fail-kit 1.5.0

F.A.I.L. Kit adapter for LangChain agents - Receipts, auditing, and policy enforcement

fail-kit-langchain

v1.5.0 - LangChain adapter for F.A.I.L. Kit (Python)

Drop-in adapter for integrating LangChain agents with the F.A.I.L. Kit audit framework.

Installation

pip install fail-kit-langchain

With FastAPI support:

pip install fail-kit-langchain[fastapi]

With LangGraph support:

pip install fail-kit-langchain[langgraph]

All extras:

pip install fail-kit-langchain[all]

Quick Start

from fastapi import FastAPI
from langchain.agents import AgentExecutor
from fail_kit_langchain import (
    create_fail_kit_endpoint,
    ReceiptGeneratingTool
)

app = FastAPI()

# Define tools with automatic receipt generation
class EmailTool(ReceiptGeneratingTool):
    name = "email_sender"
    description = "Send an email"
    
    def _execute(self, to: str, subject: str, body: str):
        send_email(to, subject, body)
        return {"status": "sent", "message_id": "msg_123"}

# Create agent
tools = [EmailTool()]
agent_executor = AgentExecutor(agent=agent, tools=tools)

# Add F.A.I.L. Kit endpoint
app.include_router(
    create_fail_kit_endpoint(agent_executor),
    prefix="/eval"
)

Features

• ✅ Automatic receipt generation from tool executions
• ✅ Full RECEIPT_SCHEMA.json compliance
• ✅ Native LangGraph support
• ✅ Async/await support
• ✅ Custom metadata in receipts
• ✅ Error handling with failure receipts
• ✅ SHA256 hashing for verification

API Reference

create_fail_kit_endpoint(agent_executor, config=None)

Creates a FastAPI router with the /run endpoint.

Parameters:

• agent_executor: LangChain AgentExecutor instance
• config: Optional FailKitConfig

Returns: APIRouter

ReceiptGeneratingTool

Base class for tools with automatic receipt generation.

Methods:

• _execute(*args, **kwargs): Override with your tool logic
• get_receipts(): Get all receipts
• clear_receipts(): Clear receipt history

extract_receipts_from_agent_executor(executor, result, config=None)

Extract receipts from AgentExecutor intermediate steps.

wrap_tool_with_receipts(tool)

Wrap a legacy LangChain tool to generate receipts.

Examples

See examples/langchain-python/ for a complete working example.

Testing

pytest

Related

• @fail-kit/core - Core receipt generation library (npm)
• F.A.I.L. Kit CLI - Command-line audit tool
• F.A.I.L. Kit VS Code Extension - IDE integration

License

MIT License - See LICENSE