fix(langgraph): validate ID-mapped resumes before committing them

A resume passed as Command(resume={interrupt_id: value}) is already in
the scratchpad when interrupt() runs, so it took the replay branch, which
queued the RESUME write before validation. A rejected value was therefore
persisted and every later correction re-validated it.

libs/langgraph/langgraph/types.py

@@ -20,6 +20,7 @@ from warnings import warn
 from langchain_core.messages import AnyMessage
 from langchain_core.runnables import Runnable, RunnableConfig
 from langgraph.checkpoint.base import BaseCheckpointSaver, CheckpointMetadata
+from pydantic import TypeAdapter
 from typing_extensions import NotRequired, TypeAliasType, TypedDict, Unpack, deprecated
 from xxhash import xxh3_128_hexdigest
 
@@ -596,13 +597,19 @@ class Interrupt:
     id: str
     """The ID of the interrupt. Can be used to resume the interrupt directly."""
 
+    response_schema: dict[str, Any] | None = None
+    """JSON Schema for the value expected when resuming this interrupt, if the graph provided one."""
+
     def __init__(
         self,
         value: Any,
         id: str = _DEFAULT_INTERRUPT_ID,
+        *,
+        response_schema: dict[str, Any] | None = None,
         **deprecated_kwargs: Unpack[DeprecatedKwargs],
     ) -> None:
         self.value = value
+        self.response_schema = response_schema
 
         if (
             (ns := deprecated_kwargs.get("ns", MISSING)) is not MISSING
@@ -614,8 +621,14 @@ class Interrupt:
             self.id = id
 
     @classmethod
-    def from_ns(cls, value: Any, ns: str) -> Interrupt:
-        return cls(value=value, id=xxh3_128_hexdigest(ns.encode()))
+    def from_ns(
+        cls, value: Any, ns: str, *, response_schema: dict[str, Any] | None = None
+    ) -> Interrupt:
+        return cls(
+            value=value,
+            id=xxh3_128_hexdigest(ns.encode()),
+            response_schema=response_schema,
+        )
 
     @property
     @deprecated("`interrupt_id` is deprecated. Use `id` instead.", category=None)
@@ -848,7 +861,9 @@ class Command(Generic[N], ToolOutputMixin):
     PARENT: ClassVar[Literal["__parent__"]] = "__parent__"
 
 
-def interrupt(value: Any) -> Any:
+def interrupt(
+    value: Any, *, response_schema: dict[str, Any] | type[Any] | None = None
+) -> Any:
     """Interrupt the graph with a resumable exception from within a node.
 
     The `interrupt` function enables human-in-the-loop workflows by pausing graph
@@ -918,7 +933,7 @@ def interrupt(value: Any) -> Any:
         for chunk in graph.stream({\"foo\": \"abc\"}, config):
             print(chunk)
 
-        # > {'__interrupt__': (Interrupt(value='what is your age?', id='45fda8478b2ef754419799e10992af06'),)}
+        # > {'__interrupt__': (Interrupt(value='what is your age?', id='45fda8478b2ef754419799e10992af06', response_schema=None),)}
 
         command = Command(resume=\"some input from a human!!!\")
 
@@ -931,12 +946,20 @@ def interrupt(value: Any) -> Any:
 
     Args:
         value: The value to surface to the client when the graph is interrupted.
+        response_schema: Optional schema for the value expected on resume, surfaced
+            to clients so they can render a typed input form. Accepts a JSON Schema
+            `dict` (used as-is, resume values are not validated), or a Pydantic model
+            class, `TypedDict`, or dataclass, which are converted to JSON Schema for
+            clients and used to validate the resume value; the validated object is
+            what `interrupt` returns.
 
     Returns:
-        Any: On subsequent invocations within the same node (same task to be precise), returns the value provided during the first invocation
+        Any: On subsequent invocations within the same node (same task to be precise), returns the value provided during the first invocation,
+            validated against `response_schema` when one that supports validation was given.
 
     Raises:
         GraphInterrupt: On the first invocation within the node, halts execution and surfaces the provided value to the client.
+        pydantic.ValidationError: When a resume value does not match a Pydantic model, `TypedDict`, or dataclass `response_schema`.
     """
     from langgraph._internal._constants import (
         CONFIG_KEY_CHECKPOINT_NS,
@@ -948,27 +971,36 @@ def interrupt(value: Any) -> Any:
     from langgraph.errors import GraphInterrupt
 
     conf = get_config()["configurable"]
+    adapter = (
+        None
+        if response_schema is None or isinstance(response_schema, dict)
+        else TypeAdapter(response_schema)
+    )
     # track interrupt index
     scratchpad = conf[CONFIG_KEY_SCRATCHPAD]
     idx = scratchpad.interrupt_counter()
     # find previous resume values
     if scratchpad.resume:
         if idx < len(scratchpad.resume):
+            v = scratchpad.resume[idx]
+            validated = adapter.validate_python(v) if adapter else v
             conf[CONFIG_KEY_SEND]([(RESUME, scratchpad.resume)])
-            return scratchpad.resume[idx]
+            return validated
     # find current resume value
     v = scratchpad.get_null_resume(True)
     if v is not None:
         assert len(scratchpad.resume) == idx, (scratchpad.resume, idx)
+        validated = adapter.validate_python(v) if adapter else v
         scratchpad.resume.append(v)
         conf[CONFIG_KEY_SEND]([(RESUME, scratchpad.resume)])
-        return v
+        return validated
     # no resume value found
     raise GraphInterrupt(
         (
             Interrupt.from_ns(
                 value=value,
                 ns=conf[CONFIG_KEY_CHECKPOINT_NS],
+                response_schema=adapter.json_schema() if adapter else response_schema,
             ),
         )
     )

libs/langgraph/tests/test_interruption.py

@@ -1,9 +1,13 @@
+from typing import Any
+
 import pytest
 from langgraph.checkpoint.base import BaseCheckpointSaver
+from pydantic import BaseModel, ValidationError
 from typing_extensions import TypedDict
 
 from langgraph.graph import END, START, StateGraph
-from langgraph.types import Durability
+from langgraph.types import Command, Durability, Interrupt, interrupt
+from tests.any_str import AnyStr
 
 pytestmark = pytest.mark.anyio
 
@@ -90,3 +94,101 @@ async def test_interruption_without_state_updates_async(
     assert (await graph.aget_state(thread)).next == ()
     n_checkpoints = len([c async for c in graph.aget_state_history(thread)])
     assert n_checkpoints == (5 if durability != "exit" else 3)
+
+
+class Decision(BaseModel):
+    approved: bool
+    note: str | None = None
+
+
+class DecisionDict(TypedDict):
+    approved: bool
+
+
+RAW_SCHEMA = {"type": "object", "properties": {"approved": {"type": "boolean"}}}
+
+
+@pytest.mark.parametrize(
+    ("response_schema", "expected_schema", "expected_answer"),
+    [
+        (None, None, {"approved": True, "extra": 1}),
+        (RAW_SCHEMA, RAW_SCHEMA, {"approved": True, "extra": 1}),
+        (Decision, Decision.model_json_schema(), Decision(approved=True)),
+        (
+            DecisionDict,
+            {
+                "properties": {"approved": {"title": "Approved", "type": "boolean"}},
+                "required": ["approved"],
+                "title": "DecisionDict",
+                "type": "object",
+            },
+            {"approved": True},
+        ),
+    ],
+    ids=["none", "raw_dict", "pydantic", "typeddict"],
+)
+def test_interrupt_response_schema(
+    sync_checkpointer: BaseCheckpointSaver,
+    response_schema: Any,
+    expected_schema: dict[str, Any] | None,
+    expected_answer: Any,
+) -> None:
+    class State(TypedDict):
+        answer: Any
+
+    def node(state: State) -> State:
+        return {
+            "answer": interrupt(
+                {"question": "approve?"}, response_schema=response_schema
+            )
+        }
+
+    graph = (
+        StateGraph(State)
+        .add_node("node", node)
+        .add_edge(START, "node")
+        .compile(checkpointer=sync_checkpointer)
+    )
+    config = {"configurable": {"thread_id": "1"}}
+    expected = Interrupt(
+        value={"question": "approve?"}, id=AnyStr(), response_schema=expected_schema
+    )
+
+    assert list(graph.stream({"answer": None}, config)) == [
+        {"__interrupt__": (expected,)}
+    ]
+    assert graph.get_state(config).tasks[0].interrupts == (expected,)
+    assert graph.invoke(Command(resume={"approved": True, "extra": 1}), config) == {
+        "answer": expected_answer
+    }
+
+
+@pytest.mark.parametrize("resume_style", ["null", "map"])
+def test_interrupt_response_schema_rejects_invalid_resume(
+    sync_checkpointer: BaseCheckpointSaver, resume_style: str
+) -> None:
+    class State(TypedDict):
+        answer: Any
+
+    def node(state: State) -> State:
+        return {"answer": interrupt("approve?", response_schema=Decision)}
+
+    graph = (
+        StateGraph(State)
+        .add_node("node", node)
+        .add_edge(START, "node")
+        .compile(checkpointer=sync_checkpointer)
+    )
+    config = {"configurable": {"thread_id": "1"}}
+    graph.invoke({"answer": None}, config)
+    [pending] = graph.get_state(config).tasks[0].interrupts
+
+    def resume(value: dict[str, Any]) -> Command:
+        return Command(resume=value if resume_style == "null" else {pending.id: value})
+
+    with pytest.raises(ValidationError, match="approved"):
+        graph.invoke(resume({"approved": "nope"}), config)
+
+    assert graph.invoke(resume({"approved": False}), config) == {
+        "answer": Decision(approved=False)
+    }

libs/langgraph/tests/test_pregel.py

@@ -5583,6 +5583,7 @@ def test_falsy_return_from_task(sync_checkpointer: BaseCheckpointSaver):
                 "interrupts": [
                     {
                         "id": AnyStr(),
+                        "response_schema": None,
                         "value": "test",
                     },
                 ],
@@ -5627,6 +5628,7 @@ def test_falsy_return_from_task(sync_checkpointer: BaseCheckpointSaver):
                         "interrupts": (
                             {
                                 "id": AnyStr(),
+                                "response_schema": None,
                                 "value": "test",
                             },
                         ),

libs/sdk-py/langgraph_sdk/schema.py

@@ -295,6 +295,8 @@ class Interrupt(TypedDict):
     """The value associated with the interrupt."""
     id: str
     """The ID of the interrupt. Can be used to resume the interrupt."""
+    response_schema: NotRequired[dict[str, Any]]
+    """JSON Schema for the value expected when resuming this interrupt, if the graph provided one."""
 
 
 class Thread(TypedDict):