diff --git a/codex-rs/core/tests/suite/config_warnings.rs b/codex-rs/core/tests/suite/config_warnings.rs
new file mode 100644
index 0000000000..b4d8f5b9d6
--- /dev/null
+++ b/codex-rs/core/tests/suite/config_warnings.rs
@@ -0,0 +1,49 @@
+use codex_config::CONFIG_TOML_FILE;
+use codex_protocol::config_types::Verbosity;
+use codex_protocol::protocol::AskForApproval;
+use codex_protocol::protocol::EventMsg;
+use codex_protocol::protocol::WarningEvent;
+use core_test_support::responses::start_mock_server;
+use core_test_support::test_codex::test_codex;
+use core_test_support::wait_for_event;
+use pretty_assertions::assert_eq;
+
+const INVALID_SANDBOX_WARNING: &str =
+    "Ignoring invalid config value at sandbox_mode: \"hyperdrive\"";
+
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn invalid_enum_config_emits_startup_warning_and_keeps_valid_settings() {
+    let server = start_mock_server().await;
+    let config_toml = r#"
+model = "gpt-4o"
+approval_policy = "never"
+sandbox_mode = "hyperdrive"
+model_verbosity = "high"
+"#;
+    let mut builder = test_codex().with_pre_build_hook(move |home| {
+        std::fs::write(home.join(CONFIG_TOML_FILE), config_toml).expect("seed config.toml");
+    });
+
+    let test = builder.build(&server).await.expect("create conversation");
+
+    assert_eq!(
+        (
+            test.session_configured.model.as_str(),
+            test.session_configured.approval_policy,
+            test.config.model_verbosity,
+        ),
+        ("gpt-4o", AskForApproval::Never, Some(Verbosity::High)),
+    );
+
+    let warning = wait_for_event(&test.codex, |event| {
+        matches!(
+            event,
+            EventMsg::Warning(WarningEvent { message }) if message == INVALID_SANDBOX_WARNING
+        )
+    })
+    .await;
+    let EventMsg::Warning(WarningEvent { message }) = warning else {
+        panic!("expected invalid config warning");
+    };
+    assert_eq!(message, INVALID_SANDBOX_WARNING);
+}
diff --git a/codex-rs/core/tests/suite/mod.rs b/codex-rs/core/tests/suite/mod.rs
index ad3280ebf0..f0e8b9bf3d 100644
--- a/codex-rs/core/tests/suite/mod.rs
+++ b/codex-rs/core/tests/suite/mod.rs
@@ -44,6 +44,7 @@ mod collaboration_instructions;
 mod compact;
 mod compact_remote;
 mod compact_resume_fork;
+mod config_warnings;
 mod deprecation_notice;
 mod exec;
 mod exec_policy;