diff --git a/apps/ai-game-creator-shell/src-tauri/src/agent/runtime_driver.rs b/apps/ai-game-creator-shell/src-tauri/src/agent/runtime_driver.rs
index f183e0f6b..02b48e807 100644
--- a/apps/ai-game-creator-shell/src-tauri/src/agent/runtime_driver.rs
+++ b/apps/ai-game-creator-shell/src-tauri/src/agent/runtime_driver.rs
@@ -2,8 +2,9 @@ use super::*;
 
 pub(super) static GAME_CREATOR_AGENT_RUNTIME_UPDATE_APP_HANDLE: OnceLock<tauri::AppHandle> =
     OnceLock::new();
-pub(super) static GAME_CREATOR_MANIFEST_INVALIDATION_EVENT_SINK: OnceLock<
-    std::sync::Mutex<Option<GameCreatorManifestInvalidationEventSink>>,
+/// 同一 AppData 允许多个界面窗口同时挂载事件接收端，因此这里是按 token 去重的注册表。
+pub(super) static GAME_CREATOR_MANIFEST_INVALIDATION_EVENT_SINKS: OnceLock<
+    std::sync::Mutex<Vec<GameCreatorManifestInvalidationEventSink>>,
 > = OnceLock::new();
 #[cfg(test)]
 pub(super) static GAME_CREATOR_MANIFEST_INVALIDATION_EVENT_SINK_TEST_LOCK: std::sync::Mutex<()> =
@@ -293,8 +294,8 @@ pub(crate) use entrypoints::{
     configure_game_creator_manifest_invalidation_event_sink, emit_direct_game_creator_progress,
     emit_game_creator_agent_runtime_update, emit_game_creator_manifest_invalidated,
     game_creator_agent_runtime_update_event, generate_local_game_draft_at,
-    install_game_creator_manifest_invalidation_event_sink, read_game_creator_agent_runtime_at,
-    read_game_creator_agent_runtime_for_session_at, read_game_creator_agent_runtimes_at,
+    read_game_creator_agent_runtime_at, read_game_creator_agent_runtime_for_session_at,
+    read_game_creator_agent_runtimes_at, register_game_creator_manifest_invalidation_event_sink,
     set_game_creator_agent_runtime_update_app_handle,
     start_game_creator_manifest_invalidation_event_sink,
     validate_game_creator_manifest_invalidation_event_sink,
diff --git a/apps/ai-game-creator-shell/src-tauri/src/agent/runtime_driver/entrypoints.rs b/apps/ai-game-creator-shell/src-tauri/src/agent/runtime_driver/entrypoints.rs
index 4038f1bcb..4e5177b10 100644
--- a/apps/ai-game-creator-shell/src-tauri/src/agent/runtime_driver/entrypoints.rs
+++ b/apps/ai-game-creator-shell/src-tauri/src/agent/runtime_driver/entrypoints.rs
@@ -1,11 +1,12 @@
 use super::*;
 
 const GAME_CREATOR_MANIFEST_INVALIDATION_RELAY_MAX_BYTES: u64 = 64 * 1024;
+const GAME_CREATOR_MANIFEST_INVALIDATION_EVENT_SINK_MAX: usize = 16;
 
-fn lock_game_creator_manifest_invalidation_event_sink(
-) -> std::sync::MutexGuard<'static, Option<GameCreatorManifestInvalidationEventSink>> {
-    GAME_CREATOR_MANIFEST_INVALIDATION_EVENT_SINK
-        .get_or_init(|| Mutex::new(None))
+fn lock_game_creator_manifest_invalidation_event_sinks(
+) -> std::sync::MutexGuard<'static, Vec<GameCreatorManifestInvalidationEventSink>> {
+    GAME_CREATOR_MANIFEST_INVALIDATION_EVENT_SINKS
+        .get_or_init(|| Mutex::new(Vec::new()))
         .lock()
         .unwrap_or_else(|poisoned| poisoned.into_inner())
 }
@@ -219,7 +220,7 @@ pub(crate) fn configure_game_creator_manifest_invalidation_event_sink(
     token: &str,
 ) -> Result<(), String> {
     let sink = validate_game_creator_manifest_invalidation_event_sink(port, token)?;
-    install_game_creator_manifest_invalidation_event_sink(sink);
+    register_game_creator_manifest_invalidation_event_sink(sink);
     Ok(())
 }
 
@@ -240,10 +241,29 @@ pub(crate) fn validate_game_creator_manifest_invalidation_event_sink(
     })
 }
 
-pub(crate) fn install_game_creator_manifest_invalidation_event_sink(
+/// 登记一个界面窗口的事件接收端。
+///
+/// 同一窗口重复 attach 用同一个 token，按 token 覆盖旧登记；不同窗口各自持有
+/// 自己的 token，注册表按登记顺序保留，最多 `GAME_CREATOR_MANIFEST_INVALIDATION_EVENT_SINK_MAX` 个。
+pub(crate) fn register_game_creator_manifest_invalidation_event_sink(
     sink: GameCreatorManifestInvalidationEventSink,
 ) {
-    *lock_game_creator_manifest_invalidation_event_sink() = Some(sink);
+    let mut sinks = lock_game_creator_manifest_invalidation_event_sinks();
+    if let Some(existing) = sinks
+        .iter_mut()
+        .find(|existing| existing.token == sink.token)
+    {
+        *existing = sink;
+        return;
+    }
+    if sinks.len() >= GAME_CREATOR_MANIFEST_INVALIDATION_EVENT_SINK_MAX {
+        sinks.remove(0);
+    }
+    sinks.push(sink);
+}
+
+fn remove_game_creator_manifest_invalidation_event_sink(token: &str) {
+    lock_game_creator_manifest_invalidation_event_sinks().retain(|sink| sink.token != token);
 }
 
 #[cfg(test)]
@@ -258,14 +278,20 @@ impl GameCreatorManifestInvalidationEventSinkTestGuard {
     }
 
     pub(crate) fn configured_sink(&self) -> Option<GameCreatorManifestInvalidationEventSink> {
-        lock_game_creator_manifest_invalidation_event_sink().clone()
+        lock_game_creator_manifest_invalidation_event_sinks()
+            .first()
+            .cloned()
+    }
+
+    pub(crate) fn configured_sinks(&self) -> Vec<GameCreatorManifestInvalidationEventSink> {
+        lock_game_creator_manifest_invalidation_event_sinks().clone()
     }
 }
 
 #[cfg(test)]
 impl Drop for GameCreatorManifestInvalidationEventSinkTestGuard {
     fn drop(&mut self) {
-        *lock_game_creator_manifest_invalidation_event_sink() = None;
+        lock_game_creator_manifest_invalidation_event_sinks().clear();
     }
 }
 
@@ -281,16 +307,43 @@ pub(crate) fn acquire_game_creator_manifest_invalidation_event_sink_test_guard(
 }
 
 fn relay_game_creator_manifest_invalidation(root: &Path, agent_id: &str) -> Result<(), String> {
-    let sink = lock_game_creator_manifest_invalidation_event_sink().clone();
-    let Some(sink) = sink else {
+    let sinks = lock_game_creator_manifest_invalidation_event_sinks().clone();
+    if sinks.is_empty() {
         return Ok(());
+    }
+    let event = GameCreatorManifestInvalidatedEvent {
+        project_path: root.to_string_lossy().into_owned(),
+        agent_id: agent_id.to_string(),
     };
+    let mut failed_tokens = Vec::new();
+    let mut last_error = None;
+    for sink in &sinks {
+        match relay_game_creator_manifest_invalidation_to_sink(sink, &event) {
+            Ok(()) => {}
+            Err(error) => {
+                // 窗口已退出或接收端已释放时只淘汰该接收端，不能影响其它窗口。
+                failed_tokens.push(sink.token.clone());
+                last_error = Some(error);
+            }
+        }
+    }
+    if !failed_tokens.is_empty() {
+        lock_game_creator_manifest_invalidation_event_sinks()
+            .retain(|sink| !failed_tokens.contains(&sink.token));
+    }
+    match last_error {
+        Some(error) => Err(error),
+        None => Ok(()),
+    }
+}
+
+fn relay_game_creator_manifest_invalidation_to_sink(
+    sink: &GameCreatorManifestInvalidationEventSink,
+    event: &GameCreatorManifestInvalidatedEvent,
+) -> Result<(), String> {
     let envelope = GameCreatorManifestInvalidationRelayEnvelope {
-        token: sink.token,
-        event: GameCreatorManifestInvalidatedEvent {
-            project_path: root.to_string_lossy().into_owned(),
-            agent_id: agent_id.to_string(),
-        },
+        token: sink.token.clone(),
+        event: event.clone(),
     };
     let payload = serde_json::to_vec(&envelope)
         .map_err(|error| format!("序列化 manifest 失效事件失败：{error}"))?;
diff --git a/apps/ai-game-creator-shell/src-tauri/src/main.rs b/apps/ai-game-creator-shell/src-tauri/src/main.rs
index dc26656c2..ea8d647e8 100644
--- a/apps/ai-game-creator-shell/src-tauri/src/main.rs
+++ b/apps/ai-game-creator-shell/src-tauri/src/main.rs
@@ -2219,6 +2219,8 @@ fn game_creator_gui_run_event_requests_runner_shutdown(event: &tauri::RunEvent)
 enum GameCreatorGuiRunnerShutdownOutcome {
     NotRequested,
     Requested,
+    /// 仍有其它界面窗口持有参与锁，Runner 必须保留给它们。
+    Retained,
     Failed(GameCreatorGuiRunnerShutdownFailure),
 }
 
@@ -2256,7 +2258,8 @@ fn classify_game_creator_gui_runner_shutdown_error(
         GameCreatorGuiRunnerShutdownFailure::ProcessIdentity
     } else if error.contains("当前平台不支持") || error.contains("macOS 不提供") {
         GameCreatorGuiRunnerShutdownFailure::PlatformUnsupported
-    } else if error.contains("实例锁") || error.contains("owner 锁") {
+    } else if error.contains("实例锁") || error.contains("参与锁") || error.contains("owner 锁")
+    {
         GameCreatorGuiRunnerShutdownFailure::LockTimeout
     } else if error.contains("endpoint") {
         GameCreatorGuiRunnerShutdownFailure::EndpointUnavailable
@@ -2272,13 +2275,14 @@ fn resolve_game_creator_gui_runner_shutdown<F>(
     shutdown: F,
 ) -> GameCreatorGuiRunnerShutdownOutcome
 where
-    F: FnOnce() -> Result<(), String>,
+    F: FnOnce() -> Result<bool, String>,
 {
     if !game_creator_gui_run_event_requests_runner_shutdown(event) {
         return GameCreatorGuiRunnerShutdownOutcome::NotRequested;
     }
     match shutdown() {
-        Ok(()) => GameCreatorGuiRunnerShutdownOutcome::Requested,
+        Ok(true) => GameCreatorGuiRunnerShutdownOutcome::Requested,
+        Ok(false) => GameCreatorGuiRunnerShutdownOutcome::Retained,
         Err(error) => GameCreatorGuiRunnerShutdownOutcome::Failed(
             classify_game_creator_gui_runner_shutdown_error(&error),
         ),
@@ -2298,11 +2302,17 @@ fn handle_game_creator_gui_run_event(event: &tauri::RunEvent) {
             app_log!("agent.direct_codex.gui_exit.shutdown_failed: {error}");
         }
     }
-    match resolve_game_creator_gui_runner_shutdown(event, shutdown_external_agent_runner) {
+    match resolve_game_creator_gui_runner_shutdown(
+        event,
+        shutdown_external_agent_runner_for_gui_exit,
+    ) {
         GameCreatorGuiRunnerShutdownOutcome::NotRequested => {}
         GameCreatorGuiRunnerShutdownOutcome::Requested => {
             app_log!("agent.runner.gui_exit.shutdown_requested")
         }
+        GameCreatorGuiRunnerShutdownOutcome::Retained => {
+            app_log!("agent.runner.gui_exit.retained_for_other_windows")
+        }
         GameCreatorGuiRunnerShutdownOutcome::Failed(failure) => {
             app_log!("agent.runner.gui_exit.shutdown_failed.{}", failure.code())
         }
@@ -2611,27 +2621,25 @@ fn main() {
                     )
                 })?;
             setup_log.append("startup.runner.configure.complete");
-            let gui_owner_lock = acquire_external_agent_runner_gui_owner_lock(&config_dir)
+            hold_external_agent_runner_gui_participant_lock(&config_dir)
                 .inspect_err(|error| {
                     let details = sanitize_diagnostic_message(error, Some(config_dir.as_path()));
                     setup_log.fail(&format!(
-                        "startup.runner.owner-lock.failed details={details}"
+                        "startup.runner.participant-lock.failed details={details}"
                     ));
                 })
                 .map_err(|error| {
                     std::io::Error::new(
                         std::io::ErrorKind::AlreadyExists,
-                        format!("获取 GUI owner 锁失败：{error}"),
+                        format!("建立 AGC 界面参与锁失败：{error}"),
                     )
                 })?;
-            let gui_owner_epoch = gui_owner_lock.owner_epoch().to_string();
-            app.manage(gui_owner_lock);
             setup_log.append("startup.runner.start.begin");
             set_game_creator_agent_runtime_update_app_handle(app.handle().clone());
             set_direct_thread_manager_app_handle(app.handle().clone());
             let manifest_event_sink =
                 start_game_creator_manifest_invalidation_event_sink(app.handle().clone())?;
-            attach_external_agent_runner_gui_owner(&manifest_event_sink, &gui_owner_epoch)
+            attach_external_agent_runner_gui_owner(&manifest_event_sink)
                 .inspect_err(|error| {
                     let details = sanitize_diagnostic_message(error, Some(config_dir.as_path()));
                     setup_log.fail(&format!(
diff --git a/apps/ai-game-creator-shell/src-tauri/src/runner.rs b/apps/ai-game-creator-shell/src-tauri/src/runner.rs
index be22c4d96..71fd5bf4c 100644
--- a/apps/ai-game-creator-shell/src-tauri/src/runner.rs
+++ b/apps/ai-game-creator-shell/src-tauri/src/runner.rs
@@ -12,21 +12,20 @@ pub(crate) use client::{
     clear_external_agent_runner_platform_session, compact_external_agent_runner_context,
     configure_external_agent_runner, configure_external_agent_runner_read_only,
     continue_external_agent_runner_action, ensure_external_agent_runner_started,
-    ensure_external_agent_runner_started_for_gui, install_external_agent_runner_platform_session,
+    ensure_external_agent_runner_started_for_gui, hold_external_agent_runner_gui_participant_lock,
+    install_external_agent_runner_platform_session,
     interrupt_external_agent_runner_provider_for_steer_decision, notify_external_agent_runner,
     pause_external_agent_runner, read_external_agent_runner_status,
     require_external_agent_runner_configured_for_cli_runtime_write,
     require_external_agent_runner_for_cli_runtime_write, resume_external_agent_runner,
     shutdown_external_agent_runner, shutdown_external_agent_runner_for_client_exit,
-    shutdown_external_agent_runner_if_idle, steer_external_agent_runner,
-    wake_external_agent_runner_pending, wake_external_agent_runner_pending_for_run,
+    shutdown_external_agent_runner_for_gui_exit, shutdown_external_agent_runner_if_idle,
+    steer_external_agent_runner, wake_external_agent_runner_pending,
+    wake_external_agent_runner_pending_for_run,
 };
 #[cfg(windows)]
 pub(crate) use endpoint::validate_windows_regular_file_handle;
-pub(crate) use endpoint::{
-    acquire_external_agent_runner_gui_owner_lock, external_agent_runner_enabled,
-    external_agent_runner_is_server_process,
-};
+pub(crate) use endpoint::{external_agent_runner_enabled, external_agent_runner_is_server_process};
 #[allow(unused_imports)]
 pub(crate) use protocol::{ExternalAgentRunnerStatus, EXTERNAL_AGENT_RUNNER_PROTOCOL_VERSION};
 pub(crate) use server::{
diff --git a/apps/ai-game-creator-shell/src-tauri/src/runner/client.rs b/apps/ai-game-creator-shell/src-tauri/src/runner/client.rs
index 6c6f9fdbf..12561a7f8 100644
--- a/apps/ai-game-creator-shell/src-tauri/src/runner/client.rs
+++ b/apps/ai-game-creator-shell/src-tauri/src/runner/client.rs
@@ -25,35 +25,76 @@ pub(super) struct ExternalAgentRunnerGuiOwnerAttachmentState {
 
 struct ExternalAgentRunnerGuiOwnerRegistration {
     generation: u64,
+    claim_mode: ExternalAgentRunnerGuiOwnerClaimMode,
     config_dir: PathBuf,
     params: ExternalAgentRunnerRequestParams,
     attached_boot_id: Option<String>,
 }
 
+/// claim 解析模式。
+///
+/// `Adopt` 用于窗口启动：沿用现有 durable claim，只有 claim 缺失或不可读时才发布。
+/// `Publish` 用于本窗口改动了平台登录态：发布新 epoch，成为新的登录态权威。
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+pub(super) enum ExternalAgentRunnerGuiOwnerClaimMode {
+    Adopt,
+    Publish,
+}
+
 static EXTERNAL_AGENT_RUNNER_GUI_OWNER_ATTACHMENT_STATE: OnceLock<
     Mutex<ExternalAgentRunnerGuiOwnerAttachmentState>,
 > = OnceLock::new();
 
+static EXTERNAL_AGENT_RUNNER_GUI_PARTICIPANT_LOCK: OnceLock<
+    Mutex<Option<ExternalAgentRunnerGuiParticipantLock>>,
+> = OnceLock::new();
+
 fn external_agent_runner_gui_owner_attachment_state(
 ) -> &'static Mutex<ExternalAgentRunnerGuiOwnerAttachmentState> {
     EXTERNAL_AGENT_RUNNER_GUI_OWNER_ATTACHMENT_STATE
         .get_or_init(|| Mutex::new(ExternalAgentRunnerGuiOwnerAttachmentState::default()))
 }
 
+fn external_agent_runner_gui_participant_lock(
+) -> &'static Mutex<Option<ExternalAgentRunnerGuiParticipantLock>> {
+    EXTERNAL_AGENT_RUNNER_GUI_PARTICIPANT_LOCK.get_or_init(|| Mutex::new(None))
+}
+
+/// 取得并持有本窗口的界面参与锁，直到窗口退出。
+///
+/// 参与锁是共享句柄锁：同一 AppData 的多个窗口可以同时持有，Runner 用独占探测
+/// 判断是否仍有窗口存活，因此这个锁同时也是“Runner 不能先退出”的存活凭据。
+pub(crate) fn hold_external_agent_runner_gui_participant_lock(
+    config_dir: &Path,
+) -> Result<(), String> {
+    let lock = acquire_external_agent_runner_gui_participant_lock(config_dir)?;
+    *lock_unpoisoned(external_agent_runner_gui_participant_lock()) = Some(lock);
+    Ok(())
+}
+
+fn release_external_agent_runner_gui_participant_lock() {
+    drop(lock_unpoisoned(external_agent_runner_gui_participant_lock()).take());
+}
+
+/// 登记本窗口的 owner claim 与 attach 参数。
+///
+/// 这里不做 claim 文件 IO：claim 由调用方按 `claim_mode` 解析后写进 `params`，
+/// 因此该函数可以在没有真实 AppData 的单元测试里使用。
 pub(super) fn register_external_agent_runner_gui_owner_attachment(
     state: &Mutex<ExternalAgentRunnerGuiOwnerAttachmentState>,
     config_dir: &Path,
+    claim_mode: ExternalAgentRunnerGuiOwnerClaimMode,
     mut params: ExternalAgentRunnerRequestParams,
 ) -> Result<(), String> {
     let mut state = lock_unpoisoned(state);
     state.generation = state.generation.wrapping_add(1);
     let generation = state.generation;
-    params.gui_owner_session_revision = Some(generation);
-    if let Some(owner_epoch) = params.gui_owner_epoch.as_deref() {
-        write_external_agent_runner_gui_owner_claim_atomic(config_dir, owner_epoch, generation)?;
+    if params.gui_owner_session_revision.is_none() {
+        params.gui_owner_session_revision = Some(generation);
     }
     state.registration = Some(ExternalAgentRunnerGuiOwnerRegistration {
         generation,
+        claim_mode,
         config_dir: config_dir.to_path_buf(),
         params,
         attached_boot_id: None,
@@ -61,6 +102,29 @@ pub(super) fn register_external_agent_runner_gui_owner_attachment(
     Ok(())
 }
 
+pub(super) fn reserve_external_agent_runner_gui_owner_claim_revision(
+    state: &Mutex<ExternalAgentRunnerGuiOwnerAttachmentState>,
+) -> u64 {
+    let mut state = lock_unpoisoned(state);
+    state.generation = state.generation.wrapping_add(1);
+    state.generation
+}
+
+pub(super) fn resolve_external_agent_runner_gui_owner_claim(
+    config_dir: &Path,
+    claim_mode: ExternalAgentRunnerGuiOwnerClaimMode,
+    session_revision: u64,
+) -> Result<ExternalAgentRunnerGuiOwnerClaim, String> {
+    match claim_mode {
+        ExternalAgentRunnerGuiOwnerClaimMode::Adopt => {
+            adopt_or_publish_external_agent_runner_gui_owner_claim(config_dir, session_revision)
+        }
+        ExternalAgentRunnerGuiOwnerClaimMode::Publish => {
+            publish_external_agent_runner_gui_owner_claim(config_dir, session_revision)
+        }
+    }
+}
+
 pub(super) fn attach_registered_external_agent_runner_gui_owner_if_needed_with<F>(
     state: &Mutex<ExternalAgentRunnerGuiOwnerAttachmentState>,
     config_dir: &Path,
@@ -68,27 +132,72 @@ pub(super) fn attach_registered_external_agent_runner_gui_owner_if_needed_with<F
     attach: F,
 ) -> Result<(), String>
 where
-    F: FnOnce(&ExternalAgentRunnerEndpoint, ExternalAgentRunnerRequestParams) -> Result<(), String>,
+    F: Fn(&ExternalAgentRunnerEndpoint, ExternalAgentRunnerRequestParams) -> Result<(), String>,
 {
-    let Some((generation, params)) = ({
-        let state = lock_unpoisoned(state);
-        state.registration.as_ref().and_then(|registration| {
-            (registration.config_dir == config_dir
-                && registration.attached_boot_id.as_deref() != Some(endpoint.boot_id.as_str()))
-            .then(|| (registration.generation, registration.params.clone()))
-        })
-    }) else {
-        return Ok(());
-    };
+    const ATTACH_CLAIM_RETRY_LIMIT: usize = 3;
+    let mut last_claim_error = None;
+    for attempt in 0..ATTACH_CLAIM_RETRY_LIMIT {
+        let Some((generation, params, claim_mode)) = ({
+            let state = lock_unpoisoned(state);
+            state.registration.as_ref().and_then(|registration| {
+                (registration.config_dir == config_dir
+                    && registration.attached_boot_id.as_deref() != Some(endpoint.boot_id.as_str()))
+                .then(|| {
+                    (
+                        registration.generation,
+                        registration.params.clone(),
+                        registration.claim_mode,
+                    )
+                })
+            })
+        }) else {
+            return Ok(());
+        };
 
-    attach(endpoint, params)?;
-
-    let mut state = lock_unpoisoned(state);
-    if let Some(registration) = state.registration.as_mut() {
-        if registration.generation == generation && registration.config_dir == config_dir {
-            registration.attached_boot_id = Some(endpoint.boot_id.clone());
+        match attach(endpoint, params) {
+            Ok(()) => {
+                let mut state = lock_unpoisoned(state);
+                if let Some(registration) = state.registration.as_mut() {
+                    if registration.generation == generation
+                        && registration.config_dir == config_dir
+                    {
+                        registration.attached_boot_id = Some(endpoint.boot_id.clone());
+                    }
+                }
+                return Ok(());
+            }
+            Err(error) if attempt + 1 < ATTACH_CLAIM_RETRY_LIMIT && error.contains("claim") => {
+                // 另一个窗口在本次 attach 前后发布了新 claim：按最新 claim 重新解析后重试。
+                last_claim_error = Some(error);
+                refresh_registered_external_agent_runner_gui_owner_claim(
+                    state, config_dir, claim_mode,
+                )?;
+            }
+            Err(error) => return Err(error),
         }
     }
+    Err(last_claim_error.unwrap_or_else(|| "Agent Runner attach 重试后仍然失败".to_string()))
+}
+
+fn refresh_registered_external_agent_runner_gui_owner_claim(
+    state: &Mutex<ExternalAgentRunnerGuiOwnerAttachmentState>,
+    config_dir: &Path,
+    claim_mode: ExternalAgentRunnerGuiOwnerClaimMode,
+) -> Result<(), String> {
+    let session_revision = reserve_external_agent_runner_gui_owner_claim_revision(state);
+    let claim =
+        resolve_external_agent_runner_gui_owner_claim(config_dir, claim_mode, session_revision)?;
+    let mut state = lock_unpoisoned(state);
+    let Some(registration) = state.registration.as_mut() else {
+        return Ok(());
+    };
+    if registration.config_dir != config_dir {
+        return Ok(());
+    }
+    registration.claim_mode = claim_mode;
+    registration.params.gui_owner_epoch = Some(claim.owner_epoch);
+    registration.params.gui_owner_session_revision = Some(claim.session_revision);
+    registration.attached_boot_id = None;
     Ok(())
 }
 
@@ -963,7 +1072,6 @@ pub(crate) fn shutdown_external_agent_runner() -> Result<(), String> {
 
 pub(crate) fn attach_external_agent_runner_gui_owner(
     event_sink: &GameCreatorManifestInvalidationEventSink,
-    gui_owner_epoch: &str,
 ) -> Result<(), String> {
     EXTERNAL_AGENT_RUNNER_GUI_OWNER_REQUIRED_CLIENT
         .store(true, std::sync::atomic::Ordering::Release);
@@ -971,13 +1079,25 @@ pub(crate) fn attach_external_agent_runner_gui_owner(
     let config_dir = external_agent_runner_config_dir()
         .ok_or_else(|| "外部 Agent Runner 尚未配置 AppData；请显式传入 --config-dir".to_string())?;
     let platform_session = crate::current_platform_session();
+    // 启动阶段先采纳现有 durable claim：第二个及后续窗口与第一个窗口共享同一
+    // epoch，因此不会被判定为抢走登录态权威；claim 缺失或不可读时才发布新 claim。
+    let session_revision = reserve_external_agent_runner_gui_owner_claim_revision(
+        external_agent_runner_gui_owner_attachment_state(),
+    );
+    let claim = resolve_external_agent_runner_gui_owner_claim(
+        &config_dir,
+        ExternalAgentRunnerGuiOwnerClaimMode::Adopt,
+        session_revision,
+    )?;
     register_external_agent_runner_gui_owner_attachment(
         external_agent_runner_gui_owner_attachment_state(),
         &config_dir,
+        ExternalAgentRunnerGuiOwnerClaimMode::Adopt,
         ExternalAgentRunnerRequestParams {
             event_sink_port: Some(event_sink.port),
             event_sink_token: Some(event_sink.token.clone()),
-            gui_owner_epoch: Some(gui_owner_epoch.to_string()),
+            gui_owner_epoch: Some(claim.owner_epoch),
+            gui_owner_session_revision: Some(claim.session_revision),
             platform_user_id: platform_session
                 .as_ref()
                 .map(|session| session.user_id.clone()),
@@ -1107,7 +1227,7 @@ pub(super) fn remember_external_agent_runner_platform_session(
         state,
         session,
         generation,
-        write_external_agent_runner_gui_owner_claim_atomic,
+        publish_external_agent_runner_gui_owner_claim,
     )
 }
 
@@ -1115,7 +1235,7 @@ pub(super) fn remember_external_agent_runner_platform_session_with(
     state: &Mutex<ExternalAgentRunnerGuiOwnerAttachmentState>,
     session: Option<(&str, &str, &str)>,
     generation: u64,
-    write_claim: impl FnOnce(&Path, &str, u64) -> Result<(), String>,
+    publish_claim: impl FnOnce(&Path, u64) -> Result<ExternalAgentRunnerGuiOwnerClaim, String>,
 ) -> Result<(), String> {
     let mut state = lock_unpoisoned(state);
     let Some(registration) = state.registration.as_ref() else {
@@ -1147,21 +1267,23 @@ pub(super) fn remember_external_agent_runner_platform_session_with(
     }
     state.generation = state.generation.wrapping_add(1);
     let registration_generation = state.generation;
-    let claim = state.registration.as_ref().and_then(|registration| {
-        registration
-            .params
-            .gui_owner_epoch
-            .as_deref()
-            .map(|owner_epoch| (registration.config_dir.clone(), owner_epoch.to_string()))
-    });
-    if let Some((config_dir, owner_epoch)) = claim {
-        write_claim(&config_dir, &owner_epoch, registration_generation)?;
-    }
+    // 本窗口改动了平台登录态：发布新 epoch 的 claim，成为新的登录态权威。
+    // 并发发布以最后一次成功写入为准，落败窗口在 attach 阶段按最新 claim 重试。
+    // 只有已经建立过 claim 的登记才需要发布：没有 epoch 的登记（纯 CLI / 单元测试替身）
+    // 不写任何 claim 文件。
+    let published_claim = state
+        .registration
+        .as_ref()
+        .filter(|registration| registration.params.gui_owner_epoch.is_some())
+        .map(|registration| registration.config_dir.clone())
+        .map(|config_dir| publish_claim(&config_dir, registration_generation))
+        .transpose()?;
     let registration = state
         .registration
         .as_mut()
         .expect("checked GUI owner registration must remain present while locked");
     registration.generation = registration_generation;
+    registration.claim_mode = ExternalAgentRunnerGuiOwnerClaimMode::Publish;
     registration.attached_boot_id = None;
     registration.params.platform_user_id = session.map(|(user_id, _, _)| user_id.to_string());
     registration.params.platform_access_token =
@@ -1169,7 +1291,10 @@ pub(super) fn remember_external_agent_runner_platform_session_with(
     registration.params.platform_api_base_url =
         session.map(|(_, _, api_base_url)| api_base_url.to_string());
     registration.params.platform_auth_generation = Some(generation);
-    registration.params.gui_owner_session_revision = Some(registration_generation);
+    if let Some(claim) = published_claim {
+        registration.params.gui_owner_epoch = Some(claim.owner_epoch);
+        registration.params.gui_owner_session_revision = Some(claim.session_revision);
+    }
     Ok(())
 }
 
@@ -1263,6 +1388,25 @@ pub(crate) fn shutdown_external_agent_runner_for_client_exit() -> Result<bool, S
     shutdown_external_agent_runner_for_client_exit_at(&config_dir)
 }
 
+/// 窗口退出的收尾：先释放本窗口参与锁，再决定 Runner 是否需要关闭。
+///
+/// 返回 `Ok(false)` 表示仍检测到其它窗口持有参与锁，Runner 必须保留给它们；
+/// 返回 `Ok(true)` 表示本窗口是最后一个界面进程，Runner 已请求关闭。
+pub(crate) fn shutdown_external_agent_runner_for_gui_exit() -> Result<bool, String> {
+    let _configure = lock_unpoisoned(external_agent_runner_configure_lock());
+    let Some(config_dir) = external_agent_runner_config_dir() else {
+        return Ok(true);
+    };
+    release_external_agent_runner_gui_participant_lock();
+    if external_agent_runner_lock_is_held(&external_agent_runner_gui_participant_lock_path(
+        &config_dir,
+    ))? {
+        return Ok(false);
+    }
+    shutdown_external_agent_runner_at(&config_dir)?;
+    Ok(true)
+}
+
 pub(super) fn wait_for_external_agent_runner(
     config_dir: &Path,
     child: &mut Child,
@@ -1301,34 +1445,12 @@ pub(super) fn ensure_external_agent_runner(
 ) -> Result<ExternalAgentRunnerEndpoint, String> {
     let endpoint_path = external_agent_runner_endpoint_path(config_dir);
     let executable_fingerprint = current_external_agent_runner_executable_fingerprint()?;
-    if let Ok(endpoint) = read_external_agent_runner_endpoint(&endpoint_path) {
-        match external_agent_runner_endpoint_reuse_decision(&endpoint, &executable_fingerprint) {
-            ExternalAgentRunnerReuseDecision::Reuse => {
-                if ping_external_agent_runner(&endpoint).is_ok() {
-                    attach_registered_external_agent_runner_gui_owner_if_needed(
-                        config_dir, &endpoint,
-                    )?;
-                    return Ok(endpoint);
-                }
-            }
-            ExternalAgentRunnerReuseDecision::Retire => {
-                let incompatible_ping = send_external_agent_runner_request_with_protocol_and_id(
-                    &endpoint,
-                    endpoint.protocol_version,
-                    random_identifier(b"genarrative-agent-runner-upgrade-ping-id")?,
-                    "runner.ping",
-                    ExternalAgentRunnerRequestParams::default(),
-                );
-                if incompatible_ping.is_ok() {
-                    retire_incompatible_external_agent_runner(
-                        &endpoint_path,
-                        &endpoint,
-                        EXTERNAL_AGENT_RUNNER_GUI_OWNER_REQUIRED_CLIENT
-                            .load(std::sync::atomic::Ordering::Acquire),
-                    )?;
-                }
-            }
-        }
+    if let Some(endpoint) = reuse_or_retire_external_agent_runner_endpoint(
+        config_dir,
+        &endpoint_path,
+        &executable_fingerprint,
+    )? {
+        return Ok(endpoint);
     }
     let mut launched = launch_external_agent_runner(config_dir)?;
     match wait_for_external_agent_runner(config_dir, &mut launched.child, &executable_fingerprint) {
@@ -1345,11 +1467,57 @@ pub(super) fn ensure_external_agent_runner(
         Err(error) => {
             let _ = launched.child.kill();
             let _ = launched.child.wait();
+            // 同一 AppData 的另一个窗口可能在这段时间里已经启动了 Runner：
+            // 实例锁竞争失败不能立刻报成启动失败，先按最新 endpoint 复用一次。
+            if let Some(endpoint) = reuse_or_retire_external_agent_runner_endpoint(
+                config_dir,
+                &endpoint_path,
+                &executable_fingerprint,
+            )? {
+                return Ok(endpoint);
+            }
             Err(error)
         }
     }
 }
 
+fn reuse_or_retire_external_agent_runner_endpoint(
+    config_dir: &Path,
+    endpoint_path: &Path,
+    executable_fingerprint: &str,
+) -> Result<Option<ExternalAgentRunnerEndpoint>, String> {
+    if let Ok(endpoint) = read_external_agent_runner_endpoint(&endpoint_path) {
+        match external_agent_runner_endpoint_reuse_decision(&endpoint, executable_fingerprint) {
+            ExternalAgentRunnerReuseDecision::Reuse => {
+                if ping_external_agent_runner(&endpoint).is_ok() {
+                    attach_registered_external_agent_runner_gui_owner_if_needed(
+                        config_dir, &endpoint,
+                    )?;
+                    return Ok(Some(endpoint));
+                }
+            }
+            ExternalAgentRunnerReuseDecision::Retire => {
+                let incompatible_ping = send_external_agent_runner_request_with_protocol_and_id(
+                    &endpoint,
+                    endpoint.protocol_version,
+                    random_identifier(b"genarrative-agent-runner-upgrade-ping-id")?,
+                    "runner.ping",
+                    ExternalAgentRunnerRequestParams::default(),
+                );
+                if incompatible_ping.is_ok() {
+                    retire_incompatible_external_agent_runner(
+                        endpoint_path,
+                        &endpoint,
+                        EXTERNAL_AGENT_RUNNER_GUI_OWNER_REQUIRED_CLIENT
+                            .load(std::sync::atomic::Ordering::Acquire),
+                    )?;
+                }
+            }
+        }
+    }
+    Ok(None)
+}
+
 pub(crate) fn configure_external_agent_runner(config_dir: impl AsRef<Path>) -> Result<(), String> {
     let _configure = lock_unpoisoned(external_agent_runner_configure_lock());
     let config_dir = normalize_external_agent_runner_config_dir(config_dir.as_ref())?;
diff --git a/apps/ai-game-creator-shell/src-tauri/src/runner/dispatch.rs b/apps/ai-game-creator-shell/src-tauri/src/runner/dispatch.rs
index b254c88f9..344d478e8 100644
--- a/apps/ai-game-creator-shell/src-tauri/src/runner/dispatch.rs
+++ b/apps/ai-game-creator-shell/src-tauri/src/runner/dispatch.rs
@@ -1,6 +1,6 @@
 use super::{endpoint::*, project_owner::*, protocol::*, state::*};
 use crate::{
-    install_game_creator_manifest_invalidation_event_sink,
+    register_game_creator_manifest_invalidation_event_sink,
     validate_game_creator_manifest_invalidation_event_sink,
 };
 use serde::Deserialize;
@@ -116,9 +116,9 @@ fn apply_external_agent_runner_gui_owner_attachment(
         .gui_owner_session_revision
         .ok_or_else(|| "Agent Runner GUI owner 缺少 session revision".to_string())?;
     let config_dir = state
-        .gui_owner_lock_path
+        .gui_participant_lock_path
         .parent()
-        .ok_or_else(|| "Agent Runner GUI owner 锁缺少 AppData 父目录".to_string())?;
+        .ok_or_else(|| "AGC 界面参与锁缺少 AppData 父目录".to_string())?;
     let mut active_claim = lock_unpoisoned(&state.gui_owner_platform_session_claim);
     let durable_claim = read_external_agent_runner_gui_owner_claim(config_dir)?;
     if durable_claim.owner_epoch != requested_epoch
@@ -127,7 +127,14 @@ fn apply_external_agent_runner_gui_owner_attachment(
         return Err("Agent Runner GUI owner claim 已过期".to_string());
     }
     let requested_claim = (requested_epoch.to_string(), requested_revision);
-    let replace_claim = active_claim.as_ref() != Some(&requested_claim);
+    // 同一 AppData 的多个窗口共享同一个 epoch：只有 epoch 变化（本窗口发布了新的
+    // 登录态权威）才允许强制替换会话。同一 epoch 内的重复 attach 只做单调校验，
+    // 因此后开窗口的“无登录态 attach”不会清空已有会话。
+    let epoch_changed = match active_claim.as_ref() {
+        Some(active) => active.0 != requested_epoch,
+        None => true,
+    };
+    let replace_claim = epoch_changed;
     let result = match (
         params.platform_user_id.as_deref(),
         params.platform_access_token.as_deref(),
@@ -159,7 +166,7 @@ fn apply_external_agent_runner_gui_owner_attachment(
                 crate::clear_platform_session_checked(generation)
             }
         }
-        (None, None, None, None) if replace_claim => {
+        (None, None, None, None) if epoch_changed => {
             crate::clear_platform_session_for_gui_owner(0);
             Ok(())
         }
@@ -185,7 +192,7 @@ fn apply_external_agent_runner_gui_owner_attachment(
         return Err("Agent Runner GUI owner claim 在 attach 提交期间已变化".to_string());
     }
     if let Some(event_sink) = event_sink {
-        install_game_creator_manifest_invalidation_event_sink(event_sink);
+        register_game_creator_manifest_invalidation_event_sink(event_sink);
     }
     *active_claim = Some(requested_claim);
     Ok(())
@@ -195,9 +202,9 @@ pub(super) fn validate_external_agent_runner_gui_owner_claim_current(
     state: &ExternalAgentRunnerServerState,
 ) -> Result<(), String> {
     let config_dir = state
-        .gui_owner_lock_path
+        .gui_participant_lock_path
         .parent()
-        .ok_or_else(|| "Agent Runner GUI owner 锁缺少 AppData 父目录".to_string())?;
+        .ok_or_else(|| "AGC 界面参与锁缺少 AppData 父目录".to_string())?;
     let mut active_claim = lock_unpoisoned(&state.gui_owner_platform_session_claim);
     let durable_claim = read_external_agent_runner_gui_owner_claim(config_dir);
     let matches = durable_claim.as_ref().is_ok_and(|claim| {
@@ -768,7 +775,7 @@ pub(super) fn dispatch_external_agent_runner_runtime_request_with_owner_claim(
             }
         }
         "runner.attach_gui_owner" => {
-            match external_agent_runner_gui_owner_is_locked(&state.gui_owner_lock_path) {
+            match external_agent_runner_lock_is_held(&state.gui_participant_lock_path) {
                 Ok(true) => {
                     let event_sink = request
                         .params
@@ -810,7 +817,7 @@ pub(super) fn dispatch_external_agent_runner_runtime_request_with_owner_claim(
                 Ok(false) => ExternalAgentRunnerResponse::failure(
                     &request.request_id,
                     "gui-owner-missing",
-                    "Agent Runner 未检测到活跃 GUI owner 锁",
+                    "Agent Runner 未检测到活跃的 AGC 界面进程",
                 ),
                 Err(error) => ExternalAgentRunnerResponse::failure(
                     &request.request_id,
diff --git a/apps/ai-game-creator-shell/src-tauri/src/runner/endpoint.rs b/apps/ai-game-creator-shell/src-tauri/src/runner/endpoint.rs
index bfbd56241..de3ade0ae 100644
--- a/apps/ai-game-creator-shell/src-tauri/src/runner/endpoint.rs
+++ b/apps/ai-game-creator-shell/src-tauri/src/runner/endpoint.rs
@@ -6,7 +6,12 @@ use std::io::{self, Read, Seek, SeekFrom, Write};
 use std::path::{Path, PathBuf};
 use std::sync::atomic::Ordering;
 use std::sync::Mutex;
-use std::time::{SystemTime, UNIX_EPOCH};
+use std::thread;
+use std::time::{Duration, Instant, SystemTime, UNIX_EPOCH};
+
+const EXTERNAL_AGENT_RUNNER_GUI_PARTICIPANT_LOCK_ACQUIRE_TIMEOUT: Duration = Duration::from_secs(5);
+const EXTERNAL_AGENT_RUNNER_GUI_PARTICIPANT_LOCK_RETRY_INTERVAL: Duration =
+    Duration::from_millis(40);
 
 pub(super) fn external_agent_runner_config_dir_lock() -> &'static Mutex<Option<PathBuf>> {
     EXTERNAL_AGENT_RUNNER_CONFIG_DIR.get_or_init(|| Mutex::new(None))
@@ -305,8 +310,8 @@ pub(super) fn external_agent_runner_lock_path(config_dir: &Path) -> PathBuf {
     config_dir.join(EXTERNAL_AGENT_RUNNER_LOCK_FILE_NAME)
 }
 
-pub(super) fn external_agent_runner_gui_owner_lock_path(config_dir: &Path) -> PathBuf {
-    config_dir.join(EXTERNAL_AGENT_RUNNER_GUI_OWNER_LOCK_FILE_NAME)
+pub(super) fn external_agent_runner_gui_participant_lock_path(config_dir: &Path) -> PathBuf {
+    config_dir.join(EXTERNAL_AGENT_RUNNER_GUI_PARTICIPANT_LOCK_FILE_NAME)
 }
 
 pub(super) fn external_agent_runner_gui_owner_claim_path(config_dir: &Path) -> PathBuf {
@@ -341,8 +346,9 @@ pub(super) fn read_external_agent_runner_gui_owner_claim(
     Ok(claim)
 }
 
-pub(super) fn external_agent_runner_gui_owner_is_locked(path: &Path) -> Result<bool, String> {
-    match try_open_external_agent_runner_lock(path, "Agent Runner GUI owner 锁")? {
+/// 独占探测：返回 `true` 表示仍有界面进程持有该参与锁。
+pub(super) fn external_agent_runner_lock_is_held(path: &Path) -> Result<bool, String> {
+    match try_open_external_agent_runner_lock(path, "AGC 界面参与锁")? {
         Some(lock) => {
             drop(lock);
             Ok(false)
@@ -743,10 +749,21 @@ pub(super) fn read_current_external_agent_runner_endpoint(
         })
 }
 
+/// 锁文件的两种打开方式。
+///
+/// `Exclusive` 是权威探测：能否独占取得句柄决定“还有没有存活持有者”。
+/// `Shared` 是参与者持有：同一 AppData 的多个界面进程可以同时持有。
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+pub(super) enum ExternalAgentRunnerLockMode {
+    Exclusive,
+    Shared,
+}
+
 #[cfg(unix)]
-pub(super) fn try_open_external_agent_runner_lock(
+pub(super) fn open_external_agent_runner_lock_file(
     path: &Path,
     label: &str,
+    mode: ExternalAgentRunnerLockMode,
 ) -> Result<Option<File>, String> {
     use std::os::fd::AsRawFd;
     use std::os::unix::fs::{MetadataExt, OpenOptionsExt, PermissionsExt};
@@ -809,14 +826,30 @@ pub(super) fn try_open_external_agent_runner_lock(
             path.display()
         ));
     }
+    let flock_operation = match mode {
+        ExternalAgentRunnerLockMode::Exclusive => libc::LOCK_EX | libc::LOCK_NB,
+        ExternalAgentRunnerLockMode::Shared => libc::LOCK_SH | libc::LOCK_NB,
+    };
     // SAFETY: flock only observes the valid fd owned by `file`; `file` remains alive on success.
-    let result = unsafe { libc::flock(file.as_raw_fd(), libc::LOCK_EX | libc::LOCK_NB) };
+    let result = unsafe { libc::flock(file.as_raw_fd(), flock_operation) };
     if result == 0 {
         return Ok(Some(file));
     }
     let error = io::Error::last_os_error();
     if error.kind() == io::ErrorKind::WouldBlock {
-        Ok(None)
+        return match mode {
+            ExternalAgentRunnerLockMode::Exclusive => Ok(None),
+            ExternalAgentRunnerLockMode::Shared => Err(format!(
+                "{label} 正被独占探测或持有，稍后重试：{}",
+                path.display()
+            )),
+        };
+    }
+    if mode == ExternalAgentRunnerLockMode::Shared {
+        Err(format!(
+            "以共享方式获取 {label} 失败：{}: {error}",
+            path.display()
+        ))
     } else {
         Err(format!(
             "获取 {label} 系统锁失败：{}: {error}",
@@ -825,39 +858,58 @@ pub(super) fn try_open_external_agent_runner_lock(
     }
 }
 
+#[cfg(unix)]
+pub(super) fn try_open_external_agent_runner_lock(
+    path: &Path,
+    label: &str,
+) -> Result<Option<File>, String> {
+    open_external_agent_runner_lock_file(path, label, ExternalAgentRunnerLockMode::Exclusive)
+}
+
 #[cfg(windows)]
 pub(super) fn windows_external_agent_runner_lock_is_busy_error(error: &io::Error) -> bool {
     matches!(error.raw_os_error(), Some(32 | 33))
 }
 
 #[cfg(windows)]
-pub(super) fn try_open_external_agent_runner_lock(
+pub(super) fn open_external_agent_runner_lock_file(
     path: &Path,
     label: &str,
+    mode: ExternalAgentRunnerLockMode,
 ) -> Result<Option<File>, String> {
     use std::os::windows::fs::OpenOptionsExt;
 
     const FILE_FLAG_OPEN_REPARSE_POINT: u32 = 0x0020_0000;
+    const FILE_SHARE_READ: u32 = 0x0000_0001;
+    const FILE_SHARE_WRITE: u32 = 0x0000_0002;
+    const FILE_SHARE_DELETE: u32 = 0x0000_0004;
 
     let parent = path
         .parent()
         .ok_or_else(|| format!("{label} 缺少 AppData 父目录：{}", path.display()))?;
     let private_parent = crate::inspect_game_creator_runtime_config_dir(parent)?;
     let runner_lock_path = private_parent.join(EXTERNAL_AGENT_RUNNER_LOCK_FILE_NAME);
-    let gui_owner_lock_path = private_parent.join(EXTERNAL_AGENT_RUNNER_GUI_OWNER_LOCK_FILE_NAME);
-    if path != runner_lock_path && path != gui_owner_lock_path {
+    let gui_participant_lock_path =
+        private_parent.join(EXTERNAL_AGENT_RUNNER_GUI_PARTICIPANT_LOCK_FILE_NAME);
+    if path != runner_lock_path && path != gui_participant_lock_path {
         return Err(format!(
             "{label} 必须位于已验证的私有 AppData 固定锁路径：{} 或 {}",
             runner_lock_path.display(),
-            gui_owner_lock_path.display()
+            gui_participant_lock_path.display()
         ));
     }
 
+    let share_mode = match mode {
+        ExternalAgentRunnerLockMode::Exclusive => 0,
+        ExternalAgentRunnerLockMode::Shared => {
+            FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE
+        }
+    };
     match OpenOptions::new()
         .create(true)
         .read(true)
         .write(true)
-        .share_mode(0)
+        .share_mode(share_mode)
         .custom_flags(FILE_FLAG_OPEN_REPARSE_POINT)
         .open(path)
     {
@@ -875,16 +927,30 @@ pub(super) fn try_open_external_agent_runner_lock(
                 ));
             }
             validate_windows_regular_file_handle(&file, label)?;
-            // share_mode(0) gives this process an exclusive handle. At this point the fixed
-            // lock path is known to be a stale, single-link, non-reparse regular file inside
-            // the current TokenUser's private AppData. Repairing its owner is therefore safe
-            // and is required when Windows creates it with TokenOwner=Administrators.
+            // The fixed lock path is known to be a single-link, non-reparse regular file
+            // inside the current TokenUser's private AppData. Repairing its owner is
+            // therefore safe and is required when Windows creates it with
+            // TokenOwner=Administrators.
             crate::initialize_windows_game_creator_file_owner_for_current_user(path)?;
             validate_windows_regular_file_handle(&file, label)?;
             crate::secure_windows_game_creator_path_for_current_user(path, false, false)?;
             Ok(Some(file))
         }
-        Err(error) if windows_external_agent_runner_lock_is_busy_error(&error) => Ok(None),
+        Err(error)
+            if mode == ExternalAgentRunnerLockMode::Exclusive
+                && windows_external_agent_runner_lock_is_busy_error(&error) =>
+        {
+            Ok(None)
+        }
+        Err(error)
+            if mode == ExternalAgentRunnerLockMode::Shared
+                && windows_external_agent_runner_lock_is_busy_error(&error) =>
+        {
+            Err(format!(
+                "{label} 正被独占探测或持有，稍后重试：{}",
+                path.display()
+            ))
+        }
         Err(error) => Err(format!(
             "安全打开 {label} 失败：{}: {error}",
             path.display()
@@ -892,12 +958,29 @@ pub(super) fn try_open_external_agent_runner_lock(
     }
 }
 
+#[cfg(windows)]
+pub(super) fn try_open_external_agent_runner_lock(
+    path: &Path,
+    label: &str,
+) -> Result<Option<File>, String> {
+    open_external_agent_runner_lock_file(path, label, ExternalAgentRunnerLockMode::Exclusive)
+}
+
+#[cfg(not(any(unix, windows)))]
+pub(super) fn open_external_agent_runner_lock_file(
+    path: &Path,
+    label: &str,
+    _mode: ExternalAgentRunnerLockMode,
+) -> Result<Option<File>, String> {
+    Err(format!("当前平台不支持 {label} 系统锁：{}", path.display()))
+}
+
 #[cfg(not(any(unix, windows)))]
 pub(super) fn try_open_external_agent_runner_lock(
     path: &Path,
     label: &str,
 ) -> Result<Option<File>, String> {
-    Err(format!("当前平台不支持 {label} 系统锁：{}", path.display()))
+    open_external_agent_runner_lock_file(path, label, ExternalAgentRunnerLockMode::Exclusive)
 }
 
 pub(super) fn acquire_external_agent_runner_instance_lock(
@@ -929,40 +1012,90 @@ pub(super) fn acquire_external_agent_runner_instance_lock(
     Ok(ExternalAgentRunnerInstanceLock { _file: file })
 }
 
-pub(crate) fn acquire_external_agent_runner_gui_owner_lock(
+/// 取得本窗口在该 AppData 下的界面参与锁。
+///
+/// 参与锁以共享句柄打开：同一 AppData 可以同时持有任意数量的界面窗口。
+/// Runner 侧用同文件的独占探测判断“是否仍有界面进程存活”，探测窗口很短，
+/// 所以这里遇到瞬时冲突时按 `EXTERNAL_AGENT_RUNNER_GUI_PARTICIPANT_LOCK_RETRY_INTERVAL`
+/// 重试，直到 `EXTERNAL_AGENT_RUNNER_GUI_PARTICIPANT_LOCK_ACQUIRE_TIMEOUT` 截止。
+pub(crate) fn acquire_external_agent_runner_gui_participant_lock(
     config_dir: &Path,
-) -> Result<ExternalAgentRunnerGuiOwnerLock, String> {
-    let path = external_agent_runner_gui_owner_lock_path(config_dir);
-    let Some(mut file) = try_open_external_agent_runner_lock(&path, "Agent Runner GUI owner 锁")?
-    else {
-        return Err("AI 游戏创作界面已由同一 AppData 目录中的其他进程运行".to_string());
-    };
-    let owner_epoch = uuid::Uuid::new_v4().to_string();
-    let acquired_at = unix_millis();
+) -> Result<ExternalAgentRunnerGuiParticipantLock, String> {
+    let path = external_agent_runner_gui_participant_lock_path(config_dir);
+    let deadline = Instant::now() + EXTERNAL_AGENT_RUNNER_GUI_PARTICIPANT_LOCK_ACQUIRE_TIMEOUT;
+    let mut last_error = "AGC 界面参与锁未知失败".to_string();
+    loop {
+        match open_external_agent_runner_lock_file(
+            &path,
+            "AGC 界面参与锁",
+            ExternalAgentRunnerLockMode::Shared,
+        ) {
+            Ok(Some(mut file)) => {
+                write_external_agent_runner_gui_participant_diagnostic(&mut file, &path)?;
+                return Ok(ExternalAgentRunnerGuiParticipantLock { _file: file });
+            }
+            Ok(None) => {
+                last_error = format!("AGC 界面参与锁无法以共享方式取得：{}", path.display());
+            }
+            Err(error) => last_error = error,
+        }
+        if Instant::now() >= deadline {
+            return Err(format!("取得 AGC 界面参与锁失败：{last_error}"));
+        }
+        thread::sleep(EXTERNAL_AGENT_RUNNER_GUI_PARTICIPANT_LOCK_RETRY_INTERVAL);
+    }
+}
+
+/// 参与锁诊断内容只由首个窗口写入，后续窗口不覆写，避免并发写坏 JSON。
+fn write_external_agent_runner_gui_participant_diagnostic(
+    file: &mut File,
+    path: &Path,
+) -> Result<(), String> {
+    let existing_len = file.metadata().map(|metadata| metadata.len()).unwrap_or(0);
+    if existing_len > 0 {
+        return Ok(());
+    }
     let diagnostic = serde_json::to_vec(&json!({
         "protocolVersion": EXTERNAL_AGENT_RUNNER_PROTOCOL_VERSION,
         "pid": std::process::id(),
-        "ownerEpoch": owner_epoch,
-        "acquiredAt": acquired_at,
+        "instanceId": uuid::Uuid::new_v4().to_string(),
+        "acquiredAt": unix_millis(),
     }))
-    .map_err(|error| format!("生成 Agent Runner GUI owner 锁信息失败：{error}"))?;
+    .map_err(|error| format!("生成 AGC 界面参与锁信息失败：{error}"))?;
     file.set_len(0)
         .and_then(|_| file.seek(SeekFrom::Start(0)).map(|_| ()))
         .and_then(|_| file.write_all(&diagnostic))
         .and_then(|_| file.sync_data())
-        .map_err(|error| {
-            format!(
-                "写入 Agent Runner GUI owner 锁信息失败：{}: {error}",
-                path.display()
-            )
-        })?;
-    write_external_agent_runner_gui_owner_claim_atomic(config_dir, &owner_epoch, 0)?;
-    Ok(ExternalAgentRunnerGuiOwnerLock {
-        _file: file,
+        .map_err(|error| format!("写入 AGC 界面参与锁信息失败：{}: {error}", path.display()))
+}
+
+/// 发布新的 durable claim：新 epoch + 本次会话 revision。
+///
+/// 发布是“谁改动登录态谁成为新 epoch 权威”的实现；并发发布以最后一次
+/// 成功写入为准，落败窗口按最新 claim 重试。
+pub(crate) fn publish_external_agent_runner_gui_owner_claim(
+    config_dir: &Path,
+    session_revision: u64,
+) -> Result<ExternalAgentRunnerGuiOwnerClaim, String> {
+    let owner_epoch = uuid::Uuid::new_v4().to_string();
+    write_external_agent_runner_gui_owner_claim_atomic(config_dir, &owner_epoch, session_revision)?;
+    Ok(ExternalAgentRunnerGuiOwnerClaim {
         owner_epoch,
+        session_revision,
     })
 }
 
+/// 采纳现有 durable claim；只有 claim 缺失或不可读时才发布新 claim。
+pub(crate) fn adopt_or_publish_external_agent_runner_gui_owner_claim(
+    config_dir: &Path,
+    session_revision: u64,
+) -> Result<ExternalAgentRunnerGuiOwnerClaim, String> {
+    match read_external_agent_runner_gui_owner_claim(config_dir) {
+        Ok(claim) => Ok(claim),
+        Err(_) => publish_external_agent_runner_gui_owner_claim(config_dir, session_revision),
+    }
+}
+
 pub(super) fn write_external_agent_runner_gui_owner_claim_atomic(
     config_dir: &Path,
     owner_epoch: &str,
diff --git a/apps/ai-game-creator-shell/src-tauri/src/runner/protocol.rs b/apps/ai-game-creator-shell/src-tauri/src/runner/protocol.rs
index 4f0e3d555..0728e9050 100644
--- a/apps/ai-game-creator-shell/src-tauri/src/runner/protocol.rs
+++ b/apps/ai-game-creator-shell/src-tauri/src/runner/protocol.rs
@@ -13,8 +13,8 @@ pub(crate) const EXTERNAL_AGENT_RUNNER_PROTOCOL_VERSION: u32 = 7;
 
 pub(super) const EXTERNAL_AGENT_RUNNER_ENDPOINT_FILE_NAME: &str = "agent-runner.endpoint.json";
 pub(super) const EXTERNAL_AGENT_RUNNER_LOCK_FILE_NAME: &str = "agent-runner.lock";
-pub(super) const EXTERNAL_AGENT_RUNNER_GUI_OWNER_LOCK_FILE_NAME: &str =
-    "agent-runner.gui-owner.lock";
+pub(super) const EXTERNAL_AGENT_RUNNER_GUI_PARTICIPANT_LOCK_FILE_NAME: &str =
+    "agent-runner.gui-participant.lock";
 pub(super) const EXTERNAL_AGENT_RUNNER_GUI_OWNER_CLAIM_FILE_NAME: &str =
     "agent-runner.gui-owner.claim.json";
 pub(super) const EXTERNAL_AGENT_RUNNER_PROJECT_OWNER_FILE_NAME: &str = "execution-owner.lock";
diff --git a/apps/ai-game-creator-shell/src-tauri/src/runner/server.rs b/apps/ai-game-creator-shell/src-tauri/src/runner/server.rs
index cde54a691..998ca0e9f 100644
--- a/apps/ai-game-creator-shell/src-tauri/src/runner/server.rs
+++ b/apps/ai-game-creator-shell/src-tauri/src/runner/server.rs
@@ -156,7 +156,7 @@ fn external_agent_runner_watchdog_tick(state: &ExternalAgentRunnerServerState) -
     if !state.gui_owner_attached.load(Ordering::Acquire) {
         return false;
     }
-    match external_agent_runner_gui_owner_is_locked(&state.gui_owner_lock_path) {
+    match external_agent_runner_lock_is_held(&state.gui_participant_lock_path) {
         Ok(true) => {
             let _ = validate_external_agent_runner_gui_owner_claim_current(state);
             false
@@ -224,7 +224,7 @@ pub(crate) fn run_external_agent_runner_server(
     )?;
     let gui_owner_present_at_start = resolve_external_agent_runner_initial_gui_owner(
         gui_owner_required,
-        external_agent_runner_gui_owner_is_locked(&external_agent_runner_gui_owner_lock_path(
+        external_agent_runner_lock_is_held(&external_agent_runner_gui_participant_lock_path(
             &config_dir,
         ))?,
     )?;
diff --git a/apps/ai-game-creator-shell/src-tauri/src/runner/state.rs b/apps/ai-game-creator-shell/src-tauri/src/runner/state.rs
index 3070039b6..7dda8ab43 100644
--- a/apps/ai-game-creator-shell/src-tauri/src/runner/state.rs
+++ b/apps/ai-game-creator-shell/src-tauri/src/runner/state.rs
@@ -16,7 +16,7 @@ pub(super) struct ExternalAgentRunnerServerState {
     pub(super) draining: AtomicBool,
     pub(super) active_connections: AtomicUsize,
     pub(super) known_roots: Mutex<BTreeSet<PathBuf>>,
-    pub(super) gui_owner_lock_path: PathBuf,
+    pub(super) gui_participant_lock_path: PathBuf,
     pub(super) project_execution_owners:
         Mutex<BTreeMap<PathBuf, ExternalAgentRunnerProjectExecutionOwnerEntry>>,
     project_execution_owner_recovery_changed: Condvar,
@@ -80,10 +80,10 @@ impl Drop for ExternalAgentRunnerProjectExecutionOwnerRecoveryGuard<'_> {
 
 impl ExternalAgentRunnerServerState {
     pub(super) fn new(endpoint_path: PathBuf, endpoint: ExternalAgentRunnerEndpoint) -> Self {
-        let gui_owner_lock_path = endpoint_path
+        let gui_participant_lock_path = endpoint_path
             .parent()
-            .map(external_agent_runner_gui_owner_lock_path)
-            .unwrap_or_else(|| PathBuf::from(EXTERNAL_AGENT_RUNNER_GUI_OWNER_LOCK_FILE_NAME));
+            .map(external_agent_runner_gui_participant_lock_path)
+            .unwrap_or_else(|| PathBuf::from(EXTERNAL_AGENT_RUNNER_GUI_PARTICIPANT_LOCK_FILE_NAME));
         Self {
             endpoint_path,
             endpoint: Mutex::new(endpoint),
@@ -94,7 +94,7 @@ impl ExternalAgentRunnerServerState {
             draining: AtomicBool::new(false),
             active_connections: AtomicUsize::new(0),
             known_roots: Mutex::new(BTreeSet::new()),
-            gui_owner_lock_path,
+            gui_participant_lock_path,
             project_execution_owners: Mutex::new(BTreeMap::new()),
             project_execution_owner_recovery_changed: Condvar::new(),
             write_request_cache: Mutex::new(ExternalAgentRunnerRequestCache::default()),
@@ -231,16 +231,10 @@ pub(super) struct ExternalAgentRunnerInstanceLock {
     pub(super) _file: File,
 }
 
+/// 界面进程持有的参与锁。共享句柄，同一 AppData 可同时存在多个窗口。
 #[derive(Debug)]
-pub(crate) struct ExternalAgentRunnerGuiOwnerLock {
+pub(crate) struct ExternalAgentRunnerGuiParticipantLock {
     pub(super) _file: File,
-    pub(super) owner_epoch: String,
-}
-
-impl ExternalAgentRunnerGuiOwnerLock {
-    pub(crate) fn owner_epoch(&self) -> &str {
-        &self.owner_epoch
-    }
 }
 
 pub(super) struct ExternalAgentRunnerProjectOwnerStorage {
diff --git a/apps/ai-game-creator-shell/src-tauri/src/runner/tests.rs b/apps/ai-game-creator-shell/src-tauri/src/runner/tests.rs
index 20a6dfc0d..8e9bcb08b 100644
--- a/apps/ai-game-creator-shell/src-tauri/src/runner/tests.rs
+++ b/apps/ai-game-creator-shell/src-tauri/src/runner/tests.rs
@@ -44,6 +44,23 @@ fn private_runner_test_config_dir(directory: &TestDirectoryGuard) -> PathBuf {
         .expect("prepare private runner AppData")
 }
 
+/// 模拟一个界面窗口：持有界面参与锁，并发布自己的 owner claim。
+struct TestGuiParticipant {
+    _lock: ExternalAgentRunnerGuiParticipantLock,
+    owner_epoch: String,
+}
+
+fn acquire_test_gui_participant(config_dir: &Path, session_revision: u64) -> TestGuiParticipant {
+    let lock = acquire_external_agent_runner_gui_participant_lock(config_dir)
+        .expect("acquire GUI participant lock");
+    let claim = publish_external_agent_runner_gui_owner_claim(config_dir, session_revision)
+        .expect("publish GUI owner claim");
+    TestGuiParticipant {
+        _lock: lock,
+        owner_epoch: claim.owner_epoch,
+    }
+}
+
 fn acquire_project_owner_after_release(
     root: &Path,
     boot_id: &str,
@@ -574,8 +591,13 @@ fn gui_owner_registration_replays_once_for_each_runner_boot() {
         event_sink_token: Some(event_sink_token.clone()),
         ..ExternalAgentRunnerRequestParams::default()
     };
-    register_external_agent_runner_gui_owner_attachment(&state, &config_dir, params)
-        .expect("register GUI owner attachment");
+    register_external_agent_runner_gui_owner_attachment(
+        &state,
+        &config_dir,
+        ExternalAgentRunnerGuiOwnerClaimMode::Adopt,
+        params,
+    )
+    .expect("register GUI owner attachment");
 
     let calls = std::cell::RefCell::new(Vec::new());
     let endpoint_a = test_endpoint(
@@ -657,6 +679,7 @@ fn gui_owner_registration_replays_only_the_latest_platform_session() {
     register_external_agent_runner_gui_owner_attachment(
         &state,
         &config_dir,
+        ExternalAgentRunnerGuiOwnerClaimMode::Adopt,
         ExternalAgentRunnerRequestParams {
             event_sink_port: Some(31_330),
             event_sink_token: Some("f".repeat(64)),
@@ -725,6 +748,7 @@ fn gui_owner_platform_session_change_marks_the_same_boot_for_reattach() {
     register_external_agent_runner_gui_owner_attachment(
         &state,
         &config_dir,
+        ExternalAgentRunnerGuiOwnerClaimMode::Adopt,
         ExternalAgentRunnerRequestParams {
             event_sink_port: Some(31_331),
             event_sink_token: Some("d".repeat(64)),
@@ -776,6 +800,7 @@ fn stale_gui_owner_attach_completion_cannot_mark_new_session_as_attached() {
     register_external_agent_runner_gui_owner_attachment(
         &state,
         &config_dir,
+        ExternalAgentRunnerGuiOwnerClaimMode::Adopt,
         ExternalAgentRunnerRequestParams {
             platform_user_id: Some("user-a".to_string()),
             platform_access_token: Some("token-a".to_string()),
@@ -827,8 +852,7 @@ fn stale_gui_owner_attach_completion_cannot_mark_new_session_as_attached() {
 fn gui_owner_platform_session_payload_clears_runner_session() {
     let directory = unique_test_directory();
     let config_dir = private_runner_test_config_dir(&directory);
-    let owner = acquire_external_agent_runner_gui_owner_lock(&config_dir)
-        .expect("acquire platform-session clear owner");
+    let owner = acquire_test_gui_participant(&config_dir, 0);
     let state = ExternalAgentRunnerServerState::new(
         config_dir.join(EXTERNAL_AGENT_RUNNER_ENDPOINT_FILE_NAME),
         test_endpoint("platform-clear-token", "platform-clear-boot", 31_333),
@@ -841,7 +865,7 @@ fn gui_owner_platform_session_payload_clears_runner_session() {
     apply_external_agent_runner_gui_owner_platform_session(
         &state,
         &ExternalAgentRunnerRequestParams {
-            gui_owner_epoch: Some(owner.owner_epoch().to_string()),
+            gui_owner_epoch: Some(owner.owner_epoch.clone()),
             gui_owner_session_revision: Some(0),
             platform_auth_generation: Some(2),
             ..ExternalAgentRunnerRequestParams::default()
@@ -855,8 +879,7 @@ fn gui_owner_platform_session_payload_clears_runner_session() {
 fn gui_owner_partial_platform_session_payload_fails_without_mutation() {
     let directory = unique_test_directory();
     let config_dir = private_runner_test_config_dir(&directory);
-    let owner = acquire_external_agent_runner_gui_owner_lock(&config_dir)
-        .expect("acquire partial-session owner");
+    let owner = acquire_test_gui_participant(&config_dir, 0);
     let state = ExternalAgentRunnerServerState::new(
         config_dir.join(EXTERNAL_AGENT_RUNNER_ENDPOINT_FILE_NAME),
         test_endpoint("platform-partial-token", "platform-partial-boot", 31_334),
@@ -870,7 +893,7 @@ fn gui_owner_partial_platform_session_payload_fails_without_mutation() {
     let error = apply_external_agent_runner_gui_owner_platform_session(
         &state,
         &ExternalAgentRunnerRequestParams {
-            gui_owner_epoch: Some(owner.owner_epoch().to_string()),
+            gui_owner_epoch: Some(owner.owner_epoch.clone()),
             gui_owner_session_revision: Some(0),
             platform_user_id: Some("runner-owner-b".to_string()),
             platform_api_base_url: Some("https://dev.genarrative.world".to_string()),
@@ -896,9 +919,8 @@ fn new_gui_owner_epoch_replaces_higher_generation_runner_session_and_rejects_old
         "runner-token-seed",
         "https://dev.genarrative.world",
     );
-    let owner_a = acquire_external_agent_runner_gui_owner_lock(&config_dir)
-        .expect("acquire old GUI owner epoch");
-    let owner_a_epoch = owner_a.owner_epoch().to_string();
+    let owner_a = acquire_test_gui_participant(&config_dir, 0);
+    let owner_a_epoch = owner_a.owner_epoch.clone();
     apply_external_agent_runner_gui_owner_platform_session(
         &state,
         &ExternalAgentRunnerRequestParams {
@@ -914,12 +936,11 @@ fn new_gui_owner_epoch_replaces_higher_generation_runner_session_and_rejects_old
     .expect("old GUI installs high-generation owner A");
     drop(owner_a);
 
-    let owner_b = acquire_external_agent_runner_gui_owner_lock(&config_dir)
-        .expect("acquire new GUI owner epoch");
+    let owner_b = acquire_test_gui_participant(&config_dir, 0);
     apply_external_agent_runner_gui_owner_platform_session(
         &state,
         &ExternalAgentRunnerRequestParams {
-            gui_owner_epoch: Some(owner_b.owner_epoch().to_string()),
+            gui_owner_epoch: Some(owner_b.owner_epoch.clone()),
             gui_owner_session_revision: Some(0),
             platform_user_id: Some("runner-owner-b".to_string()),
             platform_access_token: Some("runner-token-b".to_string()),
@@ -963,8 +984,7 @@ fn durable_claim_revision_change_clears_runner_session_and_blocks_runtime_until_
         config_dir.join(EXTERNAL_AGENT_RUNNER_ENDPOINT_FILE_NAME),
         test_endpoint(token, "platform-claim-gate-boot", 31_337),
     );
-    let owner = acquire_external_agent_runner_gui_owner_lock(&config_dir)
-        .expect("acquire claim gate owner");
+    let owner = acquire_test_gui_participant(&config_dir, 0);
     let _session = crate::install_test_platform_session(
         "runner-owner-seed",
         "runner-token-seed",
@@ -973,7 +993,7 @@ fn durable_claim_revision_change_clears_runner_session_and_blocks_runtime_until_
     apply_external_agent_runner_gui_owner_platform_session(
         &state,
         &ExternalAgentRunnerRequestParams {
-            gui_owner_epoch: Some(owner.owner_epoch().to_string()),
+            gui_owner_epoch: Some(owner.owner_epoch.clone()),
             gui_owner_session_revision: Some(0),
             platform_user_id: Some("runner-owner-a".to_string()),
             platform_access_token: Some("runner-token-a".to_string()),
@@ -985,7 +1005,7 @@ fn durable_claim_revision_change_clears_runner_session_and_blocks_runtime_until_
     .expect("attach owner A claim");
     state.gui_owner_attached.store(true, Ordering::Release);
 
-    write_external_agent_runner_gui_owner_claim_atomic(&config_dir, owner.owner_epoch(), 1)
+    write_external_agent_runner_gui_owner_claim_atomic(&config_dir, owner.owner_epoch.as_str(), 1)
         .expect("advance durable claim before reattach");
     assert!(
         !external_agent_runner_shutdown_if_gui_owner_lost(&state)
@@ -996,7 +1016,7 @@ fn durable_claim_revision_change_clears_runner_session_and_blocks_runtime_until_
     apply_external_agent_runner_gui_owner_platform_session(
         &state,
         &ExternalAgentRunnerRequestParams {
-            gui_owner_epoch: Some(owner.owner_epoch().to_string()),
+            gui_owner_epoch: Some(owner.owner_epoch.clone()),
             gui_owner_session_revision: Some(1),
             platform_user_id: Some("runner-owner-b".to_string()),
             platform_access_token: Some("runner-token-b".to_string()),
@@ -1041,14 +1061,14 @@ fn failed_platform_session_sync_fences_runner_before_returning_error() {
 fn failed_gui_owner_claim_write_is_fenced_before_local_session_can_change() {
     let directory = unique_test_directory();
     let config_dir = private_runner_test_config_dir(&directory);
-    let owner = acquire_external_agent_runner_gui_owner_lock(&config_dir)
-        .expect("acquire claim-write failure owner");
+    let owner = acquire_test_gui_participant(&config_dir, 0);
     let state = Mutex::new(ExternalAgentRunnerGuiOwnerAttachmentState::default());
     register_external_agent_runner_gui_owner_attachment(
         &state,
         &config_dir,
+        ExternalAgentRunnerGuiOwnerClaimMode::Adopt,
         ExternalAgentRunnerRequestParams {
-            gui_owner_epoch: Some(owner.owner_epoch().to_string()),
+            gui_owner_epoch: Some(owner.owner_epoch.clone()),
             platform_user_id: Some("runner-owner-a".to_string()),
             platform_access_token: Some("runner-token-a".to_string()),
             platform_api_base_url: Some("https://dev.genarrative.world".to_string()),
@@ -1069,7 +1089,7 @@ fn failed_gui_owner_claim_write_is_fenced_before_local_session_can_change() {
                     "https://dev.genarrative.world",
                 )),
                 2,
-                |_, _, _| Err("injected durable claim write failure".to_string()),
+                |_, _| Err("injected durable claim write failure".to_string()),
             )
         },
         || {
@@ -1118,6 +1138,7 @@ fn gui_owner_registration_failed_replay_remains_pending_for_same_boot() {
     register_external_agent_runner_gui_owner_attachment(
         &state,
         &config_dir,
+        ExternalAgentRunnerGuiOwnerClaimMode::Adopt,
         ExternalAgentRunnerRequestParams::default(),
     )
     .expect("register GUI owner attachment");
@@ -1166,6 +1187,7 @@ fn gui_owner_registration_missing_event_sink_confirmation_retries_same_boot() {
     register_external_agent_runner_gui_owner_attachment(
         &state,
         &config_dir,
+        ExternalAgentRunnerGuiOwnerClaimMode::Adopt,
         ExternalAgentRunnerRequestParams {
             event_sink_port: Some(31_322),
             event_sink_token: Some("c".repeat(64)),
@@ -1215,6 +1237,7 @@ fn gui_owner_registration_false_event_sink_confirmation_retries_same_boot() {
     register_external_agent_runner_gui_owner_attachment(
         &state,
         &config_dir,
+        ExternalAgentRunnerGuiOwnerClaimMode::Adopt,
         ExternalAgentRunnerRequestParams {
             event_sink_port: Some(31_323),
             event_sink_token: Some("d".repeat(64)),
@@ -1267,6 +1290,7 @@ fn gui_owner_registration_does_not_cross_config_dirs() {
     register_external_agent_runner_gui_owner_attachment(
         &state,
         &registered_config_dir,
+        ExternalAgentRunnerGuiOwnerClaimMode::Adopt,
         ExternalAgentRunnerRequestParams {
             event_sink_port: Some(31_324),
             event_sink_token: Some(event_sink_token.clone()),
@@ -1316,18 +1340,113 @@ fn gui_owner_registration_does_not_cross_config_dirs() {
 }
 
 #[test]
-fn gui_owner_lock_allows_only_one_frontend_process_per_appdata() {
+fn gui_participant_lock_allows_multiple_windows_and_tracks_liveness() {
     let directory = unique_test_directory();
     let config_dir = private_runner_test_config_dir(&directory);
-    let first =
-        acquire_external_agent_runner_gui_owner_lock(&config_dir).expect("first GUI owns AppData");
-    let error = acquire_external_agent_runner_gui_owner_lock(&config_dir)
-        .expect_err("second GUI must not share the same Runner owner");
-    assert!(error.contains("其他进程运行"));
+    let participant_lock_path = external_agent_runner_gui_participant_lock_path(&config_dir);
+    assert!(!external_agent_runner_lock_is_held(&participant_lock_path)
+        .expect("probe without any window"));
 
+    let first = acquire_external_agent_runner_gui_participant_lock(&config_dir)
+        .expect("first window participates");
+    assert!(external_agent_runner_lock_is_held(&participant_lock_path)
+        .expect("first window keeps the runner alive"));
+    let second = acquire_external_agent_runner_gui_participant_lock(&config_dir)
+        .expect("second window shares the same AppData");
+
+    drop(second);
+    assert!(
+        external_agent_runner_lock_is_held(&participant_lock_path)
+            .expect("remaining window keeps the runner alive"),
+        "runner must survive while any window is still open"
+    );
     drop(first);
-    acquire_external_agent_runner_gui_owner_lock(&config_dir)
-        .expect("GUI owner lock is recoverable after the first frontend exits");
+    assert!(
+        !external_agent_runner_lock_is_held(&participant_lock_path)
+            .expect("last window releases the participant lock"),
+        "runner may stop once every window has exited"
+    );
+}
+
+#[test]
+fn gui_owner_claim_adoption_keeps_epoch_and_publication_rotates_it() {
+    let directory = unique_test_directory();
+    let config_dir = private_runner_test_config_dir(&directory);
+    let published =
+        publish_external_agent_runner_gui_owner_claim(&config_dir, 3).expect("publish claim");
+    assert_eq!(published.session_revision, 3);
+
+    let adopted = adopt_or_publish_external_agent_runner_gui_owner_claim(&config_dir, 9)
+        .expect("adopt existing claim");
+    assert_eq!(adopted.owner_epoch, published.owner_epoch);
+    assert_eq!(
+        adopted.session_revision, 3,
+        "采纳路径必须沿用现有 claim，不能推进 revision 或换 epoch"
+    );
+
+    let rotated =
+        publish_external_agent_runner_gui_owner_claim(&config_dir, 9).expect("publish new claim");
+    assert_ne!(rotated.owner_epoch, published.owner_epoch);
+    assert_eq!(rotated.session_revision, 9);
+    assert_eq!(
+        read_external_agent_runner_gui_owner_claim(&config_dir)
+            .expect("read durable claim")
+            .session_revision,
+        9
+    );
+}
+
+#[test]
+fn second_window_attach_with_same_claim_keeps_runner_platform_session() {
+    let directory = unique_test_directory();
+    let config_dir = private_runner_test_config_dir(&directory);
+    let state = ExternalAgentRunnerServerState::new(
+        config_dir.join(EXTERNAL_AGENT_RUNNER_ENDPOINT_FILE_NAME),
+        test_endpoint(
+            "multi-window-claim-token-multi-window-claim-token",
+            "multi-window-claim-boot",
+            31_338,
+        ),
+    );
+    let _session = crate::install_test_platform_session(
+        "runner-owner-a",
+        "runner-token-a",
+        "https://dev.genarrative.world",
+    );
+    let owner = acquire_test_gui_participant(&config_dir, 0);
+    apply_external_agent_runner_gui_owner_platform_session(
+        &state,
+        &ExternalAgentRunnerRequestParams {
+            gui_owner_epoch: Some(owner.owner_epoch.clone()),
+            gui_owner_session_revision: Some(0),
+            platform_user_id: Some("runner-owner-a".to_string()),
+            platform_access_token: Some("runner-token-a".to_string()),
+            platform_api_base_url: Some("https://dev.genarrative.world".to_string()),
+            platform_auth_generation: Some(7),
+            ..ExternalAgentRunnerRequestParams::default()
+        },
+    )
+    .expect("first window installs its session");
+    assert_eq!(
+        crate::current_platform_session().map(|session| (session.user_id, session.generation)),
+        Some(("runner-owner-a".to_string(), 7))
+    );
+
+    // 第二个窗口启动时本身还没有登录态：同 claim 的 attach 只能是空操作。
+    apply_external_agent_runner_gui_owner_platform_session(
+        &state,
+        &ExternalAgentRunnerRequestParams {
+            gui_owner_epoch: Some(owner.owner_epoch.clone()),
+            gui_owner_session_revision: Some(0),
+            ..ExternalAgentRunnerRequestParams::default()
+        },
+    )
+    .expect("second window attaches with the same claim");
+    assert_eq!(
+        crate::current_platform_session().map(|session| (session.user_id, session.generation)),
+        Some(("runner-owner-a".to_string(), 7)),
+        "同一 claim 的第二个窗口不得清空平台登录态"
+    );
 }
 
 #[test]
@@ -1341,8 +1460,7 @@ fn manifest_invalidation_sink_isolation_gui_owner_attach_configures_and_cleans_u
         config_dir.join(EXTERNAL_AGENT_RUNNER_ENDPOINT_FILE_NAME),
         test_endpoint(token, "gui-owner-monitor-boot", 31319),
     );
-    let owner =
-        acquire_external_agent_runner_gui_owner_lock(&config_dir).expect("acquire GUI owner lock");
+    let owner = acquire_test_gui_participant(&config_dir, 0);
     let attached = handle_external_agent_runner_request(
         ExternalAgentRunnerRequest {
             protocol_version: EXTERNAL_AGENT_RUNNER_PROTOCOL_VERSION,
@@ -1352,7 +1470,7 @@ fn manifest_invalidation_sink_isolation_gui_owner_attach_configures_and_cleans_u
             params: ExternalAgentRunnerRequestParams {
                 event_sink_port: Some(31_318),
                 event_sink_token: Some("b".repeat(64)),
-                gui_owner_epoch: Some(owner.owner_epoch().to_string()),
+                gui_owner_epoch: Some(owner.owner_epoch.clone()),
                 gui_owner_session_revision: Some(0),
                 ..ExternalAgentRunnerRequestParams::default()
             },
@@ -1372,7 +1490,7 @@ fn manifest_invalidation_sink_isolation_gui_owner_attach_configures_and_cleans_u
         !external_agent_runner_shutdown_if_gui_owner_lost(&state).expect("owner remains present")
     );
 
-    write_external_agent_runner_gui_owner_claim_atomic(&config_dir, owner.owner_epoch(), 1)
+    write_external_agent_runner_gui_owner_claim_atomic(&config_dir, owner.owner_epoch.as_str(), 1)
         .expect("advance owner claim revision");
     let replacement = handle_external_agent_runner_request(
         ExternalAgentRunnerRequest {
@@ -1383,7 +1501,7 @@ fn manifest_invalidation_sink_isolation_gui_owner_attach_configures_and_cleans_u
             params: ExternalAgentRunnerRequestParams {
                 event_sink_port: Some(31_319),
                 event_sink_token: Some("c".repeat(64)),
-                gui_owner_epoch: Some(owner.owner_epoch().to_string()),
+                gui_owner_epoch: Some(owner.owner_epoch.clone()),
                 gui_owner_session_revision: Some(1),
                 ..ExternalAgentRunnerRequestParams::default()
             },
@@ -1392,11 +1510,18 @@ fn manifest_invalidation_sink_isolation_gui_owner_attach_configures_and_cleans_u
     );
     assert!(replacement.ok);
     assert_eq!(
-        sink_guard.configured_sink(),
-        Some(crate::GameCreatorManifestInvalidationEventSink {
-            port: 31_319,
-            token: "c".repeat(64),
-        })
+        sink_guard.configured_sinks(),
+        vec![
+            crate::GameCreatorManifestInvalidationEventSink {
+                port: 31_318,
+                token: "b".repeat(64),
+            },
+            crate::GameCreatorManifestInvalidationEventSink {
+                port: 31_319,
+                token: "c".repeat(64),
+            },
+        ],
+        "第二个窗口 attach 必须让两个接收端同时保留"
     );
 
     let stale_replay = handle_external_agent_runner_request(
@@ -1408,7 +1533,7 @@ fn manifest_invalidation_sink_isolation_gui_owner_attach_configures_and_cleans_u
             params: ExternalAgentRunnerRequestParams {
                 event_sink_port: Some(31_318),
                 event_sink_token: Some("b".repeat(64)),
-                gui_owner_epoch: Some(owner.owner_epoch().to_string()),
+                gui_owner_epoch: Some(owner.owner_epoch.clone()),
                 gui_owner_session_revision: Some(0),
                 ..ExternalAgentRunnerRequestParams::default()
             },
@@ -1421,11 +1546,17 @@ fn manifest_invalidation_sink_isolation_gui_owner_attach_configures_and_cleans_u
         Some("platform-session-invalid")
     );
     assert_eq!(
-        sink_guard.configured_sink(),
-        Some(crate::GameCreatorManifestInvalidationEventSink {
-            port: 31_319,
-            token: "c".repeat(64),
-        }),
+        sink_guard.configured_sinks(),
+        vec![
+            crate::GameCreatorManifestInvalidationEventSink {
+                port: 31_318,
+                token: "b".repeat(64),
+            },
+            crate::GameCreatorManifestInvalidationEventSink {
+                port: 31_319,
+                token: "c".repeat(64),
+            },
+        ],
         "旧 claim 的迟到或缓存 attach 不能覆盖当前事件接收端"
     );
 
diff --git a/apps/ai-game-creator-shell/src-tauri/src/tests/mod.rs b/apps/ai-game-creator-shell/src-tauri/src/tests/mod.rs
index f12416e7d..a91336e16 100644
--- a/apps/ai-game-creator-shell/src-tauri/src/tests/mod.rs
+++ b/apps/ai-game-creator-shell/src-tauri/src/tests/mod.rs
@@ -202,9 +202,13 @@ fn gui_final_exit_is_the_only_run_event_that_requests_runner_shutdown() {
         GameCreatorGuiRunnerShutdownOutcome::NotRequested
     );
     assert_eq!(
-        resolve_game_creator_gui_runner_shutdown(&tauri::RunEvent::Exit, || Ok(())),
+        resolve_game_creator_gui_runner_shutdown(&tauri::RunEvent::Exit, || Ok(true)),
         GameCreatorGuiRunnerShutdownOutcome::Requested
     );
+    assert_eq!(
+        resolve_game_creator_gui_runner_shutdown(&tauri::RunEvent::Exit, || Ok(false)),
+        GameCreatorGuiRunnerShutdownOutcome::Retained
+    );
     assert_eq!(
         resolve_game_creator_gui_runner_shutdown(&tauri::RunEvent::Exit, || {
             Err("private shutdown diagnostic".to_string())
diff --git a/apps/ai-game-creator-shell/src-tauri/tests/runner_gui_owner_lifecycle.rs b/apps/ai-game-creator-shell/src-tauri/tests/runner_gui_owner_lifecycle.rs
index c49ef18c1..d9cd7e56b 100644
--- a/apps/ai-game-creator-shell/src-tauri/tests/runner_gui_owner_lifecycle.rs
+++ b/apps/ai-game-creator-shell/src-tauri/tests/runner_gui_owner_lifecycle.rs
@@ -10,7 +10,7 @@ use std::time::{Duration, Instant, SystemTime, UNIX_EPOCH};
 
 const RUNNER_ENDPOINT_FILE_NAME: &str = "agent-runner.endpoint.json";
 const RUNNER_LOCK_FILE_NAME: &str = "agent-runner.lock";
-const GUI_OWNER_LOCK_FILE_NAME: &str = "agent-runner.gui-owner.lock";
+const GUI_PARTICIPANT_LOCK_FILE_NAME: &str = "agent-runner.gui-participant.lock";
 
 struct TestDirectory(PathBuf);
 
@@ -50,8 +50,9 @@ fn open_locked_file(path: &Path) -> File {
         .custom_flags(libc::O_CLOEXEC | libc::O_NOFOLLOW)
         .open(path)
         .expect("open isolated lock file");
+    // 模拟一个界面窗口：参与锁以共享锁持有，多个窗口可以同时持有。
     // SAFETY: file owns a live descriptor and flock does not retain pointers.
-    assert_eq!(unsafe { libc::flock(file.as_raw_fd(), libc::LOCK_EX) }, 0);
+    assert_eq!(unsafe { libc::flock(file.as_raw_fd(), libc::LOCK_SH) }, 0);
     file
 }
 
@@ -101,7 +102,7 @@ fn runner_binary() -> &'static str {
 #[test]
 fn gui_owned_runner_rejects_start_when_owner_dies_before_first_check() {
     let directory = TestDirectory::new("owner-lost-before-check");
-    let owner = open_locked_file(&directory.path().join(GUI_OWNER_LOCK_FILE_NAME));
+    let owner = open_locked_file(&directory.path().join(GUI_PARTICIPANT_LOCK_FILE_NAME));
     let script =
         "kill -STOP $$; exec \"$1\" --agent-runner --config-dir \"$2\" --gui-owner-required";
     let mut child = Command::new("/bin/sh")
@@ -139,7 +140,7 @@ fn gui_owned_runner_rejects_start_when_owner_dies_before_first_check() {
 #[test]
 fn gui_owned_runner_exits_and_cleans_endpoint_after_established_owner_dies() {
     let directory = TestDirectory::new("owner-lost-after-start");
-    let owner = open_locked_file(&directory.path().join(GUI_OWNER_LOCK_FILE_NAME));
+    let owner = open_locked_file(&directory.path().join(GUI_PARTICIPANT_LOCK_FILE_NAME));
     let mut child = Command::new(runner_binary())
         .arg("--agent-runner")
         .arg("--config-dir")
diff --git a/docs/project-memory/plans/【实施计划】AGC同AppData多窗口共享Runner-2026-09-16.md b/docs/project-memory/plans/【实施计划】AGC同AppData多窗口共享Runner-2026-09-16.md
new file mode 100644
index 000000000..29bdd0703
--- /dev/null
+++ b/docs/project-memory/plans/【实施计划】AGC同AppData多窗口共享Runner-2026-09-16.md
@@ -0,0 +1,41 @@
+---
+Version: 1
+Status: Active
+Date: 2026-09-16
+Milestone: 【里程碑】AGC同AppData多窗口共享Runner-2026-09-16.md
+---
+
+# 【实施计划】AGC 同 AppData 多窗口共享 Agent Runner
+
+## 代码边界
+
+| 顺序 | 文件 | 修改 |
+| --- | --- | --- |
+| 1 | `runner/endpoint.rs` | 参与锁改名与共享句柄打开；新增 claim 发布；锁路径白名单同步 |
+| 2 | `runner/state.rs` | `ExternalAgentRunnerGuiOwnerLock` → 参与者锁；服务端状态字段改名 |
+| 3 | `runner/dispatch.rs` | attach 只在 epoch 变化时强制替换登录态；同 claim 重复 attach 为幂等空操作；事件接收端改为注册表 |
+| 4 | `runner/server.rs` | watchdog 与启动检查按“参与者存活”判定 |
+| 5 | `runner/client.rs` | 启动采纳 claim、平台登录态变化发布新 claim、attach 失败按最新 claim 重试 |
+| 6 | `agent/runtime_driver*` | 事件接收端从单槽改为按 token 去重的注册表并广播 |
+| 7 | `main.rs` | 启动阶段取参与者锁并 attach，不再要求独占 owner |
+| 8 | `runner/tests.rs` | 重写独占锁断言，补齐多窗口、广播、存活判定与失败关闭用例 |
+
+## 修改顺序
+
+先改 runner 内部（endpoint / state / dispatch / server），再改 GUI 客户端（client / main），最后改事件注册表与测试。每步保持可编译。
+
+## 验证命令
+
+```
+cargo test --manifest-path apps/ai-game-creator-shell/src-tauri/Cargo.toml
+npm run check:encoding
+git diff --check
+```
+
+真实二进制 smoke 在构建产物可用后执行：同一 AppData 启动两个 GUI，核对 `diagnostics/startup.log` 两次 `startup.setup.complete`、只有一个 `--agent-runner` 进程、关闭一个窗口后另一个仍可 attach。
+
+## 风险与回滚
+
+- 风险：共享参与锁后，Runner 可能在无窗口时仍存活。回滚点是 watchdog 的存活判定函数，恢复为独占 owner 语义即可。
+- 风险：claim 发布竞态。缓解为 bounded retry + 失败关闭，不做隐式合并。
+- 回滚：本里程碑只影响本机 GUI ↔ Runner 协议，回滚提交即可恢复单窗口语义；claim 与参与锁文件都是可重新生成的运行时产物。
diff --git a/docs/project-memory/plans/【里程碑】AGC同AppData多窗口共享Runner-2026-09-16.md b/docs/project-memory/plans/【里程碑】AGC同AppData多窗口共享Runner-2026-09-16.md
new file mode 100644
index 000000000..78f6ad7f2
--- /dev/null
+++ b/docs/project-memory/plans/【里程碑】AGC同AppData多窗口共享Runner-2026-09-16.md
@@ -0,0 +1,39 @@
+---
+Version: 1
+Status: Active
+Date: 2026-09-16
+Parent Spec: docs/technical/【技术方案】AI游戏创作智能体App实施计划-2026-06-24.md
+---
+
+# 【里程碑】AGC 同 AppData 多窗口共享 Agent Runner
+
+## 目标
+
+同一个 AppData 允许同时运行多个 AGC 界面进程；它们共享同一个 Agent Runner、同一份平台登录态权威和同一份项目事实，并且都继续收到 Runtime / manifest 失效事件。
+
+## 边界
+
+- 参与本次变化的只有 GUI 与 Agent Runner 之间的本机协议：窗口参与锁、owner claim 发布与采纳、attach 语义、事件接收端注册表、Runner 存活判定与启动诊断。
+- 不修改平台 HTTP 契约、SpacetimeDB schema、`/api/external/v1`、渲染层 generation 语义和项目级 `.agent/project.lock`。
+- 一个项目同一时刻仍然只允许一个写者；多窗口不能并行写同一项目。
+
+## 行为合同
+
+1. 窗口启动不再因为“同一 AppData 已有界面进程”而失败。参与锁是共享句柄锁：任何数量的界面进程都可以同时持有；Runner 通过“能否独占取得该锁”判断是否还有界面进程存活。
+2. 启动时窗口先采纳现有 owner claim；只有在 claim 缺失、不可读，或本窗口主动发布平台登录态变化时，才写入新的 claim（新 epoch + 本窗口 generation）。
+3. 同一 claim 的重复 attach 不得清空 Runner 平台登录态；只有 epoch 变化或明确的登出参数才允许替换 / 清空登录态。
+4. Runner 必须把 manifest 失效与 runtime update relay 广播给全部已登记事件接收端（按 token 去重、失败即淘汰），不得因为第二个窗口 attach 而让第一个窗口失去事件。
+5. Runner 生命周期跟随“是否仍有界面进程存活”，不跟随某一个窗口；全部窗口退出后必须在有界时间内关停并清理 endpoint。
+6. 平台登录态仍保持单调 generation 与 claim 一致性校验：claim 不匹配时继续失败关闭并隔离登录态，不做隐式兼容。
+
+## 验收标准
+
+- 定向 Rust 测试覆盖：第二个参与者可同时持有参与锁；参与者全部退出后存活判定为假；同 claim 重复 attach 不改写登录态；epoch 变化才强制替换；两个事件接收端都能收到同一事件；claim 采纳与发布路径的失败关闭。
+- 真实二进制 smoke：同一 AppData 启动两个 GUI，两个进程都完成 `startup.setup.complete`，Runner 只存在一个实例，关闭其中一个后另一个仍可继续使用 Runner。
+- 边界验证：项目级写锁仍然拒绝两个窗口同时写同一项目；密钥、token、绝对路径不出现在新增日志与错误文案中。
+
+## 依赖
+
+- `apps/ai-game-creator-shell/src-tauri/src/runner/`（endpoint / state / dispatch / server / client）
+- `apps/ai-game-creator-shell/src-tauri/src/agent/runtime_driver/`（事件接收端注册表）
+- `apps/ai-game-creator-shell/src-tauri/src/main.rs`（启动阶段）
diff --git a/docs/project-memory/shared-memory/decision-log.md b/docs/project-memory/shared-memory/decision-log.md
index d778bcade..360df2121 100644
--- a/docs/project-memory/shared-memory/decision-log.md
+++ b/docs/project-memory/shared-memory/decision-log.md
@@ -2,6 +2,18 @@
 
 > 用途：记录已经确认、会影响后续开发的长期技术/产品/协作决策。短期讨论不要写在这里。
 > 当前口径：历史条目的旧路径、旧版本和已退役对象只用于追溯，不构成现行实现依据；如与当前代码或 `docs/README.md` 冲突，以当前代码和最新专题文档为准。
+
+## 2026-09-16 AGC 同 AppData 多窗口共享 Agent Runner
+
+- 背景：双击或再次启动 AGC 客户端时报「应用启动失败」，启动日志为 `startup.runner.owner-lock.failed details=AI 游戏创作界面已由同一 AppData 目录中的其他进程运行`。原设计（2026-07-27 / 2026-08-23）要求同一 AppData 只有一个 GUI owner，第二个界面进程在 setup 阶段就失败退出。
+- 决策（锁语义）：`agent-runner.gui-owner.lock` 改为**界面参与锁** `agent-runner.gui-participant.lock`，以共享句柄打开，同一 AppData 的任意数量窗口可同时持有；Runner 的启动检查、attach 门禁与 watchdog 只用“能否独占取得该文件”判断是否仍有窗口存活。全部窗口退出后才关停 Runner 并清理 endpoint。
+- 决策（claim 采纳与发布）：窗口启动先**采纳**durable claim（同一 epoch/revision），只有 claim 缺失或不可读才发布新 claim；登录、refresh、退出或换号才发布新 claim（新 epoch + 本窗口 revision），成为新的登录态权威。同一 claim 的重复 attach 是幂等空操作，不再清空 Runner 登录态；只有 epoch 变化或携带明确登出参数才允许替换 / 清空。并发发布以最后一次成功写入的 claim 为准，落败窗口按最新 claim 有界重试。
+- 决策（事件与退出）：manifest 失效与 Runtime update relay 的接收端从单槽改为按 `event_sink_token` 去重的注册表并广播，发送失败只淘汰该接收端；GUI 退出先释放本窗口参与锁，仍有其它窗口时保留 Runner（`agent.runner.gui_exit.retained_for_other_windows`），最后一个窗口才请求关闭。Runner 启动失败时先按最新 endpoint 复用一次，避免两个窗口同时冷启动时的实例锁竞争被误报成启动失败。
+- 边界：本机 GUI ↔ Runner 协议方法与参数不变，不引入多 Runner、不做跨 AppData 会话共享；项目级 `.agent/project.lock` 不变，多窗口仍不能并行写同一项目；平台登录态 generation 单调与 claim 失配失败关闭语义保持不变；混用新旧版本二进制访问同一 AppData 不属于支持场景。
+- 验证：定向 Rust `runner::tests::gui_owner_*` 11 条与新增的参与锁多窗口 / 存活判定 / claim 采纳与轮换 / 同 claim 第二个窗口不清空登录态用例全部通过；真实 debug 二进制 Windows smoke 证明同一 AppData 两个 GUI 都完成 `startup.setup.complete`、只存在一个 `--agent-runner` 进程、关闭一个窗口后另一个窗口与 Runner 继续存活、最后一个窗口退出后 Runner 退出并删除 endpoint；`npm run check:encoding`、`npm run check:doc-index`、`git diff --check` 通过。
+- 未验证 / 已知环境问题：真实安装包双开需要重新构建发布后才能验证；`durable_provider_handoff_prevents_shutdown_even_when_corrupt`、`durable_provider_retry_prevents_shutdown_and_reopens_writes`、`runtime_interrupt_for_true_steer_decision_only_interrupts_older_provider_cursor` 三条用例在本机改动前的基线上即失败（Windows 安全对象 owner 校验与 Provider 请求重复），与本决策无关。
+- 关联文档：`docs/technical/【技术方案】AI游戏创作智能体App实施计划-2026-06-24.md`（2026-09-16 节）、`docs/project-memory/plans/【里程碑】AGC同AppData多窗口共享Runner-2026-09-16.md`。
+
 ## 2026-09-16 图标图集自动拆图上限提高到 256
 
 - 背景：AGC 图标图集自动连通域识别在一次生成中识别出 86 个区域，原有 64 片上限在后处理阶段阻断了请求；该上限同时影响 api-server 自动 / 手动切片、SpacetimeDB 批量落库和统一生成结果 item 数量。
diff --git a/docs/project-memory/shared-memory/pitfalls.md b/docs/project-memory/shared-memory/pitfalls.md
index e8d132d9f..3b2461b1a 100644
--- a/docs/project-memory/shared-memory/pitfalls.md
+++ b/docs/project-memory/shared-memory/pitfalls.md
@@ -1,5 +1,11 @@
 # 踩坑与排障记录
 
+## 2026-09-16 从 Codex 里启动 AGC 客户端会看到被重定向的 `%APPDATA%`
+
+- **现象**：在 Codex 会话里用 `Start-Process` 启动 `genarrative-ai-game-creator-shell.exe` 做排障时，子进程写 `C:\Users\<user>\AppData\Roaming\world.genarrative.ai-game-creator\...` 的内容会落到 `C:\Users\<user>\AppData\Local\Packages\OpenAI.Codex_2p2nqsd0c76g0\LocalCache\Roaming\...`；同一个 `Test-Path` / `Get-ChildItem` 命中的是重定向视图，只有 `\\?\C:\Users\...` 形式能区分真实路径。
+- **影响**：用 agent 拉起的客户端复现「多开 / 登录态冲突 / 锁文件被占用」类问题时，可能与用户双击开始菜单快捷方式的真实进程不是同一份 AppData，从而得出「两个实例没有互相冲突」或「日志里没有那条失败」的错误结论。
+- **处理**：把用户双击快捷方式（或从 Codex 之外启动）的进程作为唯一用户侧证据；核对待查文件时同时比对真实 `AppData\Roaming` 路径与 `Packages\...\LocalCache\Roaming` 路径；排障结论里写明客户端是「谁启动的」。
+
 ## Windows 已登记生图资产未刷新
 
 Direct 工具桥会 canonicalize 项目根，事件中的路径可能带 `\\?\` / `\\?\UNC\`，而前端项目路径仍是普通盘符或 UNC。失效监听不能直接比较原始字符串；识别为同一项目后，用当前项目路径重读 manifest，保留项目切换与 revision 门禁。普通 `agc_generate_image` 成功提交也必须发出失效通知，不能依赖整轮 Agent 结束。回归需覆盖两种 Windows 前缀、其它项目事件拒收，以及 Agent 尚未结束和后续失败时已登记图片卡片仍可见。
diff --git a/docs/technical/【技术方案】AI游戏创作智能体App实施计划-2026-06-24.md b/docs/technical/【技术方案】AI游戏创作智能体App实施计划-2026-06-24.md
index 06089fbd6..61c651581 100644
--- a/docs/technical/【技术方案】AI游戏创作智能体App实施计划-2026-06-24.md
+++ b/docs/technical/【技术方案】AI游戏创作智能体App实施计划-2026-06-24.md
@@ -548,6 +548,7 @@ Agent Runtime 负责：
 - 2026-07-10 补充：`agent.delegate` 已形成可恢复的父子任务闭环。`delegationId` 由 durable pending action 的 `actionId` 派生，子任务记录会保存 `parentAgentId / parentRunId / delegationId`，终态记录额外保存经过统一凭据清洗和安全截断的 `terminalDetail`；同一委派的提交和回执分别受 delegation 级 OS 文件锁保护，同一目标 Agent 的 runId 分配与 pending 追加还受任务账本 OS 锁保护。子任务进入 `completed / failed / cancelled / budget-exhausted` 任一终态时，Runtime 按 `delegationId` 幂等生成且至多生成一次 `agent.delegate.result` 回执，失败、排队或活跃取消、预算耗尽都必须回传，不能只覆盖成功。回执会向父 Agent 既有队列追加固定 runId、`source=agent-delegate-receipt` 的续跑任务，把完整的已清洗 `terminalDetail` 交回父 run，不再只保留 80 字符 UI 摘要；回执 prompt 明确禁止重复同一委派，排队期间不提前写入父会话，真正开始执行时才幂等落盘，用户消息或回执消息落盘失败时不会进入 LLM。回执任务保留父 run 关联，并在真正开始或恢复前再次检查父 run 状态，关联缺失或父 run 不存在时失败关闭；该续跑仍受父 Agent 原有 FIFO、per-Agent OS 锁、权限确认、取消、恢复和 `needs-reconciliation` 屏障约束，不直接重入父 run、不插队、不新增独立 worker；父 run 已取消或普通失败时只保留 suppressed receipt 审计，不自动复活，父 Session 归档与切换会被未结束委派阻止，极端归档竞态下回执回落到父 Agent 当前可写 Session。恢复先恢复 pending action / reconciliation 屏障，再扫描“子任务终态已落盘但回执未提交”的窗口并补齐缺失回执；`needs-reconciliation` 本身不回执，只有人工核对后最终取消才回传 `cancelled`。
 - 历史记录（已由 V1.1 独立 Runner 替代）：Runtime 最初通过 `resume_game_creator_agent_runtime_tasks` 把本地 JSONL 队列重接到当前 App 进程。当前恢复入口仍保留权限、任务顺序和 `agent.runtime.background_task.recovered` 审计语义，但实际由独立 Runner 接管原 run / session；已发出的上游 LLM 请求仍不能从网络中间点续传。2026-07-27 起，Runner 归 Tauri GUI 生命周期所有，同一 AppData 只允许一个 GUI owner。GUI 启动子进程会显式声明 `--gui-owner-required` 并在就绪后 attach owner；Runner 若在启动检查前已发现 owner 释放则直接失败，不得退化成 CLI-owned Runner。Runner 使用独立 watchdog 线程每 100ms 监控 owner OS 锁，不依赖服务端主循环继续推进；owner 丢失后先触发 1.5 秒共享 deadline 的 draining、Provider 中断和 process session 回收，若主循环或排空链路卡死则在 1.75 秒后由 Runner 自身进程安全硬退出并清理匹配 bootId 的 endpoint。GUI 客户端还必须把完整 `runner.attach_gui_owner` 参数作为绑定规范化 AppData 的进程内登记保存；`ensure_external_agent_runner` 无论复用既有 endpoint 还是启动新 Runner，都要在把 endpoint 交给 Runtime 写请求前按新 `bootId` 补登记。同一登记 generation 在同一 boot 上幂等，补登记失败不得记录成功 boot 且本次 `ensure` 失败关闭；未建立 GUI 登记的普通 CLI 不执行该重放。OS owner 锁与 watchdog 已成立只代表进程受 GUI 生命周期约束，不能替代事件 sink 等进程内附加能力的逐 boot 恢复。因此正常最终退出、panic、SIGKILL 和 setup 中途失败都不会再因 busy 或主循环卡死而残留后台进程。endpoint 缺失 / 读取失败必须结合 Runner 实例锁判断；GUI 客户端强制兜底在 Linux 使用 pidfd、Windows 使用稳定进程 handle。macOS 没有等价稳定句柄，客户端不得在 start identity 检查后按裸 PID 强杀，而由跨平台 Runner 自身 watchdog 提供硬退出兜底。旧 endpoint 缺 start identity 时，只有认证 ping 精确匹配 PID + bootId 才允许迁移 busy 旧 Runner。未完成任务保持 durable 状态并在下一次启动走 reconciliation / recovery，不能伪造 completed 或重放副作用。关闭单个 WebView / 子窗口和普通 CLI 退出不触发该行为，版本切换与人工命令仍可使用只关闭空闲实例的 `runner.shutdown_if_idle`。
 - 2026-08-23 Runner 协议 v7 GUI owner 会话权威补充：GUI 取得 owner OS 锁时产生随机 `owner epoch`，并在私有 AppData 持久化只含 `owner epoch + session revision` 的 claim；每次登录、refresh、退出或换号都必须先单调推进 durable session revision，再同步 Runner。`runner.attach_gui_owner` 是 Runner 接受平台会话快照的唯一授权入口；只有 attach 携带的 epoch/revision 与 durable claim 完全一致才可安装或清除会话，新 GUI epoch 可替换旧进程留下的高 `authGeneration`，不用可在新 WebView 重置的 generation 猜测进程所有权。Runner 在 claim 缺失、不可读或与当前 attach 身份失配时立即清空进程内平台会话，并阻断除重新 attach 及必要管理请求以外的 Runtime 工作；旧 `platform.session.install/clear` 协议不再是授权入口。GUI 会话同步未得到完整 attach 确认时本地变更必须失败，并隔离或停止旧 Runner；即使进程终止失败，claim 失配门禁也不允许旧账号继续发起 Runtime 请求。claim 不保存 Access Token，Token 只随当次受保护的 attach IPC 进入 Runner 内存。
+- 2026-09-16 多窗口更正：同一 AppData 不再只允许一个 GUI 界面进程。原 owner OS 锁改为可被多个界面进程同时持有的参与者锁（`agent-runner.gui-participant.lock`），Runner 以“能否独占取得该锁”判断是否仍有界面进程存活，watchdog 与 attach 门禁都改用该判定。新增窗口默认只**采纳** durable claim（读同一 epoch/revision 并 attach），只有登录、refresh、退出或换号才发布新 claim（新 epoch + 本窗口 revision），因此同 claim 的重复 attach 不再清空平台会话，epoch 变化才允许强制替换。事件接收端从单槽改为按 token 去重的注册表并广播，保证第二个窗口 attach 后第一个窗口仍收到 manifest 失效与 Runtime update relay。claim 一致性与失败关闭语义不变。详见同文档「2026-09-16 AGC 同 AppData 多窗口共享 Agent Runner」。
 - 2026-08-05 GUI owner attachment 确认补充：登记参数必须保存 GUI manifest 事件接收端的真实 `event_sink_port` 与 `event_sink_token`，不得借用 actionId 等无关字段作为测试替身。每次 attach RPC 只有同时返回 `attached=true` 与 `eventSinkAttached=true` 才能把当前 `bootId` 标记为已登记；`eventSinkAttached` 缺失、为 false 或普通 RPC 失败都保持当前 boot 待重试。sink token 只留在私有进程内登记和 RPC 参数中，不进入日志、错误文本或公共状态。
 - 2026-07-10 补充，2026-07-16 由 V1.28 澄清：后台 planning 与预算内 final reply 使用专用最小上下文，只预置 Agent 身份、sessionId、runId、执行模式和工具策略；Agent 私有记忆、项目记忆、黑板、对话、资产、项目索引与文件正文只能经对应工具通过权限 gate 后作为 observation 进入下一轮。只有开发窗口的专业 Agent 前台直调可使用对应角色上下文；正式用户前台现已统一进入 `project-supervisor`。长黑板、记忆和对话按尾部截断，确保最新结论与最新定向消息优先保留。
 - 2026-07-10 补充，2026-07-16 由 V1.28 澄清：同一 Agent 的开发前台直调、流式调试和后台任务统一使用 `.agent/runtime/locks/<agentId>.lock` OS 文件锁。开发前台不再在整个 LLM 请求期间占用项目级写锁；同 Agent 后台任务在开发前台运行时只入队，前台成功或失败后把当前 Agent 锁直接移交给 drain，不重新抢锁，也不允许 drain 启动异常把已经完成的调试结果改判为失败。正式用户 GUI 不通过该入口直聊专业 Agent；不同 Agent 继续并行，真实项目写工具只在副作用执行期间短暂申请项目写锁。
@@ -1447,3 +1448,42 @@ Direct 回合的所有权属于进程内项目身份锁，不属于当前页面
 - 运行中的正文和工具按原有唯一回合流实时显示；完成后，除最终回复和失败提示外，中间文本与所有工具调用统一放入默认收起的“执行过程”，允许手动展开，刷新或重新进入仍默认收起。
 - 最终回复沿用 Runtime 的最后一个 assistant item 合同，不按文本长度或相似度判断。失败回合不把最后一句过程输出伪装成最终回复。无流历史按同一用户消息边界划分，只保留最后一条 assistant 回复在外；用户消息与失败提示始终保留。
 - 验收覆盖已完成回合重进、真实活动回合恢复、跨项目迟到快照、运行到完成自动收起、历史无流、失败、发送时间刷新和旧记录时间缺失。不改变实际工具执行、鉴权、数据库或用户项目内容。
+
+## 2026-09-16 AGC 同 AppData 多窗口共享 Agent Runner
+
+### 目标与非目标
+
+- 目标：同一个 AppData 可以同时运行多个 AGC 界面进程，它们共享同一个 Agent Runner、同一份平台登录态权威和同一份项目事实，并且都继续收到 manifest 失效与 Runtime update relay。
+- 非目标：不引入多 Runner、不做跨 AppData 的会话共享、不改变渲染层 generation 语义、不修改平台 HTTP 契约、SpacetimeDB schema 与 `/api/external/v1`。
+
+### 参与入口、状态与跨模块边界
+
+- 界面进程持有的 OS 锁改为**参与者锁** `agent-runner.gui-participant.lock`：它以共享句柄打开，任意数量的界面进程可同时持有；Runner、watchdog 与 attach 门禁只做“能否独占取得该锁”的探测，独占成功即表示已无界面进程存活。
+- durable claim `agent-runner.gui-owner.claim.json` 仍是唯一的 owner 授权记录，内容仍为 `ownerEpoch + sessionRevision`；claim 不保存 Access Token。
+- 项目级 `.agent/project.lock` 不变：多窗口共享 Runner 不等于共享项目写权，同一项目同一时刻仍只有一个写者。
+
+### 正常、失败、重试与幂等行为
+
+- 采纳：窗口启动时先读取 durable claim 并以同一 `epoch/revision` attach；claim 缺失或不可读时才发布新 claim。采纳路径不写 claim。
+- 发布：登录、refresh、退出或换号时，窗口写入新 claim（新 epoch + 本窗口 revision）再 attach；同一次发布在多个窗口并发发生时以最后一次成功写入的 claim 为准，落败窗口按最新 claim 重试，重试仍有界失败时向用户暴露错误，不做隐式合并。
+- 幂等：同一 claim 的重复 attach 是空操作，不得清空或替换 Runner 平台登录态；只有 epoch 变化或携带明确登出参数的 attach 才允许替换 / 清空。
+- 失败关闭：attach 携带的 epoch/revision 与 durable claim 不一致、claim 不可读、或 claim 在 attach 提交期间变化时，Runner 继续清空进程内平台会话并阻断除重新 attach 与必要管理请求以外的 Runtime 工作。
+- 事件：manifest 失效与 Runtime update relay 广播到全部已登记接收端（按 `event_sink_token` 去重，发送失败即淘汰该接收端），单个窗口退出或接收端失效不得影响其它窗口。
+- 生命周期：Runner 跟随“是否仍有界面进程存活”，不跟随某一个窗口；全部窗口退出后必须在有界时间内关停并清理 endpoint、释放实例锁。
+
+### 契约与兼容
+
+- 本机 GUI ↔ Runner 协议方法与参数不变；变化只在参与锁语义、claim 采纳/发布时机与事件接收端注册表。
+- 已退役的“同一 AppData 只允许一个 GUI owner”行为不再保留兼容分支；`startup.runner.owner-lock.failed` 诊断分类改名为参与者锁失败，仅在真正无法建立参与锁时出现。
+- 混用新旧版本二进制访问同一 AppData 不属于支持场景：旧版本仍以独占方式持有旧锁文件，可能让新版本判定为“仍有界面进程存活”。
+
+### 验收标准与证据来源
+
+- 定向 Rust 测试：参与者锁可多进程同时持有、全部释放后存活判定为假；同 claim 重复 attach 不改写登录态；epoch 变化才强制替换；两个接收端都收到同一事件；claim 采纳与发布的失败关闭路径。
+- 运行时 smoke：同一 AppData 启动两个真实 GUI，两个进程都完成 `startup.setup.complete`，`--agent-runner` 进程只有一个，关闭其中一个后另一个仍可继续使用 Runner。
+- 边界：项目级写锁继续拒绝两个窗口同时写同一项目；新增日志与错误文案不含 Token、Access Token、API Key 与绝对路径。
+
+### 未决问题
+
+- 两个窗口同时对同一项目发起 Runtime 写请求时，用户体验仍由项目级写锁串行决定；本次不引入跨窗口排队提示。
+- 平台会话在窗口间传播依赖共享 localStorage 与 Runner 权威；渲染层不做跨窗口事件推送，另一个窗口在下一次会话校验或刷新时收敛。