diff --git a/src/agentkit/experts/orchestrator.py b/src/agentkit/experts/orchestrator.py
index 2bb80c4..a39cd4a 100644
--- a/src/agentkit/experts/orchestrator.py
+++ b/src/agentkit/experts/orchestrator.py
@@ -55,6 +55,7 @@ class TeamOrchestrator:
     MAX_PHASES = 10  # Maximum phases Lead Expert can decompose
     MAX_RETRIES = 1  # Retry once on phase failure before marking failed
     MAX_DEBATE_ROUNDS = 4  # Hard cap on debate rounds per phase
+    MAX_DEBATES = 3  # Hard cap on auto-inserted debate phases per execution
     STOP_COMMANDS = frozenset({"/stop", "停止", "stop", "结束"})
 
     def __init__(self, team: ExpertTeam) -> None:
@@ -62,6 +63,8 @@ class TeamOrchestrator:
         # Track temporary agent names created for context isolation (KTD3)
         # Maps phase_id -> temp_agent_name for cleanup
         self._temp_agents: dict[str, str] = {}
+        # Count of auto-inserted debate phases (bounded by MAX_DEBATES)
+        self._debate_count = 0
 
     async def execute(self, task: str) -> dict[str, Any]:
         """Execute a task in pipeline mode.
@@ -135,6 +138,9 @@ class TeamOrchestrator:
 
         plan.phases = phases[: self.MAX_PHASES]
 
+        # U3: Optionally add plan review debate before execution
+        await self._maybe_add_plan_review_debate(lead, plan, task)
+
         # 3. Emit plan_update with phase list
         await self._broadcast_event(
             "plan_update",
@@ -149,13 +155,22 @@ class TeamOrchestrator:
         phase_results: dict[str, dict[str, Any]] = {}
 
         try:
-            # Topological sort phases into execution layers
-            layers = plan.topological_sort()
+            # Execute layers sequentially, phases within layer in parallel.
+            # U3: while-loop re-computes topological_sort each iteration so
+            # dynamically inserted DEBATE phases (from divergence detection)
+            # are picked up correctly.
+            while True:
+                layers = plan.topological_sort()
+                # Find the next layer that still has PENDING phases
+                current_layer: list[PlanPhase] | None = None
+                for layer in layers:
+                    if any(ph.status == PhaseStatus.PENDING for ph in layer):
+                        current_layer = layer
+                        break
+                if current_layer is None:
+                    break  # No more pending phases — done
 
-            # Execute layers sequentially, phases within layer in parallel
-            for layer in layers:
-                # Filter out already-failed phases (from dependency failures)
-                ready = [ph for ph in layer if ph.status == PhaseStatus.PENDING]
+                ready = [ph for ph in current_layer if ph.status == PhaseStatus.PENDING]
                 if not ready:
                     continue
 
@@ -186,6 +201,17 @@ class TeamOrchestrator:
                     else:
                         phase_results[ph.id] = result
 
+                # U3: Divergence detection — check completed phases for conflicts
+                # and dynamically insert DEBATE phases if needed
+                if self._debate_count < self.MAX_DEBATES:
+                    completed_now = [
+                        ph for ph in ready if ph.status == PhaseStatus.COMPLETED
+                    ]
+                    if completed_now:
+                        await self._check_divergence_and_insert_debates(
+                            lead, plan, completed_now
+                        )
+
             # 5. Check if all phases failed
             completed = plan.completed_phases
             if not completed:
@@ -946,6 +972,223 @@ class TeamOrchestrator:
                 return True
         return False
 
+    # ── U3: Divergence detection + dynamic debate insertion ────────────
+
+    async def _maybe_add_plan_review_debate(
+        self, lead: Expert, plan: TeamPlan, task: str
+    ) -> None:
+        """Optionally add a plan review debate phase before execution.
+
+        Skips for simple tasks (<= 2 phases) or when LLM judges it unnecessary.
+        When added, all existing phases depend on the debate phase so it runs first.
+        """
+        if len(plan.phases) <= 2:
+            return  # Simple task, skip plan review
+
+        if self._debate_count >= self.MAX_DEBATES:
+            return
+
+        gateway = self._get_llm_gateway(lead)
+        if not gateway:
+            return
+
+        member_names = [
+            e.config.name
+            for e in self._team.active_experts
+            if e.config.name != lead.config.name
+        ]
+        if not member_names:
+            return
+
+        prompt = (
+            f"你是团队 Lead {lead.config.name}，需要判断以下任务是否需要方案评审辩论。\n\n"
+            f"任务：{task}\n"
+            f"分解的阶段：{', '.join(ph.name for ph in plan.phases)}\n"
+            f"团队成员：{', '.join(member_names)}\n\n"
+            "以下情况需要方案评审：\n"
+            "1) 任务复杂，涉及多个技术方向\n"
+            "2) 方案选择影响重大，值得先讨论再执行\n"
+            "3) 团队成员可能有不同观点\n"
+            "简单任务不需要评审。\n\n"
+            "只回答 true 或 false。"
+        )
+
+        try:
+            response = await gateway.chat(
+                messages=[{"role": "user", "content": prompt}],
+                model=self._get_model(lead),
+            )
+            if not response.content.strip().lower().startswith("true"):
+                return
+        except Exception as e:
+            logger.warning(f"Plan review judgment failed: {e}")
+            return
+
+        # Insert plan review DEBATE phase at the head
+        debate_phase = PlanPhase(
+            name="方案评审",
+            assigned_expert=lead.config.name,
+            task_description=f"方案评审：{task}",
+            depends_on=[],
+            phase_type=PhaseType.DEBATE,
+            debate_config={
+                "topic": f"方案评审：{task}",
+                "participants": member_names,
+                "max_rounds": 2,
+            },
+        )
+
+        # All existing phases now depend on the debate phase
+        for ph in plan.phases:
+            ph.depends_on.append(debate_phase.id)
+
+        plan.phases.insert(0, debate_phase)
+        self._debate_count += 1
+        logger.info(f"Added plan review debate phase {debate_phase.id}")
+
+    async def _detect_divergence(
+        self, lead: Expert, completed_phase: PlanPhase, plan: TeamPlan
+    ) -> bool:
+        """Use LLM to detect if a completed phase's output has divergence worth debating.
+
+        Returns False if LLM unavailable, detection fails, or no other completed
+        phases to compare against. Prefers false negatives over false positives.
+        """
+        gateway = self._get_llm_gateway(lead)
+        if not gateway:
+            return False
+
+        # Need other completed phases to compare against
+        other_completed = [
+            ph
+            for ph in plan.completed_phases
+            if ph.id != completed_phase.id and ph.result
+        ]
+        if not other_completed:
+            return False
+
+        other_outputs = []
+        for ph in other_completed:
+            content = ph.result.get("content", str(ph.result)) if ph.result else ""
+            other_outputs.append(f"[{ph.name}]:\n{content[:300]}")
+
+        current_output = ""
+        if completed_phase.result:
+            current_output = completed_phase.result.get(
+                "content", str(completed_phase.result)
+            )[:500]
+
+        prompt = (
+            f"你是团队 Lead {lead.config.name}，需要判断刚完成的阶段产出是否与其他阶段存在分歧。\n\n"
+            f"原始任务：{plan.task}\n\n"
+            f"刚完成的阶段：{completed_phase.name}\n"
+            f"产出：{current_output}\n\n"
+            f"其他已完成阶段的产出：\n"
+            + "\n---\n".join(other_outputs)
+            + "\n\n"
+            "请判断是否值得发起辩论。以下情况值得辩论：\n"
+            "1) 两个阶段产出存在矛盾或冲突\n"
+            "2) 阶段产出与原始任务约束冲突\n"
+            "3) 存在多个合理方案需要抉择\n"
+            "其他情况不值得辩论。\n\n"
+            "只回答 true 或 false，不要其他文字。"
+        )
+
+        try:
+            response = await gateway.chat(
+                messages=[{"role": "user", "content": prompt}],
+                model=self._get_model(lead),
+            )
+            return response.content.strip().lower().startswith("true")
+        except Exception as e:
+            logger.warning(f"Divergence detection failed: {e}")
+            return False
+
+    def _insert_debate_phase(
+        self,
+        plan: TeamPlan,
+        trigger_phase: PlanPhase,
+        topic: str,
+        participants: list[str],
+    ) -> PlanPhase | None:
+        """Insert a DEBATE phase after the trigger phase, rewiring dependents.
+
+        Phases that depended on trigger_phase now depend on the DEBATE phase,
+        so they wait for the debate conclusion before executing.
+        """
+        if not participants:
+            return None
+
+        lead = self._team.lead_expert
+        assigned = lead.config.name if lead else trigger_phase.assigned_expert
+
+        debate_phase = PlanPhase(
+            name=f"辩论: {topic[:20]}",
+            assigned_expert=assigned,
+            task_description=topic,
+            depends_on=[trigger_phase.id],
+            phase_type=PhaseType.DEBATE,
+            debate_config={
+                "topic": topic,
+                "participants": participants,
+                "max_rounds": 2,
+            },
+        )
+
+        # Rewire: phases that depended on trigger_phase now depend on debate_phase
+        for ph in plan.phases:
+            if trigger_phase.id in ph.depends_on:
+                ph.depends_on.remove(trigger_phase.id)
+                ph.depends_on.append(debate_phase.id)
+
+        plan.phases.append(debate_phase)
+        self._debate_count += 1
+        logger.info(f"Inserted debate phase {debate_phase.id} after {trigger_phase.id}")
+        return debate_phase
+
+    async def _check_divergence_and_insert_debates(
+        self,
+        lead: Expert,
+        plan: TeamPlan,
+        completed_in_layer: list[PlanPhase],
+    ) -> None:
+        """Check for divergence on newly completed phases and insert debates.
+
+        Called after each layer completes. Stops early if MAX_DEBATES is reached.
+        """
+        for ph in completed_in_layer:
+            if ph.status != PhaseStatus.COMPLETED:
+                continue
+            if self._debate_count >= self.MAX_DEBATES:
+                logger.info(
+                    f"Max debates ({self.MAX_DEBATES}) reached, skipping divergence detection"
+                )
+                return
+
+            has_divergence = await self._detect_divergence(lead, ph, plan)
+            if not has_divergence:
+                continue
+
+            # Determine participants: all active experts except lead
+            participants = [
+                e.config.name
+                for e in self._team.active_experts
+                if e.config.name != lead.config.name
+            ]
+            topic = f"阶段 '{ph.name}' 产出分歧"
+            debate = self._insert_debate_phase(plan, ph, topic, participants)
+            if debate:
+                await self._broadcast_event(
+                    "plan_update",
+                    {
+                        "plan_id": plan.id,
+                        "plan_phases": [p.to_dict() for p in plan.phases],
+                        "debate_inserted": debate.id,
+                    },
+                )
+
+    # ── U3 end ─────────────────────────────────────────────────────────
+
     async def _get_isolated_agent(self, expert: Expert, phase: PlanPhase) -> ConfigDrivenAgent:
         """Get an isolated ConfigDrivenAgent instance for the phase.
 
diff --git a/tests/unit/experts/test_divergence_detection.py b/tests/unit/experts/test_divergence_detection.py
new file mode 100644
index 0000000..073ce21
--- /dev/null
+++ b/tests/unit/experts/test_divergence_detection.py
@@ -0,0 +1,756 @@
+"""TeamOrchestrator 分歧检测 + 方案评审辩论单元测试 (U3)
+
+测试覆盖：
+- 方案评审辩论 (_maybe_add_plan_review_debate)
+  * Happy path: LLM 判断需要评审 → 插入 DEBATE phase，所有原 phase 依赖它
+  * 边界: phases <= 2 时跳过
+  * 边界: MAX_DEBATES 已达上限时跳过
+  * 边界: 无其他成员时跳过
+  * 错误路径: LLM 不可用时跳过
+  * 错误路径: LLM 抛异常时跳过
+- 分歧检测 (_detect_divergence)
+  * Happy path: LLM 判断有分歧 → 返回 True
+  * Happy path: LLM 判断无分歧 → 返回 False
+  * 边界: 无其他已完成阶段时返回 False
+  * 错误路径: LLM 不可用时返回 False
+  * 错误路径: LLM 抛异常时返回 False
+- 动态插入辩论 (_insert_debate_phase)
+  * Happy path: 插入 DEBATE，依赖重 wiring
+  * 边界: participants 为空时返回 None
+- 协调入口 (_check_divergence_and_insert_debates)
+  * Happy path: 检测到分歧 → 插入辩论 + 广播 plan_update
+  * Happy path: 无分歧 → 不插入
+  * 边界: MAX_DEBATES 达上限时跳过
+- 集成: 插入的 DEBATE phase 在 topological_sort 中正确分层
+"""
+
+from __future__ import annotations
+
+from unittest.mock import AsyncMock, MagicMock
+
+import pytest
+
+from agentkit.core.handoff_transport import InProcessHandoffTransport
+from agentkit.experts.config import ExpertConfig
+from agentkit.experts.orchestrator import TeamOrchestrator
+from agentkit.experts.plan import PhaseStatus, PhaseType, PlanPhase, TeamPlan
+from agentkit.experts.team import ExpertTeam
+
+
+# ── 辅助函数 ──────────────────────────────────────────────
+
+
+def _make_expert_config(
+    name: str = "test_expert",
+    is_lead: bool = False,
+) -> ExpertConfig:
+    return ExpertConfig(
+        name=name,
+        agent_type="expert",
+        persona=f"{name}的角色描述",
+        thinking_style="逻辑推理",
+        speaking_style="简洁直接",
+        decision_framework="数据驱动决策",
+        bound_skills=["skill_a"],
+        is_lead=is_lead,
+        task_mode="llm_generate",
+        prompt={"identity": "测试"},
+    )
+
+
+def _make_mock_expert(
+    name: str = "test_expert",
+    is_lead: bool = False,
+    is_active: bool = True,
+    gateway: MagicMock | None = None,
+) -> MagicMock:
+    config = _make_expert_config(name=name, is_lead=is_lead)
+    expert = MagicMock()
+    expert.config = config
+    expert.is_active = is_active
+    expert.team_id = None
+    expert.get_capabilities_summary.return_value = {
+        "name": name,
+        "persona": config.persona,
+        "thinking_style": config.thinking_style,
+        "bound_skills": config.bound_skills,
+        "is_lead": is_lead,
+    }
+    mock_agent = MagicMock()
+    mock_agent._llm_gateway = gateway
+    expert.agent = mock_agent
+    return expert
+
+
+def _make_team_with_experts(
+    expert_names: list[str] | None = None,
+    lead_name: str = "lead",
+    gateway: MagicMock | None = None,
+) -> ExpertTeam:
+    team = ExpertTeam()
+    transport = AsyncMock(spec=InProcessHandoffTransport)
+    team._handoff_transport = transport
+
+    if expert_names is None:
+        expert_names = [lead_name, "member1", "member2"]
+
+    for name in expert_names:
+        is_lead = name == lead_name
+        expert = _make_mock_expert(name=name, is_lead=is_lead, gateway=gateway)
+        team._experts[name] = expert
+        if is_lead:
+            team._lead_expert_name = name
+
+    return team
+
+
+def _make_execution_phase(
+    phase_id: str = "phase_1",
+    name: str = "阶段一",
+    assigned_expert: str = "member1",
+    depends_on: list[str] | None = None,
+    status: PhaseStatus = PhaseStatus.PENDING,
+    result: dict | None = None,
+) -> PlanPhase:
+    """创建测试用 EXECUTION 阶段"""
+    return PlanPhase(
+        id=phase_id,
+        name=name,
+        assigned_expert=assigned_expert,
+        task_description=f"{name}的任务描述",
+        depends_on=depends_on or [],
+        phase_type=PhaseType.EXECUTION,
+        status=status,
+        result=result,
+    )
+
+
+def _make_plan(
+    phases: list[PlanPhase],
+    task: str = "测试任务",
+    lead_expert: str = "lead",
+) -> TeamPlan:
+    return TeamPlan(
+        id="test_plan",
+        task=task,
+        phases=phases,
+        lead_expert=lead_expert,
+    )
+
+
+def _make_bool_gateway(
+    responses: list[bool],
+) -> AsyncMock:
+    """创建返回 true/false 字符串的 mock LLM gateway
+
+    Args:
+        responses: 按调用顺序返回的布尔值列表
+    """
+    queue = list(responses)
+
+    async def chat_side_effect(messages, model=None, **kwargs):
+        if not queue:
+            # Default to false if exhausted
+            response = MagicMock()
+            response.content = "false"
+            return response
+        val = queue.pop(0)
+        response = MagicMock()
+        response.content = "true" if val else "false"
+        return response
+
+    gateway = AsyncMock()
+    gateway.chat = AsyncMock(side_effect=chat_side_effect)
+    return gateway
+
+
+def _make_error_gateway() -> AsyncMock:
+    """创建总是抛异常的 mock LLM gateway"""
+
+    async def chat_side_effect(messages, model=None, **kwargs):
+        raise RuntimeError("LLM unavailable")
+
+    gateway = AsyncMock()
+    gateway.chat = AsyncMock(side_effect=chat_side_effect)
+    return gateway
+
+
+# ── 方案评审辩论测试 ─────────────────────────────────────
+
+
+class TestMaybeAddPlanReviewDebate:
+    """_maybe_add_plan_review_debate 测试"""
+
+    @pytest.mark.asyncio
+    async def test_adds_plan_review_debate_when_llm_says_yes(self):
+        """LLM 判断需要评审 → 插入 DEBATE phase，所有原 phase 依赖它"""
+        gateway = _make_bool_gateway([True])
+        team = _make_team_with_experts(gateway=gateway)
+        orchestrator = TeamOrchestrator(team)
+
+        # 3 个执行阶段（>2 才会考虑评审）
+        phases = [
+            _make_execution_phase(phase_id="p1", name="阶段一"),
+            _make_execution_phase(phase_id="p2", name="阶段二"),
+            _make_execution_phase(phase_id="p3", name="阶段三"),
+        ]
+        plan = _make_plan(phases=phases, task="复杂任务")
+
+        await orchestrator._maybe_add_plan_review_debate(
+            team.lead_expert, plan, "复杂任务"
+        )
+
+        # 应该插入一个 DEBATE phase 在最前面
+        assert len(plan.phases) == 4
+        review_phase = plan.phases[0]
+        assert review_phase.phase_type == PhaseType.DEBATE
+        assert review_phase.name == "方案评审"
+        assert review_phase.assigned_expert == "lead"
+        assert review_phase.debate_config is not None
+        assert review_phase.debate_config["participants"] == ["member1", "member2"]
+        assert review_phase.debate_config["max_rounds"] == 2
+
+        # 所有原 phase 都应该依赖 review_phase
+        for ph in plan.phases[1:]:
+            assert review_phase.id in ph.depends_on
+
+        # debate_count 应该 +1
+        assert orchestrator._debate_count == 1
+
+    @pytest.mark.asyncio
+    async def test_skips_when_llm_says_no(self):
+        """LLM 判断不需要评审 → 不插入"""
+        gateway = _make_bool_gateway([False])
+        team = _make_team_with_experts(gateway=gateway)
+        orchestrator = TeamOrchestrator(team)
+
+        phases = [
+            _make_execution_phase(phase_id="p1"),
+            _make_execution_phase(phase_id="p2"),
+            _make_execution_phase(phase_id="p3"),
+        ]
+        plan = _make_plan(phases=phases)
+
+        await orchestrator._maybe_add_plan_review_debate(
+            team.lead_expert, plan, "简单任务"
+        )
+
+        assert len(plan.phases) == 3
+        assert orchestrator._debate_count == 0
+
+    @pytest.mark.asyncio
+    async def test_skips_when_phases_le_two(self):
+        """phases <= 2 时跳过（简单任务）"""
+        gateway = _make_bool_gateway([True])
+        team = _make_team_with_experts(gateway=gateway)
+        orchestrator = TeamOrchestrator(team)
+
+        phases = [
+            _make_execution_phase(phase_id="p1"),
+            _make_execution_phase(phase_id="p2"),
+        ]
+        plan = _make_plan(phases=phases)
+
+        await orchestrator._maybe_add_plan_review_debate(
+            team.lead_expert, plan, "任务"
+        )
+
+        assert len(plan.phases) == 2
+        assert orchestrator._debate_count == 0
+
+    @pytest.mark.asyncio
+    async def test_skips_when_max_debates_reached(self):
+        """MAX_DEBATES 已达上限时跳过"""
+        gateway = _make_bool_gateway([True])
+        team = _make_team_with_experts(gateway=gateway)
+        orchestrator = TeamOrchestrator(team)
+        orchestrator._debate_count = orchestrator.MAX_DEBATES
+
+        phases = [
+            _make_execution_phase(phase_id="p1"),
+            _make_execution_phase(phase_id="p2"),
+            _make_execution_phase(phase_id="p3"),
+        ]
+        plan = _make_plan(phases=phases)
+
+        await orchestrator._maybe_add_plan_review_debate(
+            team.lead_expert, plan, "任务"
+        )
+
+        assert len(plan.phases) == 3
+        assert orchestrator._debate_count == orchestrator.MAX_DEBATES
+
+    @pytest.mark.asyncio
+    async def test_skips_when_no_other_members(self):
+        """无其他成员时跳过（只有 lead）"""
+        gateway = _make_bool_gateway([True])
+        team = _make_team_with_experts(
+            expert_names=["lead"], gateway=gateway
+        )
+        orchestrator = TeamOrchestrator(team)
+
+        phases = [
+            _make_execution_phase(phase_id="p1"),
+            _make_execution_phase(phase_id="p2"),
+            _make_execution_phase(phase_id="p3"),
+        ]
+        plan = _make_plan(phases=phases)
+
+        await orchestrator._maybe_add_plan_review_debate(
+            team.lead_expert, plan, "任务"
+        )
+
+        assert len(plan.phases) == 3
+        assert orchestrator._debate_count == 0
+
+    @pytest.mark.asyncio
+    async def test_skips_when_llm_unavailable(self):
+        """LLM gateway 为 None 时跳过"""
+        team = _make_team_with_experts(gateway=None)
+        orchestrator = TeamOrchestrator(team)
+
+        phases = [
+            _make_execution_phase(phase_id="p1"),
+            _make_execution_phase(phase_id="p2"),
+            _make_execution_phase(phase_id="p3"),
+        ]
+        plan = _make_plan(phases=phases)
+
+        await orchestrator._maybe_add_plan_review_debate(
+            team.lead_expert, plan, "任务"
+        )
+
+        assert len(plan.phases) == 3
+        assert orchestrator._debate_count == 0
+
+    @pytest.mark.asyncio
+    async def test_skips_when_llm_raises_exception(self):
+        """LLM 抛异常时跳过，不抛出"""
+        gateway = _make_error_gateway()
+        team = _make_team_with_experts(gateway=gateway)
+        orchestrator = TeamOrchestrator(team)
+
+        phases = [
+            _make_execution_phase(phase_id="p1"),
+            _make_execution_phase(phase_id="p2"),
+            _make_execution_phase(phase_id="p3"),
+        ]
+        plan = _make_plan(phases=phases)
+
+        # 不应该抛异常
+        await orchestrator._maybe_add_plan_review_debate(
+            team.lead_expert, plan, "任务"
+        )
+
+        assert len(plan.phases) == 3
+        assert orchestrator._debate_count == 0
+
+
+# ── 分歧检测测试 ─────────────────────────────────────────
+
+
+class TestDetectDivergence:
+    """_detect_divergence 测试"""
+
+    @pytest.mark.asyncio
+    async def test_returns_true_when_llm_detects_divergence(self):
+        """LLM 判断有分歧 → 返回 True"""
+        gateway = _make_bool_gateway([True])
+        team = _make_team_with_experts(gateway=gateway)
+        orchestrator = TeamOrchestrator(team)
+
+        # 两个已完成的阶段，产出不同
+        phase_a = _make_execution_phase(
+            phase_id="a",
+            name="阶段A",
+            status=PhaseStatus.COMPLETED,
+            result={"content": "采用 React"},
+        )
+        phase_b = _make_execution_phase(
+            phase_id="b",
+            name="阶段B",
+            status=PhaseStatus.COMPLETED,
+            result={"content": "采用 Vue"},
+        )
+        plan = _make_plan(phases=[phase_a, phase_b])
+
+        result = await orchestrator._detect_divergence(
+            team.lead_expert, phase_a, plan
+        )
+
+        assert result is True
+
+    @pytest.mark.asyncio
+    async def test_returns_false_when_llm_says_no_divergence(self):
+        """LLM 判断无分歧 → 返回 False"""
+        gateway = _make_bool_gateway([False])
+        team = _make_team_with_experts(gateway=gateway)
+        orchestrator = TeamOrchestrator(team)
+
+        phase_a = _make_execution_phase(
+            phase_id="a",
+            status=PhaseStatus.COMPLETED,
+            result={"content": "结果A"},
+        )
+        phase_b = _make_execution_phase(
+            phase_id="b",
+            status=PhaseStatus.COMPLETED,
+            result={"content": "结果B"},
+        )
+        plan = _make_plan(phases=[phase_a, phase_b])
+
+        result = await orchestrator._detect_divergence(
+            team.lead_expert, phase_a, plan
+        )
+
+        assert result is False
+
+    @pytest.mark.asyncio
+    async def test_returns_false_when_no_other_completed_phases(self):
+        """无其他已完成阶段时返回 False（无法比较）"""
+        gateway = _make_bool_gateway([True])
+        team = _make_team_with_experts(gateway=gateway)
+        orchestrator = TeamOrchestrator(team)
+
+        phase_a = _make_execution_phase(
+            phase_id="a",
+            status=PhaseStatus.COMPLETED,
+            result={"content": "结果A"},
+        )
+        # 另一个阶段还在 PENDING
+        phase_b = _make_execution_phase(phase_id="b", status=PhaseStatus.PENDING)
+        plan = _make_plan(phases=[phase_a, phase_b])
+
+        result = await orchestrator._detect_divergence(
+            team.lead_expert, phase_a, plan
+        )
+
+        assert result is False
+
+    @pytest.mark.asyncio
+    async def test_returns_false_when_llm_unavailable(self):
+        """LLM gateway 为 None 时返回 False"""
+        team = _make_team_with_experts(gateway=None)
+        orchestrator = TeamOrchestrator(team)
+
+        phase_a = _make_execution_phase(
+            phase_id="a",
+            status=PhaseStatus.COMPLETED,
+            result={"content": "结果A"},
+        )
+        phase_b = _make_execution_phase(
+            phase_id="b",
+            status=PhaseStatus.COMPLETED,
+            result={"content": "结果B"},
+        )
+        plan = _make_plan(phases=[phase_a, phase_b])
+
+        result = await orchestrator._detect_divergence(
+            team.lead_expert, phase_a, plan
+        )
+
+        assert result is False
+
+    @pytest.mark.asyncio
+    async def test_returns_false_when_llm_raises_exception(self):
+        """LLM 抛异常时返回 False，不抛出"""
+        gateway = _make_error_gateway()
+        team = _make_team_with_experts(gateway=gateway)
+        orchestrator = TeamOrchestrator(team)
+
+        phase_a = _make_execution_phase(
+            phase_id="a",
+            status=PhaseStatus.COMPLETED,
+            result={"content": "结果A"},
+        )
+        phase_b = _make_execution_phase(
+            phase_id="b",
+            status=PhaseStatus.COMPLETED,
+            result={"content": "结果B"},
+        )
+        plan = _make_plan(phases=[phase_a, phase_b])
+
+        result = await orchestrator._detect_divergence(
+            team.lead_expert, phase_a, plan
+        )
+
+        assert result is False
+
+
+# ── 动态插入辩论测试 ─────────────────────────────────────
+
+
+class TestInsertDebatePhase:
+    """_insert_debate_phase 测试"""
+
+    def test_inserts_debate_and_rewires_dependencies(self):
+        """插入 DEBATE phase，依赖重 wiring：原依赖 trigger 的 phase 现在依赖 DEBATE"""
+        gateway = _make_bool_gateway([])
+        team = _make_team_with_experts(gateway=gateway)
+        orchestrator = TeamOrchestrator(team)
+
+        trigger = _make_execution_phase(phase_id="trigger", name="触发阶段")
+        dependent = _make_execution_phase(
+            phase_id="dependent",
+            name="依赖阶段",
+            depends_on=["trigger"],
+        )
+        plan = _make_plan(phases=[trigger, dependent])
+
+        debate = orchestrator._insert_debate_phase(
+            plan, trigger, "产出分歧", ["member1", "member2"]
+        )
+
+        assert debate is not None
+        assert debate.phase_type == PhaseType.DEBATE
+        assert debate.depends_on == ["trigger"]
+        assert debate.debate_config["topic"] == "产出分歧"
+        assert debate.debate_config["participants"] == ["member1", "member2"]
+        assert debate.debate_config["max_rounds"] == 2
+
+        # dependent 现在依赖 debate，不再直接依赖 trigger
+        assert debate.id in dependent.depends_on
+        assert "trigger" not in dependent.depends_on
+
+        # debate 被加入 plan
+        assert debate in plan.phases
+        assert orchestrator._debate_count == 1
+
+    def test_returns_none_when_no_participants(self):
+        """participants 为空时返回 None"""
+        gateway = _make_bool_gateway([])
+        team = _make_team_with_experts(gateway=gateway)
+        orchestrator = TeamOrchestrator(team)
+
+        trigger = _make_execution_phase(phase_id="trigger")
+        plan = _make_plan(phases=[trigger])
+
+        debate = orchestrator._insert_debate_phase(
+            plan, trigger, "产出分歧", []
+        )
+
+        assert debate is None
+        assert orchestrator._debate_count == 0
+
+    def test_debate_assigned_to_lead(self):
+        """DEBATE phase 的 assigned_expert 是 lead"""
+        gateway = _make_bool_gateway([])
+        team = _make_team_with_experts(gateway=gateway)
+        orchestrator = TeamOrchestrator(team)
+
+        trigger = _make_execution_phase(phase_id="trigger")
+        plan = _make_plan(phases=[trigger])
+
+        debate = orchestrator._insert_debate_phase(
+            plan, trigger, "分歧", ["member1"]
+        )
+
+        assert debate is not None
+        assert debate.assigned_expert == "lead"
+
+
+# ── 协调入口测试 ─────────────────────────────────────────
+
+
+class TestCheckDivergenceAndInsertDebates:
+    """_check_divergence_and_insert_debates 测试"""
+
+    @pytest.mark.asyncio
+    async def test_inserts_debate_when_divergence_detected(self):
+        """检测到分歧 → 插入辩论 + 广播 plan_update"""
+        gateway = _make_bool_gateway([True])  # 检测到分歧
+        team = _make_team_with_experts(gateway=gateway)
+        orchestrator = TeamOrchestrator(team)
+
+        phase_a = _make_execution_phase(
+            phase_id="a",
+            name="阶段A",
+            status=PhaseStatus.COMPLETED,
+            result={"content": "采用 React"},
+        )
+        phase_b = _make_execution_phase(
+            phase_id="b",
+            name="阶段B",
+            status=PhaseStatus.COMPLETED,
+            result={"content": "采用 Vue"},
+        )
+        plan = _make_plan(phases=[phase_a, phase_b])
+
+        await orchestrator._check_divergence_and_insert_debates(
+            team.lead_expert, plan, [phase_a]
+        )
+
+        # 应该插入一个 DEBATE phase
+        assert len(plan.phases) == 3
+        debate = plan.phases[-1]
+        assert debate.phase_type == PhaseType.DEBATE
+        assert orchestrator._debate_count == 1
+
+        # 应该广播 plan_update 事件
+        transport = team._handoff_transport
+        assert transport.send.called
+        # 最后一次 send 应该是 plan_update
+        last_call = transport.send.call_args_list[-1]
+        event_data = last_call[0][1]  # 第二个位置参数是 data dict
+        assert event_data["type"] == "plan_update"
+        assert "debate_inserted" in event_data
+
+    @pytest.mark.asyncio
+    async def test_no_debate_when_no_divergence(self):
+        """无分歧 → 不插入辩论"""
+        gateway = _make_bool_gateway([False])
+        team = _make_team_with_experts(gateway=gateway)
+        orchestrator = TeamOrchestrator(team)
+
+        phase_a = _make_execution_phase(
+            phase_id="a",
+            status=PhaseStatus.COMPLETED,
+            result={"content": "结果A"},
+        )
+        phase_b = _make_execution_phase(
+            phase_id="b",
+            status=PhaseStatus.COMPLETED,
+            result={"content": "结果B"},
+        )
+        plan = _make_plan(phases=[phase_a, phase_b])
+
+        await orchestrator._check_divergence_and_insert_debates(
+            team.lead_expert, plan, [phase_a]
+        )
+
+        assert len(plan.phases) == 2
+        assert orchestrator._debate_count == 0
+
+    @pytest.mark.asyncio
+    async def test_skips_when_max_debates_reached(self):
+        """MAX_DEBATES 达上限时跳过检测"""
+        gateway = _make_bool_gateway([True])
+        team = _make_team_with_experts(gateway=gateway)
+        orchestrator = TeamOrchestrator(team)
+        orchestrator._debate_count = orchestrator.MAX_DEBATES
+
+        phase_a = _make_execution_phase(
+            phase_id="a",
+            status=PhaseStatus.COMPLETED,
+            result={"content": "结果A"},
+        )
+        phase_b = _make_execution_phase(
+            phase_id="b",
+            status=PhaseStatus.COMPLETED,
+            result={"content": "结果B"},
+        )
+        plan = _make_plan(phases=[phase_a, phase_b])
+
+        await orchestrator._check_divergence_and_insert_debates(
+            team.lead_expert, plan, [phase_a]
+        )
+
+        assert len(plan.phases) == 2
+        assert orchestrator._debate_count == orchestrator.MAX_DEBATES
+
+    @pytest.mark.asyncio
+    async def test_skips_non_completed_phases(self):
+        """非 COMPLETED 状态的 phase 被跳过"""
+        gateway = _make_bool_gateway([True])
+        team = _make_team_with_experts(gateway=gateway)
+        orchestrator = TeamOrchestrator(team)
+
+        # 传入一个 PENDING 的 phase（不应该被检测）
+        phase_pending = _make_execution_phase(
+            phase_id="pending", status=PhaseStatus.PENDING
+        )
+        phase_completed = _make_execution_phase(
+            phase_id="completed",
+            status=PhaseStatus.COMPLETED,
+            result={"content": "结果"},
+        )
+        plan = _make_plan(phases=[phase_pending, phase_completed])
+
+        await orchestrator._check_divergence_and_insert_debates(
+            team.lead_expert, plan, [phase_pending, phase_completed]
+        )
+
+        # phase_pending 被跳过；phase_completed 无其他完成阶段可比较 → 无分歧
+        assert orchestrator._debate_count == 0
+
+
+# ── 集成测试 ─────────────────────────────────────────────
+
+
+class TestInsertedDebateLayering:
+    """插入的 DEBATE phase 在 topological_sort 中正确分层"""
+
+    def test_inserted_debate_blocks_dependents(self):
+        """插入的 DEBATE phase 应该在 trigger 之后、dependent 之前"""
+        gateway = _make_bool_gateway([])
+        team = _make_team_with_experts(gateway=gateway)
+        orchestrator = TeamOrchestrator(team)
+
+        trigger = _make_execution_phase(
+            phase_id="trigger",
+            name="触发阶段",
+            status=PhaseStatus.COMPLETED,
+            result={"content": "触发结果"},
+        )
+        dependent = _make_execution_phase(
+            phase_id="dependent",
+            name="依赖阶段",
+            depends_on=["trigger"],
+        )
+        plan = _make_plan(phases=[trigger, dependent])
+
+        debate = orchestrator._insert_debate_phase(
+            plan, trigger, "分歧", ["member1", "member2"]
+        )
+
+        assert debate is not None
+
+        layers = plan.topological_sort()
+        # 找到各 phase 所在的层
+        trigger_layer = None
+        debate_layer = None
+        dependent_layer = None
+        for i, layer in enumerate(layers):
+            for ph in layer:
+                if ph.id == "trigger":
+                    trigger_layer = i
+                elif ph.id == debate.id:
+                    debate_layer = i
+                elif ph.id == "dependent":
+                    dependent_layer = i
+
+        assert trigger_layer is not None
+        assert debate_layer is not None
+        assert dependent_layer is not None
+        # trigger < debate < dependent
+        assert trigger_layer < debate_layer
+        assert debate_layer < dependent_layer
+
+    @pytest.mark.asyncio
+    async def test_plan_review_debate_runs_first(self):
+        """方案评审 DEBATE 应该在第 0 层，所有执行阶段在后续层"""
+        gateway = _make_bool_gateway([True])
+        team = _make_team_with_experts(gateway=gateway)
+        orchestrator = TeamOrchestrator(team)
+
+        phases = [
+            _make_execution_phase(phase_id="p1", name="阶段一"),
+            _make_execution_phase(phase_id="p2", name="阶段二"),
+            _make_execution_phase(phase_id="p3", name="阶段三"),
+        ]
+        plan = _make_plan(phases=phases, task="复杂任务")
+
+        await orchestrator._maybe_add_plan_review_debate(
+            team.lead_expert, plan, "复杂任务"
+        )
+
+        layers = plan.topological_sort()
+        # 第 0 层应该只有方案评审 DEBATE
+        assert len(layers[0]) == 1
+        assert layers[0][0].phase_type == PhaseType.DEBATE
+        assert layers[0][0].name == "方案评审"
+
+        # 所有执行阶段在后续层
+        for layer in layers[1:]:
+            for ph in layer:
+                assert ph.phase_type == PhaseType.EXECUTION
diff --git a/tests/unit/experts/test_team_orchestrator.py b/tests/unit/experts/test_team_orchestrator.py
index 57c9db5..d884a0c 100644
--- a/tests/unit/experts/test_team_orchestrator.py
+++ b/tests/unit/experts/test_team_orchestrator.py
@@ -130,7 +130,17 @@ def _make_mock_llm_gateway(
         decomp_response.content = phases_json
         synth_response = MagicMock()
         synth_response.content = synthesis_content
-        gateway.chat = AsyncMock(side_effect=[decomp_response, synth_response, synth_response])
+        # U3: 分歧检测会在 decomposition 与 synthesis 之间插入额外的 LLM 调用，
+        # 因此用函数式 side_effect：首次返回 decomposition，其余一律返回 synthesis。
+        call_count = [0]
+
+        async def chat_side_effect(messages, model=None, **kwargs):
+            call_count[0] += 1
+            if call_count[0] == 1:
+                return decomp_response
+            return synth_response
+
+        gateway.chat = AsyncMock(side_effect=chat_side_effect)
     else:
         response = MagicMock()
         response.content = synthesis_content