kmcheung12/janus

Janus

Software development isn't a pipeline from idea to product. A product is what generates the next idea - what broke, what confused users, what worked better than expected. Janus closes that loop.

Most coding agents work from specs and diffs. They don't know what actually happened in the browser. Janus captures real sessions - interactions, errors, network calls - and pipes them directly into Claude, so your agent starts from what's true instead of what's assumed.

No more copy-pasting interaction traces into Claude. Your browser and terminal can do that itself.

Demo

<video src="https://github.com/user-attachments/assets/c956bf30-9810-4a03-9030-65a5ce0cfffc" controls width="100%"></video>

Dev workflow for splendor.

Architecture

  Browser                Terminal
┌──────────┐          ┌───────────┐
│Extension │          │ janus cli │
└────┬─────┘          └─────┬─────┘
     │ WebSocket            │ WebSocket
     │ ws://localhost:3457  │ 
     │                      │
     └──────────────────────┘
                    │
             ┌──────▼──────┐
             │  MCP server │
             └──────┬──────┘
                    │ SSE
             ┌──────▼──────┐
             │    Claude   │
             └─────────────┘

Extension - works standalone without the MCP server. Captures interactions in the sidebar and lets you copy a formatted prompt directly. The MCP server adds ambient, queryable access for Claude.

janus CLI - without the MCP server it's a no-op passthrough. The MCP server is required for CLI journeys to be queryable.

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Table of contents

• Install the extension
• Install the MCP server
• Install the janus CLI

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Install the extension

Run from the repo root (/path/to/janus)

Chrome:

1. npm install && npm run build
2. Open chrome://extensions, enable Developer Mode, cli