LangGraphPersistenceLoadError
langgraph.checkpointer.LangGraphPersistenceLoadError
Stack trace
Traceback (most recent call last):
File "app.py", line 42, in <module>
graph = checkpointer.load("graph_state.chkpt") # triggers error
File "/usr/local/lib/python3.9/site-packages/langgraph/checkpointer.py", line 88, in load
raise LangGraphPersistenceLoadError(f"Failed to load checkpoint: {e}")
langgraph.checkpointer.LangGraphPersistenceLoadError: Failed to load checkpoint: EOFError: Ran out of input Why it happens
LangGraph's checkpointer expects a valid serialized checkpoint file to restore graph state. This error occurs when the checkpoint file is missing, corrupted, truncated, or saved with an incompatible version or serialization format. It can also happen if the file path is incorrect or the file is locked by another process.
Detection
Monitor exceptions during checkpointer.load calls and log the file path and error details. Implement pre-load file existence and integrity checks to catch issues before attempting to load.
Causes & fixes
Checkpoint file is missing or the file path is incorrect
Verify the checkpoint file path is correct and the file exists before calling load. Use os.path.exists() to check presence.
Checkpoint file is corrupted or truncated due to incomplete save or disk issues
Ensure atomic writes during checkpoint save, use temporary files and rename after successful write, and verify disk health.
Checkpoint file was saved with a different or incompatible serialization format or LangGraph version
Maintain backward compatibility or migrate old checkpoint files using provided migration utilities before loading.
File is locked or in use by another process preventing proper read
Ensure no concurrent processes are writing or locking the checkpoint file during load operations.
Code: broken vs fixed
from langgraph.checkpointer import Checkpointer
checkpointer = Checkpointer()
graph = checkpointer.load("graph_state.chkpt") # triggers LangGraphPersistenceLoadError if file missing or corrupted
print(graph)import os
from langgraph.checkpointer import Checkpointer
checkpointer = Checkpointer()
checkpoint_path = "graph_state.chkpt"
if not os.path.exists(checkpoint_path):
raise FileNotFoundError(f"Checkpoint file not found: {checkpoint_path}")
graph = checkpointer.load(checkpoint_path) # fixed: verify file exists before load
print(graph) # confirms successful loadWorkaround
Wrap the load call in try/except LangGraphPersistenceLoadError, and if caught, delete the corrupted checkpoint file and initialize a new graph state to continue running.
Prevention
Implement atomic checkpoint saves with file locks and versioned serialization formats. Validate checkpoint files before loading and maintain backward compatibility or migration paths for saved states.