Showboat: Agents Demonstrate Their Work

"I never trust any feature until I've seen it running with my own eye." -- Simon Willison

Showboat is a CLI tool that helps coding agents construct Markdown documents demonstrating exactly what their code can do. Each section is built from real command execution -- not hallucinated output.

Quick Start

# No install needed -- uvx runs it directly
uvx showboat --help

# Build a demo document
uvx showboat init demo.md "My Feature Demo"
uvx showboat note demo.md "Here's what the feature does:"
uvx showboat exec demo.md python "python my_script.py --example"
uvx showboat image demo.md "python make_chart.py && echo chart.png"

The --help text teaches an agent everything it needs. Tell your agent:

Run "uvx showboat --help" and then use showboat to create a demo.md document describing the feature you just built.

Commands

Real-Time Streaming (datasette-showboat)

Set an environment variable to stream doc fragments to a Datasette instance:

export SHOWBOAT_REMOTE_URL="https://your-server/-/showboat/receive?token=secret"

Every init, note, exec, image command will POST updates to that endpoint. The document updates in the browser in real-time.

Ecosystem

Showboat works with companion CLI tools through loose conventions:

• Rodney (uvx rodney): Browser automation -- open pages, click, inject JS, take screenshots. Designed for showboat image.
• Chartroom (uvx chartroom): Generate charts from CSV/SQL data. Designed for showboat image.
• datasette-showboat: Datasette plugin that receives streaming updates and displays documents in a web UI.

The "--help as Skill" Pattern

Simon designed showboat --help to be a complete instruction set for agents. This is the same insight as MOOLLM's semantic image pyramid: a single file (or help text) that tells the LLM everything it needs to operate the tool.

The difference: MOOLLM skills use YAML frontmatter + Markdown body. Showboat uses CLI help text. Same function, different format.

cursor-mirror Integration

Showboat can demo cursor-mirror features with real output:

uvx showboat init demo.md "cursor-mirror Status Report"
uvx showboat exec demo.md python "scripts/cursor_mirror.py status"
uvx showboat exec demo.md python "scripts/cursor_mirror.py list-workspaces -n 5"
uvx showboat exec demo.md python "scripts/cursor_mirror.py tail @1 -n 3"
uvx showboat note demo.md "Feature flag drift detected:"
uvx showboat exec demo.md python "scripts/cursor_mirror.py status-features"

This produces a shareable Markdown document proving cursor-mirror works against your actual Cursor installation, with real data.

Key Design Decisions

• CLI, not library: agents run shell commands; showboat is a shell command
• Markdown output: renderable anywhere (VS Code, GitHub, Datasette)
• exec captures real output: can't fake it (though agents try -- Simon filed a bug)
• 172 lines of Go: small, fast, single binary
• uvx for zero-install: uvx showboat works immediately

About

Created by Simon Willison (Feb 2026). Go binary with Python wrapper. Part of his "How I use LLMs" series.

• Source: https://github.com/simonw/showboat
• Blog: https://simonwillison.net/2026/Feb/10/showboat-and-rodney/
• Ecosystem: https://simonwillison.net/2026/Feb/17/chartroom-and-datasette-showboat/

Part of MOOLLM

This is a MOOLLM skill. See the MOOLLM README and skills index for context.