Inconsistent app interface name validation across contracts in App Lab

[mrcointreau]

Subject of the issue

Duplicate app interface name validation does not trigger consistently across contracts in App Lab

Your environment

Chrome 142.0.7444.60 (Official Build) (arm64)

CounterApp.arc56.json

HelloWorldContract.arc56.json

Steps to reproduce

1. In App Lab, go to: Create App Interface → Deploy New App
2. Select a spec (for example, CounterApp or HelloWorldContract).
3. Deploy the app successfully.
   For HelloWorldContract, you can use the following template variable values to test:

   ACC_ADDR -> Y76M3MSY6DKBRHBL7C3NNDXGS5IIMQVQVUAB6MP4XEMMGVF2QWNPL226CA
   ACC_AVM_BYTES -> x/zNsljw1BicK/i21o7ml1CGQrCtAB8x/LkYw1S6hZo=
   ACC_ARC4_BYTES -> x/zNsljw1BicK/i21o7ml1CGQrCtAB8x/LkYw1S6hZo=
   

4. Try to deploy another app using the same app interface name.

Expected behaviour

The validation message "App interface with this name already exists" should appear immediately upon visiting the deployment page when an app interface with that name already exists, consistently for all contracts.

Actual behaviour

For some contracts, like CounterApp, the validation appears immediately as expected, for other contracts, like HelloWorldContract, the validation does not trigger automatically until the user attempts deployment.

[neilcampbell]

Interesting. It must be to do with template variables.