langchain-ai/langgraph
1
0
Fork 0
mirror of https://github.com/langchain-ai/langgraph.git synced 2026-07-15 12:35:43 -04:00
Code Issues 314 Packages Projects Releases 17 Wiki Activity

[PR #6162] fix(langgraph): fix PostgresSaver crashing when loading older checkpoints #4879

New Issue
Closed
opened 2026-02-20 17:50:53 -05:00 by yindo · 0 comments
yindo commented 2026-02-20 17:50:53 -05:00
Owner
Copy Link
Copy Source

Original Pull Request: https://github.com/langchain-ai/langgraph/pull/6162

State: closed
Merged: Yes

Description

https://github.com/langchain-ai/langgraph/issues/6137 and https://github.com/langchain-ai/langgraph/issues/5677 reported issues where older checkpoints read by AsyncPostgresSaver/PostgresSaver from langgraph-checkpoint-postgres==2.0.19 fail to read channel values, throwing NoneType object is not a mapping. This was due to a bug in how channel_values is assembled:

"channel_values": {
    **value["checkpoint"].get("channel_values"),  # <--- if channel_values doesn't exist (old checkpoint), **None errors
    **self._load_blobs(value["channel_values"]),
},

This bug was observed for checkpoints generated by langgraph-checkpoint-postgres<=2.0.19.

Fixed by providing a fallback to value["checkpoint"].get("channel_values"):

**value["checkpoint"],
"channel_values": {
    **(
        value["checkpoint"].get("channel_values") or {}
    ),  # 'or {}' needed for backwards compat with v3 checkpoints and below, as v4 introduced channel_values key
    **self._load_blobs(value["channel_values"]),
},

Tests

Added test for AsyncPostgresSaver and test for PostgresSaver, using monkeypatch to remove channel_values before CheckpointTuple is assembled in _load_checkpoint_tuple.

Solves

https://github.com/langchain-ai/langgraph/issues/6137 and https://github.com/langchain-ai/langgraph/issues/5677

**Original Pull Request:** https://github.com/langchain-ai/langgraph/pull/6162 **State:** closed **Merged:** Yes --- ### Description https://github.com/langchain-ai/langgraph/issues/6137 and https://github.com/langchain-ai/langgraph/issues/5677 reported issues where older checkpoints read by AsyncPostgresSaver/PostgresSaver from `langgraph-checkpoint-postgres==2.0.19` fail to read channel values, throwing `NoneType object is not a mapping`. This was due to a bug in how `channel_values` is assembled: ```python "channel_values": { **value["checkpoint"].get("channel_values"), # <--- if channel_values doesn't exist (old checkpoint), **None errors **self._load_blobs(value["channel_values"]), }, ``` This bug was observed for checkpoints generated by `langgraph-checkpoint-postgres<=2.0.19`. Fixed by providing a fallback to `value["checkpoint"].get("channel_values")`: ```python **value["checkpoint"], "channel_values": { **( value["checkpoint"].get("channel_values") or {} ), # 'or {}' needed for backwards compat with v3 checkpoints and below, as v4 introduced channel_values key **self._load_blobs(value["channel_values"]), }, ``` ### Tests Added test for AsyncPostgresSaver and test for PostgresSaver, using monkeypatch to remove `channel_values` before CheckpointTuple is assembled in `_load_checkpoint_tuple`. ### Solves https://github.com/langchain-ai/langgraph/issues/6137 and https://github.com/langchain-ai/langgraph/issues/5677
yindo added the pull-request label 2026-02-20 17:50:53 -05:00
yindo closed this issue 2026-02-20 17:50:53 -05:00
Sign in to join this conversation.
No Branch/Tag Specified
Branches Tags
Labels
Clear labels
agents
awaiting author revision
bug
change
chat models
checkpointer
ci
code quality
code quality
dependencies
documentation
drawing
duplicate
enhancement
good first issue
help wanted
invalid
maintainer
meta
missing information
not maintained by langchain
open-swe-auto
open-swe-max
open-swe-max-auto
pending
performance
pull-request
Mirrored from GitHub Pull Request
 question
requires design
sdk
server
stale
studio
tests
type checking
usage question
v0.5
v1.1
No Label pull-request
Milestone
No items
No Milestone
Projects
Clear projects
No project
Assignees
Clear assignees
yindo
No Assignees
1 Participants
Notifications
Due Date
No due date set.
Dependencies

No dependencies set.

Reference: langchain-ai/langgraph#4879
Delete Branch "%!s()"

Deleting a branch is permanent. Although the deleted branch may continue to exist for a short time before it actually gets removed, it CANNOT be undone in most cases. Continue?