Since bridge 7 external models get Codex's classic tools. One desktop tool has a top-level union schema,
which Claude rejects ("input_schema does not support oneOf, allOf, or anyOf at the top level"), so every
Opus request from the desktop app failed with a bare "upstream 400". The earlier context-size diagnosis
was wrong: the request still failed after compaction (239 KB).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
