ci(test-tiers): per-PR gate for a package adopting a tier file without reading the switch

scripts/nightly-tiers.mjs moved the e2e and live tiers off the per-PR and
merge-queue runs onto a nightly, gated by OS_TEST_TIERS. A package that adopts
its first *.e2e.test.* or *.live.test.* file without reading that switch runs
the file in the merge queue and its whole suite under the nightly, both
silently; --check makes that loud only on the nightly, one night late, and its
refusal then blocks the whole tier run for one package's omission.

check-tier-file-adoption.mjs is the per-PR half. It is the STATIC route: --check
boots vitest twice per tier-owning package to measure what it collects, which is
the right instrument for a nightly and the wrong one for every PR. This shares
--check's own tier-file predicate and package walk (tierPackages) and spawns
nothing.

The detector walks the vitest config's local import closure rather than grepping
for the variable: on the one package that owns tier files today, the name
appears 9 times raw and 0 times with comments masked -- every occurrence is
prose, and the real read is an import edge. Both wrong detectors are pinned as
controls.

Zero tier files is a green that PRINTS THE ZERO: a gate reporting clean by never
looking is indistinguishable from one that looked, unless the count is on the
screen.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_012GKcPZbMoGq7WPzKLfRBTU

Author: claude

.github/workflows/lint.yml

@@ -3676,6 +3676,27 @@ jobs:
       - name: Live-server database isolation
         run: pnpm check:live-db-isolation
 
+      # Nightly-tier file adoption (#16494). `scripts/nightly-tiers.mjs` moved
+      # the `e2e` and `live` tiers off the per-PR and merge-queue runs onto a
+      # nightly, gated by OS_TEST_TIERS — and a package that adopts its first
+      # `*.e2e.test.*` or `*.live.test.*` file WITHOUT reading that switch runs
+      # the file in the merge queue (nothing excludes it) and its WHOLE suite
+      # under the nightly (nothing narrows it), both silently. That drift was
+      # already loud on the NIGHTLY: `nightly-tiers.mjs --check` refuses to run
+      # past such a package — but the refusal blocks the whole tier run for one
+      # package's omission, one nightly after the PR that introduced it landed.
+      # This is the per-PR half, and it is deliberately the STATIC one: --check
+      # boots vitest twice per tier-owning package to measure what it collects,
+      # which is the right instrument for a nightly and the wrong one for every
+      # PR. This gate spawns nothing and shares --check's own tier-file
+      # predicate and package walk, so the two cannot disagree about which
+      # files are tier files. It is a SPELLING gate (the config routes through
+      # the one reader), never a claim the partition is right — its header
+      # carries that boundary and the measurement behind the detector.
+      # Reads ~80 manifests and a handful of configs; sub-second.
+      - name: Nightly-tier file adoption
+        run: pnpm check:tier-file-adoption
+
       # LAYER C of the gate above (#10379). That gate verifies two of the three
       # layers a cross-package declaration has: it finds the escaping tests
       # itself, and `--verify` makes turbo.json hash every declared glob so the

package.json

@@ -147,6 +147,7 @@
     "check:required-contexts": "node scripts/check-required-contexts.mjs --self-test && node scripts/check-required-contexts.mjs",
     "check:cross-package-test-inputs": "node scripts/check-cross-package-test-inputs.mjs --self-test && node scripts/check-cross-package-test-inputs.mjs",
     "check:live-db-isolation": "node scripts/check-live-db-isolation.mjs --self-test && node scripts/check-live-db-isolation.mjs",
+    "check:tier-file-adoption": "node scripts/check-tier-file-adoption.mjs --self-test && node scripts/check-tier-file-adoption.mjs",
     "check:examples-live-imports": "node scripts/check-examples-live-imports.mjs --self-test && node scripts/check-examples-live-imports.mjs",
     "examples:live-imports": "node scripts/check-examples-live-imports.mjs --list",
     "check:test-source-alias": "node scripts/check-test-source-alias.mjs --self-test && node scripts/check-test-source-alias.mjs",