Tip: Access GPT-5.5 via Codex CLI Credential Hijack Before Official API Rollout
Simon Willison·medium signal
Simon Willison released llm-openai-via-codex, a plugin that uses Codex CLI's OAuth credentials to make GPT-5.5 API calls before the model is officially available through standard API endpoints. This works because Codex CLI authenticates against a 'semi-official backdoor API' that already serves GPT-5.5. Useful for early testing, but relies on an undocumented endpoint that could change.