diff --git a/app/seed/evolution_tracks.json b/app/seed/evolution_tracks.json
index a4bd1f0..4f06142 100644
--- a/app/seed/evolution_tracks.json
+++ b/app/seed/evolution_tracks.json
@@ -1,5 +1,29 @@
 [
-  {"name": "Batter", "card_type": "batter", "formula": "pa+tb*2", "t1": 37, "t2": 149, "t3": 448, "t4": 896},
-  {"name": "Starting Pitcher", "card_type": "sp", "formula": "ip+k", "t1": 10, "t2": 40, "t3": 120, "t4": 240},
-  {"name": "Relief Pitcher", "card_type": "rp", "formula": "ip+k", "t1": 3, "t2": 12, "t3": 35, "t4": 70}
+  {
+    "name": "Batter Track",
+    "card_type": "batter",
+    "formula": "pa + tb * 2",
+    "t1_threshold": 37,
+    "t2_threshold": 149,
+    "t3_threshold": 448,
+    "t4_threshold": 896
+  },
+  {
+    "name": "Starting Pitcher Track",
+    "card_type": "sp",
+    "formula": "ip + k",
+    "t1_threshold": 10,
+    "t2_threshold": 40,
+    "t3_threshold": 120,
+    "t4_threshold": 240
+  },
+  {
+    "name": "Relief Pitcher Track",
+    "card_type": "rp",
+    "formula": "ip + k",
+    "t1_threshold": 3,
+    "t2_threshold": 12,
+    "t3_threshold": 35,
+    "t4_threshold": 70
+  }
 ]
diff --git a/app/seed/evolution_tracks.py b/app/seed/evolution_tracks.py
index 178f68e..3875a95 100644
--- a/app/seed/evolution_tracks.py
+++ b/app/seed/evolution_tracks.py
@@ -1,41 +1,62 @@
-"""Seed data fixture for EvolutionTrack.
+"""Seed script for EvolutionTrack records.
 
-Inserts the three universal evolution tracks (Batter, Starting Pitcher,
-Relief Pitcher) if they do not already exist.  Safe to call multiple times
-thanks to get_or_create — depends on WP-01 (EvolutionTrack model) to run.
+Loads track definitions from evolution_tracks.json and upserts them into the
+database using get_or_create keyed on name. Existing tracks have their
+thresholds and formula updated to match the JSON in case values have changed.
+
+Can be run standalone:
+    python -m app.seed.evolution_tracks
 """
 
 import json
-import os
+from pathlib import Path
 
-_JSON_PATH = os.path.join(os.path.dirname(__file__), "evolution_tracks.json")
+from app.db_engine import EvolutionTrack
+
+_JSON_PATH = Path(__file__).parent / "evolution_tracks.json"
 
 
-def load_tracks():
-    """Return the locked list of evolution track dicts from the JSON fixture."""
-    with open(_JSON_PATH) as fh:
-        return json.load(fh)
+def seed_evolution_tracks() -> list[EvolutionTrack]:
+    """Upsert evolution tracks from JSON seed data.
 
-
-def seed(model_class=None):
-    """Insert evolution tracks that are not yet in the database.
-
-    Args:
-        model_class: Peewee model with get_or_create support.  Defaults to
-            ``app.db_engine.EvolutionTrack`` (imported lazily so this module
-            can be imported before WP-01 lands).
-
-    Returns:
-        List of (instance, created) tuples from get_or_create.
+    Returns a list of EvolutionTrack instances that were created or updated.
     """
-    if model_class is None:
-        from app.db_engine import EvolutionTrack as model_class  # noqa: PLC0415
+    raw = _JSON_PATH.read_text(encoding="utf-8")
+    track_defs = json.loads(raw)
 
-    results = []
-    for track in load_tracks():
-        instance, created = model_class.get_or_create(
-            card_type=track["card_type"],
-            defaults=track,
+    results: list[EvolutionTrack] = []
+
+    for defn in track_defs:
+        track, created = EvolutionTrack.get_or_create(
+            name=defn["name"],
+            defaults={
+                "card_type": defn["card_type"],
+                "formula": defn["formula"],
+                "t1_threshold": defn["t1_threshold"],
+                "t2_threshold": defn["t2_threshold"],
+                "t3_threshold": defn["t3_threshold"],
+                "t4_threshold": defn["t4_threshold"],
+            },
         )
-        results.append((instance, created))
+
+        if not created:
+            # Update mutable fields in case the JSON values changed.
+            track.card_type = defn["card_type"]
+            track.formula = defn["formula"]
+            track.t1_threshold = defn["t1_threshold"]
+            track.t2_threshold = defn["t2_threshold"]
+            track.t3_threshold = defn["t3_threshold"]
+            track.t4_threshold = defn["t4_threshold"]
+            track.save()
+
+        action = "created" if created else "updated"
+        print(f"  [{action}] {track.name} (card_type={track.card_type})")
+        results.append(track)
+
     return results
+
+
+if __name__ == "__main__":
+    print("Seeding evolution tracks...")
+    tracks = seed_evolution_tracks()
+    print(f"Done. {len(tracks)} track(s) processed.")