OneDrive Chunk Upload: Getting HTTP 416 Only on Last Chunk, Despite Matching nextExpectedRanges and Active Session

Question

I'm using OneDrive chunked upload for a file of 80MB, with a chunk size of 50MB.

All chunks except the last one are successfully uploaded. The last chunk always returns HTTP 416 (Range Not Satisfiable). The nextExpectedRanges matches my Content-Range exactly. The upload session is still active. Steps Taken & Debugging So Far:

• Checked nextExpectedRanges from OneDrive's response before sending the last chunk. ✅

• Verified Content-Range calculation to ensure the last byte is correct (bytes start-end/total). ✅

• Confirmed InputStream is positioned correctly before reading the last chunk. ✅

• Ensured only the expected bytes are being read and sent (no extra/missing bytes). ✅

• Checked that previous chunks were fully received before uploading the last one. ✅

• Session is active (expirationDateTime is in the future). ✅

Example of My Last Chunk Request: css Copy Edit

Content-Range: bytes 52428800-81539536/81539537 (nextExpectedRanges also returns "52428800-81539536" before this request.)

Despite everything matching, the last chunk still fails with HTTP 416.

Question: What could be causing OneDrive to reject only the last chunk? Are there any additional conditions for the final chunk in a chunked upload?