Interpretability and World-Model Debugging › Summary

In a model-based control pipeline, aggregate return combines perception, transition, cost, and search effects. The diagnostics here narrow explanations through controlled comparisons rather than automatically separating a unique cause.

• Probes are fitted instruments. They measure accessibility to a chosen readout on a chosen distribution, not intrinsic content, sufficiency, or downstream use.
• CAVs define fitted concept directions. TCAV measures and aggregates directional sensitivity of chosen outputs. Decodability, sensitivity, finite intervention effects, and physical causal fidelity are distinct questions.
• A shuffled-target refit is a randomized-label baseline, not a selectivity bound. Type-level controls preserve specified properties; disclose their construction and which confounds the comparison addresses.
• Rollout visualization must distinguish teacher-forced prediction, recursive prediction, and closed-loop outcomes. Retain reconstructable inputs and computations; a detailed trace should specify identity, resets, actions, residual definitions, and horizons. Recursive error need not grow monotonically, and projections hide dimensions.
• Interchange causal-abstraction tests evaluate a specified high-level/network alignment. Other intervention protocols test other hypotheses. Support, nuisance changes, coordinate choices, recurrent memory, and dose constrain semantic interpretation.
• Component substitution compares configurations under a disclosed interface and distribution. It does not guarantee improvement or unique causal attribution; oracle comparators are not proven optimal bounds, and fault interactions need not be additive.
• The laboratory built a deterministic point-mass system with a handcrafted representation, episode-grouped splits, a validation-selected ridge probe, a shuffled control, a rotation, a nuisance coordinate, two component faults and a short-horizon alternative, component substitutions, a mixed-fault comparison, and a representation dose sweep. Its findings apply to the specified episodes and protocol, not every world model.

The habit to take away is to write down the protocol with every diagnostic: what was frozen, what was split, what was controlled, what was substituted, and what the scope of the claim is. A diagnostic that respects its own limits is the only kind worth running.