agentui

A small, opinionated Python library for building coding-agent terminal UIs.

Streaming markdown, tool-call blocks, unified diffs, confirmation prompts, slash commands, and an @-file picker — all in linear scrollback with zero flicker.

Why

Every coding agent — Claude Code, Codex, Aider, Toad — converges on the same terminal UX: linear scrollback, streaming markdown that updates in place without flicker, collapsible tool calls, unified diffs, slash commands, an @-file picker. But in Python, no library delivers this shape as a coherent primitive.

The options today are bad:

• Textual is a full TUI framework optimized for multi-pane applications. It owns the alt-buffer, breaks native terminal selection, and forces a CSS/widget mental model that's overkill for a chat-shaped agent loop.
• prompt_toolkit + Rich in REPL mode preserves scrollback and copy-paste, but offers no agent-specific primitives. Every project reinvents streaming markdown, tool-call panels, diff rendering, confirmation prompts, and slash commands from scratch.

Other ecosystems have closed this gap — pi-tui in TypeScript (powering Mastra Code), claude-code-kit (extracted Claude Code components), Bubble Tea + Lip Gloss in Go, Ratatui in Rust. Python had no equivalent.

agentui exists because building a polished agent UI shouldn't require 2000 lines of rendering plumbing. It should take 30.

Install

pip install agentui

For .gitignore-aware @-file completion:

uv pip install agentui[gitignore]

Quick Start

import asyncio
from agentui import Session

async def main():
    async with Session() as ui:
        while True:
            user_input = await ui.prompt("> ")
            if user_input.startswith("/"):
                await ui.handle_command(user_input)
                continue

            async with ui.assistant_turn() as turn:
                async for chunk in your_llm.stream(user_input):
                    await turn.append_markdown(chunk.text)

asyncio.run(main())

That's a working agent chat UI in 14 lines.

Features

Streaming Markdown

Accepts an async iterator of string chunks. Updates in place using synchronized output (CSI ?2026h/l) — zero flicker on modern terminals, graceful degradation elsewhere. When the turn completes, content commits to permanent scrollback.

async with ui.assistant_turn() as turn:
    async for chunk in stream:
        await turn.append_markdown(chunk)

Tool Call Blocks

Structured rendering with name, JSON-pretty arguments, status badge (pending/running/done/error), and result. Collapses automatically after completion.

async with turn.tool_call("search", {"query": "test", "limit": 5}) as tc:
    result = await execute_search(...)
    await tc.complete(result)

Unified Diffs

Colored diff rendering with line numbers, green additions, red deletions. Supports an inline confirmation prompt.

block = turn.diff("src/main.py", unified_diff_string)
approved = await block.confirm()  # prompts user inline

Confirmation Prompts

Yes/no, multi-choice, and free-text — all keyboard-driven, rendered in scrollback.

if await ui.confirm("Apply changes?"):
    apply()

choice = await ui.choose("Pick a model:", ["gpt-4", "claude", "local"])

name = await ui.input("Project name:", default="my-project")

Slash Commands

Register handlers and get tab-completion for free. Built-ins: /help, /quit, /clear.

@ui.command("model", help_text="Switch the active model")
async def cmd_model(session, args):
    session.print(f"Switched to {args}")

@-File Picker

Type @ in the prompt to fuzzy-match files in the current directory. Respects .gitignore (uses pathspec if installed, falls back to basic glob matching).

Interrupt Handling

Ctrl-C during streaming cancels the in-flight turn. Partial content commits cleanly to scrollback — terminal state is never corrupted.

async with ui.assistant_turn() as turn:
    async for chunk in stream:
        if turn.cancelled:
            break
        await turn.append_markdown(chunk)

Architecture

agentui is a thin orchestration layer over two battle-tested libraries:

• Rich — rendering (markdown, syntax highlighting, panels, tables)
• prompt_toolkit — input (history, key bindings, completion)

The core innovation is a scrollback-aware live region manager. Only the currently-streaming turn uses a managed region wrapped in synchronized output sequences. When the turn completes, the content becomes ordinary terminal scrollback. Native copy-paste, tmux scrollback, and Cmd-F search keep working.

User application (agent loop)
         |
         | render calls + input prompts
         v
agentui
  ┌────────────┐   ┌───────────────┐
  │ Live region │   │ Input session  │
  │ manager     │   │ (slash cmds,   │
  │ (sync out)  │   │  file picker)  │
  └──────┬──────┘   └───────┬───────┘
         │                  │
  ┌──────▼──────┐   ┌───────▼───────┐
  │    Rich     │   │ prompt_toolkit │
  │   Console   │   │ PromptSession  │
  └─────────────┘   └───────────────┘

API Reference

Session

The main entry point. Async context manager.

Method	Description
prompt(message)	Async user input with slash command and @-file completion
assistant_turn()	Returns a Turn async context manager
print(*args)	Print to scrollback (delegates to Rich Console)
confirm(message, default)	Yes/no prompt, returns bool
choose(message, options, default)	Multi-choice, returns int index
input(message, default)	Free-text input, returns str
handle_command(command)	Dispatch a /command to its handler
command(name, help_text)	Decorator to register a slash command
register_command(name, handler)	Non-decorator command registration

Turn

A single assistant response. Async context manager opened via session.assistant_turn().

Method	Description
append_markdown(text)	Stream a markdown chunk
tool_call(name, args)	Returns a ToolCallContext async context manager
diff(path, patch)	Render a unified diff block, returns DiffBlock
cancelled	bool — whether Ctrl-C was pressed

ToolCallContext

Async context manager for tool execution within a turn.

Method	Description
complete(result)	Mark done with optional result string
error(message)	Mark as errored

DiffBlock

Rendered diff with optional inline confirmation.

Method	Description
confirm()	Async — prompts user to accept/reject, returns bool
approved	`bool

Non-Goals

• Not a general TUI framework. Use Textual for multi-pane dashboards.
• Not an agent framework. No LLM client, no tool dispatcher, no memory store. The library renders; you drive.
• Not alt-buffer / full-screen. The whole point is to preserve native scrollback.

Requirements

• Python 3.13+
• rich >= 13.0
• prompt-toolkit >= 3.0

License

MIT