Several setups migrating one SQLite secret store at once (mxaccessgw's parallel test hosts on the
per-process store) failed intermittently on Windows with "cannot start a transaction within a
transaction" from SqliteSecretsStoreMigrator.MigrateAsync. That message means the BEGIN ran on a
handle that was already in a transaction: the pinned Microsoft.Data.Sqlite 10.0.7 can hand one
pooled handle to two owners (dotnet/efcore#39009, fixed in 10.0.13) and no 10.0.x refuses to
re-pool a handle whose rollback failed (dotnet/efcore#39082).
The migrator now serialises migrations of one store per process behind a gate keyed on the
normalised path, runs each attempt on a dedicated unpooled connection inside BEGIN IMMEDIATE, and
retries SQLITE_BUSY/SQLITE_LOCKED (another process past the busy timeout) with equal-jitter
exponential backoff. Store operations and the Microsoft.Data.Sqlite pin are unchanged.
Tests: concurrent-init (16 hosts x 20 rounds on fresh and existing stores, two path spellings,
16 AddZbSecrets containers running the pre-host migrator + hosted service), gate sharing/waiting,
BUSY retry past the 5 s busy timeout, transient-code classification.
Claude-Session: https://claude.ai/code/session_01GT67AEHd2Acv1YPwGfXEoV
Joseph Doherty
f21f2e551d