My current thinking on this is:

1. We'll create a .cta.json file in the target directory that contains the current configuration.
2. When the customer does npx create-tsrouter-app@latest add clerk (clerk is just an example there) we would read the current configuration and merge in the new add-on, then update the code with the delta for the new add-on.
3. We'd update the .cta.json with the updated configuration.

As an additional option we could support something like:

npx create-tsrouter-app@latest add https://raw.github.com/clerk/setup/start.json

And it would read the add-on information from that URL. That would require a single JSON file. So I might also add npx create-tsrouter-app@latest init-add-on and npx create-tsrouter-app@latest compile-add-on to initialize an add-on project, and then compile an add-on into a single JSON file format for publication to S3/GitHub/etc.

The potential issues I see are around merging into an existing file. On that note we can try a 3-way merge similar to what git does. And if that has conflicts we can look for an AI API key and ask the AI to do the merge.

Caveats:

• This would not apply to projects created before .cta.json
• This would not handle migrations from code-router to file-router or from solid to react or vice versa