Issue with zod/mini and t3-env and t3-oss/env-nextjs

[varghesethomase]

Zod mini failed in github action workflow(not locally in an osx or either when testing using act) when used together with t3-oss/t3-env and t3-oss/env-nextjs.
The issue encountered is as shown in the image below.

The expectation was that t3env and t3-oss/env-nextjs supports everything adhering to standard schema. For confirming if its an issue with zod/mini, I tried migrating the file to valibot. And it works well and as expected which confirms that its either an issue with zod/mini or with the t3-oss/env-nextjs or t3-env.

Its hard to reliably reproduce this issue as it occurs only when building the application in vercel, or when its run as a part of a workflow in github actions pipeline which makes me wonder if its related to the operating system but do not have any proof to confirm it. I would appreciate any help here.

[dosubot]

Hi @varghesethomase! I'm Dosu and I’m helping the zod team.

I'm a bot trained on Zod's codebase and issues. The error you're seeing (Cannot read properties of undefined (reading 'onattach')) in CI environments with zod/mini, t3-env, and t3-oss/env-nextjs is likely due to a schema initialization bug that was recently fixed in Zod. Specifically, PR #5263 (merged 2025-09-20) changed how object shapes are cached and initialized in both Zod Classic and Mini, which can prevent this kind of runtime error in CI or Vercel builds.

Please make sure you're using a version of Zod/mini that includes this fix. Also, double-check that all imports are from zod/v4/core as recommended in the docs—importing from zod/v4 or zod/v4/mini can cause subtle compatibility issues, especially in complex environments.

If you still see the error after upgrading, please share your exact versions of Zod/mini, t3-env, t3-oss/env-nextjs, and Node.js in the failing environment, and provide a minimal reproduction if possible. This will help pinpoint any remaining edge cases.

Let me know if this resolves your issue or if you need more help! If your question is answered, please close the issue.

To reply, just mention @dosu.

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[varghesethomase]

I am using zod/mini which is supposed to be based on standard schema and t3-env already supports standard schema. I also use 4.1.12 version of the zod package. So I assume the PR mentioned above is already fixed there. I would like to have some expert help here.

[dosubot]

You're correct that Zod/mini v4.1.12 is designed to fully support the Standard Schema spec and should interoperate with t3-env and t3-oss/env-nextjs. The PR I mentioned (#5263)—which fixed shape caching and schema initialization bugs—was merged before 4.1.12, so your version does include that fix.

However, the Cannot read properties of undefined (reading 'onattach') error in CI/Vercel is almost always caused by schema objects (or their internal "checks") being shallow-copied, serialized, or otherwise manipulated outside of Zod's own APIs. This can happen if an integration (like t3-env or t3-oss/env-nextjs) spreads, serializes, or clones schemas or their internals, which strips non-enumerable or prototype properties like onattach. This is especially likely in CI or SSR environments, where module resolution and bundling can differ from local dev.

Zod Mini and Zod Classic both guarantee that onattach is always present when using official APIs, and the codebase is robust against normal usage. The error only arises when something outside Zod mutates or copies schema internals unsafely. Migrating to Valibot works because it doesn't use the same internal structure.

Recommended actions:

• Double-check that all schema manipulations in your code and in any wrappers (like t3-env) use Zod's own APIs—never spread, serialize, or shallow-copy schemas or their checks.
• If you have custom logic that inspects or clones schemas, switch to using Zod's .clone() or related methods.
• If you can, try to isolate a minimal reproduction or check if t3-env or t3-oss/env-nextjs is manipulating schemas in a way that could strip prototype fields.

If you have a minimal reproduction or can point to a specific integration step, I can help dig deeper. If this answers your question, please close the issue!

To reply, just mention @dosu.

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[colinhacks]

I believe I've fixed this locally. Should land shortly.

[varghesethomase]

Thanks for your support. Please update when the changes are released.