OpenAI APIKey accounts with base_url pointing to third-party OpenAI-compatible
upstreams (DeepSeek, Kimi, GLM, Qwen, etc.) were failing because the gateway
unconditionally converted Chat Completions requests to Responses format and
forwarded to {base_url}/v1/responses, which only exists on OpenAI's official
endpoint.
Detection-based routing:
- Probe upstream capability on account create/update via a minimal POST to
/v1/responses; HTTP 404/405 means 'unsupported', any other response means
'supported'.
- Persist result as accounts.extra.openai_responses_supported (bool).
- ForwardAsChatCompletions branches at function entry: APIKey accounts with
explicit support=false go through new forwardAsRawChatCompletions which
passthrough-forwards CC body to /v1/chat/completions without protocol
conversion.
Default behavior for accounts without the marker preserves the legacy
'always Responses' path — existing OpenAI APIKey accounts that were working
before this change continue to work without modification (the 'reality is
evidence' principle: an account that has been running implies upstream
capability).
Probe is fired async after Create / Update / BatchCreate; failures only log,
never block the admin flow. BulkUpdate omitted (low signal of base_url
changes; can be added if needed).
Implementation:
- New pkg internal/pkg/openai_compat: marker key + ShouldUseResponsesAPI
- New service file openai_apikey_responses_probe.go: probe + persist
- New service file openai_gateway_chat_completions_raw.go: CC pass-through
- Account test endpoint short-circuits with explicit message for
probed-unsupported accounts (full CC test path is a TODO)
Zero schema changes, zero migrations, zero frontend changes, zero wire
modifications — all wired through existing AccountTestService injection.
Closes: DeepSeek-OpenAI account (id=128) production failure
