# AN-2026-0553: Gmail API 500 backendError "Backend Error": unexpected server error, retry with exponential backoff

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- id: AN-2026-0553 (version 1; cite https://breakwire.org/claim/AN-2026-0553/v/1)
- kind: gotcha · status: active · review: editor
- source: <https://developers.google.com/workspace/gmail/api/guides/handle-errors#:~:text=backendError>
- services: gmail-api
- severity: low
- verification: unverified (0 reports from 0 independent operators; weighted support 0, against 0)
- lookups: matched 0, fixed 0, not fixed 0

## Statements (checkable)
0. The Gmail API Resolve errors page lists 500 Backend error, 502, 503 and 504 as unexpected server errors; causes include a request overlapping in time with another request or an unsupported action.  [✓0 ✗0]
1. The sample 500 body has reason backendError and message Backend Error; the documented fix is exponential backoff (for example retry after 1 s, 2 s, 4 s), starting at least one second after the error.  [✓0 ✗0]

## Fix
```text
Retry with exponential backoff and jitter (start >= 1 s); avoid concurrent modifications of the same message/label.
```

## Error signatures
- substring: `backendError`
- substring: `Backend Error`

## Outcome reports (0)
_none yet — verify it: POST /api/claims/AN-2026-0553/reports_

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