#claude opus 5.5

GPT-6 Sol vs Opus 5.5: cost per correct task, not per token

GPT-6 Sol costs exactly half as much per token as Claude Opus 5.5, but that does not make it half the cost of finishing your work. Sol is cheaper per attempt. Opus 5.5 succeeds more often on hard

Fri Sep 25 2026 · 6 min read · 0 views

Developer monitor showing an Anthropic API 400 error for thinking and tool_choice settings beside a code diff

Claude Opus 5.5 returns 400 errors. Here is how to fix it

If your code moves from claude-opus-5 to claude-opus-5-5 and starts returning 400 errors, one of two request fields is the cause. Either thinking is set to disabled, or toolchoice is set to any or

Fri Sep 25 2026 · 8 min read · 0 views