Genesyscloud_flow_ivr 422 on custom speech model ref in au-1 byoc

stuck on ivr flow deployment. terraform plan passes but apply fails with 422 unprocessable entity.

resource “genesyscloud_flow_ivr” “main” {
name = “main_ivr”
language = “en-AU”

settings {
speech_model = “genesyscloud_speech_model_custom” # custom model id
timeout_seconds = 10
}
}

error is specific to the speech_model field. api returns 422 saying “invalid speech model reference”. the model exists in the same org and is active. i can see it via gc-cli get speech-models.

env: au-1 byoc
tf provider: 2.5.1
provider version: 2.5.1

tried hardcoding the model id directly. still 422. tried referencing by name. same error.

is there a specific permission needed for the service account to link custom speech models to ivr nodes via terraform? or is this a known bug in the au-1 byoc api? the standard models work fine. just the custom ones fail.

anyone have a working example of linking a custom speech model to an ivr resource in terraform? pasting the full error log below if needed.