You can Send(..., timeout=...) now. Much fun.
This would allow us to do something like adding support for an
annotation to let the LLM to pick a timeout for a given tool call, etc.
---------
Co-authored-by: Will Fu-Hinthorn <will@langchain.dev>
## Description
Updates the X/Twitter social links to point to the new `@langchain_oss`
account across README badges and Python package metadata.
## Test Plan
- [ ] Verify README badges and package metadata point to
`@langchain_oss` on X
_Opened collaboratively by Mason Daugherty and open-swe._
---------
Co-authored-by: open-swe[bot] <open-swe@users.noreply.github.com>
Co-authored-by: Mason Daugherty <61371264+mdrxy@users.noreply.github.com>
Co-authored-by: Mason Daugherty <mason@langchain.dev>
prune was not previously implemented on InMemorySaver (raised
NotImplementedError); adding a DeltaChannel-aware implementation is a
follow-up concern, not required for the core feature.
DELTA_SENTINEL is now serialized as a msgpack ext code (EXT_DELTA_SENTINEL=8)
alongside _DeltaSnapshot (ext 7), keeping both sentinel types in the same
codec path. The dedicated "delta" string type tag and its special-case in
dumps_typed/loads_typed are removed — no migration needed since this is
introduced fresh.
InMemorySaver.prune() updated to deserialize blobs and check `is DELTA_SENTINEL`
rather than comparing the raw type tag string, making it codec-agnostic.
Co-Authored-By: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>
Dropped after removing the _DeltaSnapshot special-case in the seed-terminator
logic — write-collection ordering fix handles both blob types uniformly.
Co-Authored-By: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>
Adds _get_tuple_raw / _aget_tuple_raw as the pure-storage-read layer that
_get_channel_writes_history calls instead of get_tuple. Default
implementation delegates to get_tuple for full backward compatibility — no
changes needed for existing savers whose get_tuple is a plain storage query.
Savers that perform channel hydration inside get_tuple can override
_get_tuple_raw with the raw read to structurally break any possible cycle;
a Python RecursionError surfaces the problem if they don't, rather than the
previous silent data corruption (returning empty writes).
Also fixes write-collection ordering in the reference implementation: pending
writes from the seed-terminator ancestor were silently dropped because the
terminator check fired before the collection loop. Writes are now collected
first so the seed ancestor's transition writes are included in reconstruction.
Co-Authored-By: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>
## Summary
Fixes#7498 — `MESSAGE_COERCION_FAILURE` when resuming threads
checkpointed before v1.0.1.
**Root cause:** PR #6269 (v1.0.1) added an `_allowed_json_modules`
security gate to `JsonPlusSerializer._reviver`. The gate defaults to
`None`, so old `"json"`-format checkpoint blobs containing `lc=2`
constructor dicts (the pre-msgpack serialization format for pydantic
objects like `HumanMessage`) are now returned as raw dicts instead of
being reconstructed. Those raw dicts reach `add_messages →
convert_to_messages`, which sees `type="constructor"` and raises
`MESSAGE_COERCION_FAILURE`. Fresh first-turn messages are unaffected
because current `dumps_typed` only writes `"msgpack"` blobs.
**Fix:** `_reviver` now reconstructs `lc=2` blobs whose target class is
already in `SAFE_MSGPACK_TYPES` — the same curated allowlist already
used by the msgpack deserialization path (includes all standard
LangChain message types). Unknown classes are still blocked, preserving
the security intent of #6269.
## Changes
- `libs/checkpoint/langgraph/checkpoint/serde/jsonplus.py` — add
`_is_safe_json_type()` helper; update `_reviver` and
`_check_allowed_json_modules` to allow safe types without an explicit
allowlist
- `libs/checkpoint/tests/test_jsonplus.py` — two new regression tests:
safe-type `lc=2` blobs revive correctly; unknown-type `lc=2` blobs stay
blocked
## Test plan
- [ ] `test_lc2_json_safe_type_revives_without_allowlist` —
`HumanMessage`/`AIMessage` lc=2 JSON blobs round-trip to proper
`BaseMessage` objects with no allowlist configured
- [ ] `test_lc2_json_unknown_type_stays_blocked_without_allowlist` —
`pprint.pprint` lc=2 blob still returns raw dict (not reconstructed)
- [ ] `test_deserde_invalid_module` — existing behaviour unchanged
- [ ] Full `test_jsonplus.py` suite: 93/93 passing
Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>
Restructure DeltaChannel reconstruction so the hydration path matches
pregel's storage axes (blobs + writes) without leaking internal DTOs
into the public checkpoint contract.
Key changes:
* Deleted `DeltaChannelWrites` dataclass and `SEED_UNSET` sentinel.
Reconstruction data no longer flows through `Checkpoint.channel_values`
as a wrapped DTO — that field now carries a value or `DELTA_SENTINEL`,
never a reconstruction shape.
* Added private `_ChannelWritesHistory(seed: Any, writes: list[PendingWrite])`
NamedTuple as the return type for the new storage-level query.
* Added private, experimental `_get_channel_writes_history` /
`_aget_channel_writes_history` on `BaseCheckpointSaver` — reference
impl via `get_tuple` + `parent_config` walk, overridden on
`InMemorySaver` / `PostgresSaver` / `AsyncPostgresSaver` for perf.
Fixes a latent migration bug in the base fallback (now inspects
ancestor `channel_values` for pre-delta seed).
* `DeltaChannel.from_checkpoint(seed)` simplified to two cases
(sentinel/MISSING → empty, else → seed). New `replay_writes` method
folds `list[PendingWrite]` through the reducer.
* Delta hydration consolidated inside `channels_from_checkpoint` via
optional `saver` + `config` kwargs (+ async mirror
`achannels_from_checkpoint`). All six pregel call sites updated.
`get_tuple` no longer patches `channel_values` — removed
`_resolve_delta_channels` (memory) and per-tuple reconstruction from
`_load_checkpoint_tuple` (postgres sync + async).
* Hydration short-circuits on the target's own blob: if
`channel_values[k]` is a real value (pre-migration tip, `update_state`
result), use it directly. Only walks ancestors when the target holds
sentinel or is missing. Fixes a correctness bug where migration-tip
and `update_state` values would be lost.
* New test_delta_channel_migration.py: 10 scenarios covering
BinaryOperatorAggregate → DeltaChannel migration (basic + async,
time-travel, fork, `update_state`, tip-of-pre-migration, base-saver
fallback parity, cross-thread isolation).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
snapshot_every was a knob for bounding reconstruction cost on deep threads.
Benchmarks (notes/add_messages_replay_problem.md + scratch work on
sr/add-messages-replay-bench) showed the add_messages fast-path
(optimize/add-messages-fast-path) closes the quadratic replay cost for
threads under ~1000 turns, where the crossover to snapshots makes sense.
For deeper threads we'll ship a first-class compaction primitive instead.
Removals:
* DeltaChannel: snapshot_every ctor param, _writes_since_snapshot counter,
should_snapshot() / snapshot_write() methods, counter threading through
_apply_write / update / from_checkpoint / copy.
* Pregel loop: post-checkpoint snapshot-injection block and
SNAPSHOT_TASK_ID import + constant.
* Checkpoint base: _overwrite_types() helper and the ancestor-walk
short-circuit on user-emitted Overwrite in sync + async
get_channel_writes.
* InMemory + Postgres savers: same walk-terminator shortcut. The
pre-delta blob terminator (seed-from-ancestor-blob) stays — it's
required for migration correctness, not a snapshot optimization.
* Tests for all of the above.
Preserved:
* Channel-level Overwrite semantics in DeltaChannel / BinOpAggregate:
Overwrite still resets the value at reducer level; same-super-step
dedup and InvalidUpdateError on multiple Overwrites still enforced.
* Pre-delta migration seeding.
Four fixes from an independent review of the reconstruction pipeline, plus
a structural cleanup:
1. Ancestor walk excludes the target checkpoint itself (matches pregel:
writes stored under checkpoint_id=T are pending for the NEXT step and
applied separately via apply_writes). Memory saver previously included
them, diverging from Postgres and causing pending writes to be folded
into the reconstructed snapshot — visible via get_state during
interrupts and time-travel into a non-leaf checkpoint.
2. Pre-delta blob terminator. When the walk hits an ancestor whose blob
for the channel is a real value (not DELTA_SENTINEL), bind that blob
as DeltaChannelWrites.seed and stop. Without this, threads migrated
from pre-delta storage would replay ancestor writes to the root
forever AND lose any value that lived only in the old blob
(e.g. from update_state). Per-ancestor, the blob is checked BEFORE
its writes — a pre-delta blob subsumes writes at the same checkpoint,
so including them would double-count.
3. Base-fallback get_channel_writes follows parent_checkpoint_id instead
of list(before=...). The previous form returned every tuple with
id<target, including sibling branches on forked threads.
4. seed replaces the Overwrite-wrapping hack for pre-delta values.
DeltaChannelWrites(writes, seed=SEED_UNSET) makes the saver's
reconstruction terminator semantically explicit; drops the lazy
_make_overwrite import dance. User-emitted Overwrite still reset the
chain via _apply_write as before.
Postgres: recursive CTE enumerates on-path ancestors and joins once
against checkpoint_writes and once against checkpoint_blobs for every
delta channel in the get_tuple — one roundtrip instead of the previous
3 queries × N channels.
Tests added:
- Pre-delta blob seeding (seed binding, no double-counting of ancestor
writes at the terminator, pending-at-target excluded).
- Root checkpoint returns empty writes.
- Seed-based from_checkpoint replay (three scenarios: with writes,
seed-only, seed=None distinct from SEED_UNSET).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
DeltaChannel.checkpoint() now returns a zero-byte DeltaChannelSentinel
instead of duplicating delta data in checkpoint_blobs. Reconstruction
walks the parent checkpoint chain via checkpoint_writes (which already
holds per-step writes) and replays them through the operator.
In-memory benchmark (100 turns, ~20K tokens):
storage: 10.2 MB → 40.5 KB (251x reduction)
read: 0.6ms → 7.9ms (reconstruction cost, amortized by storage savings)
InMemorySaver and PostgresSaver override get_channel_writes() with
efficient implementations (Python dict walk and recursive CTE respectively).
The base class fallback uses self.list() with a thread-local recursion guard.
Rely on the runtime raise in DeltaChannel.from_checkpoint() instead of
a compile-time boolean flag. Savers that assemble DeltaChainValue inside
_load_blobs work transparently; savers that don't will pass through a raw
DeltaValue and hit a clear ValueError on first reload.
Removes: BaseCheckpointSaver.supports_delta_channels, the attribute on
InMemorySaver / PostgresSaver / AsyncPostgresSaver, the compile-time
UserWarning in StateGraph.compile(), and the associated test.
- Add DeltaValue to SAFE_MSGPACK_TYPES so SQLite and other msgpack-based
savers don't emit "Deserializing unregistered type" warnings.
- Rename _is_diff_delta → _is_delta_value (leftover from DiffChannel rename).
- Parametrize benchmark by checkpointer: runs InMemory (fast-path) and
SQLite (get_tuple fallback) in the same table, sharing the _run_turns helper.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
- Fix InMemorySaver.get_channel_blob: use correct storage[thread_id][ns]
nesting and deserialize the checkpoint before extracting channel_versions.
- Pass checkpoint_id to after_checkpoint() in channels_from_checkpoint so
DeltaChannel seeds _last_checkpoint_id correctly on load; without this
every turn broke the chain at its boundary.
- Wire _assemble_delta_channels into _prepare_state_snapshot and
_aprepare_state_snapshot (get_state / get_state_history paths) and into
perform_superstep / aperform_superstep (update_state paths) — previously
only the loop __enter__ path did assembly.
- Fix test_get_channel_blob to use the correct storage structure.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
- Add logger.warning when a mid-chain blob is missing (fixes silent truncation bug)
- Add cycle guard to prevent infinite loops on corrupt blob stores
- Fix type annotation on diff_channels from dict[str, Any] to dict[str, str]
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Replace duck-typing check with lazy import inside _is_diff_delta helper
function to avoid module-level circular dependency while using proper
isinstance semantics.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Add serde support for DiffDelta by implementing dump/load for the "diff" type tag.
This allows the checkpoint system to efficiently store delta objects by serializing
them as msgpack-encoded dicts with {"d": delta, "p": prev_version} structure.
The implementation uses runtime type checking to avoid circular imports and
leverages the existing msgpack ext hooks for proper deserialization of complex
types like LangChain messages.
Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>
## Summary
- Add `LANGGRAPH_STRICT_MSGPACK=true` guidance to `JsonPlusSerializer`
docstring and inline comments
- Update the warning message emitted for unregistered types to mention
the env var
- Add module docstring to `_msgpack.py` explaining the safety controls
- Add Security sections to checkpoint, checkpoint-postgres, and
checkpoint-sqlite READMEs
## Context
Multiple security advisories have reported the same msgpack
deserialization pattern (`ext_hook` → `importlib.import_module` →
`getattr` → call). The underlying behavior is documented in the repo's
threat model as T1, but the `LANGGRAPH_STRICT_MSGPACK` env var that
mitigates it is not surfaced in user-facing docs, docstrings, or warning
messages. This PR closes that gap.
## Test plan
- [x] Verify READMEs render correctly on GitHub (callout boxes use `>
[!IMPORTANT]` syntax)
- [x] Verify `JsonPlusSerializer` docstring renders in IDE tooltips
- [x] Confirm warning message format: `LANGGRAPH_STRICT_MSGPACK=true
PYTHON_CMD 2>&1 | grep -i strict`
---------
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
