Diff Lifecycle

Tauren's session diff system tracks file changes by session. It is separate from Git and exists to make agent work reviewable.

Main files

• src/diff/sessionDiffController.ts owns controller integration, session-file binding, snapshot restore/save, refresh dedupe, and state posting.
• src/diff/sessionDiffTracker.ts owns changed-line baselines, net line diff stats, reconstructed per-file snapshot diffs, and edit/write fallback diffs.
• src/diff/sessionDiffViewer.ts owns read-only virtual snapshot documents and the VS Code multi-file diff adapter.
• src/diff/sessionDiffUri.ts owns Tauren diff URI helpers.
• src/diff/sessionDiffStorage.ts owns storage and file-watcher helpers.

Why not just Git diff

Git diff answers: "What differs from Git history?"

Tauren session diff answers: "What changed during this session?"

Those are related but not identical, especially with background sessions, resumed sessions, generated files, or unrelated local edits.

Tracking model

The tracker maintains per-session baselines and reconstructs diffs from observed file state. Tool edit/write records provide fallback detail when available.

The viewer presents those snapshots through read-only virtual documents so VS Code can display a normal diff UI.

Contributor guidance

• Keep Git integration separate from session-diff tracking.
• Do not replace the sidebar counter or session changes view with raw git diff.
• Keep the current VS Code diff adapter isolated so a future custom annotated diff UI can replace it later.
• Add tests for tracker behavior when changing diff reconstruction logic.

Verification

For diff changes, verify:

• fresh session edits,
• resumed sessions,
• write tool output,
• edit tool output,
• deleted or renamed files where applicable,
• background session changes,
• unsupported or generated files.