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Phase 3 of docs/frost-batch-signing.md. A session can now be proposed over several events, and the whole batch is signed in one round of four group events with one approval. 356 jvmTest and 224 testDebugUnitTest pass. ## The wire, and the compatibility rule that shapes it FrostSigningEvents.encodeProposal serialises a batch of one as the bare event object it always was, and only a genuine batch as a JSON array. That is not tidiness. A build predating this reads an array with Event.fromJsonOrNull, gets null, and drops the proposal -- so an old device refuses a batch outright rather than signing part of one, while single signing keeps working right through a mixed-version rollout. Emitting an array unconditionally would break every one-event session for those devices and buy nothing. decodeProposal accepts both forms permanently: proposals in the old shape do not stop arriving because this build stopped writing them. It is all-or-nothing -- an array with one unreadable element is refused rather than silently shortened, because the batch's length is what every later payload is checked against, and a proposal that quietly lost an event would have every signer's contribution rejected for being the wrong size: a stall with nothing to blame. ## MAX_BATCH_SIZE, checked twice 64, enforced in proposeSigningBatch and again, independently, in acceptProposal. The second check is the one that matters. A proposal is the only place in this protocol where a remote party decides how much work everyone else does -- k native key generations, k signatures, and a group event carrying k payloads, from a single message -- and until batching that was bounded only by never being more than one. ## acceptProposal over a list Each element is rebuilt from its own fields under this device's own reading of the room's path and checked against the id it claims, exactly as before but per item, and the whole proposal is dropped if any one fails. The write-once rule widens from "the event this session signs" to "the ordered list of events this session signs": a second proposal under the same id whose list differs anywhere is logged and ignored. ## The API FrostSigningManager.proposeSigningBatch(events: List<EventTemplate<*>>) is public here rather than in Phase 4, because without it there is no way to produce a k>1 session and everything above would ship untested. proposeSigning keeps its signature as the one-event form, so no caller moves. Each template carries its own createdAt. ## Tests - FrostProposalCodecTest (new, commonTest): a batch of one is byte-for-byte the old JSON object -- the assertion that stands in for the old build nobody can run here -- plus order preservation, old-form decoding, and refusal of empty, malformed and partly-unreadable arrays. - SignedGroupKeyStateTest: a k=3 batch between two devices over two databases. Three signatures verifying against the room, three dialects applied on both devices in order, five messages from the coordinator and two from the other signer, and one approval line rather than three. - The negative test that matters: no two items of a batch share an aggregated nonce or a seed, and the two devices' seeds do not intersect. Every positive test still passes if two items share a nonce -- the signatures verify fine; what sharing costs is the secret share. - The cap is refused when proposed. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
mantra docs
Notes on the parts of this app whose behaviour is not recoverable by reading the code alone — where the reasoning lives in a protocol, a failure mode that is silent, or a decision that looked arbitrary and was not.
| document | covers |
|---|---|
| shared-key-ceremony.md | ChillDKG over NIP-17: the rounds, the approval gates, the chat transcript, participant ordering |
| shared-key-derivation.md | deriving further keys from the group's threshold key with FROST tweaks — why not BIP32, why no chain code, and the one rule that must not be broken |
| frost-batch-signing.md | signing several events in one ceremony — why one nonce can never cover two messages, and the phased schema, wire and UI work that follows from it |
| marmot-membership.md | how members join an MLS group, and the epoch race that makes a missing member look like a successful invite |
| marmot-direct-messages.md | a one-to-one message inside a group as a stock NIP-59 gift wrap — what its MIP-03 carve-out costs, why the sender cannot read their own, and the one query that would broadcast it |
| mls-skipped-keys.md | why a group event that arrives a moment late is dropped for good, which flows trigger it, the quartz fix, and the partial mitigation in this app |
| long-running-sync.md | the chat subscriptions that stay open instead of pulling once per screen — why the request queue could not simply hold one, and how the group filter follows the room list |
| dead-code.md | code in the sync and relay stack that nothing calls, why each piece is still there, and which of it is a bug rather than a leftover |
| jvm-target.md | what desktop support cost, phased — why the native chain was already done, why an empty source set in our phoenix fork was the real blocker, and why DAO tests need none of it |
Start with the ceremony if you are new to this area; the Marmot notes all assume it. Read the skipped-keys note before debugging any "the other device never got it" report — it is silent, and it looks like every other kind of delivery failure. The sync note stands alone, and the dead-code inventory reads as a follow-up to it. The batch-signing note is a plan rather than a description of what is there: read it after the derivation note, whose one rule is the same one it is built around. The jvm-target note is unrelated to all of them: it is a build and packaging story.