perf(checkpoint): linearize message write merging (#4421)

* perf(checkpoint): linearize message write merging

* test(checkpoint): address message reducer review
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Vanzeren 2026-07-25 21:19:24 +08:00 committed by GitHub
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3 changed files with 290 additions and 7 deletions

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@ -291,6 +291,15 @@ tool graph or subagent executor during state/schema imports.
**ThreadState** (`packages/harness/deerflow/agents/thread_state.py`):
- Extends `AgentState` with: `sandbox`, `thread_data`, `title`, `artifacts`, `todos`, `uploaded_files`, `viewed_images`, `goal`, `promoted`, `delegations`, `skill_context`, `summary_text`
- Uses custom reducers: `merge_artifacts` (deduplicate), `merge_viewed_images` (merge/clear), `merge_goal` (preserve the active goal across ordinary state updates unless the goal writer replaces it), `merge_promoted` (catalog-hash-scoped deferred tool promotions), `merge_delegations` (append task delegation entries, same id latest wins, terminal status never downgraded, capped to the most recent entries), and `merge_skill_context` (dedupe active-skill references by path, keep the most recently read entries; entries store a name/path/description reference, not the SKILL.md body). `summary_text` is a LastValue channel updated by summarization and projected into model requests as durable context data instead of being stored as a `messages` item.
- Delta-mode `merge_message_writes` normalizes the current message state once,
then folds normalized writes in order with message-ID position indexes and
deferred tombstone compaction. It preserves public `add_messages` behavior,
including duplicate IDs, replacement position, removal errors,
`REMOVE_ALL_MESSAGES`, null-write errors, and missing-ID allocation order,
without rescanning the accumulated state for every write. Keep this
full-parity contract covered by differential tests: LangGraph's private
`_messages_delta_reducer` is also linear, but intentionally omits some of
those public `add_messages` semantics and cannot be substituted directly.
**Runtime Configuration** (via `config.configurable`):
- `thinking_enabled` - Enable model's extended thinking

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@ -1,12 +1,19 @@
import copy
import uuid
from collections.abc import Mapping, Sequence
from functools import cache
from typing import Annotated, Any, NotRequired, TypedDict, get_type_hints
from typing import Annotated, Any, NotRequired, TypedDict, cast, get_type_hints
from langchain.agents import AgentState
from langchain_core.messages import AnyMessage
from langchain_core.messages import (
AnyMessage,
BaseMessageChunk,
RemoveMessage,
convert_to_messages,
message_chunk_to_message,
)
from langgraph.channels import DeltaChannel
from langgraph.graph.message import add_messages
from langgraph.graph.message import REMOVE_ALL_MESSAGES
import deerflow.checkpoint_patches as _checkpoint_patches # noqa: F401 - import-time saver fixes
from deerflow.agents.goal_state import GoalState
@ -258,11 +265,91 @@ class ThreadState(AgentState):
summary_text: NotRequired[str | None]
def _normalize_messages(value: Any) -> list[AnyMessage]:
values = value if isinstance(value, list) else [value]
messages = [message_chunk_to_message(cast(BaseMessageChunk, message)) for message in convert_to_messages(values)]
for message in messages:
if message.id is None:
message.id = str(uuid.uuid4())
return messages
def _index_messages(
messages: list[AnyMessage | None],
) -> tuple[dict[str, int], dict[str, list[int]]]:
latest_position: dict[str, int] = {}
positions_by_id: dict[str, list[int]] = {}
for position, message in enumerate(messages):
if message is None:
continue
message_id = cast(str, message.id)
latest_position[message_id] = position
positions_by_id.setdefault(message_id, []).append(position)
return latest_position, positions_by_id
def _raise_null_write(has_messages: bool) -> None:
# ``add_messages(left, None)`` reports only ``left`` when the accumulated
# message list is non-empty; with an empty list, it reports only ``right``.
received = "left" if has_messages else "right"
raise ValueError(f"Must specify non-null arguments for both 'left' and 'right'. Only received: '{received}'.")
def merge_message_writes(state: list[AnyMessage], writes: Sequence[Any]) -> list[AnyMessage]:
result = list(state)
"""Fold DeltaChannel writes with ``add_messages`` semantics in linear time.
LangGraph's private ``_messages_delta_reducer`` is also linear, but does
not preserve the public reducer's full coercion, ID, removal, and
``REMOVE_ALL_MESSAGES`` behavior.
"""
if not writes:
return list(state)
if writes[0] is None:
_raise_null_write(bool(state))
messages: list[AnyMessage | None] = _normalize_messages(state)
latest_position, positions_by_id = _index_messages(messages)
for write in writes:
result = list(add_messages(result, write))
return result
if write is None:
_raise_null_write(bool(latest_position))
normalized_write = _normalize_messages(write)
remove_all_idx = None
for position, message in enumerate(normalized_write):
if isinstance(message, RemoveMessage) and message.id == REMOVE_ALL_MESSAGES:
remove_all_idx = position
if remove_all_idx is not None:
messages = list(normalized_write[remove_all_idx + 1 :])
latest_position, positions_by_id = _index_messages(messages)
continue
ids_to_remove: set[str] = set()
for message in normalized_write:
message_id = cast(str, message.id)
existing_position = latest_position.get(message_id)
if existing_position is not None:
if isinstance(message, RemoveMessage):
ids_to_remove.add(message_id)
else:
ids_to_remove.discard(message_id)
messages[existing_position] = message
continue
if isinstance(message, RemoveMessage):
raise ValueError(f"Attempting to delete a message with an ID that doesn't exist ('{message_id}')")
position = len(messages)
messages.append(message)
latest_position[message_id] = position
positions_by_id[message_id] = [position]
for message_id in ids_to_remove:
for position in positions_by_id.pop(message_id):
messages[position] = None
del latest_position[message_id]
return [message for message in messages if message is not None]
DELTA_MESSAGES_FIELD = Annotated[

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@ -1,3 +1,4 @@
import copy
from typing import get_type_hints
import pytest
@ -6,7 +7,7 @@ from hypothesis import strategies as st
from langchain.agents import AgentState, create_agent
from langchain.agents.middleware import AgentMiddleware
from langchain_core.language_models.fake_chat_models import FakeMessagesListChatModel
from langchain_core.messages import AIMessage, AIMessageChunk, HumanMessage, RemoveMessage
from langchain_core.messages import AIMessage, AIMessageChunk, HumanMessage, RemoveMessage, ToolMessageChunk
from langgraph.channels import DeltaChannel
from langgraph.checkpoint.memory import InMemorySaver
from langgraph.graph import StateGraph
@ -29,6 +30,57 @@ def _fold(state: list, writes: list) -> list:
return result
def _outcome(call):
try:
return ("result", call())
except Exception as exc:
return ("error", type(exc), str(exc))
@st.composite
def _message_merge_cases(draw):
message_ids = ["a", "b", "c", "missing"]
state_ids = draw(st.lists(st.sampled_from(message_ids[:-1]), max_size=6))
state = [
{
"role": draw(st.sampled_from(["user", "assistant"])),
"content": f"state-{index}",
"id": message_id,
}
for index, message_id in enumerate(state_ids)
]
operation = st.one_of(
st.tuples(
st.just("message"),
st.sampled_from(message_ids),
st.sampled_from(["user", "assistant", "ai_chunk", "tool_chunk"]),
st.text(max_size=12),
),
st.tuples(
st.just("remove"),
st.sampled_from([*message_ids, REMOVE_ALL_MESSAGES]),
st.none(),
st.none(),
),
)
raw_writes = draw(st.lists(st.lists(operation, max_size=6), max_size=8))
writes = []
for raw_write in raw_writes:
write = []
for kind, message_id, role, content in raw_write:
if kind == "remove":
write.append(RemoveMessage(id=message_id))
elif role == "ai_chunk":
write.append(AIMessageChunk(id=message_id, content=content))
elif role == "tool_chunk":
write.append(ToolMessageChunk(id=message_id, content=content, tool_call_id=f"call-{message_id}"))
else:
write.append({"role": role, "content": content, "id": message_id})
writes.append(write)
return state, writes
@pytest.mark.parametrize(
"writes",
[
@ -45,6 +97,16 @@ def test_merge_message_writes_matches_sequential_add_messages(writes: list) -> N
assert merge_message_writes([], writes) == _fold([], writes)
@given(case=_message_merge_cases())
def test_merge_message_writes_randomized_differential(case: tuple[list, list]) -> None:
state, writes = case
expected = _outcome(lambda: _fold(copy.deepcopy(state), copy.deepcopy(writes)))
actual = _outcome(lambda: merge_message_writes(copy.deepcopy(state), copy.deepcopy(writes)))
assert actual == expected
@given(split=st.integers(min_value=0, max_value=3))
def test_merge_message_writes_is_batching_invariant(split: int) -> None:
state = [HumanMessage(id="h0", content="seed")]
@ -58,6 +120,20 @@ def test_merge_message_writes_is_batching_invariant(split: int) -> None:
assert merge_message_writes(merge_message_writes(state, xs), ys) == merge_message_writes(state, writes)
@given(case=_message_merge_cases(), data=st.data())
def test_merge_message_writes_randomized_batching_invariance(case: tuple[list, list], data: st.DataObject) -> None:
state, writes = case
split = data.draw(st.integers(min_value=0, max_value=len(writes)))
expected = _outcome(lambda: merge_message_writes(copy.deepcopy(state), copy.deepcopy(writes)))
def batched():
intermediate = merge_message_writes(copy.deepcopy(state), copy.deepcopy(writes[:split]))
return merge_message_writes(intermediate, copy.deepcopy(writes[split:]))
assert _outcome(batched) == expected
def test_merge_message_writes_matches_unknown_remove_error() -> None:
writes = [[RemoveMessage(id="missing")]]
@ -69,6 +145,117 @@ def test_merge_message_writes_matches_unknown_remove_error() -> None:
assert str(actual.value) == str(expected.value)
@pytest.mark.parametrize(
("state", "writes"),
[
(
[HumanMessage(id="duplicate", content="first"), HumanMessage(id="duplicate", content="second")],
[[AIMessage(id="duplicate", content="replacement")]],
),
(
[HumanMessage(id="duplicate", content="first"), HumanMessage(id="duplicate", content="second")],
[[RemoveMessage(id="duplicate")]],
),
(
[HumanMessage(id="same", content="old")],
[[RemoveMessage(id="same"), AIMessage(id="same", content="same-write replacement")]],
),
(
[HumanMessage(id="same", content="old")],
[[RemoveMessage(id="same")], [AIMessage(id="same", content="later-write append")]],
),
(
[HumanMessage(id="seed", content="old")],
[
[
RemoveMessage(id="unknown-but-ignored"),
RemoveMessage(id=REMOVE_ALL_MESSAGES),
RemoveMessage(id="suffix-is-returned-verbatim"),
]
],
),
],
ids=[
"duplicate-id-replacement",
"duplicate-id-removal",
"same-write-remove-then-replace",
"cross-write-remove-then-append",
"remove-all-short-circuit",
],
)
def test_merge_message_writes_preserves_add_messages_edge_semantics(state: list, writes: list) -> None:
assert merge_message_writes(copy.deepcopy(state), copy.deepcopy(writes)) == _fold(copy.deepcopy(state), copy.deepcopy(writes))
@pytest.mark.parametrize(
("state", "writes"),
[
([], [None]),
([HumanMessage(id="seed", content="seed")], [None]),
([], [[HumanMessage(id="added", content="added")], None]),
(
[HumanMessage(id="removed", content="removed")],
[[RemoveMessage(id="removed")], None],
),
],
)
def test_merge_message_writes_preserves_null_write_errors(state: list, writes: list) -> None:
expected = _outcome(lambda: _fold(copy.deepcopy(state), copy.deepcopy(writes)))
actual = _outcome(lambda: merge_message_writes(copy.deepcopy(state), copy.deepcopy(writes)))
assert actual == expected
def test_merge_message_writes_preserves_missing_id_allocation_order(monkeypatch: pytest.MonkeyPatch) -> None:
state = [HumanMessage(content="state")]
writes = [
[AIMessage(content="first"), HumanMessage(content="second")],
[AIMessage(content="third")],
]
expected_ids = iter(["state-id", "first-id", "second-id", "third-id"])
monkeypatch.setattr("langgraph.graph.message.uuid.uuid4", lambda: next(expected_ids))
expected = _fold(copy.deepcopy(state), copy.deepcopy(writes))
actual_ids = iter(["state-id", "first-id", "second-id", "third-id"])
monkeypatch.setattr("langgraph.graph.message.uuid.uuid4", lambda: next(actual_ids))
actual = merge_message_writes(copy.deepcopy(state), copy.deepcopy(writes))
assert actual == expected
def test_merge_message_writes_normalizes_state_and_each_write_once(monkeypatch: pytest.MonkeyPatch) -> None:
import deerflow.agents.thread_state as thread_state
state = [HumanMessage(id="state", content="state")]
writes = [
[AIMessage(id="first", content="first")],
[AIMessage(id="second", content="second")],
[AIMessage(id="third", content="third")],
]
original = thread_state.convert_to_messages
normalized_inputs = []
def record_conversion(messages):
normalized_inputs.append(messages)
return original(messages)
monkeypatch.setattr(thread_state, "convert_to_messages", record_conversion)
merge_message_writes(state, writes)
assert normalized_inputs == [state, *writes]
def test_merge_message_writes_empty_batch_does_not_assign_state_ids() -> None:
state = [HumanMessage(content="unchanged")]
result = merge_message_writes(state, [])
assert result == state
assert state[0].id is None
@pytest.mark.parametrize(
"write",
[