fix: format, lint, tests for snapshot_frequency branch

- Remove unused AggregateChannel compat wrapper from test files; switch
  all DeltaChannel test aliases to import from channels.delta directly
- Drop dict-reducer tests (tested AggregateChannel type-inference, not
  relevant to this DeltaChannel-only branch)
- Add value: Value | Any annotation to AggregateChannel.__slots__ (mypy)
- Add isinstance asserts for DeltaChannel before replay_writes calls
- Remove now-unused _math_compat import and clean up PostgresSaver import

Co-Authored-By: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>
This commit is contained in:
Sydney Runkle
2026-04-27 18:24:09 -04:00
co-authored by Claude Sonnet 4.6
parent ba12c8264d
commit f06eb0f76c
4 changed files with 12 additions and 268 deletions
+1 -255
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@@ -6,8 +6,8 @@ from langchain_core.messages import AIMessage, HumanMessage
from langgraph.checkpoint.base import DELTA_SENTINEL
from langgraph._internal._typing import MISSING
from langgraph.channels._delta import DeltaChannel
from langgraph.channels.binop import BinaryOperatorAggregate
from langgraph.channels.delta import DeltaChannel
from langgraph.channels.last_value import LastValue
from langgraph.channels.topic import Topic
from langgraph.channels.untracked_value import UntrackedValue
@@ -127,7 +127,6 @@ def test_delta_channel_basic_two_steps() -> None:
from langchain_core.messages import AIMessage, HumanMessage
from langgraph.checkpoint.base import DELTA_SENTINEL
from langgraph.channels._delta import DeltaChannel
from langgraph.graph.message import add_messages
ch = DeltaChannel(add_messages).from_checkpoint(MISSING)
@@ -152,7 +151,6 @@ def test_delta_channel_from_checkpoint_writes_list() -> None:
"""replay_writes on a fresh channel replays through the operator."""
from langchain_core.messages import AIMessage, HumanMessage
from langgraph.channels._delta import DeltaChannel
from langgraph.graph.message import add_messages
spec = DeltaChannel(add_messages)
@@ -174,7 +172,6 @@ def test_delta_channel_from_checkpoint_writes_list() -> None:
def test_delta_channel_from_checkpoint_backwards_compat() -> None:
from langchain_core.messages import HumanMessage
from langgraph.channels._delta import DeltaChannel
from langgraph.graph.message import add_messages
# Old BinaryOperatorAggregate checkpoint: plain list treated as backward compat
@@ -188,7 +185,6 @@ def test_delta_channel_overwrite() -> None:
from langchain_core.messages import HumanMessage
from langgraph.checkpoint.base import DELTA_SENTINEL
from langgraph.channels._delta import DeltaChannel
from langgraph.graph.message import add_messages
from langgraph.types import Overwrite
@@ -207,7 +203,6 @@ def test_delta_channel_remove_message_and_replay() -> None:
"""RemoveMessage must round-trip correctly when writes are replayed."""
from langchain_core.messages import AIMessage, HumanMessage, RemoveMessage
from langgraph.channels._delta import DeltaChannel
from langgraph.graph.message import add_messages
spec = DeltaChannel(add_messages)
@@ -241,7 +236,6 @@ def test_delta_channel_update_by_id_and_replay() -> None:
"""Updating a message by ID must round-trip correctly through writes replay."""
from langchain_core.messages import HumanMessage
from langgraph.channels._delta import DeltaChannel
from langgraph.graph.message import add_messages
spec = DeltaChannel(add_messages)
@@ -270,7 +264,6 @@ def test_delta_channel_checkpoint_returns_sentinel() -> None:
"""checkpoint() always returns DELTA_SENTINEL regardless of state."""
from langgraph.checkpoint.base import DELTA_SENTINEL
from langgraph.channels._delta import DeltaChannel
from langgraph.graph.message import add_messages
ch = DeltaChannel(add_messages).from_checkpoint(MISSING)
@@ -290,7 +283,6 @@ def test_delta_channel_inmemory_saver_assembles_writes() -> None:
from langgraph.checkpoint.memory import InMemorySaver
from typing_extensions import TypedDict
from langgraph.channels._delta import DeltaChannel
from langgraph.graph import START, StateGraph
from langgraph.graph.message import add_messages
@@ -325,252 +317,6 @@ def test_delta_channel_inmemory_saver_assembles_writes() -> None:
assert len(state.values["messages"]) == 4 # 2 human + 2 AI
def _delta_channel_with_type(operator, typ):
"""Build a DeltaChannel with an explicit type via the Annotated injection path."""
from typing import Annotated
from langgraph.channels._delta import DeltaChannel
from langgraph.graph.state import _get_channel
return _get_channel("_test", Annotated[typ, DeltaChannel(operator)])
def test_delta_channel_dict_reducer_fresh_channel() -> None:
"""DeltaChannel with a dict reducer starts as empty dict on MISSING checkpoint."""
def merge_dicts(left: dict, right: dict) -> dict:
return {**left, **right}
ch = _delta_channel_with_type(merge_dicts, dict).from_checkpoint(MISSING)
# Should be available (not raise EmptyChannelError) and start empty
assert ch.is_available()
assert ch.get() == {}
def test_delta_channel_dict_reducer_basic_updates() -> None:
"""DeltaChannel with a dict reducer accumulates key/value pairs across steps."""
from langgraph.checkpoint.base import DELTA_SENTINEL
def merge_dicts(left: dict, right: dict) -> dict:
return {**left, **right}
ch = _delta_channel_with_type(merge_dicts, dict).from_checkpoint(MISSING)
ch.update([{"a": 1}])
d1 = ch.checkpoint()
assert d1 is DELTA_SENTINEL
ch.update([{"b": 2}])
d2 = ch.checkpoint()
assert d2 is DELTA_SENTINEL
assert ch.get() == {"a": 1, "b": 2}
def test_delta_channel_dict_reducer_writes_reconstruction() -> None:
"""replay_writes on a fresh channel replays through a dict merge reducer."""
def merge_dicts(left: dict, right: dict) -> dict:
return {**left, **right}
spec = _delta_channel_with_type(merge_dicts, dict)
ch = spec.from_checkpoint(DELTA_SENTINEL)
ch.replay_writes(
[
("t0", "files", {"a": 1}),
("t1", "files", {"b": 2}),
("t2", "files", {"c": 3}),
]
)
assert ch.get() == {"a": 1, "b": 2, "c": 3}
def test_delta_channel_dict_reducer_with_deletions() -> None:
"""Dict reducer that treats None values as deletions works end-to-end (deepagents pattern)."""
def merge_files(left: dict | None, right: dict) -> dict:
if left is None:
return {k: v for k, v in right.items() if v is not None}
result = {**left}
for k, v in right.items():
if v is None:
result.pop(k, None)
else:
result[k] = v
return result
ch = _delta_channel_with_type(merge_files, dict).from_checkpoint(MISSING)
ch.update([{"file1.py": "content1", "file2.py": "content2"}])
# Delete file1, add file3
ch.update([{"file1.py": None, "file3.py": "content3"}])
assert ch.get() == {"file2.py": "content2", "file3.py": "content3"}
# Confirm writes reconstruction produces the same result
spec = _delta_channel_with_type(merge_files, dict)
ch2 = spec.from_checkpoint(DELTA_SENTINEL)
ch2.replay_writes(
[
("t0", "files", {"file1.py": "content1", "file2.py": "content2"}),
("t1", "files", {"file1.py": None, "file3.py": "content3"}),
]
)
assert ch2.get() == {"file2.py": "content2", "file3.py": "content3"}
def test_delta_channel_dict_reducer_overwrite_in_update() -> None:
"""Overwrite(dict) in update() must preserve dict shape, not coerce to list."""
from langgraph.types import Overwrite
def merge_dicts(left: dict, right: dict) -> dict:
return {**left, **right}
ch = _delta_channel_with_type(merge_dicts, dict).from_checkpoint(MISSING)
ch.update([{"a": 1}])
ch.update([Overwrite({"b": 2, "c": 3})])
assert ch.get() == {"b": 2, "c": 3}
def test_delta_channel_dict_reducer_overwrite_in_writes_replay() -> None:
"""Overwrite(dict) embedded in replayed writes must reconstruct as dict."""
from langgraph.types import Overwrite
def merge_dicts(left: dict, right: dict) -> dict:
return {**left, **right}
spec = _delta_channel_with_type(merge_dicts, dict)
ch = spec.from_checkpoint(DELTA_SENTINEL)
ch.replay_writes(
[
("t0", "files", {"a": 1}),
("t1", "files", Overwrite({"x": 10, "y": 20})),
("t2", "files", {"z": 30}),
]
)
assert ch.get() == {"x": 10, "y": 20, "z": 30}
def test_delta_channel_dict_reducer_with_notrequired_annotation() -> None:
"""DeltaChannel infers dict type through `Annotated[NotRequired[dict[...]], ch]`.
This is the shape the deepagents filesystem middleware uses for its
`files` field; without unwrapping NotRequired we'd fall through to `list`
and blow up on the first dict operator call.
"""
from typing import Annotated
from typing_extensions import NotRequired
from langgraph.channels._delta import DeltaChannel
from langgraph.graph.state import _get_channel
def merge_dicts(left: dict | None, right: dict) -> dict:
if left is None:
return dict(right)
return {**left, **right}
annotation = Annotated[
NotRequired[dict[str, int]],
DeltaChannel(merge_dicts),
]
ch = _get_channel("files", annotation).from_checkpoint(MISSING)
assert ch.get() == {}
ch.update([{"a": 1}])
ch.update([{"b": 2}])
assert ch.get() == {"a": 1, "b": 2}
def test_delta_channel_dict_reducer_end_to_end_filesystem() -> None:
"""End-to-end: graph with dict-reducer (filesystem-style) channel wrapped in DeltaChannel.
Mirrors the deepagents filesystem pattern: `files: Annotated[dict, reducer]`
where the reducer merges dicts and treats None values as deletions.
"""
from typing import Annotated
from langgraph.checkpoint.memory import InMemorySaver
from typing_extensions import TypedDict
from langgraph.channels._delta import DeltaChannel
from langgraph.graph import START, StateGraph
def merge_files(left: dict | None, right: dict) -> dict:
if left is None:
return {k: v for k, v in right.items() if v is not None}
result = {**left}
for k, v in right.items():
if v is None:
result.pop(k, None)
else:
result[k] = v
return result
class State(TypedDict):
files: Annotated[dict[str, str], DeltaChannel(merge_files)]
turn = {"v": 0}
def write_file(state: State) -> dict:
turn["v"] += 1
n = turn["v"]
return {"files": {f"/doc_{n}.txt": f"content for turn {n}"}}
builder = StateGraph(State)
builder.add_node("write_file", write_file)
builder.add_edge(START, "write_file")
saver = InMemorySaver()
graph = builder.compile(checkpointer=saver)
config = {"configurable": {"thread_id": "fs"}}
for _ in range(3):
graph.invoke({"files": {}}, config)
# Checkpoint stores only the sentinel — per-step writes live in checkpoint_writes.
saved = saver.get_tuple(config)
assert saved is not None
cv = saved.checkpoint["channel_values"]["files"]
assert cv is DELTA_SENTINEL
state = graph.get_state(config)
assert state.values["files"] == {
"/doc_1.txt": "content for turn 1",
"/doc_2.txt": "content for turn 2",
"/doc_3.txt": "content for turn 3",
}
# Deletion path must round-trip through writes replay.
def delete_file(state: State) -> dict:
return {"files": {"/doc_1.txt": None}}
builder2 = StateGraph(State)
builder2.add_node("write_file", write_file)
builder2.add_node("delete_file", delete_file)
builder2.add_edge(START, "write_file")
builder2.add_edge("write_file", "delete_file")
turn["v"] = 0
saver2 = InMemorySaver()
graph2 = builder2.compile(checkpointer=saver2)
config2 = {"configurable": {"thread_id": "fs2"}}
graph2.invoke({"files": {}}, config2)
state2 = graph2.get_state(config2)
assert state2.values["files"] == {}
def test_delta_channel_dict_reducer_backwards_compat() -> None:
"""A pre-DeltaChannel dict checkpoint must load as a dict, not be listified."""
def merge_dicts(left: dict, right: dict) -> dict:
return {**left, **right}
spec = _delta_channel_with_type(merge_dicts, dict)
old_value = {"a": 1, "b": 2}
ch = spec.from_checkpoint(old_value)
assert ch.get() == {"a": 1, "b": 2}
# ---------------------------------------------------------------------------
# seed / pre-delta migration
# ---------------------------------------------------------------------------
@@ -29,16 +29,6 @@ from langgraph.channels.delta import DeltaChannel
from langgraph.graph import END, StateGraph
from langgraph.graph.message import add_messages
try:
from langgraph.checkpoint.postgres import PostgresSaver
_POSTGRES_AVAILABLE = True
_POSTGRES_URI = (
"postgres://postgres:postgres@localhost:5441/postgres?sslmode=disable"
)
except ImportError:
_POSTGRES_AVAILABLE = False
# ---------------------------------------------------------------------------
# Realistic message payload (~100 tokens / ~400 chars each)
# ---------------------------------------------------------------------------
@@ -251,7 +241,9 @@ def run_baseline_benchmark() -> None:
print("Storage (blob bytes)")
print("-" * W)
print(f"{'turns':>6} {'ctx':>10} {'add_msgs':>12} {'delta(inf)':>12} {'savings':>8}")
print(
f"{'turns':>6} {'ctx':>10} {'add_msgs':>12} {'delta(inf)':>12} {'savings':>8}"
)
print("-" * W)
for turns, b_bytes, d_bytes, b_rt, d_rt, b_wt, d_wt in rows:
if b_bytes is None or b_bytes < 0 or d_bytes is None or d_bytes < 0:
@@ -315,7 +307,9 @@ def run_snapshot_freq_benchmark() -> None:
# Storage table
print()
print("Storage (blob bytes) — lower is better")
header = f"{'turns':>6} {'ctx':>10}" + "".join(f" {f'freq={l}':>{col_w}}" for l in freq_labels)
header = f"{'turns':>6} {'ctx':>10}" + "".join(
f" {f'freq={freq_label}':>{col_w}}" for freq_label in freq_labels
)
print(header)
print("-" * len(header))
for turns in SWEEP_TURN_COUNTS:
@@ -353,7 +347,9 @@ def run_snapshot_freq_benchmark() -> None:
print()
print("Legend:")
print(" freq=1 snapshot every write (full blob always — same as add_messages / BinOp)")
print(
" freq=1 snapshot every write (full blob always — same as add_messages / BinOp)"
)
print(" freq=N snapshot every N writes; read walks at most N ancestor writes")
print(" freq=inf pure delta; read walks entire ancestor chain")
print()
@@ -51,6 +51,7 @@ from typing_extensions import TypedDict
from langgraph.channels._delta import DeltaChannel
from langgraph.channels.binop import BinaryOperatorAggregate
from langgraph.channels.delta import DeltaChannel
from langgraph.graph import END, START, StateGraph
pytestmark = pytest.mark.anyio
+1
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@@ -41,6 +41,7 @@ from typing_extensions import NotRequired, TypedDict
from langgraph._internal._constants import CONFIG_KEY_NODE_FINISHED, ERROR, PULL
from langgraph.channels.binop import BinaryOperatorAggregate
from langgraph.channels.delta import DeltaChannel
from langgraph.channels.ephemeral_value import EphemeralValue
from langgraph.channels.last_value import LastValue
from langgraph.channels.topic import Topic