White Noise groups reach every device of an account

An invitation adds all of a person's fresh KeyPackages (one per slot, at
most ten) instead of one, and where our account is an admin a device that
finds a sibling's KeyPackage not yet in a group adds it, so the Welcome
reaches the other device through our own inbox. These are the same-account
rules Marmot's multi-device direction marks as valid today; the device
group and pairing it plans are not here. Verified against MDK (wn): a group
with two coinos leaves of one npub plus a wn member, all three reading and
writing (tools/marmot-multidevice-test.js). marmotClient takes an
injectable store for tests.

Co-Authored-By: Claude Fable 5.1 <[email protected]>
Claude-Session: https://claude.ai/code/session_01YRC6aKhwAud231ot9FPmhi

1 files changed, 11 insertions, 4 deletions

diff --git a/src/marmot.js b/src/marmot.js
index 7dd55d6..f6153a0 100644
--- a/src/marmot.js
+++ b/src/marmot.js
@@ -382,6 +382,7 @@ export function readKeyPackageEvent(ev, at = now()) {
     return {
       id: ev.id, pubkey: ev.pubkey, slot: d, ref: i, created_at: ev.created_at, lastResort,
       keyPackage: kp.keyPackage,
+      sigKey: bytesToHex(kp.leaf.signatureKey), // which device: the leaf it would occupy
       components: idList.dec(comp(kp.leaf.extensions, COMP.APP_COMPONENTS)),
       extensions: caps.extensions, proposals: caps.proposals,
       client: ev.tags.find((t) => t[0] === "client")?.[1] || "",
@@ -389,17 +390,23 @@ export function readKeyPackageEvent(ev, at = now()) {
   } catch { return null; }
 }
 
-// One candidate per (author, slot) — the newest, lower id on a tie — then
-// single-use packages before last-resort ones, fresher first, lower ref last.
-export function pickKeyPackage(candidates) {
+// One candidate per (author, slot) — the newest, lower id on a tie: a slot
+// is one installation, so this is one package per device. Ordered single-use
+// before last-resort, fresher first, lower ref last; at most `max` of them
+// (Marmot's multi-device direction caps an account at ten leaves).
+export const MAX_DEVICES = 10;
+export function pickKeyPackages(candidates, max = MAX_DEVICES) {
   const slots = new Map();
   for (const c of candidates) {
     const k = c.pubkey + c.slot, cur = slots.get(k);
     if (!cur || c.created_at > cur.created_at || (c.created_at === cur.created_at && c.id < cur.id)) slots.set(k, c);
   }
   return [...slots.values()].sort((a, b) =>
-    (a.lastResort - b.lastResort) || (b.created_at - a.created_at) || (a.ref < b.ref ? -1 : 1))[0] || null;
+    (a.lastResort - b.lastResort) || (b.created_at - a.created_at) || (a.ref < b.ref ? -1 : 1)).slice(0, max);
 }
+export const pickKeyPackage = (candidates) => pickKeyPackages(candidates, 1)[0] || null;
+// the signature keys of every leaf in a state: which devices are already in
+export const leafKeys = (state) => mls.members(state).map((m) => bytesToHex(m.signatureKey));
 
 // Can this KeyPackage join a group in this state?
 export function fits(state, cand) {