diff --git a/engine/adapters/__init__.py b/engine/adapters/__init__.py
new file mode 100644
index 0000000..6a94df0
--- /dev/null
+++ b/engine/adapters/__init__.py
@@ -0,0 +1 @@
+"""Adapters package."""
diff --git a/engine/adapters/control_plane/__init__.py b/engine/adapters/control_plane/__init__.py
new file mode 100644
index 0000000..06f5004
--- /dev/null
+++ b/engine/adapters/control_plane/__init__.py
@@ -0,0 +1 @@
+"""Control-plane adapters package."""
diff --git a/engine/app/backend_adapters.py b/engine/adapters/control_plane/backend.py
similarity index 100%
rename from engine/app/backend_adapters.py
rename to engine/adapters/control_plane/backend.py
diff --git a/engine/app/main.py b/engine/app/main.py
index 5625061..09ffa1d 100644
--- a/engine/app/main.py
+++ b/engine/app/main.py
@@ -20,11 +20,11 @@ except ImportError:
     logger.warning("aiortc not available - WebRTC endpoint will be disabled")
 
 from app.config import settings
-from app.backend_adapters import build_backend_adapter_from_settings
-from core.transports import SocketTransport, WebRtcTransport, BaseTransport
-from core.session import Session
+from adapters.control_plane.backend import build_backend_adapter_from_settings
+from runtime.transports import SocketTransport, WebRtcTransport, BaseTransport
+from runtime.session.manager import Session
 from processors.tracks import Resampled16kTrack
-from core.events import get_event_bus, reset_event_bus
+from runtime.events import get_event_bus, reset_event_bus
 
 # Check interval for heartbeat/timeout (seconds)
 _HEARTBEAT_CHECK_INTERVAL_SEC = 5
diff --git a/engine/core/__init__.py b/engine/core/__init__.py
deleted file mode 100644
index 0110686..0000000
--- a/engine/core/__init__.py
+++ /dev/null
@@ -1,20 +0,0 @@
-"""Core Components Package"""
-
-from core.events import EventBus, get_event_bus
-from core.transports import BaseTransport, SocketTransport, WebRtcTransport
-from core.session import Session
-from core.conversation import ConversationManager, ConversationState, ConversationTurn
-from core.duplex_pipeline import DuplexPipeline
-
-__all__ = [
-    "EventBus",
-    "get_event_bus",
-    "BaseTransport",
-    "SocketTransport",
-    "WebRtcTransport",
-    "Session",
-    "ConversationManager",
-    "ConversationState",
-    "ConversationTurn",
-    "DuplexPipeline",
-]
diff --git a/engine/docs/backend_integration.md b/engine/docs/backend_integration.md
index bcd44fc..22fa09e 100644
--- a/engine/docs/backend_integration.md
+++ b/engine/docs/backend_integration.md
@@ -27,15 +27,15 @@ Assistant config source behavior:
 
 ## Architecture
 
-- Ports: `core/ports/control_plane.py`
-- Adapters: `app/backend_adapters.py`
+- Ports: `runtime/ports/control_plane.py`
+- Adapters: `adapters/control_plane/backend.py`
 
 `Session` and `DuplexPipeline` receive backend capabilities via injected adapter
 methods instead of hard-coding backend client imports.
 
 ## Async History Writes
 
-Session history persistence is handled by `core/history_bridge.py`.
+Session history persistence is handled by `runtime/history/bridge.py`.
 
 Design:
 
diff --git a/engine/docs/extension_ports.md b/engine/docs/extension_ports.md
index 47f596a..8566194 100644
--- a/engine/docs/extension_ports.md
+++ b/engine/docs/extension_ports.md
@@ -4,31 +4,31 @@ This document defines the draft port set used to keep core runtime extensible.
 
 ## Port Modules
 
-- `core/ports/control_plane.py`
+- `runtime/ports/control_plane.py`
   - `AssistantRuntimeConfigProvider`
   - `ConversationHistoryStore`
   - `KnowledgeRetriever`
   - `ToolCatalog`
   - `ControlPlaneGateway`
-- `core/ports/llm.py`
+- `runtime/ports/llm.py`
   - `LLMServiceSpec`
   - `LLMPort`
   - optional extensions: `LLMCancellable`, `LLMRuntimeConfigurable`
-- `core/ports/tts.py`
+- `runtime/ports/tts.py`
   - `TTSServiceSpec`
   - `TTSPort`
-- `core/ports/asr.py`
+- `runtime/ports/asr.py`
   - `ASRServiceSpec`
   - `ASRPort`
   - optional extensions: `ASRInterimControl`, `ASRBufferControl`
-- `core/ports/service_factory.py`
+- `runtime/ports/service_factory.py`
   - `RealtimeServiceFactory`
 
 ## Adapter Layer
 
-- `app/service_factory.py` provides `DefaultRealtimeServiceFactory`.
+- `providers/factory/default.py` provides `DefaultRealtimeServiceFactory`.
 - It maps resolved provider specs to concrete adapters.
-- Core orchestration (`core/duplex_pipeline.py`) depends on the factory port/specs, not concrete provider classes.
+- Runtime orchestration (`runtime/pipeline/duplex.py`) depends on the factory port/specs, not concrete provider classes.
 
 ## Provider Behavior (Current)
 
diff --git a/engine/docs/high_level_architecture.md b/engine/docs/high_level_architecture.md
index 91e6845..bdae564 100644
--- a/engine/docs/high_level_architecture.md
+++ b/engine/docs/high_level_architecture.md
@@ -14,19 +14,19 @@ This document describes the runtime architecture of `engine` for realtime voice/
 ```mermaid
 flowchart LR
   C[Client\nWeb / Mobile / Device] <-- WS v1 + PCM --> A[FastAPI App\napp/main.py]
-  A --> S[Session\ncore/session.py]
-  S --> D[Duplex Pipeline\ncore/duplex_pipeline.py]
+  A --> S[Session\nruntime/session/manager.py]
+  S --> D[Duplex Pipeline\nruntime/pipeline/duplex.py]
 
   D --> P[Processors\nVAD / EOU / Tracks]
-  D --> R[Workflow Runner\ncore/workflow_runner.py]
-  D --> E[Event Bus + Models\ncore/events.py + models/*]
+  D --> R[Workflow Runner\nworkflow/runner.py]
+  D --> E[Event Bus + Models\nruntime/events.py + protocol/ws_v1/*]
 
-  R --> SV[Service Layer\nservices/asr.py\nservices/llm.py\nservices/tts.py]
-  R --> TE[Tool Executor\ncore/tool_executor.py]
+  R --> SV[Service Layer\nproviders/asr/*\nproviders/llm/*\nproviders/tts/*]
+  R --> TE[Tool Executor\ntools/executor.py]
 
-  S --> HB[History Bridge\ncore/history_bridge.py]
-  S --> BA[Control Plane Port\ncore/ports/control_plane.py]
-  BA --> AD[Adapters\napp/backend_adapters.py]
+  S --> HB[History Bridge\nruntime/history/bridge.py]
+  S --> BA[Control Plane Port\nruntime/ports/control_plane.py]
+  BA --> AD[Adapters\nadapters/control_plane/backend.py]
 
   AD --> B[(External Backend API\noptional)]
   SV --> M[(ASR/LLM/TTS Providers)]
@@ -58,7 +58,7 @@ flowchart LR
 
 ### 2) Session + Orchestration Layer
 
-- Core: `core/session.py`, `core/duplex_pipeline.py`, `core/conversation.py`
+- Core: `runtime/session/manager.py`, `runtime/pipeline/duplex.py`, `runtime/conversation.py`
 - Responsibilities:
   - Per-session state machine
   - Turn boundaries and interruption/cancel handling
@@ -75,7 +75,7 @@ flowchart LR
 
 ### 4) Workflow + Tooling Layer
 
-- Modules: `core/workflow_runner.py`, `core/tool_executor.py`
+- Modules: `workflow/runner.py`, `tools/executor.py`
 - Responsibilities:
   - Assistant workflow execution
   - Tool call planning/execution and timeout handling
@@ -83,7 +83,7 @@ flowchart LR
 
 ### 5) Service Integration Layer
 
-- Modules: `services/*`
+- Modules: `providers/*`
 - Responsibilities:
   - Abstracting ASR/LLM/TTS provider differences
   - Streaming token/audio adaptation
@@ -91,8 +91,8 @@ flowchart LR
 
 ### 6) Backend Integration Layer (Optional)
 
-- Port: `core/ports/control_plane.py`
-- Adapters: `app/backend_adapters.py`
+- Port: `runtime/ports/control_plane.py`
+- Adapters: `adapters/control_plane/backend.py`
 - Responsibilities:
   - Fetching assistant runtime config
   - Persisting call/session metadata and history
@@ -100,7 +100,7 @@ flowchart LR
 
 ### 7) Persistence / Reliability Layer
 
-- Module: `core/history_bridge.py`
+- Module: `runtime/history/bridge.py`
 - Responsibilities:
   - Non-blocking queue-based history writes
   - Retry with backoff on backend failures
diff --git a/engine/docs/import_migration.md b/engine/docs/import_migration.md
new file mode 100644
index 0000000..eaeba1c
--- /dev/null
+++ b/engine/docs/import_migration.md
@@ -0,0 +1,21 @@
+# Canonical Module Layout
+
+This MVP uses a single canonical module layout without legacy import shims.
+
+## Runtime and protocol
+
+- `protocol.ws_v1.schema`
+- `runtime.session.manager`
+- `runtime.pipeline.duplex`
+- `runtime.history.bridge`
+- `runtime.events`
+- `runtime.transports`
+- `runtime.conversation`
+- `runtime.ports.*`
+
+## Integrations and orchestration
+
+- `providers.*`
+- `adapters.control_plane.backend`
+- `workflow.runner`
+- `tools.executor`
diff --git a/engine/docs/ws_v1_schema_zh.md b/engine/docs/ws_v1_schema_zh.md
index ce5f175..1681c23 100644
--- a/engine/docs/ws_v1_schema_zh.md
+++ b/engine/docs/ws_v1_schema_zh.md
@@ -7,9 +7,9 @@
 - 握手顺序、状态机、错误语义与实现细节。
 
 实现对照来源：
-- `models/ws_v1.py`
-- `core/session.py`
-- `core/duplex_pipeline.py`
+- `protocol/ws_v1/schema.py`
+- `runtime/session/manager.py`
+- `runtime/pipeline/duplex.py`
 - `app/main.py`
 
 ---
diff --git a/engine/models/__init__.py b/engine/models/__init__.py
deleted file mode 100644
index 924d5fd..0000000
--- a/engine/models/__init__.py
+++ /dev/null
@@ -1 +0,0 @@
-"""Data Models Package"""
diff --git a/engine/models/commands.py b/engine/models/commands.py
deleted file mode 100644
index 5bcf47e..0000000
--- a/engine/models/commands.py
+++ /dev/null
@@ -1,143 +0,0 @@
-"""Protocol command models matching the original active-call API."""
-
-from typing import Optional, Dict, Any
-from pydantic import BaseModel, Field
-
-
-class InviteCommand(BaseModel):
-    """Invite command to initiate a call."""
-
-    command: str = Field(default="invite", description="Command type")
-    option: Optional[Dict[str, Any]] = Field(default=None, description="Call configuration options")
-
-
-class AcceptCommand(BaseModel):
-    """Accept command to accept an incoming call."""
-
-    command: str = Field(default="accept", description="Command type")
-    option: Optional[Dict[str, Any]] = Field(default=None, description="Call configuration options")
-
-
-class RejectCommand(BaseModel):
-    """Reject command to reject an incoming call."""
-
-    command: str = Field(default="reject", description="Command type")
-    reason: str = Field(default="", description="Reason for rejection")
-    code: Optional[int] = Field(default=None, description="SIP response code")
-
-
-class RingingCommand(BaseModel):
-    """Ringing command to send ringing response."""
-
-    command: str = Field(default="ringing", description="Command type")
-    recorder: Optional[Dict[str, Any]] = Field(default=None, description="Call recording configuration")
-    early_media: bool = Field(default=False, description="Enable early media")
-    ringtone: Optional[str] = Field(default=None, description="Custom ringtone URL")
-
-
-class TTSCommand(BaseModel):
-    """TTS command to convert text to speech."""
-
-    command: str = Field(default="tts", description="Command type")
-    text: str = Field(..., description="Text to synthesize")
-    speaker: Optional[str] = Field(default=None, description="Speaker voice name")
-    play_id: Optional[str] = Field(default=None, description="Unique identifier for this TTS session")
-    auto_hangup: bool = Field(default=False, description="Auto hangup after TTS completion")
-    streaming: bool = Field(default=False, description="Streaming text input")
-    end_of_stream: bool = Field(default=False, description="End of streaming input")
-    wait_input_timeout: Optional[int] = Field(default=None, description="Max time to wait for input (seconds)")
-    option: Optional[Dict[str, Any]] = Field(default=None, description="TTS provider specific options")
-
-
-class PlayCommand(BaseModel):
-    """Play command to play audio from URL."""
-
-    command: str = Field(default="play", description="Command type")
-    url: str = Field(..., description="URL of audio file to play")
-    auto_hangup: bool = Field(default=False, description="Auto hangup after playback")
-    wait_input_timeout: Optional[int] = Field(default=None, description="Max time to wait for input (seconds)")
-
-
-class InterruptCommand(BaseModel):
-    """Interrupt command to interrupt current playback."""
-
-    command: str = Field(default="interrupt", description="Command type")
-    graceful: bool = Field(default=False, description="Wait for current TTS to complete")
-
-
-class PauseCommand(BaseModel):
-    """Pause command to pause current playback."""
-
-    command: str = Field(default="pause", description="Command type")
-
-
-class ResumeCommand(BaseModel):
-    """Resume command to resume paused playback."""
-
-    command: str = Field(default="resume", description="Command type")
-
-
-class HangupCommand(BaseModel):
-    """Hangup command to end the call."""
-
-    command: str = Field(default="hangup", description="Command type")
-    reason: Optional[str] = Field(default=None, description="Reason for hangup")
-    initiator: Optional[str] = Field(default=None, description="Who initiated the hangup")
-
-
-class HistoryCommand(BaseModel):
-    """History command to add conversation history."""
-
-    command: str = Field(default="history", description="Command type")
-    speaker: str = Field(..., description="Speaker identifier")
-    text: str = Field(..., description="Conversation text")
-
-
-class ChatCommand(BaseModel):
-    """Chat command for text-based conversation."""
-
-    command: str = Field(default="chat", description="Command type")
-    text: str = Field(..., description="Chat text message")
-
-
-# Command type mapping
-COMMAND_TYPES = {
-    "invite": InviteCommand,
-    "accept": AcceptCommand,
-    "reject": RejectCommand,
-    "ringing": RingingCommand,
-    "tts": TTSCommand,
-    "play": PlayCommand,
-    "interrupt": InterruptCommand,
-    "pause": PauseCommand,
-    "resume": ResumeCommand,
-    "hangup": HangupCommand,
-    "history": HistoryCommand,
-    "chat": ChatCommand,
-}
-
-
-def parse_command(data: Dict[str, Any]) -> BaseModel:
-    """
-    Parse a command from JSON data.
-
-    Args:
-        data: JSON data as dictionary
-
-    Returns:
-        Parsed command model
-
-    Raises:
-        ValueError: If command type is unknown
-    """
-    command_type = data.get("command")
-
-    if not command_type:
-        raise ValueError("Missing 'command' field")
-
-    command_class = COMMAND_TYPES.get(command_type)
-
-    if not command_class:
-        raise ValueError(f"Unknown command type: {command_type}")
-
-    return command_class(**data)
diff --git a/engine/models/config.py b/engine/models/config.py
deleted file mode 100644
index 009411e..0000000
--- a/engine/models/config.py
+++ /dev/null
@@ -1,126 +0,0 @@
-"""Configuration models for call options."""
-
-from typing import Optional, Dict, Any, List
-from pydantic import BaseModel, Field
-
-
-class VADOption(BaseModel):
-    """Voice Activity Detection configuration."""
-
-    type: str = Field(default="silero", description="VAD algorithm type (silero, webrtc)")
-    samplerate: int = Field(default=16000, description="Audio sample rate for VAD")
-    speech_padding: int = Field(default=250, description="Speech padding in milliseconds")
-    silence_padding: int = Field(default=100, description="Silence padding in milliseconds")
-    ratio: float = Field(default=0.5, description="Voice detection ratio threshold")
-    voice_threshold: float = Field(default=0.5, description="Voice energy threshold")
-    max_buffer_duration_secs: int = Field(default=50, description="Maximum buffer duration in seconds")
-    silence_timeout: Optional[int] = Field(default=None, description="Silence timeout in milliseconds")
-    endpoint: Optional[str] = Field(default=None, description="Custom VAD service endpoint")
-    secret_key: Optional[str] = Field(default=None, description="VAD service secret key")
-    secret_id: Optional[str] = Field(default=None, description="VAD service secret ID")
-
-
-class ASROption(BaseModel):
-    """Automatic Speech Recognition configuration."""
-
-    provider: str = Field(..., description="ASR provider (tencent, aliyun, openai, etc.)")
-    language: Optional[str] = Field(default=None, description="Language code (zh-CN, en-US)")
-    app_id: Optional[str] = Field(default=None, description="Application ID")
-    secret_id: Optional[str] = Field(default=None, description="Secret ID for authentication")
-    secret_key: Optional[str] = Field(default=None, description="Secret key for authentication")
-    model_type: Optional[str] = Field(default=None, description="ASR model type (16k_zh, 8k_en)")
-    buffer_size: Optional[int] = Field(default=None, description="Audio buffer size in bytes")
-    samplerate: Optional[int] = Field(default=None, description="Audio sample rate")
-    endpoint: Optional[str] = Field(default=None, description="Custom ASR service endpoint")
-    extra: Optional[Dict[str, Any]] = Field(default=None, description="Additional parameters")
-    start_when_answer: bool = Field(default=False, description="Start ASR when call is answered")
-
-
-class TTSOption(BaseModel):
-    """Text-to-Speech configuration."""
-
-    samplerate: Optional[int] = Field(default=None, description="TTS output sample rate")
-    provider: str = Field(default="msedge", description="TTS provider (tencent, aliyun, deepgram, msedge)")
-    speed: float = Field(default=1.0, description="Speech speed multiplier")
-    app_id: Optional[str] = Field(default=None, description="Application ID")
-    secret_id: Optional[str] = Field(default=None, description="Secret ID for authentication")
-    secret_key: Optional[str] = Field(default=None, description="Secret key for authentication")
-    volume: Optional[int] = Field(default=None, description="Speech volume level (1-10)")
-    speaker: Optional[str] = Field(default=None, description="Voice speaker name")
-    codec: Optional[str] = Field(default=None, description="Audio codec")
-    subtitle: bool = Field(default=False, description="Enable subtitle generation")
-    emotion: Optional[str] = Field(default=None, description="Speech emotion")
-    endpoint: Optional[str] = Field(default=None, description="Custom TTS service endpoint")
-    extra: Optional[Dict[str, Any]] = Field(default=None, description="Additional parameters")
-    max_concurrent_tasks: Optional[int] = Field(default=None, description="Max concurrent tasks")
-
-
-class RecorderOption(BaseModel):
-    """Call recording configuration."""
-
-    recorder_file: str = Field(..., description="Path to recording file")
-    samplerate: int = Field(default=16000, description="Recording sample rate")
-    ptime: int = Field(default=200, description="Packet time in milliseconds")
-
-
-class MediaPassOption(BaseModel):
-    """Media pass-through configuration for external audio processing."""
-
-    url: str = Field(..., description="WebSocket URL for media streaming")
-    input_sample_rate: int = Field(default=16000, description="Sample rate of audio received from WebSocket")
-    output_sample_rate: int = Field(default=16000, description="Sample rate of audio sent to WebSocket")
-    packet_size: int = Field(default=2560, description="Packet size in bytes")
-    ptime: Optional[int] = Field(default=None, description="Buffered playback period in milliseconds")
-
-
-class SipOption(BaseModel):
-    """SIP protocol configuration."""
-
-    username: Optional[str] = Field(default=None, description="SIP username")
-    password: Optional[str] = Field(default=None, description="SIP password")
-    realm: Optional[str] = Field(default=None, description="SIP realm/domain")
-    headers: Optional[Dict[str, str]] = Field(default=None, description="Additional SIP headers")
-
-
-class HandlerRule(BaseModel):
-    """Handler routing rule."""
-
-    caller: Optional[str] = Field(default=None, description="Caller pattern (regex)")
-    callee: Optional[str] = Field(default=None, description="Callee pattern (regex)")
-    playbook: Optional[str] = Field(default=None, description="Playbook file path")
-    webhook: Optional[str] = Field(default=None, description="Webhook URL")
-
-
-class CallOption(BaseModel):
-    """Comprehensive call configuration options."""
-
-    # Basic options
-    denoise: bool = Field(default=False, description="Enable noise reduction")
-    offer: Optional[str] = Field(default=None, description="SDP offer string")
-    callee: Optional[str] = Field(default=None, description="Callee SIP URI or phone number")
-    caller: Optional[str] = Field(default=None, description="Caller SIP URI or phone number")
-
-    # Audio codec
-    codec: str = Field(default="pcm", description="Audio codec (pcm, pcma, pcmu, g722)")
-
-    # Component configurations
-    recorder: Optional[RecorderOption] = Field(default=None, description="Call recording config")
-    asr: Optional[ASROption] = Field(default=None, description="ASR configuration")
-    vad: Optional[VADOption] = Field(default=None, description="VAD configuration")
-    tts: Optional[TTSOption] = Field(default=None, description="TTS configuration")
-    media_pass: Optional[MediaPassOption] = Field(default=None, description="Media pass-through config")
-    sip: Optional[SipOption] = Field(default=None, description="SIP configuration")
-
-    # Timeouts and networking
-    handshake_timeout: Optional[int] = Field(default=None, description="Handshake timeout in seconds")
-    enable_ipv6: bool = Field(default=False, description="Enable IPv6 support")
-    inactivity_timeout: Optional[int] = Field(default=None, description="Inactivity timeout in seconds")
-
-    # EOU configuration
-    eou: Optional[Dict[str, Any]] = Field(default=None, description="End of utterance detection config")
-
-    # Extra parameters
-    extra: Optional[Dict[str, Any]] = Field(default=None, description="Additional custom parameters")
-
-    class Config:
-        populate_by_name = True
diff --git a/engine/models/events.py b/engine/models/events.py
deleted file mode 100644
index 031b8be..0000000
--- a/engine/models/events.py
+++ /dev/null
@@ -1,231 +0,0 @@
-"""Protocol event models matching the original active-call API."""
-
-from typing import Optional, Dict, Any
-from pydantic import BaseModel, Field
-from datetime import datetime
-
-
-def current_timestamp_ms() -> int:
-    """Get current timestamp in milliseconds."""
-    return int(datetime.now().timestamp() * 1000)
-
-
-# Base Event Model
-class BaseEvent(BaseModel):
-    """Base event model."""
-
-    event: str = Field(..., description="Event type")
-    track_id: str = Field(..., description="Unique track identifier")
-    timestamp: int = Field(default_factory=current_timestamp_ms, description="Event timestamp in milliseconds")
-
-
-# Lifecycle Events
-class IncomingEvent(BaseEvent):
-    """Incoming call event (SIP only)."""
-
-    event: str = Field(default="incoming", description="Event type")
-    caller: Optional[str] = Field(default=None, description="Caller's SIP URI")
-    callee: Optional[str] = Field(default=None, description="Callee's SIP URI")
-    sdp: Optional[str] = Field(default=None, description="SDP offer from caller")
-
-
-class AnswerEvent(BaseEvent):
-    """Call answered event."""
-
-    event: str = Field(default="answer", description="Event type")
-    sdp: Optional[str] = Field(default=None, description="SDP answer from server")
-
-
-class RejectEvent(BaseEvent):
-    """Call rejected event."""
-
-    event: str = Field(default="reject", description="Event type")
-    reason: Optional[str] = Field(default=None, description="Rejection reason")
-    code: Optional[int] = Field(default=None, description="SIP response code")
-
-
-class RingingEvent(BaseEvent):
-    """Call ringing event."""
-
-    event: str = Field(default="ringing", description="Event type")
-    early_media: bool = Field(default=False, description="Early media available")
-
-
-class HangupEvent(BaseModel):
-    """Call hangup event."""
-
-    event: str = Field(default="hangup", description="Event type")
-    timestamp: int = Field(default_factory=current_timestamp_ms, description="Event timestamp")
-    reason: Optional[str] = Field(default=None, description="Hangup reason")
-    initiator: Optional[str] = Field(default=None, description="Who initiated hangup")
-    start_time: Optional[str] = Field(default=None, description="Call start time (ISO 8601)")
-    hangup_time: Optional[str] = Field(default=None, description="Hangup time (ISO 8601)")
-    answer_time: Optional[str] = Field(default=None, description="Answer time (ISO 8601)")
-    ringing_time: Optional[str] = Field(default=None, description="Ringing time (ISO 8601)")
-    from_: Optional[Dict[str, Any]] = Field(default=None, alias="from", description="Caller info")
-    to: Optional[Dict[str, Any]] = Field(default=None, description="Callee info")
-    extra: Optional[Dict[str, Any]] = Field(default=None, description="Additional metadata")
-
-    class Config:
-        populate_by_name = True
-
-
-# VAD Events
-class SpeakingEvent(BaseEvent):
-    """Speech detected event."""
-
-    event: str = Field(default="speaking", description="Event type")
-    start_time: int = Field(default_factory=current_timestamp_ms, description="Speech start time")
-
-
-class SilenceEvent(BaseEvent):
-    """Silence detected event."""
-
-    event: str = Field(default="silence", description="Event type")
-    start_time: int = Field(default_factory=current_timestamp_ms, description="Silence start time")
-    duration: int = Field(default=0, description="Silence duration in milliseconds")
-
-
-# AI/ASR Events
-class AsrFinalEvent(BaseEvent):
-    """ASR final transcription event."""
-
-    event: str = Field(default="asrFinal", description="Event type")
-    index: int = Field(..., description="ASR result sequence number")
-    start_time: Optional[int] = Field(default=None, description="Speech start time")
-    end_time: Optional[int] = Field(default=None, description="Speech end time")
-    text: str = Field(..., description="Transcribed text")
-
-
-class AsrDeltaEvent(BaseEvent):
-    """ASR partial transcription event (streaming)."""
-
-    event: str = Field(default="asrDelta", description="Event type")
-    index: int = Field(..., description="ASR result sequence number")
-    start_time: Optional[int] = Field(default=None, description="Speech start time")
-    end_time: Optional[int] = Field(default=None, description="Speech end time")
-    text: str = Field(..., description="Partial transcribed text")
-
-
-class EouEvent(BaseEvent):
-    """End of utterance detection event."""
-
-    event: str = Field(default="eou", description="Event type")
-    completed: bool = Field(default=True, description="Whether utterance was completed")
-
-
-# Audio Track Events
-class TrackStartEvent(BaseEvent):
-    """Audio track start event."""
-
-    event: str = Field(default="trackStart", description="Event type")
-    play_id: Optional[str] = Field(default=None, description="Play ID from TTS/Play command")
-
-
-class TrackEndEvent(BaseEvent):
-    """Audio track end event."""
-
-    event: str = Field(default="trackEnd", description="Event type")
-    duration: int = Field(..., description="Track duration in milliseconds")
-    ssrc: int = Field(..., description="RTP SSRC identifier")
-    play_id: Optional[str] = Field(default=None, description="Play ID from TTS/Play command")
-
-
-class InterruptionEvent(BaseEvent):
-    """Playback interruption event."""
-
-    event: str = Field(default="interruption", description="Event type")
-    play_id: Optional[str] = Field(default=None, description="Play ID that was interrupted")
-    subtitle: Optional[str] = Field(default=None, description="TTS text being played")
-    position: Optional[int] = Field(default=None, description="Word index position")
-    total_duration: Optional[int] = Field(default=None, description="Total TTS duration")
-    current: Optional[int] = Field(default=None, description="Elapsed time when interrupted")
-
-
-# System Events
-class ErrorEvent(BaseEvent):
-    """Error event."""
-
-    event: str = Field(default="error", description="Event type")
-    sender: str = Field(..., description="Component that generated the error")
-    error: str = Field(..., description="Error message")
-    code: Optional[int] = Field(default=None, description="Error code")
-
-
-class MetricsEvent(BaseModel):
-    """Performance metrics event."""
-
-    event: str = Field(default="metrics", description="Event type")
-    timestamp: int = Field(default_factory=current_timestamp_ms, description="Event timestamp")
-    key: str = Field(..., description="Metric key")
-    duration: int = Field(..., description="Duration in milliseconds")
-    data: Optional[Dict[str, Any]] = Field(default=None, description="Additional metric data")
-
-
-class AddHistoryEvent(BaseModel):
-    """Conversation history entry added event."""
-
-    event: str = Field(default="addHistory", description="Event type")
-    timestamp: int = Field(default_factory=current_timestamp_ms, description="Event timestamp")
-    sender: Optional[str] = Field(default=None, description="Component that added history")
-    speaker: str = Field(..., description="Speaker identifier")
-    text: str = Field(..., description="Conversation text")
-
-
-class DTMFEvent(BaseEvent):
-    """DTMF tone detected event."""
-
-    event: str = Field(default="dtmf", description="Event type")
-    digit: str = Field(..., description="DTMF digit (0-9, *, #, A-D)")
-
-
-class HeartBeatEvent(BaseModel):
-    """Server-to-client heartbeat to keep connection alive."""
-
-    event: str = Field(default="heartBeat", description="Event type")
-    timestamp: int = Field(default_factory=current_timestamp_ms, description="Event timestamp in milliseconds")
-
-
-# Event type mapping
-EVENT_TYPES = {
-    "incoming": IncomingEvent,
-    "answer": AnswerEvent,
-    "reject": RejectEvent,
-    "ringing": RingingEvent,
-    "hangup": HangupEvent,
-    "speaking": SpeakingEvent,
-    "silence": SilenceEvent,
-    "asrFinal": AsrFinalEvent,
-    "asrDelta": AsrDeltaEvent,
-    "eou": EouEvent,
-    "trackStart": TrackStartEvent,
-    "trackEnd": TrackEndEvent,
-    "interruption": InterruptionEvent,
-    "error": ErrorEvent,
-    "metrics": MetricsEvent,
-    "addHistory": AddHistoryEvent,
-    "dtmf": DTMFEvent,
-    "heartBeat": HeartBeatEvent,
-}
-
-
-def create_event(event_type: str, **kwargs) -> BaseModel:
-    """
-    Create an event model.
-
-    Args:
-        event_type: Type of event to create
-        **kwargs: Event fields
-
-    Returns:
-        Event model instance
-
-    Raises:
-        ValueError: If event type is unknown
-    """
-    event_class = EVENT_TYPES.get(event_type)
-
-    if not event_class:
-        raise ValueError(f"Unknown event type: {event_type}")
-
-    return event_class(event=event_type, **kwargs)
diff --git a/engine/protocol/__init__.py b/engine/protocol/__init__.py
new file mode 100644
index 0000000..311e510
--- /dev/null
+++ b/engine/protocol/__init__.py
@@ -0,0 +1 @@
+"""Protocol package."""
diff --git a/engine/protocol/ws_v1/__init__.py b/engine/protocol/ws_v1/__init__.py
new file mode 100644
index 0000000..6b76589
--- /dev/null
+++ b/engine/protocol/ws_v1/__init__.py
@@ -0,0 +1 @@
+"""WS v1 protocol package."""
diff --git a/engine/models/ws_v1.py b/engine/protocol/ws_v1/schema.py
similarity index 100%
rename from engine/models/ws_v1.py
rename to engine/protocol/ws_v1/schema.py
diff --git a/engine/providers/__init__.py b/engine/providers/__init__.py
new file mode 100644
index 0000000..2209974
--- /dev/null
+++ b/engine/providers/__init__.py
@@ -0,0 +1 @@
+"""Providers package."""
diff --git a/engine/providers/asr/__init__.py b/engine/providers/asr/__init__.py
new file mode 100644
index 0000000..2efe6a9
--- /dev/null
+++ b/engine/providers/asr/__init__.py
@@ -0,0 +1 @@
+"""ASR providers."""
diff --git a/engine/services/asr.py b/engine/providers/asr/buffered.py
similarity index 98%
rename from engine/services/asr.py
rename to engine/providers/asr/buffered.py
index 51ab584..ce1a248 100644
--- a/engine/services/asr.py
+++ b/engine/providers/asr/buffered.py
@@ -9,7 +9,7 @@ import json
 from typing import AsyncIterator, Optional
 from loguru import logger
 
-from services.base import BaseASRService, ASRResult, ServiceState
+from providers.common.base import BaseASRService, ASRResult, ServiceState
 
 # Try to import websockets for streaming ASR
 try:
diff --git a/engine/services/openai_compatible_asr.py b/engine/providers/asr/openai_compatible.py
similarity index 99%
rename from engine/services/openai_compatible_asr.py
rename to engine/providers/asr/openai_compatible.py
index 182d7a0..1a2083b 100644
--- a/engine/services/openai_compatible_asr.py
+++ b/engine/providers/asr/openai_compatible.py
@@ -19,7 +19,7 @@ except ImportError:
     AIOHTTP_AVAILABLE = False
     logger.warning("aiohttp not available - OpenAICompatibleASRService will not work")
 
-from services.base import BaseASRService, ASRResult, ServiceState
+from providers.common.base import BaseASRService, ASRResult, ServiceState
 
 
 class OpenAICompatibleASRService(BaseASRService):
diff --git a/engine/services/siliconflow_asr.py b/engine/providers/asr/siliconflow.py
similarity index 75%
rename from engine/services/siliconflow_asr.py
rename to engine/providers/asr/siliconflow.py
index 2cb95dc..d0aeb50 100644
--- a/engine/services/siliconflow_asr.py
+++ b/engine/providers/asr/siliconflow.py
@@ -1,6 +1,6 @@
 """Backward-compatible imports for legacy siliconflow_asr module."""
 
-from services.openai_compatible_asr import OpenAICompatibleASRService
+from providers.asr.openai_compatible import OpenAICompatibleASRService
 
 # Backward-compatible alias
 SiliconFlowASRService = OpenAICompatibleASRService
diff --git a/engine/providers/common/__init__.py b/engine/providers/common/__init__.py
new file mode 100644
index 0000000..8550c10
--- /dev/null
+++ b/engine/providers/common/__init__.py
@@ -0,0 +1 @@
+"""Common provider types."""
diff --git a/engine/services/base.py b/engine/providers/common/base.py
similarity index 100%
rename from engine/services/base.py
rename to engine/providers/common/base.py
diff --git a/engine/services/streaming_text.py b/engine/providers/common/streaming_text.py
similarity index 100%
rename from engine/services/streaming_text.py
rename to engine/providers/common/streaming_text.py
diff --git a/engine/providers/factory/__init__.py b/engine/providers/factory/__init__.py
new file mode 100644
index 0000000..9be8bc5
--- /dev/null
+++ b/engine/providers/factory/__init__.py
@@ -0,0 +1 @@
+"""Provider factories."""
diff --git a/engine/app/service_factory.py b/engine/providers/factory/default.py
similarity index 91%
rename from engine/app/service_factory.py
rename to engine/providers/factory/default.py
index 6bdb64c..4294d3c 100644
--- a/engine/app/service_factory.py
+++ b/engine/providers/factory/default.py
@@ -6,7 +6,7 @@ from typing import Any
 
 from loguru import logger
 
-from core.ports import (
+from runtime.ports import (
     ASRPort,
     ASRServiceSpec,
     LLMPort,
@@ -15,12 +15,12 @@ from core.ports import (
     TTSPort,
     TTSServiceSpec,
 )
-from services.asr import BufferedASRService
-from services.dashscope_tts import DashScopeTTSService
-from services.llm import MockLLMService, OpenAILLMService
-from services.openai_compatible_asr import OpenAICompatibleASRService
-from services.openai_compatible_tts import OpenAICompatibleTTSService
-from services.tts import MockTTSService
+from providers.asr.buffered import BufferedASRService
+from providers.tts.dashscope import DashScopeTTSService
+from providers.llm.openai import MockLLMService, OpenAILLMService
+from providers.asr.openai_compatible import OpenAICompatibleASRService
+from providers.tts.openai_compatible import OpenAICompatibleTTSService
+from providers.tts.mock import MockTTSService
 
 _OPENAI_COMPATIBLE_PROVIDERS = {"openai_compatible", "openai-compatible", "siliconflow"}
 _SUPPORTED_LLM_PROVIDERS = {"openai", *_OPENAI_COMPATIBLE_PROVIDERS}
diff --git a/engine/providers/llm/__init__.py b/engine/providers/llm/__init__.py
new file mode 100644
index 0000000..3258a10
--- /dev/null
+++ b/engine/providers/llm/__init__.py
@@ -0,0 +1 @@
+"""LLM providers."""
diff --git a/engine/services/llm.py b/engine/providers/llm/openai.py
similarity index 98%
rename from engine/services/llm.py
rename to engine/providers/llm/openai.py
index c4d539e..02735fe 100644
--- a/engine/services/llm.py
+++ b/engine/providers/llm/openai.py
@@ -10,8 +10,8 @@ import uuid
 from typing import AsyncIterator, Optional, List, Dict, Any, Callable, Awaitable
 from loguru import logger
 
-from app.backend_adapters import build_backend_adapter_from_settings
-from services.base import BaseLLMService, LLMMessage, LLMStreamEvent, ServiceState
+from adapters.control_plane.backend import build_backend_adapter_from_settings
+from providers.common.base import BaseLLMService, LLMMessage, LLMStreamEvent, ServiceState
 
 # Try to import openai
 try:
diff --git a/engine/providers/realtime/__init__.py b/engine/providers/realtime/__init__.py
new file mode 100644
index 0000000..0d4cb46
--- /dev/null
+++ b/engine/providers/realtime/__init__.py
@@ -0,0 +1 @@
+"""Realtime providers."""
diff --git a/engine/services/realtime.py b/engine/providers/realtime/service.py
similarity index 100%
rename from engine/services/realtime.py
rename to engine/providers/realtime/service.py
diff --git a/engine/providers/tts/__init__.py b/engine/providers/tts/__init__.py
new file mode 100644
index 0000000..531ecfa
--- /dev/null
+++ b/engine/providers/tts/__init__.py
@@ -0,0 +1 @@
+"""TTS providers."""
diff --git a/engine/services/dashscope_tts.py b/engine/providers/tts/dashscope.py
similarity index 99%
rename from engine/services/dashscope_tts.py
rename to engine/providers/tts/dashscope.py
index 1ddcbff..c0b3fdb 100644
--- a/engine/services/dashscope_tts.py
+++ b/engine/providers/tts/dashscope.py
@@ -12,7 +12,7 @@ from typing import Any, AsyncIterator, Dict, Optional, Tuple
 
 from loguru import logger
 
-from services.base import BaseTTSService, ServiceState, TTSChunk
+from providers.common.base import BaseTTSService, ServiceState, TTSChunk
 
 try:
     import dashscope
diff --git a/engine/services/tts.py b/engine/providers/tts/mock.py
similarity index 95%
rename from engine/services/tts.py
rename to engine/providers/tts/mock.py
index 0ed629d..1d1e143 100644
--- a/engine/services/tts.py
+++ b/engine/providers/tts/mock.py
@@ -5,7 +5,7 @@ from typing import AsyncIterator
 
 from loguru import logger
 
-from services.base import BaseTTSService, TTSChunk, ServiceState
+from providers.common.base import BaseTTSService, TTSChunk, ServiceState
 
 
 class MockTTSService(BaseTTSService):
diff --git a/engine/services/openai_compatible_tts.py b/engine/providers/tts/openai_compatible.py
similarity index 98%
rename from engine/services/openai_compatible_tts.py
rename to engine/providers/tts/openai_compatible.py
index 41e3e45..767ad12 100644
--- a/engine/services/openai_compatible_tts.py
+++ b/engine/providers/tts/openai_compatible.py
@@ -13,8 +13,8 @@ from typing import AsyncIterator, Optional
 from urllib.parse import urlparse, urlunparse
 from loguru import logger
 
-from services.base import BaseTTSService, TTSChunk, ServiceState
-from services.streaming_tts_adapter import StreamingTTSAdapter  # backward-compatible re-export
+from providers.common.base import BaseTTSService, TTSChunk, ServiceState
+from providers.tts.streaming_adapter import StreamingTTSAdapter  # backward-compatible re-export
 
 
 class OpenAICompatibleTTSService(BaseTTSService):
diff --git a/engine/services/siliconflow_tts.py b/engine/providers/tts/siliconflow.py
similarity index 72%
rename from engine/services/siliconflow_tts.py
rename to engine/providers/tts/siliconflow.py
index 3cdf32a..3b894d9 100644
--- a/engine/services/siliconflow_tts.py
+++ b/engine/providers/tts/siliconflow.py
@@ -1,6 +1,6 @@
 """Backward-compatible imports for legacy siliconflow_tts module."""
 
-from services.openai_compatible_tts import OpenAICompatibleTTSService, StreamingTTSAdapter
+from providers.tts.openai_compatible import OpenAICompatibleTTSService, StreamingTTSAdapter
 
 # Backward-compatible alias
 SiliconFlowTTSService = OpenAICompatibleTTSService
diff --git a/engine/services/streaming_tts_adapter.py b/engine/providers/tts/streaming_adapter.py
similarity index 95%
rename from engine/services/streaming_tts_adapter.py
rename to engine/providers/tts/streaming_adapter.py
index d4cb745..853e7ab 100644
--- a/engine/services/streaming_tts_adapter.py
+++ b/engine/providers/tts/streaming_adapter.py
@@ -4,8 +4,8 @@ import asyncio
 
 from loguru import logger
 
-from services.base import BaseTTSService
-from services.streaming_text import extract_tts_sentence, has_spoken_content
+from providers.common.base import BaseTTSService
+from providers.common.streaming_text import extract_tts_sentence, has_spoken_content
 
 
 class StreamingTTSAdapter:
diff --git a/engine/pyproject.toml b/engine/pyproject.toml
index 8786905..c0031f0 100644
--- a/engine/pyproject.toml
+++ b/engine/pyproject.toml
@@ -31,7 +31,17 @@ Issues = "https://github.com/yourusername/py-active-call-cc/issues"
 
 [tool.setuptools.packages.find]
 where = ["."]
-include = ["app*"]
+include = [
+    "app*",
+    "adapters*",
+    "protocol*",
+    "providers*",
+    "processors*",
+    "runtime*",
+    "tools*",
+    "utils*",
+    "workflow*",
+]
 exclude = ["tests*", "scripts*", "reference*"]
 
 [tool.black]
diff --git a/engine/runtime/__init__.py b/engine/runtime/__init__.py
new file mode 100644
index 0000000..1364082
--- /dev/null
+++ b/engine/runtime/__init__.py
@@ -0,0 +1 @@
+"""Runtime package."""
diff --git a/engine/core/conversation.py b/engine/runtime/conversation.py
similarity index 99%
rename from engine/core/conversation.py
rename to engine/runtime/conversation.py
index 08b23c6..fe21c01 100644
--- a/engine/core/conversation.py
+++ b/engine/runtime/conversation.py
@@ -10,7 +10,7 @@ from dataclasses import dataclass, field
 from enum import Enum
 from loguru import logger
 
-from services.base import LLMMessage
+from providers.common.base import LLMMessage
 
 
 class ConversationState(Enum):
diff --git a/engine/core/events.py b/engine/runtime/events.py
similarity index 100%
rename from engine/core/events.py
rename to engine/runtime/events.py
diff --git a/engine/runtime/history/__init__.py b/engine/runtime/history/__init__.py
new file mode 100644
index 0000000..44329ff
--- /dev/null
+++ b/engine/runtime/history/__init__.py
@@ -0,0 +1 @@
+"""Runtime history package."""
diff --git a/engine/core/history_bridge.py b/engine/runtime/history/bridge.py
similarity index 99%
rename from engine/core/history_bridge.py
rename to engine/runtime/history/bridge.py
index 70a681b..bacd682 100644
--- a/engine/core/history_bridge.py
+++ b/engine/runtime/history/bridge.py
@@ -9,7 +9,7 @@ from typing import Optional
 
 from loguru import logger
 
-from core.ports import ConversationHistoryStore
+from runtime.ports import ConversationHistoryStore
 
 
 @dataclass
diff --git a/engine/runtime/pipeline/__init__.py b/engine/runtime/pipeline/__init__.py
new file mode 100644
index 0000000..8861a22
--- /dev/null
+++ b/engine/runtime/pipeline/__init__.py
@@ -0,0 +1 @@
+"""Runtime pipeline package."""
diff --git a/engine/runtime/pipeline/asr_flow.py b/engine/runtime/pipeline/asr_flow.py
new file mode 100644
index 0000000..1b539f5
--- /dev/null
+++ b/engine/runtime/pipeline/asr_flow.py
@@ -0,0 +1,13 @@
+"""ASR flow helpers extracted from the duplex pipeline.
+
+This module is intentionally lightweight for phase-wise migration.
+"""
+
+from __future__ import annotations
+
+from providers.common.base import ASRResult
+
+
+def is_final_result(result: ASRResult) -> bool:
+    """Return whether an ASR result is final."""
+    return bool(result.is_final)
diff --git a/engine/runtime/pipeline/constants.py b/engine/runtime/pipeline/constants.py
new file mode 100644
index 0000000..0109925
--- /dev/null
+++ b/engine/runtime/pipeline/constants.py
@@ -0,0 +1,6 @@
+"""Shared constants for the runtime duplex pipeline."""
+
+TRACK_AUDIO_IN = "audio_in"
+TRACK_AUDIO_OUT = "audio_out"
+TRACK_CONTROL = "control"
+PCM_FRAME_BYTES = 640  # 16k mono pcm_s16le, 20ms
diff --git a/engine/core/duplex_pipeline.py b/engine/runtime/pipeline/duplex.py
similarity index 99%
rename from engine/core/duplex_pipeline.py
rename to engine/runtime/pipeline/duplex.py
index bbf3d47..aacd0c7 100644
--- a/engine/core/duplex_pipeline.py
+++ b/engine/runtime/pipeline/duplex.py
@@ -26,10 +26,10 @@ import aiohttp
 from loguru import logger
 
 from app.config import settings
-from app.service_factory import DefaultRealtimeServiceFactory
-from core.conversation import ConversationManager, ConversationState
-from core.events import get_event_bus
-from core.ports import (
+from providers.factory.default import DefaultRealtimeServiceFactory
+from runtime.conversation import ConversationManager, ConversationState
+from runtime.events import get_event_bus
+from runtime.ports import (
     ASRPort,
     ASRServiceSpec,
     LLMPort,
@@ -38,13 +38,13 @@ from core.ports import (
     TTSPort,
     TTSServiceSpec,
 )
-from core.tool_executor import execute_server_tool
-from core.transports import BaseTransport
-from models.ws_v1 import ev
+from tools.executor import execute_server_tool
+from runtime.transports import BaseTransport
+from protocol.ws_v1.schema import ev
 from processors.eou import EouDetector
 from processors.vad import SileroVAD, VADProcessor
-from services.base import LLMMessage, LLMStreamEvent
-from services.streaming_text import extract_tts_sentence, has_spoken_content
+from providers.common.base import LLMMessage, LLMStreamEvent
+from providers.common.streaming_text import extract_tts_sentence, has_spoken_content
 
 
 class DuplexPipeline:
diff --git a/engine/runtime/pipeline/events_out.py b/engine/runtime/pipeline/events_out.py
new file mode 100644
index 0000000..dabbafb
--- /dev/null
+++ b/engine/runtime/pipeline/events_out.py
@@ -0,0 +1,12 @@
+"""Output-event shaping helpers for the runtime pipeline."""
+
+from __future__ import annotations
+
+from typing import Any, Dict
+
+
+def assistant_text_delta_event(text: str, **extra: Any) -> Dict[str, Any]:
+    """Build a normalized assistant text delta payload."""
+    payload: Dict[str, Any] = {"type": "assistant.text.delta", "text": str(text)}
+    payload.update(extra)
+    return payload
diff --git a/engine/runtime/pipeline/interrupts.py b/engine/runtime/pipeline/interrupts.py
new file mode 100644
index 0000000..1960d56
--- /dev/null
+++ b/engine/runtime/pipeline/interrupts.py
@@ -0,0 +1,8 @@
+"""Interruption-related helpers extracted from the duplex pipeline."""
+
+from __future__ import annotations
+
+
+def should_interrupt(min_duration_ms: int, detected_ms: int) -> bool:
+    """Decide whether interruption conditions are met."""
+    return int(detected_ms) >= max(0, int(min_duration_ms))
diff --git a/engine/runtime/pipeline/llm_flow.py b/engine/runtime/pipeline/llm_flow.py
new file mode 100644
index 0000000..d938fb0
--- /dev/null
+++ b/engine/runtime/pipeline/llm_flow.py
@@ -0,0 +1,13 @@
+"""LLM flow helpers extracted from the duplex pipeline.
+
+This module is intentionally lightweight for phase-wise migration.
+"""
+
+from __future__ import annotations
+
+from providers.common.base import LLMStreamEvent
+
+
+def is_done_event(event: LLMStreamEvent) -> bool:
+    """Return whether an LLM stream event signals completion."""
+    return str(event.type) == "done"
diff --git a/engine/runtime/pipeline/tooling.py b/engine/runtime/pipeline/tooling.py
new file mode 100644
index 0000000..459dceb
--- /dev/null
+++ b/engine/runtime/pipeline/tooling.py
@@ -0,0 +1,13 @@
+"""Tooling helpers extracted from the duplex pipeline."""
+
+from __future__ import annotations
+
+from typing import Any
+
+
+def normalize_tool_name(name: Any, aliases: dict[str, str]) -> str:
+    """Normalize tool name with alias mapping."""
+    normalized = str(name or "").strip()
+    if not normalized:
+        return ""
+    return aliases.get(normalized, normalized)
diff --git a/engine/runtime/pipeline/tts_flow.py b/engine/runtime/pipeline/tts_flow.py
new file mode 100644
index 0000000..156547e
--- /dev/null
+++ b/engine/runtime/pipeline/tts_flow.py
@@ -0,0 +1,15 @@
+"""TTS flow helpers extracted from the duplex pipeline.
+
+This module is intentionally lightweight for phase-wise migration.
+"""
+
+from __future__ import annotations
+
+from providers.common.base import TTSChunk
+
+
+def chunk_duration_ms(chunk: TTSChunk) -> float:
+    """Estimate chunk duration in milliseconds for pcm16 mono."""
+    if chunk.sample_rate <= 0:
+        return 0.0
+    return (len(chunk.audio) / 2.0 / float(chunk.sample_rate)) * 1000.0
diff --git a/engine/core/ports/__init__.py b/engine/runtime/ports/__init__.py
similarity index 56%
rename from engine/core/ports/__init__.py
rename to engine/runtime/ports/__init__.py
index 2ae96c4..a7cbce3 100644
--- a/engine/core/ports/__init__.py
+++ b/engine/runtime/ports/__init__.py
@@ -1,16 +1,16 @@
-"""Port interfaces for engine-side integration boundaries."""
+"""Port interfaces for runtime integration boundaries."""
 
-from core.ports.asr import ASRBufferControl, ASRInterimControl, ASRPort, ASRServiceSpec
-from core.ports.control_plane import (
+from runtime.ports.asr import ASRBufferControl, ASRInterimControl, ASRPort, ASRServiceSpec
+from runtime.ports.control_plane import (
     AssistantRuntimeConfigProvider,
     ControlPlaneGateway,
     ConversationHistoryStore,
     KnowledgeRetriever,
     ToolCatalog,
 )
-from core.ports.llm import LLMCancellable, LLMPort, LLMRuntimeConfigurable, LLMServiceSpec
-from core.ports.service_factory import RealtimeServiceFactory
-from core.ports.tts import TTSPort, TTSServiceSpec
+from runtime.ports.llm import LLMCancellable, LLMPort, LLMRuntimeConfigurable, LLMServiceSpec
+from runtime.ports.service_factory import RealtimeServiceFactory
+from runtime.ports.tts import TTSPort, TTSServiceSpec
 
 __all__ = [
     "ASRPort",
diff --git a/engine/core/ports/asr.py b/engine/runtime/ports/asr.py
similarity index 97%
rename from engine/core/ports/asr.py
rename to engine/runtime/ports/asr.py
index fa302cd..8621ed0 100644
--- a/engine/core/ports/asr.py
+++ b/engine/runtime/ports/asr.py
@@ -5,7 +5,7 @@ from __future__ import annotations
 from dataclasses import dataclass
 from typing import AsyncIterator, Awaitable, Callable, Optional, Protocol
 
-from services.base import ASRResult
+from providers.common.base import ASRResult
 
 TranscriptCallback = Callable[[str, bool], Awaitable[None]]
 
diff --git a/engine/core/ports/control_plane.py b/engine/runtime/ports/control_plane.py
similarity index 100%
rename from engine/core/ports/control_plane.py
rename to engine/runtime/ports/control_plane.py
diff --git a/engine/core/ports/llm.py b/engine/runtime/ports/llm.py
similarity index 96%
rename from engine/core/ports/llm.py
rename to engine/runtime/ports/llm.py
index ca515ac..a591985 100644
--- a/engine/core/ports/llm.py
+++ b/engine/runtime/ports/llm.py
@@ -5,7 +5,7 @@ from __future__ import annotations
 from dataclasses import dataclass, field
 from typing import Any, AsyncIterator, Awaitable, Callable, Dict, List, Optional, Protocol
 
-from services.base import LLMMessage, LLMStreamEvent
+from providers.common.base import LLMMessage, LLMStreamEvent
 
 KnowledgeRetrieverFn = Callable[..., Awaitable[List[Dict[str, Any]]]]
 
diff --git a/engine/core/ports/service_factory.py b/engine/runtime/ports/service_factory.py
similarity index 79%
rename from engine/core/ports/service_factory.py
rename to engine/runtime/ports/service_factory.py
index d1d8476..7ce8b77 100644
--- a/engine/core/ports/service_factory.py
+++ b/engine/runtime/ports/service_factory.py
@@ -4,9 +4,9 @@ from __future__ import annotations
 
 from typing import Protocol
 
-from core.ports.asr import ASRPort, ASRServiceSpec
-from core.ports.llm import LLMPort, LLMServiceSpec
-from core.ports.tts import TTSPort, TTSServiceSpec
+from runtime.ports.asr import ASRPort, ASRServiceSpec
+from runtime.ports.llm import LLMPort, LLMServiceSpec
+from runtime.ports.tts import TTSPort, TTSServiceSpec
 
 
 class RealtimeServiceFactory(Protocol):
diff --git a/engine/core/ports/tts.py b/engine/runtime/ports/tts.py
similarity index 96%
rename from engine/core/ports/tts.py
rename to engine/runtime/ports/tts.py
index 0693cdb..523dc3c 100644
--- a/engine/core/ports/tts.py
+++ b/engine/runtime/ports/tts.py
@@ -5,7 +5,7 @@ from __future__ import annotations
 from dataclasses import dataclass
 from typing import AsyncIterator, Optional, Protocol
 
-from services.base import TTSChunk
+from providers.common.base import TTSChunk
 
 
 @dataclass(frozen=True)
diff --git a/engine/runtime/session/__init__.py b/engine/runtime/session/__init__.py
new file mode 100644
index 0000000..d224fb9
--- /dev/null
+++ b/engine/runtime/session/__init__.py
@@ -0,0 +1 @@
+"""Runtime session package."""
diff --git a/engine/runtime/session/lifecycle.py b/engine/runtime/session/lifecycle.py
new file mode 100644
index 0000000..9fd8ebf
--- /dev/null
+++ b/engine/runtime/session/lifecycle.py
@@ -0,0 +1,10 @@
+"""Lifecycle helper utilities for runtime sessions."""
+
+from __future__ import annotations
+
+from datetime import datetime, timezone
+
+
+def utc_now_iso() -> str:
+    """Return current UTC timestamp in ISO 8601 format."""
+    return datetime.now(timezone.utc).isoformat()
diff --git a/engine/core/session.py b/engine/runtime/session/manager.py
similarity index 98%
rename from engine/core/session.py
rename to engine/runtime/session/manager.py
index eff77a6..1f65ea7 100644
--- a/engine/core/session.py
+++ b/engine/runtime/session/manager.py
@@ -9,22 +9,22 @@ from enum import Enum
 from typing import Optional, Dict, Any, List
 from loguru import logger
 
-from app.backend_adapters import build_backend_adapter_from_settings
-from core.transports import BaseTransport
-from core.ports import (
+from adapters.control_plane.backend import build_backend_adapter_from_settings
+from runtime.transports import BaseTransport
+from runtime.ports import (
     AssistantRuntimeConfigProvider,
     ControlPlaneGateway,
     ConversationHistoryStore,
     KnowledgeRetriever,
     ToolCatalog,
 )
-from core.duplex_pipeline import DuplexPipeline
-from core.conversation import ConversationTurn
-from core.history_bridge import SessionHistoryBridge
-from core.workflow_runner import WorkflowRunner, WorkflowTransition, WorkflowNodeDef, WorkflowEdgeDef
+from runtime.pipeline.duplex import DuplexPipeline
+from runtime.conversation import ConversationTurn
+from runtime.history.bridge import SessionHistoryBridge
+from workflow.runner import WorkflowRunner, WorkflowTransition, WorkflowNodeDef, WorkflowEdgeDef
 from app.config import settings
-from services.base import LLMMessage
-from models.ws_v1 import (
+from providers.common.base import LLMMessage
+from protocol.ws_v1.schema import (
     parse_client_message,
     ev,
     SessionStartMessage,
diff --git a/engine/runtime/session/metadata.py b/engine/runtime/session/metadata.py
new file mode 100644
index 0000000..ab32971
--- /dev/null
+++ b/engine/runtime/session/metadata.py
@@ -0,0 +1,9 @@
+"""Metadata helpers extracted from session manager."""
+
+from __future__ import annotations
+
+import re
+from typing import Pattern
+
+DYNAMIC_VARIABLE_KEY_RE: Pattern[str] = re.compile(r"^[a-zA-Z_][a-zA-Z0-9_]{0,63}$")
+DYNAMIC_VARIABLE_PLACEHOLDER_RE: Pattern[str] = re.compile(r"\{\{\s*([a-zA-Z_][a-zA-Z0-9_]*)\s*\}\}")
diff --git a/engine/runtime/session/workflow_bridge.py b/engine/runtime/session/workflow_bridge.py
new file mode 100644
index 0000000..e03d939
--- /dev/null
+++ b/engine/runtime/session/workflow_bridge.py
@@ -0,0 +1,12 @@
+"""Workflow bridge helpers for runtime session orchestration."""
+
+from __future__ import annotations
+
+from typing import Optional
+
+from workflow.runner import WorkflowRunner
+
+
+def has_active_workflow(workflow_runner: Optional[WorkflowRunner]) -> bool:
+    """Return whether a workflow runner exists and has a current node."""
+    return bool(workflow_runner and workflow_runner.current_node is not None)
diff --git a/engine/core/transports.py b/engine/runtime/transports.py
similarity index 100%
rename from engine/core/transports.py
rename to engine/runtime/transports.py
diff --git a/engine/services/__init__.py b/engine/services/__init__.py
deleted file mode 100644
index f64ef05..0000000
--- a/engine/services/__init__.py
+++ /dev/null
@@ -1,52 +0,0 @@
-"""AI Services package.
-
-Provides ASR, LLM, TTS, and Realtime API services for voice conversation.
-"""
-
-from services.base import (
-    ServiceState,
-    ASRResult,
-    LLMMessage,
-    TTSChunk,
-    BaseASRService,
-    BaseLLMService,
-    BaseTTSService,
-)
-from services.llm import OpenAILLMService, MockLLMService
-from services.dashscope_tts import DashScopeTTSService
-from services.tts import MockTTSService
-from services.asr import BufferedASRService, MockASRService
-from services.openai_compatible_asr import OpenAICompatibleASRService, SiliconFlowASRService
-from services.openai_compatible_tts import OpenAICompatibleTTSService, SiliconFlowTTSService
-from services.streaming_tts_adapter import StreamingTTSAdapter
-from services.realtime import RealtimeService, RealtimeConfig, RealtimePipeline
-
-__all__ = [
-    # Base classes
-    "ServiceState",
-    "ASRResult",
-    "LLMMessage",
-    "TTSChunk",
-    "BaseASRService",
-    "BaseLLMService",
-    "BaseTTSService",
-    # LLM
-    "OpenAILLMService",
-    "MockLLMService",
-    # TTS
-    "DashScopeTTSService",
-    "MockTTSService",
-    # ASR
-    "BufferedASRService",
-    "MockASRService",
-    "OpenAICompatibleASRService",
-    "SiliconFlowASRService",
-    # TTS (SiliconFlow)
-    "OpenAICompatibleTTSService",
-    "SiliconFlowTTSService",
-    "StreamingTTSAdapter",
-    # Realtime
-    "RealtimeService",
-    "RealtimeConfig",
-    "RealtimePipeline",
-]
diff --git a/engine/tests/test_backend_adapters.py b/engine/tests/test_backend_adapters.py
index 347df45..70f569e 100644
--- a/engine/tests/test_backend_adapters.py
+++ b/engine/tests/test_backend_adapters.py
@@ -1,7 +1,7 @@
 import aiohttp
 import pytest
 
-from app.backend_adapters import (
+from adapters.control_plane.backend import (
     AssistantConfigSourceAdapter,
     LocalYamlAssistantConfigAdapter,
     build_backend_adapter,
@@ -120,7 +120,7 @@ async def test_http_backend_adapter_create_call_record_posts_expected_payload(mo
                 },
             )
 
-    monkeypatch.setattr("app.backend_adapters.aiohttp.ClientSession", _FakeClientSession)
+    monkeypatch.setattr("adapters.control_plane.backend.aiohttp.ClientSession", _FakeClientSession)
 
     config_dir = tmp_path / "assistants"
     config_dir.mkdir(parents=True, exist_ok=True)
@@ -198,7 +198,7 @@ async def test_with_backend_url_uses_backend_for_assistant_config(monkeypatch, t
             _ = (url, json)
             return _FakeResponse(status=200, payload={"id": "call_1"})
 
-    monkeypatch.setattr("app.backend_adapters.aiohttp.ClientSession", _FakeClientSession)
+    monkeypatch.setattr("adapters.control_plane.backend.aiohttp.ClientSession", _FakeClientSession)
 
     config_dir = tmp_path / "assistants"
     config_dir.mkdir(parents=True, exist_ok=True)
@@ -234,7 +234,7 @@ async def test_backend_mode_disabled_uses_local_assistant_config_even_with_url(m
             _ = timeout
             raise AssertionError("HTTP client should not be created when backend_mode=disabled")
 
-    monkeypatch.setattr("app.backend_adapters.aiohttp.ClientSession", _FailIfCalledClientSession)
+    monkeypatch.setattr("adapters.control_plane.backend.aiohttp.ClientSession", _FailIfCalledClientSession)
 
     config_dir = tmp_path / "assistants"
     config_dir.mkdir(parents=True, exist_ok=True)
diff --git a/engine/tests/test_dynamic_variables.py b/engine/tests/test_dynamic_variables.py
index f7982c7..d6744af 100644
--- a/engine/tests/test_dynamic_variables.py
+++ b/engine/tests/test_dynamic_variables.py
@@ -1,4 +1,4 @@
-from core.session import Session
+from runtime.session.manager import Session
 
 
 def _session() -> Session:
diff --git a/engine/tests/test_history_bridge.py b/engine/tests/test_history_bridge.py
index 2f9dd80..d70fa6e 100644
--- a/engine/tests/test_history_bridge.py
+++ b/engine/tests/test_history_bridge.py
@@ -3,7 +3,7 @@ import time
 
 import pytest
 
-from core.history_bridge import SessionHistoryBridge
+from runtime.history.bridge import SessionHistoryBridge
 
 
 class _FakeHistoryWriter:
diff --git a/engine/tests/test_tool_call_flow.py b/engine/tests/test_tool_call_flow.py
index 11a7b77..d820643 100644
--- a/engine/tests/test_tool_call_flow.py
+++ b/engine/tests/test_tool_call_flow.py
@@ -4,10 +4,10 @@ from typing import Any, Dict, List
 
 import pytest
 
-from core.conversation import ConversationState
-from core.duplex_pipeline import DuplexPipeline
-from models.ws_v1 import OutputAudioPlayedMessage, ToolCallResultsMessage, parse_client_message
-from services.base import LLMStreamEvent
+from runtime.conversation import ConversationState
+from runtime.pipeline.duplex import DuplexPipeline
+from protocol.ws_v1.schema import OutputAudioPlayedMessage, ToolCallResultsMessage, parse_client_message
+from providers.common.base import LLMStreamEvent
 
 
 class _DummySileroVAD:
@@ -86,9 +86,9 @@ class _CaptureGenerateLLM:
 
 
 def _build_pipeline(monkeypatch, llm_rounds: List[List[LLMStreamEvent]]) -> tuple[DuplexPipeline, List[Dict[str, Any]]]:
-    monkeypatch.setattr("core.duplex_pipeline.SileroVAD", _DummySileroVAD)
-    monkeypatch.setattr("core.duplex_pipeline.VADProcessor", _DummyVADProcessor)
-    monkeypatch.setattr("core.duplex_pipeline.EouDetector", _DummyEouDetector)
+    monkeypatch.setattr("runtime.pipeline.duplex.SileroVAD", _DummySileroVAD)
+    monkeypatch.setattr("runtime.pipeline.duplex.VADProcessor", _DummyVADProcessor)
+    monkeypatch.setattr("runtime.pipeline.duplex.EouDetector", _DummyEouDetector)
 
     pipeline = DuplexPipeline(
         transport=_FakeTransport(),
@@ -112,7 +112,7 @@ def _build_pipeline(monkeypatch, llm_rounds: List[List[LLMStreamEvent]]) -> tupl
 
 def test_pipeline_uses_default_tools_from_settings(monkeypatch):
     monkeypatch.setattr(
-        "core.duplex_pipeline.settings.tools",
+        "runtime.pipeline.duplex.settings.tools",
         [
             "current_time",
             "calculator",
@@ -141,7 +141,7 @@ def test_pipeline_uses_default_tools_from_settings(monkeypatch):
 
 
 def test_pipeline_exposes_unknown_string_tools_with_fallback_schema(monkeypatch):
-    monkeypatch.setattr("core.duplex_pipeline.settings.tools", ["custom_system_cmd"])
+    monkeypatch.setattr("runtime.pipeline.duplex.settings.tools", ["custom_system_cmd"])
     pipeline, _events = _build_pipeline(monkeypatch, [[LLMStreamEvent(type="done")]])
 
     schemas = pipeline._resolved_tool_schemas()
@@ -151,7 +151,7 @@ def test_pipeline_exposes_unknown_string_tools_with_fallback_schema(monkeypatch)
 
 
 def test_pipeline_assigns_default_client_executor_for_system_string_tools(monkeypatch):
-    monkeypatch.setattr("core.duplex_pipeline.settings.tools", ["increase_volume"])
+    monkeypatch.setattr("runtime.pipeline.duplex.settings.tools", ["increase_volume"])
     pipeline, _events = _build_pipeline(monkeypatch, [[LLMStreamEvent(type="done")]])
 
     tool_call = {
@@ -221,9 +221,9 @@ async def test_pipeline_applies_default_args_to_tool_call(monkeypatch):
 
 @pytest.mark.asyncio
 async def test_generated_opener_prompt_uses_system_prompt_only(monkeypatch):
-    monkeypatch.setattr("core.duplex_pipeline.SileroVAD", _DummySileroVAD)
-    monkeypatch.setattr("core.duplex_pipeline.VADProcessor", _DummyVADProcessor)
-    monkeypatch.setattr("core.duplex_pipeline.EouDetector", _DummyEouDetector)
+    monkeypatch.setattr("runtime.pipeline.duplex.SileroVAD", _DummySileroVAD)
+    monkeypatch.setattr("runtime.pipeline.duplex.VADProcessor", _DummyVADProcessor)
+    monkeypatch.setattr("runtime.pipeline.duplex.EouDetector", _DummyEouDetector)
 
     llm = _CaptureGenerateLLM("你好")
     pipeline = DuplexPipeline(
@@ -662,7 +662,7 @@ async def test_server_tool_timeout_emits_504_and_continues(monkeypatch):
             "status": {"code": 200, "message": "ok"},
         }
 
-    monkeypatch.setattr("core.duplex_pipeline.execute_server_tool", _slow_execute)
+    monkeypatch.setattr("runtime.pipeline.duplex.execute_server_tool", _slow_execute)
 
     pipeline, events = _build_pipeline(
         monkeypatch,
diff --git a/engine/tests/test_tool_executor.py b/engine/tests/test_tool_executor.py
index 17345c7..aada0c1 100644
--- a/engine/tests/test_tool_executor.py
+++ b/engine/tests/test_tool_executor.py
@@ -1,6 +1,6 @@
 import pytest
 
-from core.tool_executor import execute_server_tool
+from tools.executor import execute_server_tool
 
 
 @pytest.mark.asyncio
@@ -38,7 +38,7 @@ async def test_current_time_uses_local_system_clock(monkeypatch):
     async def _should_not_be_called(_tool_id):
         raise AssertionError("fetch_tool_resource should not be called for current_time")
 
-    monkeypatch.setattr("core.tool_executor.fetch_tool_resource", _should_not_be_called)
+    monkeypatch.setattr("tools.executor.fetch_tool_resource", _should_not_be_called)
 
     result = await execute_server_tool(
         {
diff --git a/engine/tests/test_ws_protocol_session_start.py b/engine/tests/test_ws_protocol_session_start.py
index ad68674..e055c75 100644
--- a/engine/tests/test_ws_protocol_session_start.py
+++ b/engine/tests/test_ws_protocol_session_start.py
@@ -1,7 +1,7 @@
 import pytest
 
-from core.session import Session, WsSessionState
-from models.ws_v1 import OutputAudioPlayedMessage, SessionStartMessage, parse_client_message
+from runtime.session.manager import Session, WsSessionState
+from protocol.ws_v1.schema import OutputAudioPlayedMessage, SessionStartMessage, parse_client_message
 
 
 def _session() -> Session:
@@ -194,7 +194,7 @@ async def test_handle_session_start_requires_assistant_id_and_closes_transport()
 
 @pytest.mark.asyncio
 async def test_handle_session_start_applies_whitelisted_overrides_and_ignores_workflow(monkeypatch):
-    monkeypatch.setattr("core.session.settings.ws_emit_config_resolved", False)
+    monkeypatch.setattr("runtime.session.manager.settings.ws_emit_config_resolved", False)
 
     session = Session.__new__(Session)
     session.id = "sess_start_ok"
@@ -289,9 +289,9 @@ async def test_handle_session_start_applies_whitelisted_overrides_and_ignores_wo
 
 @pytest.mark.asyncio
 async def test_handle_session_start_emits_config_resolved_when_enabled(monkeypatch):
-    monkeypatch.setattr("core.session.settings.ws_emit_config_resolved", True)
-    monkeypatch.setattr("core.session.settings.ws_protocol_version", "v1-custom")
-    monkeypatch.setattr("core.session.settings.default_codec", "pcmu")
+    monkeypatch.setattr("runtime.session.manager.settings.ws_emit_config_resolved", True)
+    monkeypatch.setattr("runtime.session.manager.settings.ws_protocol_version", "v1-custom")
+    monkeypatch.setattr("runtime.session.manager.settings.default_codec", "pcmu")
 
     session = Session.__new__(Session)
     session.id = "sess_start_emit_config"
@@ -385,8 +385,8 @@ async def test_handle_session_start_emits_config_resolved_when_enabled(monkeypat
 
 @pytest.mark.asyncio
 async def test_handle_audio_uses_chunk_size_for_frame_validation(monkeypatch):
-    monkeypatch.setattr("core.session.settings.sample_rate", 16000)
-    monkeypatch.setattr("core.session.settings.chunk_size_ms", 10)
+    monkeypatch.setattr("runtime.session.manager.settings.sample_rate", 16000)
+    monkeypatch.setattr("runtime.session.manager.settings.chunk_size_ms", 10)
 
     session = Session.__new__(Session)
     session.id = "sess_chunk_frame"
diff --git a/engine/tools/__init__.py b/engine/tools/__init__.py
new file mode 100644
index 0000000..29a67f0
--- /dev/null
+++ b/engine/tools/__init__.py
@@ -0,0 +1 @@
+"""Tools package."""
diff --git a/engine/core/tool_executor.py b/engine/tools/executor.py
similarity index 99%
rename from engine/core/tool_executor.py
rename to engine/tools/executor.py
index 899d930..0049cbc 100644
--- a/engine/core/tool_executor.py
+++ b/engine/tools/executor.py
@@ -8,7 +8,7 @@ from typing import Any, Awaitable, Callable, Dict, Optional
 
 import aiohttp
 
-from app.backend_adapters import build_backend_adapter_from_settings
+from adapters.control_plane.backend import build_backend_adapter_from_settings
 
 ToolResourceFetcher = Callable[[str], Awaitable[Optional[Dict[str, Any]]]]
 
diff --git a/engine/workflow/__init__.py b/engine/workflow/__init__.py
new file mode 100644
index 0000000..35ffe2e
--- /dev/null
+++ b/engine/workflow/__init__.py
@@ -0,0 +1 @@
+"""Workflow package."""
diff --git a/engine/core/workflow_runner.py b/engine/workflow/runner.py
similarity index 100%
rename from engine/core/workflow_runner.py
rename to engine/workflow/runner.py