every.channel/evolution/proposals/ECP-0109-local-hdhr-publishers-submit-observation-rail.md

ECP-0109: Local HDHomeRun publishers submit observation rail commitments

Status: Draft

Problem / context

ecp-forge has the Ethereum / OP Stack direction and observation ledger contracts, while local nodes have the HDHomeRun tuners and can already produce verified manifests. The missing bridge is a publisher path that can run on the local LAN, observe real tuner-derived epochs, and submit compact observation headers to the remote chain without moving media bytes on chain.

Decision

Add an optional observation-rail sink to ec-node moq-publish:

• each published manifest epoch can become one EveryChannelObservationLedger.ObservationHeader,
• streamHash is keccak256(stream_id),
• epochHash is keccak256(epoch_id),
• dataRoot is the manifest's Ethereum data-root commitment,
• locatorHash commits to a compact JSON locator for the manifest and MoQ broadcast,
• observedUnixMs and sequence come from the manifest body, and
• submission uses a configured RPC URL, ledger address, and witness private key.

The sink is disabled unless explicitly configured. It is intended for a local publisher talking to the remote every.channel chain through the remote host's local-only RPC surface, typically via an SSH tunnel. The OP Stack L2 RPC uses a distinct local port from the full Ethereum nodes on the same host so publisher submissions do not accidentally target mainnet or Sepolia L1 RPC.

Consequences

• Local HDHomeRun boxes can act as reality witnesses without running the full chain locally.
• The chain stores compact observation commitments only; media segments and full manifests remain on MoQ / iroh / archive storage.
• The first implementation uses Foundry cast for transaction submission so the repo can validate end-to-end with Anvil before committing to an embedded Rust transaction signer.
• A quorum greater than one still requires additional witnesses to attest; the local publisher only proposes and self-attests when the configured key is a registry witness.

Alternatives considered

• Run the full chain locally next to the HDHomeRuns. Rejected because the desired validation target is the remote every.channel chain, and a local chain would hide remote reachability/configuration failures.
• Push full media or manifests on chain. Rejected because the observation rail only needs compact commitments and locators.
• Add an embedded Rust transaction signer immediately. Deferred until the end-to-end rail proves useful with Foundry tooling.

Rollout / teardown

1. Add manifest-to-observation derivation in ec-eth.
2. Add optional ec-node moq-publish flags and environment fallbacks for observation submission.
3. Add an ignored HDHomeRun + Anvil E2E test and a wrapper script.
4. Point local publishers at the remote RPC once the remote chain is reachable.

Teardown is simply disabling the observation options; local manifest publication remains unchanged.