fix(chat): align scrollbar/keyboard detach with wheel/touch re-engage threshold

[waleedlatif1]

Summary

• Follow-up to fix(chat): keep autoscroll pinned when the virtualizer re-scrolls during streaming #5093. That PR's onScroll detach branch set only stickyRef.current = false, leaving userDetachedRef false — so a scrollbar-drag or keyboard detach kept the lenient 30px (STICK_THRESHOLD) re-engage threshold instead of the strict 5px (REATTACH_THRESHOLD) used after wheel/touch.
• Consequence: a programmatic react-virtual re-pin landing within 30px of the bottom could snap autoscroll back on right after the user deliberately scrolled away — the same spurious re-engagement fix(chat): keep autoscroll pinned when the virtualizer re-scrolls during streaming #5093 fixes in the other direction.
• Fix: reuse the existing detach() helper in that branch so every detach path sets userDetachedRef consistently. One line.

Type of Change

• Bug fix

Testing

Verified in headless Chromium against the exact onScroll logic: after a scrollbar-drag detach, a re-pin landing 20px from the bottom (within 30px, outside 5px) no longer re-engages (it did before this change); genuine return to within 5px still re-engages. tsc clean, biome clean.

Checklist

• Code follows project style guidelines
• Self-reviewed my changes
• Tests added/updated and passing
• No new warnings introduced
• I confirm that I have read and agree to the terms outlined in the Contributor License Agreement (CLA)

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1 Skipped Deployment

Project	Deployment	Actions	Updated (UTC)
docs	Skipped		Jun 16, 2026 6:39am

[cursor]

PR Summary

Low Risk
Single-line behavior fix in chat auto-scroll detach logic; no auth, data, or API surface changes.

Overview
Fixes inconsistent auto-scroll detach behavior in use-auto-scroll when the user scrolls up via the scrollbar or keyboard.

The onScroll detach branch previously only cleared stickyRef, leaving userDetachedRef false. That meant re-attach still used the lenient 30px STICK_THRESHOLD instead of the strict 5px REATTACH_THRESHOLD used after wheel/touch detaches. A programmatic virtualizer re-pin within 30px of the bottom could wrongly turn auto-scroll back on after the user had intentionally scrolled away.

The branch now calls the shared detach() helper (same as wheel/touch), so both refs update and detached users must return within 5px to re-engage.

^{Reviewed by Cursor Bugbot for commit caf77ad. Configure here.}

[greptile-apps]

Greptile Summary

This is a one-line follow-up bug fix to PR #5093. The onScroll detach branch (which handles scrollbar-drag and keyboard-initiated upward scrolls) was calling stickyRef.current = false directly instead of the shared detach() helper, leaving userDetachedRef.current as false. This caused subsequent re-engagement checks to use the lenient STICK_THRESHOLD (30 px) instead of the stricter REATTACH_THRESHOLD (5 px), which could let a react-virtual programmatic re-pin within 30 px silently snap auto-scroll back on after a deliberate user scroll-away.

• Fix: replaces the bare stickyRef.current = false in the onScroll else-if branch with the existing detach() call, which also sets userDetachedRef.current = true, making all four detach paths (wheel, touch, scrollbar drag, keyboard) consistent.
• Scope: single line, no new API surface, no behavioral change for wheel/touch detaches (they already called detach() directly).

Confidence Score: 5/5

Safe to merge — the change is a one-line correction to a clearly identified inconsistency between detach paths.

The only code touched is the else-if branch inside onScroll that was the sole remaining caller not using the shared detach() helper. All four detach paths now set both refs identically. The fix introduces no new logic and cannot regress wheel or touch detaches, which already went through detach(). The re-engagement condition is unchanged; only the threshold used after a scrollbar/keyboard detach tightens from 30px to 5px, which is the intended behavior documented throughout the hook.

No files require special attention.

Important Files Changed

Filename	Overview
apps/sim/hooks/use-auto-scroll.ts	Single-line fix: replaces bare stickyRef.current = false with detach() in the onScroll upward-scroll branch, ensuring userDetachedRef is set on all detach paths so the strict REATTACH_THRESHOLD is honored after scrollbar/keyboard detaches.

_{Reviews (1): Last reviewed commit: "fix(chat): align scrollbar/keyboard deta..." | Re-trigger Greptile}