Hands off the bars, a rider shifts hips and the bike turns. What actually steers the front wheel?

Answer: Geometry steers the wheel

Body lean alone turns — Not quite. Body motion matters, but the sources do not describe no-hands riding as body lean alone magically curving the bike. Fajans says hip thrust can help establish the required lean, and then trail becomes important. Heine gives the riding version: the front wheel automatically countersteers, then the bike leans and turns.

Geometry steers the wheel ✓ — Correct. No-hands riding still uses steering; you just trigger it without touching the bars. Fajans describes hip thrust as one way to generate the lean, with trail coupling lean to steering. Heine describes the same practical loop: the front wheel countersteers automatically, then the bike leans and turns.

Gyro forces choose direction — No. Gyroscopic effects are a different bicycle-stability topic, but they are not the mechanism described by the no-hands sources here. Those sources explain the turn through hip motion, lean, trail, and automatic countersteering. The question asks what actually steers the front wheel when your hands are off the bars.