Model comparison
Claude Opus 5.5 vs Kimi K2 (Jul 2025)
Claude Opus 5.5 is the stronger model overall, scoring 68.6 to 41.2 on the Noometry Index. Kimi K2 (Jul 2025) costs 8.0× less per token, which makes it the better buy when Claude Opus 5.5's lead doesn't matter for your workload.
Last verified . 17 shared benchmarks.
Summary
- They share 17 benchmarks with published results for both. Claude Opus 5.5 scores higher in 9 categories and Kimi K2 (Jul 2025) in 0 categories; 9 gaps are clear of the uncertainty.
- The widest gap is in reasoning, where Claude Opus 5.5 leads 80.2 to 23.3.
- Kimi K2 (Jul 2025) is cheaper at $0.57 / $2.30 per million input/output tokens, against $4 / $20 for Claude Opus 5.5.
- Claude Opus 5.5 accepts more context: 1M tokens versus 262K.
- Kimi K2 (Jul 2025) has downloadable open weights; the other is API-only.
Side by side
| Claude Opus 5.5 | Kimi K2 (Jul 2025) | |
|---|---|---|
| Provider | Anthropic | Moonshot AI |
| Noometry Index | 68.6 | 41.2 |
| Released | 2026-09-22 | 2025-07-12 |
| Weights | Proprietary | Open |
| Context window | 1M | 262K |
| Max output | 128K | 262K |
| Input $ / M tokens | $4 | $0.57 |
| Output $ / M tokens | $20 | $2.30 |
| Results tracked | 44 | 42 |
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Category by category
Coding Claude Opus 5.5 leads
Claude Opus 5.5: 71.9 (#3), Kimi K2 (Jul 2025): 42.4 (#102)
| Benchmark | Claude Opus 5.5 | Kimi K2 (Jul 2025) |
|---|---|---|
| LMArena Coding | 1547 | 1399 |
| ALE-Bench | 2,147 | 597.5 |
| FrontierCode | 54.6% | — |
| SWE-bench Verified (bash only) | — | 63.4% |
| Aider Polyglot | — | 59.1% |
| CursorBench | 57.8% | — |
| LMArena WebDev | 1813 | — |
| FrontierSWE | 62.3% | — |
| SciCode | 66.9% | — |
| GSO | — | 4.9% |
| WeirdML | — | 42.8% |
| MirrorCode | 77.4% | — |
Agentic & Tool Use Claude Opus 5.5 leads
Claude Opus 5.5: 45.3 (#15), Kimi K2 (Jul 2025): 32.4 (#64)
| Benchmark | Claude Opus 5.5 | Kimi K2 (Jul 2025) |
|---|---|---|
| Terminal-Bench | — | 35.7% |
| APEX-Agents | 73.5% | — |
| Berkeley Function Calling Leaderboard | — | 59.1% |
| GDP.pdf | 30.6% | — |
| METR Time Horizons | — | 59.2% |
| Vending-Bench 2 | 9,235 | — |
Reasoning Claude Opus 5.5 leads
Claude Opus 5.5: 80.2 (#3), Kimi K2 (Jul 2025): 23.3 (#179)
| Benchmark | Claude Opus 5.5 | Kimi K2 (Jul 2025) |
|---|---|---|
| LMArena Hard Prompts | 1535 | 1384 |
| Epoch Capabilities Index | 167.33 | 146.01 |
| ARC-AGI-2 | 93.3% | — |
| SimpleBench | — | 26.3% |
| Kagi LLM Benchmark | — | 64.4% |
| NYT Connections (extended) | 88.5% | — |
| ARC-AGI-1 | 98.5% | — |
| CritPt | 31.7% | — |
| EBR-Bench | 71.4% | — |
| Mystery Game Puzzles | 71% | — |
| DTBench | 98.9% | — |
| LMCA | 68.2% | — |
| ForecastBench | — | 60.2 |
Math Claude Opus 5.5 leads
Claude Opus 5.5: 91.8 (#3), Kimi K2 (Jul 2025): 42.7 (#83)
| Benchmark | Claude Opus 5.5 | Kimi K2 (Jul 2025) |
|---|---|---|
| LMArena Math | 1506 | 1397 |
| FrontierMath (Tiers 1-3) | 91.2% | — |
| FrontierMath Tier 4 | 95% | — |
| OTIS Mock AIME 2024-2025 | 100% | — |
| ProofBench | 100% | — |
| Omni-MATH | — | 65.4% |
| FrontierMath (Feb 2025 set) | — | 21.4% |
| FrontierMath Erdős | 2.9% | — |
| FrontierMath Tier 4 (v1) | — | 0% |
Knowledge Claude Opus 5.5 leads
Claude Opus 5.5: 66.4 (#10), Kimi K2 (Jul 2025): 37.3 (#157)
| Benchmark | Claude Opus 5.5 | Kimi K2 (Jul 2025) |
|---|---|---|
| LMArena Expert | 1547 | 1365 |
| GPQA Diamond | 90.6% | — |
| SimpleQA Verified | 72.2% | — |
| MMLU-Pro | — | 81.9% |
| Confabulations | — | 20.4% |
| Vectara Hallucination Rate | — | 17.9% |
| GPQA (HELM) | — | 65.3% |
Multimodal Not comparable
Claude Opus 5.5: 57.8 (#1), Kimi K2 (Jul 2025): —
| Benchmark | Claude Opus 5.5 | Kimi K2 (Jul 2025) |
|---|---|---|
| LMArena Vision | 1321 | — |
| Blueprint-Bench 2 | 51.2% | — |
| Furniture Assembly | 83.3% | — |
Multilingual Claude Opus 5.5 leads
Claude Opus 5.5: 59.1 (#2), Kimi K2 (Jul 2025): 49.6 (#130)
| Benchmark | Claude Opus 5.5 | Kimi K2 (Jul 2025) |
|---|---|---|
| LMArena Non-English | 1507 | 1372 |
| LMArena Chinese | 1588 | 1415 |
| LMArena French | 1514 | 1379 |
| LMArena Russian | 1520 | 1385 |
| LMArena Spanish | 1507 | 1386 |
| LMArena German | — | 1387 |
| LMArena Japanese | — | 1349 |
| LMArena Korean | — | 1325 |
Instruction Following Claude Opus 5.5 leads
Claude Opus 5.5: 80.0 (#3), Kimi K2 (Jul 2025): 71.1 (#156)
| Benchmark | Claude Opus 5.5 | Kimi K2 (Jul 2025) |
|---|---|---|
| LMArena Instruction Following | 1537 | 1348 |
| IFEval | — | 85% |
Long Context Claude Opus 5.5 leads
Claude Opus 5.5: 47.1 (#19), Kimi K2 (Jul 2025): 41.2 (#145)
| Benchmark | Claude Opus 5.5 | Kimi K2 (Jul 2025) |
|---|---|---|
| LMArena Longer Query | 1532 | 1353 |
| Fiction.LiveBench | — | 66.7% |
| CL-bench | — | 17.6% |
Writing & Preference Claude Opus 5.5 leads
Claude Opus 5.5: 78.2 (#3), Kimi K2 (Jul 2025): 62.3 (#78)
| Benchmark | Claude Opus 5.5 | Kimi K2 (Jul 2025) |
|---|---|---|
| LMArena Text | 1515 | 1380 |
| LMArena Creative Writing | 1533 | 1350 |
| EQ-Bench Creative Writing | 2050 | 1666 |
| LMArena Multi-Turn | 1499 | 1371 |
| Short-Story Creative Writing | — | 85.6% |
| WildBench | — | 86.2% |
Frequently asked questions
Is Claude Opus 5.5 better than Kimi K2 (Jul 2025)?
Claude Opus 5.5 is the stronger model overall, scoring 68.6 to 41.2 on the Noometry Index. Kimi K2 (Jul 2025) costs 8.0× less per token, which makes it the better buy when Claude Opus 5.5's lead doesn't matter for your workload.
Which is cheaper, Claude Opus 5.5 or Kimi K2 (Jul 2025)?
Kimi K2 (Jul 2025) is cheaper. It lists at $0.57 per million input tokens and $2.30 per million output tokens; Claude Opus 5.5 lists at $4 and $20.
Is Claude Opus 5.5 or Kimi K2 (Jul 2025) better for coding?
Claude Opus 5.5 scores higher on coding benchmarks: 71.9 versus 42.4 in the Noometry coding category.
Which has the bigger context window?
Claude Opus 5.5 does, with 1M tokens against 262K.
How many benchmarks do Claude Opus 5.5 and Kimi K2 (Jul 2025) share?
17 benchmarks have published results for both models. Claude Opus 5.5 has 44 scored results on Noometry and Kimi K2 (Jul 2025) has 42.