In the case of very low-mass objects that never reach fusion temperatures, what ultimately halts gravitational contraction?

Answer

Electron degeneracy pressure, a quantum mechanical effect.

For objects below $0.08 M_{ ext{sun}}$, fusion temperatures are never reached. Contraction is instead halted by electron degeneracy pressure, a quantum mechanical pressure independent of heat content, resulting in a brown dwarf.

In the case of very low-mass objects that never reach fusion temperatures, what ultimately halts gravitational contraction?
gravitystar formationpressurecollapseinterstellar cloud