diff --git a/packages/db/migrations/0037_add_extra_large_to_pet_size_category.sql b/packages/db/migrations/0037_add_extra_large_to_pet_size_category.sql
new file mode 100644
index 0000000..e7eac1a
--- /dev/null
+++ b/packages/db/migrations/0037_add_extra_large_to_pet_size_category.sql
@@ -0,0 +1,19 @@
+-- Migration: 0037_add_extra_large_to_pet_size_category.sql
+-- GRO-1979: Adds the 'extra_large' value to the pet_size_category enum.
+--
+-- 0031_buffer_rules.sql created pet_size_category with values
+-- ('small', 'medium', 'large', 'xlarge'), but seed.ts and the drizzle
+-- schema (PetSizeCategory type) both use 'extra_large' — a mismatch that
+-- caused the UAT seed job to fail with:
+--   invalid input value for enum pet_size_category: "extra_large"
+--
+-- 0035/0036 (GRO-1971) registered 'short'/'medium'/'silky' in coat_type.
+-- This migration is the pet_size_category counterpart: register
+-- 'extra_large' so seed.ts can write the value the schema declares.
+--
+-- Postgres restriction: ALTER TYPE ADD VALUE cannot run inside a
+-- transaction block. The drizzle migrate runner does not wrap
+-- individual statements in an explicit transaction, so this applies
+-- as a single auto-commit DDL.
+
+ALTER TYPE "pet_size_category" ADD VALUE IF NOT EXISTS 'extra_large';
diff --git a/packages/db/migrations/meta/_journal.json b/packages/db/migrations/meta/_journal.json
index 1c7c56a..5ae5432 100644
--- a/packages/db/migrations/meta/_journal.json
+++ b/packages/db/migrations/meta/_journal.json
@@ -253,6 +253,13 @@
       "when": 1751480000000,
       "tag": "0036_add_missing_coat_type_values",
       "breakpoints": true
+    },
+    {
+      "idx": 37,
+      "version": "7",
+      "when": 1751500000000,
+      "tag": "0037_add_extra_large_to_pet_size_category",
+      "breakpoints": true
     }
   ]
 }
\ No newline at end of file