Package Exports

@meldscience/mcp-stream-parser
@meldscience/mcp-stream-parser/dist/index.js

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Readme

MCP Stream Parser

A lightweight parser for Claude's streaming responses that detects and structures three types of messages:

Text messages (regular content)
Thought messages ({"thought": "..."})
Tool usage messages ({"tool": {...}})

Installation

npm install @meldscience/mcp-stream-parser

Quick Start

import { MCPStreamParser } from '@meldscience/mcp-stream-parser';
import { Anthropic } from '@anthropic-ai/sdk';

const parser = new MCPStreamParser();
const anthropic = new Anthropic({ apiKey: 'your-api-key' });

// Set up handlers for each message type
parser.onMessage(text => {
  console.log('Text:', text);  // e.g., "Let me help you with that."
});

parser.onThought(thought => {
  console.log('Thought:', thought);  // e.g., "I should search the codebase first"
});

parser.onTool(tool => {
  console.log('Tool:', tool);  // e.g., { name: "codebase_search", params: { query: "..." } }
});

// Optional error handling
parser.onError(error => {
  console.error('Error:', error);
});

// Process Claude's response
const response = await anthropic.messages.create({
  model: 'claude-3-sonnet-20240229',
  max_tokens: 1024,
  messages: [{ role: 'user', content: 'Hello!' }],
  stream: true
});

await parser.processStream(response);

Features

Real-time Processing: Emits each message as soon as it's complete
Minimal Buffering: Only buffers between clear message boundaries
Type Safety: Full TypeScript support with exported types
Error Handling: Continues processing after errors, with optional strict mode

Message Types

Text Messages

Regular content from Claude:

Let me help you with that.

Thought Messages

Claude's internal thought process:

{"thought": "I should search the codebase first"}

Tool Usage

Claude using a tool:

{"tool": {
  "name": "codebase_search",
  "params": {
    "query": "find main function"
  }
}}

Configuration

const parser = new MCPStreamParser({
  debug: false,  // Enable debug logging
  strict: false  // Strict mode fails on any error
});

Requirements

Node.js >= 18
ESM module support

License

MIT