The new rules of context engineering for Claude 5 models

Thariq Shihipar’s article argues that newer Claude models change the context-engineering tradeoff: less duplicated rule-setting, more model judgement, interface design, progressive disclosure, and high-fidelity references. One concrete reported result is that Anthropic removed over 80% of Claude Code’s system prompt for newer models with no measurable loss on its coding evaluations. The attached note keeps the article’s five “then/now” shifts together and maps the intended jobs of the system prompt, CLAUDE.md, skills and tools, references, and memory. It also keeps the evidence boundary visible: this is the author’s report, not an independently published benchmark.