diff --git a/tests/test_synthetic_fixtures.py b/tests/test_synthetic_fixtures.py
index dc8375a..9feea87 100644
--- a/tests/test_synthetic_fixtures.py
+++ b/tests/test_synthetic_fixtures.py
@@ -7,7 +7,6 @@
 import shutil
 import sqlite3
 import struct
-import sys
 import zipfile
 from pathlib import Path
 
@@ -148,18 +147,22 @@ def test_public_fixture_is_synthetic_sealed_and_exactly_bound(
 def _is_the_reference_builder() -> bool:
     """Report whether this interpreter regenerates the committed bytes exactly.
 
-    Python 3.12 with the required SQLite and SQLAlchemy is the one environment
-    that `test_public_fixtures_match_the_source_generator_byte_for_byte` proves
-    reproduces every committed byte. A tamper test is only meaningful there: on
-    any other builder a raised `generated bytes are stale` could report the
-    builder rather than the tamper.
+    The determinants are the ones the provenance `builder` block names: this
+    repository's writer code plus the required SQLite and SQLAlchemy versions.
+    The Python version is not among them. CPython 3.10.20, 3.11.15 and 3.12.13,
+    each carrying SQLite 3.53.1 and SQLAlchemy 2.0.52, regenerate all ten
+    committed artifacts identically, so every lane whose libraries match runs
+    the byte check and the tamper tests rather than skipping them.
+
+    A tamper test is meaningful only on a matching builder: elsewhere a raised
+    `generated bytes are stale` could report the builder rather than the tamper.
     """
     import sqlalchemy
 
-    return sys.version_info[:2] == (3, 12) and (
-        sqlite3.sqlite_version,
-        sqlalchemy.__version__,
-    ) == (REQUIRED_SQLITE_VERSION, REQUIRED_SQLALCHEMY_VERSION)
+    return (sqlite3.sqlite_version, sqlalchemy.__version__) == (
+        REQUIRED_SQLITE_VERSION,
+        REQUIRED_SQLALCHEMY_VERSION,
+    )
 
 
 REFERENCE_BUILDER_ONLY = pytest.mark.skipif(
@@ -175,24 +178,26 @@ def _copy_committed_fixtures(destination: Path) -> Path:
 
 
 def test_public_fixtures_match_the_source_generator_byte_for_byte() -> None:
-    import sqlalchemy
+    """Every lane asserts one of the two outcomes, and none asserts nothing.
 
-    if sys.version_info[:2] != (3, 12):
-        actual = (sqlite3.sqlite_version, sqlalchemy.__version__)
-        expected = (REQUIRED_SQLITE_VERSION, REQUIRED_SQLALCHEMY_VERSION)
-        if actual != expected:
-            with pytest.raises(RuntimeError, match="synthetic capture generation requires"):
-                check_generated(
-                    spec_root=CAPTURE_ROOT / "specs",
-                    output_root=CAPTURE_ROOT,
-                    generator_path=GENERATOR,
-                )
+    A matching builder regenerates the committed bytes and compares them. A
+    non-matching builder cannot reproduce them, so it asserts that the
+    generator refuses to write instead of emitting bytes it cannot certify.
+    """
+    if _is_the_reference_builder():
+        check_generated(
+            spec_root=CAPTURE_ROOT / "specs",
+            output_root=CAPTURE_ROOT,
+            generator_path=GENERATOR,
+        )
         return
-    check_generated(
-        spec_root=CAPTURE_ROOT / "specs",
-        output_root=CAPTURE_ROOT,
-        generator_path=GENERATOR,
-    )
+
+    with pytest.raises(RuntimeError, match="synthetic capture generation requires"):
+        check_generated(
+            spec_root=CAPTURE_ROOT / "specs",
+            output_root=CAPTURE_ROOT,
+            generator_path=GENERATOR,
+        )
 
 
 @REFERENCE_BUILDER_ONLY