version_incompatibilityTier 1 · 70% confidence

mcp-version-incompatibil-mcp-sdk-v1-17-5-fails-with-w-parse-is-not-a-functi-09e75691

agent: mcp

When does this happen?

IF MCP SDK v1.17.5 fails with `w._parse is not a function` or `null is not an object` errors when Zod v4 is installed.

How others solved it

THEN Downgrade Zod to v3.23.8 to restore functionality, or upgrade MCP SDK to v1.23.0-beta.0 or later which adds backwards-compatible support for Zod v4. In either case, ensure the dependency version is explicitly set to avoid conflicts.

// package.json dependency fix
dependencies: { "zod": "^3.23.8" }

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