Child process pipes

ProcessPipe starts a child program with UTF-8 stdin, stdout, and stderr pipes. A Windows job object manages the child process tree.

Development capability

Require features.processPipe in --capabilities. This API is part of the demonstrated working-tree build.

A bounded read

p := ProcessPipe(A_AhkPath, ["/Headless", A_ScriptDir "\child.ahk"])
try {
    Print(p.ReadLine(10))
    Print("exit={}", p.Wait(10))
} finally {
    if p.Running
        p.Kill()
}

The worker recipe supplies both scripts.

Interface

Member	Behavior
ProcessPipe(command, args?, workingDir?)	Start a program; prefer an argument array for quoting
Send(text, timeout?), SendLine(text, timeout?)	Write UTF-8; the latter appends a newline
ReadLine(timeout?)	Read a stdout line without its terminator
Read(timeout?)	Read buffered stdout; optionally wait for data
ReadStdErr()	Drain buffered stderr
Wait(timeout?)	Wait for exit and return the exit code
Close()	Close stdin, sending EOF; it is not a process-kill method
Kill()	Terminate the job's process tree
PID, Running, ExitCode, AtEOF	Inspect process state

Timeouts are in seconds for this API. Expiry throws TimeoutError. A timed-out write may already have delivered a prefix. MCP execution tool timeouts use milliseconds instead.

Lifetime and buffering

Both output pipes are drained during waits and writes. Script timers and hotkeys can continue processing while a wait is in progress. Releasing the object closes the job and terminates remaining child processes.

Keep stdin EOF distinct from a blank output line. In a child reading a pipe, File.AtEOF can appear true while the pipe is momentarily empty; design an explicit message/EOF protocol and test it.

Together with ClautoHotkey

A worker can return JSONL that an AHK test asserts against. ClautoHotkey can then validate the edit and run the test through the same engine. Its dry-run shim does not establish safety for arbitrary ProcessPipe children; keep demonstration commands controlled.