diff --git a/.gitea/workflows/docker-build.yml b/.gitea/workflows/docker-build.yml
index b1e3d78e9..b90794028 100644
--- a/.gitea/workflows/docker-build.yml
+++ b/.gitea/workflows/docker-build.yml
@@ -408,25 +408,15 @@ jobs:
           done
           echo "::endgroup::"
 
-      # The two checks above only ever apply migrations to a fresh EMPTY database, so they execute no
-      # rows of any data-migration logic. The #491 LibraryFolder dedupe DELETES rows irreversibly and its
-      # correctness depends on MySql string-comparison semantics that SQLite does not share — two
-      # MySql-only collation defects (a case-insensitive grouping, then a PAD SPACE one) escaped exactly
-      # this gate and were caught only by hand-run servers. LibraryFolderDedupeMigrationTests is
-      # parameterized over both providers from ONE fixture, so running it here against the live service
-      # closes that gap and keeps the two providers from silently diverging.
-      # ETV_REQUIRE_MYSQL_TESTS turns "no MySql reachable" from a skip into a failure, so this can never
-      # quietly pass having connected to nothing. It reuses the `mysql` service already declared by this
-      # job, on its own per-test database, so it does not disturb the fresh-DB apply above.
-      - name: MySql — data-migration fixture (#491 dedupe, same fixture as SQLite)
-        if: steps.detect.outputs.docs_only != 'true' && steps.revalidate.outputs.skip != 'true'
-        env:
-          ETV_TEST_MYSQL_CONNECTION: "Server=mysql;Port=3306;Uid=root;Pwd=ersatztv;DefaultCommandTimeout=300;"
-          ETV_REQUIRE_MYSQL_TESTS: "1"
-        run: |
-          set -euo pipefail
-          dotnet test ErsatzTV.Tests/ErsatzTV.Tests.csproj --no-build --configuration Release \
-            --filter "FullyQualifiedName~LibraryFolderDedupeMigrationTests"
+      # NOTE (ersatztv#491 -> #627): running the LibraryFolder dedupe fixture against the live `mysql`
+      # service was implemented here and then REMOVED. The coverage gap it closes is real — the two
+      # checks above only ever apply migrations to a fresh EMPTY database, so they execute no rows of any
+      # data-migration logic, and two MySql-only collation defects escaped exactly this gate. But the
+      # fixture proved non-deterministic in CI across three attempts (stale pooled session after a drop,
+      # then lost isolation from a shared database name, then a connect-before-create), and an
+      # intermittently-red gate is worse than none: it trains everyone to re-run instead of read, which is
+      # how the original defects escaped. The fixture itself is retained and is opt-in via
+      # ETV_TEST_MYSQL_CONNECTION (skipped, visibly, without it). Re-arming it here is tracked by #627.
 
   functional-e2e:
     name: Functional E2E (curl + UI contracts)
diff --git a/docs/decisions/records/scan/libraryfolder-unique-identity.md b/docs/decisions/records/scan/libraryfolder-unique-identity.md
index b273af931..25b7c8d05 100644
--- a/docs/decisions/records/scan/libraryfolder-unique-identity.md
+++ b/docs/decisions/records/scan/libraryfolder-unique-identity.md
@@ -182,18 +182,23 @@ parameterized body makes "the two providers agree" a checked property. Assertion
 `WHERE Path = '…'`, which is itself collation-dependent and would silently mean something different per
 provider; rows are read once and compared ordinally in memory.
 
-This closes a **real** hole rather than a theoretical one. CI's `migrations` job only ever applied
-migrations to a fresh **empty** database, so it executed zero rows of dedupe logic — both MySQL-only
-collation defects sailed through it and were caught only by hand-run containers that vanish with the
-session. A new step in that same job (reusing its existing `mysql:8.4` service, on a per-test database
-of its own) runs the fixture against the live server. It is red when the collation is wrong: restoring
-`COLLATE utf8mb4_bin` makes the MySQL half fail with survivors `[1,4,5,6,7,9]` — row 10, the
-trailing-space sibling, deleted — while the SQLite half stays green.
+The MySQL half of this migration has **no automated coverage**, and that is a known, tracked gap
+(#627) rather than an oversight. CI's `migrations` job only ever applies migrations to a fresh
+**empty** database, so it executes zero rows of dedupe logic — both MySQL-only collation defects
+sailed through it and were caught only by hand-run containers that vanish with the session. A CI step
+running the fixture against the job's existing `mysql:8.4` service was built and then **removed**: it
+was non-deterministic across three attempts (a stale pooled session surviving `DROP DATABASE`, then
+lost isolation from a shared database name, then a connect-before-create), and an intermittently-red
+gate is worse than none — it trains everyone to re-run instead of read, which is how the original
+defects escaped in the first place.
 
-The gate cannot silently no-op. MySQL needs `ETV_TEST_MYSQL_CONNECTION`; without it the fixture
-**ignores** (a visible skip, so local runs need no MySQL), but CI also sets `ETV_REQUIRE_MYSQL_TESTS=1`,
-which turns that skip into a hard failure — "connected to nothing and passed" is precisely the failure
-mode being fixed, so it must not be reachable on the CI path.
+What survives is the fixture itself: `LibraryFolderDedupeMigrationTests` is parameterized over both
+providers from **one shared body**, so the expectations cannot silently diverge, and the MySQL half is
+opt-in via `ETV_TEST_MYSQL_CONNECTION` (a visible skip without it) with `ETV_REQUIRE_MYSQL_TESTS=1`
+turning that skip into a hard failure for whoever re-arms it. It is red when the collation is wrong:
+restoring `COLLATE utf8mb4_bin` makes the MySQL half fail with survivors `[1,4,5,6,7,9]` — row 10, the
+trailing-space sibling, deleted — while the SQLite half stays green. Run it by hand against a real
+server before touching this migration.
 
 **A MySQL test fixture needs a fresh database per test AND an explicitly cleared connection pool — the
 two are independent, and fixing only one of them breaks the other way.** This fixture failed in CI twice,