Codex

Codex uses the ChatGPT subscription Responses endpoint at https://chatgpt.com/backend-api/codex/responses.

Account and authentication

Sign in with a ChatGPT Plus or Pro account, not OpenAI API credentials.

claude-code-proxy codex auth login
# Headless device-code flow
claude-code-proxy codex auth device
claude-code-proxy codex auth status

The proxy owns its tokens and does not read native Codex CLI credentials. It refreshes expiring access tokens with a single-flight guard. See Files and storage for credential locations.

Models and fast mode

Use claude-code-proxy models as the current catalog. Model access depends on your ChatGPT account. A model rejected by the subscription produces the upstream error verbatim.

Append -fast to any registered Codex model to request service_tier: "priority". For example, gpt-5.6-sol-fast selects gpt-5.6-sol with fast service. CCP_CODEX_SERVICE_TIER or codex.serviceTier takes precedence.

Reasoning

Claude Code’s /effort value maps to Codex reasoning.effort: low, medium, high, xhigh, or max. A proxy override can also force none.

When reasoning is enabled, the proxy requests an automatic reasoning summary and translates summary deltas into Claude Code thinking blocks. Codex may omit a summary for a simple prompt. CCP_CODEX_REASONING_SUMMARY=off suppresses summaries while preserving effort and encrypted continuation content.

Claude Code summary compaction requests are capped at low effort by default because they perform extraction over a large transcript. CCP_COMPACT_EFFORT=off disables the cap, none removes reasoning, and another valid effort sets a different maximum. The cap never raises effort.

Tools and multimodal input

• Claude function tools and tool results map to Responses API function calls and outputs.
• Claude Code hosted web search maps to Codex web_search, including supported domain filters and forced tool choice.
• Top-level base64 user images map to input_image.
• Supported base64 images nested in tool results also map to input_image.
• Remote image URLs, malformed images, and unsupported tool-result image forms remain textual placeholders.
• Strict JSON schema output maps to Responses text.format.

Transport and continuation

WebSocket is the default transport. Set CCP_CODEX_TRANSPORT=http for HTTP SSE, or auto to use WebSocket with HTTP fallback only when setup fails before a request is sent.

CCP_CODEX_PREVIOUS_RESPONSE_ID=1 enables append-only WebSocket continuation. It reuses a session connection and sends previous_response_id only when the translated request shape and transcript extension are safe. State is in memory, keyed by Claude Code session ID.

Server compaction

Codex server compaction is opt-in:

CCP_CODEX_SERVER_COMPACTION=1 claude-code-proxy serve

At a Claude Code compaction boundary, the proxy requests native Codex compaction, keeps the encrypted item in memory for the matching session and model, and anchors replay to Claude Code’s portable summary. Branches, restarts, model changes, malformed responses, expiry, or memory limits fall back to portable history. State can remain in memory for up to 30 minutes.

The boundary adds one Codex request. Structured events named server_compaction_triggered, server_compaction_completed, and server_compaction_failed report its outcome.

Native Responses API

CCP_CODEX_RESPONSES_API=1 enables POST /v1/responses. The proxy replaces incoming credentials with stored Codex auth and preserves native JSON or SSE response bodies. This route covers registered Codex models. Images API, response retrieval or deletion, and WebSocket ingress are outside its scope.

See Configuration for every Codex setting and Troubleshooting for auth, model, and transport failures.