emit a metric when we can't spawn powershell (#10125)

This will help diagnose and measure the impact of a user-reported bug
with the elevated sandbox and powershell

codex-rs/core/src/exec.rs

@@ -232,6 +232,72 @@ pub(crate) async fn execute_exec_env(
     finalize_exec_result(raw_output_result, sandbox, duration)
 }
 
+#[cfg(target_os = "windows")]
+fn extract_create_process_as_user_error_code(err: &str) -> Option<String> {
+    let marker = "CreateProcessAsUserW failed: ";
+    let start = err.find(marker)? + marker.len();
+    let tail = &err[start..];
+    let digits: String = tail.chars().take_while(char::is_ascii_digit).collect();
+    if digits.is_empty() {
+        None
+    } else {
+        Some(digits)
+    }
+}
+
+#[cfg(target_os = "windows")]
+fn windowsapps_path_kind(path: &str) -> &'static str {
+    let lower = path.to_ascii_lowercase();
+    if lower.contains("\\program files\\windowsapps\\") {
+        return "windowsapps_package";
+    }
+    if lower.contains("\\appdata\\local\\microsoft\\windowsapps\\") {
+        return "windowsapps_alias";
+    }
+    if lower.contains("\\windowsapps\\") {
+        return "windowsapps_other";
+    }
+    "other"
+}
+
+#[cfg(target_os = "windows")]
+fn record_windows_sandbox_spawn_failure(
+    command_path: Option<&str>,
+    windows_sandbox_level: codex_protocol::config_types::WindowsSandboxLevel,
+    err: &str,
+) {
+    let Some(error_code) = extract_create_process_as_user_error_code(err) else {
+        return;
+    };
+    let path = command_path.unwrap_or("unknown");
+    let exe = Path::new(path)
+        .file_name()
+        .and_then(|name| name.to_str())
+        .unwrap_or("unknown")
+        .to_ascii_lowercase();
+    let path_kind = windowsapps_path_kind(path);
+    let level = if matches!(
+        windows_sandbox_level,
+        codex_protocol::config_types::WindowsSandboxLevel::Elevated
+    ) {
+        "elevated"
+    } else {
+        "legacy"
+    };
+    if let Some(metrics) = codex_otel::metrics::global() {
+        let _ = metrics.counter(
+            "codex.windows_sandbox.createprocessasuserw_failed",
+            1,
+            &[
+                ("error_code", error_code.as_str()),
+                ("path_kind", path_kind),
+                ("exe", exe.as_str()),
+                ("level", level),
+            ],
+        );
+    }
+}
+
 #[cfg(target_os = "windows")]
 async fn exec_windows_sandbox(
     params: ExecParams,
@@ -265,7 +331,9 @@ async fn exec_windows_sandbox(
             "windows sandbox: failed to resolve codex_home: {err}"
         )))
     })?;
-    let use_elevated = matches!(windows_sandbox_level, WindowsSandboxLevel::Elevated);
+    let command_path = command.first().cloned();
+    let sandbox_level = windows_sandbox_level;
+    let use_elevated = matches!(sandbox_level, WindowsSandboxLevel::Elevated);
     let spawn_res = tokio::task::spawn_blocking(move || {
         if use_elevated {
             run_windows_sandbox_capture_elevated(
@@ -294,6 +362,11 @@ async fn exec_windows_sandbox(
     let capture = match spawn_res {
         Ok(Ok(v)) => v,
         Ok(Err(err)) => {
+            record_windows_sandbox_spawn_failure(
+                command_path.as_deref(),
+                sandbox_level,
+                &err.to_string(),
+            );
             return Err(CodexErr::Io(io::Error::other(format!(
                 "windows sandbox: {err}"
             ))));