FN-6326: quarantine deferred-hook title summarization test

Quarantine the flaky deferred-hook title summarization coverage while preserving focused store-create coverage.

- Extract the deferred task-created hook summarization test into its own file.
- Exclude the extracted test file from the core Vitest suite.
- Record the flake investigation and quarantine rationale in the test quarantine ledger.

Files changed:
 .../store-create-summarize-deferred-hook.test.ts   | 67 ++++++++++++++++++++++
 packages/core/src/__tests__/store-create.test.ts   | 44 --------------
 packages/core/vitest.config.ts                     |  1 +
 scripts/lib/test-quarantine.json                   |  5 ++
 4 files changed, 73 insertions(+), 44 deletions(-)

Fusion-Task-Id: FN-6326

Fusion-Task-Lineage: a37189b3-b88b-483f-b2bf-471fde806b35

packages/core/src/__tests__/store-create-summarize-deferred-hook.test.ts

@@ -0,0 +1,67 @@
+import { describe, it, expect, beforeEach, afterEach, vi } from "vitest";
+
+import { setCreateFnAgent } from "../ai-engine-loader.js";
+import { TaskStore } from "../store.js";
+import { setTaskCreatedHook } from "../task-creation-hooks.js";
+import { createTaskStoreTestHarness } from "./store-test-helpers.js";
+
+describe("TaskStore createTask title summarization deferred hook", () => {
+  const harness = createTaskStoreTestHarness();
+  let store: TaskStore;
+
+  beforeEach(async () => {
+    await harness.beforeEach();
+    store = harness.store();
+  });
+
+  afterEach(async () => {
+    setTaskCreatedHook(undefined);
+    setCreateFnAgent(undefined);
+    await harness.afterEach();
+  });
+
+  it("defers the task-created hook until store-managed summarize completes", async () => {
+    const longDescription = "a".repeat(201);
+    let releasePrompt!: () => void;
+    const promptStarted = vi.fn();
+    const promptDone = new Promise<void>((resolve) => {
+      releasePrompt = resolve;
+    });
+    setCreateFnAgent(vi.fn(async () => ({
+      session: {
+        prompt: vi.fn(async () => {
+          promptStarted();
+          await promptDone;
+        }),
+        state: { messages: [{ role: "assistant", content: "Deferred Hook Title" }] },
+      },
+    })));
+    const hookSpy = vi.fn();
+    setTaskCreatedHook(hookSpy);
+
+    const task = await store.createTask(
+      { description: longDescription, summarize: true },
+      {
+        settings: {
+          autoSummarizeTitles: false,
+          titleSummarizerProvider: "mock",
+          titleSummarizerModelId: "title-model",
+        },
+      },
+    );
+
+    await vi.waitFor(() => expect(promptStarted).toHaveBeenCalled());
+    expect(hookSpy).not.toHaveBeenCalled();
+
+    releasePrompt();
+    await vi.waitFor(() => {
+      expect(hookSpy).toHaveBeenCalledWith(
+        expect.objectContaining({
+          id: task.id,
+          title: "Deferred Hook Title",
+        }),
+        store,
+      );
+    });
+  });
+});

packages/core/src/__tests__/store-create.test.ts

@@ -501,50 +501,6 @@ describe("TaskStore", () => {
       expect(promptSpy).toHaveBeenCalledWith(expect.stringContaining(longDescription));
     });
 
-    it("defers the task-created hook until store-managed summarize completes", async () => {
-      const longDescription = "a".repeat(201);
-      let releasePrompt!: () => void;
-      const promptStarted = vi.fn();
-      const promptDone = new Promise<void>((resolve) => {
-        releasePrompt = resolve;
-      });
-      setCreateFnAgent(vi.fn(async () => ({
-        session: {
-          prompt: vi.fn(async () => {
-            promptStarted();
-            await promptDone;
-          }),
-          state: { messages: [{ role: "assistant", content: "Deferred Hook Title" }] },
-        },
-      })));
-      const hookSpy = vi.fn();
-      setTaskCreatedHook(hookSpy);
-
-      const task = await store.createTask(
-        { description: longDescription, summarize: true },
-        {
-          settings: {
-            autoSummarizeTitles: false,
-            titleSummarizerProvider: "mock",
-            titleSummarizerModelId: "title-model",
-          },
-        },
-      );
-
-      await vi.waitFor(() => expect(promptStarted).toHaveBeenCalled());
-      expect(hookSpy).not.toHaveBeenCalled();
-
-      releasePrompt();
-      await vi.waitFor(() => {
-        expect(hookSpy).toHaveBeenCalledWith(
-          expect.objectContaining({
-            id: task.id,
-            title: "Deferred Hook Title",
-          }),
-          store,
-        );
-      });
-    });
 
     it("should ignore malformed confirmation-prose generated titles", async () => {
       const mockOnSummarize = vi

packages/core/vitest.config.ts

@@ -18,6 +18,7 @@ export default defineConfig({
       "src/__tests__/db.test.ts",
       "src/__tests__/soft-delete-tasks.test.ts",
       "src/__tests__/store-get-task-columns.test.ts",
+      "src/__tests__/store-create-summarize-deferred-hook.test.ts",
       "src/__tests__/task-dependency-mutation.test.ts",
       "src/__tests__/task-node-override.test.ts",
     ],

scripts/lib/test-quarantine.json

@@ -55,6 +55,11 @@
       "file": "packages/core/src/__tests__/db.test.ts",
       "reason": "Flake observed during FN-6299 verification: broad `pnpm --filter @fusion/core test` timed out in `Database.recoverIfCorrupt startup guard > rebuilds a malformed database and preserves the corrupt original` after 15s; earlier `pnpm test` attempt SIGTERM'd the core package and leaked a fusion-test-workers temp dir. Follow-up FN-6334.",
       "quarantinedAt": "2026-06-12"
+    },
+    {
+      "file": "packages/core/src/__tests__/store-create-summarize-deferred-hook.test.ts",
+      "reason": "Flake observed during FN-6320 final broad `pnpm test`: `store-create.test.ts > TaskStore > createTask with title summarization > defers the task-created hook until store-managed summarize completes` timed out because the registered task-created hook had zero calls after the gated store-managed summarizer prompt was released. FN-6326 cross-check: the test passed twice standalone after FN-6313, and product code in `TaskStore.createTask` suppresses the synchronous hook only while `hasPendingSummarization` is true, then unconditionally refreshes the task and calls `invokeTaskCreatedHook(latestTask)` after `onSummarize` settles across success/null/throw branches. The broad/package load failure was therefore classified as suite-load/harness sensitivity rather than a confirmed product defect; the single flaky `it` was extracted so the rest of `store-create.test.ts` remains covered.",
+      "quarantinedAt": "2026-06-12"
     }
   ]
 }