Background 02a tauri wry facts

Research note dated 2026-10-09. Read for reasoning, not current fact; later decisions in docs/decisions.md and docs/architecture-decisions.md win.

An appendix to note 02. Its wry facts still matter; its Tauri facts were overtaken by D3. Note 08 rechecks the wry details Syrinx depends on. Notes 07 and 08 correct parts of the earlier notes, and note 03 assumes Tauri.

Moved from docs/research/02a-tauri-wry-facts.md (original at af3de53) on 2026-10-16.

Tauri 2 and wry: what a browser tab can and can't do

Checked 2026-10-09 against tauri 2.12.2, wry 0.57.0 and the tauri-apps plugins. A helper of the browser-scope researcher (02-browser-v1-scope.md) gathered this and reported after that note was written, so it is kept here as an appendix. Confidence is marked (high, medium, low) as the helper gave it.

Short answer

Tabs as child webviews work, but:

• on Linux they don't lay out (child bounds are ignored);
• app keyboard shortcuts don't reach Syrinx while a page has focus, on Windows and on macOS;
• the Svelte UI cannot draw over a tab, because there is no z-order API and a child webview always draws above the main one;
• Tauri's maintainers said in September 2025 they have no capacity for multiwebview bugs.

The blockers are listed at the end.

A. What a browser tab can do

1. Webview and WebviewBuilder (high)

WebviewBuilder and Window::add_child need the unstable feature. On Windows the builder can deadlock if used from synchronous commands, so use async ones. Since 2.12.0, Tauri pins the unstable crates to minor versions (#15887).

• All desktop platforms: navigate, url, reload, eval, set_focus, set_auto_resize (child webviews are fixed-size by default), set_bounds, show / hide, reparent.
• Back and forward: Tauri has no native back/forward. go_back, go_forward and can_go_back exist on wry's WebView but Tauri doesn't expose them. Use JS history.back() or the raw platform webview.
• Zoom: set_zoom on all desktops (macOS 11+). zoom_hotkeys_enabled is native on Windows and a JS polyfill on macOS and Linux.
• Print: print is "currently only supported on macOS"; window.print() works everywhere.
• Navigation and loading: on_navigation can cancel a navigation by returning false. on_page_load gives Started and Finished only, with no progress and no load-error event.
• Downloads: on_download gives Requested (the save path can be changed) and Finished. On macOS the path in Finished is always empty.
• New windows and titles: on_new_window and on_document_title_changed arrived in 2.8.0 (August 2025). NewWindowResponse::Create accepts only a WebviewWindow, so a popup cannot be handed back as a new tab.
• Browsing data: clear_all_browsing_data is asynchronous. On Linux it clears the whole shared WebKit context; on Windows it errors on an old WebView2 runtime.
• Cookies: cookies, cookies_for_url, set_cookie, delete_cookie. On Windows they can deadlock in synchronous handlers.
• Storage: data_directory. On WKWebView the replacement is data_store_identifier, which needs macOS 14+.
• Private browsing: incognito needs WebView2 101+ on Windows and uses a non-persistent data store on macOS.
• Devtools: release builds need the devtools feature. On macOS it is a private API (not allowed in App Store builds). close_devtools and is_devtools_open are unsupported on Windows.
• Other builder options:
  • background_throttling needs macOS 14+.
  • proxy_url takes http:// or socks5://; macOS needs 14+ and the macos-proxy feature.
  • user_agent must be set per builder, because the config value isn't applied to child webviews (#9492, closed as not planned).
• Raw platform access: with_webview gives the platform objects:
  • Windows: ICoreWebView2Controller and its environment;
  • macOS: the WKWebView, its WKUserContentController and the NSWindow;
  • Linux: the webkit2gtk::WebView.
• No webview focus event: WebviewEvent only has DragDrop.

Sources: https://docs.rs/tauri/latest/tauri/webview/struct.Webview.html, https://docs.rs/tauri/latest/tauri/webview/struct.WebviewBuilder.html, https://docs.rs/tauri/latest/tauri/webview/enum.NewWindowResponse.html, https://docs.rs/wry/latest/wry/struct.WebView.html, https://v2.tauri.app/release/tauri/v2.8.0/

2. Window level (high)

• Fullscreen: set_fullscreen works on all desktops; set_simple_fullscreen is native on macOS only.
• Window effects: set_effects needs a transparent window and is unsupported on Linux. Mica and Tabbed are Windows 11 only. Acrylic has resize performance warnings. macOS has vibrancy materials, plus Liquid Glass on macOS 26.
• Shortcuts on Windows: menu accelerators do not fire while a webview has focus. wry #451 has been open since December 2021, priority high; WebView2 appears to consume the keys.
• Shortcuts on macOS: "global shortcuts not working in multiwebview" (wry #1177) is open. On 2025-09-23 a maintainer said the team "currently ha[s] no capacity to look into multiwebview issues". Tauri #9257 (the unstable feature breaks Cmd+A/C/V) is open.
• global-shortcut plugin: it registers OS-wide shortcuts, which makes it unsuitable for in-app shortcuts like Ctrl T. (medium)

Source: https://docs.rs/tauri/latest/tauri/window/enum.Effect.html, https://v2.tauri.app/plugin/global-shortcut/

3. Open multiwebview issues (23 under "scope: unstable flag")

• Focus: #13466 (Alt+Tab back leaves content unfocused on Windows) is open, though the 2.12.0 notes (2026-09-26) claim fixes in #15625 and #15950.
• macOS input: #8705 (double characters), #10194 (arrow keys print invalid characters), #10148 (undo/redo), all open.
• Z-order:
  • #11124: no API to order webviews (open);
  • #15682: a child webview always draws over the main one, so the DOM cannot overlay it (open);
  • #9798: new children appearing behind on Windows (fixed).
• Linux: #10420 (children are packed into a vertical GTK box, so set_bounds is ignored; fix PR #15463 open) and #15656 (wrong bounds on Wayland).
• Custom title bars: #12207 (can't resize a custom-titlebar window with unstable on Windows) and #14072 (macOS traffic-light position broken).
• Accessibility: tracking issue #207 has been open since 2019. #12901 (NVDA reads nothing in frameless windows on Windows, a regression since 2.3) is open.

B. Plugins and shipping

4. Updater, plugin 2.13.2 (high)

• Signing is mandatory ("This cannot be disabled"). It uses a minisign key pair from tauri signer generate, with the public key content in config.
• Server: either a static JSON file keyed OS-ARCH, or a dynamic server answering 204 (no update) or 200 with JSON.
• Windows install modes: passive (the default), basicUi or quiet. The app exits during the install.
• Artifacts:
  • macOS: .app.tar.gz;
  • Windows: -setup.exe or .msi, plus a .sig file;
  • Linux: AppImage (deb and rpm per the 2.10.0 changelog).
• TLS is enforced.

Source: https://v2.tauri.app/plugin/updater/

5. Deep links and single instance (medium)

• Custom schemes go in plugins.deep-link.desktop.schemes. Registering at runtime works on Windows and Linux only.
• Delivery: on Windows and Linux a link arrives as a new process's arguments. single-instance with its deep-link feature forwards them to the running instance. On macOS the running app gets on_open_url.
• http and https: Tauri has no desktop API for becoming the http/https handler (discussion #9184). Default-browser registry entries on Windows are not covered anywhere, so Syrinx writes them through installer hooks.

Sources: https://v2.tauri.app/plugin/deep-linking/, https://v2.tauri.app/plugin/single-instance/, https://github.com/orgs/tauri-apps/discussions/9184

6. Bundler (high)

• Windows: an NSIS -setup.exe or a WiX v3 .msi.
• macOS: .app and .dmg.
• Linux:
  • AppImage, 70+ MB; build it on the oldest distro with WebKitGTK 4.1;
  • deb and rpm;
  • Flatpak and Snap only as manual guides.
• Browser registration: bundle.fileAssociations registers file types. Extra registry entries, such as a browser's Capabilities key, go through NSIS installerHooks, WiX fragments, or a custom template.

Source: https://v2.tauri.app/distribute/windows-installer/

7. WebView2 install modes (high)

Mode	Added size	Notes
downloadBootstrapper	0 MB	The default; needs internet
embedBootstrapper	~1.8 MB
offlineInstaller	~127 MB
fixedVersion	~180 MB	You ship WebView2's security updates yourself
skip	0 MB	The app won't work without the runtime

8. Windows signing (high)

• SmartScreen: "Since 2024, an EV Certificate no longer gives your app an immediate reputation with Microsoft SmartScreen."
• Supported signing: certificate thumbprints, Azure Key Vault (through relic), and Azure Artifact Signing (through artifact-signing-cli as signCommand).

Source: https://v2.tauri.app/distribute/sign/windows/

9. macOS signing (high)

• Account: a paid Apple Developer account ($99 a year).
• Certificate: "Developer ID Application" outside the App Store.
• Notarization is required.

Source: https://v2.tauri.app/distribute/sign/macos/

10. Microsoft Store (high)

• No MSIX: Tauri only makes EXE and MSI installers.
• Store requirements: the installer must be the offline type, signed, install silently, and handle its own updates.

Source: https://v2.tauri.app/distribute/microsoft-store/

11. Crash reporting and telemetry (low)

• No official Tauri guidance covers crash reporting or states a telemetry policy; issue #166 (opt-in telemetry) is open with no decision.
• sentry-tauri is a community plugin.
• Tauri's own data collection: the helper found no evidence that Tauri itself collects data, but did not audit the source.

Would block a daily-use browser built on Tauri multiwebview

1. Linux tabs don't lay out. Child webview bounds are ignored (#10420).
2. App shortcuts don't reach Syrinx while a tab has focus: wry #451 on Windows; wry #1177 and Tauri #9257 on macOS.
3. No z-order and no overlay. The Svelte UI cannot draw over tab content (#11124, #15682), so the palette, the sidebar peek and any menus over a page need their own webview or another approach.
4. Missing tab APIs:
   • no back/forward or can_go_back in Tauri;
   • no load progress or load-error event;
   • no webview focus event;
   • print works on macOS only;
   • on_new_window can only return a window, not a tab.
5. macOS 14 floor for separate data stores and for the proxy.
6. NVDA reads nothing in frameless windows on Windows (#12901), which matters if Syrinx uses a custom title bar.
7. No maintainer capacity for the unstable multiwebview (stated September 2025).