fix(web): maintain sidebar scroll position when navigating between chats

[brendan-kellam]

Fixes SOU-1483

The sidebar lives in the @sidebar parallel route slot, whose catch-all segment remounts when navigating between chats (/chat/A → /chat/B). That remount reset the SidebarContent scroll container back to the top each time.

This persists the scroll position in a module-level variable and restores it (via useLayoutEffect, to avoid flicker) whenever SidebarBase remounts, so the sidebar stays where you left it. The value resets on a full page reload.

Summary by CodeRabbit

• Bug Fixes
  • Sidebar scroll position is now preserved when switching between chats, instead of resetting to the top.
  • The sidebar’s “scrolled” visual state is restored correctly after navigation.
• Documentation
  • Updated the changelog under Unreleased to note the sidebar scroll position fix.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: ff4b4d29-88d1-4de7-848b-60faf8a1b04f

📥 Commits

Reviewing files that changed from the base of the PR and between cc29ef0 and 6a20965.

📒 Files selected for processing (1)

• CHANGELOG.md

✅ Files skipped from review due to trivial changes (1)

• CHANGELOG.md

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Walkthrough

This change adds sidebar scroll position persistence across remounts by restoring the saved scroll offset on mount and updating it during scrolling. A changelog entry records the behavior change.

Changes

Sidebar Scroll Persistence

Layer / File(s)	Summary
Scroll persistence implementation packages/web/src/app/(app)/@sidebar/components/sidebarBase.tsx	Adds a module-scoped lastScrollTop variable, updates React imports (ReactNode, useLayoutEffect), adds a useLayoutEffect to restore scroll position on mount and set isScrolled, and updates the scroll handler to persist scroll position.
Changelog entry CHANGELOG.md	Adds a Fixed entry noting sidebar scroll position is maintained when navigating between chats.

Estimated code review effort: 1 (Trivial) | ~5 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly matches the main change: preserving sidebar scroll position when switching chats.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch brendan/sou-1483-maintain-sidebar-scroll-position-when-opening-a-e6d7

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Caution

Some comments are outside the diff and can’t be posted inline due to platform limitations.

⚠️ Outside diff range comments (1)

packages/web/src/app/(app)/@sidebar/components/sidebarBase.tsx (1)

51-91: 🎯 Functional Correctness | 🟠 Major | ⚡ Quick win

Scroll position bleeds across sidebar variants.

lastScrollTop is a single module-level value shared by every mount of SidebarBase. DefaultSidebar and SettingsSidebar (see packages/web/src/app/(app)/@sidebar/components/defaultSidebar/index.tsx and .../settingsSidebar/index.tsx) both render SidebarBase with very different content. Scrolling the chat sidebar, then navigating to settings (or back), restores an unrelated offset from the other variant instead of resetting/restoring correctly for the current one.

Consider keying the stored value by a stable identifier for the sidebar variant (e.g. pathname prefix or a prop) so restoration only applies within the same sidebar type.

💡 Possible approach

-let lastScrollTop = 0;
+const lastScrollTopByKey: Record<string, number> = {};

Then read/write lastScrollTopByKey[variantKey] where variantKey is derived from the sidebar's identity (e.g. a prop passed by DefaultSidebar/SettingsSidebar).

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@packages/web/src/app/`(app)/@sidebar/components/sidebarBase.tsx around lines
51 - 91, The scroll position is stored in a single module-level `lastScrollTop`,
so `SidebarBase` shares one offset across both `DefaultSidebar` and
`SettingsSidebar`. Update `SidebarBase` to scope the saved scroll position by a
stable sidebar identity passed in from its callers (for example a variant key
prop from `defaultSidebar/index.tsx` and `settingsSidebar/index.tsx`), and
read/write that keyed value in the `useLayoutEffect` and scroll listener instead
of the global value. Ensure restoration only happens for the matching sidebar
variant and resets independently for others.

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Outside diff comments:
In `@packages/web/src/app/`(app)/@sidebar/components/sidebarBase.tsx:
- Around line 51-91: The scroll position is stored in a single module-level
`lastScrollTop`, so `SidebarBase` shares one offset across both `DefaultSidebar`
and `SettingsSidebar`. Update `SidebarBase` to scope the saved scroll position
by a stable sidebar identity passed in from its callers (for example a variant
key prop from `defaultSidebar/index.tsx` and `settingsSidebar/index.tsx`), and
read/write that keyed value in the `useLayoutEffect` and scroll listener instead
of the global value. Ensure restoration only happens for the matching sidebar
variant and resets independently for others.

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 469f9424-dcb3-41fc-9b79-f4cdc3be7213

📥 Commits

Reviewing files that changed from the base of the PR and between e706330 and cc29ef0.

📒 Files selected for processing (2)

• CHANGELOG.md
• packages/web/src/app/(app)/@sidebar/components/sidebarBase.tsx