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deepseek-harness/packages/pty/pty-local/README.md
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@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 current session-level sandbox override is resolved at spawn and remains fixed for the PTY lifetime.

Linux readiness combines a private bash prompt marker, foreground-process-group syscall inspection, silence fallback, and absolute timeout. macOS uses the prompt marker plus silence/timeout because it has no /proc syscall surface. Unrecognized or unreadable process state is never a positive exact-idle signal.

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.