eUTxO and ZK

Experimental — no real funds

This family is EXPERIMENTAL and pre-production. It is not a Cardano bridge product, a custody product, or a rollup you should put value into. The ZK modules ship development Groth16 setup keys that are test-only; production release is blocked until the governing ADR’s ceremony, audit, data-availability, and operational gates are satisfied.

Use a devnet or a Cardano test network with disposable keys.

What it is

A deterministic, Cardano-shaped eUTxO state machine that runs as an app-chain capability. Its first milestone is a no-real-funds experimental ledger — a place to execute Conway-shaped transactions against an app chain’s threshold finality and proofs rather than against L1.

Three layers, each optional on top of the previous:

flowchart LR
    L["eutxo-ledger<br/>deterministic UTxO state machine"] --> B["eutxo-cardano-bridge<br/>federated deposit / withdrawal"]
    L --> Z["eutxo-zeroj-validity<br/>Groth16 validity proofs"]
    B --> R["eutxo-zeroj-preview<br/>proof-settled rollup lifecycle"]
    Z --> R

The virtual ledger

Select the eutxo-ledger recipe for a JVM project. It combines the reusable state:eutxo-ledger engine with profile:eutxo-plutus-v3 and the separate funding:eutxo-genesis capability:

yano:
  app-chain:
    chains:
      - chain-id: payments-eutxo
        state-machine: eutxo-ledger
        machines:
          eutxo:
            profile: yano-eutxo-v2-plutus-v3
            expected-profile-digest: 8cd4adb72def2c31dc8551a02f67429ea468bb2024dbe85a1dc7300590c9d1bf
            genesis:
              address: addr_test1...
              lovelace: 100000000

The profile commitment is SHA-256 over its canonical, versioned consensus fields. All members must use the same profile, digest, and genesis allocation — this is chain identity, not a tunable.

The ZeroJ development recipe uses profile:eutxo-key-payments instead, so exactly one immutable ledger profile owns the consensus settings at a time.

The capabilities

Recipe	Availability	What it adds
eutxo-ledger	FIRST_PARTY_OPTIONAL	The deterministic UTxO ledger.
eutxo-cardano-bridge	EXPERIMENTAL	Federated deposit and withdrawal against Cardano.
eutxo-zeroj-validity	EXPERIMENTAL	ZeroJ Groth16 validity proofs over batches.
eutxo-zeroj-preview	EXPERIMENTAL	The full lifecycle: L1 deposit → L2 transaction → proof → root settlement → L1 withdrawal.

The base eUTxO ledger has no ZeroJ or JuLC dependency and behaves exactly as it does without them unless machines.eutxo.validity.enabled=true.

The plugin-conflict rule

The standard eUTxO runtime and the eUTxO ZK runtime both intentionally provide the app-state-machine/eutxo-ledger contribution. Exactly one may be installed.

That is why the ZK runtime ships under optional-plugins/ rather than plugins/. To switch:

# On EVERY member:
rm plugins/<standard-eutxo-ledger-bundle>.jar
cp optional-plugins/<eutxo-zk-runtime-bundle>.jar plugins/
tools/yano-plugins/bin/yano-plugins validate plugins/*.jar

Copying both into plugins/ is a hard catalog error, and the node will refuse to start rather than pick one.

Indexing and lifecycle

The optional, provider-neutral validity lifecycle is projected by the common eUTxO indexer. The indexer core has no ZeroJ dependency, and its projections are rebuildable read indexes — they live in appchain-indexers/ and must never be treated as authoritative state or placed below L1 chainstate.

Where to start

Goal	Guide
The disposable three-scenario quick start	eUTxO demos
Status and module verification	ZK getting started
Deposit → L2 tx → proof → settlement → withdrawal	Devnet walkthrough
Indexer API, SQLite, recovery, metrics	Indexer operations
The eUTxO product family overview	ledgers/eutxo/README.md
ZK milestone notes (Z0–Z4)	ledgers/eutxo-zk/

The demo guide is the shortest path — it covers the virtual ledger, the Cardano bridge, and the optional ZeroJ proof experience without JShell or manual YAML editing.