[juliusmarminge]

Problem

On desktop, a mostly vertical two-finger trackpad scroll can navigate back or forward. If the first ~8px of the scroll lean sideways (e.g. 5px x / 3px y), HistorySwipeNavigation locks onto the horizontal axis. After that it ignores deltaY, so the small sideways drift of a long vertical scroll adds up to the 120px trigger, and releasing the scroll (or its momentum) navigates. Reproduced on main cefb544af3 in the desktop app: a scroll 15° off vertical navigates back, also without momentum, and the mirrored scroll navigates forward.

Change

The gesture now counts total horizontal and vertical travel. Once it has moved 30px, horizontal travel must stay more than twice the vertical travel. If it doesn't, the gesture is dropped: the indicator hides, nothing navigates, and the rest of the gesture is ignored as before. The same check applies when the axis locks, so one large diagonal event cannot lock and navigate. Below 30px the direction is still noise, so swipes whose first events lean diagonally still navigate.

Scope and approval

Fixes #30160

Verification

• vp test run apps/web/src/components/HistorySwipeNavigation.browser.test.tsx apps/web/src/components/HistorySwipeNavigation.test.ts: 17 passed. New cases:
  • a vertical scroll that starts slightly diagonally keeps the thread: fails on main (navigateHistory called with "back"), passes here.
  • a swipe that turns into a vertical scroll keeps the thread: fails on main, passes here.
  • a swipe whose first events lean diagonally navigates and a swipe that leans diagonally for two events navigates: pass on main and here (guard real swipes with a diagonal start).
  • a single diagonal event past the trigger keeps the thread: fails on main, passes here.
• vp run check:changed: format, lint, knip, typecheck, tests and React compiler all pass.
• Desktop app (vp run dev:desktop on Linux/Xvfb, fresh database, back history #/new → #/pull-requests). A driver over CDP replayed each gesture as one latched sequence of wheel events over the main content. CDP mouse-wheel input gets its own Chromium gesture per event, so the driver sends one CDP wheel to fire the gesture begin/end reset and then dispatches the sequence in the page. Same driver on both sides:

Gesture (replayed wheel deltas)	Totals	Before cefb544af3	After 3f9b2380e4
reporter: diagonal start (5x/3y), vertical scroll with slight leftward drift, momentum	dx=-148 dy=539 (15° off vertical)	navigated	stayed
variant: same scroll, gesture ends when the fingers lift (no momentum)	dx=-125 dy=453 (15° off vertical)	navigated	stayed
variant: rightward drift with forward history	dx=148 dy=539 (15° off vertical)	navigated	stayed
variant: diagonal start, then perfectly vertical	dx=-5 dy=539 (1° off vertical)	stayed	stayed
swipe whose first events lean diagonally	dx=-186 dy=-3 (89° off vertical)	navigated	navigated
swipe that leans diagonally for two events	dx=-157 dy=5 (88° off vertical)	navigated	navigated
swipe that turns into a vertical scroll	dx=-153 dy=536 (16° off vertical)	navigated	stayed
swipe 18° off horizontal	dx=-180 dy=60 (72° off vertical)	navigated	navigated
swipe 34° off horizontal	dx=-180 dy=120 (56° off vertical)	navigated	stayed
control: clearly horizontal swipe	dx=-180 dy=15 (85° off vertical)	navigated	navigated

Replay driver (not committed)

// Repro driver for pingdotgg/t3code#30160 against the running desktop app (CDP on :9342).
// CDP mouseWheel events each get their own Chromium gesture (begin/end around every event), so the
// latched trackpad gesture is replayed as in-page wheel events over the settings content instead.
// Usage: node repro.mjs <dir that resolves playwright> <output dir>
import { createRequire } from "node:module";
import { mkdirSync, writeFileSync } from "node:fs";

const require = createRequire(process.argv[2] + "/");
const { chromium } = require("playwright");
const outDir = process.argv[3];
mkdirSync(outDir, { recursive: true });

const browser = await chromium.connectOverCDP("http://localhost:9342");
const page = browser
  .contexts()
  .flatMap((c) => c.pages())
  .find((p) => p.url().startsWith("t3code-dev://app"));
const log = [];
const note = (line) => {
  log.push(line);
  console.log(line);
};

// Wheel deltas as the DOM sees them (natural scrolling already applied).
const vertical = (n, drift) => Array.from({ length: n }, () => [drift, 15]);
const momentum = (drift) =>
  Array.from({ length: 12 }, (_, k) => [drift * 0.85 ** k, 15 * 0.85 ** k]);
const scenarios = [
  {
    name: "reporter: diagonal start (5x/3y), vertical scroll with slight leftward drift, momentum",
    events: [[-5, 3], ...vertical(30, -4), ...momentum(-4)],
  },
  {
    name: "variant: same scroll, gesture ends when the fingers lift (no momentum)",
    events: [[-5, 3], ...vertical(30, -4), [0, 0]],
  },
  {
    name: "variant: rightward drift with forward history",
    forward: true,
    events: [[5, 3], ...vertical(30, 4), ...momentum(4)],
  },
  {
    name: "variant: diagonal start, then perfectly vertical",
    events: [[-5, 3], ...vertical(30, 0), ...momentum(0)],
  },
  {
    name: "swipe whose first events lean diagonally",
    events: [[-1, -1], [-2, -1], [-3, -1], ...Array.from({ length: 15 }, () => [-12, 0]), [0, 0]],
  },
  {
    name: "swipe that leans diagonally for two events",
    events: [[-5, 3], [-2, 2], ...Array.from({ length: 15 }, () => [-10, 0]), [0, 0]],
  },
  {
    name: "swipe that turns into a vertical scroll",
    events: [[-10, 0], ...vertical(30, -4), ...momentum(-4)],
  },
  {
    name: "swipe 18° off horizontal",
    events: [...Array.from({ length: 15 }, () => [-12, 4]), [0, 0]],
  },
  {
    name: "swipe 34° off horizontal",
    events: [...Array.from({ length: 15 }, () => [-12, 8]), [0, 0]],
  },
  {
    name: "control: clearly horizontal swipe",
    events: [...Array.from({ length: 15 }, () => [-12, 1]), [0, 0]],
  },
];

async function go(hash) {
  await page.evaluate((h) => (location.hash = h), hash);
  await page.waitForTimeout(700);
}

for (const [index, scenario] of scenarios.entries()) {
  await go("#/new");
  await go("#/pull-requests");
  if (scenario.forward) {
    await page.goBack();
    await page.waitForTimeout(700);
  }
  // A real trackpad gesture starts with Chromium's gestureScrollBegin/End, which resets the
  // component's per-gesture state; one tiny CDP wheel does that before the latched sequence.
  const cdp = await page.context().newCDPSession(page);
  await cdp.send("Input.dispatchMouseEvent", { type: "mouseWheel", x: 700, y: 400, deltaX: 0, deltaY: 1 });
  await page.waitForTimeout(300);
  const before = page.url();
  const history = await page.evaluate(() => ({
    back: navigation.canGoBack,
    forward: navigation.canGoForward,
  }));
  await page.screenshot({ path: `${outDir}/${index}-before.png` });
  const sums = await page.evaluate(async (events) => {
    const target = document.elementFromPoint(700, 400) ?? document.body;
    if (target.closest('[role="dialog"]')) throw new Error("target is inside a dialog");
    let x = 0;
    let y = 0;
    for (const [deltaX, deltaY] of events) {
      x += deltaX;
      y += deltaY;
      target.dispatchEvent(
        new WheelEvent("wheel", { deltaX, deltaY, bubbles: true, composed: true, clientX: 700, clientY: 400 }),
      );
      await new Promise((resolve) => setTimeout(resolve, 8));
    }
    return { x: Math.round(x), y: Math.round(y) };
  }, scenario.events);
  await page.waitForTimeout(800);
  const after = page.url();
  await page.screenshot({ path: `${outDir}/${index}-after.png` });
  note(
    `${scenario.name}\n  total dx=${sums.x} dy=${sums.y} (${Math.round(
      (Math.atan2(Math.abs(sums.x), Math.abs(sums.y)) * 180) / Math.PI,
    )}° off vertical); history ${JSON.stringify(history)}\n  ${before} -> ${after}: ${
      before === after ? "stayed" : "NAVIGATED"
    }`,
  );
}

writeFileSync(`${outDir}/result.txt`, log.join("\n") + "\n");
process.exit(0);

• SwipeIndicator rendering is unchanged; what changes is how long it stays up. Sampled in the same desktop app, same replay method: a swipe that starts [-10,0] and turns into a vertical scroll (no release event). Indicator circle style after each event:

Event	Before cefb544af3	After 3f9b2380e4
1 [-10,0]	opacity 1, translateX(-95.8333%)	opacity 1, translateX(-95.8333%)
2 [-4,15]	opacity 1, translateX(-94.1667%)	opacity 0, translateX(-95.8333%)
3 [-4,15]	opacity 1, translateX(-92.5%)	opacity 0, translateX(-95.8333%)
4 [-4,15]	opacity 1, translateX(-90.8333%)	opacity 0, translateX(-95.8333%)
5 [-4,15]	opacity 1, translateX(-89.1667%)	opacity 0, translateX(-95.8333%)
6 [-4,15]	opacity 1, translateX(-87.5%)	opacity 0, translateX(-95.8333%)
7 [-4,15]	opacity 1, translateX(-85.8333%)	opacity 0, translateX(-95.8333%)
8 [-4,15]	opacity 1, translateX(-84.1667%)	opacity 0, translateX(-95.8333%)
9 [-4,15]	opacity 1, translateX(-82.5%)	opacity 0, translateX(-95.8333%)
10 [-4,15]	opacity 1, translateX(-80.8333%)	opacity 0, translateX(-95.8333%)
11 [-4,15]	opacity 1, translateX(-79.1667%)	opacity 0, translateX(-95.8333%)

Before, the indicator stays visible and keeps growing through the vertical scroll; after, it hides once the gesture reaches 30px of travel and the route stays.

• cannot-verify wayland: not checked with a real libinput touchpad on GNOME Wayland (the reporter's setup); the events above are synthetic.
• cannot-verify macos: not checked with a real macOS trackpad and its momentum/gesture bracketing.

Model and harness: Claude Opus 5.5 in Claude Code (via T3 Code) for triage, tests and fix; reviews by GPT-6.1 sol (Codex) and Claude Opus 5.5.

🤖 Generated with Claude Code

[macroscopeapp]

Approvability

Verdict: Approved at 4e325e8

Macroscope's review found this PR approvable — The change rejects mostly vertical trackpad gestures instead of treating their sideways drift as history navigation. Its effects are limited to macOS desktop gesture handling, with existing navigation safeguards preserved.

^{You can add or adjust custom eligibility rules. Learn more.}

[coderabbitai]

No actionable comments were generated in the recent review.

Walkthrough

HistorySwipeNavigation now evaluates cumulative horizontal and vertical travel when locking and tracking gestures. It discards gestures that meet the vertical-scroll rule and hides the indicator. Browser tests check navigation outcomes for diagonal wheel-event sequences.

Changes: Swipe gesture tracking

Layer / File(s)	Summary
Track and cancel diagonal gestures apps/web/src/components/HistorySwipeNavigation.tsx, apps/web/src/components/HistorySwipeNavigation.browser.test.tsx	The gesture state records cumulative horizontal and vertical travel. The component ignores gestures when total travel reaches 30 pixels and horizontal travel is no more than twice vertical travel. Browser tests cover vertical-dominant and diagonal sequences.

Estimated code review effort: 2 (Simple) | ~10 minutes

Change: Bug fix · Severity of issue fixed: Medium

Suggested reviewers: etanhey

Merge Risk: Minimal · up to 4e325

Mostly vertical trackpad scrolls should no longer trigger back or forward navigation, and deliberate horizontal swipes should still navigate. No concrete merge-blocking risk remains. Real trackpad behavior on Linux and macOS was not tested.

Pre-merge checks: 4

Check name	Status	Explanation
Title check		The title names the main change: mostly vertical trackpad scrolls no longer trigger back or forward navigation. The raw summary and objectives both confirm this is the core fix in HistorySwipeNavigati…
Description check		The description covers the problem, the change, scope, and verification. It has a clear problem statement with reproduction details, an explanation of the 30px and 2:1 ratio fix, and a linked issue (#…
Linked Issues check		Issue #30160 requires that mostly vertical two-finger scrolls not trigger history navigation, and that navigation require a clearly horizontal swipe. The whole-PR diff against the merge base (f313d0a…
Out of Scope Changes check		The whole-PR source diff for apps/web/src/components/HistorySwipeNavigation.tsx contains only the travel-tracking, dominance constants (SWIPE_HORIZONTAL_DOMINANCE, SWIPE_DOMINANCE_DISTANCE), `is…

Full details: Title check

Explanation

The title names the main change: mostly vertical trackpad scrolls no longer trigger back or forward navigation. The raw summary and objectives both confirm this is the core fix in HistorySwipeNavigation. It follows the conventional commit form and is specific enough for a teammate scanning history.

Full details: Description check

Explanation

The description covers the problem, the change, scope, and verification. It has a clear problem statement with reproduction details, an explanation of the 30px and 2:1 ratio fix, and a linked issue (#30160). Verification is detailed with test names, a before/after table, and a replay driver. It names what could not be checked (Wayland, macOS). The template's comment about approval and scope is partly addressed by the link to the issue. The 'Scope and approval' section is brief and does not say whether a maintainer requested the PR. The model and harness line is present. Overall the description is mostly complete.

Full details: Linked Issues check

Explanation

Issue #30160 requires that mostly vertical two-finger scrolls not trigger history navigation, and that navigation require a clearly horizontal swipe. The whole-PR diff against the merge base (f313d0a) shows HistorySwipeNavigation.tsx now: (1) tracks cumulative travelX and travelY on the tracking gesture; (2) defines isVerticalScroll, which returns true when total travel is at least 30px and travelX <= 2 * travelY; (3) applies that check in lockSwipeAxis, so an axis lock cannot occur on a vertical-dominant gesture; (4) on each tracking event, adds both travel values and, when isVerticalScroll is true, sets the gesture to ignored and hides the indicator, so no navigation follows. This matches the issue's suggested fix (lock on clear horizontal intent after about 20–30px, track vertical travel, cancel when vertical movement becomes significant). Gestures below 30px keep the prior behavior, so real diagonal-start swipes can still navigate. The issue's optional trigger-distance and setting changes are not required. The PR's browser tests cover the named cases; their results were not re-run in this assessment. Real libinput and macOS trackpad behavior is device validation, not a coding requirement. Assessment is based on the whole-PR source diff; the incremental diff from the previous reviewed head could not be read, so the current code was assessed directly.

Full details: Out of Scope Changes check

Explanation

The whole-PR source diff for apps/web/src/components/HistorySwipeNavigation.tsx contains only the travel-tracking, dominance constants (SWIPE_HORIZONTAL_DOMINANCE, SWIPE_DOMINANCE_DISTANCE), isVerticalScroll, and axis-lock and tracking-branch changes that serve issue #30160. The PR summary and raw summary report that the only other changed file is HistorySwipeNavigation.browser.test.tsx, which adds tests for the same gesture behavior. No refactor, setting, trigger-distance change, or unrelated product behavior was identified. The PR comment about the automated capture pipeline and the request for Julius describe process, not code changes. The browser test file diff was not read directly in this assessment, relying on the summary for its content.

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Files selected for processing: 2

• apps/web/src/components/HistorySwipeNavigation.browser.test.tsx
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[coderabbitai]

• Fix comments: Fix CodeRabbit comments on this PR

Dismissing prior approval to re-evaluate 3f9b238

[juliusmarminge]

The automated pipeline stopped on this pull request and will not merge it:

the capture step could not show the problem on the base commit, so there is nothing to prove fixed.

Visit synthetic Thread A, then Thread B; expand the long notes and position the chat at scrollTop 600. Inject deltaX=-9, deltaY=3, followed by 34 packets of deltaX=-4, deltaY=22 at approximately 20 ms intervals, then pause for release. Use Back to establish forward history and repeat with mirrored positive horizontal deltas. Attempt deliberate horizontal navigation with single ±145 px wheel packets. The vertical sequences scrolled from 600 to 1351 without changing threads on either commit.

It stays open for a person to finish or close.

[SunkenInTime]

Please save us julius

Dismissing prior approval to re-evaluate 4e325e8

[juliusmarminge]

The automated pipeline stopped on this pull request and will not merge it:

the fix is written and reviewed, but proving it needs something no worker has:

• Permanent blocker: A macOS desktop environment with two-finger trackpad input is required and unavailable on this VM. Mostly vertical scrolling in both history directions, indicator dismissal, continued content scrolling, and deliberate horizontal navigation remain unverified.

It stays open for a person to finish or close.