The first-party Claude API allows request bodies up to 128 MB for Messages and Token Counting. Applications sending large PDFs or many images need to track that boundary separately from token capacity.
Bytes and tokens answer different questions
Body size measures the data sent to the service. Context limits concern the information the model can process in tokens. Space under one limit does not establish space under the other.
Check the endpoint’s own limit
The error documentation lists 128 MB for Messages and Token Counting, 256 MB for Batch and 500 MB for Files. These describe the first-party service; other platforms have their own conditions.
Record the facts behind a 413
An oversized request can return HTTP 413 with request_too_large. Record the endpoint and body size, then compare them with the relevant limit rather than resending the unchanged request.
Oliver’s assessment
Small detail. Big difference. A large body and a full context window are not the same failure. Separate endpoint, byte size and token count so the correction reaches the right layer.
