langgraph-human-in-loop

# LangGraph Human-in-the-Loop

Pause workflows for human intervention and approval.

## Basic Interrupt

```python
workflow = StateGraph(State)
workflow.add_node("draft", generate_draft)
workflow.add_node("review", human_review)
workflow.add_node("publish", publish_content)

# Interrupt before review
app = workflow.compile(interrupt_before=["review"])

# Step 1: Generate draft (stops at review)
config = {"configurable": {"thread_id": "doc-123"}}
result = app.invoke({"topic": "AI"}, config=config)
# Workflow pauses here
```

## Resume After Approval

```python
# Step 2: Human reviews and updates state
state = app.get_state(config)
print(f"Draft: {state.values['draft']}")

# Human decision
state.values["approved"] = True
state.values["feedback"] = "Looks good"
app.update_state(config, state.values)

# Step 3: Resume workflow
result = app.invoke(None, config=config)  # Continues to publish
```

## Approval Gate Node

```python
def approval_gate(state: WorkflowState) -> WorkflowState:
    """Check if human approved."""
    if not state.get("human_reviewed"):
        # Will pause here due to interrupt_before
        return state

    if state["approved"]:
        state["next"] = "publish"
    else:
        state["next"] = "revise"

    return state

workflow.add_node("approval_gate", approval_gate)

# Pause before this node
app = workflow.compile(interrupt_before=["approval_gate"])
```

## Feedback Loop Pattern

```python
import uuid_utils  # pip install uuid-utils (UUID v7 for Python < 3.14)

async def run_with_feedback(initial_state: dict):
    """Run until human approves."""
    config = {"configurable": {"thread_id": str(uuid_utils.uuid7())}}

    while True:
        # Run until interrupt
        result = app.invoke(initial_state, config=config)

        # Get current state
        state = app.get_state(config)

        # Present to human
        print(f"Output: {state.values['output']}")
        feedback = input("Approve? (yes/no/feedback): ")

        if feedback.l