# STACK B / STACK G — DIAGONAL AND FIGURA TERTIA BOUNDARY

Version: `0.1.0-STACK-B-G-BOUNDARY`  
Status: `CANDIDATE BOUNDARY NOTE / NON_RUNTIME / NO_AUTHORITY_EFFECT`

## 1. Exact partition

For `Σ = {B,C,D,E,F,G,H,I,K}`:

```text
DIAGONAL_B = {(X,X) | X in Σ}                         => 9
FIGURA_TERTIA = {{X,Y} | X,Y in Σ and X != Y}         => 36
UNORDERED PAIRS WITH REPETITION                        => 45
```

The sets are disjoint. Stack B does not add its diagonals to ROTAS G, and Stack G does not own Stack B's cross-regime diagonal compilation.

## 2. Medium law

For two admitted regime meanings on one perfectly aligned carrier, `SER` is the given diagonal medium. This licenses no shortcut for a heterogeneous chamber.

```text
X@r_i + X@r_j + lawful predicative support -> SER eligible
X@r_i + Y@r_j where X != Y                 -> OPERA G medium discovery remains required
```

A surface sentence in a heterogeneous chamber may contain a copula. That copula is not automatically the inferential medium discovered by Evacuatio.

## 3. Stack G invariant retained

For each heterogeneous chamber, Stack G / OPERA G retains:

- 12 statements;
- one discovered medium for each statement;
- 12 media;
- 24 questions;
- the subsequent resolution discipline.

Stack B may provide aligned fixtures or validation context but cannot generate these objects.

## 4. Reflection test categories

| Case | Expected disposition |
|---|---|
| canonical medium and admitted carrier-preserving application | reflection candidate |
| corrupted applied carrier | reject |
| bad or untraced contraction | suspend or reject |
| insufficient subject/species admission | suspend |
| failed reflection | diagnose application, medium, or admission; do not rewrite canonical meanings |

Reflection remains a hypothesis to test. The procedural trace stays useful even when the stronger morphism-like hypothesis fails.

## 5. Authority boundary

This note describes a candidate division of labor already authorized by the active M2M. It neither executes OPERA G nor canonizes a Graphus or Stack B provider.