From 323fe80df1f0a78fb2c8d1dfca7a635fd5e0a3c3 Mon Sep 17 00:00:00 2001
From: justanotheranonymoususer
 <justanotheranonymoususer@users.noreply.github.com>
Date: Fri, 9 Oct 2026 21:24:24 +0300
Subject: [PATCH] fix(single-instance): forward non-Unicode arguments and cwd
 (#3644)

* Update windows.rs

* Create single-instance-non-unicode-args.md

* fix on linux and windows too

---------

Co-authored-by: Lucas Nogueira <lucas@tauri.app>
---
 .changes/single-instance-non-unicode-args.md         |  5 +++++
 plugins/single-instance/src/lib.rs                   |  5 +++--
 plugins/single-instance/src/platform_impl/linux.rs   |  8 +++++---
 plugins/single-instance/src/platform_impl/macos.rs   | 10 ++++++----
 plugins/single-instance/src/platform_impl/windows.rs |  7 +++++--
 5 files changed, 24 insertions(+), 11 deletions(-)
 create mode 100644 .changes/single-instance-non-unicode-args.md

diff --git a/.changes/single-instance-non-unicode-args.md b/.changes/single-instance-non-unicode-args.md
new file mode 100644
index 000000000..9c6147b7a
--- /dev/null
+++ b/.changes/single-instance-non-unicode-args.md
@@ -0,0 +1,5 @@
+---
+"single-instance": patch
+---
+
+A second instance no longer panics when a command-line argument is not valid Unicode: such an argument is forwarded with its invalid parts replaced by U+FFFD. A working directory that is not valid Unicode is now forwarded the same way instead of as an empty string.
diff --git a/plugins/single-instance/src/lib.rs b/plugins/single-instance/src/lib.rs
index eaf358486..a5c35c582 100644
--- a/plugins/single-instance/src/lib.rs
+++ b/plugins/single-instance/src/lib.rs
@@ -39,8 +39,9 @@ pub(crate) type SingleInstanceCallback<R> =
 /// [`Builder::build`]. Use [`Builder`] directly if you need to set a custom [`Builder::dbus_id`].
 ///
 /// `f` is called with the app handle, the second instance's command line arguments
-/// (as collected by [`std::env::args`], so the first element is the executable path) and its
-/// current working directory. If the `deep-link` feature is enabled, the arguments are first
+/// (as collected by [`std::env::args_os`], so the first element is the executable path) and its
+/// current working directory. Arguments and the working directory that are not valid Unicode
+/// have their invalid parts replaced by U+FFFD. If the `deep-link` feature is enabled, the arguments are first
 /// forwarded to [`tauri-plugin-deep-link`](https://crates.io/crates/tauri-plugin-deep-link)
 /// before `f` runs.
 ///
diff --git a/plugins/single-instance/src/platform_impl/linux.rs b/plugins/single-instance/src/platform_impl/linux.rs
index 107f3e743..9ddadafbc 100644
--- a/plugins/single-instance/src/platform_impl/linux.rs
+++ b/plugins/single-instance/src/platform_impl/linux.rs
@@ -74,11 +74,13 @@ pub fn init<R: Runtime>(
                             Some("org.SingleInstance.DBus"),
                             "ExecuteCallback",
                             &(
-                                std::env::args().collect::<Vec<String>>(),
+                                std::env::args_os()
+                                    .map(|arg| arg.to_string_lossy().into_owned())
+                                    .collect::<Vec<String>>(),
                                 std::env::current_dir()
                                     .unwrap_or_default()
-                                    .to_str()
-                                    .unwrap_or_default(),
+                                    .to_string_lossy()
+                                    .as_ref(),
                             ),
                         );
                     }
diff --git a/plugins/single-instance/src/platform_impl/macos.rs b/plugins/single-instance/src/platform_impl/macos.rs
index ccd66f360..c038ff251 100644
--- a/plugins/single-instance/src/platform_impl/macos.rs
+++ b/plugins/single-instance/src/platform_impl/macos.rs
@@ -80,12 +80,14 @@ fn notify_singleton(socket: &PathBuf) -> Result<(), Error> {
     let mut bf = BufWriter::new(&stream);
     let cwd = std::env::current_dir()
         .unwrap_or_default()
-        .to_str()
-        .unwrap_or_default()
-        .to_string();
+        .to_string_lossy()
+        .into_owned();
     bf.write_all(cwd.as_bytes())?;
     bf.write_all(b"\0\0")?;
-    let args_joined = std::env::args().collect::<Vec<String>>().join("\0");
+    let args_joined = std::env::args_os()
+        .map(|arg| arg.to_string_lossy().into_owned())
+        .collect::<Vec<String>>()
+        .join("\0");
     bf.write_all(args_joined.as_bytes())?;
     bf.flush()?;
     drop(bf);
diff --git a/plugins/single-instance/src/platform_impl/windows.rs b/plugins/single-instance/src/platform_impl/windows.rs
index b19feb584..256c3f181 100644
--- a/plugins/single-instance/src/platform_impl/windows.rs
+++ b/plugins/single-instance/src/platform_impl/windows.rs
@@ -86,9 +86,12 @@ pub fn init<R: Runtime>(callback: Box<SingleInstanceCallback<R>>) -> TauriPlugin
                         }
 
                         let cwd = std::env::current_dir().unwrap_or_default();
-                        let cwd = cwd.to_str().unwrap_or_default();
+                        let cwd = cwd.to_string_lossy();
 
-                        let args = std::env::args().collect::<Vec<String>>().join("|");
+                        let args = std::env::args_os()
+                            .map(|arg| arg.to_string_lossy().into_owned())
+                            .collect::<Vec<String>>()
+                            .join("|");
 
                         let data = format!("{cwd}|{args}\0",);