LLM-State Contract — Schema Agreement Between App and AI

_↴ Ported from [flutter/genui#640](https://github.com/flutter/genui/issues/640) — originally opened by [leoafarias](https://github.com/leoafarias) on 2025-12-23._
_Original labels: front-line-handled_

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**Is your feature request related to a problem? Please describe.**
There is no agreement between app and AI about state structure. The LLM receives widget schemas but not a state manifest, so it guesses paths, can create arbitrary ones, and can vary paths between turns. Ownership of state structure (app vs. AI) is undefined.

**Describe the solution you'd like**
A defined state contract: a discoverable schema/manifest of allowed paths, plus guidance on ownership. Preferably, app state is the source of truth and `DataModel` is a derived view, with validation for path creation.

**Describe alternatives you've considered**
Letting the LLM create state freely, or constraining via prompt-only guidance. Both lead to brittle results (non-reactive UIs, invented paths, or inconsistent regeneration).

**Additional context**
Discussion: https://github.com/flutter/genui/discussions/609

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### 1 comment(s) from the original issue

**[yjbanov](https://github.com/yjbanov)** commented on 2025-12-29:

An agreement system between the app and the AI on data structure, but also read/write permissions, makes sense. Treating app state as the source of truth with `DataModel` being a derived view is an interesting idea. I can actually see this extending into a wider "BusinessModel" containing both data and business logic (actions/events), with structure and rules defined in a way that's easy to describe to the LLM (like we do for the widget catalog) and, crucially, easy to enforce (e.g. as part of upholding the required trust model and/or as protection for certains kinds of hallucinations).

Review the linked discussion #609 to understand the current state and widget schema system. Examine how the DataModel is currently derived from app state. The goal is to design a schema/manifest system for state paths and permissions that integrates with the existing LLM interaction model. 'Done' means a proposed design for the state contract and its validation.

Written by the indexing model from the issue text.