Anthropic：删80%系统提示，上下文工程新规则

A great piece from Thariq (Anthropic) - "The new rules of context engineering" in Claude.

Anthropic removed over 80% of the system prompt for Claude Code and saw no negative impact on its coding evaluations.

There was a reason the old prompt was long : early models needed strict guidelines to prevent file deletions or unprofessional comments.

The team therefore wrote strict rules, such as not writing multi-line comment blocks, and recognized that the rule would sometimes be wrong.

But when the new models could figure out a situation and make their own decisions, that tradeoff didn’t make sense anymore.

To make matters worse, these old rules began to clash with each other : a skill might tell the user not to add comments, while the user asks about documentation.

Claude can still figure out what you mean, but his thinking goes off on tangents reconciling instructions instead of solving your real problem.

The fix was to delete the rules and describe the goal, so the new prompt simply says write code that matches the surrounding code.

The same logic subsequently permeated the whole of the context.

While previous best advice for tool use has been examples, the model is now forced to copy the example instead of exploring.

It is better to design the tool itself, since a status field limited to pending, in_progress and completed shows proper usage without a single example.

Front-loading has also been eliminated due to the inclusion of code review and verification in skills that are only turned on when needed.

Some tools are hidden until the agent discovers them, meaning they don’t need any context until they’re needed.

The same was true for repetition, since instructions are now in tool descriptions rather than repeated in the system prompt.

Your CLAUDE .md no longer has to be a notebook, memory saves itself automatically.

Short. Tokens into gotchas not obvious from the repo. Rest into skills.

The result was more comprehensive references; a test suite, an HTML mockup or a rubric conveys more information than a paragraph of description.

Prompt bloat now functions like technical debt: every guardrail you build for a less-capable model will still be a cost to you on a more capable one.

What really changed is that context engineering went from writing rules to building how well the model can read.