diff --git a/backend/alembic/versions/039_add_session_ratings_and_analytics_indexes.py b/backend/alembic/versions/039_add_session_ratings_and_analytics_indexes.py
new file mode 100644
index 00000000..0baf92ec
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+++ b/backend/alembic/versions/039_add_session_ratings_and_analytics_indexes.py
@@ -0,0 +1,45 @@
+"""Add session_ratings table and analytics indexes
+
+Revision ID: 039
+Revises: 038
+Create Date: 2026-02-16
+"""
+from alembic import op
+import sqlalchemy as sa
+from sqlalchemy.dialects.postgresql import UUID
+
+revision = '039'
+down_revision = '038'
+
+def upgrade():
+    # New session_ratings table for flow CSAT ratings
+    op.create_table(
+        'session_ratings',
+        sa.Column('id', UUID(as_uuid=True), server_default=sa.text('gen_random_uuid()'), primary_key=True),
+        sa.Column('session_id', UUID(as_uuid=True), sa.ForeignKey('sessions.id', ondelete='CASCADE'), nullable=False),
+        sa.Column('user_id', UUID(as_uuid=True), sa.ForeignKey('users.id', ondelete='CASCADE'), nullable=False),
+        sa.Column('tree_id', UUID(as_uuid=True), sa.ForeignKey('trees.id', ondelete='CASCADE'), nullable=False),
+        sa.Column('account_id', UUID(as_uuid=True), sa.ForeignKey('accounts.id', ondelete='CASCADE'), nullable=False),
+        sa.Column('rating', sa.Integer, nullable=False),
+        sa.Column('comment', sa.String(500), nullable=True),
+        sa.Column('created_at', sa.DateTime(timezone=True), server_default=sa.text('NOW()'), nullable=False),
+        sa.CheckConstraint('rating >= 1 AND rating <= 5', name='ck_session_ratings_rating_range'),
+        sa.UniqueConstraint('session_id', name='uq_session_ratings_session_id'),
+    )
+
+    # Analytics indexes
+    op.create_index('ix_session_ratings_tree_created', 'session_ratings', ['tree_id', 'created_at'])
+    op.create_index('ix_session_ratings_account_created', 'session_ratings', ['account_id', 'created_at'])
+    op.create_index('ix_sessions_completed', 'sessions', ['completed_at'])
+    op.create_index('ix_step_ratings_step_helpful', 'step_ratings', ['step_id', 'was_helpful'])
+
+    # Make step_ratings.rating column nullable (thumbs-only mode)
+    op.alter_column('step_ratings', 'rating', nullable=True)
+
+def downgrade():
+    op.alter_column('step_ratings', 'rating', nullable=False)
+    op.drop_index('ix_step_ratings_step_helpful', 'step_ratings')
+    op.drop_index('ix_sessions_completed', 'sessions')
+    op.drop_index('ix_session_ratings_account_created', 'session_ratings')
+    op.drop_index('ix_session_ratings_tree_created', 'session_ratings')
+    op.drop_table('session_ratings')