# @deepseek-ai/dsh-tui

The interactive terminal front door for DeepSeek Harness agents, built on [`@earendil-works/pi-tui`](https://www.npmjs.com/package/@earendil-works/pi-tui). It requires stdin and stdout TTYs; scripts and Loader pipes should use the headless [`@deepseek-ai/dsh-cli-demo`](../../examples/cli-demo/README.md) app instead.

The implemented [TUI feature Agent Note](../../../.agents/notes/implemented/feature/2026-07-17-dedicated-full-screen-tui-front-door.md) owns the front-door decision; the [terminal-state snapshot Agent Note](../../../.agents/notes/implemented/testing/2026-07-18-tui-terminal-state-snapshots.md) owns its verification strategy.

Interactive terminals on macOS, Linux, and Windows are supported. Windows uses pi-tui's native console VT-input handling, and the [Windows support Agent Note](../../../.agents/notes/implemented/feature/2026-07-20-windows-tui-support.md) owns the platform decision and ConPTY process verification.

This package owns interactive terminal presentation and input only. It injects `agents`, [`commands`](../commands/README.md), `llm`, `systemPrompt`, `tokenMeter`, `tools`, and `userInteraction`, then drives an agent created or resumed by app or developer code. Agent lifecycle, persistence, and the model-facing [`ask_user_question`](../tool-ask-user/README.md) tool remain separate composition entries.

The TUI rebuilds resumed history from the active session surface, renders Markdown responses and reasoning, applies each tool's `presentCall` / `presentResult` intent to terminal, diff, or generic cards, keeps the latest `todo/write` plan above the editor, and presents `ctx.userInteraction` questions in a wide bottom-left keyboard panel with progress, numbered options, and aligned descriptions. The latest logged session title becomes the header subtitle, with `welcome` before a title exists, and the terminal window title becomes `<session title> — <configured title>`. A durable `llm/retry` event retracts the failed step's live chunks and renders the scheduled retry count, delay, and failure in the transcript; success, exhaustion, and cancellation then settle through ordinary session events. The footer totals each logged model step's usage once, including failed attempts, while treating committed-message usage as a fallback for logs without a usage chunk. Its idle view compares token-meter pressure with `ctx.llm.resolveModelContext()` for the current route, displays `context unknown` when the adapter has no capacity metadata, and also shows tool-card mode and the current model with reasoning state; while the agent runs, an elapsed working indicator and `esc interrupt` replace that summary. Surface replacement events rebuild the transcript so compacted history does not reappear.

An embedding may provide `TuiRuntime.formatCwd` when its logical workspace label differs from the session's host directory. The override changes only the footer label; tools continue to use the session `cwd`.

Before model output, session events, tool presenters, questions, configuration, or diagnostics reach pi-tui's ANSI-aware renderers or the terminal title, the TUI renders C0 and C1 controls other than line feeds as visible `\xNN` text. Those sources cannot add terminal control sequences; the TUI and pi-tui retain ownership of terminal rendering and styling.

While the agent is running, ordinary editor submissions call `agent.steer()`; otherwise they call `agent.send()`. A slash at the start of the submitted line enters `ctx.commands` instead: known commands execute directly, unknown commands produce a warning, and neither path reaches the model. The TUI registers `/help`, `/model`, `/clear`, `/cancel`, `/reasoning`, `/tools`, `/redraw`, and `/exit` as agent-scoped definitions; every other effective command joins autocomplete and `/help` dynamically. Ctrl+C or Escape cancels a running turn. Tool cards collapse long bodies into a configurable head/tail preview; Ctrl+O toggles every card between its preview and full output. Ctrl+R toggles reasoning, Ctrl+L redraws, and Ctrl+D exits while idle.

`/model` opens the advisory `ctx.llm` catalog as a keyboard selector: Up/Down moves, Enter selects, and Escape closes it. `/model <model>` still selects an unambiguous model id directly, while `/model <provider>/<model>` selects an exact target. The configured target or latest logged request header initializes the selector, and an unlisted current model remains visible because catalogs are advisory. Selection is local to this TUI session. Prompt assembly snapshots the target for one step, replaces `{{provider}}` and `{{model}}`, and applies the same pair through `agent/request`; a switch during assembly therefore starts with a later step. The request header durably records targets that reach the model, while an unused selection remains process-local.

## Config

| Key | Default | Meaning |
|---|---|---|
| `welcome` | `ready.` | Header subtitle until the session has a logged title. |
| `sessionId` | `main` | Exact shared agent/session identity driven by the terminal |
| `showReasoning` | `true` | Render reasoning blocks |
| `maxToolOutputLines` | `6` | Output lines retained across a collapsed tool card's head/tail preview |
| `maxQuestionOptions` | `8` | Visible options in a question panel |
| `maxModelOptions` | `8` | Visible models in the model selector |
| `questionDialogWidth` | `200` | Question-panel width in columns, clamped to the terminal |
| `questionDialogMaxHeight` | `20` | Question-panel maximum rows |
| `modelDialogWidth` | `72` | Model-selector width in columns |
| `modelDialogMaxHeight` | `20` | Model-selector maximum rows |
| `showHardwareCursor` | `false` | Show the hardware cursor at pi-tui's IME marker |
| `color` | `true` | Apply the built-in ANSI palette (see [Color](#color)) |
| `title` | `DeepSeek Harness` | Product suffix for the terminal window title. |

```yaml
- id: terminal
  name: '@deepseek-ai/dsh-tui'
  config:
    welcome: 'Coding agent ready.'
    sessionId: main-session-123
    showReasoning: true
    maxToolOutputLines: 6
```

Startup fails before mounting when either process stream is not a TTY. The composing app must mount the TUI before its config-created agent so the front door can observe `agent-loop/config-start-failed`; a matching exact-session failure is written before fullscreen mode starts and exits with status 1 instead of leaving a blank terminal. Disposal aborts running commands, removes the TUI definitions, stops loaders, rejects pending questions, drains terminal input, restores terminal state, unregisters event listeners and the user-interaction provider, and never exits a replacement process during HMR.

## Color

The palette uses the standard 16-color ANSI foregrounds and SGR attributes, which every terminal remaps to its active color scheme, so it stays readable on light and dark backgrounds alike. Body text keeps the terminal's default foreground rather than a fixed shade. Grouped regions (user prompts, tool cards) use a colored left-gutter bar instead of a filled background block; the question panel emphasizes its active row with bold accent text, while selectors use reverse video. These treatments are foreground-only, so they never collide with the terminal background. Set `color: false` to strip all styling.

## Model Experience

### Interactive prompt input

#### What the model sees

Each non-empty ordinary editor submission becomes one text block, sent with `agent.send()` while the target agent is idle and `agent.steer()` while it is running. Slash commands and keybindings are TUI-only; command results remain terminal notices.

#### Token effect

Submitted text is retained under the agent loop's normal session-history and compaction rules. Headers, the logged title, cards, Markdown rendering, status lines, plans, and help text add no tokens.

#### KV Cache effect

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

### Session model selection

#### What the model sees

The `/model` command text and keyboard-selector input are not logged or sent. New steps receive the selected provider/model pair in both prompt variables and request routing.

#### Token effect

The selector adds no messages. A target change may alter interpolated system-prompt text and sends subsequent requests to the selected model.

#### KV Cache effect

Changing provider or model enters that target's cache domain; no cache reuse across distinct targets is assumed.

### Interactive user-question answers

#### What the model sees

When a consumer calls `ctx.userInteraction.ask()`, this provider presents each question in order and returns selected option labels or `custom` text. Abort, cancellation, or UI disposal becomes `Error: ask_user_question was interrupted before the user answered` through `dsh-tool-ask-user`.

#### Token effect

Waiting and terminal overlays 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 owns the transcript and editor** — questions from other agents can still use the shared overlay provider, but session rendering and prompt input remain bound to `sessionId`.
- **Tool cards are text terminal presentations** — terminal, diff, and generic cards use tool-owned titles/content, but session content currently has no image block for inline image rendering.
- **Non-TTY operation is intentionally unsupported** — automation must use the headless app rather than expecting an internal fallback.
