"We removed over 80% of Claude Code's system prompt for Opus 5 and Fable 5"

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Thariq on X: "We removed ~80% of the Claude Code system prompt for our newest models, this is what we've learned about writing system prompts, skills and Claude.MDs for them. https://t.co/6DZwSrZjE9" / X<br>Post

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Thariq

@trq212

We removed ~80% of the Claude Code system prompt for our newest models, this is what we've learned about writing system prompts, skills and Claude.MDs for them.<br>The new rules of context engineering for Claude 5 models

span:not(:empty)~span:not(:empty)]:before:content-['·'] [&>span:not(:empty)~span:not(:empty)]:before:px-1 [&>span:not(:empty)~span:not(:empty)]:before:shrink-0">5:45 PM · Jul 24, 20261.2MViews

213<br>822<br>8.2K<br>16K

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@trq212

8h

this is also available on the Claude Blog here:

The new rules of context engineering for Claude 5 generation models | Claude by Anthropic

From claude.com

13<br>217<br>svg]:size-5 text-body hover:bg-mix-current hover:bg-mix-amount-10 active:bg-mix-current active:bg-mix-amount-15 focus-visible:bg-mix-current focus-visible:bg-mix-amount-10 outline-current -m-2 shrink-0 cursor-pointer border-transparent p-0 text-body size-9 [&>svg]:size-[1.25em] [&>[data-engagement-icon]]:size-[1.25em] group-hover:bg-mix-current group-hover:bg-mix-amount-10" aria-label="View count" type="button" data-state="closed" href="/trq212/status/2080711577867845645/quotes">40K

span:not(:empty)~span:not(:empty)]:before:content-['·'] [&>span:not(:empty)~span:not(:empty)]:before:px-1 [&>span:not(:empty)~span:not(:empty)]:before:shrink-0 min-w-0 overflow-hidden">BowTied Biohacker

@BowTiedUM

7h

Appreciate it! Opus 5 is performing a lot better

Was stuck relying on 4.6 + other models for biology stuff until now

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Relevant people<br>Thariq@trq212Follow<br>Claude Code @anthropicai. prev YC W20, @southpkcommons, @medialab

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