On macOS, trackpad-scrolling quickly to the end of a long chat thread stops dead instead of rubber-banding the way Safari, Notes and other Mac apps do. This happens in the desktop app and in Chrome on Mac.
Two things stop the bounce in Chromium, and the fix needs both:
webPreferences.scrollBounce (its scroll_bounce_flag.patch gates IsElasticOverscrollSupported on the renderer's --scroll-bounce switch). The main window now sets scrollBounce: true on macOS, following the disableAutoHideCursor pattern next to it.overscroll-behavior for every scroller, though, and drops the stretch when that is none. html, body { overscroll-behavior: none } (added for iOS safe areas in #2392) therefore turned the bounce off everywhere. On fine-pointer devices the vertical axis is now contain. Touch-primary devices keep none against page bounce and pull-to-refresh. The horizontal axis stays none so swipe navigation stays off.The page itself still can't bounce: body overflow: hidden makes the viewport not user-scrollable, which Chromium checks before stretching the root.
Fixes pingdotgg/t3code#29019
vp run check:changed: format, lint, knip, typecheck (3 packages) and apps/desktop/src/window/DesktopWindow.test.ts (22 tests) all pass.patches/chromium/scroll_bounce_flag.patch.cc/input/input_handler.cc passes ActiveTree().overscroll_behavior() with each scroll result.blink/.../elastic_overscroll_controller.cc zeroes the stretch without local border effects.cc/base/features.cc has kOverscrollEffectOnNonRootScrollers enabled by default.overscroll-behavior: contain scroller, and the root set to none, auto and contain.Input.synthesizeScrollGesture (mouse and touch), and chrome.gpuBenchmarking touchpad gestures, with and without scrollBounce and --enable-features=ElasticOverscroll.cannot-verify macos. On a Mac:scrollBounce windows can't use Electron's spare renderer.Model and harness: Claude Opus 5.5 (Claude Code in T3 Code), reviews by GPT-6.1 Sol (Codex) and Claude Opus 5.5.
🤖 Generated with Claude Code
Added 4 commits
Verdict: Needs Human Approval
Macroscope's review found this PR requires human approval — This enables macOS desktop scroll bounce and changes vertical overscroll behavior for fine-pointer web users. Human review is needed to confirm the new default scrolling experience and its broader web scope.
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[gpt-6.1-sol][Codex] on behalf of shivam.
Issue watch started a separate investigation of https://github.com/pingdotgg/t3code/issues/29019. I found this PR and am handing that work over to Julius, with no competing changes.
The initial source search at main commit 4a5251b1c4b867ad2d89bf59d7a062ca8c40f2a6 found document-level overscroll-behavior: none in apps/web/src/index.css and overscroll-y-contain on the chat timeline in MessagesTimeline.tsx. No runtime reproduction, device testing, or checks were started before discovering the takeover. The macOS bounce remains unverified by this investigation.
No actionable comments were generated in the recent review.
e2fffbea-704e-430e-a696-798d729138f9Reviewing files that changed from the base of the PR and between 4a5251b1c4b867ad2d89bf59d7a062ca8c40f2a6 and 33ca649d051540db7eaca72e5622870a8acfcce9.
apps/desktop/src/window/DesktopWindow.tsapps/web/src/index.cssIncluded review availability: This review used your included allowance. Your plan provides up to 10 included reviews per hour; 6 remain after this review.
macOS desktop windows now enable Electron scroll bounce. Fine-pointer devices use contained vertical overscroll on html and body. Other pointer types and horizontal overscroll behavior remain unchanged.
Changes: Scroll overscroll behavior
| Layer / File(s) | Summary |
|---|---|
Platform-specific overscroll settings apps/desktop/src/window/DesktopWindow.ts, apps/web/src/index.css | The main window enables scrollBounce on macOS. A fine-pointer media rule sets vertical overscroll behavior to contain on html and body. |
Estimated code review effort: 2 (Simple) | ~8 minutes
Change: Bug fix · Severity of issue fixed: Medium
Suggested reviewers: t3dotgg
33ca6No actionable merge-blocking issue was identified. macOS gesture behavior still needs the planned manual check.
| Check name | Status | Explanation |
|---|---|---|
| Title check | Passed | The title names the fix (chat scrolling rubber-banding on macOS) and the desktop scope. The changeset enables scrollBounce for the macOS main window in DesktopWindow.ts and adds fine-pointer overscrol… |
| Description check | Passed | The description follows the template. It has Problem, Change, Scope and approval, and Verification sections. The Problem section states the expected behavior and the environment. The Change section ex… |
| Linked Issues check | Passed | Issue #29019 requires rubber-band scrolling for long chat threads in the desktop app. The macOS main window now passes scrollBounce: true to Electron. The web document keeps horizontal overscroll di… |
| Out of Scope Changes check | Passed | The changes stay within issue #29019. The apps/web CSS change is required by the stated Chromium behavior and affects the renderer used by the desktop app. The macOS-only Electron option limits the … |
Explanation
The title names the fix (chat scrolling rubber-banding on macOS) and the desktop scope. The changeset enables scrollBounce for the macOS main window in DesktopWindow.ts and adds fine-pointer overscroll-behavior-y: contain in index.css, which together target that bounce. The title is short, specific, and follows the conventional commit form the template asks for. It covers the desktop part but not the web CSS part, which is expected for a title.
Explanation
The description follows the template. It has Problem, Change, Scope and approval, and Verification sections. The Problem section states the expected behavior and the environment. The Change section explains both the desktop and web causes and why both edits are needed. Scope links issue #29019. Verification lists the tests run, the Linux reproduction attempts with their results, and the macOS manual steps that remain unverified. The description also names what was not checked. Two template points are weaker: the Scope section links an issue but does not show a maintainer approval comment, and no before/after screenshot or recording is included. The UI-change template asks for these, but the bug is motion-related and the author states it cannot be reproduced on Linux, so the gap is minor. The model and harness line is present.
Explanation
Issue #29019 requires rubber-band scrolling for long chat threads in the desktop app. The macOS main window now passes scrollBounce: true to Electron. The web document keeps horizontal overscroll disabled and changes vertical overscroll to contain for fine-pointer devices. The existing body { overflow: hidden } remains unchanged. These changes address the reported desktop behavior. The PR also reports passing typecheck, lint, format, and 22 desktop window tests.
Explanation
The changes stay within issue #29019. The apps/web CSS change is required by the stated Chromium behavior and affects the renderer used by the desktop app. The macOS-only Electron option limits the native change to the affected platform. No unrelated product behavior or unrelated files were changed.
Thanks, Julius, for the earlier investigation and fix. Closing this as a duplicate of #29047 by @electrum, which addresses the same macOS desktop bounce and includes a real Mac trackpad verification. This older PR has had no push or reply in over a week, and main has changed both files since its base. If Chrome browser bounce remains important separately, a focused follow-up would be welcome.