diff --git a/airflow-core/src/airflow/jobs/scheduler_job_runner.py b/airflow-core/src/airflow/jobs/scheduler_job_runner.py
index 98e743ae42382..ee93b674ddd97 100644
--- a/airflow-core/src/airflow/jobs/scheduler_job_runner.py
+++ b/airflow-core/src/airflow/jobs/scheduler_job_runner.py
@@ -3034,7 +3034,9 @@ def _exceeds_max_active_runs(
                 session=session,
             )
             active_non_backfill_runs = runs_dict.get(dag_model.dag_id, 0)
-        exceeds = active_non_backfill_runs >= dag_model.max_active_runs
+        exceeds = (
+            dag_model.max_active_runs is not None and active_non_backfill_runs >= dag_model.max_active_runs
+        )
         return exceeds, active_non_backfill_runs
 
 
diff --git a/airflow-core/src/airflow/models/trigger.py b/airflow-core/src/airflow/models/trigger.py
index 3e5d3a95ec978..942b811ce6509 100644
--- a/airflow-core/src/airflow/models/trigger.py
+++ b/airflow-core/src/airflow/models/trigger.py
@@ -98,7 +98,7 @@ class Trigger(Base):
     encrypted_kwargs: Mapped[str] = mapped_column("kwargs", Text, nullable=False)
     created_date: Mapped[datetime.datetime] = mapped_column(UtcDateTime, nullable=False)
     triggerer_id: Mapped[int | None] = mapped_column(Integer, nullable=True)
-    queue: Mapped[str] = mapped_column(String(256), nullable=True)
+    queue: Mapped[str | None] = mapped_column(String(256), nullable=True)
 
     triggerer_job = relationship(
         "Job",
diff --git a/providers/amazon/src/airflow/providers/amazon/aws/hooks/athena_sql.py b/providers/amazon/src/airflow/providers/amazon/aws/hooks/athena_sql.py
index e12589a75d12d..ad6c815223b3e 100644
--- a/providers/amazon/src/airflow/providers/amazon/aws/hooks/athena_sql.py
+++ b/providers/amazon/src/airflow/providers/amazon/aws/hooks/athena_sql.py
@@ -25,7 +25,7 @@
 try:
     from sqlalchemy.engine.url import URL
 except ImportError:
-    URL = None
+    URL = None  # type: ignore[assignment,misc]
 
 from airflow.providers.amazon.aws.hooks.base_aws import AwsBaseHook
 from airflow.providers.amazon.aws.utils.connection_wrapper import AwsConnectionWrapper
diff --git a/providers/amazon/src/airflow/providers/amazon/aws/hooks/redshift_sql.py b/providers/amazon/src/airflow/providers/amazon/aws/hooks/redshift_sql.py
index 33f2e4c83b2a8..4fc414cd28159 100644
--- a/providers/amazon/src/airflow/providers/amazon/aws/hooks/redshift_sql.py
+++ b/providers/amazon/src/airflow/providers/amazon/aws/hooks/redshift_sql.py
@@ -27,7 +27,7 @@
     from sqlalchemy import create_engine
     from sqlalchemy.engine.url import URL
 except ImportError:
-    URL = create_engine = None
+    URL = create_engine = None  # type: ignore[assignment,misc]
 
 from airflow.exceptions import AirflowOptionalProviderFeatureException
 from airflow.providers.amazon.aws.hooks.base_aws import AwsBaseHook
diff --git a/providers/common/sql/src/airflow/providers/common/sql/hooks/sql.py b/providers/common/sql/src/airflow/providers/common/sql/hooks/sql.py
index 0841030efdfac..8ab5e887c4c78 100644
--- a/providers/common/sql/src/airflow/providers/common/sql/hooks/sql.py
+++ b/providers/common/sql/src/airflow/providers/common/sql/hooks/sql.py
@@ -35,11 +35,11 @@
     from sqlalchemy.engine import make_url
     from sqlalchemy.exc import ArgumentError, NoSuchModuleError
 except ImportError:
-    create_engine = None
-    inspect = None
-    make_url = None
-    ArgumentError = Exception
-    NoSuchModuleError = Exception
+    create_engine = None  # type: ignore[assignment]
+    inspect = None  # type: ignore[assignment]
+    make_url = None  # type: ignore[assignment]
+    ArgumentError = Exception  # type: ignore[misc,assignment]
+    NoSuchModuleError = Exception  # type: ignore[misc,assignment]
 
 
 from airflow.exceptions import AirflowOptionalProviderFeatureException, AirflowProviderDeprecationWarning
diff --git a/providers/exasol/src/airflow/providers/exasol/hooks/exasol.py b/providers/exasol/src/airflow/providers/exasol/hooks/exasol.py
index cf2aa1629c96c..77ca004880917 100644
--- a/providers/exasol/src/airflow/providers/exasol/hooks/exasol.py
+++ b/providers/exasol/src/airflow/providers/exasol/hooks/exasol.py
@@ -28,7 +28,7 @@
 try:
     from sqlalchemy.engine import URL
 except ImportError:
-    URL = None
+    URL = None  # type: ignore[assignment,misc]
 
 from airflow.exceptions import AirflowOptionalProviderFeatureException, AirflowProviderDeprecationWarning
 from airflow.providers.common.sql.hooks.handlers import return_single_query_results
diff --git a/providers/openlineage/tests/unit/openlineage/plugins/test_listener.py b/providers/openlineage/tests/unit/openlineage/plugins/test_listener.py
index 1281e95a26019..d226abb8c74ef 100644
--- a/providers/openlineage/tests/unit/openlineage/plugins/test_listener.py
+++ b/providers/openlineage/tests/unit/openlineage/plugins/test_listener.py
@@ -208,7 +208,7 @@ def sample_callable(**kwargs):
             task_instance = create_task_instance(
                 t,
                 run_id=run_id,
-                dag_version_id=dagrun.created_dag_version_id,
+                dag_version_id=uuid.UUID(dagrun.created_dag_version_id),
             )
         else:
             task_instance = TaskInstance(t, run_id=run_id)  # type: ignore
diff --git a/providers/standard/tests/unit/standard/operators/test_hitl.py b/providers/standard/tests/unit/standard/operators/test_hitl.py
index 426f61760bef7..97c4ce9160b61 100644
--- a/providers/standard/tests/unit/standard/operators/test_hitl.py
+++ b/providers/standard/tests/unit/standard/operators/test_hitl.py
@@ -256,7 +256,7 @@ def test_execute(self, dag_maker: DagMaker, session: Session) -> None:
 
         expected_params_in_trigger_kwargs: dict[str, dict[str, Any]]
         # trigger_kwargs are encoded via BaseSerialization in versions < 3.2
-        expected_ti_id = ti.id
+        expected_ti_id: str | UUID = ti.id
         if AIRFLOW_V_3_2_PLUS:
             expected_params_in_trigger_kwargs = expected_params
             # trigger_kwargs are encoded via serde from task sdk in versions >= 3.2
diff --git a/task-sdk/src/airflow/sdk/serde/__init__.py b/task-sdk/src/airflow/sdk/serde/__init__.py
index b02ad36313645..5716f2a9c625e 100644
--- a/task-sdk/src/airflow/sdk/serde/__init__.py
+++ b/task-sdk/src/airflow/sdk/serde/__init__.py
@@ -25,7 +25,7 @@
 from fnmatch import fnmatch
 from importlib import import_module
 from re import Pattern
-from typing import TYPE_CHECKING, Any, TypeVar, cast
+from typing import TYPE_CHECKING, Any, TypeVar, cast, overload
 
 import attr
 
@@ -85,6 +85,14 @@ def decode(d: dict[str, Any]) -> tuple[str, int, Any]:
     return classname, version, data
 
 
+@overload
+def serialize(o: dict, depth: int = 0) -> dict: ...
+@overload
+def serialize(o: None, depth: int = 0) -> None: ...
+@overload
+def serialize(o: object, depth: int = 0) -> U | None: ...
+
+
 def serialize(o: object, depth: int = 0) -> U | None:
     """
     Serialize an object into a representation consisting only built-in types.