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Grok 4 Fast (Reasoning)

Retired

Retired from xAI API on 2026-05-15 12:00 PM PT; redirects to grok-4.3 with 'low' reasoning effort, slug still resolves. Specs/pricing no longer on docs; left null. (Oracle OCI mirror lists deprecated 2026-05-15, retires 2026-08-15 on their platform, but the xAI-native retirement date is 2026-05-15.)

Grok 4 Fast (Reasoning) by xAI is tracked live in our LLM catalog. It has been retired (shut down 15 May 2026); the recommended migration is Grok 4.3.

Last verified: 13 Aug 2026 · sourced from official provider documentation

Lifecycle warning

This model has been retired. Scheduled shutdown: 15 May 2026. Recommended migration: Grok 4.3.

Read the Grok 4 Fast (Reasoning) migration guide → replacement & cheapest alternatives

Provider
xAI
Status
Retired
Input price
—
Output price
—
Cached input
—
Blended price
—
Context window
—
Max output
—
Modality
text-in, image-in, text-out
Open weights
No — API only
Knowledge cutoff
—
Released
—
API string
grok-4-fast-reasoning

Source: xAI official documentation ↗

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FAQ

Grok 4 Fast (Reasoning) — questions & answers

Is Grok 4 Fast (Reasoning) still available?

Grok 4 Fast (Reasoning) has been retired and is no longer available. Its scheduled shutdown date is 15 May 2026. The recommended migration is Grok 4.3.

Does Grok 4 Fast (Reasoning) support image or vision input?

Yes — Grok 4 Fast (Reasoning) accepts image input. Listed modalities: text-in, image-in, text-out.

Can I self-host Grok 4 Fast (Reasoning)?

No — Grok 4 Fast (Reasoning) is proprietary. Its weights are not publicly released, so it is available only through xAI's API (or hosted partners), not for self-hosting.

What is the API model string for Grok 4 Fast (Reasoning)?

The API model identifier for Grok 4 Fast (Reasoning) is "grok-4-fast-reasoning" when calling xAI's API.