diff --git a/backend/alembic/versions/0006_recipe_engine_thin.py b/backend/alembic/versions/0006_recipe_engine_thin.py
new file mode 100644
index 0000000..898ee14
--- /dev/null
+++ b/backend/alembic/versions/0006_recipe_engine_thin.py
@@ -0,0 +1,96 @@
+"""thin phase 4: ingredient.aliases, recipe.calories_per_serving, ingredient_grocery_match
+
+Revision ID: 0006_recipe_engine_thin
+Revises: 0005_grocery_item_external_id
+Create Date: 2026-05-05
+"""
+from alembic import op
+import sqlalchemy as sa
+from sqlalchemy.dialects import postgresql
+from sqlalchemy.dialects.postgresql import UUID, ARRAY
+
+
+revision = "0006"
+down_revision = "0005"
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    op.add_column(
+        "ingredient",
+        sa.Column(
+            "aliases",
+            ARRAY(sa.Text()),
+            nullable=False,
+            server_default="{}",
+        ),
+    )
+
+    op.add_column(
+        "recipe",
+        sa.Column("calories_per_serving", sa.Integer(), nullable=True),
+    )
+
+    op.execute(
+        "CREATE TYPE ingredient_match_source_enum AS ENUM ('auto', 'manual')"
+    )
+
+    op.create_table(
+        "ingredient_grocery_match",
+        sa.Column(
+            "id",
+            UUID(as_uuid=True),
+            primary_key=True,
+            server_default=sa.text("gen_random_uuid()"),
+        ),
+        sa.Column(
+            "ingredient_id",
+            UUID(as_uuid=True),
+            sa.ForeignKey("ingredient.id", ondelete="CASCADE"),
+            nullable=False,
+        ),
+        sa.Column(
+            "grocery_item_id",
+            UUID(as_uuid=True),
+            sa.ForeignKey("grocery_item.id", ondelete="CASCADE"),
+            nullable=False,
+        ),
+        sa.Column("confidence", sa.Numeric(4, 3), nullable=False),
+        sa.Column(
+            "source",
+            postgresql.ENUM(
+                name="ingredient_match_source_enum",
+                create_type=False,
+            ),
+            nullable=False,
+        ),
+        sa.Column(
+            "updated_at",
+            sa.DateTime(timezone=True),
+            server_default=sa.func.now(),
+            nullable=False,
+        ),
+        sa.UniqueConstraint(
+            "ingredient_id",
+            "grocery_item_id",
+            name="uq_ingredient_grocery_match_pair",
+        ),
+    )
+
+    op.create_index(
+        "ix_ingredient_grocery_match_ingredient_confidence",
+        "ingredient_grocery_match",
+        ["ingredient_id", sa.text("confidence DESC")],
+    )
+
+
+def downgrade() -> None:
+    op.drop_index(
+        "ix_ingredient_grocery_match_ingredient_confidence",
+        table_name="ingredient_grocery_match",
+    )
+    op.drop_table("ingredient_grocery_match")
+    op.execute("DROP TYPE IF EXISTS ingredient_match_source_enum")
+    op.drop_column("recipe", "calories_per_serving")
+    op.drop_column("ingredient", "aliases")