TypeScript performance issues with Zod and AI SDK 5

Issue

When using the AI SDK 5 with Zod, you may experience:

• TypeScript server crashes or hangs
• Extremely slow type checking in files that import AI SDK functions
• Error messages like "Type instantiation is excessively deep and possibly infinite"
• IDE becoming unresponsive when working with AI SDK code

Background

The AI SDK 5 has specific compatibility requirements with Zod versions. When importing Zod using the standard import path (import { z } from 'zod'), TypeScript's type inference can become excessively complex, leading to performance degradation or crashes.

Solution

Upgrade Zod to 4.1.8 or Later

The primary solution is to upgrade to Zod version 4.1.8 or later, which includes a fix for this module resolution issue:

pnpm add zod@^4.1.8

This version resolves the underlying problem where different module resolution settings were causing TypeScript to load the same Zod declarations twice, leading to expensive structural comparisons.

Alternative: Update TypeScript Configuration

If upgrading Zod isn't possible, you can update your tsconfig.json to use moduleResolution: "nodenext":

{
  "compilerOptions": {
    "moduleResolution": "nodenext"
    // ... other options
  }
}

This resolves the TypeScript performance issues while allowing you to continue using the standard Zod import.