chore: more back pressure#7499
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William FH (hinthornw) wants to merge 4 commits into
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Sydney Runkle (sydney-runkle)
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some questions / comments
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| def _put_checkpoint(self, metadata: CheckpointMetadata) -> None: | ||
| raise NotImplementedError |
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are we worried this will break for folks?
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| if self.durability == "exit" and ( | ||
| not self.is_nested | ||
| or exc_value is not None | ||
| or all(NS_END not in part for part in self.checkpoint_ns) | ||
| ): |
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can we add the comments bacK?
| self._dispatch_checkpoint_request(request) | ||
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| def after_tick(self) -> None: | ||
| if request := self._after_tick(): |
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this pattern feels confusing to me
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| if self.durability == "exit" and ( | ||
| not self.is_nested | ||
| or exc_value is not None | ||
| or all(NS_END not in part for part in self.checkpoint_ns) | ||
| ): | ||
| if request := self._prepare_checkpoint(self.checkpoint_metadata): | ||
| await self._dispatch_checkpoint_request(request) |
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bug that we didn't have this before?
Christian Bromann (christian-bromann)
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Jun 10, 2026
## Summary Ports Python time-travel fixes ([#7038](langchain-ai/langgraph#7038), [#7115](langchain-ai/langgraph#7115), [#7498](langchain-ai/langgraph#7498), [#7499](langchain-ai/langgraph#7499)) into `@langchain/langgraph` so replay/fork behave correctly with interrupts and nested subgraphs. - **Stale `RESUME` on replay** — Replaying from a checkpoint before an interrupt no longer consumes cached resume writes; interrupts re-fire with the correct payload. - **Subgraph checkpoint loading on time travel** — Introduces `ReplayState` (`CONFIG_KEY_REPLAY_STATE`) so nested subgraphs load the checkpoint that existed at the replay point on first visit, then resume normal head loading within the same run. - **Parent fork checkpoints on replay** — Time travel runs through `PregelLoop._first()` (not `stream()` delegation on the parent `Pregel`), creating an eager `source: "fork"` checkpoint and propagating `ReplayState` to subgraphs. - **Direct-to-subgraph time travel** — `getState()` subgraph delegation is guarded with `CONFIG_KEY_READ`; direct subgraph configs strip stale `RESUME` writes and prefer explicit `checkpoint_id` over `checkpoint_map` when both are set. - **Streaming** — Fixes subgraph interrupt namespace when streaming with `subgraphs: true` (empty `checkpoint_ns` no longer becomes `[""]`; parent emits interrupts under the deepest `checkpoint_map` namespace). Closes #2325 (supersedes the earlier partial port). ### Implementation notes | Area | Change | |------|--------| | `pregel/replay.ts` | New `ReplayState` class (mirrors Python) | | `pregel/loop.ts` | Replay/time-travel detection, fork creation, `RESUME` stripping, `ReplayState` wiring, stream namespace helpers | | `pregel/index.ts` | `getState` subgraph delegation guard only (removed `stream()` bypass that skipped parent fork creation) | | Tests | `time_travel.test.ts` (14), `time_travel_extended.test.ts` (33), shared `time_travel_helpers.ts`, Vitest matchers `toBeInterrupted` / `toHaveInterruptValue` | --------- Co-authored-by: Cursor <cursoragent@cursor.com>
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#7094