windows smoke: opt-in WebView2 DevTools port via LOTUS_WEBVIEW2_DEBUG_PORT (#19)

WebView2's WEBVIEW2_ADDITIONAL_BROWSER_ARGUMENTS is ignored because the app
sets its browser arguments explicitly (seen on the runner: the WebView2
command line had only the app's arguments). The app now appends
--remote-debugging-port only when LOTUS_WEBVIEW2_DEBUG_PORT holds a valid
port (>= 1024); otherwise the arguments are exactly as before.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PPmy3tPq869XDW4njjVaKA

.gitea/workflows/windows-smoke.yml

@@ -0,0 +1,132 @@
+# cinny-desktop #19: smoke-test the Windows app on the `windows` runner.
+#
+# Installs the NSIS bundle silently, starts the installed app with WebView2's
+# DevTools port open, and drives its real page with scripts/windows-smoke.mjs
+# (playwright-core over CDP): boots to the login screen, local server address,
+# microphone permission for the app and not for a foreign page, the call page's
+# own origin + isolation, the Credential Manager round trip. Features a build
+# doesn't have are reported "n/a".
+#
+# Run it from the Actions tab (workflow_dispatch):
+# - no `ref`: tests the published nightly installer (a couple of minutes);
+# - `ref` = a branch (e.g. a PR branch): builds that branch, then tests it.
+name: Windows smoke
+
+on:
+  workflow_dispatch:
+    inputs:
+      ref:
+        description: 'Branch to build and test (empty: test the published nightly)'
+        required: false
+        default: ''
+
+env:
+  GITEA_URL: ${{ github.server_url }}
+  REPO: ${{ github.repository }}
+
+jobs:
+  smoke:
+    runs-on: windows
+    timeout-minutes: 90
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-node@v4
+        with:
+          node-version-file: .node-version
+
+      - name: Download the published nightly installer
+        if: ${{ inputs.ref == '' }}
+        shell: powershell
+        run: |
+          New-Item -ItemType Directory -Force -Path smoke-installer | Out-Null
+          Invoke-WebRequest -Uri "$env:GITEA_URL/$env:REPO/releases/download/latest/LotusChat-x86_64-setup.exe" -OutFile smoke-installer\setup.exe
+          Get-Item smoke-installer\setup.exe | Select-Object Name, Length
+
+      - name: Check out the branch to build
+        if: ${{ inputs.ref != '' }}
+        uses: actions/checkout@v4
+        with:
+          ref: ${{ inputs.ref }}
+          path: build-src
+
+      - name: Build the branch
+        if: ${{ inputs.ref != '' }}
+        shell: powershell
+        env:
+          TAURI_SIGNING_PRIVATE_KEY: ${{ secrets.TAURI_SIGNING_PRIVATE_KEY }}
+          TAURI_SIGNING_PRIVATE_KEY_PASSWORD: ''
+          NODE_OPTIONS: '--max_old_space_size=4096'
+          CARGO_REGISTRIES_CRATES_IO_PROTOCOL: sparse
+          CARGO_HTTP_MULTIPLEXING: 'false'
+          CARGO_NET_RETRY: '5'
+        run: |
+          cd build-src
+          git submodule update --init --depth=1
+          cd cinny; npm ci; cd ..
+          node scripts/sync-web-config.mjs
+          npm ci
+          $env:PATH = "$env:USERPROFILE\.cargo\bin;$env:PATH"
+          $toolchain = Get-ChildItem "$env:USERPROFILE\.rustup\toolchains" -Directory -ErrorAction SilentlyContinue |
+                       Where-Object { $_.Name -match 'stable' } | Select-Object -First 1
+          if ($toolchain) { $env:PATH = "$($toolchain.FullName)\bin;$env:PATH" }
+          npm run tauri -- build --bundles nsis
+          New-Item -ItemType Directory -Force -Path ..\smoke-installer | Out-Null
+          $exe = Get-ChildItem src-tauri\target\release\bundle\nsis\*-setup.exe | Select-Object -First 1
+          Copy-Item $exe.FullName ..\smoke-installer\setup.exe
+
+      - name: Install silently
+        shell: powershell
+        run: |
+          Get-Process cinny -ErrorAction SilentlyContinue | Stop-Process -Force
+          Start-Process smoke-installer\setup.exe -ArgumentList '/S' -Wait
+          $app = Join-Path $env:LOCALAPPDATA 'Lotus Chat\cinny.exe'
+          if (-not (Test-Path $app)) { Write-Error "not installed at $app"; exit 1 }
+          (Get-Item $app).VersionInfo | Select-Object ProductVersion, FileVersion
+
+      - name: Start the app and smoke test it
+        shell: powershell
+        run: |
+          New-Item -ItemType Directory -Force -Path smoke-deps | Out-Null
+          Push-Location smoke-deps
+          npm init -y | Out-Null
+          npm install --no-audit --no-fund playwright-core@1 | Out-Null
+          Pop-Location
+          Copy-Item scripts\windows-smoke.mjs smoke-deps\windows-smoke.mjs
+          # Same step as the test: a process started in an earlier step may be
+          # cleaned up when that step ends.
+          # The app sets its own WebView2 arguments, so WebView2's env var doesn't
+          # apply; the app opens the DevTools port itself when asked (#19).
+          $env:LOTUS_WEBVIEW2_DEBUG_PORT = '9222'
+          $app = Join-Path $env:LOCALAPPDATA 'Lotus Chat\cinny.exe'
+          Start-Process $app
+          Start-Sleep -Seconds 15
+          Write-Host "--- processes"
+          Get-Process cinny, msedgewebview2 -ErrorAction SilentlyContinue | Select-Object Name, Id, SessionId | Format-Table | Out-String | Write-Host
+          Write-Host "--- listening ports 9222/44548"
+          Get-NetTCPConnection -State Listen -ErrorAction SilentlyContinue | Where-Object { $_.LocalPort -in 9222, 44548 } | Select-Object LocalAddress, LocalPort, OwningProcess | Format-Table | Out-String | Write-Host
+          Write-Host "--- WebView2 runtime"
+          Get-ItemProperty 'HKLM:\SOFTWARE\WOW6432Node\Microsoft\EdgeUpdate\Clients\{F3017226-FE2A-4295-8BDF-00C3A9A7E4C5}' -ErrorAction SilentlyContinue | Select-Object pv | Out-String | Write-Host
+          Write-Host "--- whoami: $(whoami)"
+          Write-Host "--- webview2 command lines"
+          Get-CimInstance Win32_Process -Filter "Name='msedgewebview2.exe'" | Select-Object -First 2 | ForEach-Object { Write-Host $_.CommandLine.Substring(0, [Math]::Min(600, $_.CommandLine.Length)) }
+          Write-Host "--- netstat"
+          netstat -ano | Select-String "LISTENING" | Select-String ":9222 |:44548 " | ForEach-Object { Write-Host $_ }
+          Write-Host "--- http probes"
+          try { (Invoke-WebRequest -UseBasicParsing http://127.0.0.1:9222/json/version -TimeoutSec 5).Content | Write-Host } catch { Write-Host "9222: $($_.Exception.Message)" }
+          try { (Invoke-WebRequest -UseBasicParsing http://localhost:44548/ -TimeoutSec 5).StatusCode | Write-Host } catch { Write-Host "44548: $($_.Exception.Message)" }
+          node smoke-deps\windows-smoke.mjs smoke-out
+
+      - name: Stop the app
+        if: ${{ always() }}
+        shell: powershell
+        run: |
+          Get-Process cinny -ErrorAction SilentlyContinue | Stop-Process -Force
+          if (Test-Path smoke-out\results.json) { Get-Content smoke-out\results.json }
+
+      - name: Upload results and screenshots
+        if: ${{ always() }}
+        uses: actions/upload-artifact@v3
+        with:
+          name: windows-smoke
+          path: smoke-out

config.json

@@ -24,5 +24,16 @@
     "basename": "/"
   },
   "gifApiKey": "",
-  "webAppUrl": "https://chat.lotusguild.org"
+  "webAppUrl": "https://chat.lotusguild.org",
+  "statusPages": {
+    "matrix.lotusguild.org": {
+      "url": "https://isitup.lotusguild.org",
+      "slug": "matrix",
+      "groups": {
+        "homeserver": "Homeserver",
+        "calls": "Voice calls",
+        "login": "Login"
+      }
+    }
+  }
 }

scripts/windows-smoke.mjs

@@ -0,0 +1,175 @@
+// cinny-desktop #19: Windows smoke test against the INSTALLED app.
+//
+// The app is started with WebView2's DevTools port open
+// (WEBVIEW2_ADDITIONAL_BROWSER_ARGUMENTS=--remote-debugging-port=9222) and this
+// script drives its real page over CDP with playwright-core. No login: every
+// check runs on the login screen or through the app's own Tauri commands.
+//
+//   node scripts/windows-smoke.mjs <outDir>
+//
+// Checks whose feature isn't in the build under test are reported "n/a"
+// instead of failing, so the same script runs on main and on PR branches.
+import { writeFileSync, mkdirSync } from 'node:fs';
+import { execSync } from 'node:child_process';
+import { chromium } from 'playwright-core';
+
+const OUT = process.argv[2] || 'smoke-out';
+mkdirSync(OUT, { recursive: true });
+const APP = 'http://localhost:44548';
+const results = [];
+const record = (name, status, detail = '') => {
+  results.push({ name, status, detail });
+  console.log(`${status.toUpperCase().padEnd(4)} ${name}${detail ? ` — ${detail}` : ''}`);
+};
+
+const until = async (fn, ms, step = 500) => {
+  const end = Date.now() + ms;
+  for (;;) {
+    let v;
+    try {
+      v = await fn();
+    } catch {
+      v = undefined;
+    }
+    if (v || Date.now() > end) return v;
+    await new Promise((r) => setTimeout(r, step));
+  }
+};
+
+// 1. Connect to the running app's WebView2.
+const browser = await until(() => chromium.connectOverCDP('http://127.0.0.1:9222'), 60_000, 1000);
+if (!browser) {
+  record('connect to the app over CDP', 'fail', 'no DevTools endpoint on :9222');
+  writeFileSync(`${OUT}/results.json`, JSON.stringify(results, null, 2));
+  process.exit(1);
+}
+const page = await until(
+  () => browser.contexts().flatMap((c) => c.pages()).find((p) => p.url().startsWith(APP)),
+  60_000,
+);
+if (!page) {
+  record('app page found', 'fail', browser.contexts().flatMap((c) => c.pages()).map((p) => p.url()).join(', '));
+  process.exit(1);
+}
+record('app page found', 'pass', page.url());
+
+// 2. Boots to the login screen.
+const booted = await until(async () => /Login|Homeserver/.test(await page.locator('body').innerText()), 60_000);
+record('boots to the login screen', booted ? 'pass' : 'fail');
+await page.screenshot({ path: `${OUT}/01-login.png` });
+
+// 3. The local server's address (cinny #43 binds 127.0.0.1 explicitly).
+try {
+  const listen = execSync(
+    'powershell -NoProfile -Command "(Get-NetTCPConnection -LocalPort 44548 -State Listen).LocalAddress -join \',\'"',
+  )
+    .toString()
+    .trim();
+  record('local server listening', listen ? 'pass' : 'fail', listen);
+} catch (e) {
+  record('local server listening', 'fail', String(e).slice(0, 120));
+}
+
+const cfg = await page.evaluate(() => fetch('/config.json').then((r) => r.json()));
+
+// 4. Microphone for the app itself (WebView2 PermissionRequested handler, #22).
+const appMic = await page.evaluate(async () => {
+  try {
+    const s = await navigator.mediaDevices.getUserMedia({ audio: true });
+    s.getTracks().forEach((t) => t.stop());
+    return 'ok';
+  } catch (e) {
+    return `${e.name}: ${e.message}`;
+  }
+});
+record('microphone allowed for the app', appMic === 'ok' ? 'pass' : 'fail', appMic);
+
+// 5. Call page on its own origin, isolated from the app (cinny #43 / #27).
+if (cfg.desktopCallOrigin) {
+  const src = `${cfg.desktopCallOrigin}/public/element-call/index.html`;
+  await page.evaluate((s) => {
+    const f = document.createElement('iframe');
+    f.id = 'smoke-call';
+    f.src = s;
+    f.allow = 'microphone; camera; display-capture; autoplay; clipboard-write;';
+    f.sandbox = 'allow-forms allow-scripts allow-same-origin allow-popups allow-modals allow-downloads';
+    document.body.appendChild(f);
+  }, src);
+  const frame = await until(() => page.frames().find((f) => f.url().startsWith(src)), 30_000);
+  if (!frame) {
+    record('call page loads from its own origin', 'fail', 'frame did not load (CSP?)');
+  } else {
+    await frame.waitForLoadState('domcontentloaded').catch(() => undefined);
+    const iso = await frame.evaluate(async () => {
+      const r = { origin: location.origin };
+      try {
+        r.parentStorage = String(parent.localStorage.length);
+      } catch (e) {
+        r.parentStorage = e.name;
+      }
+      try {
+        const s = await navigator.mediaDevices.getUserMedia({ audio: true });
+        s.getTracks().forEach((t) => t.stop());
+        r.mic = 'ok';
+      } catch (e) {
+        r.mic = e.name;
+      }
+      return r;
+    });
+    record('call page loads from its own origin', 'pass', iso.origin);
+    record('call page cannot read the app storage', iso.parentStorage === 'SecurityError' ? 'pass' : 'fail', iso.parentStorage);
+    record('call page gets the microphone', iso.mic === 'ok' ? 'pass' : 'fail', iso.mic);
+  }
+} else {
+  record('call page on its own origin', 'n/a', 'desktopCallOrigin not set in this build');
+}
+
+// 6. OS keychain round trip (cinny #105, step 1).
+const kc = await page.evaluate(async () => {
+  const inv = window.__TAURI_INTERNALS__?.invoke;
+  if (!inv) return { error: 'no Tauri bridge' };
+  try {
+    const supported = await inv('secure_session_supported');
+    if (!supported) return { supported };
+    const tokens = { userId: '@smoke:ci.invalid', deviceId: 'SMOKE', accessToken: `smoke-${Date.now()}` };
+    const before = await inv('secure_session_get');
+    await inv('secure_session_set', { tokens });
+    const back = await inv('secure_session_get');
+    // Put back whatever was there (nothing, on a clean runner).
+    if (before) await inv('secure_session_set', { tokens: before });
+    else await inv('secure_session_clear');
+    const after = await inv('secure_session_get');
+    return { supported, roundTrip: back?.accessToken === tokens.accessToken, restored: JSON.stringify(after) === JSON.stringify(before ?? null) };
+  } catch (e) {
+    return { error: String(e).slice(0, 160) };
+  }
+});
+if (kc.error && /not found/i.test(kc.error)) record('keychain round trip', 'n/a', 'commands not in this build');
+else if (kc.error) record('keychain round trip', 'fail', kc.error);
+else if (!kc.supported) record('keychain round trip', 'fail', 'secure_session_supported = false on Windows');
+else record('keychain round trip', kc.roundTrip && kc.restored ? 'pass' : 'fail', JSON.stringify(kc));
+
+// 7. A foreign page loaded in the window must not get the microphone (#22).
+await page.goto('https://example.com/').catch(() => undefined);
+const foreignMic = await page.evaluate(async () => {
+  try {
+    const s = await navigator.mediaDevices.getUserMedia({ audio: true });
+    s.getTracks().forEach((t) => t.stop());
+    return 'ok';
+  } catch (e) {
+    return e.name;
+  }
+});
+record(
+  'microphone refused to a foreign page',
+  foreignMic === 'NotAllowedError' ? 'pass' : 'info',
+  `${foreignMic}${foreignMic === 'ok' ? ' (build without the #22 origin check)' : ''}`,
+);
+await page.goto(APP).catch(() => undefined);
+await page.screenshot({ path: `${OUT}/02-end.png` }).catch(() => undefined);
+
+writeFileSync(`${OUT}/results.json`, JSON.stringify(results, null, 2));
+await browser.close().catch(() => undefined);
+const failed = results.filter((r) => r.status === 'fail');
+console.log(`\n${results.filter((r) => r.status === 'pass').length} passed, ${failed.length} failed`);
+process.exit(failed.length ? 1 : 0);

src-tauri/src/gpu_workarounds.rs

@@ -1,17 +1,22 @@
 //! WebKitGTK workarounds for NVIDIA's proprietary driver on Linux.
 //!
-//! On NVIDIA + Wayland (reported on CachyOS/KDE, driver 615, webkit2gtk 2.52)
-//! the app never shows a window: GDK dies with "Error 71 (Protocol error)
-//! dispatching to Wayland display", and under XWayland WebKit's DMA-BUF
-//! renderer then fails with "Failed to create GBM buffer … Invalid argument".
-//! `WEBKIT_DISABLE_DMABUF_RENDERER=1 GDK_BACKEND=x11` makes it run normally.
+//! Diagnosed on CachyOS/KDE Wayland, RTX 3070, driver 615.71.09, webkit2gtk
+//! 2.52.6 (reported 2026-09-27, WAYLAND_DEBUG trace in the PR):
+//! - Native Wayland: the compositor kills the connection with
+//!   `wp_linux_drm_syncobj_surface_v1 … "explicit sync is used, but no acquire
+//!   point is set"` (GDK: "Error 71 (Protocol error)"), i.e. an explicit-sync
+//!   bug between WebKit and the driver, not a buffer-format problem.
+//!   `__NV_DISABLE_EXPLICIT_SYNC=1` fixes it and keeps WebKit's GPU (DMA-BUF)
+//!   renderer, so that is the default on native Wayland.
+//! - X11 / XWayland: the DMA-BUF renderer can't allocate or import buffers
+//!   ("Failed to create GBM buffer … Invalid argument", "Failed to import
+//!   DMABuf"), so there it is disabled (`WEBKIT_DISABLE_DMABUF_RENDERER=1`,
+//!   shared-memory frames). We never force X11 any more.
 //!
-//! So, before GTK/WebKit initialise, and only when the NVIDIA driver is loaded:
-//! - `WEBKIT_DISABLE_DMABUF_RENDERER=1`;
-//! - on a Wayland session with XWayland available, `GDK_BACKEND=x11`.
-//!
-//! Anything the user already set wins, and `LOTUS_NO_GPU_WORKAROUNDS=1`
-//! disables all of it (e.g. once a newer driver/WebKit fixes this).
+//! Opt-ins / opt-outs (anything the user already set always wins):
+//! - `LOTUS_GPU_SAFE_MODE=1`: last resort, shared-memory rendering on Wayland
+//!   too (slower, especially at high resolutions).
+//! - `LOTUS_NO_GPU_WORKAROUNDS=1`: change nothing.
 
 /// Environment variables to set: pure, for tests.
 pub(crate) fn decide(
@@ -22,15 +27,30 @@ pub(crate) fn decide(
     if !nvidia || set("LOTUS_NO_GPU_WORKAROUNDS") {
         return Vec::new();
     }
-    let mut out = Vec::new();
-    if !set("WEBKIT_DISABLE_DMABUF_RENDERER") {
-        out.push(("WEBKIT_DISABLE_DMABUF_RENDERER", "1"));
-    }
-    let wayland = set("WAYLAND_DISPLAY")
+    let wayland_session = set("WAYLAND_DISPLAY")
         || get("XDG_SESSION_TYPE").is_some_and(|v| v.eq_ignore_ascii_case("wayland"));
-    // Only fall back to X11 when there is an X server (XWayland) to talk to.
-    if wayland && set("DISPLAY") && !set("GDK_BACKEND") {
-        out.push(("GDK_BACKEND", "x11"));
+    // GTK uses Wayland unless GDK_BACKEND says otherwise (it may list
+    // several, e.g. "wayland,x11": the first one wins).
+    let native_wayland = wayland_session
+        && get("GDK_BACKEND").map_or(true, |v| {
+            v.is_empty()
+                || v.trim_start().to_ascii_lowercase().starts_with("wayland")
+                || v.trim() == "*"
+        });
+
+    let mut out = Vec::new();
+    let mut want = |k: &'static str, v: &'static str| {
+        if !set(k) {
+            out.push((k, v));
+        }
+    };
+    if native_wayland {
+        want("__NV_DISABLE_EXPLICIT_SYNC", "1");
+        if set("LOTUS_GPU_SAFE_MODE") {
+            want("WEBKIT_DISABLE_DMABUF_RENDERER", "1");
+        }
+    } else {
+        want("WEBKIT_DISABLE_DMABUF_RENDERER", "1");
     }
     out
 }
@@ -44,9 +64,20 @@ fn nvidia_driver_loaded() -> bool {
 /// Call first thing in `main`, before anything starts GTK or spawns threads.
 pub fn apply() {
     #[cfg(target_os = "linux")]
-    for (key, value) in decide(nvidia_driver_loaded(), |k| std::env::var(k).ok()) {
-        eprintln!("gpu-workarounds: NVIDIA driver detected, setting {key}={value} (LOTUS_NO_GPU_WORKAROUNDS=1 to disable)");
-        std::env::set_var(key, value);
+    {
+        let changes = decide(nvidia_driver_loaded(), |k| std::env::var(k).ok());
+        if changes.is_empty() {
+            return;
+        }
+        let list: Vec<String> = changes.iter().map(|(k, v)| format!("{k}={v}")).collect();
+        eprintln!(
+            "gpu-workarounds: NVIDIA driver detected, setting {} \
+             (LOTUS_GPU_SAFE_MODE=1 for shared-memory rendering, LOTUS_NO_GPU_WORKAROUNDS=1 to disable)",
+            list.join(" ")
+        );
+        for (key, value) in changes {
+            std::env::set_var(key, value);
+        }
     }
 }
 
@@ -71,51 +102,70 @@ mod tests {
     }
 
     #[test]
-    fn nvidia_wayland_gets_both() {
+    fn nvidia_wayland_keeps_gpu_renderer_and_disables_explicit_sync() {
         assert_eq!(
             run(true, WAYLAND),
-            vec![
-                ("WEBKIT_DISABLE_DMABUF_RENDERER", "1"),
-                ("GDK_BACKEND", "x11")
-            ]
+            vec![("__NV_DISABLE_EXPLICIT_SYNC", "1")]
         );
     }
 
     #[test]
-    fn nvidia_x11_session_only_disables_dmabuf() {
-        assert_eq!(
-            run(true, &[("DISPLAY", ":0")]),
-            vec![("WEBKIT_DISABLE_DMABUF_RENDERER", "1")]
-        );
-    }
-
-    #[test]
-    fn wayland_without_xwayland_keeps_wayland() {
-        assert_eq!(
-            run(true, &[("WAYLAND_DISPLAY", "wayland-0")]),
-            vec![("WEBKIT_DISABLE_DMABUF_RENDERER", "1")]
-        );
+    fn never_forces_x11() {
+        for env in [
+            WAYLAND,
+            &[("DISPLAY", ":0")][..],
+            &[("WAYLAND_DISPLAY", "w")][..],
+        ] {
+            assert!(run(true, env).iter().all(|(k, _)| *k != "GDK_BACKEND"));
+        }
     }
 
     #[test]
     fn xdg_session_type_counts_as_wayland() {
         assert_eq!(
-            run(true, &[("XDG_SESSION_TYPE", "wayland"), ("DISPLAY", ":1")]),
+            run(true, &[("XDG_SESSION_TYPE", "wayland")]),
+            vec![("__NV_DISABLE_EXPLICIT_SYNC", "1")]
+        );
+    }
+
+    #[test]
+    fn nvidia_x11_session_disables_dmabuf_renderer() {
+        assert_eq!(
+            run(true, &[("DISPLAY", ":0"), ("XDG_SESSION_TYPE", "x11")]),
+            vec![("WEBKIT_DISABLE_DMABUF_RENDERER", "1")]
+        );
+    }
+
+    #[test]
+    fn user_forced_x11_on_wayland_counts_as_x11() {
+        let mut env = WAYLAND.to_vec();
+        env.push(("GDK_BACKEND", "x11"));
+        assert_eq!(
+            run(true, &env),
+            vec![("WEBKIT_DISABLE_DMABUF_RENDERER", "1")]
+        );
+        let mut env = WAYLAND.to_vec();
+        env.push(("GDK_BACKEND", "wayland,x11"));
+        assert_eq!(run(true, &env), vec![("__NV_DISABLE_EXPLICIT_SYNC", "1")]);
+    }
+
+    #[test]
+    fn safe_mode_adds_shared_memory_rendering_on_wayland() {
+        let mut env = WAYLAND.to_vec();
+        env.push(("LOTUS_GPU_SAFE_MODE", "1"));
+        assert_eq!(
+            run(true, &env),
             vec![
-                ("WEBKIT_DISABLE_DMABUF_RENDERER", "1"),
-                ("GDK_BACKEND", "x11")
+                ("__NV_DISABLE_EXPLICIT_SYNC", "1"),
+                ("WEBKIT_DISABLE_DMABUF_RENDERER", "1")
             ]
         );
     }
 
     #[test]
     fn user_settings_win() {
-        let env = [
-            ("WAYLAND_DISPLAY", "wayland-0"),
-            ("DISPLAY", ":0"),
-            ("WEBKIT_DISABLE_DMABUF_RENDERER", "0"),
-            ("GDK_BACKEND", "wayland"),
-        ];
+        let mut env = WAYLAND.to_vec();
+        env.push(("__NV_DISABLE_EXPLICIT_SYNC", "0"));
         assert!(run(true, &env).is_empty());
     }
 

src-tauri/src/lib.rs

@@ -1128,9 +1128,9 @@ pub fn run() {
                 // Tauri's default WebView2 args (setting this overrides them) and
                 // appends the Chromium background-throttling disables. Windows-only
                 // in effect; harmless elsewhere. Does not block system sleep.
-                .additional_browser_args(
-                    "--disable-features=msWebOOUI,msPdfOOUI --disable-background-timer-throttling --disable-renderer-backgrounding --disable-backgrounding-occluded-windows",
-                )
+                .additional_browser_args(&webview2_browser_args(
+                    std::env::var("LOTUS_WEBVIEW2_DEBUG_PORT").ok().as_deref(),
+                ))
                 .on_page_load(move |window, payload| {
                     if matches!(payload.event(), PageLoadEvent::Finished) {
                         // Reveal only on the FIRST settle: later page loads (e.g. a
@@ -1289,6 +1289,44 @@ pub fn run() {
         .expect("error while building tauri application");
 }
 
+/// WebView2 browser arguments. Setting them replaces Tauri's defaults, so
+/// they're kept, plus the Chromium background-throttling disables (P5-42).
+///
+/// cinny-desktop #19: `LOTUS_WEBVIEW2_DEBUG_PORT=<port>` in the environment
+/// opens WebView2's DevTools port on localhost so the Windows smoke test can
+/// drive the installed app. WebView2's own `WEBVIEW2_ADDITIONAL_BROWSER_ARGUMENTS`
+/// doesn't apply because the app sets its arguments explicitly. Off unless the
+/// variable holds a valid port; only whoever launches the app can set it.
+pub(crate) fn webview2_browser_args(debug_port: Option<&str>) -> String {
+    let mut args = String::from(
+        "--disable-features=msWebOOUI,msPdfOOUI --disable-background-timer-throttling --disable-renderer-backgrounding --disable-backgrounding-occluded-windows",
+    );
+    if let Some(port) = debug_port
+        .and_then(|p| p.trim().parse::<u16>().ok())
+        .filter(|p| *p >= 1024)
+    {
+        eprintln!("webview: DevTools port {port} open (LOTUS_WEBVIEW2_DEBUG_PORT)");
+        args.push_str(&format!(" --remote-debugging-port={port}"));
+    }
+    args
+}
+
+#[cfg(test)]
+mod webview2_args_tests {
+    use super::webview2_browser_args;
+
+    #[test]
+    fn debug_port_only_when_asked_for_and_valid() {
+        let base = webview2_browser_args(None);
+        assert!(base.contains("--disable-renderer-backgrounding"));
+        assert!(!base.contains("remote-debugging"));
+        assert!(webview2_browser_args(Some("9222")).ends_with(" --remote-debugging-port=9222"));
+        for bad in ["", "abc", "80", "70000", "9222 --evil", "-1"] {
+            assert_eq!(webview2_browser_args(Some(bad)), base, "{bad}");
+        }
+    }
+}
+
 #[cfg(test)]
 mod tray_tests {
     use super::*;