diff --git a/src/mcpd/tests/secret-backend-rotator-loop.test.ts b/src/mcpd/tests/secret-backend-rotator-loop.test.ts
new file mode 100644
index 0000000..197ff47
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+++ b/src/mcpd/tests/secret-backend-rotator-loop.test.ts
@@ -0,0 +1,155 @@
+/**
+ * SecretBackendRotatorLoop had no coverage at all, despite being the boot-time
+ * detector added after an upstream OpenBao re-init silently broke every secret
+ * write for four days (e51b924). These pin the behaviours that matter when that
+ * recurs: the boot health check fires, it reports through the injected logger
+ * (so `mcpctl errors` sees it), and stop() genuinely stops.
+ */
+import { describe, it, expect, vi } from 'vitest';
+import type { SecretBackend } from '@prisma/client';
+import { SecretBackendRotatorLoop } from '../src/services/secret-backend-rotator-loop.js';
+import type { SecretBackendService } from '../src/services/secret-backend.service.js';
+import type { SecretBackendRotator } from '../src/services/secret-backend-rotator.service.js';
+
+function backend(overrides: Partial<SecretBackend> = {}): SecretBackend {
+  return {
+    id: 'b1', name: 'bao', type: 'openbao',
+    config: { url: 'http://bao.example:8200', rotation: { enabled: true, tokenRole: 'r', intervalHours: 24 } },
+    isDefault: true, description: '', version: 1,
+    createdAt: new Date(), updatedAt: new Date(),
+    ...overrides,
+  } as SecretBackend;
+}
+
+interface Harness {
+  loop: SecretBackendRotatorLoop;
+  rotator: { isRotatable: ReturnType<typeof vi.fn>; isOverdue: ReturnType<typeof vi.fn>; healthCheck: ReturnType<typeof vi.fn>; rotateOne: ReturnType<typeof vi.fn> };
+  logs: { info: string[]; warn: string[]; error: Array<{ obj: Record<string, unknown>; msg: string }> };
+  timers: Array<{ cb: () => void; ms: number }>;
+  cleared: number;
+}
+
+function harness(opts: {
+  rows?: SecretBackend[];
+  rotatable?: boolean;
+  overdue?: boolean;
+  health?: { ok: boolean; message?: string } | Error;
+} = {}): Harness {
+  const rows = opts.rows ?? [backend()];
+  const logs: Harness['logs'] = { info: [], warn: [], error: [] };
+  const timers: Harness['timers'] = [];
+  const state = { cleared: 0 };
+
+  const rotator = {
+    isRotatable: vi.fn(() => opts.rotatable ?? true),
+    isOverdue: vi.fn(() => opts.overdue ?? false),
+    healthCheck: vi.fn(async () => {
+      if (opts.health instanceof Error) throw opts.health;
+      return opts.health ?? { ok: true };
+    }),
+    rotateOne: vi.fn(async () => ({})),
+  };
+
+  const loop = new SecretBackendRotatorLoop({
+    backends: {
+      list: async () => rows,
+      getById: async (id: string) => rows.find((r) => r.id === id) ?? rows[0]!,
+    } as unknown as SecretBackendService,
+    rotator: rotator as unknown as SecretBackendRotator,
+    setTimeout: ((cb: () => void, ms: number) => { timers.push({ cb, ms }); return { id: timers.length } as unknown as NodeJS.Timeout; }),
+    clearTimeout: (() => { state.cleared++; }),
+    log: {
+      info: (m) => { logs.info.push(m); },
+      warn: (m) => { logs.warn.push(m); },
+      error: (obj, msg) => { logs.error.push({ obj, msg }); },
+    },
+  });
+
+  return { loop, rotator, logs, timers, get cleared() { return state.cleared; } } as Harness;
+}
+
+/** The boot health check is fire-and-forget; let its microtasks settle. */
+const settle = async (): Promise<void> => { await Promise.resolve(); await Promise.resolve(); await Promise.resolve(); };
+
+describe('SecretBackendRotatorLoop', () => {
+  it('stays idle when nothing is rotatable', async () => {
+    const h = harness({ rotatable: false });
+    await h.loop.start();
+    expect(h.logs.info.join(' ')).toMatch(/no rotatable backends/);
+    expect(h.timers).toHaveLength(0);
+    expect(h.rotator.healthCheck).not.toHaveBeenCalled();
+  });
+
+  it('runs a boot-time health check for every rotatable backend', async () => {
+    const h = harness({ rows: [backend(), backend({ id: 'b2', name: 'bao2' })] });
+    await h.loop.start();
+    await settle();
+    expect(h.rotator.healthCheck).toHaveBeenCalledTimes(2);
+  });
+
+  it('emits BACKEND_TOKEN_DEAD through the logger, not console', async () => {
+    // The regression that made `mcpctl errors` blind to it: this used to be a
+    // bare console.error, which bypasses the pino stream feeding ErrorLogBuffer.
+    const h = harness({ health: { ok: false, message: 'token rejected' } });
+    await h.loop.start();
+    await settle();
+    expect(h.logs.error).toHaveLength(1);
+    expect(h.logs.error[0]?.obj).toMatchObject({ kind: 'BACKEND_TOKEN_DEAD', backend: 'bao' });
+    expect(h.logs.error[0]?.msg).toBe('token rejected');
+  });
+
+  it('does not log a fatal when the backend is healthy', async () => {
+    const h = harness({ health: { ok: true } });
+    await h.loop.start();
+    await settle();
+    expect(h.logs.error).toHaveLength(0);
+  });
+
+  it('survives a health check that throws', async () => {
+    const h = harness({ health: new Error('network down') });
+    await expect(h.loop.start()).resolves.toBeUndefined();
+    await settle();
+    expect(h.logs.warn.join(' ')).toMatch(/health check threw: network down/);
+  });
+
+  it('rotates immediately when a backend is overdue, and still schedules', async () => {
+    const h = harness({ overdue: true });
+    await h.loop.start();
+    await settle();
+    expect(h.rotator.rotateOne).toHaveBeenCalledWith('b1');
+    expect(h.timers).toHaveLength(1);
+  });
+
+  it('does not rotate on boot when not overdue', async () => {
+    const h = harness({ overdue: false });
+    await h.loop.start();
+    await settle();
+    expect(h.rotator.rotateOne).not.toHaveBeenCalled();
+    expect(h.timers).toHaveLength(1);
+  });
+
+  it('never schedules sooner than the 60s floor, even with adversarial jitter', async () => {
+    // intervalHours tiny + default jitter would otherwise produce a negative delay.
+    const rows = [backend({ config: { url: 'u', rotation: { enabled: true, tokenRole: 'r', intervalHours: 0.0001 } } } as Partial<SecretBackend>)];
+    for (let i = 0; i < 50; i++) {
+      const h = harness({ rows });
+      await h.loop.start();
+      expect(h.timers[0]?.ms).toBeGreaterThanOrEqual(60_000);
+    }
+  });
+
+  it('stop() clears timers and suppresses further scheduling', async () => {
+    const h = harness();
+    await h.loop.start();
+    expect(h.timers).toHaveLength(1);
+
+    h.loop.stop();
+    expect(h.cleared).toBeGreaterThan(0);
+
+    // The `stopped` guard has never been exercised: a firing timer must not
+    // reschedule after stop().
+    const before = h.timers.length;
+    await h.loop.rotateNow('b1').catch(() => undefined);
+    expect(h.timers).toHaveLength(before);
+  });
+});