Head-to-head comparison across 4benchmark categories. Overall scores shown here use BenchLM's provisional ranking lane.
Claude Mythos Preview
99
GPT-5.4
94
Verified leaderboard positions: Claude Mythos Preview #1 · GPT-5.4 #3
Pick Claude Mythos Preview if you want the stronger benchmark profile. GPT-5.4 only becomes the better choice if knowledge is the priority or you want the cheaper token bill.
Agentic
+5.4 difference
Coding
+26.1 difference
Knowledge
+17.9 difference
Multimodal
+11.5 difference
Claude Mythos Preview
GPT-5.4
$25 / $125
$2.5 / $15
N/A
74 t/s
N/A
151.79s
1M
1.05M
Pick Claude Mythos Preview if you want the stronger benchmark profile. GPT-5.4 only becomes the better choice if knowledge is the priority or you want the cheaper token bill.
Claude Mythos Preview is clearly ahead on the provisional aggregate, 99 to 94. 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 coding, where it averages 83.8 against 57.7. The single biggest benchmark swing on the page is SWE-bench Pro, 77.8% to 57.7%. GPT-5.4 does hit back in knowledge, so the answer changes if that is the part of the workload you care about most.
Claude Mythos Preview is also the more expensive model on tokens at $25.00 input / $125.00 output per 1M tokens, versus $2.50 input / $15.00 output per 1M tokens for GPT-5.4. That is roughly 8.3x on output cost alone. GPT-5.4 gives you the larger context window at 1.05M, compared with 1M for Claude Mythos Preview.
Claude Mythos Preview is ahead on BenchLM's provisional leaderboard, 99 to 94. The biggest single separator in this matchup is SWE-bench Pro, where the scores are 77.8% and 57.7%.
GPT-5.4 has the edge for knowledge tasks in this comparison, averaging 92.8 versus 74.9. Inside this category, HLE w/o tools 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 57.7. 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 77. 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 81.2. Inside this category, MMMU-Pro is the benchmark that creates the most daylight between them.
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