## Summary
Adds a sqlite-specific override of
`BaseCheckpointSaver.get_delta_channel_history` (and async). Before this
PR, `SqliteSaver` / `AsyncSqliteSaver` inherited the default impl, which
calls `get_tuple` once per ancestor — N round-trips, full pending-writes
fetch per step regardless of channel relevance.
The override mirrors the postgres two-stage shape (ancestor walk +
per-channel UNION ALL writes fetch) but adapted for sqlite:
- **No JSONB** → stage 1 streams the cursor row-by-row in
`checkpoint_id` DESC order. The merged walk advances one row at a time,
deserializing only on-path checkpoints and dropping each before
advancing — peak in-flight is one deserialized checkpoint, no
`fetchall()` materialization.
- **No separate blob table** → `channel_values` lives inline in the
checkpoint blob, so seeds come back from stage 1 with no second fetch.
- **Single merged walk (not K independent walks)**: each visited cid is
deserialized exactly once, regardless of how many channels are still
seeking their seed.
- **Stage 2** stays per-channel UNION ALL to avoid over-fetching writes
when channels have different chain depths — same rationale as postgres.
`AsyncSqliteSaver.get_delta_channel_history` bridges to its async form
via `run_coroutine_threadsafe`, matching the same cross-thread guard
used by `get_tuple` / `delete_thread`.
## Tests
- New `tests/test_delta_channel_migration.py`: covers the
`BinaryOperatorAggregate -> DeltaChannel` migration path on sqlite (sync
round-trip, sync continuation with post-migration delta folding, async
round-trip). Mirrors
`libs/langgraph/tests/test_delta_channel_migration.py` (which covered
`InMemorySaver`); without these, the override's behavior on
pre-migration threads was unverified — the override has to identify a
plain accumulated `channel_values[ch]` at a pre-migration ancestor as a
valid `seed`, not just `_DeltaSnapshot` sentinels.
- Existing `tests/test_get_delta_channel_history.py` (7 tests) continues
to pass and now exercises the optimized override end-to-end (previously
hit the inherited default impl).
- `make format`, `make lint`, `make test`: clean. 97/97 in the non-flaky
sqlite suite (the one ignored test, `test_async_asearch_refresh_ttl`, is
a known TTL-store timing flake on a separate module unrelated to this
PR).
## Benchmarks
### `get_delta_channel_history` micro-bench (override vs inherited
default impl)
1000-turn synthetic threads with sentinel snapshots + per-step writes;
`bench_sqlite_delta_history.py`. Per-call latency in microseconds.
| Scenario | min | median | mean |
|---|---:|---:|---:|
| S1 single channel, root-only snapshot | **4.60x** | **4.90x** |
**5.13x** |
| S2 mixed cadence (every-50 + root-only), 2 channels | **6.08x** |
**6.37x** | **6.84x** |
| S3 K=8 channels, root-only snapshot | 1.23x | 1.27x | 0.90x |
S2 wins biggest because per-channel UNION ALL avoids over-fetching
writes for the shallow channel. S3 is the worst case for sqlite (8
channels all walking to root, 1000 deserializations either way) — the
override still wins on min/median.
### Long-running thread mem/storage bench (delta vs no-delta)
`bench_sqlite_delta_memory.py`. `delta` mode uses `DeltaChannel` + the
override; `no_delta` uses `Annotated[list, _messages_delta_reducer]`
(full state in every blob). Same workload, file-backed sqlite. Latency
measured untraced (30 iterations); peak heap measured separately under
tracemalloc.
| Scenario | Turns | Storage Δ | Peak heap Δ | Read latency Δ |
|---|---:|---|---|---|
| K=1, freq=50 | 200 | **-96%** (942 KB vs 25.1 MB) | +21% (504 KB vs
418 KB) | **+13%** |
| K=1, freq=50 | 500 | **-98%** (2.9 MB vs 152.3 MB) | +20% (1.2 MB vs
1.0 MB) | **-6%** (delta wins) |
| K=3, freq=50 uniform | 200 | **-98%** (1.7 MB vs 73.5 MB) | +7% (1.3
MB vs 1.2 MB) | **+10%** |
| K=3, freq=50 uniform | 500 | **-99%** (6.0 MB vs 452.5 MB) | +7% (3.3
MB vs 3.0 MB) | **+6%** |
| K=3, freq=mixed | 200 | **-98%** (1.4 MB vs 73.5 MB) | +5% (1.3 MB vs
1.2 MB) | +190% (5.1 ms vs 1.7 ms abs) |
| K=3, freq=mixed | 500 | **-99%** (4.1 MB vs 452.5 MB) | +8% (3.3 MB vs
3.0 MB) | +377% (20.9 ms vs 4.4 ms abs) |
- **Storage**: -96 to -99% on long threads (a 500-turn K=3 thread
shrinks from 452 MB to 6 MB on disk). This is the headline win.
- **Peak heap**: within +5 to +21% of the no-delta path — the streaming
cursor + merged walk + drop-after-deserialize keep peak in-flight at one
checkpoint at a time.
- **Read latency**: equivalent-ish (within ~15%) on uniform-cadence
scenarios; at K=1/500 turns delta even wins by 6%. The mixed-cadence
rows have one channel with `snapshot_frequency=1000` walking to root on
a 500-turn thread — by configuration. Absolute mixed-delta latency is
still 5-21 ms per read.
Bench scripts (not committed; workspace-root convention matches other
`bench_*.py` files):
- `bench_sqlite_delta_history.py`
- `bench_sqlite_delta_memory.py`
## Test plan
- [x] `cd libs/checkpoint-sqlite && make format` clean
- [x] `cd libs/checkpoint-sqlite && make lint` clean
- [x] `cd libs/checkpoint-sqlite && make test` — 97 passed (1 known
flake unrelated)
- [x] `tests/test_get_delta_channel_history.py` — 7/7 (now exercises the
override)
- [x] `tests/test_delta_channel_migration.py` — 3/3 (new)
## 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>
`aiosqlite` changed it's Connection type to no longer subclass
`threading.Thread`. This removed the is_alive method, which is called
proactively in setup().
This PR handles this in a backwards compat way.
In this PR:
- Bump `langgraph-checkpoint` to 3.0
- Bump `langgraph-checkpoint-sqlite` to 3.0; Update
`langgraph-checkpoint` deps to >=3,<4
- Bump `langgraph-checkpoint-postgres` to 3.0; Update
`langgraph-checkpoint` max to <4 (keep prior min since the deprecated
functionality wasn't explicitly used)
- Bump `langgraph` to 1.0.1; update `langgraph-checkpoint` max bound to
4
- Bump `prebuilt` to 1.0.1; update `langgraph-checkpoint` max bound to 4
* catching error thrown by asyncio
* using 2nd check for annotations given Pydantic 2.12 changes
* skipping tests for remote graph bc langgraph-api is dependent on
`jsonschema-rs`
* skipping tests w/ pydantic v1 models
```bash
hint: This usually indicates a problem with the package or the build environment.
help: `jsonschema-rs` (v0.29.1) was included because `langgraph:dev` (v1.0.0rc1) depends on `langgraph-cli[inmem]` which
depends on `langgraph-api` (v0.4.29) which depends on `jsonschema-rs`
```
not yet testing for free threaded python, that'll be much more involved!
ended up separating lint / testing deps during this process bc I was
getting a ton of not required deps while testing that were complicating
things :/
* Migrate to `uv`
* Format `pyproject.toml` files properly
* Remove upper bounds on dependencies, and bounds on dev dependencies
(we should be using latest)
* Move to hatch for packaing
In the future we should:
* Set up dependabot / automate lockfile updates and tests
* Add tests for min compatible versions (I'll do this right after merge)
* Use dynamic versioning
* Bump `pydantic` to v2.11.4 in the lockfile, we have some tests failing
