Browser Stop control reloads instead of cancelling loading #29474

While a main document is still loading in the built-in Browser, the navigation control is labeled Stop, but clicking it reloads the page and starts the request again.

Reproduce with a main HTML response held open: open the URL, wait for Stop, then click it once. Expected: cancel the current navigation. Actual on baseline ac8dce0: request8 was cancelled but request9 immediately started for the same URL, and native address-bar navigation showed “Could not open this address.” Idle Refresh should continue to reload.

This was reproduced in real Electron44.10.0 with synthetic isolated state; baseline verification ran on private Xvfb. The source remains unchanged at current main8657eecb. Native renderer screenshots/video omit the embedded guest pixels; the linked evidence includes separate genuine webContents.capturePage guest PNGs, without composites. The implementation also covers standalone server-streamed tabs and clears Loading when Chromium stops a committed document without Playwright load/requestfailed events.

Reproduction fixture, native before/after PNGs, recordings and runtime transcript.

One-problem scope: correct the cancellation behavior already promised by the existing Stop control across its native and streamed owners. This fits CONTRIBUTING.md’s focused obvious-bug exception; it adds no setting, shortcut, product default or agent-stop behavior. PR searches found no dedicated fix; #28814 concerns redirect/supersession error handling and #28154 concerns navigating away from unresponsive scripts.

Investigated with GPT-6.1 Sol (xhigh) in the Codex harness through T3 Code.