fix(vibe): keep playback advancing with full plans

backend/src/services/db.service.test.ts

@@ -55,6 +55,7 @@ describe('DbService v2 methods', () => {
       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[8][0]).toContain('ELSE $3::real 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);
     });

backend/src/services/db.service.ts

@@ -1664,12 +1664,12 @@ export class DbService {
 
       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)),
+         SET exploration_coefficient = GREATEST(0, LEAST(1, exploration_coefficient + CASE WHEN $4 THEN 0::real ELSE $3::real 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))),
+             discovery_radius = GREATEST(0.15, LEAST(0.9, 0.2 + (GREATEST(0, LEAST(1, exploration_coefficient + CASE WHEN $4 THEN 0::real ELSE $3::real 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
+               WHEN goals->>'type' IN ('discovery', 'surprise', 'artist_introduction') AND NOT $4 AND $3::real > 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()

backend/src/services/generators.service.ts

@@ -60,6 +60,7 @@ export interface GeneratorContext {
 export type Generator = (db: DbService, ctx: GeneratorContext) => Promise<Candidate[]>;
 
 const OBJECTIVE_USER = '00000000-0000-0000-0000-000000000000';
+const FALLBACK_CANDIDATE_LIMIT = 60;
 
 // ---------------------------------------------------------------------------
 // 1. COMFORT — Top artists by longterm affinity > 0.5
@@ -536,6 +537,33 @@ async function contextualGenerator(db: DbService, ctx: GeneratorContext): Promis
   });
 }
 
+// ---------------------------------------------------------------------------
+// 9. LIBRARY FALLBACK — keeps a Vibe usable when the metadata graph is sparse
+// ---------------------------------------------------------------------------
+async function libraryFallbackGenerator(db: DbService, ctx: GeneratorContext): Promise<Candidate[]> {
+  const res = await db.pgClient.query(
+    `SELECT t.id
+     FROM tracks t
+     WHERE t.state = 'LIBRARY'
+       AND NOT (t.id = ANY($1::uuid[]))
+     ORDER BY RANDOM()
+     LIMIT $2`,
+    [ctx.recentExclusions, FALLBACK_CANDIDATE_LIMIT],
+  );
+
+  return (res.rows as { id: string }[]).map(row => ({
+    trackId: row.id,
+    generatorId: 'library-fallback',
+    relevance: 0.05,
+    explanation: [{
+      subjectType: 'track', subjectId: row.id,
+      predicate: 'library_fallback',
+      objectType: 'track', objectId: row.id,
+      fusedValue: 0.05,
+    }],
+  }));
+}
+
 // ---------------------------------------------------------------------------
 // All generators, ordered by priority (comfort first, experimental last)
 // ---------------------------------------------------------------------------
@@ -548,4 +576,5 @@ export const ALL_GENERATORS: Generator[] = [
   noveltyGenerator,
   contextualGenerator,
   experimentalGenerator,
+  libraryFallbackGenerator,
 ];

backend/src/services/generators.test.ts

@@ -199,8 +199,8 @@ describe('generators', () => {
 });
 
 describe('ALL_GENERATORS', () => {
-  it('contains 8 generators', () => {
+  it('contains 9 generators', () => {
-    expect(ALL_GENERATORS).toHaveLength(8);
+    expect(ALL_GENERATORS).toHaveLength(9);
     ALL_GENERATORS.forEach(g => expect(typeof g).toBe('function'));
   });
 });