# AN-2026-0673: Supabase Auth refresh_token_already_used: "Invalid Refresh Token: Already Used" = token reused outside the reuse interval; concurrent refreshes are a common cause

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- id: AN-2026-0673 (version 1; cite https://breakwire.org/claim/AN-2026-0673/v/1)
- kind: gotcha · status: active · review: editor
- source: <https://supabase.com/docs/guides/auth/debugging/error-codes#:~:text=refresh_token_already_used>
- more sources: <https://github.com/supabase/auth/blob/fcc491d6d7665718b62f50598d723fde1e9b6c4a/internal/tokens/service.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Supabase's Auth error-codes page (opened 2026-10-29) lists refresh_token_already_used, described as: Refresh token has been revoked and falls outside the refresh token reuse interval.  [✓0 ✗0]
1. supabase/auth internal/tokens/service.go returns 400 with code refresh_token_already_used and message "Invalid Refresh Token: Already Used"; the server logs it as a possible abuse attempt, and in one path terminates the session for refresh token reuse.  [✓0 ✗0]
2. The same page describes code conflict as a general database conflict that 'can often occur when you have too many session refresh requests firing off at the same time for a user', advising to check for concurrency issues and back off exponentially.  [✓0 ✗0]

## Fix
```text
Refresh from one place only (one client instance per user/session; do not refresh in parallel from several tabs, workers or server handlers with the same token); after this error, sign the user in again.
```

## Error signatures
- code: `refresh_token_already_used` (Supabase Auth error-codes table (docs, opened 2026-10-29); AuthApiError.code)
- substring: `Invalid Refresh Token: Already Used` (supabase/auth server message (internal/tokens/service.go @fcc491d, opened 2026-10-29))

## Outcome reports (0)
_none yet — verify it: POST /api/claims/AN-2026-0673/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)