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The platform is three Python packages that stack in a strict line, plus a desktop UI over a running server. Each package depends only on the ones to its left, so the interfaces stay free of implementation and an alternative server remains possible.

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tai42-contract — the interfaces

tai42-contract is the pure interface leaf: protocols, ABCs, and pydantic models, no logic. At runtime it imports nothing but pydantic, and its behaviour is a narrow whitelist — the tai42_app forwarding handle, model validators, the storage path guard, and Agent’s default stream drain. Vendor types (fastmcp, langchain, starlette, mcp) appear only inside TYPE_CHECKING blocks, so they are never loaded when the code runs. Because the contract carries no implementation, a plugin author codes against stable interfaces — the Agent ABC, the Storage ABC, the connector and webhook-verifier protocols — and never against the server’s internals.

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tai42-kit — the helpers

tai42-kit is generic leaf helpers: settings primitives, pooled clients, MCP transports, LLM/embedding factories, the SSRF network guard with its safe URL fetching, and structured-logging setup. Among tai42-* packages its only dependency is tai42-contract — it implements the contract’s BaseClient protocol and consumes its manifest types. The skeleton reuses these helpers rather than re-declaring them.

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tai42-skeleton — the server

tai42-skeleton is the framework body: the concrete TaiMCP server and the runtime engines behind every contract protocol — the tool registry and adapters, the agent registry, the OAuth connector engine, the access-control middleware, the hooks router, the storage and template manager, the manifest loader, and the transport layer. It depends only on tai42-contract and tai42-kit. The app is constructed once and exposed as the tai42_app contract handle. Tools, agents, and extensions register against it — the same handle every quickstart tool uses:

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Plugins register through the handle

Providers — OAuth connectors, storage backends, config providers, worker backends, monitoring — ship as separate plugins. A plugin registers through tai42_app when the manifest loads its module; no plugin imports the skeleton. This is what keeps the core free of provider code and the ecosystem open-ended.

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The Studio

The Studio is the desktop UI over a running server. It calls the same /api/* HTTP surface the tai CLI calls, so anything you can do in the UI you can do from a terminal, and vice versa. The Studio section tours its screens — running tools, the admin console, and API-key provisioning. See the Python SDK reference for the exact public surface of tai42-contract, tai42-kit, and the skeleton.