Same issue.
It's a jard job to migrate. It could be very helpfull to migrate vee-validate once our own code is fixed !

The main problem is that vee-validate v3 has relied on exactly that. The VNode private API. Which is now completely different. And it worked well till some early alphas of Vue 3 where a change to directive representation in VNode completely killed that possibility.

To elaborate, vee-validate v3 relies on walking the node tree and trying to locate any nodes with v-model applied to them. It did a lot of black magic to make it work. With Vue 3 VNode API, you cannot find nodes with v-model anymore because there is no way to identify the directives anymore. Basically v-model in Vue 3 looks the same as any other directive object in the VNode API.

Now vee-validate v4 does a better job since it uses public APIs of Vue.js to achieve almost the same feature set. That sadly means there is no direct upgrade path between v3 and v4 in that regard.

If there was something I can do I would have done it by now, but there is no way the old API works in Vue 3. No compatibility hacks or workarounds. This means a new vee-validate had to be built from scratch which is what happened with v4.

For other libraries, it is straightforward as long as they find alternatives to the APIs they use. But this is not the case here. The one thing v3 relied upon was identifying directives and that's gone out of the window. The silver lining is we ended up with a much better API but at the cost of some effort to re-write or migrate.

I'm writing a migration guide, but that's just that. a guide that will take you through how to get the same functionality working again with some changes and some conversion examples. Basically, it would tell you how to re-write v3 code in v4. It won't be 100% foolproof and will probably be lacking for a lot of use cases but it should help a bit.

Closing but feel free to continue the discussion or send suggestions.

Any update on the migration guide?

@logaretm Can we find the migration guide anywhere ?

Similar case with for VeeValidate 2.x