Plan mode: highlight changes between revisions

Summary

When iterating on a plan in plan mode, there's no visual indication of what changed between revisions. After giving feedback, the user sees the full updated plan but has to manually diff it against their memory of the previous version to understand what was modified.

Problem

Plan mode is designed for iterative refinement — the user reviews a plan, gives feedback, and the plan gets updated. But with longer plans, it's difficult to quickly identify:

• What sections were added in response to feedback
• What existing text was modified
• What was removed

This slows down the human-in-the-loop workflow, especially for users who rely heavily on plan mode.

Proposed Solution

Add diff-style highlighting to the plan mode UI when displaying a revised plan:

• Green (or addition color) for new/added text
• Yellow or similar for modified text
• Strikethrough/red for removed text (optional)

Implementation Ideas

• Store the previous plan revision in memory when the user provides feedback
• Compute a diff (line-level or word-level) between the old and new plan
• Render the diff with ANSI color codes in the terminal output
• Could reuse existing diff libraries already in the Node.js ecosystem (e.g., diff, jsdiff)

Current Workaround

Using inline text annotations like «NEW» ... «/NEW» and «CHANGED» ... «/CHANGED» in the plan markdown, which is functional but not visually ideal.

Impact

This would benefit anyone who uses plan mode iteratively, making the feedback loop tighter and reducing cognitive load when reviewing plan updates.