Chat completions passthrough

POST /api/{provider}/v1/chat/completions

Relays a provider’s own chat-completions payload and returns that provider’s own response, byte for byte. Respan authenticates the request, applies your limits and budgets, and writes the log row. It does not rewrite the request or recompute usage.

Use this when correctness matters more than portability: agent frameworks pinned to one provider’s exact semantics, tuned tool-calling behavior, or any payload where a translation layer is a liability. For one request shape across many providers, use the unified router at POST /api/chat/completions instead. That endpoint normalizes; this one does not.

{provider} is the provider id (for example openai, xai, groq). Authorization carries your Respan key, not the provider’s.

$
curl https://api.respan.ai/api/openai/v1/chat/completions \
>
  -H "Authorization: Bearer $RESPAN_API_KEY" \
>
  -H "Content-Type: application/json" \
>
  -d '{
>
    "model": "gpt-5.5",
>
    "messages": [{"role": "user", "content": "Reply with exactly: CODE_OK"}],
>
    "tools": [{"type": "function", "function": {"name": "submit_patch", "parameters": {"type": "object"}}}],
>
    "tool_choice": {"type": "function", "function": {"name": "submit_patch"}},
>
    "reasoning_effort": "medium",
>
    "parallel_tool_calls": false,
>
    "store": false
>
  }'

Grok is the same call with a different path segment:

$
curl https://api.respan.ai/api/xai/v1/chat/completions \
>
  -H "Authorization: Bearer $RESPAN_API_KEY" \
>
  -H "Content-Type: application/json" \
>
  -d '{"model": "grok-4.3", "messages": [{"role": "user", "content": "hi"}]}'

With the OpenAI SDK, repoint base_url and pass your Respan key. Nothing else changes:

1
from openai import OpenAI
2
3
client = OpenAI(
4
    api_key="YOUR_RESPAN_API_KEY",
5
    base_url="https://api.respan.ai/api/openai/v1",
6
)
7
client.chat.completions.create(model="gpt-5.5", messages=[{"role": "user", "content": "Hi"}])

What is guaranteed

Headers

Forwarded upstream: accept, accept-language, content-type, user-agent, plus that provider’s x-{provider}-* extension headers. Everything else (cookies, Respan’s own headers) is dropped, so nothing leaks to the provider.

Returned to you:

Errors and limits

Provider errors pass through with the provider’s status code and body, so your existing error handling keeps working. Respan’s own errors:

Respan imposes no request-body size, context-length, or truncation limit below the provider’s own, and never silently truncates. If a provider limit is exceeded, the provider’s error is returned. The request timeout is 600s so long reasoning calls complete.

Supported providers

azure_deepseek, azure_openai, baseten, cerebras, chutes, deepseek, empiriolabs, featherless, fireworks, friendliai, gonka24, groq, inceptron, inference_net, ionet, makora, minimax, mistral, moonshot, morphllm, nebius, nextbit256, novita, openai, openai_compatible, openrouter, parasail, perplexity, qwen, tera, togetherai, wafer, xai, zai

Providers whose API is not OpenAI-shaped (Anthropic, Google, Bedrock, Cohere) have their own native passthrough endpoints. See Routing & passthrough.

OpenRouter

OpenRouter has its own path and uses your OpenRouter key rather than an org integration:

$
curl https://api.respan.ai/api/openrouter/v1/chat/completions \
>
  -H "Authorization: Bearer $RESPAN_API_KEY" \
>
  -H "x-openrouter-api-key: $OPENROUTER_API_KEY" \
>
  -H "Content-Type: application/json" \
>
  -d '{"model": "anthropic/claude-sonnet-4-5", "messages": [{"role": "user", "content": "hi"}]}'

Authorization is your Respan key; x-openrouter-api-key is your OpenRouter key. A missing OpenRouter key returns 400. OpenRouter’s attribution headers http-referer and x-title are forwarded so your app still appears on their rankings.

See Routing & passthrough for how the OpenRouter passthrough compares to the unified router, and when to reach for each.