Endless Mode is officially listed as a full-game feature for pushing buildcraft beyond normal stage limits. The useful prep is the same: scalable damage, movement speed, reliable coverage and a grid that still has room to improve.
What is confirmed
The official Steam description says Endless Mode lets players test buildcraft to its limit.
What is not confirmed yet
Demo-era sources do not provide a complete Endless Mode rule set, reward table or enemy scaling formula; this page is being rechecked on the live build.
Build priorities
Prefer effects that scale with more parts or longer fights over one-off early-run convenience.
Survival
Movement speed and crowd control become increasingly important as screen density rises.
Update plan
This page is being expanded with unlock conditions, scaling and rewards verified against the live build rather than the demo.
Build 1.0.4 (September 29): Endless cannot complete
The layer select screen now explains that an endless dive cannot be completed, so it never unlocks the next difficulty modifier. If you are chasing the next modifier, run a finishable dive instead.