FAQ

Short answers to the questions people ask most, with links to the full explanation.

The basics

Is an app ledger the same as an app chain? Yes. These guides say app ledger; Yano’s command line, configuration, and APIs say app chain (./yano.sh appchain, yano.app-chain.*, /api/v1/app-chain/). See What is an app ledger?

Is it a public blockchain? No. Membership is a configured list of member keys. There is no stake, no slashing, and no open participation. The ledger replicates only to its members; outsiders get proofs and, optionally, roots anchored on Cardano.

Does every block wait for Cardano? No. Finality comes from the members’ threshold signatures. Anchoring a root on Cardano is optional and happens later. See Cardano anchoring.

Why are no blocks being produced? A ledger produces a block only when there are pending messages. An idle ledger stays at the same height.

Messages and results

My submission returned 202. Did it succeed? Not yet. 202 means one member accepted the message into its pending pool. Wait until the message is final, then read the application’s result. See the life of a message.

The message is final. Did my command succeed? Not necessarily. A command that breaks a business rule when the block runs is recorded as a deterministic no-op on every member, and its message id is used up. Read the result, and submit a new message to retry.

Do my applications sign messages? No. The member that accepts a message signs its envelope with the member key. When a person or organization must approve something, their actor signature travels inside the message body. See Keys and trust.

How large can a message be? 64 KiB by default (max-message-bytes). Store large content elsewhere and record its hash.

Do effects run inside consensus? No. A transition emits an effect record; an executor performs the external action after finality, outside consensus, at least once. Receivers should use the effect id to ignore duplicates. See Effects.

Faults and recovery

How many members can fail? With the default fault bound of 0, up to n − t members can be offline, where t is the threshold, but no member is assumed to lie. A threshold of 2 of 3 survives one member being down, not one dishonest member. See Keys and trust.

What happens if the leader is down? The round times out, a threshold of members certifies the timeout, and the next member in order leads. No configuration change is needed.

What happens when a member restarts or falls behind? It keeps its blocks, state, and vote locks, loses its pending message pool, and catches up by verifying every missed block and certificate itself. See Restart, catch-up and snapshots.

Can I delete appchain-indexers/? Yes. It holds rebuildable read indexes, which rebuild from finalized blocks. Never restore it as authoritative state, and never delete chainstate/ or appchain-chainstate/ to fix an error. See Where data lives.

Identity and proofs

Can I change the commitment profile or genesis id later? No. They are fixed when the ledger is created, together with the format fingerprint. Changing them means a new ledger. See Chain identity.

MPF or JMT? MPF, mpf-blake2b256-v1, unless you have a reason. Only MPF proofs can be checked on Cardano. The choice is made at genesis.

Does an exclusion proof show that something never happened? No. It shows that a key was absent from this dataset under this root. A pruned height is unavailable, which is different from absent. See State and proofs.

A verifier said INTERNAL_CONSISTENCY_ONLY. Is that bad? It means the proof agrees with itself and nothing more. Pin the members or check an anchor to reach a level you can rely on. See Keys and trust.

Operating

Are plugins sandboxed? Does the node check their signatures? No, and no. Plugins are trusted in-process code, and publisher signatures are checked by Yano X tooling, not by the node at load time. Install only plugins you trust. See Keys and trust.

cluster status says MISMATCH. Is the ledger broken? Not necessarily. It compares the current state roots the members report, without aligning heights, so a member that is one block behind shows MISMATCH. Run it again. See Troubleshooting.

Can I run the showcase in production? No. The showcase runs every member under one operator with demonstration keys. Yano is pre-release; see Production deployment for what changes.