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Anthropic Messages API¶

Overview¶

Compatible with the Anthropic Messages API.
Endpoints: POST /api/v1/messages, POST /v1/messages
Count tokens: POST /api/v1/messages/count_tokens, POST /v1/messages/count_tokens
Native providers: anthropic, llama.cpp
Non-native providers are converted to OpenAI chat requests and mapped back to Anthropic responses.
Streaming responses use Anthropic SSE events; for non-native providers, SSE events are synthesized from OpenAI streams.

Auth + Headers¶

Single-user: X-API-KEY: <key>
Multi-user: Authorization: Bearer <JWT>
Provider keys come from config or BYOK. No x-anthropic-api-key passthrough.
Optional headers passed to native providers:
anthropic-version (default 2023-06-01)
anthropic-beta (unvalidated passthrough)
llama.cpp can use llama_api.api_key (Authorization: Bearer) for password-protected endpoints.

Provider Selection¶

model is required. Supports provider/model prefixes (example: anthropic/claude-3-7-sonnet-20250219).
api_provider can force a provider when the model has no prefix.
llama.cpp base URL comes from llama_api.api_ip or llama_api.api_base_url.

Request Highlights¶

messages: array of Anthropic user/assistant messages.
system: optional string or content blocks.
max_tokens, temperature, top_p, top_k, stop_sequences
tools and tool_choice supported. When converting to OpenAI, tool_choice="any" maps to OpenAI required.
stream: when true, returns SSE events.

Examples¶

Non-streaming:

curl -s -X POST http://127.0.0.1:8000/api/v1/messages \
  -H "Content-Type: application/json" \
  -H "X-API-KEY: $API_KEY" \
  -d '{
    "model": "anthropic/claude-3-7-sonnet-20250219",
    "max_tokens": 256,
    "messages": [{"role":"user","content":"Hello!"}]
  }'

Streaming (SSE):

curl -N -X POST http://127.0.0.1:8000/v1/messages \
  -H "Content-Type: application/json" \
  -H "X-API-KEY: $API_KEY" \
  -d '{
    "model": "llama.cpp/local-model",
    "stream": true,
    "messages": [{"role":"user","content":"Stream this response."}]
  }'

Count tokens:

curl -s -X POST http://127.0.0.1:8000/api/v1/messages/count_tokens \
  -H "Content-Type: application/json" \
  -H "X-API-KEY: $API_KEY" \
  -d '{
    "model": "anthropic/claude-opus-4-20250514",
    "messages": [{"role":"user","content":"Count my tokens."}]
  }'

Notes¶

count_tokens is only supported for Anthropic-compatible providers (anthropic, llama.cpp).
Non-native providers may ignore unsupported fields.