diff --git a/src/app/api/ai/test/__tests__/route.test.ts b/src/app/api/ai/test/__tests__/route.test.ts
index 8fec8e4e0..2cf725575 100644
--- a/src/app/api/ai/test/__tests__/route.test.ts
+++ b/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",
+    );
+  });
+});
diff --git a/src/app/api/insights/chat/__tests__/route-snapshot-once.test.ts b/src/app/api/insights/chat/__tests__/route-snapshot-once.test.ts
index 39423d43b..d7f2c4299 100644
--- a/src/app/api/insights/chat/__tests__/route-snapshot-once.test.ts
+++ b/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);
+  });
+});
diff --git a/src/lib/insights/__tests__/status-provider-budget.test.ts b/src/lib/insights/__tests__/status-provider-budget.test.ts
new file mode 100644
index 000000000..9e5bd760d
--- /dev/null
+++ b/src/lib/insights/__tests__/status-provider-budget.test.ts
@@ -0,0 +1,196 @@
+/**
+ * Cost accounting for the status/reference provider chokepoint.
+ *
+ * `runStatusCompletion` is the single provider entry for every status and
+ * reference generator — the specialised status cards, the generic metric
+ * cards, biomarker cards, the batched assessment, the derived scores, the
+ * period narrative, and the off-request Coach memory workers. It previously
+ * ran with NO budget accounting whatsoever: nothing reserved, nothing
+ * recorded, no ceiling. Everything behind it spent invisibly, and on an
+ * operator-key account that was unmetered operator spend.
+ *
+ * These tests drive the REAL budget module (`reserveBudget` / `reconcileSpend`
+ * / `resolveDailyCap`) against a stateful in-memory stand-in for the
+ * `coach_usage` row, so they exercise the actual atomic-upsert path rather
+ * than merely asserting that a mock was called.
+ */
+import { describe, it, expect, vi, beforeEach } from "vitest";
+
+/** In-memory stand-in for the day's `coach_usage.total_tokens`. */
+let ledgerTotal = 0;
+
+vi.mock("@/lib/db", () => ({
+  prisma: {
+    // `reserveBudget`'s atomic upsert-increment. Tagged-template call shape:
+    // (strings, userId, dateKey, reserved, reserved).
+    $queryRaw: vi.fn(
+      async (_strings: TemplateStringsArray, ...v: unknown[]) => {
+        ledgerTotal += Number(v[2] ?? 0);
+        return [{ total_tokens: ledgerTotal }];
+      },
+    ),
+    // `reconcileSpend` (+delta) and `refundReservation` (-reserved).
+    $executeRaw: vi.fn(
+      async (strings: TemplateStringsArray, ...v: unknown[]) => {
+        const sql = strings.join("?");
+        const amount = Number(v[0] ?? 0);
+        if (sql.includes("total_tokens + ")) ledgerTotal += amount;
+        else if (sql.includes("total_tokens - ")) ledgerTotal -= amount;
+        ledgerTotal = Math.max(0, ledgerTotal);
+        return 1;
+      },
+    ),
+    user: {
+      findUnique: vi.fn(async () => ({ aiResponseTimeoutSeconds: null })),
+    },
+  },
+}));
+
+vi.mock("@/lib/logging/context", () => ({ annotate: vi.fn() }));
+
+const { resolveProviderChain, resolveProvider } = vi.hoisted(() => ({
+  resolveProviderChain: vi.fn(),
+  resolveProvider: vi.fn(),
+}));
+vi.mock("@/lib/ai/provider", () => ({ resolveProviderChain, resolveProvider }));
+
+const { runRawCompletionWithFallback } = vi.hoisted(() => ({
+  runRawCompletionWithFallback: vi.fn(),
+}));
+vi.mock("@/lib/ai/provider-runner", () => ({
+  AllProvidersFailedError: class extends Error {},
+  runRawCompletionWithFallback,
+}));
+
+// Consent gate is exercised by its own suite; keep it open here so the budget
+// behaviour is what these tests isolate.
+vi.mock("@/lib/ai/consent-guard", () => ({
+  chainRequiresServerManagedConsent: vi.fn(() => false),
+  hasActiveConsentForSurface: vi.fn(async () => true),
+}));
+
+import { runStatusCompletion } from "../status-provider";
+import { annotate } from "@/lib/logging/context";
+import { OPERATOR_COST_CAP, USER_PLAN_CAP } from "@/lib/ai/coach/budget";
+
+const OPERATOR_CHAIN = [{ providerType: "admin-openai", instance: {} }];
+const BYOK_CHAIN = [{ providerType: "anthropic", instance: {} }];
+
+function completionArgs(overrides: Record<string, unknown> = {}) {
+  return {
+    userId: "u1",
+    cacheAction: "status:test",
+    systemPrompt: "system",
+    userPrompt: "user",
+    consentSurface: "insights" as const,
+    ...overrides,
+  };
+}
+
+/** A successful provider reply reporting `tokensUsed`. */
+function mockProviderReply(tokensUsed: number | null) {
+  runRawCompletionWithFallback.mockResolvedValue({
+    result: { content: '{"summary":"ok"}', model: "m", tokensUsed },
+    workingProvider: { providerType: "admin-openai" },
+  });
+}
+
+beforeEach(() => {
+  vi.clearAllMocks();
+  ledgerTotal = 0;
+  resolveProviderChain.mockResolvedValue(OPERATOR_CHAIN);
+  resolveProvider.mockResolvedValue({ type: "none" });
+});
+
+describe("runStatusCompletion — ledger accounting", () => {
+  it("lands a successful generation on the day's ledger", async () => {
+    mockProviderReply(1234);
+
+    const result = await runStatusCompletion(completionArgs());
+
+    expect(result.kind).toBe("ok");
+    // Reserved an estimate, then reconciled down to what the provider
+    // actually reported. Either way the spend is now ON the ledger — before
+    // this wiring existed the total stayed at zero forever.
+    expect(ledgerTotal).toBe(1234);
+  });
+
+  it("charges the reservation when the provider reports no token count", async () => {
+    mockProviderReply(null);
+
+    await runStatusCompletion(completionArgs());
+
+    // An unreported generation must not bill as free.
+    expect(ledgerTotal).toBeGreaterThan(0);
+  });
+
+  it("refuses a generation once the day's cap is already spent", async () => {
+    ledgerTotal = OPERATOR_COST_CAP;
+    mockProviderReply(500);
+
+    const result = await runStatusCompletion(completionArgs());
+
+    // Refused BEFORE any provider egress, and reported as a transient miss
+    // (`error`) rather than `none` — callers cache `none` as the settled
+    // "no provider configured" assessment, which a budget refusal is not.
+    expect(runRawCompletionWithFallback).not.toHaveBeenCalled();
+    expect(result.kind).toBe("error");
+    expect(annotate).toHaveBeenCalledWith(
+      expect.objectContaining({
+        action: { name: "insights.status.budget_exceeded" },
+      }),
+    );
+    // The refused reservation was refunded, not left on the row.
+    expect(ledgerTotal).toBe(OPERATOR_COST_CAP);
+  });
+
+  it("refunds the reservation when the provider errors", async () => {
+    runRawCompletionWithFallback.mockRejectedValue(new Error("upstream down"));
+
+    const result = await runStatusCompletion(completionArgs());
+
+    expect(result.kind).toBe("error");
+    expect(ledgerTotal).toBe(0);
+  });
+});
+
+describe("runStatusCompletion — cost owner decides the ceiling", () => {
+  it("measures an operator-key chain against the operator ceiling", async () => {
+    // Just under the operator ceiling: an operator-key user is refused here.
+    ledgerTotal = OPERATOR_COST_CAP;
+    mockProviderReply(100);
+
+    const result = await runStatusCompletion(completionArgs());
+
+    expect(result.kind).toBe("error");
+    expect(runRawCompletionWithFallback).not.toHaveBeenCalled();
+  });
+
+  it("measures a BYOK chain against the user-plan ceiling, not the operator's", async () => {
+    // Same spend that locked the operator-key user out above. A self-hoster on
+    // their own key pays their own bill, so the operator's ceiling is a
+    // category error for them — they must still be served.
+    resolveProviderChain.mockResolvedValue(BYOK_CHAIN);
+    ledgerTotal = OPERATOR_COST_CAP;
+    runRawCompletionWithFallback.mockResolvedValue({
+      result: { content: '{"summary":"ok"}', model: "m", tokensUsed: 100 },
+      workingProvider: { providerType: "anthropic" },
+    });
+
+    const result = await runStatusCompletion(completionArgs());
+
+    expect(result.kind).toBe("ok");
+    expect(runRawCompletionWithFallback).toHaveBeenCalled();
+  });
+
+  it("still bounds a BYOK chain at the user-plan ceiling", async () => {
+    resolveProviderChain.mockResolvedValue(BYOK_CHAIN);
+    ledgerTotal = USER_PLAN_CAP;
+    mockProviderReply(100);
+
+    const result = await runStatusCompletion(completionArgs());
+
+    expect(result.kind).toBe("error");
+    expect(runRawCompletionWithFallback).not.toHaveBeenCalled();
+  });
+});