Grok 4 Fast vs Kimi K2-Thinking-0905: Specs & Benchmark Comparison
| Characteristic | Grok 4 Fast | Kimi K2-Thinking-0905 |
|---|---|---|
| Company | xAI | Moonshot AI |
| Release Date | August 27, 2025 | September 4, 2025 |
| Parameters | — | 1.0T |
| Multimodal | Yes | No |
| Context (input) | 2.0M | 262K |
| Context (output) | 30K | 66K |
| Input Price / 1M | $0.20 | $0.60 |
| Output Price / 1M | $0.50 | $2.40 |
| Average Score | 0.8 | 0.9 |
| Benchmarks | ||
| AIME 2025 | 0.9 | 1.0 |
| HMMT 2025 | 0.9 | 1.0 |
| GPQA | 0.9 | 0.8 |
Visual Benchmark Comparison
Grok 4 Fast
Kimi K2-Thinking-0905
AIME 20250.9 vs 1.0
0.9
1.0
HMMT 20250.9 vs 1.0
0.9
1.0
GPQA0.9 vs 0.8
0.9
0.8
Verdict
Grok 4 Fast leads in 2 out of 4 comparison categories.
Overall Performance
Both models show comparable average scores: Grok 4 Fast — 0.8, Kimi K2-Thinking-0905 — 0.9.
API Cost
Grok 4 Fast is 4.3x cheaper: input $0.20/1M vs $0.60/1M tokens.
Context Window
Grok 4 Fast supports a larger context: 2M vs 262K tokens.
Recency
Both models were released around the same time: 8/27/2025 and 9/4/2025.
More About These Models
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Frequently Asked Questions
Which is better for coding — Grok 4 Fast or Kimi K2-Thinking-0905?
Direct comparison on the SWE-Bench benchmark is not available. We recommend reviewing other metrics on the comparison page.
Which model is cheaper — Grok 4 Fast or Kimi K2-Thinking-0905?
Grok 4 Fast is cheaper for input: $0.20 per 1M tokens vs $0.60.
Which has a larger context window — Grok 4 Fast or Kimi K2-Thinking-0905?
Grok 4 Fast supports a larger context: 2,000,000 tokens vs 262,144.
The Grok 4 Fast and Kimi K2-Thinking-0905 comparison is updated for 2026. Data includes benchmark results, API pricing, context window size and other specifications. For more detailed information, visit the Grok 4 Fast or Kimi K2-Thinking-0905 page. See also the complete list of AI model comparisons.