[ENHANCEMENT] Checkpoints UX refactor: timeline + restore to any point

[hannesrudolph]

Type

Enhancement

Problem / Value

Checkpoints should be a first-class timeline feature so users can jump/rollback a chat to any point, instead of checkpoint restore being mainly tied to edit/delete flows.

Context

Today, checkpoint restore is primarily presented when editing or deleting a message (with messaging that implies deleting later messages). We want a clearer, more flexible “checkpoints timeline” experience where users can see checkpoints and restore to them directly.

Constraints/Preferences

Keep the UX simple and "one-click restore" oriented.

I've analyzed this issue and here's my proposed implementation plan:

Current State

Currently, checkpoints appear inline with chat messages as checkpoint_saved entries, with restore actions available through a hover menu. The restore UX is primarily tied to edit/delete message flows via CheckpointRestoreDialog.

Proposed Solution: Checkpoint Timeline Dropdown

I propose adding a Timeline Dropdown in the TaskHeader that provides a centralized view of all checkpoints with one-click restore functionality:

1. New Component: CheckpointTimeline.tsx

• A dropdown button with a clock/timeline icon in the TaskHeader
• Lists all checkpoints chronologically with timestamps
• Shows "current" indicator for the active checkpoint
• Each checkpoint entry has:
  • Relative timestamp (e.g., "2 min ago")
  • Quick "Restore" button for one-click restore
  • Optional "View Diff" action

2. UI Integration

• Add the timeline button in TaskHeader.tsx near the context window info
• The dropdown shows checkpoints from clineMessages filtered by say === 'checkpoint_saved'
• Uses existing checkpointRestore message type to trigger restores

3. Backend Changes

• No backend changes needed - leverages existing checkpointRestore and checkpointDiff handlers
• The checkpoint list is already available in clineMessages

4. UX Considerations

• Keep existing inline checkpoint markers for context
• The timeline provides a "bird's eye view" of all checkpoints
• One-click restore with a confirmation step for "Restore Files + Task" (destructive action)
• "Restore Files Only" as the primary/default action (non-destructive preview)

Files to Modify

• webview-ui/src/components/chat/TaskHeader.tsx - Add timeline button
• webview-ui/src/components/chat/checkpoints/CheckpointTimeline.tsx - New component
• webview-ui/src/components/chat/checkpoints/index.ts - Export new component
• Add i18n keys for timeline labels

This approach:

• Maintains simplicity with minimal UI footprint
• Provides "one-click restore" functionality as requested
• Does not require backend changes
• Complements rather than replaces existing checkpoint UX

Please mention @roomote in a comment saying that you approve this plan, and I'll proceed with the implementation.