AI Architecture

City client / Agent
        |
        v
CityModel (LanguageModelV3)
        |
        v
Federation AIService
  auth -> model lookup -> fallback -> reasoning -> metering
        |
        v
AIChannel.stream(ctx, LanguageModelV3CallOptions)
        |
        v
AI SDK model or private upstream adapter

CityModel is the client-side executable model. It knows the public CityModelDescriptor and the Federation transport, but never knows upstream keys or vendor protocol details.

AIService is the server-side orchestrator. It owns route selection, fallback, reasoning validation, usage normalization, and billing.

AIChannel is the server-side upstream boundary. It owns connection configuration, upstream model selection, AI SDK providerOptions, and conversion into LanguageModelV3StreamResult.

The OpenAI-compatible endpoint is an adapter, not another execution path:

OpenAI JSON/SSE -> V3 call -> AIService -> AIChannel.stream -> V3 stream -> OpenAI JSON/SSE