out.toByteArray()));
 		assertEquals(3, midx.getPackNames().length);
-		assertEquals(0, midx.findPosition(ObjectId
-				.fromString("0000000000000000000000000000000000000001")));
-		assertEquals(1, midx.findPosition(ObjectId
-				.fromString("0000000000000000000000000000000000000002")));
-		assertEquals(2, midx.findPosition(ObjectId
-				.fromString("0000000000000000000000000000000000000003")));
-		assertEquals(3, midx.findPosition(ObjectId
-				.fromString("0000000000000000000000000000000000000004")));
-		assertEquals(4, midx.findPosition(ObjectId
-				.fromString("0000000000000000000000000000000000000005")));
-		assertEquals(5, midx.findPosition(ObjectId
-				.fromString("0000000000000000000000000000000000000007")));
-		assertEquals(6, midx.findPosition(ObjectId
-				.fromString("0000000000000000000000000000000000000010")));
-		assertEquals(7, midx.findPosition(ObjectId
-				.fromString("0000000000000000000000000000000000000012")));
-		assertEquals(8, midx.findPosition(ObjectId
-				.fromString("0000000000000000000000000000000000000015")));
+		assertEquals(0, midx.findPosition(oid("001")));
+		assertEquals(oid("001"), midx.getObjectAt(0));
+		assertEquals(1, midx.findPosition(oid("002")));
+		assertEquals(oid("002"), midx.getObjectAt(1));
+		assertEquals(2, midx.findPosition(oid("003")));
+		assertEquals(oid("003"), midx.getObjectAt(2));
+		assertEquals(3, midx.findPosition(oid("004")));
+		assertEquals(oid("004"), midx.getObjectAt(3));
+		assertEquals(4, midx.findPosition(oid("005")));
+		assertEquals(oid("005"), midx.getObjectAt(4));
+		assertEquals(5, midx.findPosition(oid("007")));
+		assertEquals(oid("007"), midx.getObjectAt(5));
+		assertEquals(6, midx.findPosition(oid("010")));
+		assertEquals(oid("010"), midx.getObjectAt(6));
+		assertEquals(7, midx.findPosition(oid("012")));
+		assertEquals(oid("012"), midx.getObjectAt(7));
+		assertEquals(8, midx.findPosition(oid("015")));
+		assertEquals(oid("015"), midx.getObjectAt(8));
 
 		assertNull(midx.find(ObjectId.zeroId()));
 	}
@@ -460,6 +461,129 @@ public void jgit_getObjectCount_emtpy() throws IOException {
 		assertEquals(0, midx.getObjectCount());
 	}
 
+	@Test
+	public void jgit_findBitmapPosition() throws IOException {
+		PackIndex idxOne = FakeIndexFactory.indexOf(List.of(
+				new FakeIndexFactory.IndexObject(
+						"0000000000000000000000000000000000000001", 500),
+				new FakeIndexFactory.IndexObject(
+						"0000000000000000000000000000000000000005", 12),
+				new FakeIndexFactory.IndexObject(
+						"0000000000000000000000000000000000000010", 1500)));
+		PackIndex idxTwo = FakeIndexFactory.indexOf(List.of(
+				new FakeIndexFactory.IndexObject(
+						"0000000000000000000000000000000000000002", 501),
+				new FakeIndexFactory.IndexObject(
+						"0000000000000000000000000000000000000003", 13),
+				new FakeIndexFactory.IndexObject(
+						"0000000000000000000000000000000000000015", 1501)));
+		PackIndex idxThree = FakeIndexFactory.indexOf(List.of(
+				new FakeIndexFactory.IndexObject(
+						"0000000000000000000000000000000000000004", 502),
+				new FakeIndexFactory.IndexObject(
+						"0000000000000000000000000000000000000007", 14),
+				new FakeIndexFactory.IndexObject(
+						"0000000000000000000000000000000000000012", 1502)));
+
+		LinkedHashMap<String, PackIndex> packs = orderedMapOf("p1", idxOne,
+				"p2", idxTwo, "p3", idxThree);
+		MultiPackIndexWriter writer = new MultiPackIndexWriter();
+		ByteArrayOutputStream out = new ByteArrayOutputStream();
+		writer.write(NullProgressMonitor.INSTANCE, out, packs);
+
+		MultiPackIndex midx = MultiPackIndexLoader
+				.read(new ByteArrayInputStream(out.toByteArray()));
+		MultiPackIndex.PackOffset packOffset;
+		packOffset = midx.find(ObjectId
+				.fromString("0000000000000000000000000000000000000005"));
+		assertEquals(0, midx.findBitmapPosition(packOffset));
+		packOffset = midx.find(ObjectId
+				.fromString("0000000000000000000000000000000000000001"));
+		assertEquals(1, midx.findBitmapPosition(packOffset));
+		packOffset = midx.find(ObjectId
+				.fromString("0000000000000000000000000000000000000010"));
+		assertEquals(2, midx.findBitmapPosition(packOffset));
+		packOffset = midx.find(ObjectId
+				.fromString("0000000000000000000000000000000000000003"));
+		assertEquals(3, midx.findBitmapPosition(packOffset));
+		packOffset = midx.find(ObjectId
+				.fromString("0000000000000000000000000000000000000002"));
+		assertEquals(4, midx.findBitmapPosition(packOffset));
+		packOffset = midx.find(ObjectId
+				.fromString("0000000000000000000000000000000000000015"));
+		assertEquals(5, midx.findBitmapPosition(packOffset));
+		packOffset = midx.find(ObjectId
+				.fromString("0000000000000000000000000000000000000007"));
+		assertEquals(6, midx.findBitmapPosition(packOffset));
+		packOffset = midx.find(ObjectId
+				.fromString("0000000000000000000000000000000000000004"));
+		assertEquals(7, midx.findBitmapPosition(packOffset));
+		packOffset = midx.find(ObjectId
+				.fromString("0000000000000000000000000000000000000012"));
+		assertEquals(8, midx.findBitmapPosition(packOffset));
+	}
+
+	@Test
+	public void jgit_getObjectAtBitmapPosition() throws IOException {
+		PackIndex idxOne = FakeIndexFactory.indexOf(List.of(
+				new FakeIndexFactory.IndexObject(
+						"0000000000000000000000000000000000000001", 500),
+				new FakeIndexFactory.IndexObject(
+						"0000000000000000000000000000000000000005", 12),
+				new FakeIndexFactory.IndexObject(
+						"0000000000000000000000000000000000000010", 1500)));
+		PackIndex idxTwo = FakeIndexFactory.indexOf(List.of(
+				new FakeIndexFactory.IndexObject(
+						"0000000000000000000000000000000000000002", 501),
+				new FakeIndexFactory.IndexObject(
+						"0000000000000000000000000000000000000003", 13),
+				new FakeIndexFactory.IndexObject(
+						"0000000000000000000000000000000000000015", 1501)));
+		PackIndex idxThree = FakeIndexFactory.indexOf(List.of(
+				new FakeIndexFactory.IndexObject(
+						"0000000000000000000000000000000000000004", 502),
+				new FakeIndexFactory.IndexObject(
+						"0000000000000000000000000000000000000007", 14),
+				new FakeIndexFactory.IndexObject(
+						"0000000000000000000000000000000000000012", 1502)));
+
+		LinkedHashMap<String, PackIndex> packs = orderedMapOf("p1", idxOne,
+				"p2", idxTwo, "p3", idxThree);
+		MultiPackIndexWriter writer = new MultiPackIndexWriter();
+		ByteArrayOutputStream out = new ByteArrayOutputStream();
+		writer.write(NullProgressMonitor.INSTANCE, out, packs);
+
+		MultiPackIndex midx = MultiPackIndexLoader
+				.read(new ByteArrayInputStream(out.toByteArray()));
+		assertEquals(
+				ObjectId.fromString("0000000000000000000000000000000000000005"),
+				midx.getObjectAtBitmapPosition(0));
+		assertEquals(
+				ObjectId.fromString("0000000000000000000000000000000000000001"),
+				midx.getObjectAtBitmapPosition(1));
+		assertEquals(
+				ObjectId.fromString("0000000000000000000000000000000000000010"),
+				midx.getObjectAtBitmapPosition(2));
+		assertEquals(
+				ObjectId.fromString("0000000000000000000000000000000000000003"),
+				midx.getObjectAtBitmapPosition(3));
+		assertEquals(
+				ObjectId.fromString("0000000000000000000000000000000000000002"),
+				midx.getObjectAtBitmapPosition(4));
+		assertEquals(
+				ObjectId.fromString("0000000000000000000000000000000000000015"),
+				midx.getObjectAtBitmapPosition(5));
+		assertEquals(
+				ObjectId.fromString("0000000000000000000000000000000000000007"),
+				midx.getObjectAtBitmapPosition(6));
+		assertEquals(
+				ObjectId.fromString("0000000000000000000000000000000000000004"),
+				midx.getObjectAtBitmapPosition(7));
+		assertEquals(
+				ObjectId.fromString("0000000000000000000000000000000000000012"),
+				midx.getObjectAtBitmapPosition(8));
+	}
+
 	private static PackIndex indexWith(String... oids) {
 		List<FakeIndexFactory.IndexObject> idxObjs = new ArrayList<>(
 				oids.length);
@@ -497,4 +621,10 @@ private static LinkedHashMap<String, PackIndex> orderedMapOf(String s1,
 		map.put(s3, pi3);
 		return map;
 	}
+
+	private static ObjectId oid(String last3chars) {
+		assertEquals(3, last3chars.length());
+		return ObjectId.fromString(
+				"0000000000000000000000000000000000000" + last3chars);
+	}
 }
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/dfs/DfsMidxWriter.java b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/dfs/DfsMidxWriter.java
index 28ef98d..8302694 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/dfs/DfsMidxWriter.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/dfs/DfsMidxWriter.java
@@ -68,6 +68,7 @@ public static DfsPackDescription writeMidx(ProgressMonitor pm,
 			MultiPackIndexWriter w = new MultiPackIndexWriter();
 			MultiPackIndexWriter.Result result = w.write(pm, out, inputs);
 			midxPackDesc.addFileExt(MULTI_PACK_INDEX);
+			midxPackDesc.setFileSize(MULTI_PACK_INDEX, result.bytesWritten());
 			midxPackDesc.setObjectCount(result.objectCount());
 
 			Map<String, DfsPackDescription> byName = packs.stream()
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/dfs/DfsPackFile.java b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/dfs/DfsPackFile.java
index ecc97e9..4997b90 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/dfs/DfsPackFile.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/dfs/DfsPackFile.java
@@ -241,20 +241,6 @@ void setPackIndex(PackIndex idx) {
 	}
 
 	/**
-	 * Get the PackIndex for this PackFile.
-	 *
-	 * @param ctx
-	 *            reader context to support reading from the backing store if
-	 *            the index is not already loaded in memory.
-	 * @return the PackIndex.
-	 * @throws java.io.IOException
-	 *             the pack index is not available, or is corrupt.
-	 */
-	public PackIndex getPackIndex(DfsReader ctx) throws IOException {
-		return idx(ctx);
-	}
-
-	/**
 	 * Get a view of this packfile as a set of objects
 	 * <p>
 	 * To use when the caller only needs to check inclusion (without specific
@@ -267,10 +253,20 @@ public PackIndex getPackIndex(DfsReader ctx) throws IOException {
 	 *             cannot load the backing data from storage
 	 */
 	public ObjectIdSet asObjectIdSet(DfsReader ctx) throws IOException {
-		return idx(ctx);
+		return getPackIndex(ctx);
 	}
 
-	private PackIndex idx(DfsReader ctx) throws IOException {
+	/**
+	 * Get the PackIndex for this PackFile.
+	 *
+	 * @param ctx
+	 *            reader context to support reading from the backing store if
+	 *            the index is not already loaded in memory.
+	 * @return the PackIndex.
+	 * @throws java.io.IOException
+	 *             the pack index is not available, or is corrupt.
+	 */
+	public PackIndex getPackIndex(DfsReader ctx) throws IOException {
 		if (index != null) {
 			return index;
 		}
@@ -399,7 +395,8 @@ public PackReverseIndex getReverseIdx(DfsReader ctx) throws IOException {
 			return reverseIndex;
 		}
 
-		reverseIndex = indexFactory.getPackIndexes().reverseIndex(ctx, idx(ctx));
+		reverseIndex = indexFactory.getPackIndexes().reverseIndex(ctx,
+				getPackIndex(ctx));
 		if (reverseIndex == null) {
 			throw new IOException(
 					"Couldn't get a reference to the reverse index"); //$NON-NLS-1$
@@ -460,12 +457,12 @@ private PackObjectSizeIndex getObjectSizeIndex(DfsReader ctx)
 	 *             the pack index is not available, or is corrupt.
 	 */
 	public boolean hasObject(DfsReader ctx, AnyObjectId id) throws IOException {
-		final long offset = idx(ctx).findOffset(id);
+		final long offset = getPackIndex(ctx).findOffset(id);
 		return 0 < offset && !isCorrupt(offset);
 	}
 
 	int findIdxPosition(DfsReader ctx, AnyObjectId id) throws IOException {
-		return idx(ctx).findPosition(id);
+		return getPackIndex(ctx).findPosition(id);
 	}
 
 	/**
@@ -482,12 +479,12 @@ int findIdxPosition(DfsReader ctx, AnyObjectId id) throws IOException {
 	 */
 	ObjectLoader get(DfsReader ctx, AnyObjectId id)
 			throws IOException {
-		long offset = idx(ctx).findOffset(id);
+		long offset = getPackIndex(ctx).findOffset(id);
 		return 0 < offset && !isCorrupt(offset) ? load(ctx, offset) : null;
 	}
 
 	long findOffset(DfsReader ctx, AnyObjectId id) throws IOException {
-		return idx(ctx).findOffset(id);
+		return getPackIndex(ctx).findOffset(id);
 	}
 
 	/**
@@ -513,7 +510,7 @@ List<DfsObjectToPack> findAllFromPack(DfsReader ctx,
 			if (skipFound && otp.isFound()) {
 				continue;
 			}
-			long p = idx(ctx).findOffset(otp);
+			long p = getPackIndex(ctx).findOffset(otp);
 			if (p <= 0 || isCorrupt(p)) {
 				continue;
 			}
@@ -526,7 +523,7 @@ List<DfsObjectToPack> findAllFromPack(DfsReader ctx,
 
 	void resolve(DfsReader ctx, Set<ObjectId> matches, AbbreviatedObjectId id,
 			int matchLimit) throws IOException {
-		idx(ctx).resolve(matches, id, matchLimit);
+		getPackIndex(ctx).resolve(matches, id, matchLimit);
 	}
 
 	private byte[] decompress(long position, int sz, DfsReader ctx)
@@ -703,11 +700,11 @@ void copyAsIs(PackOutputStream out, DfsObjectToPack src,
 		try {
 			quickCopy = ctx.quickCopy(this, dataOffset, dataLength);
 
-			if (validate && idx(ctx).hasCRC32Support()) {
+			if (validate && getPackIndex(ctx).hasCRC32Support()) {
 				assert(crc1 != null);
 				// Index has the CRC32 code cached, validate the object.
 				//
-				expectedCRC = idx(ctx).findCRC32(src);
+				expectedCRC = getPackIndex(ctx).findCRC32(src);
 				if (quickCopy != null) {
 					quickCopy.crc32(crc1, dataOffset, (int) dataLength);
 				} else {
@@ -1000,7 +997,7 @@ ObjectLoader load(DfsReader ctx, long pos)
 
 	private long findDeltaBase(DfsReader ctx, ObjectId baseId)
 			throws IOException, MissingObjectException {
-		long ofs = idx(ctx).findOffset(baseId);
+		long ofs = getPackIndex(ctx).findOffset(baseId);
 		if (ofs < 0) {
 			throw new MissingObjectException(baseId,
 					JGitText.get().missingDeltaBase);
@@ -1094,7 +1091,7 @@ int getObjectType(DfsReader ctx, long pos) throws IOException {
 	}
 
 	long getObjectSize(DfsReader ctx, AnyObjectId id) throws IOException {
-		final long offset = idx(ctx).findOffset(id);
+		final long offset = getPackIndex(ctx).findOffset(id);
 		return 0 < offset ? getObjectSize(ctx, offset) : -1;
 	}
 
@@ -1545,7 +1542,8 @@ public LoadResult loadPackBitmapIndex(DfsReader ctx, DfsPackFile pack)
 				PackBitmapIndex bmidx;
 				try {
 					bmidx = PackBitmapIndex.read(alignTo8kBlocks(rc),
-							() -> pack.idx(ctx), () -> pack.getReverseIdx(ctx),
+							() -> pack.getPackIndex(ctx),
+							() -> pack.getReverseIdx(ctx),
 							ctx.getOptions().shouldLoadRevIndexInParallel());
 				} finally {
 					size = rc.position();
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/dfs/DfsPackFileMidx.java b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/dfs/DfsPackFileMidx.java
index 0f96593..ba4d5f6 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/dfs/DfsPackFileMidx.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/dfs/DfsPackFileMidx.java
@@ -11,7 +11,9 @@
 
 import java.io.IOException;
 import java.util.ArrayList;
+import java.util.Iterator;
 import java.util.List;
+import java.util.Set;
 import java.util.zip.DataFormatException;
 
 import org.eclipse.jgit.annotations.Nullable;
@@ -19,6 +21,9 @@
 import org.eclipse.jgit.internal.storage.file.PackIndex;
 import org.eclipse.jgit.internal.storage.file.PackReverseIndex;
 import org.eclipse.jgit.internal.storage.pack.PackOutputStream;
+import org.eclipse.jgit.lib.AbbreviatedObjectId;
+import org.eclipse.jgit.lib.AnyObjectId;
+import org.eclipse.jgit.lib.ObjectId;
 import org.eclipse.jgit.lib.ObjectLoader;
 
 /**
@@ -104,6 +109,24 @@ public List<DfsPackFile> getAllCoveredPacks() {
 	}
 
 	/**
+	 * Get the objectId at the corresponding position in the midx chain up to
+	 * this point
+	 * <p>
+	 * In a chain with midx-tip (100 objects) and midx-base (50 objects),
+	 * positions 0-49 belong to the base midx and 50-149 to the tip midx.
+	 *
+	 * @param ctx
+	 *            a reader for the midx data
+	 * @param nthPosition
+	 *            position in midx chain
+	 * @return the objectId
+	 * @throws IOException
+	 *             a problem reading midx bytes
+	 */
+	abstract ObjectId getObjectAt(DfsReader ctx, long nthPosition)
+			throws IOException;
+
+	/**
 	 * Count of objects in this <b>pack</b> (i.e. including, recursively, its
 	 * base)
 	 *
@@ -117,17 +140,25 @@ protected int getObjectCount(DfsReader ctx) throws IOException {
 		return (int) getPackDescription().getObjectCount();
 	}
 
+	/**
+	 * Return checksum of the midx
+	 *
+	 * @param ctx
+	 *            a reader
+	 * @return checksum of the midx
+	 * @throws IOException
+	 *             an error reading the file
+	 */
+	protected abstract byte[] getChecksum(DfsReader ctx) throws IOException;
+
 	@Override
-	public PackIndex getPackIndex(DfsReader ctx) {
-		throw new IllegalStateException(
-				"Shouldn't use multipack index if the primary index is needed"); //$NON-NLS-1$
+	public final PackIndex getPackIndex(DfsReader ctx) {
+		return new MidxPackIndex(this, ctx);
 	}
 
 	@Override
-	public PackReverseIndex getReverseIdx(DfsReader ctx) {
-		throw new IllegalStateException(
-				"Shouldn't use multipack index if the reverse index is needed"); //$NON-NLS-1$
-	}
+	public abstract PackReverseIndex getReverseIdx(DfsReader ctx)
+			throws IOException;
 
 	@Override
 	ObjectLoader load(DfsReader ctx, long midxOffset) throws IOException {
@@ -335,4 +366,101 @@ long getPackOffset() {
 			return midxOffset - packStart;
 		}
 	}
+
+	private static class MidxPackIndex implements PackIndex {
+
+		private final DfsPackFileMidx pack;
+
+		private final DfsReader ctx;
+
+		MidxPackIndex(DfsPackFileMidx pack, DfsReader ctx) {
+			this.pack = pack;
+			this.ctx = ctx;
+		}
+
+		@Override
+		public Iterator<MutableEntry> iterator() {
+			throw new UnsupportedOperationException("Not implemented yet");
+		}
+
+		@Override
+		public long getObjectCount() {
+			try {
+				return pack.getObjectCount(ctx);
+			} catch (IOException e) {
+				throw new RuntimeException(e);
+			}
+		}
+
+		@Override
+		public long getOffset64Count() {
+			// TODO(ifrade): This method seems to be used only for stats.
+			// Maybe we can just remove it.
+			return 0;
+		}
+
+		@Override
+		public ObjectId getObjectId(long nthPosition) {
+			try {
+				return pack.getObjectAt(ctx, nthPosition);
+			} catch (IOException e) {
+				throw new RuntimeException(e);
+			}
+		}
+
+		@Override
+		public long getOffset(long nthPosition) {
+			ObjectId objectAt;
+			try {
+				objectAt = pack.getObjectAt(ctx, nthPosition);
+			} catch (IOException e) {
+				throw new RuntimeException(e);
+			}
+			if (objectAt == null) {
+				return -1;
+			}
+
+			return findOffset(objectAt);
+		}
+
+		@Override
+		public long findOffset(AnyObjectId objId) {
+			try {
+				return pack.findOffset(ctx, objId);
+			} catch (IOException e) {
+				throw new RuntimeException(e);
+			}
+		}
+
+		@Override
+		public int findPosition(AnyObjectId objId) {
+			try {
+				return pack.findIdxPosition(ctx, objId);
+			} catch (IOException e) {
+				throw new RuntimeException(e);
+			}
+		}
+
+		@Override
+		public long findCRC32(AnyObjectId objId)
+				throws UnsupportedOperationException {
+			throw new UnsupportedOperationException();
+		}
+
+		@Override
+		public boolean hasCRC32Support() {
+			return false;
+		}
+
+		@Override
+		public void resolve(Set<ObjectId> matches, AbbreviatedObjectId id,
+				int matchLimit) throws IOException {
+			pack.resolve(ctx, matches, id, matchLimit);
+		}
+
+		@Override
+		public byte[] getChecksum() {
+			throw new UnsupportedOperationException();
+		}
+	}
 }
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/dfs/DfsPackFileMidxNPacks.java b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/dfs/DfsPackFileMidxNPacks.java
index 6ff078a..9bc3cb1 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/dfs/DfsPackFileMidxNPacks.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/dfs/DfsPackFileMidxNPacks.java
@@ -9,6 +9,7 @@
  */
 package org.eclipse.jgit.internal.storage.dfs;
 
+import static org.eclipse.jgit.internal.storage.pack.PackExt.BITMAP_INDEX;
 import static org.eclipse.jgit.internal.storage.pack.PackExt.MULTI_PACK_INDEX;
 import static org.eclipse.jgit.internal.storage.pack.PackExt.PACK;
 
@@ -23,8 +24,11 @@
 import java.util.stream.Collectors;
 
 import org.eclipse.jgit.annotations.Nullable;
+import org.eclipse.jgit.errors.CorruptObjectException;
+import org.eclipse.jgit.errors.PackMismatchException;
 import org.eclipse.jgit.internal.storage.commitgraph.CommitGraph;
 import org.eclipse.jgit.internal.storage.file.PackBitmapIndex;
+import org.eclipse.jgit.internal.storage.file.PackReverseIndex;
 import org.eclipse.jgit.internal.storage.midx.MultiPackIndex;
 import org.eclipse.jgit.internal.storage.midx.MultiPackIndex.PackOffset;
 import org.eclipse.jgit.internal.storage.midx.MultiPackIndexLoader;
@@ -130,7 +134,7 @@ private record RefWithSize(MultiPackIndex idx, long size) {
 
 	// Visible for testing
 	@Override
-	protected VOffsetCalculator getOffsetCalculator() {
+	protected VOffsetCalculatorNPacks getOffsetCalculator() {
 		return offsetCalculator;
 	}
 
@@ -140,16 +144,19 @@ public ObjectIdSet asObjectIdSet(DfsReader ctx) throws IOException {
 		return multiPackIndex::hasObject;
 	}
 
-
 	@Override
 	public PackBitmapIndex getBitmapIndex(DfsReader ctx) throws IOException {
-		// TODO(ifrade): at some point we will have bitmaps over the multipack
-		// index
-		// At the moment bitmap is in GC, at the end of the chain
+		// We have bitmaps only at the bottom of the midx or pack stack
 		if (base != null) {
 			return base.getBitmapIndex(ctx);
 		}
 
+		if (ctx.getOptions().shouldUseMidxBitmaps()
+				&& getPackDescription().hasFileExt(BITMAP_INDEX)) {
+			// Return our own bitmaps
+			return super.getBitmapIndex(ctx);
+		}
+
 		for (DfsPackFile pack : packsInIdOrder) {
 			PackBitmapIndex bitmapIndex = pack.getBitmapIndex(ctx);
 			if (bitmapIndex != null) {
@@ -188,6 +195,14 @@ public CommitGraph getCommitGraph(DfsReader ctx) throws IOException {
 		return null;
 	}
 
+	@Override
+	public PackReverseIndex getReverseIdx(DfsReader ctx) throws IOException {
+		return new MidxReverseIndex(ctx, this,
+				base == null ? 0 : base.getObjectCount(ctx),
+				getOffsetCalculator().baseMaxOffset,
+				base == null ? null : base.getReverseIdx(ctx));
+	}
+
 	/**
 	 * Count of objects in this <b>pack</b> (i.e. including, recursively, its
 	 * base)
@@ -204,6 +219,11 @@ protected int getObjectCount(DfsReader ctx) throws IOException {
 		return midx(ctx).getObjectCount() + baseObjectCount;
 	}
 
+	@Override
+	protected byte[] getChecksum(DfsReader ctx) throws IOException {
+		return midx(ctx).getChecksum();
+	}
+
 	/**
 	 * Packs indexed by this multipack index (base NOT included)
 	 *
@@ -227,6 +247,17 @@ public DfsPackFileMidx getMultipackIndexBase() {
 	}
 
 	@Override
+	ObjectId getObjectAt(DfsReader ctx, long nthPosition) throws IOException {
+		int baseObjectCount = base == null ? 0 : base.getObjectCount(ctx);
+		if (nthPosition >= baseObjectCount) {
+			long localPosition = nthPosition - baseObjectCount;
+			return midx(ctx).getObjectAt((int) localPosition);
+		}
+
+		return base.getObjectAt(ctx, nthPosition);
+	}
+
+	@Override
 	public int findIdxPosition(DfsReader ctx, AnyObjectId id)
 			throws IOException {
 		int p = midx(ctx).findPosition(id);
@@ -363,7 +394,6 @@ List<DfsObjectToPack> findAllFromPack(DfsReader ctx,
 		return tmp;
 	}
 
-
 	// Visible for testing
 	static class VOffsetCalculatorNPacks implements VOffsetCalculator {
 		private final DfsPackFile[] packs;
@@ -376,6 +406,8 @@ static class VOffsetCalculatorNPacks implements VOffsetCalculator {
 
 		private final DfsPackOffset poBuffer = new DfsPackOffset();
 
+		private final PackOffset localPoBuffer = new PackOffset();
+
 		static VOffsetCalculatorNPacks fromPacks(DfsPackFile[] packsInIdOrder,
 				VOffsetCalculator baseOffsetCalculator) {
 			long[] accSizes = new long[packsInIdOrder.length + 1];
@@ -406,6 +438,22 @@ long encode(MultiPackIndex.PackOffset location) {
 					+ baseMaxOffset;
 		}
 
+		MultiPackIndex.PackOffset decodeLocal(long voffset) {
+			if (voffset == -1 || voffset < baseMaxOffset
+					|| voffset > getMaxOffset()) {
+				return null;
+			}
+
+			long localOffset = voffset - baseMaxOffset;
+			for (int i = 1; i < accSizes.length; i++) {
+				if (localOffset <= accSizes[i]) {
+					return localPoBuffer.setValues(i - 1,
+							localOffset - accSizes[i - 1]);
+				}
+			}
+			return null;
+		}
+
 		@Override
 		public DfsPackOffset decode(long voffset) {
 			if (voffset == -1) {
@@ -431,4 +479,94 @@ public long getMaxOffset() {
 			return accSizes[accSizes.length - 1] + baseMaxOffset;
 		}
 	}
+
+	private static final class MidxReverseIndex implements PackReverseIndex {
+		private final PackReverseIndex parentRidx;
+
+		private final DfsPackFileMidxNPacks localMidx;
+
+		private final DfsReader ctx;
+
+		private final long baseObjectCount;
+
+		private final long baseMaxOffset;
+
+		MidxReverseIndex(DfsReader ctx, DfsPackFileMidxNPacks localMidx,
+				long baseObjectCount, long baseMaxOffset,
+				PackReverseIndex parentRidx) {
+			this.ctx = ctx;
+			this.parentRidx = parentRidx;
+			this.localMidx = localMidx;
+			this.baseObjectCount = baseObjectCount;
+			this.baseMaxOffset = baseMaxOffset;
+		}
+
+		@Override
+		public void verifyPackChecksum(String packFilePath)
+				throws PackMismatchException {
+
+		}
+
+		private MultiPackIndex loadLocalMidx() {
+			try {
+				return localMidx.midx(ctx);
+			} catch (IOException e) {
+				throw new RuntimeException(e);
+			}
+		}
+
+		@Override
+		public ObjectId findObject(long offset) {
+			if (offset < baseMaxOffset) {
+				return parentRidx.findObject(offset);
+			}
+
+			PackOffset localPo = localMidx.getOffsetCalculator()
+					.decodeLocal(offset);
+			if (localPo == null) {
+				return null;
+			}
+
+			int p = loadLocalMidx().findBitmapPosition(localPo);
+			if (p == -1) {
+				// If we found the local
+				// position, this should NOT
+				// happen
+				throw new IllegalStateException();
+			}
+
+			return loadLocalMidx().getObjectAtBitmapPosition(p);
+		}
+
+		@Override
+		public long findNextOffset(long offset, long maxOffset)
+				throws CorruptObjectException {
+			throw new UnsupportedOperationException();
+		}
+
+		@Override
+		public int findPosition(long offset) {
+			if (offset < baseMaxOffset) {
+				return parentRidx.findPosition(offset);
+			}
+
+			PackOffset localPo = localMidx.getOffsetCalculator()
+					.decodeLocal(offset);
+			if (localPo == null) {
+				return -1;
+			}
+
+			return loadLocalMidx().findBitmapPosition(localPo)
+					+ (int) baseObjectCount;
+		}
+
+		@Override
+		public ObjectId findObjectByPosition(int nthPosition) {
+			if (nthPosition < baseObjectCount) {
+				return parentRidx.findObjectByPosition(nthPosition);
+			}
+			return loadLocalMidx().getObjectAtBitmapPosition(
+					nthPosition - (int) baseObjectCount);
+		}
+	}
 }
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/dfs/DfsPackFileMidxSingle.java b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/dfs/DfsPackFileMidxSingle.java
index 60fd7d5..72d6998 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/dfs/DfsPackFileMidxSingle.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/dfs/DfsPackFileMidxSingle.java
@@ -9,14 +9,21 @@
  */
 package org.eclipse.jgit.internal.storage.dfs;
 
+import static org.eclipse.jgit.internal.storage.pack.PackExt.MULTI_PACK_INDEX;
+
 import java.io.IOException;
+import java.io.InputStream;
+import java.nio.channels.Channels;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Set;
 
 import org.eclipse.jgit.annotations.Nullable;
+import org.eclipse.jgit.errors.CorruptObjectException;
+import org.eclipse.jgit.errors.PackMismatchException;
 import org.eclipse.jgit.internal.storage.commitgraph.CommitGraph;
 import org.eclipse.jgit.internal.storage.file.PackBitmapIndex;
+import org.eclipse.jgit.internal.storage.file.PackReverseIndex;
 import org.eclipse.jgit.internal.storage.midx.MultiPackIndex.PackOffset;
 import org.eclipse.jgit.internal.storage.pack.ObjectToPack;
 import org.eclipse.jgit.internal.storage.pack.PackExt;
@@ -28,6 +35,7 @@
 import org.eclipse.jgit.lib.ObjectIdSet;
 import org.eclipse.jgit.lib.ObjectLoader;
 import org.eclipse.jgit.util.BlockList;
+import org.eclipse.jgit.util.IO;
 
 /**
  * A single pack that looks like a midx, to be used in the midx chain
@@ -39,6 +47,8 @@ public final class DfsPackFileMidxSingle extends DfsPackFileMidx {
 
 	private final DfsPackFileMidx base;
 
+	private byte[] checksum;
+
 	private final LocalPackOffset poBuffer = new LocalPackOffset();
 
 	DfsPackFileMidxSingle(DfsBlockCache cache, DfsPackDescription midxDesc,
@@ -63,6 +73,14 @@ public ObjectIdSet asObjectIdSet(DfsReader ctx) throws IOException {
 	}
 
 	@Override
+	public PackReverseIndex getReverseIdx(DfsReader ctx) throws IOException {
+		return new MidxReverseIndex(pack.getReverseIdx(ctx),
+				offsetCalculator.baseMaxOffset,
+				base == null ? null : base.getReverseIdx(ctx),
+				base == null ? 0 : base.getObjectCount(ctx));
+	}
+
+	@Override
 	public PackBitmapIndex getBitmapIndex(DfsReader ctx) throws IOException {
 		// TODO(ifrade): at some point we will have bitmaps over the multipack
 		// index
@@ -112,6 +130,24 @@ protected int getObjectCount(DfsReader ctx) throws IOException {
 				+ baseObjectCount;
 	}
 
+	@Override
+	protected byte[] getChecksum(DfsReader ctx) throws IOException {
+		if (checksum == null) {
+			long checksumPos = desc.getFileSize(MULTI_PACK_INDEX) - 20;
+			if (checksumPos <= 0) {
+				throw new IllegalStateException("Midx stream too short");
+			}
+
+			try (ReadableChannel rc = ctx.db.openFile(desc, MULTI_PACK_INDEX);
+					InputStream in = Channels.newInputStream(rc)) {
+				checksum = new byte[20];
+				in.skip(checksumPos);
+				IO.readFully(in, checksum, 0, 20);
+			}
+		}
+		return checksum;
+	}
+
 	/**
 	 * Packs indexed by this multipack index (base NOT included)
 	 *
@@ -151,6 +187,17 @@ public int findIdxPosition(DfsReader ctx, AnyObjectId id)
 	}
 
 	@Override
+	ObjectId getObjectAt(DfsReader ctx, long nthPosition) throws IOException {
+		int baseObjects = base == null ? 0 : base.getObjectCount(ctx);
+		if (nthPosition >= baseObjects) {
+			long localPosition = nthPosition - baseObjects;
+			return pack.getPackIndex(ctx).getObjectId(localPosition);
+		}
+
+		return base.getObjectAt(ctx, nthPosition);
+	}
+
+	@Override
 	public boolean hasObject(DfsReader ctx, AnyObjectId id) throws IOException {
 		if (pack.hasObject(ctx, id)) {
 			return true;
@@ -351,4 +398,66 @@ void setOffset(long offset) {
 			super.setValues(0, offset);
 		}
 	}
+
+	private static class MidxReverseIndex implements PackReverseIndex {
+		private final long baseMaxOffset;
+
+		private final long baseObjectCount;
+
+		private final PackReverseIndex baseRidx;
+
+		private final PackReverseIndex ridx;
+
+		MidxReverseIndex(PackReverseIndex ridx, long baseMaxOffset,
+				PackReverseIndex baseRidx, long baseObjectCount) {
+			this.ridx = ridx;
+			this.baseMaxOffset = baseMaxOffset;
+			this.baseRidx = baseRidx;
+			this.baseObjectCount = baseObjectCount;
+
+		}
+
+		@Override
+		public void verifyPackChecksum(String packFilePath)
+				throws PackMismatchException {
+
+		}
+
+		@Override
+		public ObjectId findObject(long offset) {
+			if (offset < baseMaxOffset) {
+				return baseRidx.findObject(offset);
+			}
+
+			long localOffset = offset - baseMaxOffset;
+			return ridx.findObject(localOffset);
+		}
+
+		@Override
+		public long findNextOffset(long offset, long maxOffset)
+				throws CorruptObjectException {
+			// TODO(ifrade): In this single-pack midx we can actually implement
+			// this
+			throw new UnsupportedOperationException();
+		}
+
+		@Override
+		public int findPosition(long offset) {
+			if (offset < baseMaxOffset) {
+				return baseRidx.findPosition(offset);
+			}
+			long localOffset = offset - baseMaxOffset;
+			return ridx.findPosition(localOffset) + (int) baseObjectCount;
+		}
+
+		@Override
+		public ObjectId findObjectByPosition(int nthPosition) {
+			if (nthPosition < baseObjectCount) {
+				return baseRidx.findObjectByPosition(nthPosition);
+			}
+			long localPosition = nthPosition - baseObjectCount;
+			// TODO(ifrade): Check downcasting
+			return ridx.findObjectByPosition((int) localPosition);
+		}
+	}
 }
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/dfs/DfsReaderOptions.java b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/dfs/DfsReaderOptions.java
index c397469..e1d7047 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/dfs/DfsReaderOptions.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/dfs/DfsReaderOptions.java
@@ -40,6 +40,8 @@ public class DfsReaderOptions {
 
 	private boolean useObjectSizeIndex;
 
+	private boolean useMidxBitmaps;
+
 	/**
 	 * Create a default reader configuration.
 	 */
@@ -163,6 +165,29 @@ public DfsReaderOptions setUseObjectSizeIndex(boolean useObjectSizeIndex) {
 	}
 
 	/**
+	 * Use bitmaps in the midx if available.
+	 *
+	 * @return true if a midx pack should use its own bitmaps. false to fallback
+	 *         to GC bitmaps.
+	 */
+	public boolean shouldUseMidxBitmaps() {
+		return useMidxBitmaps;
+	}
+
+	/**
+	 * Set if the midx packs should use their bitmaps or fallback to bitmaps in
+	 * GC pack.
+	 *
+	 * @param useMidxBitmaps
+	 *            useMidxBitmaps to set
+	 * @return {@code this}
+	 */
+	public DfsReaderOptions setUseMidxBitmaps(boolean useMidxBitmaps) {
+		this.useMidxBitmaps = useMidxBitmaps;
+		return this;
+	}
+
+	/**
 	 * Update properties by setting fields from the configuration.
 	 * <p>
 	 * If a property is not defined in the configuration, then it is left
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/midx/MultiPackIndex.java b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/midx/MultiPackIndex.java
index edaa221..31fea79 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/midx/MultiPackIndex.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/midx/MultiPackIndex.java
@@ -26,7 +26,7 @@ public interface MultiPackIndex {
 	 * <p>
 	 * The pack ids correspond to positions in this list.
 	 *
-	 * @return array of packnames refered in this multipak index
+	 * @return array of packnames refered in this multipack index
 	 */
 	String[] getPackNames();
 
@@ -66,6 +66,35 @@ public interface MultiPackIndex {
 	int findPosition(AnyObjectId objectId);
 
 	/**
+	 * Return the position in offset order (i.e. ridx or bitmap position) for
+	 * the (packId, offset) pair.
+	 *
+	 * @param po
+	 *            a location in the midx (packId, offset)
+	 * @return the position in the midx, in offset order
+	 */
+	int findBitmapPosition(PackOffset po);
+
+	/**
+	 * Object id at the specified position in offset order (i.e. position in the
+	 * ridx or bitmap)
+	 *
+	 * @param bitmapPosition
+	 *            position in the bitmap
+	 * @return object id at that position.
+	 */
+	ObjectId getObjectAtBitmapPosition(int bitmapPosition);
+
+	/**
+	 * ObjectId at this position in the midx
+	 *
+	 * @param position
+	 *            position inside this midx in sha1 order
+	 * @return the object id at that position
+	 */
+	ObjectId getObjectAt(int position);
+
+	/**
 	 * Number of objects in this midx
 	 * <p>
 	 * This number doesn't match with the sum of objects in each covered pack
@@ -90,6 +119,13 @@ public interface MultiPackIndex {
 	void resolve(Set<ObjectId> matches, AbbreviatedObjectId id, int matchLimit);
 
 	/**
+	 * Index checksum of the contents of this midx file
+	 *
+	 * @return checksum of the contents of this midx file
+	 */
+	byte[] getChecksum();
+
+	/**
 	 * Memory size of this multipack index
 	 *
 	 * @return size of this multipack index in memory, in bytes
@@ -102,7 +138,7 @@ public interface MultiPackIndex {
 	 * Mutable object to avoid creating many instances while looking for objects
 	 * in the pack. Use #copy() to get a new instance with the data.
 	 */
-	class PackOffset {
+	class PackOffset implements Comparable<PackOffset> {
 
 		private int packId;
 
@@ -123,7 +159,7 @@ public static PackOffset create(int packId, long offset) {
 			return new PackOffset().setValues(packId, offset);
 		}
 
-		protected PackOffset setValues(int packId, long offset) {
+		public PackOffset setValues(int packId, long offset) {
 			this.packId = packId;
 			this.offset = offset;
 			return this;
@@ -141,5 +177,15 @@ public PackOffset copy() {
 			PackOffset copy = new PackOffset();
 			return copy.setValues(this.packId, this.offset);
 		}
+
+		@Override
+		public int compareTo(PackOffset packOffset) {
+			int cmp = this.packId - packOffset.packId;
+			if (cmp != 0) {
+				return cmp;
+			}
+
+			return Long.compare(this.offset, packOffset.offset);
+		}
 	}
 }
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/midx/MultiPackIndexLoader.java b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/midx/MultiPackIndexLoader.java
index 8501b63..4b70c2c 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/midx/MultiPackIndexLoader.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/midx/MultiPackIndexLoader.java
@@ -195,6 +195,9 @@ public static MultiPackIndex read(InputStream fd)
 						Integer.toHexString(chunkId)));
 			}
 		}
+		byte[] checksum = new byte[20];
+		IO.readFully(fd, checksum, 0, 20);
+		builder.addChecksum(checksum);
 		return builder.build();
 	}
 
@@ -226,6 +229,8 @@ static class MultiPackIndexBuilder {
 		// Optional
 		private byte[] bitmapPackOrder;
 
+		private byte[] checksum;
+
 		private MultiPackIndexBuilder(int hashLength) {
 			this.hashLength = hashLength;
 		}
@@ -304,7 +309,7 @@ MultiPackIndex build() throws MultiPackIndexFormatException {
 			assertPackCounts(packCount, packNames.length);
 			return new MultiPackIndexV1(hashLength, oidFanout, oidLookup,
 					packNames, bitmappedPackfiles, objectOffsets,
-					largeObjectOffsets, bitmapPackOrder);
+					largeObjectOffsets, bitmapPackOrder, checksum);
 		}
 
 		private static void assertChunkNotNull(Object object, int chunkId)
@@ -334,6 +339,10 @@ private static void assertPackCounts(int headerCount,
 						Integer.valueOf(packfileNamesCount)));
 			}
 		}
+
+		public void addChecksum(byte[] checksum) {
+			this.checksum = checksum;
+		}
 	}
 
 	/**
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/midx/MultiPackIndexV1.java b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/midx/MultiPackIndexV1.java
index d1eb11c..08e4bfc 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/midx/MultiPackIndexV1.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/midx/MultiPackIndexV1.java
@@ -34,24 +34,25 @@ class MultiPackIndexV1 implements MultiPackIndex {
 
 	private final String[] packNames;
 
-	private final byte[] bitmappedPackfiles;
-
-	private final byte[] bitmapPackOrder;
-
 	private final OffsetLookup offsets;
 
 	private final PackOffset result = new PackOffset();
 
+	private final ReverseIndex ridx;
+
+	private final byte[] checksum;
+
 	MultiPackIndexV1(int hashLength, @NonNull byte[] oidFanout,
 			@NonNull byte[] oidLookup, String[] packNames,
 			byte[] bitmappedPackfiles, byte[] objectOffsets,
-			byte[] largeObjectOffsets, byte[] bitmapPackOrder)
+			byte[] largeObjectOffsets, byte[] bitmapPackOrder, byte[] checksum)
 			throws MultiPackIndexFormatException {
-		this.bitmappedPackfiles = bitmappedPackfiles;
-		this.bitmapPackOrder = bitmapPackOrder;
 		this.idx = new OidLookup(hashLength, oidFanout, oidLookup);
 		this.offsets = new OffsetLookup(objectOffsets, largeObjectOffsets);
 		this.packNames = packNames;
+		this.ridx = new ReverseIndex(bitmapPackOrder, idx, offsets,
+				bitmappedPackfiles);
+		this.checksum = checksum;
 	}
 
 	@Override
@@ -70,6 +71,21 @@ public int findPosition(AnyObjectId oid) {
 	}
 
 	@Override
+	public int findBitmapPosition(PackOffset po) {
+		return ridx.findBitmapPosition(po);
+	}
+
+	@Override
+	public ObjectId getObjectAtBitmapPosition(int bitmapPosition) {
+		return ridx.getObjectId(bitmapPosition);
+	}
+
+	@Override
+	public ObjectId getObjectAt(int position) {
+		return idx.getObjectAt(position);
+	}
+
+	@Override
 	public int getObjectCount() {
 		return idx.getObjectCount();
 	}
@@ -92,26 +108,26 @@ public void resolve(Set<ObjectId> matches, AbbreviatedObjectId id,
 	}
 
 	@Override
+	public byte[] getChecksum() {
+		return checksum;
+	}
+
+	@Override
 	public long getMemorySize() {
 		int packNamesSize = Arrays.stream(packNames)
 				.mapToInt(s -> s.getBytes(StandardCharsets.UTF_8).length).sum();
-		return packNamesSize + byteArrayLengh(bitmappedPackfiles)
-				+ byteArrayLengh(bitmapPackOrder)
-				+ idx.getMemorySize() + offsets.getMemorySize();
+		return packNamesSize + ridx.getMemorySize() + idx.getMemorySize()
+				+ offsets.getMemorySize() + checksum.length;
 	}
 
 	@Override
 	public String toString() {
 		return "MultiPackIndexV1 {idx=" + idx + ", packfileNames=" //$NON-NLS-1$ //$NON-NLS-2$
-				+ Arrays.toString(packNames) + ", bitmappedPackfiles=" //$NON-NLS-1$
-				+ byteArrayToString(bitmappedPackfiles) + ", objectOffsets=" //$NON-NLS-1$
+				+ Arrays.toString(packNames) + ", ridx=" //$NON-NLS-1$
+				+ ridx + ", objectOffsets=" //$NON-NLS-1$
 				+ offsets + '}';
 	}
 
-	private static String byteArrayToString(byte[] array) {
-		return array == null ? "null" : new String(array); //$NON-NLS-1$
-	}
-
 	private static int byteArrayLengh(byte[] array) {
 		return array == null ? 0 : array.length;
 	}
@@ -251,6 +267,11 @@ int findMultiPackIndexPosition(AnyObjectId id) {
 			return -1;
 		}
 
+		ObjectId getObjectAt(int midxPosition) {
+			int rawOffset = hashLength * midxPosition;
+			return ObjectId.fromRaw(oidLookup, rawOffset);
+		}
+
 		void resolve(Set<ObjectId> matches, AbbreviatedObjectId id,
 				int matchLimit) {
 			if (matches.size() >= matchLimit) {
@@ -313,4 +334,77 @@ int getObjectCount() {
 			return fanoutTable[FANOUT - 1];
 		}
 	}
+
+	private static class ReverseIndex {
+		private final byte[] bitmappedPackfiles;
+
+		private final byte[] bitmapPackOrder;
+
+		private final OffsetLookup offsets;
+
+		private final OidLookup oids;
+
+		ReverseIndex(byte[] bitmapPackOrder, OidLookup oids,
+				OffsetLookup offsets, byte[] bitmappedPackfiles) {
+			this.bitmappedPackfiles = bitmappedPackfiles;
+			this.bitmapPackOrder = bitmapPackOrder;
+			this.oids = oids;
+			this.offsets = offsets;
+		}
+
+		public int findBitmapPosition(PackOffset po) {
+			if (bitmapPackOrder == null || bitmappedPackfiles == null) {
+				return -1;
+			}
+
+			/*
+			 * Bitmapped Packfiles (ID: {'B', 'T', 'M', 'P'}) Stores a table of
+			 * two 4-byte unsigned integers in network order. Each table entry
+			 * corresponds to a single pack (in the order that they appear above
+			 * in the `PNAM` chunk). The values for each table entry are as
+			 * follows: - The first bit position (in pseudo-pack order, see
+			 * below) to contain an object from that pack. - The number of bits
+			 * whose objects are selected from that pack.
+			 */
+			int packStartBit = NB.decodeInt32(bitmappedPackfiles,
+					po.getPackId() * 8);
+			int packBitLength = NB.decodeInt32(bitmappedPackfiles,
+					(po.getPackId() * 8) + 4);
+			return binarySearch(packStartBit, packStartBit + packBitLength, po);
+		}
+
+		private int binarySearch(int start, int end, PackOffset needle) {
+			PackOffset result = new PackOffset();
+			int low = start;
+			int high = end;
+			while (low < high) {
+				int mid = (low + high) >>> 1;
+				int midxPosition = NB.decodeInt32(bitmapPackOrder, mid * 4);
+				offsets.getObjectOffset(midxPosition, result);
+				int cmp = needle.compareTo(result);
+				if (cmp < 0) {
+					high = mid;
+				} else if (cmp == 0) {
+					return mid;
+				} else {
+					low = mid + 1;
+				}
+			}
+			return -1;
+		}
+
+		public ObjectId getObjectId(int bitmapPosition) {
+			if (bitmapPackOrder == null) {
+				return null;
+			}
+			int midxPosition = NB.decodeInt32(bitmapPackOrder,
+					bitmapPosition * 4);
+			return oids.getObjectAt(midxPosition);
+		}
+
+		public long getMemorySize() {
+			return (long) byteArrayLengh(bitmapPackOrder)
+					+ byteArrayLengh(bitmappedPackfiles);
+		}
+	}
 }
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/pack/BitmapCommit.java b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/pack/BitmapCommit.java
index 33c478e..41cbe4b 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/pack/BitmapCommit.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/pack/BitmapCommit.java
@@ -30,8 +30,21 @@ public final class BitmapCommit extends ObjectId {
 		this.addToIndex = false;
 	}
 
-	BitmapCommit(AnyObjectId objectId, boolean reuseWalker, int flags,
-				 boolean addToIndex) {
+	// Visible for testing
+	/**
+	 * Commit that should get a bitmap
+	 *
+	 * @param objectId
+	 *            objectId of the commit
+	 * @param reuseWalker
+	 *            if the bitmap walker can be reused
+	 * @param flags
+	 *            flags
+	 * @param addToIndex
+	 *            if the bitmap should be added to the index
+	 */
+	public BitmapCommit(AnyObjectId objectId, boolean reuseWalker, int flags,
+			boolean addToIndex) {
 		super(objectId);
 		this.reuseWalker = reuseWalker;
 		this.flags = flags;
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/pack/PackBitmapCalculator.java b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/pack/PackBitmapCalculator.java
new file mode 100644
index 0000000..7fa635f
--- /dev/null
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/pack/PackBitmapCalculator.java
@@ -0,0 +1,101 @@
+/*
+ * Copyright (C) 2026, Google LLC.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Distribution License v. 1.0 which is available at
+ * https://www.eclipse.org/org/documents/edl-v10.php.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+package org.eclipse.jgit.internal.storage.pack;
+
+import java.io.IOException;
+import java.text.MessageFormat;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.Set;
+
+import org.eclipse.jgit.internal.JGitText;
+import org.eclipse.jgit.internal.storage.file.PackBitmapIndexBuilder;
+import org.eclipse.jgit.lib.AnyObjectId;
+import org.eclipse.jgit.lib.BitmapIndex;
+import org.eclipse.jgit.lib.ObjectId;
+import org.eclipse.jgit.lib.ObjectReader;
+import org.eclipse.jgit.lib.ProgressMonitor;
+import org.eclipse.jgit.revwalk.BitmapWalker;
+import org.eclipse.jgit.storage.pack.PackConfig;
+
+/**
+ * Helper to find out interesting commits, create their bitmaps and write them
+ * into the PackBitmapIndexBuilder.
+ */
+public class PackBitmapCalculator {
+
+	private final PackConfig config;
+
+	/**
+	 * Constructor
+	 *
+	 * @param config
+	 *            configuration
+	 */
+	public PackBitmapCalculator(PackConfig config) {
+		this.config = config;
+	}
+
+	/**
+	 * Choose commits, create bitmaps and send them to the builder
+	 *
+	 * @param reader
+	 *            an object reader
+	 * @param pm
+	 *            a progress monitor
+	 * @param wants
+	 *            where to start walking looking for commits to bitmap
+	 * @param numCommits
+	 *            expected number of new commits to include in the bitmap
+	 * @param excludeFromBitmapSelection
+	 *            commits to ignore
+	 * @param writeBitmaps
+	 *            store of newly created bitmaps
+	 * @throws IOException
+	 *             an error
+	 */
+	public void calculate(ObjectReader reader, ProgressMonitor pm,
+			int numCommits, Set<? extends ObjectId> wants,
+			Set<? extends ObjectId> excludeFromBitmapSelection,
+			PackBitmapIndexBuilder writeBitmaps) throws IOException {
+		PackWriterBitmapPreparer bitmapPreparer = new PackWriterBitmapPreparer(
+				reader, writeBitmaps, pm, wants, config);
+
+		Collection<BitmapCommit> selectedCommits = bitmapPreparer
+				.selectCommits(numCommits, excludeFromBitmapSelection);
+		pm.beginTask(JGitText.get().buildingBitmaps, selectedCommits.size());
+
+		BitmapWalker walker = bitmapPreparer.newBitmapWalker();
+		AnyObjectId last = null;
+		for (BitmapCommit cmit : selectedCommits) {
+			if (!cmit.isReuseWalker()) {
+				walker = bitmapPreparer.newBitmapWalker();
+			}
+			BitmapIndex.BitmapBuilder bitmap = walker
+					.findObjects(Collections.singleton(cmit), null, false);
+
+			if (last != null && cmit.isReuseWalker() && !bitmap.contains(last))
+				throw new IllegalStateException(
+						MessageFormat.format(JGitText.get().bitmapMissingObject,
+								cmit.name(), last.name()));
+			last = BitmapCommit.copyFrom(cmit).build();
+			writeBitmaps.processBitmapForWrite(cmit, bitmap.build(),
+					cmit.getFlags());
+
+			// The bitmap walker should stop when the walk hits the previous
+			// commit, which saves time.
+			walker.setPrevCommit(last);
+			walker.setPrevBitmap(bitmap);
+
+			pm.update(1);
+		}
+		pm.endTask();
+	}
+}
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/pack/PackWriter.java b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/pack/PackWriter.java
index 27fb814..c2d7577 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/pack/PackWriter.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/pack/PackWriter.java
@@ -2534,40 +2534,10 @@ public boolean prepareBitmapIndex(ProgressMonitor pm) throws IOException {
 		// Allow byName to be GC'd if JVM GC runs before the end of the method.
 		byName = null;
 
-		PackWriterBitmapPreparer bitmapPreparer = new PackWriterBitmapPreparer(
-				reader, writeBitmaps, pm, stats.interestingObjects, config);
+		PackBitmapCalculator bitmapWrite = new PackBitmapCalculator(config);
+		bitmapWrite.calculate(reader, pm, numCommits, stats.interestingObjects,
+				excludeFromBitmapSelection, writeBitmaps);
 
-		Collection<BitmapCommit> selectedCommits = bitmapPreparer
-				.selectCommits(numCommits, excludeFromBitmapSelection);
-
-		beginPhase(PackingPhase.BUILDING_BITMAPS, pm, selectedCommits.size());
-
-		BitmapWalker walker = bitmapPreparer.newBitmapWalker();
-		AnyObjectId last = null;
-		for (BitmapCommit cmit : selectedCommits) {
-			if (!cmit.isReuseWalker()) {
-				walker = bitmapPreparer.newBitmapWalker();
-			}
-			BitmapBuilder bitmap = walker.findObjects(
-					Collections.singleton(cmit), null, false);
-
-			if (last != null && cmit.isReuseWalker() && !bitmap.contains(last))
-				throw new IllegalStateException(MessageFormat.format(
-						JGitText.get().bitmapMissingObject, cmit.name(),
-						last.name()));
-			last = BitmapCommit.copyFrom(cmit).build();
-			writeBitmaps.processBitmapForWrite(cmit, bitmap.build(),
-					cmit.getFlags());
-
-			// The bitmap walker should stop when the walk hits the previous
-			// commit, which saves time.
-			walker.setPrevCommit(last);
-			walker.setPrevBitmap(bitmap);
-
-			pm.update(1);
-		}
-
-		endPhase(pm);
 		return true;
 	}
 
diff --git a/pom.xml b/pom.xml
index 0469980..d8a0b3e 100644
--- a/pom.xml
+++ b/pom.xml
@@ -146,9 +146,9 @@
     <maven-compiler-plugin-version>3.14.1</maven-compiler-plugin-version>
     <plexus-compiler-version>2.16.1</plexus-compiler-version>
     <hamcrest-version>3.0</hamcrest-version>
-    <assertj-version>3.27.6</assertj-version>
+    <assertj-version>3.27.7</assertj-version>
     <jna-version>5.18.1</jna-version>
-    <byte-buddy-version>1.18.2</byte-buddy-version>
+    <byte-buddy-version>1.18.4</byte-buddy-version>
 
     <!-- Properties to enable jacoco code coverage analysis -->
     <sonar.core.codeCoveragePlugin>jacoco</sonar.core.codeCoveragePlugin>
diff --git a/tools/maven-central/Pipfile.lock b/tools/maven-central/Pipfile.lock
index 40358c9..e566398 100644
--- a/tools/maven-central/Pipfile.lock
+++ b/tools/maven-central/Pipfile.lock
@@ -27,104 +27,138 @@
         },
         "certifi": {
             "hashes": [
-                "sha256:e564105f78ded564e3ae7c923924435e1daa7463faeab5bb932bc53ffae63407",
-                "sha256:f6c12493cfb1b06ba2ff328595af9350c65d6644968e5d3a2ffd78699af217a5"
+                "sha256:9943707519e4add1115f44c2bc244f782c0249876bf51b6599fee1ffbedd685c",
+                "sha256:ac726dd470482006e014ad384921ed6438c457018f4b3d204aea4281258b2120"
             ],
             "markers": "python_version >= '3.7'",
-            "version": "==2025.8.3"
+            "version": "==2026.1.4"
         },
         "charset-normalizer": {
             "hashes": [
-                "sha256:00237675befef519d9af72169d8604a067d92755e84fe76492fef5441db05b91",
-                "sha256:02425242e96bcf29a49711b0ca9f37e451da7c70562bc10e8ed992a5a7a25cc0",
-                "sha256:027b776c26d38b7f15b26a5da1044f376455fb3766df8fc38563b4efbc515154",
-                "sha256:07a0eae9e2787b586e129fdcbe1af6997f8d0e5abaa0bc98c0e20e124d67e601",
-                "sha256:0cacf8f7297b0c4fcb74227692ca46b4a5852f8f4f24b3c766dd94a1075c4884",
-                "sha256:0e78314bdc32fa80696f72fa16dc61168fda4d6a0c014e0380f9d02f0e5d8a07",
-                "sha256:0f2be7e0cf7754b9a30eb01f4295cc3d4358a479843b31f328afd210e2c7598c",
-                "sha256:13faeacfe61784e2559e690fc53fa4c5ae97c6fcedb8eb6fb8d0a15b475d2c64",
-                "sha256:14c2a87c65b351109f6abfc424cab3927b3bdece6f706e4d12faaf3d52ee5efe",
-                "sha256:1606f4a55c0fd363d754049cdf400175ee96c992b1f8018b993941f221221c5f",
-                "sha256:16a8770207946ac75703458e2c743631c79c59c5890c80011d536248f8eaa432",
-                "sha256:18343b2d246dc6761a249ba1fb13f9ee9a2bcd95decc767319506056ea4ad4dc",
-                "sha256:18b97b8404387b96cdbd30ad660f6407799126d26a39ca65729162fd810a99aa",
-                "sha256:1bb60174149316da1c35fa5233681f7c0f9f514509b8e399ab70fea5f17e45c9",
-                "sha256:1e8ac75d72fa3775e0b7cb7e4629cec13b7514d928d15ef8ea06bca03ef01cae",
-                "sha256:1ef99f0456d3d46a50945c98de1774da86f8e992ab5c77865ea8b8195341fc19",
-                "sha256:2001a39612b241dae17b4687898843f254f8748b796a2e16f1051a17078d991d",
-                "sha256:23b6b24d74478dc833444cbd927c338349d6ae852ba53a0d02a2de1fce45b96e",
-                "sha256:252098c8c7a873e17dd696ed98bbe91dbacd571da4b87df3736768efa7a792e4",
-                "sha256:257f26fed7d7ff59921b78244f3cd93ed2af1800ff048c33f624c87475819dd7",
-                "sha256:2c322db9c8c89009a990ef07c3bcc9f011a3269bc06782f916cd3d9eed7c9312",
-                "sha256:30a96e1e1f865f78b030d65241c1ee850cdf422d869e9028e2fc1d5e4db73b92",
-                "sha256:30d006f98569de3459c2fc1f2acde170b7b2bd265dc1943e87e1a4efe1b67c31",
-                "sha256:31a9a6f775f9bcd865d88ee350f0ffb0e25936a7f930ca98995c05abf1faf21c",
-                "sha256:320e8e66157cc4e247d9ddca8e21f427efc7a04bbd0ac8a9faf56583fa543f9f",
-                "sha256:34a7f768e3f985abdb42841e20e17b330ad3aaf4bb7e7aeeb73db2e70f077b99",
-                "sha256:3653fad4fe3ed447a596ae8638b437f827234f01a8cd801842e43f3d0a6b281b",
-                "sha256:3cd35b7e8aedeb9e34c41385fda4f73ba609e561faedfae0a9e75e44ac558a15",
-                "sha256:3cfb2aad70f2c6debfbcb717f23b7eb55febc0bb23dcffc0f076009da10c6392",
-                "sha256:416175faf02e4b0810f1f38bcb54682878a4af94059a1cd63b8747244420801f",
-                "sha256:41d1fc408ff5fdfb910200ec0e74abc40387bccb3252f3f27c0676731df2b2c8",
-                "sha256:42e5088973e56e31e4fa58eb6bd709e42fc03799c11c42929592889a2e54c491",
-                "sha256:4ca4c094de7771a98d7fbd67d9e5dbf1eb73efa4f744a730437d8a3a5cf994f0",
-                "sha256:511729f456829ef86ac41ca78c63a5cb55240ed23b4b737faca0eb1abb1c41bc",
-                "sha256:53cd68b185d98dde4ad8990e56a58dea83a4162161b1ea9272e5c9182ce415e0",
-                "sha256:585f3b2a80fbd26b048a0be90c5aae8f06605d3c92615911c3a2b03a8a3b796f",
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-                "sha256:5d8d01eac18c423815ed4f4a2ec3b439d654e55ee4ad610e153cf02faf67ea40",
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-                "sha256:fdabf8315679312cfa71302f9bd509ded4f2f263fb5b765cf1433b39106c3cc9"
+                "sha256:027f6de494925c0ab2a55eab46ae5129951638a49a34d87f4c3eda90f696b4ad",
+                "sha256:077fbb858e903c73f6c9db43374fd213b0b6a778106bc7032446a8e8b5b38b93",
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+                "sha256:0d3d8f15c07f86e9ff82319b3d9ef6f4bf907608f53fe9d92b28ea9ae3d1fd89",
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+                "sha256:11d694519d7f29d6cd09f6ac70028dba10f92f6cdd059096db198c283794ac86",
+                "sha256:194f08cbb32dc406d6e1aea671a68be0823673db2832b38405deba2fb0d88f63",
+                "sha256:1bee1e43c28aa63cb16e5c14e582580546b08e535299b8b6158a7c9c768a1f3d",
+                "sha256:21d142cc6c0ec30d2efee5068ca36c128a30b0f2c53c1c07bd78cb6bc1d3be5f",
+                "sha256:2437418e20515acec67d86e12bf70056a33abdacb5cb1655042f6538d6b085a8",
+                "sha256:244bfb999c71b35de57821b8ea746b24e863398194a4014e4c76adc2bbdfeff0",
+                "sha256:2677acec1a2f8ef614c6888b5b4ae4060cc184174a938ed4e8ef690e15d3e505",
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+                "sha256:2aaba3b0819274cc41757a1da876f810a3e4d7b6eb25699253a4effef9e8e4af",
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+                "sha256:362d61fd13843997c1c446760ef36f240cf81d3ebf74ac62652aebaf7838561e",
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+                "sha256:4bd5d4137d500351a30687c2d3971758aac9a19208fc110ccb9d7188fbe709e8",
+                "sha256:4fe7859a4e3e8457458e2ff592f15ccb02f3da787fcd31e0183879c3ad4692a1",
+                "sha256:542d2cee80be6f80247095cc36c418f7bddd14f4a6de45af91dfad36d817bba2",
+                "sha256:554af85e960429cf30784dd47447d5125aaa3b99a6f0683589dbd27e2f45da44",
+                "sha256:5833d2c39d8896e4e19b689ffc198f08ea58116bee26dea51e362ecc7cd3ed26",
+                "sha256:5947809c8a2417be3267efc979c47d76a079758166f7d43ef5ae8e9f92751f88",
+                "sha256:5ae497466c7901d54b639cf42d5b8c1b6a4fead55215500d2f486d34db48d016",
+                "sha256:5bd2293095d766545ec1a8f612559f6b40abc0eb18bb2f5d1171872d34036ede",
+                "sha256:5bfbb1b9acf3334612667b61bd3002196fe2a1eb4dd74d247e0f2a4d50ec9bbf",
+                "sha256:5cb4d72eea50c8868f5288b7f7f33ed276118325c1dfd3957089f6b519e1382a",
+                "sha256:5dbe56a36425d26d6cfb40ce79c314a2e4dd6211d51d6d2191c00bed34f354cc",
+                "sha256:5f819d5fe9234f9f82d75bdfa9aef3a3d72c4d24a6e57aeaebba32a704553aa0",
+                "sha256:64b55f9dce520635f018f907ff1b0df1fdc31f2795a922fb49dd14fbcdf48c84",
+                "sha256:6515f3182dbe4ea06ced2d9e8666d97b46ef4c75e326b79bb624110f122551db",
+                "sha256:65e2befcd84bc6f37095f5961e68a6f077bf44946771354a28ad434c2cce0ae1",
+                "sha256:6aee717dcfead04c6eb1ce3bd29ac1e22663cdea57f943c87d1eab9a025438d7",
+                "sha256:6b39f987ae8ccdf0d2642338faf2abb1862340facc796048b604ef14919e55ed",
+                "sha256:6e1fcf0720908f200cd21aa4e6750a48ff6ce4afe7ff5a79a90d5ed8a08296f8",
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             "markers": "python_version >= '3.7'",
-            "version": "==3.4.3"
+            "version": "==3.4.4"
         },
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             "hashes": [
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-            "markers": "python_version >= '3.6'",
-            "version": "==3.10"
+            "markers": "python_version >= '3.8'",
+            "version": "==3.11"
         },
         "pyyaml": {
             "hashes": [
@@ -217,11 +251,11 @@
         },
         "urllib3": {
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             "markers": "python_version >= '3.9'",
-            "version": "==2.5.0"
+            "version": "==2.6.3"
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     },
     "develop": {