Bug report: Thin reports are bloated when saved

[j_kee]

I've noticed, since April 2025, Power BI Desktop opens a lot slower than usual.

Yesterday, I noticed that a simple change to a (thin) report bloated the filesize from 83 kb to 2442 kb.

Today, speaking extensively with Copilot, I realize the following:

bloat is caused by two built-in themes: Bloom.json and Tidal.json.

I can strip them both down to 1 kb a piece by Copilot, and copy them in.

Now, opening the pbip-based report is fast!

However, saving the very same report as pbix once again returns the bloated theme files!!

In short, I have hit a roadblock here, and I smell a bug in a recent release of Power BI Desktop (I run "Version: 2.144.878.0 64-bit (juni 2025)") which causes too long opening times in general, and too big files for some edge cases - one of them triggered by myself yesterday.

If only I keep the pbip structure, I have no problem. The problem arise in the pbix save moment - and the original themes are super-inefficient in two specific cases as mentioned above.