diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 8187aa0d..974684bd 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -85,7 +85,7 @@ jobs:
         run: |
           hatch run typing:test
           hatch run lint:style
-          pipx run interrogate -vv .
+          pipx run interrogate -vv . --fail-under 90
           pipx run doc8 --max-line-length=200
 
   check_release:
diff --git a/ipykernel/debugger.py b/ipykernel/debugger.py
index 509f0f26..c1af0092 100644
--- a/ipykernel/debugger.py
+++ b/ipykernel/debugger.py
@@ -4,6 +4,7 @@
 import sys
 import typing as t
 from math import inf
+from typing import Any
 
 import zmq
 from anyio import Event, create_memory_object_stream
@@ -116,9 +117,9 @@ def __init__(self, event_callback, log):
         self.tcp_buffer = ""
         self._reset_tcp_pos()
         self.event_callback = event_callback
-        self.message_send_stream, self.message_receive_stream = create_memory_object_stream(
-            max_buffer_size=inf
-        )
+        self.message_send_stream, self.message_receive_stream = create_memory_object_stream[
+            dict[str, Any]
+        ](max_buffer_size=inf)
         self.log = log
 
     def _reset_tcp_pos(self):
@@ -287,7 +288,6 @@ def disconnect_tcp_socket(self):
         """Disconnect from the tcp socket."""
         self.debugpy_socket.disconnect(self._get_endpoint())
         self.routing_id = None
-        self.init_event = Event()
         self.init_event_seq = -1
         self.wait_for_attach = True
 
@@ -343,9 +343,9 @@ def __init__(
         self.is_started = False
         self.event_callback = event_callback
         self.just_my_code = just_my_code
-        self.stopped_send_stream, self.stopped_receive_stream = create_memory_object_stream(
-            max_buffer_size=inf
-        )
+        self.stopped_send_stream, self.stopped_receive_stream = create_memory_object_stream[
+            dict[str, Any]
+        ](max_buffer_size=inf)
 
         self.started_debug_handlers = {}
         for msg_type in Debugger.started_debug_msg_types:
diff --git a/ipykernel/inprocess/ipkernel.py b/ipykernel/inprocess/ipkernel.py
index 087b323a..faf3caa5 100644
--- a/ipykernel/inprocess/ipkernel.py
+++ b/ipykernel/inprocess/ipkernel.py
@@ -49,11 +49,11 @@ class InProcessKernel(IPythonKernel):
     # Kernel interface
     # -------------------------------------------------------------------------
 
-    shell_class = Type(allow_none=True)
+    shell_class = Type(allow_none=True)  # type:ignore[assignment]
     _underlying_iopub_socket = Instance(DummySocket, (False,))
     iopub_thread: IOPubThread = Instance(IOPubThread)  # type:ignore[assignment]
 
-    shell_socket = Instance(DummySocket, (True,))
+    shell_socket = Instance(DummySocket, (True,))  # type:ignore[arg-type]
 
     @default("iopub_thread")
     def _default_iopub_thread(self):
diff --git a/ipykernel/inprocess/manager.py b/ipykernel/inprocess/manager.py
index 04c718c6..6716677e 100644
--- a/ipykernel/inprocess/manager.py
+++ b/ipykernel/inprocess/manager.py
@@ -3,6 +3,8 @@
 # Copyright (c) IPython Development Team.
 # Distributed under the terms of the Modified BSD License.
 
+from typing import Any
+
 from anyio import TASK_STATUS_IGNORED
 from anyio.abc import TaskStatus
 from jupyter_client.manager import KernelManager
@@ -43,7 +45,7 @@ def _default_session(self):
     # Kernel management methods
     # --------------------------------------------------------------------------
 
-    async def start_kernel(self, *, task_status: TaskStatus = TASK_STATUS_IGNORED, **kwds) -> None:
+    async def start_kernel(self, *, task_status: TaskStatus = TASK_STATUS_IGNORED, **kwds: Any) -> None:  # type: ignore[explicit-override, override]
         """Start the kernel."""
         from ipykernel.inprocess.ipkernel import InProcessKernel
 
@@ -56,20 +58,26 @@ def shutdown_kernel(self):
             self.kernel.iopub_thread.stop()
             self._kill_kernel()
 
-    async def restart_kernel(
-        self, now=False, *, task_status: TaskStatus = TASK_STATUS_IGNORED, **kwds
+    async def restart_kernel(  # type: ignore[explicit-override, override]
+        self,
+        now: bool = False,
+        newports: bool = False,
+        *,
+        task_status: TaskStatus = TASK_STATUS_IGNORED,
+        **kw: Any,
     ) -> None:
         """Restart the kernel."""
         self.shutdown_kernel()
-        await self.start_kernel(task_status=task_status, **kwds)
+        await self.start_kernel(task_status=task_status, **kw)
 
     @property
     def has_kernel(self):
         return self.kernel is not None
 
     def _kill_kernel(self):
-        self.kernel.stop()
-        self.kernel = None
+        if self.kernel:
+            self.kernel.stop()
+            self.kernel = None
 
     def interrupt_kernel(self):
         """Interrupt the kernel."""
diff --git a/ipykernel/inprocess/socket.py b/ipykernel/inprocess/socket.py
index 3e79297c..18035725 100644
--- a/ipykernel/inprocess/socket.py
+++ b/ipykernel/inprocess/socket.py
@@ -4,6 +4,7 @@
 # Distributed under the terms of the Modified BSD License.
 
 from math import inf
+from typing import Any
 
 import zmq
 from anyio import create_memory_object_stream
@@ -31,12 +32,12 @@ def __init__(self, is_shell, *args, **kwargs):
         self.is_shell = is_shell
         self.on_recv = None
         if is_shell:
-            self.in_send_stream, self.in_receive_stream = create_memory_object_stream(
-                max_buffer_size=inf
-            )
-            self.out_send_stream, self.out_receive_stream = create_memory_object_stream(
-                max_buffer_size=inf
-            )
+            self.in_send_stream, self.in_receive_stream = create_memory_object_stream[
+                dict[str, Any]
+            ](max_buffer_size=inf)
+            self.out_send_stream, self.out_receive_stream = create_memory_object_stream[
+                dict[str, Any]
+            ](max_buffer_size=inf)
 
     def put(self, msg):
         self.in_send_stream.send_nowait(msg)
diff --git a/ipykernel/kernelapp.py b/ipykernel/kernelapp.py
index adf03ac3..7b2a1db0 100644
--- a/ipykernel/kernelapp.py
+++ b/ipykernel/kernelapp.py
@@ -550,7 +550,7 @@ def init_signal(self):
 
     def init_kernel(self):
         """Create the Kernel object itself"""
-        kernel_factory = self.kernel_class.instance
+        kernel_factory = self.kernel_class.instance  # type:ignore[attr-defined]
 
         kernel = kernel_factory(
             parent=self,
diff --git a/ipykernel/kernelbase.py b/ipykernel/kernelbase.py
index d1ea79fc..f780c6dd 100644
--- a/ipykernel/kernelbase.py
+++ b/ipykernel/kernelbase.py
@@ -314,6 +314,9 @@ async def process_shell(self):
             raise e
 
     async def process_shell_message(self, msg=None):
+        assert self.shell_socket is not None
+        assert self.session is not None
+
         no_msg = msg is None if self._is_test else not await self.shell_socket.poll(0)
 
         msg = msg or await self.shell_socket.recv_multipart()
@@ -398,6 +401,9 @@ async def process_control(self):
             raise e
 
     async def process_control_message(self, msg=None):
+        assert self.control_socket is not None
+        assert self.session is not None
+
         msg = msg or await self.control_socket.recv_multipart()
         idents, msg = self.session.feed_identities(msg, copy=True)
         try:
@@ -666,6 +672,7 @@ async def execute_request(self, socket, ident, parent):
 
         self.log.debug("%s", reply_msg)
 
+        assert reply_msg is not None
         if not silent and reply_msg["content"]["status"] == "error" and stop_on_error:
             # while this flag is true,
             # execute requests will be aborted
@@ -768,7 +775,7 @@ async def connect_request(self, socket, ident, parent):
         """Handle a connect request."""
         if not self.session:
             return
-        content = self._recorded_ports.copy() if self._recorded_ports is not None else {}
+        content = self._recorded_ports.copy() if self._recorded_ports else {}
         content["status"] = "ok"
         msg = self.session.send(socket, "connect_reply", content, parent, ident)
         self.log.debug("%s", msg)
@@ -1049,6 +1056,7 @@ async def _send_abort_reply(self, socket, msg, idents):
         md = self.finish_metadata(msg, md, status)
         md.update(status)
 
+        assert self.session is not None
         self.session.send(
             socket,
             reply_type,