diff --git a/packages/testing/src/execution_testing/cli/extract_config.py b/packages/testing/src/execution_testing/cli/extract_config.py
index 10cf25c965..af98b15a9d 100755
--- a/packages/testing/src/execution_testing/cli/extract_config.py
+++ b/packages/testing/src/execution_testing/cli/extract_config.py
@@ -36,7 +36,7 @@
 )
 from execution_testing.fixtures.blockchain import FixtureHeader
 from execution_testing.fixtures.file import Fixtures
-from execution_testing.fixtures.pre_alloc_groups import PreAllocGroup
+from execution_testing.fixtures.pre_alloc_groups import PreAllocGroupBuilder
 from execution_testing.forks import Fork
 
 
@@ -176,8 +176,9 @@ def from_fixture(cls, fixture_path: Path) -> Self:
             pass
 
         try:
-            # Try to load pre-allocation group
-            pre_alloc_group = PreAllocGroup.model_validate_json(fixture_bytes)
+            # Load as builder format and compute genesis on-demand
+            builder = PreAllocGroupBuilder.model_validate_json(fixture_bytes)
+            pre_alloc_group = builder.build()
             return cls(
                 header=pre_alloc_group.genesis,
                 alloc=pre_alloc_group.pre,
diff --git a/packages/testing/src/execution_testing/fixtures/pre_alloc_groups.py b/packages/testing/src/execution_testing/fixtures/pre_alloc_groups.py
index 6ade0d7666..69e69fcf21 100644
--- a/packages/testing/src/execution_testing/fixtures/pre_alloc_groups.py
+++ b/packages/testing/src/execution_testing/fixtures/pre_alloc_groups.py
@@ -17,7 +17,7 @@
     Tuple,
 )
 
-from pydantic import Field, PrivateAttr, ValidationError
+from pydantic import Field, PrivateAttr
 
 from execution_testing.base_types import (
     CamelModel,
@@ -340,21 +340,13 @@ def from_file(cls, file: Path) -> Self:
         """
         Load a pre-allocation group from a JSON file.
 
-        Handles both builder format (without genesis) and full format (with
-        genesis). If genesis is missing, computes it from the pre-allocation
-        state. This ensures state root computation happens exactly once when
-        loading in Phase 2, not during Phase 1 merging.
+        Files are stored in builder format (without genesis). Genesis is
+        computed on-demand when loading, ensuring state root computation
+        happens exactly once in Phase 2, not during Phase 1 merging.
         """
         with open(file) as f:
             data = f.read()
 
-        # Try loading as full PreAllocGroup first (backwards compatibility)
-        try:
-            return cls.model_validate_json(data)
-        except ValidationError:
-            pass
-
-        # Load as builder format and compute genesis
         builder = PreAllocGroupBuilder.model_validate_json(data)
         built = builder.build()
         # Use cls.model_validate to ensure proper Self return type