[BUG] Browser preview auto-opens on every HTML file edit and crashes the renderer (Windows/MSIX) — regression since v1.26832.0

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

On Windows, editing an .html file automatically starts an html-preview server and
opens a preview tab — with no tool call and no user action. That automatic open is what
crashes the main webview renderer, leaving the window painting only its background colour.
The app then has to be force-quit.

This is not "the desktop app sometimes goes blank". The trigger is reproducible and it
lives in the Claude Code Browser preview subsystem: 9 out of 9 renderer preload failures
happened in the same second as [PreviewContext] Opened preview user tab.

Evidence that the preview opens by itself (no preview tool was invoked in this turn —
only Bash, Edit and Read):

transcript 01:52:45Z assistant tool_use: Edit file_path=...\mockup.html
main.log 10:52:45 [Preview] Created session preview context
main.log 10:52:45 [PreviewContext] Opened preview user tab { tabId: 'tab-1' }
main.log 10:52:45 [Launch] Updating active servers store ... "html-preview-...","status":"running"

transcript 01:52:51Z assistant tool_use: Edit (same file)
main.log 10:52:51 [PreviewContext] Closed preview tab -> Opened preview user tab

There is no launch.json in this project, so this is not a configured dev server — it is
automatic HTML file preview.

Any workflow where Claude edits HTML files repeatedly — iterating on a static page, for
example — triggers this constantly, and there is no setting to turn it off.

Impact: app restarts went from ~1 every few days to 5 on 2026-08-12 and 13 on 2026-08-13.

What Should Happen?

1. A setting to stop the Browser preview from opening automatically when an HTML file is

edited. This alone makes the app usable for HTML/mockup work.

1. Creating a preview tab should not be able to kill the main webview renderer.
2. For MSIX builds, expose a GPU / compositing toggle in Settings, since command-line

flags are unavailable by design (ELECTRON_EXTRA_LAUNCH_ARGS is ignored by the package).

1. Do not auto-capture preview screenshots while the Browser pane is hidden.

Error Messages/Logs

--- unknown-window.log : 9 occurrences, 2026-08-10 .. 08-13, ALL in the same second as
--- "[PreviewContext] Opened preview user tab". Zero in the preceding month.

[error] Electron sandboxed_renderer.bundle.js script failed to run
[error] TypeError: Cannot destructure property 'preloadScripts' of 'binding.startupData' as it is null.

--- main.log : the renderer then dies. -1073741819 = 0xC0000005 (access violation).

2026-08-12 20:43:01 [info] Main webview render process gone: { reason: 'crashed', exitCode: -1073741819 }
2026-08-13 11:13:01 [info] Main webview render process gone: { reason: 'crashed', exitCode: 3 }
2026-08-13 11:33:21 [info] Main webview render process gone: { reason: 'crashed', exitCode: -1073741819 }
2026-08-13 11:46:23 [info] Main webview render process gone: { reason: 'crashed', exitCode: 3 }

--- and the app records that a reload cannot recover it:

2026-08-13 11:33:27 [error] Network Service process gone (reason=crashed, exitCode=3) outside app quit
                            - main-process networking is broken until relaunch

--- same subsystem, 19 occurrences:

[warn] [Preview] capturePreviewScreenshot failed: {
  error: Error: Screenshot timed out after 5s: the Browser pane is not displayed,
         so the page is not compositing frames. Display the pane and retry.

--- baseline: across 3.5 months of retained logs (from 2026-05-03) there is exactly ONE
--- other "render process gone", on 2026-07-10, with reason 'oom' - a different failure.
--- Four crashes in two days is new.

--- NOTE: Windows records nothing for this. No WER report, no Application Error 1000 for
--- Claude.exe, and Crashpad\reports is empty. (An unrelated desktop app on the same
--- machine produced 6 crash dumps the same day, so WER itself is working.) This is why
--- earlier reports of this symptom have no crash data to attach.

Steps to Reproduce

1. Use the Windows desktop app (MSIX build from claude.com/download).
2. In a Claude Code session, have Claude edit any local .html file with the Edit tool.

No launch.json is needed and no preview tool is invoked.

1. Observe main.log: in the same second as the Edit, the app logs

[Preview] Created session preview context
[PreviewContext] Opened preview user tab
[Launch] Updating active servers store ... "serverId":"html-preview-...","status":"running"

1. Have Claude keep editing that file. Each Edit opens a preview again; a session that

iterates on one HTML page produces dozens of these opens.

1. Intermittently, at the moment a preview tab opens, unknown-window.log logs

Electron sandboxed_renderer.bundle.js script failed to run
TypeError: Cannot destructure property 'preloadScripts' of 'binding.startupData' as it is null.
and main.log logs "Main webview render process gone".

1. The window is now blank (background colour only) and unresponsive. Only a full restart

recovers it; once the Network Service also dies, the app itself logs that networking is
broken until relaunch.

Observed 4 renderer crashes in 2 days. A clean instance:
11:46:07 session opened
11:46:13 message sent
11:46:23 Main webview render process gone <- blank window, 10 s later
11:47:00 force quit
11:47:03 relaunch

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

Claude Desktop v1.24012.9 (in use through 2026-08-07) was stable: ~1 app restart every few days. v1.26832.0 (in use from 2026-08-09) - preview preload errors start 08-10, first renderer crash 08-12. v1.28929.0 (from 2026-08-13) - crashes continue. v1.26832.0's changelog changed this exact subsystem: "Removed the 'Always allow' option when approving dev server starts in the Browser preview; each new server start now asks, and a server that has crashed asks again instead of restarting silently." and added session-window restore (more renderers at launch).

Claude Code Version

2.1.227

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Other

Additional Information

Note on versions (updated 2026-08-15)
This report was filed on 1.28929.0. The app has since updated to 1.30096.1
(Claude Code 2.1.229) and the problem still reproduces - within 5 minutes of
updating - so the "latest version" checkbox is now accurate. Details in the
comments below.

For the record: the update applied on a normal app restart, with no PC reboot.
An earlier version of this note claimed a full OS reboot was required. That was
based on two observations and did not hold up.

Note on the Terminal/Shell field: not a terminal. This is the Claude Desktop app (MSIX).

Environment
Claude Desktop v1.30096.1 (MSIX / Store package family Claude_pzs8sxrjxfjjc)
Claude Code 2.1.229
OS Windows 11 Pro 10.0.26200 (build 26200.9168)
GPU NVIDIA RTX 4090, driver 32.0.15.9579
RAM 128 GB (~70 GB free at crash time - not a memory issue)
Install source claude.com/download -> Windows (x64). Note this delivers MSIX, not a
Squirrel .exe; Windows downloads have been MSIX-only since 2026-02-10.

Why there is no workaround on Windows

1. No setting disables the auto-preview. Nothing preview-related exists in settings.json

or %APPDATA%\Claude\config.json.

1. The MSIX package ignores ELECTRON_EXTRA_LAUNCH_ARGS, so --disable-gpu /

--disable-gpu-compositing cannot be passed (#45031, open since Feb 2026).

1. No alternative packaging exists to fall back to.
2. v1.30096.1 (2026-08-13) contains no fix for this; its only crash fix is Linux-specific.

Suggested labels: area:desktop, platform:windows, regression, has repro

Related issues - the symptom is already reported several times, but always as "the app goes
blank" with no trigger and no crash data, and each was closed as not planned / invalid:
#44558 - same symptom, same empty-Crashpad signature, same
"WUDFRd ... ROOT\DISPLAY\0000 (Status: 0xC0000365)" line in the Windows event log
#49551 - blank on Windows, requires Task Manager to kill all claude.exe
#68364 - Store/MSIX, repeated "Failed to set title bar overlay" (also present in my logs)
#45031 - MSIX cannot receive GPU flags (the reason no workaround exists)
#38014, #51143, #25929

What is new here is the trigger: the Browser preview opening itself on every HTML file edit,
correlated 9/9 at one-second resolution, with the regression bracketed to v1.26832.0.