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Guest protocol: tty and window resize for StartProcess #104
Description
ax ssh (soon ax exec, google/ax#492) runs commands through the env guest ProcessService, which has no pty today: -i gives a prompt but no job control or full-screen tools (google/ax#374). Proposal, all additive:
StartProcessRequestgets an optionalttywithrows/cols. When set, the tracker allocates a pty (Setsid + Setctty), puts merged output on stdout, and treats EIO on the master as EOF.- A unary
ResizeProcess(process_id, rows, cols)RPC (SIGNAL_WINCHcarries no size). - tty processes exempt from the 10 MB output cap, or use a ring buffer, so long
top/vimsessions don't go silent.
Old clients and servers keep working. Happy to send the PR if this shape works for you.
Activity
tomergee commentedon Oct 18, 2026
Confirmed and implemented in #107.
Summary of Changes
proto/ateenv/v1alpha/guest.proto): Addedmessage TTY { uint32 rows = 1; uint32 cols = 2; },TTY tty = 6onStartProcessRequest, andrpc ResizeProcess(ResizeProcessRequest) returns (ResizeProcessResponse)onProcessService(regenerated Go and Python stubs).guest/process/pty_linux.go,guest/process/tracker.go,guest/process/service.go):/dev/ptmx+TIOCGPTPEER), applies initial window dimensions viaTIOCSWINSZ, and launches the child withSetsid: true, Setctty: true, Ctty: 0withStdin/Stdout/Stderrbound to the slave fd.stdoutspool (stderrremains empty), exemptsttyprocesses from the 10 MBMaxLogBytestruncation cap, and treatsEIOwhen the last slave closes as clean EOF.ResizeProcessviaTIOCSWINSZon the master fd (deliveringSIGWINCHto the foreground process group) and returnsFailedPreconditionif the process was started withoutttyor has already exited.internal/apiservice/server.go,clients/go/process.go): AddedServer.ResizeProcessproxy forwarding and(*Process).Resize(ctx, rows, cols).anzal1 commentedon Oct 18, 2026
Thanks for picking this up so fast! I'll do the ax client side (raw mode, SIGWINCH resize,
~.escape) on top of #107 and google/ax#492 once they land.