8th Light describes a structured agentic development harness built around Claude Code for a real healthcare startup project. The framework adapts the Research-Plan-Implement methodology with a CLAUDE.md knowledge root, path-scoped rules files that load context-relevant conventions automatically, MCP integrations connecting Linear and Figma directly to the agent, and two core workflow skills: /story-writer for research and planning, and /tdd-build for TDD-driven implementation. A key innovation is a test-writer subagent that operates in a fresh context window with no visibility into implementation code, enforced by a hook that restricts file writes to test paths only. The result: a two-developer team delivered a multi-tenant platform with an AI coaching companion while maintaining code quality, architectural consistency, and tight product-design-engineering feedback loops.
