AWS Bedrock

llmock supports the AWS Bedrock Claude invoke endpoint. Point the AWS SDK at your llmock instance and fixtures match against the Bedrock-format requests, returning Anthropic Messages API responses — the same format Bedrock uses for Claude models.

How It Works

AWS Bedrock uses a URL pattern of /model/{modelId}/invoke to call foundation models. The request body uses the Anthropic Messages format with an additional anthropic_version field, and does not include a model field in the body (the model is in the URL).

llmock detects the Bedrock URL pattern, extracts the model ID, translates the request to the internal fixture-matching format, and returns the response in the Anthropic Messages API format — which is identical to the Bedrock Claude response format.

URL Pattern

Request Format

Bedrock Claude requests use the Anthropic Messages format. The anthropic_version field is accepted but not validated. The model is taken from the URL path, not the request body.

{
  "anthropic_version": "bedrock-2023-05-31",
  "max_tokens": 512,
  "messages": [
    { "role": "user", "content": "Hello" }
  ],
  "system": "You are helpful"
}

Response Format

Bedrock Claude responses are identical to the Anthropic Messages API non-streaming responses:

{
  "id": "msg_...",
  "type": "message",
  "role": "assistant",
  "content": [{ "type": "text", "text": "Hello!" }],
  "stop_reason": "end_turn",
  "stop_sequence": null,
  "usage": { "input_tokens": 10, "output_tokens": 5 }
}

Model Resolution

The model ID is extracted from the URL path. This is used both for fixture matching and included in the response body. Bedrock model IDs typically look like:

• anthropic.claude-3-5-sonnet-20241022-v2:0
• anthropic.claude-3-haiku-20240307-v1:0
• anthropic.claude-3-opus-20240229-v1:0

Write fixtures that match by Bedrock model ID:

{
  "match": {
    "model": "anthropic.claude-3-5-sonnet-20241022-v2:0",
    "userMessage": "hello"
  },
  "response": {
    "content": "Hello from Bedrock!"
  }
}

SDK Configuration

To point the AWS SDK Bedrock Runtime client at llmock, configure the endpoint URL:

import { BedrockRuntimeClient, InvokeModelCommand } from "@aws-sdk/client-bedrock-runtime";

const client = new BedrockRuntimeClient({
  region: "us-east-1",
  endpoint: "http://localhost:4005",  // llmock URL
  credentials: { accessKeyId: "mock", secretAccessKey: "mock" },
});

const response = await client.send(new InvokeModelCommand({
  modelId: "anthropic.claude-3-5-sonnet-20241022-v2:0",
  contentType: "application/json",
  body: JSON.stringify({
    anthropic_version: "bedrock-2023-05-31",
    max_tokens: 512,
    messages: [{ role: "user", content: "Hello" }],
  }),
}));

Fixture Examples

{
  "fixtures": [
    {
      "match": { "userMessage": "hello" },
      "response": { "content": "Hi there!" }
    },
    {
      "match": { "userMessage": "weather" },
      "response": {
        "toolCalls": [{
          "name": "get_weather",
          "arguments": "{\"city\":\"SF\"}"
        }]
      }
    }
  ]
}