bug: fix model save (#3525)

Fix those 2 behaviors:
1. The model does not get saved if we don't CTRL + S
2. The reasoning effort get saved

codex-rs/core/src/codex.rs

@@ -9,9 +9,6 @@ use std::sync::atomic::AtomicU64;
 use std::time::Duration;
 
 use crate::AuthManager;
-use crate::config_edit::CONFIG_KEY_EFFORT;
-use crate::config_edit::CONFIG_KEY_MODEL;
-use crate::config_edit::persist_non_null_overrides;
 use crate::event_mapping::map_response_item_to_event_messages;
 use async_channel::Receiver;
 use async_channel::Sender;
@@ -1170,21 +1167,6 @@ async fn submission_loop(
                 turn_context = Arc::new(new_turn_context);
 
                 // Optionally persist changes to model / effort
-                let effort_str = effort.map(|_| effective_effort.to_string());
-
-                if let Err(e) = persist_non_null_overrides(
-                    &config.codex_home,
-                    config.active_profile.as_deref(),
-                    &[
-                        (&[CONFIG_KEY_MODEL], model.as_deref()),
-                        (&[CONFIG_KEY_EFFORT], effort_str.as_deref()),
-                    ],
-                )
-                .await
-                {
-                    warn!("failed to persist overrides: {e:#}");
-                }
-
                 if cwd.is_some() || approval_policy.is_some() || sandbox_policy.is_some() {
                     sess.record_conversation_items(&[ResponseItem::from(EnvironmentContext::new(
                         cwd,

codex-rs/core/tests/suite/mod.rs

@@ -7,6 +7,7 @@ mod exec;
 mod exec_stream_events;
 mod fork_conversation;
 mod live_cli;
+mod model_overrides;
 mod prompt_caching;
 mod seatbelt;
 mod stream_error_allows_next_turn;

codex-rs/core/tests/suite/model_overrides.rs

@@ -0,0 +1,92 @@
+use codex_core::CodexAuth;
+use codex_core::ConversationManager;
+use codex_core::protocol::EventMsg;
+use codex_core::protocol::Op;
+use codex_core::protocol_config_types::ReasoningEffort;
+use core_test_support::load_default_config_for_test;
+use core_test_support::wait_for_event;
+use pretty_assertions::assert_eq;
+use tempfile::TempDir;
+
+const CONFIG_TOML: &str = "config.toml";
+
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn override_turn_context_does_not_persist_when_config_exists() {
+    let codex_home = TempDir::new().unwrap();
+    let config_path = codex_home.path().join(CONFIG_TOML);
+    let initial_contents = "model = \"gpt-4o\"\n";
+    tokio::fs::write(&config_path, initial_contents)
+        .await
+        .expect("seed config.toml");
+
+    let mut config = load_default_config_for_test(&codex_home);
+    config.model = "gpt-4o".to_string();
+
+    let conversation_manager =
+        ConversationManager::with_auth(CodexAuth::from_api_key("Test API Key"));
+    let codex = conversation_manager
+        .new_conversation(config)
+        .await
+        .expect("create conversation")
+        .conversation;
+
+    codex
+        .submit(Op::OverrideTurnContext {
+            cwd: None,
+            approval_policy: None,
+            sandbox_policy: None,
+            model: Some("o3".to_string()),
+            effort: Some(ReasoningEffort::High),
+            summary: None,
+        })
+        .await
+        .expect("submit override");
+
+    codex.submit(Op::Shutdown).await.expect("request shutdown");
+    wait_for_event(&codex, |ev| matches!(ev, EventMsg::ShutdownComplete)).await;
+
+    let contents = tokio::fs::read_to_string(&config_path)
+        .await
+        .expect("read config.toml after override");
+    assert_eq!(contents, initial_contents);
+}
+
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn override_turn_context_does_not_create_config_file() {
+    let codex_home = TempDir::new().unwrap();
+    let config_path = codex_home.path().join(CONFIG_TOML);
+    assert!(
+        !config_path.exists(),
+        "test setup should start without config"
+    );
+
+    let config = load_default_config_for_test(&codex_home);
+
+    let conversation_manager =
+        ConversationManager::with_auth(CodexAuth::from_api_key("Test API Key"));
+    let codex = conversation_manager
+        .new_conversation(config)
+        .await
+        .expect("create conversation")
+        .conversation;
+
+    codex
+        .submit(Op::OverrideTurnContext {
+            cwd: None,
+            approval_policy: None,
+            sandbox_policy: None,
+            model: Some("o3".to_string()),
+            effort: Some(ReasoningEffort::Medium),
+            summary: None,
+        })
+        .await
+        .expect("submit override");
+
+    codex.submit(Op::Shutdown).await.expect("request shutdown");
+    wait_for_event(&codex, |ev| matches!(ev, EventMsg::ShutdownComplete)).await;
+
+    assert!(
+        !config_path.exists(),
+        "override should not create config.toml"
+    );
+}