Unable to upgrade to zod@4 as a consumer of the npm package

[Nefleex]

Reproduction Repository

https://github.com/Nefleex/meteor-rpc-types
zod4 branch

git clone https://github.com/Nefleex/meteor-rpc-types
cd meteor-rpc-types
git checkout zod4
meteor npm install
npm run typecheck

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Description:

When a project uses zod@4.x, TypeScript reports type errors in meteor-rpc's library files.

Errors:

node_modules/meteor-rpc/lib/createMethod.ts(44,11): error TS2322: Type 'unknown' is not assignable to type 'output<Schema>'.
node_modules/meteor-rpc/lib/createModule.ts(29,52): error TS2345: Type 'input<Schema>' is not assignable to type 'output<Schema>'.

Likely Root Cause:

meteor-rpc has zod@^3.18.0 as a devDependency. Zod 4 introduced breaking changes to the z.input<T> and z.output<T> utility types, which meteor-rpc uses extensively.

Workaround:

Downgrade to zod 3.x.