Found while auditing the error-narrowing choke point for #242 / #270. This is separate from BUSY.
bridge_mobile_system.zig returns BridgeError.WebViewHandleNotSet from topmostViewController() and keyWindowScene() when the iOS dispatcher has no webview. ios_dispatch.asBridgeError currently recognizes the established handler-error subset plus Busy; an unlisted explicit bridge error falls through to NativeCallFailed. The page therefore receives NATIVE_CALL_FAILED instead of the more specific WEBVIEW_HANDLE_NOT_SET.
Relevant production returns:
packages/zig/src/bridge_mobile_system.zig:696packages/zig/src/bridge_mobile_system.zig:732- narrowing at
packages/zig/src/ios_dispatch.zig(asBridgeError)
The #270 fix deliberately preserves the pre-existing narrowing vocabulary except for adding Busy, so it does not silently broaden that corrective PR. A focused follow-up should decide whether all BridgeError members must survive narrowing, add a table-driven assertion for every protocol variant that handlers can return, and pin an affected system action end to end.