test(qa): cover subagent completion fallback

extensions/qa-lab/src/providers/mock-openai/server.test.ts

@@ -68,6 +68,7 @@ function makeUserInput(text: string) {
 }
 
 const SESSIONS_SPAWN_TOOL = { type: "function", name: "sessions_spawn" } as const;
+const SESSIONS_YIELD_TOOL = { type: "function", name: "sessions_yield" } as const;
 const THREAD_SUBAGENT_CHILD_ERROR_TOKEN = "QA_SUBAGENT_CHILD_ERROR";
 const THREAD_SUBAGENT_TOOL_ERROR =
   "thread=true requested but thread delivery is unavailable in this test harness.";
@@ -707,6 +708,75 @@ describe("qa mock openai server", () => {
     });
   });
 
+  it("drives yielded-parent subagent fallback QA through sessions_spawn and sessions_yield", async () => {
+    const server = await startMockServer();
+    const prompt =
+      "Subagent direct fallback QA check: spawn one worker and yield until QA-SUBAGENT-DIRECT-FALLBACK-OK is delivered.";
+
+    await expectResponsesText(server, {
+      stream: true,
+      tools: [SESSIONS_SPAWN_TOOL, SESSIONS_YIELD_TOOL],
+      input: [makeUserInput(prompt)],
+    });
+
+    await expect(
+      (await fetch(`${server.baseUrl}/debug/last-request`)).json(),
+    ).resolves.toMatchObject({
+      plannedToolName: "sessions_spawn",
+      plannedToolArgs: {
+        label: "qa-direct-fallback-worker",
+        thread: false,
+        mode: "run",
+      },
+    });
+
+    const body = await expectResponsesText(server, {
+      stream: true,
+      tools: [SESSIONS_SPAWN_TOOL, SESSIONS_YIELD_TOOL],
+      input: [
+        makeUserInput(prompt),
+        {
+          type: "function_call_output",
+          call_id: "call_mock_sessions_spawn_1",
+          output: JSON.stringify({
+            status: "accepted",
+            childSessionKey: "agent:qa:subagent:child",
+            runId: "run-child-1",
+          }),
+        },
+      ],
+    });
+
+    expect(body).toContain('"name":"sessions_yield"');
+    expect(body).toContain("QA-SUBAGENT-DIRECT-FALLBACK-OK");
+    await expect(
+      (await fetch(`${server.baseUrl}/debug/last-request`)).json(),
+    ).resolves.toMatchObject({
+      plannedToolName: "sessions_yield",
+    });
+  });
+
+  it("returns no visible announce output for the direct fallback QA marker", async () => {
+    const server = await startMockServer();
+
+    const body = await expectResponsesJson<{
+      output?: Array<{ content?: Array<{ text?: string }> }>;
+    }>(server, {
+      stream: false,
+      input: [
+        makeUserInput(
+          [
+            "[Internal task completion event]",
+            "Task: qa-direct-fallback-worker",
+            "Result: QA-SUBAGENT-DIRECT-FALLBACK-OK",
+          ].join("\n"),
+        ),
+      ],
+    });
+
+    expect(body.output?.[0]?.content?.[0]?.text).toBe("");
+  });
+
   it("surfaces sessions_spawn tool errors instead of echoing child-task tokens", async () => {
     const server = await startMockServer();
 

extensions/qa-lab/src/providers/mock-openai/server.ts

@@ -147,6 +147,9 @@ const QA_EMPTY_RESPONSE_RECOVERY_PROMPT_RE = /empty response continuation qa che
 const QA_EMPTY_RESPONSE_EXHAUSTION_PROMPT_RE = /empty response exhaustion qa check/i;
 const QA_QUIET_STREAMING_PROMPT_RE = /quiet streaming qa check/i;
 const QA_BLOCK_STREAMING_PROMPT_RE = /block streaming qa check/i;
+const QA_SUBAGENT_DIRECT_FALLBACK_PROMPT_RE = /subagent direct fallback qa check/i;
+const QA_SUBAGENT_DIRECT_FALLBACK_WORKER_RE = /subagent direct fallback worker/i;
+const QA_SUBAGENT_DIRECT_FALLBACK_MARKER = "QA-SUBAGENT-DIRECT-FALLBACK-OK";
 const QA_REASONING_ONLY_RETRY_NEEDLE =
   "recorded reasoning but did not produce a user-visible answer";
 const QA_EMPTY_RESPONSE_RETRY_NEEDLE =
@@ -784,6 +787,9 @@ function buildAssistantText(
   if (/fanout worker beta/i.test(prompt)) {
     return "BETA-OK";
   }
+  if (QA_SUBAGENT_DIRECT_FALLBACK_WORKER_RE.test(prompt)) {
+    return QA_SUBAGENT_DIRECT_FALLBACK_MARKER;
+  }
   if (/report the visible code/i.test(prompt) && /FORKED-CONTEXT-ALPHA/i.test(allInputText)) {
     return "FORKED-CONTEXT-ALPHA";
   }
@@ -1153,6 +1159,29 @@ async function buildResponsesPayload(
   const hasReasoningOnlyRetryInstruction = allInputText.includes(QA_REASONING_ONLY_RETRY_NEEDLE);
   const hasEmptyResponseRetryInstruction = allInputText.includes(QA_EMPTY_RESPONSE_RETRY_NEEDLE);
   const canCallSessionsSpawn = hasDeclaredTool(body, "sessions_spawn");
+  const canCallSessionsYield = hasDeclaredTool(body, "sessions_yield");
+  if (
+    allInputText.includes(QA_SUBAGENT_DIRECT_FALLBACK_MARKER) &&
+    /Internal task completion event/i.test(allInputText)
+  ) {
+    return buildAssistantEvents("");
+  }
+  if (QA_SUBAGENT_DIRECT_FALLBACK_PROMPT_RE.test(allInputText)) {
+    if (!toolOutput && canCallSessionsSpawn) {
+      return buildToolCallEventsWithArgs("sessions_spawn", {
+        task: `Subagent direct fallback worker: finish with exactly ${QA_SUBAGENT_DIRECT_FALLBACK_MARKER}.`,
+        label: "qa-direct-fallback-worker",
+        thread: false,
+        mode: "run",
+        runTimeoutSeconds: 30,
+      });
+    }
+    if (toolOutput && canCallSessionsYield && !/\byielded\b/i.test(toolOutput)) {
+      return buildToolCallEventsWithArgs("sessions_yield", {
+        message: `Waiting for ${QA_SUBAGENT_DIRECT_FALLBACK_MARKER}.`,
+      });
+    }
+  }
   if (/remember this fact/i.test(prompt)) {
     return buildAssistantEvents(buildAssistantText(input, body, scenarioState));
   }