Replicating Anthropic's Generator-Evaluator Harness with Kiro CLI: A 12-Iteration Website Build
A developer replicated Anthropic's Generator-Evaluator harness design for long-running apps, inspired by GANs. The architecture: a Planner (runs once) then Generator ↔ Evaluator loop for 12 iterations. Each agent is a separate CLI process with zero shared context, communicating only through files (spec.md, eval-report.md). The Evaluator uses Playwright to browse the live site—not just read code.
Key Architecture Details
- Clean slate per invocation: Each agent starts fresh, reads only its input files. Prevents context anxiety.
- Playwright MCP for testing: Navigates, clicks, resizes viewports. Catches visual bugs code review never would.
- Anthropic's frontend design skill: Explicitly penalizes generic AI patterns (Inter font, purple gradients, card layouts). Forces creative risk-taking.
- Continuous iteration, not retry-on-failure: All 12 rounds run regardless. Each one improves.
Results & Stats
Iteration 1: functional but forgettable. Iteration 4: Generator pivoted to "Terminal Noir"—IBM Plex Mono, amber on black, grain textures, scanlines. Iterations 5-12: polish, accessibility, responsive fixes, reduced-motion support.
- Total time: 3h 20min
- Iterations: 12 (generator + evaluator each)
- Manual code written: 0 lines (a few visual issues fixed after)
- Tech: Next.js, Tailwind, Framer Motion, TypeScript
Live Result
https://mnemo-mcp.github.io/Mnemo/
Key Takeaway
The model is the engine. The harness—constraints, feedback loops, and adversarial structure—determines whether you get AI slop or something genuinely distinctive.
📖 Read the full source: r/ClaudeAI
👀 See Also
Understanding AI Agent Autonomy in Real-World Applications
Anthropic's recent research analyzes millions of human-agent interactions to measure the autonomy of AI agents like Claude Code in various domains.
Claude Code Agent Teams Build Micro SaaS Products in 4 Hours Using Obsidian Vault
A developer built an end-to-end system where Claude Code agent teams handle the complete SaaS lifecycle from idea discovery to deployment in 4 hours. The system uses an Obsidian vault as persistent memory and specialized agent teams for research, validation, development, and distribution.
Developer Switches from Cursor to Claude for Unlimited Opus Access
A developer migrated from Cursor to Claude's $100 Max plan to get unlimited Sonnet and Opus usage, finding it more cost-effective than Cursor's $120 monthly expense with credits.
Multi-Agent AI Teams Using Context Baptism to Improve Code Reviews
A developer running 18 generations of AI agent teams discovered that agents who read letters and retrospectives from previous generations write significantly better code reviews than those who only read the code, calling this practice 'Context Baptism.'