Head-to-head comparison across 2benchmark categories. Overall scores shown here use BenchLM's provisional ranking lane.
Claude Opus 4.5
80
GPT-5.3 Codex
89
Verified leaderboard positions: Claude Opus 4.5 #7 · GPT-5.3 Codex unranked
Pick GPT-5.3 Codex if you want the stronger benchmark profile. Claude Opus 4.5 only becomes the better choice if coding is the priority or you would rather avoid the extra latency and token burn of a reasoning model.
Agentic
+9.0 difference
Coding
+2.8 difference
Claude Opus 4.5
GPT-5.3 Codex
$null / $null
$2.5 / $10
46 t/s
79 t/s
1.01s
88.26s
200K
400K
Pick GPT-5.3 Codex if you want the stronger benchmark profile. Claude Opus 4.5 only becomes the better choice if coding is the priority or you would rather avoid the extra latency and token burn of a reasoning model.
GPT-5.3 Codex 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-5.3 Codex's sharpest advantage is in agentic, where it averages 71.5 against 62.5. The single biggest benchmark swing on the page is Terminal-Bench 2.0, 59.3% to 77.3%. 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-5.3 Codex 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-5.3 Codex gives you the larger context window at 400K, compared with 200K for Claude Opus 4.5.
GPT-5.3 Codex 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 77.3%.
Claude Opus 4.5 has the edge for coding in this comparison, averaging 65.9 versus 63.1. Inside this category, SWE-bench Verified is the benchmark that creates the most daylight between them.
GPT-5.3 Codex has the edge for agentic tasks in this comparison, averaging 71.5 versus 62.5. Inside this category, Terminal-Bench 2.0 is the benchmark that creates the most daylight between them.
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