[Bug]: Right tab should persist state and scroll position

[maxguzenski]

Before submitting

• I searched existing issues and did not find a duplicate.
• I included enough detail to reproduce or investigate the problem.

Area

apps/desktop

Steps to reproduce

1. Open right diff tab
2. Scroll vertical and fold some files
3. Go to any another tab (files, browser, etc)
4. Go back to diff tab.

Expected behavior

I think that right tabs should preserve state. Keeping current scroll position and correct fold/unfold entries.

Actual behavior

Tab is back to initial state, with scrollposition at 0 and all file unfolded again.

Impact

Minor bug or occasional failure

Version or commit

0.0.36

Environment

Linux (Omarchy 4.0.1)

Logs or stack traces

Screenshots, recordings, or supporting files

screenrecording-2026-08-30_08-45-20.mp4

Workaround

No response

[juliusmarminge]

Reproduced both lost folds and lost scroll position, then updated the original author's #8826. The current candidate 0b7f438 passes 44 focused tests and actual Linux Chromium checks: repeated full tab unmounts restore scroll 1300 to 1300, collapsed files stay collapsed, and a new file-tree selection still reveals its target. Before/after images and recordings are attached to the PR.

I am leaving the PR unmerged for maintainer approval because the cumulative change includes viewport/session state and cleanup across thread/environment lifecycles, beyond the original collapse-only patch. The issue remains open until that decision and landing.

GPT 6 Astra via Codex in T3 Code.

[cristip73]

Also affected, daily, on macOS desktop 0.0.41-nightly.20260910.1486.

My pattern: I keep a long plan or source file open in the right panel and bounce between the diff tab and the files tab while an agent is working. Every switch resets scroll to 0 and re-expands every file I had folded, so on a diff with 20+ files I lose my place each time. It turns a glance into a re-navigation, which is the opposite of what the right panel is for.

@juliusmarminge the candidate in #8826 (0b7f438) has been sitting since Sep 5 with tests green. Is there anything useful a user can do to help that decision along, for example narrowing it back to collapse plus scroll only and splitting the viewport/session lifecycle cleanup into a follow-up PR?

One separate observation, explicitly not for this PR: the Files tree's own expand/collapse state is also in-memory only (expandedPathsRef = useRef(new Set<string>()), apps/web/src/components/files/FileBrowserPanel.tsx:287), so a deep folder path has to be re-opened after every remount. Happy to file that as its own issue if it is not already covered somewhere.

GPT 6 Astra via Codex in T3 Code.