fix(lint): remove redundant cast flagged by mypy

chore: apply ruff format/lint fixes
fix(message): full add_messages parity for _messages_delta_reducer
2026-10-14 12:15:25 +02:00 · 2026-05-06 15:08:37 -04:00 · 2026-05-06 15:03:13 -04:00 · 2026-05-06 14:59:12 -04:00 · 2026-05-06 14:42:36 -04:00
71 changed files with 980 additions and 3822 deletions
@@ -58,18 +58,14 @@ jobs:
          } >> "$GITHUB_OUTPUT"
      - name: Annotation
        uses: actions/github-script@v9
-        env:
-          CHANGED_FILES: ${{ steps.files.outputs.added_modified_renamed }}
-          BENCHMARK_OUTPUT: ${{ steps.benchmark.outputs.OUTPUT }}
-          COMPARE_OUTPUT: ${{ steps.compare.outputs.OUTPUT }}
        with:
          script: |
-            const file = JSON.parse(process.env.CHANGED_FILES || "[]")[0]
-            core.notice(process.env.BENCHMARK_OUTPUT || "", {
+            const file = JSON.parse(`${{ steps.files.outputs.added_modified_renamed }}`)[0]
+            core.notice(`${{ steps.benchmark.outputs.OUTPUT }}`, {
              title: 'Benchmark results',
              file,
            })
-            core.notice(process.env.COMPARE_OUTPUT || "", {
+            core.notice(`${{ steps.compare.outputs.OUTPUT }}`, {
              title: 'Comparison against main',
              file,
            })
@@ -32,7 +32,6 @@ jobs:
        with:
          python-version: ${{ env.PYTHON_VERSION }}
          cache-suffix: "release"
-          enable-cache: false
          working-directory: ${{ inputs.working-directory }}

      # We want to keep this build stage *separate* from the release stage,
@@ -269,7 +268,6 @@ jobs:
        with:
          python-version: ${{ env.PYTHON_VERSION }}
          cache-suffix: "release"
-          enable-cache: false
          working-directory: ${{ inputs.working-directory }}

      - uses: actions/download-artifact@v8
@@ -311,7 +309,6 @@ jobs:
        with:
          python-version: ${{ env.PYTHON_VERSION }}
          cache-suffix: "release"
-          enable-cache: false
          working-directory: ${{ inputs.working-directory }}

      - uses: actions/download-artifact@v8
@@ -63,7 +63,6 @@ The suite tests **base** capabilities (required) and **extended** capabilities (
 | `delete_for_runs` | no | `adelete_for_runs` |
 | `copy_thread` | no | `acopy_thread` |
 | `prune` | no | `aprune` |
-| `delta_channel_history` | no | `aget_delta_channel_history` |

 Extended capabilities are detected by checking whether the method is overridden from `BaseCheckpointSaver`. If not overridden, those tests are skipped.

@@ -23,7 +23,6 @@ class Capability(str, Enum):
    DELETE_FOR_RUNS = "delete_for_runs"
    COPY_THREAD = "copy_thread"
    PRUNE = "prune"
-    DELTA_CHANNEL_HISTORY = "delta_channel_history"


 # Capabilities that every checkpointer must support.
@@ -43,7 +42,6 @@ EXTENDED_CAPABILITIES = frozenset(
        Capability.DELETE_FOR_RUNS,
        Capability.COPY_THREAD,
        Capability.PRUNE,
-        Capability.DELTA_CHANNEL_HISTORY,
    }
 )

@@ -59,7 +57,6 @@ _CAPABILITY_METHOD_MAP: dict[Capability, str] = {
    Capability.DELETE_FOR_RUNS: "adelete_for_runs",
    Capability.COPY_THREAD: "acopy_thread",
    Capability.PRUNE: "aprune",
-    Capability.DELTA_CHANNEL_HISTORY: "aget_delta_channel_history",
 }


@@ -9,9 +9,6 @@ from langgraph.checkpoint.conformance.spec.test_delete_for_runs import (
 from langgraph.checkpoint.conformance.spec.test_delete_thread import (
    run_delete_thread_tests,
 )
-from langgraph.checkpoint.conformance.spec.test_delta_channel_history import (
-    run_delta_channel_history_tests,
-)
 from langgraph.checkpoint.conformance.spec.test_get_tuple import run_get_tuple_tests
 from langgraph.checkpoint.conformance.spec.test_list import run_list_tests
 from langgraph.checkpoint.conformance.spec.test_prune import run_prune_tests
@@ -27,5 +24,4 @@ __all__ = [
    "run_delete_for_runs_tests",
    "run_copy_thread_tests",
    "run_prune_tests",
-    "run_delta_channel_history_tests",
 ]
@@ -1,99 +0,0 @@
-"""Shared fixtures for delta-channel conformance tests.
-
-Builds a parent chain with `_DeltaSnapshot` blobs at known positions via
-direct `aput` / `aput_writes` calls. No langgraph or Pregel dependency.
-"""
-
-from __future__ import annotations
-
-from collections.abc import Sequence
-from typing import Any
-from uuid import uuid4
-
-from langchain_core.runnables import RunnableConfig
-from langgraph.checkpoint.base import BaseCheckpointSaver, Checkpoint
-from langgraph.checkpoint.base.id import uuid6
-
-from langgraph.checkpoint.conformance.test_utils import generate_metadata
-
-
-async def build_delta_chain(
-    saver: BaseCheckpointSaver,
-    *,
-    thread_id: str | None = None,
-    checkpoint_ns: str = "",
-    channel: str = "messages",
-    snapshots_at_steps: Sequence[int] = (0,),
-    total_steps: int = 6,
-    write_value_fn: Any | None = None,
-) -> list[RunnableConfig]:
-    """Build a parent chain with `_DeltaSnapshot` at known positions.
-
-    Args:
-        saver: Checkpointer instance.
-        thread_id: Defaults to a random UUID.
-        checkpoint_ns: Namespace (default root).
-        channel: Channel name used for snapshots and writes.
-        snapshots_at_steps: Steps at which a `_DeltaSnapshot` blob is stored
-            in `channel_values[channel]`. Step 0 is the oldest checkpoint.
-        total_steps: Number of checkpoints in the chain.
-        write_value_fn: Callable(step) -> write value. Defaults to step index.
-
-    Returns:
-        List of stored configs (oldest first), one per step.
-    """
-    if write_value_fn is None:
-
-        def write_value_fn(step: int) -> Any:
-            return step
-
-    from langgraph.checkpoint.serde.types import _DeltaSnapshot
-
-    thread_id = thread_id or str(uuid4())
-    snapshot_set = set(snapshots_at_steps)
-    stored: list[RunnableConfig] = []
-    parent_cfg: RunnableConfig | None = None
-
-    for step in range(total_steps):
-        config: RunnableConfig = {
-            "configurable": {
-                "thread_id": thread_id,
-                "checkpoint_ns": checkpoint_ns,
-            }
-        }
-        if parent_cfg:
-            config["configurable"]["checkpoint_id"] = parent_cfg["configurable"][
-                "checkpoint_id"
-            ]
-
-        channel_values: dict[str, Any] = {}
-        channel_versions: dict[str, int] = {}
-        if step in snapshot_set:
-            channel_values[channel] = _DeltaSnapshot(
-                write_value_fn(step),
-            )
-            channel_versions[channel] = step + 1
-
-        cp = Checkpoint(
-            v=1,
-            id=str(uuid6(clock_seq=-1)),
-            ts="",
-            channel_values=channel_values,
-            channel_versions=channel_versions,
-            versions_seen={},
-            updated_channels=None,
-        )
-        new_versions = dict(channel_versions)
-        parent_cfg = await saver.aput(
-            config, cp, generate_metadata(step=step), new_versions
-        )
-        stored.append(parent_cfg)
-
-        # Write a pending write for non-snapshot steps so the walk has
-        # something to collect.
-        if step not in snapshot_set:
-            await saver.aput_writes(
-                parent_cfg, [(channel, write_value_fn(step))], str(uuid4())
-            )
-
-    return stored
@@ -1,247 +0,0 @@
-"""DELTA_CHANNEL_HISTORY capability tests — aget_delta_channel_history contract."""
-
-from __future__ import annotations
-
-import traceback
-from collections.abc import Callable
-from uuid import uuid4
-
-from langgraph.checkpoint.base import BaseCheckpointSaver
-
-from langgraph.checkpoint.conformance.spec._delta_fixtures import build_delta_chain
-
-
-async def test_history_returns_writes_oldest_first(
-    saver: BaseCheckpointSaver,
-) -> None:
-    """Writes are returned oldest-to-newest."""
-    tid = str(uuid4())
-    # 5 steps: snapshot at 0, writes at 1,2,3,4.
-    # Head is step 4. Walk starts at step 3 (parent of head).
-    # Collects writes from steps 1,2,3 (between snapshot at 0 and head's parent).
-    configs = await build_delta_chain(
-        saver, thread_id=tid, channel="ch", snapshots_at_steps=[0], total_steps=5
-    )
-    head = configs[-1]
-    result = await saver.aget_delta_channel_history(config=head, channels=["ch"])
-    writes = result["ch"]["writes"]
-    values = [w[2] for w in writes]
-    assert values == [1, 2, 3], f"Expected [1,2,3], got {values}"
-
-
-async def test_history_seed_is_nearest_snapshot(
-    saver: BaseCheckpointSaver,
-) -> None:
-    """Seed is the value from the nearest ancestor with channel_values populated."""
-    tid = str(uuid4())
-    # 6 steps: snapshots at 0 and 3, writes at 1,2,4,5.
-    # Head is step 5. Walk from step 4 backward stops at step 3 (snapshot).
-    # Collects writes from step 4 only (between step 3 and head's parent step 4).
-    configs = await build_delta_chain(
-        saver,
-        thread_id=tid,
-        channel="ch",
-        snapshots_at_steps=[0, 3],
-        total_steps=6,
-    )
-    head = configs[-1]
-    result = await saver.aget_delta_channel_history(config=head, channels=["ch"])
-    assert "seed" in result["ch"], "Expected seed from snapshot at step 3"
-    seed = result["ch"]["seed"]
-    from langgraph.checkpoint.serde.types import _DeltaSnapshot
-
-    actual_value = seed.value if isinstance(seed, _DeltaSnapshot) else seed
-    assert actual_value == 3, f"Expected seed value 3 (step 3), got {actual_value}"
-    writes = result["ch"]["writes"]
-    values = [w[2] for w in writes]
-    assert values == [4], f"Expected [4], got {values}"
-
-
-async def test_history_excludes_target_pending_writes(
-    saver: BaseCheckpointSaver,
-) -> None:
-    """Target's own pending_writes are NOT included in the history."""
-    tid = str(uuid4())
-    configs = await build_delta_chain(
-        saver, thread_id=tid, channel="ch", snapshots_at_steps=[0], total_steps=3
-    )
-    head = configs[-1]
-    # Add writes directly to the head checkpoint
-    await saver.aput_writes(head, [("ch", "extra")], str(uuid4()))
-    result = await saver.aget_delta_channel_history(config=head, channels=["ch"])
-    writes = result["ch"]["writes"]
-    values = [w[2] for w in writes]
-    assert "extra" not in values, f"Target's writes should be excluded, got {values}"
-
-
-async def test_history_multi_channel(
-    saver: BaseCheckpointSaver,
-) -> None:
-    """Multiple channels have independent walk termination."""
-    tid = str(uuid4())
-    configs: list = []
-    parent_cfg = None
-    from langgraph.checkpoint.base import Checkpoint
-    from langgraph.checkpoint.base.id import uuid6
-    from langgraph.checkpoint.serde.types import _DeltaSnapshot
-
-    from langgraph.checkpoint.conformance.test_utils import generate_metadata
-
-    for step in range(5):
-        config = {"configurable": {"thread_id": tid, "checkpoint_ns": ""}}
-        if parent_cfg:
-            config["configurable"]["checkpoint_id"] = parent_cfg["configurable"][
-                "checkpoint_id"
-            ]
-        cv: dict = {}
-        cvs: dict = {}
-        if step == 1:
-            cv["a"] = _DeltaSnapshot("snap_a")
-            cvs["a"] = step + 1
-        if step == 3:
-            cv["b"] = _DeltaSnapshot("snap_b")
-            cvs["b"] = step + 1
-        cp = Checkpoint(
-            v=1,
-            id=str(uuid6(clock_seq=-1)),
-            ts="",
-            channel_values=cv,
-            channel_versions=cvs,
-            versions_seen={},
-            updated_channels=None,
-        )
-        parent_cfg = await saver.aput(config, cp, generate_metadata(step=step), cvs)
-        configs.append(parent_cfg)
-        await saver.aput_writes(parent_cfg, [("a", step), ("b", step)], str(uuid4()))
-
-    head = configs[-1]
-    result = await saver.aget_delta_channel_history(config=head, channels=["a", "b"])
-    a_writes = [w[2] for w in result["a"]["writes"]]
-    b_writes = [w[2] for w in result["b"]["writes"]]
-    assert a_writes == [1, 2, 3], f"Expected a writes [1,2,3], got {a_writes}"
-    assert b_writes == [3], f"Expected b writes [3], got {b_writes}"
-
-
-async def test_history_empty_channels_returns_empty(
-    saver: BaseCheckpointSaver,
-) -> None:
-    """Empty channels list returns empty mapping."""
-    tid = str(uuid4())
-    configs = await build_delta_chain(
-        saver, thread_id=tid, channel="ch", snapshots_at_steps=[0], total_steps=3
-    )
-    result = await saver.aget_delta_channel_history(config=configs[-1], channels=[])
-    assert result == {}
-
-
-async def test_history_walk_to_root_no_seed(
-    saver: BaseCheckpointSaver,
-) -> None:
-    """Walk reaches root without finding seed — no 'seed' key in result."""
-    tid = str(uuid4())
-    configs = await build_delta_chain(
-        saver,
-        thread_id=tid,
-        channel="ch",
-        snapshots_at_steps=[],
-        total_steps=4,
-    )
-    head = configs[-1]
-    result = await saver.aget_delta_channel_history(config=head, channels=["ch"])
-    assert "seed" not in result["ch"], f"Expected no seed, got {result['ch']}"
-
-
-async def test_history_migration_plain_value_as_seed(
-    saver: BaseCheckpointSaver,
-) -> None:
-    """Pre-delta plain value in channel_values acts as seed (migration case).
-
-    When a thread was originally using a regular channel (BinaryOperatorAggregate)
-    and later switches to DeltaChannel, the old checkpoint has a plain value in
-    channel_values[ch] (not a _DeltaSnapshot). The walk should treat it as the
-    seed and terminate there.
-    """
-    from langgraph.checkpoint.base import Checkpoint
-    from langgraph.checkpoint.base.id import uuid6
-
-    from langgraph.checkpoint.conformance.test_utils import generate_metadata
-
-    tid = str(uuid4())
-    configs: list = []
-    parent_cfg = None
-
-    for step in range(4):
-        config = {"configurable": {"thread_id": tid, "checkpoint_ns": ""}}
-        if parent_cfg:
-            config["configurable"]["checkpoint_id"] = parent_cfg["configurable"][
-                "checkpoint_id"
-            ]
-        cv: dict = {}
-        cvs: dict = {}
-        # Step 1: plain value (migration case — old checkpoint before delta)
-        if step == 1:
-            cv["ch"] = [10, 20, 30]
-            cvs["ch"] = step + 1
-        cp = Checkpoint(
-            v=1,
-            id=str(uuid6(clock_seq=-1)),
-            ts="",
-            channel_values=cv,
-            channel_versions=cvs,
-            versions_seen={},
-            updated_channels=None,
-        )
-        parent_cfg = await saver.aput(config, cp, generate_metadata(step=step), cvs)
-        configs.append(parent_cfg)
-        if step != 1:
-            await saver.aput_writes(parent_cfg, [("ch", step)], str(uuid4()))
-
-    head = configs[-1]
-    result = await saver.aget_delta_channel_history(config=head, channels=["ch"])
-    # Seed should be the plain value from step 1
-    assert "seed" in result["ch"], "Expected seed from migration plain value at step 1"
-    seed = result["ch"]["seed"]
-    assert seed == [10, 20, 30], f"Expected plain value [10,20,30], got {seed}"
-    # Writes should be from step 2 only (between seed at step 1 and head's parent step 2)
-    writes = result["ch"]["writes"]
-    values = [w[2] for w in writes]
-    assert values == [2], f"Expected [2], got {values}"
-
-
-ALL_DELTA_CHANNEL_HISTORY_TESTS = [
-    test_history_returns_writes_oldest_first,
-    test_history_seed_is_nearest_snapshot,
-    test_history_excludes_target_pending_writes,
-    test_history_multi_channel,
-    test_history_empty_channels_returns_empty,
-    test_history_walk_to_root_no_seed,
-    test_history_migration_plain_value_as_seed,
-]
-
-
-async def run_delta_channel_history_tests(
-    saver: BaseCheckpointSaver,
-    on_test_result: Callable[[str, str, bool, str | None], None] | None = None,
-) -> tuple[int, int, list[str]]:
-    """Run all delta_channel_history tests. Returns (passed, failed, failure_names)."""
-    passed = 0
-    failed = 0
-    failures: list[str] = []
-    for test_fn in ALL_DELTA_CHANNEL_HISTORY_TESTS:
-        try:
-            await test_fn(saver)
-            passed += 1
-            if on_test_result:
-                on_test_result("delta_channel_history", test_fn.__name__, True, None)
-        except Exception:
-            failed += 1
-            msg = f"{test_fn.__name__}: {traceback.format_exc()}"
-            failures.append(msg)
-            if on_test_result:
-                on_test_result(
-                    "delta_channel_history",
-                    test_fn.__name__,
-                    False,
-                    traceback.format_exc(),
-                )
-    return passed, failed, failures
@@ -19,9 +19,6 @@ from langgraph.checkpoint.conformance.spec.test_delete_for_runs import (
 from langgraph.checkpoint.conformance.spec.test_delete_thread import (
    run_delete_thread_tests,
 )
-from langgraph.checkpoint.conformance.spec.test_delta_channel_history import (
-    run_delta_channel_history_tests,
-)
 from langgraph.checkpoint.conformance.spec.test_get_tuple import run_get_tuple_tests
 from langgraph.checkpoint.conformance.spec.test_list import run_list_tests
 from langgraph.checkpoint.conformance.spec.test_prune import run_prune_tests
@@ -38,7 +35,6 @@ _RUNNERS = {
    Capability.DELETE_FOR_RUNS: run_delete_for_runs_tests,
    Capability.COPY_THREAD: run_copy_thread_tests,
    Capability.PRUNE: run_prune_tests,
-    Capability.DELTA_CHANNEL_HISTORY: run_delta_channel_history_tests,
 }


@@ -43,11 +43,7 @@ asyncio_mode = "auto"
 # The extended methods (acopy_thread, adelete_for_runs, aprune) are checked
 # at runtime via capability detection and may not exist on the installed
 # base class. Dict literal inference is also overly strict for RunnableConfig.
-# Delta-channel tests import from `langgraph` (not a declared dep of this
-# package — at test time it is installed alongside); private `_DeltaSnapshot`
-# imports are intentional (beta surface).
 unresolved-attribute = "ignore"
-unresolved-import = "ignore"
 invalid-argument-type = "ignore"
 invalid-return-type = "ignore"

@@ -62,9 +58,6 @@ lint.select = [
 lint.ignore = ["E501", "B008"]
 target-version = "py310"

-[tool.uv.sources]
-langgraph-checkpoint = {path = "../checkpoint", editable = true}
-
 [[tool.uv.index]]
 name = "testpypi"
 url = "https://test.pypi.org/simple/"
@@ -279,8 +279,8 @@ def _build_delta_stage2_sql(
        )
    for _ in channels_with_seed:
        branches.append(
-            "SELECT 'b'::text AS _kind, NULL::text AS checkpoint_id, channel, "
-            "type, blob, NULL::text AS task_id, NULL::int AS idx, version "
+            "SELECT 'b'::text, NULL, channel, "
+            "type, blob, NULL, NULL, version "
            "FROM checkpoint_blobs "
            "WHERE thread_id = %s AND checkpoint_ns = %s AND channel = %s "
            "AND version = %s"
@@ -4,7 +4,7 @@ build-backend = "hatchling.build"

 [project]
 name = "langgraph-checkpoint-postgres"
-version = "3.1.0"
+version = "3.1.0a4"
 description = "Library with a Postgres implementation of LangGraph checkpoint saver."
 authors = []
 requires-python = ">=3.10"
@@ -12,7 +12,7 @@ readme = "README.md"
 license = "MIT"
 license-files = ['LICENSE']
 dependencies = [
-  "langgraph-checkpoint>=4.1.0,<5.0.0",
+  "langgraph-checkpoint>=4.1.0a4,<5.0.0",
  "orjson>=3.11.5",
  "psycopg>=3.2.0",
  "psycopg-pool>=3.2.0",
@@ -244,7 +244,7 @@ wheels = [

 [[package]]
 name = "langchain-core"
-version = "1.3.3"
+version = "1.3.2"
 source = { registry = "https://pypi.org/simple" }
 dependencies = [
    { name = "jsonpatch" },
@@ -257,9 +257,9 @@ dependencies = [
    { name = "typing-extensions" },
    { name = "uuid-utils" },
 ]
-sdist = { url = "https://files.pythonhosted.org/packages/d3/ae/8b74458fc3850ec3d150eb9f45e857db129dafa801fb5cf173dfc9f8bbf3/langchain_core-1.3.3.tar.gz", hash = "sha256:fa510a5db8efdc0c6ff41c0939fb5c00a0183c11f6b84233e892e3227ff69182", size = 915041, upload-time = "2026-05-05T19:02:36.612Z" }
+sdist = { url = "https://files.pythonhosted.org/packages/a8/03/7219502e8ca728d65eb44d7a3eb60239230742a70dbfc9241b9bfd61c4ab/langchain_core-1.3.2.tar.gz", hash = "sha256:fd7a50b2f28ba561fd9d7f5d2760bc9e06cf00cdf820a3ccafe88a94ffa8d5b7", size = 911813, upload-time = "2026-04-24T15:49:23.699Z" }
 wheels = [
-    { url = "https://files.pythonhosted.org/packages/1f/01/4771b7ab2af1d1aba5b710bd8f13d9225c609425214b357590a17b01be77/langchain_core-1.3.3-py3-none-any.whl", hash = "sha256:18aae8506f37da7f74398492279a7d6efcee4f8e23c4c41c7af080eeb7ef7bd1", size = 543857, upload-time = "2026-05-05T19:02:34.52Z" },
+    { url = "https://files.pythonhosted.org/packages/7d/d5/8fa4431007cbb7cfed7590f4d6a5dea3ad724f4174d248f6642ef5ce7d05/langchain_core-1.3.2-py3-none-any.whl", hash = "sha256:d44a66127f9f8db735bdfd0ab9661bccb47a97113cfd3f2d89c74864422b7274", size = 542390, upload-time = "2026-04-24T15:49:21.991Z" },
 ]

 [[package]]
@@ -276,7 +276,7 @@ wheels = [

 [[package]]
 name = "langgraph-checkpoint"
-version = "4.1.0"
+version = "4.1.0a4"
 source = { editable = "../checkpoint" }
 dependencies = [
    { name = "langchain-core" },
@@ -324,7 +324,7 @@ test = [

 [[package]]
 name = "langgraph-checkpoint-postgres"
-version = "3.1.0"
+version = "3.1.0a4"
 source = { editable = "." }
 dependencies = [
    { name = "langgraph-checkpoint" },
@@ -399,7 +399,7 @@ test = [

 [[package]]
 name = "langsmith"
-version = "0.8.0"
+version = "0.7.31"
 source = { registry = "https://pypi.org/simple" }
 dependencies = [
    { name = "httpx" },
@@ -412,9 +412,9 @@ dependencies = [
    { name = "xxhash" },
    { name = "zstandard" },
 ]
-sdist = { url = "https://files.pythonhosted.org/packages/a8/64/95f1f013531395f4e8ed73caeee780f65c7c58fe028cb543f8937b45611b/langsmith-0.8.0.tar.gz", hash = "sha256:59fe5b2a56bbbe14a08aa76691f84b49e8675dd21e11b57d80c6db8c08bac2e3", size = 4432996, upload-time = "2026-04-30T22:13:07.341Z" }
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 [[package]]
@@ -4,7 +4,7 @@ build-backend = "hatchling.build"

 [project]
 name = "langgraph-checkpoint-sqlite"
-version = "3.1.0"
+version = "3.1.0a1"
 description = "Library with a SQLite implementation of LangGraph checkpoint saver."
 authors = []
 requires-python = ">=3.10"
@@ -12,7 +12,7 @@ readme = "README.md"
 license = "MIT"
 license-files = ['LICENSE']
 dependencies = [
-    "langgraph-checkpoint>=4.1.0,<5.0.0",
+    "langgraph-checkpoint>=4.1.0a4,<5.0.0",
    "aiosqlite>=0.20",
    "sqlite-vec>=0.1.6",
 ]
@@ -1,35 +0,0 @@
-"""Run delta-channel conformance capabilities against AsyncSqliteSaver."""
-
-from __future__ import annotations
-
-import pytest
-
-pytest.importorskip(
-    "langgraph.checkpoint.conformance",
-    reason="langgraph-checkpoint-conformance not installed",
-)
-pytest.importorskip("aiosqlite", reason="aiosqlite not installed")
-
-
-@pytest.mark.asyncio
-async def test_delta_channel_conformance():
-    from langgraph.checkpoint.conformance import validate
-    from langgraph.checkpoint.conformance.initializer import checkpointer_test
-
-    from langgraph.checkpoint.sqlite.aio import AsyncSqliteSaver
-
-    @checkpointer_test(name="AsyncSqliteSaver")
-    async def sqlite_saver():
-        async with AsyncSqliteSaver.from_conn_string(":memory:") as saver:
-            yield saver
-
-    report = await validate(
-        sqlite_saver,
-        capabilities={
-            "delta_channel_history",
-        },
-    )
-    for cap, result in report.results.items():
-        if result.passed is False:
-            details = "\n".join(result.failures or [])
-            pytest.fail(f"Capability {cap} failed:\n{details}")
@@ -214,11 +214,11 @@ wheels = [

 [[package]]
 name = "idna"
-version = "3.15"
+version = "3.11"
 source = { registry = "https://pypi.org/simple" }
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 [[package]]
@@ -253,11 +253,10 @@ wheels = [

 [[package]]
 name = "langchain-core"
-version = "1.3.3"
+version = "1.2.28"
 source = { registry = "https://pypi.org/simple" }
 dependencies = [
    { name = "jsonpatch" },
-    { name = "langchain-protocol" },
    { name = "langsmith" },
    { name = "packaging" },
    { name = "pydantic" },
@@ -266,26 +265,14 @@ dependencies = [
    { name = "typing-extensions" },
    { name = "uuid-utils" },
 ]
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-]
-
-[[package]]
-name = "langchain-protocol"
-version = "0.0.15"
-source = { registry = "https://pypi.org/simple" }
-dependencies = [
-    { name = "typing-extensions" },
-]
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+    { url = "https://files.pythonhosted.org/packages/a8/92/32f785f077c7e898da97064f113c73fbd9ad55d1e2169cf3a391b183dedb/langchain_core-1.2.28-py3-none-any.whl", hash = "sha256:80764232581eaf8057bcefa71dbf8adc1f6a28d257ebd8b95ba9b8b452e8c6ac", size = 508727, upload-time = "2026-04-08T18:19:32.823Z" },
 ]

 [[package]]
 name = "langgraph-checkpoint"
-version = "4.1.0"
+version = "4.1.0a4"
 source = { editable = "../checkpoint" }
 dependencies = [
    { name = "langchain-core" },
@@ -333,7 +320,7 @@ test = [

 [[package]]
 name = "langgraph-checkpoint-sqlite"
-version = "3.1.0"
+version = "3.1.0a1"
 source = { editable = "." }
 dependencies = [
    { name = "aiosqlite" },
@@ -402,7 +389,7 @@ test = [

 [[package]]
 name = "langsmith"
-version = "0.8.0"
+version = "0.7.31"
 source = { registry = "https://pypi.org/simple" }
 dependencies = [
    { name = "httpx" },
@@ -415,9 +402,9 @@ dependencies = [
    { name = "xxhash" },
    { name = "zstandard" },
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+    { url = "https://files.pythonhosted.org/packages/1d/a1/a013cf458c301cda86a213dd153ce0a01c93f1ab5833f951e6a44c9763ce/langsmith-0.7.31-py3-none-any.whl", hash = "sha256:0291d49203f6e80dda011af1afda61eb0595a4d697adb684590a8805e1d61fb6", size = 373276, upload-time = "2026-04-14T17:55:39.677Z" },
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 [[package]]
@@ -1161,11 +1148,11 @@ wheels = [

 [[package]]
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+    { url = "https://files.pythonhosted.org/packages/39/08/aaaad47bc4e9dc8c725e68f9d04865dbcb2052843ff09c97b08904852d84/urllib3-2.6.3-py3-none-any.whl", hash = "sha256:bf272323e553dfb2e87d9bfd225ca7b0f467b919d7bbd355436d3fd37cb0acd4", size = 131584, upload-time = "2026-01-07T16:24:42.685Z" },
 ]

 [[package]]
@@ -60,29 +60,15 @@ class CheckpointMetadata(TypedDict, total=False):
    """
    run_id: str
    """The ID of the run that created this checkpoint."""
-    counters_since_delta_snapshot: dict[str, tuple[int, int]]
-    """Per-channel counters since the last `_DeltaSnapshot` was written.
+    delta_updates_since_snapshot: dict[str, int]
+    """Per-channel update count since the last `_DeltaSnapshot` was written.

-    !!! warning "Beta"
-
-        This metadata field backs `DeltaChannel` (beta). The key name and
-        contents may change while the delta-channel design stabilizes.
-
-    Maps channel name -> `(updates, supersteps)`:
-
-    - index 0 (`updates`): number of supersteps that wrote to this channel
-      since its last snapshot blob.
-    - index 1 (`supersteps`): total supersteps elapsed since this channel's
-      last snapshot, regardless of whether the channel was written.
-
-    A snapshot fires when EITHER `updates >= ch.snapshot_frequency` OR
-    `supersteps >= DELTA_MAX_SUPERSTEPS_SINCE_SNAPSHOT` (system-wide bound,
-    default 5000, env `LANGGRAPH_DELTA_MAX_SUPERSTEPS_SINCE_SNAPSHOT`).
-    The supersteps bound prevents unbounded ancestor walks on threads where
-    a delta channel exists but is no longer being updated.
-
-    Absent on threads that don't use delta channels. Persisted as a
-    2-element list in JSON (no native tuple).
+    Maps channel name → number of supersteps that wrote to this channel
+    since its last snapshot blob. Used by `pregel.create_checkpoint` to
+    decide when to write the next snapshot (when the count reaches the
+    channel's `snapshot_frequency`, snapshot fires and the count resets
+    to 0). Absent on threads that don't use delta channels. Version-format
+    independent — works for int, float, and string version schemes.
    """


@@ -149,11 +135,6 @@ class CheckpointTuple(NamedTuple):
 class DeltaChannelHistory(TypedDict):
    """Per-channel result entry from `BaseCheckpointSaver.get_delta_channel_history`.

-    !!! warning "Beta"
-
-        Part of the `DeltaChannel` support surface; in beta. Field names and
-        semantics may change.
-
    Storage-level view of what one channel contributed across the ancestor
    chain of a target checkpoint:

@@ -336,14 +317,6 @@ class BaseCheckpointSaver(Generic[V]):

        Args:
            run_ids: The run IDs whose checkpoints should be deleted.
-
-        !!! warning "DeltaChannel"
-
-            Deleting a run that produced ancestor `checkpoint_writes` — or
-            the only `_DeltaSnapshot` blob — for a still-live thread will
-            break reconstruction of any `DeltaChannel` whose history
-            depended on those rows. See the `DeltaChannel` note on `prune`
-            for safe-recovery strategies.
        """
        raise NotImplementedError

@@ -357,17 +330,6 @@ class BaseCheckpointSaver(Generic[V]):
        Args:
            source_thread_id: The thread ID to copy from.
            target_thread_id: The thread ID to copy to.
-
-        !!! warning "DeltaChannel"
-
-            Implementations must copy the **complete** parent chain (all
-            ancestor checkpoints and their `checkpoint_writes`) — copying
-            only the head checkpoint will leave the target thread with
-            `DeltaChannel` state that cannot be reconstructed (no path back
-            to a `_DeltaSnapshot` ancestor). Equivalently, the copy must
-            include enough ancestors that every `DeltaChannel`-backed key
-            has either a `_DeltaSnapshot` in `channel_values` somewhere in
-            the chain, or a complete write history back to the chain root.
        """
        raise NotImplementedError

@@ -383,34 +345,6 @@ class BaseCheckpointSaver(Generic[V]):
            thread_ids: The thread IDs to prune.
            strategy: The pruning strategy. `"keep_latest"` retains only the most
                recent checkpoint per namespace. `"delete"` removes all checkpoints.
-
-        !!! warning "DeltaChannel"
-
-            Custom implementations must be `DeltaChannel`-aware. `DeltaChannel`
-            stores only a sentinel in `channel_values` for non-snapshot steps;
-            reconstruction walks the parent chain via
-            `get_delta_channel_history`, accumulating rows from
-            `checkpoint_writes` until it reaches an ancestor whose
-            `channel_values` contains a `_DeltaSnapshot` blob (written every
-            `snapshot_frequency` updates).
-
-            A naive `"keep_latest"` that drops intermediate checkpoints and
-            their writes can sever that chain: the surviving "latest"
-            checkpoint is rarely a snapshot point itself, so its delta
-            channels would silently reconstruct as empty (no error raised —
-            `get_delta_channel_history` simply returns no `seed`). Safe
-            options when the graph uses `DeltaChannel`:
-
-            * Walk back from each kept checkpoint and preserve every
-              ancestor (plus its `checkpoint_writes`) up to the nearest one
-              whose `channel_values` already contains a `_DeltaSnapshot` for
-              every `DeltaChannel`-backed key.
-            * Force a fresh snapshot on the kept checkpoint before deleting
-              ancestors — rewrite `channel_values[k] = _DeltaSnapshot(value)`
-              for each delta channel `k` (resolving `value` via the existing
-              ancestor walk first), then prune.
-            * Skip pruning threads whose graph uses `DeltaChannel` until one
-              of the above is implemented.
        """
        raise NotImplementedError

@@ -527,13 +461,6 @@ class BaseCheckpointSaver(Generic[V]):

        Args:
            run_ids: The run IDs whose checkpoints should be deleted.
-
-        !!! warning "DeltaChannel"
-
-            See `delete_for_runs` — deleting rows a still-live thread's
-            `DeltaChannel` reconstruction depends on (writes between the
-            head and its nearest `_DeltaSnapshot` ancestor) will silently
-            corrupt that channel's state.
        """
        raise NotImplementedError

@@ -547,13 +474,6 @@ class BaseCheckpointSaver(Generic[V]):
        Args:
            source_thread_id: The thread ID to copy from.
            target_thread_id: The thread ID to copy to.
-
-        !!! warning "DeltaChannel"
-
-            See `copy_thread` — the copy must carry the complete parent
-            chain (or at least back to a `_DeltaSnapshot` ancestor for every
-            `DeltaChannel`) so the target thread can reconstruct delta
-            state.
        """
        raise NotImplementedError

@@ -569,13 +489,6 @@ class BaseCheckpointSaver(Generic[V]):
            thread_ids: The thread IDs to prune.
            strategy: The pruning strategy. `"keep_latest"` retains only the most
                recent checkpoint per namespace. `"delete"` removes all checkpoints.
-
-        !!! warning "DeltaChannel"
-
-            See `prune` for the full `DeltaChannel` caveat. In short:
-            `"keep_latest"` must not drop ancestor checkpoints / writes that
-            sit between the kept checkpoint and the nearest `_DeltaSnapshot`
-            ancestor, or delta channels will silently reconstruct as empty.
        """
        raise NotImplementedError

@@ -584,14 +497,6 @@ class BaseCheckpointSaver(Generic[V]):
    ) -> Mapping[str, DeltaChannelHistory]:
        """Walk the parent chain returning per-channel writes + seed.

-        !!! warning "Beta"
-
-            This method is part of the `DeltaChannel` support surface and is
-            in beta. The signature, return shape (`DeltaChannelHistory`), and
-            interaction with `_DeltaSnapshot` blobs may change. Override at
-            your own risk; the default implementation will continue to work
-            against the public `BaseCheckpointSaver` contract.
-
        For each requested channel, walks ancestors of the checkpoint
        identified by `config` (following `parent_config`) and accumulates
        `pending_writes` for that channel. The walk terminates per-channel
@@ -651,13 +556,7 @@ class BaseCheckpointSaver(Generic[V]):
    async def aget_delta_channel_history(
        self, *, config: RunnableConfig, channels: Sequence[str]
    ) -> Mapping[str, DeltaChannelHistory]:
-        """Async version of `get_delta_channel_history`.
-
-        !!! warning "Beta"
-
-            This method is part of the `DeltaChannel` support surface and is
-            in beta. See `get_delta_channel_history` for caveats.
-        """
+        """Async version of `get_delta_channel_history`."""
        if not channels:
            return {}
        collected_by_ch: dict[str, list[PendingWrite]] = {c: [] for c in channels}
@@ -44,7 +44,7 @@ if TYPE_CHECKING:
        AllowedMsgpackModules,
    )

-LC_REVIVER = Reviver(allowed_objects="core")
+LC_REVIVER = Reviver()
 EMPTY_BYTES = b""
 logger = logging.getLogger(__name__)

@@ -4,7 +4,7 @@ build-backend = "hatchling.build"

 [project]
 name = "langgraph-checkpoint"
-version = "4.1.0"
+version = "4.1.0a4"
 description = "Library with base interfaces for LangGraph checkpoint savers."
 authors = []
 requires-python = ">=3.10"
@@ -1,33 +0,0 @@
-"""Run delta-channel conformance capabilities against InMemorySaver."""
-
-from __future__ import annotations
-
-import pytest
-
-conformance = pytest.importorskip(
-    "langgraph.checkpoint.conformance",
-    reason="langgraph-checkpoint-conformance not installed",
-)
-
-
-@pytest.mark.asyncio
-async def test_delta_channel_conformance():
-    from langgraph.checkpoint.conformance import validate
-    from langgraph.checkpoint.conformance.initializer import checkpointer_test
-
-    from langgraph.checkpoint.memory import InMemorySaver
-
-    @checkpointer_test(name="InMemorySaver")
-    async def mem_saver():
-        yield InMemorySaver()
-
-    report = await validate(
-        mem_saver,
-        capabilities={
-            "delta_channel_history",
-        },
-    )
-    for cap, result in report.results.items():
-        if result.passed is False:
-            details = "\n".join(result.failures or [])
-            pytest.fail(f"Capability {cap} failed:\n{details}")
@@ -268,7 +268,7 @@ wheels = [

 [[package]]
 name = "langchain-core"
-version = "1.3.3"
+version = "1.3.2"
 source = { registry = "https://pypi.org/simple" }
 dependencies = [
    { name = "jsonpatch" },
@@ -281,9 +281,9 @@ dependencies = [
    { name = "typing-extensions" },
    { name = "uuid-utils" },
 ]
-sdist = { url = "https://files.pythonhosted.org/packages/d3/ae/8b74458fc3850ec3d150eb9f45e857db129dafa801fb5cf173dfc9f8bbf3/langchain_core-1.3.3.tar.gz", hash = "sha256:fa510a5db8efdc0c6ff41c0939fb5c00a0183c11f6b84233e892e3227ff69182", size = 915041, upload-time = "2026-05-05T19:02:36.612Z" }
+sdist = { url = "https://files.pythonhosted.org/packages/a8/03/7219502e8ca728d65eb44d7a3eb60239230742a70dbfc9241b9bfd61c4ab/langchain_core-1.3.2.tar.gz", hash = "sha256:fd7a50b2f28ba561fd9d7f5d2760bc9e06cf00cdf820a3ccafe88a94ffa8d5b7", size = 911813, upload-time = "2026-04-24T15:49:23.699Z" }
 wheels = [
-    { url = "https://files.pythonhosted.org/packages/1f/01/4771b7ab2af1d1aba5b710bd8f13d9225c609425214b357590a17b01be77/langchain_core-1.3.3-py3-none-any.whl", hash = "sha256:18aae8506f37da7f74398492279a7d6efcee4f8e23c4c41c7af080eeb7ef7bd1", size = 543857, upload-time = "2026-05-05T19:02:34.52Z" },
+    { url = "https://files.pythonhosted.org/packages/7d/d5/8fa4431007cbb7cfed7590f4d6a5dea3ad724f4174d248f6642ef5ce7d05/langchain_core-1.3.2-py3-none-any.whl", hash = "sha256:d44a66127f9f8db735bdfd0ab9661bccb47a97113cfd3f2d89c74864422b7274", size = 542390, upload-time = "2026-04-24T15:49:21.991Z" },
 ]

 [[package]]
@@ -300,7 +300,7 @@ wheels = [

 [[package]]
 name = "langgraph-checkpoint"
-version = "4.1.0"
+version = "4.1.0a4"
 source = { editable = "." }
 dependencies = [
    { name = "langchain-core" },
@@ -383,7 +383,7 @@ test = [

 [[package]]
 name = "langsmith"
-version = "0.8.0"
+version = "0.7.31"
 source = { registry = "https://pypi.org/simple" }
 dependencies = [
    { name = "httpx" },
@@ -396,9 +396,9 @@ dependencies = [
    { name = "xxhash" },
    { name = "zstandard" },
 ]
-sdist = { url = "https://files.pythonhosted.org/packages/a8/64/95f1f013531395f4e8ed73caeee780f65c7c58fe028cb543f8937b45611b/langsmith-0.8.0.tar.gz", hash = "sha256:59fe5b2a56bbbe14a08aa76691f84b49e8675dd21e11b57d80c6db8c08bac2e3", size = 4432996, upload-time = "2026-04-30T22:13:07.341Z" }
+sdist = { url = "https://files.pythonhosted.org/packages/e6/11/696019490992db5c87774dc20515529ef42a01e1d770fb754ed6d9b12fb0/langsmith-0.7.31.tar.gz", hash = "sha256:331ee4f7c26bb5be4022b9859b7d7b122cbf8c9d01d9f530114c1914b0349ffb", size = 1178480, upload-time = "2026-04-14T17:55:41.242Z" }
 wheels = [
-    { url = "https://files.pythonhosted.org/packages/f3/e1/a4be2e696c9473bb53298df398237da5674704d781d4b748ed35aeef592a/langsmith-0.8.0-py3-none-any.whl", hash = "sha256:12cc4bc5622b835a6d841964d6034df3617bdb912dae0c1381fd0a68a9b3a3ef", size = 393268, upload-time = "2026-04-30T22:13:05.56Z" },
+    { url = "https://files.pythonhosted.org/packages/1d/a1/a013cf458c301cda86a213dd153ce0a01c93f1ab5833f951e6a44c9763ce/langsmith-0.7.31-py3-none-any.whl", hash = "sha256:0291d49203f6e80dda011af1afda61eb0595a4d697adb684590a8805e1d61fb6", size = 373276, upload-time = "2026-04-14T17:55:39.677Z" },
 ]

 [[package]]
@@ -1463,11 +1463,11 @@ wheels = [

 [[package]]
 name = "urllib3"
-version = "2.7.0"
+version = "2.6.3"
 source = { registry = "https://pypi.org/simple" }
-sdist = { url = "https://files.pythonhosted.org/packages/53/0c/06f8b233b8fd13b9e5ee11424ef85419ba0d8ba0b3138bf360be2ff56953/urllib3-2.7.0.tar.gz", hash = "sha256:231e0ec3b63ceb14667c67be60f2f2c40a518cb38b03af60abc813da26505f4c", size = 433602, upload-time = "2026-05-07T16:13:18.596Z" }
+sdist = { url = "https://files.pythonhosted.org/packages/c7/24/5f1b3bdffd70275f6661c76461e25f024d5a38a46f04aaca912426a2b1d3/urllib3-2.6.3.tar.gz", hash = "sha256:1b62b6884944a57dbe321509ab94fd4d3b307075e0c2eae991ac71ee15ad38ed", size = 435556, upload-time = "2026-01-07T16:24:43.925Z" }
 wheels = [
-    { url = "https://files.pythonhosted.org/packages/7f/3e/5db95bcf282c52709639744ca2a8b149baccf648e39c8cc87553df9eae0c/urllib3-2.7.0-py3-none-any.whl", hash = "sha256:9fb4c81ebbb1ce9531cce37674bbc6f1360472bc18ca9a553ede278ef7276897", size = 131087, upload-time = "2026-05-07T16:13:17.151Z" },
+    { url = "https://files.pythonhosted.org/packages/39/08/aaaad47bc4e9dc8c725e68f9d04865dbcb2052843ff09c97b08904852d84/urllib3-2.6.3-py3-none-any.whl", hash = "sha256:bf272323e553dfb2e87d9bfd225ca7b0f467b919d7bbd355436d3fd37cb0acd4", size = 131584, upload-time = "2026-01-07T16:24:42.685Z" },
 ]

 [[package]]
@@ -3675,11 +3675,12 @@ keyv@^4.5.4:
    json-buffer "3.0.1"

 "langsmith@>=0.5.0 <1.0.0":
-  version "0.6.3"
-  resolved "https://registry.yarnpkg.com/langsmith/-/langsmith-0.6.3.tgz#a3d8ad58d66a47d3697e3c69b2be3f6df5233190"
-  integrity sha512-pXrQ4/4myQvjFFOAUmt5pWRrLEZR20gzIJD7MNdUH+5/S5nLI4ZRBo/SYKC6coaYj9pYTfQdBIzcs+3kfJ5uDA==
+  version "0.5.20"
+  resolved "https://registry.yarnpkg.com/langsmith/-/langsmith-0.5.20.tgz#4021847d2ccd5a86c5eb96060f9bb5f19f80eca5"
+  integrity sha512-ULhLM8RswvQDXufLtNtvclHrWCBx8Cb5UPI6lAZC+8Dq59iHsVPz/3Ac9khWNm1VIvChRsuykixD/WrmzuuA3Q==
  dependencies:
    p-queue "6.6.2"
+    uuid "10.0.0"

 leven@^3.1.0:
  version "3.1.0"
@@ -4847,7 +4848,7 @@ uri-js@^4.2.2:
  dependencies:
    punycode "^2.1.0"

-uuid@^10.0.0:
+uuid@10.0.0, uuid@^10.0.0:
  version "10.0.0"
  resolved "https://registry.yarnpkg.com/uuid/-/uuid-10.0.0.tgz#5a95aa454e6e002725c79055fd42aaba30ca6294"
  integrity sha512-8XkAphELsDnEGrDxUOHB3RGvXz6TeuYSGEZBOjtTtPm2lwhGBjLgOzLHB63IUWfBpNucQjND6d3AOudO+H3RWQ==
@@ -17,7 +17,7 @@
    "lint": "eslint 'apps/**/*.ts' 'libs/**/*.ts'"
  },
  "devDependencies": {
-    "turbo": "^2.9.14",
+    "turbo": "^2.9.7",
    "typescript": "^5.9.3",
    "@tsconfig/recommended": "^1.0.13",
    "@eslint/eslintrc": "^3.3.5",
@@ -166,35 +166,35 @@
  resolved "https://registry.yarnpkg.com/@tsconfig/recommended/-/recommended-1.0.13.tgz#269fce3ad04ca70b93269ff44cca81b950f542da"
  integrity sha512-sySRuBfMKyKO/j2ZAhR8kSembhjuPEV4Ra3AHtmWLq51+iGaudr45crPSzNC5b7/Ctrh9dfUpBuTlYrH6rM58Q==

-"@turbo/darwin-64@2.9.14":
-  version "2.9.14"
-  resolved "https://registry.yarnpkg.com/@turbo/darwin-64/-/darwin-64-2.9.14.tgz#b9ec6ac637b9c5fdba5dae9d743f5d121f091242"
-  integrity sha512-t7QiPflaEyBE4oayeZtSmu4mEfjgIrcNlNNl1z1dmIVPqEdtA7+CfTf8d7KXsOGPh6aNgWjKxyvQg9uGfDQF+A==
+"@turbo/darwin-64@2.9.7":
+  version "2.9.7"
+  resolved "https://registry.yarnpkg.com/@turbo/darwin-64/-/darwin-64-2.9.7.tgz#46fddae01ea7817192dc6ff36a678cc3879b753b"
+  integrity sha512-wnvOWuVWJ5EUHNKxExEWiGlTeVpLG1L0PCu5MUozyC1P2SHGiWsmpW6/yAuShH91Fa2TAHOvdCRBzriZh4j4Eg==

-"@turbo/darwin-arm64@2.9.14":
-  version "2.9.14"
-  resolved "https://registry.yarnpkg.com/@turbo/darwin-arm64/-/darwin-arm64-2.9.14.tgz#99d19f3e59842c595d2828c72a2e4ef537408f38"
-  integrity sha512-d23147mC9BsCPA9mJ0h/ubcpbRgcJBXbcG3+Vq7YLhjz3IXuvQsJ1UXH8f4MD76ZjJ4m/E4aRdJV+MW88CDfbw==
+"@turbo/darwin-arm64@2.9.7":
+  version "2.9.7"
+  resolved "https://registry.yarnpkg.com/@turbo/darwin-arm64/-/darwin-arm64-2.9.7.tgz#cd7cf3a024509af0f59ae3885216d62fd090fdb6"
+  integrity sha512-mA0FIPMwwN3lodDkQYaGxj6PeT7ZaN5aCEbkKn/WB+ZB9yJdVWA4J83GH7t43jqDc5dcnVluVN5UFx3plRiXhA==

-"@turbo/linux-64@2.9.14":
-  version "2.9.14"
-  resolved "https://registry.yarnpkg.com/@turbo/linux-64/-/linux-64-2.9.14.tgz#9c907434f091cd75529f5496516f79b71935d2bb"
-  integrity sha512-P3ZKB5tuUDdDQWuAsACGUR1qv9W7BNWxdxqVJ0kZNuNNPRaVYTPPikLcp79+GiEcW3npsR+KyP38lnQiBc5aSA==
+"@turbo/linux-64@2.9.7":
+  version "2.9.7"
+  resolved "https://registry.yarnpkg.com/@turbo/linux-64/-/linux-64-2.9.7.tgz#25ee9a2cb3042498a3203e14653b14041105020f"
+  integrity sha512-fEbUYpgb5l7P+q+5tsWF2gw+/GSjUsuUTcnfm+f0lozUjgcjLKyOat6PgtAChmIFcTPchCL/8rJ3TvkBy01gfA==

-"@turbo/linux-arm64@2.9.14":
-  version "2.9.14"
-  resolved "https://registry.yarnpkg.com/@turbo/linux-arm64/-/linux-arm64-2.9.14.tgz#79ae9060e6ee9e0fb784ae0747e980f582e75313"
-  integrity sha512-ZRTlzcUMrrPv9ZuDzRF9n60Ym13bKeG9jDB8WjxyLhWNzV+AJQN+zdpIk3NJYf2zQsGUm1mNar2P0elRzLw25g==
+"@turbo/linux-arm64@2.9.7":
+  version "2.9.7"
+  resolved "https://registry.yarnpkg.com/@turbo/linux-arm64/-/linux-arm64-2.9.7.tgz#5b19d6249a50cb8153b8f2bc22ad10bbda614fbe"
+  integrity sha512-VkUjulo9ytfHKUHOS5gy0XPoh4CTKPXWCL8nLdrlHVi9fSut31ECeUqnm/dAbETP5D4xo9mH9XkJ+qMzGe/zmg==

-"@turbo/windows-64@2.9.14":
-  version "2.9.14"
-  resolved "https://registry.yarnpkg.com/@turbo/windows-64/-/windows-64-2.9.14.tgz#68a80f299f35189314184c88301caad982d1c0c2"
-  integrity sha512-exanwN6sIduZwykYeiTQj8kCmOhazP5WOz3bvXMcYtjhL6Z3iRWLewKrXCBq0bqwSP3iBMb/AerRCnHI4lx46A==
+"@turbo/windows-64@2.9.7":
+  version "2.9.7"
+  resolved "https://registry.yarnpkg.com/@turbo/windows-64/-/windows-64-2.9.7.tgz#900645776fa44ff8333e801d890992736f6dbc72"
+  integrity sha512-/GWdY6/x4aIHqkYJq596Rpdk1x0MkpRPkJcLAoB3yGRwyUms0+u2F1GnV54IbyAZTeKLRWSJKzNC+QwVGdYchA==

-"@turbo/windows-arm64@2.9.14":
-  version "2.9.14"
-  resolved "https://registry.yarnpkg.com/@turbo/windows-arm64/-/windows-arm64-2.9.14.tgz#4dc16684f0ddce53fafe56ad8f55205c4473d17a"
-  integrity sha512-fVdCsnmYoKICsycbWuuGp6Jvi51/3G/UluFWuAUCvR8PIW5IJkAk5BM9UF8PSm0Q2IphWHFZjYEgjHsh3B9y/g==
+"@turbo/windows-arm64@2.9.7":
+  version "2.9.7"
+  resolved "https://registry.yarnpkg.com/@turbo/windows-arm64/-/windows-arm64-2.9.7.tgz#e678d73fdbcbb12a679403fe7ba070fb67f37810"
+  integrity sha512-xBBgxCC5PK2+WZ1PPRZdp+aJ0bMBcEbweXWux3RUHJvX9ZodcoQySkrW6qt+ahb+uk8ZjyQodLfDwtVSoYds1w==

 "@types/esrecurse@^4.3.1":
  version "4.3.1"
@@ -1327,11 +1327,12 @@ keyv@^4.5.4:
    json-buffer "3.0.1"

 "langsmith@>=0.5.0 <1.0.0":
-  version "0.7.1"
-  resolved "https://registry.yarnpkg.com/langsmith/-/langsmith-0.7.1.tgz#d721ad2e5211f9a5373e8a84eb4fed36b5621971"
-  integrity sha512-Wjk90UjNoY5cBHMlNAC/eZx5clI8jnjBOBW8uJu8+MWBtx0QesNjsUiLtjI+I3UnrpxFFpDqGXcnhBjH654Mqg==
+  version "0.5.20"
+  resolved "https://registry.yarnpkg.com/langsmith/-/langsmith-0.5.20.tgz#4021847d2ccd5a86c5eb96060f9bb5f19f80eca5"
+  integrity sha512-ULhLM8RswvQDXufLtNtvclHrWCBx8Cb5UPI6lAZC+8Dq59iHsVPz/3Ac9khWNm1VIvChRsuykixD/WrmzuuA3Q==
  dependencies:
    p-queue "6.6.2"
+    uuid "10.0.0"

 levn@^0.4.1:
  version "0.4.1"
@@ -1813,17 +1814,17 @@ tsconfig-paths@^3.15.0:
    minimist "^1.2.6"
    strip-bom "^3.0.0"

-turbo@^2.9.14:
-  version "2.9.14"
-  resolved "https://registry.yarnpkg.com/turbo/-/turbo-2.9.14.tgz#d412fcc4c9bd8dba29cec5bbd54d5a74ab2b1bee"
-  integrity sha512-BQqXRr4UoWI3UPFrtznCLykYHxwxWh53iCB57x092jPMjIlW1wnm3N895g5irpiXmnxUhREBB0n6+y8BHhs4nw==
+turbo@^2.9.7:
+  version "2.9.7"
+  resolved "https://registry.yarnpkg.com/turbo/-/turbo-2.9.7.tgz#da6d5a821f0bde5174e1a55af6690dad5c2fb004"
+  integrity sha512-epxzqVO2s0IxcSWcgb+qKrtco8isfe7g3VtiS6hkYnEK4A9XQDZbrtavQ6MtWR1KoQn+1fUomaQth2rfRHlUlg==
  optionalDependencies:
-    "@turbo/darwin-64" "2.9.14"
-    "@turbo/darwin-arm64" "2.9.14"
-    "@turbo/linux-64" "2.9.14"
-    "@turbo/linux-arm64" "2.9.14"
-    "@turbo/windows-64" "2.9.14"
-    "@turbo/windows-arm64" "2.9.14"
+    "@turbo/darwin-64" "2.9.7"
+    "@turbo/darwin-arm64" "2.9.7"
+    "@turbo/linux-64" "2.9.7"
+    "@turbo/linux-arm64" "2.9.7"
+    "@turbo/windows-64" "2.9.7"
+    "@turbo/windows-arm64" "2.9.7"

 type-check@^0.4.0, type-check@~0.4.0:
  version "0.4.0"
@@ -1899,7 +1900,7 @@ uri-js@^4.2.2:
  dependencies:
    punycode "^2.1.0"

-uuid@^10.0.0:
+uuid@10.0.0, uuid@^10.0.0:
  version "10.0.0"
  resolved "https://registry.yarnpkg.com/uuid/-/uuid-10.0.0.tgz#5a95aa454e6e002725c79055fd42aaba30ca6294"
  integrity sha512-8XkAphELsDnEGrDxUOHB3RGvXz6TeuYSGEZBOjtTtPm2lwhGBjLgOzLHB63IUWfBpNucQjND6d3AOudO+H3RWQ==
@@ -1 +1 @@
-__version__ = "0.4.26"
+__version__ = "0.4.24"
@@ -35,12 +35,6 @@ DISALLOWED_BUILD_COMMAND_CHARS = [
 # This blocks background execution (cmd &) while allowing command
 # chaining (cmd1 && cmd2) which is common in build commands.
 _SINGLE_AMPERSAND_RE = re.compile(r"(?<!&)&(?:&&)*(?!&)")
-_API_VERSION_PATTERN = re.compile(
-    r"^(?P<major>\d+)"
-    r"(?:\.(?P<minor>\d+))?"
-    r"(?:\.(?P<patch>\d+))?"
-    r"(?:(?:\.|)(?:[A-Za-z][0-9A-Za-z]*))?$"
-)


 def has_disallowed_build_command_content(command: str) -> bool:
@@ -129,18 +123,6 @@ def _parse_node_version(version_str: str) -> int:
        ) from None


-def _parse_api_version_parts(version_str: str) -> tuple[int, ...]:
-    """Parse an API version into numeric components.
-
-    Supports optional prerelease suffixes, e.g. `0.9.0rc1`.
-    """
-    version_core = version_str.split("-", 1)[0]
-    match = _API_VERSION_PATTERN.fullmatch(version_core)
-    if not match:
-        raise ValueError("Version must be major or major.minor or major.minor.patch.")
-    return tuple(int(part) for part in match.groups() if part is not None)
-
-
 def _is_node_graph(spec: str | dict) -> bool:
    """Check if a graph is a Node.js graph based on the file extension."""
    if isinstance(spec, dict):
@@ -194,12 +176,12 @@ def validate_config(config: Config) -> Config:
            )
    if api_version:
        try:
-            parts = _parse_api_version_parts(api_version)
+            parts = tuple(map(int, api_version.split("-")[0].split(".")))
            if len(parts) > 3:
                raise ValueError(
                    "Version must be major or major.minor or major.minor.patch."
                )
-        except (TypeError, ValueError):
+        except TypeError:
            raise click.UsageError(
                f"Invalid version format: {api_version}.\n\n"
                "Pin to a minor version, e.g.:\n"
@@ -2944,23 +2944,6 @@ def test_docker_tag_with_api_version(in_config: bool):
    assert tag == f"langchain/langgraph-server:{version}-py3.11"


-@pytest.mark.parametrize("in_config", [False, True])
-@pytest.mark.parametrize("version", ["0.9.0rc1", "0.9.0.dev1"])
-def test_docker_tag_with_prerelease_api_version(version: str, in_config: bool):
-    """Test docker_tag with prerelease and dev api_version values."""
-    config = validate_config(
-        {
-            "python_version": "3.11",
-            "dependencies": ["."],
-            "graphs": {"agent": "./agent.py:graph"},
-            "api_version": version if in_config else None,
-        }
-    )
-
-    tag = docker_tag(config, api_version=version if not in_config else None)
-    assert tag == f"langchain/langgraph-api:{version}-py3.11"
-
-
 def test_config_to_docker_with_api_version():
    """Test config_to_docker function with api_version parameter."""

@@ -5,7 +5,7 @@ description = "uv workspace monorepo example for LangGraph CLI integration test"
 requires-python = ">=3.11"
 dependencies = [
    "langgraph>=0.6.0,<2",
-    "langchain-core>=1.3.3",
+    "langchain-core>=0.2.14",
 ]

 [tool.uv.workspace]
@@ -215,11 +215,10 @@ wheels = [

 [[package]]
 name = "langchain-core"
-version = "1.3.3"
+version = "1.2.28"
 source = { registry = "https://pypi.org/simple" }
 dependencies = [
    { name = "jsonpatch" },
-    { name = "langchain-protocol" },
    { name = "langsmith" },
    { name = "packaging" },
    { name = "pydantic" },
@@ -228,21 +227,9 @@ dependencies = [
    { name = "typing-extensions" },
    { name = "uuid-utils" },
 ]
-sdist = { url = "https://files.pythonhosted.org/packages/d3/ae/8b74458fc3850ec3d150eb9f45e857db129dafa801fb5cf173dfc9f8bbf3/langchain_core-1.3.3.tar.gz", hash = "sha256:fa510a5db8efdc0c6ff41c0939fb5c00a0183c11f6b84233e892e3227ff69182", size = 915041, upload-time = "2026-05-05T19:02:36.612Z" }
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@@ -724,7 +711,7 @@ dependencies = [

 [package.metadata]
 requires-dist = [
-    { name = "langchain-core", specifier = ">=1.3.3" },
+    { name = "langchain-core", specifier = ">=0.2.14" },
    { name = "langgraph", specifier = ">=0.6.0,<2" },
 ]

@@ -5,7 +5,7 @@ description = "Simple single-package uv example for LangGraph CLI integration te
 requires-python = ">=3.11"
 dependencies = [
    "langgraph>=0.6.0,<2",
-    "langchain-core>=1.3.3",
+    "langchain-core>=0.2.14",
 ]

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+version = "1.2.28"
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-    { name = "langchain-protocol" },
    { name = "langsmith" },
    { name = "packaging" },
    { name = "pydantic" },
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@@ -627,7 +614,7 @@ dependencies = [

 [package.metadata]
 requires-dist = [
-    { name = "langchain-core", specifier = ">=1.3.3" },
+    { name = "langchain-core", specifier = ">=0.2.14" },
    { name = "langgraph", specifier = ">=0.6.0,<2" },
 ]

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 [[package]]
@@ -946,11 +946,10 @@ wheels = [

 [[package]]
 name = "langchain-core"
-version = "1.3.3"
+version = "1.3.0"
 source = { registry = "https://pypi.org/simple" }
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-    { name = "langchain-protocol", marker = "python_full_version >= '3.11'" },
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    { name = "packaging", marker = "python_full_version >= '3.11'" },
    { name = "pydantic", marker = "python_full_version >= '3.11'" },
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@@ -2320,11 +2307,11 @@ wheels = [

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 [[package]]
@@ -29,9 +29,6 @@ from langgraph._internal._constants import (
 )

 DEFAULT_RECURSION_LIMIT = int(getenv("LANGGRAPH_DEFAULT_RECURSION_LIMIT", "10007"))
-DELTA_MAX_SUPERSTEPS_SINCE_SNAPSHOT = int(
-    getenv("LANGGRAPH_DELTA_MAX_SUPERSTEPS_SINCE_SNAPSHOT", "5000")
-)


 def recast_checkpoint_ns(ns: str) -> str:
@@ -26,15 +26,6 @@ class DeltaChannel(Generic[Value], BaseChannel[Any, Any, Any]):
    """Reducer channel that stores only a sentinel in checkpoint blobs and
    reconstructs state by replaying ancestor writes through the reducer.

-    !!! warning "Beta"
-
-        `DeltaChannel` is in beta. The API and on-disk representation may
-        change in future releases. Threads written with `DeltaChannel` today
-        are expected to remain readable, but the surrounding contract
-        (`BaseCheckpointSaver.get_delta_channel_history`, the
-        `_DeltaSnapshot` blob shape, the `counters_since_delta_snapshot`
-        metadata field) is not yet stable.
-
    The reducer receives the current accumulated value and a batch of writes
    in one call: `reducer(state, [write1, write2, ...]) -> new_state`.

@@ -47,12 +38,9 @@ class DeltaChannel(Generic[Value], BaseChannel[Any, Any, Any]):
    This lets LangGraph replay checkpointed writes in larger batches than they
    were originally produced without changing reconstructed state.

-    Snapshot cadence is driven by two counters: per-channel update count and
-    total supersteps since last snapshot. `create_checkpoint` writes a full
-    `_DeltaSnapshot` blob when EITHER the update count reaches
-    `snapshot_frequency` OR the supersteps count reaches the system-wide
-    `DELTA_MAX_SUPERSTEPS_SINCE_SNAPSHOT` bound (default 5000), bounding
-    replay depth even for channels that stop receiving writes.
+    Snapshot cadence is driven by per-channel update count. `create_checkpoint`
+    writes a full `_DeltaSnapshot` blob every `snapshot_frequency` updates to
+    this channel, bounding replay depth.

    Parameters:
        reducer: `(state, list[writes]) -> new_state`. Must be deterministic
@@ -249,17 +249,15 @@ def _messages_delta_reducer(
 ) -> list[AnyMessage]:
    """**Experimental.** Batch reducer for use with `DeltaChannel`.

-    Processes all writes in one pass — dedup by ID, `RemoveMessage`
-    tombstoning — without calling `add_messages`.
+    Provides full `add_messages` parity: dedup by ID, `RemoveMessage`
+    tombstoning, `REMOVE_ALL_MESSAGES` reset, `BaseMessageChunk` coercion,
+    and UUID assignment for ID-less messages — all in a single batched pass.

    This reducer is batching-invariant, as required by `DeltaChannel`:
    `reducer(reducer(state, xs), ys) == reducer(state, xs + ys)`.

    Raw dict / string / tuple inputs are coerced to typed `BaseMessage`
-    objects so that HTTP-driven graphs work without a separate coercion
-    step. This is not full `add_messages` parity — `REMOVE_ALL_MESSAGES`,
-    unknown-id `RemoveMessage` errors, missing-id UUID assignment, and
-    `BaseMessageChunk` conversion are not handled here.
+    objects so that HTTP-driven graphs work without a separate coercion step.

    Example::

@@ -280,24 +278,51 @@ def _messages_delta_reducer(
            flat.extend(w)
        else:
            flat.append(w)
-    # Steady state: the reducer's own output is already typed, so skip
-    # `convert_to_messages` on state when the first element is a BaseMessage.
+    # Steady state: the reducer's own output is already typed BaseMessages
+    # (never chunks), so skip convert_to_messages on the fast path.
    # Only raw input (initial dicts, deserialized blobs) hits the slow path.
    if state and isinstance(state[0], BaseMessage):
        state_msgs = state
    else:
-        state_msgs = cast("list[AnyMessage]", convert_to_messages(state))
-    msgs = cast("list[AnyMessage]", convert_to_messages(flat))
+        state_msgs = cast(
+            "list[AnyMessage]",
+            [
+                message_chunk_to_message(cast(BaseMessageChunk, m))
+                for m in convert_to_messages(state)
+            ],
+        )
+    # Coerce chunks to full messages — streaming nodes can emit BaseMessageChunk.
+    msgs = cast(
+        "list[AnyMessage]",
+        [
+            message_chunk_to_message(cast(BaseMessageChunk, m))
+            for m in convert_to_messages(flat)
+        ],
+    )

-    index: dict[str, int] = {
-        m.id: i for i, m in enumerate(state_msgs) if m.id is not None
-    }
+    # REMOVE_ALL_MESSAGES resets everything; find the last sentinel and
+    # discard all state plus all writes before it.
+    remove_all_idx = None
+    for idx, m in enumerate(msgs):
+        if isinstance(m, RemoveMessage) and m.id == REMOVE_ALL_MESSAGES:
+            remove_all_idx = idx
+    if remove_all_idx is not None:
+        state_msgs = []
+        msgs = msgs[remove_all_idx + 1 :]
+
+    # Build index and assign missing IDs in one pass (parity with add_messages
+    # so that eviction and RemoveMessage tombstoning work on ID-less messages).
+    index: dict[str, int] = {}
+    for i, m in enumerate(state_msgs):
+        if m.id is None:
+            m.id = str(uuid.uuid4())
+        index[m.id] = i
    result: list[AnyMessage | None] = list(state_msgs)
    for msg in msgs:
+        if msg.id is None:
+            msg.id = str(uuid.uuid4())
        mid = msg.id
-        if mid is None:
-            result.append(msg)
-        elif isinstance(msg, RemoveMessage):
+        if isinstance(msg, RemoveMessage):
            if mid in index:
                result[index[mid]] = None
                del index[mid]
@@ -6,7 +6,7 @@ import typing
 import warnings
 from collections import defaultdict
 from collections.abc import Awaitable, Callable, Hashable, Sequence
-from dataclasses import dataclass, is_dataclass
+from dataclasses import is_dataclass
 from datetime import timedelta
 from functools import partial
 from inspect import isclass, isfunction, ismethod, signature
@@ -95,17 +95,6 @@ __all__ = ("StateGraph", "CompiledStateGraph")
 logger = logging.getLogger(__name__)

 _CHANNEL_BRANCH_TO = "branch:to:{}"
-_DEFAULT_ERROR_HANDLER_NODE = "__default_error_handler__"
-
-
-@dataclass(slots=True)
-class _NodeDefaults:
-    """Default node policies applied to every node at compile time."""
-
-    retry_policy: RetryPolicy | Sequence[RetryPolicy] | None = None
-    cache_policy: CachePolicy | None = None
-    error_handler: StateNode[Any, Any] | None = None
-    timeout: TimeoutPolicy | None = None


 def _warn_invalid_state_schema(schema: type[Any] | Any) -> None:
@@ -262,77 +251,10 @@ class StateGraph(Generic[StateT, ContextT, InputT, OutputT]):
        self.output_schema = cast(type[OutputT], output_schema or state_schema)
        self.context_schema = context_schema

-        self._node_defaults: _NodeDefaults = _NodeDefaults()
-
        self._add_schema(self.state_schema)
        self._add_schema(self.input_schema, allow_managed=False)
        self._add_schema(self.output_schema, allow_managed=False)

-    def set_node_defaults(
-        self,
-        *,
-        retry_policy: RetryPolicy | Sequence[RetryPolicy] | None = None,
-        cache_policy: CachePolicy | None = None,
-        error_handler: StateNode[Any, ContextT] | None = None,
-        timeout: float | timedelta | TimeoutPolicy | None = None,
-    ) -> Self:
-        """Set default node policies that apply to every node in this graph.
-
-        Per-node values passed to `add_node` always take precedence over these
-        defaults. Defaults are applied at `compile()` time. Policies set here
-        are **not** inherited by subgraphs.
-
-        `retry_policy` and `timeout` defaults apply to **all** nodes,
-        including error-handler nodes. `cache_policy` and `error_handler`
-        defaults only apply to regular nodes -- caching error-handler results
-        is unsafe, and handlers must never catch themselves.
-
-        Args:
-            retry_policy: Default retry policy for nodes that don't specify
-                their own via `add_node(..., retry_policy=...)`. Also applies
-                to error-handler nodes.
-            cache_policy: Default cache policy for nodes that don't specify
-                their own via `add_node(..., cache_policy=...)`. Does **not**
-                apply to error-handler nodes.
-            error_handler: Default error handler invoked when any regular node
-                raises and does not have its own `error_handler` set via
-                `add_node`. The handler is **not** invoked when an
-                error-handler node itself raises -- handler failures fail the
-                run.
-            timeout: Default timeout policy for nodes that don't specify their
-                own via `add_node(..., timeout=...)`. Also applies to
-                error-handler nodes. Accepts a `TimeoutPolicy`, a number of
-                seconds (`float`), or a `timedelta`.
-
-        Returns:
-            Self: The builder instance, for chaining.
-
-        Example:
-            ```python
-            graph = (
-                StateGraph(State)
-                .set_node_defaults(
-                    retry_policy=RetryPolicy(max_attempts=3),
-                    error_handler=my_fallback_handler,
-                )
-                .add_node("a", node_a)
-                .add_node("b", node_b, retry_policy=custom_retry)  # overrides default
-                .add_edge(START, "a")
-                .compile()
-            )
-            ```
-        """
-        defaults = self._node_defaults
-        if retry_policy is not None:
-            defaults.retry_policy = retry_policy
-        if cache_policy is not None:
-            defaults.cache_policy = cache_policy
-        if error_handler is not None:
-            defaults.error_handler = error_handler
-        if timeout is not None:
-            defaults.timeout = coerce_timeout_policy(timeout)
-        return self
-
    @property
    def _all_edges(self) -> set[tuple[str, str]]:
        return self.edges | {
@@ -1271,63 +1193,10 @@ class StateGraph(Generic[StateT, ContextT, InputT, OutputT]):
                key for key, val in self.channels.items() if not is_managed_value(val)
            ]
        )
-        # Apply builder defaults to node specs. Per-node values always win.
-        # Error-handler routing and cache_policy are only assigned to regular
-        # nodes. Retry and timeout defaults also apply to error-handler nodes.
-        defaults = self._node_defaults
-        default_handler_name: str | None = None
-        if defaults.error_handler is not None:
-            if _DEFAULT_ERROR_HANDLER_NODE in self.nodes:
-                raise ValueError(
-                    f"Auto-generated default error handler node "
-                    f"`{_DEFAULT_ERROR_HANDLER_NODE}` already exists."
-                )
-            default_handler_name = _DEFAULT_ERROR_HANDLER_NODE
-            self.nodes[default_handler_name] = StateNodeSpec[Any, ContextT](
-                coerce_to_runnable(
-                    defaults.error_handler,  # type: ignore[arg-type]
-                    name=default_handler_name,
-                    trace=False,
-                ),
-                metadata=None,
-                input_schema=self.state_schema,
-                retry_policy=None,
-                cache_policy=None,
-                is_error_handler=True,
-            )
-
-        # Apply builder defaults to node specs. Per-node values always win.
-        for spec in self.nodes.values():
-            # error_handler: regular nodes only — handlers must never
-            # catch themselves or other handlers.
-            if (
-                not spec.is_error_handler
-                and default_handler_name is not None
-                and spec.error_handler_node is None
-            ):
-                spec.error_handler_node = default_handler_name
-            # retry: all nodes — handlers should be retried on transient
-            # failures just like regular nodes.
-            if defaults.retry_policy is not None and spec.retry_policy is None:
-                spec.retry_policy = defaults.retry_policy
-            # cache: regular nodes only — caching an error-handler result
-            # is unsafe because the input (failed-node state) may differ
-            # across failures even when the cache key matches.
-            if (
-                not spec.is_error_handler
-                and defaults.cache_policy is not None
-                and spec.cache_policy is None
-            ):
-                spec.cache_policy = defaults.cache_policy
-            # timeout: all nodes — a stuck handler should be cancelled the
-            # same way a stuck regular node would be.
-            if defaults.timeout is not None and spec.timeout is None:
-                spec.timeout = defaults.timeout
-
        node_error_handler_map = {
            node_name: spec.error_handler_node
            for node_name, spec in self.nodes.items()
-            if not spec.is_error_handler and spec.error_handler_node is not None
+            if spec.error_handler_node is not None
        }

        compiled = CompiledStateGraph[StateT, ContextT, InputT, OutputT](
@@ -8,11 +8,11 @@ from langchain_core.runnables import RunnableConfig
 from langgraph.checkpoint.base import (
    BaseCheckpointSaver,
    Checkpoint,
+    CheckpointMetadata,
 )
 from langgraph.checkpoint.base.id import uuid6
 from langgraph.checkpoint.serde.types import _DeltaSnapshot

-from langgraph._internal._config import DELTA_MAX_SUPERSTEPS_SINCE_SNAPSHOT
 from langgraph._internal._typing import MISSING
 from langgraph.channels.base import BaseChannel
 from langgraph.channels.delta import DeltaChannel
@@ -34,28 +34,28 @@ def empty_checkpoint() -> Checkpoint:
    )


-def delta_channels_to_snapshot(
-    channels: Mapping[str, BaseChannel],
-    counters_since_delta_snapshot: Mapping[str, tuple[int, int]],
-) -> set[str]:
-    """Return the set of DeltaChannel names that should snapshot now.
+def _should_snapshot_delta(
+    name: str,
+    ch: DeltaChannel,
+    updates_since_snapshot: Mapping[str, int],
+    *,
+    force: bool,
+) -> bool:
+    """Decide whether `ch` should write a `_DeltaSnapshot` this step.

-    A channel snapshots when EITHER its accumulated update count reaches
-    `snapshot_frequency` OR the total supersteps since its last snapshot
-    reaches `DELTA_MAX_SUPERSTEPS_SINCE_SNAPSHOT`. This is a pure
-    predicate — no mutation.
+    Triggers:
+      * `force` — always snapshot (used by `durability="exit"`).
+      * Update-count: this channel has accumulated at least
+        `snapshot_frequency` updates since its last snapshot. The count
+        is supplied by the caller via `updates_since_snapshot[name]` and
+        is reset to `0` whenever a snapshot fires.
+
+    Version-format-independent: works for `int`, `float`, and `str`
+    versioning schemes alike.
    """
-    result: set[str] = set()
-    for name, ch in channels.items():
-        if not isinstance(ch, DeltaChannel) or not ch.is_available():
-            continue
-        updates, supersteps = counters_since_delta_snapshot.get(name, (0, 0))
-        if (
-            updates >= ch.snapshot_frequency
-            or supersteps >= DELTA_MAX_SUPERSTEPS_SINCE_SNAPSHOT
-        ):
-            result.add(name)
-    return result
+    if force:
+        return True
+    return updates_since_snapshot.get(name, 0) >= ch.snapshot_frequency


 def create_checkpoint(
@@ -66,19 +66,34 @@ def create_checkpoint(
    id: str | None = None,
    updated_channels: set[str] | None = None,
    get_next_version: GetNextVersion | None = None,
-    channels_to_snapshot: set[str] | None = None,
+    force_delta_snapshot: bool = False,
+    updates_since_snapshot: Mapping[str, int] | None = None,
+    new_updates_since_snapshot: dict[str, int] | None = None,
 ) -> Checkpoint:
-    """Build a new Checkpoint from the previous one and live channel state.
+    """Create a checkpoint for the given channels.

-    For each name in `channels_to_snapshot`, a `_DeltaSnapshot(value)` blob
-    is written into `channel_values[k]`. Other delta channels are omitted
-    from `channel_values` — the ancestor walk reconstructs their state
-    from `checkpoint_writes`. Callers compute the set via
-    `delta_channels_to_snapshot(channels, counters)`; defaults to empty
-    (no snapshots) when not provided.
+    For each `DeltaChannel`, a `_DeltaSnapshot(value)` blob is written into
+    `channel_values[k]` when this channel has accumulated at least
+    `snapshot_frequency` updates since its last snapshot (counter supplied
+    via `updates_since_snapshot`). Otherwise the channel is omitted from
+    `channel_values`; its `channel_versions` entry still bumps so that the
+    saver tracks the channel and the ancestor walk can replay writes.
+
+    Snapshots are eager: even if the channel had no write this step, a
+    version bump is forced (via `get_next_version`) so `put()` includes
+    the channel in `new_versions` and stores the blob.
+
+    `force_delta_snapshot` ignores the cadence and always snapshots —
+    used by `durability="exit"` where intermediate writes are not stored
+    as ancestor `checkpoint_writes`.
+
+    If `new_updates_since_snapshot` is provided, the function resets the
+    counter to `0` for any channel that snapshotted this step. Counters
+    for channels that did not snapshot are left untouched (the caller is
+    responsible for incrementing them based on `updated_channels`).
    """
    ts = datetime.now(timezone.utc).isoformat()
-    channels_to_snapshot = channels_to_snapshot or set()
+    counts = updates_since_snapshot or {}
    if channels is None:
        values = checkpoint["channel_values"]
        channel_versions = checkpoint["channel_versions"]
@@ -89,23 +104,25 @@ def create_checkpoint(
            if k not in channel_versions:
                continue
            ch = channels[k]
-            if k in channels_to_snapshot:
-                # In exit mode, the snapshot decision is deferred to exit
-                # time (intermediate steps have do_checkpoint=False). The
-                # channel's count may have reached snapshot_frequency over
-                # several supersteps, but the LAST superstep may not have
-                # written to this channel. In that case apply_writes()
-                # (in _algo.py) didn't bump this channel's version, so
-                # saver.put() wouldn't include it in new_versions and
-                # the snapshot blob would be silently dropped. The manual
-                # bump below closes the gap. In sync/async durability this
-                # branch is effectively dead code (the step that pushes
-                # the count to freq always writes the channel).
+            if (
+                isinstance(ch, DeltaChannel)
+                and ch.is_available()
+                and _should_snapshot_delta(
+                    k,
+                    ch,
+                    counts,
+                    force=force_delta_snapshot,
+                )
+            ):
+                # Eager snapshot: bump version if not already written this step
+                # so put() includes this channel in new_versions and stores blob.
                if get_next_version is not None and (
                    updated_channels is None or k not in updated_channels
                ):
                    channel_versions[k] = get_next_version(channel_versions[k], None)
                values[k] = _DeltaSnapshot(ch.get())
+                if new_updates_since_snapshot is not None:
+                    new_updates_since_snapshot[k] = 0
            else:
                v = ch.checkpoint()
                if v is not MISSING:
@@ -236,3 +253,17 @@ def copy_checkpoint(checkpoint: Checkpoint) -> Checkpoint:
        versions_seen={k: v.copy() for k, v in checkpoint["versions_seen"].items()},
        updated_channels=checkpoint.get("updated_channels", None),
    )
+
+
+def read_delta_updates_since_snapshot(
+    metadata: CheckpointMetadata | None,
+) -> dict[str, int]:
+    """Read the per-channel update counter from checkpoint metadata.
+
+    Returns an empty dict for missing/None metadata; the dict is
+    `total=False` on `CheckpointMetadata`, so absence means "no prior
+    delta-channel activity tracked."
+    """
+    if not metadata:
+        return {}
+    return dict(metadata.get("delta_updates_since_snapshot", {}) or {})
@@ -100,7 +100,6 @@ from langgraph.pregel._checkpoint import (
    channels_from_checkpoint,
    copy_checkpoint,
    create_checkpoint,
-    delta_channels_to_snapshot,
    empty_checkpoint,
 )
 from langgraph.pregel._executor import (
@@ -195,46 +194,8 @@ class PregelLoop:
    _migrate_checkpoint: Callable[[Checkpoint], None] | None
    submit: Submit
    channels: Mapping[str, BaseChannel]
-    # Futures from `checkpointer.put_writes` calls that produced delta-channel
-    # writes. `_checkpointer_put_after_previous` drains this list (swap to a
-    # local `futs` then reset to `[]` and wait/gather) before putting the
-    # next checkpoint, so a checkpoint never becomes durable before the
-    # writes that produced it. Initialised to `[]` in both sync and async
-    # `__enter__`; stays `None` only when no checkpointer.
+    # Only set on AsyncPregelLoop; sync loops keep this as None.
    _delta_write_futs: list[Any] | None = None
-
-    # Same pattern as `_delta_write_futs` but for error-handler writes.
-    # When `put_writes` persists an ERROR_SOURCE_NODE marker, the future is
-    # appended here.  `schedule_error_handler` / `aschedule_error_handler`
-    # drain this list so the write is durable before the handler starts.
-    _error_handler_write_futs: list[Any] | None = None
-
-    # Exit-mode accumulator: every delta-channel write produced during this
-    # run (input writes from `_first` + per-superstep writes captured in
-    # `after_tick`). At exit, `_put_exit_delta_writes` filters out channels
-    # that will snapshot, then persists the rest under an anchor parent.
-    # `None` when not in exit mode (so the capture sites are no-ops).
-    # Each tuple is `(step, task_id, channel, value)` — `step` drives the
-    # synthetic step-prefixed task_id used to preserve chronological order
-    # under the saver's `ORDER BY task_id, idx` sorting.
-    _exit_delta_writes: list[tuple[int, str, str, Any]] | None = None
-
-    # The checkpoint_config that points at the parent loaded at `__enter__`
-    # (or the synthetic-empty checkpoint, on first run). We capture it
-    # eagerly because every `_put_checkpoint` advances `self.checkpoint_config`
-    # to the newly-saved checkpoint's id — by exit time the original parent
-    # config would otherwise be lost. `_put_exit_delta_writes` uses this:
-    # on resumed runs as the anchor for exit delta writes; on first runs
-    # to derive the lazy stub's config (its `checkpoint_id` is the
-    # synthetic-empty id we want the stub persisted under).
-    _initial_checkpoint_config: RunnableConfig
-
-    # True iff the saver actually returned a tuple at `__enter__`. False
-    # on the first-ever run for a thread (no parent persisted yet).
-    # `_put_exit_delta_writes` uses this to decide between anchoring on
-    # the existing parent (True) or creating a lazy stub (False).
-    _has_persisted_parent: bool = False
-
    managed: ManagedValueMapping
    checkpoint: Checkpoint
    checkpoint_id_saved: str
@@ -480,13 +441,6 @@ class PregelLoop:
                isinstance(self.specs.get(c), DeltaChannel) for c, _ in writes_to_save
            ):
                self._delta_write_futs.append(fut)
-            # ERROR_SOURCE_NODE is only appended by commit() when the task
-            # has an error handler (_should_route_to_error_handler), so this
-            # check naturally limits future collection to those tasks.
-            if self._error_handler_write_futs is not None and any(
-                c == ERROR_SOURCE_NODE for c, _ in writes
-            ):
-                self._error_handler_write_futs.append(fut)
        # output writes
        if hasattr(self, "tasks"):
            self.output_writes(task_id, writes)
@@ -566,7 +520,7 @@ class PregelLoop:
            self.tasks[pushed.id] = pushed
            # match any pending writes to the new task
            if not self.is_replaying:
-                self._reapply_writes_to_succeeded_nodes({pushed.id: pushed})
+                self._match_writes({pushed.id: pushed})
            # return the new task, to be started if not run before
            return pushed

@@ -644,8 +598,7 @@ class PregelLoop:

        # if there are pending writes from a previous loop, apply them
        if not self.is_replaying and self.checkpoint_pending_writes:
-            self._reapply_writes_to_succeeded_nodes(self.tasks)
-            self._resume_error_handlers_if_applicable()
+            self._match_writes(self.tasks)

        # before execution, check if we should interrupt
        if self.interrupt_before and should_interrupt(
@@ -684,11 +637,6 @@ class PregelLoop:
            self._emit(
                "values", map_output_values, self.output_keys, writes, self.channels
            )
-        # capture delta-channel writes for exit-mode accumulator before clearing
-        if self._exit_delta_writes is not None:
-            for tid, ch, v in self.checkpoint_pending_writes:
-                if isinstance(self.specs.get(ch), DeltaChannel):
-                    self._exit_delta_writes.append((self.step, tid, ch, v))
        # clear pending writes
        self.checkpoint_pending_writes.clear()
        # only replay (re-execute) done tasks on the first tick
@@ -712,88 +660,13 @@ class PregelLoop:

    # private

-    def _reapply_writes_to_succeeded_nodes(
-        self, tasks: Mapping[str, PregelExecutableTask]
-    ) -> None:
-        """Restore successful channel writes from checkpoint to in-memory tasks.
-
-        Skips control signals (ERROR, ERROR_SOURCE_NODE, INTERRUPT, RESUME)
-        so that failed/interrupted tasks remain with empty writes and will be
-        re-executed (or routed to error handlers) by the runner.
-        """
+    def _match_writes(self, tasks: Mapping[str, PregelExecutableTask]) -> None:
        for tid, k, v in self.checkpoint_pending_writes:
            if k in (ERROR, ERROR_SOURCE_NODE, INTERRUPT, RESUME):
                continue
            if task := tasks.get(tid):
                task.writes.append((k, v))

-    def _resume_error_handlers_if_applicable(self) -> None:
-        """On resume, schedule error handlers for tasks that failed in a prior run.
-
-        Called right after ``_reapply_writes_to_succeeded_nodes`` during ``tick()``.
-        At that point, ``_reapply_writes_to_succeeded_nodes`` has already skipped
-        ERROR / ERROR_SOURCE_NODE writes, so a previously-failed task still has
-        empty ``writes``.  Without intervention the runner (which executes only
-        tasks where ``not t.writes``) would re-run the original node.
-
-        This method prevents that re-execution for nodes that have an error
-        handler:
-
-        1. Scan ``checkpoint_pending_writes`` for ERROR_SOURCE_NODE markers
-           persisted by a prior ``commit()``.  Each marker means "this task
-           already failed and was routed to an error handler".
-        2. For each such task, write ``(ERROR, error)`` into ``task.writes``
-           so the task is no longer empty — the runner will skip it.
-        3. Prepare a fresh error-handler task and add it to ``self.tasks``.
-           Because the handler task starts with empty ``writes``, the runner
-           will pick it up and execute it.
-        """
-        # Phase 1: collect task-ids that have ERROR_SOURCE_NODE + ERROR pairs.
-        failed: dict[str, BaseException] = {}
-        for tid, chan, val in self.checkpoint_pending_writes:
-            if chan == ERROR_SOURCE_NODE:
-                error = next(
-                    (
-                        v
-                        for t, c, v in self.checkpoint_pending_writes
-                        if t == tid and c == ERROR
-                    ),
-                    None,
-                )
-                if error is not None:
-                    failed[tid] = error
-        # Phase 2: mark originals as done, schedule handler tasks.
-        for task_id, error in failed.items():
-            task = self.tasks.get(task_id)
-            if task is None:
-                continue
-            handler_node = self.nodes[task.name].error_handler_node
-            if not handler_node:
-                continue
-            # Non-empty writes → runner's `not t.writes` filter skips this task.
-            task.writes.append((ERROR, error))
-            # The handler task starts with empty writes → runner will execute it.
-            handler_task = prepare_node_error_handler_task(
-                task,
-                handler_node_name=handler_node,
-                failed_error=error,
-                checkpoint=self.checkpoint,
-                pending_writes=self.checkpoint_pending_writes,
-                processes=self.nodes,
-                channels=self.channels,
-                managed=self.managed,
-                config=task.config,
-                step=self.step,
-                stop=self.stop,
-                store=self.store,
-                checkpointer=self.checkpointer,
-                manager=self.manager,
-                retry_policy=self.retry_policy,
-                cache_policy=self.cache_policy,
-            )
-            if handler_task is not None:
-                self.tasks[handler_task.id] = handler_task
-
    def _pending_interrupts(self) -> set[str]:
        """Return the set of interrupt ids that are pending without corresponding resume values."""
        # mapping of task ids to interrupt ids
@@ -981,27 +854,6 @@ class PregelLoop:
                self.checkpointer_get_next_version,
                self.trigger_to_nodes,
            )
-            # Input writes go through `apply_writes` directly (above) — they
-            # never enter `checkpoint_pending_writes`, so the after_tick
-            # capture site does not see them. In exit mode, capture them
-            # here so `_exit_delta_writes` includes the input's delta writes
-            # alongside per-superstep writes; otherwise the input would be
-            # lost on read (it's not in final_checkpoint.channel_values for
-            # sub-freq channels, and walks ignore target.pending_writes).
-            if self._exit_delta_writes is not None:
-                for c, v in input_writes:
-                    if isinstance(self.specs.get(c), DeltaChannel):
-                        self._exit_delta_writes.append((self.step, NULL_TASK_ID, c, v))
-            # Persist delta-channel input writes so sub-freq inputs are
-            # recoverable via ancestor walk (mirrors the Command input path).
-            if self.durability != "exit":
-                delta_input = [
-                    (c, v)
-                    for c, v in input_writes
-                    if isinstance(self.specs.get(c), DeltaChannel)
-                ]
-                if delta_input:
-                    self.put_writes(NULL_TASK_ID, delta_input)
            # save input checkpoint
            self.updated_channels = updated_channels
            self._put_checkpoint({"source": "input"})
@@ -1053,66 +905,36 @@ class PregelLoop:
        return updated_channels

    def _put_checkpoint(self, metadata: CheckpointMetadata) -> None:
-        # `is` (object identity) — not `==`. Three of four call sites pass a
-        # fresh dict ({"source":"input"|"loop"|"fork"}); only
-        # `_suppress_interrupt`(will rename to _on_loop_exit soon)
-        # at exit reuses the existing `self.checkpoint_metadata` instance. So
-        # `metadata is self.checkpoint_metadata` is True only on the exit call,
-        # which is what we use to gate exit-only behaviour (skip count-bump,
-        # don't replace metadata). Could be replaced by an explicit
-        # `exiting: bool = False` parameter; left as-is to match the existing
-        # idiom in this file.
-        # TODO: replace with an explicit `exiting: bool = False` parameter.
+        # assign step and parents
        exiting = metadata is self.checkpoint_metadata
        if exiting and self.checkpoint["id"] == self.checkpoint_id_saved:
            # checkpoint already saved
            return
-        # Per-delta-channel counter bookkeeping.
-        #
-        # Each delta channel tracks a (updates, supersteps) tuple:
-        # - `updates` increments only when the channel is written this step.
-        # - `supersteps` increments every superstep regardless.
-        #
-        # `_put_checkpoint` is called once per superstep with a fresh
-        # metadata dict (source="input"|"loop"|"fork") — those are the
-        # intermediate calls that bump counters. In exit mode,
-        # `_suppress_interrupt`(will rename to _on_loop_exit soon)
-        # additionally calls `_put_checkpoint(self.checkpoint_metadata)` AT
-        # EXIT to commit the final checkpoint — this runs *after* the last
-        # intermediate call already counted the last superstep. So the
-        # exit call must NOT bump again or it would double-count the last
-        # superstep.
+        # Carry per-delta-channel update bookkeeping forward across
+        # supersteps. Capture from the OLD metadata before potentially
+        # replacing it with a fresh dict that wouldn't contain it. Then
+        # increment for any delta channel updated this step (so the count
+        # reflects "supersteps that wrote to this channel since last
+        # snapshot"). create_checkpoint will reset entries to 0 for any
+        # channel that fires a snapshot this step.
+        prev_counts = dict(
+            self.checkpoint_metadata.get("delta_updates_since_snapshot", {}) or {}
+        )
+        new_counts = dict(prev_counts)
+        if self.updated_channels:
+            for ch_name in self.updated_channels:
+                ch_obj = self.channels.get(ch_name)
+                if isinstance(ch_obj, DeltaChannel):
+                    new_counts[ch_name] = new_counts.get(ch_name, 0) + 1
        if not exiting:
-            prev_counters = dict(
-                self.checkpoint_metadata.get("counters_since_delta_snapshot") or {}
-            )
-            new_counters: dict[str, tuple[int, int]] = {}
-            updated = self.updated_channels or set()
-            for ch_name, ch in self.channels.items():
-                if not isinstance(ch, DeltaChannel):
-                    continue
-                u, s = prev_counters.get(ch_name, (0, 0))
-                s += 1
-                if ch_name in updated:
-                    u += 1
-                new_counters[ch_name] = (u, s)
            metadata["step"] = self.step
            metadata["parents"] = self.config[CONF].get(CONFIG_KEY_CHECKPOINT_MAP, {})
            self.checkpoint_metadata = metadata
-        else:
-            new_counters = dict(
-                self.checkpoint_metadata.get("counters_since_delta_snapshot") or {}
-            )
        # do checkpoint?
        do_checkpoint = self._checkpointer_put_after_previous is not None and (
            exiting or self.durability != "exit"
        )
        # create new checkpoint
-        channels_to_snapshot = (
-            delta_channels_to_snapshot(self.channels, new_counters)
-            if do_checkpoint
-            else set()
-        )
        self.checkpoint = create_checkpoint(
            self.checkpoint,
            self.channels if do_checkpoint else None,
@@ -1122,15 +944,14 @@ class PregelLoop:
            get_next_version=self.checkpointer_get_next_version
            if do_checkpoint
            else None,
-            channels_to_snapshot=channels_to_snapshot,
+            force_delta_snapshot=exiting and self.durability == "exit",
+            updates_since_snapshot=new_counts,
+            new_updates_since_snapshot=new_counts,
        )
-        for k in channels_to_snapshot:
-            new_counters[k] = (0, 0)
-        non_zero = {k: v for k, v in new_counters.items() if v != (0, 0)}
-        if non_zero:
-            self.checkpoint_metadata["counters_since_delta_snapshot"] = non_zero
-        elif "counters_since_delta_snapshot" in self.checkpoint_metadata:
-            del self.checkpoint_metadata["counters_since_delta_snapshot"]
+        if new_counts:
+            self.checkpoint_metadata["delta_updates_since_snapshot"] = new_counts
+        elif "delta_updates_since_snapshot" in self.checkpoint_metadata:
+            del self.checkpoint_metadata["delta_updates_since_snapshot"]
        # sanitize TASK channel in the checkpoint before saving (durability=="exit")
        if TASKS in self.checkpoint["channel_values"] and any(
            isinstance(channel, UntrackedValue) for channel in self.channels.values()
@@ -1189,99 +1010,6 @@ class PregelLoop:
            # increment step
            self.step += 1

-    def _put_exit_delta_writes(self) -> None:
-        """Stage stub + accumulated delta writes so final_checkpoint's put
-        waits on them (visibility invariant: both must be durable before
-        final_checkpoint becomes visible to readers).
-
-        Stub is created lazily — only when no persisted parent exists AND at
-        least one delta channel has writes that won't be snapshotted.
-        """
-        if (
-            not self._exit_delta_writes
-            or self.checkpointer is None
-            or self._checkpointer_put_after_previous is None
-            or self.checkpointer_put_writes is None
-        ):
-            return
-
-        counters = dict(
-            self.checkpoint_metadata.get("counters_since_delta_snapshot") or {}
-        )
-        channels_to_snapshot = delta_channels_to_snapshot(self.channels, counters)
-
-        pending = [
-            (step, tid, ch, v)
-            for (step, tid, ch, v) in self._exit_delta_writes
-            if ch not in channels_to_snapshot
-        ]
-        if not pending:
-            return
-
-        if self._has_persisted_parent:
-            # _initial_checkpoint_config's checkpoint_id is the saved parent's
-            # id (saver returned a real tuple at __enter__).
-            anchor_config = self._initial_checkpoint_config
-        else:
-            stub_cp = empty_checkpoint()
-            stub_cp["id"] = self.checkpoint_id_saved
-            stub_cp["ts"] = datetime.now(timezone.utc).isoformat()
-            # Stub has no parent (checkpoint_id=None in config).
-            stub_put_config = patch_configurable(
-                self._initial_checkpoint_config,
-                {CONFIG_KEY_CHECKPOINT_ID: None},
-            )
-            # Anchor config for put_writes: checkpoint_id = stub's id.
-            anchor_config = patch_configurable(
-                self._initial_checkpoint_config,
-                {CONFIG_KEY_CHECKPOINT_ID: stub_cp["id"]},
-            )
-            self._put_checkpoint_fut = self.submit(
-                self._checkpointer_put_after_previous,
-                getattr(self, "_put_checkpoint_fut", None),
-                stub_put_config,
-                stub_cp,
-                {"step": -2},
-                {},
-            )
-            # Set checkpoint_config so final_checkpoint's _put_checkpoint
-            # sees the stub as its parent.
-            self.checkpoint_config = anchor_config
-
-        # Step-prefixed synthetic task_id preserves chronological superstep
-        # order under the saver's ORDER BY task_id, idx sorting.
-        grouped: dict[tuple[int, str], list[tuple[str, Any]]] = {}
-        for step, tid, ch, v in pending:
-            grouped.setdefault((step, tid), []).append((ch, v))
-        anchor_write_config = patch_configurable(
-            anchor_config,
-            {
-                CONFIG_KEY_CHECKPOINT_NS: self.config[CONF].get(
-                    CONFIG_KEY_CHECKPOINT_NS, ""
-                ),
-                CONFIG_KEY_CHECKPOINT_ID: anchor_config[CONF][CONFIG_KEY_CHECKPOINT_ID],
-            },
-        )
-        for (step, tid), entries in grouped.items():
-            synth_tid = f"{step:08d}-{tid}"
-            if self.checkpointer_put_writes_accepts_task_path:
-                fut = self.submit(
-                    self.checkpointer_put_writes,
-                    anchor_write_config,
-                    entries,
-                    synth_tid,
-                    "",
-                )
-            else:
-                fut = self.submit(
-                    self.checkpointer_put_writes,
-                    anchor_write_config,
-                    entries,
-                    synth_tid,
-                )
-            if self._delta_write_futs is not None:
-                self._delta_write_futs.append(fut)
-
    def _suppress_interrupt(
        self,
        exc_type: type[BaseException] | None,
@@ -1297,7 +1025,6 @@ class PregelLoop:
            # or a nested graph with checkpointer=True
            or all(NS_END not in part for part in self.checkpoint_ns)
        ):
-            self._put_exit_delta_writes()
            self._put_checkpoint(self.checkpoint_metadata)
            self._put_pending_writes()
        # suppress interrupt
@@ -1503,9 +1230,6 @@ class SyncPregelLoop(PregelLoop, AbstractContextManager):
        metadata: CheckpointMetadata,
        new_versions: ChannelVersions,
    ) -> RunnableConfig:
-        if self._delta_write_futs:
-            futs, self._delta_write_futs = self._delta_write_futs, []
-            concurrent.futures.wait(futs)
        try:
            if prev is not None:
                prev.result()
@@ -1543,10 +1267,12 @@ class SyncPregelLoop(PregelLoop, AbstractContextManager):
        handler_node = self.nodes[failed_task.name].error_handler_node
        if not handler_node:
            return None
-        # ensure error + ERROR_SOURCE_NODE writes are durable before handler runs
-        if self._error_handler_write_futs:
-            futs, self._error_handler_write_futs = self._error_handler_write_futs, []
-            concurrent.futures.wait(futs)
+        writes = list(failed_task.writes)
+        writes.append((ERROR_SOURCE_NODE, failed_task.name))
+        self.put_writes(
+            failed_task.id,
+            writes,
+        )
        handler_task = prepare_node_error_handler_task(
            failed_task,
            handler_node_name=handler_node,
@@ -1569,7 +1295,7 @@ class SyncPregelLoop(PregelLoop, AbstractContextManager):
            return None
        self.tasks[handler_task.id] = handler_task
        if not self.is_replaying:
-            self._reapply_writes_to_succeeded_nodes({handler_task.id: handler_task})
+            self._match_writes({handler_task.id: handler_task})
        for task in self.match_cached_writes():
            self.output_writes(task.id, task.writes, cached=True)
        return handler_task
@@ -1621,10 +1347,6 @@ class SyncPregelLoop(PregelLoop, AbstractContextManager):
            # graph/thread. Returns None on first invocation.
            saved = self.checkpointer.get_tuple(self.checkpoint_config)

-        # Capture before the synthetic-empty fallback below overwrites `saved`.
-        # `_put_exit_delta_writes` uses this on first run (no persisted parent)
-        # to lazy-create a stub instead of anchoring delta writes on a parent.
-        self._has_persisted_parent = saved is not None
        if saved is None:
            saved = CheckpointTuple(
                self.checkpoint_config, empty_checkpoint(), {"step": -2}, None, []
@@ -1640,7 +1362,6 @@ class SyncPregelLoop(PregelLoop, AbstractContextManager):
                **saved.config.get(CONF, {}),
            },
        }
-        self._initial_checkpoint_config = self.checkpoint_config
        self.prev_checkpoint_config = saved.parent_config
        self.checkpoint_id_saved = saved.checkpoint["id"]
        self.checkpoint = saved.checkpoint
@@ -1650,11 +1371,6 @@ class SyncPregelLoop(PregelLoop, AbstractContextManager):
            if saved.pending_writes is not None
            else []
        )
-        self._delta_write_futs = []
-        self._error_handler_write_futs = []
-        self._exit_delta_writes = (
-            [] if self.durability == "exit" and self.checkpointer is not None else None
-        )
        self.submit = self.stack.enter_context(BackgroundExecutor(self.config))
        self.channels, self.managed = channels_from_checkpoint(
            self.specs,
@@ -1797,10 +1513,12 @@ class AsyncPregelLoop(PregelLoop, AbstractAsyncContextManager):
        handler_node = self.nodes[failed_task.name].error_handler_node
        if not handler_node:
            return None
-        # ensure error + ERROR_SOURCE_NODE writes are durable before handler runs
-        if self._error_handler_write_futs:
-            futs, self._error_handler_write_futs = self._error_handler_write_futs, []
-            await asyncio.gather(*futs)
+        writes = list(failed_task.writes)
+        writes.append((ERROR_SOURCE_NODE, failed_task.name))
+        self.put_writes(
+            failed_task.id,
+            writes,
+        )
        handler_task = prepare_node_error_handler_task(
            failed_task,
            handler_node_name=handler_node,
@@ -1823,7 +1541,7 @@ class AsyncPregelLoop(PregelLoop, AbstractAsyncContextManager):
            return None
        self.tasks[handler_task.id] = handler_task
        if not self.is_replaying:
-            self._reapply_writes_to_succeeded_nodes({handler_task.id: handler_task})
+            self._match_writes({handler_task.id: handler_task})
        for task in await self.amatch_cached_writes():
            self.output_writes(task.id, task.writes, cached=True)
        return handler_task
@@ -1878,10 +1596,6 @@ class AsyncPregelLoop(PregelLoop, AbstractAsyncContextManager):
            # graph/thread. Returns None on first invocation.
            saved = await self.checkpointer.aget_tuple(self.checkpoint_config)

-        # Capture before the synthetic-empty fallback below overwrites `saved`.
-        # `_put_exit_delta_writes` uses this on first run (no persisted parent)
-        # to lazy-create a stub instead of anchoring delta writes on a parent.
-        self._has_persisted_parent = saved is not None
        if saved is None:
            saved = CheckpointTuple(
                self.checkpoint_config, empty_checkpoint(), {"step": -2}, None, []
@@ -1897,7 +1611,6 @@ class AsyncPregelLoop(PregelLoop, AbstractAsyncContextManager):
                **saved.config.get(CONF, {}),
            },
        }
-        self._initial_checkpoint_config = self.checkpoint_config
        self.prev_checkpoint_config = saved.parent_config
        self.checkpoint_id_saved = saved.checkpoint["id"]
        self.checkpoint = saved.checkpoint
@@ -1908,10 +1621,6 @@ class AsyncPregelLoop(PregelLoop, AbstractAsyncContextManager):
            else []
        )
        self._delta_write_futs = []
-        self._error_handler_write_futs = []
-        self._exit_delta_writes = (
-            [] if self.durability == "exit" and self.checkpointer is not None else None
-        )
        self.submit = await self.stack.enter_async_context(
            AsyncBackgroundExecutor(self.config)
        )
@@ -10,7 +10,7 @@ from typing import (
 from uuid import UUID, uuid4

 from langchain_core.callbacks import BaseCallbackHandler
-from langchain_core.messages import BaseMessage, ToolMessage
+from langchain_core.messages import BaseMessage
 from langchain_core.outputs import ChatGeneration, ChatGenerationChunk, LLMResult
 from pydantic import BaseModel

@@ -303,35 +303,6 @@ class StreamMessagesHandlerV2(StreamMessagesHandler, _V2StreamingCallbackHandler
        super().__init__(stream, subgraphs, parent_ns=parent_ns)
        self._streamed_run_ids: set[UUID] = set()

-    def _find_and_emit_messages(self, meta: Meta, response: Any) -> None:
-        """Like the v1 handler, but skip ToolMessage from node outputs.
-
-        Tool results belong on the tools channel / state in v3; v2-flagged streams
-        must not replay finalized ToolMessages as chat tokens (see MessagesTransformer).
-        Legacy v1-only `stream_mode="messages"` still emits ToolMessages (see subgraph
-        streaming tests).
-        """
-        if isinstance(response, BaseMessage) and not isinstance(response, ToolMessage):
-            self._emit(meta, response, dedupe=True)
-        elif isinstance(response, Sequence):
-            for value in response:
-                if isinstance(value, BaseMessage) and not isinstance(
-                    value, ToolMessage
-                ):
-                    self._emit(meta, value, dedupe=True)
-        else:
-            for value in _state_values(response):
-                if isinstance(value, BaseMessage) and not isinstance(
-                    value, ToolMessage
-                ):
-                    self._emit(meta, value, dedupe=True)
-                elif isinstance(value, Sequence):
-                    for item in value:
-                        if isinstance(item, BaseMessage) and not isinstance(
-                            item, ToolMessage
-                        ):
-                            self._emit(meta, item, dedupe=True)
-
    def on_llm_end(
        self,
        response: LLMResult,
@@ -31,7 +31,6 @@ from langgraph._internal._constants import (
    CONFIG_KEY_CALL,
    CONFIG_KEY_SCRATCHPAD,
    ERROR,
-    ERROR_SOURCE_NODE,
    INTERRUPT,
    NO_WRITES,
    RESUME,
@@ -598,7 +597,7 @@ class PregelRunner:
                if self._should_route_to_error_handler(task) and not isinstance(
                    exception, GraphBubbleUp
                ):
-                    task.writes.append((ERROR_SOURCE_NODE, task.name))
+                    # Mark early in commit path; loop-side routing may happen later.
                    self._handled_exception_ids.add(id(exception))
                self.put_writes()(task.id, task.writes)  # type: ignore[misc]
        else:
@@ -62,14 +62,6 @@ class StreamMux:
        `extensions`, `_native` keys are recorded in `native_keys`, and
        any StreamChannel instances are bound and (if named) wired.

-        Transformers with `StreamTransformer.before_builtins = True` are
-        registered ahead of the rest, preserving relative order within
-        each lane. This lets content-mutating transformers (PII
-        redaction, content filters, etc.) run before built-ins like
-        `MessagesTransformer` that eagerly snapshot text fields into
-        their projections. See `StreamTransformer.before_builtins` for
-        the contract and foot-guns.
-
        Args:
            transformers: Already-built transformer instances. Registered
                only on this mux — they are NOT cloned into child
@@ -120,31 +112,14 @@ class StreamMux:
        self._pump_fn: Callable[[], bool] | None = None
        self._apump_fn: Callable[[], Awaitable[bool]] | None = None

-        # Factories run first (they propagate to child mini-muxes via
-        # `_make_child`), then any pre-built `transformers=` instances
-        # are registered as root-only — they aren't cloned for child
-        # scopes. Within each group, transformers with
-        # `before_builtins = True` are registered ahead of the rest so
-        # they observe (and may mutate) events before built-ins like
-        # `MessagesTransformer`. The order *within* each lane matches
-        # the supplied sequence.
-        pre: list[StreamTransformer] = []
-        rest: list[StreamTransformer] = []
+        # Factories run first (they propagate to child mini-muxes
+        # via `_make_child`), then any pre-built `transformers=`
+        # instances are registered as root-only — they aren't cloned
+        # for child scopes.
        if factories is not None:
            for factory in factories:
-                transformer = factory(scope)
-                (
-                    pre if getattr(transformer, "before_builtins", False) else rest
-                ).append(transformer)
-            for transformer in (*pre, *rest):
-                self._register(transformer)
-            pre.clear()
-            rest.clear()
+                self._register(factory(scope))
        for transformer in transformers or ():
-            (pre if getattr(transformer, "before_builtins", False) else rest).append(
-                transformer
-            )
-        for transformer in (*pre, *rest):
            self._register(transformer)

    def transformer_by_key(self, key: str) -> StreamTransformer | None:
@@ -91,28 +91,11 @@ class StreamTransformer(ABC):
            which modes a `stream_events(version="v3")` run requests from the graph.
            Empty tuple means the transformer consumes only synthetic
            events (or is purely passive).
-        before_builtins: Opt-in for transformers that must run *before*
-            built-in transformers like `MessagesTransformer` and
-            `ToolCallTransformer`. The mux partitions factories by this
-            flag at registration time: `before_builtins = True`
-            transformers are registered first, then everything else in
-            the order supplied. Within each lane, registration order is
-            preserved. This is the supported hook for content-mutating
-            transformers (PII redaction, profanity filters, etc.) whose
-            mutations must land before built-ins eagerly snapshot text
-            fields into their projections. **Foot-gun:** transformers
-            in this lane see `tasks` events before `LifecycleTransformer`
-            and `SubgraphTransformer` consume them — mutating
-            `event["params"]["namespace"]` or the data dict's
-            `id` / `result` / `error` / `interrupts` fields will desync
-            their bookkeeping. Observe freely; mutate only fields no
-            built-in reads (e.g. `delta.text` on `messages` events).
    """

    requires_async: ClassVar[bool] = False
    supports_sync: ClassVar[bool] = False
    required_stream_modes: ClassVar[tuple[str, ...]] = ()
-    before_builtins: ClassVar[bool] = False

    def __init__(self, scope: tuple[str, ...] = ()) -> None:
        """Initialize the transformer with its mux's scope.
@@ -8,7 +8,7 @@ from langchain_core.language_models.chat_model_stream import (
    AsyncChatModelStream,
    ChatModelStream,
 )
-from langchain_core.messages import AIMessageChunk, BaseMessage, ToolMessage
+from langchain_core.messages import AIMessageChunk, BaseMessage
 from langchain_protocol.protocol import MessagesData
 from typing_extensions import NotRequired, TypedDict

@@ -203,7 +203,6 @@ class MessagesTransformer(StreamTransformer):
        # Correlate protocol events back to a ChatModelStream by run_id
        # (attached to the event's metadata by StreamMessagesHandler).
        self._by_run: dict[str, ChatModelStream] = {}
-        self._ignored_runs: set[str] = set()
        self._pump_fn: Callable[[], bool] | None = None
        self._apump_fn: Callable[[], Awaitable[bool]] | None = None
        # Cached as a list once for cheap equality with the protocol
@@ -277,10 +276,8 @@ class MessagesTransformer(StreamTransformer):
            self._route_protocol_event(
                cast("MessagesData", payload), run_id=run_id, node=node
            )
-        elif (
-            isinstance(payload, BaseMessage)
-            and not isinstance(payload, AIMessageChunk)
-            and not isinstance(payload, ToolMessage)
+        elif isinstance(payload, BaseMessage) and not isinstance(
+            payload, AIMessageChunk
        ):
            self._route_whole_message(payload, node=node)
        # Legacy AIMessageChunk tuples (from on_llm_new_token) are ignored;
@@ -298,11 +295,6 @@ class MessagesTransformer(StreamTransformer):
    ) -> None:
        event_type = event.get("event")
        if event_type == "message-start":
-            # Tool results are exposed on the tools projection and state
-            # snapshots; run.messages is the chat-token projection.
-            if event.get("role") == "tool":
-                self._ignored_runs.add(run_id)
-                return
            message_id = event.get("message_id")
            stream = self._make_stream(
                namespace=[],
@@ -312,9 +304,6 @@ class MessagesTransformer(StreamTransformer):
            self._by_run[run_id] = stream
            self._log.push(stream)
            stream.dispatch(event)
-        elif run_id in self._ignored_runs:
-            if event_type == "message-finish":
-                self._ignored_runs.discard(run_id)
        elif run_id in self._by_run:
            stream = self._by_run[run_id]
            stream.dispatch(event)
@@ -330,14 +319,12 @@ class MessagesTransformer(StreamTransformer):
    def finalize(self) -> None:
        """Clear any routing state — streams close themselves via `message-finish`."""
        self._by_run.clear()
-        self._ignored_runs.clear()

    def fail(self, err: BaseException) -> None:
        """Propagate run error to any streams still open when the graph fails."""
        for stream in list(self._by_run.values()):
            stream.fail(err)
        self._by_run.clear()
-        self._ignored_runs.clear()


 SubgraphStatus = Literal["started", "completed", "failed", "interrupted", "drained"]
@@ -4,7 +4,7 @@ build-backend = "hatchling.build"

 [project]
 name = "langgraph"
-version = "1.2.1"
+version = "1.2.0a7"
 description = "Building stateful, multi-actor applications with LLMs"
 authors = []
 requires-python = ">=3.10"
@@ -24,10 +24,10 @@ classifiers = [
    'Programming Language :: Python :: 3.13',
 ]
 dependencies = [
-    "langchain-core>=1.4.0,<2",
-    "langgraph-checkpoint>=4.1.0,<5.0.0",
+    "langchain-core>=1.4.0a2,<2",
+    "langgraph-checkpoint>=4.1.0a4,<5.0.0",
    "langgraph-sdk>=0.3.0,<0.4.0",
-    "langgraph-prebuilt>=1.1.0,<1.2.0",
+    "langgraph-prebuilt>=1.1.0a2,<1.2.0",
    "xxhash>=3.5.0",
    "pydantic>=2.7.4",
 ]
@@ -3,7 +3,12 @@ from collections.abc import Sequence
 from typing import Annotated

 import pytest
-from langchain_core.messages import AIMessage, HumanMessage, RemoveMessage
+from langchain_core.messages import (
+    AIMessage,
+    AIMessageChunk,
+    HumanMessage,
+    RemoveMessage,
+)
 from langgraph.checkpoint.memory import InMemorySaver
 from langgraph.checkpoint.serde.types import _DeltaSnapshot
 from typing_extensions import NotRequired, TypedDict
@@ -16,7 +21,7 @@ from langgraph.channels.topic import Topic
 from langgraph.channels.untracked_value import UntrackedValue
 from langgraph.errors import EmptyChannelError, InvalidUpdateError
 from langgraph.graph import START, StateGraph
-from langgraph.graph.message import _messages_delta_reducer
+from langgraph.graph.message import REMOVE_ALL_MESSAGES, _messages_delta_reducer
 from langgraph.graph.state import _get_channel
 from langgraph.types import Overwrite

@@ -284,6 +289,61 @@ def test_messages_delta_reducer_tuple_write_is_one_message() -> None:
    assert result[0].content == "hi"


+def test_messages_delta_reducer_assigns_uuid_to_id_less_messages() -> None:
+    """Messages without IDs get UUIDs assigned, matching add_messages behavior.
+
+    Without UUID assignment, RemoveMessage tombstoning fails on messages that
+    were created without explicit IDs.
+    """
+    m1 = HumanMessage(content="hi")
+    m2 = AIMessage(content="hello")
+    assert m1.id is None
+    assert m2.id is None
+
+    result = _messages_delta_reducer([], [[m1, m2]])
+    assert len(result) == 2
+    assert result[0].id is not None
+    assert result[1].id is not None
+
+    # RemoveMessage tombstoning must work on the now-assigned IDs.
+    result2 = _messages_delta_reducer(result, [RemoveMessage(id=result[1].id)])
+    assert len(result2) == 1
+    assert result2[0].content == "hi"
+
+
+def test_messages_delta_reducer_remove_all_messages() -> None:
+    """REMOVE_ALL_MESSAGES sentinel clears all state and preceding writes."""
+    state = [HumanMessage(content="old", id="h1"), AIMessage(content="prior", id="a1")]
+
+    # Sentinel mid-batch: everything before it (including state) is discarded.
+    result = _messages_delta_reducer(
+        state,
+        [
+            [
+                RemoveMessage(id=REMOVE_ALL_MESSAGES),
+                HumanMessage(content="fresh", id="h2"),
+            ]
+        ],
+    )
+    assert len(result) == 1
+    assert result[0].content == "fresh"
+
+    # Batching-invariant: split across two calls must equal one combined call.
+    step1 = _messages_delta_reducer(state, [[RemoveMessage(id=REMOVE_ALL_MESSAGES)]])
+    step2 = _messages_delta_reducer(step1, [[HumanMessage(content="fresh", id="h2")]])
+    assert step2 == result
+
+
+def test_messages_delta_reducer_coerces_message_chunks() -> None:
+    """BaseMessageChunk writes are coerced to full messages."""
+    chunk = AIMessageChunk(content="hello", id="a1")
+    result = _messages_delta_reducer([], [[chunk]])
+    assert len(result) == 1
+    assert not isinstance(result[0], AIMessageChunk)
+    assert result[0].content == "hello"
+    assert result[0].id == "a1"
+
+
 def test_delta_channel_checkpoint_returns_missing() -> None:
    """checkpoint() always returns MISSING regardless of state.

@@ -1,372 +0,0 @@
-"""Tests for exit-mode delta channel persistence redesign.
-
-Validates that `durability="exit"` correctly persists delta-channel writes
-using count-based snapshot decisions (rather than force-snapshotting every
-channel), lazy stub creation when no parent exists, and proper read-path
-reconstruction via ancestor walks.
-"""
-
-from typing import Annotated, Any
-
-import pytest
-from langchain_core.messages import AIMessage, HumanMessage
-from langgraph.checkpoint.memory import InMemorySaver
-from langgraph.checkpoint.serde.types import _DeltaSnapshot
-from typing_extensions import TypedDict
-
-from langgraph.channels.delta import DeltaChannel
-from langgraph.graph import START, StateGraph
-from langgraph.graph.message import _messages_delta_reducer
-
-pytestmark = pytest.mark.anyio
-
-
-def _build_graph(
-    checkpointer: InMemorySaver,
-    *,
-    freq: int = 1000,
-) -> Any:
-    channel = DeltaChannel(_messages_delta_reducer, snapshot_frequency=freq)
-    # Functional TypedDict form: class form can't reference `channel` (a
-    # local variable) inside Annotated due to forward-ref evaluation rules.
-    State = TypedDict("State", {"messages": Annotated[list, channel]})  # type: ignore[call-overload]  # noqa: UP013
-
-    def respond(state: dict) -> dict:
-        i = len(state["messages"])
-        return {"messages": [AIMessage(content=f"reply-{i}", id=f"ai{i}")]}
-
-    builder = StateGraph(State)
-    builder.add_node("respond", respond)
-    builder.add_edge(START, "respond")
-    return builder.compile(checkpointer=checkpointer)
-
-
-# ---------------------------------------------------------------------------
-# 8a. Write-path / structural tests
-# ---------------------------------------------------------------------------
-
-
-async def test_exit_first_run_no_delta_writes() -> None:
-    """Graph with delta channel invoked with input that doesn't touch it.
-    Only one checkpoint row, no stub."""
-    State = TypedDict(  # noqa: UP013
-        "State",
-        {
-            "messages": Annotated[list, DeltaChannel(_messages_delta_reducer)],
-            "value": str,
-        },
-    )  # type: ignore[call-overload]
-
-    def noop(state: dict) -> dict:
-        return {"value": "done"}
-
-    saver = InMemorySaver()
-    builder = StateGraph(State)
-    builder.add_node("noop", noop)
-    builder.add_edge(START, "noop")
-    graph = builder.compile(checkpointer=saver)
-    config = {"configurable": {"thread_id": "no-delta-writes"}}
-
-    graph.invoke({"value": "start"}, config, durability="exit")
-
-    checkpoints = list(saver.list(config))
-    assert len(checkpoints) == 1
-    stubs = [t for t in checkpoints if t.metadata.get("step") == -2]
-    assert len(stubs) == 0
-
-
-async def test_exit_first_run_all_snapshot() -> None:
-    """snapshot_frequency=1 forces every channel to snapshot.
-    No stub needed; final_checkpoint has _DeltaSnapshot."""
-    saver = InMemorySaver()
-    graph = _build_graph(saver, freq=1)
-    config = {"configurable": {"thread_id": "all-snapshot"}}
-
-    result = graph.invoke(
-        {"messages": [HumanMessage(content="hi", id="h1")]},
-        config,
-        durability="exit",
-    )
-    assert len(result["messages"]) == 2
-
-    checkpoints = list(saver.list(config))
-    stubs = [t for t in checkpoints if t.metadata.get("step") == -2]
-    assert len(stubs) == 0
-
-    head = saver.get_tuple(config)
-    assert head is not None
-    assert isinstance(head.checkpoint["channel_values"].get("messages"), _DeltaSnapshot)
-
-    state = graph.get_state(config)
-    assert [m.content for m in state.values["messages"]] == ["hi", "reply-1"]
-
-
-async def test_exit_first_run_sub_freq_with_writes() -> None:
-    """First run with default snapshot_frequency (1000), writes below threshold.
-    A stub is created; writes are anchored under it; get_state reconstructs."""
-    saver = InMemorySaver()
-    graph = _build_graph(saver)
-    config = {"configurable": {"thread_id": "sub-freq-first"}}
-
-    result = graph.invoke(
-        {"messages": [HumanMessage(content="hello", id="h1")]},
-        config,
-        durability="exit",
-    )
-    assert [m.content for m in result["messages"]] == ["hello", "reply-1"]
-
-    checkpoints = list(saver.list(config))
-    stubs = [t for t in checkpoints if t.metadata.get("step") == -2]
-    assert len(stubs) == 1, f"Expected 1 stub, got {len(stubs)}"
-
-    head = saver.get_tuple(config)
-    assert head is not None
-    assert "messages" not in head.checkpoint["channel_values"]
-    assert "messages" in head.checkpoint["channel_versions"]
-
-    state = graph.get_state(config)
-    assert [m.content for m in state.values["messages"]] == ["hello", "reply-1"]
-
-
-async def test_exit_resumed_run_sub_freq() -> None:
-    """Two consecutive exit runs. Second run anchors on the first's
-    final_checkpoint (no new stub). Ordering preserved."""
-    saver = InMemorySaver()
-    graph = _build_graph(saver)
-    config = {"configurable": {"thread_id": "resumed-sub-freq"}}
-
-    graph.invoke(
-        {"messages": [HumanMessage(content="msg1", id="h1")]},
-        config,
-        durability="exit",
-    )
-
-    graph.invoke(
-        {"messages": [HumanMessage(content="msg2", id="h2")]},
-        config,
-        durability="exit",
-    )
-
-    checkpoints = list(saver.list(config))
-    stubs = [t for t in checkpoints if t.metadata.get("step") == -2]
-    assert len(stubs) == 1
-
-    state = graph.get_state(config)
-    contents = [m.content for m in state.values["messages"]]
-    assert len(contents) == 4
-    assert contents[0] == "msg1"
-    assert contents[2] == "msg2"
-    assert contents[0:4:2] == ["msg1", "msg2"]
-
-
-async def test_exit_count_parity_sync_vs_exit() -> None:
-    """Sync and exit durability produce the same update count in
-    counters_since_delta_snapshot after an equivalent run."""
-    for durability in ("sync", "exit"):
-        saver = InMemorySaver()
-        graph = _build_graph(saver)
-        config = {"configurable": {"thread_id": f"parity-{durability}"}}
-
-        graph.invoke(
-            {"messages": [HumanMessage(content="hi", id="h1")]},
-            config,
-            durability=durability,
-        )
-
-        head = saver.get_tuple(config)
-        assert head is not None
-        counters = head.metadata.get("counters_since_delta_snapshot", {})
-        updates, supersteps = counters.get("messages", (0, 0))
-        assert updates == 2, (
-            f"durability={durability}: expected updates=2, got {updates}"
-        )
-        assert supersteps >= 2, (
-            f"durability={durability}: expected supersteps>=2, got {supersteps}"
-        )
-
-
-async def test_exit_snapshot_fires_at_frequency() -> None:
-    """With snapshot_frequency=3, after 3 exit runs (each incrementing count
-    by 2: input + superstep), the 2nd run hits count=4>=3, triggering snapshot.
-    After that run, count resets to 0 and channel_values has _DeltaSnapshot."""
-    saver = InMemorySaver()
-    graph = _build_graph(saver, freq=3)
-    config = {"configurable": {"thread_id": "snapshot-at-freq"}}
-
-    graph.invoke(
-        {"messages": [HumanMessage(content="m1", id="h1")]},
-        config,
-        durability="exit",
-    )
-    head = saver.get_tuple(config)
-    assert head is not None
-    counters1 = head.metadata.get("counters_since_delta_snapshot", {})
-    updates1 = counters1.get("messages", (0, 0))[0]
-    assert updates1 == 2
-
-    graph.invoke(
-        {"messages": [HumanMessage(content="m2", id="h2")]},
-        config,
-        durability="exit",
-    )
-    head = saver.get_tuple(config)
-    assert head is not None
-    counters2 = head.metadata.get("counters_since_delta_snapshot", {})
-    updates2 = counters2.get("messages", (0, 0))[0]
-    assert updates2 == 0, f"Expected reset to 0 after snapshot, got {updates2}"
-    assert isinstance(head.checkpoint["channel_values"].get("messages"), _DeltaSnapshot)
-
-
-async def test_exit_mixed_snapshot_and_non_snapshot() -> None:
-    """One delta channel at freq=1 (always snapshot) and one at freq=1000
-    (never snapshot within this test). Verify correct behavior for both."""
-
-    fast_ch = DeltaChannel(_messages_delta_reducer, snapshot_frequency=1)
-    slow_ch = DeltaChannel(_messages_delta_reducer, snapshot_frequency=1000)
-    State = TypedDict(  # noqa: UP013
-        "State",
-        {"fast": Annotated[list, fast_ch], "slow": Annotated[list, slow_ch]},
-    )  # type: ignore[call-overload]
-
-    def respond(state: dict) -> dict:
-        return {
-            "fast": [AIMessage(content="fast-reply", id="f1")],
-            "slow": [AIMessage(content="slow-reply", id="s1")],
-        }
-
-    saver = InMemorySaver()
-    builder = StateGraph(State)
-    builder.add_node("respond", respond)
-    builder.add_edge(START, "respond")
-    graph = builder.compile(checkpointer=saver)
-    config = {"configurable": {"thread_id": "mixed-freq"}}
-
-    graph.invoke(
-        {
-            "fast": [HumanMessage(content="fast-in", id="fi")],
-            "slow": [HumanMessage(content="slow-in", id="si")],
-        },
-        config,
-        durability="exit",
-    )
-
-    head = saver.get_tuple(config)
-    assert head is not None
-    assert isinstance(head.checkpoint["channel_values"].get("fast"), _DeltaSnapshot)
-    assert "slow" not in head.checkpoint["channel_values"]
-
-    state = graph.get_state(config)
-    assert [m.content for m in state.values["fast"]] == ["fast-in", "fast-reply"]
-    assert [m.content for m in state.values["slow"]] == ["slow-in", "slow-reply"]
-
-
-# ---------------------------------------------------------------------------
-# 8b. Read-path tests
-# ---------------------------------------------------------------------------
-
-
-async def test_exit_multi_run_replay_chain() -> None:
-    """K=4 consecutive exit runs, each adding a message. After each run,
-    get_state returns all messages in chronological order."""
-    saver = InMemorySaver()
-    graph = _build_graph(saver)
-    config = {"configurable": {"thread_id": "replay-chain"}}
-
-    for i in range(4):
-        graph.invoke(
-            {"messages": [HumanMessage(content=f"user-{i}", id=f"h{i}")]},
-            config,
-            durability="exit",
-        )
-
-        state = graph.get_state(config)
-        contents = [m.content for m in state.values["messages"]]
-        user_msgs = [c for c in contents if c.startswith("user-")]
-        assert user_msgs == [f"user-{j}" for j in range(i + 1)], (
-            f"After run {i}: user messages out of order: {user_msgs}"
-        )
-        assert len(contents) == (i + 1) * 2
-
-
-async def test_exit_metadata_round_trip() -> None:
-    """K=5 consecutive exit runs with snapshot_frequency=5. Verify metadata
-    counters_since_delta_snapshot increments correctly across runs."""
-    freq = 5
-    saver = InMemorySaver()
-    graph = _build_graph(saver, freq=freq)
-    config = {"configurable": {"thread_id": "metadata-rt"}}
-
-    for i in range(1, 6):
-        graph.invoke(
-            {"messages": [HumanMessage(content=f"m{i}", id=f"h{i}")]},
-            config,
-            durability="exit",
-        )
-        head = saver.get_tuple(config)
-        assert head is not None
-        counters = head.metadata.get("counters_since_delta_snapshot", {})
-        updates = counters.get("messages", (0, 0))[0]
-        cumulative = i * 2
-        if cumulative >= freq:
-            assert updates == 0 or updates == cumulative % freq or updates < freq, (
-                f"After run {i}: updates={updates} should have reset or be partial"
-            )
-        else:
-            assert updates == cumulative, (
-                f"After run {i}: expected {cumulative}, got {updates}"
-            )
-
-
-async def test_exit_mixed_durability_round_trip() -> None:
-    """Alternate sync and exit durability; verify counts stay monotonic
-    and state accumulates correctly."""
-    saver = InMemorySaver()
-    graph = _build_graph(saver)
-    config = {"configurable": {"thread_id": "mixed-durability"}}
-
-    for i, dur in enumerate(["sync", "exit", "sync", "exit"]):
-        graph.invoke(
-            {"messages": [HumanMessage(content=f"msg-{i}", id=f"h{i}")]},
-            config,
-            durability=dur,
-        )
-
-        state = graph.get_state(config)
-        contents = [m.content for m in state.values["messages"]]
-        user_msgs = [c for c in contents if c.startswith("msg-")]
-        assert user_msgs == [f"msg-{j}" for j in range(i + 1)], (
-            f"After run {i} (durability={dur}): {user_msgs}"
-        )
-        assert len(contents) == (i + 1) * 2
-
-
-async def test_exit_snapshot_then_tail_deltas() -> None:
-    """Run 1 forces snapshot (freq=1). Run 2 at freq=1000 adds more writes
-    that don't snapshot. Reading after run 2 must combine the snapshot seed
-    with the tail deltas."""
-    saver = InMemorySaver()
-
-    graph1 = _build_graph(saver, freq=1)
-    config = {"configurable": {"thread_id": "snapshot-then-tail"}}
-    graph1.invoke(
-        {"messages": [HumanMessage(content="seed-msg", id="h1")]},
-        config,
-        durability="exit",
-    )
-
-    head = saver.get_tuple(config)
-    assert head is not None
-    assert isinstance(head.checkpoint["channel_values"].get("messages"), _DeltaSnapshot)
-
-    graph2 = _build_graph(saver, freq=1000)
-    graph2.invoke(
-        {"messages": [HumanMessage(content="tail-msg", id="h2")]},
-        config,
-        durability="exit",
-    )
-
-    state = graph2.get_state(config)
-    contents = [m.content for m in state.values["messages"]]
-    assert "seed-msg" in contents
-    assert "tail-msg" in contents
-    assert contents.index("seed-msg") < contents.index("tail-msg")
@@ -1,195 +0,0 @@
-"""Tests for the supersteps-since-last-snapshot bound on DeltaChannel.
-
-Validates that a delta channel which stops receiving writes is still
-force-snapshotted after DELTA_MAX_SUPERSTEPS_SINCE_SNAPSHOT supersteps,
-preventing unbounded ancestor walks.
-"""
-
-from typing import Annotated, Any
-from unittest.mock import patch
-
-import pytest
-from langgraph.checkpoint.memory import InMemorySaver
-from langgraph.checkpoint.serde.types import _DeltaSnapshot
-from typing_extensions import TypedDict
-
-from langgraph.channels.delta import DeltaChannel
-from langgraph.graph import END, START, StateGraph
-from langgraph.pregel._checkpoint import delta_channels_to_snapshot
-
-pytestmark = pytest.mark.anyio
-
-
-def _simple_reducer(current: list, updates: list) -> list:
-    """Flatten updates into current list (each update is itself a list)."""
-    result = list(current)
-    for u in updates:
-        if isinstance(u, list):
-            result.extend(u)
-        else:
-            result.append(u)
-    return result
-
-
-def _build_two_channel_graph(
-    checkpointer: InMemorySaver,
-    *,
-    freq_a: int = 10_000,
-    freq_b: int = 10_000,
-    n_loops: int = 1,
-) -> Any:
-    """Graph with two delta channels A and B.
-
-    The node only writes to channel A; B is never written by the node.
-    `n_loops` controls how many supersteps the graph runs (via chained nodes).
-    """
-    ch_a = DeltaChannel(_simple_reducer, list, snapshot_frequency=freq_a)
-    ch_b = DeltaChannel(_simple_reducer, list, snapshot_frequency=freq_b)
-    State = TypedDict(  # noqa: UP013
-        "State",
-        {"a": Annotated[list, ch_a], "b": Annotated[list, ch_b]},
-    )  # type: ignore[call-overload]
-
-    builder = StateGraph(State)
-
-    for i in range(n_loops):
-        name = f"step_{i}"
-
-        def node_fn(state: dict, _i: int = i) -> dict:
-            return {"a": [f"a-val-{_i}"]}
-
-        builder.add_node(name, node_fn)
-        if i == 0:
-            builder.add_edge(START, name)
-        else:
-            builder.add_edge(f"step_{i - 1}", name)
-        if i == n_loops - 1:
-            builder.add_edge(name, END)
-
-    return builder.compile(checkpointer=checkpointer)
-
-
-async def test_forced_snapshot_single_run() -> None:
-    """A single invoke with enough supersteps triggers snapshot on the
-    unwritten channel B via the supersteps bound."""
-    max_ss = 3
-    with patch(
-        "langgraph.pregel._checkpoint.DELTA_MAX_SUPERSTEPS_SINCE_SNAPSHOT",
-        max_ss,
-    ):
-        saver = InMemorySaver()
-        graph = _build_two_channel_graph(saver, n_loops=4)
-        config = {"configurable": {"thread_id": "single-run-ss"}}
-
-        graph.invoke({"a": ["seed-a"], "b": ["seed-b"]}, config)
-
-        head = saver.get_tuple(config)
-        assert head is not None
-        assert isinstance(head.checkpoint["channel_values"].get("b"), _DeltaSnapshot), (
-            "Channel B should have been force-snapshotted via supersteps bound"
-        )
-
-        state = graph.get_state(config)
-        assert state.values["b"] == ["seed-b"]
-        assert "seed-a" in state.values["a"]
-
-
-async def test_forced_snapshot_accumulates_across_runs() -> None:
-    """Supersteps counter for an unwritten channel persists across separate
-    invoke() calls. After enough runs, the channel is force-snapshotted."""
-    max_ss = 5
-    with patch(
-        "langgraph.pregel._checkpoint.DELTA_MAX_SUPERSTEPS_SINCE_SNAPSHOT",
-        max_ss,
-    ):
-        saver = InMemorySaver()
-        graph = _build_two_channel_graph(saver, n_loops=1)
-        config = {"configurable": {"thread_id": "multi-run-ss"}}
-
-        graph.invoke({"a": ["init-a"], "b": ["init-b"]}, config)
-
-        for i in range(1, 6):
-            graph.invoke({"a": [f"run-{i}"]}, config)
-
-            head = saver.get_tuple(config)
-            assert head is not None
-            counters = head.metadata.get("counters_since_delta_snapshot", {})
-            b_counters = counters.get("b", (0, 0))
-
-            if b_counters == (0, 0):
-                assert isinstance(
-                    head.checkpoint["channel_values"].get("b"), _DeltaSnapshot
-                ), f"Run {i}: counter reset but no snapshot blob for B"
-                break
-        else:
-            pytest.fail("Channel B was never force-snapshotted after multiple runs")
-
-        state = graph.get_state(config)
-        assert state.values["b"] == ["init-b"]
-        assert "init-a" in state.values["a"]
-
-
-async def test_predicate_fires_on_supersteps_overflow() -> None:
-    """Unit test: delta_channels_to_snapshot fires when supersteps >= MAX
-    even when updates == 0."""
-    ch = DeltaChannel(_simple_reducer, list, snapshot_frequency=10_000)
-    ch.key = "x"
-    ch_instance = ch.from_checkpoint(None)
-
-    channels = {"x": ch_instance}
-    counters: dict[str, tuple[int, int]] = {"x": (0, 5000)}
-
-    result = delta_channels_to_snapshot(channels, counters)
-    assert "x" in result
-
-    counters_below: dict[str, tuple[int, int]] = {"x": (0, 4999)}
-    result2 = delta_channels_to_snapshot(channels, counters_below)
-    assert "x" not in result2
-
-
-async def test_counter_reset_after_supersteps_snapshot() -> None:
-    """After the supersteps bound triggers a snapshot, the counters for
-    that channel reset. Verify by using a bound higher than one run's
-    supersteps so we can see the counter in an intermediate state."""
-    max_ss = 15
-    with patch(
-        "langgraph.pregel._checkpoint.DELTA_MAX_SUPERSTEPS_SINCE_SNAPSHOT",
-        max_ss,
-    ):
-        saver = InMemorySaver()
-        graph = _build_two_channel_graph(saver, n_loops=4)
-        config = {"configurable": {"thread_id": "counter-reset"}}
-
-        graph.invoke({"a": ["seed-a"], "b": ["seed-b"]}, config)
-
-        head = saver.get_tuple(config)
-        assert head is not None
-        counters = head.metadata.get("counters_since_delta_snapshot", {})
-        b_counters = counters.get("b", (0, 0))
-        run1_supersteps = b_counters[1]
-        assert run1_supersteps > 0, "Should have some supersteps"
-        assert b_counters[0] == 1, "B written once (input step)"
-
-        graph.invoke({"a": ["more-a"]}, config)
-        head2 = saver.get_tuple(config)
-        assert head2 is not None
-        counters2 = head2.metadata.get("counters_since_delta_snapshot", {})
-        b_counters2 = counters2.get("b", (0, 0))
-        run2_supersteps = b_counters2[1]
-        assert run2_supersteps > run1_supersteps, "Supersteps should accumulate"
-        assert b_counters2[0] == 1, "B written once total (only original input)"
-
-        graph.invoke({"a": ["even-more"]}, config)
-        head3 = saver.get_tuple(config)
-        assert head3 is not None
-        assert isinstance(
-            head3.checkpoint["channel_values"].get("b"), _DeltaSnapshot
-        ), "B should have snapshotted at supersteps >= max_ss"
-        counters3 = head3.metadata.get("counters_since_delta_snapshot", {})
-        b_counters3 = counters3.get("b", (0, 0))
-        assert b_counters3[1] < max_ss, (
-            f"After snapshot, supersteps should have reset, got {b_counters3}"
-        )
-
-        state = graph.get_state(config)
-        assert state.values["b"] == ["seed-b"]
@@ -15,7 +15,7 @@ from langchain_core.callbacks import AsyncCallbackManagerForLLMRun, BaseCallback
 from langchain_core.language_models.fake_chat_models import GenericFakeChatModel
 from langchain_core.messages import AIMessage, AIMessageChunk, BaseMessage, HumanMessage
 from langchain_core.outputs import ChatGeneration, ChatGenerationChunk, ChatResult
-from langchain_core.runnables import RunnableConfig, RunnableLambda, RunnableParallel
+from langchain_core.runnables import RunnableLambda, RunnableParallel
 from langgraph.checkpoint.memory import InMemorySaver, MemorySaver
 from langgraph.checkpoint.serde.jsonplus import JsonPlusSerializer
 from typing_extensions import TypedDict
@@ -1674,28 +1674,15 @@ async def test_arun_with_retry_timeout_observer_tracks_attempts():
 async def test_arun_with_retry_timeout_observer_emits_progress_on_heartbeat():
    events: list = []

-    # `_TimedAttemptScope.__init__` sets `_last_progress` to `time.monotonic()`,
-    # but the watchdog itself doesn't start running until after `wrap_config`
-    # and task scheduling — under CI load that gap can be large enough to eat
-    # the entire idle window before the task body's first await even runs. We
-    # defend against that by:
-    #   1. Using a generous idle_timeout so scheduling slack stays well within it.
-    #   2. Calling `runtime.heartbeat()` BEFORE the first sleep, which resets
-    #      `_last_progress` to "now" the moment the task body actually starts.
-    idle_timeout_s = 1.0
-
    class HeartbeatProc:
        async def ainvoke(self, input, config):
            runtime = config[CONF][CONFIG_KEY_RUNTIME]
-            runtime.heartbeat()  # reset the idle clock at task-body entry
            for _ in range(8):
                await asyncio.sleep(0.05)
                runtime.heartbeat()
            return "ok"

-    task = _make_task(
-        HeartbeatProc(), timeout=_idle_timeout(idle_timeout_s), name="heartbeat"
-    )
+    task = _make_task(HeartbeatProc(), timeout=_idle_timeout(0.2), name="heartbeat")
    task.config[CONF][CONFIG_KEY_TIMED_ATTEMPT_OBSERVER] = events.append
    assert await arun_with_retry(task, retry_policy=None) == "ok"

@@ -1704,13 +1691,13 @@ async def test_arun_with_retry_timeout_observer_emits_progress_on_heartbeat():
    assert by_event[-1] == "finish"
    progress = [ev for ev in events if ev.event == "progress"]
    assert progress, "expected at least one progress event from heartbeat"
-    # Rate limit is `idle_timeout / 4` = 0.25s; with the task running for
-    # ~400ms we expect 1–2 progress events (well below the 9 heartbeats).
+    # Rate limit is `idle_timeout / 4` = 0.05s; with 8 heartbeats spaced ~0.05s
+    # we should see at most ~one progress event per heartbeat (well below 8).
    assert len(progress) <= len(by_event)
    for ev in progress:
        assert ev.context.task_name == "heartbeat"
        assert ev.context.attempt == 1
-        assert ev.context.idle_timeout_secs == idle_timeout_s
+        assert ev.context.idle_timeout_secs == 0.2
        assert isinstance(ev.progress_at, datetime)


@@ -2280,525 +2267,3 @@ def test_node_without_error_handler_still_fails_run():

    with pytest.raises(ValueError, match="no handler"):
        graph.invoke({"foo": ""})
-
-
-# ---------------------------------------------------------------------------
-# set_node_defaults()
-# ---------------------------------------------------------------------------
-
-
-def test_set_node_defaults_error_handler_catches_all_nodes():
-    class State(TypedDict):
-        route: str
-        foo: Annotated[list[str], operator.add]
-
-    def route_node(state: State) -> Command:
-        return Command(goto=state["route"])
-
-    def fail_a(state: State) -> State:
-        raise RuntimeError("a failed")
-
-    def fail_b(state: State) -> State:
-        raise RuntimeError("b failed")
-
-    captured: dict[str, list[str]] = {"nodes": []}
-
-    def default_handler(state: State, error: NodeError) -> State:
-        captured["nodes"].append(error.node)
-        return {"foo": [f"handled_{error.node}"]}
-
-    graph = (
-        StateGraph(State)
-        .set_node_defaults(error_handler=default_handler)
-        .add_node("route_node", route_node)
-        .add_node("fail_a", fail_a)
-        .add_node("fail_b", fail_b)
-        .add_edge(START, "route_node")
-        .add_conditional_edges(
-            "route_node", lambda s: s["route"], path_map=["fail_a", "fail_b"]
-        )
-        .compile()
-    )
-
-    result_a = graph.invoke({"route": "fail_a", "foo": []})
-    result_b = graph.invoke({"route": "fail_b", "foo": []})
-    assert result_a["foo"] == ["handled_fail_a"]
-    assert result_b["foo"] == ["handled_fail_b"]
-    assert "fail_a" in captured["nodes"]
-    assert "fail_b" in captured["nodes"]
-
-
-def test_set_node_defaults_error_handler_overridden_by_node_handler():
-    class State(TypedDict):
-        route: str
-        foo: Annotated[list[str], operator.add]
-
-    def route_node(state: State) -> Command:
-        return Command(goto=state["route"])
-
-    def fail_a(state: State) -> State:
-        raise RuntimeError("a failed")
-
-    def fail_b(state: State) -> State:
-        raise RuntimeError("b failed")
-
-    captured: dict[str, list[str]] = {"handler": []}
-
-    def node_handler(state: State, error: NodeError) -> State:
-        captured["handler"].append(f"node:{error.node}")
-        return {"foo": [f"node_handled_{error.node}"]}
-
-    def default_handler(state: State, error: NodeError) -> State:
-        captured["handler"].append(f"default:{error.node}")
-        return {"foo": [f"default_handled_{error.node}"]}
-
-    graph = (
-        StateGraph(State)
-        .set_node_defaults(error_handler=default_handler)
-        .add_node("route_node", route_node)
-        .add_node("fail_a", fail_a, error_handler=node_handler)
-        .add_node("fail_b", fail_b)
-        .add_edge(START, "route_node")
-        .add_conditional_edges(
-            "route_node", lambda s: s["route"], path_map=["fail_a", "fail_b"]
-        )
-        .compile()
-    )
-
-    result_a = graph.invoke({"route": "fail_a", "foo": []})
-    assert result_a["foo"] == ["node_handled_fail_a"]
-    assert "node:fail_a" in captured["handler"]
-    assert "default:fail_a" not in captured["handler"]
-
-    result_b = graph.invoke({"route": "fail_b", "foo": []})
-    assert result_b["foo"] == ["default_handled_fail_b"]
-    assert "default:fail_b" in captured["handler"]
-
-
-def test_set_node_defaults_error_handler_skips_per_node_handler_nodes():
-    """If a per-node error handler itself raises, the default handler must NOT
-    catch it -- the run should fail."""
-
-    class State(TypedDict):
-        foo: str
-
-    def always_failing(state: State) -> State:
-        raise RuntimeError("node boom")
-
-    def broken_handler(state: State, error: NodeError) -> State:
-        raise RuntimeError("handler boom")
-
-    def default_handler(state: State, error: NodeError) -> State:
-        return {"foo": "default recovered"}
-
-    graph = (
-        StateGraph(State)
-        .set_node_defaults(error_handler=default_handler)
-        .add_node("always_failing", always_failing, error_handler=broken_handler)
-        .add_edge(START, "always_failing")
-        .compile()
-    )
-
-    with pytest.raises(RuntimeError, match="handler boom"):
-        graph.invoke({"foo": ""})
-
-
-def test_set_node_defaults_error_handler_failure_fails_run():
-    """When the default handler itself raises, the run fails (no infinite
-    recursion, no double-routing)."""
-
-    class State(TypedDict):
-        foo: str
-
-    def always_failing(state: State) -> State:
-        raise RuntimeError("node boom")
-
-    def broken_default_handler(state: State, error: NodeError) -> State:
-        raise RuntimeError("default handler boom")
-
-    graph = (
-        StateGraph(State)
-        .set_node_defaults(error_handler=broken_default_handler)
-        .add_node("always_failing", always_failing)
-        .add_edge(START, "always_failing")
-        .compile()
-    )
-
-    with pytest.raises(RuntimeError, match="default handler boom"):
-        graph.invoke({"foo": ""})
-
-
-def test_set_node_defaults_error_handler_receives_runnable_config():
-    class State(TypedDict):
-        foo: str
-
-    def always_failing(state: State) -> State:
-        raise RuntimeError("boom")
-
-    captured: dict[str, Any] = {}
-
-    def default_handler(
-        state: State, error: NodeError, config: RunnableConfig
-    ) -> State:
-        captured["thread_id"] = config["configurable"].get("thread_id")
-        return {"foo": "handled"}
-
-    checkpointer = MemorySaver()
-    graph = (
-        StateGraph(State)
-        .set_node_defaults(error_handler=default_handler)
-        .add_node("always_failing", always_failing)
-        .add_edge(START, "always_failing")
-        .compile(checkpointer=checkpointer)
-    )
-
-    thread_id = str(uuid4())
-    result = graph.invoke(
-        {"foo": ""}, config={"configurable": {"thread_id": thread_id}}
-    )
-    assert result["foo"] == "handled"
-    assert captured["thread_id"] == thread_id
-
-
-def test_set_node_defaults_error_handler_collides_with_user_node():
-    class State(TypedDict):
-        foo: str
-
-    def default_handler(state: State, error: NodeError) -> State:
-        return {"foo": "handled"}
-
-    builder = (
-        StateGraph(State)
-        .set_node_defaults(error_handler=default_handler)
-        .add_node("__default_error_handler__", lambda s: s)
-        .add_edge(START, "__default_error_handler__")
-    )
-
-    with pytest.raises(ValueError, match="__default_error_handler__"):
-        builder.compile()
-
-
-def test_set_node_defaults_retry_policy():
-    class State(TypedDict):
-        foo: str
-
-    attempts = 0
-
-    def flaky_node(state: State) -> State:
-        nonlocal attempts
-        attempts += 1
-        if attempts < 3:
-            raise ValueError("not yet")
-        return {"foo": "ok"}
-
-    graph = (
-        StateGraph(State)
-        .set_node_defaults(
-            retry_policy=RetryPolicy(
-                max_attempts=3, initial_interval=0.01, jitter=False, retry_on=ValueError
-            )
-        )
-        .add_node("flaky", flaky_node)
-        .add_edge(START, "flaky")
-        .compile()
-    )
-
-    with patch("time.sleep"):
-        result = graph.invoke({"foo": ""})
-
-    assert result["foo"] == "ok"
-    assert attempts == 3
-
-
-def test_set_node_defaults_retry_policy_per_node_wins():
-    class State(TypedDict):
-        foo: str
-
-    attempts = 0
-
-    def flaky_node(state: State) -> State:
-        nonlocal attempts
-        attempts += 1
-        if attempts < 2:
-            raise ValueError("not yet")
-        return {"foo": "ok"}
-
-    graph = (
-        StateGraph(State)
-        .set_node_defaults(
-            retry_policy=RetryPolicy(
-                max_attempts=1, initial_interval=0.01, jitter=False, retry_on=ValueError
-            )
-        )
-        .add_node(
-            "flaky",
-            flaky_node,
-            retry_policy=RetryPolicy(
-                max_attempts=3,
-                initial_interval=0.01,
-                jitter=False,
-                retry_on=ValueError,
-            ),
-        )
-        .add_edge(START, "flaky")
-        .compile()
-    )
-
-    with patch("time.sleep"):
-        result = graph.invoke({"foo": ""})
-
-    assert result["foo"] == "ok"
-    assert attempts == 2
-
-
-@pytest.mark.anyio
-async def test_set_node_defaults_timeout():
-    class State(TypedDict):
-        foo: str
-
-    async def slow_node(state: State) -> State:
-        await asyncio.sleep(10)
-        return {"foo": "should-not-happen"}
-
-    graph = (
-        StateGraph(State)
-        .set_node_defaults(timeout=TimeoutPolicy(run_timeout=0.05))
-        .add_node("slow", slow_node)
-        .add_edge(START, "slow")
-        .compile()
-    )
-
-    from langgraph.errors import NodeTimeoutError
-
-    with pytest.raises(NodeTimeoutError):
-        await graph.ainvoke({"foo": ""})
-
-
-@pytest.mark.anyio
-async def test_set_node_defaults_timeout_per_node_wins():
-    """Per-node timeout overrides the default; a generous per-node timeout
-    allows a node to complete even when the builder default is very short."""
-
-    class State(TypedDict):
-        foo: str
-
-    async def quick_node(state: State) -> State:
-        await asyncio.sleep(0.05)
-        return {"foo": "done"}
-
-    graph = (
-        StateGraph(State)
-        .set_node_defaults(timeout=TimeoutPolicy(run_timeout=0.01))
-        .add_node("quick", quick_node, timeout=TimeoutPolicy(run_timeout=5.0))
-        .add_edge(START, "quick")
-        .compile()
-    )
-
-    result = await graph.ainvoke({"foo": ""})
-    assert result["foo"] == "done"
-
-
-def test_set_node_defaults_chaining():
-    """set_node_defaults() is chainable and can be called in any order relative to add_node."""
-
-    class State(TypedDict):
-        foo: str
-
-    def always_failing(state: State) -> State:
-        raise RuntimeError("boom")
-
-    def handler(state: State, error: NodeError) -> State:
-        return {"foo": "handled"}
-
-    graph = (
-        StateGraph(State)
-        .add_node("a", always_failing)
-        .add_edge(START, "a")
-        .set_node_defaults(
-            retry_policy=RetryPolicy(
-                max_attempts=1, initial_interval=0.01, jitter=False
-            ),
-            error_handler=handler,
-        )
-        .compile()
-    )
-
-    result = graph.invoke({"foo": ""})
-    assert result["foo"] == "handled"
-
-
-def test_set_node_defaults_combined_retry_and_error_handler():
-    """Retries are exhausted first, then the error handler runs."""
-
-    class State(TypedDict):
-        foo: str
-
-    attempts = 0
-    captured: dict[str, Any] = {}
-
-    def always_failing(state: State) -> State:
-        nonlocal attempts
-        attempts += 1
-        raise ValueError("Always fails")
-
-    def handler(state: State, error: NodeError) -> State:
-        captured["error"] = str(error.error)
-        return {"foo": "handled"}
-
-    graph = (
-        StateGraph(State)
-        .set_node_defaults(
-            retry_policy=RetryPolicy(
-                max_attempts=2,
-                initial_interval=0.01,
-                jitter=False,
-                retry_on=ValueError,
-            ),
-            error_handler=handler,
-        )
-        .add_node("fail", always_failing)
-        .add_edge(START, "fail")
-        .compile()
-    )
-
-    with patch("time.sleep"):
-        result = graph.invoke({"foo": ""})
-
-    assert result["foo"] == "handled"
-    assert attempts == 2
-    assert captured["error"] == "Always fails"
-
-
-def test_error_handler_resumes_after_crash():
-    """If the error handler crashes, resuming should re-schedule the handler
-    (not re-execute the original failed node)."""
-
-    class State(TypedDict):
-        foo: str
-
-    call_count = {"node": 0, "handler": 0}
-    captured_errors: list[NodeError] = []
-
-    def failing_node(state: State) -> State:
-        call_count["node"] += 1
-        raise RuntimeError("boom")
-
-    handler_should_fail = [True]
-
-    def handler(state: State, error: NodeError) -> State:
-        call_count["handler"] += 1
-        captured_errors.append(error)
-        if handler_should_fail[0]:
-            raise RuntimeError("handler crash")
-        return {"foo": "recovered"}
-
-    checkpointer = MemorySaver()
-    graph = (
-        StateGraph(State)
-        .set_node_defaults(error_handler=handler)
-        .add_node("fail", failing_node)
-        .add_edge(START, "fail")
-        .compile(checkpointer=checkpointer)
-    )
-
-    config = {"configurable": {"thread_id": "t1"}}
-
-    # First invoke: node fails -> handler runs -> handler crashes -> run fails
-    with pytest.raises(RuntimeError, match="handler crash"):
-        graph.invoke({"foo": ""}, config)
-
-    assert call_count["node"] == 1
-    assert call_count["handler"] == 1
-    assert captured_errors[0].node == "fail"
-    assert isinstance(captured_errors[0].error, RuntimeError)
-    assert str(captured_errors[0].error) == "boom"
-
-    # Resume: handler should run again, NOT the original node
-    handler_should_fail[0] = False
-    result = graph.invoke(None, config)
-
-    assert result["foo"] == "recovered"
-    assert call_count["node"] == 1  # NOT re-executed
-    assert call_count["handler"] == 2  # ran again on resume
-    # on resume the error was round-tripped through the checkpointer, so it
-    # may be deserialized as a string representation rather than the original
-    # exception type — verify the node name and that the error content matches.
-    assert captured_errors[1].node == "fail"
-    assert "boom" in str(captured_errors[1].error)
-
-
-def test_error_handler_resumes_after_crash_multiple_nodes():
-    """When multiple nodes fail in the same superstep and all have error handlers:
-    - error handlers start running while other nodes may still be in-flight
-    - resuming re-schedules each handler (not re-executes the original nodes)
-    """
-
-    class State(TypedDict):
-        results: Annotated[list[str], operator.add]
-
-    call_count = {"a": 0, "b": 0, "handler_a": 0, "handler_b": 0}
-    handler_a_started = threading.Event()
-
-    def node_a(state: State) -> State:
-        call_count["a"] += 1
-        raise RuntimeError("a failed")
-
-    def node_b(state: State) -> State:
-        call_count["b"] += 1
-        # Block until handler_a has started — proves the error handler runs
-        # concurrently with in-flight nodes in the same superstep.
-        assert handler_a_started.wait(timeout=5), "handler_a never started"
-        raise RuntimeError("b failed")
-
-    handler_should_fail = [True]
-
-    def handler_a(state: State, error: NodeError) -> State:
-        call_count["handler_a"] += 1
-        assert error.node == "a"
-        assert "a failed" in str(error.error)
-        handler_a_started.set()
-        if handler_should_fail[0]:
-            raise RuntimeError("handler_a crash")
-        return {"results": [f"recovered_a:{error.node}"]}
-
-    def handler_b(state: State, error: NodeError) -> State:
-        call_count["handler_b"] += 1
-        assert error.node == "b"
-        assert "b failed" in str(error.error)
-        if handler_should_fail[0]:
-            raise RuntimeError("handler_b crash")
-        return {"results": [f"recovered_b:{error.node}"]}
-
-    checkpointer = MemorySaver()
-    graph = (
-        StateGraph(State)
-        .add_node("a", node_a, error_handler=handler_a)
-        .add_node("b", node_b, error_handler=handler_b)
-        .add_edge(START, "a")
-        .add_edge(START, "b")
-        .compile(checkpointer=checkpointer)
-    )
-
-    config = {"configurable": {"thread_id": "t1"}}
-
-    # First invoke: node_a fails immediately -> handler_a starts (sets event) ->
-    # node_b unblocks and fails -> handler_b starts -> both handlers crash
-    with pytest.raises(RuntimeError):
-        graph.invoke({"results": []}, config)
-
-    assert call_count["a"] == 1
-    assert call_count["b"] == 1
-    assert call_count["handler_a"] == 1
-    assert call_count["handler_b"] == 1
-
-    # Resume: both handlers should run again, NOT the original nodes
-    handler_should_fail[0] = False
-    handler_a_started.clear()
-    result = graph.invoke(None, config)
-
-    assert call_count["a"] == 1  # NOT re-executed
-    assert call_count["b"] == 1  # NOT re-executed
-    assert call_count["handler_a"] == 2  # ran again on resume
-    assert call_count["handler_b"] == 2  # ran again on resume
-    assert "recovered_a:a" in result["results"]
-    assert "recovered_b:b" in result["results"]
@@ -1,296 +0,0 @@
-"""Tests for `StreamTransformer.before_builtins` lane ordering.
-
-`before_builtins = True` transformers are registered ahead of the
-rest, preserving relative order within each lane. This lets
-content-mutating transformers run before built-ins like
-`MessagesTransformer` that eagerly snapshot text fields into their
-projections.
-"""
-
-from __future__ import annotations
-
-import time
-from typing import Any, ClassVar
-
-from langgraph.stream._mux import StreamMux
-from langgraph.stream._types import StreamTransformer
-from langgraph.stream.stream_channel import StreamChannel
-from langgraph.stream.transformers import (
-    LifecycleTransformer,
-    MessagesTransformer,
-    TasksTransformer,
-)
-
-TS = int(time.time() * 1000)
-
-
-def _messages_event(namespace: list[str], data: Any) -> dict[str, Any]:
-    return {
-        "type": "event",
-        "method": "messages",
-        "params": {"namespace": namespace, "timestamp": TS, "data": data},
-    }
-
-
-class _Tap(StreamTransformer):
-    """Records the order it observed each event."""
-
-    required_stream_modes: ClassVar[tuple[str, ...]] = ()
-
-    def __init__(self, scope: tuple[str, ...] = (), *, label: str = "tap") -> None:
-        super().__init__(scope)
-        self.label = label
-        self.log: list[str] = []
-        self._channel: StreamChannel[str] = StreamChannel()
-
-    def init(self) -> dict[str, Any]:
-        return {f"tap_{self.label}": self._channel}
-
-    def process(self, event: dict[str, Any]) -> bool:
-        self.log.append(self.label)
-        return True
-
-
-class _PreTap(_Tap):
-    before_builtins: ClassVar[bool] = True
-
-
-class _TextRedactor(StreamTransformer):
-    """Mutates `text-delta` events in place to a fixed redacted string."""
-
-    before_builtins: ClassVar[bool] = True
-    required_stream_modes: ClassVar[tuple[str, ...]] = ("messages",)
-
-    def __init__(self, scope: tuple[str, ...] = ()) -> None:
-        super().__init__(scope)
-        self._channel: StreamChannel[str] = StreamChannel()
-
-    def init(self) -> dict[str, Any]:
-        return {"redactor": self._channel}
-
-    def process(self, event: dict[str, Any]) -> bool:
-        if event.get("method") != "messages":
-            return True
-        payload, _meta = event["params"]["data"]
-        if isinstance(payload, dict) and payload.get("event") == "content-block-delta":
-            delta = payload.get("delta") or {}
-            if delta.get("type") == "text-delta":
-                delta["text"] = "[REDACTED]"
-        return True
-
-
-def test_before_builtins_factories_run_before_others() -> None:
-    """A `before_builtins=True` factory is registered ahead of the rest."""
-
-    seen: list[type[StreamTransformer]] = []
-
-    class _PostTap(_Tap):
-        def __init__(self, scope: tuple[str, ...] = ()) -> None:
-            super().__init__(scope, label="post")
-
-        def process(self, event: dict[str, Any]) -> bool:
-            seen.append(_PostTap)
-            return True
-
-    class _EagerTap(_Tap):
-        before_builtins: ClassVar[bool] = True
-
-        def __init__(self, scope: tuple[str, ...] = ()) -> None:
-            super().__init__(scope, label="eager")
-
-        def process(self, event: dict[str, Any]) -> bool:
-            seen.append(_EagerTap)
-            return True
-
-    mux = StreamMux(
-        factories=[_PostTap, _EagerTap],
-        scope=(),
-        is_async=False,
-    )
-    # `_EagerTap` was supplied second but should be registered first.
-    types_in_order = [type(t) for t in mux._transformers]
-    assert types_in_order.index(_EagerTap) < types_in_order.index(_PostTap)
-
-    mux.push(
-        _messages_event([], ({"event": "message-start", "role": "ai", "id": "m1"}, {}))
-    )
-    # And it ran first when the event was dispatched.
-    assert seen == [_EagerTap, _PostTap]
-
-
-def test_within_lane_order_preserved() -> None:
-    """Within each lane, the supplied order is the registration order."""
-
-    class _A(_PreTap):
-        pass
-
-    class _B(_PreTap):
-        pass
-
-    class _C(_Tap):
-        pass
-
-    class _D(_Tap):
-        pass
-
-    mux = StreamMux(
-        factories=[
-            lambda scope: _C(scope, label="c"),
-            lambda scope: _A(scope, label="a"),
-            lambda scope: _D(scope, label="d"),
-            lambda scope: _B(scope, label="b"),
-        ],
-        scope=(),
-        is_async=False,
-    )
-    order = [t.label for t in mux._transformers]  # type: ignore[attr-defined]
-    # Pre lane (a, b) ahead of default lane (c, d). Within each, supplied order kept.
-    assert order == ["a", "b", "c", "d"]
-
-
-def test_redactor_runs_before_messages_transformer() -> None:
-    """Content mutated by a pre-lane transformer reaches `MessagesTransformer`."""
-
-    # Order supplied: built-ins first (as in pregel/main.py), then the
-    # opt-in pre-lane redactor. Partitioning should still register the
-    # redactor first.
-    mux = StreamMux(
-        factories=[MessagesTransformer, _TextRedactor],
-        scope=(),
-        is_async=False,
-    )
-    types_in_order = [type(t) for t in mux._transformers]
-    assert types_in_order.index(_TextRedactor) < types_in_order.index(
-        MessagesTransformer
-    )
-
-
-def test_lifecycle_unaffected_by_pre_lane_observer() -> None:
-    """An observer-only pre-lane transformer doesn't break lifecycle bookkeeping."""
-
-    class _NoopPreObserver(StreamTransformer):
-        before_builtins: ClassVar[bool] = True
-        required_stream_modes: ClassVar[tuple[str, ...]] = ("tasks",)
-
-        def __init__(self, scope: tuple[str, ...] = ()) -> None:
-            super().__init__(scope)
-            self._channel: StreamChannel[str] = StreamChannel()
-            self.seen: list[tuple[str, ...]] = []
-
-        def init(self) -> dict[str, Any]:
-            return {"noop_observer": self._channel}
-
-        def process(self, event: dict[str, Any]) -> bool:
-            if event.get("method") == "tasks":
-                self.seen.append(tuple(event["params"]["namespace"]))
-            return True
-
-    mux = StreamMux(
-        factories=[LifecycleTransformer, TasksTransformer, _NoopPreObserver],
-        scope=(),
-        is_async=False,
-    )
-    types_in_order = [type(t) for t in mux._transformers]
-    assert types_in_order.index(_NoopPreObserver) < types_in_order.index(
-        LifecycleTransformer
-    )
-
-    observer = next(t for t in mux._transformers if isinstance(t, _NoopPreObserver))
-    lifecycle = next(
-        t for t in mux._transformers if isinstance(t, LifecycleTransformer)
-    )
-
-    # Push a synthetic `tasks` event that lifecycle would normally track.
-    mux.push(
-        {
-            "type": "event",
-            "method": "tasks",
-            "params": {
-                "namespace": ["child:abc"],
-                "timestamp": TS,
-                "data": {"name": "child"},
-            },
-        }
-    )
-
-    # Pre-lane observer saw the event, AND lifecycle's bookkeeping still
-    # registered the new namespace (the observer didn't mutate anything).
-    assert observer.seen == [("child:abc",)]
-    assert ("child:abc",) in lifecycle._seen  # type: ignore[attr-defined]
-
-
-def test_default_is_false() -> None:
-    """`StreamTransformer.before_builtins` defaults to False."""
-
-    assert StreamTransformer.before_builtins is False
-    assert MessagesTransformer.before_builtins is False
-    assert LifecycleTransformer.before_builtins is False
-
-
-def test_pre_lane_mutation_lands_in_messages_projection() -> None:
-    """End-to-end: text mutated by a pre-lane transformer is what
-    `MessagesTransformer` snapshots into its `ChatModelStream` projection.
-
-    Without `before_builtins`, the redactor would run after
-    MessagesTransformer's eager extraction and the projection would
-    contain the raw, un-redacted text.
-    """
-
-    mux = StreamMux(
-        factories=[MessagesTransformer, _TextRedactor],
-        scope=(),
-        is_async=False,
-    )
-    messages_transformer = next(
-        t for t in mux._transformers if isinstance(t, MessagesTransformer)
-    )
-    # Unblock both the mux's main log and the messages projection log so
-    # synthetic pushes are accepted without a real consumer attached.
-    mux._events._subscribed = True
-    messages_transformer._log._subscribed = True
-
-    meta = {"langgraph_node": "model", "run_id": "run-1"}
-
-    # message-start → MessagesTransformer creates a ChatModelStream.
-    mux.push(
-        _messages_event(
-            [],
-            ({"event": "message-start", "role": "ai", "id": "msg-1"}, meta),
-        )
-    )
-
-    # content-block-delta carrying the secret. The redactor (pre-lane)
-    # mutates `delta.text` BEFORE MessagesTransformer snapshots it.
-    mux.push(
-        _messages_event(
-            [],
-            (
-                {
-                    "event": "content-block-delta",
-                    "index": 0,
-                    "delta": {"type": "text-delta", "text": "secret@example.com"},
-                },
-                meta,
-            ),
-        )
-    )
-
-    # Capture the still-open stream before message-finish removes it from
-    # MessagesTransformer's `_by_run` dict.
-    chat_stream = messages_transformer._by_run["run-1"]  # type: ignore[attr-defined]
-
-    # message-finish → closes the stream.
-    mux.push(
-        _messages_event(
-            [],
-            ({"event": "message-finish"}, meta),
-        )
-    )
-
-    # The redactor mutated `delta.text` to "[REDACTED]" before
-    # MessagesTransformer snapshotted the string into the text
-    # accumulator. Without `before_builtins`, the accumulator would hold
-    # the raw "secret@example.com".
-    assert chat_stream._text_acc == "[REDACTED]", (  # type: ignore[attr-defined]
-        f"expected redacted text in projection, got {chat_stream._text_acc!r}"
-    )
@@ -12,7 +12,7 @@ from langchain_core.language_models.chat_model_stream import (
    AsyncChatModelStream,
    ChatModelStream,
 )
-from langchain_core.messages import AIMessage, AIMessageChunk, ToolMessage
+from langchain_core.messages import AIMessage, AIMessageChunk
 from langchain_core.runnables import RunnableConfig
 from typing_extensions import TypedDict

@@ -213,23 +213,6 @@ class TestProtocolEventRouting:
        log.close()
        assert _unstamped(log._items) == []

-    def test_tool_role_protocol_events_are_ignored(self) -> None:
-        t, log = _make_sync_transformer()
-        for evt in [
-            {"event": "message-start", "role": "tool", "message_id": "tool-msg-1"},
-            {
-                "event": "content-block-delta",
-                "index": 0,
-                "content_block": {"type": "text", "text": "[]"},
-            },
-            {"event": "message-finish", "reason": "stop"},
-        ]:
-            t.process(_proto_event(evt, run_id="tool-run"))
-
-        log.close()
-        assert _unstamped(log._items) == []
-        assert t._ignored_runs == set()
-
    def test_concurrent_streams_routed_by_run_id(self) -> None:
        t, log = _make_sync_transformer()
        life_a = _lifecycle(text="aaaa", message_id="run-a")
@@ -290,29 +273,6 @@ class TestWholeMessageFallback:
        assert stream.done
        assert stream.output.text == "the full answer"

-    def test_whole_tool_message_is_ignored(self) -> None:
-        t, log = _make_sync_transformer()
-        t.process(
-            {
-                "type": "event",
-                "method": "messages",
-                "params": {
-                    "namespace": [],
-                    "timestamp": TS,
-                    "data": (
-                        ToolMessage(
-                            content="[]",
-                            id="tool-msg-1",
-                            tool_call_id="call_1",
-                        ),
-                        {"langgraph_node": "tools"},
-                    ),
-                },
-            }
-        )
-        log.close()
-        assert _unstamped(log._items) == []
-
    def test_whole_message_has_full_lifecycle(self) -> None:
        t, log = _make_sync_transformer()
        t.process(_whole_msg("full"))
@@ -889,23 +849,6 @@ class TestStreamMessagesHandlerV2Unit:

        assert emitted == []

-    def test_on_chain_end_does_not_emit_tool_messages(self) -> None:
-        from uuid import uuid4
-
-        from langgraph.pregel._messages import StreamMessagesHandlerV2
-
-        emitted: list[Any] = []
-        handler = StreamMessagesHandlerV2(emitted.append, subgraphs=False)
-        run_id = uuid4()
-        handler.metadata[run_id] = ((), {"langgraph_node": "tools"})
-
-        handler.on_chain_end(
-            {"messages": [ToolMessage(content="[]", tool_call_id="call_1")]},
-            run_id=run_id,
-        )
-
-        assert emitted == []
-
    def test_on_llm_end_dedupes_when_final_message_id_differs(self) -> None:
        """A streamed v2 message should not be emitted again from the final
        AIMessage fallback when its final id does not match `message-start`."""
@@ -871,11 +871,11 @@ wheels = [

 [[package]]
 name = "idna"
-version = "3.15"
+version = "3.11"
 source = { registry = "https://pypi.org/simple" }
-sdist = { url = "https://files.pythonhosted.org/packages/82/77/7b3966d0b9d1d31a36ddf1746926a11dface89a83409bf1483f0237aa758/idna-3.15.tar.gz", hash = "sha256:ca962446ea538f7092a95e057da437618e886f4d349216d2b1e294abfdb65fdc", size = 199245, upload-time = "2026-05-12T22:45:57.011Z" }
+sdist = { url = "https://files.pythonhosted.org/packages/6f/6d/0703ccc57f3a7233505399edb88de3cbd678da106337b9fcde432b65ed60/idna-3.11.tar.gz", hash = "sha256:795dafcc9c04ed0c1fb032c2aa73654d8e8c5023a7df64a53f39190ada629902", size = 194582, upload-time = "2025-10-12T14:55:20.501Z" }
 wheels = [
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+    { url = "https://files.pythonhosted.org/packages/0e/61/66938bbb5fc52dbdf84594873d5b51fb1f7c7794e9c0f5bd885f30bc507b/idna-3.11-py3-none-any.whl", hash = "sha256:771a87f49d9defaf64091e6e6fe9c18d4833f140bd19464795bc32d966ca37ea", size = 71008, upload-time = "2025-10-12T14:55:18.883Z" },
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 [[package]]
@@ -1350,7 +1350,7 @@ wheels = [

 [[package]]
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-version = "1.4.0"
+version = "1.4.0a2"
 source = { registry = "https://pypi.org/simple" }
 dependencies = [
    { name = "jsonpatch" },
@@ -1363,9 +1363,9 @@ dependencies = [
    { name = "typing-extensions" },
    { name = "uuid-utils" },
 ]
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+sdist = { url = "https://files.pythonhosted.org/packages/3c/93/68bafa047f8e1770d0cf0f61d6c70889f1dec42ef6bd263540d916c421b9/langchain_core-1.4.0a2.tar.gz", hash = "sha256:b723c7961b615c7f2180ce2bcf352fdad8247bc51a60adecd3d97088235c120d", size = 916486, upload-time = "2026-05-01T15:02:19.029Z" }
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 [[package]]
@@ -1382,7 +1382,7 @@ wheels = [

 [[package]]
 name = "langgraph"
-version = "1.2.1"
+version = "1.2.0a7"
 source = { editable = "." }
 dependencies = [
    { name = "langchain-core" },
@@ -1454,7 +1454,7 @@ test = [

 [package.metadata]
 requires-dist = [
-    { name = "langchain-core", specifier = ">=1.4.0,<2" },
+    { name = "langchain-core", specifier = ">=1.4.0a2,<2" },
    { name = "langgraph-checkpoint", editable = "../checkpoint" },
    { name = "langgraph-prebuilt", editable = "../prebuilt" },
    { name = "langgraph-sdk", editable = "../sdk-py" },
@@ -1563,7 +1563,7 @@ wheels = [

 [[package]]
 name = "langgraph-checkpoint"
-version = "4.1.0"
+version = "4.1.0a4"
 source = { editable = "../checkpoint" }
 dependencies = [
    { name = "langchain-core" },
@@ -1611,7 +1611,7 @@ test = [

 [[package]]
 name = "langgraph-checkpoint-postgres"
-version = "3.1.0"
+version = "3.1.0a4"
 source = { editable = "../checkpoint-postgres" }
 dependencies = [
    { name = "langgraph-checkpoint" },
@@ -1658,7 +1658,7 @@ test = [

 [[package]]
 name = "langgraph-checkpoint-sqlite"
-version = "3.1.0"
+version = "3.1.0a1"
 source = { editable = "../checkpoint-sqlite" }
 dependencies = [
    { name = "aiosqlite" },
@@ -1757,7 +1757,7 @@ test = [

 [[package]]
 name = "langgraph-prebuilt"
-version = "1.1.0"
+version = "1.1.0a2"
 source = { editable = "../prebuilt" }
 dependencies = [
    { name = "langchain-core" },
@@ -1849,14 +1849,14 @@ dev = [
    { name = "pytest-watch" },
    { name = "ruff", specifier = "==0.15.12" },
    { name = "starlette" },
-    { name = "ty", specifier = "==0.0.33" },
+    { name = "ty", specifier = "==0.0.23" },
 ]
 lint = [
    { name = "codespell" },
    { name = "mypy", specifier = "==1.20.2" },
    { name = "ruff", specifier = "==0.15.12" },
    { name = "starlette" },
-    { name = "ty", specifier = "==0.0.33" },
+    { name = "ty", specifier = "==0.0.23" },
 ]
 test = [
    { name = "pytest" },
@@ -1867,7 +1867,7 @@ test = [

 [[package]]
 name = "langsmith"
-version = "0.8.0"
+version = "0.7.31"
 source = { registry = "https://pypi.org/simple" }
 dependencies = [
    { name = "httpx" },
@@ -1880,9 +1880,9 @@ dependencies = [
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    { name = "zstandard" },
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+sdist = { url = "https://files.pythonhosted.org/packages/e6/11/696019490992db5c87774dc20515529ef42a01e1d770fb754ed6d9b12fb0/langsmith-0.7.31.tar.gz", hash = "sha256:331ee4f7c26bb5be4022b9859b7d7b122cbf8c9d01d9f530114c1914b0349ffb", size = 1178480, upload-time = "2026-04-14T17:55:41.242Z" }
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 [package.optional-dependencies]
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 [[package]]
@@ -3743,11 +3743,11 @@ wheels = [

 [[package]]
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 wheels = [
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+    { url = "https://files.pythonhosted.org/packages/39/08/aaaad47bc4e9dc8c725e68f9d04865dbcb2052843ff09c97b08904852d84/urllib3-2.6.3-py3-none-any.whl", hash = "sha256:bf272323e553dfb2e87d9bfd225ca7b0f467b919d7bbd355436d3fd37cb0acd4", size = 131584, upload-time = "2026-01-07T16:24:42.685Z" },
 ]

 [[package]]
@@ -5,42 +5,12 @@ from __future__ import annotations
 from collections.abc import Awaitable, Callable
 from typing import Any

-from langchain_core.messages import ToolMessage
 from langgraph.stream._types import ProtocolEvent, StreamTransformer
 from langgraph.stream.stream_channel import StreamChannel

 from langgraph.prebuilt._tool_call_stream import ToolCallStream


-def _is_serialized_tool_message(value: Any) -> bool:
-    """Detect a serialized LangChain `ToolMessage` payload.
-
-    Example:
-        {
-            "lc": 1,
-            "type": "constructor",
-            "id": ["langchain_core", "messages", "ToolMessage"],
-            "kwargs": {"content": "raw tool result", "tool_call_id": "call_1"},
-        }
-    """
-    return (
-        isinstance(value, dict)
-        and value.get("type") == "constructor"
-        and isinstance(value.get("id"), list)
-        and value["id"][-1] == "ToolMessage"
-    )
-
-
-def _normalize_tool_output(output: Any) -> Any:
-    if isinstance(output, ToolMessage):
-        return output.content
-    if _is_serialized_tool_message(output):
-        kwargs = output.get("kwargs")
-        if isinstance(kwargs, dict):
-            return kwargs.get("content")
-    return output
-
-
 class ToolCallTransformer(StreamTransformer):
    """Project `tools` channel events into `ToolCallStream` handles.

@@ -139,7 +109,7 @@ class ToolCallTransformer(StreamTransformer):
        elif event_type == "tool-finished":
            stream = self._active.pop(tool_call_id, None)
            if stream is not None:
-                stream._finish(_normalize_tool_output(data.get("output")))
+                stream._finish(data.get("output"))
        elif event_type == "tool-error":
            stream = self._active.pop(tool_call_id, None)
            if stream is not None:
@@ -4,7 +4,7 @@ build-backend = "hatchling.build"

 [project]
 name = "langgraph-prebuilt"
-version = "1.1.0"
+version = "1.1.0a2"
 description = "Library with high-level APIs for creating and executing LangGraph agents and tools."
 authors = []
 requires-python = ">=3.10"
@@ -6,7 +6,7 @@ import time
 from typing import Annotated, Any

 import pytest
-from langchain_core.messages import AIMessage, ToolMessage
+from langchain_core.messages import AIMessage
 from langchain_core.tools import tool
 from langgraph.constants import END, START
 from langgraph.graph import StateGraph
@@ -128,42 +128,6 @@ class TestToolCallTransformerUnit:
        assert stream.error is None
        assert "tc1" not in transformer._active

-    def test_finish_unwraps_tool_message_output(self) -> None:
-        mux, transformer = _mux()
-        mux.push(_tool_event("tool-started", "tc1", tool_name="echo"))
-        stream = transformer._active["tc1"]
-        mux.push(
-            _tool_event(
-                "tool-finished",
-                "tc1",
-                output=ToolMessage(content="done", tool_call_id="tc1"),
-            )
-        )
-        assert stream.completed is True
-        assert stream.output == "done"
-
-    def test_finish_unwraps_serialized_tool_message_output(self) -> None:
-        mux, transformer = _mux()
-        mux.push(_tool_event("tool-started", "tc1", tool_name="echo"))
-        stream = transformer._active["tc1"]
-        mux.push(
-            _tool_event(
-                "tool-finished",
-                "tc1",
-                output={
-                    "lc": 1,
-                    "type": "constructor",
-                    "id": ["langchain_core", "messages", "ToolMessage"],
-                    "kwargs": {
-                        "content": "serialized done",
-                        "tool_call_id": "tc1",
-                    },
-                },
-            )
-        )
-        assert stream.completed is True
-        assert stream.output == "serialized done"
-
    def test_error_closes_stream(self) -> None:
        mux, transformer = _mux()
        mux.push(_tool_event("tool-started", "tc1", tool_name="boom"))
@@ -214,11 +214,11 @@ wheels = [

 [[package]]
 name = "idna"
-version = "3.15"
+version = "3.11"
 source = { registry = "https://pypi.org/simple" }
-sdist = { url = "https://files.pythonhosted.org/packages/82/77/7b3966d0b9d1d31a36ddf1746926a11dface89a83409bf1483f0237aa758/idna-3.15.tar.gz", hash = "sha256:ca962446ea538f7092a95e057da437618e886f4d349216d2b1e294abfdb65fdc", size = 199245, upload-time = "2026-05-12T22:45:57.011Z" }
+sdist = { url = "https://files.pythonhosted.org/packages/6f/6d/0703ccc57f3a7233505399edb88de3cbd678da106337b9fcde432b65ed60/idna-3.11.tar.gz", hash = "sha256:795dafcc9c04ed0c1fb032c2aa73654d8e8c5023a7df64a53f39190ada629902", size = 194582, upload-time = "2025-10-12T14:55:20.501Z" }
 wheels = [
-    { url = "https://files.pythonhosted.org/packages/d2/23/408243171aa9aaba178d3e2559159c24c1171a641aa83b67bdd3394ead8e/idna-3.15-py3-none-any.whl", hash = "sha256:048adeaf8c2d788c40fee287673ccaa74c24ffd8dcf09ffa555a2fbb59f10ac8", size = 72340, upload-time = "2026-05-12T22:45:55.733Z" },
+    { url = "https://files.pythonhosted.org/packages/0e/61/66938bbb5fc52dbdf84594873d5b51fb1f7c7794e9c0f5bd885f30bc507b/idna-3.11-py3-none-any.whl", hash = "sha256:771a87f49d9defaf64091e6e6fe9c18d4833f140bd19464795bc32d966ca37ea", size = 71008, upload-time = "2025-10-12T14:55:18.883Z" },
 ]

 [[package]]
@@ -253,7 +253,7 @@ wheels = [

 [[package]]
 name = "langchain-core"
-version = "1.4.0"
+version = "1.4.0a2"
 source = { registry = "https://pypi.org/simple" }
 dependencies = [
    { name = "jsonpatch" },
@@ -266,9 +266,9 @@ dependencies = [
    { name = "typing-extensions" },
    { name = "uuid-utils" },
 ]
-sdist = { url = "https://files.pythonhosted.org/packages/59/de/679a53472c25860837e32c0442c962fa86e95317a36460e2c9d5c91b17c2/langchain_core-1.4.0.tar.gz", hash = "sha256:1dc341eed802ed9c117c0df3923c991e5e9e226571e5725c194eeb5bd93d1a7f", size = 920260, upload-time = "2026-05-11T18:42:35.919Z" }
+sdist = { url = "https://files.pythonhosted.org/packages/3c/93/68bafa047f8e1770d0cf0f61d6c70889f1dec42ef6bd263540d916c421b9/langchain_core-1.4.0a2.tar.gz", hash = "sha256:b723c7961b615c7f2180ce2bcf352fdad8247bc51a60adecd3d97088235c120d", size = 916486, upload-time = "2026-05-01T15:02:19.029Z" }
 wheels = [
-    { url = "https://files.pythonhosted.org/packages/0f/1a/86c38c27b81913a1c6c12448cab55defb5a1097c7dc9a4cea83f55477a2d/langchain_core-1.4.0-py3-none-any.whl", hash = "sha256:23cbbdb46e38ddd1dd5247e6167e96013eae74bea4c5949c550809970a9e565c", size = 548120, upload-time = "2026-05-11T18:42:33.992Z" },
+    { url = "https://files.pythonhosted.org/packages/4e/8e/933e0ba7ba0430ce264e36b178d581b255239ad45093872483142d93478c/langchain_core-1.4.0a2-py3-none-any.whl", hash = "sha256:a5c689f8404357df797120c012da7704144a953b2ae18f258df263301e7badd5", size = 546297, upload-time = "2026-05-01T15:02:17.731Z" },
 ]

 [[package]]
@@ -285,7 +285,7 @@ wheels = [

 [[package]]
 name = "langgraph"
-version = "1.2.1"
+version = "1.2.0a7"
 source = { editable = "../langgraph" }
 dependencies = [
    { name = "langchain-core" },
@@ -298,7 +298,7 @@ dependencies = [

 [package.metadata]
 requires-dist = [
-    { name = "langchain-core", specifier = ">=1.4.0,<2" },
+    { name = "langchain-core", specifier = ">=1.4.0a2,<2" },
    { name = "langgraph-checkpoint", editable = "../checkpoint" },
    { name = "langgraph-prebuilt", editable = "." },
    { name = "langgraph-sdk", editable = "../sdk-py" },
@@ -369,7 +369,7 @@ test = [

 [[package]]
 name = "langgraph-checkpoint"
-version = "4.1.0"
+version = "4.1.0a4"
 source = { editable = "../checkpoint" }
 dependencies = [
    { name = "langchain-core" },
@@ -417,7 +417,7 @@ test = [

 [[package]]
 name = "langgraph-checkpoint-postgres"
-version = "3.1.0"
+version = "3.1.0a4"
 source = { editable = "../checkpoint-postgres" }
 dependencies = [
    { name = "langgraph-checkpoint" },
@@ -464,7 +464,7 @@ test = [

 [[package]]
 name = "langgraph-checkpoint-sqlite"
-version = "3.1.0"
+version = "3.1.0a1"
 source = { editable = "../checkpoint-sqlite" }
 dependencies = [
    { name = "aiosqlite" },
@@ -507,7 +507,7 @@ test = [

 [[package]]
 name = "langgraph-prebuilt"
-version = "1.1.0"
+version = "1.1.0a2"
 source = { editable = "." }
 dependencies = [
    { name = "langchain-core" },
@@ -618,14 +618,14 @@ dev = [
    { name = "pytest-watch" },
    { name = "ruff", specifier = "==0.15.12" },
    { name = "starlette" },
-    { name = "ty", specifier = "==0.0.33" },
+    { name = "ty", specifier = "==0.0.23" },
 ]
 lint = [
    { name = "codespell" },
    { name = "mypy", specifier = "==1.20.2" },
    { name = "ruff", specifier = "==0.15.12" },
    { name = "starlette" },
-    { name = "ty", specifier = "==0.0.33" },
+    { name = "ty", specifier = "==0.0.23" },
 ]
 test = [
    { name = "pytest" },
@@ -636,7 +636,7 @@ test = [

 [[package]]
 name = "langsmith"
-version = "0.8.0"
+version = "0.7.31"
 source = { registry = "https://pypi.org/simple" }
 dependencies = [
    { name = "httpx" },
@@ -649,9 +649,9 @@ dependencies = [
    { name = "xxhash" },
    { name = "zstandard" },
 ]
-sdist = { url = "https://files.pythonhosted.org/packages/a8/64/95f1f013531395f4e8ed73caeee780f65c7c58fe028cb543f8937b45611b/langsmith-0.8.0.tar.gz", hash = "sha256:59fe5b2a56bbbe14a08aa76691f84b49e8675dd21e11b57d80c6db8c08bac2e3", size = 4432996, upload-time = "2026-04-30T22:13:07.341Z" }
+sdist = { url = "https://files.pythonhosted.org/packages/e6/11/696019490992db5c87774dc20515529ef42a01e1d770fb754ed6d9b12fb0/langsmith-0.7.31.tar.gz", hash = "sha256:331ee4f7c26bb5be4022b9859b7d7b122cbf8c9d01d9f530114c1914b0349ffb", size = 1178480, upload-time = "2026-04-14T17:55:41.242Z" }
 wheels = [
-    { url = "https://files.pythonhosted.org/packages/f3/e1/a4be2e696c9473bb53298df398237da5674704d781d4b748ed35aeef592a/langsmith-0.8.0-py3-none-any.whl", hash = "sha256:12cc4bc5622b835a6d841964d6034df3617bdb912dae0c1381fd0a68a9b3a3ef", size = 393268, upload-time = "2026-04-30T22:13:05.56Z" },
+    { url = "https://files.pythonhosted.org/packages/1d/a1/a013cf458c301cda86a213dd153ce0a01c93f1ab5833f951e6a44c9763ce/langsmith-0.7.31-py3-none-any.whl", hash = "sha256:0291d49203f6e80dda011af1afda61eb0595a4d697adb684590a8805e1d61fb6", size = 373276, upload-time = "2026-04-14T17:55:39.677Z" },
 ]

 [[package]]
@@ -1490,11 +1490,11 @@ wheels = [

 [[package]]
 name = "urllib3"
-version = "2.7.0"
+version = "2.6.3"
 source = { registry = "https://pypi.org/simple" }
-sdist = { url = "https://files.pythonhosted.org/packages/53/0c/06f8b233b8fd13b9e5ee11424ef85419ba0d8ba0b3138bf360be2ff56953/urllib3-2.7.0.tar.gz", hash = "sha256:231e0ec3b63ceb14667c67be60f2f2c40a518cb38b03af60abc813da26505f4c", size = 433602, upload-time = "2026-05-07T16:13:18.596Z" }
+sdist = { url = "https://files.pythonhosted.org/packages/c7/24/5f1b3bdffd70275f6661c76461e25f024d5a38a46f04aaca912426a2b1d3/urllib3-2.6.3.tar.gz", hash = "sha256:1b62b6884944a57dbe321509ab94fd4d3b307075e0c2eae991ac71ee15ad38ed", size = 435556, upload-time = "2026-01-07T16:24:43.925Z" }
 wheels = [
-    { url = "https://files.pythonhosted.org/packages/7f/3e/5db95bcf282c52709639744ca2a8b149baccf648e39c8cc87553df9eae0c/urllib3-2.7.0-py3-none-any.whl", hash = "sha256:9fb4c81ebbb1ce9531cce37674bbc6f1360472bc18ca9a553ede278ef7276897", size = 131087, upload-time = "2026-05-07T16:13:17.151Z" },
+    { url = "https://files.pythonhosted.org/packages/39/08/aaaad47bc4e9dc8c725e68f9d04865dbcb2052843ff09c97b08904852d84/urllib3-2.6.3-py3-none-any.whl", hash = "sha256:bf272323e553dfb2e87d9bfd225ca7b0f467b919d7bbd355436d3fd37cb0acd4", size = 131584, upload-time = "2026-01-07T16:24:42.685Z" },
 ]

 [[package]]
@@ -110,7 +110,7 @@ def get_client(
    if url is None:
        url = "http://api"
        if os.environ.get("__LANGGRAPH_DEFER_LOOPBACK_TRANSPORT") == "true":
-            transport = get_asgi_transport()(app=None, root_path="/noauth")  # ty: ignore[invalid-argument-type]
+            transport = get_asgi_transport()(app=None, root_path="/noauth")  # type: ignore[invalid-argument-type]
            _registered_transports.append(transport)
        else:
            try:
@@ -122,7 +122,7 @@ def get_client(
                    "Failed to connect to in-process LangGraph server. Deferring configuration.",
                    exc_info=True,
                )
-                transport = get_asgi_transport()(app=None, root_path="/noauth")  # ty: ignore[invalid-argument-type]
+                transport = get_asgi_transport()(app=None, root_path="/noauth")  # type: ignore[invalid-argument-type]
                _registered_transports.append(transport)

    if transport is None:
@@ -131,7 +131,7 @@ def get_client(
        base_url=url,
        transport=transport,
        timeout=(
-            httpx.Timeout(timeout)  # ty: ignore[invalid-argument-type]
+            httpx.Timeout(timeout)  # type: ignore[arg-type]
            if timeout is not None
            else httpx.Timeout(connect=5, read=300, write=300, pool=5)
        ),
@@ -18,7 +18,6 @@ from langgraph_sdk.schema import (
    CronSortBy,
    Durability,
    Input,
-    Json,
    OnCompletionBehavior,
    QueryParamTypes,
    Run,
@@ -414,7 +413,6 @@ class CronClient:
        assistant_id: str | None = None,
        thread_id: str | None = None,
        enabled: bool | None = None,
-        metadata: Json = None,
        limit: int = 10,
        offset: int = 0,
        sort_by: CronSortBy | None = None,
@@ -429,8 +427,6 @@ class CronClient:
            assistant_id: The assistant ID or graph name to search for.
            thread_id: the thread ID to search for.
            enabled: The enabled status to search for.
-            metadata: Metadata to filter by. Exact match filter for each KV pair.
-                !!! version-added "Added in Agent Server version 0.9.0"
            limit: The maximum number of results to return.
            offset: The number of results to skip.
            headers: Optional custom headers to include with the request.
@@ -485,8 +481,6 @@ class CronClient:
            "limit": limit,
            "offset": offset,
        }
-        if metadata:
-            payload["metadata"] = metadata
        if sort_by:
            payload["sort_by"] = sort_by
        if sort_order:
@@ -503,7 +497,6 @@ class CronClient:
        *,
        assistant_id: str | None = None,
        thread_id: str | None = None,
-        metadata: Json = None,
        headers: Mapping[str, str] | None = None,
        params: QueryParamTypes | None = None,
    ) -> int:
@@ -512,8 +505,6 @@ class CronClient:
        Args:
            assistant_id: Assistant ID to filter by.
            thread_id: Thread ID to filter by.
-            metadata: Metadata to filter by. Exact match filter for each KV pair.
-                !!! version-added "Added in Agent Server version 0.9.0"
            headers: Optional custom headers to include with the request.
            params: Optional query parameters to include with the request.

@@ -525,8 +516,6 @@ class CronClient:
            payload["assistant_id"] = assistant_id
        if thread_id:
            payload["thread_id"] = thread_id
-        if metadata:
-            payload["metadata"] = metadata
        return await self.http.post(
            "/runs/crons/count", json=payload, headers=headers, params=params
        )
@@ -49,7 +49,7 @@ async def _wrap_stream_v2(
    async for part in raw:
        v2 = _sse_to_v2_dict(part.event, part.data)
        if v2 is not None:
-            yield v2  # ty: ignore[invalid-yield]
+            yield v2


 class RunsClient:
@@ -144,9 +144,8 @@ def _resolve_timezone(tz: str | tzinfo | ZoneInfo | None) -> str | None:
        return tz
    if isinstance(tz, tzinfo):
        # ZoneInfo objects have a .key attribute with the IANA name
-        key = getattr(tz, "key", None)
-        if isinstance(key, str):
-            return key
+        if hasattr(tz, "key"):
+            return tz.key  # type: ignore[union-attr]
        # Fall back to tzname for fixed-offset timezones like datetime.timezone.utc
        name = tz.tzname(None)
        if name is not None:
@@ -210,7 +209,7 @@ def configure_loopback_transports(app: Any) -> None:
@functools.lru_cache(maxsize=1)
 def get_asgi_transport() -> type[httpx.ASGITransport]:
    try:
-        from langgraph_api import asgi_transport  # ty: ignore[unresolved-import]
+        from langgraph_api import asgi_transport  # type: ignore[unresolved-import]

        return asgi_transport.ASGITransport
    except ImportError:
@@ -77,7 +77,7 @@ def get_sync_client(
        base_url=url,
        transport=transport,
        timeout=(
-            httpx.Timeout(timeout)  # ty: ignore[invalid-argument-type]
+            httpx.Timeout(timeout)  # type: ignore[arg-type]
            if timeout is not None
            else httpx.Timeout(connect=5, read=300, write=300, pool=5)
        ),
@@ -18,7 +18,6 @@ from langgraph_sdk.schema import (
    CronSortBy,
    Durability,
    Input,
-    Json,
    OnCompletionBehavior,
    QueryParamTypes,
    Run,
@@ -403,7 +402,6 @@ class SyncCronClient:
        assistant_id: str | None = None,
        thread_id: str | None = None,
        enabled: bool | None = None,
-        metadata: Json = None,
        limit: int = 10,
        offset: int = 0,
        sort_by: CronSortBy | None = None,
@@ -418,8 +416,6 @@ class SyncCronClient:
            assistant_id: The assistant ID or graph name to search for.
            thread_id: the thread ID to search for.
            enabled: Whether the cron job is enabled.
-            metadata: Metadata to filter by. Exact match filter for each KV pair.
-                !!! version-added "Added in Agent Server version 0.9.0"
            limit: The maximum number of results to return.
            offset: The number of results to skip.
            headers: Optional custom headers to include with the request.
@@ -472,8 +468,6 @@ class SyncCronClient:
            "limit": limit,
            "offset": offset,
        }
-        if metadata:
-            payload["metadata"] = metadata
        if sort_by:
            payload["sort_by"] = sort_by
        if sort_order:
@@ -490,7 +484,6 @@ class SyncCronClient:
        *,
        assistant_id: str | None = None,
        thread_id: str | None = None,
-        metadata: Json = None,
        headers: Mapping[str, str] | None = None,
        params: QueryParamTypes | None = None,
    ) -> int:
@@ -499,8 +492,6 @@ class SyncCronClient:
        Args:
            assistant_id: Assistant ID to filter by.
            thread_id: Thread ID to filter by.
-            metadata: Metadata to filter by. Exact match filter for each KV pair.
-                !!! version-added "Added in Agent Server version 0.9.0"
            headers: Optional custom headers to include with the request.
            params: Optional query parameters to include with the request.

@@ -512,8 +503,6 @@ class SyncCronClient:
            payload["assistant_id"] = assistant_id
        if thread_id:
            payload["thread_id"] = thread_id
-        if metadata:
-            payload["metadata"] = metadata
        return self.http.post(
            "/runs/crons/count", json=payload, headers=headers, params=params
        )
@@ -49,7 +49,7 @@ def _wrap_stream_v2_sync(
    for part in raw:
        v2 = _sse_to_v2_dict(part.event, part.data)
        if v2 is not None:
-            yield v2  # ty: ignore[invalid-yield]
+            yield v2


 class SyncRunsClient:
@@ -16,10 +16,10 @@ T = TypeVar("T")
 CacheStatus = Literal["miss", "fresh", "stale", "expired"]

 try:
-    from langgraph_api.cache import (  # ty: ignore[unresolved-import]
+    from langgraph_api.cache import (  # type: ignore[unresolved-import]
        cache_get as _cache_get,
    )
-    from langgraph_api.cache import (  # ty: ignore[unresolved-import]
+    from langgraph_api.cache import (  # type: ignore[unresolved-import]
        cache_set as _cache_set,
    )
 except ImportError:
@@ -28,8 +28,8 @@ except ImportError:


 try:
-    from langgraph_api.cache import SWRResult  # ty: ignore[unresolved-import]
-    from langgraph_api.cache import swr as _api_swr  # ty: ignore[unresolved-import]
+    from langgraph_api.cache import SWRResult  # type: ignore[unresolved-import]
+    from langgraph_api.cache import swr as _api_swr  # type: ignore[unresolved-import]

 except ImportError:
    _api_swr = None
@@ -40,10 +40,7 @@ except ImportError:
        value: T
        status: CacheStatus

-        async def mutate(
-            self,
-            value: T = ...,  # ty: ignore[invalid-parameter-default]
-        ) -> T:  # ty: ignore[empty-body]
+        async def mutate(self, value: T = ...) -> T:  # type: ignore[assignment]
            """Update or revalidate the cached value."""
            ...

@@ -37,7 +37,7 @@ class APIError(httpx.HTTPStatusError, LangGraphError):
            req = response_or_request
            response = None

-        httpx.HTTPStatusError.__init__(self, message, request=req, response=response)  # ty: ignore[invalid-argument-type]
+        httpx.HTTPStatusError.__init__(self, message, request=req, response=response)  # type: ignore[arg-type]
        LangGraphError.__init__(self, message)

        self.request = req
@@ -156,7 +156,7 @@ class _ExecutionRuntime(_ServerRuntimeBase[ContextT], Generic[ContextT]):
        This API is in beta and may change in future releases.
    """

-    context: ContextT = field(default=None)  # ty: ignore[invalid-assignment]
+    context: ContextT = field(default=None)  # type: ignore[assignment]
    """The graph run context, typed by the graph's `context_schema`.

    Only available during `threads.create_run`.
@@ -55,7 +55,7 @@ class BytesLineDecoder:
            # Include any existing buffer in the first portion of the
            # splitlines result.
            self.buffer.extend(lines[0])
-            lines = [self.buffer, *lines[1:]]
+            lines = cast(list[BytesLike], [self.buffer, *lines[1:]])
            self.buffer = bytearray()

        if not trailing_newline:
@@ -69,7 +69,7 @@ class BytesLineDecoder:
        if not self.buffer and not self.trailing_cr:
            return []

-        lines: list[BytesLike] = [self.buffer]
+        lines = [self.buffer]
        self.buffer = bytearray()
        self.trailing_cr = False
        return lines
@@ -102,7 +102,7 @@ class SSEDecoder:

            sse = StreamPart(
                event=self._event,
-                data=orjson.loads(self._data) if self._data else None,  # ty: ignore[invalid-argument-type]
+                data=orjson.loads(self._data) if self._data else None,  # type: ignore[invalid-argument-type]
                id=self.last_event_id,
            )

@@ -33,7 +33,7 @@ lint = [
    "ruff==0.15.12",
    "codespell",
    "mypy==1.20.2",
-    "ty==0.0.33",
+    "ty==0.0.23",
    "starlette",
 ]
 dev = [
@@ -388,7 +388,7 @@ async def test_async_stream_v2_client_side_conversion() -> None:
            event="values", data={"messages": [{"role": "user", "content": "hi"}]}
        )
        yield StreamPart(event="updates|sub:abc", data={"node": {"out": 1}})
-        yield StreamPart(event="end", data=None)  # ty: ignore[invalid-argument-type]
+        yield StreamPart(event="end", data=None)  # type: ignore[arg-type]

    parts: list[StreamPartV2] = [part async for part in _wrap_stream_v2(mock_stream())]
    assert len(parts) == 3
@@ -420,7 +420,7 @@ def test_sync_stream_v2_client_side_conversion() -> None:
    def mock_stream() -> Any:
        yield StreamPart(event="metadata", data={"run_id": "r1"})
        yield StreamPart(event="values", data={"state": "full"})
-        yield StreamPart(event="end", data=None)  # ty: ignore[invalid-argument-type]
+        yield StreamPart(event="end", data=None)  # type: ignore[arg-type]

    parts: list[StreamPartV2] = list(_wrap_stream_v2_sync(mock_stream()))
    assert len(parts) == 2
@@ -485,165 +485,3 @@ def test_sync_update_with_enabled_parameter(enabled_value):
        )

    assert result == cron
-
-
-@pytest.mark.asyncio
-async def test_async_search_with_metadata():
-    """Test that CronClient.search forwards metadata in the request body."""
-    cron = _cron_response()
-
-    async def handler(request: httpx.Request) -> httpx.Response:
-        assert request.method == "POST"
-        assert request.url.path == "/runs/crons/search"
-
-        body = json.loads(request.content)
-        assert body["metadata"] == {"owner": "alice"}
-        assert body["limit"] == 10
-        assert body["offset"] == 0
-
-        return httpx.Response(200, json=[cron])
-
-    transport = httpx.MockTransport(handler)
-    async with httpx.AsyncClient(
-        transport=transport, base_url="https://example.com"
-    ) as client:
-        http_client = HttpClient(client)
-        cron_client = CronClient(http_client)
-        result = await cron_client.search(metadata={"owner": "alice"})
-
-    assert result == [cron]
-
-
-@pytest.mark.asyncio
-async def test_async_search_omits_empty_metadata():
-    """Test that CronClient.search does not send metadata when not provided."""
-    cron = _cron_response()
-
-    async def handler(request: httpx.Request) -> httpx.Response:
-        body = json.loads(request.content)
-        assert "metadata" not in body
-        return httpx.Response(200, json=[cron])
-
-    transport = httpx.MockTransport(handler)
-    async with httpx.AsyncClient(
-        transport=transport, base_url="https://example.com"
-    ) as client:
-        http_client = HttpClient(client)
-        cron_client = CronClient(http_client)
-        await cron_client.search()
-
-
-@pytest.mark.asyncio
-async def test_async_count_with_metadata():
-    """Test that CronClient.count forwards metadata in the request body."""
-
-    async def handler(request: httpx.Request) -> httpx.Response:
-        assert request.method == "POST"
-        assert request.url.path == "/runs/crons/count"
-
-        body = json.loads(request.content)
-        assert body["metadata"] == {"team": "infra"}
-
-        return httpx.Response(200, json=2)
-
-    transport = httpx.MockTransport(handler)
-    async with httpx.AsyncClient(
-        transport=transport, base_url="https://example.com"
-    ) as client:
-        http_client = HttpClient(client)
-        cron_client = CronClient(http_client)
-        result = await cron_client.count(metadata={"team": "infra"})
-
-    assert result == 2
-
-
-@pytest.mark.asyncio
-async def test_async_count_omits_empty_metadata():
-    """Test that CronClient.count does not send metadata when not provided."""
-
-    async def handler(request: httpx.Request) -> httpx.Response:
-        body = json.loads(request.content)
-        assert "metadata" not in body
-        return httpx.Response(200, json=0)
-
-    transport = httpx.MockTransport(handler)
-    async with httpx.AsyncClient(
-        transport=transport, base_url="https://example.com"
-    ) as client:
-        http_client = HttpClient(client)
-        cron_client = CronClient(http_client)
-        await cron_client.count()
-
-
-def test_sync_search_with_metadata():
-    """Test that SyncCronClient.search forwards metadata in the request body."""
-    cron = _cron_response()
-
-    def handler(request: httpx.Request) -> httpx.Response:
-        assert request.method == "POST"
-        assert request.url.path == "/runs/crons/search"
-
-        body = json.loads(request.content)
-        assert body["metadata"] == {"owner": "alice"}
-
-        return httpx.Response(200, json=[cron])
-
-    transport = httpx.MockTransport(handler)
-    with httpx.Client(transport=transport, base_url="https://example.com") as client:
-        http_client = SyncHttpClient(client)
-        cron_client = SyncCronClient(http_client)
-        result = cron_client.search(metadata={"owner": "alice"})
-
-    assert result == [cron]
-
-
-def test_sync_search_omits_empty_metadata():
-    """Test that SyncCronClient.search does not send metadata when not provided."""
-    cron = _cron_response()
-
-    def handler(request: httpx.Request) -> httpx.Response:
-        body = json.loads(request.content)
-        assert "metadata" not in body
-        return httpx.Response(200, json=[cron])
-
-    transport = httpx.MockTransport(handler)
-    with httpx.Client(transport=transport, base_url="https://example.com") as client:
-        http_client = SyncHttpClient(client)
-        cron_client = SyncCronClient(http_client)
-        cron_client.search()
-
-
-def test_sync_count_with_metadata():
-    """Test that SyncCronClient.count forwards metadata in the request body."""
-
-    def handler(request: httpx.Request) -> httpx.Response:
-        assert request.method == "POST"
-        assert request.url.path == "/runs/crons/count"
-
-        body = json.loads(request.content)
-        assert body["metadata"] == {"team": "infra"}
-
-        return httpx.Response(200, json=2)
-
-    transport = httpx.MockTransport(handler)
-    with httpx.Client(transport=transport, base_url="https://example.com") as client:
-        http_client = SyncHttpClient(client)
-        cron_client = SyncCronClient(http_client)
-        result = cron_client.count(metadata={"team": "infra"})
-
-    assert result == 2
-
-
-def test_sync_count_omits_empty_metadata():
-    """Test that SyncCronClient.count does not send metadata when not provided."""
-
-    def handler(request: httpx.Request) -> httpx.Response:
-        body = json.loads(request.content)
-        assert "metadata" not in body
-        return httpx.Response(200, json=0)
-
-    transport = httpx.MockTransport(handler)
-    with httpx.Client(transport=transport, base_url="https://example.com") as client:
-        http_client = SyncHttpClient(client)
-        cron_client = SyncCronClient(http_client)
-        cron_client.count()
@@ -67,6 +67,6 @@ class TestHandlerValidation:

        with pytest.raises(TypeError, match="must accept exactly 2 parameters"):

-            @encryption.encrypt.blob  # ty: ignore[invalid-argument-type]
+            @encryption.encrypt.blob  # type: ignore[arg-type]
            async def wrong_params(ctx):
                return ctx
@@ -227,11 +227,11 @@ wheels = [

 [[package]]
 name = "idna"
-version = "3.15"
+version = "3.11"
 source = { registry = "https://pypi.org/simple" }
-sdist = { url = "https://files.pythonhosted.org/packages/82/77/7b3966d0b9d1d31a36ddf1746926a11dface89a83409bf1483f0237aa758/idna-3.15.tar.gz", hash = "sha256:ca962446ea538f7092a95e057da437618e886f4d349216d2b1e294abfdb65fdc", size = 199245, upload-time = "2026-05-12T22:45:57.011Z" }
+sdist = { url = "https://files.pythonhosted.org/packages/6f/6d/0703ccc57f3a7233505399edb88de3cbd678da106337b9fcde432b65ed60/idna-3.11.tar.gz", hash = "sha256:795dafcc9c04ed0c1fb032c2aa73654d8e8c5023a7df64a53f39190ada629902", size = 194582, upload-time = "2025-10-12T14:55:20.501Z" }
 wheels = [
-    { url = "https://files.pythonhosted.org/packages/d2/23/408243171aa9aaba178d3e2559159c24c1171a641aa83b67bdd3394ead8e/idna-3.15-py3-none-any.whl", hash = "sha256:048adeaf8c2d788c40fee287673ccaa74c24ffd8dcf09ffa555a2fbb59f10ac8", size = 72340, upload-time = "2026-05-12T22:45:55.733Z" },
+    { url = "https://files.pythonhosted.org/packages/0e/61/66938bbb5fc52dbdf84594873d5b51fb1f7c7794e9c0f5bd885f30bc507b/idna-3.11-py3-none-any.whl", hash = "sha256:771a87f49d9defaf64091e6e6fe9c18d4833f140bd19464795bc32d966ca37ea", size = 71008, upload-time = "2025-10-12T14:55:18.883Z" },
 ]

 [[package]]
@@ -266,7 +266,7 @@ wheels = [

 [[package]]
 name = "langchain-core"
-version = "1.4.0"
+version = "1.4.0a2"
 source = { registry = "https://pypi.org/simple" }
 dependencies = [
    { name = "jsonpatch" },
@@ -279,9 +279,9 @@ dependencies = [
    { name = "typing-extensions" },
    { name = "uuid-utils" },
 ]
-sdist = { url = "https://files.pythonhosted.org/packages/59/de/679a53472c25860837e32c0442c962fa86e95317a36460e2c9d5c91b17c2/langchain_core-1.4.0.tar.gz", hash = "sha256:1dc341eed802ed9c117c0df3923c991e5e9e226571e5725c194eeb5bd93d1a7f", size = 920260, upload-time = "2026-05-11T18:42:35.919Z" }
+sdist = { url = "https://files.pythonhosted.org/packages/3c/93/68bafa047f8e1770d0cf0f61d6c70889f1dec42ef6bd263540d916c421b9/langchain_core-1.4.0a2.tar.gz", hash = "sha256:b723c7961b615c7f2180ce2bcf352fdad8247bc51a60adecd3d97088235c120d", size = 916486, upload-time = "2026-05-01T15:02:19.029Z" }
 wheels = [
-    { url = "https://files.pythonhosted.org/packages/0f/1a/86c38c27b81913a1c6c12448cab55defb5a1097c7dc9a4cea83f55477a2d/langchain_core-1.4.0-py3-none-any.whl", hash = "sha256:23cbbdb46e38ddd1dd5247e6167e96013eae74bea4c5949c550809970a9e565c", size = 548120, upload-time = "2026-05-11T18:42:33.992Z" },
+    { url = "https://files.pythonhosted.org/packages/4e/8e/933e0ba7ba0430ce264e36b178d581b255239ad45093872483142d93478c/langchain_core-1.4.0a2-py3-none-any.whl", hash = "sha256:a5c689f8404357df797120c012da7704144a953b2ae18f258df263301e7badd5", size = 546297, upload-time = "2026-05-01T15:02:17.731Z" },
 ]

 [[package]]
@@ -298,7 +298,7 @@ wheels = [

 [[package]]
 name = "langgraph"
-version = "1.2.1"
+version = "1.2.0a7"
 source = { editable = "../langgraph" }
 dependencies = [
    { name = "langchain-core" },
@@ -311,7 +311,7 @@ dependencies = [

 [package.metadata]
 requires-dist = [
-    { name = "langchain-core", specifier = ">=1.4.0,<2" },
+    { name = "langchain-core", specifier = ">=1.4.0a2,<2" },
    { name = "langgraph-checkpoint", editable = "../checkpoint" },
    { name = "langgraph-prebuilt", editable = "../prebuilt" },
    { name = "langgraph-sdk", editable = "." },
@@ -382,7 +382,7 @@ test = [

 [[package]]
 name = "langgraph-checkpoint"
-version = "4.1.0"
+version = "4.1.0a4"
 source = { editable = "../checkpoint" }
 dependencies = [
    { name = "langchain-core" },
@@ -430,7 +430,7 @@ test = [

 [[package]]
 name = "langgraph-prebuilt"
-version = "1.1.0"
+version = "1.1.0a2"
 source = { editable = "../prebuilt" }
 dependencies = [
    { name = "langchain-core" },
@@ -533,14 +533,14 @@ dev = [
    { name = "pytest-watch" },
    { name = "ruff", specifier = "==0.15.12" },
    { name = "starlette" },
-    { name = "ty", specifier = "==0.0.33" },
+    { name = "ty", specifier = "==0.0.23" },
 ]
 lint = [
    { name = "codespell" },
    { name = "mypy", specifier = "==1.20.2" },
    { name = "ruff", specifier = "==0.15.12" },
    { name = "starlette" },
-    { name = "ty", specifier = "==0.0.33" },
+    { name = "ty", specifier = "==0.0.23" },
 ]
 test = [
    { name = "pytest" },
@@ -551,7 +551,7 @@ test = [

 [[package]]
 name = "langsmith"
-version = "0.8.0"
+version = "0.7.31"
 source = { registry = "https://pypi.org/simple" }
 dependencies = [
    { name = "httpx" },
@@ -564,9 +564,9 @@ dependencies = [
    { name = "xxhash" },
    { name = "zstandard" },
 ]
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+sdist = { url = "https://files.pythonhosted.org/packages/e6/11/696019490992db5c87774dc20515529ef42a01e1d770fb754ed6d9b12fb0/langsmith-0.7.31.tar.gz", hash = "sha256:331ee4f7c26bb5be4022b9859b7d7b122cbf8c9d01d9f530114c1914b0349ffb", size = 1178480, upload-time = "2026-04-14T17:55:41.242Z" }
 wheels = [
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 [[package]]
@@ -1275,26 +1275,26 @@ wheels = [

 [[package]]
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-version = "0.0.33"
+version = "0.0.23"
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Author	SHA1	Message	Date
Sydney Runkle	2239aae856	fix(lint): remove redundant cast flagged by mypy	2026-05-06 15:08:37 -04:00
Sydney Runkle	e8c6d9cc31	chore: apply ruff format/lint fixes	2026-05-06 15:03:13 -04:00
Sydney Runkle	6c43a254ef	fix(message): full add_messages parity for _messages_delta_reducer Add REMOVE_ALL_MESSAGES sentinel handling and BaseMessageChunk coercion, completing parity with add_messages. REMOVE_ALL_MESSAGES resets state and discards all preceding writes; chunks are coerced to full messages via message_chunk_to_message. Both properties are batching-invariant.	2026-05-06 14:59:12 -04:00
Sydney Runkle	eddfb40703	fix(message): assign UUIDs to ID-less messages in _messages_delta_reducer Without UUID assignment, message eviction and RemoveMessage tombstoning fail for messages created without explicit IDs. Matches the behavior of add_messages. IDs are now assigned inline within the existing iterations over state_msgs and msgs to avoid an extra pass.	2026-05-06 14:42:36 -04:00