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I was debugging some chunking regressions in an app I work on when updating from Vite 7 to Vite 8. I got an AI to generate a tool to help figuring out what was wrong, and I uploaded it at nicolo-ribaudo.github.io/vite-compare/ in case it's useful for anybody else.

Thanks for sharing! What was the outcome in your case(s)? 👀

Interesting! Did you try using `attachDebugInfo` (which should give insights why certain chunks were created)? rolldown.rs/reference/In...

Tried now, unfortunately it's not very helpful. In my case it's telling me that chunk C is its own chunk because it's imported both by chunk A and chunk B, which is indeed true, but it does not explain why it cannot just put it inside chunk A (where chunk B is only imported through import() by A)

I'll see if I can create a reproduction in the next days

Actually, this AI-generated and not Vite-generated graph shows exactly my situation 😛 With this graph shape, Rolldown is automatically splitting what's called "vendor" here into its own chunk, while Rollup was putting it together with "index". There is no reason to split it as far as I can tell.

And this was happening for a whole bunch of modules, causing the number of chunks to increase from ~50 to ~80. The solution in this example would be to manually define a group containing the entry point of the "index" chunk, and then it automatically includes what would otherwise be in "vendor"

Which isn't a very good solution and should be addressed by the rolldown team. Thanks for creating light into this complex topic

Thanks a lot for looking into this! We will investigate.