diff --git a/api/dependencies.py b/api/dependencies.py
index 5ae85d9..5eac1a6 100644
--- a/api/dependencies.py
+++ b/api/dependencies.py
@@ -33,6 +33,8 @@ def get_provider() -> NvidiaNimProvider:
 async def cleanup_provider():
     """Cleanup provider resources."""
     global _provider
-    if _provider and hasattr(_provider, "_client"):
-        await _provider._client.aclose()
+    if _provider:
+        client = getattr(_provider, "_client", None)
+        if client and hasattr(client, "aclose"):
+            await client.aclose()
     _provider = None
diff --git a/api/request_utils.py b/api/request_utils.py
index 31f83e7..5c5e579 100644
--- a/api/request_utils.py
+++ b/api/request_utils.py
@@ -40,7 +40,8 @@ def is_quota_check_request(request_data: MessagesRequest) -> bool:
         # Check list content
         elif isinstance(content, list):
             for block in content:
-                if hasattr(block, "text") and "quota" in block.text.lower():
+                text = getattr(block, "text", "")
+                if text and isinstance(text, str) and "quota" in text.lower():
                     return True
     return False
 
@@ -66,7 +67,8 @@ def is_title_generation_request(request_data: MessagesRequest) -> bool:
         # Check list content
         elif isinstance(content, list):
             for block in content:
-                if hasattr(block, "text") and target_phrase in block.text.lower():
+                text = getattr(block, "text", "")
+                if text and isinstance(text, str) and target_phrase in text.lower():
                     return True
     return False
 
@@ -159,8 +161,9 @@ def is_prefix_detection_request(request_data: MessagesRequest) -> Tuple[bool, st
         content = msg.content
     elif isinstance(msg.content, list):
         for block in msg.content:
-            if hasattr(block, "text"):
-                content += block.text
+            text = getattr(block, "text", "")
+            if text and isinstance(text, str):
+                content += text
 
     if "<policy_spec>" in content and "Command:" in content:
         try:
diff --git a/cli/parser.py b/cli/parser.py
index b7f6bf1..29baa0c 100644
--- a/cli/parser.py
+++ b/cli/parser.py
@@ -1,7 +1,7 @@
 """CLI event parser for Claude Code CLI output."""
 
 import logging
-from typing import Dict, List
+from typing import Dict, List, Any
 
 logger = logging.getLogger(__name__)
 
@@ -10,7 +10,7 @@ class CLIParser:
     """Helper to structure raw CLI events."""
 
     @staticmethod
-    def parse_event(event: Dict) -> List[Dict]:
+    def parse_event(event: Any) -> List[Dict]:
         """
         Parse a CLI event and return a structured result.
 
diff --git a/cli/session.py b/cli/session.py
index 812e19e..8f64400 100644
--- a/cli/session.py
+++ b/cli/session.py
@@ -4,7 +4,7 @@ import asyncio
 import os
 import json
 import logging
-from typing import AsyncGenerator, Optional, Dict, List
+from typing import AsyncGenerator, Optional, Dict, List, Any
 
 logger = logging.getLogger(__name__)
 
@@ -186,7 +186,7 @@ class CLISession:
             logger.debug(f"Non-JSON output: {line_str[:100]}")
             yield {"type": "raw", "content": line_str}
 
-    def _extract_session_id(self, event: Dict) -> Optional[str]:
+    def _extract_session_id(self, event: Any) -> Optional[str]:
         """Extract session ID from CLI event."""
         if not isinstance(event, dict):
             return None
diff --git a/messaging/base.py b/messaging/base.py
index f147bf7..1b12a5b 100644
--- a/messaging/base.py
+++ b/messaging/base.py
@@ -1,17 +1,29 @@
 """Abstract base class for messaging platforms."""
 
 from abc import ABC, abstractmethod
-from typing import Callable, Awaitable, Optional, Protocol, Tuple, runtime_checkable
+from typing import (
+    Callable,
+    Awaitable,
+    Optional,
+    Protocol,
+    Tuple,
+    runtime_checkable,
+    AsyncGenerator,
+    Any,
+    Dict,
+)
 from .models import IncomingMessage
 
 
-class CLISession(ABC):
-    """Abstract base for CLI session - avoid circular import from cli package."""
+@runtime_checkable
+class CLISession(Protocol):
+    """Protocol for CLI session - avoid circular import from cli package."""
 
-    @abstractmethod
-    async def start_task(self, prompt: str, session_id: Optional[str] = None):
+    def start_task(
+        self, prompt: str, session_id: Optional[str] = None
+    ) -> AsyncGenerator[Dict, Any]:
         """Start a task in the CLI session."""
-        pass
+        ...
 
     @property
     @abstractmethod
@@ -162,6 +174,11 @@ class MessagingPlatform(ABC):
         """
         pass
 
+    @abstractmethod
+    def fire_and_forget(self, task: Awaitable[Any]) -> None:
+        """Execute a coroutine without awaiting it."""
+        pass
+
     @property
     def is_connected(self) -> bool:
         """Check if the platform is connected."""
diff --git a/messaging/event_parser.py b/messaging/event_parser.py
index b609561..5de5e34 100644
--- a/messaging/event_parser.py
+++ b/messaging/event_parser.py
@@ -4,12 +4,12 @@ Extracted from cli.parser to avoid tight coupling between messaging and cli pack
 """
 
 import logging
-from typing import Dict, List
+from typing import Dict, List, Any
 
 logger = logging.getLogger(__name__)
 
 
-def parse_cli_event(event: Dict) -> List[Dict]:
+def parse_cli_event(event: Any) -> List[Dict]:
     """
     Parse a CLI event and return a structured result.
 
diff --git a/messaging/handler.py b/messaging/handler.py
index d7b2c50..3c375ee 100644
--- a/messaging/handler.py
+++ b/messaging/handler.py
@@ -72,14 +72,13 @@ class ClaudeMessageHandler:
         parent_node_id = None
         tree = None
 
-        if incoming.is_reply():
+        if incoming.is_reply() and incoming.reply_to_message_id:
             # Look up if the replied-to message is in any tree (could be a node or status message)
-            tree = self.tree_queue.get_tree_for_node(incoming.reply_to_message_id)
+            reply_id = incoming.reply_to_message_id
+            tree = self.tree_queue.get_tree_for_node(reply_id)
             if tree:
                 # Resolve to actual node ID (handles status message replies)
-                parent_node_id = self.tree_queue.resolve_parent_node_id(
-                    incoming.reply_to_message_id
-                )
+                parent_node_id = self.tree_queue.resolve_parent_node_id(reply_id)
                 if parent_node_id:
                     logger.info(f"Found tree for reply, parent node: {parent_node_id}")
                 else:
@@ -106,7 +105,7 @@ class ClaudeMessageHandler:
         )
 
         # Create or extend tree
-        if parent_node_id and tree:
+        if parent_node_id and tree and status_msg_id:
             # Reply to existing node - add as child
             tree, node = await self.tree_queue.add_to_tree(
                 parent_node_id=parent_node_id,
@@ -118,7 +117,7 @@ class ClaudeMessageHandler:
             self.tree_queue.register_node(status_msg_id, tree.root_id)
             self.session_store.register_node(status_msg_id, tree.root_id)
             self.session_store.register_node(node_id, tree.root_id)
-        else:
+        elif status_msg_id:
             # New conversation - create new tree
             tree = await self.tree_queue.create_tree(
                 node_id=node_id,
@@ -131,7 +130,8 @@ class ClaudeMessageHandler:
             self.session_store.register_node(status_msg_id, tree.root_id)
 
         # Persist tree
-        self.session_store.save_tree(tree.root_id, tree.to_dict())
+        if tree:
+            self.session_store.save_tree(tree.root_id, tree.to_dict())
 
         # Enqueue for processing
         was_queued = await self.tree_queue.enqueue(
@@ -139,7 +139,7 @@ class ClaudeMessageHandler:
             processor=self._process_node,
         )
 
-        if was_queued:
+        if was_queued and status_msg_id:
             # Update status to show queue position
             queue_size = self.tree_queue.get_queue_size(node_id)
             await self.platform.queue_edit_message(
@@ -454,7 +454,7 @@ class ClaudeMessageHandler:
         parent_node_id: Optional[str],
     ) -> str:
         """Get initial status message text."""
-        if tree:
+        if tree and parent_node_id:
             # Reply to existing tree
             if self.tree_queue.is_node_tree_busy(parent_node_id):
                 queue_size = self.tree_queue.get_queue_size(parent_node_id) + 1
diff --git a/messaging/limiter.py b/messaging/limiter.py
index 727b4b6..985f4df 100644
--- a/messaging/limiter.py
+++ b/messaging/limiter.py
@@ -115,8 +115,13 @@ class GlobalRateLimiter:
                             logger.error(
                                 f"FloodWait detected! Pausing worker for {seconds}s"
                             )
+                            wait_secs = (
+                                float(seconds)
+                                if isinstance(seconds, (int, float, str))
+                                else 30.0
+                            )
                             self._paused_until = (
-                                asyncio.get_event_loop().time() + seconds
+                                asyncio.get_event_loop().time() + wait_secs
                             )
                         else:
                             logger.error(
diff --git a/messaging/models.py b/messaging/models.py
index 5337b3d..d1aa11c 100644
--- a/messaging/models.py
+++ b/messaging/models.py
@@ -2,7 +2,7 @@
 
 from dataclasses import dataclass, field
 from typing import Optional, Any
-from datetime import datetime
+from datetime import datetime, timezone
 
 
 @dataclass
@@ -22,7 +22,7 @@ class IncomingMessage:
     # Optional fields
     reply_to_message_id: Optional[str] = None
     username: Optional[str] = None
-    timestamp: datetime = field(default_factory=datetime.utcnow)
+    timestamp: datetime = field(default_factory=lambda: datetime.now(timezone.utc))
 
     # Platform-specific raw event for edge cases
     raw_event: Any = None
diff --git a/messaging/session.py b/messaging/session.py
index 1bb7075..9e82af3 100644
--- a/messaging/session.py
+++ b/messaging/session.py
@@ -8,7 +8,7 @@ and message trees for conversation continuation.
 import json
 import os
 import logging
-from datetime import datetime
+from datetime import datetime, timezone
 from typing import Optional, Dict
 from dataclasses import dataclass, asdict
 import threading
@@ -116,7 +116,7 @@ class SessionStore:
     ) -> None:
         """Save a new session mapping."""
         with self._lock:
-            now = datetime.utcnow().isoformat()
+            now = datetime.now(timezone.utc).isoformat()
             record = SessionRecord(
                 session_id=session_id,
                 chat_id=str(chat_id),
@@ -152,7 +152,7 @@ class SessionStore:
 
             record = self._sessions[session_id]
             record.last_msg_id = str(msg_id)
-            record.updated_at = datetime.utcnow().isoformat()
+            record.updated_at = datetime.now(timezone.utc).isoformat()
             new_key = self._make_key(record.platform, record.chat_id, str(msg_id))
             self._msg_to_session[new_key] = session_id
             self._save()
@@ -167,7 +167,7 @@ class SessionStore:
 
             record = self._sessions.pop(old_id)
             record.session_id = new_id
-            record.updated_at = datetime.utcnow().isoformat()
+            record.updated_at = datetime.now(timezone.utc).isoformat()
             self._sessions[new_id] = record
 
             items_to_update = [
@@ -190,7 +190,7 @@ class SessionStore:
     def cleanup_old_sessions(self, max_age_days: int = 30) -> int:
         """Remove sessions older than max_age_days."""
         with self._lock:
-            cutoff = datetime.utcnow()
+            cutoff = datetime.now(timezone.utc)
             removed = 0
 
             to_remove = []
@@ -284,7 +284,7 @@ class SessionStore:
     def cleanup_old_trees(self, max_age_days: int = 30) -> int:
         """Remove trees older than max_age_days."""
         with self._lock:
-            cutoff = datetime.utcnow()
+            cutoff = datetime.now(timezone.utc)
             removed = 0
             to_remove = []
 
diff --git a/messaging/telegram.py b/messaging/telegram.py
index e987a51..cc40921 100644
--- a/messaging/telegram.py
+++ b/messaging/telegram.py
@@ -105,9 +105,10 @@ class TelegramPlatform(MessagingPlatform):
                 await self._application.start()
 
                 # Start polling (non-blocking way for integration)
-                await self._application.updater.start_polling(
-                    drop_pending_updates=False
-                )
+                if self._application.updater:
+                    await self._application.updater.start_polling(
+                        drop_pending_updates=False
+                    )
 
                 self._connected = True
                 break
@@ -141,7 +142,7 @@ class TelegramPlatform(MessagingPlatform):
 
     async def stop(self) -> None:
         """Stop the bot."""
-        if self._application:
+        if self._application and self._application.updater:
             await self._application.updater.stop()
             await self._application.stop()
             await self._application.shutdown()
@@ -175,9 +176,11 @@ class TelegramPlatform(MessagingPlatform):
                     raise
             except RetryAfter as e:
                 # Telegram explicitly tells us to wait
-                wait_secs = e.retry_after
-                if hasattr(wait_secs, "total_seconds"):
-                    wait_secs = wait_secs.total_seconds()
+                retry_after = e.retry_after
+                if hasattr(retry_after, "total_seconds"):
+                    wait_secs = float(retry_after.total_seconds())  # type: ignore
+                else:
+                    wait_secs = float(retry_after)
 
                 logger.warning(f"Rate limited by Telegram, waiting {wait_secs}s...")
                 await asyncio.sleep(wait_secs)
@@ -201,11 +204,12 @@ class TelegramPlatform(MessagingPlatform):
         parse_mode: Optional[str] = "Markdown",
     ) -> str:
         """Send a message to a chat."""
-        if not self._application:
-            raise RuntimeError("Telegram application not initialized")
+        if not self._application or not self._application.bot:
+            raise RuntimeError("Telegram application or bot not initialized")
 
         async def _do_send(mode=parse_mode):
-            msg = await self._application.bot.send_message(
+            bot = self._application.bot  # type: ignore
+            msg = await bot.send_message(
                 chat_id=chat_id,
                 text=text,
                 reply_to_message_id=int(reply_to) if reply_to else None,
@@ -223,11 +227,12 @@ class TelegramPlatform(MessagingPlatform):
         parse_mode: Optional[str] = "Markdown",
     ) -> None:
         """Edit an existing message."""
-        if not self._application:
-            raise RuntimeError("Telegram application not initialized")
+        if not self._application or not self._application.bot:
+            raise RuntimeError("Telegram application or bot not initialized")
 
         async def _do_edit(mode=parse_mode):
-            await self._application.bot.edit_message_text(
+            bot = self._application.bot  # type: ignore
+            await bot.edit_message_text(
                 chat_id=chat_id,
                 message_id=int(message_id),
                 text=text,
@@ -281,7 +286,10 @@ class TelegramPlatform(MessagingPlatform):
 
     def fire_and_forget(self, task: Awaitable[Any]) -> None:
         """Execute a coroutine without awaiting it."""
-        asyncio.create_task(task)
+        if asyncio.iscoroutine(task):
+            asyncio.create_task(task)  # type: ignore
+        else:
+            asyncio.ensure_future(task)
 
     def on_message(
         self,
@@ -299,7 +307,8 @@ class TelegramPlatform(MessagingPlatform):
         self, update: Update, context: ContextTypes.DEFAULT_TYPE
     ) -> None:
         """Handle /start command."""
-        await update.message.reply_text("👋 Hello! I am the Claude Code Proxy Bot.")
+        if update.message:
+            await update.message.reply_text("👋 Hello! I am the Claude Code Proxy Bot.")
         # We can also treat this as a message if we want it to trigger something
         await self._on_telegram_message(update, context)
 
@@ -307,7 +316,12 @@ class TelegramPlatform(MessagingPlatform):
         self, update: Update, context: ContextTypes.DEFAULT_TYPE
     ) -> None:
         """Handle incoming updates."""
-        if not update.message or not update.message.text:
+        if (
+            not update.message
+            or not update.message.text
+            or not update.effective_user
+            or not update.effective_chat
+        ):
             return
 
         user_id = str(update.effective_user.id)
diff --git a/messaging/tree_data.py b/messaging/tree_data.py
index a51d6fa..e51dc9e 100644
--- a/messaging/tree_data.py
+++ b/messaging/tree_data.py
@@ -6,7 +6,7 @@ Contains MessageState, MessageNode, and MessageTree classes.
 import asyncio
 import logging
 from enum import Enum
-from datetime import datetime
+from datetime import datetime, timezone
 from typing import Dict, Optional, List, Any
 from dataclasses import dataclass, field
 
@@ -42,7 +42,7 @@ class MessageNode:
     parent_id: Optional[str] = None  # Parent node ID (None for root)
     session_id: Optional[str] = None  # Claude session ID (forked from parent)
     children_ids: List[str] = field(default_factory=list)
-    created_at: datetime = field(default_factory=datetime.utcnow)
+    created_at: datetime = field(default_factory=lambda: datetime.now(timezone.utc))
     completed_at: Optional[datetime] = None
     error_message: Optional[str] = None
     context: Any = None  # Additional context if needed
@@ -221,7 +221,7 @@ class MessageTree:
             if error_message:
                 node.error_message = error_message
             if state in (MessageState.COMPLETED, MessageState.ERROR):
-                node.completed_at = datetime.utcnow()
+                node.completed_at = datetime.now(timezone.utc)
 
             logger.debug(f"Node {node_id} state -> {state.value}")
 
diff --git a/providers/base.py b/providers/base.py
index fe2b610..550eec9 100644
--- a/providers/base.py
+++ b/providers/base.py
@@ -30,7 +30,8 @@ class BaseProvider(ABC):
         self, request: Any, input_tokens: int = 0
     ) -> AsyncIterator[str]:
         """Stream response in Anthropic SSE format."""
-        pass
+        if False:
+            yield ""
 
     @abstractmethod
     def convert_response(self, response_json: dict, original_request: Any) -> Any:
diff --git a/providers/logging_utils.py b/providers/logging_utils.py
index 906aba3..348c859 100644
--- a/providers/logging_utils.py
+++ b/providers/logging_utils.py
@@ -8,7 +8,7 @@ import hashlib
 import json
 import logging
 import os
-from datetime import datetime
+from datetime import datetime, timezone
 from typing import Any, Dict, List, Optional
 
 logger = logging.getLogger(__name__)
@@ -133,7 +133,7 @@ def log_full_payload(request_id: str, payload: Dict[str, Any]) -> None:
     try:
         handler = _get_debug_handler()
         record = {
-            "timestamp": datetime.utcnow().isoformat(),
+            "timestamp": datetime.now(timezone.utc).isoformat(),
             "request_id": request_id,
             "payload": payload,
         }
diff --git a/tests/conftest.py b/tests/conftest.py
index f4ffb15..3d5b090 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -92,6 +92,10 @@ def incoming_message_factory():
             "platform": "telegram",
         }
         defaults.update(kwargs)
-        return IncomingMessage(**defaults)
+        if "timestamp" in defaults and isinstance(defaults["timestamp"], str):
+            from datetime import datetime
+
+            defaults["timestamp"] = datetime.fromisoformat(defaults["timestamp"])
+        return IncomingMessage(**defaults)  # type: ignore
 
     return _create
diff --git a/tests/test_messaging.py b/tests/test_messaging.py
index 5f10bd6..8cd8711 100644
--- a/tests/test_messaging.py
+++ b/tests/test_messaging.py
@@ -3,7 +3,7 @@
 import pytest
 import json
 import os
-from datetime import datetime, timedelta
+from datetime import datetime, timedelta, timezone
 from unittest.mock import patch
 
 # --- Existing Tests ---
@@ -125,6 +125,7 @@ class TestSessionStore:
 
         # Verify record updated
         record = store.get_session_record("sess_1")
+        assert record is not None
         assert record.last_msg_id == "msg_2"
 
     def test_update_last_message_unknown_session(self, tmp_path):
@@ -194,7 +195,7 @@ class TestSessionStore:
         store = SessionStore(storage_path=str(tmp_path / "sessions.json"))
 
         # Create an old session manually
-        old_date = (datetime.utcnow() - timedelta(days=40)).isoformat()
+        old_date = (datetime.now(timezone.utc) - timedelta(days=40)).isoformat()
         store.save_session("old_sess", "c_old", "m_old")
         # Manipulate the created_at directly
         store._sessions["old_sess"].created_at = old_date
@@ -261,6 +262,7 @@ class TestSessionStore:
         store.update_tree_node("r1", "n2", {"data": "test"})
 
         tree = store.get_tree("r1")
+        assert tree is not None
         assert "n2" in tree["nodes"]
         assert tree["nodes"]["n2"]["data"] == "test"
         assert store.get_tree_root_for_node("n2") == "r1"
@@ -286,7 +288,7 @@ class TestSessionStore:
 
         store = SessionStore(storage_path=str(tmp_path / "sessions.json"))
 
-        old_date = (datetime.utcnow() - timedelta(days=40)).isoformat()
+        old_date = (datetime.now(timezone.utc) - timedelta(days=40)).isoformat()
 
         # Old tree
         store.save_tree(
@@ -296,7 +298,11 @@ class TestSessionStore:
         # New tree
         store.save_tree(
             "new_root",
-            {"nodes": {"new_root": {"created_at": datetime.utcnow().isoformat()}}},
+            {
+                "nodes": {
+                    "new_root": {"created_at": datetime.now(timezone.utc).isoformat()}
+                }
+            },
         )
 
         removed = store.cleanup_old_trees(30)
@@ -334,6 +340,7 @@ class TestSessionStore:
 
         store = SessionStore(storage_path=str(p))
         rec = store.get_session_record("s1")
+        assert rec is not None
 
         assert rec.chat_id == "123"  # Converted to str
         assert rec.platform == "telegram"  # Defaulted
diff --git a/tests/test_tree_queue.py b/tests/test_tree_queue.py
index 7556ce5..2d6194b 100644
--- a/tests/test_tree_queue.py
+++ b/tests/test_tree_queue.py
@@ -155,7 +155,9 @@ class TestMessageTree:
         assert child.node_id == "child"
         assert child.parent_id == "root"
         assert "child" in tree.get_root().children_ids
-        assert tree.get_parent("child").node_id == "root"
+        parent = tree.get_parent("child")
+        assert parent is not None
+        assert parent.node_id == "root"
 
     @pytest.mark.asyncio
     async def test_update_state(self):
@@ -171,10 +173,13 @@ class TestMessageTree:
         tree = MessageTree(root)
 
         await tree.update_state("m1", MessageState.IN_PROGRESS)
-        assert tree.get_node("m1").state == MessageState.IN_PROGRESS
+        node = tree.get_node("m1")
+        assert node is not None
+        assert node.state == MessageState.IN_PROGRESS
 
         await tree.update_state("m1", MessageState.COMPLETED, session_id="sess_abc")
         node = tree.get_node("m1")
+        assert node is not None
         assert node.state == MessageState.COMPLETED
         assert node.session_id == "sess_abc"
         assert node.completed_at is not None
@@ -224,7 +229,9 @@ class TestMessageTree:
         restored = MessageTree.from_dict(data)
 
         assert restored.root_id == "m1"
-        assert restored.get_node("m1").session_id == "sess_1"
+        node = restored.get_node("m1")
+        assert node is not None
+        assert node.session_id == "sess_1"
 
 
 class TestTreeQueueManager:
diff --git a/tests/test_tree_repository.py b/tests/test_tree_repository.py
index 048d8b4..3fc0b8b 100644
--- a/tests/test_tree_repository.py
+++ b/tests/test_tree_repository.py
@@ -129,8 +129,9 @@ def test_to_from_dict(repository, sample_tree):
     assert data["node_to_tree"]["root_id"] == "root_id"
 
     new_repo = TreeRepository.from_dict(data)
-    assert new_repo.get_tree("root_id") is not None
-    assert new_repo.get_tree("root_id").root_id == "root_id"
+    tree = new_repo.get_tree("root_id")
+    assert tree is not None
+    assert tree.root_id == "root_id"
     assert new_repo._node_to_tree["root_id"] == "root_id"