The AI Agent Problem for Smalltalk

Using AI coding agents with Smalltalk doesn't work well out of the box:

• No knowledge of Pharo — AI doesn't know how to interact with the environment
• Unknown project structure — Typical Tonel/package layout is unfamiliar
• No testing/debugging skills — Can't run tests or diagnose errors
• No library access — Can't browse existing classes or methods
• Poor coding style — Doesn't know Smalltalk idioms and conventions

This is a major barrier for developers who want AI assistance in Smalltalk.

Enter smalltalk-dev-plugin

We gave AI the complete skillset for Smalltalk development:

Result: AI becomes a reliable Smalltalk development partner!

Core Philosophy

"AI editor as the source of truth"

Edit Tonel files in the AI editor, import to Pharo, test, and iterate.

At a Glance

• 9 slash commands
• 4 specialized AI skills
• 27+ MCP tools for Pharo interaction
• Automated code quality checks and documentation generation

Supported AI Agents

The rest of this presentation focuses on the Claude Code version.

Installation (1) — Install the Plugin

# Add marketplace from GitHub
claude plugin marketplace add mumez/smalltalk-dev-plugin

# Install the plugin
claude plugin install smalltalk-dev

Installation (2) — Set Up Pharo Side

Install the interop server in Pharo:

Metacello new
  baseline: 'PharoSmalltalkInteropServer';
  repository: 'github://mumez/PharoSmalltalkInteropServer:master/src';
  load.

Start the server:

SisServer current start.

That's it — you're ready to go.

Installation — Other AI Agents

Setup scripts are provided for Cursor, Windsurf, and Antigravity:

./extra/setup-cursor.sh [target-directory]
./extra/setup-windsurf.sh [target-directory]
./extra/setup-antigravity.sh [target-directory]

Limitations

• Commands use st- prefix instead of st:
• Some features may differ depending on the agent
• Pharo-side setup is the same as for Claude Code

Where to Launch Claude

Run claude in an empty directory or your project source directory.

• You can also point to an Iceberg repository directory
• However, to avoid conflicts, it is better to clone the repo into a separate directory and use that instead

/st:buddy — Main Entry Point

/st:buddy is a friendly assistant that routes to the right tool.

Just describe what you want in natural language:

/st:buddy I want to create a Person class with name and age

The assistant will:

1. Load the appropriate skill automatically
2. Create the Tonel files
3. Guide you through linting, importing, and testing

/st:buddy — Intelligent Routing

You don't need to remember which tool to use — just talk to /st:buddy.

Skills (1) — Developer & Debugger

smalltalk-developer

The core development skill. Knows Tonel format, package structure, and the full Edit → Lint → Import → Test workflow.

smalltalk-debugger

Systematic debugging specialist. Diagnoses errors, runs incremental code execution with /st:eval, and guides you to the fix.

Skills (2) — Finder Skills

smalltalk-usage-finder

Discovers how classes and methods are used. Finds examples, analyzes usage patterns, and helps you understand unfamiliar APIs.

smalltalk-implementation-finder

Finds method implementations across class hierarchies. Useful for learning coding idioms and assessing refactoring impact.

Slash Commands

Sub-Agent: @smalltalk-commenter

Automatically suggests CRC-style class comments for undocumented classes.

• Triggered after file edits via hooks
• Non-intrusive — suggests, doesn't force
• Analyzes complexity and prioritizes classes that need documentation

MCP Servers

Two MCP servers power the integration behind the scenes:

pharo-interop (22 tools)

Pharo communication — eval, import/export, tests, code navigation, etc.

smalltalk-validator (5 tools)

Tonel validation and linting.

Note: You rarely need to interact with these directly.
/st:buddy handles orchestration for you.

Example 1 — Starting from Scratch

A simple use case: starting from an empty directory as a Smalltalk beginner.

/st:buddy I'm a Smalltalk beginner. I want to create a Money class
that can perform arithmetic operations across different currency units.
Please help me from the project initialization.

Example 2 — Graph Algorithms

A more complex use case for someone familiar with Smalltalk.

/st:buddy I want to create GrNode and GrArc to represent directed graphs
and solve shortest path problems. Nodes have a name, arcs have a score.
Let's start this as a GraphGear project.

Example 3 — GUI Programming

Building a GUI application with Spec2.

/st:buddy I want to make a simple to-do list using the Spec2 framework.
Include a checkbox for each item, plus an input field 
with Add/Remove buttons at the bottom.
Only checked items can be removed. Start developing.

Summary

smalltalk-dev-plugin makes Pharo Smalltalk development with AI assistants practical and productive.

Just type /st:buddy and start building.