fix(windows-path): preserve PATH order; include core env vars

codex-cli/bin/codex.js

@@ -73,9 +73,10 @@ const binaryPath = path.join(archRoot, "codex", codexBinaryName);
 function getUpdatedPath(newDirs) {
   const pathSep = process.platform === "win32" ? ";" : ":";
   const existingPath = process.env.PATH || "";
+  // Preserve caller PATH precedence by appending any additional dirs.
   const updatedPath = [
-    ...newDirs,
     ...existingPath.split(pathSep).filter(Boolean),
+    ...newDirs,
   ].join(pathSep);
   return updatedPath;
 }

codex-rs/arg0/src/lib.rs

@@ -179,9 +179,11 @@ fn prepend_path_entry_for_apply_patch() -> std::io::Result<TempDir> {
     const PATH_SEPARATOR: &str = ";";
 
     let path_element = path.display();
+    // Append our temp dir to PATH rather than prepending to avoid
+    // disturbing user PATH ordering (e.g., virtualenvs, shims).
     let updated_path_env_var = match std::env::var("PATH") {
         Ok(existing_path) => {
-            format!("{path_element}{PATH_SEPARATOR}{existing_path}")
+            format!("{existing_path}{PATH_SEPARATOR}{path_element}")
         }
         Err(_) => {
             format!("{path_element}")

codex-rs/rmcp-client/src/utils.rs

@@ -76,13 +76,37 @@ pub(crate) fn create_env_for_mcp_server(
     extra_env: Option<HashMap<String, String>>,
     env_vars: &[String],
 ) -> HashMap<String, String> {
-    DEFAULT_ENV_VARS
+    #[cfg(windows)]
+    let mut map: HashMap<String, String> = DEFAULT_ENV_VARS
         .iter()
         .copied()
         .chain(env_vars.iter().map(String::as_str))
         .filter_map(|var| env::var(var).ok().map(|value| (var.to_string(), value)))
         .chain(extra_env.unwrap_or_default())
-        .collect()
+        .collect();
+
+    #[cfg(not(windows))]
+    let map: HashMap<String, String> = DEFAULT_ENV_VARS
+        .iter()
+        .copied()
+        .chain(env_vars.iter().map(String::as_str))
+        .filter_map(|var| env::var(var).ok().map(|value| (var.to_string(), value)))
+        .chain(extra_env.unwrap_or_default())
+        .collect();
+
+    #[cfg(windows)]
+    {
+        // Some Windows programs look up the canonical-cased key `Path`.
+        // Ensure both `PATH` and `Path` are present with identical values.
+        if let Some(path_val) = map.get("PATH").cloned() {
+            map.entry("Path".to_string()).or_insert(path_val);
+        } else if let Ok(system_path) = env::var("PATH") {
+            map.insert("PATH".to_string(), system_path.clone());
+            map.entry("Path".to_string()).or_insert(system_path);
+        }
+    }
+
+    map
 }
 
 pub(crate) fn build_default_headers(
@@ -171,13 +195,33 @@ pub(crate) const DEFAULT_ENV_VARS: &[&str] = &[
 
 #[cfg(windows)]
 pub(crate) const DEFAULT_ENV_VARS: &[&str] = &[
+    // Core path resolution
     "PATH",
     "PATHEXT",
+    // Shell and system roots
+    "COMSPEC",
+    "SYSTEMROOT",
+    "SYSTEMDRIVE",
+    // User context and profiles
     "USERNAME",
     "USERDOMAIN",
     "USERPROFILE",
+    "HOMEDRIVE",
+    "HOMEPATH",
+    // Program locations
+    "PROGRAMFILES",
+    "PROGRAMFILES(X86)",
+    "PROGRAMW6432",
+    "PROGRAMDATA",
+    // App data and caches
+    "LOCALAPPDATA",
+    "APPDATA",
+    // Temp locations
     "TEMP",
     "TMP",
+    // Common shells/pwsh hints
+    "POWERSHELL",
+    "PWSH",
 ];
 
 #[cfg(test)]
@@ -223,6 +267,16 @@ mod tests {
         }
     }
 
+    #[test]
+    #[cfg(windows)]
+    fn windows_path_alias_is_present() {
+        let _guard = EnvVarGuard::set("PATH", r"C:\\Windows;C:\\Windows\\System32");
+        let env = create_env_for_mcp_server(None, &[]);
+        assert!(env.contains_key("PATH"));
+        assert!(env.contains_key("Path"));
+        assert_eq!(env.get("PATH"), env.get("Path"));
+    }
+
     #[tokio::test]
     async fn create_env_honors_overrides() {
         let value = "custom".to_string();