diff --git a/src/debugpy/adapter/__main__.py b/src/debugpy/adapter/__main__.py
index e18ecd56..06d601fc 100644
--- a/src/debugpy/adapter/__main__.py
+++ b/src/debugpy/adapter/__main__.py
@@ -8,6 +8,7 @@ import codecs
 import locale
 import os
 import sys
+from typing import Any
 
 # WARNING: debugpy and submodules must not be imported on top level in this module,
 # and should be imported locally inside main() instead.
@@ -53,7 +54,7 @@ def main(args):
     if args.for_server is None:
         adapter.access_token = codecs.encode(os.urandom(32), "hex").decode("ascii")
 
-    endpoints = {}
+    endpoints: dict[str, Any] = {}
     try:
         client_host, client_port = clients.serve(args.host, args.port)
     except Exception as exc:
diff --git a/src/debugpy/adapter/clients.py b/src/debugpy/adapter/clients.py
index ee1d1514..afd9257b 100644
--- a/src/debugpy/adapter/clients.py
+++ b/src/debugpy/adapter/clients.py
@@ -6,7 +6,9 @@ from __future__ import annotations
 
 import atexit
 import os
+import socket
 import sys
+from typing import Literal, Union
 
 import debugpy
 from debugpy import adapter, common, launcher
@@ -41,7 +43,7 @@ class Client(components.Component):
             "pathFormat": json.enum("path", optional=True),  # we don't support "uri"
         }
 
-    def __init__(self, sock):
+    def __init__(self, sock: Union[Literal["stdio"], socket.socket]):
         if sock == "stdio":
             log.info("Connecting to client over stdio...", self)
             self.using_stdio = True
@@ -67,7 +69,7 @@ class Client(components.Component):
             fully handled.
             """
 
-            self.start_request = None
+            self.start_request: Union[messaging.Request, None] = None
             """The "launch" or "attach" request as received from the client.
             """
 
@@ -124,11 +126,12 @@ class Client(components.Component):
             self.client.channel.propagate(event)
 
     def _propagate_deferred_events(self):
-        log.debug("Propagating deferred events to {0}...", self.client)
-        for event in self._deferred_events:
-            log.debug("Propagating deferred {0}", event.describe())
-            self.client.channel.propagate(event)
-        log.info("All deferred events propagated to {0}.", self.client)
+        if self._deferred_events is not None:
+            log.debug("Propagating deferred events to {0}...", self.client)
+            for event in self._deferred_events:
+                log.debug("Propagating deferred {0}", event.describe())
+                self.client.channel.propagate(event)
+            log.info("All deferred events propagated to {0}.", self.client)
         self._deferred_events = None
 
     # Generic event handler. There are no specific handlers for client events, because
@@ -202,9 +205,10 @@ class Client(components.Component):
     #
     # See https://github.com/microsoft/vscode/issues/4902#issuecomment-368583522
     # for the sequence of request and events necessary to orchestrate the start.
+    @staticmethod
     def _start_message_handler(f):
         @components.Component.message_handler
-        def handle(self, request):
+        def handle(self, request: messaging.Message):
             assert request.is_request("launch", "attach")
             if self._initialize_request is None:
                 raise request.isnt_valid("Session is not initialized yet")
@@ -215,15 +219,16 @@ class Client(components.Component):
             if self.session.no_debug:
                 servers.dont_wait_for_first_connection()
 
+            request_options = request("debugOptions", json.array(str))
             self.session.debug_options = debug_options = set(
-                request("debugOptions", json.array(str))
+                
             )
 
             f(self, request)
-            if request.response is not None:
+            if isinstance(request, messaging.Request) and request.response is not None:
                 return
 
-            if self.server:
+            if self.server and isinstance(request, messaging.Request):
                 self.server.initialize(self._initialize_request)
                 self._initialize_request = None
 
@@ -267,7 +272,7 @@ class Client(components.Component):
                 except messaging.MessageHandlingError as exc:
                     exc.propagate(request)
 
-            if self.session.no_debug:
+            if self.session.no_debug and isinstance(request, messaging.Request):
                 self.start_request = request
                 self.has_started = True
                 request.respond({})
@@ -335,6 +340,7 @@ class Client(components.Component):
             launcher_python = python[0]
 
         program = module = code = ()
+        args = []
         if "program" in request:
             program = request("program", str)
             args = [program]
@@ -391,7 +397,7 @@ class Client(components.Component):
         if cwd == ():
             # If it's not specified, but we're launching a file rather than a module,
             # and the specified path has a directory in it, use that.
-            cwd = None if program == () else (os.path.dirname(program) or None)
+            cwd = None if program == () else (os.path.dirname(str(program)) or None)
 
         sudo = bool(property_or_debug_option("sudo", "Sudo"))
         if sudo and sys.platform == "win32":
@@ -484,7 +490,7 @@ class Client(components.Component):
         else:
             if not servers.is_serving():
                 servers.serve()
-            host, port = servers.listener.getsockname()
+            host, port = servers.listener.getsockname() if servers.listener is not None else ("", 0)
 
         # There are four distinct possibilities here.
         #
@@ -576,9 +582,9 @@ class Client(components.Component):
             request.cant_handle("{0} is already being debugged.", conn)
 
     @message_handler
-    def configurationDone_request(self, request):
+    def configurationDone_request(self, request: messaging.Request):
         if self.start_request is None or self.has_started:
-            request.cant_handle(
+            raise request.cant_handle(
                 '"configurationDone" is only allowed during handling of a "launch" '
                 'or an "attach" request'
             )
@@ -623,7 +629,8 @@ class Client(components.Component):
         def handle_response(response):
             request.respond(response.body)
 
-        propagated_request.on_response(handle_response)
+        if propagated_request is not None:
+            propagated_request.on_response(handle_response)
 
         return messaging.NO_RESPONSE
 
@@ -649,7 +656,7 @@ class Client(components.Component):
         result = {"debugpy": {"version": debugpy.__version__}}
         if self.server:
             try:
-                pydevd_info = self.server.channel.request("pydevdSystemInfo")
+                pydevd_info: messaging.AssociatableMessageDict = self.server.channel.request("pydevdSystemInfo")
             except Exception:
                 # If the server has already disconnected, or couldn't handle it,
                 # report what we've got.
@@ -754,7 +761,7 @@ class Client(components.Component):
         if "host" not in body["connect"]:
             body["connect"]["host"] = host if host is not None else "127.0.0.1"
         if "port" not in body["connect"]:
-            if port is None:
+            if port is None and listener is not None:
                 _, port = listener.getsockname()
             body["connect"]["port"] = port
 
@@ -770,7 +777,7 @@ class Client(components.Component):
 
 def serve(host, port):
     global listener
-    listener = sockets.serve("Client", Client, host, port)
+    listener = sockets.serve("Client", Client, host, port) # type: ignore
     sessions.report_sockets()
     return listener.getsockname()
 
diff --git a/src/debugpy/adapter/components.py b/src/debugpy/adapter/components.py
index 038e8883..448713fa 100644
--- a/src/debugpy/adapter/components.py
+++ b/src/debugpy/adapter/components.py
@@ -3,7 +3,7 @@
 # for license information.
 
 import functools
-from typing import Union
+from typing import Type, TypeVar, Union, cast
 
 from debugpy.adapter.sessions import Session
 from debugpy.common import json, log, messaging, util
@@ -33,7 +33,7 @@ class Component(util.Observable):
     to wait_for() a change caused by another component.
     """
 
-    def __init__(self, session: Session, stream: Union[messaging.JsonIOStream, None]=None, channel=None):
+    def __init__(self, session: Session, stream: Union[messaging.JsonIOStream, None]=None, channel: Union[messaging.JsonMessageChannel, None]=None):
         assert (stream is None) ^ (channel is None)
 
         try:
@@ -53,6 +53,7 @@ class Component(util.Observable):
         elif channel is not None:
             channel.name = channel.stream.name = str(self)
             channel.handlers = self
+        assert channel is not None
         self.channel = channel
         self.is_connected = True
 
@@ -110,8 +111,9 @@ class Component(util.Observable):
             self.is_connected = False
             self.session.finalize("{0} has disconnected".format(self))
 
+T = TypeVar('T')
 
-def missing(session, type):
+def missing(session, type: Type[T]) -> T:
     class Missing(object):
         """A dummy component that raises ComponentNotAvailable whenever some
         attribute is accessed on it.
@@ -126,7 +128,7 @@ def missing(session, type):
         except Exception as exc:
             log.reraise_exception("{0} in {1}", exc, session)
 
-    return Missing()
+    return cast(type, Missing())
 
 
 class Capabilities(dict):
diff --git a/src/debugpy/adapter/servers.py b/src/debugpy/adapter/servers.py
index 03ef6d46..996784b9 100644
--- a/src/debugpy/adapter/servers.py
+++ b/src/debugpy/adapter/servers.py
@@ -292,7 +292,7 @@ class Server(components.Component):
 
     # Generic request handler, used if there's no specific handler below.
     @message_handler
-    def request(self, request):
+    def request(self, request: messaging.Message):
         # Do not delegate requests from the server by default. There is a security
         # boundary between the server and the adapter, and we cannot trust arbitrary
         # requests sent over that boundary, since they may contain arbitrary code
@@ -397,7 +397,7 @@ class Server(components.Component):
 
 def serve(host="127.0.0.1", port=0):
     global listener
-    listener = sockets.serve("Server", Connection, host, port)
+    listener = sockets.serve("Server", Connection, host, port) # type: ignore
     sessions.report_sockets()
     return listener.getsockname()
 
@@ -422,21 +422,21 @@ def connections():
         return list(_connections)
 
 
-def wait_for_connection(session, predicate, timeout=None):
+def wait_for_connection(session, predicate, timeout: Union[float, None]=None):
     """Waits until there is a server matching the specified predicate connected to
     this adapter, and returns the corresponding Connection.
 
     If there is more than one server connection already available, returns the oldest
     one.
     """
-
     def wait_for_timeout():
-        time.sleep(timeout)
-        wait_for_timeout.timed_out = True
+        if timeout is not None:
+            time.sleep(timeout)
+        setattr(wait_for_timeout, "timed_out", True)
         with _lock:
             _connections_changed.set()
 
-    wait_for_timeout.timed_out = timeout == 0
+    setattr(wait_for_timeout, "timed_out", timeout == 0)
     if timeout:
         thread = threading.Thread(
             target=wait_for_timeout, name="servers.wait_for_connection() timeout"
@@ -451,7 +451,7 @@ def wait_for_connection(session, predicate, timeout=None):
             _connections_changed.clear()
             conns = (conn for conn in _connections if predicate(conn))
             conn = next(conns, None)
-            if conn is not None or wait_for_timeout.timed_out:
+            if conn is not None or getattr(wait_for_timeout, "timed_out") is True:
                 return conn
         _connections_changed.wait()
 
@@ -479,7 +479,7 @@ def dont_wait_for_first_connection():
 
 
 def inject(pid, debugpy_args, on_output):
-    host, port = listener.getsockname()
+    host, port = listener.getsockname() if listener is not None else ("", 0)
 
     cmdline = [
         sys.executable,
diff --git a/src/debugpy/adapter/sessions.py b/src/debugpy/adapter/sessions.py
index 24b492b9..0eaeb750 100644
--- a/src/debugpy/adapter/sessions.py
+++ b/src/debugpy/adapter/sessions.py
@@ -7,7 +7,7 @@ import os
 import signal
 import threading
 import time
-from typing import Union
+from typing import Union, cast
 
 from debugpy import common
 from debugpy.common import log, util
@@ -182,7 +182,7 @@ class Session(util.Observable):
                     # can ask the launcher to kill it, do so instead of disconnecting
                     # from the server to prevent debuggee from running any more code.
                     self.launcher.terminate_debuggee()
-                else:
+                elif self.server.channel is not None:
                     # Otherwise, let the server handle it the best it can.
                     try:
                         self.server.channel.request(
@@ -220,7 +220,8 @@ class Session(util.Observable):
             self.wait_for(lambda: not self.launcher.is_connected)
 
             try:
-                self.launcher.channel.close()
+                if self.launcher.channel is not None:
+                    self.launcher.channel.close()
             except Exception:
                 log.swallow_exception()
 
@@ -232,7 +233,8 @@ class Session(util.Observable):
                 if self.client.restart_requested:
                     body["restart"] = True
                 try:
-                    self.client.channel.send_event("terminated", body)
+                    if self.client.channel is not None:
+                        self.client.channel.send_event("terminated", body)
                 except Exception:
                     pass
 
diff --git a/src/debugpy/common/json.py b/src/debugpy/common/json.py
index 6f3e2b21..2de77aca 100644
--- a/src/debugpy/common/json.py
+++ b/src/debugpy/common/json.py
@@ -9,6 +9,7 @@ import builtins
 import json
 import numbers
 import operator
+from typing import Any, Callable, Literal, Tuple, Union
 
 
 JsonDecoder = json.JSONDecoder
@@ -21,14 +22,14 @@ class JsonEncoder(json.JSONEncoder):
     result is serialized instead of the object itself.
     """
 
-    def default(self, value):
+    def default(self, o):
         try:
-            get_state = value.__getstate__
+            get_state = o.__getstate__
         except AttributeError:
             pass
         else:
             return get_state()
-        return super().default(value)
+        return super().default(o)
 
 
 class JsonObject(object):
@@ -93,12 +94,12 @@ class JsonObject(object):
 # some substitutions - e.g. replacing () with some default value.
 
 
-def _converter(value, classinfo):
+def _converter(value: str, classinfo) -> Any:
     """Convert value (str) to number, otherwise return None if is not possible"""
     for one_info in classinfo:
         if issubclass(one_info, numbers.Number):
             try:
-                return one_info(value)
+                return one_info(value) # pyright: ignore
             except ValueError:
                 pass
 
@@ -171,7 +172,7 @@ def enum(*values, **kwargs):
     return validate
 
 
-def array(validate_item=False, vectorize=False, size=None):
+def array(validate_item: Union[Callable[..., Any], Literal[False]]=False, vectorize=False, size=None):
     """Returns a validator for a JSON array.
 
     If the property is missing, it is treated as if it were []. Otherwise, it must
@@ -213,11 +214,11 @@ def array(validate_item=False, vectorize=False, size=None):
         )
     elif isinstance(size, tuple):
         assert 1 <= len(size) <= 2
-        size = tuple(operator.index(n) for n in size)
-        min_len, max_len = (size + (None,))[0:2]
+        sizes = tuple(operator.index(n) for n in size)
+        min_len, max_len = (sizes + (None,))[0:2]
         validate_size = lambda value: (
             "must have at least {0} elements".format(min_len)
-            if len(value) < min_len
+            if min_len is None or len(value) < min_len
             else "must have at most {0} elements".format(max_len)
             if max_len is not None and len(value) < max_len
             else True
@@ -250,7 +251,7 @@ def array(validate_item=False, vectorize=False, size=None):
     return validate
 
 
-def object(validate_value=False):
+def object(validate_value: Union[Callable[..., Any], Tuple, Literal[False]]=False):
     """Returns a validator for a JSON object.
 
     If the property is missing, it is treated as if it were {}. Otherwise, it must
diff --git a/src/debugpy/common/messaging.py b/src/debugpy/common/messaging.py
index 644c1ba2..3429040a 100644
--- a/src/debugpy/common/messaging.py
+++ b/src/debugpy/common/messaging.py
@@ -344,7 +344,7 @@ class MessageDict(collections.OrderedDict):
     such guarantee for outgoing messages.
     """
 
-    def __init__(self, message, items=None):
+    def __init__(self, message, items: Union[dict, None]=None):
         assert message is None or isinstance(message, Message)
 
         if items is None:
@@ -683,7 +683,7 @@ class Request(Message):
             arguments.associate_with(self)
         self.arguments = arguments
 
-        self.response = None
+        self.response: Union[Response, None] = None
         """Response to this request.
 
         For incoming requests, it is set as soon as the request handler returns.
@@ -809,7 +809,7 @@ class OutgoingRequest(Request):
             while self.response is None:
                 self.channel._handlers_enqueued.wait()
 
-        if raise_if_failed and not self.response.success and isinstance( self.response.body, Exception):
+        if raise_if_failed and not self.response.success and isinstance( self.response.body, BaseException):
             raise self.response.body
         return self.response.body
 
@@ -1297,7 +1297,10 @@ class JsonMessageChannel(object):
 
     def request(self, *args, **kwargs):
         """Same as send_request(...).wait_for_response()"""
-        return self.send_request(*args, **kwargs).wait_for_response()
+        # This should always raise an exception on failure
+        result = self.send_request(*args, **kwargs).wait_for_response()
+        assert not isinstance(result, BaseException)
+        return result
 
     def propagate(self, message):
         """Sends a new message with the same type and payload.
diff --git a/src/debugpy/common/singleton.py b/src/debugpy/common/singleton.py
index d515a4ab..f8da9ec3 100644
--- a/src/debugpy/common/singleton.py
+++ b/src/debugpy/common/singleton.py
@@ -86,12 +86,16 @@ class Singleton(object):
 
     def __enter__(self):
         """Lock this singleton to prevent concurrent access."""
-        type(self)._lock.acquire()
+        lock = type(self)._lock
+        assert lock is not None 
+        lock.acquire()
         return self
 
     def __exit__(self, exc_type, exc_value, exc_tb):
         """Unlock this singleton to allow concurrent access."""
-        type(self)._lock.release()
+        lock = type(self)._lock
+        assert lock is not None 
+        lock.release()
 
     def share(self):
         """Share this singleton, if it was originally created with shared=False."""
@@ -138,7 +142,7 @@ class ThreadSafeSingleton(Singleton):
     # ensure thread safety for the callers.
 
     @staticmethod
-    def assert_locked(self):
+    def assert_locked(self): # type: ignore
         lock = type(self)._lock
         assert lock.acquire(blocking=False), (
             "ThreadSafeSingleton accessed without locking. Either use with-statement, "