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New on the Anthropic Engineering Blog: How we use a multi-agent harness to push Claude further in frontend design and long-running autonomous software engineering. Read more: https://t.co/HWvmXk1ykn
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View on XAnthropic Shares Multi-Agent Harness Design for Long-Running App Development
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Anthropic published an engineering post on how a generator-evaluator multi-agent architecture tackles poor self-evaluation and context degradation in long-running coding tasks. A standalone evaluator uses the Playwright Model Context Protocol (MCP) to interact with live pages, scoring against design quality, originality, craft, and functionality criteria — feeding critique back across 5–15 iterations. Applied to full-stack development, a three-agent planner-generator-evaluator system produced a working retro game maker; a solo run produced a broken one.
Agents reliably praise their own work — a tuned, skeptical evaluator gives the generator concrete feedback to iterate against, which is more tractable than self-critique. With Claude Opus 4.6, stronger long-context performance let the team drop sprint constructs and session resets the earlier harness required.
Apply the generator-evaluator pattern to your own agent harness for tasks where quality is subjective or hard to verify in one pass. The post includes sprint contract examples and evaluator tuning notes.
