diff --git a/migrations/versions/phase_b_mobile_local_id.py b/migrations/versions/phase_b_mobile_local_id.py
index 56c10ec..9658fd0 100644
--- a/migrations/versions/phase_b_mobile_local_id.py
+++ b/migrations/versions/phase_b_mobile_local_id.py
@@ -7,69 +7,73 @@ on the device (mobile_local_id).  The server checks this field before creating
 a new record so that network retries never produce duplicate rows.
 
 Revision ID:  phase_b_mobile_local_id
-Revises:      phase9_user_full_name
+Revises:      phase12_performance_indexes
 """
 
 from alembic import op
 import sqlalchemy as sa
 
 revision      = 'phase_b_mobile_local_id'
-down_revision = 'phase9_user_full_name'
+down_revision = 'phase12_performance_indexes'
 branch_labels = None
 depends_on    = None
 
 
+def _column_exists(conn, table, column):
+    result = conn.execute(sa.text(
+        "SELECT COUNT(*) FROM INFORMATION_SCHEMA.COLUMNS "
+        "WHERE TABLE_SCHEMA = DATABASE() "
+        "AND TABLE_NAME = :table AND COLUMN_NAME = :column"
+    ), {"table": table, "column": column})
+    return result.scalar() > 0
+
+
+def _index_exists(conn, table, index):
+    result = conn.execute(sa.text(
+        "SELECT COUNT(*) FROM INFORMATION_SCHEMA.STATISTICS "
+        "WHERE TABLE_SCHEMA = DATABASE() "
+        "AND TABLE_NAME = :table AND INDEX_NAME = :index"
+    ), {"table": table, "index": index})
+    return result.scalar() > 0
+
+
 def upgrade():
+    conn = op.get_bind()
+
     # ── inspections.mobile_local_id ───────────────────────────────────────
-    with op.batch_alter_table('inspections') as batch_op:
-        # Check if column already exists (safe re-run)
-        conn    = op.get_bind()
-        columns = [row[1] for row in conn.execute(sa.text('PRAGMA table_info(inspections)')).fetchall()] \
-                  if conn.dialect.name == 'sqlite' \
-                  else [row['COLUMN_NAME'] for row in conn.execute(
-                      sa.text(
-                          "SELECT COLUMN_NAME FROM INFORMATION_SCHEMA.COLUMNS "
-                          "WHERE TABLE_NAME = 'inspections' AND TABLE_SCHEMA = DATABASE()"
-                      )
-                  ).mappings()]
+    if not _column_exists(conn, 'inspections', 'mobile_local_id'):
+        op.execute(sa.text(
+            "ALTER TABLE inspections ADD COLUMN mobile_local_id VARCHAR(64) NULL"
+        ))
 
-        if 'mobile_local_id' not in columns:
-            batch_op.add_column(
-                sa.Column('mobile_local_id', sa.String(64), nullable=True)
-            )
-
-    # Index for fast idempotency lookups
-    op.execute(sa.text(
-        "CREATE INDEX IF NOT EXISTS idx_inspections_mobile_local_id "
-        "ON inspections(mobile_local_id)"
-    ))
+    if not _index_exists(conn, 'inspections', 'idx_inspections_mobile_local_id'):
+        op.execute(sa.text(
+            "CREATE INDEX idx_inspections_mobile_local_id ON inspections(mobile_local_id)"
+        ))
 
     # ── issues.mobile_local_id ────────────────────────────────────────────
-    with op.batch_alter_table('issues') as batch_op:
-        conn    = op.get_bind()
-        columns = [row[1] for row in conn.execute(sa.text('PRAGMA table_info(issues)')).fetchall()] \
-                  if conn.dialect.name == 'sqlite' \
-                  else [row['COLUMN_NAME'] for row in conn.execute(
-                      sa.text(
-                          "SELECT COLUMN_NAME FROM INFORMATION_SCHEMA.COLUMNS "
-                          "WHERE TABLE_NAME = 'issues' AND TABLE_SCHEMA = DATABASE()"
-                      )
-                  ).mappings()]
+    if not _column_exists(conn, 'issues', 'mobile_local_id'):
+        op.execute(sa.text(
+            "ALTER TABLE issues ADD COLUMN mobile_local_id VARCHAR(64) NULL"
+        ))
 
-        if 'mobile_local_id' not in columns:
-            batch_op.add_column(
-                sa.Column('mobile_local_id', sa.String(64), nullable=True)
-            )
-
-    op.execute(sa.text(
-        "CREATE INDEX IF NOT EXISTS idx_issues_mobile_local_id "
-        "ON issues(mobile_local_id)"
-    ))
+    if not _index_exists(conn, 'issues', 'idx_issues_mobile_local_id'):
+        op.execute(sa.text(
+            "CREATE INDEX idx_issues_mobile_local_id ON issues(mobile_local_id)"
+        ))
 
 
 def downgrade():
-    with op.batch_alter_table('inspections') as batch_op:
-        batch_op.drop_column('mobile_local_id')
+    conn = op.get_bind()
 
-    with op.batch_alter_table('issues') as batch_op:
-        batch_op.drop_column('mobile_local_id')
\ No newline at end of file
+    if _index_exists(conn, 'inspections', 'idx_inspections_mobile_local_id'):
+        op.execute(sa.text("DROP INDEX idx_inspections_mobile_local_id ON inspections"))
+
+    if _column_exists(conn, 'inspections', 'mobile_local_id'):
+        op.execute(sa.text("ALTER TABLE inspections DROP COLUMN mobile_local_id"))
+
+    if _index_exists(conn, 'issues', 'idx_issues_mobile_local_id'):
+        op.execute(sa.text("DROP INDEX idx_issues_mobile_local_id ON issues"))
+
+    if _column_exists(conn, 'issues', 'mobile_local_id'):
+        op.execute(sa.text("ALTER TABLE issues DROP COLUMN mobile_local_id"))
\ No newline at end of file