## Summary
Add a user-facing design doc and `get_delta_channel_keepset` helper for
third-party `BaseCheckpointSaver` authors who need to support graphs
using `DeltaChannel`.
**Deliverables:**
1. ~~**`docs/delta-channel-checkpointer-guide.md`** — comprehensive
guide covering~~:
moved to docs repo
2. **`BaseCheckpointSaver.get_delta_channel_keepset` /
`aget_delta_channel_keepset`** — returns the minimum set of ancestor
`checkpoint_id`s that must survive deletion for a given head's
`DeltaChannel` reconstruction to remain intact. Enables safe `prune`
implementations without silently corrupting delta history.
3. **Docstring warnings** on `prune`, `aprune`, `delete_for_runs`,
`adelete_for_runs`, `copy_thread`, `acopy_thread` explaining the
DeltaChannel pitfall (silent data loss if ancestor writes/snapshots are
deleted).
4. **Three new conformance capabilities** in
`libs/checkpoint-conformance`:
- `delta_channel_history` — validates the `aget_delta_channel_history`
walk contract
- `delta_channel_keepset` — validates the keep-set contract
- `delta_channel_reconstruction` — end-to-end round-trip (aput +
aput_writes + history + reconstruct)
## Test plan
- [x] `make format lint` passes in `libs/checkpoint`,
`libs/checkpoint-conformance`
- [x] All three new conformance capabilities pass against
`InMemorySaver`
- [x] Run conformance against SQLite saver
- [x] Run conformance against Postgres saver
---------
Co-authored-by: Cursor <cursoragent@cursor.com>
## Summary
- Remove `test_list_global_search` from the conformance test suite. This
test required cross-thread `alist(None, filter=...)` support that not
all checkpointer implementations provide.
- Remove the corresponding entry from `ALL_LIST_TESTS`.
- Bump `langgraph-checkpoint-conformance` version from 0.0.1 to 0.0.2.
## Test plan
- [x] Verify `test_list_global_search` function definition is fully
removed
- [x] Verify `test_list_global_search` is removed from `ALL_LIST_TESTS`
- [x] Verify version bumped to 0.0.2 in pyproject.toml
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-authored-by: Will Fu-Hinthorn <will@langchain.dev>
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Add some conformance tests for checkpointer implementations. Includes
additona methods that will be useful if you want to integarte in the
agent server.
