Derived not working in external .svelte.js function

[signalize]

Describe the bug

Derived not working in a function that is declared in a .svelte.js file.

Reproduction

https://svelte.dev/playground/hello-world?version=5.19.6#H4sIAAAAAAAAE31SwW6jQAz9Fe9opSYSImqPNFTqpdLuYfewx9IDCSZ1O3jQjMmmQvx7NcAAidIiIaTH87P9_FrFeYUqUXgStJxrKNDSEQtgI_Df2Hfig4pUSRqdSp5bJR-153tARaH6sa5jd0QtHtvlDq_he8OCLE4lauv2lmp5yBgAgKraWIF2bzEXfDK26qC0poJMxRtNu1EifnOZus94KNIocMx1g5DCXLhqhURjAjeCTm66dc_PJBPPr0xBJWFxByn8HBdd_f7390_sxBIfqPxY9ZpxSagLt4YfaTp0iY2lA3GuJ8X-3W6mTTLevt4-_HKuwe3m9XZAiOtGYEdcJL1M2i71437YbjNwa_-R0CeB9rxx57t5zkh0kgsm0H43_2XNzpp3ZLDoGi1Th2DLJXs8_0yf_BuZKlKCJ1GJ2Aa76ItwnF3wPB-XvxYRwVMfirLhvZDh5Y2JSSjXa2jnKAwL-7v2vkyc-5kSjIQULjwb3Vpww6bLoEz1PhTXFYKERWksh_n8MxCiGQhqCyg0HZAu4-7c4JfuExKxUGqvAwAA

Logs

System Info

svelte: ^5.0.0 => 5.19.6

Severity

annoyance

[Conduitry]

This is expected. With an external .svelte.js file like this, there's nothing to hook into to get a reactive value. createForm is returning an unreactive version of the value. One way to deal with this is to use a getter in your external file - get modified() { return modified; }.