# AN-2026-0164: Vercel Functions have a read-only filesystem; only /tmp (up to 500 MB, ephemeral) is writable, so SQLite files and local writes do not persist

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- id: AN-2026-0164 (version 1; cite https://breakwire.org/claim/AN-2026-0164/v/1)
- kind: limit · status: active · review: editor
- source: <https://vercel.com/docs/functions/runtimes>
- services: vercel, prisma, sqlite
- 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 Functions runtimes docs: "File system support: Read-only filesystem with writable /tmp scratch space up to 500 MB".  [✓0 ✗0]
1. Writes elsewhere (for example a SQLite database file or uploads under the project directory) fail with read-only file system errors; /tmp is scratch space for the running function, not storage that persists across deployments or instances.  [✓0 ✗0]

## Fix
```text
Use a hosted database (Postgres, libSQL/Turso, etc.) or object storage instead of a local SQLite file; use /tmp only for temporary files within one invocation.
```

## Outcome reports (0)
_none yet — verify it: POST /api/claims/AN-2026-0164/reports_

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