diff --git a/backend/package/yuxi/channels/adapters/signal/__init__.py b/backend/package/yuxi/channels/adapters/signal/__init__.py
index c7f002dc..506185b2 100644
--- a/backend/package/yuxi/channels/adapters/signal/__init__.py
+++ b/backend/package/yuxi/channels/adapters/signal/__init__.py
@@ -1,13 +1,15 @@
-from yuxi.channels.registry import register_builtin_adapter
+from yuxi.channels.adapters.signal import (
+    daemon,  # noqa: F401
+    entity_cache,  # noqa: F401
+    event_queue,  # noqa: F401
+    exec_auth,  # noqa: F401
+    monitor,  # noqa: F401
+    normalize,  # noqa: F401
+    security,  # noqa: F401
+    send,  # noqa: F401
+    sse_reconnect,  # noqa: F401
+)
 from yuxi.channels.adapters.signal.channel import SignalChannel
-from yuxi.channels.adapters.signal import send  # noqa: F401
-from yuxi.channels.adapters.signal import monitor  # noqa: F401
-from yuxi.channels.adapters.signal import daemon  # noqa: F401
-from yuxi.channels.adapters.signal import security  # noqa: F401
-from yuxi.channels.adapters.signal import exec_auth  # noqa: F401
-from yuxi.channels.adapters.signal import sse_reconnect  # noqa: F401
-from yuxi.channels.adapters.signal import normalize  # noqa: F401
-from yuxi.channels.adapters.signal import event_queue  # noqa: F401
-from yuxi.channels.adapters.signal import entity_cache  # noqa: F401
+from yuxi.channels.registry import register_builtin_adapter
 
-register_builtin_adapter(SignalChannel)
\ No newline at end of file
+register_builtin_adapter(SignalChannel)
diff --git a/backend/package/yuxi/channels/adapters/signal/channel.py b/backend/package/yuxi/channels/adapters/signal/channel.py
index 3a3868f5..4f3c5c53 100644
--- a/backend/package/yuxi/channels/adapters/signal/channel.py
+++ b/backend/package/yuxi/channels/adapters/signal/channel.py
@@ -10,18 +10,6 @@ from typing import Any, ClassVar
 
 import aiohttp
 
-from yuxi.channels.base import BaseChannelAdapter
-from yuxi.channels.infra.circuit_breaker import CircuitBreaker, CircuitBreakerOpenError
-from yuxi.channels.models import (
-    ChannelMessage,
-    ChannelResponse,
-    ChannelStatus,
-    ChannelType,
-    ChatType,
-    DeliveryResult,
-    HealthStatus,
-    MessageType,
-)
 from yuxi.channels.adapters.signal.accounts import (
     list_enabled_signal_accounts,
 )
@@ -42,13 +30,31 @@ from yuxi.channels.adapters.signal.normalize import (
     parse_signal_receipt,
 )
 from yuxi.channels.adapters.signal.reaction_level import ReactionLevelController
-from yuxi.channels.adapters.signal.send import SignalSender
 from yuxi.channels.adapters.signal.security import SignalSecurityPolicy
+from yuxi.channels.adapters.signal.send import SignalSender
+from yuxi.channels.adapters.signal.streaming import (
+    STREAM_BUFFER_MAX_ENTRIES,
+    STREAM_BUFFER_TTL,
+    StreamBuffer,
+    StreamCoalescer,
+)
+from yuxi.channels.base import BaseChannelAdapter
+from yuxi.channels.capabilities import ChannelCapabilities
+from yuxi.channels.infra.circuit_breaker import CircuitBreaker, CircuitBreakerOpenError
+from yuxi.channels.meta import ChannelMeta
+from yuxi.channels.models import (
+    ChannelMessage,
+    ChannelResponse,
+    ChannelStatus,
+    ChannelType,
+    ChatType,
+    DeliveryResult,
+    HealthStatus,
+    MessageType,
+)
 
 logger = logging.getLogger(__name__)
 
-STREAM_BUFFER_MAX_ENTRIES = 100
-STREAM_BUFFER_TTL = 300
 DAEMON_STARTUP_TIMEOUT_MS = 30000
 
 
@@ -61,6 +67,37 @@ class SignalChannel(BaseChannelAdapter):
     streaming_modes: ClassVar[list[str]] = ["off", "block", "progress"]
     max_media_size_mb: ClassVar[int] = 100
 
+    capabilities = ChannelCapabilities(
+        chat_types=["direct", "group"],
+        reactions=True,
+        edit=True,
+        unsend=True,
+        reply=True,
+        media=True,
+        pin=True,
+        unpin=True,
+        native_commands=True,
+        supports_markdown=True,
+        supports_streaming=True,
+        streaming_modes=["off", "block", "progress"],
+        text_chunk_limit=4000,
+        max_media_size_mb=100,
+        typing=True,
+        send_ephemeral=True,
+        block_streaming=True,
+        group_management=False,
+        threads=False,
+        polls=False,
+    )
+
+    meta = ChannelMeta(
+        id="signal",
+        label="Signal",
+        aliases=["signal"],
+        markdown_capable=True,
+        selection_label="Signal (signal-cli REST API)",
+    )
+
     def __init__(self, config: dict[str, Any] | None = None):
         super().__init__(config)
         self._status = ChannelStatus.DISCONNECTED
@@ -71,7 +108,6 @@ class SignalChannel(BaseChannelAdapter):
         self._account_number: str = ""
         self._account_uuid: str | None = None
         self._supports_edit: bool = False
-        self._stream_buffer: dict[str, tuple[str, float]] = {}
         self._security: SignalSecurityPolicy | None = None
         self._circuit_breaker = CircuitBreaker(failure_threshold=5, recovery_timeout=60)
         self._enabled = self.config.get("enabled", True)
@@ -84,6 +120,17 @@ class SignalChannel(BaseChannelAdapter):
         coalesce_cfg = self.config.get("block_streaming_coalesce", {})
         self._stream_coalesce_min_chars: int = coalesce_cfg.get("min_chars", 1500)
         self._stream_coalesce_idle_ms: int = coalesce_cfg.get("idle_ms", 1000)
+        self._stream_buffer = StreamBuffer(
+            max_entries=STREAM_BUFFER_MAX_ENTRIES,
+            ttl=STREAM_BUFFER_TTL,
+        )
+        self._lane_separator = self.config.get("lane_separator", "---")
+        self._stream_coalescer = StreamCoalescer(
+            buffer=self._stream_buffer,
+            min_chars=self._stream_coalesce_min_chars,
+            idle_ms=self._stream_coalesce_idle_ms,
+            lane_separator=self._lane_separator,
+        )
         reaction_level = self.config.get("reaction_level", "minimal")
         self._reaction_controller = ReactionLevelController(reaction_level)
         self._state_change_handlers: list[Callable[[ChannelStatus], Awaitable[None]]] = []
@@ -103,7 +150,6 @@ class SignalChannel(BaseChannelAdapter):
         self._audit_enabled = self.config.get("audit", {}).get("enabled", False)
         ai_vision_cfg = self.config.get("ai_vision", {})
         self._ai_vision_enabled = ai_vision_cfg.get("enabled", False)
-        self._lane_separator = self.config.get("lane_separator", "---")
         self._warned_once: set[str] = set()
         self._vision_analyzer = MediaVisionAnalyzer(
             llm_call_fn=self.config.get("vision_llm_call"),
@@ -115,6 +161,26 @@ class SignalChannel(BaseChannelAdapter):
             self._warned_once.add(key)
             logger.warning(f"[Signal] {message}")
 
+    def _validate_config(self) -> None:
+        errors = []
+
+        accounts = list_enabled_signal_accounts(self.config)
+        for account in accounts:
+            if not account.get("signal_number"):
+                errors.append(f"signal_number is required for account {account}")
+
+        command_double_auth = self.config.get("command_double_auth", False)
+        security_cfg = self.config.get("security", {})
+        require_mention = security_cfg.get("require_mention", False)
+        if command_double_auth and not require_mention:
+            logger.warning(
+                "command_double_auth is enabled but require_mention is disabled; "
+                "commands in groups will not trigger mention check"
+            )
+
+        if errors:
+            raise ValueError(f"Signal config validation failed: {'; '.join(errors)}")
+
     def on_state_change(self, handler: Callable[[ChannelStatus], Awaitable[None]]) -> None:
         self._state_change_handlers.append(handler)
 
@@ -151,6 +217,8 @@ class SignalChannel(BaseChannelAdapter):
             self._status = ChannelStatus.DISABLED
             return
 
+        self._validate_config()
+
         self._status = ChannelStatus.CONNECTING
         logger.info(f"[Signal] Starting channel '{self.config.get('name', self.channel_id)}'")
 
@@ -562,42 +630,67 @@ class SignalChannel(BaseChannelAdapter):
             duration_ms=duration_ms,
         )
 
+    async def create_group(self, group_name: str, members: list[str]) -> DeliveryResult:
+        if not self._sender:
+            return DeliveryResult(success=False, error="Sender not initialized")
+        return await self._call_with_cb(
+            self._sender.create_group,
+            group_name=group_name,
+            members=members,
+        )
+
+    async def delete_group(self, group_id: str) -> DeliveryResult:
+        if not self._sender:
+            return DeliveryResult(success=False, error="Sender not initialized")
+        return await self._call_with_cb(
+            self._sender.delete_group,
+            group_id=group_id,
+        )
+
+    async def manage_group_members(
+        self, group_id: str, add: list[str] | None = None, remove: list[str] | None = None
+    ) -> DeliveryResult:
+        if not self._sender:
+            return DeliveryResult(success=False, error="Sender not initialized")
+        return await self._call_with_cb(
+            self._sender.manage_members,
+            group_id=group_id,
+            add=add,
+            remove=remove,
+        )
+
     async def send_stream_chunk(self, chat_id: str, msg_id: str, chunk: str, finished: bool) -> DeliveryResult:
         if not self._sender or not self._rpc_client:
             return DeliveryResult(success=False, error="Not initialized")
 
-        if "lane:reasoning:" in chunk:
+        if self._stream_coalescer.is_reasoning_chunk(chunk):
             return await self._handle_reasoning_chunk(chat_id, msg_id, chunk, finished)
 
         block_streaming = self.config.get("block_streaming", False)
         if block_streaming:
             return await self._flush_stream(chat_id, msg_id, chunk, finished)
 
-        now = time.monotonic()
-        buffered, last_ts = self._stream_buffer.get(chat_id, ("", 0))
-
-        idle_ms = (now - last_ts) * 1000 if last_ts else 0
-        if buffered and idle_ms >= self._stream_coalesce_idle_ms:
+        if self._stream_coalescer.should_flush_on_idle(chat_id):
+            buffered = self._stream_buffer.pop(chat_id) or ""
             flushed = await self._flush_stream(chat_id, msg_id, buffered, False)
             if not flushed.success:
                 return flushed
-            buffered = ""
 
-        accumulated = buffered + chunk
+        self._stream_buffer.set(chat_id, self._stream_buffer.get(chat_id) + chunk)
 
-        if finished or len(accumulated) >= self._stream_coalesce_min_chars:
-            self._stream_buffer.pop(chat_id, None)
+        if finished or self._stream_coalescer.should_flush_on_size(chat_id):
+            accumulated = self._stream_buffer.pop(chat_id) or ""
+            self._stream_buffer.prune()
             return await self._flush_stream(chat_id, msg_id, accumulated, finished)
 
-        self._stream_buffer[chat_id] = (accumulated, now)
-        self._prune_stream_buffer()
+        self._stream_buffer.prune()
         return DeliveryResult(success=True, message_id=msg_id)
 
     async def _flush_stream(self, chat_id: str, msg_id: str, content: str, finished: bool) -> DeliveryResult:
         if not msg_id:
             result = await self._call_with_cb(self._sender.send_text, recipient=chat_id, message_body=content)
             if not finished:
-                self._stream_buffer[chat_id] = (content, time.monotonic())
+                self._stream_buffer.set(chat_id, content)
             return result
 
         if not finished:
@@ -621,21 +714,6 @@ class SignalChannel(BaseChannelAdapter):
             )
         return await self._call_with_cb(self._sender.send_text, recipient=chat_id, message_body=content)
 
-    def _prune_stream_buffer(self) -> None:
-        now = time.monotonic()
-        expired = [k for k, (_, ts) in self._stream_buffer.items() if now - ts > STREAM_BUFFER_TTL]
-        for k in expired:
-            self._stream_buffer.pop(k, None)
-
-        if len(self._stream_buffer) > STREAM_BUFFER_MAX_ENTRIES:
-            sorted_keys = sorted(
-                self._stream_buffer.keys(),
-                key=lambda k: self._stream_buffer[k][1],
-            )
-            excess = len(self._stream_buffer) - STREAM_BUFFER_MAX_ENTRIES
-            for k in sorted_keys[:excess]:
-                self._stream_buffer.pop(k, None)
-
     def _build_formatted_body(self, content: str) -> Any:
         markdown_enabled = self.config.get("markdown_enabled", True)
         if not markdown_enabled or not content:
@@ -709,19 +787,19 @@ class SignalChannel(BaseChannelAdapter):
                     if self._ingest_enabled:
                         await self._ingest_group_message(message)
                     return
-                if not self._security.check_require_mention(message):
-                    if self._audit_enabled:
-                        self._log_audit(message, "filtered", "require_mention")
-                    if self._ingest_enabled:
-                        await self._ingest_group_message(message)
-                    return
                 if self._security.require_mention:
-                    if message.mentions and message.mentions.is_bot_mentioned:
-                        if not self._security.check_command_double_auth(message):
-                            logger.info(f"[Signal] Command double-auth failed for {message.identity.channel_user_id}")
-                            if self._audit_enabled:
-                                self._log_audit(message, "denied", "command_double_auth")
-                            return
+                    if not self._security.check_require_mention(message):
+                        if self._audit_enabled:
+                            self._log_audit(message, "filtered", "require_mention")
+                        if self._ingest_enabled:
+                            await self._ingest_group_message(message)
+                        return
+                if self._security._command_double_auth:
+                    if not self._security.check_command_double_auth(message):
+                        logger.info(f"[Signal] Command double-auth failed for {message.identity.channel_user_id}")
+                        if self._audit_enabled:
+                            self._log_audit(message, "denied", "command_double_auth")
+                        return
             else:
                 if not self._security.check_dm_permission(message):
                     logger.debug(f"[Signal] DM blocked by security: {message.identity.channel_user_id}")
@@ -977,10 +1055,8 @@ class SignalChannel(BaseChannelAdapter):
             return False
 
     async def _handle_reasoning_chunk(self, chat_id: str, msg_id: str, chunk: str, finished: bool) -> DeliveryResult:
-        reasoning_content = chunk.replace("lane:reasoning:", "")
-        sep = self._lane_separator
-        prefix = f"(thinking)\n{reasoning_content}\n{sep}\n"
-        return await self._flush_stream(chat_id, msg_id, prefix, finished)
+        formatted = self._stream_coalescer.format_reasoning(chunk)
+        return await self._flush_stream(chat_id, msg_id, formatted, finished)
 
     async def _send_with_exec_auth(self, chat_id: str, message: ChannelMessage) -> bool:
         action = message.metadata.get("command") or message.event_type.value
diff --git a/backend/package/yuxi/channels/adapters/signal/daemon.py b/backend/package/yuxi/channels/adapters/signal/daemon.py
index 5543c303..832b8cf1 100644
--- a/backend/package/yuxi/channels/adapters/signal/daemon.py
+++ b/backend/package/yuxi/channels/adapters/signal/daemon.py
@@ -3,10 +3,10 @@ from __future__ import annotations
 import asyncio
 import logging
 import shutil
-from collections.abc import Callable, Awaitable
+from collections.abc import Awaitable, Callable
 
-from yuxi.channels.models import HealthStatus
 from yuxi.channels.adapters.signal.client import RpcClient
+from yuxi.channels.models import HealthStatus
 
 logger = logging.getLogger(__name__)
 
diff --git a/backend/package/yuxi/channels/adapters/signal/exec_auth.py b/backend/package/yuxi/channels/adapters/signal/exec_auth.py
index 2cb3ff3c..1491d24d 100644
--- a/backend/package/yuxi/channels/adapters/signal/exec_auth.py
+++ b/backend/package/yuxi/channels/adapters/signal/exec_auth.py
@@ -2,9 +2,9 @@ from __future__ import annotations
 
 import asyncio
 import logging
+from collections.abc import Awaitable, Callable
 from enum import StrEnum
 from typing import Any
-from collections.abc import Awaitable, Callable
 
 logger = logging.getLogger(__name__)
 
diff --git a/backend/package/yuxi/channels/adapters/signal/install.py b/backend/package/yuxi/channels/adapters/signal/install.py
index 63d7a56f..5a6ed282 100644
--- a/backend/package/yuxi/channels/adapters/signal/install.py
+++ b/backend/package/yuxi/channels/adapters/signal/install.py
@@ -1,11 +1,11 @@
+import json
 import logging
 import os
 import platform
 import shutil
 import subprocess
 import tempfile
-from urllib.request import urlopen, Request
-import json
+from urllib.request import Request, urlopen
 
 logger = logging.getLogger(__name__)
 
diff --git a/backend/package/yuxi/channels/adapters/signal/message_actions.py b/backend/package/yuxi/channels/adapters/signal/message_actions.py
index 8c432519..2ed32a27 100644
--- a/backend/package/yuxi/channels/adapters/signal/message_actions.py
+++ b/backend/package/yuxi/channels/adapters/signal/message_actions.py
@@ -2,7 +2,6 @@ from __future__ import annotations
 
 from typing import Any
 
-
 SIGNAL_MESSAGE_ACTIONS = {
     "send": {
         "description": "Send a text message to a Signal chat",
@@ -65,6 +64,41 @@ SIGNAL_MESSAGE_ACTIONS = {
             "channel_user_id": {"type": "str", "description": "E.164 number of the user"},
         },
     },
+    "send_sticker": {
+        "description": "Send a sticker to a Signal chat",
+        "params": {
+            "recipient": {"type": "str", "description": "Recipient E.164 number or group:ID"},
+            "pack_id": {"type": "str", "description": "Sticker pack ID"},
+            "sticker_id": {"type": "int", "description": "Sticker ID within the pack"},
+        },
+    },
+    "send_voice": {
+        "description": "Send a voice message to a Signal chat",
+        "params": {
+            "recipient": {"type": "str", "description": "Recipient E.164 number or group:ID"},
+            "audio_data": {"type": "bytes", "description": "Base64-encoded audio/ogg data"},
+        },
+    },
+    "send_silent": {
+        "description": "Send a silent text message without notification",
+        "params": {
+            "recipient": {"type": "str", "description": "Recipient E.164 number or group:ID"},
+            "message_body": {"type": "str", "description": "Message content"},
+        },
+    },
+    "pin": {
+        "description": "Pin a message to the top of a Signal chat",
+        "params": {
+            "recipient": {"type": "str", "description": "Recipient E.164 number or group:ID"},
+            "timestamp": {"type": "int", "description": "Timestamp of the message to pin"},
+        },
+    },
+    "unpin": {
+        "description": "Unpin a previously pinned message",
+        "params": {
+            "recipient": {"type": "str", "description": "Recipient E.164 number or group:ID"},
+        },
+    },
 }
 
 
diff --git a/backend/package/yuxi/channels/adapters/signal/monitor.py b/backend/package/yuxi/channels/adapters/signal/monitor.py
index c465637b..96d6c58b 100644
--- a/backend/package/yuxi/channels/adapters/signal/monitor.py
+++ b/backend/package/yuxi/channels/adapters/signal/monitor.py
@@ -3,9 +3,8 @@ from __future__ import annotations
 import asyncio
 import json
 import logging
-from collections.abc import Callable, Awaitable
+from collections.abc import Awaitable, Callable
 
-from yuxi.channels.models import ChannelMessage, EventType
 from yuxi.channels.adapters.signal.client import RpcClient
 from yuxi.channels.adapters.signal.event_queue import OrderedEventQueue
 from yuxi.channels.adapters.signal.normalize import (
@@ -19,6 +18,7 @@ from yuxi.channels.adapters.signal.normalize import (
     parse_signal_reaction,
 )
 from yuxi.channels.adapters.signal.sse_reconnect import sse_event_stream
+from yuxi.channels.models import ChannelMessage, EventType
 
 logger = logging.getLogger(__name__)
 
diff --git a/backend/package/yuxi/channels/adapters/signal/normalize.py b/backend/package/yuxi/channels/adapters/signal/normalize.py
index 38bd07b1..4675976e 100644
--- a/backend/package/yuxi/channels/adapters/signal/normalize.py
+++ b/backend/package/yuxi/channels/adapters/signal/normalize.py
@@ -2,7 +2,7 @@ from __future__ import annotations
 
 import re
 import time
-from datetime import datetime, UTC
+from datetime import UTC, datetime
 
 from yuxi.channels.models import (
     Attachment,
diff --git a/backend/package/yuxi/channels/adapters/signal/outbound_session.py b/backend/package/yuxi/channels/adapters/signal/outbound_session.py
index 570f58bb..641bb987 100644
--- a/backend/package/yuxi/channels/adapters/signal/outbound_session.py
+++ b/backend/package/yuxi/channels/adapters/signal/outbound_session.py
@@ -2,8 +2,8 @@ from __future__ import annotations
 
 from dataclasses import dataclass
 
-from yuxi.channels.models import ChatType
 from yuxi.channels.adapters.signal.normalize import normalize_target
+from yuxi.channels.models import ChatType
 
 
 @dataclass
diff --git a/backend/package/yuxi/channels/adapters/signal/probe.py b/backend/package/yuxi/channels/adapters/signal/probe.py
index 29f311c6..6c62a25b 100644
--- a/backend/package/yuxi/channels/adapters/signal/probe.py
+++ b/backend/package/yuxi/channels/adapters/signal/probe.py
@@ -6,8 +6,8 @@ from dataclasses import dataclass, field
 
 import aiohttp
 
-from yuxi.channels.models import HealthStatus
 from yuxi.channels.adapters.signal.client import RpcClient, RpcError
+from yuxi.channels.models import HealthStatus
 
 logger = logging.getLogger(__name__)
 
diff --git a/backend/package/yuxi/channels/adapters/signal/security.py b/backend/package/yuxi/channels/adapters/signal/security.py
index a2ce8220..b9a5c573 100644
--- a/backend/package/yuxi/channels/adapters/signal/security.py
+++ b/backend/package/yuxi/channels/adapters/signal/security.py
@@ -1,6 +1,8 @@
-from enum import StrEnum
+import asyncio
 import logging
+import time
 from collections.abc import Awaitable, Callable
+from enum import StrEnum
 
 from yuxi.channels.models import ChannelMessage
 
@@ -150,6 +152,21 @@ class SignalSecurityPolicy:
         else:
             raise ValueError(f"Unknown target_type: {target_type}, expected 'dm' or 'group'")
 
+        if self._store_write_fn:
+            try:
+                asyncio.ensure_future(
+                    self._store_write_fn(
+                        f"signal:pairing:{target_type}:{target_id}",
+                        {
+                            "user_id": target_id,
+                            "target_type": target_type,
+                            "added_at": int(time.time()),
+                        },
+                    )
+                )
+            except RuntimeError:
+                logger.debug("No running event loop, skip persist add_to_allowlist")
+
     def remove_from_allowlist(self, target_id: str, target_type: str = "dm") -> None:
         if target_type == "dm":
             self._dm_allowlist.discard(target_id)
diff --git a/backend/package/yuxi/channels/adapters/signal/send.py b/backend/package/yuxi/channels/adapters/signal/send.py
index 05e99820..7b7c529e 100644
--- a/backend/package/yuxi/channels/adapters/signal/send.py
+++ b/backend/package/yuxi/channels/adapters/signal/send.py
@@ -5,7 +5,6 @@ import base64
 import logging
 import uuid
 
-from yuxi.channels.models import DeliveryResult
 from yuxi.channels.adapters.signal.client import RpcClient, RpcError
 from yuxi.channels.adapters.signal.format import (
     FormattedText,
@@ -14,6 +13,7 @@ from yuxi.channels.adapters.signal.format import (
     split_text,
 )
 from yuxi.channels.adapters.signal.normalize import normalize_target
+from yuxi.channels.models import DeliveryResult
 
 logger = logging.getLogger(__name__)
 
@@ -103,12 +103,18 @@ class SignalSender:
         formatted_body: FormattedText | None = None,
         chunk_mode: str = "newline",
         text_mode: str = "markdown",
+        previews: list[dict] | None = None,
+        mentions: list[dict] | None = None,
     ) -> DeliveryResult:
         if text_mode == "plain" and formatted_body is not None:
-            return await self._send_formatted_text(recipient, formatted_body, reply_to_id, chunk_mode)
+            return await self._send_formatted_text(
+                recipient, formatted_body, reply_to_id, chunk_mode, previews, mentions
+            )
 
         if formatted_body is not None and text_mode == "markdown":
-            return await self._send_formatted_text(recipient, formatted_body, reply_to_id, chunk_mode)
+            return await self._send_formatted_text(
+                recipient, formatted_body, reply_to_id, chunk_mode, previews, mentions
+            )
 
         chunks = split_text(message_body, self.MAX_TEXT_LENGTH, chunk_mode)
         last_message_id = None
@@ -121,6 +127,12 @@ class SignalSender:
             }
             if reply_to_id and i == 0:
                 params["quoteTimestamp"] = int(reply_to_id)
+            if previews:
+                params["previews"] = previews
+            if mentions:
+                params["bodyRanges"] = [
+                    {"mentionUuid": m["user_id"], "start": m["start"], "length": m["length"]} for m in mentions
+                ]
 
             try:
                 result = await self._call_with_retry("send", params)
@@ -139,6 +151,8 @@ class SignalSender:
         formatted: FormattedText,
         reply_to_id: str | None = None,
         chunk_mode: str = "newline",
+        previews: list[dict] | None = None,
+        mentions: list[dict] | None = None,
     ) -> DeliveryResult:
         chunks = split_text(formatted.body, self.MAX_TEXT_LENGTH, chunk_mode)
         last_message_id = None
@@ -158,6 +172,12 @@ class SignalSender:
                 params["styles"] = [{"start": s.start, "length": s.length, "style": s.style} for s in clamped]
             if reply_to_id and i == 0:
                 params["quoteTimestamp"] = int(reply_to_id)
+            if previews:
+                params["previews"] = previews
+            if mentions:
+                params["bodyRanges"] = [
+                    {"mentionUuid": m["user_id"], "start": m["start"], "length": m["length"]} for m in mentions
+                ]
 
             try:
                 result = await self._call_with_retry("send", params)
@@ -412,6 +432,72 @@ class SignalSender:
             logger.error(f"Failed to send voice to {recipient}: {e}")
             return DeliveryResult(success=False, error=str(e))
 
+    async def create_group(
+        self,
+        group_name: str,
+        members: list[str],
+        avatar_path: str | None = None,
+    ) -> DeliveryResult:
+        try:
+            params = {
+                "account": self._account,
+                "groupName": group_name,
+                "members": members,
+            }
+            if avatar_path:
+                params["avatar"] = avatar_path
+            result = await self._rpc.call("createGroup", params)
+            group_id = result.get("groupId", "")
+            return DeliveryResult(
+                success=True,
+                message_id=group_id,
+            )
+        except Exception as e:
+            logger.error(f"Failed to create group '{group_name}': {e}")
+            return DeliveryResult(success=False, error=str(e))
+
+    async def delete_group(self, group_id: str) -> DeliveryResult:
+        try:
+            if not group_id.startswith(GROUP_PREFIX):
+                group_id = f"{GROUP_PREFIX}{group_id}"
+            params = {
+                "account": self._account,
+                "groupId": group_id,
+            }
+            await self._rpc.call("quitGroup", params)
+            return DeliveryResult(success=True)
+        except Exception as e:
+            logger.error(f"Failed to delete group {group_id}: {e}")
+            return DeliveryResult(success=False, error=str(e))
+
+    async def manage_members(
+        self,
+        group_id: str,
+        add: list[str] | None = None,
+        remove: list[str] | None = None,
+    ) -> DeliveryResult:
+        try:
+            if not group_id.startswith(GROUP_PREFIX):
+                group_id = f"{GROUP_PREFIX}{group_id}"
+            if add:
+                params = {
+                    "account": self._account,
+                    "groupId": group_id,
+                    "members": add,
+                }
+                await self._rpc.call("addMembers", params)
+            if remove:
+                params = {
+                    "account": self._account,
+                    "groupId": group_id,
+                    "members": remove,
+                }
+                await self._rpc.call("removeMembers", params)
+            return DeliveryResult(success=True)
+        except Exception as e:
+            logger.error(f"Failed to manage members for group {group_id}: {e}")
+            return DeliveryResult(success=False, error=str(e))
+
 
 def _extract_chunk_styles(styles: list[StyleRange], offset: int, chunk_len: int) -> list[StyleRange]:
     chunk_end = offset + chunk_len
diff --git a/backend/package/yuxi/channels/adapters/signal/session.py b/backend/package/yuxi/channels/adapters/signal/session.py
index 2c0a6294..28f304e4 100644
--- a/backend/package/yuxi/channels/adapters/signal/session.py
+++ b/backend/package/yuxi/channels/adapters/signal/session.py
@@ -1,5 +1,5 @@
-from yuxi.channels.models import ChannelIdentity, ChannelType
 from yuxi.channels.adapters.signal.normalize import normalize_e164
+from yuxi.channels.models import ChannelIdentity, ChannelType
 
 
 def resolve_thread(identity: ChannelIdentity, agent_id: str = "main") -> str:
diff --git a/backend/package/yuxi/channels/adapters/signal/setup.py b/backend/package/yuxi/channels/adapters/signal/setup.py
index ab19824e..c0abfa2c 100644
--- a/backend/package/yuxi/channels/adapters/signal/setup.py
+++ b/backend/package/yuxi/channels/adapters/signal/setup.py
@@ -148,6 +148,7 @@ class SetupWizard:
 
     def auto_install(self) -> dict:
         import asyncio
+
         from yuxi.channels.adapters.signal.install import auto_install_signal_cli
 
         try:
diff --git a/backend/package/yuxi/channels/adapters/signal/sse_reconnect.py b/backend/package/yuxi/channels/adapters/signal/sse_reconnect.py
index e2c68eee..8cca5bae 100644
--- a/backend/package/yuxi/channels/adapters/signal/sse_reconnect.py
+++ b/backend/package/yuxi/channels/adapters/signal/sse_reconnect.py
@@ -3,7 +3,7 @@ from __future__ import annotations
 import asyncio
 import logging
 import random
-from collections.abc import Callable, Awaitable
+from collections.abc import Awaitable, Callable
 
 import aiohttp