diff --git a/packages/testing/src/consensus_testing/test_fixtures/networking_codec.py b/packages/testing/src/consensus_testing/test_fixtures/networking_codec.py
index 7754216e6..01ac012aa 100644
--- a/packages/testing/src/consensus_testing/test_fixtures/networking_codec.py
+++ b/packages/testing/src/consensus_testing/test_fixtures/networking_codec.py
@@ -1,7 +1,7 @@
 """Networking codec test fixture for wire-format conformance testing."""
 
 from collections.abc import Callable
-from typing import Annotated, ClassVar, Final, Literal, Union
+from typing import Annotated, ClassVar, Final, Literal
 
 from pydantic import Field
 
@@ -699,20 +699,18 @@ def attempt_decode(self) -> Exception | None:
 
 
 NetworkingCodec = Annotated[
-    Union[
-        VarintRoundtrip,
-        GossipTopicRoundtrip,
-        GossipMessageIdentifier,
-        GossipsubRpcRoundtrip,
-        ReqRespRequestRoundtrip,
-        ReqRespResponseRoundtrip,
-        ReqRespResponseStream,
-        EnrRoundtrip,
-        PeerIdentifierDerivation,
-        SnappyBlockRoundtrip,
-        SnappyFrameRoundtrip,
-        DecodeFailure,
-    ],
+    VarintRoundtrip
+    | GossipTopicRoundtrip
+    | GossipMessageIdentifier
+    | GossipsubRpcRoundtrip
+    | ReqRespRequestRoundtrip
+    | ReqRespResponseRoundtrip
+    | ReqRespResponseStream
+    | EnrRoundtrip
+    | PeerIdentifierDerivation
+    | SnappyBlockRoundtrip
+    | SnappyFrameRoundtrip
+    | DecodeFailure,
     Field(discriminator="kind"),
 ]
 """Discriminated union of every networking codec case under test."""
diff --git a/packages/testing/src/consensus_testing/test_fixtures/slot_clock.py b/packages/testing/src/consensus_testing/test_fixtures/slot_clock.py
index b2c396f0a..406a392d2 100644
--- a/packages/testing/src/consensus_testing/test_fixtures/slot_clock.py
+++ b/packages/testing/src/consensus_testing/test_fixtures/slot_clock.py
@@ -1,6 +1,6 @@
 """Slot clock test fixture for timing conformance testing."""
 
-from typing import Annotated, ClassVar, Literal, Union
+from typing import Annotated, ClassVar, Literal
 
 from pydantic import Field
 
@@ -146,7 +146,7 @@ def run(self) -> TotalIntervalsOutput:
 
 
 SlotClockOperation = Annotated[
-    Union[FromUnixTime, FromSlot, CurrentSlot, CurrentInterval, TotalIntervals],
+    FromUnixTime | FromSlot | CurrentSlot | CurrentInterval | TotalIntervals,
     Field(discriminator="kind"),
 ]
 """Discriminated union of every slot clock conversion under test."""
diff --git a/packages/testing/src/consensus_testing/test_types/step_types.py b/packages/testing/src/consensus_testing/test_types/step_types.py
index b42530df2..cb449eb4a 100644
--- a/packages/testing/src/consensus_testing/test_types/step_types.py
+++ b/packages/testing/src/consensus_testing/test_types/step_types.py
@@ -1,6 +1,6 @@
 """Step types for fork choice tests: author-facing inputs and emitted results."""
 
-from typing import Annotated, Any, Literal, Union
+from typing import Annotated, Any, Literal
 
 from pydantic import Field, field_serializer, model_validator
 
@@ -173,7 +173,7 @@ class GossipAggregatedAttestationStep(BaseForkChoiceStep):
 
 # Discriminated union type for all fork choice steps
 ForkChoiceStep = Annotated[
-    Union[TickStep, BlockStep, AttestationStep, GossipAggregatedAttestationStep],
+    TickStep | BlockStep | AttestationStep | GossipAggregatedAttestationStep,
     Field(discriminator="step_type"),
 ]
 
@@ -281,11 +281,9 @@ class FilledGossipAggregatedAttestationStep(BaseFilledStep):
 
 # Discriminated union type for all emitted fork choice steps
 FilledForkChoiceStep = Annotated[
-    Union[
-        FilledTickStep,
-        FilledBlockStep,
-        FilledAttestationStep,
-        FilledGossipAggregatedAttestationStep,
-    ],
+    FilledTickStep
+    | FilledBlockStep
+    | FilledAttestationStep
+    | FilledGossipAggregatedAttestationStep,
     Field(discriminator="step_type"),
 ]