diff --git a/src/test_suite/fuzz_interface.py b/src/test_suite/fuzz_interface.py
index 0e29745..7eac292 100644
--- a/src/test_suite/fuzz_interface.py
+++ b/src/test_suite/fuzz_interface.py
@@ -27,8 +27,10 @@
 
 
 def generic_effects_prune(
-    ctx: ContextType, effects: dict[str, EffectsType]
-) -> dict[str, EffectsType]:
+    ctx: str | None, effects: dict[str, str | None]
+) -> dict[str, str | None] | None:
+    if ctx is None:
+        return None
     return effects
 
 
@@ -52,7 +54,7 @@ class HarnessCtx:
     ignore_fields_for_consensus: list[str] = field(default_factory=list)
     diff_effect_fn: Callable[[EffectsType, EffectsType], bool] = generic_effects_diff
     prune_effects_fn: Callable[
-        [ContextType, dict[str, EffectsType]], dict[str, EffectsType]
+        [str | None, dict[str, str | None]], dict[str, str | None] | None
     ] = generic_effects_prune
     context_human_encode_fn: Callable[[ContextType], None] = generic_human_encode
     context_human_decode_fn: Callable[[ContextType], None] = generic_human_decode
diff --git a/src/test_suite/instr/prune_utils.py b/src/test_suite/instr/prune_utils.py
index fec58dc..5e9cb43 100644
--- a/src/test_suite/instr/prune_utils.py
+++ b/src/test_suite/instr/prune_utils.py
@@ -5,14 +5,14 @@
 
 
 def prune_execution_result(
-    serialized_context: str,
+    serialized_context: str | None,
     targets_to_serialized_effects: dict[str, str | None],
 ) -> dict[str, str | None] | None:
     """
     Prune execution result to only include actually modified accounts.
 
     Args:
-        - serialized_context (str): Serialized instruction context.
+        - serialized_context (str | None): Serialized instruction context.
         - targets_to_serialized_effects (dict[str, str | None]): Dictionary of target library names and serialized instruction effects.
 
     Returns:
diff --git a/src/test_suite/test_suite.py b/src/test_suite/test_suite.py
index a3eadf2..7740525 100644
--- a/src/test_suite/test_suite.py
+++ b/src/test_suite/test_suite.py
@@ -23,10 +23,10 @@
 import tqdm
 from test_suite.fuzz_context import *
 
-globals.harness_ctx = InstrHarness
+# globals.harness_ctx = InstrHarness
 # globals.harness_ctx = SyscallHarness
 # globals.harness_ctx = ValidateVM
-# globals.harness_ctx = TxnHarness
+globals.harness_ctx = TxnHarness
 
 app = typer.Typer(
     help="Validate instruction effects from clients using instruction context Protobuf messages."
diff --git a/src/test_suite/txn/prune_utils.py b/src/test_suite/txn/prune_utils.py
index e1c206f..e6fac94 100644
--- a/src/test_suite/txn/prune_utils.py
+++ b/src/test_suite/txn/prune_utils.py
@@ -4,14 +4,14 @@
 
 
 def prune_execution_result(
-    serialized_context: str,
+    serialized_context: str | None,
     targets_to_serialized_effects: dict[str, str | None],
 ) -> dict[str, str | None] | None:
     """
     Prune execution result to only include actually modified accounts.
 
     Args:
-        - serialized_context (str): Serialized context.
+        - serialized_context (str | None): Serialized context.
         - targets_to_serialized_effects (dict[str, str | None]): Dictionary of target library names and serialized effects.
 
     Returns: