deepseek-harness/packages/ui/stdio

@deepseek-ai/dsh-stdio

The terminal readline front door for DeepSeek Harness agents. It reads prompts from stdin, sends or steers them through ctx.agents, renders the durable session/event transcript to stdout, and answers ctx.userInteraction requests in the same terminal.

This package owns the terminal channel only. It injects agents and userInteraction, then drives an agent created or resumed by app or developer code. The agent spine, agent lifecycle, console logger, and model-facing ask_user_question tool remain separate composition entries.

Config

Key	Default	Meaning
welcome	ready.	Banner printed before the first prompt
sessionId	main	Exact agent/session identity driven by stdin and observed for EOF shutdown

The plugin seeds display labels from the live agent registry, then tracks agent/created and agent/disposed so HMR and externally managed agents render consistently. While an initial exact identity is pending, it buffers nonblank input until agent/session-start and observes live agent-loop/config-start-failed; a matching failure drops queued lines, reports the loss, and lets piped EOF finish instead of hanging. The composing app must mount this front door before its config-created agent. Disposal closes readline and unregisters every listener/provider through Cordis effects.

- id: stdio
  name: '@deepseek-ai/dsh-stdio'
  config:
    welcome: 'agent REPL ready. Give it a coding task.'
    sessionId: main

Model Experience

Readline prompt input

What the model sees

Each non-empty terminal line outside an active question becomes one text block, sent with agent.send() while the target agent is idle and agent.steer() while it is running.

Token effect

Submitted text is retained under the agent loop's normal session-history and compaction rules. The welcome banner, > prompt, rendered transcript, and [tool call] / [tool result] terminal lines add no tokens. A replacement tool/result remains model-visible through the session surface but is not rendered as a second execution; stdio keeps the original full-fidelity result line.

KV Cache effect

Append-only; newly visible content follows the reusable request prefix and does not invalidate existing KV-cache entries.

Terminal user-interaction answers

What the model sees

When a consumer calls ctx.userInteraction.ask(), this provider renders the question in the terminal and returns selected option labels or custom text. Through dsh-tool-ask-user, closed stdin becomes Error: ask_user_question cannot be answered because stdin is closed; disposal or abort becomes Error: ask_user_question was interrupted before the user answered.

Token effect

Waiting and terminal prompts add no tokens; the resolved answer or error is model-visible only through the calling tool or plugin's result.

KV Cache effect

Append-only; newly visible content follows the reusable request prefix and does not invalidate existing KV-cache entries.

Known Limitations and Deferred Work

• One configured session receives stdin — the session/event renderer can print output from any session, but input lines always drive the configured sessionId rather than routing by the visible label.
• Terminal questions are text-only and sequential — the provider queues asks, supports option labels plus custom text, and has no richer UI shapes such as file pickers or diff previews.
• Closed stdin ends the terminal channel — EOF rejects active or queued questions and exits after submitted work reaches idle; there is no reconnect path for a long-lived process.