Interrupts

Interrupts allow you to pause graph execution at specific points and wait for external input before continuing. This enables human-in-the-loop patterns where you need external input to proceed. When an interrupt is triggered, LangGraph saves the graph state using its persistence layer and waits indefinitely until you resume execution.

Interrupts work by calling the interrupt() function at any point in your graph nodes. The function accepts any JSON-serializable value which is surfaced to the caller. When you’re ready to continue, you resume execution by re-invoking the graph using Command, which then becomes the return value of the interrupt() call from inside the node.

Unlike static breakpoints (which pause before or after specific nodes), interrupts are dynamic—they can be placed anywhere in your code and can be conditional based on your application logic.

• Checkpointing keeps your place: the checkpointer writes the exact graph state so you can resume later, even when in an error state.
• thread_id is your pointer: set config={"configurable": {"thread_id": ...}} to tell the checkpointer which state to load.
• Interrupt payloads surface as __interrupt__: the values you pass to interrupt() return to the caller in the __interrupt__ field so you know what the graph is waiting on.

The thread_id you choose is effectively your persistent cursor. Reusing it resumes the same checkpoint; using a new value starts a brand-new thread with an empty state.

Pause using interrupt

The interrupt function pauses graph execution and returns a value to the caller. When you call interrupt within a node, LangGraph saves the current graph state and waits for you to resume execution with input.

To use interrupt, you need:

1. A checkpointer to persist the graph state (use a durable checkpointer in production)
2. A thread ID in your config so the runtime knows which state to resume from
3. To call interrupt() where you want to pause (payload must be JSON-serializable)

from langgraph.types import interrupt

def approval_node(state: State):
    # Pause and ask for approval
    approved = interrupt("Do you approve this action?")

    # When you resume, Command(resume=...) returns that value here
    return {"approved": approved}

When you call interrupt, here’s what happens:

1. Graph execution gets suspended at the exact point where interrupt is called
2. State is saved using the checkpointer so execution can be resumed later, In production, this should be a persistent checkpointer (e.g. backed by a database)
3. Value is returned to the caller under __interrupt__; it can be any JSON-serializable value (string, object, array, etc.)
4. Graph waits indefinitely until you resume execution with a response
5. Response is passed back into the node when you resume, becoming the return value of the interrupt() call

Resuming interrupts

After an interrupt pauses execution, you resume the graph by invoking it again with a Command that contains the resume value. The resume value is passed back to the interrupt call, allowing the node to continue execution with the external input.

from langgraph.types import Command

# Initial run - hits the interrupt and pauses
# thread_id is the persistent pointer (stores a stable ID in production)
config = {"configurable": {"thread_id": "thread-1"}}
result = graph.invoke({"input": "data"}, config=config)

# Check what was interrupted
# __interrupt__ contains the payload that was passed to interrupt()
print(result["__interrupt__"])
# > [Interrupt(value='Do you approve this action?')]

# Resume with the human's response
# The resume payload becomes the return value of interrupt() inside the node
graph.invoke(Command(resume=True), config=config)

Key points about resuming:

• You must use the same thread ID when resuming that was used when the interrupt occurred
• The value passed to Command(resume=...) becomes the return value of the interrupt call
• The node restarts from the beginning of the node where the interrupt was called when resumed, so any code before the interrupt runs again
• You can pass any JSON-serializable value as the resume value

Common patterns

The key thing that interrupts unlock is the ability to pause execution and wait for external input. This is useful for a variety of use cases, including:

• Approval workflows: Pause before executing critical actions (API calls, database changes, financial transactions)
• Review and edit: Let humans review and modify LLM outputs or tool calls before continuing
• Interrupting tool calls: Pause before executing tool calls to review and edit the tool call before execution
• Validating human input: Pause before proceeding to the next step to validate human input

Approve or reject

One of the most common uses of interrupts is to pause before a critical action and ask for approval. For example, you might want to ask a human to approve an API call, a database change, or any other important decision.

from typing import Literal
from langgraph.types import interrupt, Command

def approval_node(state: State) -> Command[Literal["proceed", "cancel"]]:
    # Pause execution; payload shows up under result["__interrupt__"]
    is_approved = interrupt({
        "question": "Do you want to proceed with this action?",
        "details": state["action_details"]
    })

    # Route based on the response
    if is_approved:
        return Command(goto="proceed")  # Runs after the resume payload is provided
    else:
        return Command(goto="cancel")

When you resume the graph, pass true to approve or false to reject:

# To approve
graph.invoke(Command(resume=True), config=config)

# To reject
graph.invoke(Command(resume=False), config=config)

Full example

from typing import Literal, Optional, TypedDict

from langgraph.checkpoint.memory import MemorySaver
from langgraph.graph import StateGraph, START, END
from langgraph.types import Command, interrupt


class ApprovalState(TypedDict):
    action_details: str
    status: Optional[Literal["pending", "approved", "rejected"]]


def approval_node(state: ApprovalState) -> Command[Literal["proceed", "cancel"]]:
    # Expose details so the caller can render them in a UI
    decision = interrupt({
        "question": "Approve this action?",
        "details": state["action_details"],
    })

    # Route to the appropriate node after resume
    return Command(goto="proceed" if decision else "cancel")


def proceed_node(state: ApprovalState):
    return {"status": "approved"}


def cancel_node(state: ApprovalState):
    return {"status": "rejected"}


builder = StateGraph(ApprovalState)
builder.add_node("approval", approval_node)
builder.add_node("proceed", proceed_node)
builder.add_node("cancel", cancel_node)
builder.add_edge(START, "approval")
builder.add_edge("proceed", END)
builder.add_edge("cancel", END)

# Use a more durable checkpointer in production
checkpointer = MemorySaver()
graph = builder.compile(checkpointer=checkpointer)

config = {"configurable": {"thread_id": "approval-123"}}
initial = graph.invoke(
    {"action_details": "Transfer $500", "status": "pending"},
    config=config,
)
print(initial["__interrupt__"])  # -> [Interrupt(value={'question': ..., 'details': ...})]

# Resume with the decision; True routes to proceed, False to cancel
resumed = graph.invoke(Command(resume=True), config=config)
print(resumed["status"])  # -> "approved"

Review and edit state

Sometimes you want to let a human review and edit part of the graph state before continuing. This is useful for correcting LLMs, adding missing information, or making adjustments.

from langgraph.types import interrupt

def review_node(state: State):
    # Pause and show the current content for review (surfaces in result["__interrupt__"])
    edited_content = interrupt({
        "instruction": "Review and edit this content",
        "content": state["generated_text"]
    })

    # Update the state with the edited version
    return {"generated_text": edited_content}

When resuming, provide the edited content:

graph.invoke(
    Command(resume="The edited and improved text"),  # Value becomes the return from interrupt()
    config=config
)

Full example

import sqlite3
from typing import TypedDict

from langgraph.checkpoint.memory import MemorySaver
from langgraph.graph import StateGraph, START, END
from langgraph.types import Command, interrupt


class ReviewState(TypedDict):
    generated_text: str


def review_node(state: ReviewState):
    # Ask a reviewer to edit the generated content
    updated = interrupt({
        "instruction": "Review and edit this content",
        "content": state["generated_text"],
    })
    return {"generated_text": updated}


builder = StateGraph(ReviewState)
builder.add_node("review", review_node)
builder.add_edge(START, "review")
builder.add_edge("review", END)

checkpointer = MemorySaver()
graph = builder.compile(checkpointer=checkpointer)

config = {"configurable": {"thread_id": "review-42"}}
initial = graph.invoke({"generated_text": "Initial draft"}, config=config)
print(initial["__interrupt__"])  # -> [Interrupt(value={'instruction': ..., 'content': ...})]

# Resume with the edited text from the reviewer
final_state = graph.invoke(
    Command(resume="Improved draft after review"),
    config=config,
)
print(final_state["generated_text"])  # -> "Improved draft after review"

Interrupts in tools

You can also place interrupts directly inside tool functions. This makes the tool itself pause for approval whenever it’s called, and allows for human review and editing of the tool call before it is executed.

First, define a tool that uses interrupt:

from langchain.tools import tool
from langgraph.types import interrupt

@tool
def send_email(to: str, subject: str, body: str):
    """Send an email to a recipient."""

    # Pause before sending; payload surfaces in result["__interrupt__"]
    response = interrupt({
        "action": "send_email",
        "to": to,
        "subject": subject,
        "body": body,
        "message": "Approve sending this email?"
    })

    if response.get("action") == "approve":
        # Resume value can override inputs before executing
        final_to = response.get("to", to)
        final_subject = response.get("subject", subject)
        final_body = response.get("body", body)
        return f"Email sent to {final_to} with subject '{final_subject}'"
    return "Email cancelled by user"

This approach is useful when you want the approval logic to live with the tool itself, making it reusable across different parts of your graph. The LLM can call the tool naturally, and the interrupt will pause execution whenever the tool is invoked, allowing you to approve, edit, or cancel the action.

Full example

import sqlite3
from typing import TypedDict

from langchain.tools import tool
from langchain_anthropic import ChatAnthropic
from langgraph.checkpoint.sqlite import SqliteSaver
from langgraph.graph import StateGraph, START, END
from langgraph.types import Command, interrupt


class AgentState(TypedDict):
    messages: list[dict]


@tool
def send_email(to: str, subject: str, body: str):
    """Send an email to a recipient."""

    # Pause before sending; payload surfaces in result["__interrupt__"]
    response = interrupt({
        "action": "send_email",
        "to": to,
        "subject": subject,
        "body": body,
        "message": "Approve sending this email?",
    })

    if response.get("action") == "approve":
        final_to = response.get("to", to)
        final_subject = response.get("subject", subject)
        final_body = response.get("body", body)

        # Actually send the email (your implementation here)
        print(f"[send_email] to={final_to} subject={final_subject} body={final_body}")
        return f"Email sent to {final_to}"

    return "Email cancelled by user"


model = ChatAnthropic(model="claude-sonnet-4-5-20250929").bind_tools([send_email])


def agent_node(state: AgentState):
    # LLM may decide to call the tool; interrupt pauses before sending
    result = model.invoke(state["messages"])
    return {"messages": state["messages"] + [result]}


builder = StateGraph(AgentState)
builder.add_node("agent", agent_node)
builder.add_edge(START, "agent")
builder.add_edge("agent", END)

checkpointer = SqliteSaver(sqlite3.connect("tool-approval.db"))
graph = builder.compile(checkpointer=checkpointer)

config = {"configurable": {"thread_id": "email-workflow"}}
initial = graph.invoke(
    {
        "messages": [
            {"role": "user", "content": "Send an email to [e-mail] about the meeting"}
        ]
    },
    config=config,
)
print(initial["__interrupt__"])  # -> [Interrupt(value={'action': 'send_email', ...})]

# Resume with approval and optionally edited arguments
resumed = graph.invoke(
    Command(resume={"action": "approve", "subject": "Updated subject"}),
    config=config,
)
print(resumed["messages"][-1])  # -> Tool result returned by send_email

Validating human input

Sometimes you need to validate input from humans and ask again if it’s invalid. You can do this using multiple interrupt calls in a loop.

from langgraph.types import interrupt

def get_age_node(state: State):
    prompt = "What is your age?"

    while True:
        answer = interrupt(prompt)  # payload surfaces in result["__interrupt__"]

        # Validate the input
        if isinstance(answer, int) and answer > 0:
            # Valid input - continue
            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 time you resume the graph with invalid input, it will ask again with a clearer message. Once valid input is provided, the node completes and the graph continues.

Full example

import sqlite3
from typing import TypedDict

from langgraph.checkpoint.sqlite import SqliteSaver
from langgraph.graph import StateGraph, START, END
from langgraph.types import Command, interrupt


class FormState(TypedDict):
    age: int | None


def get_age_node(state: FormState):
    prompt = "What is your age?"

    while True:
        answer = interrupt(prompt)  # payload surfaces in result["__interrupt__"]

        if isinstance(answer, int) and answer > 0:
            return {"age": answer}

        prompt = f"'{answer}' is not a valid age. Please enter a positive number."


builder = StateGraph(FormState)
builder.add_node("collect_age", get_age_node)
builder.add_edge(START, "collect_age")
builder.add_edge("collect_age", END)

checkpointer = SqliteSaver(sqlite3.connect("forms.db"))
graph = builder.compile(checkpointer=checkpointer)

config = {"configurable": {"thread_id": "form-1"}}
first = graph.invoke({"age": None}, config=config)
print(first["__interrupt__"])  # -> [Interrupt(value='What is your age?', ...)]

# Provide invalid data; the node re-prompts
retry = graph.invoke(Command(resume="thirty"), config=config)
print(retry["__interrupt__"])  # -> [Interrupt(value="'thirty' is not a valid age...", ...)]

# Provide valid data; loop exits and state updates
final = graph.invoke(Command(resume=30), config=config)
print(final["age"])  # -> 30

Rules of interrupts

When you call interrupt within a node, LangGraph suspends execution by raising an exception that signals the runtime to pause. This exception propagates up through the call stack and is caught by the runtime, which notifies the graph to save the current state and wait for external input.

When execution resumes (after you provide the requested input), the runtime restarts the entire node from the beginning—it does not resume from the exact line where interrupt was called. This means any code that ran before the interrupt will execute again. Because of this, there’s a few important rules to follow when working with interrupts to ensure they behave as expected.

Do not wrap interrupt calls in try/except

The way that interrupt pauses execution at the point of the call is by throwing a special exception. If you wrap the interrupt call in a try/except block, you will catch this exception and the interrupt will not be passed back to the graph.

• ✅ Separate interrupt calls from error-prone code
• ✅ Use specific exception types in try/except blocks

Separating logic

def node_a(state: State):
    # ✅ Good: interrupting first, then handling
    # error conditions separately
    interrupt("What's your name?")
    try:
        fetch_data()  # This can fail
    except Exception as e:
        print(e)
    return state

def node_a(state: State):
    # ✅ Good: catching specific exception types
    # will not catch the interrupt exception
    try:
        name = interrupt("What's your name?")
        fetch_data()  # This can fail
    except NetworkException as e:
        print(e)
    return state

• 🔴 Do not wrap interrupt calls in bare try/except blocks

def node_a(state: State):
    # ❌ Bad: wrapping interrupt in bare try/except
    # will catch the interrupt exception
    try:
        interrupt("What's your name?")
    except Exception as e:
        print(e)
    return state

Do not reorder interrupt calls within a node

It’s common to use multiple interrupts in a single node, however this can lead to unexpected behavior if not handled carefully.

When a node contains multiple interrupt calls, LangGraph keeps a list of resume values specific to the task executing the node. Whenever execution resumes, it starts at the beginning of the node. For each interrupt encountered, LangGraph checks if a matching value exists in the task’s resume list. Matching is strictly index-based, so the order of interrupt calls within the node is important.

• ✅ Keep interrupt calls consistent across node executions

def node_a(state: State):
    # ✅ Good: interrupt calls happen in the same order every time
    name = interrupt("What's your name?")
    age = interrupt("What's your age?")
    city = interrupt("What's your city?")

    return {
        "name": name,
        "age": age,
        "city": city
    }

• 🔴 Do not conditionally skip interrupt calls within a node
• 🔴 Do not loop interrupt calls using logic that isn’t deterministic across executions

Skipping interrupts

def node_a(state: State):
    # ❌ Bad: conditionally skipping interrupts changes the order
    name = interrupt("What's your name?")

    # On first run, this might skip the interrupt
    # On resume, it might not skip it - causing index mismatch
    if state.get("needs_age"):
        age = interrupt("What's your age?")

    city = interrupt("What's your city?")

    return {"name": name, "city": city}

def node_a(state: State):
    # ❌ Bad: looping based on non-deterministic data
    # The number of interrupts changes between executions
    results = []
    for item in state.get("dynamic_list", []):  # List might change between runs
        result = interrupt(f"Approve {item}?")
        results.append(result)

    return {"results": results}

Do not return complex values in interrupt calls

Depending on which checkpointer is used, complex values may not be serializable (e.g. you can’t serialize a function). To make your graphs adaptable to any deployment, it’s best practice to only use values that can be reasonably serialized.

• ✅ Pass simple, JSON-serializable types to interrupt
• ✅ Pass dictionaries/objects with simple values

Simple values

def node_a(state: State):
    # ✅ Good: passing simple types that are serializable
    name = interrupt("What's your name?")
    count = interrupt(42)
    approved = interrupt(True)

    return {"name": name, "count": count, "approved": approved}

def node_a(state: State):
    # ✅ Good: passing dictionaries with simple values
    response = interrupt({
        "question": "Enter user details",
        "fields": ["name", "email", "age"],
        "current_values": state.get("user", {})
    })

    return {"user": response}

• 🔴 Do not pass functions, class instances, or other complex objects to interrupt

Functions

def validate_input(value):
    return len(value) > 0

def node_a(state: State):
    # ❌ Bad: passing a function to interrupt
    # The function cannot be serialized
    response = interrupt({
        "question": "What's your name?",
        "validator": validate_input  # This will fail
    })
    return {"name": response}

class DataProcessor:
    def __init__(self, config):
        self.config = config

def node_a(state: State):
    processor = DataProcessor({"mode": "strict"})

    # ❌ Bad: passing a class instance to interrupt
    # The instance cannot be serialized
    response = interrupt({
        "question": "Enter data to process",
        "processor": processor  # This will fail
    })
    return {"result": response}

Side effects called before interrupt must be idempotent

Because interrupts work by re-running the nodes they were called from, side effects called before interrupt should (ideally) be idempotent. For context, idempotency means that the same operation can be applied multiple times without changing the result beyond the initial execution.

As an example, you might have an API call to update a record inside of a node. If interrupt is called after that call is made, it will be re-run multiple times when the node is resumed, potentially overwriting the initial update or creating duplicate records.

• ✅ Use idempotent operations before interrupt
• ✅ Place side effects after interrupt calls
• ✅ Separate side effects into separate nodes when possible

Idempotent operations

def node_a(state: State):
    # ✅ Good: using upsert operation which is idempotent
    # Running this multiple times will have the same result
    db.upsert_user(
        user_id=state["user_id"],
        status="pending_approval"
    )

    approved = interrupt("Approve this change?")

    return {"approved": approved}

def node_a(state: State):
    # ✅ Good: placing side effect after the interrupt
    # This ensures it only runs once after approval is received
    approved = interrupt("Approve this change?")

    if approved:
        db.create_audit_log(
            user_id=state["user_id"],
            action="approved"
        )

    return {"approved": approved}

def approval_node(state: State):
    # ✅ Good: only handling the interrupt in this node
    approved = interrupt("Approve this change?")

    return {"approved": approved}

def notification_node(state: State):
    # ✅ Good: side effect happens in a separate node
    # This runs after approval, so it only executes once
    if (state.approved):
        send_notification(
            user_id=state["user_id"],
            status="approved"
        )

    return state

• 🔴 Do not perform non-idempotent operations before interrupt
• 🔴 Do not create new records without checking if they exist

Creating records

def node_a(state: State):
    # ❌ Bad: creating a new record before interrupt
    # This will create duplicate records on each resume
    audit_id = db.create_audit_log({
        "user_id": state["user_id"],
        "action": "pending_approval",
        "timestamp": datetime.now()
    })

    approved = interrupt("Approve this change?")

    return {"approved": approved, "audit_id": audit_id}

def node_a(state: State):
    # ❌ Bad: appending to a list before interrupt
    # This will add duplicate entries on each resume
    db.append_to_history(state["user_id"], "approval_requested")

    approved = interrupt("Approve this change?")

    return {"approved": approved}

Using with subgraphs called as functions

When invoking a subgraph within a node, the parent graph will resume execution from the beginning of the node where the subgraph was invoked and the interrupt was triggered. Similarly, the subgraph will also resume from the beginning of the node where interrupt was called.

def node_in_parent_graph(state: State):
    some_code()  # <-- This will re-execute when resumed
    # Invoke a subgraph as a function.
    # The subgraph contains an `interrupt` call.
    subgraph_result = subgraph.invoke(some_input)
    # ...

def node_in_subgraph(state: State):
    some_other_code()  # <-- This will also re-execute when resumed
    result = interrupt("What's your name?")
    # ...

Debugging with interrupts

To debug and test a graph, you can use static interrupts as breakpoints to step through the graph execution one node at a time. Static interrupts are triggered at defined points either before or after a node executes. You can set these by specifying interrupt_before and interrupt_after when compiling the graph.

Static interrupts are not recommended for human-in-the-loop workflows. Use the interrupt function instead.

At compile time

graph = builder.compile(
    interrupt_before=["node_a"],  
    interrupt_after=["node_b", "node_c"],  
    checkpointer=checkpointer,
)

# Pass a thread ID to the graph
config = {
    "configurable": {
        "thread_id": "some_thread"
    }
}

# Run the graph until the breakpoint
graph.invoke(inputs, config=config)  

# Resume the graph
graph.invoke(None, config=config)  

1. The breakpoints are set during compile time.
2. interrupt_before specifies the nodes where execution should pause before the node is executed.
3. interrupt_after specifies the nodes where execution should pause after the node is executed.
4. A checkpointer is required to enable breakpoints.
5. The graph is run until the first breakpoint is hit.
6. The graph is resumed by passing in None for the input. This will run the graph until the next breakpoint is hit.

At run time

config = {
    "configurable": {
        "thread_id": "some_thread"
    }
}

# Run the graph until the breakpoint
graph.invoke(
    inputs,
    interrupt_before=["node_a"],  
    interrupt_after=["node_b", "node_c"],  
    config=config,
)

# Resume the graph
graph.invoke(None, config=config)  

1. graph.invoke is called with the interrupt_before and interrupt_after parameters. This is a run-time configuration and can be changed for every invocation.
2. interrupt_before specifies the nodes where execution should pause before the node is executed.
3. interrupt_after specifies the nodes where execution should pause after the node is executed.
4. The graph is run until the first breakpoint is hit.
5. The graph is resumed by passing in None for the input. This will run the graph until the next breakpoint is hit.

Using LangGraph Studio

You can use LangGraph Studio to set static interrupts in your graph in the UI before running the graph. You can also use the UI to inspect the graph state at any point in the execution.

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