Mid-session effort switching on Opus 5.5 preserves prompt cache in Claude Code v2.1.280+

lydiahallie · x · 2026-09-23

Lydia Hallie confirms that switching effort levels mid-session on Opus 5.5 no longer invalidates your prompt cache in Claude Code — as long as you're on version v2.1.280 or later.

Practical cost tip for anyone toggling between high reasoning and cheaper modes within a long session.

Related event: Claude Code update keeps prompt cache intact when switching effort(3 posts)→

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