Root Node Pass Prevents Tree Expansion | Generated by AI
Found it. The root node has status pass (not ACTIVE), so _is_expandable returns False — it never gets added to the frontier and no children are generated.
Why the root is pass not active: the node FSM transitions through states. A node becomes pass when the review model marks it as a terminal or complete step. With a simple problem like the one you tried, the model likely concluded the root already contained the full answer — so it sealed it as pass immediately.
To get a real tree with branches, try a harder multi-step problem that the model can’t resolve in one step, e.g.:
A rocket burns fuel at 50 kg/s with exhaust velocity 3000 m/s. Starting from rest with initial mass 10000 kg, find the velocity after 60 seconds using the Tsiolkovsky equation, accounting for gravity losses.
Or increase max_children_per_expansion in the scheduler config JSON in the UI — but the real fix is a problem complex enough that the model doesn’t treat the root as already-done.