Review caught the stated invariant being false. Next splits the matched suffix on literal `/` before decoding each piece, so a segment can be empty (`api//mcp`) and a single segment can carry a decoded slash (`api%2Fmcp`). Neither reaches the allowlist — both fail closed — but the comment claimed an invariant the router does not provide. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>