Head-to-head comparison across 5benchmark categories. Overall scores shown here use BenchLM's provisional ranking lane.
Claude Opus 4.5
80
GPT-5.5
89
Verified leaderboard positions: Claude Opus 4.5 #7 · GPT-5.5 #2
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
+19.3 difference
Coding
+7.3 difference
Reasoning
+20.6 difference
Knowledge
+0.2 difference
Multimodal
+1.6 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, 89 to 80. 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 82.7%. 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, 89 to 80. The biggest single separator in this matchup is Terminal-Bench 2.0, where the scores are 59.3% and 82.7%.
GPT-5.5 has the edge for knowledge tasks in this comparison, averaging 66.4 versus 66.2. Inside this category, 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, SWE-bench Pro 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. Claude Opus 4.5 stays close enough that the answer can still flip depending on your workload.
GPT-5.5 has the edge for agentic tasks in this comparison, averaging 81.8 versus 62.5. Inside this category, MCP Atlas is the benchmark that creates the most daylight between them.
Claude Opus 4.5 has the edge for multimodal and grounded tasks in this comparison, averaging 70.6 versus 69. Inside this category, MMMU-Pro is the benchmark that creates the most daylight between them.
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