Human-in-the-Loop Complaint Handler

A customer complaint handler built with LangGraph that uses the interrupt() and Command(resume=...) pattern to insert human approval gates into an automated workflow. The agent drafts a response, pauses for human review, and then sends or rejects based on the reviewer's decision. Includes LangSmith tracing and LLM-as-judge evaluations.

Prerequisites

• Python 3.11+
• Anthropic API key
• LangSmith API key

Setup

python -m venv venv
source venv/bin/activate
pip install -r requirements.txt
cp .env.example .env
# Edit .env with your API keys

Environment Variables

Variable	Required	Description
ANTHROPIC_API_KEY	Yes	Anthropic API key for Claude
LANGSMITH_API_KEY	Yes	LangSmith API key for tracing and evals
LANGSMITH_TRACING	Yes	Set to true to enable tracing

Running

python complaint_handler.py

To run evaluations:

python evals.py

Article

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