Model comparison
Claude Mythos Preview vs Claude Opus 4.5
Claude Opus 4.5 has enough public results to be ranked (#47); Claude Mythos Preview does not yet, so treat this comparison as directional.
Last verified . 1 shared benchmarks.
Summary
- They share 1 benchmark with published results for both. Claude Mythos Preview scores higher in 0 categories and Claude Opus 4.5 in 1 category; one gap is clear of the uncertainty.
- The widest gap is in agentic & tool use, where Claude Opus 4.5 leads 47.3 to 41.4.
Side by side
| Claude Mythos Preview | Claude Opus 4.5 | |
|---|---|---|
| Provider | Anthropic | Anthropic |
| Noometry Index | 41.2 | 50.5 |
| Released | 2026-04-07 | 2025-11-01 |
| Weights | Proprietary | Proprietary |
| Context window | — | 200K |
| Max output | — | 64K |
| Input $ / M tokens | — | $5 |
| Output $ / M tokens | — | $25 |
| Results tracked | 2 | 69 |
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Category by category
Coding Not comparable
Claude Mythos Preview: —, Claude Opus 4.5: 54.8 (#27)
| Benchmark | Claude Mythos Preview | Claude Opus 4.5 |
|---|---|---|
| SWE-bench Verified | — | 76.7% |
| SWE-bench Verified (bash only) | — | 76.8% |
| LMArena WebDev | — | 1494 |
| SWE-bench Multilingual | — | 70.7% |
| GSO | — | 26.5% |
| WeirdML | — | 63.7% |
| LMArena Coding | — | 1504 |
| ALE-Bench | — | 1,025 |
| AlgoTune | — | 1.77 |
Agentic & Tool Use Claude Opus 4.5 leads
Claude Mythos Preview: 41.4, Claude Opus 4.5: 47.3 (#12)
| Benchmark | Claude Mythos Preview | Claude Opus 4.5 |
|---|---|---|
| METR Time Horizons | 85.2% | 75% |
| Terminal-Bench | — | 63.1% |
| Berkeley Function Calling Leaderboard | — | 77.5% |
| GDPval | — | 45.5% |
| Remote Labor Index | — | 3.8% |
| τ²-bench Airline | — | 84% |
| τ²-bench Banking | — | 24.7% |
| τ²-bench Retail | — | 79.6% |
| τ²-bench Telecom | — | 92.3% |
| Cybench | — | 82% |
| DeepResearch Bench | — | 54.8% |
| OSWorld | — | 66.3% |
| BALROG | — | 43.5% |
| ExploitBench | 73.8% | — |
| LMArena Search | — | 1180 |
| Vending-Bench 2 | — | 4,967 |
Reasoning Not comparable
Claude Mythos Preview: —, Claude Opus 4.5: 42.6 (#51)
| Benchmark | Claude Mythos Preview | Claude Opus 4.5 |
|---|---|---|
| ARC-AGI-2 | — | 37.6% |
| SimpleBench | — | 62% |
| Kagi LLM Benchmark | — | 80.2% |
| NYT Connections (extended) | — | 52.5% |
| ARC-AGI-1 | — | 80% |
| Chess Puzzles | — | 12% |
| EnigmaEval | — | 11.9% |
| EBR-Bench | — | 14.3% |
| LMArena Hard Prompts | — | 1476 |
| Mystery Game Puzzles | — | 22% |
| DTBench | — | 89.9% |
| LMCA | — | 44.5% |
| Epoch Capabilities Index | — | 150.09 |
| ForecastBench | — | 60.7 |
Math Not comparable
Claude Mythos Preview: —, Claude Opus 4.5: 38.6 (#132)
| Benchmark | Claude Mythos Preview | Claude Opus 4.5 |
|---|---|---|
| FrontierMath (Tiers 1-3) | — | 34.4% |
| FrontierMath Tier 4 | — | 4.9% |
| OTIS Mock AIME 2024-2025 | — | 86.1% |
| ProofBench | — | 36% |
| LMArena Math | — | 1463 |
| FrontierMath (Feb 2025 set) | — | 20.7% |
| FrontierMath Tier 4 (v1) | — | 4.2% |
Knowledge Not comparable
Claude Mythos Preview: —, Claude Opus 4.5: 56.5 (#44)
| Benchmark | Claude Mythos Preview | Claude Opus 4.5 |
|---|---|---|
| GPQA Diamond | — | 86% |
| Humanity's Last Exam | — | 25.2% |
| SimpleQA Verified | — | 45.7% |
| Vectara Hallucination Rate | — | 10.9% |
| LMArena Expert | — | 1487 |
Multimodal Not comparable
Claude Mythos Preview: —, Claude Opus 4.5: 31.4 (#107)
| Benchmark | Claude Mythos Preview | Claude Opus 4.5 |
|---|---|---|
| GeoBench | — | 75% |
| VPCT | — | 40% |
| Furniture Assembly | — | 28.3% |
| LMArena Document | — | 1462 |
Multilingual Not comparable
Claude Mythos Preview: —, Claude Opus 4.5: 54.3 (#47)
| Benchmark | Claude Mythos Preview | Claude Opus 4.5 |
|---|---|---|
| LMArena Non-English | — | 1438 |
| LMArena Chinese | — | 1470 |
| LMArena French | — | 1471 |
| LMArena German | — | 1449 |
| LMArena Japanese | — | 1416 |
| LMArena Korean | — | 1424 |
| LMArena Russian | — | 1447 |
| LMArena Spanish | — | 1458 |
Instruction Following Not comparable
Claude Mythos Preview: —, Claude Opus 4.5: 77.5 (#19)
| Benchmark | Claude Mythos Preview | Claude Opus 4.5 |
|---|---|---|
| LMArena Instruction Following | — | 1478 |
Long Context Not comparable
Claude Mythos Preview: —, Claude Opus 4.5: 46.5 (#22)
| Benchmark | Claude Mythos Preview | Claude Opus 4.5 |
|---|---|---|
| CL-bench | — | 21.1% |
| LMArena Longer Query | — | 1480 |
Writing & Preference Not comparable
Claude Mythos Preview: —, Claude Opus 4.5: 68.1 (#28)
| Benchmark | Claude Mythos Preview | Claude Opus 4.5 |
|---|---|---|
| LMArena Text | — | 1451 |
| LMArena Creative Writing | — | 1445 |
| EQ-Bench Creative Writing | — | 1687 |
| LMArena Multi-Turn | — | 1466 |
Frequently asked questions
Is Claude Mythos Preview better than Claude Opus 4.5?
Claude Opus 4.5 has enough public results to be ranked (#47); Claude Mythos Preview does not yet, so treat this comparison as directional.
How many benchmarks do Claude Mythos Preview and Claude Opus 4.5 share?
1 benchmark has published results for both models. Claude Mythos Preview has 2 scored results on Noometry and Claude Opus 4.5 has 69.