Model comparison
Claude Sonnet 4.5 Thinking vs Grok 4 Fast (Reasoning)
Head-to-head evidence from 1 shared benchmark result across 1 category. Overall scores shown here use the public BenchAlign v5 ranking lane.
Public leaderboard positions: Claude Sonnet 4.5 Thinking unranked (Not scored); Grok 4 Fast (Reasoning) #76 (Supported). Intervals and evidence labels describe ranking uncertainty, not a guarantee for a specific workload.
Evidence parity. Claude Sonnet 4.5 Thinking and Grok 4 Fast (Reasoning) share 1 comparable benchmark result. 0 of 8 categories are comparable. 1 result is unique to Claude Sonnet 4.5 Thinking; 12 to Grok 4 Fast (Reasoning).
Updated July 23, 2026- Shared results
- 1
- Claude Sonnet 4.5 Thinking only
- 1
- Grok 4 Fast (Reasoning) only
- 12
- Comparable categories
- 0 / 8
Benchmark data for Claude Sonnet 4.5 Thinking and Grok 4 Fast (Reasoning) is coming soon on BenchLM.
Confidence note. This is a partial-evidence comparison with 1 shared benchmark result across 1 evidence category; 0 of 8 categories currently have scoreable aggregates for both models. Treat the verdict as directional until coverage is more balanced.
Why this result
BenchLM has partial data for these models, but not enough overlapping benchmark coverage to produce a fair score-level comparison yet.
Grok 4 Fast (Reasoning) has the larger context window at 2M, compared with 200K for Claude Sonnet 4.5 Thinking.
Category breakdown
Exact category averages are shown below. Not measured means BenchLM does not have enough sourced public coverage for that model and category.
Operational comparison
Runtime and commercial metrics are compared only when both models have a complete sourced value.
| Metric | Claude Sonnet 4.5 Thinking | Grok 4 Fast (Reasoning) | Comparison |
|---|---|---|---|
| Input / output priceUSD per 1M tokens | Claude Sonnet 4.5 ThinkingNot available | Grok 4 Fast (Reasoning)Not available | A complete price comparison is not available. |
| Generation speedtokens per second | Claude Sonnet 4.5 ThinkingNot available | Grok 4 Fast (Reasoning)Not available | A complete speed comparison is not available. |
| First-answer latencyseconds to first token | Claude Sonnet 4.5 ThinkingNot available | Grok 4 Fast (Reasoning)Not available | A complete latency comparison is not available. |
| Context windowmaximum listed tokens | Claude Sonnet 4.5 Thinking200K | Grok 4 Fast (Reasoning)2M | Grok 4 Fast (Reasoning) lists the larger context window. |
Benchmark Deep Dive
Agentic1 benchmarks
| Benchmark | Claude Sonnet 4.5 Thinking | Grok 4 Fast (Reasoning) | Result |
|---|---|---|---|
| τ²-bench resultsSource | — | 65.8% | Not comparable |
Coding2 benchmarks
Reasoning2 benchmarks
Knowledge6 benchmarks
| Benchmark | Claude Sonnet 4.5 Thinking | Grok 4 Fast (Reasoning) | Result |
|---|---|---|---|
| Artificial Analysis Intelligence IndexSource | — | 27.4% | Not comparable |
| AA-GPQA DiamondSource | — | 84.7% | Not comparable |
| AA-HLESource | — | 17.0% | Not comparable |
| AA-Omniscience IndexSource | — | -28.4% | Not comparable |
| AA-Omniscience AccuracySource | — | 22.6% | Not comparable |
| AA-Omniscience Hallucination RateSource | — | 66.0% | Not comparable |
Multimodal2 benchmarks
Inst. Following1 benchmarks
| Benchmark | Claude Sonnet 4.5 Thinking | Grok 4 Fast (Reasoning) | Result |
|---|---|---|---|
| AA-IFBenchSource | — | 50.5% | Not comparable |
Frequently Asked Questions (2)
Can I compare Claude Sonnet 4.5 Thinking and Grok 4 Fast (Reasoning) on BenchLM yet?
Not fully yet. BenchLM is tracking both models, but the sourced benchmark breakdown for this comparison is still coming soon.
Why does this comparison show “coming soon”?
BenchLM only shows category winners and benchmark-level calls when we have sourced results that can be compared fairly. For these models, the public benchmark coverage is not complete enough yet.
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