Firebase CLI in Firebase Studio (IDX) Fails to Recognize App Check Emulator in `firebase.json`

[TuomasTiira]

The Firebase CLI (versions 14.4.0, 14.3.1, and 13.11.2 tested) running within the Firebase Studio (IDX) environment consistently fails to start the App Check emulator. The primary issue appears to be that the CLI does not recognize app-check as a valid property within the emulators object in firebase.json, even though this configuration is supported by these CLI versions.

Environment:

• Platform: Firebase Studio (IDX)
• Firebase CLI Version(s) Tried: 14.4.0, 14.3.1, 13.11.2
• Node.js Version: Node.js version 20
• Operating System: Firebase Studio Ubuntu/Linux

**firebase.json (relevant emulators section):** json
{
"emulators": {
"auth": {
"port": 9902,
"host": "0.0.0.0"
},
"app-check": {
"port": 9095,
"host": "0.0.0.0"
},
"firestore": {
"port": 9901,
"host": "0.0.0.0"
},
"functions": {
"port": 5001,
"host": "0.0.0.0"
},
"hosting": {
"port": 5000,
"host": "0.0.0.0"
},
"ui": {
"enabled": true,
"port": 9900,
"host": "0.0.0.0"
},
"singleProjectMode": true
}
}

Problem Details:

When running firebase emulators:start, the App Check emulator is not listed among the emulators being started, and it does not run.
When attempting to start App Check explicitly using firebase emulators:start --only app-check[,...], the CLI reports: Error: app-check is not a valid emulator name, valid options are: ["apphosting","auth","functions","firestore","database","hosting","pubsub","storage","eventarc","dataconnect","tasks"] This error occurred even with CLI version 14.4.0.
The most revealing finding comes from the debug output (firebase --debug emulators:start): [timestamp] Object "/emulators" in "firebase.json" has unknown property: {"additionalProperty":"app-check"}

Steps Taken to Troubleshoot:

Confirmed app-check entry exists in firebase.json with correct port and host.
Updated and downgraded firebase-tools (versions 14.4.0, 14.3.1, 13.11.2).
Ensured the correct firebase executable was being run (verified version and path).
Restarted the Firebase Studio environment multiple times to ensure no lingering processes or "multiple instances" warnings from the emulator suite.
Simplified firebase.json to only include auth, firestore, ui, and app-check emulators; the issue persisted.
Ran emulators with and without the --only flag.
Ran firebase --debug emulators:start to get detailed logs.

Expected Behavior:

The Firebase CLI should recognize the app-check property in firebase.json and start the App Check emulator alongside other configured emulators.

Actual Behavior:

The Firebase CLI ignores the app-check configuration. Debug logs indicate the CLI considers app-check an "unknown property" in the firebase.json /emulators object, preventing the App Check emulator from starting. This leads to downstream issues when client applications attempt to get App Check tokens (e.g., 403 errors when trying to exchange debug tokens with the production App Check service, as the client can't connect to an emulated App Check service).

Request:

Could you please investigate why the Firebase CLI, within the Firebase Studio (IDX) environment, fails to correctly parse the app-check emulator configuration from firebase.json, even with CLI versions that fully support this feature?

[2025-05-27T09:04:59.190Z] Object "/emulators" in "firebase.json" has unknown property: {"additionalProperty":"app-check"}