Claude Code's creator just leaked a hidden mode

@vibewithkevin

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Claude Codeseen in 193 videos →

Why it worked

The post leverages curiosity by revealing 'hidden' or 'undocumented' features of a popular AI tool, presented as exclusive insights from its creator. This creates a sense of insider knowledge and encourages engagement through sharing and saving.

Summary

This slideshow reveals hidden modes and undocumented features of Claude Code, an AI tool. It explains how these features can alter the AI's behavior and performance, suggesting that the AI might be more intelligent with fewer prompts.

Structure

1Introduction to Claude Code's hidden mode
2Reveal 1: Undocumented simple mode
3Reveal 2: Custom system prompts
4Reveal 3: Model smarter with no prompt
5Reveal 4: Prompt injection no longer works
6Reveal 5: Runs for days without user input
7

Original caption

The one I'd run tonight: CLAUDE_CODE_SIMPLE=1 claude. undocumented env var, strips every system prompt out of the harness including the ones on the tools. anthropic uses it internally as an ablation to check whether a prompt is actually earning its slot. and the finding they got back is the uncomfortable one. the model is a little more intelligent with no prompts at all. the prompts are in there so the product behaves the way you expect. making the model think better was never their job. there's also --system-prompt, which swaps the whole thing for yours. boris literally says go experiment with it. the other two: they can't get prompt injection to work anymore. three layers. aligned model, a classifier watching which neurons light up during an injection, and the auto mode classifier. and opus 5 in auto mode runs for days, weeks, months without stopping, with no scaffolding at all. his parting advice was be brave enough to press delete. they wipe the system prompt every model release and add it back line by line. which of these did you already know? because i didn't know about simple mode. #claudecode #ai #coding #claudeai #aiagents

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On-screen text

BORIS CHERNY 00:00 01 / 07 5 MINUTES, 5 REVEALS Claude Code's creator just leaked a hidden mode He sat down with Y Combinator and spent the first 5 minutes casually dropping things that aren't in any doc. One of them you can run tonight. Boris Cherny Y Combinator interview Jul 2026 @vibewithkevin SWIPE → BORIS CHERNY 04:45 02 / 07 REVEAL 01 There's an undocumented simple mode It strips every system prompt out of Claude Code, including the ones on the tools. Anthropic runs it internally as an ablation. TRY IT CLAUDE_CODE_SIMPLE=1 claude Boris Cherny Y Combinator interview Jul 2026 @vibewithkevin SWIPE → BORIS CHERNY 04:36 03 / 07 REVEAL 02 You can hand it a brain you wrote One flag swaps the entire system prompt for whatever you want. Boris says it on stage: go experiment with it. TRY IT claude --system-prompt "..." Boris Cherny Y Combinator interview Jul 2026 @vibewithkevin SWIPE → BORIS CHERNY 05:05 04 / 07 REVEAL 03 The model is smarter with no prompt at all That is the finding from the ablation. The prompts stay because they make the product behave, not the model think. THE FINDING Boris Cherny Y Combinator interview Jul 2026 @vibewithkevin SWIPE → BORIS CHERNY 02:00 05 / 07 REVEAL 04 They can't get prompt injection to work anymore An aligned model, a classifier watching which neurons light up during an injection, and the auto- mode classifier. THREE LAYERS Boris Cherny Y Combinator interview Jul 2026 @vibewithkevin SWIPE → BORIS CHERNY 01:26 06 / 07 REVEAL 05 It will run for days without you Opus 5 in auto mode goes for days, weeks, months. No scaffolding, no orchestration layer, no babysitting loop. AUTO MODE Boris Cherny Y Combinator interview Jul 2026 @vibewithkevin SWIPE → BORIS CHERNY 06:00 07 / 07 SCREENSHOT THIS Be brave enough to press delete Every model release, they delete the system prompt and add it back one line at a time to see what each line is worth. His advice to everyone else building on this: do the same. SAVE. SHARE. FOLLOW. KEEP BUILDING