grok-4-1-fast-reasoning vs kimi-k2.5
grok-4-1-fast-reasoning is 3.0× cheaper on input than kimi-k2.5.
| grok-4-1-fast-reasoning | kimi-k2.5 | |
|---|---|---|
| Input / 1M | $0.20 | $0.60 |
| Cached input / 1M | $0.05 | $0.10 |
| Output / 1M | $0.50 | $3.00 |
| Context window | 2M | 262K |
| Max output | 2M | 262K |
| Provider | xAI | Moonshot |
| Vision | Yes | Yes |
| Tool calling | Yes | Yes |
| Token count | estimated | estimated |
Capability for the money
Independent measurement · Artificial Analysis · read 2026-08-11Not the same tier: kimi-k2.5 leads grok-4-1-fast-reasoning by 17.5 points on following instructions (IFBench), for 4.4× the price. They are level on tool use (τ²-bench) and hard reasoning (GPQA Diamond), so the premium only pays off on following instructions work.
Following instructions
extraction, classification, sticking to a format
IFBenchkimi-k2.5 +17.5
Tool use
multi-step agent work against real tools
τ²-benchkimi-k2.5 +2.6
Hard reasoning
graduate-level science and multi-step analysis
GPQA Diamondkimi-k2.5 +2.6
Averaged over the benchmarks both models sat, grok-4-1-fast-reasoning returns 280.4 points of pass rate per dollar of blended price against 70.6 — the ratio that decides whether the dearer model earns its rate.
Each figure is a pass rate: the share of that test set the model answered correctly, measured by a third party rather than self-reported by the lab. Rows are different tests of different difficulty, so compare a model against the other model, not one row against the next. No published coding score for one of these models, so that lens is omitted. And a benchmark is not your workload — it narrows the shortlist, it does not pick for you.
Which to pick
- Cheaper input: grok-4-1-fast-reasoning
- Cheaper output: grok-4-1-fast-reasoning
- Larger context: grok-4-1-fast-reasoning
- Better at following instructions: kimi-k2.5 (52.7% vs 70.2% on IFBench)
- Better at tool use: kimi-k2.5 (93.3% vs 95.9% on τ²-bench)
- Better at hard reasoning: kimi-k2.5 (85.3% vs 87.9% on GPQA Diamond)
List price is not production cost. Output length, cache hit rate, retries and task quality move the real number more than the headline rate does — price your own prompt on the token ledger before deciding.
Related comparisons
grok-4-1-fast-reasoning detail · kimi-k2.5 detail · All xAI pricing · All comparisons