Claude Mythos 5.1 is the stronger all-rounder.Claude Opus 5 is cheaper.
Scores updated · 16 tests both models report · How we compare
Where each one wins
Tests won in each of the two areas where both have results. Each piece is one test, so a longer bar means more evidence; grey means the two scored within a point of each other.
What it costs
Prices per million tokens, roughly 750,000 words. The bars show the cost of a million tokens read plus a million written.
Claude Opus 5 costs 50% less for the same work.
The biggest differences
The tests each model wins by the widest margin, up to three each. Scores are out of 100.
Where Claude Mythos 5.1 pulls ahead
- Very hard expert questions across many subjectsHumanity's Last Exam+6points ahead
- Long, multi-file coding tasks in real codebasesSWE-bench Pro+2points ahead
Where Claude Opus 5 pulls ahead
No clear win on a test scored out of 100.
Every test, side by side
All 16 tests both models report. The winning score is in its model's colour; marks a score checked independently.
CodingClaude Mythos 5.1
- SWE-bench ProClaude Mythos 5.1 by 281.279.2+2
- SWE-bench Multilingualtie89.189.5tie
ReasoningClaude Mythos 5.1
- Humanity's Last ExamClaude Mythos 5.1 by 660.954.9+6
- ARC-AGI-2tie9090.4tie
Other results12 tests, not counted
Tests outside the eight areas. They are not counted above: several are summary scores built from other tests, or the same test under another name.
- Terminal-Bench-Science 0.1Claude Mythos 5.1 by 23.652.629+23.6
- Terminal-Bench 4.0Claude Mythos 5.1 by 9.160.951.8+9.1
- SWE-bench MultimodalClaude Opus 5 by 4.754.759.4+4.7
- GDPval-AA v2Claude Mythos 5.1 by 29 rating points18531824+29 rating
- OSWorld 2.0 (partial)Claude Mythos 5.1 by 2.577.975.4+2.5
- HealthBench ProfessionalClaude Mythos 5.1 by 2.362.159.8+2.3
- Program BenchClaude Mythos 5.1 by 2.287.685.4+2.2
- OSWorld 2.0 (strict)Claude Mythos 5.1 by 2.141.739.6+2.1
- ProteinGym HardClaude Mythos 5.1 by 1.649.347.7+1.6
- DeepSWE 1.1Claude Opus 5 by 1.467.468.8+1.4
- HLE (with tools)Claude Mythos 5.1 by 1.46563.6+1.4
- ARC-AGI-1tie97.597.5tie
Questions people ask
Which is better, Claude Mythos 5.1 or Claude Opus 5?
Claude Mythos 5.1 wins all two areas where both have results: coding and reasoning. Claude Opus 5 wins none, but costs 50% less.
Which is better for coding?
Claude Mythos 5.1. It wins 1 of the 2 coding tests both models report; Claude Opus 5 wins none, and 1 is a tie.
Which is cheaper?
Claude Mythos 5.1 costs $10.00 per million input tokens and $50.00 per million output tokens; Claude Opus 5 costs $5.00 and $25.00. That makes Claude Opus 5 about 50% cheaper for the same work.
How do you compare the two?
We use the 16 benchmark tests both models have published scores on. The verdict counts the 4 tests in the eight capability areas, and a gap under one point (ten on rating-style scales) counts as a tie. The other 12 are listed but not counted, because several are summary scores or repeat a test. Each score is the one shown on the model's own page.