Brainback
story

How one bad homework session started a company.

A short, honest history. Not glamorous. That's kind of the point.

since fall 2024

The origin story is not glamorous. In the fall of 2024, one of us was on the phone with a nephew who had just used ChatGPT to write his entire English paper. He was proud of it. He’d gotten an A. He couldn’t tell us, three days later, what the paper had argued.

We spent that weekend arguing. Not with the nephew — with each other. Was this a temporary displacement, like calculators once were? Or was this something more corrosive, aimed at the exact substrate that made learning possible?

We decided it was the second thing. Then we spent a year building the product that was our answer.

the timeline

How it went, in order.

Each step is a decision we could easily have gotten wrong.

  1. Sept 2024 · the moment

    A nephew calls, proud he got an A on an English paper he can't summarize three days later. The founding disagreement starts on that call.

  2. Oct 2024 · the first weekend

    Not with the nephew — with each other. Is this a temporary displacement like calculators, or is it aimed at the substrate of learning itself?

  3. Nov 2024 · the first prototype

    A Python script with a Claude call and a system prompt that said 'do not give the final answer.' It worked 40% of the time.

  4. Dec 2024 · the output guard

    Regex first, Haiku cross-reference second. Leak rate dropped to under 1%. The product had a spine.

  5. Feb 2025 · the workflow crystallized

    Attempt-gate. Hint ladder. Explain-back. Spaced recall. Brain score. Each piece a small refusal of the shortcut.

  6. Aug 2025 · v1 shipped

    Free tier live. First 1,000 students. First institutional pilot. First 'this changed my semester' email.

  7. today · the compound

    Seven people. Distributed. Growing steadily and stubbornly. Every design decision still checked against the manifesto.

What we learned building it

The stance is easier to say than to keep. It took us four months to realize a system prompt was not enough — the output guard, the attempt gate, the sanitizer, the classifier all exist because we watched the base model drift under pressure. Every guardrail is a specific memory of a specific leak.

The other thing we learned: students are not the problem. They are the ones asking the right question. “Why does this feel bad?” They knew. We built the product they were already asking for.

We built the product they were already asking for.
the whole reason

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