Week 42 · 2026

Highlights

1 PR merged, 11 others opened and 9 commits across two repos, with no releases or issues opened or closed. Last week's cardano-node and cardano-api upgrade merged Tuesday. The new PRs cover experimental Windows support, an extension of the solvency proofs, and a nine-part stack on rollbacks, snapshot handling and tests. All eleven were still open at the week's end.

Maintenance and DevX (M5). cardano-node moved from 11.1.2 to 11.1.3 and cardano-api to 11.7.0.0 (#2897). The cluster tests, tutorial and demo compose file were updated alongside the dependency pins. Plutus moved from 1.63 to 1.68, producing smaller compiled scripts, but stops short of the node's 1.70: from 1.69 the compiler uses a builtin Data operation that the ledger only enables at protocol version 12, so those validators would fail on mainnet.

The upgrade also removes the workaround for non-canonical inline datums, which cardano-api now reads itself, and enables its pending regression test. Transaction construction was adapted to the new APIs, including attaching collateral only when running a Plutus script. The existing tagged IP JSON encoding was preserved with compatibility tests. Migrating to Cardano.Api.Experimental remains separate work in #2896.

The solvency proof extension opened Monday (#2900, addressing #2870). The Agda theorem previously omitted the close and contest cases that use the snapshot's second signed accumulator, representing what the head owes after a pending increment or decrement has landed. The PR adds those cases and strengthens the full-fanout result to show that every owed output is distributed. A separate theorem covers the final partial-fanout batch. These bring the proofs into line with checks already in the validator; intermediate partial-fanout steps remain outside the solvency relation, and the proof still assumes honest construction of the signed sets and L2 value preservation.

The rollback stack also includes a structural refactor (#2908), separating HeadLogic into modules for snapshot requests, snapshot handling, settlements, closing and fanout, and state aggregation. Input dispatch and the existing public interface remain in Hydra.HeadLogic.

Operational Excellence (M3). The rollback and snapshot work described in W39 returned as a nine-PR stack (#2901 to #2908, plus #2910). A chain rollback can erase several settled increments or decrements after newer snapshots have confirmed. The first PR retains each settlement with its signed snapshot so it can be replayed in version order, and prevents the same deposit being claimed by two retained settlements (#2901). A new partial-fanout fix records each landed step and restores its outputs and previous driver mode if that step is rolled back (#2910, opened Wednesday).

The next parts derive retention from the network's genesis parameters instead of a fixed horizon (#2902), retry the earliest erased settlement on block ticks while preserving observations that arrive before local snapshot confirmation (#2903), and hold retries back during chain catch-up (#2904). The latter also keeps old DepositInFlight events decodable. Recovery still depends on the erased settlements being replayable.

The snapshot changes make refusal decisions depend on shared state, waiting when different local chain views could explain a disagreement (#2905). One party refusing a round that the others sign can stop the head, since a snapshot round cannot be abandoned. Another PR checks each acknowledgement's signature before recording it, so a bad or stale signature cannot occupy a party's slot and exclude its later valid acknowledgement (#2907); the matching specification and Agda transition update was still outstanding.

Supporting model tests introduce a party that substitutes faulty proposals and check the balances of snapshots actually confirmed, including runs that stall (#2906). That PR was subsequently closed unmerged, with the general model tests absorbed into #2901.

Ecosystem Support (M4). Experimental Windows support opened Wednesday (#2909, addressing #2360). The target cross-builds hydra-node.exe on Linux with Nix and packages it with its runtime DLLs, embedding Windows etcd and the Plutus scripts compiled by the native build. The PR adds Windows artifacts to the binaries workflow and a nightly smoke test on Windows Server 2022. That test compares the script catalogue with the native exporter and exercises two offline nodes' APIs, peer connectivity, shutdown and restart from paths containing spaces. Runtime fixes cover Windows socket handling and stopping embedded etcd without hanging on its reader threads. The package contains hydra-node only; live Cardano connectivity and TLS remain untested.

KPI & Outcome Achievement (M6). Routine only: the W41 note published.