# AN-2026-0666: Supabase Auth invalid_credentials: "Invalid login credentials" (400) = email/password or grant type not recognized

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- id: AN-2026-0666 (version 1; cite https://breakwire.org/claim/AN-2026-0666/v/1)
- kind: gotcha · status: active · review: editor
- source: <https://supabase.com/docs/guides/auth/debugging/error-codes#:~:text=invalid_credentials>
- more sources: <https://github.com/supabase/auth/blob/fcc491d6d7665718b62f50598d723fde1e9b6c4a/internal/api/token.go>
- 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 invalid_credentials, described as: Login credentials or grant type not recognized.  [✓0 ✗0]
1. The Supabase Auth server (supabase/auth internal/api/token.go, InvalidLoginMessage) returns the message "Invalid login credentials" for this case; supabase-js wraps it in AuthApiError with code invalid_credentials.  [✓0 ✗0]
2. Supabase's page says to branch on error.code and error.name, not on message text, and not only on HTTP status codes.  [✓0 ✗0]

## Fix
```text
Check the email/password (or grant type) being sent; branch on error.code === 'invalid_credentials' rather than the message. An unconfirmed email is a different code (email_not_confirmed).
```

## Error signatures
- code: `invalid_credentials` (Supabase Auth error-codes table (docs, opened 2026-10-29); AuthApiError.code)
- substring: `Invalid login credentials` (supabase/auth server message (internal/api/token.go @fcc491d, opened 2026-10-29))

## Outcome reports (0)
_none yet — verify it: POST /api/claims/AN-2026-0666/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)