Head-to-head comparison across 4benchmark categories. Overall scores shown here use BenchLM's provisional ranking lane.
Claude Mythos Preview
99
Claude Opus 4.5
80
Verified leaderboard positions: Claude Mythos Preview #1 · Claude Opus 4.5 #5
Pick Claude Mythos Preview if you want the stronger benchmark profile. Claude Opus 4.5 only becomes the better choice if you would rather avoid the extra latency and token burn of a reasoning model.
Agentic
+19.9 difference
Coding
+17.9 difference
Knowledge
+8.7 difference
Multimodal
+22.1 difference
Claude Mythos Preview
Claude Opus 4.5
$25 / $125
$null / $null
N/A
46 t/s
N/A
1.01s
1M
200K
Pick Claude Mythos Preview if you want the stronger benchmark profile. Claude Opus 4.5 only becomes the better choice if you would rather avoid the extra latency and token burn of a reasoning model.
Claude Mythos Preview is clearly ahead on the provisional aggregate, 99 to 80. The gap is large enough that you do not need to squint at the spreadsheet to see the difference.
Claude Mythos Preview's sharpest advantage is in multimodal & grounded, where it averages 92.7 against 70.6. The single biggest benchmark swing on the page is HLE, 64.7% to 30.8%.
Claude Mythos Preview is the reasoning model in the pair, while Claude Opus 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 Mythos Preview gives you the larger context window at 1M, compared with 200K for Claude Opus 4.5.
Claude Mythos Preview is ahead on BenchLM's provisional leaderboard, 99 to 80. The biggest single separator in this matchup is HLE, where the scores are 64.7% and 30.8%.
Claude Mythos Preview has the edge for knowledge tasks in this comparison, averaging 74.9 versus 66.2. Inside this category, HLE is the benchmark that creates the most daylight between them.
Claude Mythos Preview has the edge for coding in this comparison, averaging 83.8 versus 65.9. Inside this category, SWE-bench Pro is the benchmark that creates the most daylight between them.
Claude Mythos Preview has the edge for agentic tasks in this comparison, averaging 82.4 versus 62.5. Inside this category, Terminal-Bench 2.0 is the benchmark that creates the most daylight between them.
Claude Mythos Preview has the edge for multimodal and grounded tasks in this comparison, averaging 92.7 versus 70.6. Inside this category, MMMU-Pro is the benchmark that creates the most daylight between them.
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