Claude Opus 4.5 vs Step 3.7 Flash

Pick Claude Opus 4.5 if you want the stronger benchmark profile. Step 3.7 Flash only becomes the better choice if agentic is the priority or you want the cheaper token bill.

Claude Opus 4.5 is clearly ahead on the provisional aggregate, 76 to 72. The gap is large enough that you do not need to squint at the spreadsheet to see the difference.

Claude Opus 4.5's sharpest advantage is in coding, where it averages 65.9 against 56.3. The single biggest benchmark swing on the page is SWE-bench Pro, 57.1% to 56.3%. Step 3.7 Flash does hit back in agentic, so the answer changes if that is the part of the workload you care about most.

Claude Opus 4.5 is also the more expensive model on tokens at $5.00 input / $25.00 output per 1M tokens, versus $0.20 input / $1.15 output per 1M tokens for Step 3.7 Flash. That is roughly 21.7x on output cost alone. Step 3.7 Flash 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. Step 3.7 Flash gives you the larger context window at 256K, compared with 200K for Claude Opus 4.5.