diff --git a/test_runner/fixtures/benchmark_fixture.py b/test_runner/fixtures/benchmark_fixture.py
index 74fe39ef53..d3419bd8b1 100644
--- a/test_runner/fixtures/benchmark_fixture.py
+++ b/test_runner/fixtures/benchmark_fixture.py
@@ -80,7 +80,13 @@ class PgBenchRunResult:
     ):
         stdout_lines = stdout.splitlines()
 
+        number_of_clients = 0
+        number_of_threads = 0
+        number_of_transactions_actually_processed = 0
+        latency_average = 0.0
         latency_stddev = None
+        tps = 0.0
+        scale = 0
 
         # we know significant parts of these values from test input
         # but to be precise take them from output
diff --git a/test_runner/fixtures/compare_fixtures.py b/test_runner/fixtures/compare_fixtures.py
index 2195ae8225..85b6e7a3b8 100644
--- a/test_runner/fixtures/compare_fixtures.py
+++ b/test_runner/fixtures/compare_fixtures.py
@@ -8,7 +8,7 @@ from contextlib import _GeneratorContextManager, contextmanager
 
 # Type-related stuff
 from pathlib import Path
-from typing import TYPE_CHECKING
+from typing import TYPE_CHECKING, final
 
 import pytest
 from _pytest.fixtures import FixtureRequest
@@ -70,12 +70,12 @@ class PgCompare(ABC):
 
     @contextmanager
     @abstractmethod
-    def record_pageserver_writes(self, out_name: str):
+    def record_pageserver_writes(self, out_name: str) -> Iterator[None]:
         pass
 
     @contextmanager
     @abstractmethod
-    def record_duration(self, out_name: str):
+    def record_duration(self, out_name: str) -> Iterator[None]:
         pass
 
     @contextmanager
@@ -105,6 +105,7 @@ class PgCompare(ABC):
         return results
 
 
+@final
 class NeonCompare(PgCompare):
     """PgCompare interface for the neon stack."""
 
@@ -206,6 +207,7 @@ class NeonCompare(PgCompare):
         return self.zenbenchmark.record_duration(out_name)
 
 
+@final
 class VanillaCompare(PgCompare):
     """PgCompare interface for vanilla postgres."""
 
@@ -271,6 +273,7 @@ class VanillaCompare(PgCompare):
         return self.zenbenchmark.record_duration(out_name)
 
 
+@final
 class RemoteCompare(PgCompare):
     """PgCompare interface for a remote postgres instance."""
 
diff --git a/test_runner/fixtures/h2server.py b/test_runner/fixtures/h2server.py
index 92783e1fb2..e890b2bcf1 100644
--- a/test_runner/fixtures/h2server.py
+++ b/test_runner/fixtures/h2server.py
@@ -4,11 +4,14 @@ https://python-hyper.org/projects/hyper-h2/en/stable/asyncio-example.html
 auth-broker -> local-proxy needs a h2 connection, so we need a h2 server :)
 """
 
+from __future__ import annotations
+
 import asyncio
 import collections
 import io
 import json
 from collections.abc import AsyncIterable
+from typing import TYPE_CHECKING, final
 
 import pytest_asyncio
 from h2.config import H2Configuration
@@ -25,34 +28,45 @@ from h2.events import (
 )
 from h2.exceptions import ProtocolError, StreamClosedError
 from h2.settings import SettingCodes
+from typing_extensions import override
+
+if TYPE_CHECKING:
+    from typing import Any, Optional
+
 
 RequestData = collections.namedtuple("RequestData", ["headers", "data"])
 
 
+@final
 class H2Server:
-    def __init__(self, host, port) -> None:
+    def __init__(self, host: str, port: int) -> None:
         self.host = host
         self.port = port
 
 
+@final
 class H2Protocol(asyncio.Protocol):
     def __init__(self):
         config = H2Configuration(client_side=False, header_encoding="utf-8")
         self.conn = H2Connection(config=config)
-        self.transport = None
-        self.stream_data = {}
-        self.flow_control_futures = {}
+        self.transport: Optional[asyncio.Transport] = None
+        self.stream_data: dict[int, RequestData] = {}
+        self.flow_control_futures: dict[int, asyncio.Future[Any]] = {}
 
-    def connection_made(self, transport: asyncio.Transport):  # type: ignore[override]
+    @override
+    def connection_made(self, transport: asyncio.BaseTransport):
+        assert isinstance(transport, asyncio.Transport)
         self.transport = transport
         self.conn.initiate_connection()
         self.transport.write(self.conn.data_to_send())
 
-    def connection_lost(self, _exc):
+    @override
+    def connection_lost(self, exc: Optional[Exception]):
         for future in self.flow_control_futures.values():
             future.cancel()
         self.flow_control_futures = {}
 
+    @override
     def data_received(self, data: bytes):
         assert self.transport is not None
         try:
@@ -77,7 +91,7 @@ class H2Protocol(asyncio.Protocol):
                     self.window_updated(event.stream_id, event.delta)
                 elif isinstance(event, RemoteSettingsChanged):
                     if SettingCodes.INITIAL_WINDOW_SIZE in event.changed_settings:
-                        self.window_updated(None, 0)
+                        self.window_updated(0, 0)
 
                 self.transport.write(self.conn.data_to_send())
 
@@ -123,7 +137,7 @@ class H2Protocol(asyncio.Protocol):
         else:
             stream_data.data.write(data)
 
-    def stream_reset(self, stream_id):
+    def stream_reset(self, stream_id: int):
         """
         A stream reset was sent. Stop sending data.
         """
@@ -131,7 +145,7 @@ class H2Protocol(asyncio.Protocol):
             future = self.flow_control_futures.pop(stream_id)
             future.cancel()
 
-    async def send_data(self, data, stream_id):
+    async def send_data(self, data: bytes, stream_id: int):
         """
         Send data according to the flow control rules.
         """
@@ -161,7 +175,7 @@ class H2Protocol(asyncio.Protocol):
             self.transport.write(self.conn.data_to_send())
             data = data[chunk_size:]
 
-    async def wait_for_flow_control(self, stream_id):
+    async def wait_for_flow_control(self, stream_id: int):
         """
         Waits for a Future that fires when the flow control window is opened.
         """
@@ -169,7 +183,7 @@ class H2Protocol(asyncio.Protocol):
         self.flow_control_futures[stream_id] = f
         await f
 
-    def window_updated(self, stream_id, delta):
+    def window_updated(self, stream_id: int, delta):
         """
         A window update frame was received. Unblock some number of flow control
         Futures.
diff --git a/test_runner/fixtures/neon_fixtures.py b/test_runner/fixtures/neon_fixtures.py
index 83c68794c3..79baa8a32d 100644
--- a/test_runner/fixtures/neon_fixtures.py
+++ b/test_runner/fixtures/neon_fixtures.py
@@ -1857,7 +1857,7 @@ class NeonStorageController(MetricsGetter, LogUtils):
         shard_count: Optional[int] = None,
         shard_stripe_size: Optional[int] = None,
         tenant_config: Optional[dict[Any, Any]] = None,
-        placement_policy: Optional[Union[dict[Any, Any] | str]] = None,
+        placement_policy: Optional[Union[dict[Any, Any], str]] = None,
     ):
         """
         Use this rather than pageserver_api() when you need to include shard parameters
diff --git a/test_runner/fixtures/pageserver/http.py b/test_runner/fixtures/pageserver/http.py
index 57a5d6875e..d1a9b5921a 100644
--- a/test_runner/fixtures/pageserver/http.py
+++ b/test_runner/fixtures/pageserver/http.py
@@ -316,7 +316,7 @@ class PageserverHttpClient(requests.Session, MetricsGetter):
     def tenant_location_conf(
         self,
         tenant_id: Union[TenantId, TenantShardId],
-        location_conf=dict[str, Any],
+        location_conf: dict[str, Any],
         flush_ms=None,
         lazy: Optional[bool] = None,
     ):
diff --git a/test_runner/fixtures/pageserver/utils.py b/test_runner/fixtures/pageserver/utils.py
index 4c4306be9e..ac7497ee6c 100644
--- a/test_runner/fixtures/pageserver/utils.py
+++ b/test_runner/fixtures/pageserver/utils.py
@@ -56,6 +56,8 @@ def wait_for_upload(
     lsn: Lsn,
 ):
     """waits for local timeline upload up to specified lsn"""
+
+    current_lsn = Lsn(0)
     for i in range(20):
         current_lsn = remote_consistent_lsn(pageserver_http, tenant, timeline)
         if current_lsn >= lsn:
@@ -203,6 +205,8 @@ def wait_for_last_record_lsn(
     lsn: Lsn,
 ) -> Lsn:
     """waits for pageserver to catch up to a certain lsn, returns the last observed lsn."""
+
+    current_lsn = Lsn(0)
     for i in range(1000):
         current_lsn = last_record_lsn(pageserver_http, tenant, timeline)
         if current_lsn >= lsn:
diff --git a/test_runner/fixtures/paths.py b/test_runner/fixtures/paths.py
index d950f2356d..60221573eb 100644
--- a/test_runner/fixtures/paths.py
+++ b/test_runner/fixtures/paths.py
@@ -112,7 +112,7 @@ def compatibility_snapshot_dir() -> Iterator[Path]:
 
 
 @pytest.fixture(scope="session")
-def compatibility_neon_binpath() -> Optional[Iterator[Path]]:
+def compatibility_neon_binpath() -> Iterator[Optional[Path]]:
     if os.getenv("REMOTE_ENV"):
         return
     comp_binpath = None
@@ -133,7 +133,7 @@ def pg_distrib_dir(base_dir: Path) -> Iterator[Path]:
 
 
 @pytest.fixture(scope="session")
-def compatibility_pg_distrib_dir() -> Optional[Iterator[Path]]:
+def compatibility_pg_distrib_dir() -> Iterator[Optional[Path]]:
     compat_distrib_dir = None
     if env_compat_postgres_bin := os.environ.get("COMPATIBILITY_POSTGRES_DISTRIB_DIR"):
         compat_distrib_dir = Path(env_compat_postgres_bin).resolve()
diff --git a/test_runner/performance/test_copy.py b/test_runner/performance/test_copy.py
index 743604a381..d571fab6b5 100644
--- a/test_runner/performance/test_copy.py
+++ b/test_runner/performance/test_copy.py
@@ -2,11 +2,13 @@ from __future__ import annotations
 
 from contextlib import closing
 from io import BufferedReader, RawIOBase
-from typing import Optional
+from typing import Optional, final
 
 from fixtures.compare_fixtures import PgCompare
+from typing_extensions import override
 
 
+@final
 class CopyTestData(RawIOBase):
     def __init__(self, rows: int):
         self.rows = rows
@@ -14,6 +16,7 @@ class CopyTestData(RawIOBase):
         self.linebuf: Optional[bytes] = None
         self.ptr = 0
 
+    @override
     def readable(self):
         return True
 
diff --git a/test_runner/regress/test_pageserver_generations.py b/test_runner/regress/test_pageserver_generations.py
index 11ebb81023..8f6c9f16fd 100644
--- a/test_runner/regress/test_pageserver_generations.py
+++ b/test_runner/regress/test_pageserver_generations.py
@@ -656,6 +656,7 @@ def test_upgrade_generationless_local_file_paths(
     workload.write_rows(1000)
 
     attached_pageserver = env.get_tenant_pageserver(tenant_id)
+    assert attached_pageserver is not None
     secondary_pageserver = list([ps for ps in env.pageservers if ps.id != attached_pageserver.id])[
         0
     ]
diff --git a/test_runner/regress/test_proxy_websockets.py b/test_runner/regress/test_proxy_websockets.py
index 071ca7c54e..ea01252ce4 100644
--- a/test_runner/regress/test_proxy_websockets.py
+++ b/test_runner/regress/test_proxy_websockets.py
@@ -37,7 +37,7 @@ async def test_websockets(static_proxy: NeonProxy):
         startup_message.extend(b"\0")
         length = (4 + len(startup_message)).to_bytes(4, byteorder="big")
 
-        await websocket.send([length, startup_message])
+        await websocket.send([length, bytes(startup_message)])
 
         startup_response = await websocket.recv()
         assert isinstance(startup_response, bytes)
diff --git a/test_runner/regress/test_sharding.py b/test_runner/regress/test_sharding.py
index 3a249bbdb4..ec633e352c 100644
--- a/test_runner/regress/test_sharding.py
+++ b/test_runner/regress/test_sharding.py
@@ -256,6 +256,7 @@ def test_sharding_split_compaction(
     # Cleanup part 1: while layers are still in PITR window, we should only drop layers that are fully redundant
     for shard in shards:
         ps = env.get_tenant_pageserver(shard)
+        assert ps is not None
 
         # Invoke compaction: this should drop any layers that don't overlap with the shard's key stripes
         detail_before = ps.http_client().timeline_detail(shard, timeline_id)
diff --git a/test_runner/regress/test_storage_controller.py b/test_runner/regress/test_storage_controller.py
index c8de292588..a069e0d01c 100644
--- a/test_runner/regress/test_storage_controller.py
+++ b/test_runner/regress/test_storage_controller.py
@@ -1237,6 +1237,7 @@ def test_storage_controller_tenant_deletion(
     # Assert attachments all have local content
     for shard_id in shard_ids:
         pageserver = env.get_tenant_pageserver(shard_id)
+        assert pageserver is not None
         assert pageserver.tenant_dir(shard_id).exists()
 
     # Assert all shards have some content in remote storage
@@ -2745,6 +2746,7 @@ def test_storage_controller_validate_during_migration(neon_env_builder: NeonEnvB
 
     # Upload but don't compact
     origin_pageserver = env.get_tenant_pageserver(tenant_id)
+    assert origin_pageserver is not None
     dest_ps_id = [p.id for p in env.pageservers if p.id != origin_pageserver.id][0]
     origin_pageserver.http_client().timeline_checkpoint(
         tenant_id, timeline_id, wait_until_uploaded=True, compact=False
diff --git a/test_runner/regress/test_storage_scrubber.py b/test_runner/regress/test_storage_scrubber.py
index 05db0fe977..11ad2173ae 100644
--- a/test_runner/regress/test_storage_scrubber.py
+++ b/test_runner/regress/test_storage_scrubber.py
@@ -245,6 +245,7 @@ def test_scrubber_physical_gc_ancestors(
     workload.write_rows(100, upload=False)
     for shard in shards:
         ps = env.get_tenant_pageserver(shard)
+        assert ps is not None
         log.info(f"Waiting for shard {shard} on pageserver {ps.id}")
         ps.http_client().timeline_checkpoint(
             shard, timeline_id, compact=False, wait_until_uploaded=True
@@ -270,6 +271,7 @@ def test_scrubber_physical_gc_ancestors(
     workload.churn_rows(100)
     for shard in shards:
         ps = env.get_tenant_pageserver(shard)
+        assert ps is not None
         ps.http_client().timeline_compact(shard, timeline_id, force_image_layer_creation=True)
         ps.http_client().timeline_gc(shard, timeline_id, 0)
 
@@ -336,12 +338,15 @@ def test_scrubber_physical_gc_timeline_deletion(neon_env_builder: NeonEnvBuilder
 
     # Issue a deletion queue flush so that the parent shard can't leave behind layers
     # that will look like unexpected garbage to the scrubber
-    env.get_tenant_pageserver(tenant_id).http_client().deletion_queue_flush(execute=True)
+    ps = env.get_tenant_pageserver(tenant_id)
+    assert ps is not None
+    ps.http_client().deletion_queue_flush(execute=True)
 
     new_shard_count = 4
     shards = env.storage_controller.tenant_shard_split(tenant_id, shard_count=new_shard_count)
     for shard in shards:
         ps = env.get_tenant_pageserver(shard)
+        assert ps is not None
         log.info(f"Waiting for shard {shard} on pageserver {ps.id}")
         ps.http_client().timeline_checkpoint(
             shard, timeline_id, compact=False, wait_until_uploaded=True
diff --git a/test_runner/regress/test_tenant_size.py b/test_runner/regress/test_tenant_size.py
index b41f1709bd..0c431fa453 100644
--- a/test_runner/regress/test_tenant_size.py
+++ b/test_runner/regress/test_tenant_size.py
@@ -315,6 +315,7 @@ def test_single_branch_get_tenant_size_grows(
         tenant_id: TenantId,
         timeline_id: TimelineId,
     ) -> tuple[Lsn, int]:
+        size = 0
         consistent = False
         size_debug = None
 
@@ -360,7 +361,7 @@ def test_single_branch_get_tenant_size_grows(
         collected_responses.append(("CREATE", current_lsn, size))
 
         batch_size = 100
-
+        prev_size = 0
         for i in range(3):
             with endpoint.cursor() as cur:
                 cur.execute(
diff --git a/test_runner/regress/test_threshold_based_eviction.py b/test_runner/regress/test_threshold_based_eviction.py
index 5f211ec4d4..68e9385035 100644
--- a/test_runner/regress/test_threshold_based_eviction.py
+++ b/test_runner/regress/test_threshold_based_eviction.py
@@ -146,6 +146,7 @@ def test_threshold_based_eviction(
                 out += [f"  {remote} {layer.layer_file_name}"]
             return "\n".join(out)
 
+    stable_for: float = 0
     observation_window = 8 * eviction_threshold
     consider_stable_when_no_change_for_seconds = 3 * eviction_threshold
     poll_interval = eviction_threshold / 3
diff --git a/test_runner/regress/test_wal_acceptor.py b/test_runner/regress/test_wal_acceptor.py
index 157390c01c..e224d5eb01 100644
--- a/test_runner/regress/test_wal_acceptor.py
+++ b/test_runner/regress/test_wal_acceptor.py
@@ -1506,15 +1506,10 @@ class SafekeeperEnv:
             port=port.http,
             auth_token=None,
         )
-        try:
-            safekeeper_process = start_in_background(
-                cmd, safekeeper_dir, "safekeeper.log", safekeeper_client.check_status
-            )
-            return safekeeper_process
-        except Exception as e:
-            log.error(e)
-            safekeeper_process.kill()
-            raise Exception(f"Failed to start safekepeer as {cmd}, reason: {e}") from e
+        safekeeper_process = start_in_background(
+            cmd, safekeeper_dir, "safekeeper.log", safekeeper_client.check_status
+        )
+        return safekeeper_process
 
     def get_safekeeper_connstrs(self):
         assert self.safekeepers is not None, "safekeepers are not initialized"