When running the app's Docker web container on a non-default port (e.g. 3003 instead of 3000), Spotify OAuth login fails with "Failed to authenticate". Three separate issues compound: 1) CORS blocks the OPTIONS preflight because the new origin isn't in FastAPI's allow_origins list, 2) The .env file overrides docker-compose defaults for SPOTIFY_REDIRECT_URI causing a redirect_uri mismatch during Spotify token exchange (frontend sends port 3003, backend sends port 3000), 3) Missing database columns (users.youtube_channel_id) cause a 500 error after successful token exchange because alembic migrations were incomplete.

Multi-word searches like react hydration returned irrelevant entries because tag/keyword/framework layer scoring over-weighted multi-layer matches for a single term. An entry matching react in both tags and framework got score 55, passing the 40 percent noise threshold against a top score of 115.