OpenAI publishes its Codex degradation investigation and finds smaller issues, not one large cause

After public reports that Codex performed worse around the gpt-5-codex launch on September 15, 2025, the Codex team investigated full time, removed over 60 feature flags, and reported a combination of behavior shifts (such as compaction) and smaller concrete issues rather than one large regression.

Who is affected:

Codex CLI and cloud users who saw weaker results in September and October 2025.

What to do:

Update the Codex CLI and start new conversations for targeted tasks instead of relying on repeated compaction.