Head-to-head comparison across 4benchmark categories. Overall scores shown here use BenchLM's provisional ranking lane.
Claude Mythos 5
99
GPT-5.4
88
Verified leaderboard positions: Claude Mythos 5 #1 · GPT-5.4 #18
Pick Claude Mythos 5 if you want the stronger benchmark profile. GPT-5.4 only becomes the better choice if you want the cheaper token bill or you need the larger 1.05M context window.
Agentic
+10.0 difference
Coding
+28.2 difference
Knowledge
+8.5 difference
Multimodal
+20.0 difference
Claude Mythos 5
GPT-5.4
$10 / $50
$2.5 / $15
N/A
74 t/s
N/A
151.79s
1M+
1.05M
Pick Claude Mythos 5 if you want the stronger benchmark profile. GPT-5.4 only becomes the better choice if you want the cheaper token bill or you need the larger 1.05M context window.
Claude Mythos 5 is clearly ahead on the provisional aggregate, 99 to 88. The gap is large enough that you do not need to squint at the spreadsheet to see the difference.
Claude Mythos 5's sharpest advantage is in coding, where it averages 85.9 against 57.7. The single biggest benchmark swing on the page is SWE-bench Pro, 80.3% to 57.7%.
Claude Mythos 5 is also the more expensive model on tokens at $10.00 input / $50.00 output per 1M tokens, versus $2.50 input / $15.00 output per 1M tokens for GPT-5.4. That is roughly 3.3x on output cost alone. GPT-5.4 gives you the larger context window at 1.05M, compared with 1M+ for Claude Mythos 5.
Claude Mythos 5 is ahead on BenchLM's provisional leaderboard, 99 to 88. The biggest single separator in this matchup is SWE-bench Pro, where the scores are 80.3% and 57.7%.
Claude Mythos 5 has the edge for knowledge tasks in this comparison, averaging 74.6 versus 66.1. Inside this category, HLE w/o tools is the benchmark that creates the most daylight between them.
Claude Mythos 5 has the edge for coding in this comparison, averaging 85.9 versus 57.7. Inside this category, SWE-bench Pro is the benchmark that creates the most daylight between them.
Claude Mythos 5 has the edge for agentic tasks in this comparison, averaging 87 versus 77. Inside this category, GDPval-AA is the benchmark that creates the most daylight between them.
Claude Mythos 5 has the edge for multimodal and grounded tasks in this comparison, averaging 92.7 versus 72.7. Inside this category, MMMU-Pro is the benchmark that creates the most daylight between them.
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