`reattach()` read `_state.value`, found it `Idle`, and then handed the job
to `observe()` -- which launches a *separate* coroutine that cannot write
until its `collect` has resumed with a `WorkInfo`. So the check happened at
one moment and the write landed at another, with a whole pick able to fit
in between: the user tapped, their metadata query suspended, the guard saw
an empty screen, and the finished job from an earlier session wrote over
`Ready(picked)` a moment later.
The comment above that guard said "no suspension point between this check
and the assignment below, so nothing can interleave". There is no
assignment below, and the two lines are in different coroutines. That
sentence is why this sat as flaky CI for two days rather than being read as
the product race it is.
`ScreenOwnership` makes the answer the test already encodes -- the user's
pick wins -- true rather than probable. A claim is taken synchronously when
the user acts; every write that lands after a suspension point checks the
claim it was made under and drops itself if that claim has been superseded.
Dropped, not reordered: a write that is dropped cannot come back later.
Cancelling the superseded observer was never enough on its own. `Job.cancel`
is honoured at the next suspension point, and a collector that has already
resumed and is on its way to `_state.value = ...` has none left; the write
lands anyway. It also cannot help at all in the case reported, where nothing
supersedes the observation until after it has been launched.
`JoinViewModel` had the identical shape and nothing watching it, so it gets
the same fix and the counterpart test that was missing. Its pick dispatcher
becomes injectable for the same reason `ConversionViewModel`'s already was:
without that seam there is no way to ask what happens while a pick is still
in flight.
Closes#49
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
JMR-devandClaude Opus 5
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