Model comparison
Claude Sonnet 4.5 vs Kimi K2.5 (Reasoning)
Head-to-head evidence from 6 shared benchmark results across 5 categories. Overall scores shown here use the public BenchAlign v5 ranking lane.
Public leaderboard positions: Claude Sonnet 4.5 #96 (Estimated); Kimi K2.5 (Reasoning) #57 (Estimated). Intervals and evidence labels describe ranking uncertainty, not a guarantee for a specific workload.
Evidence parity. Claude Sonnet 4.5 and Kimi K2.5 (Reasoning) share 6 comparable benchmark results. 3 of 8 categories are comparable. 6 results are unique to Claude Sonnet 4.5; 21 to Kimi K2.5 (Reasoning).
Updated July 20, 2026- Shared results
- 6
- Claude Sonnet 4.5 only
- 6
- Kimi K2.5 (Reasoning) only
- 21
- Comparable categories
- 3 / 8
Pick Kimi K2.5 (Reasoning) if you want the stronger benchmark profile. Claude Sonnet 4.5 only becomes the better choice if coding is the priority or you need the larger 200K context window.
Confidence note. This is a partial-evidence comparison with 6 shared benchmark results across 5 evidence categories; 3 of 8 categories currently have scoreable aggregates for both models. Treat the verdict as directional until coverage is more balanced.
Why this result
Kimi K2.5 (Reasoning) is clearly ahead on the BenchAlign aggregate, 59.35 to 53.61. The gap is large enough that you do not need to squint at the spreadsheet to see the difference.
Kimi K2.5 (Reasoning)'s sharpest advantage is in knowledge, where it averages 87.2 against 83.4. The single biggest benchmark swing on the page is GPQA, 83.4% to 87.6%. Claude Sonnet 4.5 does hit back in coding, so the answer changes if that is the part of the workload you care about most.
Claude Sonnet 4.5 is also the more expensive model on tokens at $3.00 input / $15.00 output per 1M tokens, versus $0.60 input / $3.00 output per 1M tokens for Kimi K2.5 (Reasoning). That is roughly 5.0x on output cost alone. Kimi K2.5 (Reasoning) is the reasoning model in the pair, while Claude Sonnet 4.5 is not. That usually helps on harder chain-of-thought-heavy tests, but it can also mean more latency and more token spend in real use. Claude Sonnet 4.5 gives you the larger context window at 200K, compared with 128K for Kimi K2.5 (Reasoning).
Category breakdown
Exact category averages are shown below. Not measured means BenchLM does not have enough sourced public coverage for that model and category.
| Category | Claude Sonnet 4.5 | Δ | Kimi K2.5 (Reasoning) |
|---|---|---|---|
| Knowledge | Claude Sonnet 4.583.4 | Margin→ 3.8 | Kimi K2.5 (Reasoning)87.2 |
| Coding | Claude Sonnet 4.577.2 | Margin← 0.4 | Kimi K2.5 (Reasoning)76.8 |
| Agentic | Claude Sonnet 4.555.4 | Margin← 0.4 | Kimi K2.5 (Reasoning)55.0 |
| Reasoning | Claude Sonnet 4.513.6 | MarginNo overlap | Kimi K2.5 (Reasoning)Not measured |
| Math | Claude Sonnet 4.511.2 | MarginNo overlap | Kimi K2.5 (Reasoning)Not measured |
| Multimodal | Claude Sonnet 4.5Not measured | MarginNo overlap | Kimi K2.5 (Reasoning)78.5 |
Decisive benchmark drivers
The largest measured benchmark gaps in this matchup, with exact reported values.
More
- Source ↗
GPQA
KnowledgeA 83.4%B 87.6%Winner: Kimi K2.5 (Reasoning)Δ 4.2GPQA: Claude Sonnet 4.5 scored 83.4%; Kimi K2.5 (Reasoning) scored 87.6%. Kimi K2.5 (Reasoning) wins this benchmark. - Source ↗
Terminal-Bench 2.0
AgenticA 50%B 50.8%Winner: Kimi K2.5 (Reasoning)Δ 0.8Terminal-Bench 2.0: Claude Sonnet 4.5 scored 50%; Kimi K2.5 (Reasoning) scored 50.8%. Kimi K2.5 (Reasoning) wins this benchmark. - Source ↗
SWE-bench Verified
CodingA 77.2%B 76.8%Winner: Claude Sonnet 4.5Δ 0.4SWE-bench Verified: Claude Sonnet 4.5 scored 77.2%; Kimi K2.5 (Reasoning) scored 76.8%. Claude Sonnet 4.5 wins this benchmark.
Operational comparison
Runtime and commercial metrics are compared only when both models have a complete sourced value.
| Metric | Claude Sonnet 4.5 | Kimi K2.5 (Reasoning) | Comparison |
|---|---|---|---|
| Input / output priceUSD per 1M tokens | Claude Sonnet 4.5$3 input / $15 output | Kimi K2.5 (Reasoning)$0.6 input / $3 output | Kimi K2.5 (Reasoning) has the lower combined listed price. |
| Generation speedtokens per second | Claude Sonnet 4.5Not available | Kimi K2.5 (Reasoning)Not available | A complete speed comparison is not available. |
| First-answer latencyseconds to first token | Claude Sonnet 4.5Not available | Kimi K2.5 (Reasoning)Not available | A complete latency comparison is not available. |
| Context windowmaximum listed tokens | Claude Sonnet 4.5200K | Kimi K2.5 (Reasoning)128K | Claude Sonnet 4.5 lists the larger context window. |
Benchmark Deep Dive
AgenticClaude Sonnet 4.5 wins11 benchmarks
| Benchmark | Claude Sonnet 4.5 | Kimi K2.5 (Reasoning) | Result |
|---|---|---|---|
| Terminal-Bench 2.0Source | 50% | 50.8% | Kimi K2.5 (Reasoning) leads |
| OSWorld-VerifiedSource | 61.4% | — | Not comparable |
| VITA-BenchSource | 17.0% | — | Not comparable |
| Gert LabsSource | 48.51% | 32.58% | Claude Sonnet 4.5 leads |
| JobBenchSource | 27.7% | — | Not comparable |
| BrowseCompSource | — | 60.6% | Not comparable |
| APEX-Agents-AASource | — | 11.5% | Not comparable |
| τ²-bench resultsSource | — | 95.9% | Not comparable |
| AA Agentic IndexSource | — | 21.7% | Not comparable |
| GDPval-AASource | — | 25.4% | Not comparable |
| GDPval-AASource | — | 1009 | Not comparable |
CodingClaude Sonnet 4.5 wins4 benchmarks
Reasoning3 benchmarks
KnowledgeKimi K2.5 (Reasoning) wins8 benchmarks
| Benchmark | Claude Sonnet 4.5 | Kimi K2.5 (Reasoning) | Result |
|---|---|---|---|
| GPQASource | 83.4% | 87.6% | Kimi K2.5 (Reasoning) leads |
| MMLU-ProSource | — | 87.1% | Not comparable |
| Artificial Analysis Intelligence IndexSource | — | 35.4% | Not comparable |
| AA-GPQA DiamondSource | — | 87.9% | Not comparable |
| AA-HLESource | — | 29.4% | Not comparable |
| AA-Omniscience IndexSource | — | -8.1% | Not comparable |
| AA-Omniscience AccuracySource | — | 34.3% | Not comparable |
| AA-Omniscience Hallucination RateSource | — | 64.6% | Not comparable |
Math3 benchmarks
Multimodal3 benchmarks
Inst. Following1 benchmarks
| Benchmark | Claude Sonnet 4.5 | Kimi K2.5 (Reasoning) | Result |
|---|---|---|---|
| AA-IFBenchSource | — | 70.2% | Not comparable |
Frequently Asked Questions (4)
Which is better, Claude Sonnet 4.5 or Kimi K2.5 (Reasoning)?
Kimi K2.5 (Reasoning) is ahead on BenchLM's BenchAlign leaderboard, 59.35 to 53.61. The biggest single separator in this matchup is GPQA, where the scores are 83.4% and 87.6%.
Which is better for knowledge tasks, Claude Sonnet 4.5 or Kimi K2.5 (Reasoning)?
Kimi K2.5 (Reasoning) has the edge for knowledge tasks in this comparison, averaging 87.2 versus 83.4. Inside this category, GPQA is the benchmark that creates the most daylight between them.
Which is better for coding, Claude Sonnet 4.5 or Kimi K2.5 (Reasoning)?
Claude Sonnet 4.5 has the edge for coding in this comparison, averaging 77.2 versus 76.8. Inside this category, SWE-bench Verified is the benchmark that creates the most daylight between them.
Which is better for agentic tasks, Claude Sonnet 4.5 or Kimi K2.5 (Reasoning)?
Claude Sonnet 4.5 has the edge for agentic tasks in this comparison, averaging 55.4 versus 55. Inside this category, Gert Labs is the benchmark that creates the most daylight between them.
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