When using the "biosphere" in the lost cities mod, I want to prevent monsters from spawning inside the sphere, but using the "insphere" rule does not work.
Please help.

I need a LOT more info. What did you do exactly? Show your entire rule file and explain what is happening (or not happening)

This is "spawn.json" file.
Monsters spawn inside the city sphere.

[
{
"onjoin":true,
"insphere": true,
"result": "deny"
}
]

How are you testing this?

When I create a world with that setting and set the time to night, the monsters spawn inside the sphere.

What mobs are spawning exactly? Vanilla or modded? What happens if you remove the "insphere": true test?

All mobs,vanilla and modded are spawning.
And I removed "incities", mobs don't spawn.
It seems that the "in control" itself is working, but the "insphere" rule is not working.

incities? You mean insphere I suppose?

Try removing "onjoin": true but with "insphere": true

I see.

hmm,mobs are still spawning.

No clue then. It might have been broken in 1.12 but I thought it worked. Anyway I no longer work on 1.12 so if it doesn't work then I'm afraid it will remain not working. Make sure you're using the last version of all my mods though

Yes I using latest version.
It doesn't matter if there is no solution.
Thanks for answering my question!

Oh, I can do something similar with the "minspawndist" rule! (in "biosphere" the spawn point is inside the sphere)