diff --git a/scripts/truth.py b/scripts/truth.py
index 5611d882..7ef05940 100644
--- a/scripts/truth.py
+++ b/scripts/truth.py
@@ -18,6 +18,9 @@ from hashing import parse_md5_list
 from validation import filter_files_by_mode, read_from_system_dir
 
 
+
+_CONFLICTS_SHOWN: set[tuple[str, ...]] = set()
+
 def _serialize_source_ref(sr: object) -> str:
     """Convert a source_ref value to a clean string for serialization."""
     if isinstance(sr, str):
@@ -260,11 +263,16 @@ def _merge_hashes(
                 existing[h] = [*o_list, *added]
             continue
         if not {str(v).lower() for v in t_list} & {str(v).lower() for v in o_list}:
-            print(
-                f"WARNING: hash conflict for {file_entry['name']} "
-                f"({h}: {ours} vs {theirs}, core {emu_name})",
-                file=sys.stderr,
-            )
+            # Once per process: a run over every platform met the same pair
+            # once per platform and opened its output on six copies.
+            key = (file_entry["name"], h, str(ours), str(theirs), emu_name)
+            if key not in _CONFLICTS_SHOWN:
+                _CONFLICTS_SHOWN.add(key)
+                print(
+                    f"WARNING: hash conflict for {file_entry['name']} "
+                    f"({h}: {ours} vs {theirs}, core {emu_name})",
+                    file=sys.stderr,
+                )
 
 
 def _merge_priority(existing: dict, theirs: int | None) -> None:
diff --git a/tests/test_audit_regressions.py b/tests/test_audit_regressions.py
index 341eddee..a6394a7b 100644
--- a/tests/test_audit_regressions.py
+++ b/tests/test_audit_regressions.py
@@ -5553,5 +5553,24 @@ class AStepThatCannotFailTheRunIsNotShownFailed(unittest.TestCase):
                       (ROOT / "scripts" / "pipeline.py").read_text(encoding="utf-8"))
 
 
+class AHashConflictIsReportedOnce(unittest.TestCase):
+    """check_freshness opened on six copies of one truth.py warning, one per
+    platform whose model met the same two GameIndex.yaml declarations."""
+
+    def test_the_same_pair_prints_once(self):
+        import contextlib
+        import io
+
+        import truth
+
+        truth._CONFLICTS_SHOWN.clear()
+        err = io.StringIO()
+        with contextlib.redirect_stderr(err):
+            for _platform in range(6):
+                existing = {"name": "x.yaml", "sha1": "a" * 40}
+                truth._merge_hashes(existing, {"name": "x.yaml", "sha1": "b" * 40}, "core")
+        self.assertEqual(err.getvalue().count("WARNING"), 1)
+
+
 if __name__ == "__main__":
     unittest.main()