langgraph-human-in-the-loop

1<overview>
2LangGraph's human-in-the-loop patterns let you pause graph execution, surface data to users, and resume with their input:
3 
4- **`interrupt(value)`** — pauses execution, surfaces a value to the caller
5- **`Command(resume=value)`** — resumes execution, providing the value back to `interrupt()`
6- **Checkpointer** — required to save state while paused
7- **Thread ID** — required to identify which paused execution to resume
8</overview>
9 
10---
11 
12## Requirements
13 
14Three things are required for interrupts to work:
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161. **Checkpointer** — compile with `checkpointer=InMemorySaver()` (dev) or `PostgresSaver` (prod)
172. **Thread ID** — pass `{"configurable": {"thread_id": "..."}}` to every `invoke`/`stream` call
183. **JSON-serializable payload** — the value passed to `interrupt()` must be JSON-serializable
19 
20---
21 
22## Basic Interrupt + Resume
23 
24`interrupt(value)` pauses the graph. The value surfaces in the result under `__interrupt__`. `Command(resume=value)` resumes — the resume value becomes the return value of `interrupt()`.
25 
26**Critical**: when the graph resumes, the node restarts from the **beginning** — all code before `interrupt()` re-runs.
27 
28<ex-basic-interrupt-resume>
29<python>
30Pause execution for human review and resume with Command.
31 
32```python
33from langgraph.types import interrupt, Command
34from langgraph.checkpoint.memory import InMemorySaver
35from langgraph.graph import StateGraph, START, END
36from typing_extensions import TypedDict
37 
38class State(TypedDict):
39    approved: bool
40…