# Row 27 — Blind Fine-Structure / Electromagnetic Checkpoint

Status: `POST_RELEASE_RESEARCH`, nonblocking diagnostic.

Row 27 is deliberately placed before the proton-stability gate because electromagnetic/UV coupling closure is upstream of the unification/proton calculation.

## Executable scope

The gate checks the frozen August 14, 2026 research record:

- closest legitimate blind intermediate checkpoint: `alpha^-1(0) = 137.03735243`;
- withheld post-freeze comparison value: `137.035999177`;
- difference: `+0.001353253`;
- absolute percentage difference: approximately `0.0009875164%`;
- later verified mixed-correction rung: `137.00222764`;
- historical bracket: `137.00222764 < 137.035999177 < 137.03735243`.

It also verifies the SHA-256 of the frozen independent-verification bundle and validates every file listed in the bundle's internal `SHA256SUMS.txt`.

## Scientific boundary

`PASS` means this gate's declared checks pass: the blind intermediate checkpoint, blind contract, arithmetic comparison, and archived verification provenance are internally reproducible. It does **not** mean the final source-complete fine-structure derivation is closed.

The remaining hard gate is to independently derive the hardened-bridge -> GRIFFIN weak-angle handoff/Jacobian, reproduce `137.00222764` with unfinished terms disabled, enable only the confirmed remaining higher-order terms, freeze the result, and only then compare with the holdout.

Independent verification remains `REQUESTED_PENDING` unless a separate final verifier statement is later supplied.
