Tianyi Cui
3.4 KiB
@deepseek-ai/dsh-pty-local
Local node-pty backend for ctx.pty. It starts an interactive shell under the shared ctx.sandboxPolicy, strips credential-shaped ambient environment variables, retains bounded line-oriented output, detects readiness, and tears down the captured process tree rooted at the node-pty child.
Plugin (pty-local)
The plugin injects pty, sandbox, and sandboxPolicy, then registers the configured backend type (shell). danger-full-access starts the shell directly; confined modes wrap the exact shell argv through ctx.sandbox. The effective session mode is resolved at spawn. A change to a different effective mode is rejected before its sandbox/mode event commits while that owner has an open PTY or a spawn in progress; the fence is attached to the exact owner and therefore outlives a local-provider reload that retains existing sessions. Wait for creation to settle and close the sessions before changing modes, so a terminal opened with wider access cannot survive a downgrade.
Linux readiness combines a foreground-verified private bash prompt marker, foreground-process-group syscall inspection, silence fallback, and absolute timeout. macOS uses the verified prompt marker plus silence/timeout because it has no /proc syscall surface. A marker is not ready until printable prompt text arrives, including when the OSC marker and PS1 are split across data callbacks. Unrecognized or unreadable process state is never a positive exact-idle signal. During unpublished startup, a fallback requires observed output; zero-output silence cannot publish an empty session, and timeout rejects the spawn. Incomplete terminal-control sequences are bounded by maxReadBytes and discarded through their terminator after crossing that limit; a trailing carriage return is carried across callbacks so split CRLF becomes one newline.
Send cancellation resolves the current foreground process group and delivers a real SIGINT; it never emulates interruption by writing \x03, so raw-mode programs remain cancellable. Close sends SIGTERM to descendants, waits, then sends SIGKILL to the union of captured survivors and newly scanned descendants so reparenting cannot hide a process from teardown. It verifies that every retained identity left the process table while the shell can still reap it and only then stops the shell. A survivor failure does not cache a permanently rejected close; a later close retries the teardown.
Model Experience
Indirect consumer
What the model sees
Nothing directly. Through @deepseek-ai/dsh-tool-pty, the model may receive bounded MOTD, send deltas, scrollback pages, readiness reasons, and cleanup errors.
Token effect
None until a consumer returns bounded backend output. Retained PTY scrollback is not placed in model history by this package.
KV Cache effect
No direct invalidation; the consumer owns prompts, schemas, and appended results.
Known Limitations and Deferred Work
- Line-oriented output is normalized; full-screen alternate-buffer interaction is unsupported.
- Linux exact probes support x64 and arm64 UAPI tables; other architectures use prompt-marker and silence/timeout readiness.
- A descendant that daemonizes and reparents before teardown leaves the captured tree; cleanup never broadens to the launcher PID's POSIX session because that can include unrelated processes.
- Sessions do not survive harness process exit.