# Open protocol discrepancies

## NSID-001 — Separate authority-length limit

Status: **open; strict NSID fixture compatibility fails**. Checked 2026-10-04.

The current [NSID specification](https://atproto.com/specs/nsid) separately
requires authority length <=253 and complete NSID length <=317. The pinned
TypeScript validator at atproto revision
`a7c8604d876a200a1e4fa4aec83d4189ac4f1c12` checks total and segment lengths,
but does not enforce the separate authority bound. The current online validator
also omits it when rechecked. The reference regex in the specification does not
encode that bound either; it needs a separate length check.

The unchanged valid fixture at interop revision
`056e5741bb330757205d6b16db5266fffcae937b`,
`syntax/nsid_syntax_valid.txt`, line 4, is `com.middle...middle.foo`:

| Property | Fixture | Specification limit |
| --- | --- | --- |
| Authority length, including periods | 283 | 253 |
| Final name length (`foo`) | 3 | 63 |
| Complete identifier length | 287 | 317 |

All segments are individually within their length bounds. Thus passing the
total bound does not imply passing the authority bound. Our parse returns
`Error(AuthorityTooLong)` while the upstream fixture expects acceptance.

Decision: enforce the specification's explicit authority bound, as required by
the implementation plan. This is a deliberate, tested difference from the
pinned fixture/reference behavior. No runtime compatibility exception is added.
This source discrepancy has not been resolved by reorganizing the checks.

Reproduce from the project directory:

```sh
gleam test
gleam run -m pds/nsid_interop
```

The first command checks our normative parser/path contracts, all record-key
fixtures, and all invalid NSID fixtures: 82 tests pass at the latest M2.2 checkpoint. Authority 253/254 and
NSID 317/318 boundaries have explicit regression tests in
`test/pds/nsid_test.gleam` and `test/pds/nsid_authority_test.gleam`.

The second command independently checks **all 52 unchanged NSID fixture
expectations**: 51 pass, 1 fails, zero skipped; it exits nonzero. The adapter
reports both valid and invalid groups before failing. Required validation runs
both commands; a passing `gleam test` alone does not prove compatibility.
M1.2's compatibility completion remains pending.

Resolution requires authoritative clarification or corrected source revisions
that reconcile the separate limit and fixture expectation. Recheck this issue
when updating the specification or pinned sources, then update the parser or
fixtures only with that evidence and rerun both commands. A new mismatch must
also fail the strict comparison. No upstream issue has been filed in this session.

Copied source files, exact embedded cases, license, revision and checksums remain
in `test/fixtures/interop/` and `test/pds/fixtures/nsid_cases.gleam`.