I work on an open-source coding agent, and one design choice we made is to keep conversations append-only. No editing past prompts.

Many would argue this feels restrictive. Isn’t it just better to edit an earlier message or tweak the prompt and move on? And this is what most coding agents allow, and on the front, it looks convenient. But realistically, editing conversation history throws away the most valuable signal you have.

When you edit the past prompts, it's basically erasing the part on how the agent actually reasoned. You lose the failed attempts, the wrong assumptions, the dead ends, and the recovery steps. That history is exactly what you need to understand why something worked or didn’t.

So instead of allowing you to edit a past prompt and erase the following history, we worked on allowing you to fork from the point instead. With our append-only model approach, every attempt becomes a checkpoint. You can fork from different moments, try alternative approaches, and compare outcomes side by side.

That way, you don’t have to pretend the first attempt was correct; you acknowledge that AI coding is inherently trial-and-error.

If you give an agent one shot, you get one outcome. If you give it five attempts from the same starting point, your chances of getting what you want go up dramatically. And append-only history makes that exploration cheap and safe, allowing you to treat failure as data and not something to hide or overwrite.

And to look at it, isn’t that how we already work as engineers? We don’t rewrite Git history every time an experiment fails. We branch instead. This allows us to explore and keep a record of what happened so we can reason about it later.

Thoughts?