Files
langgraph/libs
Caspar BroekhuizenandGitHub 3c75e414e5 fix(langgraph): do not apply pending writes when updating state (#6389)
PR #6195 fixed `bulk_update_state` to populate `task.result` by calling
`prepare_next_tasks` to discover task IDs. Before #6195,
prepare_next_tasks was gated by the condition `CONFIG_KEY_CHECKPOINT_ID
not in config[CONF]` - so it only ran if we were resuming from an empty
checkpoint. This check was removed in order to properly populate task
results. However, the removal of this check inadvertently applied
pending writes during manual state updates which caused issues when
forking:

- When you fork from a checkpoint by calling `update_state(config,
new_values, as_node="mynode")`, pending writes from the original
execution were being applied
- This caused stale data to leak into forked threads (eg. old tool call
results appearing in forked execution)

Changes

Removed pending writes application from `bulk_update_state` and
`abulk_update_state`:
- Still call `prepare_next_tasks` to discover task IDs, but skip the
code that applies null writes and regular pending writes

Tests

- Added `test_fork_does_not_apply_pending_writes` for sync and async
which verifies forking doesn't include stale pending writes from
original execution
2025-11-04 14:38:40 -08:00
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