Grok 4.20 Beta 0309 Reasoning
SpaceXSI
Key facts · verified Oct 29, 2026
Grok 4.20 Beta 0309 Reasoning is a SpaceXSI model. Its API price is $1.25 per million input tokens and $2.50 per million output tokens (under 200k prompt tokens; $2.50 / $5.00 at 200k and above). Its context window is 1M tokens. It ranks #47 on LMArena's text leaderboard (Elo 1472, read 1 Nov 2026). Source: docs.x.ai.
Grok 4.20 Beta 0309 Reasoning is the beta checkpoint of SpaceXSI's Grok 4.20 reasoning model; xAI's API lists the model as grok-4.20-0309-reasoning with a 1M-token context window. xAI prices it at $1.25 per million input tokens and $2.50 per million output tokens for prompts under 200k tokens, with higher rates at 200k and above. On LMArena's text leaderboard: 1472 Elo (rank 47).
Pricing & specs checkedSource: vendor documentation · checked Oct 29, 2026LMArena: 1472 Elo (rank 47) · source · retrieved Nov 1, 2026
Full Specifications
$1.25 / $2.50 per million tokens | |
|---|---|
| Identity | |
| Developer | SpaceXSI |
| Status | Beta checkpoint; served on the xAI API as GA grok-4.20-0309-reasoning. |
| Licence | Proprietary |
| Self-hostable | No |
| Cost | |
| Blended $/1M tokensinput × 0.75 + output × 0.25 | $1.563 / 1M tokens |
| Input price | $1.250 / 1M tokens |
| Output price | $2.500 / 1M tokens |
| Capacity | |
| Context window | 1M tokens |
| Measured quality | |
| LMArena Elo | 1472 (checked Nov 2026) |
| LMArena rank | Rank 47 |
| Elo per dollarLMArena Elo ÷ blended $/1M tokens | 942 |