Finsliparn

Swedish: the honer — from finslipa, meaning "to hone", "to fine-tune" or "to put the finishing touches on."

Finsliparn is a Bun-native MCP Server and Claude Code Plugin that transforms single-attempt coding into a multi-attempt, test-validated refinement loop. It adapts the philosophy of Poetiq's ARC-AGI solver to general software development.

🎯 Core Value Proposition

LLMs often generate code that looks correct but fails in edge cases. Finsliparn solves this by enforcing a Refinement Loop:

1. Iterate: The LLM implements a solution.

2. Validate: Finsliparn runs your actual test suite (not just a syntax check).

3. Feedback: Test failures are fed back to the LLM as structured, actionable directives.

4. Select: If multiple attempts are made, the best one (highest score, lowest complexity) is selected.

"Test results are the objective truth—not diffs, not prompts, not opinions."

Related MCP server: Debugging MCP Server

🏗 Architecture

Finsliparn uses a Filesystem-as-IPC architecture to support multiple AI platforms with a single core engine.

graph LR
    subgraph "AI Client"
        Claude[Claude Code]
        Copilot[GitHub Copilot]
    end

    subgraph "Finsliparn Core"
        MCP[MCP Server]
        Directive[Directive.md]
        Tests[Test Runner]
    end

    Claude --"Hooks"--> MCP
    Copilot --"Agent"--> MCP
    MCP --"Writes"--> Directive
    Directive --"Reads"--> Claude
    Directive --"Reads"--> Copilot
    MCP --"Executes"--> Tests

• directive.md: The single source of truth. It tells the LLM exactly what to do next (e.g., "Fix failing tests in src/foo.ts").

• Git Worktrees: Every iteration runs in an isolated worktree, ensuring your main branch stays clean until a solution is verified.

🚀 Getting Started

Prerequisites

• Bun v1.3+

• Git

Installation (Development)

# Clone the repository
git clone https://github.com/jgabor/finsliparn.git
cd finsliparn

# Install dependencies
bun install

# Link the plugin (for Claude Code)
# (Coming soon)

📖 Documentation

• Technical Specification (v1.0.0): The core architecture and Claude Code integration.

• Copilot CLI Support (v2.0.0): Adaptation for GitHub Copilot CLI agents.

• Roadmap: Development plan and status.

🛠 Usage

With Claude Code

# Start a refinement session
/finslipa Implement a fibonacci function in src/math.ts

Finsliparn will automatically intercept your edits, run tests, and guide you until the tests pass.

With GitHub Copilot CLI

# Start the agent
copilot run --agent finsliparn "Implement a fibonacci function"

The agent will autonomously loop through the directive.md instructions until completion.

Author

Jonathan Gabor