A Codex Desktop update broke every turn with a subagent tool-configuration error

OpenAI (Codex Desktop users)·OpenAI Codex (Desktop app)Fixed

After updating to a new Codex Desktop build, users hit a fatal error on every action — "Function 'functions.spawn_agent' declares encrypted parameters but is not configured for encrypted tool use by this model" — making the app unusable, with no in-app way to downgrade to the previous working version.

Blast radius

Reporters described the app as completely unusable after the update, blocking all Codex Desktop sessions until a fix shipped; no downgrade path was offered.

Root cause

A shipped subagent/multi-agent (spawn_agent) tool-schema change left encrypted tool-use misconfigured for the model, so it failed on every turn instead of degrading gracefully.

How it was caught

Users reported the failure immediately on GitHub after installing the new build.

What changed

Tracked and resolved as a duplicate of issue #27205 in a subsequent release.

Take-awayShip agent tool-schema changes like encrypted tool use behind a compatibility check or feature flag, so a misconfiguration can't brick every session on a new build.