diff --git a/src/main/java/com/google/devtools/build/lib/remote/UploadManifest.java b/src/main/java/com/google/devtools/build/lib/remote/UploadManifest.java
index 742c74f3074404..07c02ac35688db 100644
--- a/src/main/java/com/google/devtools/build/lib/remote/UploadManifest.java
+++ b/src/main/java/com/google/devtools/build/lib/remote/UploadManifest.java
@@ -31,6 +31,7 @@
 import com.google.common.annotations.VisibleForTesting;
 import com.google.common.base.Preconditions;
 import com.google.common.collect.ImmutableList;
+import com.google.common.collect.Lists;
 import com.google.devtools.build.lib.actions.ActionExecutionMetadata;
 import com.google.devtools.build.lib.actions.ActionUploadFinishedEvent;
 import com.google.devtools.build.lib.actions.ActionUploadStartedEvent;
@@ -54,10 +55,12 @@
 import com.google.devtools.build.lib.vfs.PathFragment;
 import com.google.devtools.build.lib.vfs.Symlinks;
 import com.google.protobuf.ByteString;
+import com.google.protobuf.CodedOutputStream;
 import com.google.protobuf.Timestamp;
 import io.reactivex.rxjava3.core.Completable;
 import io.reactivex.rxjava3.core.Flowable;
 import io.reactivex.rxjava3.core.Single;
+import java.io.ByteArrayOutputStream;
 import java.io.IOException;
 import java.time.Duration;
 import java.time.Instant;
@@ -65,9 +68,11 @@
 import java.util.Collection;
 import java.util.Comparator;
 import java.util.HashMap;
+import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Map;
 import java.util.Optional;
+import java.util.Set;
 import java.util.stream.Collectors;
 import javax.annotation.Nullable;
 
@@ -303,25 +308,43 @@ private void addFile(Digest digest, Path file) throws IOException {
     digestToFile.put(digest, file);
   }
 
+  // Field numbers of the 'root' and 'directory' fields in the Tree message.
+  private static final int TREE_ROOT_FIELD_NUMBER =
+      Tree.getDescriptor().findFieldByName("root").getNumber();
+  private static final int TREE_CHILDREN_FIELD_NUMBER =
+      Tree.getDescriptor().findFieldByName("children").getNumber();
+
   private void addDirectory(Path dir) throws ExecException, IOException {
-    Tree.Builder tree = Tree.newBuilder();
-    Directory root = computeDirectory(dir, tree);
-    tree.setRoot(root);
+    Set<ByteString> directories = new LinkedHashSet<>();
+    var ignored = computeDirectory(dir, directories);
+
+    // Convert individual Directory messages to a Tree message. As we want the
+    // records to be topologically sorted (parents before children), we iterate
+    // over the directories in reverse insertion order.
+    ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
+    CodedOutputStream codedOutputStream = CodedOutputStream.newInstance(byteArrayOutputStream);
+    int fieldNumber = TREE_ROOT_FIELD_NUMBER;
+    for (ByteString directory : Lists.reverse(new ArrayList<ByteString>(directories))) {
+      codedOutputStream.writeBytes(fieldNumber, directory);
+      fieldNumber = TREE_CHILDREN_FIELD_NUMBER;
+    }
+    codedOutputStream.flush();
 
-    ByteString data = tree.build().toByteString();
+    ByteString data = ByteString.copyFrom(byteArrayOutputStream.toByteArray());
     Digest digest = digestUtil.compute(data.toByteArray());
 
     if (result != null) {
       result
           .addOutputDirectoriesBuilder()
           .setPath(remotePathResolver.localPathToOutputPath(dir))
-          .setTreeDigest(digest);
+          .setTreeDigest(digest)
+          .setIsTopologicallySorted(true);
     }
 
     digestToBlobs.put(digest, data);
   }
 
-  private Directory computeDirectory(Path path, Tree.Builder tree)
+  private ByteString computeDirectory(Path path, Set<ByteString> directories)
       throws ExecException, IOException {
     Directory.Builder b = Directory.newBuilder();
 
@@ -332,9 +355,8 @@ private Directory computeDirectory(Path path, Tree.Builder tree)
       String name = dirent.getName();
       Path child = path.getRelative(name);
       if (dirent.getType() == Dirent.Type.DIRECTORY) {
-        Directory dir = computeDirectory(child, tree);
-        b.addDirectoriesBuilder().setName(name).setDigest(digestUtil.compute(dir));
-        tree.addChildren(dir);
+        ByteString dir = computeDirectory(child, directories);
+        b.addDirectoriesBuilder().setName(name).setDigest(digestUtil.compute(dir.toByteArray()));
       } else if (dirent.getType() == Dirent.Type.SYMLINK) {
         PathFragment target = child.readSymbolicLink();
         if (!followSymlinks && !target.isAbsolute()) {
@@ -353,9 +375,8 @@ private Directory computeDirectory(Path path, Tree.Builder tree)
           b.addFilesBuilder().setName(name).setDigest(digest).setIsExecutable(child.isExecutable());
           digestToFile.put(digest, child);
         } else if (statFollow.isDirectory()) {
-          Directory dir = computeDirectory(child, tree);
-          b.addDirectoriesBuilder().setName(name).setDigest(digestUtil.compute(dir));
-          tree.addChildren(dir);
+          ByteString dir = computeDirectory(child, directories);
+          b.addDirectoriesBuilder().setName(name).setDigest(digestUtil.compute(dir.toByteArray()));
         } else {
           illegalOutput(child);
         }
@@ -368,7 +389,9 @@ private Directory computeDirectory(Path path, Tree.Builder tree)
       }
     }
 
-    return b.build();
+    ByteString directory = b.build().toByteString();
+    directories.add(directory);
+    return directory;
   }
 
   private void illegalOutput(Path path) throws ExecException {
diff --git a/src/test/java/com/google/devtools/build/lib/remote/GrpcCacheClientTest.java b/src/test/java/com/google/devtools/build/lib/remote/GrpcCacheClientTest.java
index 4df12d4cb1e107..9f7b55148c6330 100644
--- a/src/test/java/com/google/devtools/build/lib/remote/GrpcCacheClientTest.java
+++ b/src/test/java/com/google/devtools/build/lib/remote/GrpcCacheClientTest.java
@@ -369,7 +369,11 @@ public void updateActionResult(
         .setPath("a/foo")
         .setDigest(fooDigest)
         .setIsExecutable(true);
-    expectedResult.addOutputDirectoriesBuilder().setPath("bar").setTreeDigest(barDigest);
+    expectedResult
+        .addOutputDirectoriesBuilder()
+        .setPath("bar")
+        .setTreeDigest(barDigest)
+        .setIsTopologicallySorted(true);
     assertThat(result).isEqualTo(expectedResult.build());
   }
 
@@ -409,7 +413,11 @@ public void updateActionResult(
 
     ActionResult result = uploadDirectory(remoteCache, ImmutableList.<Path>of(barDir));
     ActionResult.Builder expectedResult = ActionResult.newBuilder();
-    expectedResult.addOutputDirectoriesBuilder().setPath("bar").setTreeDigest(barDigest);
+    expectedResult
+        .addOutputDirectoriesBuilder()
+        .setPath("bar")
+        .setTreeDigest(barDigest)
+        .setIsTopologicallySorted(true);
     assertThat(result).isEqualTo(expectedResult.build());
   }
 
@@ -472,7 +480,11 @@ public void updateActionResult(
 
     ActionResult result = uploadDirectory(remoteCache, ImmutableList.of(barDir));
     ActionResult.Builder expectedResult = ActionResult.newBuilder();
-    expectedResult.addOutputDirectoriesBuilder().setPath("bar").setTreeDigest(barDigest);
+    expectedResult
+        .addOutputDirectoriesBuilder()
+        .setPath("bar")
+        .setTreeDigest(barDigest)
+        .setIsTopologicallySorted(true);
     assertThat(result).isEqualTo(expectedResult.build());
   }
 
diff --git a/src/test/java/com/google/devtools/build/lib/remote/RemoteExecutionServiceTest.java b/src/test/java/com/google/devtools/build/lib/remote/RemoteExecutionServiceTest.java
index 8341d8ca89a1c5..1808b86d66c5ef 100644
--- a/src/test/java/com/google/devtools/build/lib/remote/RemoteExecutionServiceTest.java
+++ b/src/test/java/com/google/devtools/build/lib/remote/RemoteExecutionServiceTest.java
@@ -1314,7 +1314,11 @@ public void uploadOutputs_uploadDirectory_works() throws Exception {
         .setPath("outputs/a/foo")
         .setDigest(fooDigest)
         .setIsExecutable(true);
-    expectedResult.addOutputDirectoriesBuilder().setPath("outputs/bar").setTreeDigest(barDigest);
+    expectedResult
+        .addOutputDirectoriesBuilder()
+        .setPath("outputs/bar")
+        .setTreeDigest(barDigest)
+        .setIsTopologicallySorted(true);
     assertThat(manifest.getActionResult()).isEqualTo(expectedResult.build());
 
     ImmutableList<Digest> toQuery = ImmutableList.of(fooDigest, quxDigest, barDigest);
@@ -1352,7 +1356,11 @@ public void uploadOutputs_uploadEmptyDirectory_works() throws Exception {
 
     // assert
     ActionResult.Builder expectedResult = ActionResult.newBuilder();
-    expectedResult.addOutputDirectoriesBuilder().setPath("outputs/bar").setTreeDigest(barDigest);
+    expectedResult
+        .addOutputDirectoriesBuilder()
+        .setPath("outputs/bar")
+        .setTreeDigest(barDigest)
+        .setIsTopologicallySorted(true);
     assertThat(manifest.getActionResult()).isEqualTo(expectedResult.build());
     assertThat(
             getFromFuture(
@@ -1417,7 +1425,11 @@ public void uploadOutputs_uploadNestedDirectory_works() throws Exception {
 
     // assert
     ActionResult.Builder expectedResult = ActionResult.newBuilder();
-    expectedResult.addOutputDirectoriesBuilder().setPath("outputs/bar").setTreeDigest(barDigest);
+    expectedResult
+        .addOutputDirectoriesBuilder()
+        .setPath("outputs/bar")
+        .setTreeDigest(barDigest)
+        .setIsTopologicallySorted(true);
     assertThat(manifest.getActionResult()).isEqualTo(expectedResult.build());
 
     ImmutableList<Digest> toQuery = ImmutableList.of(wobbleDigest, quxDigest, barDigest);
diff --git a/src/test/java/com/google/devtools/build/lib/remote/UploadManifestTest.java b/src/test/java/com/google/devtools/build/lib/remote/UploadManifestTest.java
index bc758073d7a9c9..7f28efb8efb9d9 100644
--- a/src/test/java/com/google/devtools/build/lib/remote/UploadManifestTest.java
+++ b/src/test/java/com/google/devtools/build/lib/remote/UploadManifestTest.java
@@ -14,6 +14,7 @@
 package com.google.devtools.build.lib.remote;
 
 import static com.google.common.truth.Truth.assertThat;
+import static com.google.common.truth.extensions.proto.ProtoTruth.assertThat;
 import static org.junit.Assert.assertThrows;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.when;
@@ -41,6 +42,8 @@
 import com.google.devtools.build.lib.vfs.SyscallCache;
 import com.google.devtools.build.lib.vfs.inmemoryfs.InMemoryFileSystem;
 import java.io.IOException;
+import java.util.ArrayList;
+import java.util.List;
 import org.junit.Before;
 import org.junit.Test;
 import org.junit.runner.RunWith;
@@ -249,7 +252,11 @@ public void actionResult_followSymlinks_absoluteDirectorySymlinkAsDirectory() th
     Digest treeDigest = digestUtil.compute(tree);
 
     ActionResult.Builder expectedResult = ActionResult.newBuilder();
-    expectedResult.addOutputDirectoriesBuilder().setPath("link").setTreeDigest(treeDigest);
+    expectedResult
+        .addOutputDirectoriesBuilder()
+        .setPath("link")
+        .setTreeDigest(treeDigest)
+        .setIsTopologicallySorted(true);
     assertThat(result.build()).isEqualTo(expectedResult.build());
   }
 
@@ -309,7 +316,11 @@ public void actionResult_noFollowSymlinks_absoluteDirectorySymlinkAsDirectory()
     Digest treeDigest = digestUtil.compute(tree);
 
     ActionResult.Builder expectedResult = ActionResult.newBuilder();
-    expectedResult.addOutputDirectoriesBuilder().setPath("link").setTreeDigest(treeDigest);
+    expectedResult
+        .addOutputDirectoriesBuilder()
+        .setPath("link")
+        .setTreeDigest(treeDigest)
+        .setIsTopologicallySorted(true);
     assertThat(result.build()).isEqualTo(expectedResult.build());
   }
 
@@ -369,7 +380,11 @@ public void actionResult_followSymlinks_relativeDirectorySymlinkAsDirectory() th
     Digest treeDigest = digestUtil.compute(tree);
 
     ActionResult.Builder expectedResult = ActionResult.newBuilder();
-    expectedResult.addOutputDirectoriesBuilder().setPath("link").setTreeDigest(treeDigest);
+    expectedResult
+        .addOutputDirectoriesBuilder()
+        .setPath("link")
+        .setTreeDigest(treeDigest)
+        .setIsTopologicallySorted(true);
     assertThat(result.build()).isEqualTo(expectedResult.build());
   }
 
@@ -570,7 +585,11 @@ public void actionResult_followSymlinks_absoluteFileSymlinkInDirectoryAsFile() t
     Digest treeDigest = digestUtil.compute(tree);
 
     ActionResult.Builder expectedResult = ActionResult.newBuilder();
-    expectedResult.addOutputDirectoriesBuilder().setPath("dir").setTreeDigest(treeDigest);
+    expectedResult
+        .addOutputDirectoriesBuilder()
+        .setPath("dir")
+        .setTreeDigest(treeDigest)
+        .setIsTopologicallySorted(true);
     assertThat(result.build()).isEqualTo(expectedResult.build());
   }
 
@@ -615,7 +634,11 @@ public void actionResult_followSymlinks_absoluteDirectorySymlinkInDirectoryAsDir
     Digest treeDigest = digestUtil.compute(tree);
 
     ActionResult.Builder expectedResult = ActionResult.newBuilder();
-    expectedResult.addOutputDirectoriesBuilder().setPath("dir").setTreeDigest(treeDigest);
+    expectedResult
+        .addOutputDirectoriesBuilder()
+        .setPath("dir")
+        .setTreeDigest(treeDigest)
+        .setIsTopologicallySorted(true);
     assertThat(result.build()).isEqualTo(expectedResult.build());
   }
 
@@ -651,7 +674,11 @@ public void actionResult_noFollowSymlinks_absoluteFileSymlinkInDirectoryAsFile()
     Digest treeDigest = digestUtil.compute(tree);
 
     ActionResult.Builder expectedResult = ActionResult.newBuilder();
-    expectedResult.addOutputDirectoriesBuilder().setPath("dir").setTreeDigest(treeDigest);
+    expectedResult
+        .addOutputDirectoriesBuilder()
+        .setPath("dir")
+        .setTreeDigest(treeDigest)
+        .setIsTopologicallySorted(true);
     assertThat(result.build()).isEqualTo(expectedResult.build());
   }
 
@@ -696,7 +723,11 @@ public void actionResult_noFollowSymlinks_absoluteDirectorySymlinkInDirectoryAsD
     Digest treeDigest = digestUtil.compute(tree);
 
     ActionResult.Builder expectedResult = ActionResult.newBuilder();
-    expectedResult.addOutputDirectoriesBuilder().setPath("dir").setTreeDigest(treeDigest);
+    expectedResult
+        .addOutputDirectoriesBuilder()
+        .setPath("dir")
+        .setTreeDigest(treeDigest)
+        .setIsTopologicallySorted(true);
     assertThat(result.build()).isEqualTo(expectedResult.build());
   }
 
@@ -731,7 +762,11 @@ public void actionResult_followSymlinks_relativeFileSymlinkInDirectoryAsFile() t
     Digest treeDigest = digestUtil.compute(tree);
 
     ActionResult.Builder expectedResult = ActionResult.newBuilder();
-    expectedResult.addOutputDirectoriesBuilder().setPath("dir").setTreeDigest(treeDigest);
+    expectedResult
+        .addOutputDirectoriesBuilder()
+        .setPath("dir")
+        .setTreeDigest(treeDigest)
+        .setIsTopologicallySorted(true);
     assertThat(result.build()).isEqualTo(expectedResult.build());
   }
 
@@ -776,7 +811,11 @@ public void actionResult_followSymlinks_relativeDirectorySymlinkInDirectoryAsDir
     Digest treeDigest = digestUtil.compute(tree);
 
     ActionResult.Builder expectedResult = ActionResult.newBuilder();
-    expectedResult.addOutputDirectoriesBuilder().setPath("dir").setTreeDigest(treeDigest);
+    expectedResult
+        .addOutputDirectoriesBuilder()
+        .setPath("dir")
+        .setTreeDigest(treeDigest)
+        .setIsTopologicallySorted(true);
     assertThat(result.build()).isEqualTo(expectedResult.build());
   }
 
@@ -811,7 +850,11 @@ public void actionResult_noFollowSymlinks_relativeFileSymlinkInDirectoryAsSymlin
     Digest treeDigest = digestUtil.compute(tree);
 
     ActionResult.Builder expectedResult = ActionResult.newBuilder();
-    expectedResult.addOutputDirectoriesBuilder().setPath("dir").setTreeDigest(treeDigest);
+    expectedResult
+        .addOutputDirectoriesBuilder()
+        .setPath("dir")
+        .setTreeDigest(treeDigest)
+        .setIsTopologicallySorted(true);
     assertThat(result.build()).isEqualTo(expectedResult.build());
   }
 
@@ -848,7 +891,11 @@ public void actionResult_noFollowSymlinks_relativeDirectorySymlinkInDirectoryAsS
     Digest treeDigest = digestUtil.compute(tree);
 
     ActionResult.Builder expectedResult = ActionResult.newBuilder();
-    expectedResult.addOutputDirectoriesBuilder().setPath("dir").setTreeDigest(treeDigest);
+    expectedResult
+        .addOutputDirectoriesBuilder()
+        .setPath("dir")
+        .setTreeDigest(treeDigest)
+        .setIsTopologicallySorted(true);
     assertThat(result.build()).isEqualTo(expectedResult.build());
   }
 
@@ -933,7 +980,11 @@ public void actionResult_noFollowSymlinks_relativeDirectorySymlinkInDirectoryAsS
     Digest treeDigest = digestUtil.compute(tree);
 
     ActionResult.Builder expectedResult = ActionResult.newBuilder();
-    expectedResult.addOutputDirectoriesBuilder().setPath("dir").setTreeDigest(treeDigest);
+    expectedResult
+        .addOutputDirectoriesBuilder()
+        .setPath("dir")
+        .setTreeDigest(treeDigest)
+        .setIsTopologicallySorted(true);
     assertThat(result.build()).isEqualTo(expectedResult.build());
   }
 
@@ -968,7 +1019,11 @@ public void actionResult_noFollowSymlinks_relativeDirectorySymlinkInDirectoryAsS
     Digest treeDigest = digestUtil.compute(tree);
 
     ActionResult.Builder expectedResult = ActionResult.newBuilder();
-    expectedResult.addOutputDirectoriesBuilder().setPath("dir").setTreeDigest(treeDigest);
+    expectedResult
+        .addOutputDirectoriesBuilder()
+        .setPath("dir")
+        .setTreeDigest(treeDigest)
+        .setIsTopologicallySorted(true);
     assertThat(result.build()).isEqualTo(expectedResult.build());
   }
 
@@ -1053,6 +1108,70 @@ public void actionResult_followSymlinks_specialFileSymlinkInDirectoryError() thr
     assertThat(e).hasMessageThat().contains("dir/link");
   }
 
+  @Test
+  public void actionResult_topologicallySortedAndDeduplicatedTree() throws Exception {
+    // Create 5^3 identical files named "dir/%d/%d/%d/file".
+    Path dir = execRoot.getRelative("dir");
+    dir.createDirectory();
+    byte[] fileContents = new byte[] {1, 2, 3, 4, 5};
+    final int childrenPerDirectory = 5;
+    for (int a = 0; a < childrenPerDirectory; a++) {
+      Path pathA = dir.getRelative(Integer.toString(a));
+      pathA.createDirectory();
+      for (int b = 0; b < childrenPerDirectory; b++) {
+        Path pathB = pathA.getRelative(Integer.toString(b));
+        pathB.createDirectory();
+        for (int c = 0; c < childrenPerDirectory; c++) {
+          Path pathC = pathB.getRelative(Integer.toString(c));
+          pathC.createDirectory();
+          Path file = pathC.getRelative("file");
+          FileSystemUtils.writeContent(file, fileContents);
+        }
+      }
+    }
+
+    ActionResult.Builder result = ActionResult.newBuilder();
+    UploadManifest um =
+        new UploadManifest(
+            digestUtil,
+            remotePathResolver,
+            result,
+            /*followSymlinks=*/ false,
+            /*allowDanglingSymlinks=*/ false,
+            /*allowAbsoluteSymlinks=*/ false);
+    um.addFiles(ImmutableList.of(dir));
+
+    // Even though we constructed 1 + 5 + 5^2 + 5^3 directories, the resulting
+    // Tree message should only contain four unique instances. The directories
+    // should also be topologically sorted.
+    List<Directory> children = new ArrayList<>();
+    Directory root =
+        Directory.newBuilder()
+            .addFiles(
+                FileNode.newBuilder().setName("file").setDigest(digestUtil.compute(fileContents)))
+            .build();
+    for (int depth = 0; depth < 3; depth++) {
+      Directory.Builder b = Directory.newBuilder();
+      Digest parentDigest = digestUtil.compute(root.toByteArray());
+      for (int i = 0; i < childrenPerDirectory; i++) {
+        b.addDirectories(
+            DirectoryNode.newBuilder().setName(Integer.toString(i)).setDigest(parentDigest));
+      }
+      children.add(0, root);
+      root = b.build();
+    }
+    Tree tree = Tree.newBuilder().setRoot(root).addAllChildren(children).build();
+    Digest treeDigest = digestUtil.compute(tree);
+
+    ActionResult.Builder expectedResult = ActionResult.newBuilder();
+    expectedResult
+        .addOutputDirectoriesBuilder()
+        .setPath("dir")
+        .setTreeDigest(treeDigest)
+        .setIsTopologicallySorted(true);
+    assertThat(result.build()).isEqualTo(expectedResult.build());
+  }
+
   private Path createSpecialFile(String execPath) throws IOException {
     Path special = mock(Path.class);
     when(special.statIfFound(Symlinks.NOFOLLOW)).thenReturn(SPECIAL_FILE_STATUS);
diff --git a/third_party/remoteapis/build/bazel/remote/asset/v1/remote_asset.proto b/third_party/remoteapis/build/bazel/remote/asset/v1/remote_asset.proto
index e11fc7b174a7ad..4d9be8175a9885 100644
--- a/third_party/remoteapis/build/bazel/remote/asset/v1/remote_asset.proto
+++ b/third_party/remoteapis/build/bazel/remote/asset/v1/remote_asset.proto
@@ -23,7 +23,7 @@ import "google/protobuf/timestamp.proto";
 import "google/rpc/status.proto";
 
 option csharp_namespace = "Build.Bazel.Remote.Asset.v1";
-option go_package = "remoteasset";
+option go_package = "github.com/bazelbuild/remote-apis/build/bazel/remote/asset/v1;remoteasset";
 option java_multiple_files = true;
 option java_outer_classname = "RemoteAssetProto";
 option java_package = "build.bazel.remote.asset.v1";
diff --git a/third_party/remoteapis/build/bazel/remote/execution/v2/remote_execution.proto b/third_party/remoteapis/build/bazel/remote/execution/v2/remote_execution.proto
index 9b5806449a5fcf..60753f78ab59a5 100644
--- a/third_party/remoteapis/build/bazel/remote/execution/v2/remote_execution.proto
+++ b/third_party/remoteapis/build/bazel/remote/execution/v2/remote_execution.proto
@@ -26,7 +26,7 @@ import "google/protobuf/wrappers.proto";
 import "google/rpc/status.proto";
 
 option csharp_namespace = "Build.Bazel.Remote.Execution.V2";
-option go_package = "remoteexecution";
+option go_package = "github.com/bazelbuild/remote-apis/build/bazel/remote/execution/v2;remoteexecution";
 option java_multiple_files = true;
 option java_outer_classname = "RemoteExecutionProto";
 option java_package = "build.bazel.remote.execution.v2";
@@ -255,10 +255,11 @@ service ActionCache {
 //
 // When attempting an upload, if another client has already completed the upload
 // (which may occur in the middle of a single upload if another client uploads
-// the same blob concurrently), the request will terminate immediately with
-// a response whose `committed_size` is the full size of the uploaded file
-// (regardless of how much data was transmitted by the client). If the client
-// completes the upload but the
+// the same blob concurrently), the request will terminate immediately without
+// error, and with a response whose `committed_size` is the value `-1` if this
+// is a compressed upload, or with the full size of the uploaded file if this is
+// an uncompressed upload (regardless of how much data was transmitted by the
+// client). If the client completes the upload but the
 // [Digest][build.bazel.remote.execution.v2.Digest] does not match, an
 // `INVALID_ARGUMENT` error will be returned. In either case, the client should
 // not attempt to retry the upload.
@@ -423,6 +424,8 @@ service Capabilities {
   //   CacheCapabilities and ExecutionCapabilities.
   // * Execution only endpoints should return ExecutionCapabilities.
   // * CAS + Action Cache only endpoints should return CacheCapabilities.
+  //
+  // There are no method-specific errors.
   rpc GetCapabilities(GetCapabilitiesRequest) returns (ServerCapabilities) {
     option (google.api.http) = {
       get: "/v2/{instance_name=**}/capabilities"
@@ -475,6 +478,14 @@ message Action {
   // timeout that is longer than the server's maximum timeout, the server MUST
   // reject the request.
   //
+  // The timeout is only intended to cover the "execution" of the specified
+  // action and not time in queue nor any overheads before or after execution
+  // such as marshalling inputs/outputs. The server SHOULD avoid including time
+  // spent the client doesn't have control over, and MAY extend or reduce the
+  // timeout to account for delays or speedups that occur during execution
+  // itself (e.g., lazily loading data from the Content Addressable Storage,
+  // live migration of virtual machines, emulation overhead).
+  //
   // The timeout is a part of the
   // [Action][build.bazel.remote.execution.v2.Action] message, and
   // therefore two `Actions` with different timeouts are different, even if they
@@ -529,9 +540,21 @@ message Command {
     string value = 2;
   }
 
-  // The arguments to the command. The first argument must be the path to the
-  // executable, which must be either a relative path, in which case it is
-  // evaluated with respect to the input root, or an absolute path.
+  // The arguments to the command.
+  //
+  // The first argument specifies the command to run, which may be either an
+  // absolute path, a path relative to the working directory, or an unqualified
+  // path (without path separators) which will be resolved using the operating
+  // system's equivalent of the PATH environment variable. Path separators
+  // native to the operating system running on the worker SHOULD be used. If the
+  // `environment_variables` list contains an entry for the PATH environment
+  // variable, it SHOULD be respected. If not, the resolution process is
+  // implementation-defined.
+  //
+  // Changed in v2.3. v2.2 and older require that no PATH lookups are performed,
+  // and that relative paths are resolved relative to the input root. This
+  // behavior can, however, not be relied upon, as most implementations already
+  // followed the rules described above.
   repeated string arguments = 1;
 
   // The environment variables to set when running the program. The worker may
@@ -605,10 +628,10 @@ message Command {
   // The type of the output (file or directory) is not specified, and will be
   // determined by the server after action execution. If the resulting path is
   // a file, it will be returned in an
-  // [OutputFile][build.bazel.remote.execution.v2.OutputFile]) typed field.
+  // [OutputFile][build.bazel.remote.execution.v2.OutputFile] typed field.
   // If the path is a directory, the entire directory structure will be returned
   // as a [Tree][build.bazel.remote.execution.v2.Tree] message digest, see
-  // [OutputDirectory][build.bazel.remote.execution.v2.OutputDirectory])
+  // [OutputDirectory][build.bazel.remote.execution.v2.OutputDirectory]
   // Other files or directories that may be created during command execution
   // are discarded.
   //
@@ -942,6 +965,25 @@ message ExecutedActionMetadata {
   // When the worker completed executing the action command.
   google.protobuf.Timestamp execution_completed_timestamp = 8;
 
+  // New in v2.3: the amount of time the worker spent executing the action
+  // command, potentially computed using a worker-specific virtual clock.
+  //
+  // The virtual execution duration is only intended to cover the "execution" of
+  // the specified action and not time in queue nor any overheads before or
+  // after execution such as marshalling inputs/outputs. The server SHOULD avoid
+  // including time spent the client doesn't have control over, and MAY extend
+  // or reduce the execution duration to account for delays or speedups that
+  // occur during execution itself (e.g., lazily loading data from the Content
+  // Addressable Storage, live migration of virtual machines, emulation
+  // overhead).
+  //
+  // The method of timekeeping used to compute the virtual execution duration
+  // MUST be consistent with what is used to enforce the
+  // [Action][[build.bazel.remote.execution.v2.Action]'s `timeout`. There is no
+  // relationship between the virtual execution duration and the values of
+  // `execution_start_timestamp` and `execution_completed_timestamp`.
+  google.protobuf.Duration virtual_execution_duration = 12;
+
   // When the worker started uploading action outputs.
   google.protobuf.Timestamp output_upload_start_timestamp = 9;
 
@@ -1105,6 +1147,7 @@ message ActionResult {
   // [GetActionResultRequest][build.bazel.remote.execution.v2.GetActionResultRequest]
   // message. The server MAY omit inlining, even if requested, and MUST do so if inlining
   // would cause the response to exceed message size limits.
+  // Clients SHOULD NOT populate this field when uploading to the cache.
   bytes stdout_raw = 5;
 
   // The digest for a blob containing the standard output of the action, which
@@ -1117,6 +1160,7 @@ message ActionResult {
   // [GetActionResultRequest][build.bazel.remote.execution.v2.GetActionResultRequest]
   // message. The server MAY omit inlining, even if requested, and MUST do so if inlining
   // would cause the response to exceed message size limits.
+  // Clients SHOULD NOT populate this field when uploading to the cache.
   bytes stderr_raw = 7;
 
   // The digest for a blob containing the standard error of the action, which
@@ -1151,6 +1195,7 @@ message OutputFile {
   // [GetActionResultRequest][build.bazel.remote.execution.v2.GetActionResultRequest]
   // message. The server MAY omit inlining, even if requested, and MUST do so if inlining
   // would cause the response to exceed message size limits.
+  // Clients SHOULD NOT populate this field when uploading to the cache.
   bytes contents = 5;
 
   // The supported node properties of the OutputFile, if requested by the Action.
@@ -1169,6 +1214,9 @@ message Tree {
   // recursively, all its children. In order to reconstruct the directory tree,
   // the client must take the digests of each of the child directories and then
   // build up a tree starting from the `root`.
+  // Servers SHOULD ensure that these are ordered consistently such that two
+  // actions producing equivalent output directories on the same server
+  // implementation also produce Tree messages with matching digests.
   repeated Directory children = 2;
 }
 
@@ -1187,6 +1235,43 @@ message OutputDirectory {
   // [Tree][build.bazel.remote.execution.v2.Tree] proto containing the
   // directory's contents.
   Digest tree_digest = 3;
+
+  // If set, consumers MAY make the following assumptions about the
+  // directories contained in the the Tree, so that it may be
+  // instantiated on a local file system by scanning through it
+  // sequentially:
+  //
+  // - All directories with the same binary representation are stored
+  //   exactly once.
+  // - All directories, apart from the root directory, are referenced by
+  //   at least one parent directory.
+  // - Directories are stored in topological order, with parents being
+  //   stored before the child. The root directory is thus the first to
+  //   be stored.
+  //
+  // Additionally, the Tree MUST be encoded as a stream of records,
+  // where each record has the following format:
+  //
+  // - A tag byte, having one of the following two values:
+  //   - (1 << 3) | 2 == 0x0a: First record (the root directory).
+  //   - (2 << 3) | 2 == 0x12: Any subsequent records (child directories).
+  // - The size of the directory, encoded as a base 128 varint.
+  // - The contents of the directory, encoded as a binary serialized
+  //   Protobuf message.
+  //
+  // This encoding is a subset of the Protobuf wire format of the Tree
+  // message. As it is only permitted to store data associated with
+  // field numbers 1 and 2, the tag MUST be encoded as a single byte.
+  // More details on the Protobuf wire format can be found here:
+  // https://developers.google.com/protocol-buffers/docs/encoding
+  //
+  // It is recommended that implementations using this feature construct
+  // Tree objects manually using the specification given above, as
+  // opposed to using a Protobuf library to marshal a full Tree message.
+  // As individual Directory messages already need to be marshaled to
+  // compute their digests, constructing the Tree object manually avoids
+  // redundant marshaling.
+  bool is_topologically_sorted = 4;
 }
 
 // An `OutputSymlink` is similar to a
@@ -1334,6 +1419,17 @@ message ExecuteResponse {
 }
 
 // The current stage of action execution.
+//
+// Even though these stages are numbered according to the order in which
+// they generally occur, there is no requirement that the remote
+// execution system reports events along this order. For example, an
+// operation MAY transition from the EXECUTING stage back to QUEUED
+// in case the hardware on which the operation executes fails.
+//
+// If and only if the remote execution system reports that an operation
+// has reached the COMPLETED stage, it MUST set the [done
+// field][google.longrunning.Operation.done] of the
+// [Operation][google.longrunning.Operation] and terminate the stream.
 message ExecutionStage {
   enum Value {
     // Invalid value.
@@ -1469,6 +1565,12 @@ message BatchUpdateBlobsRequest {
 
     // The raw binary data.
     bytes data = 2;
+
+    // The format of `data`. Must be `IDENTITY`/unspecified, or one of the
+    // compressors advertised by the 
+    // [CacheCapabilities.supported_batch_compressors][build.bazel.remote.execution.v2.CacheCapabilities.supported_batch_compressors]
+    // field.
+    Compressor.Value compressor = 3;
   }
 
   // The instance of the execution system to operate against. A server may
@@ -1510,6 +1612,10 @@ message BatchReadBlobsRequest {
 
   // The individual blob digests.
   repeated Digest digests = 2;
+
+  // A list of acceptable encodings for the returned inlined data, in no
+  // particular order. `IDENTITY` is always allowed even if not specified here.
+  repeated Compressor.Value acceptable_compressors = 3;
 }
 
 // A response message for
@@ -1523,6 +1629,10 @@ message BatchReadBlobsResponse {
     // The raw binary data.
     bytes data = 2;
 
+    // The format the data is encoded in. MUST be `IDENTITY`/unspecified,
+    // or one of the acceptable compressors specified in the `BatchReadBlobsRequest`.
+    Compressor.Value compressor = 4;
+
     // The result of attempting to download that blob.
     google.rpc.Status status = 3;
   }
@@ -1724,6 +1834,11 @@ message CacheCapabilities {
   // Note that this does not imply which if any compressors are supported by
   // the server at the gRPC level.
   repeated Compressor.Value supported_compressors = 6;
+
+  // Compressors supported for inlined data in
+  // [BatchUpdateBlobs][build.bazel.remote.execution.v2.ContentAddressableStorage.BatchUpdateBlobs]
+  // requests.
+  repeated Compressor.Value supported_batch_update_compressors = 7;
 }
 
 // Capabilities of the remote execution system.
diff --git a/third_party/remoteapis/build/bazel/semver/semver.proto b/third_party/remoteapis/build/bazel/semver/semver.proto
index 3b626b7e47c050..44f83f857648af 100644
--- a/third_party/remoteapis/build/bazel/semver/semver.proto
+++ b/third_party/remoteapis/build/bazel/semver/semver.proto
@@ -17,7 +17,7 @@ syntax = "proto3";
 package build.bazel.semver;
 
 option csharp_namespace = "Build.Bazel.Semver";
-option go_package = "semver";
+option go_package = "github.com/bazelbuild/remote-apis/build/bazel/semver";
 option java_multiple_files = true;
 option java_outer_classname = "SemverProto";
 option java_package = "build.bazel.semver";