ValueError
builtins.ValueError
Stack trace
ValueError: chunk overlap larger than chunk size
File "/app/main.py", line 25, in split_text
chunks = text_splitter.split_text(text)
File "/usr/local/lib/python3.9/site-packages/langchain/text_splitter.py", line 78, in split_text
raise ValueError("chunk overlap larger than chunk size") Why it happens
Text splitters require the chunk overlap to be smaller than or equal to the chunk size to logically create overlapping segments. Setting overlap larger than chunk size breaks this logic, causing the ValueError.
Detection
Validate chunk_size and chunk_overlap parameters before splitting text; assert chunk_overlap <= chunk_size to catch this error early.
Causes & fixes
chunk_overlap parameter is set larger than chunk_size in the text splitter configuration
Set chunk_overlap to a value less than or equal to chunk_size to ensure valid chunking logic.
Dynamic calculation or user input sets chunk_overlap incorrectly without validation
Add input validation or assertions to enforce chunk_overlap <= chunk_size before calling the splitter.
Misunderstanding of chunk_overlap meaning, confusing it with chunk_size or total text length
Review documentation and ensure chunk_overlap is configured as the number of overlapping characters or tokens, not total chunk size.
Code: broken vs fixed
from langchain.text_splitter import RecursiveCharacterTextSplitter
text_splitter = RecursiveCharacterTextSplitter(chunk_size=100, chunk_overlap=150)
text = "Some long text to split into chunks."
chunks = text_splitter.split_text(text) # This line raises ValueErrorimport os
from langchain.text_splitter import RecursiveCharacterTextSplitter
# Fixed: chunk_overlap <= chunk_size
text_splitter = RecursiveCharacterTextSplitter(chunk_size=150, chunk_overlap=50)
text = "Some long text to split into chunks."
chunks = text_splitter.split_text(text)
print(chunks) # Works without errorWorkaround
Wrap the split_text call in try/except ValueError, catch the error, and programmatically adjust chunk_overlap to be at most chunk_size before retrying.
Prevention
Always validate or assert chunk_overlap <= chunk_size in your text splitting logic or configuration to prevent this error from occurring.