processx

func ConfigureCancellation ¶

func ConfigureCancellation(cmd *exec.Cmd)

ConfigureCancellation makes exec.CommandContext cancellation reliable for local agent CLIs that spawn their own child processes (for example Claude Code plan-mode sub-agents, or a PowerShell/cmd shim on Windows).

The problem it solves: drivers stream the CLI's stdout/stderr by draining the pipes to EOF before calling cmd.Wait (see internal/clihelper). A child process inherits those pipe file descriptors, so killing only the top-level process leaves the children holding the write end open. The drain never observes EOF, cmd.Wait is never reached, the driver Run never returns, and the surrounding SDK run hangs — which in turn keeps the session lease held (renewed) instead of releasing it. The next run on the same session key then fails with ErrSessionBusy even though the user already cancelled.

The fix has two cooperating parts:

• configureProcessGroup (before Start) isolates the command so the whole process tree can be addressed together.
• terminate (on cancel) signals the entire group/tree, not just the leader, so inherited pipes are closed and the drain unblocks.

WaitDelay only bounds the window inside cmd.Wait; it is NOT a backstop for a descendant that escapes the group (e.g. by calling setsid) while still holding an inherited stdout/stderr pipe. In that case clihelper's drain (wg.Wait) blocks before cmd.Wait is ever reached, so WaitDelay never fires and the run still hangs. That escape is a known residual risk; the group kill above is what covers the common case.

func PrepareCommand ¶

func PrepareCommand(command string, args []string) (string, []string, error)

PrepareCommand resolves a command into a form exec.Command can launch on the current platform. Windows CLI installations commonly expose .cmd, .bat, or .ps1 shims instead of native executables; CreateProcess cannot execute those scripts directly, so route them through their owning shell. Keeping this below the Driver layer makes one-shot and persistent transports apply the same launch semantics.