Series: The Learn Arc — 50 posts through the Active Inference workbench.

Previous: Part 42 — Session §8.3: Action on sensors

Hero line. Session 8.4 is the sandbox. Continuous-time agent running Eq 4.19, live sliders on every precision and every derivative order, a world you can perturb at will. The session where intuition finally outruns equations.

Why a play session

Chapter 8 taught three heavy concepts in a row: generalized coordinates, the quadratic F , and action via sensory gradient descent. Each is cleaner in isolation than in combination. Session 8.4 is the antidote — a free-form workbench where you break one knob at a time and watch the whole agent react.

Five beats

Every precision is a slider. Sensory, dynamical, state, action, per-order. Push one up and the agent trusts that channel more. Push one to zero and that channel effectively disappears from the gradient.

Order truncation is a dial. Start at order 2 (position + velocity). Bump to 4 (add acceleration + jerk).…