diff --git a/apps/ai-game-creator-shell/src-tauri/src/browser.rs b/apps/ai-game-creator-shell/src-tauri/src/browser.rs
index 919fb7467..16b4ed4bd 100644
--- a/apps/ai-game-creator-shell/src-tauri/src/browser.rs
+++ b/apps/ai-game-creator-shell/src-tauri/src/browser.rs
@@ -6,6 +6,7 @@ mod model;
 mod network_policy;
 mod playtest;
 mod process;
+mod sweep;
 
 pub use discovery::discover_chrome_or_edge;
 #[allow(unused_imports)]
@@ -22,6 +23,7 @@ pub(crate) use process::validate_local_preview_in_browser_with_cancellation;
 pub use process::{
     validate_local_preview_in_browser, validate_local_preview_in_browser_with_interaction,
 };
+pub(crate) use sweep::sweep_stale_browser_processes;
 
 pub(crate) use model::required_viewport_playtests_passed;
 pub(crate) use playtest::browser_playtest_scenario_fingerprint;
diff --git a/apps/ai-game-creator-shell/src-tauri/src/browser/process.rs b/apps/ai-game-creator-shell/src-tauri/src/browser/process.rs
index 38545eed1..129cc17ef 100644
--- a/apps/ai-game-creator-shell/src-tauri/src/browser/process.rs
+++ b/apps/ai-game-creator-shell/src-tauri/src/browser/process.rs
@@ -22,7 +22,9 @@ use super::network_policy::{preview_proxy_bypass_list, validate_input};
 #[cfg(windows)]
 use crate::process_session::WindowsProcessJob;
 
-fn browser_process_temp_root() -> PathBuf {
+pub(super) const BROWSER_TEMP_PREFIX: &str = "ga-browser-";
+
+pub(super) fn browser_process_temp_root() -> PathBuf {
     #[cfg(unix)]
     {
         PathBuf::from("/tmp")
@@ -35,7 +37,7 @@ fn browser_process_temp_root() -> PathBuf {
 
 pub(super) fn create_browser_process_temp_dir() -> Result<TempDir, String> {
     TempDirBuilder::new()
-        .prefix("ga-browser-")
+        .prefix(BROWSER_TEMP_PREFIX)
         .tempdir_in(browser_process_temp_root())
         .map_err(|error| format!("创建浏览器临时目录失败：{error}"))
 }
@@ -278,6 +280,8 @@ impl Drop for OwnedBrowser {
 /// 的一切子进程由 Job 全覆盖。
 async fn launch_owned_browser(
     config: BrowserConfig,
+    executable: &std::path::Path,
+    temp_root: &std::path::Path,
 ) -> Result<OwnedBrowser, OwnedBrowserLaunchError> {
     let child = config
         .launch()
@@ -293,6 +297,10 @@ async fn launch_owned_browser(
         #[cfg(windows)]
         job,
     };
+    // 跨会话清扫的身份锚点：写入失败时该目录之后按旧残留只删不杀。
+    if let Some(pid) = process.child.inner.id() {
+        super::sweep::write_browser_process_owner(temp_root, pid, executable);
+    }
     let (url, reader) = match devtools_ws_url_from_stderr(&mut process.child, BROWSER_TIMEOUT).await
     {
         Ok(pair) => pair,
@@ -342,13 +350,15 @@ pub(crate) async fn check_browser_health() -> Result<BrowserIdentity, String> {
     let temporary = create_browser_process_temp_dir().map_err(|_| "browser-temp-unavailable")?;
     let config = browser_config(&discovered.executable_path, &temporary, "<-loopback>")
         .map_err(|_| "browser-config-invalid")?;
-    let owned = launch_owned_browser(config).await.map_err(|error| {
-        if error.is_timeout() {
-            "browser-start-timeout"
-        } else {
-            "browser-start-failed"
-        }
-    })?;
+    let owned = launch_owned_browser(config, &discovered.executable_path, temporary.path())
+        .await
+        .map_err(|error| {
+            if error.is_timeout() {
+                "browser-start-timeout"
+            } else {
+                "browser-start-failed"
+            }
+        })?;
     let version = tokio::time::timeout(Duration::from_secs(5), owned.browser().version()).await;
     if owned.shutdown().await.is_err() {
         return Err("browser-cleanup-failed".into());
@@ -413,7 +423,13 @@ pub(crate) async fn validate_local_preview_in_browser_with_cancellation(
         &proxy_bypass_list,
     )?;
 
-    let owned = launch_owned_browser(config).await.map_err(|error| {
+    let owned = launch_owned_browser(
+        config,
+        &browser_executable.executable_path,
+        browser_temp.path(),
+    )
+    .await
+    .map_err(|error| {
         if error.is_timeout() {
             "启动浏览器超时".to_string()
         } else {
diff --git a/apps/ai-game-creator-shell/src-tauri/src/browser/sweep.rs b/apps/ai-game-creator-shell/src-tauri/src/browser/sweep.rs
new file mode 100644
index 000000000..d5042ca9c
--- /dev/null
+++ b/apps/ai-game-creator-shell/src-tauri/src/browser/sweep.rs
@@ -0,0 +1,417 @@
+//! 跨会话清扫陈旧的无头浏览器进程与临时目录。
+//!
+//! 运行期 launch 会把 owner.json 写进 ga-browser-* 目录；启动与每次预检前
+//! 按「进程身份 + 可信浏览器路径」双重校验收割遗留进程树并删除目录。
+//! 没有 owner.json 的旧版本残留只删目录，绝不按猜测杀进程。
+
+use std::fs;
+use std::path::Path;
+use std::time::Duration;
+
+use serde::{Deserialize, Serialize};
+
+use super::discovery::system_browser_candidates;
+use super::process::{browser_process_temp_root, BROWSER_TEMP_PREFIX};
+
+const OWNER_FILE: &str = "owner.json";
+const OWNER_SCHEMA: &str = "agc-browser-process.v1";
+/// 过新的目录可能属于正在进行中的预检（含 owner.json 写失败的极端情况），跳过。
+const SWEEP_MIN_AGE: Duration = Duration::from_secs(5 * 60);
+const TREE_KILL_MAX_PASSES: u32 = 20;
+const TREE_KILL_PASS_INTERVAL: Duration = Duration::from_millis(50);
+
+#[derive(Serialize, Deserialize)]
+#[serde(rename_all = "camelCase", deny_unknown_fields)]
+pub(super) struct BrowserProcessOwner {
+    schema_version: String,
+    browser_pid: u32,
+    browser_start_identity: String,
+    executable: String,
+    owner_pid: u32,
+    owner_start_identity: String,
+    created_unix_ms: u64,
+}
+
+/// 运行期 launch 的身份锚点；任何一步拿不到身份证明都不写，
+/// 该目录之后按旧残留只删不杀。
+pub(super) fn write_browser_process_owner(temp_root: &Path, browser_pid: u32, executable: &Path) {
+    let identity = crate::runner::external_agent_runner_process_start_identity(browser_pid);
+    let owner_identity =
+        crate::runner::external_agent_runner_process_start_identity(std::process::id());
+    let (Ok(Some(identity)), Ok(Some(owner_identity))) = (identity, owner_identity) else {
+        return;
+    };
+    let owner = BrowserProcessOwner {
+        schema_version: OWNER_SCHEMA.into(),
+        browser_pid,
+        browser_start_identity: identity,
+        executable: executable.to_string_lossy().into_owned(),
+        owner_pid: std::process::id(),
+        owner_start_identity: owner_identity,
+        created_unix_ms: super::evidence::unix_time_ms(),
+    };
+    let Ok(bytes) = serde_json::to_vec_pretty(&owner) else {
+        return;
+    };
+    let _ = fs::write(temp_root.join(OWNER_FILE), bytes);
+}
+
+fn read_browser_process_owner(dir: &Path) -> Option<BrowserProcessOwner> {
+    let bytes = fs::read(dir.join(OWNER_FILE)).ok()?;
+    if bytes.len() > 16 * 1024 {
+        return None;
+    }
+    let owner: BrowserProcessOwner = serde_json::from_slice(&bytes).ok()?;
+    if owner.schema_version != OWNER_SCHEMA
+        || owner.browser_pid == 0
+        || owner.owner_pid == 0
+        || owner.browser_start_identity.is_empty()
+        || owner.browser_start_identity.len() > 128
+        || owner.owner_start_identity.is_empty()
+        || owner.owner_start_identity.len() > 128
+        || owner.executable.is_empty()
+        || owner.executable.len() > 1024
+    {
+        return None;
+    }
+    Some(owner)
+}
+
+/// PID 存活且启动身份一致（创建时间相同），排除 PID 复用。
+fn process_identity_matches(pid: u32, identity: &str) -> bool {
+    crate::runner::external_agent_runner_process_start_identity(pid)
+        .ok()
+        .flatten()
+        .is_some_and(|live| live == identity)
+}
+
+/// exe 必须仍是系统标准路径下的可信浏览器，防止伪造 owner.json 借刀杀进程。
+fn trusted_browser_executable(path: &Path) -> bool {
+    let canonical = path.canonicalize().unwrap_or_else(|_| path.to_path_buf());
+    if !canonical.is_file() {
+        return false;
+    }
+    system_browser_candidates()
+        .into_iter()
+        .any(|(candidate, _)| candidate.canonicalize().unwrap_or(candidate) == canonical)
+}
+
+fn kill_browser_process_tree(root_pid: u32, expected_identity: &str) -> Result<(), String> {
+    #[cfg(windows)]
+    {
+        for _ in 0..TREE_KILL_MAX_PASSES {
+            // 每轮先复核 root 身份：进程已退出或 PID 被复用时立即停止。
+            if !process_identity_matches(root_pid, expected_identity) {
+                return Ok(());
+            }
+            let pids = windows_process_tree_pids(root_pid)?;
+            if pids.is_empty() {
+                return Ok(());
+            }
+            for pid in &pids {
+                windows_terminate_process(*pid);
+            }
+            std::thread::sleep(TREE_KILL_PASS_INTERVAL);
+        }
+        return Err("browser-sweep-tree-not-reaped".into());
+    }
+    #[cfg(not(windows))]
+    {
+        // 只杀 root：子进程随 IPC 断开级联退出（与运行期收割语义一致）。
+        if process_identity_matches(root_pid, expected_identity) {
+            unsafe { libc::kill(root_pid as i32, libc::SIGKILL) };
+        }
+        Ok(())
+    }
+}
+
+#[cfg(windows)]
+fn windows_process_tree_pids(root_pid: u32) -> Result<Vec<u32>, String> {
+    use windows_sys::Win32::Foundation::{CloseHandle, INVALID_HANDLE_VALUE};
+    use windows_sys::Win32::System::Diagnostics::ToolHelp::{
+        CreateToolhelp32Snapshot, Process32FirstW, Process32NextW, PROCESSENTRY32W,
+        TH32CS_SNAPPROCESS,
+    };
+    // SAFETY: 快照句柄非 INVALID_HANDLE_VALUE 时由 CloseHandle 释放。
+    let snapshot = unsafe { CreateToolhelp32Snapshot(TH32CS_SNAPPROCESS, 0) };
+    if snapshot == INVALID_HANDLE_VALUE {
+        return Err("browser-sweep-snapshot-failed".into());
+    }
+    let mut entry = PROCESSENTRY32W::default();
+    entry.dwSize = std::mem::size_of::<PROCESSENTRY32W>() as u32;
+    let mut processes = Vec::new();
+    // SAFETY: entry 指向可写的 PROCESSENTRY32W，dwSize 已初始化。
+    let mut available = unsafe { Process32FirstW(snapshot, &mut entry) };
+    while available != 0 {
+        processes.push((entry.th32ProcessID, entry.th32ParentProcessID));
+        // SAFETY: 同上。
+        available = unsafe { Process32NextW(snapshot, &mut entry) };
+    }
+    // SAFETY: snapshot 是本函数持有的合法句柄。
+    unsafe { CloseHandle(snapshot) };
+    if !processes.iter().any(|(pid, _)| *pid == root_pid) {
+        return Ok(Vec::new());
+    }
+    let mut tree = vec![root_pid];
+    let mut index = 0;
+    while index < tree.len() {
+        let parent = tree[index];
+        for (pid, ppid) in &processes {
+            if *ppid == parent && !tree.contains(pid) {
+                tree.push(*pid);
+            }
+        }
+        index += 1;
+        if tree.len() > 512 {
+            return Err("browser-sweep-tree-too-large".into());
+        }
+    }
+    Ok(tree)
+}
+
+#[cfg(windows)]
+fn windows_terminate_process(pid: u32) {
+    use windows_sys::Win32::Foundation::CloseHandle;
+    use windows_sys::Win32::System::Threading::{OpenProcess, TerminateProcess};
+    const PROCESS_TERMINATE: u32 = 0x0001;
+    // SAFETY: 句柄非空时由 CloseHandle 释放；空句柄直接返回。
+    let handle = unsafe { OpenProcess(PROCESS_TERMINATE, 0, pid) };
+    if handle.is_null() {
+        return;
+    }
+    // SAFETY: handle 是刚打开的合法进程句柄，退出码仅作占位。
+    unsafe { TerminateProcess(handle, 1) };
+    // SAFETY: 同上。
+    unsafe { CloseHandle(handle) };
+}
+
+/// 清扫陈旧的无头浏览器进程与临时目录，返回逐条处置记录供启动日志留痕。
+pub(crate) fn sweep_stale_browser_processes() -> Vec<String> {
+    sweep_stale_browser_processes_at(&browser_process_temp_root(), SWEEP_MIN_AGE)
+}
+
+fn sweep_stale_browser_processes_at(root: &Path, min_age: Duration) -> Vec<String> {
+    let mut notes = Vec::new();
+    let Ok(entries) = fs::read_dir(root) else {
+        return notes;
+    };
+    for entry in entries.flatten() {
+        let name = entry.file_name().to_string_lossy().into_owned();
+        if !name.starts_with(BROWSER_TEMP_PREFIX) {
+            continue;
+        }
+        let dir = entry.path();
+        let Ok(metadata) = entry.metadata() else {
+            continue;
+        };
+        if !metadata.is_dir() {
+            continue;
+        }
+        let too_young = metadata
+            .created()
+            .or_else(|_| metadata.modified())
+            .ok()
+            .and_then(|time| time.elapsed().ok())
+            .is_some_and(|age| age < min_age);
+        if too_young {
+            continue;
+        }
+        match read_browser_process_owner(&dir) {
+            Some(owner) => sweep_owned_directory(&dir, &name, &owner, &mut notes),
+            None => match fs::remove_dir_all(&dir) {
+                Ok(()) => notes.push(format!("removed-legacy-dir:{name}")),
+                Err(_) => notes.push(format!("kept-legacy-dir-in-use:{name}")),
+            },
+        }
+    }
+    notes
+}
+
+fn sweep_owned_directory(
+    dir: &Path,
+    name: &str,
+    owner: &BrowserProcessOwner,
+    notes: &mut Vec<String>,
+) {
+    // 另一个活着的 App 实例仍持有这轮浏览器：整目录跳过。
+    if process_identity_matches(owner.owner_pid, &owner.owner_start_identity) {
+        return;
+    }
+    if !process_identity_matches(owner.browser_pid, &owner.browser_start_identity) {
+        // 进程已退出或 PID 已被复用：不动任何进程，仅删目录。
+        if fs::remove_dir_all(dir).is_ok() {
+            notes.push(format!("removed-exited-dir:{name}"));
+        }
+        return;
+    }
+    if !trusted_browser_executable(Path::new(&owner.executable)) {
+        notes.push(format!("kept-untrusted-executable:{name}"));
+        return;
+    }
+    match kill_browser_process_tree(owner.browser_pid, &owner.browser_start_identity) {
+        Ok(()) => {
+            let _ = fs::remove_dir_all(dir);
+            notes.push(format!(
+                "killed-stale-tree:{name}:pid={}",
+                owner.browser_pid
+            ));
+        }
+        Err(_) => notes.push(format!("kill-unconfirmed:{name}:pid={}", owner.browser_pid)),
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn exited_child_pid() -> u32 {
+        #[cfg(windows)]
+        let mut command = std::process::Command::new("cmd.exe");
+        #[cfg(windows)]
+        command.args(["/c", "exit", "0"]);
+        #[cfg(not(windows))]
+        let mut command = std::process::Command::new("/bin/true");
+        let mut child = command.spawn().expect("spawn exit fixture");
+        let pid = child.id();
+        child.wait().expect("reap exit fixture");
+        pid
+    }
+
+    fn write_owner(dir: &Path, owner: &BrowserProcessOwner) {
+        fs::write(
+            dir.join(OWNER_FILE),
+            serde_json::to_vec_pretty(owner).unwrap(),
+        )
+        .unwrap();
+    }
+
+    fn owner_fixture(browser_pid: u32, owner_pid: u32) -> BrowserProcessOwner {
+        BrowserProcessOwner {
+            schema_version: OWNER_SCHEMA.into(),
+            browser_pid,
+            browser_start_identity: "fixture-identity".into(),
+            executable: "C:\\fixture\\chrome.exe".into(),
+            owner_pid,
+            owner_start_identity: "fixture-owner-identity".into(),
+            created_unix_ms: super::super::evidence::unix_time_ms(),
+        }
+    }
+
+    #[test]
+    fn legacy_directory_without_owner_file_is_removed_only_when_old_enough() {
+        let root = tempfile::tempdir().unwrap();
+        let stale = root.path().join(format!("{BROWSER_TEMP_PREFIX}stale"));
+        fs::create_dir(&stale).unwrap();
+        // 默认年龄门禁：新建的目录视为可能属于进行中的预检，跳过。
+        assert!(sweep_stale_browser_processes_at(root.path(), SWEEP_MIN_AGE).is_empty());
+        assert!(stale.is_dir());
+        // 零门禁等价于“足够旧”：无 owner.json 的旧残留只删目录。
+        let notes = sweep_stale_browser_processes_at(root.path(), Duration::ZERO);
+        assert!(notes
+            .iter()
+            .any(|note| note.starts_with("removed-legacy-dir:")));
+        assert!(!stale.exists());
+    }
+
+    #[test]
+    fn directory_owned_by_a_live_app_instance_is_skipped() {
+        let root = tempfile::tempdir().unwrap();
+        let dir = root.path().join(format!("{BROWSER_TEMP_PREFIX}owned"));
+        fs::create_dir(&dir).unwrap();
+        let owner_identity =
+            crate::runner::external_agent_runner_process_start_identity(std::process::id())
+                .expect("self identity")
+                .expect("self identity present");
+        let mut owner = owner_fixture(exited_child_pid(), std::process::id());
+        owner.owner_start_identity = owner_identity;
+        write_owner(&dir, &owner);
+        assert!(sweep_stale_browser_processes_at(root.path(), Duration::ZERO).is_empty());
+        assert!(dir.is_dir());
+    }
+
+    #[test]
+    fn exited_or_reused_browser_pid_deletes_directory_without_touching_processes() {
+        let root = tempfile::tempdir().unwrap();
+        let dir = root.path().join(format!("{BROWSER_TEMP_PREFIX}exited"));
+        fs::create_dir(&dir).unwrap();
+        let owner = owner_fixture(exited_child_pid(), exited_child_pid());
+        write_owner(&dir, &owner);
+        let notes = sweep_stale_browser_processes_at(root.path(), Duration::ZERO);
+        assert!(notes
+            .iter()
+            .any(|note| note.starts_with("removed-exited-dir:")));
+        assert!(!dir.exists());
+    }
+
+    #[test]
+    fn owner_file_with_bad_schema_or_unknown_fields_is_treated_as_legacy() {
+        let root = tempfile::tempdir().unwrap();
+        let dir = root.path().join(format!("{BROWSER_TEMP_PREFIX}bad-owner"));
+        fs::create_dir(&dir).unwrap();
+        fs::write(
+            dir.join(OWNER_FILE),
+            br#"{"schemaVersion":"other","extra":true}"#,
+        )
+        .unwrap();
+        assert!(read_browser_process_owner(&dir).is_none());
+        let notes = sweep_stale_browser_processes_at(root.path(), Duration::ZERO);
+        assert!(notes
+            .iter()
+            .any(|note| note.starts_with("removed-legacy-dir:")));
+        assert!(!dir.exists());
+    }
+
+    #[test]
+    fn trusted_browser_executable_matches_system_candidates_only() {
+        assert!(!trusted_browser_executable(Path::new(
+            "C:\\fixture\\chrome.exe"
+        )));
+        let Some((installed, _)) = system_browser_candidates()
+            .into_iter()
+            .find(|(candidate, _)| candidate.is_file())
+        else {
+            // 没有安装浏览器的机器上无可信目标可断言。
+            return;
+        };
+        assert!(trusted_browser_executable(&installed));
+    }
+
+    #[cfg(windows)]
+    #[test]
+    fn kill_browser_process_tree_reaps_fixture_tree() {
+        use std::process::{Command, Stdio};
+
+        // timeout.exe 在 stdio 被重定向时会立即退出，ping 才能在 null stdio 下存活。
+        let mut child = Command::new("cmd.exe")
+            .args([
+                "/c",
+                "ping",
+                "127.0.0.1",
+                "-n",
+                "60",
+                "&",
+                "ping",
+                "127.0.0.1",
+                "-n",
+                "60",
+            ])
+            .stdin(Stdio::null())
+            .stdout(Stdio::null())
+            .stderr(Stdio::null())
+            .spawn()
+            .expect("spawn fixture");
+        let pid = child.id();
+        std::thread::sleep(Duration::from_millis(500));
+        let identity = crate::runner::external_agent_runner_process_start_identity(pid)
+            .expect("fixture identity")
+            .expect("fixture identity present");
+        let before = windows_process_tree_pids(pid).expect("tree snapshot");
+        assert!(before.len() >= 2, "fixture 必须包含子进程: {before:?}");
+        kill_browser_process_tree(pid, &identity).expect("kill tree");
+        assert!(windows_process_tree_pids(pid)
+            .map(|tree| tree.is_empty())
+            .unwrap_or(true));
+        let _ = child.kill();
+        let _ = child.wait();
+    }
+}
diff --git a/apps/ai-game-creator-shell/src-tauri/src/environment_check/web_creation.rs b/apps/ai-game-creator-shell/src-tauri/src/environment_check/web_creation.rs
index 532503c75..4378f32d7 100644
--- a/apps/ai-game-creator-shell/src-tauri/src/environment_check/web_creation.rs
+++ b/apps/ai-game-creator-shell/src-tauri/src/environment_check/web_creation.rs
@@ -304,6 +304,8 @@ async fn host_npm(
 
 pub(crate) async fn host_web_creation_preflight() -> Value {
     let started = Instant::now();
+    // 预检前顺手清扫陈旧的无头浏览器，避免残留进程放大本轮超时。
+    let _ = tokio::task::spawn_blocking(crate::browser::sweep_stale_browser_processes).await;
     let run = async {
         let fixture = tempfile::tempdir().map_err(|_| "web-preflight-temp-unavailable")?;
         let root = fixture.path();
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 151a18cfe..32b340123 100644
--- a/apps/ai-game-creator-shell/src-tauri/src/main.rs
+++ b/apps/ai-game-creator-shell/src-tauri/src/main.rs
@@ -2467,6 +2467,17 @@ fn main() {
             if let Some(directory) = game_creator_runtime_config_dir() {
                 setup_log.set(directory.join("diagnostics/startup.log"));
             }
+            // 跨会话清扫陈旧的无头浏览器（上次异常退出/被杀留下的 ga-browser-*）。
+            // 后台执行，不阻塞启动；杀树前按进程身份与可信浏览器路径双重校验。
+            tauri::async_runtime::spawn(async move {
+                let notes =
+                    tokio::task::spawn_blocking(crate::browser::sweep_stale_browser_processes)
+                        .await
+                        .unwrap_or_default();
+                if !notes.is_empty() {
+                    app_log!("startup.browser-sweep: {}", notes.join("; "));
+                }
+            });
             setup_log.append("startup.appdata.configure.complete");
             let config_dir = game_creator_runtime_config_dir().ok_or_else(|| {
                 let error = std::io::Error::new(
diff --git a/apps/ai-game-creator-shell/src-tauri/src/process_session/tests.rs b/apps/ai-game-creator-shell/src-tauri/src/process_session/tests.rs
index 1463a6c08..d421a372f 100644
--- a/apps/ai-game-creator-shell/src-tauri/src/process_session/tests.rs
+++ b/apps/ai-game-creator-shell/src-tauri/src/process_session/tests.rs
@@ -1821,10 +1821,20 @@ setInterval(() => {}, 1000);
 fn windows_process_job_terminate_reaps_process_tree() {
     use std::process::{Command, Stdio};
 
-    // cmd 启动第一个 timeout 子进程后整树存活；terminate 必须连子进程一起收割。
+    // cmd 启动第一个 ping 子进程后整树存活；terminate 必须连子进程一起收割。
+    // timeout.exe 在 stdio 被重定向时会立即退出，ping 才能在 null stdio 下存活。
     let mut child = Command::new("cmd.exe")
         .args([
-            "/c", "timeout", "/t", "60", "/nobreak", "&", "timeout", "/t", "60", "/nobreak",
+            "/c",
+            "ping",
+            "127.0.0.1",
+            "-n",
+            "60",
+            "&",
+            "ping",
+            "127.0.0.1",
+            "-n",
+            "60",
         ])
         .stdin(Stdio::null())
         .stdout(Stdio::null())
@@ -1833,6 +1843,10 @@ fn windows_process_job_terminate_reaps_process_tree() {
         .expect("spawn cmd fixture");
     let job = WindowsProcessJob::assign_std(&child).expect("assign job");
     thread::sleep(Duration::from_millis(500));
+    assert!(
+        !job.is_empty().expect("query job"),
+        "fixture 进程树必须先存活，否则收割断言是空转"
+    );
     job.terminate().expect("terminate job");
     let deadline = std::time::Instant::now() + Duration::from_secs(10);
     while !job.is_empty().expect("query job") {