Grok 4 Fast Chat
SpaceXSI
Key facts · verified Oct 29, 2026
Grok 4 Fast Chat is a SpaceXSI model released on 19 Sept 2025. It was retired on 15 May 2026. Its last listed API price was $3 per million input tokens and $15 per million output tokens. Its context window is 256K tokens. It ranks #135 on LMArena's text leaderboard (Elo 1418, read 4 Nov 2026). Source: docs.x.ai.
Grok 4 Fast Chat is the non-reasoning Grok 4 Fast model from SpaceXSI, which was available on the xAI API as grok-4-fast-non-reasoning until 15 May 2026. xAI retired it on that date and redirects requests to Grok 4.3 at no reasoning effort. LMArena listed it at $3 per million input tokens and $15 per million output tokens, with a 256K-token context window. On LMArena's text leaderboard: 1418 Elo (rank 135, reasoning effort).
Pricing & specs checkedSource: vendor documentation · checked Oct 29, 2026LMArena: 1418 Elo (rank 135, reasoning effort) · source · retrieved Nov 4, 2026
Full Specifications
$3 / $15 per million tokens | |
|---|---|
| Identity | |
| Developer | SpaceXSI |
| Released | Sep 2025 |
| Retired | 15 May 2026 |
| Status | Retired. xAI retired grok-4-fast-non-reasoning on 15 May 2026 at 12:00 PM PT; requests redirect to grok-4.3 (reasoning effort none) and are billed at grok-4.3 rates. |
| Licence | Proprietary |
| Self-hostable | No |
| Cost | |
| Blended $/1M tokensinput × 0.75 + output × 0.25 | $6.000 / 1M tokens |
| Input price | $3.000 / 1M tokens |
| Output price | $15.000 / 1M tokens |
| Capacity | |
| Context window | 256K tokens |
| Measured quality | |
| LMArena Elo | 1418 (checked Nov 2026) |
| LMArena rank | Rank 135 |
| Elo per dollarLMArena Elo ÷ blended $/1M tokens | 236 |