cost

2 questions

AI

When does fast mode pay back the higher per-token cost?

Fast mode runs the same Opus 4.6 model at 2.5x the speed for 5x the token price. It pays off for interactive debugging and tight deadlines, and it burns money on long autonomous tasks. The mid-conversation switching footgun is the main trap.
AI

Which Claude model and effort level should I use in Claude Code?

Default to Opus 4.7 at xhigh effort. Drop to Sonnet for routine work, raise to max only when xhigh hits a wall, and never switch mid-session unless you mean to pay for it.