Another Round of Interoperability: EUDIW Unfold #4.1

Back at EUDIW Unfold. This Time With the Full Stack.

Between 21 and 25 September 2026, we took part in EUDIW Unfold #4.1 Interop Week, an online interoperability testing session run within the France Identité ecosystem. It was our second Unfold testing week, after Unfold #3.1 in June.

In June, we focused on verifying age and PID credentials. This time, we tested three LutraID components (our issuer, verifier and wallet) against solutions from other organisations across Europe and beyond.

Three Scenarios: Issuance and Presentation

Our testing covered three scenarios that sit at the core of the EUDI Wallet ecosystem:

• Remote issuance in mdoc format. Issuing credentials in the ISO mdoc format, the same family of formats used for mobile driving licences and PID.
• Remote issuance in SD-JWT VC format. Issuing credentials as SD-JWT Verifiable Credentials, which let holders share only the attributes a service actually needs.
• Remote presentation with OpenID4VP 1.0 and HAIP. Requesting and verifying credentials online using OpenID for Verifiable Presentations 1.0 together with the High Assurance Interoperability Profile (HAIP).

Supporting both formats matters: different wallets and Member States rely on different ones, and businesses should not have to care which one a user's wallet prefers.

Key Numbers from Our Testing

Over the week, we recorded 42 interoperability test executions with 20 external solutions from 16 organisations in 11 countries. 35 of those 42 executions passed (83%).

• Remote presentation (OpenID4VP 1.0 + HAIP): 27 of 32 executions passed
• Remote issuance (mdoc): 5 of 6 executions passed
• Remote issuance (SD-JWT VC): 3 of 4 executions passed

These are our own recorded results; 47 organisations took part in the event overall. Each execution that did not pass points to a concrete detail to align with a counterpart, which is exactly what interop weeks are for.

Testing Across Borders

Our counterparts came from Austria, France, Italy, Latvia, Lithuania, Luxembourg, the Netherlands, North Macedonia, Poland, Spain and Türkiye. Together with our own Slovenian participation, that makes 12 countries.

A European digital identity only works if a credential issued in one country can be presented and trusted in another.

Why We Keep Coming Back

Interoperability is not something you prove once. Specifications evolve, profiles such as HAIP tighten the rules, and every implementation interprets the details slightly differently. Regular testing confirms what works, surfaces differences early and builds direct relationships with the teams behind other implementations.

What This Means for LutraID

LutraID lets businesses adopt EUDI Wallets without tracking every specification change themselves. Unfold #4.1 tested both sides of that promise: issuing credentials in mdoc and SD-JWT VC, and verifying them with OpenID4VP 1.0 and HAIP, against real implementations from 11 other countries. We will keep testing, closing the gaps we find, and sharing what we learn.

We are excited to continue contributing to the EUDI ecosystem and helping businesses prepare for the next phase of digital identity in Europe!