Head-to-head comparison across 1benchmark categories. Overall scores shown here use BenchLM's provisional ranking lane.
Claude Sonnet 4.5
65
Composer 2.5
82
Pick Composer 2.5 if you want the stronger benchmark profile. Claude Sonnet 4.5 only becomes the better choice if you would rather avoid the extra latency and token burn of a reasoning model.
Agentic
+14.0 difference
Claude Sonnet 4.5
Composer 2.5
$3 / $15
$0.5 / $2.5
N/A
N/A
N/A
N/A
200K
200K
Pick Composer 2.5 if you want the stronger benchmark profile. Claude Sonnet 4.5 only becomes the better choice if you would rather avoid the extra latency and token burn of a reasoning model.
Composer 2.5 is clearly ahead on the provisional aggregate, 82 to 65. The gap is large enough that you do not need to squint at the spreadsheet to see the difference.
Composer 2.5's sharpest advantage is in agentic, where it averages 69.3 against 55.3. The single biggest benchmark swing on the page is Terminal-Bench 2.0, 50% to 69.3%.
Claude Sonnet 4.5 is also the more expensive model on tokens at $3.00 input / $15.00 output per 1M tokens, versus $0.50 input / $2.50 output per 1M tokens for Composer 2.5. That is roughly 6.0x on output cost alone. Composer 2.5 is the reasoning model in the pair, while Claude Sonnet 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.
Composer 2.5 is ahead on BenchLM's provisional leaderboard, 82 to 65. The biggest single separator in this matchup is Terminal-Bench 2.0, where the scores are 50% and 69.3%.
Composer 2.5 has the edge for agentic tasks in this comparison, averaging 69.3 versus 55.3. Inside this category, Terminal-Bench 2.0 is the benchmark that creates the most daylight between them.
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