Register named exec environments for app-server threads

Add execEnvironment register/list requests, thread start selection, and thread metadata plumbing so app-server threads can bind to a named exec-server environment.

Co-authored-by: Codex <noreply@openai.com>

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

@@ -241,6 +241,14 @@ client_request_definitions! {
         inspect_params: true,
         response: v2::ThreadStartResponse,
     },
+    ExecServerEnvironmentRegister => "execEnvironment/register" {
+        params: v2::ExecServerEnvironmentRegisterParams,
+        response: v2::ExecServerEnvironmentRegisterResponse,
+    },
+    ExecServerEnvironmentList => "execEnvironment/list" {
+        params: v2::ExecServerEnvironmentListParams,
+        response: v2::ExecServerEnvironmentListResponse,
+    },
     ThreadResume => "thread/resume" {
         params: v2::ThreadResumeParams,
         inspect_params: true,
@@ -1395,6 +1403,7 @@ mod tests {
                 thread: v2::Thread {
                     id: "67e55044-10b1-426f-9247-bb680e5fe0c8".to_string(),
                     forked_from_id: None,
+                    exec_environment_name: None,
                     preview: "first prompt".to_string(),
                     ephemeral: true,
                     model_provider: "openai".to_string(),
@@ -1433,6 +1442,7 @@ mod tests {
                     "thread": {
                         "id": "67e55044-10b1-426f-9247-bb680e5fe0c8",
                         "forkedFromId": null,
+                        "execEnvironmentName": null,
                         "preview": "first prompt",
                         "ephemeral": true,
                         "modelProvider": "openai",

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

@@ -2683,6 +2683,9 @@ pub struct ThreadStartParams {
     #[experimental("thread/start.mockExperimentalField")]
     #[ts(optional = nullable)]
     pub mock_experimental_field: Option<String>,
+    /// Optional named exec-server environment to use for this thread.
+    #[ts(optional = nullable)]
+    pub exec_environment_name: Option<String>,
     /// If true, opt into emitting raw Responses API items on the event stream.
     /// This is for internal use only (e.g. Codex Cloud).
     #[experimental("thread/start.experimentalRawEvents")]
@@ -2695,6 +2698,56 @@ pub struct ThreadStartParams {
     pub persist_extended_history: bool,
 }
 
+#[derive(Serialize, Deserialize, Debug, Clone, PartialEq, JsonSchema, TS)]
+#[serde(rename_all = "camelCase")]
+#[ts(export_to = "v2/")]
+pub struct ExecServerEnvironment {
+    /// Unique name used to reference this exec-server environment.
+    pub name: String,
+    /// Exec-server URL used when binding a thread to this environment.
+    pub exec_server_url: String,
+}
+
+#[derive(Serialize, Deserialize, Debug, Clone, PartialEq, Default, JsonSchema, TS)]
+#[serde(rename_all = "camelCase")]
+#[ts(export_to = "v2/")]
+pub struct ExecServerEnvironmentRegisterParams {
+    /// Human-readable name for selecting this environment in thread start.
+    pub name: String,
+    /// Exec-server URL to register under this environment name.
+    pub exec_server_url: String,
+}
+
+#[derive(Serialize, Deserialize, Debug, Clone, PartialEq, JsonSchema, TS)]
+#[serde(rename_all = "camelCase")]
+#[ts(export_to = "v2/")]
+pub struct ExecServerEnvironmentRegisterResponse {
+    /// The environment entry that was registered.
+    pub environment: ExecServerEnvironment,
+}
+
+#[derive(Serialize, Deserialize, Debug, Clone, PartialEq, Default, JsonSchema, TS)]
+#[serde(rename_all = "camelCase")]
+#[ts(export_to = "v2/")]
+pub struct ExecServerEnvironmentListParams {
+    /// Opaque pagination cursor returned by a previous call.
+    #[ts(optional = nullable)]
+    pub cursor: Option<String>,
+    /// Optional page size; defaults to a reasonable server-side value.
+    #[ts(optional = nullable)]
+    pub limit: Option<u32>,
+}
+
+#[derive(Serialize, Deserialize, Debug, Clone, PartialEq, JsonSchema, TS)]
+#[serde(rename_all = "camelCase")]
+#[ts(export_to = "v2/")]
+pub struct ExecServerEnvironmentListResponse {
+    pub data: Vec<ExecServerEnvironment>,
+    /// 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, Default, Clone, PartialEq, JsonSchema, TS)]
 #[serde(rename_all = "camelCase")]
 #[ts(export_to = "v2/")]
@@ -3718,6 +3771,8 @@ pub struct Thread {
     pub id: String,
     /// Source thread id when this thread was created by forking another thread.
     pub forked_from_id: Option<String>,
+    /// Optional named exec-server environment selected for this thread.
+    pub exec_environment_name: Option<String>,
     /// Usually the first user message in the thread, if available.
     pub preview: String,
     /// Whether the thread is ephemeral and should not be materialized on disk.
@@ -8576,6 +8631,7 @@ mod tests {
             "thread": {
                 "id": "thread-id",
                 "forkedFromId": null,
+                "execEnvironmentName": null,
                 "preview": "",
                 "ephemeral": false,
                 "modelProvider": "openai",

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

@@ -46,6 +46,11 @@ use codex_app_server_protocol::CommandExecWriteParams;
 use codex_app_server_protocol::ConversationGitInfo;
 use codex_app_server_protocol::ConversationSummary;
 use codex_app_server_protocol::DynamicToolSpec as ApiDynamicToolSpec;
+use codex_app_server_protocol::ExecServerEnvironment;
+use codex_app_server_protocol::ExecServerEnvironmentListParams;
+use codex_app_server_protocol::ExecServerEnvironmentListResponse;
+use codex_app_server_protocol::ExecServerEnvironmentRegisterParams;
+use codex_app_server_protocol::ExecServerEnvironmentRegisterResponse;
 use codex_app_server_protocol::ExperimentalFeature as ApiExperimentalFeature;
 use codex_app_server_protocol::ExperimentalFeatureListParams;
 use codex_app_server_protocol::ExperimentalFeatureListResponse;
@@ -244,6 +249,7 @@ use codex_core::sandboxing::SandboxPermissions;
 use codex_core::windows_sandbox::WindowsSandboxLevelExt;
 use codex_core::windows_sandbox::WindowsSandboxSetupMode as CoreWindowsSandboxSetupMode;
 use codex_core::windows_sandbox::WindowsSandboxSetupRequest;
+use codex_exec_server::EnvironmentManager;
 use codex_exec_server::LOCAL_FS;
 use codex_features::FEATURES;
 use codex_features::Feature;
@@ -439,6 +445,7 @@ pub(crate) struct CodexMessageProcessor {
     cli_overrides: Arc<RwLock<Vec<(String, TomlValue)>>>,
     runtime_feature_enablement: Arc<RwLock<BTreeMap<String, bool>>>,
     cloud_requirements: Arc<RwLock<CloudRequirementsLoader>>,
+    exec_environment_registry: ExecEnvironmentRegistry,
     active_login: Arc<Mutex<Option<ActiveLogin>>>,
     pending_thread_unloads: Arc<Mutex<HashSet<ThreadId>>>,
     thread_state_manager: ThreadStateManager,
@@ -472,6 +479,69 @@ struct ListenerTaskContext {
     codex_home: PathBuf,
 }
 
+#[derive(Clone, Default)]
+pub(crate) struct ExecEnvironmentRegistry {
+    environments: Arc<RwLock<BTreeMap<String, String>>>,
+}
+
+impl ExecEnvironmentRegistry {
+    fn register(
+        &self,
+        name: String,
+        exec_server_url: String,
+    ) -> Result<ExecServerEnvironment, String> {
+        let mut environments = self
+            .environments
+            .write()
+            .map_err(|_| "exec environment registry lock poisoned".to_string())?;
+        environments.insert(name.clone(), exec_server_url.clone());
+        Ok(ExecServerEnvironment {
+            name,
+            exec_server_url,
+        })
+    }
+
+    fn list(
+        &self,
+        cursor: Option<String>,
+        limit: Option<u32>,
+    ) -> Result<ExecServerEnvironmentListResponse, String> {
+        let environments = self
+            .environments
+            .read()
+            .map_err(|_| "exec environment registry lock poisoned".to_string())?;
+        let effective_limit = limit.unwrap_or(u32::MAX).max(1) as usize;
+        let mut data = Vec::new();
+        for (name, exec_server_url) in environments.iter() {
+            if cursor.as_ref().is_some_and(|cursor| name <= cursor) {
+                continue;
+            }
+            data.push(ExecServerEnvironment {
+                name: name.clone(),
+                exec_server_url: exec_server_url.clone(),
+            });
+            if data.len() >= effective_limit {
+                break;
+            }
+        }
+        let next_cursor = data.last().and_then(|last| {
+            environments
+                .range(last.name.clone()..)
+                .nth(1)
+                .map(|_| last.name.clone())
+        });
+        Ok(ExecServerEnvironmentListResponse { data, next_cursor })
+    }
+
+    fn resolve(&self, name: &str) -> Result<Option<String>, String> {
+        let environments = self
+            .environments
+            .read()
+            .map_err(|_| "exec environment registry lock poisoned".to_string())?;
+        Ok(environments.get(name).cloned())
+    }
+}
+
 #[derive(Clone, Copy, Debug, Eq, PartialEq)]
 enum EnsureConversationListenerResult {
     Attached,
@@ -599,6 +669,7 @@ pub(crate) struct CodexMessageProcessorArgs {
     pub(crate) cli_overrides: Arc<RwLock<Vec<(String, TomlValue)>>>,
     pub(crate) runtime_feature_enablement: Arc<RwLock<BTreeMap<String, bool>>>,
     pub(crate) cloud_requirements: Arc<RwLock<CloudRequirementsLoader>>,
+    pub(crate) exec_environment_registry: ExecEnvironmentRegistry,
     pub(crate) feedback: CodexFeedback,
     pub(crate) log_db: Option<LogDbLayer>,
 }
@@ -672,6 +743,7 @@ impl CodexMessageProcessor {
             cli_overrides,
             runtime_feature_enablement,
             cloud_requirements,
+            exec_environment_registry,
             feedback,
             log_db,
         } = args;
@@ -685,6 +757,7 @@ impl CodexMessageProcessor {
             cli_overrides,
             runtime_feature_enablement,
             cloud_requirements,
+            exec_environment_registry,
             active_login: Arc::new(Mutex::new(None)),
             pending_thread_unloads: Arc::new(Mutex::new(HashSet::new())),
             thread_state_manager: ThreadStateManager::new(),
@@ -852,6 +925,14 @@ impl CodexMessageProcessor {
                 )
                 .await;
             }
+            ClientRequest::ExecServerEnvironmentRegister { request_id, params } => {
+                self.exec_environment_register(to_connection_request_id(request_id), params)
+                    .await;
+            }
+            ClientRequest::ExecServerEnvironmentList { request_id, params } => {
+                self.exec_environment_list(to_connection_request_id(request_id), params)
+                    .await;
+            }
             ClientRequest::ThreadUnsubscribe { request_id, params } => {
                 self.thread_unsubscribe(to_connection_request_id(request_id), params)
                     .await;
@@ -2240,6 +2321,7 @@ impl CodexMessageProcessor {
             experimental_raw_events,
             personality,
             ephemeral,
+            exec_environment_name,
             session_start_source,
             persist_extended_history,
         } = params;
@@ -2271,6 +2353,24 @@ impl CodexMessageProcessor {
         };
         let request_trace = request_context.request_trace();
         let runtime_feature_enablement = self.current_runtime_feature_enablement();
+        let selected_exec_environment = match exec_environment_name {
+            Some(name) => match self.exec_environment_registry.resolve(&name) {
+                Ok(Some(exec_server_url)) => Some((name, exec_server_url)),
+                Ok(None) => {
+                    self.send_invalid_request_error(
+                        request_id,
+                        format!("unknown exec environment: {name}"),
+                    )
+                    .await;
+                    return;
+                }
+                Err(message) => {
+                    self.send_internal_error(request_id, message).await;
+                    return;
+                }
+            },
+            None => None,
+        };
         let thread_start_task = async move {
             Self::thread_start_task(
                 listener_task_context,
@@ -2283,6 +2383,7 @@ impl CodexMessageProcessor {
                 config,
                 typesafe_overrides,
                 dynamic_tools,
+                selected_exec_environment,
                 session_start_source,
                 persist_extended_history,
                 service_name,
@@ -2359,6 +2460,7 @@ impl CodexMessageProcessor {
         config_overrides: Option<HashMap<String, serde_json::Value>>,
         typesafe_overrides: ConfigOverrides,
         dynamic_tools: Option<Vec<ApiDynamicToolSpec>>,
+        selected_exec_environment: Option<(String, String)>,
         session_start_source: Option<codex_app_server_protocol::ThreadStartSource>,
         persist_extended_history: bool,
         service_name: Option<String>,
@@ -2496,10 +2598,17 @@ impl CodexMessageProcessor {
                 .collect()
         };
         let core_dynamic_tool_count = core_dynamic_tools.len();
+        let selected_exec_environment_name =
+            selected_exec_environment.as_ref().map(|(name, _)| name.clone());
+        let environment_manager_override = selected_exec_environment
+            .as_ref()
+            .map(|(_, exec_server_url)| {
+                Arc::new(EnvironmentManager::new(Some(exec_server_url.clone())))
+            });
 
         match listener_task_context
             .thread_manager
-            .start_thread_with_tools_and_service_name(
+            .start_thread_with_tools_service_name_and_environment_manager(
                 config,
                 match session_start_source
                     .unwrap_or(codex_app_server_protocol::ThreadStartSource::Startup)
@@ -2510,6 +2619,7 @@ impl CodexMessageProcessor {
                 core_dynamic_tools,
                 persist_extended_history,
                 service_name,
+                environment_manager_override,
                 request_trace,
             )
             .instrument(tracing::info_span!(
@@ -2552,6 +2662,7 @@ impl CodexMessageProcessor {
                     &config_snapshot,
                     session_configured.rollout_path.clone(),
                 );
+                thread.exec_environment_name = selected_exec_environment_name.clone();
 
                 // Auto-attach a thread listener when starting a thread.
                 Self::log_listener_attach_result(
@@ -2582,6 +2693,13 @@ impl CodexMessageProcessor {
                     ))
                     .await;
 
+                let thread_state = listener_task_context
+                    .thread_state_manager
+                    .thread_state(thread_id)
+                    .await;
+                thread_state.lock().await.exec_environment_name =
+                    selected_exec_environment_name.clone();
+
                 thread.status = resolve_thread_status(
                     listener_task_context
                         .thread_watch_manager
@@ -3755,18 +3873,18 @@ impl CodexMessageProcessor {
             .loaded_statuses_for_threads(status_ids)
             .await;
 
-        let data = threads
-            .into_iter()
-            .map(|(conversation_id, mut thread)| {
-                if let Some(title) = names.get(&conversation_id).cloned() {
-                    set_thread_name_from_title(&mut thread, title);
-                }
-                if let Some(status) = statuses.get(&thread.id) {
-                    thread.status = status.clone();
-                }
-                thread
-            })
-            .collect();
+        let mut data = Vec::with_capacity(threads.len());
+        for (conversation_id, mut thread) in threads {
+            if let Some(title) = names.get(&conversation_id).cloned() {
+                set_thread_name_from_title(&mut thread, title);
+            }
+            if let Some(status) = statuses.get(&thread.id) {
+                thread.status = status.clone();
+            }
+            self.attach_exec_environment_name(conversation_id, &mut thread)
+                .await;
+            data.push(thread);
+        }
         let response = ThreadListResponse { data, next_cursor };
         self.outgoing.send_response(request_id, response).await;
     }
@@ -3934,6 +4052,7 @@ impl CodexMessageProcessor {
             thread.forked_from_id = forked_from_id_from_rollout(rollout_path).await;
         }
         self.attach_thread_name(thread_uuid, &mut thread).await;
+        self.attach_exec_environment_name(thread_uuid, &mut thread).await;
 
         if include_turns && let Some(rollout_path) = rollout_path.as_ref() {
             match read_rollout_items_from_rollout(rollout_path).await {
@@ -3984,6 +4103,62 @@ impl CodexMessageProcessor {
         self.outgoing.send_response(request_id, response).await;
     }
 
+    async fn exec_environment_register(
+        &self,
+        request_id: ConnectionRequestId,
+        params: ExecServerEnvironmentRegisterParams,
+    ) {
+        if params.name.trim().is_empty() {
+            self.send_invalid_request_error(
+                request_id,
+                "exec environment name must not be empty".to_string(),
+            )
+            .await;
+            return;
+        }
+        if params.exec_server_url.trim().is_empty() {
+            self.send_invalid_request_error(
+                request_id,
+                "exec_server_url must not be empty".to_string(),
+            )
+            .await;
+            return;
+        }
+        match self
+            .exec_environment_registry
+            .register(params.name, params.exec_server_url)
+        {
+            Ok(environment) => {
+                self.outgoing
+                    .send_response(
+                        request_id,
+                        ExecServerEnvironmentRegisterResponse { environment },
+                    )
+                    .await;
+            }
+            Err(message) => self.send_internal_error(request_id, message).await,
+        }
+    }
+
+    async fn exec_environment_list(
+        &self,
+        request_id: ConnectionRequestId,
+        params: ExecServerEnvironmentListParams,
+    ) {
+        match self.exec_environment_registry.list(params.cursor, params.limit) {
+            Ok(response) => self.outgoing.send_response(request_id, response).await,
+            Err(message) => self.send_internal_error(request_id, message).await,
+        }
+    }
+
+    async fn attach_exec_environment_name(&self, thread_id: ThreadId, thread: &mut Thread) {
+        let thread_state = self.thread_state_manager.thread_state(thread_id).await;
+        if let Some(exec_environment_name) = thread_state.lock().await.exec_environment_name.clone()
+        {
+            thread.exec_environment_name = Some(exec_environment_name);
+        }
+    }
+
     pub(crate) fn thread_created_receiver(&self) -> broadcast::Receiver<ThreadId> {
         self.thread_manager.subscribe_thread_created()
     }
@@ -9608,6 +9783,7 @@ fn build_thread_from_snapshot(
     Thread {
         id: thread_id.to_string(),
         forked_from_id: None,
+        exec_environment_name: None,
         preview: String::new(),
         ephemeral: config_snapshot.ephemeral,
         model_provider: config_snapshot.model_provider_id.clone(),
@@ -9651,6 +9827,7 @@ pub(crate) fn summary_to_thread(summary: ConversationSummary) -> Thread {
     Thread {
         id: conversation_id.to_string(),
         forked_from_id: None,
+        exec_environment_name: None,
         preview,
         ephemeral: false,
         model_provider,

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

@@ -8,6 +8,7 @@ use std::sync::atomic::Ordering;
 
 use crate::codex_message_processor::CodexMessageProcessor;
 use crate::codex_message_processor::CodexMessageProcessorArgs;
+use crate::codex_message_processor::ExecEnvironmentRegistry;
 use crate::config_api::ConfigApi;
 use crate::error_code::INVALID_REQUEST_ERROR_CODE;
 use crate::external_agent_config_api::ExternalAgentConfigApi;
@@ -246,6 +247,7 @@ impl MessageProcessor {
         let cli_overrides = Arc::new(RwLock::new(cli_overrides));
         let runtime_feature_enablement = Arc::new(RwLock::new(BTreeMap::new()));
         let cloud_requirements = Arc::new(RwLock::new(cloud_requirements));
+        let exec_environment_registry = ExecEnvironmentRegistry::default();
         let codex_message_processor = CodexMessageProcessor::new(CodexMessageProcessorArgs {
             auth_manager: auth_manager.clone(),
             thread_manager: Arc::clone(&thread_manager),
@@ -256,6 +258,7 @@ impl MessageProcessor {
             cli_overrides: cli_overrides.clone(),
             runtime_feature_enablement: runtime_feature_enablement.clone(),
             cloud_requirements: cloud_requirements.clone(),
+            exec_environment_registry,
             feedback,
             log_db,
         });

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

@@ -58,6 +58,7 @@ pub(crate) struct ThreadState {
     pub(crate) pending_interrupts: PendingInterruptQueue,
     pub(crate) pending_rollbacks: Option<ConnectionRequestId>,
     pub(crate) turn_summary: TurnSummary,
+    pub(crate) exec_environment_name: Option<String>,
     pub(crate) cancel_tx: Option<oneshot::Sender<()>>,
     pub(crate) experimental_raw_events: bool,
     pub(crate) listener_generation: u64,

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

@@ -24,6 +24,8 @@ use codex_app_server_protocol::ConfigBatchWriteParams;
 use codex_app_server_protocol::ConfigReadParams;
 use codex_app_server_protocol::ConfigValueWriteParams;
 use codex_app_server_protocol::ExperimentalFeatureListParams;
+use codex_app_server_protocol::ExecServerEnvironmentListParams;
+use codex_app_server_protocol::ExecServerEnvironmentRegisterParams;
 use codex_app_server_protocol::FeedbackUploadParams;
 use codex_app_server_protocol::FsCopyParams;
 use codex_app_server_protocol::FsCreateDirectoryParams;
@@ -336,6 +338,24 @@ impl McpProcess {
         self.send_request("thread/start", params).await
     }
 
+    /// Send an `execEnvironment/register` JSON-RPC request.
+    pub async fn send_exec_environment_register_request(
+        &mut self,
+        params: ExecServerEnvironmentRegisterParams,
+    ) -> anyhow::Result<i64> {
+        let params = Some(serde_json::to_value(params)?);
+        self.send_request("execEnvironment/register", params).await
+    }
+
+    /// Send an `execEnvironment/list` JSON-RPC request.
+    pub async fn send_exec_environment_list_request(
+        &mut self,
+        params: ExecServerEnvironmentListParams,
+    ) -> anyhow::Result<i64> {
+        let params = Some(serde_json::to_value(params)?);
+        self.send_request("execEnvironment/list", params).await
+    }
+
     /// Send a `thread/resume` JSON-RPC request.
     pub async fn send_thread_resume_request(
         &mut self,

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

@@ -270,6 +270,7 @@ async fn skills_changed_notification_is_emitted_after_skill_change() -> Result<(
             developer_instructions: None,
             personality: None,
             ephemeral: None,
+            exec_environment_name: None,
             session_start_source: None,
             dynamic_tools: None,
             mock_experimental_field: None,

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

@@ -6,6 +6,10 @@ use app_test_support::to_response;
 use codex_app_server_protocol::JSONRPCError;
 use codex_app_server_protocol::JSONRPCResponse;
 use codex_app_server_protocol::RequestId;
+use codex_app_server_protocol::ExecServerEnvironmentListParams;
+use codex_app_server_protocol::ExecServerEnvironmentListResponse;
+use codex_app_server_protocol::ExecServerEnvironmentRegisterParams;
+use codex_app_server_protocol::ExecServerEnvironmentRegisterResponse;
 use codex_app_server_protocol::SessionSource;
 use codex_app_server_protocol::ThreadForkParams;
 use codex_app_server_protocol::ThreadForkResponse;
@@ -526,6 +530,101 @@ async fn thread_read_reports_system_error_idle_flag_after_failed_turn() -> Resul
     Ok(())
 }
 
+#[tokio::test]
+async fn registered_exec_environment_is_exposed_on_thread_surfaces() -> Result<()> {
+    let server = create_mock_responses_server_repeating_assistant("Done").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 register_id = mcp
+        .send_exec_environment_register_request(ExecServerEnvironmentRegisterParams {
+            name: "dev-remote".to_string(),
+            exec_server_url: "none".to_string(),
+        })
+        .await?;
+    let register_resp: JSONRPCResponse = timeout(
+        DEFAULT_READ_TIMEOUT,
+        mcp.read_stream_until_response_message(RequestId::Integer(register_id)),
+    )
+    .await??;
+    let ExecServerEnvironmentRegisterResponse { environment } =
+        to_response::<ExecServerEnvironmentRegisterResponse>(register_resp)?;
+    assert_eq!(environment.name, "dev-remote");
+    assert_eq!(environment.exec_server_url, "none");
+
+    let list_id = mcp
+        .send_exec_environment_list_request(ExecServerEnvironmentListParams {
+            cursor: None,
+            limit: Some(10),
+        })
+        .await?;
+    let list_resp: JSONRPCResponse = timeout(
+        DEFAULT_READ_TIMEOUT,
+        mcp.read_stream_until_response_message(RequestId::Integer(list_id)),
+    )
+    .await??;
+    let ExecServerEnvironmentListResponse { data, next_cursor } =
+        to_response::<ExecServerEnvironmentListResponse>(list_resp)?;
+    assert_eq!(next_cursor, None);
+    assert_eq!(data.len(), 1);
+    assert_eq!(data[0].name, "dev-remote");
+    assert_eq!(data[0].exec_server_url, "none");
+
+    let start_id = mcp
+        .send_thread_start_request(ThreadStartParams {
+            model: Some("mock-model".to_string()),
+            exec_environment_name: Some("dev-remote".to_string()),
+            ..Default::default()
+        })
+        .await?;
+    let start_resp: JSONRPCResponse = timeout(
+        DEFAULT_READ_TIMEOUT,
+        mcp.read_stream_until_response_message(RequestId::Integer(start_id)),
+    )
+    .await??;
+    let start_result = start_resp.result.clone();
+    let ThreadStartResponse { thread, .. } = to_response::<ThreadStartResponse>(start_resp)?;
+    assert_eq!(thread.exec_environment_name.as_deref(), Some("dev-remote"));
+    assert_eq!(
+        start_result
+            .get("thread")
+            .and_then(Value::as_object)
+            .and_then(|thread| thread.get("execEnvironmentName"))
+            .and_then(Value::as_str),
+        Some("dev-remote"),
+        "thread/start must serialize `thread.exec_environment_name` on the wire"
+    );
+
+    let read_id = mcp
+        .send_thread_read_request(ThreadReadParams {
+            thread_id: thread.id.clone(),
+            include_turns: false,
+        })
+        .await?;
+    let read_resp: JSONRPCResponse = timeout(
+        DEFAULT_READ_TIMEOUT,
+        mcp.read_stream_until_response_message(RequestId::Integer(read_id)),
+    )
+    .await??;
+    let read_result = read_resp.result.clone();
+    let ThreadReadResponse { thread: read_thread } = to_response::<ThreadReadResponse>(read_resp)?;
+    assert_eq!(read_thread.exec_environment_name.as_deref(), Some("dev-remote"));
+    assert_eq!(
+        read_result
+            .get("thread")
+            .and_then(Value::as_object)
+            .and_then(|thread| thread.get("execEnvironmentName"))
+            .and_then(Value::as_str),
+        Some("dev-remote"),
+        "thread/read must serialize `thread.exec_environment_name` on the wire"
+    );
+
+    Ok(())
+}
+
 // Helper to create a config.toml pointing at the mock model server.
 fn create_config_toml(codex_home: &Path, server_uri: &str) -> std::io::Result<()> {
     let config_toml = codex_home.join("config.toml");

codex-rs/core/src/agent/control.rs

@@ -238,10 +238,13 @@ impl AgentControl {
                         /*metrics_service_name*/ None,
                         inherited_shell_snapshot,
                         inherited_exec_policy,
+                        None,
                     )
                     .await?
             }
-            (None, _) => state.spawn_new_thread(config, self.clone()).await?,
+            (None, _) => state
+                .spawn_new_thread(config, self.clone(), None)
+                .await?,
         };
         agent_metadata.agent_id = Some(new_thread.thread_id);
         reservation.commit(agent_metadata.clone());

codex-rs/core/src/thread_manager.rs

@@ -496,6 +496,28 @@ impl ThreadManager {
         persist_extended_history: bool,
         metrics_service_name: Option<String>,
         parent_trace: Option<W3cTraceContext>,
+    ) -> CodexResult<NewThread> {
+        Box::pin(self.start_thread_with_tools_service_name_and_environment_manager(
+            config,
+            initial_history,
+            dynamic_tools,
+            persist_extended_history,
+            metrics_service_name,
+            /*environment_manager_override*/ None,
+            parent_trace,
+        ))
+        .await
+    }
+
+    pub async fn start_thread_with_tools_service_name_and_environment_manager(
+        &self,
+        config: Config,
+        initial_history: InitialHistory,
+        dynamic_tools: Vec<codex_protocol::dynamic_tools::DynamicToolSpec>,
+        persist_extended_history: bool,
+        metrics_service_name: Option<String>,
+        environment_manager_override: Option<Arc<EnvironmentManager>>,
+        parent_trace: Option<W3cTraceContext>,
     ) -> CodexResult<NewThread> {
         Box::pin(self.state.spawn_thread(
             config,
@@ -505,6 +527,7 @@ impl ThreadManager {
             dynamic_tools,
             persist_extended_history,
             metrics_service_name,
+            environment_manager_override,
             parent_trace,
             /*user_shell_override*/ None,
         ))
@@ -545,6 +568,7 @@ impl ThreadManager {
             Vec::new(),
             persist_extended_history,
             /*metrics_service_name*/ None,
+            /*environment_manager_override*/ None,
             parent_trace,
             /*user_shell_override*/ None,
         ))
@@ -564,6 +588,7 @@ impl ThreadManager {
             Vec::new(),
             /*persist_extended_history*/ false,
             /*metrics_service_name*/ None,
+            /*environment_manager_override*/ None,
             /*parent_trace*/ None,
             /*user_shell_override*/ Some(user_shell_override),
         ))
@@ -586,6 +611,7 @@ impl ThreadManager {
             Vec::new(),
             /*persist_extended_history*/ false,
             /*metrics_service_name*/ None,
+            /*environment_manager_override*/ None,
             /*parent_trace*/ None,
             /*user_shell_override*/ Some(user_shell_override),
         ))
@@ -694,6 +720,7 @@ impl ThreadManager {
             Vec::new(),
             persist_extended_history,
             /*metrics_service_name*/ None,
+            /*environment_manager_override*/ None,
             parent_trace,
             /*user_shell_override*/ None,
         ))
@@ -760,6 +787,7 @@ impl ThreadManagerState {
         &self,
         config: Config,
         agent_control: AgentControl,
+        environment_manager_override: Option<Arc<EnvironmentManager>>,
     ) -> CodexResult<NewThread> {
         Box::pin(self.spawn_new_thread_with_source(
             config,
@@ -769,6 +797,7 @@ impl ThreadManagerState {
             /*metrics_service_name*/ None,
             /*inherited_shell_snapshot*/ None,
             /*inherited_exec_policy*/ None,
+            environment_manager_override,
         ))
         .await
     }
@@ -783,6 +812,7 @@ impl ThreadManagerState {
         metrics_service_name: Option<String>,
         inherited_shell_snapshot: Option<Arc<ShellSnapshot>>,
         inherited_exec_policy: Option<Arc<crate::exec_policy::ExecPolicyManager>>,
+        environment_manager_override: Option<Arc<EnvironmentManager>>,
     ) -> CodexResult<NewThread> {
         Box::pin(self.spawn_thread_with_source(
             config,
@@ -795,6 +825,7 @@ impl ThreadManagerState {
             metrics_service_name,
             inherited_shell_snapshot,
             inherited_exec_policy,
+            environment_manager_override,
             /*parent_trace*/ None,
             /*user_shell_override*/ None,
         ))
@@ -822,6 +853,7 @@ impl ThreadManagerState {
             /*metrics_service_name*/ None,
             inherited_shell_snapshot,
             inherited_exec_policy,
+            /*environment_manager_override*/ None,
             /*parent_trace*/ None,
             /*user_shell_override*/ None,
         ))
@@ -850,6 +882,7 @@ impl ThreadManagerState {
             /*metrics_service_name*/ None,
             inherited_shell_snapshot,
             inherited_exec_policy,
+            /*environment_manager_override*/ None,
             /*parent_trace*/ None,
             /*user_shell_override*/ None,
         ))
@@ -867,6 +900,7 @@ impl ThreadManagerState {
         dynamic_tools: Vec<codex_protocol::dynamic_tools::DynamicToolSpec>,
         persist_extended_history: bool,
         metrics_service_name: Option<String>,
+        environment_manager_override: Option<Arc<EnvironmentManager>>,
         parent_trace: Option<W3cTraceContext>,
         user_shell_override: Option<crate::shell::Shell>,
     ) -> CodexResult<NewThread> {
@@ -881,6 +915,7 @@ impl ThreadManagerState {
             metrics_service_name,
             /*inherited_shell_snapshot*/ None,
             /*inherited_exec_policy*/ None,
+            environment_manager_override,
             parent_trace,
             user_shell_override,
         ))
@@ -900,6 +935,7 @@ impl ThreadManagerState {
         metrics_service_name: Option<String>,
         inherited_shell_snapshot: Option<Arc<ShellSnapshot>>,
         inherited_exec_policy: Option<Arc<crate::exec_policy::ExecPolicyManager>>,
+        environment_manager_override: Option<Arc<EnvironmentManager>>,
         parent_trace: Option<W3cTraceContext>,
         user_shell_override: Option<crate::shell::Shell>,
     ) -> CodexResult<NewThread> {
@@ -914,7 +950,8 @@ impl ThreadManagerState {
             config,
             auth_manager,
             models_manager: Arc::clone(&self.models_manager),
-            environment_manager: Arc::clone(&self.environment_manager),
+            environment_manager: environment_manager_override
+                .unwrap_or_else(|| Arc::clone(&self.environment_manager)),
             skills_manager: Arc::clone(&self.skills_manager),
             plugins_manager: Arc::clone(&self.plugins_manager),
             mcp_manager: Arc::clone(&self.mcp_manager),