Add config toggles for orchestrator skills and MCP (#28942)

## Why

Orchestrator-provided skills and Codex Apps MCP tools add model-visible
instructions, resources, and tools beyond the local workspace. Hosts
need config-level switches to disable those orchestrator-owned surfaces
independently, without disabling regular skills or regular MCP servers.

## What changed

- Adds `[orchestrator.skills].enabled` and `[orchestrator.mcp].enabled`
config entries, both defaulting to `true`.
- Includes the new settings in `config.schema.json` and in the config
lock so resolved thread configuration preserves the same orchestrator
exposure decisions.
- Threads `orchestrator.skills.enabled` through the app-server skills
extension so disabled orchestrator skills do not expose the `skills`
namespace or inject orchestrator skill context.
- Gates Codex Apps MCP exposure, app instructions, and app auth
eligibility on `orchestrator.mcp.enabled` while leaving non-Codex-Apps
MCP tools available.
- Updates the thread-manager sample config to disable both
orchestrator-owned surfaces.

## Verification

- Added config parsing, loading, defaulting, and schema coverage for the
new settings.
- Added MCP exposure coverage that `orchestrator.mcp.enabled = false`
removes Codex Apps tools while preserving regular MCP tools.
- Added app-server coverage that `orchestrator.skills.enabled = false`
prevents orchestrator skill tools, prompts, and resource reads from
reaching the model turn.

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

@@ -9111,6 +9111,39 @@ apps_mcp_product_sku = "tpp"
     Ok(())
 }
 
+#[tokio::test]
+async fn config_loads_orchestrator_settings_from_toml() -> std::io::Result<()> {
+    let codex_home = TempDir::new()?;
+    let cfg: ConfigToml = toml::from_str(
+        r#"
+model = "gpt-5.4"
+
+[orchestrator.skills]
+enabled = false
+
+[orchestrator.mcp]
+enabled = false
+"#,
+    )
+    .expect("TOML deserialization should succeed for orchestrator settings");
+
+    let config = Config::load_from_base_config_with_overrides(
+        cfg,
+        ConfigOverrides::default(),
+        codex_home.abs(),
+    )
+    .await?;
+
+    assert_eq!(
+        (
+            config.orchestrator_skills_enabled,
+            config.orchestrator_mcp_enabled
+        ),
+        (false, false)
+    );
+    Ok(())
+}
+
 #[tokio::test]
 async fn config_loads_mcp_oauth_callback_url_from_toml() -> std::io::Result<()> {
     let codex_home = TempDir::new()?;

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

@@ -690,6 +690,12 @@ pub struct Config {
     /// Whether to inject the `<skills_instructions>` developer block.
     pub include_skill_instructions: bool,
 
+    /// Whether orchestrator-owned skills are exposed to the model.
+    pub orchestrator_skills_enabled: bool,
+
+    /// Whether orchestrator-owned MCP tools are exposed to the model.
+    pub orchestrator_mcp_enabled: bool,
+
     /// Whether to inject the `<environment_context>` user block.
     pub include_environment_context: bool,
 
@@ -2425,6 +2431,12 @@ fn resolve_experimental_request_user_input_enabled(config_toml: &ConfigToml) ->
         .is_none_or(|config| config.enabled)
 }
 
+fn resolve_orchestrator_feature_enabled(
+    feature: Option<&codex_config::config_toml::OrchestratorFeatureToml>,
+) -> bool {
+    feature.and_then(|feature| feature.enabled).unwrap_or(true)
+}
+
 fn resolve_code_mode_config(config_toml: &ConfigToml) -> CodeModeConfig {
     let base = code_mode_toml_config(config_toml.features.as_ref());
 
@@ -2812,6 +2824,11 @@ impl Config {
 
         validate_model_providers(&cfg.model_providers)
             .map_err(|message| std::io::Error::new(std::io::ErrorKind::InvalidInput, message))?;
+        let orchestrator = cfg.orchestrator.as_ref();
+        let orchestrator_skills_enabled =
+            resolve_orchestrator_feature_enabled(orchestrator.and_then(|value| value.skills.as_ref()));
+        let orchestrator_mcp_enabled =
+            resolve_orchestrator_feature_enabled(orchestrator.and_then(|value| value.mcp.as_ref()));
         // Ensure that every field of ConfigRequirements is applied to the final
         // Config.
         let ConfigRequirements {
@@ -3688,6 +3705,8 @@ impl Config {
             include_apps_instructions,
             include_collaboration_mode_instructions,
             include_skill_instructions,
+            orchestrator_skills_enabled,
+            orchestrator_mcp_enabled,
             include_environment_context,
             // The config.toml omits "_mode" because it's a config file. However, "_mode"
             // is important in code to differentiate the mode from the store implementation.