diff --git a/app/services/refractor_boost.py b/app/services/refractor_boost.py
index 3eb1bd1..918adbf 100644
--- a/app/services/refractor_boost.py
+++ b/app/services/refractor_boost.py
@@ -322,7 +322,7 @@ def compute_variant_hash(
             identifiers).  Order is normalised — callers need not sort.
 
     Returns:
-        A positive integer in the range [1, 2^32 - 1].
+        A positive integer in the range [1, 2^31 - 1].
     """
     inputs = {
         "player_id": player_id,
@@ -330,7 +330,11 @@ def compute_variant_hash(
         "cosmetics": sorted(cosmetics or []),
     }
     raw = hashlib.sha256(json.dumps(inputs, sort_keys=True).encode()).hexdigest()
-    result = int(raw[:8], 16)
+    # Mask to 31 bits so the result fits in Postgres signed INTEGER
+    # (the type used by every variant column). Without this mask, roughly
+    # half of all players would produce hashes above 2^31 - 1 and crash
+    # tier-up writes with peewee.DataError: integer out of range.
+    result = int(raw[:8], 16) & 0x7FFFFFFF
     return result if result != 0 else 1  # variant=0 is reserved
 
 
diff --git a/tests/test_refractor_boost.py b/tests/test_refractor_boost.py
index a2f505b..282d236 100644
--- a/tests/test_refractor_boost.py
+++ b/tests/test_refractor_boost.py
@@ -878,6 +878,31 @@ class TestVariantHash:
                     f"compute_variant_hash({player_id}, {tier}) returned 0"
                 )
 
+    def test_fits_postgres_int32(self):
+        """Hash always fits in Postgres signed INTEGER range (2^31 - 1).
+
+        What: Generate hashes for player_ids 0-9999 at tiers 0-4 and assert
+        every result is <= 2147483647.
+
+        Why: The variant columns on Card, BattingCard, PitchingCard, and
+        RefractorCardState are Peewee IntegerField → Postgres INTEGER, which
+        is signed 32-bit. Before the 31-bit mask was added, the SHA-256-derived
+        hash could return values up to 2^32 - 1, causing roughly half of all
+        tier-up attempts to crash with peewee.DataError: integer out of range.
+        Discovered via /dev refractor-test on card_id=64460 (Charles Nagy),
+        whose tier-1 hash is 2874960417 — above the int32 ceiling. Masking
+        to 31 bits drops one bit of entropy but keeps ~2.1B distinct values,
+        more than enough for collision safety.
+        """
+        int32_max = 2147483647
+        for player_id in range(10000):
+            for tier in range(5):
+                result = compute_variant_hash(player_id, tier)
+                assert result <= int32_max, (
+                    f"compute_variant_hash({player_id}, {tier}) returned "
+                    f"{result}, which exceeds Postgres INTEGER max {int32_max}"
+                )
+
     def test_cosmetics_affect_hash(self):
         """Adding cosmetics to the same player/tier produces a different hash.