Stage 4: Long-Horizon Probe-Impact Testing, Behavioral Read-Only Confirmation, and Time-Scale Validation Long-Horizon Probe-Impact Testing, Behavioral Read-Only Confirmation, and Time-Scale Validation

Stage 4 advances the Reality Audit project from calibrated metric interpretation into long-horizon behavioral validation inside the real sandbox. Earlier stages established the audit layer, validation scenarios, metric mapping, ablation studies, trust calibration, and campaign infrastructure. The primary goal of Stage 4 was to resolve a central remaining question: does the presence of the audit probe change actual sandbox behavior over longer runs, or is it truly observational? According to the latest implementation report, Stage 4 completed with 451/451 tests passing, added a new long-horizon probe-impact experiment and 34 new tests, and produced a new report showing exact behavioral agreement between inactive, passive, and active-measurement probe conditions across 25-, 50-, and 100-turn runs over 3 seeds. The most important result of this stage is methodological rather than metaphysical. The project now has strong evidence that its audit layer remains behaviorally read-only at the sandbox level, not just at the metric-reporting level. Specifically, the new stage6_probe_impact_report.json reports 18/18 exact matches for passive-vs-inactive comparisons and 18/18 exact matches for active-vs-passive comparisons, with no divergences and a room-sequence identity fraction of 1.0 in both cases. This does not prove that reality is a simulation, but it materially strengthens the credibility of the audit framework by showing that the act of auditing does not itself appear to perturb the system under the tested conditions. 1. Purpose of Stage 4 The purpose of Stage 4 was to extend the project beyond short-horizon metric comparisons and directly test whether the audit layer changes the actual behavior of the sandbox. Earlier stages had shown that: • probe metrics could be collected, • passive and inactive probe modes were difficult to compare numerically because inactive mode emits no audit metrics, • and active-measurement mode did not produce detectable metric differences at a short 25-turn horizon. However, those earlier results left an ambiguity: even if inactive mode produces no audit metrics, it was still necessary to compare simulation-native outputs such as room sequences and action sequences to determine whether the audit layer changes the sandbox itself. Stage 4 was designed to resolve that ambiguity by asking: 1. Does passive probing alter sandbox behavior? 2. Does active-measurement probing alter sandbox behavior? 3. If differences emerge, at what horizon do they first appear? 4. If no differences appear, how strong is the evidence that the probe is behaviorally read-only?