Cardano Devnet-in-a-Box (cardano-node + hydra + ogmios + kupo)

What this skill is for

You are setting up a local, end-to-end rehearsal environment so we can:

• build/sign/submit real transactions (cardano-cli)
• run dApp infra (Ogmios + Kupo)
• open/close a Hydra Head and push L2 txs

…all locally before anyone even thinks about mainnet.

This skill uses Hydra’s official demo devnet as the base (because it’s the most “known-good” path), then bolts on Ogmios + Kupo as extra services.

Hydra’s docs describe this demo setup: a single fast local devnet + 3 Hydra nodes (Alice/Bob/Carol) + hydra-tui.

Kupo’s Docker image docs show the minimal container flags we reuse (--node-socket, --node-config, --host, --workdir).

Hydra publishes official Docker images at ghcr.io/cardano-scaling/hydra-node.

Assumptions

• Docker is installed and running.
• git is available.
• Ports available on host:

- 1337 (ogmios) - 1442 (kupo) - 4001-4003 (hydra API) - 3000 (grafana, optional)

The canonical setup

If the repo already has devnet-in-a-box/

Run:

cd devnet-in-a-box
chmod +x run.sh
./run.sh up

This will:

1. Clone cardano-scaling/hydra into devnet-in-a-box/.vendor/hydra
2. Copy our docker-compose.override.yml into hydra/demo/
3. Run the upstream demo scripts:

- ./prepare-devnet.sh (creates the devnet/ folder + fresh genesis start time) - ./seed-devnet.sh (publishes Hydra scripts + funds parties)

1. Start:

- cardano-node - hydra-node-1..3 - ogmios - kupo

If the repo does NOT have devnet-in-a-box/

Create it by copying these exact files from the skill repo:

• devnet-in-a-box/run.sh
• devnet-in-a-box/docker-compose.override.yml
• devnet-in-a-box/README.md

(They’re designed to be dropped into any project.)

Endpoints

• Ogmios (WebSocket): ws://localhost:1337
• Kupo (HTTP): http://localhost:1442
• Hydra API:

- Alice: http://localhost:4001 - Bob: http://localhost:4002 - Carol: http://localhost:4003

How to use it (agent playbook)

1) Bring the stack up

./devnet-in-a-box/run.sh up

2) Open a head (fastest path = TUI)

In 3 terminals:

./devnet-in-a-box/run.sh tui 1
./devnet-in-a-box/run.sh tui 2
./devnet-in-a-box/run.sh tui 3

Then inside the TUI:

• [i] init
• [c] commit
• once all parties commit, the head opens automatically

Hydra’s docs walk through this flow.

3) Validate the L1 + infra are alive

From the demo directory (the script handles paths for you), you can query the chain tip:

./devnet-in-a-box/run.sh logs cardano-node

Or directly:

cd devnet-in-a-box/.vendor/hydra/demo
docker compose exec -T cardano-node cardano-cli query tip --testnet-magic 42 --socket-path /devnet/node.socket

4) Use Ogmios + Kupo for app-level rehearsal

Typical dApp stack:

• Kupo for UTxO lookup / index queries
• Ogmios for chain sync + tx submission

This is the pair most “realistic” apps use for local integration tests.

Deterministic rehearsal (green / red)

For a no-vibes end-to-end check, run:

cd devnet-in-a-box
./run.sh rehearsal

It will:

• run a smoke test (cardano-node + hydra APIs + optional kupo health)
• create a tiny always-true Plutus script UTxO on L1 (inline datum = 42, 10 ADA)
• initialize a Hydra Head
• commit: Alice (script UTxO + collateral) + Bob + Carol
• submit one L2 transaction that spends the script UTxO inside the head
• close → wait contestation → fanout

If everything works you get GREEN. Otherwise you get RED and the failing step.

Lightweight health check:

./run.sh smoke

Troubleshooting (quick hits)

TraceNoLedgerView in cardano-node logs

That’s almost always a genesis start time drift.

Fix: rerun prepare + restart the node.

cd devnet-in-a-box/.vendor/hydra/demo
./prepare-devnet.sh
docker compose up -d --force-recreate cardano-node

Hydra docs explicitly warn about waiting too long after prepare-devnet.sh.

Ogmios/Kupo can’t open the node socket

Usually permissions on devnet/node.socket.

The run.sh tries to chmod a+w the socket from inside the container.

If it still fails:

cd devnet-in-a-box/.vendor/hydra/demo
docker compose exec -u root cardano-node chmod a+w /devnet/node.socket

Kupo is “running” but returns nothing

Make sure we’re indexing something.

We default to --match "*" for devnet so it indexes everything.

If you change it, you can accidentally index zero addresses.

Hard rule

This devnet harness is for rehearsals:

• never treat the demo keys as production keys
• never assume devnet settings ≈ mainnet settings
• always re-check protocol params, cost models, and script budgets when moving to preprod/mainnet