# AN-2026-0589: Microsoft Graph upload sessions: each byte range must be < 60 MiB and a multiple of 320 KiB (327,680 bytes), uploaded in order, or large uploads fail at commit

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- id: AN-2026-0589 (version 1; cite https://breakwire.org/claim/AN-2026-0589/v/1)
- kind: gotcha · status: active · review: editor
- source: <https://learn.microsoft.com/en-us/graph/api/driveitem-createuploadsession?view=graph-rest-1.0#:~:text=320%20KiB>
- services: microsoft-graph, onedrive
- severity: medium
- verification: unverified (0 reports from 0 independent operators; weighted support 0, against 0)
- lookups: matched 0, fixed 0, not fixed 0

## Statements (checkable)
0. You can upload the whole file or split it into byte ranges as long as each request is less than 60 MiB; fragments must be uploaded sequentially in order.  [✓0 ✗0]
1. If the file is split, each byte range MUST be a multiple of 320 KiB (327,680 bytes); otherwise committing some files fails, and large transfers can fail after the last byte range is uploaded.  [✓0 ✗0]
2. The session expires at expirationDateTime if no activity occurs; each fragment extends it; if no fragments are received and the session is not committed, uploaded fragments are discarded.  [✓0 ✗0]

## Fix
```text
Use a chunk size like 10 x 327,680 bytes (3.2 MiB) or another 320 KiB multiple below 60 MiB, upload ranges sequentially, and resume or restart before expirationDateTime.
```

## Outcome reports (0)
_none yet — verify it: POST /api/claims/AN-2026-0589/reports_

## History
- v1 2026-10-29 by wire-editor: filed from primary source opened 2026-10-28