- Host reader: the frame read and its handling are caught separately. Only the
read's I/O exceptions mean the pipe ended; anything HandleFrame's inline
completion work throws now kills that worker as ProtocolFault (outstanding
runs -> worker restarted / BadResourceUnavailable) instead of escaping a
dedicated thread (process crash) or being swallowed as a clean end (an
InvalidOperationException used to be, leaving the worker unread until a Crash
2 s later).
- Worker reader: the same catch-all around HandleFrame (exit ProtocolFault).
- Worker: Cancel() runs on the pool, so a script's blocking
ctx.CancellationToken callback cannot stop the worker reading its pipe.
- Host write-stall check: ScriptWorkerFrameWriter.WriteInProgressFor; the
heartbeat monitor kills a worker whose pipe write has been blocked longer than
max(10 s, silence limit) as KilledUnresponsive, which fails the write and
releases the producer (seam submit, deploy load, Cancel). Fixes the wrong
'heartbeat monitor ends it' comment on the pipe buffer quota.
- StopAsync sends Shutdown off the caller so its 1 s budget holds on a full pipe.
- WindowsBlockingPipeStream refuses the async surface (Stream's base versions
serialise a write behind a waiting read).
- Tests: PipeFaultTests (throwing completion callback -> ProtocolFault and a
BadResourceUnavailable sibling, shard serves again; a worker that stops reading
but heartbeats is killed within the bound and the blocked producer returns,
via the Hello.test_stall_reader_on_diag seam); BlockingPipeStreamTests dispose
with a write blocked on a full pipe, and with a read and a write both pending;
Category=ScriptWorker on the protocol, handshake and pipe test classes.
Mutation checks: no stall kill -> stall test red; catch-all without the fault
-> callback test red (Crash).
Claude-Session: https://claude.ai/code/session_01GT67AD99zQQqpLCVm3p7xk
A .NET pipe opened Asynchronous completes even its synchronous Read/Write
through the thread pool's completion port, so every frame on Windows cost a
completion packet plus a pool work item (and the pool's spin-wait). New
WindowsBlockingPipeStream issues its own overlapped ReadFile/WriteFile with the
OVERLAPPED.hEvent low bit set (no completion packet) and waits on that event on
the calling thread; reads and writes stay concurrent, unlike a synchronous
handle. ScriptWorkerFrameCodec.BlockingStream picks it on Windows and the pipe
itself on Unix, so both ends now use the dedicated blocking reader + synchronous
combining writer on every OS (UseBlockingIo and the async read loops are gone).
Claude-Session: https://claude.ai/code/session_01GT67AD99zQQqpLCVm3p7xk
Joseph Doherty