feat(app-server): add optional thread_id to experimentalFeature/list (#23335)

## Why

`experimentalFeature/list` reports effective feature enablement, but
currently does not resolve it against a working directory where
project-local config.toml files can exist and toggle on/off features
when merged into the effective config after resolving the various config
layers. That means we effectively (and incorrectly) ignore features set
in project-local config.

To address that, this PR exposes an optional `thread_id` param which
allows us to load the thread's `cwd.

## Testing

- `cargo test -p codex-app-server-protocol`
- `cargo test -p codex-app-server experimental_feature_list`

codex-rs/app-server-protocol/schema/json/ClientRequest.json

@@ -611,6 +611,13 @@
             "integer",
             "null"
           ]
+        },
+        "threadId": {
+          "description": "Optional loaded thread id. Pass this when showing feature state for an existing thread so enablement is computed from that thread's refreshed config, including project-local config for the thread's cwd.",
+          "type": [
+            "string",
+            "null"
+          ]
         }
       },
       "type": "object"

codex-rs/app-server-protocol/schema/json/codex_app_server_protocol.schemas.json

@@ -8194,6 +8194,13 @@
               "integer",
               "null"
             ]
+          },
+          "threadId": {
+            "description": "Optional loaded thread id. Pass this when showing feature state for an existing thread so enablement is computed from that thread's refreshed config, including project-local config for the thread's cwd.",
+            "type": [
+              "string",
+              "null"
+            ]
           }
         },
         "title": "ExperimentalFeatureListParams",

codex-rs/app-server-protocol/schema/json/codex_app_server_protocol.v2.schemas.json

@@ -4583,6 +4583,13 @@
             "integer",
             "null"
           ]
+        },
+        "threadId": {
+          "description": "Optional loaded thread id. Pass this when showing feature state for an existing thread so enablement is computed from that thread's refreshed config, including project-local config for the thread's cwd.",
+          "type": [
+            "string",
+            "null"
+          ]
         }
       },
       "title": "ExperimentalFeatureListParams",

codex-rs/app-server-protocol/schema/json/v2/ExperimentalFeatureListParams.json

@@ -16,6 +16,13 @@
         "integer",
         "null"
       ]
+    },
+    "threadId": {
+      "description": "Optional loaded thread id. Pass this when showing feature state for an existing thread so enablement is computed from that thread's refreshed config, including project-local config for the thread's cwd.",
+      "type": [
+        "string",
+        "null"
+      ]
     }
   },
   "title": "ExperimentalFeatureListParams",

codex-rs/app-server-protocol/schema/typescript/v2/ExperimentalFeatureListParams.ts

@@ -10,4 +10,10 @@ cursor?: string | null,
 /**
  * Optional page size; defaults to a reasonable server-side value.
  */
-limit?: number | null, };
+limit?: number | null,
+/**
+ * Optional loaded thread id. Pass this when showing feature state for an
+ * existing thread so enablement is computed from that thread's refreshed
+ * config, including project-local config for the thread's cwd.
+ */
+threadId?: string | null, };

codex-rs/app-server-protocol/src/protocol/common.rs

@@ -2721,7 +2721,33 @@ mod tests {
                 "id": 8,
                 "params": {
                     "cursor": null,
-                    "limit": null
+                    "limit": null,
+                    "threadId": null
+                }
+            }),
+            serde_json::to_value(&request)?,
+        );
+        Ok(())
+    }
+
+    #[test]
+    fn serialize_list_experimental_features_with_thread_id() -> Result<()> {
+        let request = ClientRequest::ExperimentalFeatureList {
+            request_id: RequestId::Integer(8),
+            params: v2::ExperimentalFeatureListParams {
+                cursor: Some("3".to_string()),
+                limit: Some(2),
+                thread_id: Some("00000000-0000-4000-8000-000000000001".to_string()),
+            },
+        };
+        assert_eq!(
+            json!({
+                "method": "experimentalFeature/list",
+                "id": 8,
+                "params": {
+                    "cursor": "3",
+                    "limit": 2,
+                    "threadId": "00000000-0000-4000-8000-000000000001"
                 }
             }),
             serde_json::to_value(&request)?,

codex-rs/app-server-protocol/src/protocol/v2/experimental_feature.rs

@@ -14,6 +14,11 @@ pub struct ExperimentalFeatureListParams {
     /// Optional page size; defaults to a reasonable server-side value.
     #[ts(optional = nullable)]
     pub limit: Option<u32>,
+    /// Optional loaded thread id. Pass this when showing feature state for an
+    /// existing thread so enablement is computed from that thread's refreshed
+    /// config, including project-local config for the thread's cwd.
+    #[ts(optional = nullable)]
+    pub thread_id: Option<String>,
 }
 
 #[derive(Serialize, Deserialize, Debug, Clone, PartialEq, Eq, JsonSchema, TS)]

codex-rs/app-server/README.md

@@ -188,7 +188,7 @@ Example with notification opt-out:
 - `fs/changed` — notification emitted when watched paths change, including the `watchId` and `changedPaths`.
 - `model/list` — list available models (set `includeHidden: true` to include entries with `hidden: true`), with reasoning effort options, `additionalSpeedTiers`, optional legacy `upgrade` model ids, optional `upgradeInfo` metadata (`model`, `upgradeCopy`, `modelLink`, `migrationMarkdown`), and optional `availabilityNux` metadata.
 - `modelProvider/capabilities/read` — read provider-level capabilities for the currently configured model provider.
-- `experimentalFeature/list` — list feature flags with stage metadata (`beta`, `underDevelopment`, `stable`, etc.), enabled/default-enabled state, and cursor pagination. For non-beta flags, `displayName`/`description`/`announcement` are `null`.
+- `experimentalFeature/list` — list feature flags with stage metadata (`beta`, `underDevelopment`, `stable`, etc.), enabled/default-enabled state, and cursor pagination. Pass `threadId` when showing feature state for an existing loaded thread so `enabled` is computed from that thread's refreshed config, including project-local config for the thread's cwd; if omitted, the server uses its default config resolution context. For non-beta flags, `displayName`/`description`/`announcement` are `null`.
 - `experimentalFeature/enablement/set` — patch the in-memory process-wide runtime feature enablement for the currently supported feature keys (`apps`, `memories`, `plugins`, `tool_search`, `tool_suggest`, `tool_call_mcp_elicitation`). For each feature, precedence is: cloud requirements > --enable <feature_name> > config.toml > experimentalFeature/enablement/set (new) > code default.
 - `environment/add` — experimental; add or replace a named remote environment by `environmentId` and `execServerUrl` for later selection by `thread/start` or `turn/start`; returns `{}` and does not change the default environment.
 - `collaborationMode/list` — list available collaboration mode presets (experimental, no pagination). Built-in presets do not select a model; the Plan preset selects medium reasoning effort. This response omits built-in developer instructions; clients should either pass `settings.developer_instructions: null` when setting a mode to use Codex's built-in instructions, or provide their own instructions explicitly.

codex-rs/app-server/src/request_processors/catalog_processor.rs

@@ -285,8 +285,28 @@ impl CatalogRequestProcessor {
         &self,
         params: ExperimentalFeatureListParams,
     ) -> Result<ExperimentalFeatureListResponse, JSONRPCErrorError> {
-        let ExperimentalFeatureListParams { cursor, limit } = params;
-        let config = self.load_latest_config(/*fallback_cwd*/ None).await?;
+        let ExperimentalFeatureListParams {
+            cursor,
+            limit,
+            thread_id,
+        } = params;
+        let config = match thread_id.as_deref() {
+            Some(thread_id) => {
+                let thread_id = ThreadId::from_string(thread_id)
+                    .map_err(|err| invalid_request(format!("invalid thread id: {err}")))?;
+                let thread = self
+                    .thread_manager
+                    .get_thread(thread_id)
+                    .await
+                    .map_err(|_| invalid_request(format!("thread not found: {thread_id}")))?;
+                let thread_config = thread.config().await;
+                self.config_manager
+                    .load_latest_config_for_thread(thread_config.as_ref())
+                    .await
+                    .map_err(|err| internal_error(format!("failed to reload config: {err}")))?
+            }
+            None => self.load_latest_config(/*fallback_cwd*/ None).await?,
+        };
         let auth = self.auth_manager.auth().await;
         let workspace_codex_plugins_enabled = self
             .workspace_codex_plugins_enabled(&config, auth.as_ref())

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

@@ -3,6 +3,7 @@ use std::time::Duration;
 use anyhow::Result;
 use app_test_support::ChatGptAuthFixture;
 use app_test_support::McpProcess;
+use app_test_support::create_mock_responses_server_repeating_assistant;
 use app_test_support::to_response;
 use app_test_support::write_chatgpt_auth;
 use codex_app_server_protocol::ConfigReadParams;
@@ -16,6 +17,8 @@ use codex_app_server_protocol::ExperimentalFeatureStage;
 use codex_app_server_protocol::JSONRPCError;
 use codex_app_server_protocol::JSONRPCResponse;
 use codex_app_server_protocol::RequestId;
+use codex_app_server_protocol::ThreadStartParams;
+use codex_app_server_protocol::ThreadStartResponse;
 use codex_config::LoaderOverrides;
 use codex_config::types::AuthCredentialsStoreMode;
 use codex_core::config::ConfigBuilder;
@@ -156,6 +159,104 @@ async fn experimental_feature_list_marks_apps_and_plugins_disabled_by_workspace_
     Ok(())
 }
 
+#[tokio::test]
+async fn experimental_feature_list_resolves_thread_project_config() -> Result<()> {
+    let server = create_mock_responses_server_repeating_assistant("Done").await;
+    let codex_home = TempDir::new()?;
+    let workspace = TempDir::new()?;
+    let server_uri = server.uri();
+    let workspace_key = workspace.path().to_string_lossy().replace('\\', "\\\\");
+    std::fs::write(
+        codex_home.path().join("config.toml"),
+        format!(
+            r#"model = "mock-model"
+approval_policy = "never"
+sandbox_mode = "read-only"
+model_provider = "mock_provider"
+
+[projects."{workspace_key}"]
+trust_level = "trusted"
+
+[model_providers.mock_provider]
+name = "Mock provider for test"
+base_url = "{server_uri}/v1"
+wire_api = "responses"
+request_max_retries = 0
+stream_max_retries = 0
+"#
+        ),
+    )?;
+    let project_config_dir = workspace.path().join(".codex");
+    std::fs::create_dir_all(&project_config_dir)?;
+    std::fs::write(
+        project_config_dir.join("config.toml"),
+        r#"[features]
+memories = true
+"#,
+    )?;
+
+    let mut mcp = McpProcess::new_without_managed_config(codex_home.path()).await?;
+    timeout(DEFAULT_TIMEOUT, mcp.initialize()).await??;
+
+    let thread_start_id = mcp
+        .send_thread_start_request(ThreadStartParams {
+            cwd: Some(workspace.path().display().to_string()),
+            ..Default::default()
+        })
+        .await?;
+    let ThreadStartResponse { thread, .. } =
+        read_response::<ThreadStartResponse>(&mut mcp, thread_start_id).await?;
+
+    let request_id = mcp
+        .send_experimental_feature_list_request(ExperimentalFeatureListParams {
+            cursor: None,
+            limit: None,
+            thread_id: Some(thread.id),
+        })
+        .await?;
+
+    let actual = read_response::<ExperimentalFeatureListResponse>(&mut mcp, request_id).await?;
+    let memories = actual
+        .data
+        .iter()
+        .find(|feature| feature.name == "memories")
+        .expect("memories feature should be present");
+    assert!(memories.enabled);
+
+    Ok(())
+}
+
+#[tokio::test]
+async fn experimental_feature_list_rejects_unknown_thread_id() -> Result<()> {
+    let codex_home = TempDir::new()?;
+    let mut mcp = McpProcess::new(codex_home.path()).await?;
+    timeout(DEFAULT_TIMEOUT, mcp.initialize()).await??;
+
+    let request_id = mcp
+        .send_experimental_feature_list_request(ExperimentalFeatureListParams {
+            cursor: None,
+            limit: None,
+            thread_id: Some("00000000-0000-4000-8000-000000000001".to_string()),
+        })
+        .await?;
+    let JSONRPCError { error, .. } = timeout(
+        DEFAULT_TIMEOUT,
+        mcp.read_stream_until_error_message(RequestId::Integer(request_id)),
+    )
+    .await??;
+
+    assert_eq!(error.code, -32600);
+    assert!(
+        error
+            .message
+            .contains("thread not found: 00000000-0000-4000-8000-000000000001"),
+        "{}",
+        error.message
+    );
+
+    Ok(())
+}
+
 #[tokio::test]
 async fn experimental_feature_enablement_set_applies_to_global_and_thread_config_reads()
 -> Result<()> {