Codex CLI gates the built-in image_generation tool behind
AuthMode::Chatgpt (OAuth only). When clients connect via API key
auth through CPA, the tool is absent from requests, making image
generation unavailable through the reverse proxy.
Changes:
1. Inject image_generation tool (codex_executor.go):
Add ensureImageGenerationTool() that appends
{"type":"image_generation","output_format":"png"} to the tools
array if not already present. Applied to all three execution
paths: Execute, executeCompact, and ExecuteStream.
2. Route aliases for Codex CLI direct access (server.go):
Add /backend-api/codex/responses routes that map to the same
OpenAI Responses API handlers as /v1/responses. This allows
Codex CLI to connect via chatgpt_base_url config while keeping
AuthMode::Chatgpt, which enables the built-in image_generation
tool on the client side.
3. Unit tests (codex_executor_imagegen_test.go):
Cover no-tools, existing tools, already-present, empty array,
and mixed built-in tool scenarios.
