Switching reasoning effort mid-session doesn't break Claude prompt cache on v2.1.280+

MaziyarPanahi · x · 2026-09-23

Replying to Lydia Hallie's finding, MaziyarPanahi notes that switching reasoning effort mid-session on Opus doesn't break your prompt cache, as long as you're on Claude Code v2.1.280+, adding that reasoningeffort belongs in the user's message.

Related event: Switching Effort Mid-Session in Claude Code No Longer Breaks Prompt Cache(4 posts)→

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