ActorContextAfterAwaitTests asserted that a ConfigureAwait(false)
continuation on the shared thread pool always throws NotSupportedException
when reading Self/Context. That property is a timing accident, not an Akka
guarantee: pool threads are exactly where Akka and the TestKit legitimately
install the [ThreadStatic] actor cell during mailbox runs and async
continuations, and Akka 1.5.62 has two non-throwing states besides — a
cleared cell makes ActorBase.Context return null (NullReferenceException on
.Self, not NotSupportedException) and ActorBase.Self return _clearedSelf
without any throw. Under parallel suite load the assertion failed once at
exactly that seam (2026-07-18); ironically the test's own doc comment said
the behaviour "does not reliably throw" and then asserted reliability.
The illegal reads now run on a dedicated new thread (LongRunning), the one
place the no-context state is guaranteed, while the realistic
ConfigureAwait(false) escape from the mailbox is kept. If the reads ever
unexpectedly succeed again, the failure message reports whose context the
thread was carrying. Verified 3 consecutive full-project runs green (38/38)
after 8 instrumented runs hunting the original repro.
Claude-Session: https://claude.ai/code/session_01BL2Vu1ESDQ9SCN4gVKkdts
Joseph Doherty
51bef634d0