Locus

Locus is a local-first chat interface for studying difficult technical material. Select a passage or equation to elaborate on it in a recursive side thread without cluttering the main conversation.

Features

• Recursive elaboration threads attached directly to selected text and equations
• Inline definitions, quotations, and sandboxed MetaPost or TikZ visualizations
• Markdown, syntax-highlighted code, and KaTeX rendering throughout the interface
• Streaming responses with cancellation, regeneration variants, editable prompts, usage, and cost details
• OpenAI, OpenRouter, Claude, Kimi, GLM, MiniMax, DeepSeek, Qwen, and multiple custom OpenAI-compatible providers with BYOK credentials
• Independent provider/model routing for chat, definitions, visualizations, and rewrites
• Hosted access controls with public signup, waitlists, invite links, managed API access, and account suspension
• PDF import with equation-aware Mistral OCR, rendered extracted images, and retained source documents
• Markdown import plus portable JSON import and export
• Categories, sharing, search-friendly URLs, and persistent navigation through nested threads
• Local single-user mode by default, with an optional private multi-user deployment

Run locally

Requirements: Node.js 20+ and Docker Engine or Docker Desktop.

npm install
npm run metapost:build
npm run dev

Open http://127.0.0.1:5173. The development server proxies API requests to the local API on port 8787.

Configure a provider and API key in Settings. Alternatively, place OPENAI_API_KEY.txt, OPENROUTER_API_KEY.txt, DEEPSEEK_API_KEY.txt, or QWEN_API_KEY.txt in the project directory. Local Custom OpenAI-compatible endpoints can use HTTP or HTTPS locally and may omit a key when the server does not require one.

PDF import additionally requires a Mistral API key and its persistent worker:

export MISTRAL_API_KEY='your-key'
npm run pdf:up

For a production-style local build:

npm run build:production
npm run start:production

Then open http://127.0.0.1:8787.

Local mode requires no login or database. Chats and settings are stored in data/chats.json.

Documentation

• Local configuration
• Architecture
• Hosted deployment
• Hosted operations