Merge pull request #2430 from langchain-ai/nc/15nov/command-subgraph

Handle interrupt/resume for subgraphs

libs/langgraph/langgraph/pregel/algo.py

@@ -595,7 +595,7 @@ def prepare_single_task(
                                     for tid, c, v in pending_writes
                                     if tid in (NULL_TASK_ID, task_id) and c == RESUME
                                 ),
-                                MISSING,
+                                configurable.get(CONFIG_KEY_RESUME_VALUE, MISSING),
                             ),
                         },
                     ),
@@ -720,7 +720,7 @@ def prepare_single_task(
                                         if tid in (NULL_TASK_ID, task_id)
                                         and c == RESUME
                                     ),
-                                    MISSING,
+                                    configurable.get(CONFIG_KEY_RESUME_VALUE, MISSING),
                                 ),
                             },
                         ),

libs/langgraph/langgraph/pregel/remote.py

@@ -1,3 +1,4 @@
+from dataclasses import asdict
 from typing import (
     Any,
     AsyncIterator,
@@ -27,6 +28,7 @@
     get_sync_client,
 )
 from langgraph_sdk.schema import Checkpoint, ThreadState
+from langgraph_sdk.schema import Command as CommandSDK
 from langgraph_sdk.schema import StreamMode as StreamModeSDK
 from typing_extensions import Self
 
@@ -41,7 +43,7 @@
 from langgraph.errors import GraphInterrupt
 from langgraph.pregel.protocol import PregelProtocol
 from langgraph.pregel.types import All, PregelTask, StateSnapshot, StreamMode
-from langgraph.types import Interrupt, StreamProtocol
+from langgraph.types import Command, Interrupt, StreamProtocol
 from langgraph.utils.config import merge_configs
 
 
@@ -597,11 +599,17 @@ def stream(
         stream_modes, requested, req_single, stream = self._get_stream_modes(
             stream_mode, config
         )
+        if isinstance(input, Command):
+            command: Optional[CommandSDK] = cast(CommandSDK, asdict(input))
+            input = None
+        else:
+            command = None
 
         for chunk in sync_client.runs.stream(
             thread_id=sanitized_config["configurable"].get("thread_id"),
             assistant_id=self.name,
             input=input,
+            command=command,
             config=sanitized_config,
             stream_mode=stream_modes,
             interrupt_before=interrupt_before,
@@ -680,11 +688,17 @@ async def astream(
         stream_modes, requested, req_single, stream = self._get_stream_modes(
             stream_mode, config
         )
+        if isinstance(input, Command):
+            command: Optional[CommandSDK] = cast(CommandSDK, asdict(input))
+            input = None
+        else:
+            command = None
 
         async for chunk in client.runs.stream(
             thread_id=sanitized_config["configurable"].get("thread_id"),
             assistant_id=self.name,
             input=input,
+            command=command,
             config=sanitized_config,
             stream_mode=stream_modes,
             interrupt_before=interrupt_before,

libs/langgraph/tests/test_pregel.py

@@ -8728,6 +8728,176 @@ def start(state: State) -> list[Union[Send, str]]:
     )
 
 
+@pytest.mark.parametrize("checkpointer_name", ALL_CHECKPOINTERS_SYNC)
+def test_dynamic_interrupt_subgraph(
+    request: pytest.FixtureRequest, checkpointer_name: str
+) -> None:
+    checkpointer = request.getfixturevalue(f"checkpointer_{checkpointer_name}")
+
+    class SubgraphState(TypedDict):
+        my_key: str
+        market: str
+
+    tool_two_node_count = 0
+
+    def tool_two_node(s: SubgraphState) -> SubgraphState:
+        nonlocal tool_two_node_count
+        tool_two_node_count += 1
+        if s["market"] == "DE":
+            answer = interrupt("Just because...")
+        else:
+            answer = " all good"
+        return {"my_key": answer}
+
+    subgraph = StateGraph(SubgraphState)
+    subgraph.add_node("do", tool_two_node, retry=RetryPolicy())
+    subgraph.add_edge(START, "do")
+
+    class State(TypedDict):
+        my_key: Annotated[str, operator.add]
+        market: str
+
+    tool_two_graph = StateGraph(State)
+    tool_two_graph.add_node("tool_two", subgraph.compile())
+    tool_two_graph.add_edge(START, "tool_two")
+    tool_two = tool_two_graph.compile()
+
+    tracer = FakeTracer()
+    assert tool_two.invoke(
+        {"my_key": "value", "market": "DE"}, {"callbacks": [tracer]}
+    ) == {
+        "my_key": "value",
+        "market": "DE",
+    }
+    assert tool_two_node_count == 1, "interrupts aren't retried"
+    assert len(tracer.runs) == 1
+    run = tracer.runs[0]
+    assert run.end_time is not None
+    assert run.error is None
+    assert run.outputs == {"market": "DE", "my_key": "value"}
+
+    assert tool_two.invoke({"my_key": "value", "market": "US"}) == {
+        "my_key": "value all good",
+        "market": "US",
+    }
+
+    tool_two = tool_two_graph.compile(checkpointer=checkpointer)
+
+    # missing thread_id
+    with pytest.raises(ValueError, match="thread_id"):
+        tool_two.invoke({"my_key": "value", "market": "DE"})
+
+    # flow: interrupt -> resume with answer
+    thread2 = {"configurable": {"thread_id": "2"}}
+    # stop when about to enter node
+    assert [
+        c for c in tool_two.stream({"my_key": "value ⛰️", "market": "DE"}, thread2)
+    ] == [
+        {
+            "__interrupt__": (
+                Interrupt(
+                    value="Just because...",
+                    resumable=True,
+                    ns=[AnyStr("tool_two:"), AnyStr("do:")],
+                ),
+            )
+        },
+    ]
+    # resume with answer
+    assert [c for c in tool_two.stream(Command(resume=" my answer"), thread2)] == [
+        {"tool_two": {"my_key": " my answer", "market": "DE"}},
+    ]
+
+    # flow: interrupt -> clear tasks
+    thread1 = {"configurable": {"thread_id": "1"}}
+    # stop when about to enter node
+    assert tool_two.invoke({"my_key": "value ⛰️", "market": "DE"}, thread1) == {
+        "my_key": "value ⛰️",
+        "market": "DE",
+    }
+    assert [
+        c.metadata
+        for c in tool_two.checkpointer.list(
+            {"configurable": {"thread_id": "1", "checkpoint_ns": ""}}
+        )
+    ] == [
+        {
+            "parents": {},
+            "source": "loop",
+            "step": 0,
+            "writes": None,
+            "thread_id": "1",
+        },
+        {
+            "parents": {},
+            "source": "input",
+            "step": -1,
+            "writes": {"__start__": {"my_key": "value ⛰️", "market": "DE"}},
+            "thread_id": "1",
+        },
+    ]
+    assert tool_two.get_state(thread1) == StateSnapshot(
+        values={"my_key": "value ⛰️", "market": "DE"},
+        next=("tool_two",),
+        tasks=(
+            PregelTask(
+                AnyStr(),
+                "tool_two",
+                (PULL, "tool_two"),
+                interrupts=(
+                    Interrupt(
+                        value="Just because...",
+                        resumable=True,
+                        ns=[AnyStr("tool_two:"), AnyStr("do:")],
+                    ),
+                ),
+                state={
+                    "configurable": {
+                        "thread_id": "1",
+                        "checkpoint_ns": AnyStr("tool_two:"),
+                    }
+                },
+            ),
+        ),
+        config=tool_two.checkpointer.get_tuple(thread1).config,
+        created_at=tool_two.checkpointer.get_tuple(thread1).checkpoint["ts"],
+        metadata={
+            "parents": {},
+            "source": "loop",
+            "step": 0,
+            "writes": None,
+            "thread_id": "1",
+        },
+        parent_config=[
+            *tool_two.checkpointer.list(
+                {"configurable": {"thread_id": "1", "checkpoint_ns": ""}}, limit=2
+            )
+        ][-1].config,
+    )
+    # clear the interrupt and next tasks
+    tool_two.update_state(thread1, None, as_node=END)
+    # interrupt and next tasks are cleared
+    assert tool_two.get_state(thread1) == StateSnapshot(
+        values={"my_key": "value ⛰️", "market": "DE"},
+        next=(),
+        tasks=(),
+        config=tool_two.checkpointer.get_tuple(thread1).config,
+        created_at=tool_two.checkpointer.get_tuple(thread1).checkpoint["ts"],
+        metadata={
+            "parents": {},
+            "source": "update",
+            "step": 1,
+            "writes": {},
+            "thread_id": "1",
+        },
+        parent_config=[
+            *tool_two.checkpointer.list(
+                {"configurable": {"thread_id": "1", "checkpoint_ns": ""}}, limit=2
+            )
+        ][-1].config,
+    )
+
+
 @pytest.mark.parametrize("checkpointer_name", ALL_CHECKPOINTERS_SYNC)
 def test_start_branch_then(
     snapshot: SnapshotAssertion, request: pytest.FixtureRequest, checkpointer_name: str
@@ -14471,3 +14641,35 @@ class CustomParentState(TypedDict):
         },
         tasks=(),
     )
+
+
+@pytest.mark.parametrize("checkpointer_name", ALL_CHECKPOINTERS_SYNC)
+def test_interrupt_subgraph(request: pytest.FixtureRequest, checkpointer_name: str):
+    checkpointer = request.getfixturevalue(f"checkpointer_{checkpointer_name}")
+
+    class State(TypedDict):
+        baz: str
+
+    def foo(state):
+        return {"baz": "foo"}
+
+    def bar(state):
+        value = interrupt("Please provide baz value:")
+        return {"baz": value}
+
+    child_builder = StateGraph(State)
+    child_builder.add_node(bar)
+    child_builder.add_edge(START, "bar")
+
+    builder = StateGraph(State)
+    builder.add_node(foo)
+    builder.add_node("bar", child_builder.compile())
+    builder.add_edge(START, "foo")
+    builder.add_edge("foo", "bar")
+    graph = builder.compile(checkpointer=checkpointer)
+
+    thread1 = {"configurable": {"thread_id": "1"}}
+    # First run, interrupted at bar
+    assert graph.invoke({"baz": ""}, thread1)
+    # Resume with answer
+    assert graph.invoke(Command(resume="bar"), thread1)