LangGraph Workflow Example

Example LangGraph workflows with X402 payment nodes.

Setup

1. Install dependencies:

   pip install -r requirements.txt
   

2. Create and fund wallet:

   # Run the script once to generate wallet
   python main.py
   
   # Fund the wallet with SOL (for transaction fees)
   solana airdrop 1 YOUR_WALLET_ADDRESS --url devnet
   

3. Start the FastAPI server (in another terminal):

   cd ../fastapi-server
   python main.py
   

4. Run the workflow examples:

   python main.py
   

What it does

The examples demonstrate three workflow patterns:

Example 1: Simple Workflow

Uses the convenience function to create a basic workflow with payment handling.

Example 2: Custom Workflow

Shows how to build a workflow with separate fetch and payment nodes for more control.

Example 3: Multi-Step Workflow

Demonstrates a workflow that accesses multiple paid APIs sequentially, handling payments for each.

Key Features

• Modular Design: Payment logic is isolated in dedicated nodes
• Conditional Routing: Workflows automatically route to payment nodes when needed
• Error Handling: Graceful handling of payment errors
• Composable: Easy to add payment capabilities to existing workflows

Workflow Patterns

Pattern 1: Combined Node

workflow.add_node("fetch", fetch_with_payment_node)

Simplest approach - fetch and pay in one node.

Pattern 2: Separate Nodes

workflow.add_node("fetch", fetch_node)
workflow.add_node("pay", payment_node)
workflow.add_conditional_edges("fetch", check_payment_required, {...})

More control - explicit payment step.

Pattern 3: Multi-Step

# Loop through multiple APIs
workflow.add_conditional_edges("collect", check_more_apis, {
    "fetch_next": "fetch",
    "complete": END
})

Complex workflows with multiple payments.