fix(knowledge): auto-maintain updated_at via trigger on all knowledge tables

Add a shared PostgreSQL trigger function (update_updated_at) wired to
knowledge_sources, knowledge_items, and knowledge_propositions. Any UPDATE
on these tables now automatically stamps updated_at = NOW() at the database
level, removing the need for application code to manage this column.

Author: ibacalu

src/workflows_mcp/engine/knowledge/schema.py

@@ -275,6 +275,49 @@
             WITH (m = 16, ef_construction = 64);
         """,
     ),
+    (
+        6,
+        "Add updated_at trigger to all knowledge tables that carry the column",
+        """
+        CREATE OR REPLACE FUNCTION update_updated_at()
+        RETURNS TRIGGER AS $$
+        BEGIN
+            NEW.updated_at = NOW();
+            RETURN NEW;
+        END;
+        $$ LANGUAGE plpgsql;
+
+        DO $$
+        BEGIN
+            IF NOT EXISTS (
+                SELECT 1 FROM pg_trigger
+                WHERE tgname = 'trg_ks_updated_at'
+            ) THEN
+                CREATE TRIGGER trg_ks_updated_at
+                    BEFORE UPDATE ON knowledge_sources
+                    FOR EACH ROW EXECUTE FUNCTION update_updated_at();
+            END IF;
+
+            IF NOT EXISTS (
+                SELECT 1 FROM pg_trigger
+                WHERE tgname = 'trg_ki_updated_at'
+            ) THEN
+                CREATE TRIGGER trg_ki_updated_at
+                    BEFORE UPDATE ON knowledge_items
+                    FOR EACH ROW EXECUTE FUNCTION update_updated_at();
+            END IF;
+
+            IF NOT EXISTS (
+                SELECT 1 FROM pg_trigger
+                WHERE tgname = 'trg_kp_updated_at'
+            ) THEN
+                CREATE TRIGGER trg_kp_updated_at
+                    BEFORE UPDATE ON knowledge_propositions
+                    FOR EACH ROW EXECUTE FUNCTION update_updated_at();
+            END IF;
+        END $$;
+        """,
+    ),
 ]
 
 SCHEMA_VERSION = MIGRATIONS[-1][0] if MIGRATIONS else 0

tests/test_knowledge_executor.py

@@ -882,6 +882,7 @@ def test_forget_update_sql_does_not_contain_updated_at(self) -> None:
         Some deployments omit updated_at from knowledge_propositions;
         unconditionally setting it causes 'column does not exist' errors.
         The only mutation needed is setting lifecycle_state = ARCHIVED.
+        updated_at is maintained by the trg_kp_updated_at trigger (migration v6).
         """
         import inspect
 
@@ -892,6 +893,21 @@ def test_forget_update_sql_does_not_contain_updated_at(self) -> None:
             "_op_forget must not reference updated_at — not all schemas have that column"
         )
 
+    def test_migration_v6_adds_updated_at_trigger(self) -> None:
+        """Migration v6 must wire updated_at triggers on all three knowledge tables.
+
+        Regression guard for TASK-341: archive operations were leaving updated_at
+        unchanged. One shared trigger function covers all tables that carry the column.
+        """
+        v6 = next((m for m in MIGRATIONS if m[0] == 6), None)
+        assert v6 is not None, "Migration v6 is missing from MIGRATIONS list"
+        _, description, sql = v6
+        assert "update_updated_at" in sql, "Migration v6 must create update_updated_at() function"
+        assert "BEFORE UPDATE" in sql, "Trigger must fire BEFORE UPDATE"
+        assert "trg_ks_updated_at" in sql, "Trigger missing for knowledge_sources"
+        assert "trg_ki_updated_at" in sql, "Trigger missing for knowledge_items"
+        assert "trg_kp_updated_at" in sql, "Trigger missing for knowledge_propositions"
+
 
 # ============================================================================
 # Recall Operation Tests