fix: stabilize the live recommendation path

Co-Authored-By: Claude <noreply@anthropic.com>

backend/app/api/routes.py

@@ -22,6 +22,7 @@ class ResolvedSession:
 
     session_id: str
     session: SpotifySession
+    can_logout: bool
 
 
 @router.get("/api/auth/login")
@@ -81,7 +82,12 @@ def current_session(request: Request) -> JSONResponse:
     resolved = resolve_session(request)
     if resolved is None:
         return JSONResponse({"detail": "Not authenticated"}, status_code=401)
-    return JSONResponse({"display_name": resolved.session.display_name})
+    return JSONResponse(
+        {
+            "display_name": resolved.session.display_name,
+            "can_logout": resolved.can_logout,
+        }
+    )
 
 
 @router.get("/api/suggestions")
@@ -119,16 +125,16 @@ def resolve_session(request: Request) -> ResolvedSession | None:
     application_settings = cast(Settings, request.app.state.settings)
     if application_settings.app_mode is AppMode.DEMO:
         demo_session = cast(SpotifySession, request.app.state.demo_session)
-        return ResolvedSession("demo", demo_session)
+        return ResolvedSession("demo", demo_session, can_logout=False)
     session_store = cast(SessionStore, request.app.state.session_store)
     cookie_session_id = request.cookies.get(SESSION_COOKIE_NAME)
     if cookie_session_id is not None:
         cookie_session = session_store.get(cookie_session_id)
         if cookie_session is not None:
-            return ResolvedSession(cookie_session_id, cookie_session)
+            return ResolvedSession(cookie_session_id, cookie_session, can_logout=True)
 
     seed_session_id = cast(str | None, getattr(request.app.state, "seed_session_id", None))
     seed_session = session_store.get(seed_session_id) if seed_session_id is not None else None
     if seed_session is None or seed_session_id is None:
         return None
-    return ResolvedSession(seed_session_id, seed_session)
+    return ResolvedSession(seed_session_id, seed_session, can_logout=False)

backend/app/prompts.py

@@ -64,8 +64,12 @@ Retain understandable bridges through genre, scene, production style, instrument
 energy, era, or songwriting. The profile is not exhaustive, so never claim that a
 candidate is definitely unknown. When familiarity is
 familiar, candidates may include supplied top or saved tracks, but remain responsive to the
-current request. When familiarity is mix, combine recognizable anchors with real,
-confidently identifiable adjacent discoveries rather than splitting into unrelated halves.
+current request. When familiarity is mix, the first 15 candidates must be suitable anchors
+copied from the supplied top or saved tracks: copy the title exactly and use one listed
+artist name exactly, preferring the first. Deduplicate those anchors, then fill the remaining
+candidates with confidently identifiable adjacent discoveries. If fewer than 15 supplied
+tracks fit, use every suitable one before adding discoveries. When familiarity is familiar,
+use supplied tracks for the majority of the list.
 
 Use musical knowledge conservatively. Base selection on durable, commonly knowable
 attributes of recordings. Do not invent listening statistics, personal memories, release