Update: Several reproduction sessions later, it appears that the content of one specific YAML file's PSI structure is causing a negative interaction with the system's EndpointSecurity extension process. Either one of the AV products on my work machine or the EndpointSecurity extension itself are panicking when the Pasteboard daemon attempts to output the contents. My work's IT team is awesome, so they upgraded a testing machine to 26.3b2, ran the same test, and it was also affected.

The issue was happening in Ghostty, iTerm2, and Terminal.app. It happened by (a) pasting directly into the terminal prompt with Command-V, (b) using `pbpaste` in any way (like piping it into `wc -c`), or (c) pasting into an editor like Neovim with Command-V.

It doesn't happen with any other file I tested it with. It also doesn't happen if I try to paste into another app, like Visual Studio Code, TextEdit, or IntelliJ IDEA itself.

Nothing is inherently wrong with the binary/text content of the file. It's all ASCII characters.

> Either one of the AV products on my work machine or the EndpointSecurity extension itself are panicking when the Pasteboard daemon attempts to output the contents

I guess the first step would be to disable those “AV products” to see whether they affect the issue (aside: I would already find “AV product” too much, but productS?). That way, you know who to report the issue to.

Next, reading your next comment, would be try and make the string shorter to try and find the shirted example.

The macos dev forum is very responsive to questions like these, I suggest you ask this there too https://developer.apple.com/forums/tags/macos