diff --git a/backend/src/db/migrations.test.ts b/backend/src/db/migrations.test.ts
index 148c336..6c2462f 100644
--- a/backend/src/db/migrations.test.ts
+++ b/backend/src/db/migrations.test.ts
@@ -43,3 +43,19 @@ describe('Vibe durable session migration', () => {
     expect(migration!.sql).toContain('idx_vibe_events_user_occurred');
   });
 });
+
+describe('Vibe context memory migration', () => {
+  it('adds bounded session exploration state and exactly-once projection storage', () => {
+    const migration = MIGRATIONS.find(({ id }) => id === '20260802_vibe_context_memory_exploration');
+    expect(migration?.sql).toContain('CREATE TABLE IF NOT EXISTS vibe_session_profiles');
+    expect(migration?.sql).toContain('exploration_coefficient');
+    expect(migration?.sql).toContain('vibe_session_feedback_projections');
+  });
+
+  it('backfills profiles for durable sessions created before context memory', () => {
+    const migration = MIGRATIONS.find(({ id }) => id === '20260802_vibe_session_profile_backfill');
+    expect(migration?.sql).toContain('INSERT INTO vibe_session_profiles');
+    expect(migration?.sql).toContain('SELECT id, user_id FROM vibe_sessions');
+    expect(migration?.sql).toContain('ON CONFLICT (session_id) DO NOTHING');
+  });
+});
diff --git a/backend/src/db/migrations.ts b/backend/src/db/migrations.ts
index ca57ab3..7ea215e 100644
--- a/backend/src/db/migrations.ts
+++ b/backend/src/db/migrations.ts
@@ -720,4 +720,43 @@ export const MIGRATIONS: Migration[] = [
       );
     `,
   },
+  {
+    // Session-specific exploration, goals, and deliberately lossy session
+    // fingerprints are derived from the immutable Vibe ledger. Keeping them
+    // separate from listener_beliefs prevents a transient session from
+    // rewriting permanent taste.
+    id: '20260802_vibe_context_memory_exploration',
+    sql: `
+      CREATE TABLE IF NOT EXISTS vibe_session_profiles (
+        session_id UUID PRIMARY KEY REFERENCES vibe_sessions(id) ON DELETE CASCADE,
+        user_id UUID NOT NULL,
+        fingerprint JSONB NOT NULL DEFAULT '{}'::jsonb,
+        goals JSONB NOT NULL DEFAULT '{"type":"discovery","target":1,"progress":0}'::jsonb,
+        exploration_coefficient REAL NOT NULL DEFAULT 0.30
+          CHECK (exploration_coefficient >= 0 AND exploration_coefficient <= 1),
+        discovery_radius REAL NOT NULL DEFAULT 0.38
+          CHECK (discovery_radius >= 0 AND discovery_radius <= 1),
+        updated_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
+      );
+      CREATE INDEX IF NOT EXISTS idx_vibe_session_profiles_user_updated
+        ON vibe_session_profiles (user_id, updated_at DESC);
+
+      CREATE TABLE IF NOT EXISTS vibe_session_feedback_projections (
+        event_id UUID PRIMARY KEY REFERENCES vibe_events(id) ON DELETE CASCADE,
+        projected_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
+      );
+    `,
+  },
+  {
+    // The profile table was introduced after durable sessions. Backfill every
+    // pre-existing session before feedback can claim its exactly-once marker;
+    // newly created sessions receive their context-derived initial goals in
+    // createVibeSession's transaction.
+    id: '20260802_vibe_session_profile_backfill',
+    sql: `
+      INSERT INTO vibe_session_profiles (session_id, user_id)
+      SELECT id, user_id FROM vibe_sessions
+      ON CONFLICT (session_id) DO NOTHING;
+    `,
+  },
 ];
diff --git a/backend/src/db/schema.sql b/backend/src/db/schema.sql
index 105936a..dcbba8b 100644
--- a/backend/src/db/schema.sql
+++ b/backend/src/db/schema.sql
@@ -543,6 +543,23 @@ CREATE TABLE IF NOT EXISTS vibe_sessions (
 CREATE INDEX IF NOT EXISTS idx_vibe_sessions_user_last_event
     ON vibe_sessions (user_id, last_event_at DESC);
 
+-- Compact, derived memory for the session director. Fingerprints are a
+-- deliberately lossy description of session shape (not a track list) and are
+-- used only as a soft freshness signal against recent sessions.
+CREATE TABLE IF NOT EXISTS vibe_session_profiles (
+    session_id UUID PRIMARY KEY REFERENCES vibe_sessions(id) ON DELETE CASCADE,
+    user_id UUID NOT NULL,
+    fingerprint JSONB NOT NULL DEFAULT '{}'::jsonb,
+    goals JSONB NOT NULL DEFAULT '{"type":"discovery","target":1,"progress":0}'::jsonb,
+    exploration_coefficient REAL NOT NULL DEFAULT 0.30
+        CHECK (exploration_coefficient >= 0 AND exploration_coefficient <= 1),
+    discovery_radius REAL NOT NULL DEFAULT 0.38
+        CHECK (discovery_radius >= 0 AND discovery_radius <= 1),
+    updated_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
+);
+CREATE INDEX IF NOT EXISTS idx_vibe_session_profiles_user_updated
+    ON vibe_session_profiles (user_id, updated_at DESC);
+
 CREATE TABLE IF NOT EXISTS vibe_events (
     id              UUID PRIMARY KEY DEFAULT gen_random_uuid(),
     client_event_id UUID,
@@ -570,6 +587,14 @@ CREATE TABLE IF NOT EXISTS vibe_event_projections (
     projected_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
 );
 
+-- Separate from listener-belief projection because exploration is session
+-- state. It lets a failed post-event replan safely retry the exact same
+-- adaptation without counting the feedback twice.
+CREATE TABLE IF NOT EXISTS vibe_session_feedback_projections (
+    event_id UUID PRIMARY KEY REFERENCES vibe_events(id) ON DELETE CASCADE,
+    projected_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
+);
+
 CREATE TABLE IF NOT EXISTS vibe_plan_versions (
     id                 UUID PRIMARY KEY DEFAULT gen_random_uuid(),
     session_id         UUID NOT NULL REFERENCES vibe_sessions(id) ON DELETE CASCADE,
diff --git a/backend/src/db/types.ts b/backend/src/db/types.ts
index fc51708..6a45f17 100644
--- a/backend/src/db/types.ts
+++ b/backend/src/db/types.ts
@@ -258,3 +258,16 @@ export interface VibePlanItem {
 export interface VibePlan extends VibePlanVersion {
   items: VibePlanItem[];
 }
+
+/** Derived session-director memory. The ledger remains authoritative; this
+ * compact row makes fingerprints, bounded goals, and exploration state cheap
+ * to read while planning. */
+export interface VibeSessionProfile {
+  session_id: string;
+  user_id: string;
+  fingerprint: Record<string, unknown>;
+  goals: Record<string, unknown>;
+  exploration_coefficient: number;
+  discovery_radius: number;
+  updated_at: Date;
+}
diff --git a/backend/src/routes/vibe-sessions.routes.ts b/backend/src/routes/vibe-sessions.routes.ts
index 6e2b326..8e0eaa7 100644
--- a/backend/src/routes/vibe-sessions.routes.ts
+++ b/backend/src/routes/vibe-sessions.routes.ts
@@ -6,6 +6,7 @@ import {
   VibeSessionNotFoundError,
   VibePlanNotFoundError,
 } from '../services/vibe-session-coordinator.service.js';
+import { isValidVibeContext } from '../services/vibe-context.service.js';
 
 const UUID_RE = /^[0-9a-f]{8}-[0-9a-f]{4}-[1-5][0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$/i;
 
@@ -56,6 +57,9 @@ export default async function vibeSessionsRoutes(
     if (body.context !== undefined && !isObject(body.context)) {
       return reply.code(400).send({ error: 'context must be an object' });
     }
+    if (isObject(body.context) && !isValidVibeContext(body.context)) {
+      return reply.code(400).send({ error: 'context contains an invalid structured Vibe value' });
+    }
     if (body.intent !== undefined && typeof body.intent !== 'string') {
       return reply.code(400).send({ error: 'intent must be a string' });
     }
@@ -125,6 +129,11 @@ export default async function vibeSessionsRoutes(
     if (body.payload !== undefined && !isObject(body.payload)) {
       return reply.code(400).send({ error: 'payload must be an object' });
     }
+    if (body.type === 'context_changed' && isObject(body.payload)
+      && body.payload.context !== undefined
+      && (!isObject(body.payload.context) || !isValidVibeContext(body.payload.context))) {
+      return reply.code(400).send({ error: 'context_changed payload.context must be structured Vibe context' });
+    }
     try {
       return reply.send(await coordinator.appendEvent(userId, sessionId, {
         eventId: body.eventId as string | undefined,
diff --git a/backend/src/services/db.service.test.ts b/backend/src/services/db.service.test.ts
index 8ce3ace..fecad8e 100644
--- a/backend/src/services/db.service.test.ts
+++ b/backend/src/services/db.service.test.ts
@@ -19,6 +19,46 @@ function makeTransactionalService(): { service: DbService; poolQuery: ReturnType
 
 describe('DbService v2 methods', () => {
   describe('durable Vibe sessions', () => {
+    it('projects unfamiliar feedback into exploration exactly once behind its own marker', async () => {
+      const { service, clientQuery } = makeTransactionalService();
+      const event = {
+        id: 'event-1', session_id: 'session-1', user_id: 'user-1', track_id: 'track-1',
+        type: 'completed', occurred_at: new Date(), client_event_id: null,
+        position_ms: null, duration_ms: null, payload: {},
+      } as any;
+      clientQuery
+        .mockResolvedValueOnce({ rows: [] }) // BEGIN
+        .mockResolvedValueOnce({ rows: [] }) // profile upsert/backfill
+        .mockResolvedValueOnce({ rows: [{ event_id: event.id }] }) // session feedback marker
+        .mockResolvedValueOnce({ rows: [{ familiar: false }] }) // pre-event familiarity
+        .mockResolvedValueOnce({ rows: [{ id: 'evidence-1' }] }) // evidence
+        .mockResolvedValueOnce({ rowCount: 1 }) // discovery belief
+        .mockResolvedValueOnce({ rows: [] }) // no artist/genre targets
+        .mockResolvedValueOnce({ rows: [] }) // no audio targets
+        .mockResolvedValueOnce({ rows: [{
+          exploration_coefficient: 0.36, discovery_radius: 0.434,
+          goals: { type: 'familiar', target: 1, progress: 1 },
+        }] })
+        .mockResolvedValueOnce({ rows: [] }) // session_state projection
+        .mockResolvedValueOnce({ rows: [] }) // COMMIT
+        .mockResolvedValueOnce({ rows: [] }) // BEGIN retry
+        .mockResolvedValueOnce({ rows: [] }) // profile upsert retry
+        .mockResolvedValueOnce({ rows: [] }) // marker conflict
+        .mockResolvedValueOnce({ rows: [] }); // COMMIT retry
+
+      await service.projectVibeSessionFeedback(event);
+      await service.projectVibeSessionFeedback(event);
+
+      expect(clientQuery.mock.calls[1][0]).toContain('INSERT INTO vibe_session_profiles');
+      expect(clientQuery.mock.calls[2][0]).toContain('vibe_session_feedback_projections');
+      expect(clientQuery.mock.calls[3][0]).toContain('EXISTS (SELECT 1 FROM play_history');
+      expect(clientQuery.mock.calls[4][0]).toContain('INSERT INTO evidence');
+      expect(clientQuery.mock.calls[8][0]).toContain('exploration_coefficient');
+      expect(clientQuery.mock.calls[8][0]).toContain('ELSE goals END');
+      expect(clientQuery.mock.calls[9][1][4]).toBe(JSON.stringify({ type: 'familiar', target: 1, progress: 1 }));
+      expect(clientQuery.mock.calls.filter(([sql]) => String(sql).includes('INSERT INTO evidence'))).toHaveLength(1);
+    });
+
     it('creates, reads, and ends sessions scoped to their user', async () => {
       const { service, poolQuery, clientQuery } = makeTransactionalService();
       const session = {
@@ -44,12 +84,59 @@ describe('DbService v2 methods', () => {
       expect(clientQuery.mock.calls[1][0]).toContain('pg_advisory_xact_lock');
       expect(clientQuery.mock.calls[2][0]).toContain("status = 'active' FOR UPDATE");
       expect(clientQuery.mock.calls[3][0]).toContain('INSERT INTO vibe_sessions');
-      expect(clientQuery.mock.calls[3][1]).toEqual(['user-1', null, JSON.stringify({ activity: 'focus' }), 'v2.1']);
+      expect(clientQuery.mock.calls[3][1]).toEqual(expect.arrayContaining([
+        'user-1', null, expect.any(String), 'v2.1',
+        JSON.stringify({ type: 'discovery', target: 1, progress: 0 }), 0.3, 0.38,
+      ]));
+      expect(JSON.parse(clientQuery.mock.calls[3][1][2])).toEqual(expect.objectContaining({
+        activity: 'focus',
+      }));
       expect(poolQuery.mock.calls[0][0]).toContain('id = $1 AND user_id = $2');
       expect(poolQuery.mock.calls[1][0]).toContain('COALESCE(ended_at, NOW())');
       expect(poolQuery.mock.calls[1][0]).toContain('CASE WHEN ended_at IS NULL THEN $3 ELSE status END');
     });
 
+    it('normalizes context at the persistence boundary for direct callers', async () => {
+      vi.useFakeTimers();
+      vi.setSystemTime(new Date('2026-08-02T19:00:00.000Z'));
+      const { service, clientQuery } = makeTransactionalService();
+      const session = { id: 'session-1', user_id: 'user-1', status: 'active' };
+      clientQuery
+        .mockResolvedValueOnce({ rows: [] }) // BEGIN
+        .mockResolvedValueOnce({ rows: [] }) // user advisory lock
+        .mockResolvedValueOnce({ rows: [] }) // active-session lock
+        .mockResolvedValueOnce({ rows: [session] }) // insert
+        .mockResolvedValueOnce({ rows: [] }); // COMMIT
+
+      try {
+        await service.createVibeSession({
+          userId: 'user-1',
+          policyVersion: 'v2.1',
+          context: {
+            timeZone: 'UTC',
+            activity: 'walking',
+            device: 'phone',
+            exactCoordinates: '53.1959,50.1002',
+            browserTelemetry: { batteryPercent: 4, ipAddress: '192.0.2.1' },
+            localHour: 3,
+            weekday: 1,
+          },
+        });
+
+        const insertParameters = clientQuery.mock.calls[3][1];
+        expect(insertParameters.slice(0, 2)).toEqual(['user-1', null]);
+        expect(JSON.parse(insertParameters[2])).toEqual({
+          timeZone: 'UTC', localHour: 19, weekday: 0, dayKind: 'weekend',
+          activity: 'walking', device: 'phone',
+        });
+        expect(insertParameters.slice(3)).toEqual([
+          'v2.1', JSON.stringify({ type: 'discovery', target: 1, progress: 0 }), 0.3, 0.38,
+        ]);
+      } finally {
+        vi.useRealTimers();
+      }
+    });
+
     it('replaces an owned active session and writes its terminal event before starting another', async () => {
       const { service, clientQuery } = makeTransactionalService();
       const replacement = { id: 'session-2', user_id: 'user-1', status: 'active' };
@@ -102,6 +189,63 @@ describe('DbService v2 methods', () => {
       );
     });
 
+    it('sanitizes and projects an inserted context change atomically with its ledger event', async () => {
+      const { service, clientQuery } = makeTransactionalService();
+      const event = {
+        id: 'event-1', client_event_id: null, session_id: 'session-1', user_id: 'user-1', track_id: null,
+        type: 'context_changed', occurred_at: new Date(), position_ms: null, duration_ms: null,
+        payload: { context: { activity: 'walking', localHour: 12 } },
+      };
+      clientQuery
+        .mockResolvedValueOnce({ rows: [] }) // BEGIN
+        .mockResolvedValueOnce({ rows: [{ id: 'session-1', status: 'active' }] }) // lock
+        .mockResolvedValueOnce({ rows: [event] }) // insert
+        .mockResolvedValueOnce({ rows: [] }) // session context projection
+        .mockResolvedValueOnce({ rows: [] }) // legacy session-state projection
+        .mockResolvedValueOnce({ rows: [] }) // last event timestamp
+        .mockResolvedValueOnce({ rows: [] }); // COMMIT
+
+      await service.recordVibeEvent({
+        sessionId: 'session-1', userId: 'user-1', type: 'context_changed',
+        payload: {
+          context: { activity: 'walking', exactCoordinates: '53.2,50.1' },
+          rawBrowserTelemetry: { battery: 4 },
+        },
+      });
+
+      const values = clientQuery.mock.calls[2][1];
+      const storedPayload = JSON.parse(values[8]);
+      expect(storedPayload).toEqual({ context: expect.objectContaining({ activity: 'walking' }) });
+      expect(storedPayload.context).not.toHaveProperty('exactCoordinates');
+      expect(storedPayload).not.toHaveProperty('rawBrowserTelemetry');
+      expect(clientQuery.mock.calls[3][0]).toContain('SET context = $3::jsonb');
+      expect(clientQuery.mock.calls[4][0]).toContain("jsonb_build_object('context'");
+    });
+
+    it('does not apply a retry body to an existing context-change event', async () => {
+      const { service, clientQuery } = makeTransactionalService();
+      const canonicalEvent = {
+        id: 'event-1', client_event_id: 'client-event-1', session_id: 'session-1', user_id: 'user-1', track_id: null,
+        type: 'context_changed', occurred_at: new Date(), position_ms: null, duration_ms: null,
+        payload: { context: { activity: 'focus', localHour: 12 } },
+      };
+      clientQuery
+        .mockResolvedValueOnce({ rows: [] }) // BEGIN
+        .mockResolvedValueOnce({ rows: [{ id: 'session-1', status: 'active' }] }) // lock
+        .mockResolvedValueOnce({ rows: [canonicalEvent] }) // canonical retry event
+        .mockResolvedValueOnce({ rows: [] }); // COMMIT
+
+      const result = await service.recordVibeEvent({
+        sessionId: 'session-1', userId: 'user-1', clientEventId: 'client-event-1', type: 'context_changed',
+        payload: { context: { activity: 'workout', exactCoordinates: '53.2,50.1' } },
+      });
+
+      expect(result).toEqual({ event: canonicalEvent, inserted: false });
+      expect(clientQuery.mock.calls.map(([sql]) => String(sql))).not.toContain(
+        expect.stringContaining('SET context = $3::jsonb'),
+      );
+    });
+
     it('projects material feedback once with the durable event transaction', async () => {
       const { service, clientQuery } = makeTransactionalService();
       const event = {
diff --git a/backend/src/services/db.service.ts b/backend/src/services/db.service.ts
index 7c3cb60..6c0a890 100644
--- a/backend/src/services/db.service.ts
+++ b/backend/src/services/db.service.ts
@@ -6,6 +6,7 @@ import { fileURLToPath } from 'url';
 import { dirname, join } from 'path';
 import { Pool, PoolClient } from 'pg';
 import { SearchService } from './search.service.js';
+import { normalizeVibeContext, normalizeVibeEventPayload } from './vibe-context.service.js';
 
 /** Anything with a `.query()` — either the shared Pool or a checked-out client. */
 type Queryable = Pool | PoolClient;
@@ -51,6 +52,7 @@ import type {
   RecordedVibeEvent,
   VibePlan,
   VibePlanItem,
+  VibeSessionProfile,
 } from '../db/types.js';
 import { AUDIO_PREFERENCE_BUCKETS, FEEDBACK_ACTIONS } from '../db/types.js';
 export * from '../db/types.js';
@@ -1514,7 +1516,17 @@ export class DbService {
     policyVersion: string;
     seedTrackId?: string | null;
     context?: Record<string, unknown>;
+    profile?: {
+      goals: Record<string, unknown>;
+      explorationCoefficient: number;
+      discoveryRadius: number;
+    };
   }): Promise<VibeSession> {
+    // DbService is also used directly by workers and migrations. Keep the
+    // durable storage boundary canonical even when callers bypass the HTTP
+    // coordinator, so opaque or precise client telemetry can never become
+    // session context.
+    const canonicalContext = normalizeVibeContext(params.context ?? {});
     return this.withTransaction(async (client) => {
       // Serialize starts for one listener even when there is no active row to
       // lock yet. The row lock below then safely replaces any prior session.
@@ -1542,14 +1554,25 @@ export class DbService {
         }
       }
       const res = await client.query(
-        `INSERT INTO vibe_sessions (user_id, status, seed_track_id, context, policy_version)
-         VALUES ($1, 'active', $2, $3::jsonb, $4)
-         RETURNING *`,
+        `WITH created AS (
+           INSERT INTO vibe_sessions (user_id, status, seed_track_id, context, policy_version)
+           VALUES ($1, 'active', $2, $3::jsonb, $4)
+           RETURNING *
+         ), profile AS (
+           INSERT INTO vibe_session_profiles
+             (session_id, user_id, goals, exploration_coefficient, discovery_radius)
+           SELECT id, user_id, $5::jsonb, $6::real, $7::real FROM created
+           ON CONFLICT (session_id) DO NOTHING
+         )
+         SELECT * FROM created`,
         [
           params.userId,
           params.seedTrackId ?? null,
-          JSON.stringify(params.context ?? {}),
+          JSON.stringify(canonicalContext),
           params.policyVersion,
+          JSON.stringify(params.profile?.goals ?? { type: 'discovery', target: 1, progress: 0 }),
+          params.profile?.explorationCoefficient ?? 0.3,
+          params.profile?.discoveryRadius ?? 0.38,
         ],
       );
       return res.rows[0] as VibeSession;
@@ -1565,6 +1588,141 @@ export class DbService {
     return (res.rows[0] as VibeSession) ?? null;
   }
 
+  /** Recent session shapes, excluding the active session. The fingerprint is
+   * intentionally aggregate-only and is used as a soft planning penalty. */
+  async getRecentVibeSessionFingerprints(userId: string, sessionId: string, limit = 8): Promise<Record<string, unknown>[]> {
+    const res = await this.pgClient.query(
+      `SELECT p.fingerprint
+       FROM vibe_session_profiles p
+       JOIN vibe_sessions s ON s.id = p.session_id
+       WHERE p.user_id = $1 AND p.session_id <> $2::uuid
+         AND s.status IN ('ended', 'expired', 'replaced')
+         AND p.fingerprint <> '{}'::jsonb
+       ORDER BY p.updated_at DESC
+       LIMIT $3`,
+      [userId, sessionId, limit],
+    );
+    return res.rows.map((row: { fingerprint: Record<string, unknown> }) => row.fingerprint ?? {});
+  }
+
+  async getVibeSessionProfile(sessionId: string, userId: string): Promise<VibeSessionProfile | null> {
+    const res = await this.pgClient.query(
+      `SELECT p.* FROM vibe_session_profiles p
+       JOIN vibe_sessions s ON s.id = p.session_id
+       WHERE p.session_id = $1 AND s.user_id = $2`,
+      [sessionId, userId],
+    );
+    return (res.rows[0] as VibeSessionProfile | undefined) ?? null;
+  }
+
+  /** Replace only the coarse, sanitised context attached to an active session.
+   * The immutable context_changed event remains the audit trail. */
+  async updateVibeSessionContext(sessionId: string, userId: string, context: Record<string, unknown>): Promise<void> {
+    const canonicalContext = normalizeVibeContext(context);
+    await this.withTransaction(async client => {
+      const updated = await client.query(
+        `UPDATE vibe_sessions SET context = $3::jsonb, last_event_at = NOW()
+         WHERE id = $1 AND user_id = $2 AND status = 'active'
+         RETURNING id`,
+        [sessionId, userId, JSON.stringify(canonicalContext)],
+      );
+      if (!updated.rows[0]) throw new Error('Vibe session was not found or is not owned by this user');
+      await client.query(
+        `UPDATE session_state
+         SET context = COALESCE($3::jsonb->>'activity', $3::jsonb->>'device'),
+             state_vector = state_vector || jsonb_build_object('context', $3::jsonb),
+             last_interaction = NOW()
+         WHERE session_id = $1 AND user_id = $2`,
+        [sessionId, userId, JSON.stringify(canonicalContext)],
+      );
+    });
+  }
+
+  /**
+   * Project unknown-track feedback into the session exploration controls.
+   * This deliberately runs behind its own projection marker: the immutable
+   * event has already committed, so retries after a transient failure are
+   * safe and converge on one evidence row and one coefficient adjustment.
+   */
+  async projectVibeSessionFeedback(event: VibeEvent): Promise<void> {
+    if (!event.track_id || !['completed', 'skipped', 'kept'].includes(event.type)) return;
+    const trackId = event.track_id;
+    await this.withTransaction(async client => {
+      // Old active/resumable sessions predate vibe_session_profiles. Create a
+      // neutral profile before claiming the exactly-once marker: otherwise the
+      // marker could permanently consume a feedback event without adapting its
+      // session. Existing goals are deliberately never overwritten here.
+      await client.query(
+        `INSERT INTO vibe_session_profiles (session_id, user_id)
+         VALUES ($1, $2)
+         ON CONFLICT (session_id) DO NOTHING`,
+        [event.session_id, event.user_id],
+      );
+      const marker = await client.query(
+        `INSERT INTO vibe_session_feedback_projections (event_id)
+         VALUES ($1) ON CONFLICT (event_id) DO NOTHING RETURNING event_id`,
+        [event.id],
+      );
+      if (!marker.rows[0]) return;
+
+      // This query occurs before a completed event's play_history projection
+      // can be considered. Favourites and prior evidence count as familiarity
+      // too, avoiding a false “new discovery” on a locally known track.
+      const familiarity = await client.query(
+        `SELECT (
+           EXISTS (SELECT 1 FROM play_history WHERE user_id = $1 AND track_id = $2 AND completed = true AND played_at < $3::timestamptz)
+           OR EXISTS (SELECT 1 FROM favorites WHERE user_id = $1 AND track_id = $2)
+           OR EXISTS (SELECT 1 FROM evidence WHERE user_id = $1 AND entity_type = 'track' AND entity_id = $2 AND created_at < $3::timestamptz)
+         ) AS familiar`,
+        [event.user_id, trackId, event.occurred_at],
+      );
+      const familiar = Boolean(familiarity.rows[0]?.familiar);
+
+      const delta = event.type === 'skipped' ? -0.08 : event.type === 'completed' ? 0.06 : 0.03;
+      const signal = event.type === 'skipped' ? 'skip_quick' : 'play_of_never_seen';
+      const weight = event.type === 'skipped' ? -0.05 : delta;
+      if (!familiar) {
+        await this.recordTrackEvidence({
+          user_id: event.user_id,
+          track_id: trackId,
+          signal,
+          profile: event.type === 'skipped' ? 'negative' : 'discovery',
+          weight,
+          context: { vibe_event_id: event.id, session_id: event.session_id, unfamiliar: true },
+        }, client);
+      }
+
+      const profile = await client.query(
+        `UPDATE vibe_session_profiles
+         SET exploration_coefficient = GREATEST(0, LEAST(1, exploration_coefficient + CASE WHEN $4 THEN 0 ELSE $3 END)),
+             discovery_radius = GREATEST(0.15, LEAST(0.9, 0.2 + (GREATEST(0, LEAST(1, exploration_coefficient + CASE WHEN $4 THEN 0 ELSE $3 END)) * 0.65))),
+             goals = CASE
+               WHEN goals->>'type' = 'familiar' AND $4 AND $5
+                 THEN jsonb_set(goals, '{progress}', to_jsonb(LEAST(COALESCE((goals->>'progress')::int, 0) + 1, COALESCE((goals->>'target')::int, 1))))
+               WHEN goals->>'type' IN ('discovery', 'surprise', 'artist_introduction') AND NOT $4 AND $3 > 0
+                 THEN jsonb_set(goals, '{progress}', to_jsonb(LEAST(COALESCE((goals->>'progress')::int, 0) + 1, COALESCE((goals->>'target')::int, 1))))
+               ELSE goals END,
+             updated_at = NOW()
+         WHERE session_id = $1 AND user_id = $2
+         RETURNING exploration_coefficient, discovery_radius, goals`,
+        [event.session_id, event.user_id, delta, familiar, event.type === 'completed' || event.type === 'kept'],
+      );
+      const row = profile.rows[0] as Pick<VibeSessionProfile, 'exploration_coefficient' | 'discovery_radius' | 'goals'> | undefined;
+      if (row) {
+        await client.query(
+          `UPDATE session_state
+           SET state_vector = state_vector || jsonb_build_object(
+                 'explorationCoefficient', $3::real,
+                 'discoveryRadius', $4::real,
+                 'sessionGoal', $5::jsonb
+               ), last_interaction = NOW()
+           WHERE session_id = $1 AND user_id = $2`,
+          [event.session_id, event.user_id, row.exploration_coefficient, row.discovery_radius, JSON.stringify(row.goals)],
+        );
+      }
+    });
+  }
+
   /**
    * End (or expire/replace) a session without changing its original end time
    * when a client retries the same request.
@@ -1667,6 +1825,10 @@ export class DbService {
     durationMs?: number | null;
     payload?: Record<string, unknown>;
   }): Promise<RecordedVibeEvent> {
+    // This service is also called by jobs and tests which bypass the HTTP
+    // route. Preserve the context privacy boundary at the final point before
+    // an immutable ledger write.
+    const payload = normalizeVibeEventPayload(params.type, params.payload);
     return this.withTransaction(async (client) => {
       // A session-row lock serializes both event writes and terminal state
       // transitions. In particular, it avoids the READ COMMITTED CTE snapshot
@@ -1718,7 +1880,7 @@ export class DbService {
           occurredAt,
           params.positionMs ?? null,
           params.durationMs ?? null,
-          JSON.stringify(params.payload ?? {}),
+          JSON.stringify(payload ?? {}),
         ]
       );
       const event = insertRes.rows[0] as VibeEvent | undefined;
@@ -1727,6 +1889,7 @@ export class DbService {
       }
 
       await this.projectVibeFeedback(event, client);
+      await this.projectVibeContextChanged(event, client);
 
       await client.query(
         `UPDATE vibe_sessions
@@ -1738,6 +1901,30 @@ export class DbService {
     });
   }
 
+  /** Apply the context projection in the same transaction as its *inserted*
+   * ledger event. A client-event retry returns before this method, so its body
+   * can never overwrite session state with a different context. */
+  private async projectVibeContextChanged(event: VibeEvent, client: PoolClient): Promise<void> {
+    if (event.type !== 'context_changed') return;
+    const context = event.payload?.context;
+    if (!context || typeof context !== 'object' || Array.isArray(context)) return;
+    const canonicalContext = context as Record<string, unknown>;
+    await client.query(
+      `UPDATE vibe_sessions
+       SET context = $3::jsonb
+       WHERE id = $1 AND user_id = $2 AND status = 'active'`,
+      [event.session_id, event.user_id, JSON.stringify(canonicalContext)],
+    );
+    await client.query(
+      `UPDATE session_state
+       SET context = COALESCE($3::jsonb->>'activity', $3::jsonb->>'device'),
+           state_vector = state_vector || jsonb_build_object('context', $3::jsonb),
+           last_interaction = NOW()
+       WHERE session_id = $1 AND user_id = $2`,
+      [event.session_id, event.user_id, JSON.stringify(canonicalContext)],
+    );
+  }
+
   /**
    * Materialize Vibe feedback into the listener inputs used by the incumbent
    * director. The projection marker and every write share the event's
@@ -1899,6 +2086,32 @@ export class DbService {
           feedbackEventId: params.objectiveSnapshot.feedbackEventId ?? null,
         })],
       );
+      // Store a compact session shape rather than a replayable queue. It is
+      // overwritten on each revision so a recently adapted session represents
+      // its current direction when tomorrow's session asks for freshness.
+      await client.query(
+        `WITH selected AS (
+           SELECT i.track_id, i.candidate_source
+           FROM vibe_plan_items i WHERE i.plan_version_id = $1
+         ), artists AS (
+           SELECT DISTINCT ta.artist_id::text AS value FROM selected s
+           JOIN track_artists_v2 ta ON ta.track_id = s.track_id AND ta.role = 'main'
+         ), genres AS (
+           SELECT DISTINCT tg.genre_id::text AS value FROM selected s
+           JOIN track_genre tg ON tg.track_id = s.track_id
+         ), sources AS (
+           SELECT DISTINCT candidate_source AS value FROM selected
+         )
+         UPDATE vibe_session_profiles
+         SET fingerprint = jsonb_build_object(
+               'artists', COALESCE((SELECT jsonb_agg(value ORDER BY value) FROM artists), '[]'::jsonb),
+               'genres', COALESCE((SELECT jsonb_agg(value ORDER BY value) FROM genres), '[]'::jsonb),
+               'sources', COALESCE((SELECT jsonb_agg(value ORDER BY value) FROM sources), '[]'::jsonb),
+               'context', (SELECT context FROM vibe_sessions WHERE id = $2)
+             ), updated_at = NOW()
+         WHERE session_id = $2 AND user_id = $3`,
+        [planVersion.id, params.sessionId, params.userId],
+      );
       await client.query(
         `UPDATE vibe_sessions SET last_event_at = NOW() WHERE id = $1`,
         [params.sessionId],
diff --git a/backend/src/services/generators.service.ts b/backend/src/services/generators.service.ts
index 8612b5f..6b937fd 100644
--- a/backend/src/services/generators.service.ts
+++ b/backend/src/services/generators.service.ts
@@ -49,6 +49,10 @@ export interface GeneratorContext {
     lastGenreIds: string[];
     context: string | null;
     noveltyHunger: number;
+    /** Session-local exploration controls; they never overwrite durable taste. */
+    explorationCoefficient?: number;
+    discoveryRadius?: number;
+    sessionGoal?: { type: string; target: number; progress: number };
     sessionAgeMin: number;
   };
 }
diff --git a/backend/src/services/session-director.service.ts b/backend/src/services/session-director.service.ts
index e04c621..24f107d 100644
--- a/backend/src/services/session-director.service.ts
+++ b/backend/src/services/session-director.service.ts
@@ -91,6 +91,33 @@ export interface PlanBuildOptions {
   retainedPlan?: Candidate[];
 }
 
+export interface SessionFingerprint {
+  artists?: string[];
+  genres?: string[];
+  sources?: string[];
+  context?: Record<string, unknown>;
+}
+
+/** A compact Jaccard penalty. It is deliberately capped: last night's shape
+ * should make an alternative more attractive, not make good music ineligible. */
+export function sessionSimilarityPenalty(
+  metadata: CandidateConstraintMetadata | undefined,
+  generatorId: string,
+  fingerprints: SessionFingerprint[],
+): number {
+  if (!metadata || fingerprints.length === 0) return 0;
+  let strongest = 0;
+  for (const fingerprint of fingerprints) {
+    let matches = 0;
+    let known = 0;
+    if (metadata.artistId && fingerprint.artists?.length) { known++; if (fingerprint.artists.includes(metadata.artistId)) matches++; }
+    if (metadata.genreId && fingerprint.genres?.length) { known++; if (fingerprint.genres.includes(metadata.genreId)) matches++; }
+    if (fingerprint.sources?.length) { known++; if (fingerprint.sources.includes(generatorId)) matches++; }
+    if (known > 0) strongest = Math.max(strongest, matches / known);
+  }
+  return Math.min(0.18, strongest * 0.18);
+}
+
 export interface ArcRange {
   min?: number;
   max?: number;
@@ -729,6 +756,9 @@ export class SessionDirector {
           lastGenreIds: (row.state_vector?.lastGenreIds as string[]) ?? [],
           context: row.context,
           noveltyHunger: (row.state_vector?.noveltyHunger as number) ?? 0.3,
+          explorationCoefficient: (row.state_vector?.explorationCoefficient as number) ?? 0.3,
+          discoveryRadius: (row.state_vector?.discoveryRadius as number) ?? 0.38,
+          sessionGoal: row.state_vector?.sessionGoal as { type: string; target: number; progress: number } | undefined,
           sessionAgeMin: row.started_at
             ? (Date.now() - new Date(row.started_at).getTime()) / 60000
             : 0,
@@ -745,6 +775,9 @@ export class SessionDirector {
           lastGenreIds: (latest.state_vector?.lastGenreIds as string[]) ?? [],
           context: latest.context,
           noveltyHunger: (latest.state_vector?.noveltyHunger as number) ?? 0.3,
+          explorationCoefficient: (latest.state_vector?.explorationCoefficient as number) ?? 0.3,
+          discoveryRadius: (latest.state_vector?.discoveryRadius as number) ?? 0.38,
+          sessionGoal: latest.state_vector?.sessionGoal as { type: string; target: number; progress: number } | undefined,
           sessionAgeMin: latest.started_at
             ? (Date.now() - new Date(latest.started_at).getTime()) / 60000
             : 0,
@@ -782,6 +815,9 @@ export class SessionDirector {
     if (preferredEnergy !== null && (energyBelief.rows[0]?.value ?? 0) > 0) {
       energy = energy * 0.65 + preferredEnergy * 0.35;
     }
+    // Activity/device/time supply a boot prior only. Once playback exists its
+    // contribution stays small so context never masquerades as feedback.
+    if (savedState) energy = energy * 0.85 + savedState.energy * 0.15;
 
     // Read novelty hunger from discovery profile
     const noveltyRes = await this.db.pgClient.query(
@@ -790,7 +826,12 @@ export class SessionDirector {
        LIMIT 1`,
       [userId]
     );
-    const noveltyHunger = (noveltyRes.rows[0]?.value as number) ?? 0.3;
+    const durableNovelty = (noveltyRes.rows[0]?.value as number) ?? 0.3;
+    const explorationCoefficient = Math.max(0, Math.min(1, savedState?.explorationCoefficient ?? 0.3));
+    const discoveryRadius = Math.max(0.15, Math.min(0.9, savedState?.discoveryRadius ?? 0.38));
+    // A contextual/session feedback signal is only a minority of the input;
+    // long-term discovery belief still stabilises the stream across resumes.
+    const noveltyHunger = durableNovelty * 0.65 + explorationCoefficient * 0.35;
 
     // Last distinct artist IDs from recent completed plays.
     // Use a subquery to order first, then DISTINCT — avoids PG's rule that
@@ -832,6 +873,9 @@ export class SessionDirector {
       lastGenreIds,
       context: savedState?.context ?? null,
       noveltyHunger,
+      explorationCoefficient,
+      discoveryRadius,
+      sessionGoal: savedState?.sessionGoal,
       sessionAgeMin: age,
     };
   }
@@ -1042,6 +1086,11 @@ export class SessionDirector {
   // D.4 — Arc selection
   // ---------------------------------------------------------------
   pickArc(state: GeneratorContext['state']): string {
+    const goal = state.sessionGoal;
+    if (goal && goal.progress < goal.target) {
+      if (goal.type === 'familiar') return 'comfort';
+      if (goal.type === 'discovery' || goal.type === 'artist_introduction') return 'discovery';
+    }
     if (state.energy < 0.3) return 'late-night';
     if (state.energy > 0.6 && state.noveltyHunger > 0.5) return 'discovery';
     if (state.energy > 0.6) return 'energetic';
@@ -1505,6 +1554,7 @@ export class SessionDirector {
     state: GeneratorContext['state'],
     repetitionState: RepetitionState,
     userId = '',
+    recentSessionFingerprints: SessionFingerprint[] = [],
   ): Promise<Candidate[]> {
     if (candidates.length === 0) return [];
 
@@ -1551,11 +1601,16 @@ export class SessionDirector {
       const wouldRepeat =
         repetitionState.recentTrackIds.has(c.trackId) ||
         (!!artistId && repetitionState.recentArtistIds.has(artistId));
+      const novelty = candidateNovelty(c, item);
+      const explorationFit = 1 - Math.abs(novelty - (state.discoveryRadius ?? 0.38));
+      const sessionSimilarity = sessionSimilarityPenalty(item, c.generatorId, recentSessionFingerprints);
 
       let score = W_ENJOY * c.relevance
         - W_FATIGUE * avgFatigue
         + W_DIVERSITY * diversityBonus
-        + W_ENTROPY * entropyBonus;
+        + W_ENTROPY * entropyBonus
+        + 0.08 * explorationFit
+        - sessionSimilarity;
 
       if (wouldRepeat) {
         score *= 0.1;
@@ -1597,6 +1652,9 @@ export class SessionDirector {
           lastArtistIds: state.lastArtistIds,
           lastGenreIds: state.lastGenreIds,
           noveltyHunger: state.noveltyHunger,
+          explorationCoefficient: state.explorationCoefficient ?? 0.3,
+          discoveryRadius: state.discoveryRadius ?? 0.38,
+          sessionGoal: state.sessionGoal ?? { type: 'discovery', target: 1, progress: 0 },
         }),
       ]
     );
@@ -1659,6 +1717,10 @@ export class SessionDirector {
     // disliked, or otherwise exposed track can never leak into a replacement
     // revision for this session.
     const durableSessionTrackIds = await this.db.getVibeSessionTrackIds(sessionId, userId);
+    const recentFingerprintReader = (this.db as Partial<DbService>).getRecentVibeSessionFingerprints;
+    const recentSessionFingerprints = recentFingerprintReader
+      ? await recentFingerprintReader.call(this.db, userId, sessionId) as SessionFingerprint[]
+      : [];
     // Do not let abundant track-level beliefs crowd out the artist/genre
     // affinities required by the discovery generators.
     const beliefGroups = await Promise.all([
@@ -1795,7 +1857,7 @@ export class SessionDirector {
       return [];
     }
     const ranked = await this.rankCandidates(
-      eligibleCandidates, fatigue, budgets, state, repetitionState, userId
+      eligibleCandidates, fatigue, budgets, state, repetitionState, userId, recentSessionFingerprints
     );
 
     const loopDim = await this.detectAntiLoop(state, fatigue, budgets, recentPlays);
diff --git a/backend/src/services/session-director.test.ts b/backend/src/services/session-director.test.ts
index 581035d..87a890f 100644
--- a/backend/src/services/session-director.test.ts
+++ b/backend/src/services/session-director.test.ts
@@ -1,5 +1,5 @@
 import { describe, it, expect, vi } from 'vitest';
-import { mergeUniquePlan, scoreArcTransition, selectConstrainedSequence, SessionDirector } from './session-director.service.js';
+import { mergeUniquePlan, scoreArcTransition, selectConstrainedSequence, SessionDirector, sessionSimilarityPenalty } from './session-director.service.js';
 import { DbService } from './db.service.js';
 import { ALL_GENERATORS } from './generators.service.js';
 
@@ -425,6 +425,24 @@ describe('SessionDirector', () => {
 
   });
 
+  describe('recent session fingerprint penalty', () => {
+    it('softly penalizes a repeated session shape without excluding it', () => {
+      const repeated = sessionSimilarityPenalty(
+        { artistId: 'artist-1', genreId: 'genre-1' },
+        'comfort',
+        [{ artists: ['artist-1'], genres: ['genre-1'], sources: ['comfort'] }],
+      );
+      const newShape = sessionSimilarityPenalty(
+        { artistId: 'artist-2', genreId: 'genre-2' },
+        'discovery',
+        [{ artists: ['artist-1'], genres: ['genre-1'], sources: ['comfort'] }],
+      );
+      expect(repeated).toBeGreaterThan(0);
+      expect(repeated).toBeLessThanOrEqual(0.18);
+      expect(newShape).toBe(0);
+    });
+  });
+
   describe('sequence constraints', () => {
     const slots = Array.from({ length: 10 }, (_, position) => ({ position, role: 'known' }));
     const budgets = [
diff --git a/backend/src/services/vibe-context.service.test.ts b/backend/src/services/vibe-context.service.test.ts
new file mode 100644
index 0000000..9c1bc5d
--- /dev/null
+++ b/backend/src/services/vibe-context.service.test.ts
@@ -0,0 +1,36 @@
+import { describe, expect, it } from 'vitest';
+import { initialVibeState, normalizeVibeContext, normalizeVibeEventPayload } from './vibe-context.service.js';
+
+describe('Vibe context', () => {
+  it('keeps only coarse structured values and derives time on the server', () => {
+    const context = normalizeVibeContext({
+      timeZone: 'UTC', activity: 'workout', device: 'headphones',
+      exactCoordinates: '53.2,50.1', localHour: 3,
+    }, new Date('2026-08-02T19:00:00.000Z'));
+
+    expect(context).toMatchObject({ localHour: 19, weekday: 0, dayKind: 'weekend', activity: 'workout' });
+    expect(context).not.toHaveProperty('exactCoordinates');
+    expect(context).not.toHaveProperty('localHour', 3);
+  });
+
+  it('uses context only as a bounded initial prior and gives focus a comfort goal', () => {
+    const state = initialVibeState(normalizeVibeContext({ activity: 'focus' }, new Date('2026-08-03T12:00:00.000Z')));
+    expect(state.energy).toBeGreaterThan(0);
+    expect(state.energy).toBeLessThan(1);
+    expect(state.sessionGoal).toEqual({ type: 'familiar', target: 1, progress: 0 });
+  });
+
+  it('persists only canonical context for context-change events', () => {
+    const payload = normalizeVibeEventPayload('context_changed', {
+      context: { activity: 'walking', exactCoordinates: '53.2,50.1', adId: 'do-not-store' },
+      rawBrowserTelemetry: { battery: 4 },
+    });
+
+    expect(payload).toEqual({
+      context: expect.objectContaining({ activity: 'walking' }),
+    });
+    expect(payload).not.toHaveProperty('rawBrowserTelemetry');
+    expect((payload?.context as Record<string, unknown>)).not.toHaveProperty('exactCoordinates');
+    expect((payload?.context as Record<string, unknown>)).not.toHaveProperty('adId');
+  });
+});
diff --git a/backend/src/services/vibe-context.service.ts b/backend/src/services/vibe-context.service.ts
new file mode 100644
index 0000000..4c3b497
--- /dev/null
+++ b/backend/src/services/vibe-context.service.ts
@@ -0,0 +1,120 @@
+/**
+ * Coarse, opt-in context accepted by the durable Vibe API.  It deliberately
+ * has no precise location, identifiers, or browser telemetry: clients can
+ * supply a hint, but the server owns the time fields and can ignore all of it.
+ */
+export const VIBE_CONTEXT_VALUES = {
+  device: ['desktop', 'phone', 'speaker', 'car', 'headphones'] as const,
+  activity: ['focus', 'relax', 'walking', 'workout', 'social', 'unknown'] as const,
+  locationCategory: ['home', 'work', 'gym', 'travel', 'unknown'] as const,
+  weather: ['clear', 'rain', 'snow', 'hot', 'cold', 'unknown'] as const,
+  source: ['current_track', 'artist', 'genre', 'surprise', 'resume'] as const,
+};
+
+export interface VibeContext {
+  timeZone?: string;
+  localHour?: number;
+  weekday?: number;
+  dayKind?: 'weekday' | 'weekend' | 'holiday';
+  device?: (typeof VIBE_CONTEXT_VALUES.device)[number];
+  activity?: (typeof VIBE_CONTEXT_VALUES.activity)[number];
+  locationCategory?: (typeof VIBE_CONTEXT_VALUES.locationCategory)[number];
+  weather?: (typeof VIBE_CONTEXT_VALUES.weather)[number];
+  source?: (typeof VIBE_CONTEXT_VALUES.source)[number];
+}
+
+export interface InitialVibeState {
+  contextLabel: string | undefined;
+  energy: number;
+  noveltyHunger: number;
+  explorationCoefficient: number;
+  discoveryRadius: number;
+  sessionGoal: { type: 'surprise' | 'familiar' | 'discovery' | 'artist_introduction'; target: number; progress: number };
+}
+
+const hasValue = <T extends readonly string[]>(values: T, value: unknown): value is T[number] =>
+  typeof value === 'string' && (values as readonly string[]).includes(value);
+
+function serverTime(timeZone?: string, now = new Date()): Pick<VibeContext, 'timeZone' | 'localHour' | 'weekday' | 'dayKind'> {
+  // Intl rejects bad IANA names. Falling back to the server clock is safe and
+  // still makes time a weak prior rather than client-controlled fact.
+  let zone: string | undefined;
+  try {
+    if (timeZone) new Intl.DateTimeFormat('en-US', { timeZone }).format(now);
+    zone = timeZone;
+  } catch { /* server-local fallback */ }
+  const parts = new Intl.DateTimeFormat('en-US', {
+    timeZone: zone, hour: 'numeric', weekday: 'short', hourCycle: 'h23',
+  }).formatToParts(now);
+  const hour = Number(parts.find(part => part.type === 'hour')?.value ?? now.getHours());
+  const weekdayName = parts.find(part => part.type === 'weekday')?.value;
+  const weekday = ['Sun', 'Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat'].indexOf(weekdayName ?? '');
+  return {
+    ...(zone ? { timeZone: zone } : {}),
+    localHour: Number.isInteger(hour) ? hour : now.getHours(),
+    weekday: weekday >= 0 ? weekday : now.getDay(),
+    dayKind: ([0, 6].includes(weekday >= 0 ? weekday : now.getDay()) ? 'weekend' : 'weekday'),
+  };
+}
+
+/** Remove unknown fields and derive time server-side.  This preserves old
+ * clients that send an empty object while preventing opaque context blobs from
+ * becoming a permanent behavioural profile. */
+export function normalizeVibeContext(input: Record<string, unknown> = {}, now = new Date()): VibeContext {
+  const time = serverTime(typeof input.timeZone === 'string' ? input.timeZone : undefined, now);
+  return {
+    ...time,
+    ...(hasValue(VIBE_CONTEXT_VALUES.device, input.device) ? { device: input.device } : {}),
+    ...(hasValue(VIBE_CONTEXT_VALUES.activity, input.activity) ? { activity: input.activity } : {}),
+    ...(hasValue(VIBE_CONTEXT_VALUES.locationCategory, input.locationCategory) ? { locationCategory: input.locationCategory } : {}),
+    ...(hasValue(VIBE_CONTEXT_VALUES.weather, input.weather) ? { weather: input.weather } : {}),
+    ...(hasValue(VIBE_CONTEXT_VALUES.source, input.source) ? { source: input.source } : {}),
+  };
+}
+
+/**
+ * Context changes are the only event payload with a structured, durable
+ * context body. Keep their ledger representation intentionally tiny: callers
+ * cannot smuggle precise location or arbitrary browser telemetry into an
+ * immutable event by adding sibling fields or unknown context keys.
+ */
+export function normalizeVibeEventPayload(
+  type: string,
+  payload?: Record<string, unknown>,
+): Record<string, unknown> | undefined {
+  if (type !== 'context_changed') return payload;
+  const context = payload?.context;
+  if (!context || typeof context !== 'object' || Array.isArray(context)) return {};
+  return { context: normalizeVibeContext(context as Record<string, unknown>) };
+}
+
+/** Context is intentionally a gentle prior. It can nudge the initial arc but
+ * never overrides observed playback behaviour. */
+export function initialVibeState(context: VibeContext): InitialVibeState {
+  const activityEnergy: Record<string, number> = {
+    focus: 0.42, relax: 0.34, walking: 0.58, workout: 0.72, social: 0.62, unknown: 0.5,
+  };
+  const hour = context.localHour ?? 12;
+  const hourEnergy = hour < 6 ? 0.32 : hour < 10 ? 0.46 : hour >= 22 ? 0.38 : 0.52;
+  const activity = context.activity ?? 'unknown';
+  const energy = Math.max(0, Math.min(1, activityEnergy[activity] * 0.7 + hourEnergy * 0.3));
+  const goal = activity === 'focus' || activity === 'relax'
+    ? 'familiar'
+    : activity === 'workout' || activity === 'walking' ? 'surprise' : 'discovery';
+  return {
+    contextLabel: context.activity ?? context.device,
+    energy,
+    noveltyHunger: 0.3,
+    explorationCoefficient: 0.3,
+    discoveryRadius: 0.38,
+    sessionGoal: { type: goal, target: 1, progress: 0 },
+  };
+}
+
+export function isValidVibeContext(input: Record<string, unknown>): boolean {
+  const scalar = (key: keyof typeof VIBE_CONTEXT_VALUES) => input[key] === undefined
+    || hasValue(VIBE_CONTEXT_VALUES[key], input[key]);
+  return (input.timeZone === undefined || typeof input.timeZone === 'string')
+    && scalar('device') && scalar('activity') && scalar('locationCategory')
+    && scalar('weather') && scalar('source');
+}
diff --git a/backend/src/services/vibe-session-coordinator.service.test.ts b/backend/src/services/vibe-session-coordinator.service.test.ts
index ecf149e..3c771d8 100644
--- a/backend/src/services/vibe-session-coordinator.service.test.ts
+++ b/backend/src/services/vibe-session-coordinator.service.test.ts
@@ -154,6 +154,44 @@ describe('VibeSessionCoordinator', () => {
     expect(response).toMatchObject({ replanned: true, replanReason: 'feedback:completed', planVersion: 2 });
   });
 
+  it('normalizes context before the immutable event write', async () => {
+    const { db, coordinator } = setup();
+    (db.recordVibeEvent as any).mockResolvedValueOnce({
+      event: { id: 'event-1', type: 'context_changed', payload: {} }, inserted: true,
+    });
+
+    await coordinator.appendEvent('user-1', SESSION_ID, {
+      type: 'context_changed',
+      payload: {
+        context: { activity: 'walking', exactCoordinates: '53.2,50.1' },
+        rawBrowserTelemetry: { battery: 4 },
+      },
+    });
+
+    expect(db.recordVibeEvent).toHaveBeenCalledWith(expect.objectContaining({
+      payload: {
+        context: expect.objectContaining({ activity: 'walking' }),
+      },
+    }));
+    const payload = (db.recordVibeEvent as any).mock.calls[0][0].payload;
+    expect(payload).not.toHaveProperty('rawBrowserTelemetry');
+    expect(payload.context).not.toHaveProperty('exactCoordinates');
+  });
+
+  it('creates the durable profile from the initial context goal', async () => {
+    const { db, coordinator } = setup();
+
+    await coordinator.start('user-1', { context: { activity: 'focus' } });
+
+    expect(db.createVibeSession).toHaveBeenCalledWith(expect.objectContaining({
+      profile: expect.objectContaining({
+        goals: { type: 'familiar', target: 1, progress: 0 },
+        explorationCoefficient: 0.3,
+        discoveryRadius: 0.38,
+      }),
+    }));
+  });
+
   it('passes the durable unserved callback tail into the retention-aware replan', async () => {
     const { db, director, coordinator } = setup();
     (db.getVibePlan as any).mockResolvedValue({
diff --git a/backend/src/services/vibe-session-coordinator.service.ts b/backend/src/services/vibe-session-coordinator.service.ts
index 39779d7..ad0e0db 100644
--- a/backend/src/services/vibe-session-coordinator.service.ts
+++ b/backend/src/services/vibe-session-coordinator.service.ts
@@ -1,6 +1,12 @@
 import { DbService, VibeEvent, VibePlan, VibeSession } from './db.service.js';
 import { SessionDirector } from './session-director.service.js';
 import { Candidate } from './generators.service.js';
+import {
+  initialVibeState,
+  normalizeVibeContext,
+  normalizeVibeEventPayload,
+  VibeContext,
+} from './vibe-context.service.js';
 
 /**
  * This is deliberately a narrow bridge between the durable Vibe ledger and
@@ -21,7 +27,7 @@ export type VibeEventType = (typeof VIBE_EVENT_TYPES)[number];
 
 export interface StartVibeSessionInput {
   seedTrackId?: string;
-  context?: Record<string, unknown>;
+  context?: VibeContext | Record<string, unknown>;
   intent?: string;
   policyVersion?: string;
   resumeSessionId?: string;
@@ -73,13 +79,19 @@ export class VibeSessionCoordinator {
 
   async start(userId: string, input: StartVibeSessionInput): Promise<VibeSessionResponse> {
     if (input.resumeSessionId) return this.resume(userId, input.resumeSessionId);
-    const context = input.context ?? {};
+    const context = normalizeVibeContext({ ...(input.context ?? {}) });
+    const initialState = initialVibeState(context);
     const policyVersion = input.policyVersion ?? DEFAULT_VIBE_POLICY_VERSION;
     const session = await this.db.createVibeSession({
       userId,
       policyVersion,
       seedTrackId: input.seedTrackId ?? null,
-      context,
+      context: { ...context },
+      profile: {
+        goals: initialState.sessionGoal,
+        explorationCoefficient: initialState.explorationCoefficient,
+        discoveryRadius: initialState.discoveryRadius,
+      },
     });
 
     // session_state is a derived cache used by the current director. Give it
@@ -87,8 +99,15 @@ export class VibeSessionCoordinator {
     // session while the durable tables remain the source of truth.
     await this.db.createSessionState(
       userId,
-      typeof context.activity === 'string' ? context.activity : input.intent,
-      { energy: 0.5, noveltyHunger: 0.3 },
+      initialState.contextLabel ?? input.intent,
+      {
+        energy: initialState.energy,
+        noveltyHunger: initialState.noveltyHunger,
+        explorationCoefficient: initialState.explorationCoefficient,
+        discoveryRadius: initialState.discoveryRadius,
+        sessionGoal: initialState.sessionGoal,
+        context,
+      },
       session.id,
     );
     await this.db.recordVibeEvent({
@@ -180,6 +199,11 @@ export class VibeSessionCoordinator {
     input: AppendVibeEventInput,
   ): Promise<VibeSessionResponse & { event: VibeEvent; idempotent: boolean }> {
     try {
+      // Do this before the ledger write, rather than after it, because Vibe
+      // events are immutable. The DB repeats this boundary for non-HTTP
+      // callers; keeping it here also makes coordinator callers see exactly
+      // what will be persisted.
+      const payload = normalizeVibeEventPayload(input.type, input.payload);
       const result = await this.db.recordVibeEvent({
         sessionId,
         userId,
@@ -189,8 +213,13 @@ export class VibeSessionCoordinator {
         occurredAt: input.occurredAt,
         positionMs: input.positionMs,
         durationMs: input.durationMs,
-        payload: input.payload,
+        payload,
       });
+      // The ledger write is authoritative; this idempotent projection updates
+      // exploration only after the exact event exists. Keep the compatibility
+      // guard for old coordinator test doubles during the migration.
+      const projectSessionFeedback = (this.db as Partial<DbService>).projectVibeSessionFeedback;
+      if (projectSessionFeedback) await projectSessionFeedback.call(this.db, result.event);
       if (!isMaterialFeedback(input.type)) {
         const response = await this.getPlan(userId, sessionId);
         return { ...response, event: result.event, idempotent: !result.inserted };