diff --git a/docs/adr/0011-user-profile-features.md b/docs/adr/0011-user-profile-features.md
index cc9e340..8023a8e 100644
--- a/docs/adr/0011-user-profile-features.md
+++ b/docs/adr/0011-user-profile-features.md
@@ -60,13 +60,18 @@ Initial features: `completion_rate_30d`, `dismiss_rate_30d`,
   Phase B replaces this with event-driven incremental updates subscribing to
   `signals.tip.feedback`.
 
-## Phase B (deferred)
+## Phase B
 
-- Subscribe to `signals.tip.feedback` for incremental updates instead of TTL.
-- Extend the bandit feature vector to include profile features (deliberate
-  `D` change with state-migration plan).
-- Admin page: per-user profile view + manual rebuild button.
-- Staleness/data-quality alerts in `/admin/data-quality`.
+- ✅ **B.1** — Per-user profile view + rebuild action in `/admin/users/:id`.
+- ✅ **B.2** — Event-driven invalidation: features declare `invalidatedBy`
+  subjects in the registry; `profile/subscriber.ts` deletes the affected stored
+  rows on publish so the next `getProfile` call recomputes immediately rather
+  than waiting up to `ttlSec`. TTL stays as a safety net for clock drift /
+  dropped events.
+- ✅ **B.4** — Staleness panel in `/admin/data-quality` (counts missing + stale
+  per feature across eligible users).
+- ⏳ **B.3** — Extend the bandit feature vector to include profile features
+  (deliberate `D` change with state-migration plan + shadow rollout per ADR-0002).
 
 ## Alternatives considered
 
diff --git a/services/api/src/index.ts b/services/api/src/index.ts
index e67c280..f68719c 100644
--- a/services/api/src/index.ts
+++ b/services/api/src/index.ts
@@ -20,6 +20,8 @@ import { requireAdmin } from './middleware/admin.js';
 import type { Request, Response } from 'express';
 import { connectNats } from './events/nats.js';
 import { startTodoistSyncScheduler } from './signals/scheduler.js';
+import { bus } from './events/bus.js';
+import { registerProfileSubscriptions } from './profile/subscriber.js';
 
 await mkdir(dirname(config.DATABASE_PATH), { recursive: true });
 runMigrations();
@@ -96,3 +98,7 @@ if (config.NATS_URL) {
 }
 
 startTodoistSyncScheduler(config.TODOIST_SYNC_INTERVAL_MS);
+
+// Profile features are invalidated on relevant signals (#81 phase B.2);
+// TTL stays as a safety net for clock drift / dropped events.
+registerProfileSubscriptions(bus);
diff --git a/services/api/src/profile/__tests__/subscriber.test.ts b/services/api/src/profile/__tests__/subscriber.test.ts
new file mode 100644
index 0000000..d03bf06
--- /dev/null
+++ b/services/api/src/profile/__tests__/subscriber.test.ts
@@ -0,0 +1,122 @@
+/**
+ * Profile event subscriber tests (#81 phase B.2).
+ * Constructs a fresh Bus per test, subscribes the profile invalidator,
+ * publishes events, asserts that the corresponding stored rows are deleted.
+ */
+import { describe, it, expect, vi, beforeAll, beforeEach } from 'vitest';
+import { Bus } from '../../events/bus.js';
+import { makeTestDb } from '../../test/db.js';
+import { users, userProfileFeatures } from '../../db/schema.js';
+import { eq } from 'drizzle-orm';
+
+const testDb = makeTestDb();
+vi.mock('../../db/index.js', () => ({ db: testDb, rawSqlite: testDb.rawSqlite }));
+
+const { registerProfileSubscriptions } = await import('../subscriber.js');
+
+const NOW = new Date().toISOString();
+const STALE_BASE = {
+  value: 0.42,
+  valueText: null as string | null,
+  updatedAt: NOW,
+};
+
+beforeAll(async () => {
+  await testDb.insert(users).values([
+    { id: 'sub-user-1', email: 'sub1@test.com', role: 'user', consentGiven: true, consentAt: NOW, createdAt: NOW },
+    { id: 'sub-user-2', email: 'sub2@test.com', role: 'user', consentGiven: true, consentAt: NOW, createdAt: NOW },
+  ]);
+});
+
+beforeEach(async () => {
+  await testDb.delete(userProfileFeatures);
+  // Pre-seed all 5 features for both users so we can prove which got invalidated.
+  for (const userId of ['sub-user-1', 'sub-user-2']) {
+    for (const name of [
+      'completion_rate_30d',
+      'dismiss_rate_30d',
+      'mean_dwell_ms_30d',
+      'preferred_hour',
+      'tip_volume_30d',
+    ]) {
+      await testDb.insert(userProfileFeatures).values({
+        userId,
+        name,
+        ...STALE_BASE,
+        ttlSec: 6 * 3600,
+      });
+    }
+  }
+});
+
+async function namesFor(userId: string): Promise<string[]> {
+  const rows = await testDb
+    .select({ name: userProfileFeatures.name })
+    .from(userProfileFeatures)
+    .where(eq(userProfileFeatures.userId, userId));
+  return rows.map((r) => r.name).sort();
+}
+
+describe('registerProfileSubscriptions', () => {
+  it('signals.tip.feedback invalidates the 4 reaction-derived features for the affected user only', async () => {
+    const bus = new Bus();
+    registerProfileSubscriptions(bus);
+
+    bus.publish('signals.tip.feedback', {
+      userId: 'sub-user-1',
+      tipId: 'tip:x',
+      action: 'done',
+      reward: 1,
+      dwellMs: 60_000,
+      createdAt: NOW,
+    });
+
+    // user-1 should have only tip_volume_30d remaining; others wiped
+    expect(await namesFor('sub-user-1')).toEqual(['tip_volume_30d']);
+    // user-2 untouched
+    expect((await namesFor('sub-user-2')).length).toBe(5);
+  });
+
+  it('signals.tip.served invalidates only tip_volume_30d', async () => {
+    const bus = new Bus();
+    registerProfileSubscriptions(bus);
+
+    bus.publish('signals.tip.served', {
+      userId: 'sub-user-1',
+      tipId: 'tip:y',
+      policy: 'egreedy',
+      servedAt: NOW,
+    });
+
+    expect(await namesFor('sub-user-1')).toEqual([
+      'completion_rate_30d',
+      'dismiss_rate_30d',
+      'mean_dwell_ms_30d',
+      'preferred_hour',
+    ]);
+  });
+
+  it('events without userId in payload are ignored silently', async () => {
+    const bus = new Bus();
+    registerProfileSubscriptions(bus);
+
+    // emit a feedback subject with no userId
+    (bus as unknown as { emit: (s: string, p: unknown) => void }).emit('signals.tip.feedback', {});
+
+    expect((await namesFor('sub-user-1')).length).toBe(5);
+    expect((await namesFor('sub-user-2')).length).toBe(5);
+  });
+
+  it('throws at registration if a registry entry references an unknown subject', async () => {
+    // Spike a bogus subject into one feature, attempt registration, expect throw.
+    const { FEATURES } = await import('../registry.js');
+    const original = FEATURES[0]?.invalidatedBy;
+    (FEATURES[0] as { invalidatedBy: readonly string[] }).invalidatedBy = ['signals.bogus'];
+    try {
+      const bus = new Bus();
+      expect(() => registerProfileSubscriptions(bus)).toThrow(/unknown subject/);
+    } finally {
+      (FEATURES[0] as { invalidatedBy: readonly string[] | undefined }).invalidatedBy = original;
+    }
+  });
+});
diff --git a/services/api/src/profile/registry.ts b/services/api/src/profile/registry.ts
index f38e01d..33e1ffd 100644
--- a/services/api/src/profile/registry.ts
+++ b/services/api/src/profile/registry.ts
@@ -23,6 +23,13 @@ export interface FeatureDefinition {
   ttlSec: number;
   /** Human-readable purpose; surfaced in admin UI eventually. */
   description: string;
+  /**
+   * Bus subjects whose payloads invalidate this feature for the affected user
+   * (#81 phase B.2). Subjects must be `keyof EventMap` from `events/bus.ts` —
+   * the subscriber validates this at registration. Each event payload is
+   * required to carry a `userId` field. Empty/omitted = TTL-only refresh.
+   */
+  invalidatedBy?: readonly string[];
   /** Compute the feature for one user against the live DB. */
   compute(userId: string, db: Database.Database): FeatureValue;
 }
@@ -39,6 +46,7 @@ export const FEATURES: readonly FeatureDefinition[] = [
     name: 'completion_rate_30d',
     dtype: 'numeric',
     ttlSec: 6 * HOUR,
+    invalidatedBy: ['signals.tip.feedback'],
     description: 'Fraction of tips served in the last 30 days that received a "done" reaction.',
     compute(userId, db) {
       const row = db
@@ -58,6 +66,7 @@ export const FEATURES: readonly FeatureDefinition[] = [
     name: 'dismiss_rate_30d',
     dtype: 'numeric',
     ttlSec: 6 * HOUR,
+    invalidatedBy: ['signals.tip.feedback'],
     description: 'Fraction of tips served in the last 30 days that received a "dismiss" reaction.',
     compute(userId, db) {
       const row = db
@@ -77,6 +86,7 @@ export const FEATURES: readonly FeatureDefinition[] = [
     name: 'mean_dwell_ms_30d',
     dtype: 'numeric',
     ttlSec: 6 * HOUR,
+    invalidatedBy: ['signals.tip.feedback'],
     description: 'Average dwell time (ms between served and reacted) over the last 30 days.',
     compute(userId, db) {
       const row = db
@@ -93,6 +103,7 @@ export const FEATURES: readonly FeatureDefinition[] = [
     name: 'preferred_hour',
     dtype: 'numeric',
     ttlSec: DAY,
+    invalidatedBy: ['signals.tip.feedback'],
     description: 'Hour-of-day with the most "done" reactions in the last 30 days (0–23).',
     compute(userId, db) {
       const row = db
@@ -114,6 +125,7 @@ export const FEATURES: readonly FeatureDefinition[] = [
     name: 'tip_volume_30d',
     dtype: 'numeric',
     ttlSec: HOUR,
+    invalidatedBy: ['signals.tip.served'],
     description: 'Number of tips served to the user in the last 30 days.',
     compute(userId, db) {
       const row = db
diff --git a/services/api/src/profile/subscriber.ts b/services/api/src/profile/subscriber.ts
new file mode 100644
index 0000000..e72e529
--- /dev/null
+++ b/services/api/src/profile/subscriber.ts
@@ -0,0 +1,68 @@
+/**
+ * Profile event subscriber (#81 phase B.2).
+ *
+ * Replaces (well — complements) TTL-based refresh with event-driven
+ * invalidation. When a relevant signal fires (e.g. `signals.tip.feedback`),
+ * the affected feature's stored row is deleted so the next `getProfile`
+ * call recomputes from current data instead of waiting up to `ttlSec`.
+ *
+ * The TTL itself stays as a safety net for clock drift and event drops.
+ */
+import type { Bus } from '../events/bus.js';
+import { rawSqlite } from '../db/index.js';
+import { FEATURES } from './registry.js';
+
+/**
+ * Subjects we know how to handle. Anything declared in a feature's
+ * `invalidatedBy` that isn't here triggers a registration-time error so typos
+ * don't silently disable invalidation. Keep in sync with `EventMap` in
+ * `events/bus.ts`.
+ */
+const KNOWN_SUBJECTS = [
+  'signals.tip.served',
+  'signals.tip.feedback',
+  'signals.tip.reward_failed',
+  'signals.task.synced',
+  'signals.integration.token_expired',
+] as const;
+type KnownSubject = (typeof KNOWN_SUBJECTS)[number];
+
+function isKnown(subject: string): subject is KnownSubject {
+  return (KNOWN_SUBJECTS as readonly string[]).includes(subject);
+}
+
+/** Drop the stored row for one feature so the next read recomputes it. */
+function invalidate(userId: string, featureName: string): void {
+  rawSqlite
+    .prepare(`DELETE FROM user_profile_features WHERE user_id = ? AND name = ?`)
+    .run(userId, featureName);
+}
+
+/**
+ * Walk the registry, group features by the subjects that should invalidate
+ * them, and subscribe one handler per subject (so we don't fire multiple
+ * deletes per event when several features share a subject).
+ */
+export function registerProfileSubscriptions(bus: Bus): void {
+  const bySubject = new Map<KnownSubject, string[]>();
+  for (const feature of FEATURES) {
+    for (const subject of feature.invalidatedBy ?? []) {
+      if (!isKnown(subject)) {
+        throw new Error(
+          `profile/subscriber: feature "${feature.name}" lists unknown subject "${subject}". ` +
+          `Add it to KNOWN_SUBJECTS or fix the registry.`,
+        );
+      }
+      if (!bySubject.has(subject)) bySubject.set(subject, []);
+      bySubject.get(subject)!.push(feature.name);
+    }
+  }
+
+  for (const [subject, featureNames] of bySubject) {
+    bus.subscribe(subject, (payload: unknown) => {
+      const userId = (payload as { userId?: string } | null | undefined)?.userId;
+      if (!userId) return;  // not all event shapes carry userId; skip silently
+      for (const name of featureNames) invalidate(userId, name);
+    });
+  }
+}