Codex SDK REST

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Overview

A lightweight Express server that proxies OpenAI agent streaming responses using the Codex SDK. It provides an OpenAI Chat Completions API-compatible interface (/v1/chat/completions).

Features

• OpenAI Compatible API: Supports standard Chat Completions API request/response format.
• Streaming Support: Real-time Server-Sent Events (SSE) for token-by-token responses (stream=true).

Architecture Note: Thread Reuse & Context Leaks

To mitigate the significant initialization latency of the Codex SDK, this server adopts a thread reuse strategy.

Known Limitation: This architecture interacts with the Codex CLI's internal context manager. Consequently, context leaks may occur between requests or when integrated with other context-aware systems, as the context state is persisted to ensure performance. This is a known and unavoidable trade-off in the current implementation.

Configuration

• Thread Options:
  • approvalPolicy: 'never'
  • sandboxMode: 'read-only'
  • networkAccessEnabled: false
  • webSearchEnabled: false
  • modelReasoningEffort: 'high'
  • model: 'GPT-5.1-Codex-Mini'

Usage

run

npx codex-sdk-rest

API Endpoints

GET /init

Initializes a test Codex thread (mostly for internal testing).

• Note: Does not return a response body.

POST /v1/chat/completions

Send a chat message to the agent.

Actually work Parameters (JSON Body):

• messages (array): List of messages (e.g., [{ "role": "user", "content": "Hello" }]).
• stream (boolean): If true, streams partial results via SSE.