Claude Mythos 5.1 is the stronger all-rounder.Claude Sonnet 5 is cheaper.
Scores updated · 12 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.
Reasoning rests on a single test.
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 Sonnet 5 costs 80% 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+19.6points ahead
- Long, multi-file coding tasks in real codebasesSWE-bench Pro+18points ahead
- Fixes real GitHub issues in many programming languagesSWE-bench Multilingual+10.8points ahead
Where Claude Sonnet 5 pulls ahead
No clear win on a test scored out of 100.
Every test, side by side
All 12 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 1881.263.2+18
- SWE-bench MultilingualClaude Mythos 5.1 by 10.889.178.3+10.8
ReasoningClaude Mythos 5.1
- Humanity's Last ExamClaude Mythos 5.1 by 19.660.941.3+19.6
Other results9 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 4.0Claude Mythos 5.1 by 48.560.912.4+48.5
- OSWorld 2.0 (partial)Claude Mythos 5.1 by 35.377.942.6+35.3
- SWE-bench MultimodalClaude Mythos 5.1 by 26.654.728.1+26.6
- GDPval-AA v2Claude Mythos 5.1 by 235 rating points18531618+235 rating
- DeepSWE 1.1Claude Mythos 5.1 by 13.467.454+13.4
- ProteinGym HardClaude Mythos 5.1 by 12.749.336.6+12.7
- Program BenchClaude Mythos 5.1 by 10.387.677.3+10.3
- HLE (with tools)Claude Mythos 5.1 by 7.66557.4+7.6
- HealthBench ProfessionalClaude Mythos 5.1 by 4.362.157.8+4.3
Questions people ask
Which is better, Claude Mythos 5.1 or Claude Sonnet 5?
Claude Mythos 5.1 wins all two areas where both have results: coding and reasoning. Claude Sonnet 5 wins none, but costs 80% less.
Which is better for coding?
Claude Mythos 5.1. It wins 2 of the 2 coding tests both models report; Claude Sonnet 5 wins none.
Which is cheaper?
Claude Mythos 5.1 costs $10.00 per million input tokens and $50.00 per million output tokens; Claude Sonnet 5 costs $2.00 and $10.00. That makes Claude Sonnet 5 about 80% cheaper for the same work.
How do you compare the two?
We use the 12 benchmark tests both models have published scores on. The verdict counts the 3 tests in the eight capability areas, and a gap under one point (ten on rating-style scales) counts as a tie. The other 9 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.