State properties become undefined when the app is mounted

[olinox14]

Reproduction

https://stackblitz.com/edit/nuxt-starter-bv1ucjn7?file=app.vue

Steps to reproduce the bug

Connect to the provided stackblitz.
It's configured with Nuxt (v3.15.4), Pinia (2.3.1) and @pinia/nuxt (v0.9.0), in SSR mode.

When displaying the app.vue page, the store.a property shows up, but disappear when the app is mounted.

Adding a reference to this property in the onMounted method will throw and error, saying store.a is undefined.

capture-2025-01-30_10.27.36.webm

Expected behavior

Store properties shall keep their value after hydratation.

Actual behavior

Store properties become undefined on hydratation.

Additional information

No response

[olinox14]

Update

I reproduced it with the following configurations

Nuxt	Pinia	@pinia/nuxt
3.15.4	2.2.8	0.9.0
3.11.2	2.1.7	0.9.0
3.15.4	2.2.8	0.6.0

However, the bug doesn't occur with those one :

Nuxt	Pinia	@pinia/nuxt
3.11.2	2.1.7	0.5.1
3.11.2	2.2.8	0.5.1
3.15.4	2.2.8	0.5.1

Which seems to point at the @pinia/nuxt:0.6.0 release.

[olinox14]

Update 2 : Some progress!

Actually, removing the following lines in the nuxt.config.ts solve the issue :

  experimental: {
    // Fix the 'Cannot stringify non POJO' bug
    // @see https://github.com/nuxt/nuxt/issues/20787
    renderJsonPayloads: false,
  },

https://nuxt.com/docs/guide/going-further/experimental-features#renderjsonpayloads

[posva]

Duplicate of #2864

[olinox14]

Sorry, but the issue I'm raising here is not just a warning here, it's a critical issue I'm describing. The cause may be the same, but the impact is totally different, this made our entire app crash after the upgrade.

It's caused by a legit nuxt configuration, needed itself to solve this : nuxt/nuxt#20787

I fear we'll have to stick to @pinia/nuxt:0.5.1 for the moment, but that's a short term solution...