diff --git a/desktop/src-tauri/process/src/error.rs b/desktop/src-tauri/process/src/error.rs
index 8869a463..94fec5f1 100644
--- a/desktop/src-tauri/process/src/error.rs
+++ b/desktop/src-tauri/process/src/error.rs
@@ -19,6 +19,7 @@ pub enum ProcessError {
     OpenerError(Arc<tauri_plugin_opener::Error>),
     InvalidArguments(String),
     FailedLaunch(String),
+    NotExecutable(String),
     NoCompat,
 }
 
@@ -39,6 +40,9 @@ impl Display for ProcessError {
             ProcessError::FailedLaunch(game_id) => {
                 &format!("Drop detected that the game {game_id} may have failed to launch properly")
             }
+            ProcessError::NotExecutable(command) => {
+                &format!("The command '{command}' exists but is not marked as executable")
+            }
             ProcessError::RequiredDependency(game_id, version_id) => &format!(
                 "Missing a required dependency to launch this game: {} {}",
                 game_id, version_id
diff --git a/desktop/src-tauri/process/src/parser.rs b/desktop/src-tauri/process/src/parser.rs
index 948fcf64..cbcfdc7b 100644
--- a/desktop/src-tauri/process/src/parser.rs
+++ b/desktop/src-tauri/process/src/parser.rs
@@ -1,4 +1,6 @@
-use std::path::PathBuf;
+use std::path::{Path, PathBuf};
+
+use log::info;
 
 use crate::error::ProcessError;
 
@@ -38,6 +40,41 @@ impl ParsedCommand {
             .to_string();
     }
 
+    pub fn make_command_absolute_if_local(&mut self, base: &Path) {
+        let candidate = base.join(&self.command);
+        if candidate.is_file() {
+            info!(
+                "resolved local command '{}' to absolute path '{}'",
+                self.command,
+                candidate.display()
+            );
+            self.command = candidate.to_string_lossy().to_string();
+        } else {
+            info!(
+                "command '{}' is not a local file in '{}', leaving as-is for PATH resolution",
+                self.command,
+                base.display()
+            );
+        }
+    }
+
+    pub fn ensure_executable(&self) -> Result<(), ProcessError> {
+        #[cfg(unix)]
+        {
+            use std::os::unix::fs::PermissionsExt;
+
+            if let Ok(metadata) = std::fs::metadata(&self.command) {
+                let is_executable =
+                    metadata.is_file() && metadata.permissions().mode() & 0o111 != 0;
+                if !is_executable {
+                    return Err(ProcessError::NotExecutable(self.command.clone()));
+                }
+            }
+        }
+
+        Ok(())
+    }
+
     pub fn reconstruct(self) -> String {
         let mut v = vec![];
         v.extend(self.env);
diff --git a/desktop/src-tauri/process/src/process_handlers.rs b/desktop/src-tauri/process/src/process_handlers.rs
index 977ea661..d3f343f2 100644
--- a/desktop/src-tauri/process/src/process_handlers.rs
+++ b/desktop/src-tauri/process/src/process_handlers.rs
@@ -312,9 +312,12 @@ impl ProcessHandler for UMUNativeLauncher {
         let pfx_dir = pfx_dir.join(meta.id.clone());
         create_dir_all(&pfx_dir)?;
 
+        let game_id_env = shell_words::quote(&format!("GAMEID={game_id}")).into_owned();
+        let wineprefix_env =
+            shell_words::quote(&format!("WINEPREFIX={}", pfx_dir.to_string_lossy())).into_owned();
+
         Ok(format!(
-            "GAMEID={game_id} UMU_NO_PROTON=1 WINEPREFIX={} {umu:?} {launch}",
-            pfx_dir.to_string_lossy(),
+            "{game_id_env} UMU_NO_PROTON=1 {wineprefix_env} {umu:?} {launch}",
             umu = UMU_LAUNCHER_EXECUTABLE
                 .as_ref()
                 .expect("Failed to get UMU_LAUNCHER_EXECUTABLE as ref"),
@@ -388,12 +391,17 @@ impl ProcessHandler for UMUCompatLauncher {
         if !proton_valid {
             return Err(ProcessError::NoCompat);
         }
-        let proton_env = format!("PROTONPATH={}", proton_path);
+
+        // Shell-quote the env assignments so values containing spaces (e.g. a
+        // Proton install named "Proton-GE Latest") aren't split into separate
+        // tokens and misinterpreted as the command by the launch parser.
+        let game_id_env = shell_words::quote(&format!("GAMEID={game_id}")).into_owned();
+        let proton_env = shell_words::quote(&format!("PROTONPATH={proton_path}")).into_owned();
+        let wineprefix_env =
+            shell_words::quote(&format!("WINEPREFIX={}", pfx_dir.to_string_lossy())).into_owned();
 
         Ok(format!(
-            "GAMEID={game_id} {} WINEPREFIX={} {umu:?} {launch}",
-            proton_env,
-            pfx_dir.to_string_lossy(),
+            "{game_id_env} {proton_env} {wineprefix_env} {umu:?} {launch}",
             umu = UMU_LAUNCHER_EXECUTABLE
                 .as_ref()
                 .expect("Failed to get UMU_LAUNCHER_EXECUTABLE as ref"),
diff --git a/desktop/src-tauri/process/src/process_manager.rs b/desktop/src-tauri/process/src/process_manager.rs
index e7389dec..5822c471 100644
--- a/desktop/src-tauri/process/src/process_manager.rs
+++ b/desktop/src-tauri/process/src/process_manager.rs
@@ -523,6 +523,13 @@ impl ProcessManager<'_> {
             install_dir.into(),
         );
 
+        let mut launch_parameters = launch_parameters;
+        launch_parameters
+            .0
+            .make_command_absolute_if_local(&launch_parameters.1);
+
+        launch_parameters.0.ensure_executable()?;
+
         info!(
             "launching (in {}): {:?}",
             launch_parameters.1.to_string_lossy(),