If you want to check for agent that can compute stuff, then you can let it compute sha256 of some small string... that's quite tricky for humans to do by hand :)

Pure genius! I had my agent hit the endpoint and I realized it returned a jumble of text: "if 七 wor~kers co.mplet/e{ | a job in 十七} days but 四 ] quit a^ft|e?r ^ day_ 三 ~ how many to{tal da[y;s> to fin>i?sh" but it was in japanese! Unfortunately my agent proceeded to solve the reverse CAPTCHA and got back the API key. So, I asked it to keep hitting the endpoint again until it returned another CAPTCHA that was in japanese kanji and it did (without solving it this time) and I got "a s:tore h?as ^ 二十 pe@rcent off< items- over 五十 : dollar;s and 八 ~ percent } of\f> ; i]te[ms u~nd~er: # 五十 do/ll@ars wh-ats } the c.omb>ined pri|c;e of a 一 百 二十 一 dollar item a]nd> a* 九 dollar} i!tem" And this time I was able to translate that into "a store has 20 percent off items over 50 dollars and 8 percent off items under 50 dollars what's the combined price of a 121 dollar item and a 9 dollar item?" I solved it and got 1210.8 + 90.92 = 105.08. I will admit I messed up a little bit on translating the kanji and I got a little assistance from my agent pointing out that I was wrong, but overall this was good fun, well done!

• pxc

  yesterday at 10:21 PM

  Absent any distinctive Japanese scripts or other Japanese writing in context, it probably makes more sense to call those Chinese characters, since those characters for numbers were taken directly from Chinese and still retain the same/original meanings in both languages

  • Charon77

    today at 12:46 AM

    "一 百 二十 一 dollar "

    Definitely chinese.

    In Japanese, they say 'hundred' instead of 'one hundred' "百 二十 一"

• nielsole

  today at 12:50 AM

  There's probably like 100m+ people for whom this reads like slightly jumbled math problems.

Is it even possible to have an inverse captcha without time bounds?

Humans can use agents behind the scenes to crack it, right?

• jubilanti

  today at 12:38 AM

  To me this reads as obviously a joke for marketing to the HN crowd (it worked), but their product is built around web agents, it is not a bad thing to have in the onboarding flow to make sure the agent is configured correctly.

• alfonsodev

  yesterday at 11:46 PM

  That's what I though too, maybe I'm missing something or I don't fully get it. But the human is always behind what's the difference if they go and sign up or tell an agent that they must sign up for you ?.

  My best guess is that this a way of making a system talk to your agent without you knowing what they are talking about ? As a way of not exposing the real sign up method ?

  • echoangle

    today at 12:15 AM

    Since it’s just used once, you can also just have an agent solve the captcha and then use the returned api key yourself. This has to be engagement bait.

• phoronixrly

  yesterday at 11:54 PM

  It's flame-bait.

A small detail about humans that breaks this whole scheme is that they're capable of tool use.

Very clever and fun. Two tangential observations: the bird between two trains problem I remember from childhood when we were studying for an Indian entrance exam. I thought it was in I E Irodov's problem anthology, but I cannot find it there so this must be a false memory. Looks like it's from ancient times, practically Mathematics mythology. Does anyone know the earliest books that have it? No luck with LLMs since it's such a common question today the answers I get from GPT-5.4 and Claude 4.6 Opus with search are unhelpful.

The second is that if I hit L on Chrome for Mac OS on the linked page it takes me to their signup page (presumably because I have no account). So that's a keyboard shortcut to take you to the browser-use app page. But why 'L'? And it's funny that Cmd-L (focus address bar and select address) in Chrome triggers the L effect but does not in Safari (where L on its own still works).

I aggregated a list of "reverse CAPTCHAs" here for anyone interested: https://x.com/0x_Osprey/status/2043020254289248469

Great premise but can't really agree with the execution. Felt like this makes too many implicit assumptions about LLM capabilities and traps without differentiating enough between a smart human vs AI.

Get the API key, hit the claim link, sign up for a new account, verify my email, go to the homepage:

Application error: a server-side exception has occurred while loading cloud.browser-use.com

Great first impression!

• throw1234567891

  yesterday at 10:37 PM

  Maybe they know you’re not an agent.

cool clickbait, why is this useful?

• measurablefunc

  yesterday at 11:53 PM

  It's not, it's a marketing blog post.

Speaking of browser automation, are there any LLMs or tools that hook up to actual desktop browsers and can automate the keyboard and mouse?

Which LLMs best drive these? Claude/Gemini, etc., or is anything local actually competent at it?

Can they understand layout and visual cues with a VLM or multimodality?

Are they robust enough to interact with threejs and videos and whatnot, or can they just blindly navigate the DOM?

...why? Once my agent has a key I, the human, can also use it. And surely any human use would be less intensive than any agent use.

• consumer451

  yesterday at 10:39 PM

  Exactly. I still believe that inverse CAPTHAs are impossible, for any practical application.

  Is this just a marketing stunt?

  • kingstnap

    yesterday at 11:04 PM

    To be fair, what's the practical application supposed to be for proving a user is a bot?

    Silly solutions for silly problems :^).

    • consumer451

      yesterday at 11:09 PM

      Well, when the moltbook story was everywhere, later people thought it was some big gotcha that "oh, they were actually humans."

      So, showing true agent to agent interactions is interesting, but one could never be sure that's what you were actually seeing unless you were in control of all the agents.

• jstanley

  yesterday at 10:30 PM

  But once a human has a key his agent could use that and people still like to use ordinary CAPTCHAs.

• tony_landis

  yesterday at 10:22 PM

  Right - perhaps title could be "prove you are an robot, or have access to one"

• stavros

  yesterday at 10:53 PM

  Because now you know their company exists!

“It is not you, it’s me” should do it

> TL;DR: just ask your agent to summarize this post for you.

Holy shit - why don’t they produce an AI summary and plonk it in there for everyone to use? The energy savings across all people who’ll read the summary would be staggering!

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