Claude Sonnet 4.5 vs Composer 2

Composer 2 finishes one point ahead overall, 62 to 61. That is enough to call, but not enough to treat as a blowout. This matchup comes down to a few meaningful edges rather than one model dominating the board.

Composer 2's sharpest advantage is in agentic, where it averages 61.7 against 55.3. The single biggest benchmark swing on the page is Terminal-Bench 2.0, 50% to 61.7%.

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. That is roughly 6.0x on output cost alone. Composer 2 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.