</python>
<typescript>
Pause execution for human review and resume with Command.
```typescript
import { interrupt, Command, MemorySaver, StateGraph, StateSchema, START, END } from "@langchain/langgraph";
import { z } from "zod";

const State = new StateSchema({
  approved: z.boolean().default(false),
});

const approvalNode = async (state: typeof State.State) => {
  // Pause and ask for approval
  const approved = interrupt("Do you approve this action?");
  // When resumed, Command({ resume }) returns that value here
  return { approved };
};

const checkpointer = new MemorySaver();
const graph = new StateGraph(State)
  .addNode("approval", approvalNode)
  .addEdge(START, "approval")
  .addEdge("approval", END)
  .compile({ checkpointer });

const config = { configurable: { thread_id: "thread-1" } };

// Initial run — hits interrupt and pauses
let result = await graph.invoke({ approved: false }, config);
console.log(result.__interrupt__);
// [{ value: 'Do you approve this action?', ... }]

// Resume with the human's response
result = await graph.invoke(new Command({ resume: true }), config);
console.log(result.approved);  // true

# interrupt() must come first — any code before it will re-run on resume
human_decision = interrupt({
    "email_id": state.get("email_content", ""),
    "draft_response": state.get("draft_response", ""),
    "urgency": classification.get("urgency"),
    "action": "Please review and approve/edit this response"
})

# Process the human's decision
if human_decision.get("approved"):
    return Command(
        update={"draft_response": human_decision.get("edited_response", state.get("draft_response", ""))},
        goto="send_reply"
    )
else:
    # Rejection — human will handle directly
    return Command(update={}, goto=END)

</python>
<typescript>
Interrupt for human review, then route to send or end based on the decision.
```typescript
import { interrupt, Command, END, GraphNode } from "@langchain/langgraph";

const humanReview: GraphNode<typeof EmailAgentState> = async (state) => {
  const classification = state.classification!;

  // interrupt() must come first — any code before it will re-run on resume
  const humanDecision = interrupt({
    emailId: state.emailContent,
    draftResponse: state.responseText,
    urgency: classification.urgency,
    action: "Please review and approve/edit this response",
  });

  // Process the human's decision
  if (humanDecision.approved) {
    return new Command({
      update: { responseText: humanDecision.editedResponse || state.responseText },
      goto: "sendReply",
    });
  } else {
    return new Command({ update: {}, goto: END });
  }
};

while True:
    answer = interrupt(prompt)

    # Validate the input
    if isinstance(answer, int) and answer > 0:
        break
    else:
        # Invalid input — ask again with a more specific prompt
        prompt = f"'{answer}' is not a valid age. Please enter a positive number."

return {"age": answer}

Each `Command(resume=...)` call provides the next answer. If invalid, the loop re-interrupts with a clearer message.
```python
config = {"configurable": {"thread_id": "form-1"}}
first = graph.invoke({"age": None}, config)

</python>
<typescript>
Validate human input in a loop, re-prompting until valid.
```typescript
import { interrupt } from "@langchain/langgraph";

const getAgeNode = (state: typeof State.State) => {
  let prompt = "What is your age?";

  while (true) {
    const answer = interrupt(prompt);

    // Validate the input
    if (typeof answer === "number" && answer > 0) {
      return { age: answer };
    } else {
      // Invalid input — ask again with a more specific prompt
      prompt = `'${answer}' is not a valid age. Please enter a positive number.`;
    }
  }
};

</python>
<typescript>
Resume multiple parallel interrupts by mapping interrupt IDs to values.
```typescript
import { Command, END, MemorySaver, START, StateGraph, interrupt, isInterrupted, INTERRUPT, Annotation } from "@langchain/langgraph";

const State = Annotation.Root({
  vals: Annotation<string[]>({
    reducer: (left, right) => left.concat(Array.isArray(right) ? right : [right]),
    default: () => [],
  }),
});

function nodeA(_state: typeof State.State) {
  const answer = interrupt("question_a") as string;
  return { vals: [`a:${answer}`] };
}

function nodeB(_state: typeof State.State) {
  const answer = interrupt("question_b") as string;
  return { vals: [`b:${answer}`] };
}

const graph = new StateGraph(State)
  .addNode("a", nodeA)
  .addNode("b", nodeB)
  .addEdge(START, "a")
  .addEdge(START, "b")
  .addEdge("a", END)
  .addEdge("b", END)
  .compile({ checkpointer: new MemorySaver() });

const config = { configurable: { thread_id: "1" } };

const interruptedResult = await graph.invoke({ vals: [] }, config);

// Resume all pending interrupts at once
const resumeMap: Record<string, string> = {};
if (isInterrupted(interruptedResult)) {
  for (const i of interruptedResult[INTERRUPT]) {
    if (i.id != null) {
      resumeMap[i.id] = `answer for ${i.value}`;
    }
  }
}
const result = await graph.invoke(new Command({ resume: resumeMap }), config);
// result.vals = ["a:answer for question_a", "b:answer for question_b"]

</python>
<typescript>
Idempotent operations before interrupt vs non-idempotent (wrong).
```typescript
// GOOD: Upsert is idempotent — safe before interrupt
const nodeA = async (state: typeof State.State) => {
  await db.upsertUser({ userId: state.userId, status: "pending_approval" });
  const approved = interrupt("Approve this change?");
  return { approved };
};

// GOOD: Side effect AFTER interrupt — only runs once
const nodeA = async (state: typeof State.State) => {
  const approved = interrupt("Approve this change?");
  if (approved) {
    await db.createAuditLog({ userId: state.userId, action: "approved" });
  }
  return { approved };
};

// BAD: Insert creates duplicates on each resume!
const nodeA = async (state: typeof State.State) => {
  await db.createAuditLog({  // Runs again on resume!
    userId: state.userId,
    action: "pending_approval",
  });
  const approved = interrupt("Approve this change?");
  return { approved };
};

</python>
<typescript>
```typescript
async function nodeInParentGraph(state: State) {
  someCode();  // <-- Re-executes on resume
  const subgraphResult = await subgraph.invoke(someInput);
  // ...
}

async function nodeInSubgraph(state: State) {
  someOtherCode();  // <-- Also re-executes on resume
  const result = interrupt("What's your name?");
  // ...
}

</python>
<typescript>
Checkpointer required for interrupt functionality.
```typescript
// WRONG
const graph = builder.compile();

// CORRECT
const graph = builder.compile({ checkpointer: new MemorySaver() });

</python>
<typescript>
Use Command to resume from an interrupt (regular object restarts graph).
```typescript
// WRONG
await graph.invoke({ resumeData: "approve" }, config);

// CORRECT
await graph.invoke(new Command({ resume: "approve" }), config);