System Architecture & Design

2Brain System Architecture

Core Architectural Invariants

1. Perpetual Longevity: Plaintext Git Markdown catalogs and standard SQLite storage.
2. Device-Agnostic Access: Accessible globally behind Cloudflare Zero Trust (SSO + hardware 2FA).
3. Zero-Knowledge Security: Browser Web Crypto AES-256-GCM with PBKDF2 key derivation (100,000 iterations); edge and database store only ciphertext payloads.
4. Agent-First Operability: Standard Model Context Protocol (MCP) server for autonomous AI coding agents (Antigravity, Cursor, Claude Code).
5. Zero Infrastructure Cost: Designed to run indefinitely on Cloudflare Pages, D1, Vectorize, Workers AI, AI Gateway, and R2 free tiers.

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Architectural Decision Records (ADRs)

• ADR-01: Git-Backed Plaintext Source of Truth: Plaintext Markdown with YAML frontmatter in /projects/.
• ADR-02: Cloudflare Pages + Zero Trust Identity: Worldwide CDN edge delivery locked behind Google/GitHub OAuth with mandatory 2FA.
• ADR-03: Client-Side Zero-Knowledge Encrypted Secret Vault: Web Crypto AES-256-GCM + PBKDF2 in Cloudflare D1.
• ADR-04: Static Knowledge Graph via Graphify: Build-time graph compilation into static graph.json and interactive graph.html.
• ADR-05: Hybrid Retrieval Engine: Tri-layer retrieval via Pagefind, SQLite FTS5, and Cloudflare Vectorize.
• ADR-06: Cloudflare AI Gateway with Multi-Tier Fallback: Primary Google Gemini Flash with Cloudflare Workers AI fallback.
• ADR-07: Model Context Protocol (MCP) Edge Server: Native JSON-RPC endpoint for AI coding agents.