OpenID4VP Flow - InvalidVpToken Error in Wallet Core v0.20.0

[sagar-maiyad]

Version:

Working in: 0.19.0

Failing in: 0.20.0

Issue Summary

After upgrading to Wallet Core v0.20.0, VP submission fails with:

400 Bad Request
{"error":"InvalidVpToken","description":"vp_token contains a non-string element"}

The same implementation works without issues in v0.19.0.

Details

Server Response Before Sending VP:

proof_of_age: [RespondedDocument(documentId=UisbdrdB5Xkr, format=mso_mdoc)]
VpContent: VerifiablePresentations(value={proof_of_age=[Generic(value=o2d2ZXJzaW9uYzEuMGlk)]})

Request Sent:

POST https://verifier-backend.ageverification.dev/wallet/direct_post/eWqWVd-1QeP73eJBGRpdNDoQLZblXEmE_-IJF1plI_N2td7uWwlDN4w4w_tUkSrfJu8HBdE8HR8fFR9PsXY7_A
Content-Type: application/x-www-form-urlencoded

vp_token=%7B%22proof_of_age%22%3A%5B%22o2d2ZXJzaW9uYzEuMGlkb2N1bWVudHOBo2dkb2NUeXBlcWV1LmV1cm9wYS5lYy5h.....

Server Error:

Client request invalid: 400 Bad Request
{"error":"InvalidVpToken","description":"vp_token contains a non-string element"}

Expected Behavior

VP token should be encoded and sent as a string (same behavior as v0.19.0).

Server should accept the VP token without error.

Actual Behavior

Server rejects vp_token because the VP structure produced by Wallet Core v0.20.0 seems to include a non-string element inside the VP array.