Move disable_paste_burst under [tui] (#41976)

## What changed

- Add `tui.disable_paste_burst` as the preferred configuration key.
- Keep the top-level `disable_paste_burst` key as a legacy fallback.
- Give the `[tui]` setting precedence when both keys are present, while preserving configuration-layer precedence.

## Testing

Add configuration tests covering defaults, both key locations, precedence between the keys, and command-line overrides.

GitOrigin-RevId: e7fc9337d5b19d2fd9407e08b8301cee77a11779

codex-rs/core/src/config/config_tests.rs

@@ -1210,6 +1210,7 @@ fn config_toml_deserializes_model_availability_nux() {
             notification_settings: TuiNotificationSettings::default(),
             animations: true,
             show_tooltips: true,
+            disable_paste_burst: None,
             vim_mode_default: false,
             raw_output_mode: false,
             alternate_screen: AltScreenMode::default(),
@@ -4289,6 +4290,7 @@ fn tui_config_missing_notifications_field_defaults_to_enabled() {
             notification_settings: TuiNotificationSettings::default(),
             animations: true,
             show_tooltips: true,
+            disable_paste_burst: None,
             vim_mode_default: false,
             raw_output_mode: false,
             alternate_screen: AltScreenMode::Auto,
@@ -4307,6 +4309,85 @@ fn tui_config_missing_notifications_field_defaults_to_enabled() {
     );
 }
 
+#[tokio::test]
+async fn runtime_config_resolves_disable_paste_burst() -> anyhow::Result<()> {
+    for (toml, expected) in [
+        ("", false),
+        ("disable_paste_burst = true", true),
+        ("disable_paste_burst = true\n[tui]", true),
+        ("[tui]\ndisable_paste_burst = true", true),
+        (
+            "disable_paste_burst = true\n[tui]\ndisable_paste_burst = false",
+            false,
+        ),
+        (
+            "disable_paste_burst = false\n[tui]\ndisable_paste_burst = true",
+            true,
+        ),
+    ] {
+        let config = Config::load_from_base_config_with_overrides(
+            toml::from_str(toml)?,
+            ConfigOverrides::default(),
+            tempdir()?.abs(),
+        )
+        .await?;
+
+        assert_eq!(config.disable_paste_burst, expected, "config: {toml}");
+    }
+    Ok(())
+}
+
+#[tokio::test]
+async fn disable_paste_burst_preserves_layering_and_new_key_precedence() -> anyhow::Result<()> {
+    for (toml, key, value, expected) in [
+        (
+            "disable_paste_burst = true",
+            "disable_paste_burst",
+            false,
+            false,
+        ),
+        (
+            "disable_paste_burst = true",
+            "tui.disable_paste_burst",
+            false,
+            false,
+        ),
+        (
+            "[tui]\ndisable_paste_burst = true",
+            "tui.disable_paste_burst",
+            false,
+            false,
+        ),
+        (
+            "[tui]\ndisable_paste_burst = true",
+            "disable_paste_burst",
+            false,
+            true,
+        ),
+        (
+            "[tui]\ndisable_paste_burst = false",
+            "disable_paste_burst",
+            true,
+            false,
+        ),
+    ] {
+        let codex_home = TempDir::new()?;
+        std::fs::write(codex_home.path().join(CONFIG_TOML_FILE), toml)?;
+        let config = ConfigBuilder::without_managed_config_for_tests()
+            .codex_home(codex_home.path().to_path_buf())
+            .fallback_cwd(Some(codex_home.path().to_path_buf()))
+            .cli_overrides(vec![(key.to_string(), TomlValue::Boolean(value))])
+            .build()
+            .await?;
+
+        assert_eq!(
+            config.disable_paste_burst, expected,
+            "config: {toml}, override: {key}={value}"
+        );
+    }
+    Ok(())
+}
+
 #[tokio::test]
 async fn runtime_config_resolves_terminal_resize_reflow_defaults_and_overrides() {
     let cfg = Config::load_from_base_config_with_overrides(

codex-rs/core/src/config/mod.rs

@@ -4302,7 +4302,12 @@ impl Config {
             active_project,
             notices,
             check_for_update_on_startup,
-            disable_paste_burst: cfg.disable_paste_burst.unwrap_or(false),
+            disable_paste_burst: cfg
+                .tui
+                .as_ref()
+                .and_then(|tui| tui.disable_paste_burst)
+                .or(cfg.disable_paste_burst)
+                .unwrap_or(false),
             analytics_enabled: cfg.analytics.as_ref().and_then(|a| a.enabled),
             feedback_enabled: cfg
                 .feedback