When another writer advances past the local writer, Stream.get_updates()
early-return path was jumping last_token to current_token (inflated by
the other writer) instead of minimal_local_current_token (the local
writer's actual position). This caused subsequent local writes to be
silently dropped — the streamer sent POSITION instead of RDATA, and
synchrotron workers never woke up for the affected users.
The test creates a real _StreamFromIdGen, triggers the advance, and
asserts that last_token stays at minimal_local_current_token rather
than jumping to the inflated current_token.
Coding Assistant
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