_redirects redirects my proxy rule

Maybe someone can help me out here?

I have an astro project (static export) with an

_redirects

_redirects

file with this rule:

/test-proxy /123 200

/test-proxy /123 200

When I navigate to

/test-proxy

/test-proxy

I just get a

308 Permanent Redirect

308 Permanent Redirect

/123

/123

.
Even in a new deployment / new browser so I'm pretty sure it's not an old cached redirect.

I tried to follow the docs carefully.