diff --git a/codex-rs/core/src/exec_env.rs b/codex-rs/core/src/exec_env.rs
index 83ac8ad379..2c84792b70 100644
--- a/codex-rs/core/src/exec_env.rs
+++ b/codex-rs/core/src/exec_env.rs
@@ -38,6 +38,32 @@ where
         ShellEnvironmentPolicyInherit::All => vars.into_iter().collect(),
         ShellEnvironmentPolicyInherit::None => HashMap::new(),
         ShellEnvironmentPolicyInherit::Core => {
+            #[cfg(target_os = "windows")]
+            const CORE_VARS: &[&str] = &[
+                "APPDATA",
+                "COMSPEC",
+                "HOMEDRIVE",
+                "HOMEPATH",
+                "HOME",
+                "LOCALAPPDATA",
+                "LOGNAME",
+                "PATH",
+                "PATHEXT",
+                "PROGRAMDATA",
+                "PROGRAMFILES",
+                "PROGRAMFILES(X86)",
+                "PROGRAMW6432",
+                "SHELL",
+                "SYSTEMDRIVE",
+                "SYSTEMROOT",
+                "TEMP",
+                "TMP",
+                "TMPDIR",
+                "USER",
+                "USERNAME",
+                "USERPROFILE",
+            ];
+            #[cfg(not(target_os = "windows"))]
             const CORE_VARS: &[&str] = &[
                 "HOME", "LOGNAME", "PATH", "SHELL", "USER", "USERNAME", "TMPDIR", "TEMP", "TMP",
             ];
diff --git a/codex-rs/core/src/exec_env_tests.rs b/codex-rs/core/src/exec_env_tests.rs
index 6f001b5828..80f463c312 100644
--- a/codex-rs/core/src/exec_env_tests.rs
+++ b/codex-rs/core/src/exec_env_tests.rs
@@ -192,6 +192,48 @@ fn test_core_inherit_respects_case_insensitive_names_on_windows() {
     assert_eq!(result, expected);
 }
 
+#[test]
+#[cfg(target_os = "windows")]
+fn test_core_inherit_keeps_required_windows_runtime_vars() {
+    let vars = make_vars(&[
+        ("APPDATA", "C:\\Users\\alice\\AppData\\Roaming"),
+        ("ComSpec", "C:\\Windows\\System32\\cmd.exe"),
+        ("LOCALAPPDATA", "C:\\Users\\alice\\AppData\\Local"),
+        ("Path", "C:\\Windows\\System32"),
+        ("ProgramFiles", "C:\\Program Files"),
+        ("ProgramFiles(x86)", "C:\\Program Files (x86)"),
+        ("ProgramW6432", "C:\\Program Files"),
+        ("SystemDrive", "C:"),
+        ("SystemRoot", "C:\\Windows"),
+        ("USERPROFILE", "C:\\Users\\alice"),
+        ("FOO", "bar"),
+    ]);
+
+    let policy = ShellEnvironmentPolicy {
+        inherit: ShellEnvironmentPolicyInherit::Core,
+        ignore_default_excludes: true,
+        ..Default::default()
+    };
+
+    let thread_id = ThreadId::new();
+    let result = populate_env(vars, &policy, Some(thread_id));
+    let mut expected: HashMap<String, String> = hashmap! {
+        "APPDATA".to_string() => "C:\\Users\\alice\\AppData\\Roaming".to_string(),
+        "ComSpec".to_string() => "C:\\Windows\\System32\\cmd.exe".to_string(),
+        "LOCALAPPDATA".to_string() => "C:\\Users\\alice\\AppData\\Local".to_string(),
+        "Path".to_string() => "C:\\Windows\\System32".to_string(),
+        "ProgramFiles".to_string() => "C:\\Program Files".to_string(),
+        "ProgramFiles(x86)".to_string() => "C:\\Program Files (x86)".to_string(),
+        "ProgramW6432".to_string() => "C:\\Program Files".to_string(),
+        "SystemDrive".to_string() => "C:".to_string(),
+        "SystemRoot".to_string() => "C:\\Windows".to_string(),
+        "USERPROFILE".to_string() => "C:\\Users\\alice".to_string(),
+    };
+    expected.insert(CODEX_THREAD_ID_ENV_VAR.to_string(), thread_id.to_string());
+
+    assert_eq!(result, expected);
+}
+
 #[test]
 fn test_inherit_none() {
     let vars = make_vars(&[("PATH", "/usr/bin"), ("HOME", "/home")]);