Head-to-head comparison across 5benchmark categories. Overall scores shown here use BenchLM's provisional ranking lane.
Claude Opus 4.5
76
GPT-5.5
91
Verified leaderboard positions: Claude Opus 4.5 #13 · GPT-5.5 #5
Pick GPT-5.5 if you want the stronger benchmark profile. Claude Opus 4.5 only becomes the better choice if coding is the priority or you want the cheaper token bill.
Agentic
+19.0 difference
Coding
+7.3 difference
Reasoning
+20.6 difference
Knowledge
+0.2 difference
Multimodal
+0.4 difference
Claude Opus 4.5
GPT-5.5
$5 / $25
$5 / $30
46 t/s
N/A
1.01s
N/A
200K
1M
Pick GPT-5.5 if you want the stronger benchmark profile. Claude Opus 4.5 only becomes the better choice if coding is the priority or you want the cheaper token bill.
GPT-5.5 is clearly ahead on the provisional aggregate, 91 to 76. The gap is large enough that you do not need to squint at the spreadsheet to see the difference.
GPT-5.5's sharpest advantage is in reasoning, where it averages 85 against 64.4. The single biggest benchmark swing on the page is Terminal-Bench 2.0, 59.3% to 82%. Claude Opus 4.5 does hit back in coding, so the answer changes if that is the part of the workload you care about most.
GPT-5.5 is also the more expensive model on tokens at $5.00 input / $30.00 output per 1M tokens, versus $5.00 input / $25.00 output per 1M tokens for Claude Opus 4.5. GPT-5.5 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. GPT-5.5 gives you the larger context window at 1M, compared with 200K for Claude Opus 4.5.
GPT-5.5 is ahead on BenchLM's provisional leaderboard, 91 to 76. The biggest single separator in this matchup is Terminal-Bench 2.0, where the scores are 59.3% and 82%.
GPT-5.5 has the edge for knowledge tasks in this comparison, averaging 66.4 versus 66.2. Inside this category, AA-HLE is the benchmark that creates the most daylight between them.
Claude Opus 4.5 has the edge for coding in this comparison, averaging 65.9 versus 58.6. Inside this category, Terminal-Bench Hard is the benchmark that creates the most daylight between them.
GPT-5.5 has the edge for reasoning in this comparison, averaging 85 versus 64.4. Inside this category, CritPt is the benchmark that creates the most daylight between them.
GPT-5.5 has the edge for agentic tasks in this comparison, averaging 81.5 versus 62.5. Inside this category, GDPval-AA is the benchmark that creates the most daylight between them.
GPT-5.5 has the edge for multimodal and grounded tasks in this comparison, averaging 70.4 versus 70. Inside this category, MMMU-Pro is the benchmark that creates the most daylight between them.
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