diff --git a/README.md b/README.md
index 7eddc3d..a08c233 100644
--- a/README.md
+++ b/README.md
@@ -338,6 +338,11 @@ The hook target is `understatus cmux hook-codex`. It is intentionally quiet and
 - it updates cmux with `cmux set-status` / `clear-status` only;
 - it never uses `cmux set-progress` because cmux progress is workspace-global and can clobber
   between panes;
+- CPU/memory pills are hook-event snapshots, not live polling;
+- `Stop` clears understatus Codex pills so the sidebar can be empty between turns or while idle;
+- installed hooks point at the concrete `understatus` binary path available at install time, so
+  rebuild/reinstall the hooks and re-trust them in Codex `/hooks` after changing or upgrading
+  understatus;
 - in hook mode, it only applies when a caller/environment target such as `CMUX_WORKSPACE_ID` is
   present; it will not fall back to a focused workspace.
 
@@ -378,7 +383,7 @@ macOS용 AI 코딩 CLI statusline 애드온입니다. CPU%, 메모리, 배터리
 - **세션 캐시 격리** — 체인 출력·펄스 상태·네트워크 델타 캐시는 `session_id`별로 분리되어 여러 터미널을 동시에 열어도 값이 섞이지 않습니다. 배터리는 머신 전역.
 - **Claude rate-limit 표시** — Claude Code stdin에 `rate_limits`가 들어오면 5h/weekly 사용률과 리셋 카운트다운을 네트워크 호출 없이 표시합니다.
 - **lterm/cmux·Codex 경로** — `--source lterm --surface-format cmux-status`는 cmux pill JSON을 출력합니다. Codex를 cmux 안에서 쓰는 경우 `understatus cmux install-codex-hooks`로 Codex hook을 설치하면 왼쪽 sidebar status pill이 자동 갱신됩니다. 독립 Codex/tmux 경로는 `--source codex --oneline`으로 `~/.codex`를 best-effort 보강합니다.
-- **hook 안전성** — Codex hook은 `{}`만 출력하고, 5초 timeout으로 fail-soft 동작하며, cmux에는 `set-status`/`clear-status`만 사용합니다. pane 간 전역 progress 충돌을 막기 위해 `set-progress`는 쓰지 않습니다.
+- **hook 안전성** — Codex hook은 `{}`만 출력하고, 5초 timeout으로 fail-soft 동작하며, cmux에는 `set-status`/`clear-status`만 사용합니다. CPU/mem은 hook 시점 스냅샷이고, `Stop`은 idle sidebar가 비도록 Codex pill을 지웁니다. pane 간 전역 progress 충돌을 막기 위해 `set-progress`는 쓰지 않습니다. hook은 설치 시점의 구체적 바이너리 경로를 쓰므로 understatus 변경/업그레이드 후 재설치하고 Codex `/hooks`에서 다시 trust하세요.
 
 **설치**
 
diff --git a/src/main.rs b/src/main.rs
index 47a7a9d..de37def 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -415,6 +415,17 @@ fn run_cmux_hook_codex(args: &[String]) -> ExitCode {
         window: parsed.window,
     };
     let target = cmux::resolve_target(explicit_target, true);
+    if input.hook_event_name == "Stop" {
+        if target.has_caller_target() {
+            if let Some(mode) = clamped_codex_hook_apply_mode(hook_started) {
+                let _ = cmux::clear_all_codex(target, mode);
+            }
+        }
+        print!("{}", codex_hooks::neutral_hook_stdout());
+        let _ = std::io::stdout().flush();
+        return ExitCode::SUCCESS;
+    }
+
     let surface = std::env::var("CMUX_SURFACE_ID").ok();
     let payload = codex_hooks::render_payload(&input, &target, surface.as_deref());
     let owner = parsed
@@ -422,10 +433,7 @@ fn run_cmux_hook_codex(args: &[String]) -> ExitCode {
         .unwrap_or_else(|| codex_hooks::owner_key(&input, &target, surface.as_deref()));
     if target.has_caller_target() {
         let pills = render_cmux_output_for_raw(Source::Codex, &payload);
-        if let Some(remaining_ms) = remaining_codex_hook_apply_budget_ms(hook_started) {
-            let mut mode = cmux::ApplyMode::hook();
-            mode.timeout_ms = mode.timeout_ms.min(remaining_ms);
-            mode.total_timeout_ms = Some(remaining_ms);
+        if let Some(mode) = clamped_codex_hook_apply_mode(hook_started) {
             let _ = cmux::apply_pills(&pills, &owner, target, mode);
         }
     }
@@ -434,6 +442,14 @@ fn run_cmux_hook_codex(args: &[String]) -> ExitCode {
     ExitCode::SUCCESS
 }
 
+fn clamped_codex_hook_apply_mode(hook_started: Instant) -> Option<cmux::ApplyMode> {
+    let remaining_ms = remaining_codex_hook_apply_budget_ms(hook_started)?;
+    let mut mode = cmux::ApplyMode::hook();
+    mode.timeout_ms = mode.timeout_ms.min(remaining_ms);
+    mode.total_timeout_ms = Some(remaining_ms);
+    Some(mode)
+}
+
 fn remaining_codex_hook_apply_budget_ms(hook_started: Instant) -> Option<u64> {
     let hard_timeout = Duration::from_secs(codex_hooks::HOOK_TIMEOUT_SECS);
     let reserve = Duration::from_millis(CODEX_HOOK_STDOUT_RESERVE_MS);
diff --git a/tests/oneline.rs b/tests/oneline.rs
index 20003d6..2e79864 100644
--- a/tests/oneline.rs
+++ b/tests/oneline.rs
@@ -9,6 +9,7 @@
 use std::io::Write;
 use std::process::{Command, Stdio};
 use std::sync::atomic::{AtomicU64, Ordering};
+use std::sync::Mutex;
 
 /// chain 실행 여부를 stdout으로 직접 관측하기 위한 센티널. chain_command가 도는 경우에만
 /// 자식 stdout에 합성되어 self 세그먼트와 함께 한 줄에 나타난다.
@@ -25,6 +26,7 @@ const CONFIG_LIMIT_BYTES: usize = 256 * 1024;
 /// 읽기와 경합하며 torn read(부분 판독)를 유발한다(E2E flaky 근본 원인). 매 호출마다 증가하는
 /// 전역 카운터를 경로에 섞어 충돌을 원천 차단한다.
 static UNIQUE_COUNTER: AtomicU64 = AtomicU64::new(0);
+static CMUX_FAKE_TEST_LOCK: Mutex<()> = Mutex::new(());
 
 /// 프로세스 내에서 절대 충돌하지 않는 고유 토큰(`<pid>-<nanos>-<counter>`)을 만든다.
 fn unique_token() -> String {
@@ -161,6 +163,75 @@ fn make_isolated_home(tag: &str) -> String {
     path.to_string_lossy().into_owned()
 }
 
+#[cfg(unix)]
+fn install_fake_cmux(
+    tag: &str,
+    script: &str,
+) -> (std::path::PathBuf, std::path::PathBuf, std::ffi::OsString) {
+    use std::os::unix::fs::PermissionsExt;
+
+    let token = unique_token();
+    let bin_dir = std::env::temp_dir().join(format!("understatus-fake-cmux-{tag}-{token}"));
+    let record_path =
+        std::env::temp_dir().join(format!("understatus-fake-cmux-{tag}-record-{token}.txt"));
+    std::fs::create_dir_all(&bin_dir).expect("fake cmux bin dir 생성 실패");
+
+    let cmux_path = bin_dir.join("cmux");
+    std::fs::write(&cmux_path, script).expect("fake cmux 작성 실패");
+    let mut perms = std::fs::metadata(&cmux_path)
+        .expect("fake cmux metadata")
+        .permissions();
+    perms.set_mode(0o755);
+    std::fs::set_permissions(&cmux_path, perms).expect("fake cmux chmod 실패");
+
+    let old_path = std::env::var_os("PATH").unwrap_or_default();
+    let mut paths = vec![bin_dir.clone()];
+    paths.extend(std::env::split_paths(&old_path));
+    let path = std::env::join_paths(paths).expect("PATH join 실패");
+
+    (bin_dir, record_path, path)
+}
+
+#[cfg(unix)]
+fn run_cmux_hook_codex_with_fake_cmux(
+    args: &[&str],
+    stdin: &[u8],
+    home: &str,
+    path: &std::ffi::OsStr,
+    record_path: &std::path::Path,
+    config_path: Option<&str>,
+) -> std::process::Output {
+    let mut command = Command::new(env!("CARGO_BIN_EXE_understatus"));
+    command
+        .args(["cmux", "hook-codex"])
+        .args(args)
+        .env("NO_COLOR", "1")
+        .env("HOME", home)
+        .env("PATH", path)
+        .env("CMUX_RECORD", record_path)
+        .env_remove("CMUX_WORKSPACE_ID")
+        .env_remove("CMUX_WINDOW_ID")
+        .env_remove("CMUX_WINDOW")
+        .env_remove("CMUX_SURFACE_ID")
+        .stdin(Stdio::piped())
+        .stdout(Stdio::piped())
+        .stderr(Stdio::piped());
+    if let Some(config_path) = config_path {
+        command.env("UNDERSTATUS_CONFIG", config_path);
+    }
+
+    let mut child = command
+        .spawn()
+        .expect("understatus cmux hook-codex 실행 실패");
+    child
+        .stdin
+        .take()
+        .expect("stdin 핸들 없음")
+        .write_all(stdin)
+        .expect("stdin 쓰기 실패");
+    child.wait_with_output().expect("자식 종료 대기 실패")
+}
+
 /// --oneline은 정확히 1행을 후행 개행 없이 출력해야 한다(spec §6.3).
 #[test]
 fn oneline_emits_single_line_without_trailing_newline() {
@@ -655,6 +726,213 @@ fn cmux_hook_codex_without_target_noops_and_prints_neutral_json() {
     let _ = std::fs::remove_dir_all(&empty_path);
 }
 
+/// Codex + CMUX bridge: Stop hook은 렌더링/샘플링 없이 현재 target의 관측된 Codex pill만 지운다.
+#[cfg(unix)]
+#[test]
+fn cmux_hook_codex_stop_clears_observed_understatus_keys_only() {
+    let _cmux_lock = CMUX_FAKE_TEST_LOCK.lock().expect("fake cmux test lock");
+    let home = make_isolated_home("cmux-hook-stop-clear");
+    let (bin_dir, record_path, path) = install_fake_cmux(
+        "hook-stop-clear",
+        r##"#!/bin/sh
+cmd="$1"
+{
+  printf '%s' "$cmd"
+  shift
+  for arg in "$@"; do
+    printf '\t%s' "$arg"
+  done
+  printf '\n'
+} >> "$CMUX_RECORD"
+if [ "$cmd" = "sidebar-state" ]; then
+  cat <<'STATE'
+status_count=3
+  understatus.codex.session_a.cpu=cpu 31% color=#6D8296 priority=100
+  understatus.codex.session_a.mem=mem 68% color=#A0A0A0 priority=90
+  other.tool=ok color=#00ff00 priority=1
+STATE
+fi
+exit 0
+"##,
+    );
+
+    let output = run_cmux_hook_codex_with_fake_cmux(
+        &["--workspace", "workspace:test", "--window", "window:test"],
+        br#"{"hook_event_name":"Stop","session_id":"sess-stop","cwd":"/tmp/proj"}"#,
+        &home,
+        &path,
+        &record_path,
+        None,
+    );
+    assert!(
+        output.status.success(),
+        "Stop hook은 fake sidebar clear 실패 없이 성공해야 함: {:?}, stderr={}",
+        output.status,
+        String::from_utf8_lossy(&output.stderr)
+    );
+    assert_eq!(
+        String::from_utf8(output.stdout).expect("stdout UTF-8"),
+        "{}"
+    );
+
+    let record = std::fs::read_to_string(&record_path).expect("fake cmux 호출 기록");
+    assert!(
+        record.contains("sidebar-state\t--workspace\tworkspace:test\t--window\twindow:test"),
+        "현재 CMUX status를 조회해야 함: {record:?}"
+    );
+    assert!(
+        record.contains("clear-status\tunderstatus.codex.session_a.cpu"),
+        "관측된 cpu key clear 필요: {record:?}"
+    );
+    assert!(
+        record.contains("clear-status\tunderstatus.codex.session_a.mem"),
+        "관측된 mem key clear 필요: {record:?}"
+    );
+    assert!(
+        !record.contains("clear-status\tother.tool"),
+        "다른 도구 key는 건드리면 안 됨: {record:?}"
+    );
+    assert!(
+        !record.contains("set-status"),
+        "Stop hook은 set-status를 호출하면 안 됨: {record:?}"
+    );
+
+    let _ = std::fs::remove_dir_all(&home);
+    let _ = std::fs::remove_dir_all(&bin_dir);
+    let _ = std::fs::remove_file(&record_path);
+}
+
+/// Codex + CMUX bridge: Stop hook cleanup은 sidebar-state 조회 실패에도 fail-soft여야 한다.
+#[cfg(unix)]
+#[test]
+fn cmux_hook_codex_stop_sidebar_state_failure_still_succeeds() {
+    let _cmux_lock = CMUX_FAKE_TEST_LOCK.lock().expect("fake cmux test lock");
+    let home = make_isolated_home("cmux-hook-stop-sidebar-fails");
+    let (bin_dir, record_path, path) = install_fake_cmux(
+        "hook-stop-fail",
+        r#"#!/bin/sh
+cmd="$1"
+{
+  printf '%s' "$cmd"
+  shift
+  for arg in "$@"; do
+    printf '\t%s' "$arg"
+  done
+  printf '\n'
+} >> "$CMUX_RECORD"
+if [ "$cmd" = "sidebar-state" ]; then
+  exit 7
+fi
+exit 0
+"#,
+    );
+
+    let output = run_cmux_hook_codex_with_fake_cmux(
+        &["--workspace", "workspace:test", "--window", "window:test"],
+        br#"{"hook_event_name":"Stop","session_id":"sess-stop","cwd":"/tmp/proj"}"#,
+        &home,
+        &path,
+        &record_path,
+        None,
+    );
+    assert!(
+        output.status.success(),
+        "Stop hook은 sidebar-state 실패에도 성공해야 함: {:?}, stderr={}",
+        output.status,
+        String::from_utf8_lossy(&output.stderr)
+    );
+    assert_eq!(
+        String::from_utf8(output.stdout).expect("stdout UTF-8"),
+        "{}"
+    );
+
+    let record = std::fs::read_to_string(&record_path).expect("fake cmux 호출 기록");
+    assert!(
+        record.contains("sidebar-state\t--workspace\tworkspace:test\t--window\twindow:test"),
+        "sidebar-state 시도는 필요: {record:?}"
+    );
+    assert!(
+        !record.contains("set-status"),
+        "Stop hook은 set-status를 호출하면 안 됨: {record:?}"
+    );
+
+    let _ = std::fs::remove_dir_all(&home);
+    let _ = std::fs::remove_dir_all(&bin_dir);
+    let _ = std::fs::remove_file(&record_path);
+}
+
+/// Codex + CMUX bridge: Stop이 아닌 hook-codex는 기존처럼 status pill을 적용한다.
+#[cfg(unix)]
+#[test]
+fn cmux_hook_codex_non_stop_applies_fake_cmux_set_status() {
+    let _cmux_lock = CMUX_FAKE_TEST_LOCK.lock().expect("fake cmux test lock");
+    let home = make_isolated_home("cmux-hook-non-stop");
+    let config = write_deterministic_core_config("cmux-hook-non-stop");
+    let (bin_dir, record_path, path) = install_fake_cmux(
+        "hook-set",
+        r#"#!/bin/sh
+{
+  printf '%s' "$1"
+  shift
+  for arg in "$@"; do
+    printf '\t%s' "$arg"
+  done
+  printf '\n'
+} >> "$CMUX_RECORD"
+exit 0
+"#,
+    );
+
+    let output = run_cmux_hook_codex_with_fake_cmux(
+        &[
+            "--workspace",
+            "workspace:test",
+            "--window",
+            "window:test",
+            "--session-key",
+            "it_owner",
+        ],
+        br#"{"hook_event_name":"UserPromptSubmit","session_id":"sess-live","cwd":"/tmp/proj"}"#,
+        &home,
+        &path,
+        &record_path,
+        Some(config.as_str()),
+    );
+    assert!(
+        output.status.success(),
+        "non-Stop hook은 fake cmux set-status 성공 시 성공해야 함: {:?}, stderr={}",
+        output.status,
+        String::from_utf8_lossy(&output.stderr)
+    );
+    assert_eq!(
+        String::from_utf8(output.stdout).expect("stdout UTF-8"),
+        "{}"
+    );
+
+    let record = std::fs::read_to_string(&record_path).expect("fake cmux 호출 기록");
+    assert!(
+        record.contains("set-status\tunderstatus.codex.it_owner.model"),
+        "model pill set-status 호출 필요: {record:?}"
+    );
+    assert!(
+        record.contains("set-status\tunderstatus.codex.it_owner.cpu"),
+        "cpu pill set-status 호출 필요: {record:?}"
+    );
+    assert!(
+        record.contains("set-status\tunderstatus.codex.it_owner.mem"),
+        "mem pill set-status 호출 필요: {record:?}"
+    );
+    assert!(
+        !record.contains("set-progress"),
+        "CMUX 전역 progress 명령은 호출하면 안 됨: {record:?}"
+    );
+
+    let _ = std::fs::remove_dir_all(&home);
+    let _ = std::fs::remove_file(&config);
+    let _ = std::fs::remove_dir_all(&bin_dir);
+    let _ = std::fs::remove_file(&record_path);
+}
+
 /// Codex + CMUX bridge: fake `cmux` executable을 PATH에 주입해 실제 CLI 공개 경로가
 /// `set-status`만 호출하고 `set-progress`는 절대 호출하지 않으며 workspace/window target을 전달함을 검증한다.
 #[cfg(unix)]
@@ -662,6 +940,7 @@ fn cmux_hook_codex_without_target_noops_and_prints_neutral_json() {
 fn cmux_apply_codex_invokes_fake_cmux_set_status_only() {
     use std::os::unix::fs::PermissionsExt;
 
+    let _cmux_lock = CMUX_FAKE_TEST_LOCK.lock().expect("fake cmux test lock");
     let token = unique_token();
     let home = make_isolated_home("cmux-apply-fake");
     let config = write_deterministic_core_config("cmux-apply-fake");
@@ -775,6 +1054,7 @@ exit 0
 fn cmux_apply_codex_clears_observed_legacy_session_keys() {
     use std::os::unix::fs::PermissionsExt;
 
+    let _cmux_lock = CMUX_FAKE_TEST_LOCK.lock().expect("fake cmux test lock");
     let token = unique_token();
     let home = make_isolated_home("cmux-apply-clears-observed");
     let config = write_deterministic_core_config("cmux-apply-clears-observed");
@@ -893,6 +1173,7 @@ exit 0
 fn cmux_clear_codex_without_session_key_clears_observed_understatus_keys() {
     use std::os::unix::fs::PermissionsExt;
 
+    let _cmux_lock = CMUX_FAKE_TEST_LOCK.lock().expect("fake cmux test lock");
     let token = unique_token();
     let home = make_isolated_home("cmux-clear-observed");
     let bin_dir = std::env::temp_dir().join(format!("understatus-fake-cmux-clear-all-{token}"));