POST /v1/messages

Native Anthropic Messages API format. Use this endpoint with the Anthropic Python SDK or Claude Code CLI by setting ANTHROPIC_BASE_URL.

All proxy features (PII scrubbing, RAG, rate limiting, content policy, caching) apply equally to this endpoint.

Request

POST /v1/messages
x-api-key: <api-key>
anthropic-version: 2023-06-01
Content-Type: application/json

Authorization: Bearer <api-key> is also accepted as an alternative to x-api-key.

Body

Field	Type	Required	Description
model	string	yes	Anthropic model ID (e.g. claude-3-5-sonnet-20241022)
messages	array	yes	Array of {role, content} objects
max_tokens	int	yes	Maximum output tokens
system	string	no	System prompt (prepended to context)
stream	bool	no	false (default). SSE streaming if true.
tools	array	no	Anthropic tool definitions
temperature	float	no
top_p	float	no
top_k	int	no

Example

{
  "model": "claude-3-5-sonnet-20241022",
  "max_tokens": 1024,
  "system": "You are a helpful assistant.",
  "messages": [
    {"role": "user", "content": "Explain PII scrubbing in one paragraph."}
  ]
}

Response (non-streaming)

{
  "id": "msg_01...",
  "type": "message",
  "role": "assistant",
  "content": [
    {
      "type": "text",
      "text": "PII scrubbing is the process of..."
    }
  ],
  "model": "claude-3-5-sonnet-20241022",
  "stop_reason": "end_turn",
  "stop_sequence": null,
  "usage": {
    "input_tokens": 38,
    "output_tokens": 92
  }
}

Streaming

SSE events follow the Anthropic streaming protocol:

event: message_start
data: {"type":"message_start","message":{"id":"msg_01...","type":"message","role":"assistant","content":[],"model":"claude-3-5-sonnet-20241022","stop_reason":null,"usage":{"input_tokens":38,"output_tokens":0}}}

event: content_block_start
data: {"type":"content_block_start","index":0,"content_block":{"type":"text","text":""}}

event: content_block_delta
data: {"type":"content_block_delta","index":0,"delta":{"type":"text_delta","text":"PII scrubbing"}}

event: message_stop
data: {"type":"message_stop"}

Python (Anthropic SDK)

import anthropic

client = anthropic.Anthropic(
    base_url="https://proxy.internal",
    api_key="llmp_...",
)

# Non-streaming
message = client.messages.create(
    model="claude-3-5-sonnet-20241022",
    max_tokens=1024,
    messages=[{"role": "user", "content": "Hello"}],
)
print(message.content[0].text)

# Streaming
with client.messages.stream(
    model="claude-3-5-sonnet-20241022",
    max_tokens=1024,
    messages=[{"role": "user", "content": "Count to 5"}],
) as stream:
    for text in stream.text_stream:
        print(text, end="", flush=True)

Claude Code CLI

export ANTHROPIC_BASE_URL="https://proxy.internal"
export ANTHROPIC_API_KEY="llmp_..."
claude

Or with flags:

claude --api-url https://proxy.internal --api-key llmp_...