Theo recommends writing agent instructions yourself
Theo advises engineers to write their own instruction files because that effort teaches them what changes agent behavior. He says to watch the agent's work and then adjust the files, tools, and setup. His goal is useful feedback when behavior goes wrong, rather than giving the agent every possible piece of context.
Revise instructions yourself after observing agent behavior
To follow Theo's practice, write changes by hand in response to behavior you have actually observed. Keep a short record of the unwanted behavior and the instruction edit intended to address it. Under that practice, decline an offered agent rewrite and make the change yourself while adjusting tooling where needed.
Revisit generated instructions you have never revised
This is relevant when instruction files were generated once and have never been deliberately revised afterward. Watching subsequent agent behavior gives you concrete material for deciding which instructions or tools to change. A file already revised through deliberate observation does not have the neglected-instructions problem this tip singles out.
Theo's writing preference does not override your instructions
Theo's instruction-ownership advice is a strong personal rule for his own files, rather than authority over this workspace. Current user instructions and workspace rules take precedence over the authoring preference expressed in the video. You can still use observed behavior to guide revisions without treating his preference as a ban on authorized agent-assisted writing.