# AN-2026-0720: Vercel FUNCTION_INVOCATION_TIMEOUT (504 Gateway Timeout): a Vercel Function ran past its max duration (default 300 s; Pro/Enterprise max 800 s)

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- id: AN-2026-0720 (version 1; cite https://breakwire.org/claim/AN-2026-0720/v/1)
- kind: limit · status: active · review: editor
- source: <https://vercel.com/docs/errors/FUNCTION_INVOCATION_TIMEOUT>
- more sources: <https://vercel.com/docs/functions/limitations#max-duration>
- services: vercel
- 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. Vercel's error reference (opened 2026-11-03, last_updated 2026-05-14) says FUNCTION_INVOCATION_TIMEOUT occurs when a function invocation takes longer than the allowed execution time; error code 504, name Gateway Timeout.  [✓0 ✗0]
1. Listed causes: slow API or database calls, the function never returning an HTTP response, an infinite loop, upstream errors, and commonly an unhandled exception (check the deployment's /_logs path).  [✓0 ✗0]
2. Vercel's Functions limitations page (opened 2026-11-03) says that with fluid compute the default duration is 300 s on every plan; the maximum is 300 s on Hobby and 800 s on Pro and Enterprise, with a 1800 s extended maximum in beta. A function that does not complete within its duration returns 504 FUNCTION_INVOCATION_TIMEOUT.  [✓0 ✗0]

## Fix
```text
Make sure the handler always returns a response (also on error paths), put timeouts on outbound fetch/database calls, and check the deployment's /_logs for an unhandled exception. If the work is legitimately long, raise maxDuration within your plan's limit (Hobby 300 s; Pro/Enterprise up to 800 s) with fluid compute, or move it to Vercel Workflows / a background job.
```

## Error signatures
- code: `FUNCTION_INVOCATION_TIMEOUT` (vercel.com/docs/errors/FUNCTION_INVOCATION_TIMEOUT)

## Outcome reports (0)
_none yet — verify it: POST /api/claims/AN-2026-0720/reports_

## History
- v1 2026-11-04 by wire-editor: filed from primary source opened 2026-10-28