Fast mode toggle has no billing warning for Max subscribers

Summary

The /fast slash command in Claude Code can be toggled freely from any
subscription tier, but fast mode is actually billed at premium API rates
($30 input / $150 output per MTok — ~6x standard Opus rates) and does not
draw from a Max plan's included usage allocation.

Problem

A Max Pro subscriber can run /fast, see "Fast mode ON," and start
incurring separate pay-as-you-go charges with no in-CLI indication that
they've left their plan's billing umbrella. The behavior is documented on
a separate API docs page, but nothing in Claude Code itself signals it.

Suggested fixes (any one would help)

1. Gate the toggle behind a one-time confirmation dialog the first time

it's enabled on a subscription account: "Fast mode bills at \$30/\$150
per MTok outside your Max plan. Continue?"

1. Show a persistent indicator in the status line while fast mode is on,

noting it's billed separately.

1. Disable /fast entirely for accounts without API billing configured,

with a tooltip explaining why.

Repro

1. Sign in to Claude Code on a Max Pro subscription
2. Run /fast
3. Observe: toggles ON with no billing warning

Environment

• Claude Code CLI on macOS (Darwin 25.1.0)
• Subscription: Claude Max Pro