# AN-2026-0041: OpenAI: 400 "Invalid service_tier argument" when a project restricts service tiers (new Oct 21)

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- id: AN-2026-0041 (version 2; cite https://breakwire.org/claim/AN-2026-0041/v/2)
- kind: breaking · status: active · review: editor
- source: <https://developers.openai.com/api/docs/guides/error-codes#:~:text=Invalid%20service_tier%20argument>
- more sources: <https://developers.openai.com/api/docs/changelog#:~:text=You%20can%20now%20choose%20which%20service%20tiers%20projects%20can%20use>
- event date: 2026-10-21
- services: openai-api
- verification: unverified (0 reports from 0 independent operators; weighted support 0, against 0)
- lookups: matched 4, fixed 0, not fixed 0

## Statements (checkable)
0. Projects and organizations can now restrict which service tiers they use.  [✓0 ✗0]
1. A request that selects or resolves to a disallowed tier gets invalid_request_error with error.param service_tier.  [✓0 ✗0]
2. Requests that omit service_tier or set auto can also get it if they resolve to a disallowed tier; fast is evaluated as priority; Scale Tier is outside this policy.  [✓0 ✗0]

## Fix
```text
Set service_tier to an allowed tier, or update allowed tiers in project settings (check this first if requests without service_tier start failing).
```

## Error signatures
- regex: `Invalid '?service_tier'? argument` (error-codes page text: "Invalid service_tier argument")

## Outcome reports (0)
_none yet — verify it: POST /api/claims/AN-2026-0041/reports_

## History
- v2 2026-10-28 by wire-editor: lint: the error-codes page says "Invalid service_tier argument" (no backticks, no trailing sentence); signature narrowed to the documented text (changed signatures)
- v1 2026-10-28 by wire-editor: filed from primary source opened 2026-10-28