OpenAI¶

VidaiMock implements the OpenAI surface area that real applications actually exercise — chat completions, the newer Responses API, embeddings, image generation, and moderations — with wire-shape fidelity validated byte-level against captured production responses.

Chat completions — `POST /v1/chat/completions`¶

The bundled openai/chat.json.j2 template branches on the request:

tools present → tool_calls response, finish_reason: "tool_calls", echoing the caller's declared tool name with {} arguments.
tools + a prior tool result in history → plain-text synthesis with finish_reason: "stop" (see Agentic testing).
response_format present → structured JSON-string content.
o-series model (o1/o3/o4…) → completion_tokens_details.reasoning_tokens.
default → assistant text.

curl http://localhost:8100/v1/chat/completions \
  -H "Content-Type: application/json" \
  -d '{"model": "gpt-4", "messages": [{"role": "user", "content": "Hi"}]}'

Streaming¶

"stream": true produces real token-by-token SSE. The terminal sequence matches real OpenAI exactly: a final empty-delta chunk carrying finish_reason: "stop", then (when stream_options.include_usage is set) a usage-only chunk, then data: [DONE]. Every event is blank-line terminated per the SSE spec, so strict SDK parsers iterate it cleanly.

curl -N http://localhost:8100/v1/chat/completions \
  -H "Content-Type: application/json" \
  -d '{"model": "gpt-4o", "stream": true,
       "stream_options": {"include_usage": true},
       "messages": [{"role": "user", "content": "Hi"}]}'

See Streaming for the full framing contract.

Responses API — `POST /v1/responses`¶

OpenAI's newer unified surface. Non-streaming returns the typed output[] envelope; streaming emits the typed event lifecycle (response.created, response.output_text.delta, response.completed, …) rather than plain data: chunks.

# non-streaming
curl http://localhost:8100/v1/responses -H "Content-Type: application/json" \
  -d '{"model": "gpt-4o-mini", "input": "Say hello", "max_output_tokens": 50}'

# streaming — typed SSE events
curl -N http://localhost:8100/v1/responses -H "Content-Type: application/json" \
  -d '{"model": "gpt-4o-mini", "input": "Say hello", "stream": true}'

Embeddings — `POST /v1/embeddings`¶

curl http://localhost:8100/v1/embeddings -H "Content-Type: application/json" \
  -d '{"model": "text-embedding-3-small", "input": "Hello"}'

Returns the standard data[].embedding shape with float vectors.

Images — `POST /v1/images/generations`¶

curl http://localhost:8100/v1/images/generations -H "Content-Type: application/json" \
  -d '{"model": "dall-e-2", "prompt": "a red circle", "n": 1}'

Moderations — `POST /v1/moderations`¶

curl http://localhost:8100/v1/moderations -H "Content-Type: application/json" \
  -d '{"model": "omni-moderation-latest", "input": "Hello"}'

Error envelopes¶

Any chaos/override that yields a 4xx/5xx renders the OpenAI-shaped {"error": {"message", "type", "param", "code"}} envelope, with type selected per status (invalid_request_error, rate_limit_exceeded, server_error, …). See Chaos & error injection.

OpenAI¶

Chat completions — POST /v1/chat/completions¶

Streaming¶

Responses API — POST /v1/responses¶

Embeddings — POST /v1/embeddings¶

Images — POST /v1/images/generations¶

Moderations — POST /v1/moderations¶