diff --git a/internal/acp/handlers/server_fs_read.go b/internal/acp/handlers/server_fs_read.go
index 82b818b..91b4d63 100644
--- a/internal/acp/handlers/server_fs_read.go
+++ b/internal/acp/handlers/server_fs_read.go
@@ -68,7 +68,10 @@ func sliceLines(s string, line, limit *int) string {
 	}
 	end := len(lines)
 	if limit != nil && *limit >= 0 {
-		if start+*limit < end {
+		// overflow-safe：用剩余行数为上限做钳制，避免 start+*limit 在 *limit 很大
+		// （如 math.MaxInt）时整数溢出为负，绕过下界判断后导致 lines[start:end] panic。
+		remaining := len(lines) - start
+		if *limit < remaining {
 			end = start + *limit
 		}
 	}
diff --git a/internal/acp/handlers/server_fs_read_test.go b/internal/acp/handlers/server_fs_read_test.go
index 4498fd2..5707049 100644
--- a/internal/acp/handlers/server_fs_read_test.go
+++ b/internal/acp/handlers/server_fs_read_test.go
@@ -3,6 +3,7 @@ package handlers_test
 import (
 	"context"
 	"encoding/json"
+	"math"
 	"os"
 	"path/filepath"
 	"testing"
@@ -81,6 +82,37 @@ func TestFsRead_LineLimit(t *testing.T) {
 	assert.Equal(t, "L1\nL2", out.Content)
 }
 
+// TestFsRead_HugeLimit_NoOverflow 锁定 bug #2：limit 为 math.MaxInt 时
+// start+limit 会整数溢出为负，旧逻辑下 lines[start:end] 会 panic。修复后应安全
+// 钳制到文件末尾，返回从 line 起的剩余内容。
+func TestFsRead_HugeLimit_NoOverflow(t *testing.T) {
+	t.Parallel()
+	tmp := t.TempDir()
+	require.NoError(t, os.WriteFile(filepath.Join(tmp, "f.txt"),
+		[]byte("L0\nL1\nL2\nL3\n"), 0o644))
+
+	h := handlers.NewFsReadHandler()
+	sess := handlers.SessionContext{CwdPath: tmp}
+	line := 1
+	limit := math.MaxInt
+	params := mustJSON(t, map[string]any{
+		"sessionId": "x", "path": filepath.Join(tmp, "f.txt"),
+		"line": line, "limit": limit,
+	})
+
+	var res handlers.FsResult
+	require.NotPanics(t, func() {
+		res = h.Handle(context.Background(), sess, params)
+	})
+	require.Nil(t, res.Err)
+	var out struct {
+		Content string `json:"content"`
+	}
+	require.NoError(t, json.Unmarshal(res.OK, &out))
+	// 从 line=1 到末尾（split 出 5 个元素：L0 L1 L2 L3 ""）。
+	assert.Equal(t, "L1\nL2\nL3\n", out.Content)
+}
+
 func mustJSON(t *testing.T, v any) json.RawMessage {
 	t.Helper()
 	b, err := json.Marshal(v)
diff --git a/internal/acp/permission_service.go b/internal/acp/permission_service.go
index 11ce8b3..2aea883 100644
--- a/internal/acp/permission_service.go
+++ b/internal/acp/permission_service.go
@@ -314,8 +314,13 @@ func resolvedEnvelope(reqID uuid.UUID, status PermissionStatus, chosen string) *
 	}
 }
 
-// extractToolName 尝试从 toolCall JSON 中提取工具标识。多个 agent 实现的字段名不同，
-// 依次尝试 name/toolName/kind/title；都取不到则返回空（保守走人工审批）。
+// extractToolName 尝试从 toolCall JSON 中提取真实工具标识。
+//
+// 安全约束（自动放行依据）：只接受真实工具名字段（name / toolName）。绝不回退到
+// ACP toolCall 的 'kind'（粗粒度枚举 read/edit/execute…）或 'title'（自由文本）——
+// 二者都由不可信 agent 自行填写，agent 可把一个 execute/shell 调用标成 kind='read'
+// 或冒用白名单里的 title 来绕过人工审批闸门。取不到真实名时返回空串，使 allowlistHit
+// 一律不放行（保守走人工审批），同时保留空名默认拒绝的语义。
 func extractToolName(toolCall json.RawMessage) string {
 	if len(toolCall) == 0 {
 		return ""
@@ -324,7 +329,7 @@ func extractToolName(toolCall json.RawMessage) string {
 	if err := json.Unmarshal(toolCall, &m); err != nil {
 		return ""
 	}
-	for _, k := range []string{"name", "toolName", "kind", "title"} {
+	for _, k := range []string{"name", "toolName"} {
 		if v, ok := m[k].(string); ok && v != "" {
 			return v
 		}
diff --git a/internal/acp/permission_service_internal_test.go b/internal/acp/permission_service_internal_test.go
index d854790..2e53bdc 100644
--- a/internal/acp/permission_service_internal_test.go
+++ b/internal/acp/permission_service_internal_test.go
@@ -1,6 +1,9 @@
 package acp
 
-import "testing"
+import (
+	"encoding/json"
+	"testing"
+)
 
 // TestAllowlistHit 覆盖白名单匹配的边界：空 toolName 一律不放行（含 "*"），
 // 白名单中的空串条目不误匹配。
@@ -26,3 +29,44 @@ func TestAllowlistHit(t *testing.T) {
 		})
 	}
 }
+
+// TestExtractToolName_IgnoresAgentAssertedKindTitle 锁定安全约束：extractToolName
+// 只信任真实工具名（name / toolName），绝不回退到 agent 自填的 kind / title。否则
+// agent 可把 execute/shell 调用伪装成 kind='read' 或冒用白名单 title 绕过人工审批。
+func TestExtractToolName_IgnoresAgentAssertedKindTitle(t *testing.T) {
+	cases := []struct {
+		name     string
+		toolCall string
+		want     string
+	}{
+		{"真实 name", `{"name":"shell.exec"}`, "shell.exec"},
+		{"真实 toolName", `{"toolName":"shell.exec"}`, "shell.exec"},
+		{"仅 kind 不取", `{"kind":"read"}`, ""},
+		{"仅 title 不取", `{"title":"Read file"}`, ""},
+		{"kind+title 都不取", `{"kind":"execute","title":"safe.tool"}`, ""},
+		{"name 优先于 kind/title", `{"name":"real.tool","kind":"read","title":"x"}`, "real.tool"},
+		{"空 toolCall", ``, ""},
+		{"无可识别字段", `{"unknownField":1}`, ""},
+	}
+	for _, c := range cases {
+		t.Run(c.name, func(t *testing.T) {
+			got := extractToolName(json.RawMessage(c.toolCall))
+			if got != c.want {
+				t.Fatalf("extractToolName(%q) = %q, want %q", c.toolCall, got, c.want)
+			}
+		})
+	}
+}
+
+// TestAllowlist_DoesNotHonorAgentKind 端到端验证 bug #3：即使 allowlist 含 'read'
+// 这类 kind 值，agent 把 execute 调用标成 kind='read' 也不会自动放行（extractToolName
+// 返回空 → allowlistHit 为 false）。
+func TestAllowlist_DoesNotHonorAgentKind(t *testing.T) {
+	toolName := extractToolName(json.RawMessage(`{"kind":"read","title":"safe"}`))
+	if toolName != "" {
+		t.Fatalf("kind/title 不应被当作工具名, got %q", toolName)
+	}
+	if allowlistHit([]string{"read", "safe", "*"}, toolName) {
+		t.Fatal("kind/title 伪装的调用不应命中白名单（含通配符）")
+	}
+}
diff --git a/internal/acp/relay.go b/internal/acp/relay.go
index 78f7a46..bce8fcb 100644
--- a/internal/acp/relay.go
+++ b/internal/acp/relay.go
@@ -249,7 +249,21 @@ func (r *Relay) reader(ctx context.Context, sess handlers.SessionContext) {
 }
 
 // handleAgentRequest dispatches an agent → server request to the appropriate handler.
+// 在独立 goroutine 中运行，故 defer recover 兜底任何 handler panic：记录日志并回送
+// JSON-RPC internal error，避免 agent 构造的请求 panic 掉整个进程（DoS）。
 func (r *Relay) handleAgentRequest(ctx context.Context, sess handlers.SessionContext, req *Message) {
+	defer func() {
+		if rec := recover(); rec != nil {
+			r.log.Error("acp.relay.handle_request_panic",
+				"session_id", r.sessionID, "method", req.Method, "panic", fmt.Sprintf("%v", rec))
+			resp := NewResponseErr(req.ID, JSONRPCInternalError, "internal error")
+			select {
+			case r.serverInitiated <- resp:
+			case <-ctx.Done():
+			}
+		}
+	}()
+
 	var resp *Message
 	switch req.Method {
 	case "fs/read_text_file":
diff --git a/internal/acp/supervisor.go b/internal/acp/supervisor.go
index 6c864ee..65bf907 100644
--- a/internal/acp/supervisor.go
+++ b/internal/acp/supervisor.go
@@ -108,6 +108,12 @@ type Process struct {
 	StartedAt  time.Time
 	KilledByUs atomic.Bool   // true → exited，false → crashed
 	done       chan struct{} // monitor 退出时 close
+
+	// relayCancel 取消 relay 的会话级 context。该 context 由 Spawn 用
+	// context.Background() 派生，独立于调用方的 spawn ctx（spawn ctx 在 Spawn
+	// 返回后立即取消），故 relay 的 reader/writer/persist/permission Decide 在整个
+	// 会话生命周期内都使用未取消的 ctx。onExit 调用 relayCancel 完成 relay teardown。
+	relayCancel context.CancelFunc
 }
 
 // stderrRing 是固定行数 ring buffer，monitor 退出时取 tail 写 last_error。
@@ -237,6 +243,12 @@ func (s *Supervisor) Spawn(ctx context.Context, sess *Session, kind *AgentKind,
 		s.log,
 	)
 
+	// relay 的会话级 context：独立于调用方的 spawn ctx（生产调用方在 Spawn 返回后
+	// 立即 cancel spawn ctx）。relay 的 reader/writer/persist/permission Decide 必须
+	// 在整个会话生命周期内使用未取消的 ctx，否则 prompt 被丢、事件停止持久化、权限
+	// 审批被强制拒绝。teardown 由 onExit 调 relayCancel + Relay.Close（关 r.done）完成。
+	relayCtx, relayCancel := context.WithCancel(context.Background())
+
 	proc := &Process{
 		SessionID:   sess.ID,
 		WorkspaceID: sess.WorkspaceID,
@@ -251,6 +263,7 @@ func (s *Supervisor) Spawn(ctx context.Context, sess *Session, kind *AgentKind,
 		StderrBuf:   newStderrRing(s.cfg.StderrBufferLines),
 		StartedAt:   time.Now(),
 		done:        make(chan struct{}),
+		relayCancel: relayCancel,
 	}
 
 	s.mu.Lock()
@@ -259,7 +272,7 @@ func (s *Supervisor) Spawn(ctx context.Context, sess *Session, kind *AgentKind,
 
 	go s.drainStderr(proc)
 	go s.monitorProcess(proc)
-	go relay.Run(ctx, handlers.SessionContext{
+	go relay.Run(relayCtx, handlers.SessionContext{
 		SessionID:      sess.ID,
 		WorkspaceID:    sess.WorkspaceID,
 		UserID:         sess.UserID,
@@ -268,6 +281,7 @@ func (s *Supervisor) Spawn(ctx context.Context, sess *Session, kind *AgentKind,
 		ToolAllowlist:  kind.ToolAllowlist,
 	})
 
+	// 握手仍走调用方的 spawn ctx，保留 SpawnTimeout 截止语义。
 	if err := s.handshake(ctx, sess, kind, relay, proc, extraEnv); err != nil {
 		s.log.Error("acp.handshake_failed", "session_id", sess.ID, "err", err.Error())
 		s.Kill(ctx, sess.ID, s.cfg.KillGrace)
@@ -516,6 +530,14 @@ func (s *Supervisor) onExit(ctx context.Context, proc *Process, status SessionSt
 		}
 	}
 
+	// 取消 relay 的会话级 context：停止 reader/writer，并让仍阻塞在 Decide / 已派生
+	// 的 handleAgentRequest goroutine 收到 ctx.Done 后退出。在 Relay.Close 之前调，
+	// 二者共同完成 teardown（relayCancel 停 ctx 派生的 goroutine，Close 关 r.done +
+	// 广播 session_terminated）。relayCancel 在早期 spawn 失败路径也可能为 nil。
+	if proc.relayCancel != nil {
+		proc.relayCancel()
+	}
+
 	// 最后关 relay：广播 session_terminated 给 WS subscribers。
 	proc.Relay.Close(string(status), &exitCode)
 }
diff --git a/internal/chat/streamer.go b/internal/chat/streamer.go
index efd839c..5674d44 100644
--- a/internal/chat/streamer.go
+++ b/internal/chat/streamer.go
@@ -70,26 +70,50 @@ type subscription struct {
 // the stream closes, or ctx is cancelled.
 // It returns all events from nextEventID to the current tail.
 func (sub *subscription) Next(ctx context.Context, nextEventID int64) ([]SSEEvent, bool, error) {
-	sub.st.mu.Lock()
-	defer sub.st.mu.Unlock()
+	st := sub.st
 
-	for int64(len(sub.st.events)) <= nextEventID && !sub.st.closed {
-		done := make(chan struct{})
-		go func() {
-			select {
-			case <-ctx.Done():
-				sub.st.cond.Broadcast()
-			case <-done:
-			}
-		}()
-		sub.st.cond.Wait()
-		close(done)
-		if ctx.Err() != nil {
-			return nil, false, ctx.Err()
+	// Launch a single watcher that observes ctx cancellation and wakes any
+	// waiter. It broadcasts under the lock so the signal cannot be missed by a
+	// waiter that has not yet parked on cond.Wait(); the predicate loop below
+	// re-checks ctx.Err() after every wake, so a broadcast delivered before a
+	// waiter parks is still observed on the next predicate check.
+	//
+	// done is closed (under the lock) when Next returns, which makes the watcher
+	// exit even if ctx never cancels — so neither goroutine can leak.
+	done := make(chan struct{})
+	go func() {
+		select {
+		case <-ctx.Done():
+			st.mu.Lock()
+			st.cond.Broadcast()
+			st.mu.Unlock()
+		case <-done:
 		}
+	}()
+
+	st.mu.Lock()
+	defer func() {
+		// Signal the watcher to exit, then release the lock. Closing done under
+		// the lock pairs with the watcher's Broadcast-under-lock so there is no
+		// window in which the watcher broadcasts to an unlocked, already-returned
+		// Next.
+		close(done)
+		st.mu.Unlock()
+	}()
+
+	// Wait until there is data at/after nextEventID, the stream closes, or ctx
+	// is cancelled. Each predicate component is re-checked after every wake so a
+	// missed/early broadcast cannot wedge the wait.
+	for int64(len(st.events)) <= nextEventID && !st.closed && ctx.Err() == nil {
+		st.cond.Wait()
 	}
-	out := append([]SSEEvent(nil), sub.st.events[nextEventID:]...)
-	return out, sub.st.closed, nil
+
+	if int64(len(st.events)) <= nextEventID && !st.closed && ctx.Err() != nil {
+		return nil, false, ctx.Err()
+	}
+
+	out := append([]SSEEvent(nil), st.events[nextEventID:]...)
+	return out, st.closed, nil
 }
 
 // streamerHub manages all in-flight streamers.
diff --git a/internal/chat/streamer_test.go b/internal/chat/streamer_test.go
index b1186e9..daeecb0 100644
--- a/internal/chat/streamer_test.go
+++ b/internal/chat/streamer_test.go
@@ -176,7 +176,7 @@ func (panicRepo) SoftDeleteConversation(_ context.Context, _ uuid.UUID) error {
 func (panicRepo) InsertMessage(_ context.Context, _ uuid.UUID, _ MessageRole, _ string, _ MessageStatus) (*Message, error) {
 	panic("not implemented")
 }
-func (panicRepo) GetMessage(_ context.Context, _ int64) (*Message, error)  { panic("not implemented") }
+func (panicRepo) GetMessage(_ context.Context, _ int64) (*Message, error) { panic("not implemented") }
 func (panicRepo) ListMessagesByConversation(_ context.Context, _ uuid.UUID, _ *int64, _ int) ([]Message, error) {
 	panic("not implemented")
 }
@@ -667,6 +667,77 @@ func TestStreamer_TitleGenerationTriggered(t *testing.T) {
 	}, 1*time.Second, 10*time.Millisecond, "GenerateTitle should have been triggered")
 }
 
+// TestStreamer_Next_EarlyCancel_NoLeak exercises the early-cancel race in
+// subscription.Next: when ctx is already cancelled (or cancels in the window
+// before the waiter parks on cond.Wait) and there are no new events, Next must
+// return ctx.Err() promptly instead of blocking forever, and must not leak the
+// Next goroutine or its ctx watcher.
+func TestStreamer_Next_EarlyCancel_NoLeak(t *testing.T) {
+	t.Parallel()
+
+	st := newStreamer()
+	sub := &subscription{st: st}
+
+	// Case 1: ctx already cancelled before Next is called. With no events and an
+	// open stream, the predicate is unsatisfied except for ctx, so Next must
+	// observe cancellation immediately rather than parking forever.
+	ctx, cancel := context.WithCancel(context.Background())
+	cancel()
+
+	done := make(chan struct{})
+	go func() {
+		defer close(done)
+		evs, closed, err := sub.Next(ctx, 0)
+		require.ErrorIs(t, err, context.Canceled)
+		require.Nil(t, evs)
+		require.False(t, closed)
+	}()
+
+	select {
+	case <-done:
+	case <-time.After(2 * time.Second):
+		t.Fatal("Next did not return on an already-cancelled ctx; goroutine leaked")
+	}
+
+	// Case 2: cancel concurrently while a waiter is (about to be) parked. Repeat
+	// to widen the window between launching the watcher and parking on Wait.
+	for i := 0; i < 200; i++ {
+		ctx, cancel := context.WithCancel(context.Background())
+		ret := make(chan error, 1)
+		go func() {
+			_, _, err := sub.Next(ctx, 0)
+			ret <- err
+		}()
+		cancel()
+		select {
+		case err := <-ret:
+			require.ErrorIs(t, err, context.Canceled)
+		case <-time.After(2 * time.Second):
+			t.Fatalf("iteration %d: Next wedged on concurrent cancel", i)
+		}
+	}
+}
+
+// TestStreamer_Next_DataDeliveredDespiteCancel verifies that when events are
+// already buffered, Next returns them even if ctx is cancelled (data wins over
+// a late cancel, preserving the original behavior).
+func TestStreamer_Next_DataDeliveredDespiteCancel(t *testing.T) {
+	t.Parallel()
+
+	st := newStreamer()
+	sub := &subscription{st: st}
+	st.append(SSEEvent{Event: "text_delta", Data: map[string]string{"text": "hi"}})
+
+	ctx, cancel := context.WithCancel(context.Background())
+	cancel()
+
+	evs, closed, err := sub.Next(ctx, 0)
+	require.NoError(t, err)
+	require.False(t, closed)
+	require.Len(t, evs, 1)
+	require.Equal(t, "text_delta", evs[0].Event)
+}
+
 // ===== helpers for title generation test =====
 
 // spyConvSvc is a minimal conversationService-shaped struct that calls a hook
diff --git a/internal/infra/proc/proc_unix.go b/internal/infra/proc/proc_unix.go
index 00ac383..c4c6a13 100644
--- a/internal/infra/proc/proc_unix.go
+++ b/internal/infra/proc/proc_unix.go
@@ -41,8 +41,12 @@ func (g *unixGroup) TerminateGroup(done <-chan struct{}, grace time.Duration) {
 	_ = syscall.Kill(-g.pgid, syscall.SIGTERM)
 	select {
 	case <-done:
-		return
+		// 组长已被回收（Cmd.Wait 返回），但其子孙（如 trap SIGTERM 的
+		// vite/esbuild/node）可能仍存活于同一进程组。无条件向整组补发一次
+		// SIGKILL 以确保不留下任何孤儿；若组已全灭，内核返回 ESRCH，无害。
+		_ = syscall.Kill(-g.pgid, syscall.SIGKILL)
 	case <-time.After(grace):
+		// 组长自身超过 grace 仍未退出：直接对整组 SIGKILL。
 		_ = syscall.Kill(-g.pgid, syscall.SIGKILL)
 	}
 }
diff --git a/internal/infra/proc/proc_windows.go b/internal/infra/proc/proc_windows.go
index 2dcc2d3..f63a570 100644
--- a/internal/infra/proc/proc_windows.go
+++ b/internal/infra/proc/proc_windows.go
@@ -5,6 +5,7 @@ package proc
 import (
 	"errors"
 	"os/exec"
+	"sync"
 	"time"
 	"unsafe"
 
@@ -15,7 +16,8 @@ import (
 // KILL_ON_JOB_CLOSE 的 Job，此后该进程派生的所有子孙自动归入同一 Job，
 // 关闭 Job 句柄即整树终止。优于 Process.Kill（只杀单 PID，漏 node 等子进程）。
 type windowsGroup struct {
-	job windows.Handle
+	job       windows.Handle
+	closeOnce sync.Once
 }
 
 func newGroup() Group { return &windowsGroup{} }
@@ -65,9 +67,14 @@ func (g *windowsGroup) TerminateGroup(_ <-chan struct{}, _ time.Duration) {
 	g.Close()
 }
 
+// Close 幂等且并发安全：TerminateGroup 与 monitor goroutine 可能并发调用，
+// 用 sync.Once 保证 CloseHandle 至多执行一次，避免重复关闭句柄（可能误关被复用
+// 的句柄）及对 g.job 的数据竞争。不改变 KILL_ON_JOB_CLOSE 语义：句柄关闭即整树终止。
 func (g *windowsGroup) Close() {
-	if g.job != 0 {
-		_ = windows.CloseHandle(g.job)
-		g.job = 0
-	}
+	g.closeOnce.Do(func() {
+		if g.job != 0 {
+			_ = windows.CloseHandle(g.job)
+			g.job = 0
+		}
+	})
 }
diff --git a/internal/jobs/domain.go b/internal/jobs/domain.go
index 436aa35..bb5e3c0 100644
--- a/internal/jobs/domain.go
+++ b/internal/jobs/domain.go
@@ -83,6 +83,14 @@ func IsPermanent(err error) bool {
 	return errors.As(err, &pe)
 }
 
+// ErrLeaseLost is returned by the terminal/retry write-back methods
+// (Complete, FailWithRetry, DeadLetter) when the fencing predicate matches no
+// row: the job is no longer leased by this worker (e.g. the reaper re-leased it
+// to another worker after the lease timeout). The caller must treat this as a
+// no-op — the write was correctly dropped to avoid clobbering the new run's
+// state — and must NOT surface it as a failure that triggers further retries.
+var ErrLeaseLost = errors.New("job lease lost; write-back skipped")
+
 // RunnerConfig is the per-runner configuration loaded from config.yaml.
 // Zero Interval means "use the runner's documented default".
 type RunnerConfig struct {
diff --git a/internal/jobs/module.go b/internal/jobs/module.go
index 1a3d962..4810da0 100644
--- a/internal/jobs/module.go
+++ b/internal/jobs/module.go
@@ -54,15 +54,17 @@ func NewModule(cfg Config, deps ModuleDeps) *Module {
 		sch.Add(name, entry.interval, entry.enabled, fn)
 	}
 
+	handlerTimeout := handlerTimeoutFor(cfg.JobReaper)
 	workers := make([]*Worker, cfg.Workers)
 	for i := 0; i < cfg.Workers; i++ {
 		workers[i] = NewWorker(deps.Repo, deps.Handlers, WorkerOptions{
-			ID:           workerID(i),
-			PollInterval: 200 * time.Millisecond,
-			Backoff:      deps.WorkerBackoff,
-			Clock:        clk,
-			Log:          log,
-			OnDeadLetter: deps.OnDeadLetter,
+			ID:             workerID(i),
+			PollInterval:   200 * time.Millisecond,
+			Backoff:        deps.WorkerBackoff,
+			Clock:          clk,
+			Log:            log,
+			HandlerTimeout: handlerTimeout,
+			OnDeadLetter:   deps.OnDeadLetter,
 		})
 	}
 	return &Module{cfg: cfg, scheduler: sch, workers: workers, log: log}
@@ -112,6 +114,19 @@ func (m *Module) Stop(ctx context.Context) {
 
 func workerID(i int) string { return "worker#" + strconv.Itoa(i) }
 
+// handlerTimeoutFor derives the per-job handler timeout from the reaper's lease
+// timeout, leaving a margin below it so a healthy long handler finishes (or is
+// canceled) before the reaper re-leases the job and double-runs it. Returns 0
+// (no timeout) when reaping is disabled or no positive lease timeout is set.
+func handlerTimeoutFor(rc JobReaperConfig) time.Duration {
+	if !rc.Enabled || rc.LeaseTimeout <= 0 {
+		return 0
+	}
+	// 90% of the lease window leaves headroom for the write-back to land before
+	// the reaper's cutoff.
+	return rc.LeaseTimeout - rc.LeaseTimeout/10
+}
+
 type schedEntry struct {
 	interval time.Duration
 	enabled  bool
diff --git a/internal/jobs/queries/jobs.sql b/internal/jobs/queries/jobs.sql
index b697b8e..7725c1a 100644
--- a/internal/jobs/queries/jobs.sql
+++ b/internal/jobs/queries/jobs.sql
@@ -20,28 +20,31 @@ UPDATE jobs
  )
 RETURNING *;
 
--- name: CompleteJob :exec
+-- name: CompleteJob :execrows
+-- 围栏谓词：只有持有当前租约的 worker 才能写回，防止被 reaper 重新租出后旧 worker 覆盖新一轮状态。
 UPDATE jobs
    SET status='completed', completed_at=now(),
        leased_at=NULL, leased_by=NULL, last_error=NULL,
        updated_at=now()
- WHERE id=$1;
+ WHERE id=$1 AND leased_by=$2 AND status='running';
 
--- name: FailJobWithRetry :exec
+-- name: FailJobWithRetry :execrows
+-- 围栏谓词同上。
 UPDATE jobs
    SET status='pending',
        scheduled_at=$2,
        leased_at=NULL, leased_by=NULL,
        last_error=$3,
        updated_at=now()
- WHERE id=$1;
+ WHERE id=$1 AND leased_by=$4 AND status='running';
 
--- name: DeadLetterJob :exec
+-- name: DeadLetterJob :execrows
+-- 围栏谓词同上。
 UPDATE jobs
    SET status='dead', completed_at=now(),
        leased_at=NULL, leased_by=NULL, last_error=$2,
        updated_at=now()
- WHERE id=$1;
+ WHERE id=$1 AND leased_by=$3 AND status='running';
 
 -- name: GetJob :one
 SELECT * FROM jobs WHERE id=$1;
diff --git a/internal/jobs/repository.go b/internal/jobs/repository.go
index 02b8cb4..7644beb 100644
--- a/internal/jobs/repository.go
+++ b/internal/jobs/repository.go
@@ -22,9 +22,13 @@ import (
 type Repository interface {
 	Enqueue(ctx context.Context, typ JobType, payload json.RawMessage, scheduledAt time.Time, maxAttempts int32) (*Job, error)
 	Lease(ctx context.Context, leasedBy string) (*Job, error)
-	Complete(ctx context.Context, id uuid.UUID) error
-	FailWithRetry(ctx context.Context, id uuid.UUID, scheduledAt time.Time, lastErr string) error
-	DeadLetter(ctx context.Context, id uuid.UUID, lastErr string) error
+	// Complete, FailWithRetry and DeadLetter take the leasing worker id and apply
+	// a fencing predicate (id + leased_by + status='running'); if the lease has
+	// been lost (e.g. the reaper re-leased the job) they return ErrLeaseLost so
+	// the caller drops the write instead of clobbering the new run's state.
+	Complete(ctx context.Context, id uuid.UUID, leasedBy string) error
+	FailWithRetry(ctx context.Context, id uuid.UUID, leasedBy string, scheduledAt time.Time, lastErr string) error
+	DeadLetter(ctx context.Context, id uuid.UUID, leasedBy string, lastErr string) error
 	Get(ctx context.Context, id uuid.UUID) (*Job, error)
 	ReapStuckRunningJobs(ctx context.Context, leasedBefore time.Time) ([]uuid.UUID, error)
 	PurgeCompleted(ctx context.Context, completedBefore time.Time) (int64, error)
@@ -90,11 +94,20 @@ func (r *PgRepository) Lease(ctx context.Context, leasedBy string) (*Job, error)
 	return rowToJob(row), nil
 }
 
-// Complete marks a job as completed and clears its lease/error fields.
-func (r *PgRepository) Complete(ctx context.Context, id uuid.UUID) error {
-	if err := r.q.CompleteJob(ctx, toPgUUID(id)); err != nil {
+// Complete marks a job as completed and clears its lease/error fields. The
+// update is fenced on the leasing worker id and status='running'; if no row
+// matches (lease lost to the reaper) it returns ErrLeaseLost as a no-op signal.
+func (r *PgRepository) Complete(ctx context.Context, id uuid.UUID, leasedBy string) error {
+	n, err := r.q.CompleteJob(ctx, jobssqlc.CompleteJobParams{
+		ID:       toPgUUID(id),
+		LeasedBy: &leasedBy,
+	})
+	if err != nil {
 		return errs.Wrap(err, errs.CodeInternal, "complete job")
 	}
+	if n == 0 {
+		return ErrLeaseLost
+	}
 	return nil
 }
 
@@ -102,25 +115,37 @@ func (r *PgRepository) Complete(ctx context.Context, id uuid.UUID) error {
 // the last error. Attempts is preserved (it was incremented on lease) so the
 // worker can compare against MaxAttempts to decide whether to retry or
 // dead-letter on the next failure.
-func (r *PgRepository) FailWithRetry(ctx context.Context, id uuid.UUID, scheduledAt time.Time, lastErr string) error {
-	if err := r.q.FailJobWithRetry(ctx, jobssqlc.FailJobWithRetryParams{
+func (r *PgRepository) FailWithRetry(ctx context.Context, id uuid.UUID, leasedBy string, scheduledAt time.Time, lastErr string) error {
+	n, err := r.q.FailJobWithRetry(ctx, jobssqlc.FailJobWithRetryParams{
 		ID:          toPgUUID(id),
 		ScheduledAt: pgtype.Timestamptz{Time: scheduledAt, Valid: true},
 		LastError:   &lastErr,
-	}); err != nil {
+		LeasedBy:    &leasedBy,
+	})
+	if err != nil {
 		return errs.Wrap(err, errs.CodeInternal, "fail job with retry")
 	}
+	if n == 0 {
+		return ErrLeaseLost
+	}
 	return nil
 }
 
-// DeadLetter terminally marks a job as dead and stores the last error.
-func (r *PgRepository) DeadLetter(ctx context.Context, id uuid.UUID, lastErr string) error {
-	if err := r.q.DeadLetterJob(ctx, jobssqlc.DeadLetterJobParams{
+// DeadLetter terminally marks a job as dead and stores the last error. Fenced
+// on the leasing worker id and status='running'; returns ErrLeaseLost on a
+// 0-row match so a stale worker does not overwrite a re-leased run.
+func (r *PgRepository) DeadLetter(ctx context.Context, id uuid.UUID, leasedBy string, lastErr string) error {
+	n, err := r.q.DeadLetterJob(ctx, jobssqlc.DeadLetterJobParams{
 		ID:        toPgUUID(id),
 		LastError: &lastErr,
-	}); err != nil {
+		LeasedBy:  &leasedBy,
+	})
+	if err != nil {
 		return errs.Wrap(err, errs.CodeInternal, "dead-letter job")
 	}
+	if n == 0 {
+		return ErrLeaseLost
+	}
 	return nil
 }
 
diff --git a/internal/jobs/repository_test.go b/internal/jobs/repository_test.go
index 8e1db30..8611cab 100644
--- a/internal/jobs/repository_test.go
+++ b/internal/jobs/repository_test.go
@@ -125,7 +125,7 @@ func TestComplete_ClearsLease(t *testing.T) {
 	require.NoError(t, err)
 	leased, err := repo.Lease(ctx, "h")
 	require.NoError(t, err)
-	require.NoError(t, repo.Complete(ctx, leased.ID))
+	require.NoError(t, repo.Complete(ctx, leased.ID, "h"))
 	got, err := repo.Get(ctx, job.ID)
 	require.NoError(t, err)
 	assert.Equal(t, jobs.StatusCompleted, got.Status)
@@ -133,6 +133,49 @@ func TestComplete_ClearsLease(t *testing.T) {
 	assert.Nil(t, got.LeasedBy)
 }
 
+// TestComplete_LeaseLostIsNoOp verifies the fencing predicate: a write-back
+// from a worker that no longer holds the lease (e.g. the reaper re-leased the
+// job) matches 0 rows and returns ErrLeaseLost without clobbering the new run.
+func TestComplete_LeaseLostIsNoOp(t *testing.T) {
+	t.Parallel()
+	ctx := context.Background()
+	repo, pool := setupRepo(t)
+	_, err := repo.Enqueue(ctx, jobs.TypeWebhookDeliver, json.RawMessage(`{}`), time.Now(), 5)
+	require.NoError(t, err)
+
+	// Worker A leases the job, then its handler stalls past the lease timeout.
+	leased, err := repo.Lease(ctx, "workerA")
+	require.NoError(t, err)
+	// Reaper resets it to pending; worker B re-leases it (now leased_by=workerB).
+	_, err = pool.Exec(ctx, `UPDATE jobs SET leased_at = now() - INTERVAL '10 minutes' WHERE id=$1`, leased.ID)
+	require.NoError(t, err)
+	ids, err := repo.ReapStuckRunningJobs(ctx, time.Now().Add(-5*time.Minute))
+	require.NoError(t, err)
+	require.Len(t, ids, 1)
+	reLeased, err := repo.Lease(ctx, "workerB")
+	require.NoError(t, err)
+	require.Equal(t, leased.ID, reLeased.ID)
+
+	// Stale worker A's terminal write-backs must be no-ops (ErrLeaseLost) and
+	// must not change the row that workerB now owns.
+	assert.ErrorIs(t, repo.Complete(ctx, leased.ID, "workerA"), jobs.ErrLeaseLost)
+	assert.ErrorIs(t, repo.FailWithRetry(ctx, leased.ID, "workerA", time.Now(), "stale"), jobs.ErrLeaseLost)
+	assert.ErrorIs(t, repo.DeadLetter(ctx, leased.ID, "workerA", "stale"), jobs.ErrLeaseLost)
+
+	got, err := repo.Get(ctx, leased.ID)
+	require.NoError(t, err)
+	assert.Equal(t, jobs.StatusRunning, got.Status, "row must still be owned by workerB's run")
+	require.NotNil(t, got.LeasedBy)
+	assert.Equal(t, "workerB", *got.LeasedBy)
+	assert.Nil(t, got.LastError, "stale write must not have set an error")
+
+	// Worker B (the true owner) completes successfully.
+	require.NoError(t, repo.Complete(ctx, leased.ID, "workerB"))
+	got, err = repo.Get(ctx, leased.ID)
+	require.NoError(t, err)
+	assert.Equal(t, jobs.StatusCompleted, got.Status)
+}
+
 func TestFailWithRetry_ReschedulesAndKeepsAttempts(t *testing.T) {
 	t.Parallel()
 	ctx := context.Background()
@@ -142,7 +185,7 @@ func TestFailWithRetry_ReschedulesAndKeepsAttempts(t *testing.T) {
 	leased, err := repo.Lease(ctx, "h")
 	require.NoError(t, err)
 	next := time.Now().Add(30 * time.Second)
-	require.NoError(t, repo.FailWithRetry(ctx, leased.ID, next, "boom"))
+	require.NoError(t, repo.FailWithRetry(ctx, leased.ID, "h", next, "boom"))
 	got, err := repo.Get(ctx, leased.ID)
 	require.NoError(t, err)
 	assert.Equal(t, jobs.StatusPending, got.Status)
@@ -160,7 +203,7 @@ func TestDeadLetter_FinalState(t *testing.T) {
 	require.NoError(t, err)
 	leased, err := repo.Lease(ctx, "h")
 	require.NoError(t, err)
-	require.NoError(t, repo.DeadLetter(ctx, leased.ID, "max attempts"))
+	require.NoError(t, repo.DeadLetter(ctx, leased.ID, "h", "max attempts"))
 	got, err := repo.Get(ctx, leased.ID)
 	require.NoError(t, err)
 	assert.Equal(t, jobs.StatusDead, got.Status)
@@ -204,7 +247,10 @@ func TestPurge_DeletesOldCompletedAndDead(t *testing.T) {
 	deadOld := mkOld(jobs.StatusDead)
 	freshComp, err := repo.Enqueue(ctx, jobs.TypeWebhookDeliver, json.RawMessage(`{}`), time.Now(), 5)
 	require.NoError(t, err)
-	require.NoError(t, repo.Complete(ctx, freshComp.ID))
+	leasedFresh, err := repo.Lease(ctx, "h")
+	require.NoError(t, err)
+	require.Equal(t, freshComp.ID, leasedFresh.ID)
+	require.NoError(t, repo.Complete(ctx, freshComp.ID, "h"))
 
 	rows, err := repo.PurgeCompleted(ctx, time.Now().Add(-7*24*time.Hour))
 	require.NoError(t, err)
diff --git a/internal/jobs/sqlc/jobs.sql.go b/internal/jobs/sqlc/jobs.sql.go
index 0e7c18e..d63fc87 100644
--- a/internal/jobs/sqlc/jobs.sql.go
+++ b/internal/jobs/sqlc/jobs.sql.go
@@ -11,35 +11,49 @@ import (
 	"github.com/jackc/pgx/v5/pgtype"
 )
 
-const completeJob = `-- name: CompleteJob :exec
+const completeJob = `-- name: CompleteJob :execrows
 UPDATE jobs
    SET status='completed', completed_at=now(),
        leased_at=NULL, leased_by=NULL, last_error=NULL,
        updated_at=now()
- WHERE id=$1
+ WHERE id=$1 AND leased_by=$2 AND status='running'
 `
 
-func (q *Queries) CompleteJob(ctx context.Context, id pgtype.UUID) error {
-	_, err := q.db.Exec(ctx, completeJob, id)
-	return err
+type CompleteJobParams struct {
+	ID       pgtype.UUID `json:"id"`
+	LeasedBy *string     `json:"leased_by"`
 }
 
-const deadLetterJob = `-- name: DeadLetterJob :exec
+// 围栏谓词：只有持有当前租约的 worker 才能写回，防止被 reaper 重新租出后旧 worker 覆盖新一轮状态。
+func (q *Queries) CompleteJob(ctx context.Context, arg CompleteJobParams) (int64, error) {
+	result, err := q.db.Exec(ctx, completeJob, arg.ID, arg.LeasedBy)
+	if err != nil {
+		return 0, err
+	}
+	return result.RowsAffected(), nil
+}
+
+const deadLetterJob = `-- name: DeadLetterJob :execrows
 UPDATE jobs
    SET status='dead', completed_at=now(),
        leased_at=NULL, leased_by=NULL, last_error=$2,
        updated_at=now()
- WHERE id=$1
+ WHERE id=$1 AND leased_by=$3 AND status='running'
 `
 
 type DeadLetterJobParams struct {
 	ID        pgtype.UUID `json:"id"`
 	LastError *string     `json:"last_error"`
+	LeasedBy  *string     `json:"leased_by"`
 }
 
-func (q *Queries) DeadLetterJob(ctx context.Context, arg DeadLetterJobParams) error {
-	_, err := q.db.Exec(ctx, deadLetterJob, arg.ID, arg.LastError)
-	return err
+// 围栏谓词同上。
+func (q *Queries) DeadLetterJob(ctx context.Context, arg DeadLetterJobParams) (int64, error) {
+	result, err := q.db.Exec(ctx, deadLetterJob, arg.ID, arg.LastError, arg.LeasedBy)
+	if err != nil {
+		return 0, err
+	}
+	return result.RowsAffected(), nil
 }
 
 const enqueueJob = `-- name: EnqueueJob :one
@@ -83,25 +97,35 @@ func (q *Queries) EnqueueJob(ctx context.Context, arg EnqueueJobParams) (Job, er
 	return i, err
 }
 
-const failJobWithRetry = `-- name: FailJobWithRetry :exec
+const failJobWithRetry = `-- name: FailJobWithRetry :execrows
 UPDATE jobs
    SET status='pending',
        scheduled_at=$2,
        leased_at=NULL, leased_by=NULL,
        last_error=$3,
        updated_at=now()
- WHERE id=$1
+ WHERE id=$1 AND leased_by=$4 AND status='running'
 `
 
 type FailJobWithRetryParams struct {
 	ID          pgtype.UUID        `json:"id"`
 	ScheduledAt pgtype.Timestamptz `json:"scheduled_at"`
 	LastError   *string            `json:"last_error"`
+	LeasedBy    *string            `json:"leased_by"`
 }
 
-func (q *Queries) FailJobWithRetry(ctx context.Context, arg FailJobWithRetryParams) error {
-	_, err := q.db.Exec(ctx, failJobWithRetry, arg.ID, arg.ScheduledAt, arg.LastError)
-	return err
+// 围栏谓词同上。
+func (q *Queries) FailJobWithRetry(ctx context.Context, arg FailJobWithRetryParams) (int64, error) {
+	result, err := q.db.Exec(ctx, failJobWithRetry,
+		arg.ID,
+		arg.ScheduledAt,
+		arg.LastError,
+		arg.LeasedBy,
+	)
+	if err != nil {
+		return 0, err
+	}
+	return result.RowsAffected(), nil
 }
 
 const getJob = `-- name: GetJob :one
diff --git a/internal/jobs/worker.go b/internal/jobs/worker.go
index 6116e8b..466c88a 100644
--- a/internal/jobs/worker.go
+++ b/internal/jobs/worker.go
@@ -20,6 +20,12 @@ type WorkerOptions struct {
 	Backoff      []time.Duration
 	Clock        clock.Clock
 	Log          *slog.Logger
+	// HandlerTimeout bounds a single handler invocation. It must be set slightly
+	// below the JobReaper's LeaseTimeout so a healthy long-running handler
+	// finishes (or is canceled) before the reaper re-leases the job to another
+	// worker and double-runs it. When <= 0 no per-job timeout is applied (the
+	// module always sets it from JobReaper.LeaseTimeout when reaping is enabled).
+	HandlerTimeout time.Duration
 	// OnDeadLetter, if non-nil, is invoked once after a job is moved to dead-letter
 	// (either because IsPermanent(err) or attempts exhausted). The hook runs in
 	// the worker goroutine; panics are recovered and logged but do not stop the
@@ -91,7 +97,9 @@ func (w *Worker) execute(ctx context.Context, job Job) {
 
 	h, ok := w.handlers[job.Type]
 	if !ok {
-		if derr := w.repo.DeadLetter(ctx, job.ID, fmt.Sprintf("unknown job type: %s", job.Type)); derr != nil {
+		if derr := w.repo.DeadLetter(ctx, job.ID, w.opts.ID, fmt.Sprintf("unknown job type: %s", job.Type)); w.leaseLost(derr, job, "dead_letter") {
+			return
+		} else if derr != nil {
 			w.opts.Log.Error("job.dead_letter_write_failed", "job_id", job.ID, "err", derr.Error())
 		}
 		w.opts.Log.Error("job.dead_letter", "job_id", job.ID, "job_type", job.Type, "reason", "unknown_type")
@@ -101,7 +109,9 @@ func (w *Worker) execute(ctx context.Context, job Job) {
 
 	err := w.runHandler(ctx, h, job)
 	if err == nil {
-		if cerr := w.repo.Complete(ctx, job.ID); cerr != nil {
+		if cerr := w.repo.Complete(ctx, job.ID, w.opts.ID); w.leaseLost(cerr, job, "complete") {
+			return
+		} else if cerr != nil {
 			w.opts.Log.Error("job.complete_write_failed", "job_id", job.ID, "err", cerr.Error())
 		}
 		w.opts.Log.Info("job.complete",
@@ -113,7 +123,9 @@ func (w *Worker) execute(ctx context.Context, job Job) {
 	// Permanent or attempts exhausted -> dead-letter
 	if IsPermanent(err) || job.Attempts >= job.MaxAttempts {
 		msg := truncate(err.Error(), 2000)
-		if derr := w.repo.DeadLetter(ctx, job.ID, msg); derr != nil {
+		if derr := w.repo.DeadLetter(ctx, job.ID, w.opts.ID, msg); w.leaseLost(derr, job, "dead_letter") {
+			return
+		} else if derr != nil {
 			w.opts.Log.Error("job.dead_letter_write_failed", "job_id", job.ID, "err", derr.Error())
 		}
 		w.opts.Log.Error("job.dead_letter",
@@ -126,7 +138,9 @@ func (w *Worker) execute(ctx context.Context, job Job) {
 	delay := backoffFor(w.opts.Backoff, int(job.Attempts))
 	next := w.opts.Clock.Now().Add(delay)
 	msg := truncate(err.Error(), 2000)
-	if ferr := w.repo.FailWithRetry(ctx, job.ID, next, msg); ferr != nil {
+	if ferr := w.repo.FailWithRetry(ctx, job.ID, w.opts.ID, next, msg); w.leaseLost(ferr, job, "fail_retry") {
+		return
+	} else if ferr != nil {
 		w.opts.Log.Error("job.fail_retry_write_failed", "job_id", job.ID, "err", ferr.Error())
 	}
 	w.opts.Log.Warn("job.fail_retry",
@@ -134,8 +148,30 @@ func (w *Worker) execute(ctx context.Context, job Job) {
 		"err", msg, "next_at", next.Format(time.RFC3339))
 }
 
-// runHandler wraps Handle with panic recovery, converting panics into retryable errors.
+// leaseLost reports whether writeErr is ErrLeaseLost. The fencing predicate on
+// the terminal/retry updates matched no row, meaning this worker's lease was
+// stolen (e.g. its handler outran LeaseTimeout and the reaper re-leased the
+// job). The write is correctly dropped: we only log and drop, and must NOT
+// treat it as a failure that schedules further work — the new run owns the job.
+func (w *Worker) leaseLost(writeErr error, job Job, phase string) bool {
+	if errors.Is(writeErr, ErrLeaseLost) {
+		w.opts.Log.Warn("job.lease_lost",
+			"job_id", job.ID, "job_type", job.Type, "attempt", job.Attempts, "phase", phase)
+		return true
+	}
+	return false
+}
+
+// runHandler wraps Handle with panic recovery (converting panics into retryable
+// errors) and bounds the handler to HandlerTimeout. Deriving a per-job timeout
+// below the reaper's LeaseTimeout ensures a healthy long-running handler is
+// canceled before the reaper re-leases the job, so it is never double-run.
 func (w *Worker) runHandler(ctx context.Context, h Handler, job Job) (err error) {
+	if w.opts.HandlerTimeout > 0 {
+		var cancel context.CancelFunc
+		ctx, cancel = context.WithTimeout(ctx, w.opts.HandlerTimeout)
+		defer cancel()
+	}
 	defer func() {
 		if r := recover(); r != nil {
 			err = fmt.Errorf("handler panic: %v", r)
diff --git a/internal/mcp/handler.go b/internal/mcp/handler.go
index defd2ca..958cad1 100644
--- a/internal/mcp/handler.go
+++ b/internal/mcp/handler.go
@@ -144,14 +144,14 @@ func postToken(deps AdminHandlerDeps) http.HandlerFunc {
 }
 
 type tokenRow struct {
-	ID        string  `json:"id"`
-	Name      string  `json:"name"`
-	Issuer    string  `json:"issuer"`
-	Scope     Scope   `json:"scope"`
-	ExpiresAt *string `json:"expires_at,omitempty"`
-	RevokedAt *string `json:"revoked_at,omitempty"`
+	ID         string  `json:"id"`
+	Name       string  `json:"name"`
+	Issuer     string  `json:"issuer"`
+	Scope      Scope   `json:"scope"`
+	ExpiresAt  *string `json:"expires_at,omitempty"`
+	RevokedAt  *string `json:"revoked_at,omitempty"`
 	LastUsedAt *string `json:"last_used_at,omitempty"`
-	CreatedAt string  `json:"created_at"`
+	CreatedAt  string  `json:"created_at"`
 }
 
 func listTokens(deps AdminHandlerDeps) http.HandlerFunc {
@@ -200,7 +200,7 @@ func listTokens(deps AdminHandlerDeps) http.HandlerFunc {
 func deleteToken(deps AdminHandlerDeps) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
 		rid := middleware.RequestIDFromContext(r.Context())
-		caller, _, err := resolveSessionUser(r.Context(), deps.Users, r)
+		caller, isAdmin, err := resolveSessionUser(r.Context(), deps.Users, r)
 		if err != nil {
 			httpx.WriteError(w, rid, err)
 			return
@@ -211,6 +211,15 @@ func deleteToken(deps AdminHandlerDeps) http.HandlerFunc {
 			httpx.WriteError(w, rid, errs.Wrap(err, errs.CodeInvalidInput, "id parse"))
 			return
 		}
+		// 授权：仅 admin 或 token 持有者可撤销。非 admin 时按 id 反查 token
+		// 校验归属；不归属（或不存在）一律返 NotFound，避免暴露 token 是否存在。
+		if !isAdmin {
+			tok, err := deps.Tokens.GetByID(r.Context(), id)
+			if err != nil || tok.UserID != caller {
+				httpx.WriteError(w, rid, errs.New(errs.CodeMcpTokenNotFound, "mcp token not found"))
+				return
+			}
+		}
 		if err := deps.Tokens.Revoke(r.Context(), id, caller); err != nil {
 			httpx.WriteError(w, rid, err)
 			return
diff --git a/internal/mcp/queries/mcp_tokens.sql b/internal/mcp/queries/mcp_tokens.sql
index defacfe..b80d361 100644
--- a/internal/mcp/queries/mcp_tokens.sql
+++ b/internal/mcp/queries/mcp_tokens.sql
@@ -8,11 +8,15 @@ RETURNING id, token_hash, user_id, name, issuer, scope,
           created_by, created_at;
 
 -- name: GetMcpTokenByHash :one
-SELECT id, token_hash, user_id, name, issuer, scope,
-       acp_session_id, expires_at, last_used_at, revoked_at,
-       created_by, created_at
-FROM mcp_tokens
-WHERE token_hash = $1;
+-- 鉴权用：仅返回属于 enabled 用户的 token，禁用用户的 MCP token 立即失效
+-- （与 web session 解析 GetSessionByTokenHash 的 enabled=true 约束一致）。
+SELECT t.id, t.token_hash, t.user_id, t.name, t.issuer, t.scope,
+       t.acp_session_id, t.expires_at, t.last_used_at, t.revoked_at,
+       t.created_by, t.created_at
+FROM mcp_tokens t
+JOIN users u ON u.id = t.user_id
+WHERE t.token_hash = $1
+  AND u.enabled = true;
 
 -- name: GetMcpTokenByID :one
 SELECT id, token_hash, user_id, name, issuer, scope,
diff --git a/internal/mcp/sqlc/mcp_tokens.sql.go b/internal/mcp/sqlc/mcp_tokens.sql.go
index f545e32..526857c 100644
--- a/internal/mcp/sqlc/mcp_tokens.sql.go
+++ b/internal/mcp/sqlc/mcp_tokens.sql.go
@@ -74,13 +74,17 @@ func (q *Queries) DeleteMcpTokenByID(ctx context.Context, id pgtype.UUID) error
 }
 
 const getMcpTokenByHash = `-- name: GetMcpTokenByHash :one
-SELECT id, token_hash, user_id, name, issuer, scope,
-       acp_session_id, expires_at, last_used_at, revoked_at,
-       created_by, created_at
-FROM mcp_tokens
-WHERE token_hash = $1
+SELECT t.id, t.token_hash, t.user_id, t.name, t.issuer, t.scope,
+       t.acp_session_id, t.expires_at, t.last_used_at, t.revoked_at,
+       t.created_by, t.created_at
+FROM mcp_tokens t
+JOIN users u ON u.id = t.user_id
+WHERE t.token_hash = $1
+  AND u.enabled = true
 `
 
+// 鉴权用：仅返回属于 enabled 用户的 token，禁用用户的 MCP token 立即失效
+// （与 web session 解析 GetSessionByTokenHash 的 enabled=true 约束一致）。
 func (q *Queries) GetMcpTokenByHash(ctx context.Context, tokenHash []byte) (McpToken, error) {
 	row := q.db.QueryRow(ctx, getMcpTokenByHash, tokenHash)
 	var i McpToken
diff --git a/internal/workspace/workspace_service_test.go b/internal/workspace/workspace_service_test.go
index 8989957..209a4ae 100644
--- a/internal/workspace/workspace_service_test.go
+++ b/internal/workspace/workspace_service_test.go
@@ -208,6 +208,7 @@ type fakeGit struct {
 	cloneErr  error
 	fetchErr  error
 	cloneSeen []string
+	removed   []string
 }
 
 func (f *fakeGit) Clone(_ context.Context, dst, _, _ string, _ *git.Credential) error {
@@ -222,7 +223,10 @@ func (f *fakeGit) Commit(_ context.Context, _, _ string, _ bool) (string, error)
 func (f *fakeGit) Status(_ context.Context, _ string) ([]git.FileStatus, error) { return nil, nil }
 func (f *fakeGit) MergeFFOnly(_ context.Context, _ string) error                { return nil }
 func (f *fakeGit) WorktreeAdd(_ context.Context, _, _, _, _ string) error       { return nil }
-func (f *fakeGit) WorktreeRemove(_ context.Context, _, _ string) error          { return nil }
+func (f *fakeGit) WorktreeRemove(_ context.Context, _, path string) error {
+	f.removed = append(f.removed, path)
+	return nil
+}
 func (f *fakeGit) WorktreeList(_ context.Context, _ string) ([]git.Worktree, error) {
 	return nil, nil
 }
diff --git a/internal/workspace/worktree_service.go b/internal/workspace/worktree_service.go
index 97c5372..4b22486 100644
--- a/internal/workspace/worktree_service.go
+++ b/internal/workspace/worktree_service.go
@@ -88,31 +88,34 @@ func (s *worktreeService) List(ctx context.Context, c Caller, wsID uuid.UUID) ([
 }
 
 func (s *worktreeService) Delete(ctx context.Context, c Caller, wtID uuid.UUID) error {
-	wt, err := s.repo.GetWorktreeByID(ctx, wtID)
+	ws, err := s.authorizeWorktreeWrite(ctx, c, wtID)
 	if err != nil {
 		return err
 	}
-	ws, err := s.repo.GetWorkspaceByID(ctx, wt.WorkspaceID)
-	if err != nil {
-		return err
-	}
-	if _, canWrite, err := s.pa.ResolveByID(ctx, c.UserID, c.IsAdmin, ws.ProjectID); err != nil {
-		return err
-	} else if !canWrite {
-		return errs.New(errs.CodeForbidden, "no write access")
-	}
-	if wt.Status == WorktreeStatusActive {
-		return errs.New(errs.CodeWorktreeAlreadyActive, "release before delete")
-	}
-	// 先 set pruning，再调 git rm，然后 DELETE row。中途失败 row 留 pruning。
+	// check-and-transition 必须原子：在 tx 内对行加 FOR UPDATE，确认 idle 后才转 pruning。
+	// 否则并发 Acquire（FOR UPDATE）可能刚把它置为 active，而这里用非锁读看到旧的 idle，
+	// 进而 git rm 掉 agent 正在使用的目录。仅 idle→pruning 在锁下完成。
+	var wtPath string
 	err = s.repo.InTx(ctx, func(tx Tx) error {
-		_, e := tx.SetWorktreePruning(ctx, wtID)
-		return e
+		wt, e := tx.GetWorktreeByIDForUpdate(ctx, wtID)
+		if e != nil {
+			return e
+		}
+		if wt.Status != WorktreeStatusIdle {
+			return errs.New(errs.CodeWorktreeAlreadyActive, "release before delete")
+		}
+		pruned, e := tx.SetWorktreePruning(ctx, wtID)
+		if e != nil {
+			return e
+		}
+		wtPath = pruned.Path
+		return nil
 	})
 	if err != nil {
 		return err
 	}
-	if rmErr := s.gitr.WorktreeRemove(ctx, ws.MainPath, wt.Path); rmErr != nil {
+	// 仅在守卫后的转移成功后才动磁盘。中途失败 row 留 pruning。
+	if rmErr := s.gitr.WorktreeRemove(ctx, ws.MainPath, wtPath); rmErr != nil {
 		return errs.Wrap(rmErr, errs.CodeGitCmdFailed, "git worktree remove")
 	}
 	if err := s.repo.DeleteWorktree(ctx, wtID); err != nil {
@@ -123,6 +126,9 @@ func (s *worktreeService) Delete(ctx context.Context, c Caller, wtID uuid.UUID)
 }
 
 func (s *worktreeService) Acquire(ctx context.Context, c Caller, wtID uuid.UUID) (*Worktree, error) {
+	if _, err := s.authorizeWorktreeWrite(ctx, c, wtID); err != nil {
+		return nil, err
+	}
 	holder := c.Holder()
 	var out *Worktree
 	err := s.repo.InTx(ctx, func(tx Tx) error {
@@ -157,6 +163,9 @@ func (s *worktreeService) Acquire(ctx context.Context, c Caller, wtID uuid.UUID)
 }
 
 func (s *worktreeService) Release(ctx context.Context, c Caller, wtID uuid.UUID) (*Worktree, error) {
+	if _, err := s.authorizeWorktreeWrite(ctx, c, wtID); err != nil {
+		return nil, err
+	}
 	holder := c.Holder()
 	var out *Worktree
 	err := s.repo.InTx(ctx, func(tx Tx) error {
@@ -190,6 +199,27 @@ func (s *worktreeService) ReleaseByHolder(ctx context.Context, holder string) ([
 	return s.repo.ReleaseWorktreesByHolder(ctx, holder)
 }
 
+// authorizeWorktreeWrite 把 worktree → workspace → project 解析出来并要求 write 权限，
+// 与 Delete/Create 的鉴权方式一致。返回 worktree 所属的 workspace 供调用方使用
+// （如取 MainPath）。Acquire/Release 此前缺失该校验，导致任意已登录用户可凭 UUID
+// 跨租户锁定/释放任意 worktree。
+func (s *worktreeService) authorizeWorktreeWrite(ctx context.Context, c Caller, wtID uuid.UUID) (*Workspace, error) {
+	wt, err := s.repo.GetWorktreeByID(ctx, wtID)
+	if err != nil {
+		return nil, err
+	}
+	ws, err := s.repo.GetWorkspaceByID(ctx, wt.WorkspaceID)
+	if err != nil {
+		return nil, err
+	}
+	if _, canWrite, err := s.pa.ResolveByID(ctx, c.UserID, c.IsAdmin, ws.ProjectID); err != nil {
+		return nil, err
+	} else if !canWrite {
+		return nil, errs.New(errs.CodeForbidden, "no write access")
+	}
+	return ws, nil
+}
+
 func (s *worktreeService) audit(ctx context.Context, uid *uuid.UUID, action, ttype, tid string, meta map[string]any) {
 	_ = s.rec.Record(ctx, audit.Entry{
 		UserID: uid, Action: action, TargetType: ttype, TargetID: tid, Metadata: meta,
diff --git a/internal/workspace/worktree_service_test.go b/internal/workspace/worktree_service_test.go
index c4aca9e..6794a36 100644
--- a/internal/workspace/worktree_service_test.go
+++ b/internal/workspace/worktree_service_test.go
@@ -6,8 +6,17 @@ import (
 
 	"github.com/google/uuid"
 	"github.com/stretchr/testify/require"
+
+	"github.com/yan1h/agent-coding-workflow/internal/infra/errs"
 )
 
+func requireCode(t *testing.T, err error, want errs.Code) {
+	t.Helper()
+	ae, ok := errs.As(err)
+	require.True(t, ok, "expected *errs.AppError, got %T", err)
+	require.Equal(t, want, ae.Code)
+}
+
 func newWtSvc(t *testing.T) (*worktreeService, *fakeRepo, *fakePA, *fakeGit, uuid.UUID) {
 	t.Helper()
 	pa := &fakePA{pid: uuid.New(), canRead: true, canWrite: true}
@@ -81,3 +90,55 @@ func TestWorktreeService_Delete_BlockedWhenActive(t *testing.T) {
 	err = svc.Delete(context.Background(), caller, wt.ID)
 	require.Error(t, err)
 }
+
+// Bug #5: Delete 的 check-and-transition 必须在锁下原子完成。即使 worktree 处于
+// active（被持有），Delete 也必须在事务内（GetWorktreeByIDForUpdate）发现并拒绝，
+// 返回 CodeWorktreeAlreadyActive，且不触碰磁盘 / 不删行。
+func TestWorktreeService_Delete_AtomicGuard_RefusesActive(t *testing.T) {
+	t.Parallel()
+	svc, repo, _, gitr, wsID := newWtSvc(t)
+	caller := Caller{UserID: uuid.New()}
+	wt, err := svc.Create(context.Background(), caller, wsID, CreateWorktreeInput{Branch: "feat-g"})
+	require.NoError(t, err)
+	_, err = svc.Acquire(context.Background(), caller, wt.ID)
+	require.NoError(t, err)
+
+	err = svc.Delete(context.Background(), caller, wt.ID)
+	require.Error(t, err)
+	requireCode(t, err, errs.CodeWorktreeAlreadyActive)
+	// 磁盘未被触碰，行仍存在且保持 active。
+	require.Empty(t, gitr.removed)
+	got, err := repo.GetWorktreeByID(context.Background(), wt.ID)
+	require.NoError(t, err)
+	require.Equal(t, WorktreeStatusActive, got.Status)
+}
+
+// Bug #6: Acquire 必须做 project 鉴权。无 write 权限的 caller 不得锁定 worktree。
+func TestWorktreeService_Acquire_DeniedWithoutWriteAccess(t *testing.T) {
+	t.Parallel()
+	svc, _, pa, _, wsID := newWtSvc(t)
+	caller := Caller{UserID: uuid.New()}
+	wt, err := svc.Create(context.Background(), caller, wsID, CreateWorktreeInput{Branch: "feat-a"})
+	require.NoError(t, err)
+
+	pa.canWrite = false
+	_, err = svc.Acquire(context.Background(), caller, wt.ID)
+	require.Error(t, err)
+	requireCode(t, err, errs.CodeForbidden)
+}
+
+// Bug #6: Release 同样必须做 project 鉴权（在 holder-match 之前）。
+func TestWorktreeService_Release_DeniedWithoutWriteAccess(t *testing.T) {
+	t.Parallel()
+	svc, _, pa, _, wsID := newWtSvc(t)
+	caller := Caller{UserID: uuid.New()}
+	wt, err := svc.Create(context.Background(), caller, wsID, CreateWorktreeInput{Branch: "feat-rr"})
+	require.NoError(t, err)
+	_, err = svc.Acquire(context.Background(), caller, wt.ID)
+	require.NoError(t, err)
+
+	pa.canWrite = false
+	_, err = svc.Release(context.Background(), caller, wt.ID)
+	require.Error(t, err)
+	requireCode(t, err, errs.CodeForbidden)
+}
diff --git a/migrations/0015_fix_issue_workspace_fk.down.sql b/migrations/0015_fix_issue_workspace_fk.down.sql
new file mode 100644
index 0000000..ad08134
--- /dev/null
+++ b/migrations/0015_fix_issue_workspace_fk.down.sql
@@ -0,0 +1,24 @@
+-- Revert to the original (buggy) bare ON DELETE SET NULL composite FKs so that
+-- this migration is a faithful inverse of 0015 up. Constraint names and column
+-- references match the definitions in 0003_workspace.up.sql and 0006_acp.up.sql.
+
+-- ============ acp_sessions -> requirements ============
+ALTER TABLE acp_sessions DROP CONSTRAINT acp_sessions_req_project_fk;
+ALTER TABLE acp_sessions ADD CONSTRAINT acp_sessions_req_project_fk
+  FOREIGN KEY (project_id, requirement_id)
+  REFERENCES requirements (project_id, id) MATCH SIMPLE
+  ON DELETE SET NULL;
+
+-- ============ acp_sessions -> issues ============
+ALTER TABLE acp_sessions DROP CONSTRAINT acp_sessions_issue_project_fk;
+ALTER TABLE acp_sessions ADD CONSTRAINT acp_sessions_issue_project_fk
+  FOREIGN KEY (project_id, issue_id)
+  REFERENCES issues (project_id, id) MATCH SIMPLE
+  ON DELETE SET NULL;
+
+-- ============ issues -> workspaces ============
+ALTER TABLE issues DROP CONSTRAINT issues_project_workspace_fk;
+ALTER TABLE issues ADD CONSTRAINT issues_project_workspace_fk
+  FOREIGN KEY (project_id, workspace_id)
+  REFERENCES workspaces (project_id, id) MATCH SIMPLE
+  ON DELETE SET NULL;
diff --git a/migrations/0015_fix_issue_workspace_fk.up.sql b/migrations/0015_fix_issue_workspace_fk.up.sql
new file mode 100644
index 0000000..ebbcf8d
--- /dev/null
+++ b/migrations/0015_fix_issue_workspace_fk.up.sql
@@ -0,0 +1,34 @@
+-- Fix data-integrity bug: composite FKs with bare ON DELETE SET NULL null ALL
+-- referencing columns on delete, including the NOT NULL project_id column,
+-- which raises 23502 and makes the referenced-row delete impossible.
+-- PostgreSQL 15+ supports a column-subset form: ON DELETE SET NULL (col, ...)
+-- so only the nullable column is nulled.
+
+-- ============ issues -> workspaces ============
+-- Original (0003): FOREIGN KEY (project_id, workspace_id)
+--   REFERENCES workspaces (project_id, id) MATCH SIMPLE ON DELETE SET NULL
+-- Deleting a workspace still referenced by an issue tried to null issues.project_id
+-- (NOT NULL) -> blocked workspace deletion entirely.
+ALTER TABLE issues DROP CONSTRAINT issues_project_workspace_fk;
+ALTER TABLE issues ADD CONSTRAINT issues_project_workspace_fk
+  FOREIGN KEY (project_id, workspace_id)
+  REFERENCES workspaces (project_id, id) MATCH SIMPLE
+  ON DELETE SET NULL (workspace_id);
+
+-- ============ acp_sessions -> issues ============
+-- Original (0006): FOREIGN KEY (project_id, issue_id)
+--   REFERENCES issues (project_id, id) MATCH SIMPLE ON DELETE SET NULL
+ALTER TABLE acp_sessions DROP CONSTRAINT acp_sessions_issue_project_fk;
+ALTER TABLE acp_sessions ADD CONSTRAINT acp_sessions_issue_project_fk
+  FOREIGN KEY (project_id, issue_id)
+  REFERENCES issues (project_id, id) MATCH SIMPLE
+  ON DELETE SET NULL (issue_id);
+
+-- ============ acp_sessions -> requirements ============
+-- Original (0006): FOREIGN KEY (project_id, requirement_id)
+--   REFERENCES requirements (project_id, id) MATCH SIMPLE ON DELETE SET NULL
+ALTER TABLE acp_sessions DROP CONSTRAINT acp_sessions_req_project_fk;
+ALTER TABLE acp_sessions ADD CONSTRAINT acp_sessions_req_project_fk
+  FOREIGN KEY (project_id, requirement_id)
+  REFERENCES requirements (project_id, id) MATCH SIMPLE
+  ON DELETE SET NULL (requirement_id);
diff --git a/web/src/composables/useConversationSession.ts b/web/src/composables/useConversationSession.ts
index 0e090f8..ce7ae67 100644
--- a/web/src/composables/useConversationSession.ts
+++ b/web/src/composables/useConversationSession.ts
@@ -114,6 +114,14 @@ export function useConversationSession() {
     const id = streamingMessageId.value
     if (id == null) return
     await chatApi.cancelMessage(id)
+    // 取消会 abort SSE，后端不再下发 done/error/message_meta 终止事件，
+    // 故须在此手动收尾（对齐 done/error/onError 路径）：将仍处于 pending 的
+    // 助手消息置为终态 'cancelled'，并清空 streamingMessageId 解除 isStreaming。
+    const msg = messages.value.find((m) => m.id === id)
+    if (msg && msg.status === 'pending') {
+      msg.status = 'cancelled'
+    }
+    streamingMessageId.value = null
     detachStream()
   }