LangChain Cloudflare Worker Example

This example demonstrates how to use langchain-cloudflare with Cloudflare Python Workers, using the Workers AI, Vectorize, and D1 bindings directly for optimal performance.

Features

• Basic chat completion with Workers AI
• Structured output with Pydantic models
• Tool calling
• Multi-turn conversations
• create_agent pattern (requires langchain>=0.3.0)
• Vectorize operations (insert, search, delete)
• D1 database operations

Prerequisites

1. Cloudflare account with Workers, AI, Vectorize, and D1 access
2. Python 3.12+
3. uv package manager
4. pywrangler for local development

Setup

1. Install dependencies:

   uv sync

2. Create a Vectorize index (if needed):

   npx wrangler vectorize create langchain-test-persistent --dimensions 768 --metric cosine

3. Create a D1 database (if needed):

   npx wrangler d1 create test-db

4. Update wrangler.jsonc with your database ID

Running Locally

uv run pywrangler dev

Endpoints

Endpoint	Method	Description
/	GET	API documentation
/chat	POST	Basic chat completion
/structured	POST	Structured output extraction
/tools	POST	Tool calling
/multi-turn	POST	Multi-turn conversation
/agent-structured	POST	Agent with structured output
/agent-tools	POST	Agent with tools
/vectorize-insert	POST	Insert into Vectorize
/vectorize-search	POST	Search Vectorize
/vectorize-delete	POST	Delete from Vectorize
/vectorize-info	GET	Vectorize index info
/d1-health	GET	D1 health check
/d1-create-table	POST	Create D1 table
/d1-insert	POST	Insert into D1
/d1-query	POST	Query D1
/d1-drop-table	POST	Drop D1 table

Example Usage

# Chat
curl -X POST http://localhost:8787/chat \
  -H "Content-Type: application/json" \
  -d '{"message": "Hello!"}'

# Structured output
curl -X POST http://localhost:8787/structured \
  -H "Content-Type: application/json" \
  -d '{"text": "Acme Corp announced a partnership with TechGiant."}'

# Tool calling
curl -X POST http://localhost:8787/tools \
  -H "Content-Type: application/json" \
  -d '{"message": "What is the weather in San Francisco?"}'