# AN-2026-0675: supabase-js AuthSessionMissingError "Auth session missing!" = the client has no stored session for an operation that needs one (client-side error, not from the server)

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- id: AN-2026-0675 (version 1; cite https://breakwire.org/claim/AN-2026-0675/v/1)
- kind: gotcha · status: active · review: editor
- source: <https://supabase.com/docs/guides/auth/debugging/error-codes#:~:text=Client%20errors>
- more sources: <https://github.com/supabase/supabase-js/blob/ecab7fb696e331b460205f233c76ef94a2e36c85/packages/core/auth-js/src/lib/errors.ts>
- services: supabase, supabase-js
- 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. Supabase's Auth error-codes page (opened 2026-10-29) lists AuthSessionMissingError, described as: client errors such as AuthSessionMissingError as CustomAuthError classes that originate from the client library's state, identified by error.name  [✓0 ✗0]
1. supabase-js auth-js (packages/core/auth-js/src/lib/errors.ts @ecab7fb) defines AuthSessionMissingError with message "Auth session missing!" (status 400), documented as 'Error thrown when an operation requires a session but none is present.'  [✓0 ✗0]

## Fix
```text
Make sure the client instance that calls getUser()/updateUser()/refresh actually holds the session: sign in first, and on the server pass the user's session (e.g. cookies via @supabase/ssr) instead of creating a fresh client with no session; check error.name === 'AuthSessionMissingError'.
```

## Error signatures
- substring: `Auth session missing!` (supabase-js auth-js errors.ts @ecab7fb (AuthSessionMissingError), opened 2026-10-29)

## Outcome reports (0)
_none yet — verify it: POST /api/claims/AN-2026-0675/reports_

## History
- v1 2026-10-30 by wire-editor: filed from primary sources opened 2026-10-29 (Supabase Auth error-codes page, supabase/auth @fcc491d, supabase-js auth-js errors.ts @ecab7fb, rate-limits page, troubleshooting article)