feat: add list loaded threads to app server (#8902)

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

@@ -121,6 +121,10 @@ client_request_definitions! {
         params: v2::ThreadListParams,
         response: v2::ThreadListResponse,
     },
+    ThreadLoadedList => "thread/loaded/list" {
+        params: v2::ThreadLoadedListParams,
+        response: v2::ThreadLoadedListResponse,
+    },
     SkillsList => "skills/list" {
         params: v2::SkillsListParams,
         response: v2::SkillsListResponse,

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

@@ -1139,6 +1139,27 @@ pub struct ThreadListResponse {
     pub next_cursor: Option<String>,
 }
 
+#[derive(Serialize, Deserialize, Debug, Clone, PartialEq, Default, JsonSchema, TS)]
+#[serde(rename_all = "camelCase")]
+#[ts(export_to = "v2/")]
+pub struct ThreadLoadedListParams {
+    /// Opaque pagination cursor returned by a previous call.
+    pub cursor: Option<String>,
+    /// Optional page size; defaults to no limit.
+    pub limit: Option<u32>,
+}
+
+#[derive(Serialize, Deserialize, Debug, Clone, PartialEq, JsonSchema, TS)]
+#[serde(rename_all = "camelCase")]
+#[ts(export_to = "v2/")]
+pub struct ThreadLoadedListResponse {
+    /// Thread ids for sessions currently loaded in memory.
+    pub data: Vec<String>,
+    /// Opaque cursor to pass to the next call to continue after the last item.
+    /// if None, there are no more items to return.
+    pub next_cursor: Option<String>,
+}
+
 #[derive(Serialize, Deserialize, Debug, Clone, PartialEq, JsonSchema, TS)]
 #[serde(rename_all = "camelCase")]
 #[ts(export_to = "v2/")]

codex-rs/app-server/README.md

@@ -73,6 +73,7 @@ Example (from OpenAI's official VSCode extension):
 - `thread/start` — create a new thread; emits `thread/started` and auto-subscribes you to turn/item events for that thread.
 - `thread/resume` — reopen an existing thread by id so subsequent `turn/start` calls append to it.
 - `thread/list` — page through stored rollouts; supports cursor-based pagination and optional `modelProviders` filtering.
+- `thread/loaded/list` — list the thread ids currently loaded in memory.
 - `thread/archive` — move a thread’s rollout file into the archived directory; returns `{}` on success.
 - `thread/rollback` — drop the last N turns from the agent’s in-memory context and persist a rollback marker in the rollout so future resumes see the pruned history; returns the updated `thread` (with `turns` populated) on success.
 - `turn/start` — add user input to a thread and begin Codex generation; responds with the initial `turn` object and streams `turn/started`, `item/*`, and `turn/completed` notifications.
@@ -147,6 +148,17 @@ Example:
 
 When `nextCursor` is `null`, you’ve reached the final page.
 
+### Example: List loaded threads
+
+`thread/loaded/list` returns thread ids currently loaded in memory. This is useful when you want to check which sessions are active without scanning rollouts on disk.
+
+```json
+{ "method": "thread/loaded/list", "id": 21 }
+{ "id": 21, "result": {
+    "data": ["thr_123", "thr_456"]
+} }
+```
+
 ### Example: Archive a thread
 
 Use `thread/archive` to move the persisted rollout (stored as a JSONL file on disk) into the archived sessions directory.

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

@@ -89,6 +89,8 @@ use codex_app_server_protocol::ThreadArchiveResponse;
 use codex_app_server_protocol::ThreadItem;
 use codex_app_server_protocol::ThreadListParams;
 use codex_app_server_protocol::ThreadListResponse;
+use codex_app_server_protocol::ThreadLoadedListParams;
+use codex_app_server_protocol::ThreadLoadedListResponse;
 use codex_app_server_protocol::ThreadResumeParams;
 use codex_app_server_protocol::ThreadResumeResponse;
 use codex_app_server_protocol::ThreadRollbackParams;
@@ -376,6 +378,9 @@ impl CodexMessageProcessor {
             ClientRequest::ThreadList { request_id, params } => {
                 self.thread_list(request_id, params).await;
             }
+            ClientRequest::ThreadLoadedList { request_id, params } => {
+                self.thread_loaded_list(request_id, params).await;
+            }
             ClientRequest::SkillsList { request_id, params } => {
                 self.skills_list(request_id, params).await;
             }
@@ -1591,6 +1596,61 @@ impl CodexMessageProcessor {
         self.outgoing.send_response(request_id, response).await;
     }
 
+    async fn thread_loaded_list(&self, request_id: RequestId, params: ThreadLoadedListParams) {
+        let ThreadLoadedListParams { cursor, limit } = params;
+        let mut data = self
+            .thread_manager
+            .list_thread_ids()
+            .await
+            .into_iter()
+            .map(|thread_id| thread_id.to_string())
+            .collect::<Vec<_>>();
+
+        if data.is_empty() {
+            let response = ThreadLoadedListResponse {
+                data,
+                next_cursor: None,
+            };
+            self.outgoing.send_response(request_id, response).await;
+            return;
+        }
+
+        data.sort();
+        let total = data.len();
+        let start = match cursor {
+            Some(cursor) => {
+                let cursor = match ThreadId::from_string(&cursor) {
+                    Ok(id) => id.to_string(),
+                    Err(_) => {
+                        let error = JSONRPCErrorError {
+                            code: INVALID_REQUEST_ERROR_CODE,
+                            message: format!("invalid cursor: {cursor}"),
+                            data: None,
+                        };
+                        self.outgoing.send_error(request_id, error).await;
+                        return;
+                    }
+                };
+                match data.binary_search(&cursor) {
+                    Ok(idx) => idx + 1,
+                    Err(idx) => idx,
+                }
+            }
+            None => 0,
+        };
+
+        let effective_limit = limit.unwrap_or(total as u32).max(1) as usize;
+        let end = start.saturating_add(effective_limit).min(total);
+        let page = data[start..end].to_vec();
+        let next_cursor = page.last().filter(|_| end < total).cloned();
+
+        let response = ThreadLoadedListResponse {
+            data: page,
+            next_cursor,
+        };
+        self.outgoing.send_response(request_id, response).await;
+    }
+
     async fn thread_resume(&mut self, request_id: RequestId, params: ThreadResumeParams) {
         let ThreadResumeParams {
             thread_id,

codex-rs/app-server/tests/common/mcp_process.rs

@@ -44,6 +44,7 @@ use codex_app_server_protocol::ServerRequest;
 use codex_app_server_protocol::SetDefaultModelParams;
 use codex_app_server_protocol::ThreadArchiveParams;
 use codex_app_server_protocol::ThreadListParams;
+use codex_app_server_protocol::ThreadLoadedListParams;
 use codex_app_server_protocol::ThreadResumeParams;
 use codex_app_server_protocol::ThreadRollbackParams;
 use codex_app_server_protocol::ThreadStartParams;
@@ -335,6 +336,15 @@ impl McpProcess {
         self.send_request("thread/list", params).await
     }
 
+    /// Send a `thread/loaded/list` JSON-RPC request.
+    pub async fn send_thread_loaded_list_request(
+        &mut self,
+        params: ThreadLoadedListParams,
+    ) -> anyhow::Result<i64> {
+        let params = Some(serde_json::to_value(params)?);
+        self.send_request("thread/loaded/list", params).await
+    }
+
     /// Send a `model/list` JSON-RPC request.
     pub async fn send_list_models_request(
         &mut self,

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

@@ -6,6 +6,7 @@ mod rate_limits;
 mod review;
 mod thread_archive;
 mod thread_list;
+mod thread_loaded_list;
 mod thread_resume;
 mod thread_rollback;
 mod thread_start;

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

@@ -0,0 +1,139 @@
+use anyhow::Result;
+use app_test_support::McpProcess;
+use app_test_support::create_mock_chat_completions_server;
+use app_test_support::to_response;
+use codex_app_server_protocol::JSONRPCResponse;
+use codex_app_server_protocol::RequestId;
+use codex_app_server_protocol::ThreadLoadedListParams;
+use codex_app_server_protocol::ThreadLoadedListResponse;
+use codex_app_server_protocol::ThreadStartParams;
+use codex_app_server_protocol::ThreadStartResponse;
+use pretty_assertions::assert_eq;
+use std::path::Path;
+use tempfile::TempDir;
+use tokio::time::timeout;
+
+const DEFAULT_READ_TIMEOUT: std::time::Duration = std::time::Duration::from_secs(10);
+
+#[tokio::test]
+async fn thread_loaded_list_returns_loaded_thread_ids() -> Result<()> {
+    let server = create_mock_chat_completions_server(vec![]).await;
+    let codex_home = TempDir::new()?;
+    create_config_toml(codex_home.path(), &server.uri())?;
+
+    let mut mcp = McpProcess::new(codex_home.path()).await?;
+    timeout(DEFAULT_READ_TIMEOUT, mcp.initialize()).await??;
+
+    let thread_id = start_thread(&mut mcp).await?;
+
+    let list_id = mcp
+        .send_thread_loaded_list_request(ThreadLoadedListParams::default())
+        .await?;
+    let resp: JSONRPCResponse = timeout(
+        DEFAULT_READ_TIMEOUT,
+        mcp.read_stream_until_response_message(RequestId::Integer(list_id)),
+    )
+    .await??;
+    let ThreadLoadedListResponse {
+        mut data,
+        next_cursor,
+    } = to_response::<ThreadLoadedListResponse>(resp)?;
+    data.sort();
+    assert_eq!(data, vec![thread_id]);
+    assert_eq!(next_cursor, None);
+
+    Ok(())
+}
+
+#[tokio::test]
+async fn thread_loaded_list_paginates() -> Result<()> {
+    let server = create_mock_chat_completions_server(vec![]).await;
+    let codex_home = TempDir::new()?;
+    create_config_toml(codex_home.path(), &server.uri())?;
+
+    let mut mcp = McpProcess::new(codex_home.path()).await?;
+    timeout(DEFAULT_READ_TIMEOUT, mcp.initialize()).await??;
+
+    let first = start_thread(&mut mcp).await?;
+    let second = start_thread(&mut mcp).await?;
+
+    let mut expected = [first, second];
+    expected.sort();
+
+    let list_id = mcp
+        .send_thread_loaded_list_request(ThreadLoadedListParams {
+            cursor: None,
+            limit: Some(1),
+        })
+        .await?;
+    let resp: JSONRPCResponse = timeout(
+        DEFAULT_READ_TIMEOUT,
+        mcp.read_stream_until_response_message(RequestId::Integer(list_id)),
+    )
+    .await??;
+    let ThreadLoadedListResponse {
+        data: first_page,
+        next_cursor,
+    } = to_response::<ThreadLoadedListResponse>(resp)?;
+    assert_eq!(first_page, vec![expected[0].clone()]);
+    assert_eq!(next_cursor, Some(expected[0].clone()));
+
+    let list_id = mcp
+        .send_thread_loaded_list_request(ThreadLoadedListParams {
+            cursor: next_cursor,
+            limit: Some(1),
+        })
+        .await?;
+    let resp: JSONRPCResponse = timeout(
+        DEFAULT_READ_TIMEOUT,
+        mcp.read_stream_until_response_message(RequestId::Integer(list_id)),
+    )
+    .await??;
+    let ThreadLoadedListResponse {
+        data: second_page,
+        next_cursor,
+    } = to_response::<ThreadLoadedListResponse>(resp)?;
+    assert_eq!(second_page, vec![expected[1].clone()]);
+    assert_eq!(next_cursor, None);
+
+    Ok(())
+}
+
+fn create_config_toml(codex_home: &Path, server_uri: &str) -> std::io::Result<()> {
+    let config_toml = codex_home.join("config.toml");
+    std::fs::write(
+        config_toml,
+        format!(
+            r#"
+model = "mock-model"
+approval_policy = "never"
+sandbox_mode = "read-only"
+
+model_provider = "mock_provider"
+
+[model_providers.mock_provider]
+name = "Mock provider for test"
+base_url = "{server_uri}/v1"
+wire_api = "chat"
+request_max_retries = 0
+stream_max_retries = 0
+"#
+        ),
+    )
+}
+
+async fn start_thread(mcp: &mut McpProcess) -> Result<String> {
+    let req_id = mcp
+        .send_thread_start_request(ThreadStartParams {
+            model: Some("gpt-5.1".to_string()),
+            ..Default::default()
+        })
+        .await?;
+    let resp: JSONRPCResponse = timeout(
+        DEFAULT_READ_TIMEOUT,
+        mcp.read_stream_until_response_message(RequestId::Integer(req_id)),
+    )
+    .await??;
+    let ThreadStartResponse { thread, .. } = to_response::<ThreadStartResponse>(resp)?;
+    Ok(thread.id)
+}