Enforce side-effect isolation mechanically in agent-documentation experiments

Treat always-loaded repository instructions as a routing budget, but evaluate changes only in an environment that mechanically enforces the trial envelope. Keep bootstrap guidance small, route to domain documentation when the task requires it, and preserve safety, migration, authorization, and integration rules that the task set does not exercise. Block mutation tools and prohibited history/status commands at the environment boundary rather than relying on prompt instructions alone.

Applicability and limits: task-balanced isolated runs can compare correctness and context cost for bounded maintenance work. If inherited instructions or tools cause writes outside the protocol, the run is evidence about harness leakage, not a clean estimate of the documentation intervention. Do not generalize bounded repair results to architecture, incidents, or long-running work.