The shipped guard walked `jobs.<id>` only and leaned on a text-versus-walk
cross-check to catch anything the walk could not reach. That cross-check compared
per-file NAME SETS, and the two halves cancelled on the one file the invariant is
about: measured 2026-09-05 at 59003d5a3, hoisting
env:
ETV_REGISTRY_AUTH: ${{ secrets.REGISTRY_USER }}:${{ secrets.REGISTRY_PASSWORD }}
into `.gitea/workflows/docker-build.yml`'s root `env:` — which materialises into
EVERY job on the head-authored PR route — left `pytest
scripts/tests/test_workflow_persist_credentials.py -q` at `14 passed`, rc=0. The
same hoist in `pr-checks.yml` reddened, because no job there already names those
secrets. The guard could only ever see a name NO job used; a second copy of a
reference `build` legitimately keeps naming changed no set. That is
`dont-keep-a-copy-of-a-set` / `proof-sharing-with-subject-proves-nothing`: the
proof shared its accumulator with its subject and cancelled.
Two changes, because the cross-check was being asked to do the assertion's job:
* the workflow scope (everything outside `jobs:`) is now judged in its own right
by the same structure-blind collector — it is a second entry site on equal
footing with the job subtree, not an edge case, since no job-level `if:` can
take a root `env:`/`defaults:` off the route;
* the cross-check walks the whole document and compares occurrence COUNTS. A
duplicate at an unreachable location now reddens: probed 2026-09-05, a trailing
`# ${{ secrets.REGISTRY_PASSWORD }}` on a root `env:` line reports `walk
[('REGISTRY_PASSWORD', 1)] vs text [('REGISTRY_PASSWORD', 2)]` where the set
version agreed. Under counting the comment strip becomes load-bearing rather
than the no-op the old docstring admitted it was.
Driven by a mutation on the SHIPPED `docker-build.yml`, the way the `build`-loses-
its-`if:` mutation already is, plus a direct assertion on the two collectors that
a duplicated reference changes the count and not the names. Witnessed red with the
hoist in the tree (3 failed) and green without it (17 passed).
The decision record's own claims were false in the same way and are corrected:
`rule:` said "NO job ... may name a stored secret" (a root `env:` is not a job) and
the prose said "a text-versus-walk cross-check reports any reference the walk
cannot reach".
Refs #885
Decisions-Edit: yes
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015QqCpYFsKgnAnx6jVwrKiV
timothyandClaude Fable 5.1
b71bf4d7b2