fix: prevent duplicate instances on windows by focusing existing window - #237
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Register tauri-plugin-single-instance as the first plugin on the builder, gated behind #[cfg(target_os = "windows")]. The callback shows and focuses the existing main window when a second instance is launched. macOS already handles this via RunEvent::Reopen.
kalvinnchau
approved these changes
Aug 27, 2026
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Category: fix
User Impact: On Windows, clicking the app icon when Berd is already running now focuses the existing window instead of launching a duplicate instance.
Problem: On Windows, launching Berd when it's already running starts a second full instance — duplicating log files, database connections, and the
goose servesidecar. macOS already handles this correctly viaRunEvent::Reopen.Solution: Register
tauri-plugin-single-instanceas the first plugin in the builder chain, gated behind#[cfg(target_os = "windows")]. The plugin uses a named mutex to detect an existing instance; the second instance exits early (before initializing any other plugins) and sends a message that triggers the existing instance to show and focus the main window. macOS continues using its existingRunEvent::Reopenhandler, which does the sameshow()+set_focus()pattern.Linear: BOT-1678
File changes
src-tauri/Cargo.toml
Added
tauri-plugin-single-instance = "2"dependency, matching the version pattern of all other tauri-plugin-* deps.src-tauri/Cargo.lock
Auto-generated lockfile entry for tauri-plugin-single-instance 2.4.3 and its transitive dependencies.
src-tauri/src/lib.rs
Registered the single-instance plugin as the first
.plugin()call on the builder, before all other plugins. Gated behind#[cfg(target_os = "windows")]so macOS (which usesRunEvent::Reopenat ~line 716) is unaffected. The callback callsshow()thenset_focus()on the"main"webview window —show()is required because the window starts hidden (visible: falsein tauri.conf.json).