fix: harden plugin feature gating (#15104)

Resubmit https://github.com/openai/codex/pull/15020 with correct
content.

1. Use requirement-resolved config.features as the plugin gate.
2. Guard plugin/list, plugin/read, and related flows behind that gate.
3. Skip bad marketplace.json files instead of failing the whole list.
4. Simplify plugin state and caching.

codex-rs/app-server/src/codex_message_processor.rs

@@ -4842,6 +4842,7 @@ impl CodexMessageProcessor {
             MarketplaceError::InvalidMarketplaceFile { .. }
             | MarketplaceError::PluginNotFound { .. }
             | MarketplaceError::PluginNotAvailable { .. }
+            | MarketplaceError::PluginsDisabled
             | MarketplaceError::InvalidPlugin(_) => {
                 self.send_invalid_request_error(request_id, err.to_string())
                     .await;
@@ -5363,6 +5364,13 @@ impl CodexMessageProcessor {
                 .extend(valid_extra_roots);
         }
 
+        let config = match self.load_latest_config(/*fallback_cwd*/ None).await {
+            Ok(config) => config,
+            Err(error) => {
+                self.outgoing.send_error(request_id, error).await;
+                return;
+            }
+        };
         let skills_manager = self.thread_manager.skills_manager();
         let mut data = Vec::new();
         for cwd in cwds {
@@ -5370,7 +5378,7 @@ impl CodexMessageProcessor {
                 .get(&cwd)
                 .map_or(&[][..], std::vec::Vec::as_slice);
             let outcome = skills_manager
-                .skills_for_cwd_with_extra_user_roots(&cwd, force_reload, extra_roots)
+                .skills_for_cwd_with_extra_user_roots(&cwd, &config, force_reload, extra_roots)
                 .await;
             let errors = errors_to_info(&outcome.errors);
             let skills = skills_to_info(&outcome.skills, &outcome.disabled_paths);

codex-rs/app-server/tests/suite/v2/plugin_list.rs

@@ -28,12 +28,22 @@ use wiremock::matchers::path;
 const DEFAULT_TIMEOUT: Duration = Duration::from_secs(10);
 const TEST_CURATED_PLUGIN_SHA: &str = "0123456789abcdef0123456789abcdef01234567";
 
+fn write_plugins_enabled_config(codex_home: &std::path::Path) -> std::io::Result<()> {
+    std::fs::write(
+        codex_home.join("config.toml"),
+        r#"[features]
+plugins = true
+"#,
+    )
+}
+
 #[tokio::test]
-async fn plugin_list_returns_invalid_request_for_invalid_marketplace_file() -> Result<()> {
+async fn plugin_list_skips_invalid_marketplace_file() -> Result<()> {
     let codex_home = TempDir::new()?;
     let repo_root = TempDir::new()?;
     std::fs::create_dir_all(repo_root.path().join(".git"))?;
     std::fs::create_dir_all(repo_root.path().join(".agents/plugins"))?;
+    write_plugins_enabled_config(codex_home.path())?;
     std::fs::write(
         repo_root.path().join(".agents/plugins/marketplace.json"),
         "{not json",
@@ -57,14 +67,23 @@ async fn plugin_list_returns_invalid_request_for_invalid_marketplace_file() -> R
         })
         .await?;
 
-    let err = timeout(
+    let response: JSONRPCResponse = timeout(
         DEFAULT_TIMEOUT,
-        mcp.read_stream_until_error_message(RequestId::Integer(request_id)),
+        mcp.read_stream_until_response_message(RequestId::Integer(request_id)),
     )
     .await??;
+    let response: PluginListResponse = to_response(response)?;
 
-    assert_eq!(err.error.code, -32600);
-    assert!(err.error.message.contains("invalid marketplace file"));
+    assert!(
+        response.marketplaces.iter().all(|marketplace| {
+            marketplace.path
+                != AbsolutePathBuf::try_from(
+                    repo_root.path().join(".agents/plugins/marketplace.json"),
+                )
+                .expect("absolute marketplace path")
+        }),
+        "invalid marketplace should be skipped"
+    );
     Ok(())
 }
 
@@ -98,6 +117,7 @@ async fn plugin_list_rejects_relative_cwds() -> Result<()> {
 async fn plugin_list_accepts_omitted_cwds() -> Result<()> {
     let codex_home = TempDir::new()?;
     std::fs::create_dir_all(codex_home.path().join(".agents/plugins"))?;
+    write_plugins_enabled_config(codex_home.path())?;
     std::fs::write(
         codex_home.path().join(".agents/plugins/marketplace.json"),
         r#"{
@@ -385,6 +405,7 @@ async fn plugin_list_returns_plugin_interface_with_absolute_asset_paths() -> Res
     std::fs::create_dir_all(repo_root.path().join(".git"))?;
     std::fs::create_dir_all(repo_root.path().join(".agents/plugins"))?;
     std::fs::create_dir_all(plugin_root.join(".codex-plugin"))?;
+    write_plugins_enabled_config(codex_home.path())?;
     std::fs::write(
         repo_root.path().join(".agents/plugins/marketplace.json"),
         r#"{
@@ -518,6 +539,7 @@ async fn plugin_list_accepts_legacy_string_default_prompt() -> Result<()> {
     std::fs::create_dir_all(repo_root.path().join(".git"))?;
     std::fs::create_dir_all(repo_root.path().join(".agents/plugins"))?;
     std::fs::create_dir_all(plugin_root.join(".codex-plugin"))?;
+    write_plugins_enabled_config(codex_home.path())?;
     std::fs::write(
         repo_root.path().join(".agents/plugins/marketplace.json"),
         r#"{

codex-rs/app-server/tests/suite/v2/plugin_read.rs

@@ -232,6 +232,7 @@ async fn plugin_read_accepts_legacy_string_default_prompt() -> Result<()> {
   }
 }"##,
     )?;
+    write_plugins_enabled_config(&codex_home)?;
 
     let mut mcp = McpProcess::new(codex_home.path()).await?;
     timeout(DEFAULT_TIMEOUT, mcp.initialize()).await??;
@@ -285,6 +286,7 @@ async fn plugin_read_returns_invalid_request_when_plugin_is_missing() -> Result<
   ]
 }"#,
     )?;
+    write_plugins_enabled_config(&codex_home)?;
 
     let mut mcp = McpProcess::new(codex_home.path()).await?;
     timeout(DEFAULT_TIMEOUT, mcp.initialize()).await??;
@@ -336,6 +338,7 @@ async fn plugin_read_returns_invalid_request_when_plugin_manifest_is_missing() -
   ]
 }"#,
     )?;
+    write_plugins_enabled_config(&codex_home)?;
 
     let mut mcp = McpProcess::new(codex_home.path()).await?;
     timeout(DEFAULT_TIMEOUT, mcp.initialize()).await??;
@@ -382,3 +385,13 @@ fn write_installed_plugin(
     )?;
     Ok(())
 }
+
+fn write_plugins_enabled_config(codex_home: &TempDir) -> Result<()> {
+    std::fs::write(
+        codex_home.path().join("config.toml"),
+        r#"[features]
+plugins = true
+"#,
+    )?;
+    Ok(())
+}