diff --git a/src/main/java/com/google/devtools/build/lib/actions/ActionExecutedEvent.java b/src/main/java/com/google/devtools/build/lib/actions/ActionExecutedEvent.java
index b5c3d62..6510d17 100644
--- a/src/main/java/com/google/devtools/build/lib/actions/ActionExecutedEvent.java
+++ b/src/main/java/com/google/devtools/build/lib/actions/ActionExecutedEvent.java
@@ -52,7 +52,6 @@
   private final Path stdout;
   private final Path stderr;
   private final ImmutableList<MetadataLog> actionMetadataLogs;
-  private final boolean isInMemoryFs;
   private final ErrorTiming timing;
 
   public ActionExecutedEvent(
@@ -65,8 +64,7 @@
       Path stdout,
       Path stderr,
       ImmutableList<MetadataLog> actionMetadataLogs,
-      ErrorTiming timing,
-      boolean isInMemoryFs) {
+      ErrorTiming timing) {
     this.actionId = actionId;
     this.action = action;
     this.exception = exception;
@@ -77,7 +75,6 @@
     this.stderr = stderr;
     this.timing = timing;
     this.actionMetadataLogs = actionMetadataLogs;
-    this.isInMemoryFs = isInMemoryFs;
     Preconditions.checkNotNull(this.actionMetadataLogs, this);
     Preconditions.checkState(
         (this.exception == null) == (this.timing == ErrorTiming.NO_ERROR), this);
@@ -98,10 +95,6 @@
     return timing;
   }
 
-  public boolean hasInMemoryFs() {
-    return isInMemoryFs;
-  }
-
   public String getStdout() {
     if (stdout == null) {
       return null;
diff --git a/src/main/java/com/google/devtools/build/lib/buildtool/buildevent/BuildStartingEvent.java b/src/main/java/com/google/devtools/build/lib/buildtool/buildevent/BuildStartingEvent.java
index f739e93..dee499b 100644
--- a/src/main/java/com/google/devtools/build/lib/buildtool/buildevent/BuildStartingEvent.java
+++ b/src/main/java/com/google/devtools/build/lib/buildtool/buildevent/BuildStartingEvent.java
@@ -42,6 +42,12 @@
   /** Returns the name of output file system. */
   public abstract String outputFileSystem();
 
+  /**
+   * Returns whether the build uses in-memory {@link
+   * com.google.devtools.build.lib.vfs.OutputService.ActionFileSystemType#inMemoryFileSystem()}.
+   */
+  public abstract boolean usesInMemoryFileSystem();
+
   /** Returns the active BuildRequest. */
   public abstract BuildRequest request();
 
@@ -59,6 +65,8 @@
   public static BuildStartingEvent create(CommandEnvironment env, BuildRequest request) {
     return create(
         env.determineOutputFileSystem(),
+        env.getOutputService() != null
+            && env.getOutputService().actionFileSystemType().inMemoryFileSystem(),
         request,
         env.getDirectories().getWorkspace() != null
             ? env.getDirectories().getWorkspace().toString()
@@ -68,8 +76,13 @@
 
   @VisibleForTesting
   public static BuildStartingEvent create(
-      String outputFileSystem, BuildRequest request, @Nullable String workspace, String pwd) {
-    return new AutoValue_BuildStartingEvent(outputFileSystem, request, workspace, pwd);
+      String outputFileSystem,
+      boolean usesInMemoryFileSystem,
+      BuildRequest request,
+      @Nullable String workspace,
+      String pwd) {
+    return new AutoValue_BuildStartingEvent(
+        outputFileSystem, usesInMemoryFileSystem, request, workspace, pwd);
   }
 
   @Override
diff --git a/src/main/java/com/google/devtools/build/lib/skyframe/SkyframeActionExecutor.java b/src/main/java/com/google/devtools/build/lib/skyframe/SkyframeActionExecutor.java
index 9bb7461..5cd3034 100644
--- a/src/main/java/com/google/devtools/build/lib/skyframe/SkyframeActionExecutor.java
+++ b/src/main/java/com/google/devtools/build/lib/skyframe/SkyframeActionExecutor.java
@@ -1220,7 +1220,6 @@
             /*primaryOutputMetadata=*/ null,
             action,
             actionResult,
-            actionFileSystemType().inMemoryFileSystem(),
             actionException,
             fileOutErr,
             ErrorTiming.AFTER_EXECUTION);
@@ -1233,7 +1232,6 @@
             /*primaryOutputMetadata=*/ null,
             action,
             actionResult,
-            actionFileSystemType().inMemoryFileSystem(),
             new ActionExecutionException(
                 exception,
                 action,
@@ -1260,7 +1258,6 @@
           primaryOutputMetadata,
           action,
           actionResult,
-          actionFileSystemType().inMemoryFileSystem(),
           null,
           fileOutErr,
           ErrorTiming.NO_ERROR);
@@ -1413,7 +1410,6 @@
         /*primaryOutputMetadata=*/ null,
         action,
         null,
-        actionFileSystemType().inMemoryFileSystem(),
         e,
         outErrBuffer,
         errorTiming);
@@ -1694,7 +1690,6 @@
       @Nullable FileArtifactValue primaryOutputMetadata,
       Action action,
       @Nullable ActionResult actionResult,
-      boolean isInMemoryFs,
       ActionExecutionException exception,
       FileOutErr outErr,
       ErrorTiming errorTiming) {
@@ -1726,8 +1721,7 @@
             stdout,
             stderr,
             logs,
-            errorTiming,
-            isInMemoryFs));
+            errorTiming));
   }
 
   /** An object supplying data for action execution progress reporting. */
diff --git a/src/test/java/com/google/devtools/build/lib/runtime/BuildEventStreamerTest.java b/src/test/java/com/google/devtools/build/lib/runtime/BuildEventStreamerTest.java
index ee504e5..6fc94eb 100644
--- a/src/test/java/com/google/devtools/build/lib/runtime/BuildEventStreamerTest.java
+++ b/src/test/java/com/google/devtools/build/lib/runtime/BuildEventStreamerTest.java
@@ -150,8 +150,7 @@
           /*stdout=*/ null,
           /*stderr=*/ null,
           /*actionMetadataLogs=*/ ImmutableList.of(),
-          ErrorTiming.NO_ERROR,
-          /*isInMemoryFs=*/ false);
+          ErrorTiming.NO_ERROR);
 
   private static final class RecordingBuildEventTransport implements BuildEventTransport {
     private final List<BuildEvent> events = new ArrayList<>();
@@ -1257,8 +1256,7 @@
             /*stdout=*/ null,
             /*stderr=*/ null,
             /*actionMetadataLogs=*/ ImmutableList.of(),
-            ErrorTiming.BEFORE_EXECUTION,
-            /*isInMemoryFs=*/ false);
+            ErrorTiming.BEFORE_EXECUTION);
 
     streamer.buildEvent(SUCCESSFUL_ACTION_EXECUTED_EVENT);
     streamer.buildEvent(failedActionExecutedEvent);
@@ -1302,8 +1300,7 @@
             /*stdout=*/ null,
             /*stderr=*/ null,
             /*actionMetadataLogs=*/ ImmutableList.of(),
-            ErrorTiming.BEFORE_EXECUTION,
-            /*isInMemoryFs=*/ false);
+            ErrorTiming.BEFORE_EXECUTION);
 
     streamer.buildEvent(SUCCESSFUL_ACTION_EXECUTED_EVENT);
     streamer.buildEvent(failedActionExecutedEvent);
@@ -1516,8 +1513,7 @@
         /*stdout=*/ null,
         /*stderr=*/ null,
         metadataLogs,
-        ErrorTiming.NO_ERROR,
-        /*isInMemoryFs=*/ false);
+        ErrorTiming.NO_ERROR);
   }
 
   @Test
diff --git a/src/test/java/com/google/devtools/build/lib/runtime/UiEventHandlerStdOutAndStdErrTest.java b/src/test/java/com/google/devtools/build/lib/runtime/UiEventHandlerStdOutAndStdErrTest.java
index b24d074..e6b2dee 100644
--- a/src/test/java/com/google/devtools/build/lib/runtime/UiEventHandlerStdOutAndStdErrTest.java
+++ b/src/test/java/com/google/devtools/build/lib/runtime/UiEventHandlerStdOutAndStdErrTest.java
@@ -82,7 +82,11 @@
         new UiEventHandler(outErr, uiOptions, new ManualClock(), /*workspacePathFragment=*/ null);
     uiEventHandler.buildStarted(
         BuildStartingEvent.create(
-            "outputFileSystemType", mock(BuildRequest.class), /*workspace=*/ null, "/pwd"));
+            "outputFileSystemType",
+            /*usesInMemoryFileSystem=*/ false,
+            mock(BuildRequest.class),
+            /*workspace=*/ null,
+            "/pwd"));
   }
 
   @Test