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What a 275K-Character Claude Prompt Teaches Us About Building AI Agents

This story is from 2026-09-02. It is preserved in the archive; the latest stories are on the live feed.

A GitHub repository recently published what it describes as a runtime system prompt for Claude Fable 5.1. The file contains more than 275,000 characters of instructions related to tool use, web search, memory, copyright, safety policies, and interface behaviour. That naturally produced a dramatic h…

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  1. 2026-09-02 07:23 · DEV Community — AI
    What a 275K-Character Claude Prompt Teaches Us About Building AI Agents

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