Prevent task session delivery NOT NULL crashes

* fix: coerce null endpoint_url when delivering task result to a session

* fix: also coerce null model so the session insert satisfies NOT NULL

* test: cover task session delivery on an empty database

src/task_scheduler.py

@@ -1300,8 +1300,8 @@ class TaskScheduler:
             sess = DbSession(
                 id=session_id,
                 name=f"[Task] {task.name}",
-                endpoint_url=endpoint_url,
-                model=model_name,
+                endpoint_url=endpoint_url or "",
+                model=model_name or "",
                 owner=task.owner,
                 created_at=datetime.utcnow(),
                 updated_at=datetime.utcnow(),

tests/test_task_scheduler_session_delivery.py

@@ -0,0 +1,51 @@
+"""Regression tests for task-result delivery into chat sessions (issue #326)."""
+import asyncio
+import types as _types
+
+import pytest
+
+sqlalchemy = pytest.importorskip("sqlalchemy")
+if not isinstance(sqlalchemy, _types.ModuleType):
+    pytest.skip("sqlalchemy is stubbed in this environment", allow_module_level=True)
+
+from sqlalchemy import create_engine
+from sqlalchemy.orm import sessionmaker
+
+from core.database import Base, Session as DbSession
+from src.task_scheduler import TaskScheduler
+
+
+def _make_db():
+    engine = create_engine("sqlite:///:memory:")
+    Base.metadata.create_all(engine)
+    return sessionmaker(bind=engine)()
+
+
+def _make_task():
+    return _types.SimpleNamespace(
+        id="task-1",
+        name="Chat Sessions Tidy",
+        prompt="tidy",
+        output_target="session",
+        endpoint_url=None,
+        model=None,
+        session_id=None,
+        owner=None,
+        crew_member_id=None,
+    )
+
+
+def test_session_delivery_survives_empty_database():
+    """On a fresh/wiped database there is no session to inherit endpoint/model
+    from, so _resolve_defaults returns None. The delivery must still persist a
+    session instead of crashing on the NOT NULL constraint (issue #326)."""
+    db = _make_db()
+    scheduler = TaskScheduler.__new__(TaskScheduler)
+    scheduler._session_manager = None
+
+    asyncio.run(scheduler._deliver_task_result(_make_task(), "done", db))
+
+    sessions = db.query(DbSession).all()
+    assert len(sessions) == 1
+    assert sessions[0].endpoint_url == ""
+    assert sessions[0].model == ""