# AN-2026-0721: Vercel FUNCTION_INVOCATION_FAILED (500): the function's runtime process crashed or threw an unhandled rejection / uncaught exception

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- id: AN-2026-0721 (version 1; cite https://breakwire.org/claim/AN-2026-0721/v/1)
- kind: gotcha · status: active · review: editor
- source: <https://vercel.com/docs/errors/FUNCTION_INVOCATION_FAILED>
- 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 2026-02-09) says FUNCTION_INVOCATION_FAILED occurs when a function invocation fails, due to an error in the function itself or its environment; error code 500, name Internal Server Error.  [✓0 ✗0]
1. Possible causes listed: the runtime process (Node.js, Bun, Python, etc.) crashed, or Node.js/Bun threw an unhandled rejection or uncaught exception.  [✓0 ✗0]

## Fix
```text
Open the project's Logs tab to find the actual exception, wrap the handler body in try/catch (and await every promise) so errors become HTTP responses, and check the function's configuration and environment variables in the deployed environment.
```

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

## Outcome reports (0)
_none yet — verify it: POST /api/claims/AN-2026-0721/reports_

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