## Thinking Path
> - Paperclip gives operators a workspace diff plugin so they can
inspect agent changes before review
> - The diff view needs reliable base-ref defaults and controls that
stay usable while scrolling large diffs
> - The working branch mixed those plugin improvements with unrelated
server and cloud work
> - Keeping the workspace diff plugin changes isolated makes them easy
to test and review
> - This pull request polishes the workspace diff plugin controls,
base-ref behavior, and sticky headers
> - The benefit is a more predictable diff review surface for agent
workspaces
## What Changed
- Fixed workspace diff default base-ref resolution.
- Improved split/unified and working-tree/against-ref pane controls.
- Made workspace diff headers stay sticky while scrolling.
- Added a review screenshot at
`screenshots/PAP-9841-workspace-diff.png`.
## Verification
- `pnpm install --frozen-lockfile --ignore-scripts`
- `pnpm --filter @paperclipai/plugin-sdk build`
- `pnpm --filter @paperclipai/plugin-workspace-diff exec vitest run
tests/plugin.spec.ts`
- Result: 9 tests passed.
## Risks
- UI-only plugin branch with low data risk.
- The default base-ref inference should be reviewed against unusual
worktree/upstream combinations.
> For core feature work, check [`ROADMAP.md`](ROADMAP.md) first and
discuss it in `#dev` before opening the PR. Feature PRs that overlap
with planned core work may need to be redirected — check the roadmap
first. See `CONTRIBUTING.md`.
## Model Used
- OpenAI Codex, GPT-5-based coding agent with local shell/git/tool use.
Exact hosted model ID and context-window size are not exposed by the
local Paperclip adapter runtime.
## Checklist
- [x] I have included a thinking path that traces from project context
to this change
- [x] I have specified the model used (with version and capability
details)
- [x] I have checked ROADMAP.md and confirmed this PR does not duplicate
planned core work
- [x] I have run tests locally and they pass
- [x] I have added or updated tests where applicable
- [x] If this change affects the UI, I have included before/after
screenshots
- [x] I have updated relevant documentation to reflect my changes
- [x] I have considered and documented any risks above
- [x] I will address all Greptile and reviewer comments before
requesting merge
---------
Co-authored-by: Paperclip <noreply@paperclip.ing>
Dotta