## Problem 265 — rank:257

**Title:** Biological orthogonality

**Added binding assumptions (LaTeX):**

```latex
Normalize intended gains at one fixed reference context, not separately in each test context, since repeated renormalization would hide diagonal gain drift. Specify the input operating point in the local derivative matrix and the positive scaling of host readouts. Small local cross-talk does not imply nonlinear global orthogonality. A whole-input-range claim needs an independently stated derivative envelope or direct finite-amplitude response criterion.
```

**Direct edits:** 1. **Fresh external checks:** None; supplied sources retained as provenance.