Track.get_executable_tickets (in models.py) called TrackDAG at
runtime, forcing a top-level import of src.dag_engine into models.py
and creating a 2-cycle that broke whichever module loaded second
(Ticket was not yet defined when models.py loaded first; TrackDAG
was not yet defined when dag_engine.py loaded first).
Fix: hoist the method out of the Track dataclass and into a free
function get_executable_tickets(track) in dag_engine.py. models.py
no longer needs TrackDAG at all, so the cycle is one-directional
(models -> dag_engine) and resolves cleanly in any import order.
Tests updated:
- tests/test_mma_models.py: import get_executable_tickets and call
it instead of track.get_executable_tickets() (4 call sites)
- tests/test_conductor_engine_v2.py: comment update
Verified both import orders resolve cleanly:
forward: import src.models; import src.dag_engine -> OK
reverse: import src.dag_engine; import src.models -> OK
34 tests pass (test_mma_models, test_dag_engine, test_execution_engine,
test_arch_boundary_phase3, test_track_state_schema).
ed