Messages (Anthropic-compatible)
Anthropic Messages-compatible endpoint. /anthropic/v1/messages is an equivalent alias.
Authenticate with Authorization: Bearer, or with the x-api-key header the Anthropic
SDK sends. Sending both headers with different values returns 400 AMBIGUOUS_API_KEY;
the same value in both is fine (tools such as CC Switch send both).
Errors use the Anthropic envelope shape, unlike the other endpoints here — see the 401 example.
Authorization
bearerAuth Authorization: Bearer <your RouteMux API key>.
Create keys at https://routemux.com/console/keys. New keys use the sk- prefix;
the legacy rmx_live_ prefix is still accepted.
The Anthropic SDK's x-api-key and the Google SDK's x-goog-api-key are accepted too.
Sending several key headers with different values returns 400 AMBIGUOUS_API_KEY.
In: header
Request Body
application/json
TypeScript Definitions
Use the request body type in TypeScript.
Request and response bodies match the upstream provider's official format verbatim —
RouteMux passes them through untouched. See the provider's own docs for field definitions;
the gateway itself only reads model and stream.
Response Body
application/json
application/json
application/json
application/json
curl -X POST "https://example.com/v1/messages" \ -H "Content-Type: application/json" \ -d '{ "model": "anthropic/claude-sonnet-5", "max_tokens": 256, "messages": [ { "role": "user", "content": "Hello" } ] }'{ "model": "string", "stream": true}