diff --git a/internal/cloud/code-agent-agentrun-adapter.ts b/internal/cloud/code-agent-agentrun-adapter.ts
index b07e5119..49d2193b 100644
--- a/internal/cloud/code-agent-agentrun-adapter.ts
+++ b/internal/cloud/code-agent-agentrun-adapter.ts
@@ -442,7 +442,7 @@ export async function submitAgentRunChatTurn({ params = {}, options = {}, traceI
       }, backendProfile));
       continue;
     }
-    const profileThreadId = agentRunSessionThreadIdFromEnsure(ensuredSession);
+    const profileThreadId = agentRunSessionThreadIdFromEnsure(ensuredSession, backendProfile);
     const dispatchParams = paramsWithAgentRunSessionThread(attemptParams, profileThreadId);
     if (safeOpaqueId(attemptParams.threadId) && !profileThreadId) {
       traceStore.append(traceId, agentRunTraceEvent({
@@ -1263,9 +1263,11 @@ function agentRunSessionRecordFromEnsure(value = null) {
   return session && typeof session === "object" ? session : null;
 }
 
-function agentRunSessionThreadIdFromEnsure(value = null) {
+function agentRunSessionThreadIdFromEnsure(value = null, backendProfile = null) {
   const record = agentRunSessionRecordFromEnsure(value);
   if (agentRunSessionThreadInvalidated(record)) return null;
+  const existingProfile = firstNonEmpty(record?.backendProfile, record?.metadata?.agentRunSessionProfile);
+  if (existingProfile && backendProfile && existingProfile !== backendProfile) return null;
   return safeOpaqueId(record?.threadId) || null;
 }
 
diff --git a/internal/cloud/server-agent-chat.test.ts b/internal/cloud/server-agent-chat.test.ts
index 9f4df007..43751887 100644
--- a/internal/cloud/server-agent-chat.test.ts
+++ b/internal/cloud/server-agent-chat.test.ts
@@ -1881,6 +1881,7 @@ test("cloud api AgentRun adapter keeps AgentRun sessions scoped to HWLAB session
     if (request.method === "POST" && url.pathname === "/api/v1/runs") {
       assert.equal(body.backendProfile, "minimax-m3");
       assert.equal(body.sessionRef.sessionId, minimaxSessionId);
+      assert.equal(body.sessionRef.threadId, undefined);
       assert.equal(body.sessionRef.metadata.hwlabSessionId, hwlabSessionId);
       assert.equal(body.sessionRef.metadata.agentRunSessionProfile, "minimax-m3");
       return send({ id: "run_hwlab_profile_switch_m3", status: "pending", backendProfile: "minimax-m3", sessionRef: body.sessionRef, resourceBundleRef: body.resourceBundleRef });
@@ -1889,6 +1890,7 @@ test("cloud api AgentRun adapter keeps AgentRun sessions scoped to HWLAB session
       assert.equal(body.payload.providerProfile, "minimax-m3");
       assert.equal(body.payload.sessionId, minimaxSessionId);
       assert.equal(body.payload.hwlabSessionId, hwlabSessionId);
+      assert.equal(body.payload.threadId, null);
       return send({ id: "cmd_hwlab_profile_switch_m3", runId: "run_hwlab_profile_switch_m3", state: "pending", type: "turn", seq: 1 });
     }
     if (request.method === "GET" && url.pathname === "/api/v1/runs/run_hwlab_profile_switch_m3/commands") {