Type conflict: @ag-ui/core 0.0.49 (Zod 3) breaks consumer Zod 4 type checking

[stevan-borus]

Problem

@tanstack/ai itself is on Zod 4 (^4.2.0), but pins @ag-ui/core@0.0.49 which still depends on zod: ^3.22.4. This pulls Zod 3 into the consumer's type graph as a transitive dep, even when the consumer's app is fully on Zod 4.

This breaks consumers using @hookform/resolvers/zod v5 (or any other library with Zod-3-vs-4 dual overload typings), because TypeScript's overload resolver compares two different zod/v4/core/versions.d.ts files in the same compilation:

• Zod 3.25.x's v4/core shim: version.minor: 0
• Zod 4.x: version.minor: 3 (or current)

Producing errors like:

error TS2769: No overload matches this call.
  Overload 2 of 4, '(schema: \$ZodType<...>, ...): Resolver<...>', gave the following error.
    The types of '_zod.version.minor' are incompatible between these types.
      Type '3' is not assignable to type '0'.

Repro

1. Install @tanstack/ai (any recent version)
2. Install @hookform/resolvers@5 and zod@^4.3
3. Run tsc --noEmit on any file calling zodResolver(z.object({...}))

Tracking upstream

The right long-term fix is @ag-ui/core moving to Zod 4 — tracked in ag-ui-protocol/ag-ui#1397 (open, no ETA).

Suggested workarounds for @tanstack/ai

While #1397 is unresolved:

1. Document the transitive Zod 3 footgun in the @tanstack/ai README / migration notes so consumers know to expect resolver typing breakage.
2. Vendor or shim @ag-ui/core types internally so zod/v3 doesn't surface in consumer type graphs.
3. Or just push #1397 to land — @tanstack/ai is the largest downstream consumer of @ag-ui/core and your influence there would help.

Happy to PR #1 if useful.

Local workaround we used

Module declaration override in our app:

// types/hookform-resolvers.d.ts
declare module '@hookform/resolvers/zod' {
  import type { FieldValues, Resolver } from 'react-hook-form';
  export function zodResolver<TInput extends FieldValues, TContext = unknown, TOutput = TInput>(
    schema: { _zod: { output: TOutput; input: TInput } } | { _output: TOutput; _input: TInput; _def: { typeName: string } },
    schemaOptions?: unknown,
    resolverOptions?: { mode?: 'async' | 'sync'; raw?: false },
  ): Resolver<TInput, TContext, TOutput>;
}

Runtime is fine — both Zod 3 and Zod 4 schemas are recognized at runtime by the resolver.

[AlemTuzlak]

@stevan-borus i'll fix this on ag-ui side

[AlemTuzlak]

@stevan-borus fyi I'm working at CopilotKit and I am one of the lead devs on ag-ui & copilotkit so i'll find a way out of this