diff --git a/config/agent.yaml b/config/agent.yaml
index 8295f46..0c82f80 100644
--- a/config/agent.yaml
+++ b/config/agent.yaml
@@ -78,7 +78,7 @@ sandbox:
   idle_ttl_seconds: 600      # 普通容器无 exec 活动 10 分钟回收
   max_active_execs: 6        # 宿主硬上限；前后台统一计数
   max_background_execs: 4
-  max_active_execs_per_user: 2
+  max_active_execs_per_user: 3
   min_mem_available: 1g      # 低于阈值暂停新放行，不杀已运行任务
   # 容器 DNS server 显式配置(docker run --dns,容器 /etc/resolv.conf 直接写,
   # 绕过 docker daemon 上游 DNS 探测路径;腾讯云轻量 / 部分云上 daemon 探测
diff --git a/core/executor.py b/core/executor.py
index d9895f1..699d5f0 100644
--- a/core/executor.py
+++ b/core/executor.py
@@ -35,6 +35,7 @@ class ExecCtx:
     task_id: UUID
     working_dir: Path
     cancel_check: Optional[Callable[[], bool]] = None
+    event_emit: Optional[Callable[[dict], None]] = None
 
 
 @dataclass
diff --git a/core/executor_docker.py b/core/executor_docker.py
index 04efcb0..732fbf2 100644
--- a/core/executor_docker.py
+++ b/core/executor_docker.py
@@ -163,7 +163,13 @@ class DockerExecutor(Executor):
 
     def _call_heavy_foreground(self, name: str, args: Dict[str, Any], ctx: ExecCtx) -> ToolResult:
         """前台重型工具先排共享槽；排队不进入命令 timeout。"""
-        with self.pool.capacity.foreground(str(self.user_id), ctx.cancel_check) as admitted:
+        def notify(payload: dict) -> None:
+            if ctx.event_emit is not None:
+                ctx.event_emit({"type": "execution_queue", **payload})
+
+        with self.pool.capacity.foreground(
+            str(self.user_id), ctx.cancel_check, notify
+        ) as admitted:
             if not admitted:
                 return ToolResult(content="[Error] command cancelled by user while queued", exit_code=130)
             self.pool.exec_started(self.user_id)
diff --git a/core/loop.py b/core/loop.py
index 88ef9cc..7a21a4a 100644
--- a/core/loop.py
+++ b/core/loop.py
@@ -772,6 +772,7 @@ class AgentLoop:
             task_id=self.session.task_id,
             working_dir=self.working_dir,
             cancel_check=self.cancel_check,
+            event_emit=self._emit,
         )
         tool_started_at = time.time()
         tool_result = self.executor.call_tool(name, args, ctx)
diff --git a/core/sandbox/capacity.py b/core/sandbox/capacity.py
index d742788..0a6e494 100644
--- a/core/sandbox/capacity.py
+++ b/core/sandbox/capacity.py
@@ -10,7 +10,7 @@ import json
 import os
 import time
 import uuid
-from contextlib import contextmanager
+from contextlib import contextmanager, suppress
 from pathlib import Path
 from typing import Callable, Dict, Iterator, Optional
 
@@ -18,7 +18,7 @@ from core.file_store import atomic_write_text, interprocess_file_lock
 
 DEFAULT_MAX_ACTIVE_EXECS = 6
 DEFAULT_MAX_BACKGROUND_EXECS = 4
-DEFAULT_MAX_ACTIVE_EXECS_PER_USER = 2
+DEFAULT_MAX_ACTIVE_EXECS_PER_USER = 3
 DEFAULT_MIN_MEM_AVAILABLE_BYTES = 1024 ** 3
 
 
@@ -123,13 +123,21 @@ class ExecCapacity:
             self._write(state)
             return lease_id
 
-    def acquire_foreground(self, user_id: str, cancel_check: Optional[Callable[[], bool]] = None) -> Optional[str]:
+    def acquire_foreground(
+        self,
+        user_id: str,
+        cancel_check: Optional[Callable[[], bool]] = None,
+        wait_notify: Optional[Callable[[dict], None]] = None,
+    ) -> Optional[str]:
         ticket = uuid.uuid4().hex
+        wait_notified = False
         with interprocess_file_lock(self.lock_path, timeout_seconds=None):
             state = self._read(); self._prune(state)
             state["foreground_queue"].append({"ticket": ticket, "user_id": str(user_id), "created_ts": time.time(), "owner_pid": os.getpid()})
             self._write(state)
         while True:
+            admitted = False
+            notification = None
             with interprocess_file_lock(self.lock_path, timeout_seconds=None):
                 state = self._read(); self._prune(state)
                 queue = state["foreground_queue"]
@@ -138,8 +146,41 @@ class ExecCapacity:
                     queue[:] = [q for q in queue if q.get("ticket") != ticket]
                     state["leases"][ticket] = {"lease_id": ticket, "user_id": str(user_id), "kind": "foreground", "owner_pid": os.getpid(), "started_ts": time.time()}
                     self._write(state)
-                    return ticket
-                self._write(state)
+                    admitted = True
+                else:
+                    self._write(state)
+                if not admitted and not wait_notified and wait_notify is not None:
+                    leases = list(state["leases"].values())
+                    user_running = sum(
+                        1 for lease in leases
+                        if lease.get("user_id") == str(user_id)
+                    )
+                    available = mem_available_bytes()
+                    if user_running >= self.max_per_user:
+                        reason = "per_user_limit"
+                    elif len(leases) >= self.max_active:
+                        reason = "global_limit"
+                    elif available is not None and available < self.min_mem_available:
+                        reason = "memory_pressure"
+                    else:
+                        reason = "queue_order"
+                    notification = {
+                        "state": "waiting",
+                        "reason": reason,
+                        "user_running": user_running,
+                        "user_limit": self.max_per_user,
+                        "global_running": len(leases),
+                        "global_limit": self.max_active,
+                    }
+                    wait_notified = True
+            if admitted:
+                if wait_notified and wait_notify is not None:
+                    with suppress(Exception):
+                        wait_notify({"state": "admitted"})
+                return ticket
+            if notification is not None and wait_notify is not None:
+                with suppress(Exception):
+                    wait_notify(notification)
             if cancel_check is not None and cancel_check():
                 self.cancel_waiter(ticket)
                 return None
@@ -189,8 +230,13 @@ class ExecCapacity:
             self._write(state)
 
     @contextmanager
-    def foreground(self, user_id: str, cancel_check: Optional[Callable[[], bool]] = None) -> Iterator[bool]:
-        lease = self.acquire_foreground(user_id, cancel_check)
+    def foreground(
+        self,
+        user_id: str,
+        cancel_check: Optional[Callable[[], bool]] = None,
+        wait_notify: Optional[Callable[[dict], None]] = None,
+    ) -> Iterator[bool]:
+        lease = self.acquire_foreground(user_id, cancel_check, wait_notify)
         try:
             yield lease is not None
         finally:
diff --git a/core/sinks.py b/core/sinks.py
index 8c9273e..df6c791 100644
--- a/core/sinks.py
+++ b/core/sinks.py
@@ -7,6 +7,7 @@ Loop 不直接 print,改 emit({type, ...})。Sink 决定怎么呈现。
   llm_end      {type, prompt_tokens, completion_tokens, elapsed}
   text         {type, content}                 —— assistant 文字段(整段,非流式)
   tool_call    {type, name, args, args_preview}
+  execution_queue {type, state, reason, ...}   —— 前台重型工具等待/放行
   tool_result  {type, name, result, preview, truncated}
   done         {type}                          —— 一次 run 全部结束
 
diff --git a/tests/frontend_chat_queue.test.mjs b/tests/frontend_chat_queue.test.mjs
index 8f89b3e..74266f7 100644
--- a/tests/frontend_chat_queue.test.mjs
+++ b/tests/frontend_chat_queue.test.mjs
@@ -67,6 +67,15 @@ test("composer uses one Codex-style action button for stop and queued send", ()
   assert.match(chat, /removeQueuedMessage\([\s\S]*streamSse\(r\.events_url, run\)/);
 });
 
+test("heavy execution queue exposes the blocking reason", () => {
+  const chat = readFileSync(new URL("../web/static/js/chat.js", import.meta.url), "utf8");
+  assert.match(chat, /t === "execution_queue"/);
+  assert.match(chat, /等待执行容量（当前用户/);
+  assert.match(chat, /等待执行容量（整机/);
+  assert.match(chat, /等待执行容量（宿主内存压力）/);
+  assert.match(chat, /dataset\.runningLabel/);
+});
+
 test("automatic title polling starts before a long-running response finishes", () => {
   const chat = readFileSync(new URL("../web/static/js/chat.js", import.meta.url), "utf8");
   const sendMessage = chat.indexOf("async function sendMessage(");
diff --git a/tests/test_executor_docker.py b/tests/test_executor_docker.py
index f0f61cb..595625f 100644
--- a/tests/test_executor_docker.py
+++ b/tests/test_executor_docker.py
@@ -38,9 +38,13 @@ class FakePool:
         self.mark_active_calls = []
         self.active = 0
         self.capacity = self
+        self.capacity_notices = []
 
     @contextmanager
-    def foreground(self, user_id, cancel_check=None):
+    def foreground(self, user_id, cancel_check=None, wait_notify=None):
+        if wait_notify is not None:
+            for notice in self.capacity_notices:
+                wait_notify(notice)
         yield True
 
     def exec_started(self, user_id):
@@ -174,6 +178,27 @@ class TestShellExec(unittest.TestCase):
         self.assertEqual(pool.ensure_calls, [executor.user_id])
         self.assertEqual(pool.mark_active_calls, [executor.user_id])
 
+    def test_shell_forwards_capacity_queue_events(self):
+        executor, pool, _ = make_executor()
+        pool.capacity_notices = [
+            {"state": "waiting", "reason": "per_user_limit"},
+            {"state": "admitted"},
+        ]
+        events = []
+        ctx = make_ctx(executor)
+        ctx.event_emit = events.append
+        proc = MagicMock()
+        proc.communicate.return_value = ("ok\n", "")
+        proc.returncode = 0
+
+        with patch("core.executor_docker.subprocess.Popen", return_value=proc):
+            executor.call_tool("shell", {"command": "echo ok"}, ctx)
+
+        self.assertEqual(events, [
+            {"type": "execution_queue", "state": "waiting", "reason": "per_user_limit"},
+            {"type": "execution_queue", "state": "admitted"},
+        ])
+
     def test_shell_bad_args(self):
         executor, _, _ = make_executor()
         ctx = make_ctx(executor)
diff --git a/tests/test_sandbox_capacity_packages.py b/tests/test_sandbox_capacity_packages.py
index cc65fec..f0f5320 100644
--- a/tests/test_sandbox_capacity_packages.py
+++ b/tests/test_sandbox_capacity_packages.py
@@ -34,7 +34,7 @@ class CapacityTests(unittest.TestCase):
         with tempfile.TemporaryDirectory() as td:
             cap = ExecCapacity(Path(td), {"max_active_execs": 99, "max_background_execs": 99,
                                           "max_active_execs_per_user": 99})
-            self.assertEqual((cap.max_active, cap.max_background, cap.max_per_user), (6, 4, 2))
+            self.assertEqual((cap.max_active, cap.max_background, cap.max_per_user), (6, 4, 3))
 
     def test_global_per_user_and_background_limits(self):
         with tempfile.TemporaryDirectory() as td, patch("core.sandbox.capacity.mem_available_bytes", return_value=10**12):
@@ -60,6 +60,36 @@ class CapacityTests(unittest.TestCase):
             self.assertEqual(two.snapshot()["foreground_queued"], 0)
             one.release(lease)
 
+    def test_foreground_queue_reports_limit_and_admission(self):
+        with tempfile.TemporaryDirectory() as td, patch("core.sandbox.capacity.mem_available_bytes", return_value=10**12):
+            cap = ExecCapacity(Path(td), {"max_active_execs": 2, "max_active_execs_per_user": 1})
+            held = cap.try_acquire("u1", "background", lease_id="held")
+            notices = []
+            result = []
+            t = threading.Thread(
+                target=lambda: result.append(cap.acquire_foreground("u1", wait_notify=notices.append))
+            )
+            t.start(); time.sleep(.15)
+            self.assertEqual(notices, [{
+                "state": "waiting", "reason": "per_user_limit",
+                "user_running": 1, "user_limit": 1,
+                "global_running": 1, "global_limit": 2,
+            }])
+            cap.release(held); t.join(2)
+            self.assertEqual(len(result), 1)
+            self.assertIsNotNone(result[0])
+            self.assertEqual(notices[-1], {"state": "admitted"})
+            cap.release(result[0])
+
+    def test_immediate_foreground_admission_does_not_report_queue(self):
+        with tempfile.TemporaryDirectory() as td, patch("core.sandbox.capacity.mem_available_bytes", return_value=10**12):
+            cap = ExecCapacity(Path(td), {"max_active_execs": 1})
+            notices = []
+            lease = cap.acquire_foreground("u1", wait_notify=notices.append)
+            self.assertIsNotNone(lease)
+            self.assertEqual(notices, [])
+            cap.release(lease)
+
     def test_memory_pressure_pauses_new_admission(self):
         with tempfile.TemporaryDirectory() as td, patch("core.sandbox.capacity.mem_available_bytes", return_value=100):
             cap = ExecCapacity(Path(td), {"min_mem_available": "1g"})
diff --git a/web/static/js/chat.js b/web/static/js/chat.js
index 6120f05..bacc762 100644
--- a/web/static/js/chat.js
+++ b/web/static/js/chat.js
@@ -3483,6 +3483,27 @@ function handleSseEvent(ev, asstCard, ctx) {
     if (!ctx.runId && snapshot.run_id) ctx.runId = snapshot.run_id;
     ctx.progressSteps = cloneProgressSteps(snapshot.steps);
     setTaskProgress(ctx.taskId, ctx.progressSteps);
+  } else if (t === "execution_queue") {
+    const det = ctx.runningToolEl;
+    if (!det) return;
+    const labelEl = det.querySelector(".tool-label");
+    if (!labelEl) return;
+    const queue = ev.data || {};
+    if (queue.state === "waiting") {
+      det.classList.add("waiting");
+      if (queue.reason === "per_user_limit") {
+        labelEl.textContent = `等待执行容量（当前用户 ${Number(queue.user_running) || 0}/${Number(queue.user_limit) || 0}）`;
+      } else if (queue.reason === "global_limit") {
+        labelEl.textContent = `等待执行容量（整机 ${Number(queue.global_running) || 0}/${Number(queue.global_limit) || 0}）`;
+      } else if (queue.reason === "memory_pressure") {
+        labelEl.textContent = "等待执行容量（宿主内存压力）";
+      } else {
+        labelEl.textContent = "等待执行容量（前方任务优先）";
+      }
+    } else if (queue.state === "admitted") {
+      det.classList.remove("waiting");
+      labelEl.textContent = det.dataset.runningLabel || labelEl.textContent;
+    }
   } else if (t === "tool_call") {
     const fn = (ev.data && ev.data.name) || "?";
     const args = (ev.data && ev.data.args) || "";
@@ -3506,6 +3527,7 @@ function handleSseEvent(ev, asstCard, ctx) {
     const label = toolActivityLabel(fn, args);
     const det = document.createElement("details");
     det.className = "tool-call activity running";
+    det.dataset.runningLabel = label;
     det.innerHTML = `<summary><span class="tool-state" aria-hidden="true">…</span><span class="tool-label">${escapeHtml(label)}</span><span class="tool-elapsed"></span></summary><pre>${escapeHtml(argsStr)}</pre>`;
     asstCard.appendChild(det);
     // 运行态:spinner + 跳秒,tool_result 到达时定格(区分"在执行"和"卡死")