Auto-compact warning is nearly invisible — needs color/styling customization

Problem

The "Context left until auto-compact: XX%" warning message is displayed in such a dim, low-contrast style that it's effectively invisible — especially when running multiple terminal windows simultaneously. Auto-compaction is one of the most impactful events in a Claude Code session (potential context loss, background task disconnection, workflow disruption), yet its warning is the quietest element on screen.

Current Behavior

• The warning appears in dim/muted text somewhere in the terminal
• No color customization, no bold, no ANSI styling options
• Users must actively hunt for it across multiple terminal windows
• By the time you notice it, auto-compact may have already fired

Requested Behavior

At minimum, one or more of:

1. Make the warning visually prominent by default — red, bold, or high-contrast text as context usage increases (similar to how battery warnings escalate on mobile devices)
2. Allow settings.json customization of the warning's appearance — ANSI color codes, bold, threshold for when styling changes
3. Expose a hook or notification type (e.g., context_warning) that fires at configurable thresholds, so users can trigger custom alerts (sound, toast notification, custom status line update, etc.)
4. Allow threshold configuration — CLAUDE_AUTOCOMPACT_PCT_OVERRIDE exists but isn't documented well. A proper settings.json field like autoCompactWarningThreshold would be cleaner.

Why This Matters

Power users who:

• Run multiple Claude Code sessions simultaneously
• Use custom status lines and hooks for workflow automation
• Rely on pre-compaction summaries to preserve context
• Have background tasks (file watchers, etc.) that disconnect on compaction

...need adequate warning to prepare. The current implementation treats auto-compaction as a minor footnote when it's actually a major session event.

Context

• Multiple related issues exist (#11819, #14160, #12297, #12995) requesting compaction threshold customization — all closed as not planned
• The PreCompact hook helps but only fires AFTER the decision to compact, not as an early warning
• Custom status lines (via settings.json statusLine) can show context %, but they're a workaround for what should be a first-class feature
• This is arguably an accessibility concern — dim text on terminal backgrounds is hard to read for many users

Environment

• Windows 11, multiple terminal windows
• Claude Code with custom statusLine, hooks, and background watchers
• Heavy daily usage with frequent compaction cycles

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Session: Tank (0894)