diff --git a/apps/server/src/relay/AgentAwarenessRelay.test.ts b/apps/server/src/relay/AgentAwarenessRelay.test.ts
index 30ada288bd76..a90226f67c7e 100644
--- a/apps/server/src/relay/AgentAwarenessRelay.test.ts
+++ b/apps/server/src/relay/AgentAwarenessRelay.test.ts
@@ -659,6 +659,30 @@ describe("AgentAwarenessRelay", () => {
     }),
   );
 
+  it.effect.each([
+    { label: "live", archived: false },
+    { label: "archived", archived: true },
+  ])("never publishes tombstones for $label subagent threads", ({ archived }) =>
+    Effect.gen(function* () {
+      const { relay, currentShell, publications } = yield* makeTestRelay();
+      yield* Ref.set(
+        currentShell,
+        shell({
+          lineage: {
+            rootThreadId: THREAD_ID,
+            parentThreadId: THREAD_ID,
+            relationshipToParent: "subagent",
+          },
+          ...(archived ? { archivedAt: yield* DateTime.now } : {}),
+        }),
+      );
+      yield* relay.publishThread(THREAD_ID);
+      yield* TestClock.adjust("5 seconds");
+      yield* relay.drain;
+      assert.equal(publications.length, 0);
+    }),
+  );
+
   it.effect("confirms a first completed state and respects disabling during confirmation", () =>
     Effect.gen(function* () {
       const { relay, secrets, currentShell, publications } = yield* makeTestRelay();
diff --git a/apps/server/src/relay/AgentAwarenessRelay.ts b/apps/server/src/relay/AgentAwarenessRelay.ts
index 71e74d11b913..bc0e3d233119 100644
--- a/apps/server/src/relay/AgentAwarenessRelay.ts
+++ b/apps/server/src/relay/AgentAwarenessRelay.ts
@@ -522,6 +522,16 @@ export const make = Effect.gen(function* () {
     // domain event, so materializing the full shell here would make the cost
     // of one thread's activity proportional to how many threads exist.
     const threadShell = yield* threads.getThreadShell(threadId);
+    if (
+      threadShell?.lineage.relationshipToParent === "subagent" &&
+      !(yield* Ref.get(publishedStateByThreadRef)).has(threadId)
+    ) {
+      // Subagents never project activity, so the relay holds no row to clear.
+      // Their events would otherwise publish a tombstone each, and every
+      // publish re-delivers the user's aggregate. Checked before the archive
+      // filter so archiving one stays quiet too.
+      return;
+    }
     const thread =
       threadShell === null || threadShell.archivedAt !== null
         ? Option.none<OrchestrationV2ThreadShell>()