# PR Title
Implement shared compact split and unified tool-call diff layout
---
Fixes#268
# PR Description
## Summary
This PR makes tool-call diffs more compact in both `Unified` and `Split`
views by reducing wasted horizontal space in line-number gutters and
content indentation.
## What changed
- introduced a shared compact-diff framework for tool-call diffs
- kept mobile-specific policy limited to:
- forcing unified mode below the breakpoint
- enabling wrap only in mobile unified mode
- added mode-specific compact applicators in the diff viewer:
- unified applicator
- split applicator
- reduced gutter width waste by measuring rendered line-number text and
tightening column width around it
- removed unnecessary right-side content padding
- aligned `+` / `-` markers closer to the left edge across both views
- simplified cleanup after gatekeeper review by removing extra plumbing
and residue
## Screenshots
### Before
<img width="581" height="341" alt="image"
src="https://github.com/user-attachments/assets/ec47b256-749a-4afc-8879-aaf33f0b46b6"
/>
### After
<img width="470" height="586" alt="image"
src="https://github.com/user-attachments/assets/7258a5a2-47c4-408d-84bc-1b497761c7ad"
/>
## Architectural approach
This change intentionally uses:
- shared policy in
`packages/ui/src/components/tool-call/diff-render.tsx`
- shared helper/measurement logic in
`packages/ui/src/components/diff-viewer.tsx`
- mode-specific applicators where unified and split DOM differ
- CSS for shared visual spacing and alignment cleanup
The goal was to keep the implementation architecturally clean and avoid
building separate duplicated compact-diff features for:
- mobile vs desktop
- unified vs split
Instead, the feature shares one compact-diff concept and only diverges
where the upstream diff DOM requires separate handling.
## Files changed
- `packages/ui/src/components/tool-call/diff-render.tsx`
- `packages/ui/src/components/diff-viewer.tsx`
- `packages/ui/src/styles/messaging/tool-call.css`
- `packages/ui/src/types/message.ts`
## Validation
Manual validation was performed in the running UI.
Verified manually:
- compact unified gutters on mobile
- compact unified gutters on desktop
- compact split gutters on desktop
- tighter operator alignment in both modes
Also verified:
- `npm run typecheck` passes
## Notes
- This PR is intended to address the compact diff layout problem
described in the related issue.
- Diff-specific CSS still lives in `tool-call.css`; future extraction
into a smaller dedicated stylesheet is possible but not required for
this change.
---------
Co-authored-by: Shantur Rathore <i@shantur.com>
4f236ce36f