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Verify Required Models Before Play

Both editor plugins register models per-project as Production or Experimental in the Model Manager, then download them there. If a teammate pulls a repo change that adds or replaces a registered model, that download step is easy to miss — the next time you press Play (or open the Tryll Chat window) with a stale local model cache, CreateAgent used to fail with a GraphCompilationFailed error that gave no hint a download was the fix.

The editor guard closes that gap. It runs automatically at every point an agent is about to be created in the editor. The automatic Play / PIE check is on by default and can be turned off per project if you prefer to manage model provisioning yourself — see Turning off the Play/PIE check.

What it checks

On each guarded entry point, the guard loads your project's model manifest (the same Production/Experimental registrations you set in the Model Manager), compares every registered model of every kind (language, embedding, STT, TTS, VAD) against the live ListModels status, and treats anything Absent as needing attention.

Where it runs

Entry point Behaviour
Play (Unity) / PIE (Unreal) Blocks automatically: downloads every missing registered model behind a cancelable progress dialog, then continues into Play/PIE once ready. Cancelling, or a model that fails to download, keeps you in the editor instead.
Tryll Chat window/panel Same automatic, blocking treatment as Play — the guard runs right after the session is created and before the chat agent is built.
Model Manager window/panel Lighter-touch: after the model list loads, if anything registered is missing you get a Yes/No prompt instead of an automatic download — this is also where you'd go to fix it manually.

Unity: what a cancelled Play looks like

Unity has no way to pause entering Play mid-transition, so the guard cancels the transition, runs the check with a progress dialog, and — once every model is confirmed downloaded — automatically re-enters Play for you. You don't need to press Play twice.

Turning off the Play/PIE check

The automatic Play (Unity) / PIE (Unreal) check is on by default but can be disabled per project:

  • Unreal: Project Settings → Plugins → Tryll Client → Editor → Enable Play Mode Model Guard (the bEnablePlayModeModelGuard field on UTryllRuntimeSettings, saved to DefaultGame.ini). Uncheck it to enter PIE immediately with no pre-flight model check.
  • Unity: Project Settings → Tryll Client → Play Mode (Editor) → Enable Play Mode Model Guard (the EnablePlayModeModelGuard field on TryllRuntimeSettings). Uncheck it to enter Play immediately with no pre-flight model check.

The toggle affects only the automatic Play/PIE check — the Tryll Chat window/panel still verifies models before creating its agent, and the Model Manager still prompts for missing ones. With the check off, a required model that isn't on disk surfaces as a CreateAgent failure at runtime instead of being caught (and offered for download) before Play.

A model that can't be downloaded

Some registered models are supplied as a local file path rather than a HuggingFace repo (see Use Your Own Local Model). If one of those is registered but missing on disk, the guard cannot fetch it — it surfaces a clear error naming the model instead of attempting a download. Provide the file or remove the registration in the Model Manager.

Relationship to auto model downloading

Earlier releases had a server-side allow_auto_model_downloading session flag that made the server silently fetch a model mid-CreateAgent. That flag has been removed — model registration is now the only way to acquire models deliberately. This guard is the editor-side replacement: it catches the same "model referenced but never downloaded" case, earlier, and with a clear prompt instead of a silent multi-gigabyte download hidden inside a normal request.

Editor-only in both engines — packaged/Standalone builds never run this code, since they bundle Production models at build time and never download at runtime.