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.venv/Lib/site-packages/langgraph/checkpoint/base/__init__.py

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+from __future__ import annotations
+
+import copy
+import logging
+from collections.abc import AsyncIterator, Collection, Iterator, Mapping, Sequence
+from typing import (
+    Any,
+    Generic,
+    Literal,
+    NamedTuple,
+    TypedDict,
+    TypeVar,
+)
+
+from langchain_core.runnables import RunnableConfig
+from typing_extensions import NotRequired
+
+from langgraph.checkpoint.base.id import uuid6
+from langgraph.checkpoint.serde.base import SerializerProtocol, maybe_add_typed_methods
+from langgraph.checkpoint.serde.encrypted import EncryptedSerializer
+from langgraph.checkpoint.serde.jsonplus import JsonPlusSerializer
+from langgraph.checkpoint.serde.types import (
+    ERROR,
+    INTERRUPT,
+    RESUME,
+    SCHEDULED,
+    ChannelProtocol,
+)
+
+V = TypeVar("V", int, float, str)
+PendingWrite = tuple[str, str, Any]
+
+
+logger = logging.getLogger(__name__)
+
+
+# Marked as total=False to allow for future expansion.
+class CheckpointMetadata(TypedDict, total=False):
+    """Metadata associated with a checkpoint."""
+
+    source: Literal["input", "loop", "update", "fork"]
+    """The source of the checkpoint.
+
+    - `"input"`: The checkpoint was created from an input to invoke/stream/batch.
+    - `"loop"`: The checkpoint was created from inside the pregel loop.
+    - `"update"`: The checkpoint was created from a manual state update.
+    - `"fork"`: The checkpoint was created as a copy of another checkpoint.
+    """
+    step: int
+    """The step number of the checkpoint.
+
+    `-1` for the first `"input"` checkpoint.
+    `0` for the first `"loop"` checkpoint.
+    `...` for the `nth` checkpoint afterwards.
+    """
+    parents: dict[str, str]
+    """The IDs of the parent checkpoints.
+
+    Mapping from checkpoint namespace to checkpoint ID.
+    """
+    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.
+
+    !!! 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).
+    """
+
+
+ChannelVersions = dict[str, str | int | float]
+
+
+class Checkpoint(TypedDict):
+    """State snapshot at a given point in time."""
+
+    v: int
+    """The version of the checkpoint format. Currently `1`."""
+    id: str
+    """The ID of the checkpoint.
+    
+    This is both unique and monotonically increasing, so can be used for sorting
+    checkpoints from first to last."""
+    ts: str
+    """The timestamp of the checkpoint in ISO 8601 format."""
+    channel_values: dict[str, Any]
+    """The values of the channels at the time of the checkpoint.
+    
+    Mapping from channel name to deserialized channel snapshot value.
+    """
+    channel_versions: ChannelVersions
+    """The versions of the channels at the time of the checkpoint.
+    
+    The keys are channel names and the values are monotonically increasing
+    version strings for each channel.
+    """
+    versions_seen: dict[str, ChannelVersions]
+    """Map from node ID to map from channel name to version seen.
+    
+    This keeps track of the versions of the channels that each node has seen.
+    Used to determine which nodes to execute next.
+    """
+    updated_channels: list[str] | None
+    """The channels that were updated in this checkpoint.
+    """
+
+
+def copy_checkpoint(checkpoint: Checkpoint) -> Checkpoint:
+    return Checkpoint(
+        v=checkpoint["v"],
+        ts=checkpoint["ts"],
+        id=checkpoint["id"],
+        channel_values=checkpoint["channel_values"].copy(),
+        channel_versions=checkpoint["channel_versions"].copy(),
+        versions_seen={k: v.copy() for k, v in checkpoint["versions_seen"].items()},
+        pending_sends=checkpoint.get("pending_sends", []).copy(),
+        updated_channels=checkpoint.get("updated_channels", None),
+    )
+
+
+class CheckpointTuple(NamedTuple):
+    """A tuple containing a checkpoint and its associated data."""
+
+    config: RunnableConfig
+    checkpoint: Checkpoint
+    metadata: CheckpointMetadata
+    parent_config: RunnableConfig | None = None
+    pending_writes: list[PendingWrite] | None = None
+
+
+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:
+
+    * `writes` — on-path deltas oldest→newest as `PendingWrite` tuples.
+      Always present; possibly empty. Already filtered to one channel.
+      Writes stored at the target checkpoint itself are pending for the
+      next super-step and are excluded.
+    * `seed` — the stored value at the nearest ancestor whose
+      `channel_values[ch]` is populated. Omitted if the walk reached the
+      root without finding any stored value (consumer treats absence as
+      "start empty"). Typically a `_DeltaSnapshot` for delta channels with
+      finite snapshot frequency, or a plain value for threads migrated
+      from a pre-delta channel type.
+    """
+
+    writes: list[PendingWrite]
+    seed: NotRequired[Any]
+
+
+class BaseCheckpointSaver(Generic[V]):
+    """Base class for creating a graph checkpointer.
+
+    Checkpointers allow LangGraph agents to persist their state
+    within and across multiple interactions.
+
+    When a checkpointer is configured, you should pass a `thread_id` in the config when
+    invoking the graph:
+
+    ```python
+    config = {"configurable": {"thread_id": "my-thread"}}
+    graph.invoke(inputs, config)
+    ```
+
+    The `thread_id` is the primary key used to store and retrieve checkpoints. Without
+    it, the checkpointer cannot save state, resume from interrupts, or enable
+    time-travel debugging.
+
+    How you choose ``thread_id`` depends on your use case:
+
+    - **Single-shot workflows**: Use a unique ID (e.g., uuid4) for each run when
+        executions are independent.
+    - **Conversational memory**: Reuse the same `thread_id` across invocations
+        to accumulate state (e.g., chat history) within a conversation.
+
+    Attributes:
+        serde (SerializerProtocol): Serializer for encoding/decoding checkpoints.
+
+    Note:
+        When creating a custom checkpoint saver, consider implementing async
+        versions to avoid blocking the main thread.
+    """
+
+    serde: SerializerProtocol = JsonPlusSerializer()
+
+    def __init__(
+        self,
+        *,
+        serde: SerializerProtocol | None = None,
+    ) -> None:
+        self.serde = maybe_add_typed_methods(serde or self.serde)
+
+    @property
+    def config_specs(self) -> list:
+        """Define the configuration options for the checkpoint saver.
+
+        Returns:
+            list: List of configuration field specs.
+        """
+        return []
+
+    def get(self, config: RunnableConfig) -> Checkpoint | None:
+        """Fetch a checkpoint using the given configuration.
+
+        Args:
+            config: Configuration specifying which checkpoint to retrieve.
+
+        Returns:
+            The requested checkpoint, or `None` if not found.
+        """
+        if value := self.get_tuple(config):
+            return value.checkpoint
+
+    def get_tuple(self, config: RunnableConfig) -> CheckpointTuple | None:
+        """Fetch a checkpoint tuple using the given configuration.
+
+        Args:
+            config: Configuration specifying which checkpoint to retrieve.
+
+        Returns:
+            The requested checkpoint tuple, or `None` if not found.
+
+        Raises:
+            NotImplementedError: Implement this method in your custom checkpoint saver.
+        """
+        raise NotImplementedError
+
+    def list(
+        self,
+        config: RunnableConfig | None,
+        *,
+        filter: dict[str, Any] | None = None,
+        before: RunnableConfig | None = None,
+        limit: int | None = None,
+    ) -> Iterator[CheckpointTuple]:
+        """List checkpoints that match the given criteria.
+
+        Args:
+            config: Base configuration for filtering checkpoints.
+            filter: Additional filtering criteria.
+            before: List checkpoints created before this configuration.
+            limit: Maximum number of checkpoints to return.
+
+        Returns:
+            Iterator of matching checkpoint tuples.
+
+        Raises:
+            NotImplementedError: Implement this method in your custom checkpoint saver.
+        """
+        raise NotImplementedError
+
+    def put(
+        self,
+        config: RunnableConfig,
+        checkpoint: Checkpoint,
+        metadata: CheckpointMetadata,
+        new_versions: ChannelVersions,
+    ) -> RunnableConfig:
+        """Store a checkpoint with its configuration and metadata.
+
+        Args:
+            config: Configuration for the checkpoint.
+            checkpoint: The checkpoint to store.
+            metadata: Additional metadata for the checkpoint.
+            new_versions: New channel versions as of this write.
+
+        Returns:
+            RunnableConfig: Updated configuration after storing the checkpoint.
+
+        Raises:
+            NotImplementedError: Implement this method in your custom checkpoint saver.
+        """
+        raise NotImplementedError
+
+    def put_writes(
+        self,
+        config: RunnableConfig,
+        writes: Sequence[tuple[str, Any]],
+        task_id: str,
+        task_path: str = "",
+    ) -> None:
+        """Store intermediate writes linked to a checkpoint.
+
+        Args:
+            config: Configuration of the related checkpoint.
+            writes: List of writes to store.
+            task_id: Identifier for the task creating the writes.
+            task_path: Path of the task creating the writes.
+
+        Raises:
+            NotImplementedError: Implement this method in your custom checkpoint saver.
+        """
+        raise NotImplementedError
+
+    def delete_thread(
+        self,
+        thread_id: str,
+    ) -> None:
+        """Delete all checkpoints and writes associated with a specific thread ID.
+
+        Args:
+            thread_id: The thread ID whose checkpoints should be deleted.
+        """
+        raise NotImplementedError
+
+    def delete_for_runs(
+        self,
+        run_ids: Sequence[str],
+    ) -> None:
+        """Delete all checkpoints and writes associated with the given run IDs.
+
+        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
+
+    def copy_thread(
+        self,
+        source_thread_id: str,
+        target_thread_id: str,
+    ) -> None:
+        """Copy all checkpoints and writes from one thread to another.
+
+        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
+
+    def prune(
+        self,
+        thread_ids: Sequence[str],
+        *,
+        strategy: str = "keep_latest",
+    ) -> None:
+        """Prune checkpoints for the given threads.
+
+        Args:
+            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
+
+    async def aget(self, config: RunnableConfig) -> Checkpoint | None:
+        """Asynchronously fetch a checkpoint using the given configuration.
+
+        Args:
+            config: Configuration specifying which checkpoint to retrieve.
+
+        Returns:
+            The requested checkpoint, or `None` if not found.
+        """
+        if value := await self.aget_tuple(config):
+            return value.checkpoint
+
+    async def aget_tuple(self, config: RunnableConfig) -> CheckpointTuple | None:
+        """Asynchronously fetch a checkpoint tuple using the given configuration.
+
+        Args:
+            config: Configuration specifying which checkpoint to retrieve.
+
+        Returns:
+            The requested checkpoint tuple, or `None` if not found.
+
+        Raises:
+            NotImplementedError: Implement this method in your custom checkpoint saver.
+        """
+        raise NotImplementedError
+
+    async def alist(
+        self,
+        config: RunnableConfig | None,
+        *,
+        filter: dict[str, Any] | None = None,
+        before: RunnableConfig | None = None,
+        limit: int | None = None,
+    ) -> AsyncIterator[CheckpointTuple]:
+        """Asynchronously list checkpoints that match the given criteria.
+
+        Args:
+            config: Base configuration for filtering checkpoints.
+            filter: Additional filtering criteria for metadata.
+            before: List checkpoints created before this configuration.
+            limit: Maximum number of checkpoints to return.
+
+        Returns:
+            Async iterator of matching checkpoint tuples.
+
+        Raises:
+            NotImplementedError: Implement this method in your custom checkpoint saver.
+        """
+        raise NotImplementedError
+        yield
+
+    async def aput(
+        self,
+        config: RunnableConfig,
+        checkpoint: Checkpoint,
+        metadata: CheckpointMetadata,
+        new_versions: ChannelVersions,
+    ) -> RunnableConfig:
+        """Asynchronously store a checkpoint with its configuration and metadata.
+
+        Args:
+            config: Configuration for the checkpoint.
+            checkpoint: The checkpoint to store.
+            metadata: Additional metadata for the checkpoint.
+            new_versions: New channel versions as of this write.
+
+        Returns:
+            RunnableConfig: Updated configuration after storing the checkpoint.
+
+        Raises:
+            NotImplementedError: Implement this method in your custom checkpoint saver.
+        """
+        raise NotImplementedError
+
+    async def aput_writes(
+        self,
+        config: RunnableConfig,
+        writes: Sequence[tuple[str, Any]],
+        task_id: str,
+        task_path: str = "",
+    ) -> None:
+        """Asynchronously store intermediate writes linked to a checkpoint.
+
+        Args:
+            config: Configuration of the related checkpoint.
+            writes: List of writes to store.
+            task_id: Identifier for the task creating the writes.
+            task_path: Path of the task creating the writes.
+
+        Raises:
+            NotImplementedError: Implement this method in your custom checkpoint saver.
+        """
+        raise NotImplementedError
+
+    async def adelete_thread(
+        self,
+        thread_id: str,
+    ) -> None:
+        """Delete all checkpoints and writes associated with a specific thread ID.
+
+        Args:
+            thread_id: The thread ID whose checkpoints should be deleted.
+        """
+        raise NotImplementedError
+
+    async def adelete_for_runs(
+        self,
+        run_ids: Sequence[str],
+    ) -> None:
+        """Asynchronously delete all checkpoints and writes for the given run IDs.
+
+        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
+
+    async def acopy_thread(
+        self,
+        source_thread_id: str,
+        target_thread_id: str,
+    ) -> None:
+        """Asynchronously copy all checkpoints and writes from one thread to another.
+
+        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
+
+    async def aprune(
+        self,
+        thread_ids: Sequence[str],
+        *,
+        strategy: str = "keep_latest",
+    ) -> None:
+        """Asynchronously prune checkpoints for the given threads.
+
+        Args:
+            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
+
+    def get_delta_channel_history(
+        self, *, config: RunnableConfig, channels: Sequence[str]
+    ) -> 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
+        at the nearest ancestor whose `channel_values[ch]` is populated;
+        that value is returned as `seed`. If the walk reaches the root
+        without finding a stored value, `seed` is omitted from that
+        channel's entry — the consumer treats the absence as "start
+        empty."
+
+        Walks the **parent chain** (not `list(before=...)`): for forked
+        threads, only on-path ancestors contribute.
+
+        The default implementation walks `get_tuple` + `parent_config`
+        once for all channels — each ancestor visited once, not once per
+        channel. Savers with direct storage access (`InMemorySaver`,
+        `PostgresSaver`) override for performance; the return contract is
+        fixed here.
+
+        Args:
+            config: Configuration identifying the target checkpoint.
+            channels: Channel names to walk for. Empty → empty mapping.
+
+        Returns:
+            Per-channel `DeltaChannelHistory` for every name in `channels`.
+        """
+        if not channels:
+            return {}
+        collected_by_ch: dict[str, list[PendingWrite]] = {c: [] for c in channels}
+        seed_by_ch: dict[str, Any] = {}
+        remaining: set[str] = set(channels)
+        target_tuple = self.get_tuple(config)
+        cursor_config: RunnableConfig | None = (
+            target_tuple.parent_config if target_tuple else None
+        )
+        while cursor_config is not None and remaining:
+            tup = self.get_tuple(cursor_config)
+            if tup is None:
+                break
+            if tup.pending_writes:
+                for write in reversed(tup.pending_writes):
+                    ch = write[1]
+                    if ch in remaining:
+                        collected_by_ch[ch].append(write)
+            for ch in list(remaining):
+                if ch in tup.checkpoint["channel_values"]:
+                    seed_by_ch[ch] = tup.checkpoint["channel_values"][ch]
+                    remaining.discard(ch)
+            cursor_config = tup.parent_config
+        result: dict[str, DeltaChannelHistory] = {}
+        for ch in channels:
+            entry: DeltaChannelHistory = {"writes": list(reversed(collected_by_ch[ch]))}
+            if ch in seed_by_ch:
+                entry["seed"] = seed_by_ch[ch]
+            result[ch] = entry
+        return result
+
+    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.
+        """
+        if not channels:
+            return {}
+        collected_by_ch: dict[str, list[PendingWrite]] = {c: [] for c in channels}
+        seed_by_ch: dict[str, Any] = {}
+        remaining: set[str] = set(channels)
+        target_tuple = await self.aget_tuple(config)
+        cursor_config: RunnableConfig | None = (
+            target_tuple.parent_config if target_tuple else None
+        )
+        while cursor_config is not None and remaining:
+            tup = await self.aget_tuple(cursor_config)
+            if tup is None:
+                break
+            if tup.pending_writes:
+                for write in reversed(tup.pending_writes):
+                    ch = write[1]
+                    if ch in remaining:
+                        collected_by_ch[ch].append(write)
+            for ch in list(remaining):
+                if ch in tup.checkpoint["channel_values"]:
+                    seed_by_ch[ch] = tup.checkpoint["channel_values"][ch]
+                    remaining.discard(ch)
+            cursor_config = tup.parent_config
+        result: dict[str, DeltaChannelHistory] = {}
+        for ch in channels:
+            entry: DeltaChannelHistory = {"writes": list(reversed(collected_by_ch[ch]))}
+            if ch in seed_by_ch:
+                entry["seed"] = seed_by_ch[ch]
+            result[ch] = entry
+        return result
+
+    def get_next_version(self, current: V | None, channel: None) -> V:
+        """Generate the next version ID for a channel.
+
+        Default is to use integer versions, incrementing by `1`.
+
+        If you override, you can use `str`/`int`/`float` versions, as long as they are monotonically increasing.
+
+        Args:
+            current: The current version identifier (`int`, `float`, or `str`).
+            channel: Deprecated argument, kept for backwards compatibility.
+
+        Returns:
+            V: The next version identifier, which must be increasing.
+        """
+        if isinstance(current, str):
+            raise NotImplementedError
+        elif current is None:
+            return 1
+        else:
+            return current + 1
+
+    def with_allowlist(
+        self, extra_allowlist: Collection[tuple[str, ...]]
+    ) -> BaseCheckpointSaver[V]:
+        """Return a shallow clone with a derived msgpack allowlist."""
+        serde = _with_msgpack_allowlist(self.serde, extra_allowlist)
+        if serde is self.serde:
+            return self
+        clone = copy.copy(self)
+        clone.serde = maybe_add_typed_methods(serde)
+        return clone
+
+
+def _with_msgpack_allowlist(
+    serde: SerializerProtocol, extra_allowlist: Collection[tuple[str, ...]]
+) -> SerializerProtocol:
+    if isinstance(serde, JsonPlusSerializer):
+        return serde.with_msgpack_allowlist(extra_allowlist)
+    if isinstance(serde, EncryptedSerializer):
+        inner = serde.serde
+        if isinstance(inner, JsonPlusSerializer):
+            updated_inner = inner.with_msgpack_allowlist(extra_allowlist)
+            if updated_inner is inner:
+                return serde
+            return EncryptedSerializer(serde.cipher, updated_inner)
+    logger.warning(
+        "Serializer %s does not support msgpack allowlist. "
+        "Strict msgpack deserialization will not be enforced.",
+        type(serde).__name__,
+    )
+    return serde
+
+
+class EmptyChannelError(Exception):
+    """Raised when attempting to get the value of a channel that hasn't been updated
+    for the first time yet."""
+
+    pass
+
+
+def get_checkpoint_id(config: RunnableConfig) -> str | None:
+    """Get checkpoint ID."""
+    return config["configurable"].get("checkpoint_id")
+
+
+def get_checkpoint_metadata(
+    config: RunnableConfig, metadata: CheckpointMetadata
+) -> CheckpointMetadata:
+    """Get checkpoint metadata in a backwards-compatible manner."""
+    metadata = {
+        k: v.replace("\u0000", "") if isinstance(v, str) else v
+        for k, v in metadata.items()
+    }
+    for obj in (config.get("metadata"), config.get("configurable")):
+        if not obj:
+            continue
+        for key, v in obj.items():
+            if key in metadata or key in EXCLUDED_METADATA_KEYS or key.startswith("__"):
+                continue
+            elif isinstance(v, str):
+                metadata[key] = v.replace("\u0000", "")
+            elif isinstance(v, (int, bool, float)):
+                metadata[key] = v
+    return metadata
+
+
+def get_serializable_checkpoint_metadata(
+    config: RunnableConfig, metadata: CheckpointMetadata
+) -> CheckpointMetadata:
+    """Get checkpoint metadata in a backwards-compatible manner."""
+    checkpoint_metadata = get_checkpoint_metadata(config, metadata)
+    if "writes" in checkpoint_metadata:
+        checkpoint_metadata.pop("writes")
+    return checkpoint_metadata
+
+
+"""
+Mapping from error type to error index.
+Regular writes just map to their index in the list of writes being saved.
+Special writes (e.g. errors) map to negative indices, to avoid those writes from
+conflicting with regular writes.
+Each Checkpointer implementation should use this mapping in put_writes.
+"""
+WRITES_IDX_MAP = {ERROR: -1, SCHEDULED: -2, INTERRUPT: -3, RESUME: -4}
+
+EXCLUDED_METADATA_KEYS = {
+    "thread_id",
+    "checkpoint_id",
+    "checkpoint_ns",
+    "checkpoint_map",
+    "langgraph_step",
+    "langgraph_node",
+    "langgraph_triggers",
+    "langgraph_path",
+    "langgraph_checkpoint_ns",
+}
+
+# --- below are deprecated utilities used by past versions of LangGraph ---
+
+LATEST_VERSION = 2
+
+
+def empty_checkpoint() -> Checkpoint:
+    from datetime import datetime, timezone
+
+    return Checkpoint(
+        v=LATEST_VERSION,
+        id=str(uuid6(clock_seq=-2)),
+        ts=datetime.now(timezone.utc).isoformat(),
+        channel_values={},
+        channel_versions={},
+        versions_seen={},
+        pending_sends=[],
+        updated_channels=None,
+    )
+
+
+def create_checkpoint(
+    checkpoint: Checkpoint,
+    channels: Mapping[str, ChannelProtocol] | None,
+    step: int,
+    *,
+    id: str | None = None,
+) -> Checkpoint:
+    """Create a checkpoint for the given channels."""
+    from datetime import datetime, timezone
+
+    ts = datetime.now(timezone.utc).isoformat()
+    if channels is None:
+        values = checkpoint["channel_values"]
+    else:
+        values = {}
+        for k, v in channels.items():
+            if k not in checkpoint["channel_versions"]:
+                continue
+            try:
+                values[k] = v.checkpoint()
+            except EmptyChannelError:
+                pass
+    return Checkpoint(
+        v=LATEST_VERSION,
+        ts=ts,
+        id=id or str(uuid6(clock_seq=step)),
+        channel_values=values,
+        channel_versions=checkpoint["channel_versions"],
+        versions_seen=checkpoint["versions_seen"],
+        pending_sends=checkpoint.get("pending_sends", []),
+        updated_channels=None,
+    )

.venv/Lib/site-packages/langgraph/checkpoint/base/id.py

@@ -0,0 +1,109 @@
+"""Adapted from
+https://github.com/oittaa/uuid6-python/blob/main/src/uuid6/__init__.py#L95
+Bundled in to avoid install issues with uuid6 package
+"""
+
+from __future__ import annotations
+
+import random
+import time
+import uuid
+
+_last_v6_timestamp = None
+
+
+class UUID(uuid.UUID):
+    r"""UUID draft version objects"""
+
+    __slots__ = ()
+
+    def __init__(
+        self,
+        hex: str | None = None,
+        bytes: bytes | None = None,
+        bytes_le: bytes | None = None,
+        fields: tuple[int, int, int, int, int, int] | None = None,
+        int: int | None = None,
+        version: int | None = None,
+        *,
+        is_safe: uuid.SafeUUID = uuid.SafeUUID.unknown,
+    ) -> None:
+        r"""Create a UUID."""
+
+        if int is None or [hex, bytes, bytes_le, fields].count(None) != 4:
+            return super().__init__(
+                hex=hex,
+                bytes=bytes,
+                bytes_le=bytes_le,
+                fields=fields,
+                int=int,
+                version=version,
+                is_safe=is_safe,
+            )
+        if not 0 <= int < 1 << 128:
+            raise ValueError("int is out of range (need a 128-bit value)")
+        if version is not None:
+            if not 6 <= version <= 8:
+                raise ValueError("illegal version number")
+            # Set the variant to RFC 4122.
+            int &= ~(0xC000 << 48)
+            int |= 0x8000 << 48
+            # Set the version number.
+            int &= ~(0xF000 << 64)
+            int |= version << 76
+        super().__init__(int=int, is_safe=is_safe)
+
+    @property
+    def subsec(self) -> int:
+        return ((self.int >> 64) & 0x0FFF) << 8 | ((self.int >> 54) & 0xFF)
+
+    @property
+    def time(self) -> int:
+        if self.version == 6:
+            return (
+                (self.time_low << 28)
+                | (self.time_mid << 12)
+                | (self.time_hi_version & 0x0FFF)
+            )
+        if self.version == 7:
+            return self.int >> 80
+        if self.version == 8:
+            return (self.int >> 80) * 10**6 + _subsec_decode(self.subsec)
+        return super().time
+
+
+def _subsec_decode(value: int) -> int:
+    return -(-value * 10**6 // 2**20)
+
+
+def uuid6(node: int | None = None, clock_seq: int | None = None) -> UUID:
+    r"""UUID version 6 is a field-compatible version of UUIDv1, reordered for
+    improved DB locality. It is expected that UUIDv6 will primarily be
+    used in contexts where there are existing v1 UUIDs. Systems that do
+    not involve legacy UUIDv1 SHOULD consider using UUIDv7 instead.
+
+    If 'node' is not given, a random 48-bit number is chosen.
+
+    If 'clock_seq' is given, it is used as the sequence number;
+    otherwise a random 14-bit sequence number is chosen."""
+
+    global _last_v6_timestamp
+
+    nanoseconds = time.time_ns()
+    # 0x01b21dd213814000 is the number of 100-ns intervals between the
+    # UUID epoch 1582-10-15 00:00:00 and the Unix epoch 1970-01-01 00:00:00.
+    timestamp = nanoseconds // 100 + 0x01B21DD213814000
+    if _last_v6_timestamp is not None and timestamp <= _last_v6_timestamp:
+        timestamp = _last_v6_timestamp + 1
+    _last_v6_timestamp = timestamp
+    if clock_seq is None:
+        clock_seq = random.getrandbits(14)  # instead of stable storage
+    if node is None:
+        node = random.getrandbits(48)
+    time_high_and_time_mid = (timestamp >> 12) & 0xFFFFFFFFFFFF
+    time_low_and_version = timestamp & 0x0FFF
+    uuid_int = time_high_and_time_mid << 80
+    uuid_int |= time_low_and_version << 64
+    uuid_int |= (clock_seq & 0x3FFF) << 48
+    uuid_int |= node & 0xFFFFFFFFFFFF
+    return UUID(int=uuid_int, version=6)

.venv/Lib/site-packages/langgraph/checkpoint/memory/__init__.py

@@ -0,0 +1,704 @@
+from __future__ import annotations
+
+import logging
+import os
+import pickle
+import random
+import shutil
+from collections import defaultdict
+from collections.abc import AsyncIterator, Iterator, Mapping, Sequence
+from contextlib import AbstractAsyncContextManager, AbstractContextManager, ExitStack
+from types import TracebackType
+from typing import Any
+
+from langchain_core.runnables import RunnableConfig
+
+from langgraph.checkpoint.base import (
+    WRITES_IDX_MAP,
+    BaseCheckpointSaver,
+    ChannelVersions,
+    Checkpoint,
+    CheckpointMetadata,
+    CheckpointTuple,
+    DeltaChannelHistory,
+    PendingWrite,
+    SerializerProtocol,
+    get_checkpoint_id,
+    get_checkpoint_metadata,
+)
+
+logger = logging.getLogger(__name__)
+
+
+class InMemorySaver(
+    BaseCheckpointSaver[str], AbstractContextManager, AbstractAsyncContextManager
+):
+    """An in-memory checkpoint saver.
+
+    This checkpoint saver stores checkpoints in memory using a `defaultdict`.
+
+    Note:
+        Only use `InMemorySaver` for debugging or testing purposes.
+        For production use cases we recommend installing [langgraph-checkpoint-postgres](https://pypi.org/project/langgraph-checkpoint-postgres/) and using `PostgresSaver` / `AsyncPostgresSaver`.
+
+        If you are using LangSmith Deployment, no checkpointer needs to be specified. The correct managed checkpointer will be used automatically.
+
+    Args:
+        serde: The serializer to use for serializing and deserializing checkpoints.
+
+    Example:
+        ```python
+        import asyncio
+
+        from langgraph.checkpoint.memory import InMemorySaver
+        from langgraph.graph import StateGraph
+
+        builder = StateGraph(int)
+        builder.add_node("add_one", lambda x: x + 1)
+        builder.set_entry_point("add_one")
+        builder.set_finish_point("add_one")
+
+        memory = InMemorySaver()
+        graph = builder.compile(checkpointer=memory)
+        coro = graph.ainvoke(1, {"configurable": {"thread_id": "thread-1"}})
+        asyncio.run(coro)  # Output: 2
+        ```
+    """
+
+    # thread ID ->  checkpoint NS -> checkpoint ID -> checkpoint mapping
+    storage: defaultdict[
+        str,
+        dict[str, dict[str, tuple[tuple[str, bytes], tuple[str, bytes], str | None]]],
+    ]
+    # (thread ID, checkpoint NS, checkpoint ID) -> (task ID, write idx)
+    writes: defaultdict[
+        tuple[str, str, str],
+        dict[tuple[str, int], tuple[str, str, tuple[str, bytes], str]],
+    ]
+    blobs: dict[
+        tuple[
+            str, str, str, str | int | float
+        ],  # thread id, checkpoint ns, channel, version
+        tuple[str, bytes],
+    ]
+
+    def __init__(
+        self,
+        *,
+        serde: SerializerProtocol | None = None,
+        factory: type[defaultdict] = defaultdict,
+    ) -> None:
+        super().__init__(serde=serde)
+        self.storage = factory(lambda: defaultdict(dict))
+        self.writes = factory(dict)
+        self.blobs = factory()
+        self.stack = ExitStack()
+        if factory is not defaultdict:
+            self.stack.enter_context(self.storage)  # type: ignore[arg-type]
+            self.stack.enter_context(self.writes)  # type: ignore[arg-type]
+            self.stack.enter_context(self.blobs)  # type: ignore[arg-type]
+
+    def __enter__(self) -> InMemorySaver:
+        self.stack.__enter__()
+        return self
+
+    def __exit__(
+        self,
+        exc_type: type[BaseException] | None,
+        exc_value: BaseException | None,
+        traceback: TracebackType | None,
+    ) -> bool | None:
+        return self.stack.__exit__(exc_type, exc_value, traceback)
+
+    async def __aenter__(self) -> InMemorySaver:
+        self.stack.__enter__()
+        return self
+
+    async def __aexit__(
+        self,
+        __exc_type: type[BaseException] | None,
+        __exc_value: BaseException | None,
+        __traceback: TracebackType | None,
+    ) -> bool | None:
+        return self.stack.__exit__(__exc_type, __exc_value, __traceback)
+
+    def _load_blobs(
+        self,
+        thread_id: str,
+        checkpoint_ns: str,
+        versions: ChannelVersions,
+    ) -> dict[str, Any]:
+        result: dict[str, Any] = {}
+        for k, ver in versions.items():
+            kk = (thread_id, checkpoint_ns, k, ver)
+            if kk not in self.blobs:
+                continue
+            vv = self.blobs[kk]
+            if vv[0] == "empty":
+                continue
+            result[k] = self.serde.loads_typed(vv)
+        return result
+
+    def get_delta_channel_history(
+        self, *, config: RunnableConfig, channels: Sequence[str]
+    ) -> Mapping[str, DeltaChannelHistory]:
+        """Override: walk the parent chain ONCE for all requested channels.
+
+        Each channel terminates independently at the nearest ancestor
+        whose stored blob is non-empty. Other channels keep walking until
+        they find their own terminator or hit the root.
+
+        Pre-delta plain-value blobs subsume their ancestor's pending
+        writes (the value already includes them); `_DeltaSnapshot` blobs
+        do not (snapshot is the value AT that ancestor, prior to its own
+        pending writes that produce the child).
+        """
+        if not channels:
+            return {}
+        # Imported lazily to avoid a hard checkpoint→serde-types coupling at
+        # module import; only this override needs the runtime check.
+        from langgraph.checkpoint.serde.types import _DeltaSnapshot
+
+        thread_id = config["configurable"]["thread_id"]
+        checkpoint_ns = config["configurable"].get("checkpoint_ns", "")
+        checkpoint_id = config["configurable"].get("checkpoint_id", "")
+        ns_storage = self.storage.get(thread_id, {}).get(checkpoint_ns, {})
+
+        chain: list[str] = []
+        target_entry = ns_storage.get(checkpoint_id)
+        current: str | None = target_entry[2] if target_entry is not None else None
+        while current is not None:
+            entry = ns_storage.get(current)
+            if entry is None:
+                break
+            chain.append(current)
+            _, _, parent = entry
+            current = parent
+
+        collected_by_ch: dict[str, list[PendingWrite]] = {c: [] for c in channels}
+        seed_by_ch: dict[str, Any] = {}
+        remaining: set[str] = set(channels)
+
+        for cp_id in chain:
+            if not remaining:
+                break
+            entry = ns_storage.get(cp_id)
+            ckpt = self.serde.loads_typed(entry[0]) if entry is not None else None
+
+            terminated_here: set[str] = set()
+            blob_value_by_ch: dict[str, Any] = {}
+            if ckpt is not None:
+                versions = ckpt.get("channel_versions", {})
+                for ch in remaining:
+                    ver = versions.get(ch)
+                    if ver is None:
+                        continue
+                    blob_entry = self.blobs.get((thread_id, checkpoint_ns, ch, ver))
+                    if blob_entry is None or blob_entry[0] == "empty":
+                        continue
+                    blob_value_by_ch[ch] = self.serde.loads_typed(blob_entry)
+                    terminated_here.add(ch)
+
+            step_writes = self.writes.get((thread_id, checkpoint_ns, cp_id), {})
+            for (_task_id, _idx), (tid, ch, serialized, _) in sorted(
+                step_writes.items(), reverse=True
+            ):
+                if ch not in remaining:
+                    continue
+                blob_value = blob_value_by_ch.get(ch)
+                if blob_value is not None and not isinstance(
+                    blob_value, _DeltaSnapshot
+                ):
+                    continue
+                collected_by_ch[ch].append(
+                    (tid, ch, self.serde.loads_typed(serialized))
+                )
+
+            for ch in terminated_here:
+                seed_by_ch[ch] = blob_value_by_ch[ch]
+                remaining.discard(ch)
+
+        result: dict[str, DeltaChannelHistory] = {}
+        for ch in channels:
+            entry_h: DeltaChannelHistory = {
+                "writes": list(reversed(collected_by_ch[ch]))
+            }
+            if ch in seed_by_ch:
+                entry_h["seed"] = seed_by_ch[ch]
+            result[ch] = entry_h
+        return result
+
+    async def aget_delta_channel_history(
+        self, *, config: RunnableConfig, channels: Sequence[str]
+    ) -> Mapping[str, DeltaChannelHistory]:
+        return self.get_delta_channel_history(config=config, channels=channels)
+
+    def get_tuple(self, config: RunnableConfig) -> CheckpointTuple | None:
+        """Get a checkpoint tuple from the in-memory storage.
+
+        This method retrieves a checkpoint tuple from the in-memory storage based on the
+        provided config. If the config contains a `checkpoint_id` key, the checkpoint with
+        the matching thread ID and timestamp is retrieved. Otherwise, the latest checkpoint
+        for the given thread ID is retrieved.
+
+        Args:
+            config: The config to use for retrieving the checkpoint.
+
+        Returns:
+            The retrieved checkpoint tuple, or None if no matching checkpoint was found.
+        """
+        thread_id: str = config["configurable"]["thread_id"]
+        checkpoint_ns: str = config["configurable"].get("checkpoint_ns", "")
+        if checkpoint_id := get_checkpoint_id(config):
+            if saved := self.storage[thread_id][checkpoint_ns].get(checkpoint_id):
+                checkpoint, metadata, parent_checkpoint_id = saved
+                writes = self.writes[(thread_id, checkpoint_ns, checkpoint_id)].values()
+                checkpoint_: Checkpoint = self.serde.loads_typed(checkpoint)
+                return CheckpointTuple(
+                    config=config,
+                    checkpoint={
+                        **checkpoint_,
+                        "channel_values": self._load_blobs(
+                            thread_id, checkpoint_ns, checkpoint_["channel_versions"]
+                        ),
+                    },
+                    metadata=self.serde.loads_typed(metadata),
+                    pending_writes=[
+                        (id, c, self.serde.loads_typed(v)) for id, c, v, _ in writes
+                    ],
+                    parent_config=(
+                        {
+                            "configurable": {
+                                "thread_id": thread_id,
+                                "checkpoint_ns": checkpoint_ns,
+                                "checkpoint_id": parent_checkpoint_id,
+                            }
+                        }
+                        if parent_checkpoint_id
+                        else None
+                    ),
+                )
+        else:
+            if checkpoints := self.storage[thread_id][checkpoint_ns]:
+                checkpoint_id = max(checkpoints.keys())
+                checkpoint, metadata, parent_checkpoint_id = checkpoints[checkpoint_id]
+                writes = self.writes[(thread_id, checkpoint_ns, checkpoint_id)].values()
+                checkpoint_ = self.serde.loads_typed(checkpoint)
+                return CheckpointTuple(
+                    config={
+                        "configurable": {
+                            "thread_id": thread_id,
+                            "checkpoint_ns": checkpoint_ns,
+                            "checkpoint_id": checkpoint_id,
+                        }
+                    },
+                    checkpoint={
+                        **checkpoint_,
+                        "channel_values": self._load_blobs(
+                            thread_id, checkpoint_ns, checkpoint_["channel_versions"]
+                        ),
+                    },
+                    metadata=self.serde.loads_typed(metadata),
+                    pending_writes=[
+                        (id, c, self.serde.loads_typed(v)) for id, c, v, _ in writes
+                    ],
+                    parent_config=(
+                        {
+                            "configurable": {
+                                "thread_id": thread_id,
+                                "checkpoint_ns": checkpoint_ns,
+                                "checkpoint_id": parent_checkpoint_id,
+                            }
+                        }
+                        if parent_checkpoint_id
+                        else None
+                    ),
+                )
+
+    def list(
+        self,
+        config: RunnableConfig | None,
+        *,
+        filter: dict[str, Any] | None = None,
+        before: RunnableConfig | None = None,
+        limit: int | None = None,
+    ) -> Iterator[CheckpointTuple]:
+        """List checkpoints from the in-memory storage.
+
+        This method retrieves a list of checkpoint tuples from the in-memory storage based
+        on the provided criteria.
+
+        Args:
+            config: Base configuration for filtering checkpoints.
+            filter: Additional filtering criteria for metadata.
+            before: List checkpoints created before this configuration.
+            limit: Maximum number of checkpoints to return.
+
+        Yields:
+            An iterator of matching checkpoint tuples.
+        """
+        thread_ids = (config["configurable"]["thread_id"],) if config else self.storage
+        config_checkpoint_ns = (
+            config["configurable"].get("checkpoint_ns") if config else None
+        )
+        config_checkpoint_id = get_checkpoint_id(config) if config else None
+        for thread_id in thread_ids:
+            for checkpoint_ns in self.storage[thread_id].keys():
+                if (
+                    config_checkpoint_ns is not None
+                    and checkpoint_ns != config_checkpoint_ns
+                ):
+                    continue
+
+                for checkpoint_id, (
+                    checkpoint,
+                    metadata_b,
+                    parent_checkpoint_id,
+                ) in sorted(
+                    self.storage[thread_id][checkpoint_ns].items(),
+                    key=lambda x: x[0],
+                    reverse=True,
+                ):
+                    # filter by checkpoint ID from config
+                    if config_checkpoint_id and checkpoint_id != config_checkpoint_id:
+                        continue
+
+                    # filter by checkpoint ID from `before` config
+                    if (
+                        before
+                        and (before_checkpoint_id := get_checkpoint_id(before))
+                        and checkpoint_id >= before_checkpoint_id
+                    ):
+                        continue
+
+                    # filter by metadata
+                    metadata = self.serde.loads_typed(metadata_b)
+                    if filter and not all(
+                        query_value == metadata.get(query_key)
+                        for query_key, query_value in filter.items()
+                    ):
+                        continue
+
+                    # limit search results
+                    if limit is not None and limit <= 0:
+                        break
+                    elif limit is not None:
+                        limit -= 1
+
+                    writes = self.writes[
+                        (thread_id, checkpoint_ns, checkpoint_id)
+                    ].values()
+
+                    checkpoint_: Checkpoint = self.serde.loads_typed(checkpoint)
+
+                    yield CheckpointTuple(
+                        config={
+                            "configurable": {
+                                "thread_id": thread_id,
+                                "checkpoint_ns": checkpoint_ns,
+                                "checkpoint_id": checkpoint_id,
+                            }
+                        },
+                        checkpoint={
+                            **checkpoint_,
+                            "channel_values": self._load_blobs(
+                                thread_id,
+                                checkpoint_ns,
+                                checkpoint_["channel_versions"],
+                            ),
+                        },
+                        metadata=metadata,
+                        parent_config=(
+                            {
+                                "configurable": {
+                                    "thread_id": thread_id,
+                                    "checkpoint_ns": checkpoint_ns,
+                                    "checkpoint_id": parent_checkpoint_id,
+                                }
+                            }
+                            if parent_checkpoint_id
+                            else None
+                        ),
+                        pending_writes=[
+                            (id, c, self.serde.loads_typed(v)) for id, c, v, _ in writes
+                        ],
+                    )
+
+    def put(
+        self,
+        config: RunnableConfig,
+        checkpoint: Checkpoint,
+        metadata: CheckpointMetadata,
+        new_versions: ChannelVersions,
+    ) -> RunnableConfig:
+        """Save a checkpoint to the in-memory storage.
+
+        This method saves a checkpoint to the in-memory storage. The checkpoint is associated
+        with the provided config.
+
+        Args:
+            config: The config to associate with the checkpoint.
+            checkpoint: The checkpoint to save.
+            metadata: Additional metadata to save with the checkpoint.
+            new_versions: New versions as of this write
+
+        Returns:
+            RunnableConfig: The updated config containing the saved checkpoint's timestamp.
+        """
+        c = checkpoint.copy()
+        thread_id = config["configurable"]["thread_id"]
+        checkpoint_ns = config["configurable"]["checkpoint_ns"]
+        values: dict[str, Any] = c.pop("channel_values")  # type: ignore[misc]
+        for k, v in new_versions.items():
+            self.blobs[(thread_id, checkpoint_ns, k, v)] = (
+                self.serde.dumps_typed(values[k]) if k in values else ("empty", b"")
+            )
+        self.storage[thread_id][checkpoint_ns].update(
+            {
+                checkpoint["id"]: (
+                    self.serde.dumps_typed(c),
+                    self.serde.dumps_typed(get_checkpoint_metadata(config, metadata)),
+                    config["configurable"].get("checkpoint_id"),  # parent
+                )
+            }
+        )
+        return {
+            "configurable": {
+                "thread_id": thread_id,
+                "checkpoint_ns": checkpoint_ns,
+                "checkpoint_id": checkpoint["id"],
+            }
+        }
+
+    def put_writes(
+        self,
+        config: RunnableConfig,
+        writes: Sequence[tuple[str, Any]],
+        task_id: str,
+        task_path: str = "",
+    ) -> None:
+        """Save a list of writes to the in-memory storage.
+
+        This method saves a list of writes to the in-memory storage. The writes are associated
+        with the provided config.
+
+        Args:
+            config: The config to associate with the writes.
+            writes: The writes to save.
+            task_id: Identifier for the task creating the writes.
+            task_path: Path of the task creating the writes.
+
+        Returns:
+            RunnableConfig: The updated config containing the saved writes' timestamp.
+        """
+        thread_id = config["configurable"]["thread_id"]
+        checkpoint_ns = config["configurable"].get("checkpoint_ns", "")
+        checkpoint_id = config["configurable"]["checkpoint_id"]
+        outer_key = (thread_id, checkpoint_ns, checkpoint_id)
+        outer_writes_ = self.writes.get(outer_key)
+        for idx, (c, v) in enumerate(writes):
+            inner_key = (task_id, WRITES_IDX_MAP.get(c, idx))
+            if inner_key[1] >= 0 and outer_writes_ and inner_key in outer_writes_:
+                continue
+
+            self.writes[outer_key][inner_key] = (
+                task_id,
+                c,
+                self.serde.dumps_typed(v),
+                task_path,
+            )
+
+    def delete_thread(self, thread_id: str) -> None:
+        """Delete all checkpoints and writes associated with a thread ID.
+
+        Args:
+            thread_id: The thread ID to delete.
+
+        Returns:
+            None
+        """
+        if thread_id in self.storage:
+            del self.storage[thread_id]
+        for k in list(self.writes.keys()):
+            if k[0] == thread_id:
+                del self.writes[k]
+        for k in list(self.blobs.keys()):
+            if k[0] == thread_id:
+                del self.blobs[k]
+
+    async def aget_tuple(self, config: RunnableConfig) -> CheckpointTuple | None:
+        """Asynchronous version of `get_tuple`.
+
+        This method is an asynchronous wrapper around `get_tuple` that runs the synchronous
+        method in a separate thread using asyncio.
+
+        Args:
+            config: The config to use for retrieving the checkpoint.
+
+        Returns:
+            The retrieved checkpoint tuple, or None if no matching checkpoint was found.
+        """
+        return self.get_tuple(config)
+
+    async def alist(
+        self,
+        config: RunnableConfig | None,
+        *,
+        filter: dict[str, Any] | None = None,
+        before: RunnableConfig | None = None,
+        limit: int | None = None,
+    ) -> AsyncIterator[CheckpointTuple]:
+        """Asynchronous version of `list`.
+
+        This method is an asynchronous wrapper around `list` that runs the synchronous
+        method in a separate thread using asyncio.
+
+        Args:
+            config: The config to use for listing the checkpoints.
+
+        Yields:
+            An asynchronous iterator of checkpoint tuples.
+        """
+        for item in self.list(config, filter=filter, before=before, limit=limit):
+            yield item
+
+    async def aput(
+        self,
+        config: RunnableConfig,
+        checkpoint: Checkpoint,
+        metadata: CheckpointMetadata,
+        new_versions: ChannelVersions,
+    ) -> RunnableConfig:
+        """Asynchronous version of `put`.
+
+        Args:
+            config: The config to associate with the checkpoint.
+            checkpoint: The checkpoint to save.
+            metadata: Additional metadata to save with the checkpoint.
+            new_versions: New versions as of this write
+
+        Returns:
+            RunnableConfig: The updated config containing the saved checkpoint's timestamp.
+        """
+        return self.put(config, checkpoint, metadata, new_versions)
+
+    async def aput_writes(
+        self,
+        config: RunnableConfig,
+        writes: Sequence[tuple[str, Any]],
+        task_id: str,
+        task_path: str = "",
+    ) -> None:
+        """Asynchronous version of `put_writes`.
+
+        This method is an asynchronous wrapper around `put_writes` that runs the synchronous
+        method in a separate thread using asyncio.
+
+        Args:
+            config: The config to associate with the writes.
+            writes: The writes to save, each as a (channel, value) pair.
+            task_id: Identifier for the task creating the writes.
+            task_path: Path of the task creating the writes.
+
+        Returns:
+            None
+        """
+        return self.put_writes(config, writes, task_id, task_path)
+
+    async def adelete_thread(self, thread_id: str) -> None:
+        """Delete all checkpoints and writes associated with a thread ID.
+
+        Args:
+            thread_id: The thread ID to delete.
+
+        Returns:
+            None
+        """
+        return self.delete_thread(thread_id)
+
+    def get_next_version(self, current: str | None, channel: None) -> str:
+        if current is None:
+            current_v = 0
+        elif isinstance(current, int):
+            current_v = current
+        else:
+            current_v = int(current.split(".")[0])
+        next_v = current_v + 1
+        next_h = random.random()
+        return f"{next_v:032}.{next_h:016}"
+
+
+MemorySaver = InMemorySaver  # Kept for backwards compatibility
+
+
+class PersistentDict(defaultdict):
+    """Persistent dictionary with an API compatible with shelve and anydbm.
+
+    The dict is kept in memory, so the dictionary operations run as fast as
+    a regular dictionary.
+
+    Write to disk is delayed until close or sync (similar to gdbm's fast mode).
+
+    Input file format is automatically discovered.
+    Output file format is selectable between pickle, json, and csv.
+    All three serialization formats are backed by fast C implementations.
+
+    Adapted from https://code.activestate.com/recipes/576642-persistent-dict-with-multiple-standard-file-format/
+
+    """
+
+    def __init__(self, *args: Any, filename: str, **kwds: Any) -> None:
+        self.flag = "c"  # r=readonly, c=create, or n=new
+        self.mode = None  # None or an octal triple like 0644
+        self.format = "pickle"  # 'csv', 'json', or 'pickle'
+        self.filename = filename
+        super().__init__(*args, **kwds)
+
+    def sync(self) -> None:
+        "Write dict to disk"
+        if self.flag == "r":
+            return
+        tempname = self.filename + ".tmp"
+        fileobj = open(tempname, "wb" if self.format == "pickle" else "w")
+        try:
+            self.dump(fileobj)
+        except Exception:
+            os.remove(tempname)
+            raise
+        finally:
+            fileobj.close()
+        shutil.move(tempname, self.filename)  # atomic commit
+        if self.mode is not None:
+            os.chmod(self.filename, self.mode)
+
+    def close(self) -> None:
+        self.sync()
+        self.clear()
+
+    def __enter__(self) -> PersistentDict:
+        return self
+
+    def __exit__(self, *exc_info: Any) -> None:
+        self.close()
+
+    def dump(self, fileobj: Any) -> None:
+        if self.format == "pickle":
+            pickle.dump(dict(self), fileobj, 2)
+        else:
+            raise NotImplementedError("Unknown format: " + repr(self.format))
+
+    def load(self) -> None:
+        # try formats from most restrictive to least restrictive
+        if self.flag == "n":
+            return
+        with open(self.filename, "rb" if self.format == "pickle" else "r") as fileobj:
+            for loader in (pickle.load,):
+                fileobj.seek(0)
+                try:
+                    return self.update(loader(fileobj))
+                except EOFError:
+                    return
+                except Exception:
+                    logger.error(f"Failed to load file: {fileobj.name}")
+                    raise
+            raise ValueError("File not in a supported format")

.venv/Lib/site-packages/langgraph/checkpoint/serde/_msgpack.py

@@ -0,0 +1,97 @@
+"""Msgpack deserialization safety controls.
+
+Set ``LANGGRAPH_STRICT_MSGPACK=true`` to restrict checkpoint deserialization
+to the types listed in ``SAFE_MSGPACK_TYPES``.  Without this, any Python
+callable stored in checkpoint data will be imported and executed on load.
+"""
+
+import os
+from collections.abc import Iterable
+from typing import cast
+
+STRICT_MSGPACK_ENABLED = os.getenv("LANGGRAPH_STRICT_MSGPACK", "false").lower() in (
+    "1",
+    "true",
+    "yes",
+)
+
+
+_SENTINEL = cast(None, object())
+
+SAFE_MSGPACK_TYPES: frozenset[tuple[str, ...]] = frozenset(
+    {
+        # datetime types
+        ("datetime", "datetime"),
+        ("datetime", "date"),
+        ("datetime", "time"),
+        ("datetime", "timedelta"),
+        ("datetime", "timezone"),
+        # uuid
+        ("uuid", "UUID"),
+        # numeric
+        ("decimal", "Decimal"),
+        # collections
+        ("builtins", "set"),
+        ("builtins", "frozenset"),
+        ("collections", "deque"),
+        # ip addresses
+        ("ipaddress", "IPv4Address"),
+        ("ipaddress", "IPv4Interface"),
+        ("ipaddress", "IPv4Network"),
+        ("ipaddress", "IPv6Address"),
+        ("ipaddress", "IPv6Interface"),
+        ("ipaddress", "IPv6Network"),
+        # pathlib
+        ("pathlib", "Path"),
+        ("pathlib", "PosixPath"),
+        ("pathlib", "WindowsPath"),
+        # pathlib in Python 3.13+
+        ("pathlib._local", "Path"),
+        ("pathlib._local", "PosixPath"),
+        ("pathlib._local", "WindowsPath"),
+        # zoneinfo
+        ("zoneinfo", "ZoneInfo"),
+        # regex
+        ("re", "compile"),
+        # langchain-core messages (safe container types used by graph state)
+        ("langchain_core.messages.base", "BaseMessage"),
+        ("langchain_core.messages.base", "BaseMessageChunk"),
+        ("langchain_core.messages.human", "HumanMessage"),
+        ("langchain_core.messages.human", "HumanMessageChunk"),
+        ("langchain_core.messages.ai", "AIMessage"),
+        ("langchain_core.messages.ai", "AIMessageChunk"),
+        ("langchain_core.messages.system", "SystemMessage"),
+        ("langchain_core.messages.system", "SystemMessageChunk"),
+        ("langchain_core.messages.chat", "ChatMessage"),
+        ("langchain_core.messages.chat", "ChatMessageChunk"),
+        ("langchain_core.messages.tool", "ToolMessage"),
+        ("langchain_core.messages.tool", "ToolMessageChunk"),
+        ("langchain_core.messages.function", "FunctionMessage"),
+        ("langchain_core.messages.function", "FunctionMessageChunk"),
+        ("langchain_core.messages.modifier", "RemoveMessage"),
+        # langchain-core document model
+        ("langchain_core.documents.base", "Document"),
+        # langgraph
+        ("langgraph.types", "Send"),
+        ("langgraph.types", "TimeoutPolicy"),
+        ("langgraph.types", "Interrupt"),
+        ("langgraph.types", "Command"),
+        ("langgraph.types", "StateSnapshot"),
+        ("langgraph.types", "PregelTask"),
+        ("langgraph.types", "Overwrite"),
+        ("langgraph.store.base", "Item"),
+        ("langgraph.store.base", "GetOp"),
+    }
+)
+
+# Allowed (module, name, method) triples for EXT_METHOD_SINGLE_ARG.
+# Only these specific method invocations are permitted during deserialization.
+# This is separate from SAFE_MSGPACK_TYPES which only governs construction.
+SAFE_MSGPACK_METHODS: frozenset[tuple[str, str, str]] = frozenset(
+    {
+        ("datetime", "datetime", "fromisoformat"),
+    }
+)
+
+
+AllowedMsgpackModules = Iterable[tuple[str, ...] | type]

.venv/Lib/site-packages/langgraph/checkpoint/serde/base.py

@@ -0,0 +1,64 @@
+from __future__ import annotations
+
+from typing import Any, Protocol, runtime_checkable
+
+
+class UntypedSerializerProtocol(Protocol):
+    """Protocol for serialization and deserialization of objects."""
+
+    def dumps(self, obj: Any) -> bytes: ...
+
+    def loads(self, data: bytes) -> Any: ...
+
+
+@runtime_checkable
+class SerializerProtocol(Protocol):
+    """Protocol for serialization and deserialization of objects.
+
+    - `dumps_typed`: Serialize an object to a tuple `(type, bytes)`.
+    - `loads_typed`: Deserialize an object from a tuple `(type, bytes)`.
+
+    Valid implementations include the `pickle`, `json` and `orjson` modules.
+    """
+
+    def dumps_typed(self, obj: Any) -> tuple[str, bytes]: ...
+
+    def loads_typed(self, data: tuple[str, bytes]) -> Any: ...
+
+
+class SerializerCompat(SerializerProtocol):
+    def __init__(self, serde: UntypedSerializerProtocol) -> None:
+        self.serde = serde
+
+    def dumps_typed(self, obj: Any) -> tuple[str, bytes]:
+        return type(obj).__name__, self.serde.dumps(obj)
+
+    def loads_typed(self, data: tuple[str, bytes]) -> Any:
+        return self.serde.loads(data[1])
+
+
+def maybe_add_typed_methods(
+    serde: SerializerProtocol | UntypedSerializerProtocol,
+) -> SerializerProtocol:
+    """Wrap serde old serde implementations in a class with loads_typed and dumps_typed for backwards compatibility."""
+
+    if not isinstance(serde, SerializerProtocol):
+        return SerializerCompat(serde)
+
+    return serde
+
+
+class CipherProtocol(Protocol):
+    """Protocol for encryption and decryption of data.
+
+    - `encrypt`: Encrypt plaintext.
+    - `decrypt`: Decrypt ciphertext.
+    """
+
+    def encrypt(self, plaintext: bytes) -> tuple[str, bytes]:
+        """Encrypt plaintext. Returns a tuple `(cipher name, ciphertext)`."""
+        ...
+
+    def decrypt(self, ciphername: str, ciphertext: bytes) -> bytes:
+        """Decrypt ciphertext. Returns the plaintext."""
+        ...

.venv/Lib/site-packages/langgraph/checkpoint/serde/encrypted.py

@@ -0,0 +1,80 @@
+import os
+from typing import Any
+
+from langgraph.checkpoint.serde.base import CipherProtocol, SerializerProtocol
+from langgraph.checkpoint.serde.jsonplus import JsonPlusSerializer
+
+
+class EncryptedSerializer(SerializerProtocol):
+    """Serializer that encrypts and decrypts data using an encryption protocol."""
+
+    def __init__(
+        self, cipher: CipherProtocol, serde: SerializerProtocol = JsonPlusSerializer()
+    ) -> None:
+        self.cipher = cipher
+        self.serde = serde
+
+    def dumps_typed(self, obj: Any) -> tuple[str, bytes]:
+        """Serialize an object to a tuple `(type, bytes)` and encrypt the bytes."""
+        # serialize data
+        typ, data = self.serde.dumps_typed(obj)
+        # encrypt data
+        ciphername, ciphertext = self.cipher.encrypt(data)
+        # add cipher name to type
+        return f"{typ}+{ciphername}", ciphertext
+
+    def loads_typed(self, data: tuple[str, bytes]) -> Any:
+        enc_cipher, ciphertext = data
+        # unencrypted data
+        if "+" not in enc_cipher:
+            return self.serde.loads_typed(data)
+        # extract cipher name
+        typ, ciphername = enc_cipher.split("+", 1)
+        # decrypt data
+        decrypted_data = self.cipher.decrypt(ciphername, ciphertext)
+        # deserialize data
+        return self.serde.loads_typed((typ, decrypted_data))
+
+    @classmethod
+    def from_pycryptodome_aes(
+        cls, serde: SerializerProtocol = JsonPlusSerializer(), **kwargs: Any
+    ) -> "EncryptedSerializer":
+        """Create an `EncryptedSerializer` using AES encryption."""
+        try:
+            from Crypto.Cipher import AES
+        except ImportError:
+            raise ImportError(
+                "Pycryptodome is not installed. Please install it with `pip install pycryptodome`."
+            ) from None
+
+        # check if AES key is provided
+        if "key" in kwargs:
+            key: bytes = kwargs.pop("key")
+        else:
+            key_str = os.getenv("LANGGRAPH_AES_KEY")
+            if key_str is None:
+                raise ValueError("LANGGRAPH_AES_KEY environment variable is not set.")
+            key = key_str.encode()
+            if len(key) not in (16, 24, 32):
+                raise ValueError("LANGGRAPH_AES_KEY must be 16, 24, or 32 bytes long.")
+
+        # set default mode to EAX if not provided
+        if kwargs.get("mode") is None:
+            kwargs["mode"] = AES.MODE_EAX
+
+        class PycryptodomeAesCipher(CipherProtocol):
+            def encrypt(self, plaintext: bytes) -> tuple[str, bytes]:
+                cipher = AES.new(key, **kwargs)
+                ciphertext, tag = cipher.encrypt_and_digest(plaintext)
+                return "aes", cipher.nonce + tag + ciphertext
+
+            def decrypt(self, ciphername: str, ciphertext: bytes) -> bytes:
+                assert ciphername == "aes", f"Unsupported cipher: {ciphername}"
+                nonce = ciphertext[:16]
+                tag = ciphertext[16:32]
+                actual_ciphertext = ciphertext[32:]
+
+                cipher = AES.new(key, **kwargs, nonce=nonce)
+                return cipher.decrypt_and_verify(actual_ciphertext, tag)
+
+        return cls(PycryptodomeAesCipher(), serde)

.venv/Lib/site-packages/langgraph/checkpoint/serde/event_hooks.py

@@ -0,0 +1,52 @@
+from __future__ import annotations
+
+import logging
+from collections.abc import Callable
+from threading import Lock
+from typing import TypedDict
+
+from typing_extensions import NotRequired
+
+logger = logging.getLogger(__name__)
+
+
+class SerdeEvent(TypedDict):
+    kind: str
+    module: str
+    name: str
+    method: NotRequired[str]
+
+
+SerdeEventListener = Callable[[SerdeEvent], None]
+
+_listeners: list[SerdeEventListener] = []
+_listeners_lock = Lock()
+
+
+def register_serde_event_listener(listener: SerdeEventListener) -> Callable[[], None]:
+    """Register a listener for serde allowlist events."""
+    with _listeners_lock:
+        _listeners.append(listener)
+
+    def unregister() -> None:
+        with _listeners_lock:
+            try:
+                _listeners.remove(listener)
+            except ValueError:
+                pass
+
+    return unregister
+
+
+def emit_serde_event(event: SerdeEvent) -> None:
+    """Emit a serde event to all listeners.
+
+    Listener failures are isolated and logged.
+    """
+    with _listeners_lock:
+        listeners = tuple(_listeners)
+    for listener in listeners:
+        try:
+            listener(event)
+        except Exception:
+            logger.warning("Serde listener failed", exc_info=True)

.venv/Lib/site-packages/langgraph/checkpoint/serde/jsonplus.py

@@ -0,0 +1,903 @@
+from __future__ import annotations
+
+import copy
+import dataclasses
+import decimal
+import importlib
+import json
+import logging
+import pathlib
+import pickle
+import re
+import sys
+from collections import deque
+from collections.abc import Callable, Iterable, Sequence
+from datetime import date, datetime, time, timedelta, timezone
+from enum import Enum
+from inspect import isclass
+from ipaddress import (
+    IPv4Address,
+    IPv4Interface,
+    IPv4Network,
+    IPv6Address,
+    IPv6Interface,
+    IPv6Network,
+)
+from typing import TYPE_CHECKING, Any, Literal, cast
+from uuid import UUID
+from zoneinfo import ZoneInfo
+
+import ormsgpack
+from langchain_core.load.load import Reviver
+
+from langgraph.checkpoint.serde import _msgpack as _lg_msgpack
+from langgraph.checkpoint.serde.base import SerializerProtocol
+from langgraph.checkpoint.serde.event_hooks import emit_serde_event
+from langgraph.checkpoint.serde.types import (
+    SendProtocol,
+    _DeltaSnapshot,
+)
+from langgraph.store.base import Item
+
+if TYPE_CHECKING:
+    from langgraph.checkpoint.serde._msgpack import (
+        AllowedMsgpackModules,
+    )
+
+LC_REVIVER = Reviver(allowed_objects="core")
+EMPTY_BYTES = b""
+logger = logging.getLogger(__name__)
+
+# Dedup log warnings across process lifetime; cap bounds state if types are
+# dynamically generated (also acts as a circuit breaker on warning volume).
+# Dedup is best-effort: racing threads may each emit once for the same key,
+# and warnings are silently dropped once _MAX_WARNED_TYPES is reached.
+_MAX_WARNED_TYPES = 1000
+_warned_unregistered_types: set[tuple[str, str]] = set()
+_warned_blocked_types: set[tuple[str, str]] = set()
+
+
+def _is_safe_json_type(id_list: list[str]) -> bool:
+    """Return True if an lc=2 id refers to a type in SAFE_MSGPACK_TYPES.
+
+    Safe types bypass the ``allowed_json_modules`` gate so that old "json" format
+    checkpoints (written before the msgpack migration) can be resumed without
+    requiring users to configure an explicit allowlist.
+    """
+    if len(id_list) < 2:
+        return False
+    module_name = ".".join(id_list[:-1])
+    return (module_name, id_list[-1]) in _lg_msgpack.SAFE_MSGPACK_TYPES
+
+
+def _warn_once(
+    seen: set[tuple[str, str]], key: tuple[str, str], msg: str, *args: object
+) -> None:
+    if key in seen or len(seen) >= _MAX_WARNED_TYPES:
+        return
+    seen.add(key)
+    logger.warning(msg, *args)
+
+
+class JsonPlusSerializer(SerializerProtocol):
+    """Serializer that uses ormsgpack, with optional fallbacks.
+
+    !!! warning
+
+        Security note: This serializer is intended for use within the `BaseCheckpointSaver`
+        class and called within the Pregel loop. It should not be used on untrusted
+        python objects. If an attacker can write directly to your checkpoint database,
+        they may be able to trigger code execution when data is deserialized.
+
+        Set the environment variable ``LANGGRAPH_STRICT_MSGPACK=true`` to restrict
+        deserialization to a built-in allowlist of safe types.  You can also pass
+        an explicit ``allowed_msgpack_modules`` to the constructor.
+    """
+
+    def __init__(
+        self,
+        *,
+        pickle_fallback: bool = False,
+        allowed_json_modules: Iterable[tuple[str, ...]] | Literal[True] | None = None,
+        allowed_msgpack_modules: (
+            AllowedMsgpackModules | Literal[True] | None
+        ) = _lg_msgpack._SENTINEL,
+        __unpack_ext_hook__: Callable[[int, bytes], Any] | None = None,
+    ) -> None:
+        if allowed_msgpack_modules is _lg_msgpack._SENTINEL:
+            if _lg_msgpack.STRICT_MSGPACK_ENABLED:
+                # Strict: only SAFE_MSGPACK_TYPES are allowed.
+                allowed_msgpack_modules = None
+            else:
+                # Permissive (default): all types allowed with a warning.
+                # Set LANGGRAPH_STRICT_MSGPACK=true to lock this down.
+                allowed_msgpack_modules = True
+        self.pickle_fallback = pickle_fallback
+        self._allowed_json_modules: set[tuple[str, ...]] | Literal[True] | None = (
+            _normalize_allowlist(allowed_json_modules)
+        )
+        self._allowed_msgpack_modules = _normalize_allowlist(allowed_msgpack_modules)
+
+        self._custom_unpack_ext_hook = __unpack_ext_hook__ is not None
+        self._unpack_ext_hook = (
+            __unpack_ext_hook__
+            if __unpack_ext_hook__ is not None
+            else _create_msgpack_ext_hook(self._allowed_msgpack_modules)
+        )
+
+    def with_msgpack_allowlist(
+        self, extra_allowlist: Iterable[tuple[str, ...] | type]
+    ) -> JsonPlusSerializer:
+        """Return a new serializer with a merged msgpack allowlist."""
+        base_allowlist = self._allowed_msgpack_modules
+        if base_allowlist is True or base_allowlist is False:
+            return self
+        elif base_allowlist:
+            base_allowlist = set(base_allowlist)
+        else:
+            base_allowlist = set()
+        extra = _normalize_module_keys(tuple(extra_allowlist))
+        merged = base_allowlist | extra
+        if merged == base_allowlist:
+            return self
+        allowed_msgpack_modules: AllowedMsgpackModules | Literal[True] | None
+        if merged:
+            allowed_msgpack_modules = tuple(merged)
+        elif isinstance(self._allowed_msgpack_modules, set):
+            allowed_msgpack_modules = tuple(self._allowed_msgpack_modules)
+        else:
+            allowed_msgpack_modules = self._allowed_msgpack_modules
+
+        clone = copy.copy(self)
+        clone._allowed_json_modules = _normalize_allowlist(self._allowed_json_modules)
+        clone._allowed_msgpack_modules = _normalize_allowlist(allowed_msgpack_modules)
+        if not clone._custom_unpack_ext_hook:
+            clone._unpack_ext_hook = _create_msgpack_ext_hook(
+                clone._allowed_msgpack_modules
+            )
+        return clone
+
+    def _encode_constructor_args(
+        self,
+        constructor: Callable | type[Any],
+        *,
+        method: None | str | Sequence[None | str] = None,
+        args: Sequence[Any] | None = None,
+        kwargs: dict[str, Any] | None = None,
+    ) -> dict[str, Any]:
+        out = {
+            "lc": 2,
+            "type": "constructor",
+            "id": (*constructor.__module__.split("."), constructor.__name__),
+        }
+        if method is not None:
+            out["method"] = method
+        if args is not None:
+            out["args"] = args
+        if kwargs is not None:
+            out["kwargs"] = kwargs
+        return out
+
+    def _reviver(self, value: dict[str, Any]) -> Any:
+        if (
+            value.get("lc", None) == 2
+            and value.get("type", None) == "constructor"
+            and value.get("id", None) is not None
+        ):
+            id_list = value["id"]
+            is_safe = _is_safe_json_type(id_list)
+            if self._allowed_json_modules or is_safe:
+                try:
+                    return self._revive_lc2(value)
+                except InvalidModuleError as e:
+                    if not is_safe:
+                        logger.warning(
+                            "Object %s is not in the deserialization allowlist.\n%s",
+                            value["id"],
+                            e.message,
+                        )
+
+        return LC_REVIVER(value)
+
+    def _revive_lc2(self, value: dict[str, Any]) -> Any:
+        self._check_allowed_json_modules(value)
+
+        [*module, name] = value["id"]
+        try:
+            mod = importlib.import_module(".".join(module))
+            cls = getattr(mod, name)
+            method = value.get("method")
+            if isinstance(method, str):
+                methods = [getattr(cls, method)]
+            elif isinstance(method, list):
+                methods = [cls if m is None else getattr(cls, m) for m in method]
+            else:
+                methods = [cls]
+            args = value.get("args")
+            kwargs = value.get("kwargs")
+            for method in methods:
+                try:
+                    if isclass(method) and issubclass(method, BaseException):
+                        return None
+                    if args and kwargs:
+                        return method(*args, **kwargs)
+                    elif args:
+                        return method(*args)
+                    elif kwargs:
+                        return method(**kwargs)
+                    else:
+                        return method()
+                except Exception:
+                    continue
+        except Exception:
+            return None
+
+    def _check_allowed_json_modules(self, value: dict[str, Any]) -> None:
+        needed = tuple(value["id"])
+        method = value.get("method")
+        if isinstance(method, list):
+            method_display = ",".join(m or "<init>" for m in method)
+        elif isinstance(method, str):
+            method_display = method
+        else:
+            method_display = "<init>"
+
+        dotted = ".".join(needed)
+        # Safe types (the same set already allowed for msgpack deserialization) are
+        # permitted without an explicit allowlist — they are known-safe LangGraph and
+        # LangChain types.  This restores backwards-compat for old "json" checkpoints
+        # that pre-date the msgpack migration without reopening the broader security gate.
+        if _is_safe_json_type(list(needed)):
+            return
+
+        if not self._allowed_json_modules:
+            raise InvalidModuleError(
+                f"Refused to deserialize JSON constructor: {dotted} (method: {method_display}). "
+                "No allowed_json_modules configured.\n\n"
+                "Unblock with ONE of:\n"
+                f"  • JsonPlusSerializer(allowed_json_modules=[{needed!r}, ...])\n"
+                "  • (DANGEROUS) JsonPlusSerializer(allowed_json_modules=True)\n\n"
+                "Note: Prefix allowlists are intentionally unsupported; prefer exact symbols "
+                "or plain-JSON representations revived without import-time side effects."
+            )
+
+        if self._allowed_json_modules is True:
+            return
+        if needed in self._allowed_json_modules:
+            return
+
+        raise InvalidModuleError(
+            f"Refused to deserialize JSON constructor: {dotted} (method: {method_display}). "
+            "Symbol is not in the deserialization allowlist.\n\n"
+            "Add exactly this symbol to unblock:\n"
+            f"  JsonPlusSerializer(allowed_json_modules=[{needed!r}, ...])\n"
+            "Or, as a last resort (DANGEROUS):\n"
+            "  JsonPlusSerializer(allowed_json_modules=True)"
+        )
+
+    def dumps_typed(self, obj: Any) -> tuple[str, bytes]:
+        if obj is None:
+            return "null", EMPTY_BYTES
+        elif isinstance(obj, bytes):
+            return "bytes", obj
+        elif isinstance(obj, bytearray):
+            return "bytearray", obj
+        else:
+            try:
+                return "msgpack", _msgpack_enc(obj)
+            except ormsgpack.MsgpackEncodeError as exc:
+                if self.pickle_fallback:
+                    return "pickle", pickle.dumps(obj)
+                raise exc
+
+    def loads_typed(self, data: tuple[str, bytes]) -> Any:
+        type_, data_ = data
+        if type_ == "null":
+            return None
+        elif type_ == "bytes":
+            return data_
+        elif type_ == "bytearray":
+            return bytearray(data_)
+        elif type_ == "json":
+            return json.loads(data_, object_hook=self._reviver)
+        elif type_ == "msgpack":
+            return ormsgpack.unpackb(
+                data_, ext_hook=self._unpack_ext_hook, option=ormsgpack.OPT_NON_STR_KEYS
+            )
+        elif self.pickle_fallback and type_ == "pickle":
+            return pickle.loads(data_)
+        else:
+            raise NotImplementedError(f"Unknown serialization type: {type_}")
+
+
+# --- msgpack ---
+
+EXT_CONSTRUCTOR_SINGLE_ARG = 0
+EXT_CONSTRUCTOR_POS_ARGS = 1
+EXT_CONSTRUCTOR_KW_ARGS = 2
+EXT_METHOD_SINGLE_ARG = 3
+EXT_PYDANTIC_V1 = 4
+EXT_PYDANTIC_V2 = 5
+EXT_NUMPY_ARRAY = 6
+EXT_DELTA_SNAPSHOT = 7
+
+
+def _msgpack_default(obj: Any) -> str | ormsgpack.Ext:
+    if isinstance(obj, _DeltaSnapshot):
+        return ormsgpack.Ext(EXT_DELTA_SNAPSHOT, _msgpack_enc(obj.value))
+    elif hasattr(obj, "model_dump") and callable(obj.model_dump):  # pydantic v2
+        return ormsgpack.Ext(
+            EXT_PYDANTIC_V2,
+            _msgpack_enc(
+                (
+                    obj.__class__.__module__,
+                    obj.__class__.__name__,
+                    obj.model_dump(),
+                    "model_validate_json",
+                ),
+            ),
+        )
+    elif hasattr(obj, "get_secret_value") and callable(obj.get_secret_value):
+        return ormsgpack.Ext(
+            EXT_CONSTRUCTOR_SINGLE_ARG,
+            _msgpack_enc(
+                (
+                    obj.__class__.__module__,
+                    obj.__class__.__name__,
+                    obj.get_secret_value(),
+                ),
+            ),
+        )
+    elif hasattr(obj, "dict") and callable(obj.dict):  # pydantic v1
+        return ormsgpack.Ext(
+            EXT_PYDANTIC_V1,
+            _msgpack_enc(
+                (
+                    obj.__class__.__module__,
+                    obj.__class__.__name__,
+                    obj.dict(),
+                ),
+            ),
+        )
+    elif hasattr(obj, "_asdict") and callable(obj._asdict):  # namedtuple
+        return ormsgpack.Ext(
+            EXT_CONSTRUCTOR_KW_ARGS,
+            _msgpack_enc(
+                (
+                    obj.__class__.__module__,
+                    obj.__class__.__name__,
+                    obj._asdict(),
+                ),
+            ),
+        )
+    elif isinstance(obj, pathlib.Path):
+        return ormsgpack.Ext(
+            EXT_CONSTRUCTOR_POS_ARGS,
+            _msgpack_enc(
+                (obj.__class__.__module__, obj.__class__.__name__, obj.parts),
+            ),
+        )
+    elif isinstance(obj, re.Pattern):
+        return ormsgpack.Ext(
+            EXT_CONSTRUCTOR_POS_ARGS,
+            _msgpack_enc(
+                ("re", "compile", (obj.pattern, obj.flags)),
+            ),
+        )
+    elif isinstance(obj, UUID):
+        return ormsgpack.Ext(
+            EXT_CONSTRUCTOR_SINGLE_ARG,
+            _msgpack_enc(
+                (obj.__class__.__module__, obj.__class__.__name__, obj.hex),
+            ),
+        )
+    elif isinstance(obj, decimal.Decimal):
+        return ormsgpack.Ext(
+            EXT_CONSTRUCTOR_SINGLE_ARG,
+            _msgpack_enc(
+                (obj.__class__.__module__, obj.__class__.__name__, str(obj)),
+            ),
+        )
+    elif isinstance(obj, (set, frozenset, deque)):
+        return ormsgpack.Ext(
+            EXT_CONSTRUCTOR_SINGLE_ARG,
+            _msgpack_enc(
+                (obj.__class__.__module__, obj.__class__.__name__, tuple(obj)),
+            ),
+        )
+    elif isinstance(obj, (IPv4Address, IPv4Interface, IPv4Network)):
+        return ormsgpack.Ext(
+            EXT_CONSTRUCTOR_SINGLE_ARG,
+            _msgpack_enc(
+                (obj.__class__.__module__, obj.__class__.__name__, str(obj)),
+            ),
+        )
+    elif isinstance(obj, (IPv6Address, IPv6Interface, IPv6Network)):
+        return ormsgpack.Ext(
+            EXT_CONSTRUCTOR_SINGLE_ARG,
+            _msgpack_enc(
+                (obj.__class__.__module__, obj.__class__.__name__, str(obj)),
+            ),
+        )
+    elif isinstance(obj, datetime):
+        return ormsgpack.Ext(
+            EXT_METHOD_SINGLE_ARG,
+            _msgpack_enc(
+                (
+                    obj.__class__.__module__,
+                    obj.__class__.__name__,
+                    obj.isoformat(),
+                    "fromisoformat",
+                ),
+            ),
+        )
+    elif isinstance(obj, timedelta):
+        return ormsgpack.Ext(
+            EXT_CONSTRUCTOR_POS_ARGS,
+            _msgpack_enc(
+                (
+                    obj.__class__.__module__,
+                    obj.__class__.__name__,
+                    (obj.days, obj.seconds, obj.microseconds),
+                ),
+            ),
+        )
+    elif isinstance(obj, date):
+        return ormsgpack.Ext(
+            EXT_CONSTRUCTOR_POS_ARGS,
+            _msgpack_enc(
+                (
+                    obj.__class__.__module__,
+                    obj.__class__.__name__,
+                    (obj.year, obj.month, obj.day),
+                ),
+            ),
+        )
+    elif isinstance(obj, time):
+        return ormsgpack.Ext(
+            EXT_CONSTRUCTOR_KW_ARGS,
+            _msgpack_enc(
+                (
+                    obj.__class__.__module__,
+                    obj.__class__.__name__,
+                    {
+                        "hour": obj.hour,
+                        "minute": obj.minute,
+                        "second": obj.second,
+                        "microsecond": obj.microsecond,
+                        "tzinfo": obj.tzinfo,
+                        "fold": obj.fold,
+                    },
+                ),
+            ),
+        )
+    elif isinstance(obj, timezone):
+        return ormsgpack.Ext(
+            EXT_CONSTRUCTOR_POS_ARGS,
+            _msgpack_enc(
+                (
+                    obj.__class__.__module__,
+                    obj.__class__.__name__,
+                    obj.__getinitargs__(),  # type: ignore[attr-defined]
+                ),
+            ),
+        )
+    elif isinstance(obj, ZoneInfo):
+        return ormsgpack.Ext(
+            EXT_CONSTRUCTOR_SINGLE_ARG,
+            _msgpack_enc(
+                (obj.__class__.__module__, obj.__class__.__name__, obj.key),
+            ),
+        )
+    elif isinstance(obj, Enum):
+        return ormsgpack.Ext(
+            EXT_CONSTRUCTOR_SINGLE_ARG,
+            _msgpack_enc(
+                (obj.__class__.__module__, obj.__class__.__name__, obj.value),
+            ),
+        )
+    elif isinstance(obj, SendProtocol):
+        args: tuple[Any, ...] = (obj.node, obj.arg)
+        if (timeout := getattr(obj, "timeout", None)) is not None:
+            args = (obj.node, obj.arg, timeout)
+        return ormsgpack.Ext(
+            EXT_CONSTRUCTOR_POS_ARGS,
+            _msgpack_enc(
+                (obj.__class__.__module__, obj.__class__.__name__, args),
+            ),
+        )
+    elif dataclasses.is_dataclass(obj):
+        # doesn't use dataclasses.asdict to avoid deepcopy and recursion
+        return ormsgpack.Ext(
+            EXT_CONSTRUCTOR_KW_ARGS,
+            _msgpack_enc(
+                (
+                    obj.__class__.__module__,
+                    obj.__class__.__name__,
+                    {
+                        field.name: getattr(obj, field.name)
+                        for field in dataclasses.fields(obj)
+                    },
+                ),
+            ),
+        )
+    elif isinstance(obj, Item):
+        return ormsgpack.Ext(
+            EXT_CONSTRUCTOR_KW_ARGS,
+            _msgpack_enc(
+                (
+                    obj.__class__.__module__,
+                    obj.__class__.__name__,
+                    {k: getattr(obj, k) for k in obj.__slots__},
+                ),
+            ),
+        )
+    elif (np_mod := sys.modules.get("numpy")) is not None and isinstance(
+        obj, np_mod.ndarray
+    ):
+        order = "F" if obj.flags.f_contiguous and not obj.flags.c_contiguous else "C"
+        if obj.flags.c_contiguous:
+            mv = memoryview(obj)
+            try:
+                meta = (obj.dtype.str, obj.shape, order, mv)
+                return ormsgpack.Ext(EXT_NUMPY_ARRAY, _msgpack_enc(meta))
+            finally:
+                mv.release()
+        else:
+            buf = obj.tobytes(order="A")
+            meta = (obj.dtype.str, obj.shape, order, buf)
+            return ormsgpack.Ext(EXT_NUMPY_ARRAY, _msgpack_enc(meta))
+
+    elif isinstance(obj, BaseException):
+        return repr(obj)
+    else:
+        raise TypeError(f"Object of type {obj.__class__.__name__} is not serializable")
+
+
+def _send_from_args(args: Sequence[Any]) -> Any:
+    # ya we have a cyclic import here ¯\_(ツ)_/¯
+    from langgraph.types import Send  # type: ignore
+
+    if len(args) == 2:
+        return Send(*args)
+    return Send(args[0], args[1], timeout=args[2])
+
+
+def _create_msgpack_ext_hook(
+    allowed_modules: set[tuple[str, ...]] | Literal[True] | None,
+) -> Callable[[int, bytes], Any]:
+    """Create msgpack ext hook with allowlist.
+
+    Args:
+        allowed_modules: Set of (module, name) tuples that are allowed to be
+        deserialized, or True to allow all with warnings for unregistered types, or None to only allow safe types.
+
+    Returns:
+        An ext_hook function for use with ormsgpack.unpackb.
+    """
+
+    def _check_allowed(module: str, name: str) -> bool:
+        """Check if type is allowed. Returns True if allowed, False if blocked."""
+        key = (module, name)
+
+        if key in _lg_msgpack.SAFE_MSGPACK_TYPES:
+            return True
+
+        if allowed_modules is True:
+            # default is to warn but allow unregistered types
+            emit_serde_event(
+                {
+                    "kind": "msgpack_unregistered_allowed",
+                    "module": module,
+                    "name": name,
+                }
+            )
+            _warn_once(
+                _warned_unregistered_types,
+                key,
+                "Deserializing unregistered type %s.%s from checkpoint. "
+                "This will be blocked in a future version. "
+                "Set LANGGRAPH_STRICT_MSGPACK=true to block now, or add "
+                "to allowed_msgpack_modules to allow explicitly: [(%r, %r)]",
+                module,
+                name,
+                module,
+                name,
+            )
+            return True
+        if allowed_modules is not None:
+            if key in allowed_modules:
+                return True
+        # strict mode blocks unregistered types
+        emit_serde_event(
+            {
+                "kind": "msgpack_blocked",
+                "module": module,
+                "name": name,
+            }
+        )
+        _warn_once(
+            _warned_blocked_types,
+            key,
+            "Blocked deserialization of %s.%s - not in allowed_msgpack_modules. "
+            "Add to allowed_msgpack_modules to allow: [(%r, %r)]",
+            module,
+            name,
+            module,
+            name,
+        )
+        return False
+
+    def _check_allowed_method(module: str, name: str, method: str) -> bool:
+        """Check if a method invocation is allowed."""
+        key = (module, name, method)
+        if key in _lg_msgpack.SAFE_MSGPACK_METHODS:
+            return True
+        emit_serde_event(
+            {
+                "kind": "msgpack_method_blocked",
+                "module": module,
+                "name": name,
+                "method": method,
+            }
+        )
+        logger.warning(
+            "Blocked deserialization of method call %s.%s.%s - "
+            "not in allowed methods set.",
+            module,
+            name,
+            method,
+        )
+        return False
+
+    def ext_hook(code: int, data: bytes) -> Any:
+        if code == EXT_DELTA_SNAPSHOT:
+            return _DeltaSnapshot(
+                ormsgpack.unpackb(
+                    data, ext_hook=ext_hook, option=ormsgpack.OPT_NON_STR_KEYS
+                )
+            )
+        elif code == EXT_CONSTRUCTOR_SINGLE_ARG:
+            try:
+                tup = ormsgpack.unpackb(
+                    data, ext_hook=ext_hook, option=ormsgpack.OPT_NON_STR_KEYS
+                )
+                if not _check_allowed(tup[0], tup[1]):
+                    # We default to returning the raw data. If the user
+                    # is using this in the context of a pydantic state, etc., then
+                    # it would be validated upon construction.
+                    return tup[2]
+                # module, name, arg
+                return getattr(importlib.import_module(tup[0]), tup[1])(tup[2])
+            except Exception:
+                return None
+        elif code == EXT_CONSTRUCTOR_POS_ARGS:
+            try:
+                tup = ormsgpack.unpackb(
+                    data, ext_hook=ext_hook, option=ormsgpack.OPT_NON_STR_KEYS
+                )
+                if not _check_allowed(tup[0], tup[1]):
+                    return tup[2]
+                if tup[0] == "langgraph.types" and tup[1] == "Send":
+                    return _send_from_args(tup[2])
+                # module, name, args
+                return getattr(importlib.import_module(tup[0]), tup[1])(*tup[2])
+            except Exception:
+                return None
+        elif code == EXT_CONSTRUCTOR_KW_ARGS:
+            try:
+                tup = ormsgpack.unpackb(
+                    data, ext_hook=ext_hook, option=ormsgpack.OPT_NON_STR_KEYS
+                )
+                if not _check_allowed(tup[0], tup[1]):
+                    return tup[2]
+                # module, name, kwargs
+                return getattr(importlib.import_module(tup[0]), tup[1])(**tup[2])
+            except Exception:
+                return None
+        elif code == EXT_METHOD_SINGLE_ARG:
+            try:
+                tup = ormsgpack.unpackb(
+                    data, ext_hook=ext_hook, option=ormsgpack.OPT_NON_STR_KEYS
+                )
+                if not _check_allowed_method(tup[0], tup[1], tup[3]):
+                    return tup[2]
+                # module, name, arg, method
+                return getattr(
+                    getattr(importlib.import_module(tup[0]), tup[1]), tup[3]
+                )(tup[2])
+            except Exception:
+                return None
+        elif code == EXT_PYDANTIC_V1:
+            try:
+                tup = ormsgpack.unpackb(
+                    data, ext_hook=ext_hook, option=ormsgpack.OPT_NON_STR_KEYS
+                )
+                if not _check_allowed(tup[0], tup[1]):
+                    return tup[2]
+                # module, name, kwargs
+                cls = getattr(importlib.import_module(tup[0]), tup[1])
+                try:
+                    return cls(**tup[2])
+                except Exception:
+                    return cls.construct(**tup[2])
+            except Exception:
+                # for pydantic objects we can't find/reconstruct
+                # let's return the kwargs dict instead
+                try:
+                    return tup[2]
+                except NameError:
+                    return None
+        elif code == EXT_PYDANTIC_V2:
+            try:
+                tup = ormsgpack.unpackb(
+                    data, ext_hook=ext_hook, option=ormsgpack.OPT_NON_STR_KEYS
+                )
+                if not _check_allowed(tup[0], tup[1]):
+                    return tup[2]
+                # module, name, kwargs, method
+                cls = getattr(importlib.import_module(tup[0]), tup[1])
+                try:
+                    return cls(**tup[2])
+                except Exception:
+                    return cls.model_construct(**tup[2])
+            except Exception:
+                # for pydantic objects we can't find/reconstruct
+                # let's return the kwargs dict instead
+                try:
+                    return tup[2]
+                except NameError:
+                    return None
+        elif code == EXT_NUMPY_ARRAY:
+            try:
+                import numpy as _np
+
+                dtype_str, shape, order, buf = ormsgpack.unpackb(
+                    data, ext_hook=ext_hook, option=ormsgpack.OPT_NON_STR_KEYS
+                )
+                arr = _np.frombuffer(buf, dtype=_np.dtype(dtype_str))
+                return arr.reshape(shape, order=order)
+            except Exception:
+                return None
+        return None
+
+    return ext_hook
+
+
+# Aliasing in case anyone imported it directly
+_msgpack_ext_hook = _create_msgpack_ext_hook(allowed_modules=None)
+
+
+def _msgpack_ext_hook_to_json(code: int, data: bytes) -> Any:
+    if code == EXT_CONSTRUCTOR_SINGLE_ARG:
+        try:
+            tup = ormsgpack.unpackb(
+                data,
+                ext_hook=_msgpack_ext_hook_to_json,
+                option=ormsgpack.OPT_NON_STR_KEYS,
+            )
+            if tup[0] == "uuid" and tup[1] == "UUID":
+                hex_ = tup[2]
+                return (
+                    f"{hex_[:8]}-{hex_[8:12]}-{hex_[12:16]}-{hex_[16:20]}-{hex_[20:]}"
+                )
+            # module, name, arg
+            return tup[2]
+        except Exception:
+            return
+    elif code == EXT_CONSTRUCTOR_POS_ARGS:
+        try:
+            tup = ormsgpack.unpackb(
+                data,
+                ext_hook=_msgpack_ext_hook_to_json,
+                option=ormsgpack.OPT_NON_STR_KEYS,
+            )
+            if tup[0] == "langgraph.types" and tup[1] == "Send":
+                return _send_from_args(tup[2])
+            # module, name, args
+            return tup[2]
+        except Exception:
+            return
+    elif code == EXT_CONSTRUCTOR_KW_ARGS:
+        try:
+            tup = ormsgpack.unpackb(
+                data,
+                ext_hook=_msgpack_ext_hook_to_json,
+                option=ormsgpack.OPT_NON_STR_KEYS,
+            )
+            # module, name, args
+            return tup[2]
+        except Exception:
+            return
+    elif code == EXT_METHOD_SINGLE_ARG:
+        try:
+            tup = ormsgpack.unpackb(
+                data,
+                ext_hook=_msgpack_ext_hook_to_json,
+                option=ormsgpack.OPT_NON_STR_KEYS,
+            )
+            # module, name, arg, method
+            return tup[2]
+        except Exception:
+            return
+    elif code == EXT_PYDANTIC_V1:
+        try:
+            tup = ormsgpack.unpackb(
+                data,
+                ext_hook=_msgpack_ext_hook_to_json,
+                option=ormsgpack.OPT_NON_STR_KEYS,
+            )
+            # module, name, kwargs
+            return tup[2]
+        except Exception:
+            # for pydantic objects we can't find/reconstruct
+            # let's return the kwargs dict instead
+            return
+    elif code == EXT_PYDANTIC_V2:
+        try:
+            tup = ormsgpack.unpackb(
+                data,
+                ext_hook=_msgpack_ext_hook_to_json,
+                option=ormsgpack.OPT_NON_STR_KEYS,
+            )
+            # module, name, kwargs, method
+            return tup[2]
+        except Exception:
+            return
+    elif code == EXT_NUMPY_ARRAY:
+        try:
+            import numpy as _np
+
+            dtype_str, shape, order, buf = ormsgpack.unpackb(
+                data,
+                ext_hook=_msgpack_ext_hook_to_json,
+                option=ormsgpack.OPT_NON_STR_KEYS,
+            )
+            arr = _np.frombuffer(buf, dtype=_np.dtype(dtype_str))
+            return arr.reshape(shape, order=order).tolist()
+        except Exception:
+            return
+
+
+class InvalidModuleError(Exception):
+    """Exception raised when a module is not in the allowlist."""
+
+    def __init__(self, message: str):
+        self.message = message
+
+
+_option = (
+    ormsgpack.OPT_NON_STR_KEYS
+    | ormsgpack.OPT_PASSTHROUGH_DATACLASS
+    | ormsgpack.OPT_PASSTHROUGH_DATETIME
+    | ormsgpack.OPT_PASSTHROUGH_ENUM
+    | ormsgpack.OPT_PASSTHROUGH_UUID
+    | ormsgpack.OPT_REPLACE_SURROGATES
+)
+
+
+def _msgpack_enc(data: Any) -> bytes:
+    return ormsgpack.packb(data, default=_msgpack_default, option=_option)
+
+
+def _normalize_allowlist(
+    allowlist: AllowedMsgpackModules | Literal[True] | None,
+) -> set[tuple[str, ...]] | Literal[True] | None:
+    if allowlist is True:
+        return allowlist
+    elif allowlist:
+        return _normalize_module_keys(allowlist)
+    else:
+        return None
+
+
+def _normalize_module_keys(
+    modules: AllowedMsgpackModules,
+) -> set[tuple[str, ...]]:
+    normalized: set[tuple[str, ...]] = set()
+    for module in modules:
+        if isclass(module):
+            normalized.add((module.__module__, module.__name__))
+        else:
+            normalized.add(cast(tuple[str, ...], module))
+    return normalized

.venv/Lib/site-packages/langgraph/checkpoint/serde/types.py

@@ -0,0 +1,68 @@
+from collections.abc import Sequence
+from typing import (
+    Any,
+    NamedTuple,
+    Protocol,
+    TypeVar,
+    runtime_checkable,
+)
+
+from typing_extensions import Self
+
+ERROR = "__error__"
+SCHEDULED = "__scheduled__"
+INTERRUPT = "__interrupt__"
+RESUME = "__resume__"
+TASKS = "__pregel_tasks"
+
+
+class _DeltaSnapshot(NamedTuple):
+    """Snapshot blob for a DeltaChannel with finite snapshot_frequency.
+
+    Stored in checkpoint_blobs via the `EXT_DELTA_SNAPSHOT` msgpack ext code.
+    The ancestor walk in `BaseCheckpointSaver.get_delta_channel_history` terminates
+    when it encounters this type (any non-empty channel_values entry stops
+    the walk for that channel).
+
+    `from_checkpoint` reconstructs the channel value directly from `.value`
+    without replaying writes — the snapshot IS the accumulated state.
+    """
+
+    value: Any
+
+
+Value = TypeVar("Value", covariant=True)
+Update = TypeVar("Update", contravariant=True)
+C = TypeVar("C")
+
+
+class ChannelProtocol(Protocol[Value, Update, C]):
+    # Mirrors langgraph.channels.base.BaseChannel
+    @property
+    def ValueType(self) -> Any: ...
+
+    @property
+    def UpdateType(self) -> Any: ...
+
+    def checkpoint(self) -> C | None: ...
+
+    def from_checkpoint(self, checkpoint: C | None) -> Self: ...
+
+    def update(self, values: Sequence[Update]) -> bool: ...
+
+    def get(self) -> Value: ...
+
+    def consume(self) -> bool: ...
+
+
+@runtime_checkable
+class SendProtocol(Protocol):
+    # Mirrors langgraph.constants.Send
+    node: str
+    arg: Any
+
+    def __hash__(self) -> int: ...
+
+    def __repr__(self) -> str: ...
+
+    def __eq__(self, value: object) -> bool: ...