Namespace arg0 helpers by runtime family

codex-rs/arg0/src/lib.rs

@@ -8,6 +8,7 @@ use codex_apply_patch::CODEX_CORE_APPLY_PATCH_ARG1;
 use codex_exec_server::CODEX_FS_HELPER_ARG1;
 use codex_install_context::InstallContext;
 use codex_sandboxing::landlock::CODEX_LINUX_SANDBOX_ARG0;
+use codex_utils_home_dir::arg0_temp_root_for_runtime;
 use codex_utils_home_dir::find_codex_home;
 #[cfg(unix)]
 use std::os::unix::fs::symlink;
@@ -337,7 +338,7 @@ fn prepare_path_entry_for_codex_aliases(
 
     std::fs::create_dir_all(&codex_home)?;
     // Use a CODEX_HOME-scoped temp root to avoid cluttering the top-level directory.
-    let temp_root = codex_home.join("tmp").join("arg0");
+    let temp_root = arg0_temp_root_for_runtime(codex_home.as_path());
     std::fs::create_dir_all(&temp_root)?;
     #[cfg(unix)]
     {

codex-rs/core/src/config/permissions.rs

@@ -37,6 +37,7 @@ use codex_protocol::permissions::FileSystemSpecialPath;
 use codex_protocol::permissions::NetworkSandboxPolicy;
 use codex_protocol::permissions::project_roots_glob_pattern;
 use codex_utils_absolute_path::AbsolutePathBuf;
+use codex_utils_home_dir::arg0_temp_root_for_runtime;
 
 use super::ProjectConfig;
 
@@ -483,7 +484,7 @@ pub(crate) fn get_readable_roots_required_for_codex_runtime(
     zsh_path: Option<&PathBuf>,
     main_execve_wrapper_exe: Option<&PathBuf>,
 ) -> Vec<AbsolutePathBuf> {
-    let arg0_root = AbsolutePathBuf::from_absolute_path(codex_home.join("tmp").join("arg0")).ok();
+    let arg0_root = AbsolutePathBuf::from_absolute_path(arg0_temp_root_for_runtime(codex_home)).ok();
     let zsh_path = zsh_path.and_then(|path| AbsolutePathBuf::from_absolute_path(path).ok());
     let execve_wrapper_root = main_execve_wrapper_exe.and_then(|path| {
         let path = AbsolutePathBuf::from_absolute_path(path).ok()?;

codex-rs/core/src/config/permissions_tests.rs

@@ -18,6 +18,7 @@ use codex_protocol::permissions::FileSystemSandboxEntry;
 use codex_protocol::permissions::FileSystemSandboxPolicy;
 use codex_protocol::permissions::FileSystemSpecialPath;
 use codex_utils_absolute_path::AbsolutePathBuf;
+use codex_utils_home_dir::arg0_temp_root_for_runtime;
 use pretty_assertions::assert_eq;
 use std::collections::BTreeMap;
 use tempfile::TempDir;
@@ -49,7 +50,7 @@ async fn restricted_read_implicitly_allows_helper_executables() -> std::io::Resu
     let cwd = temp_dir.path().join("workspace");
     let codex_home = temp_dir.path().join(".codex");
     let zsh_path = temp_dir.path().join("runtime").join("zsh");
-    let arg0_root = codex_home.join("tmp").join("arg0");
+    let arg0_root = arg0_temp_root_for_runtime(&codex_home);
     let allowed_arg0_dir = arg0_root.join("codex-arg0-session");
     let sibling_arg0_dir = arg0_root.join("codex-arg0-other-session");
     let execve_wrapper = allowed_arg0_dir.join("codex-execve-wrapper");

codex-rs/utils/home-dir/src/lib.rs

@@ -1,5 +1,6 @@
 use codex_utils_absolute_path::AbsolutePathBuf;
 use dirs::home_dir;
+use std::path::Path;
 use std::path::PathBuf;
 
 /// Returns the path to the Codex configuration directory, which can be
@@ -17,6 +18,23 @@ pub fn find_codex_home() -> std::io::Result<AbsolutePathBuf> {
     find_codex_home_from_env(codex_home_env.as_deref())
 }
 
+/// Returns the CODEX_HOME-scoped arg0 helper root for the current runtime
+/// family so Windows and Unix/WSL helper shims never share the same namespace.
+pub fn arg0_temp_root_for_runtime(codex_home: &Path) -> PathBuf {
+    codex_home
+        .join("tmp")
+        .join("arg0")
+        .join(current_runtime_family())
+}
+
+fn current_runtime_family() -> &'static str {
+    if cfg!(windows) {
+        "windows"
+    } else {
+        "unix"
+    }
+}
+
 fn find_codex_home_from_env(codex_home_env: Option<&str>) -> std::io::Result<AbsolutePathBuf> {
     // Honor the `CODEX_HOME` environment variable when it is set to allow users
     // (and tests) to override the default location.
@@ -64,6 +82,7 @@ fn find_codex_home_from_env(codex_home_env: Option<&str>) -> std::io::Result<Abs
 
 #[cfg(test)]
 mod tests {
+    use super::arg0_temp_root_for_runtime;
     use super::find_codex_home_from_env;
     use codex_utils_absolute_path::AbsolutePathBuf;
     use dirs::home_dir;
@@ -131,4 +150,15 @@ mod tests {
         let expected = AbsolutePathBuf::from_absolute_path(expected).expect("absolute home");
         assert_eq!(resolved, expected);
     }
+
+    #[test]
+    fn arg0_temp_root_uses_runtime_family_namespace() {
+        let codex_home = PathBuf::from("/tmp/codex-home");
+        let expected_runtime = if cfg!(windows) { "windows" } else { "unix" };
+
+        assert_eq!(
+            arg0_temp_root_for_runtime(&codex_home),
+            codex_home.join("tmp").join("arg0").join(expected_runtime)
+        );
+    }
 }