fix(api): skip the shared rate-limit budget when chat Q&A is off for the repo (#9734)

The chat-qa route counted a prior invocation and recorded a
COMMAND_RATE_LIMIT_EVENT_TYPE audit row (the SAME counter the @Loopover chat
PR-comment command uses), then built a planNextWork grounding bundle, before
calling generateChatQaAnswer -- which, on a repo where chat Q&A is not enabled,
is guaranteed to return `disabled`. So every request to a chat-disabled repo
spent a slot in the shared budget and paid for the grounding bundle for an answer
that never came, and could drive the maintainer's genuine @Loopover chat usage on
that PR to its limit.

Gate the route on isRepoChatQaEnabled(settings) -- the same predicate the
maintainer dashboard's capability map already reads, so the two can never
disagree -- immediately after resolving settings. When it is false, return
generateChatQaAnswer's own disabled result (its bundle is unused on that path)
before the rate-limit block and before planNextWork. The enabled path -- counting,
the audit row, planNextWork, and the rate_limited response -- is unchanged, and
ai-chat-qa.ts is not touched.

Adds tests asserting a disabled repo writes no audit row and never calls
planNextWork, while the existing enabled-path rate-limit/audit/rate_limited tests
continue to pass. One existing enabled-path test that had never stubbed the
chatQa-enabling manifest (and only passed because the route used to run
unconditionally) now enables it explicitly.

Closes #9714

Author: shin-core

src/api/routes.ts

@@ -3537,6 +3537,25 @@ export function createApp() {
     const [settings, pullRequest] = await Promise.all([resolveRepositorySettings(c.env, fullName), getPullRequest(c.env, fullName, number)]);
     if (!pullRequest) return c.json({ error: "pull_request_not_found" }, 404);
 
+    // When chat Q&A is disabled for the repo, generateChatQaAnswer is guaranteed to return `disabled` -- but only
+    // after this route has already spent a slot in the shared @loopover-chat rate-limit budget AND paid for the
+    // planNextWork grounding bundle (#9714). Gate on the SAME predicate the maintainer dashboard reads
+    // (isRepoChatQaEnabled at the capability map above), so the two can never disagree, and return
+    // generateChatQaAnswer's own disabled result (bundle unused on that path) rather than a second copy of it.
+    if (!isRepoChatQaEnabled(settings)) {
+      return c.json(
+        await generateChatQaAnswer(c.env, {
+          bundle: null,
+          question: parsed.data.question,
+          advisoryAiRouting: settings.advisoryAiRouting,
+          repoFullName: fullName,
+          issueNumber: number,
+          actor: resolveChatQaActor(gate.identity),
+          route: "app.maintainer_dashboard.chat_qa",
+        }),
+      );
+    }
+
     const actor = resolveChatQaActor(gate.identity);
     const targetKey = `${fullName}#${number}#chat`;
     const { policy, maxPerWindow, windowHours } = resolveChatQaRateLimit(settings);

test/unit/maintainer-chat-qa.test.ts

@@ -104,6 +104,37 @@ describe("POST /v1/repos/:owner/:repo/pulls/:number/chat-qa (#6489)", () => {
     await expect(res.json()).resolves.toEqual({ status: "disabled", reason: "Chat Q&A is not enabled on this instance (settings.advisoryAiRouting.chatQa is off)." });
   });
 
+  it("#9714: a disabled repo does NOT record a rate-limit audit row (it must not spend the shared @loopover-chat budget)", async () => {
+    const env = createTestEnv();
+    await seedRepoWithPull(env);
+    // chatQa is off (no .loopover.yml stub). The request still returns disabled, but must not have consumed a slot.
+    const res = await app.request("/v1/repos/owner/repo/pulls/11/chat-qa", { method: "POST", headers: apiHeaders(env), body: JSON.stringify({ question: "why is this blocked?" }) }, env);
+    expect(res.status).toBe(200);
+    await expect(res.json()).resolves.toMatchObject({ status: "disabled" });
+
+    const invocationRows = await env.DB.prepare("select count(*) as n from audit_events where event_type = 'github_app.command_invocation' and target_key = 'owner/repo#11#chat'").first<{ n: number }>();
+    expect(invocationRows?.n).toBe(0);
+  });
+
+  it("#9714: a disabled repo does NOT call planNextWork (it must not pay for the grounding bundle)", async () => {
+    vi.resetModules();
+    const planNextWork = vi.fn();
+    vi.doMock("../../src/services/agent-orchestrator", async () => {
+      const actual = await vi.importActual<typeof import("../../src/services/agent-orchestrator")>("../../src/services/agent-orchestrator");
+      return { ...actual, planNextWork };
+    });
+    const { createApp: createMockedApp } = await import("../../src/api/routes");
+    const mockedApp = createMockedApp();
+
+    const env = createTestEnv();
+    await seedRepoWithPull(env);
+    // chatQa off (no stub): the short-circuit must return before the planNextWork grounding-bundle build.
+    const res = await mockedApp.request("/v1/repos/owner/repo/pulls/11/chat-qa", { method: "POST", headers: apiHeaders(env), body: JSON.stringify({ question: "why?" }) }, env);
+    expect(res.status).toBe(200);
+    await expect(res.json()).resolves.toMatchObject({ status: "disabled" });
+    expect(planNextWork).not.toHaveBeenCalled();
+  });
+
   it("builds a bundle via planNextWork and passes it, the question, and settings through to generateChatQaAnswer, returning its result verbatim", async () => {
     vi.resetModules();
     const generateChatQaAnswer = vi.fn().mockResolvedValue({ status: "ok", model: "test-model", estimatedNeurons: 12, text: "This PR is blocked on a failing check." });
@@ -153,6 +184,9 @@ describe("POST /v1/repos/:owner/:repo/pulls/:number/chat-qa (#6489)", () => {
 
     const env = createTestEnv();
     await seedRepoWithPull(env, { authorLogin: null });
+    // chatQa must be ENABLED for this test to reach planNextWork -- it exercises the grounding-login fallback on
+    // the enabled path. (#9714 now short-circuits a disabled repo before planNextWork, so the enable is explicit.)
+    stubChatQaManifestFetch();
 
     const res = await mockedApp.request("/v1/repos/owner/repo/pulls/11/chat-qa", { method: "POST", headers: apiHeaders(env), body: JSON.stringify({ question: "why is this blocked?" }) }, env);
     expect(res.status).toBe(200);