Marc Andreessen’s anti-sycophancy prompt took over AI Twitter. Here it is word for word, plus my tighter, plain-English rewrite. Save them both.
In May 2026, Marc Andreessen, cofounder of Andreessen Horowitz (a16z), posted his current custom prompt on X. It tells AI to stop flattering you, say so when you’re wrong, and lead with the strongest counterargument before agreeing.
It hit a nerve because everyone has felt it. AI loves to agree with you. OpenAI even rolled back a GPT-4o update in April 2025 after Sam Altman called it "too sycophant-y."
Put one of these in your instructions and you’ll feel the difference in the first answer.
Aggressive on purpose. Use it if you want pure pushback with no softening.
Good To Know
The pushback rules are the part that works. Critics pointed out that telling AI to "never hallucinate" doesn’t stop it from making things up, and "as long as you possibly can" gets you padding. That’s why I rewrote it.
Same anti-sycophancy backbone. Less aggressive, shorter answers, and easier to live with every day.
01
A Claude Project
Best spot for big decisions. Make a Project, click Set project instructions, paste it in and save. Every chat in that Project picks it up.
02
Your settings, for every chat
In Claude, go to Settings, then Your Claude, and paste it into your instructions. In ChatGPT, go to Settings, then Personalization, then Custom instructions, and paste it into the box for how ChatGPT should respond. A ChatGPT Project’s instructions work too.
03
The top of any new chat
Not ready to commit? Paste it as your first message, then ask your question.
When Not To Use It
Brainstorming and first drafts. Early on you want energy, not pushback. Bring this back when it’s time to pressure-test.
A hard day. Don’t ask the anti-flattery AI for kind words. Different tool, different prompt.
Try It Today
Open the last serious question you asked Claude or ChatGPT. Start a fresh chat with one of these prompts, ask the same question and compare. You’ll see how much you’ve been getting buttered up.