Six model-facing tools over ctx.pty: terminal_open, terminal_send, terminal_read, terminal_signal, terminal_close, and terminal_list. Every operation requires the exact initiating Agent, so a model cannot address another agent's terminal even if it learns the id.

terminal_send(run_in_background: true) reuses ctx.tasks; task preflight occurs before any terminal write, completion is collected with task_output, and task_kill requests Ctrl-C. Foreground sends use terminal ACP cards; lifecycle, history, signal, and list calls use generic cards.

Model Experience

System prompt

What the model sees

The plugin contributes this fixed guidance section:

Terminal guidance

Use a terminal session only when work needs persistent terminal state or interactive stdin; prefer bash/read/write/edit for bounded one-shot operations. Track every terminal session id and close sessions that no longer matter. An inferred_idle or timeout result does not prove the foreground command exited.

Token effect

Small fixed input cost on every request while the plugin is active.

KV Cache effect

Prefix-stable while the registration scope and guidance text are unchanged.

Tool schemas

What the model sees

The six generated schemas are listed in the dsh-tool-pty catalog section. Their fixed schema tokens are present whenever this plugin is active; agent-scoped tool filtering may hide them.

Token effect

Fixed schema cost on requests where the tools are visible.

KV Cache effect

Prefix-stable while tool visibility and definitions are unchanged.

Tool results and task context

What the model sees

Spawn returns the id and bounded MOTD. Send/read return bounded terminal text plus readiness/history markers. Background mode returns a generic task id. Results remain in session history until compaction; incremental task reads do not repeat consumed output. Programmatic callers receive typed session snapshots, bounded send/read DTOs, signal and close outcomes, or { kind: "background", taskId }; Native rendering preserves the text above.

Token effect

Data-dependent and bounded by the backend; each returned result remains in history until compaction.

KV Cache effect

Append-only; new results follow the reusable request prefix.

Known Limitations and Deferred Work

No named key sequence, TUI, BEL, resize, auto-start, or cross-agent sharing schema is exposed.
Background mode requires both @deepseek-ai/dsh-tasks and its model-facing control surface.