refactor(chat): define chat/ai tools once as framework-agnostic specs

[bensabic]

Every tool in chat/ai was built directly with the AI SDK's tool() helper, which meant the tool definitions could only ever produce AI SDK tools. This PR separates the definition from the framework so the next PR can offer the same tools to TanStack AI.

Each tool is now a plain spec:

export const postMessageSpec = (chat, { needsApproval = true, guard } = {}): ChatToolSpec<Input, Output> => ({
  name: "postMessage",
  description: "Post a message inside an existing thread. ...",
  needsApproval,
  inputSchema: POST_MESSAGE_INPUT,
  execute: async ({ threadId, message }) => { ... },
});

and the AI SDK wrapping happens once, in toAiTool. The presets, approval flags, scope guard, and override filtering that createChatTools wires up move to a shared module, and the link and attachment plumbing behind toAiMessages moves out the same way.

Nothing changes for callers. createChatTools, toAiMessages, and the 17 standalone tool factories keep their signatures, return types, and behavior, and the existing tests are untouched. The examples in examples/nextjs-chat and examples/nuxt-chat compile as before.

One relocation worth explaining: ToolOverrides is an AI SDK Pick<Tool, ...>, and it used to live beside ChatBinding in ai/types.ts. It moves next to the AI SDK wrapper so the shared modules never reference ai, not even as a type. Without that, tsup's declaration chunking pulls an import 'ai' into any entry that shares those modules.

Changed files:

• packages/chat/src/ai/tools/spec.ts: the ChatToolSpec interface
• packages/chat/src/ai/tools/ai-sdk.ts: toAiTool, the 17 public wrappers, and ToolOverrides
• packages/chat/src/ai/toolset.ts: presets, approval, scope, and the lazy factory map
• packages/chat/src/ai/index.ts: createChatTools on top of the shared pieces
• packages/chat/src/ai/message-content.ts: shared history plumbing used by toAiMessages
• The five files under packages/chat/src/ai/tools/ are the mechanical spec conversion

Middle of a three-PR stack; no changeset of its own since nothing observable changes.

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Project	Deployment	Actions	Updated
chat	Ready	Preview, v0	Sep 16, 2026 12:13am UTC
chat-sdk-nextjs-chat	Ready	Preview, v0	Sep 16, 2026 12:13am UTC