Cover the status ledger, the locale collapse, and snapshot re-grounding

The status-provider suite drives the real budget module against an
in-memory stand-in for the day's usage row, so it exercises the atomic
reserve/reconcile path rather than asserting a mock was called: spend
lands on the ledger, an exhausted day is refused before any egress, a
failed generation is refunded, and a chain on the user's own key is
measured against the user-plan ceiling rather than the operator's.

The snapshot suite walks a 60-turn conversation and pins the full
snapshot to exactly two turns — the first and the elision crossing —
including the case where a lost reply shifts the turn parity.

src/app/api/ai/test/__tests__/route.test.ts

@@ -289,3 +289,72 @@ describe("POST /api/ai/test — dropdown-aware override", () => {
     expect(body.error).toBe("Anthropic API key not configured");
   });
 });
+
+/**
+ * Cost ceiling. The 5/min bucket bounded burst rate but nothing cumulative —
+ * sustained, it permits ~7 200 probes a day, and with an empty body this route
+ * resolves the SAME provider chain generation uses, which can be the
+ * operator's own credential. So the surface could reach the operator's key
+ * indefinitely with no daily ceiling and no ledger entry at all.
+ */
+describe("POST /api/ai/test — daily ceiling + ledger", () => {
+  function okProvider() {
+    vi.mocked(resolveProviderForTest).mockResolvedValue({
+      type: "anthropic",
+      generateCompletion: vi.fn(async () => ({
+        content: '{"ok":true}',
+        providerType: "anthropic",
+        model: "claude-3-5-sonnet-latest",
+        tokensUsed: 5,
+      })),
+    } as never);
+  }
+
+  it("refuses once the per-user daily probe limit is spent", async () => {
+    const { checkRateLimit } = await import("@/lib/rate-limit");
+    okProvider();
+    // Burst bucket fine, cumulative daily bucket exhausted.
+    vi.mocked(checkRateLimit)
+      .mockResolvedValueOnce({ allowed: true } as never)
+      .mockResolvedValueOnce({ allowed: false } as never);
+
+    const response = await POST(emptyRequest() as never);
+
+    expect(response.status).toBe(429);
+    // Refused before any provider egress.
+    expect(resolveProviderForTest).not.toHaveBeenCalled();
+  });
+
+  it("refuses when the day's token budget is already exhausted", async () => {
+    const { reserveBudget } = await import("@/lib/ai/coach/budget");
+    const generateCompletion = vi.fn();
+    vi.mocked(resolveProviderForTest).mockResolvedValue({
+      type: "admin-key",
+      generateCompletion,
+    } as never);
+    vi.mocked(reserveBudget).mockResolvedValueOnce({
+      allowed: false,
+      reserved: 32,
+      totalAfter: 200_000,
+    } as never);
+
+    const response = await POST(emptyRequest() as never);
+
+    expect(response.status).toBe(429);
+    expect(generateCompletion).not.toHaveBeenCalled();
+  });
+
+  it("records a successful probe on the ledger", async () => {
+    const { reconcileSpend } = await import("@/lib/ai/coach/budget");
+    okProvider();
+
+    await POST(emptyRequest() as never);
+
+    expect(reconcileSpend).toHaveBeenCalledWith(
+      "u-1",
+      32,
+      expect.any(Number),
+      "2026-01-01",
+    );
+  });
+});

src/app/api/insights/chat/__tests__/route-snapshot-once.test.ts

@@ -220,3 +220,92 @@ describe("coach chat — snapshot sent once per conversation (C4)", () => {
     expect(prompt).toContain("Your BP looks stable.");
   });
 });
+
+/**
+ * The erosion guard.
+ *
+ * The re-ground condition used to be the open-ended `allTurns.length >
+ * TURN_CAP`, which is true for EVERY turn past the history cap — not just the
+ * one that crosses it. So a conversation that ran long re-shipped the full
+ * ~15k-token snapshot on turn 21, 22, 23, … permanently, reinstating exactly
+ * the per-turn cost the snapshot-once design removes, and paying it on the
+ * longest (most expensive) conversations. The intent was always to re-ground
+ * ONCE, at the boundary where the original snapshot scrolls out of the
+ * verbatim window.
+ */
+describe("coach chat — snapshot re-grounds at the elision boundary only", () => {
+  const TURN_CAP = 20;
+
+  beforeEach(() => {
+    vi.clearAllMocks();
+    runStreamingRawCompletionWithFallback.mockResolvedValue({
+      result: { content: "Your BP looks stable.", tokensUsed: 42, model: "m" },
+      workingProvider: { providerType: "admin-openai" },
+    });
+  });
+
+  /** Drive one turn against a conversation that already has `n` turns on disk. */
+  async function turnWithPriorCount(n: number): Promise<string> {
+    fetchConversationWithMessages.mockResolvedValue({
+      id: "c1",
+      summary: "earlier summary",
+      messages: Array.from({ length: n }, (_, i) => ({
+        role: i % 2 === 0 ? "user" : "assistant",
+        content: `turn ${i}`,
+      })),
+    });
+    await postAndDrain({ conversationId: "c1", message: "next?" });
+    return lastUserPrompt();
+  }
+
+  it("re-grounds on the turn that crosses the cap", async () => {
+    expect(await turnWithPriorCount(TURN_CAP)).toContain(SNAPSHOT_JSON);
+  });
+
+  it("does NOT re-ship the snapshot on every turn past the cap", async () => {
+    // Well past the boundary — these are the turns that used to pay the full
+    // snapshot cost forever.
+    for (const prior of [TURN_CAP + 2, TURN_CAP + 6, TURN_CAP + 20, 58]) {
+      expect(await turnWithPriorCount(prior)).not.toContain(SNAPSHOT_JSON);
+    }
+  });
+
+  it("ships the full snapshot only twice across a 60-turn conversation", async () => {
+    let shipped = 0;
+    const shippedAt: number[] = [];
+
+    // Turn 1 starts a fresh conversation (no prior turns on disk); every later
+    // turn loads the growing history. A successful turn persists both the user
+    // and the assistant message, so the count advances by 2.
+    fetchConversationWithMessages.mockResolvedValue(null);
+    await postAndDrain({ message: "How is my BP?" });
+    if (lastUserPrompt().includes(SNAPSHOT_JSON)) {
+      shipped++;
+      shippedAt.push(0);
+    }
+
+    for (let prior = 2; prior <= 60; prior += 2) {
+      if ((await turnWithPriorCount(prior)).includes(SNAPSHOT_JSON)) {
+        shipped++;
+        shippedAt.push(prior);
+      }
+    }
+
+    // Turn 1 (grounding) + the single crossing at the cap. Under the old
+    // predicate this was 1 + every turn from 20 to 60 — 21 full snapshots.
+    expect(shippedAt).toEqual([0, TURN_CAP]);
+    expect(shipped).toBe(2);
+  });
+
+  /**
+   * The turn count does not advance in fixed steps: the user message is
+   * persisted before the provider call, the assistant message only on success,
+   * so a turn that lost its reply advances the count by 1 instead of 2. An
+   * exact `=== TURN_CAP` equality would be stepped straight over by such a
+   * conversation and would then never re-ground at all. The window must catch
+   * the crossing from either parity.
+   */
+  it("still re-grounds when a lost reply shifts the turn parity", async () => {
+    expect(await turnWithPriorCount(TURN_CAP + 1)).toContain(SNAPSHOT_JSON);
+  });
+});