# Acceptance oracle — strap-beam revision 8.0.0

123 cases. 113 accepted, 10 rejected. `sha256 ddd0f154…`

## What it is for

This is the acceptance criterion for any reimplementation of the generators. A
port is correct when it reproduces these values — not when it looks right, and
not when it renders something plausible.

## The rejected cases are part of the contract

Ten cases were rejected by the reference, each with a message naming the
parameter and the limit. **A port that accepts them is wrong**, however good its
numbers are elsewhere.

This is the part a naive reimplementation loses. Reproducing geometry is
straightforward; keeping the constraint that made the geometry trustworthy is
the actual work. `tests/test_oracle.py` asserts both directions.

## What the fields mean

| Key | Role |
|---|---|
| `MIN_WALL_ACTUAL_MM` | thinnest surviving material anywhere in the section |
| `SECTION_PARTS` | connected solids; must be 1 |
| `STRAP_CHANNELS` | separate strap slots; must equal the member count |
| `RING_*`, `FIN_*`, `AF_*`, `SPOKE_*` | solved placement values — these pin the solvers |

The first three are invariants. The solved values are what catch a port that
reaches the right shape by a different route, which will diverge later.

`tolerance` in the document governs comparison: lengths to 1e-4 mm, areas to
1e-3 mm², counts exact.

## The hash

`fixtures_sha256` covers the document **without that field**, serialised with
`indent=2` and `sort_keys=True`. Hashing the file will not reproduce it.

```bash
python3 make_fixtures.py --verify
```

That needs nothing but Python and should pass anywhere, any time.

## Regenerating

Only inside the pinned toolchain, never on a host whose OpenSCAD merely looks
similar:

```bash
./tools/reference-toolchain/verify.sh --full
```

The `frozen` date changes on every regeneration, so a one-line diff there is
expected. **Any other difference means the toolchain has drifted** — stop and
investigate. A drifting oracle is worse than no oracle.

## Coverage

Beyond the eleven default profiles: bundle counts 2 and 3; conditioned
intermediate stock at 13.4 mm and steel strap at 0.79 mm on every profile;
asymmetric walls as a chirality regression; parameter sweeps across corner
radius, corner web, leg angle, fin projection, fillet radius, bore size,
rotation, junction webs, triangle shape and rectangle aspect; and four
cross-profile isolation cases proving one profile's parameters cannot affect
another's.