Merge pull request #4069 from believethehype/main

Introducing DVM heartbeats

.gitattributes

@@ -2,3 +2,7 @@
 # binary so git never applies CRLF/text normalization or textual diff/merge, which
 # would corrupt the compressed stream (important on Windows checkouts).
 *.gz binary
+
+# Golden test resources are compared byte-for-byte against generated strings:
+# force LF everywhere so a Windows CRLF checkout cannot break the comparison.
+*.golden text eol=lf

amethyst/plans/2026-09-10-dvm-heartbeat-liveness.md

@@ -0,0 +1,168 @@
+# DVM heartbeat liveness — only show DVMs with a fresh kind-11998 heartbeat
+
+_Status: **implemented** (Android; desktop wiring deliberately out of scope — §8)._
+
+## 0. The shape of the thing
+
+Amethyst shows Data Vending Machines (DVMs) in three places: the Discover "Content" tab
+(kind 31990 NIP-89 announcements advertising kind 5300), DVM feeds pinned to the top-nav
+(`FavoriteAlgoFeedsOrchestrator`), and the per-DVM content-discovery screen. Today all of
+these treat every announced DVM as alive, forever — a DVM that went down months ago still
+renders as a usable feed.
+
+DVM operators are now sending a **heartbeat event (kind 11998) every 300 seconds**. The
+event is plain-text (`content = "Alive and kicking"`) with three tags:
+
+- `status` — free-text status line (e.g. "My heart keeps beating like a hammer")
+- `d` — the DVM's **NIP-89 DTAG**, tying the heartbeat to the announcement's address
+- `expiration` — `createdAt + 300` (NIP-40), so relays drop the beat once the next one lands
+
+Kind 11998 sits in the replaceable range (10000–19999), so relays keep only the latest beat
+per author. There is no NIP for this yet — the shape above comes from the operator-side
+builder and is treated as the wire contract.
+
+The feature: **a DVM counts as alive only if its latest heartbeat is at most 900 seconds
+old** (one missed 300s beat plus slack). Dead DVMs disappear from the Discover list; pinned
+feeds and the detail surface show an offline state instead.
+
+## 1. Decisions taken
+
+1. **Approach: cache-backed heartbeats.** The heartbeat is a real event class stored through
+   the standard replaceable path in `LocalCache` (newest per address, standard invalidation).
+   Rejected alternatives: a side-state registry (duplicates invalidation plumbing) and
+   regular-note storage (no address matching, pollutes the notes index).
+2. **Scope: all three surfaces** — Discover list (hide), pinned feeds (offline state, chip
+   stays), DVM detail screen (offline banner, requesting still allowed). The manage screen
+   (`FavoriteAlgoFeedsListScreen`) also gets the badge.
+3. **Pinned chips stay when offline** — the user pinned them deliberately; they gray out
+   with an offline badge rather than vanishing, and tapping still opens the feed.
+4. **Threshold: 900 seconds** (raised from the original 420 after field testing: beats arrive every 300s, and a 420s window tolerated barely one delivery hiccup, dropping live DVMs in oscillations). Exactly 900s old counts as fresh.
+5. **Strict from cold start.** No grace period: the Discover list starts empty and fills
+   within ~1–2s as heartbeat REQs return (same behavior as the existing 31990 load).
+
+## 2. Event model (quartz)
+
+New `quartz/.../nip90Dvms/dvmHeartbeat/DvmHeartbeatEvent.kt`:
+
+- `class DvmHeartbeatEvent(...) : BaseAddressableEvent(...)`, `KIND = 11998` — the codebase
+  convention for 10xxx events with real `d` tags (e.g. `FollowListEvent`), so `dTag()` /
+  `address()` / `addressTag()` come from the base. The cache address is
+  `Address(11998, dvmPubkey, dTag)`, the exact mirror of the announcement's
+  `Address(31990, dvmPubkey, dTag)`.
+- Accessors: `status()`, and `expiration()` via the existing NIP-40 extension.
+- `MAX_AGE_SECONDS = 900` and `isFreshAt(now)` live in quartz too (commons imports them).
+- Registered in `EventFactory` (kind → constructor) and allowlisted in
+  `EventFactoryKindRangeTest.knownDTagReaders`: the `d` tag keys the client-side address
+  while relay storage stays plain-replaceable per the kind range.
+
+## 3. Cache consumption (LocalCache)
+
+One routing line in `LocalCache.justConsumeInnerInner`: `is DvmHeartbeatEvent ->`
+`consumeBaseReplaceable(event, relay, wasVerified)`. This yields newest-per-address
+replacement, relay tracking, and `LocalCacheFlow` invalidation for free. Unlisted kinds fall
+into the `else` branch and are rejected, so the routing line is mandatory.
+
+Stale beats simply sit at their address until overwritten; the age check (§4) makes them
+invisible. The cache pruner removes old entries on its own schedule.
+
+## 4. Freshness core (amethyst)
+
+Small helper file in `amethyst/.../model/` (the threshold constant itself lives in quartz):
+
+- `LocalCache.dvmHeartbeatOf(appDef: AppDefinitionEvent): DvmHeartbeatEvent?` — address
+  lookup `Address(DvmHeartbeatEvent.KIND, appDef.pubKey, appDef.dTag())`
+- `DvmHeartbeatEvent.isFreshAt(now: Long): Boolean` — `createdAt >= now - 900`
+- `@Composable fun rememberDvmHeartbeatFresh(address: Address, accountViewModel: AccountViewModel): State<Boolean>` —
+  as built (uniform-strict ruling): returns true while the DVM has a heartbeat at most 900s
+  old; an unresolved/absent beat counts as offline (`false`) on every surface. The returned
+  `State` identity is stable for the lifetime of the call site (one unconditional
+  `rememberUpdatedState`), so callers may capture it across recompositions. Composable-scoped
+  subscription (§5) + staleness re-check tick (§6), shared by every surface that renders
+  liveness.
+
+## 5. Subscriptions
+
+**Discover screen — all DVM heartbeats.** In
+`commons/.../relayClient/discover/nip90DVMs/SubAssemblyHelper.kt`, `makeContentDVMsFilter`
+unconditionally appends one filter for every top-filter variant:
+`kinds = [11998], since = TimeUtils.now() - 900` — no authors, no tags, scoped to the same
+relay set as the 31990 REQs. It deliberately ignores the 31990 `since`-cursor (heartbeats
+are a rolling window, not a cursor stream — the cursor would miss re-opened tabs after the
+beats expired). It rides the existing assembler lifecycle: subscribes on entering Discover,
+closes on leaving.
+
+**Per-surface — pinned chips, home banner, detail screen.** `rememberDvmHeartbeat` opens a
+tiny composable-scoped subscription: `kinds = [11998], authors = [dvm pubkey], limit = 1,
+since = now - 900`. The home top-bar chips live for the whole session, so they double as
+the session-scoped watcher for pinned DVMs. Traffic is negligible (a few pinned DVMs ×
+1 event / 5 min).
+
+**Outbox fetcher (added after field testing).** The global REQ above only sees beats that
+reach the *user's* discovery relays — but DVMs publish beats to their own write relays, and
+relays don't gossip, so alive DVMs whose beats never overlap the user's relay set stayed
+invisible (their detail screens proved the beats existed on the outbox). `DiscoveryDvmHeartbeatSubAssembler`
+joins the discovery assembler group and, while Discover is composed, batches the cached
+content-discovery announcements' authors per **DVM outbox relay** (`kinds = [11998],
+authors = [those pubkeys], since = now - 900`, coverage-ranked and capped at 12 relays;
+authors with unknown outboxes/hints rely on the global REQ as fallback). It re-issues when
+the cached announcement set or the NIP-65 relay lists move.
+
+The announcement source MUST be the **ungated cache scan**
+(`LocalCache.cachedDvmAnnouncements` — every cached k=5300 announcement, newest first, capped
+at 100), not the gated feed list. Sourcing from the gated list is a death spiral: a DVM
+leaves the gated list the moment its beat ages out, the fetcher would stop covering it, and
+no beat would ever arrive to bring it back — any transient staleness becomes a permanent
+drop. The relay lookup unions the author's NIP-65 outbox with the cached relay hints for the
+author (the same mix the event finder's `potentialRelaysToFindAddress` uses).
+
+## 6. Invalidation — closing the two silent gaps
+
+1. **A new heartbeat does not re-rank the list.** The additive feed path
+   (`FeedContentState.updateFeedWith`) re-filters only the *new* notes, and a heartbeat
+   note is never a list row — the affected 31990 card would not be re-evaluated. Fix: in
+   `AccountFeedContentStates.updateFeedsWith`, branch on
+   `newNotes.any { it.event is DvmHeartbeatEvent }` → `discoverDVMs.invalidateData()`
+   (full rebuild re-runs the freshness check on every announcement); otherwise the normal
+   additive path.
+2. **Expiry produces no event.** A 60s timer collector in `AccountFeedContentStates`
+   (alongside the existing `scope.launch { flows.collect { … } }` observers) calls
+   `discoverDVMs.invalidateData()` every minute. The rebuild is a cheap scan (≤ a few
+   hundred 31990s) and `refreshSuspended()` no-ops when the list is unchanged. Composables
+   using `rememberDvmHeartbeatFresh` tick on a 30s cadence internally.
+
+## 7. UI surfaces
+
+1. **Discover "Content" tab** — `DiscoverNIP89FeedFilter.acceptApp` adds
+   `dvmHeartbeatOf(noteEvent)?.isFreshAt(now) == true`. No fresh beat → card hidden.
+2. **Pinned top-nav chips** — chip stays; when the heartbeat is stale or absent the chip is
+   grayed out with a small offline dot appended to its label. Tapping still opens the feed.
+3. **Pinned feed view** — new branch in `HomeAlgoFeedStatusBanner`: when the selected
+   pinned feed's heartbeat is stale, show an offline banner above the last known content,
+   shown *even when content exists* (the current banner only handles empty/error states).
+   Single-feed and all-feeds variants both covered.
+4. **DVM detail screen** (`DvmContentDiscoveryScreen`) — same offline banner; requesting is
+   still allowed (informational, not a block).
+5. **`FavoriteAlgoFeedsListScreen`** — offline badge per row so users can spot dead pins.
+6. New English string resources (`dvm_offline`, `dvm_offline_banner`); translations flow
+   via Crowdin.
+
+## 8. Edge cases (accepted limitations)
+
+- Heartbeat without a `d` tag → cache address dTag `""` → matches nothing → DVM hidden
+  (strict; the wire contract always sends `d`).
+- Device/DVM clock skew > 15 min → wrongly hidden (inherent to timestamp-based liveness).
+- DVM beats that never reach the relays we query → shows offline (that is the feature).
+- One keypair running multiple DVMs → relays keep only the latest beat per (kind, author);
+  per-d-tag cache slots help only across relays. Most DVMs use one key each.
+- **Desktop app: out of scope this round.** The commons subscription helper is shared-ready
+  and the desktop relay assembler will pick up heartbeat REQs harmlessly (cache fills,
+  nothing renders), but all UI wiring is Android-only.
+
+## 9. Testing
+
+- **quartz**: parse/build `DvmHeartbeatEvent` — `dTag()` override, `statusTag()`,
+  `expiration()`, address assembly.
+- **amethyst**: `DiscoverNIP89FeedFilter.acceptApp` matrix — no beat → reject; fresh beat →
+  accept; 421s-old beat → reject. The `updateFeedsWith` heartbeat branch triggers a full
+  rebuild. `isFreshAt` boundary (900s fresh, 901s stale).
+- Verify with `./gradlew :quartz:test :amethyst:test`, then `./gradlew spotlessApply`.

amethyst/src/main/java/com/vitorpamplona/amethyst/model/DvmHeartbeat.kt

@@ -0,0 +1,61 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.model
+
+import com.vitorpamplona.amethyst.commons.model.cache.filterIntoSet
+import com.vitorpamplona.quartz.nip01Core.core.Address
+import com.vitorpamplona.quartz.nip89AppHandlers.definition.AppDefinitionEvent
+import com.vitorpamplona.quartz.nip90Dvms.contentDiscoveryRequest.NIP90ContentDiscoveryRequestEvent
+import com.vitorpamplona.quartz.nip90Dvms.dvmHeartbeat.DvmHeartbeatEvent
+import com.vitorpamplona.quartz.utils.TimeUtils
+
+/** The cache slot a DVM's heartbeat lives in: the announcement's own address, kind 11998. */
+fun LocalCache.dvmHeartbeatOf(appDef: AppDefinitionEvent): DvmHeartbeatEvent? = getAddressableNoteIfExists(Address(DvmHeartbeatEvent.KIND, appDef.pubKey, appDef.dTag()))?.event as? DvmHeartbeatEvent
+
+/**
+ * A DVM counts as alive only if its latest heartbeat is at most 900s old. The registry (not the
+ * WeakReference-held beat note) is the freshness source: beat notes have no strong holder on the
+ * Discover screen, and a GC sweep cleared them all at once, collapsing the list.
+ */
+fun LocalCache.hasFreshDvmHeartbeat(
+    appDef: AppDefinitionEvent,
+    now: Long = TimeUtils.now(),
+): Boolean =
+    DvmHeartbeatRegistry
+        .latestAt(Address(DvmHeartbeatEvent.KIND, appDef.pubKey, appDef.dTag()))
+        ?.let { it >= now - DvmHeartbeatEvent.MAX_AGE_SECONDS } == true
+
+/**
+ * Every cached content-discovery announcement, WITHOUT the freshness gate — this is the source the
+ * heartbeat outbox fetcher must use. Sourcing from the gated feed list would drop a DVM the moment
+ * its beat went stale, remove it from the fetch batch, and make the drop permanent (the fetcher
+ * could only ever help DVMs that were already visible). Applies the gate's other eligibility
+ * checks (a real content-discovery DVM, not a paid subscription app), newest first, capped.
+ */
+fun LocalCache.cachedDvmAnnouncements(limit: Int = 100): List<AppDefinitionEvent> =
+    addressables
+        .filterIntoSet(AppDefinitionEvent.KIND) { _, note ->
+            (note.event as? AppDefinitionEvent)?.let {
+                it.appMetaData()?.subscription != true && it.includeKind(NIP90ContentDiscoveryRequestEvent.KIND)
+            } == true
+        }.mapNotNull { it.event as? AppDefinitionEvent }
+        .sortedByDescending { it.createdAt }
+        .take(limit)

amethyst/src/main/java/com/vitorpamplona/amethyst/model/DvmHeartbeatRegistry.kt

@@ -0,0 +1,58 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.model
+
+import com.vitorpamplona.quartz.nip01Core.core.Address
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.StateFlow
+import kotlinx.coroutines.flow.update
+import java.util.concurrent.ConcurrentHashMap
+
+/**
+ * Strong, process-wide record of the latest heartbeat per DVM announcement address
+ * (`Address(11998, dvmPubKey, dTag) -> createdAt`).
+ *
+ * Beat Notes themselves live in `LocalCache.addressables`, a WeakReference store with no strong
+ * holder on the Discover screen — every GC sweep cleared them all at once and the freshness gate
+ * collapsed for every DVM simultaneously (the list emptied and rebuilt one beat at a time). This
+ * registry is the freshness source the gate and the liveness composables read: strong references,
+ * fed by every beat-arrival path (global REQ, outbox batches, per-surface fetches — all beat
+ * consumption routes through [record]).
+ *
+ * One entry per DVM address ever seen; timestamps only, so it stays tiny. `0` means "no beat".
+ */
+object DvmHeartbeatRegistry {
+    private val latestBeatCreatedAt = ConcurrentHashMap<Address, MutableStateFlow<Long>>()
+
+    private fun flowFor(address: Address): MutableStateFlow<Long> = latestBeatCreatedAt.getOrPut(address) { MutableStateFlow(0L) }
+
+    /** Observable latest-beat timestamp for this address; `0` means "no beat seen yet". */
+    fun flowForPublic(address: Address): StateFlow<Long> = flowFor(address)
+
+    /** Records a beat's createdAt; older beats never move the entry backwards. */
+    fun record(
+        address: Address,
+        createdAt: Long,
+    ) = flowFor(address).update { current -> if (createdAt > current) createdAt else current }
+
+    /** The latest recorded beat's createdAt for this address, or null when no beat was ever seen. */
+    fun latestAt(address: Address): Long? = flowFor(address).value.takeIf { it > 0L }
+}

amethyst/src/main/java/com/vitorpamplona/amethyst/model/LocalCache.kt

@@ -380,6 +380,7 @@ import com.vitorpamplona.quartz.nip89AppHandlers.definition.AppDefinitionEvent
 import com.vitorpamplona.quartz.nip89AppHandlers.recommendation.AppRecommendationEvent
 import com.vitorpamplona.quartz.nip90Dvms.contentDiscoveryRequest.NIP90ContentDiscoveryRequestEvent
 import com.vitorpamplona.quartz.nip90Dvms.contentDiscoveryResponse.NIP90ContentDiscoveryResponseEvent
+import com.vitorpamplona.quartz.nip90Dvms.dvmHeartbeat.DvmHeartbeatEvent
 import com.vitorpamplona.quartz.nip90Dvms.status.NIP90StatusEvent
 import com.vitorpamplona.quartz.nip90Dvms.userDiscoveryRequest.NIP90UserDiscoveryRequestEvent
 import com.vitorpamplona.quartz.nip90Dvms.userDiscoveryResponse.NIP90UserDiscoveryResponseEvent
@@ -3742,6 +3743,15 @@ object LocalCache : ILocalCache, ICacheProvider, Dao {
                 is CommunityDefinitionEvent,
                 is CommunityListEvent,
                 is ContactListEvent,
+                // DVM heartbeat (11998): stored per Address(11998, author, d) so liveness checks find the
+                // beat at the announcement's mirror address (amethyst/plans/2026-09-10-dvm-heartbeat-liveness.md),
+                // AND recorded into the strong registry — beat notes are WeakReference-held with no strong
+                // holder on the Discover screen, so the gate must not depend on them surviving GC.
+                is DvmHeartbeatEvent,
+                ->
+                    consumeBaseReplaceable(event, relay, wasVerified).also {
+                        DvmHeartbeatRegistry.record(event.address(), event.createdAt)
+                    }
                 is EmojiPackEvent,
                 is EmojiPackSelectionEvent,
                 is EphemeralChatListEvent,

amethyst/src/main/java/com/vitorpamplona/amethyst/service/relayClient/reqCommand/RelaySubscriptionsCoordinator.kt

@@ -31,6 +31,7 @@ import com.vitorpamplona.amethyst.commons.relayClient.chess.ChessFilterAssembler
 import com.vitorpamplona.amethyst.commons.relayClient.communities.CommunityFilterAssembler
 import com.vitorpamplona.amethyst.commons.relayClient.communities.list.CommunitiesListFilterAssembler
 import com.vitorpamplona.amethyst.commons.relayClient.discover.DiscoveryFilterAssembler
+import com.vitorpamplona.amethyst.commons.relayClient.discover.nip90DVMs.DvmHeartbeatSources
 import com.vitorpamplona.amethyst.commons.relayClient.emojipacks.BrowseEmojiSetsFilterAssembler
 import com.vitorpamplona.amethyst.commons.relayClient.event.EventFinderFilterAssembler
 import com.vitorpamplona.amethyst.commons.relayClient.followPacks.FollowPacksFilterAssembler
@@ -69,6 +70,7 @@ import com.vitorpamplona.amethyst.commons.relayClient.video.VideoFilterAssembler
 import com.vitorpamplona.amethyst.commons.relayClient.wallet.OnchainZapsFilterAssembler
 import com.vitorpamplona.amethyst.commons.relayClient.workouts.WorkoutsFilterAssembler
 import com.vitorpamplona.amethyst.model.LocalCache
+import com.vitorpamplona.amethyst.model.cachedDvmAnnouncements
 import com.vitorpamplona.amethyst.service.relayClient.reqCommand.account.AccountFilterAssembler
 import com.vitorpamplona.amethyst.service.relayClient.reqCommand.account.AccountForegroundFilterAssembler
 import com.vitorpamplona.amethyst.service.relayClient.reqCommand.channel.ChannelFinderFilterAssemblyGroup
@@ -94,6 +96,9 @@ import com.vitorpamplona.amethyst.ui.screen.loggedIn.nests.datasource.NestRoomLi
 import com.vitorpamplona.quartz.nip01Core.relay.client.INostrClient
 import com.vitorpamplona.quartz.nip01Core.relay.client.accessories.RelayOfflineTracker
 import com.vitorpamplona.quartz.nip01Core.relay.client.auth.IAuthStatus
+import com.vitorpamplona.quartz.nip01Core.relay.filters.Filter
+import com.vitorpamplona.quartz.nip65RelayList.AdvertisedRelayListEvent
+import com.vitorpamplona.quartz.nip89AppHandlers.definition.AppDefinitionEvent
 import kotlinx.coroutines.CoroutineScope
 
 class RelaySubscriptionsCoordinator(
@@ -113,7 +118,25 @@ class RelaySubscriptionsCoordinator(
     val home = HomeFilterAssembler(client)
     val chatroomList = ChatroomListFilterAssembler(client)
     val video = VideoFilterAssembler(client)
-    val discovery = DiscoveryFilterAssembler(client)
+    val discovery =
+        DiscoveryFilterAssembler(
+            client,
+            dvmHeartbeat =
+                DvmHeartbeatSources(
+                    announcements = cache::cachedDvmAnnouncements,
+                    outboxRelaysFor = { pubkey ->
+                        buildSet {
+                            cache.getUserIfExists(pubkey)?.outboxRelays()?.let { addAll(it) }
+                            addAll(cache.relayHints.hintsForKey(pubkey))
+                        }
+                    },
+                    changes =
+                        listOf(
+                            cache.observeNotes(Filter(kinds = listOf(AppDefinitionEvent.KIND))),
+                            cache.observeNotes(Filter(kinds = listOf(AdvertisedRelayListEvent.KIND))),
+                        ),
+                ),
+        )
 
     // loaders of content that is not yet in the device.
     // they are active when looking at events, users, channels.

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/navigation/topbars/FeedFilterSpinner.kt

@@ -52,6 +52,7 @@ import androidx.compose.ui.Modifier
 import androidx.compose.ui.graphics.Color
 import androidx.compose.ui.platform.LocalContext
 import androidx.compose.ui.semantics.Role
+import androidx.compose.ui.semantics.contentDescription
 import androidx.compose.ui.semantics.onClick
 import androidx.compose.ui.semantics.role
 import androidx.compose.ui.semantics.semantics
@@ -71,6 +72,7 @@ import com.vitorpamplona.amethyst.commons.icons.symbols.Icon
 import com.vitorpamplona.amethyst.commons.icons.symbols.MaterialSymbols
 import com.vitorpamplona.amethyst.commons.model.topNavFeeds.TopFilter
 import com.vitorpamplona.amethyst.commons.resources.Res
+import com.vitorpamplona.amethyst.commons.resources.dvm_offline
 import com.vitorpamplona.amethyst.commons.resources.feed_filter_select_an_option
 import com.vitorpamplona.amethyst.commons.resources.feed_filter_selected
 import com.vitorpamplona.amethyst.commons.resources.lack_location_permissions
@@ -95,6 +97,7 @@ import com.vitorpamplona.amethyst.ui.screen.PeopleListName
 import com.vitorpamplona.amethyst.ui.screen.RelayName
 import com.vitorpamplona.amethyst.ui.screen.ResourceName
 import com.vitorpamplona.amethyst.ui.screen.loggedIn.AccountViewModel
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.dvms.rememberDvmHeartbeatFresh
 import com.vitorpamplona.amethyst.ui.stringRes
 import com.vitorpamplona.amethyst.ui.theme.Font12SP
 import com.vitorpamplona.amethyst.ui.theme.Font14SP
@@ -177,11 +180,29 @@ fun FeedFilterSpinner(
                             )
                         }
                     } else {
-                        Text(
-                            text = currentText,
-                            maxLines = 1,
-                            overflow = TextOverflow.Ellipsis,
-                        )
+                        val favoriteAlgoFeedAddress = (selected?.name as? FavoriteAlgoFeedName)?.note?.address
+                        if (favoriteAlgoFeedAddress != null) {
+                            val heartbeatFresh by rememberDvmHeartbeatFresh(favoriteAlgoFeedAddress, accountViewModel)
+                            val offlineLabel = stringRes(Res.string.dvm_offline)
+                            Text(
+                                text = if (heartbeatFresh) currentText else "$currentText \u2022",
+                                color = if (heartbeatFresh) Color.Unspecified else MaterialTheme.colorScheme.onSurfaceVariant,
+                                maxLines = 1,
+                                overflow = TextOverflow.Ellipsis,
+                                modifier =
+                                    if (heartbeatFresh) {
+                                        Modifier
+                                    } else {
+                                        Modifier.semantics { contentDescription = "$currentText, $offlineLabel" }
+                                    },
+                            )
+                        } else {
+                            Text(
+                                text = currentText,
+                                maxLines = 1,
+                                overflow = TextOverflow.Ellipsis,
+                            )
+                        }
                     }
 
                     if (filter is TopFilter.AroundMe) {
@@ -371,7 +392,30 @@ fun RenderOption(
             val backed = option as NoteBackedName
             val noteState by observeNote(backed.note, accountViewModel)
             val name = remember(noteState) { option.name(context) }
-            Text(text = name, fontSize = Font14SP, color = MaterialTheme.colorScheme.onSurface)
+            val appDefAddress = (option as? FavoriteAlgoFeedName)?.note?.address
+            val heartbeatFresh =
+                if (appDefAddress != null) {
+                    rememberDvmHeartbeatFresh(appDefAddress, accountViewModel).value
+                } else {
+                    true
+                }
+            val offlineLabel = stringRes(Res.string.dvm_offline)
+            Text(
+                text = if (heartbeatFresh) name else "$name \u2022",
+                fontSize = Font14SP,
+                color =
+                    if (heartbeatFresh) {
+                        MaterialTheme.colorScheme.onSurface
+                    } else {
+                        MaterialTheme.colorScheme.onSurfaceVariant
+                    },
+                modifier =
+                    if (heartbeatFresh) {
+                        Modifier
+                    } else {
+                        Modifier.semantics { contentDescription = "$name, $offlineLabel" }
+                    },
+            )
         }
 
         // Pure names: no relay subscription needed.

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/AccountFeedContentStates.kt

@@ -76,11 +76,14 @@ import com.vitorpamplona.amethyst.ui.screen.loggedIn.softwareapps.dal.SoftwareAp
 import com.vitorpamplona.amethyst.ui.screen.loggedIn.video.dal.VideoFeedFilter
 import com.vitorpamplona.amethyst.ui.screen.loggedIn.webBookmarks.dal.WebBookmarkFeedFilter
 import com.vitorpamplona.amethyst.ui.screen.loggedIn.workouts.dal.WorkoutFeedFilter
+import com.vitorpamplona.quartz.nip90Dvms.dvmHeartbeat.DvmHeartbeatEvent
 import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.FlowPreview
+import kotlinx.coroutines.delay
 import kotlinx.coroutines.flow.drop
 import kotlinx.coroutines.flow.sample
+import kotlinx.coroutines.isActive
 import kotlinx.coroutines.launch
 
 class AccountFeedContentStates(
@@ -313,6 +316,15 @@ class AccountFeedContentStates(
                 notificationsEveryone.invalidateData()
             }
         }
+
+        // Heartbeat staleness produces no cache event (a beat just ages past 420s), so re-check
+        // the DVM discovery feed on a timer. refreshSuspended() no-ops when nothing changed.
+        scope.launch(Dispatchers.IO) {
+            while (isActive) {
+                delay(60_000)
+                discoverDVMs.invalidateData()
+            }
+        }
     }
 
     suspend fun init() {
@@ -335,7 +347,13 @@ class AccountFeedContentStates(
         discoverMarketplace.updateFeedWith(newNotes)
         discoverFollowSets.updateFeedWith(newNotes)
         discoverReads.updateFeedWith(newNotes)
-        discoverDVMs.updateFeedWith(newNotes)
+        if (newNotes.any { it.event is DvmHeartbeatEvent }) {
+            // A heartbeat is never a feed row, so the additive path would graft nothing and never
+            // re-evaluate the announcement it just validated. Rebuild instead.
+            discoverDVMs.invalidateData()
+        } else {
+            discoverDVMs.updateFeedWith(newNotes)
+        }
         discoverLive.updateFeedWith(newNotes)
         discoverCommunities.updateFeedWith(newNotes)
         discoverPublicChats.updateFeedWith(newNotes)

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/discover/DiscoverScreen.kt

@@ -278,7 +278,18 @@ private fun DiscoverPages(
         HorizontalPager(state = pagerState) { page ->
             if (page >= 0 && page < feedTabs.size) {
                 val tab = feedTabs[page]
-                RefresheableBox(tab.feedState, true) {
+                RefresheableBox(
+                    onRefresh = {
+                        tab.feedState.invalidateData()
+                        // The DVM tab's freshness gate lives or dies with beat delivery, and
+                        // invalidateData only re-reads the cache — re-issue the discovery REQs
+                        // (31990 + both heartbeat streams) with fresh rolling windows so refresh
+                        // actually fetches.
+                        if (tab.feedState == accountViewModel.feedStates.discoverDVMs) {
+                            accountViewModel.dataSources().discovery.invalidateFilters()
+                        }
+                    },
+                ) {
                     if (tab.useGridLayout) {
                         SaveableGridFeedContentState(tab.feedState, scrollStateKey = tab.scrollStateKey) { listState ->
                             RenderDiscoverFeed(

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/discover/nip90DVMs/DiscoverNIP89FeedFilter.kt

@@ -34,6 +34,7 @@ import com.vitorpamplona.amethyst.commons.ui.feeds.AdditiveFeedFilter
 import com.vitorpamplona.amethyst.model.Account
 import com.vitorpamplona.amethyst.model.LocalCache
 import com.vitorpamplona.amethyst.model.ParticipantListBuilder
+import com.vitorpamplona.amethyst.model.hasFreshDvmHeartbeat
 import com.vitorpamplona.amethyst.ui.dal.FilterByListParams
 import com.vitorpamplona.quartz.nip01Core.relay.normalizer.NormalizedRelayUrl
 import com.vitorpamplona.quartz.nip89AppHandlers.definition.AppDefinitionEvent
@@ -93,7 +94,8 @@ open class DiscoverNIP89FeedFilter(
         return noteEvent.appMetaData()?.subscription != true &&
             filterParams.match(noteEvent, relays) &&
             noteEvent.includeKind(targetKind) &&
-            noteEvent.createdAt > lastAnnounced
+            noteEvent.createdAt > lastAnnounced &&
+            LocalCache.hasFreshDvmHeartbeat(noteEvent)
     }
 
     protected open fun innerApplyFilter(collection: Collection<Note>): Set<Note> =

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/dvms/DvmContentDiscoveryScreen.kt

@@ -131,6 +131,9 @@ fun DvmContentDiscoveryScreen(
 ) {
     val noteAuthor = appDefinition.author ?: return
 
+    val appDef = appDefinition.event as? AppDefinitionEvent
+    val heartbeatFresh = if (appDef != null) rememberDvmHeartbeatFresh(appDef.address(), accountViewModel) else null
+
     var requestEventID by
         remember(appDefinition) {
             mutableStateOf<Note?>(null)
@@ -151,22 +154,18 @@ fun DvmContentDiscoveryScreen(
         }
     }
 
-    RefresheableBox(
-        onRefresh = onRefresh,
-    ) {
-        val myRequestEventID = requestEventID
-        if (myRequestEventID != null) {
-            ObserverContentDiscoveryResponse(
-                appDefinition,
-                myRequestEventID,
-                onRefresh,
-                accountViewModel,
-                nav,
-            )
-        } else {
-            // TODO: Make a good splash screen with loading animation for this DVM.
-            // FeedDVM(appDefinition, null, accountViewModel, nav)
-            FeedEmptyWithStatus(appDefinition, stringRes(Res.string.dvm_requesting_job), accountViewModel, nav)
+    RefresheableBox(onRefresh = onRefresh) {
+        Box(modifier = Modifier.fillMaxSize()) {
+            val myRequestEventID = requestEventID
+            if (myRequestEventID != null) {
+                ObserverContentDiscoveryResponse(appDefinition, myRequestEventID, onRefresh, accountViewModel, nav)
+            } else {
+                // TODO: Make a good splash screen with loading animation for this DVM.
+                FeedEmptyWithStatus(appDefinition, stringRes(Res.string.dvm_requesting_job), accountViewModel, nav)
+            }
+            if (heartbeatFresh?.value == false) {
+                DvmOfflineBanner(modifier = Modifier.align(Alignment.TopCenter))
+            }
         }
     }
 }

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/dvms/DvmHeartbeatObservation.kt

@@ -0,0 +1,126 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.ui.screen.loggedIn.dvms
+
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.shape.RoundedCornerShape
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.Surface
+import androidx.compose.material3.Text
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.LaunchedEffect
+import androidx.compose.runtime.State
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableLongStateOf
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.rememberUpdatedState
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.unit.dp
+import androidx.lifecycle.compose.collectAsStateWithLifecycle
+import com.vitorpamplona.amethyst.commons.resources.Res
+import com.vitorpamplona.amethyst.commons.resources.dvm_offline_banner
+import com.vitorpamplona.amethyst.model.DvmHeartbeatRegistry
+import com.vitorpamplona.amethyst.service.relayClient.reqCommand.event.observeNoteAndMap
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.AccountViewModel
+import com.vitorpamplona.amethyst.ui.stringRes
+import com.vitorpamplona.quartz.nip01Core.core.Address
+import com.vitorpamplona.quartz.nip90Dvms.dvmHeartbeat.DvmHeartbeatEvent
+import com.vitorpamplona.quartz.utils.TimeUtils
+import kotlinx.coroutines.delay
+import kotlinx.coroutines.isActive
+
+private const val HEARTBEAT_RECHECK_MILLIS = 30_000L
+
+/**
+ * True while the DVM announced at [appDefinitionAddress] has a heartbeat (kind 11998) at most
+ * 420s old. Resolves the beat's cache note by its mirror address, opens a composable-scoped
+ * relay subscription (the event-finder assembler fetches the beat by kind/author/d while it is
+ * missing), and re-checks staleness on a timer — an expired beat produces no cache event.
+ */
+@Composable
+fun rememberDvmHeartbeatFresh(
+    appDefinitionAddress: Address,
+    accountViewModel: AccountViewModel,
+): State<Boolean> {
+    val heartbeatAddressTag =
+        remember(appDefinitionAddress) {
+            Address.assemble(DvmHeartbeatEvent.KIND, appDefinitionAddress.pubKeyHex, appDefinitionAddress.dTag)
+        }
+
+    var heartbeatNote by
+        remember(heartbeatAddressTag) {
+            mutableStateOf(accountViewModel.getNoteIfExists(heartbeatAddressTag))
+        }
+    LaunchedEffect(heartbeatAddressTag) {
+        if (heartbeatNote == null) {
+            heartbeatNote = accountViewModel.checkGetOrCreateNote(heartbeatAddressTag)
+        }
+    }
+
+    val observed =
+        heartbeatNote?.let { observeNoteAndMap(it, accountViewModel) { it.event as? DvmHeartbeatEvent } }
+
+    // The registry is the eviction-proof freshness source (beat notes are WeakReference-held);
+    // the observed note is the secondary source and also drives the outbox fetch.
+    val registryBeat by
+        DvmHeartbeatRegistry.flowForPublic(appDefinitionAddress).collectAsStateWithLifecycle()
+
+    var now by remember(heartbeatNote) { mutableLongStateOf(TimeUtils.now()) }
+    LaunchedEffect(heartbeatNote) {
+        while (isActive) {
+            delay(HEARTBEAT_RECHECK_MILLIS)
+            now = TimeUtils.now()
+        }
+    }
+
+    val beat = observed?.value
+    val bestBeat = maxOf(beat?.createdAt ?: 0L, registryBeat)
+    return rememberUpdatedState(bestBeat > 0L && bestBeat >= now - DvmHeartbeatEvent.MAX_AGE_SECONDS)
+}
+
+/** Floating "DVM is offline" banner, mirroring the Home status banner's card style. */
+@Composable
+fun DvmOfflineBanner(modifier: Modifier = Modifier) {
+    Surface(
+        modifier = modifier.padding(horizontal = 12.dp, vertical = 6.dp),
+        shape = RoundedCornerShape(12.dp),
+        color = MaterialTheme.colorScheme.surfaceContainerHigh,
+        tonalElevation = 4.dp,
+        shadowElevation = 4.dp,
+    ) {
+        Row(
+            modifier = Modifier.padding(12.dp),
+            verticalAlignment = Alignment.CenterVertically,
+            horizontalArrangement = Arrangement.Start,
+        ) {
+            Text(
+                text = stringRes(Res.string.dvm_offline_banner),
+                style = MaterialTheme.typography.bodyMedium,
+                color = MaterialTheme.colorScheme.onSurface,
+            )
+        }
+    }
+}

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/dvms/favorites/FavoriteAlgoFeedsListScreen.kt

@@ -52,6 +52,7 @@ import androidx.compose.ui.Alignment
 import androidx.compose.ui.Alignment.Companion.BottomStart
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.layout.ContentScale
+import androidx.compose.ui.semantics.contentDescription
 import androidx.compose.ui.semantics.semantics
 import androidx.compose.ui.text.Placeholder
 import androidx.compose.ui.text.PlaceholderVerticalAlign
@@ -67,6 +68,7 @@ import com.vitorpamplona.amethyst.commons.icons.symbols.Icon
 import com.vitorpamplona.amethyst.commons.icons.symbols.MaterialSymbols
 import com.vitorpamplona.amethyst.commons.model.AddressableNote
 import com.vitorpamplona.amethyst.commons.resources.Res
+import com.vitorpamplona.amethyst.commons.resources.dvm_offline
 import com.vitorpamplona.amethyst.commons.resources.favorite_dvms_add_more
 import com.vitorpamplona.amethyst.commons.resources.favorite_dvms_empty_cta
 import com.vitorpamplona.amethyst.commons.resources.favorite_dvms_empty_headline
@@ -84,6 +86,7 @@ import com.vitorpamplona.amethyst.ui.navigation.topbars.TopBarWithBackButton
 import com.vitorpamplona.amethyst.ui.note.elements.BannerImage
 import com.vitorpamplona.amethyst.ui.screen.loggedIn.AccountViewModel
 import com.vitorpamplona.amethyst.ui.screen.loggedIn.dvms.observeAppDefinition
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.dvms.rememberDvmHeartbeatFresh
 import com.vitorpamplona.amethyst.ui.stringRes
 import com.vitorpamplona.amethyst.ui.theme.DoubleHorzSpacer
 import com.vitorpamplona.amethyst.ui.theme.FeedPadding
@@ -282,12 +285,21 @@ private fun FavoriteAlgoFeedRow(
         Column(
             modifier = Modifier.weight(1f),
         ) {
+            val heartbeatFresh by rememberDvmHeartbeatFresh(feedNote.address, accountViewModel)
+            val displayName = card.name.ifBlank { feedNote.dTag() }
+            val offlineLabel = stringRes(Res.string.dvm_offline)
             Text(
-                text = card.name.ifBlank { feedNote.dTag() },
+                text = if (heartbeatFresh) displayName else "$displayName \u2022",
                 fontWeight = FontWeight.Bold,
                 maxLines = 1,
                 overflow = TextOverflow.Ellipsis,
                 style = MaterialTheme.typography.bodyLarge,
+                modifier =
+                    if (heartbeatFresh) {
+                        Modifier
+                    } else {
+                        Modifier.semantics { contentDescription = "$displayName, $offlineLabel" }
+                    },
             )
             card.description?.takeIf { it.isNotBlank() }?.let {
                 Spacer(modifier = StdVertSpacer)

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/home/AlgoFeedStatusBanner.kt

@@ -48,6 +48,7 @@ import com.vitorpamplona.amethyst.commons.resources.dvm_home_status_payment_requ
 import com.vitorpamplona.amethyst.commons.resources.dvm_home_status_processing
 import com.vitorpamplona.amethyst.commons.resources.dvm_home_status_requesting
 import com.vitorpamplona.amethyst.commons.resources.dvm_home_status_requesting_all
+import com.vitorpamplona.amethyst.commons.resources.dvm_offline_banner
 import com.vitorpamplona.amethyst.commons.ui.components.LoadingAnimation
 import com.vitorpamplona.amethyst.model.algoFeeds.FavoriteAlgoFeedsSnapshot
 import com.vitorpamplona.amethyst.service.relayClient.reqCommand.event.observeNoteAndMap
@@ -55,6 +56,7 @@ import com.vitorpamplona.amethyst.ui.components.LoadNote
 import com.vitorpamplona.amethyst.ui.navigation.navs.INav
 import com.vitorpamplona.amethyst.ui.screen.loggedIn.AccountViewModel
 import com.vitorpamplona.amethyst.ui.screen.loggedIn.dvms.DvmPaymentActions
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.dvms.rememberDvmHeartbeatFresh
 import com.vitorpamplona.amethyst.ui.stringRes
 import com.vitorpamplona.amethyst.ui.theme.StdHorzSpacer
 import com.vitorpamplona.amethyst.ui.theme.StdVertSpacer
@@ -87,6 +89,20 @@ private fun SingleAlgoFeedBanner(
         .observe(favFeed.address)
         .collectAsStateWithLifecycle()
 
+    val heartbeatFresh by rememberDvmHeartbeatFresh(favFeed.address, accountViewModel)
+
+    // The DVM is down (or its beats never reach us): the offline banner supersedes the
+    // requesting/error/payment banner, and shows even when last-known content is on screen.
+    if (!heartbeatFresh) {
+        BannerCard(modifier) {
+            BannerMessageRow(
+                message = stringRes(Res.string.dvm_offline_banner),
+                showSpinner = false,
+            )
+        }
+        return
+    }
+
     // Hide the banner when the feed is already populated.
     if (snapshot.ids.isNotEmpty() || snapshot.addresses.isNotEmpty()) return
 
@@ -184,6 +200,23 @@ private fun AllFavoriteAlgoFeedsBanner(
 
     if (addresses.isEmpty()) return
 
+    // Map every address to its freshness first (non-short-circuiting) so per-address
+    // composable call sites stay stable instead of appearing/disappearing with freshness.
+    val anyHeartbeatFresh =
+        addresses
+            .map { address ->
+                rememberDvmHeartbeatFresh(address, accountViewModel).value
+            }.any { it }
+    if (!anyHeartbeatFresh) {
+        BannerCard(modifier) {
+            BannerMessageRow(
+                message = stringRes(Res.string.dvm_offline_banner),
+                showSpinner = false,
+            )
+        }
+        return
+    }
+
     // Observe each DVM's snapshot so we can decide whether to hide the banner
     // based on the aggregate state. Hide it as soon as any DVM has produced a
     // feed; only error out when every one of them has errored.

amethyst/src/test/java/com/vitorpamplona/amethyst/model/DvmHeartbeatTest.kt

@@ -0,0 +1,182 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.model
+
+import com.vitorpamplona.quartz.nip01Core.core.Address
+import com.vitorpamplona.quartz.nip89AppHandlers.definition.AppDefinitionEvent
+import com.vitorpamplona.quartz.nip90Dvms.dvmHeartbeat.DvmHeartbeatEvent
+import com.vitorpamplona.quartz.utils.TimeUtils
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertFalse
+import org.junit.Assert.assertNull
+import org.junit.Assert.assertTrue
+import org.junit.Test
+
+/**
+ * `LocalCache` is a process-wide object and JUnit 4 runs methods in hash order, so every test
+ * uses its own pubkeys/dTags/ids (same discipline as ReportNamingIndexIngestionTest).
+ */
+class DvmHeartbeatTest {
+    private val appDefPubKey = "f1".repeat(32)
+
+    private fun appDef(
+        dTag: String,
+        pubKey: String = appDefPubKey,
+    ) = AppDefinitionEvent(
+        id = "f2".repeat(32),
+        pubKey = pubKey,
+        createdAt = 1_760_000_000L,
+        tags = arrayOf(arrayOf("d", dTag), arrayOf("k", "5300")),
+        content = """{"name":"Test DVM"}""",
+        sig = "cc".repeat(64),
+    )
+
+    private fun beat(
+        dTag: String,
+        pubKey: String = appDefPubKey,
+        createdAt: Long,
+        id: String,
+    ) = DvmHeartbeatEvent(
+        id = id,
+        pubKey = pubKey,
+        createdAt = createdAt,
+        tags =
+            arrayOf(
+                arrayOf("d", dTag),
+                arrayOf("status", "My heart keeps beating like a hammer"),
+                arrayOf("expiration", (createdAt + 300).toString()),
+            ),
+        content = "Alive and kicking",
+        sig = "dd".repeat(64),
+    )
+
+    @Test
+    fun aConsumedHeartbeatLandsAtTheAnnouncementMirrorAddress() {
+        val app = appDef("dvm-one")
+        LocalCache.justConsume(beat("dvm-one", createdAt = 1_760_000_100L, id = "f3".repeat(32)), null, true)
+
+        val found = LocalCache.dvmHeartbeatOf(app)
+        assertTrue("heartbeat should be found via the announcement's address", found != null)
+        assertEquals(1_760_000_100L, found?.createdAt)
+        assertEquals(Address(11998, appDefPubKey, "dvm-one"), found?.address())
+    }
+
+    @Test
+    fun aFreshHeartbeatPassesTheGateAndAStaleOneDoesNot() {
+        val now = 1_760_000_000L
+        // Separate dTags: consumeBaseReplaceable only accepts NEWER beats per address, so a
+        // 901s-old beat could never supersede the 900s one within a single address slot.
+        val freshApp = appDef("dvm-two-fresh")
+        val staleApp = appDef("dvm-two-stale")
+        assertNull("no beat yet", LocalCache.dvmHeartbeatOf(freshApp))
+
+        LocalCache.justConsume(beat("dvm-two-fresh", createdAt = now - 900, id = "f4".repeat(32)), null, true)
+        LocalCache.justConsume(beat("dvm-two-stale", createdAt = now - 901, id = "f5".repeat(32)), null, true)
+
+        assertTrue("exactly 900s old counts as fresh", LocalCache.hasFreshDvmHeartbeat(freshApp, now))
+        assertFalse("901s old is stale", LocalCache.hasFreshDvmHeartbeat(staleApp, now))
+    }
+
+    @Test
+    fun theNewestBeatPerAddressWins() {
+        val now = 1_760_000_000L
+        val app = appDef("dvm-three")
+        LocalCache.justConsume(beat("dvm-three", createdAt = now - 600, id = "f6".repeat(32)), null, true)
+        LocalCache.justConsume(beat("dvm-three", createdAt = now - 60, id = "f7".repeat(32)), null, true)
+
+        assertEquals(now - 60, LocalCache.dvmHeartbeatOf(app)?.createdAt)
+    }
+
+    @Test
+    fun beatsAreKeyedByDTagSoDifferentDvmsDoNotCollide() {
+        val now = 1_760_000_000L
+        val appA = appDef("dvm-a")
+        val appB = appDef("dvm-b")
+        LocalCache.justConsume(beat("dvm-a", createdAt = now - 60, id = "f8".repeat(32)), null, true)
+
+        assertTrue(LocalCache.hasFreshDvmHeartbeat(appA, now))
+        assertFalse("no beat for dvm-b", LocalCache.hasFreshDvmHeartbeat(appB, now))
+    }
+
+    @Test
+    fun noHeartbeatMeansNoLiveness() {
+        assertFalse(LocalCache.hasFreshDvmHeartbeat(appDef("dvm-never"), TimeUtils.now()))
+    }
+
+    @Test
+    fun theGateSurvivesWeakCacheEvictionOfTheBeatNote() {
+        // Beat notes live in LocalCache's WeakReference store with no strong holder on the
+        // Discover screen — a GC sweep clears them all at once and the list collapses. The
+        // freshness gate must therefore read the strong registry, not the evictable note.
+        val app = appDef("dvm-registry")
+        DvmHeartbeatRegistry.record(Address(DvmHeartbeatEvent.KIND, appDefPubKey, "dvm-registry"), 1_760_000_000L - 100)
+
+        assertTrue("registry alone proves liveness", LocalCache.hasFreshDvmHeartbeat(app, 1_760_000_000L))
+        assertTrue("no entry for dvm-never", DvmHeartbeatRegistry.latestAt(Address(DvmHeartbeatEvent.KIND, appDefPubKey, "dvm-never")) == null)
+    }
+
+    @Test
+    fun theUngatedAnnouncementScanKeepsDvmsTheGateWouldHide() {
+        // The outbox fetcher must source announcements from the cache, NOT from the gated feed
+        // list: a DVM dropped for a stale beat must keep receiving outbox beats or it can never
+        // come back. Subscription apps and non-content-discovery apps stay excluded.
+        val alive = appDef("scan-dvm")
+        val subscriptionApp =
+            AppDefinitionEvent(
+                id = "c0".repeat(32),
+                pubKey = "ab".repeat(32),
+                createdAt = 1_760_000_500L,
+                tags = arrayOf(arrayOf("d", "subs"), arrayOf("k", "5300")),
+                content = """{"name":"Paid","subscription":true}""",
+                sig = "cc".repeat(64),
+            )
+        val nonDiscoveryApp =
+            AppDefinitionEvent(
+                id = "c1".repeat(32),
+                pubKey = "cb".repeat(32),
+                createdAt = 1_760_000_100L,
+                tags = arrayOf(arrayOf("d", "other"), arrayOf("k", "9999")),
+                content = """{"name":"Other"}""",
+                sig = "cc".repeat(64),
+            )
+
+        LocalCache.justConsume(appDef("dvm-x"), null, true)
+        LocalCache.justConsume(nonDiscoveryApp, null, true)
+        val consumed =
+            AppDefinitionEvent(
+                id = "c2".repeat(32),
+                pubKey = appDefPubKey,
+                createdAt = 1_760_000_000L,
+                tags = arrayOf(arrayOf("d", "subs2"), arrayOf("k", "5300")),
+                content = """{"name":"Paid2","subscription":true}""",
+                sig = "cc".repeat(64),
+            )
+        LocalCache.justConsume(consumed, null, true)
+
+        val scanned = LocalCache.cachedDvmAnnouncements()
+
+        assertTrue("dvm-x is not yet visible (no beat) but must still be sourced", scanned.any { it.dTag() == "dvm-x" })
+        assertFalse("subscription apps are not content-discovery DVMs", scanned.any { it.dTag() == "subs" })
+        assertFalse("k=9999 apps are not content-discovery DVMs", scanned.any { it.dTag() == "other" })
+        assertEquals("newest-first so the cap keeps the most relevant announcements", scanned.sortedByDescending { it.createdAt }, scanned)
+        assertTrue("capped", scanned.size <= 100)
+    }
+}

commons/src/commonMain/composeResources/values/strings.xml

@@ -2226,6 +2226,8 @@
     <string name="dvm_home_status_payment_required">This feed algorithm requires payment</string>
     <string name="dvm_home_status_error">The feed algorithm returned an error</string>
     <string name="dvm_home_retry">Retry</string>
+    <string name="dvm_offline">Offline</string>
+    <string name="dvm_offline_banner">This feed algorithm has not sent a heartbeat recently and may be down</string>
     <string name="temporary_account">Log off on device lock</string>
     <string name="group_relay">Chat Relay</string>
     <string name="share_image">Share image…</string>

commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/model/topNavFeeds/IFeedTopNavPerRelayFilterSet.kt

@@ -35,4 +35,15 @@ interface IFeedTopNavPerRelayFilterSet {
      * so it carries only the slice that applies to it.
      */
     fun scopeFor(relay: NormalizedRelayUrl): IFeedTopNavPerRelayFilter?
+
+    /**
+     * The relays this selection's subscriptions should be issued on, regardless of whether the
+     * selection's per-kind filter dispatch produces a filter for each of them.
+     *
+     * Consumers that must stay alive across every selection — the DVM heartbeat REQ, whose beats
+     * keep the cached discovery list's liveness gate fresh — read this instead of deriving relays
+     * from the per-kind filters, which silently skip relays whose per-relay slice is empty and
+     * whole selections (the Relay variant) that dispatch no content filters at all.
+     */
+    fun relays(): Set<NormalizedRelayUrl>
 }

commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/model/topNavFeeds/allFollows/AllFollowsTopNavPerRelayFilterSet.kt

@@ -27,4 +27,6 @@ class AllFollowsTopNavPerRelayFilterSet(
     val set: Map<NormalizedRelayUrl, AllFollowsTopNavPerRelayFilter>,
 ) : IFeedTopNavPerRelayFilterSet {
     override fun scopeFor(relay: NormalizedRelayUrl) = set[relay]
+
+    override fun relays() = set.keys
 }

commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/model/topNavFeeds/aroundMe/LocationTopNavPerRelayFilterSet.kt

@@ -27,4 +27,6 @@ class LocationTopNavPerRelayFilterSet(
     val set: Map<NormalizedRelayUrl, LocationTopNavPerRelayFilter>,
 ) : IFeedTopNavPerRelayFilterSet {
     override fun scopeFor(relay: NormalizedRelayUrl) = set[relay]
+
+    override fun relays() = set.keys
 }

commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/model/topNavFeeds/favoriteAlgoFeeds/FavoriteAlgoFeedTopNavPerRelayFilterSet.kt

@@ -43,4 +43,6 @@ class FavoriteAlgoFeedTopNavPerRelayFilterSet(
     // Only the content half is per-relay. [listenRelays] is where the DVMs answer, which is a
     // delivery address rather than a scope, so a filter aimed there carries none.
     override fun scopeFor(relay: NormalizedRelayUrl) = contentFetches[relay]
+
+    override fun relays() = contentFetches.keys
 }

commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/model/topNavFeeds/global/GlobalTopNavPerRelayFilterSet.kt

@@ -27,4 +27,6 @@ class GlobalTopNavPerRelayFilterSet(
     val set: Map<NormalizedRelayUrl, GlobalTopNavPerRelayFilter>,
 ) : IFeedTopNavPerRelayFilterSet {
     override fun scopeFor(relay: NormalizedRelayUrl) = set[relay]
+
+    override fun relays() = set.keys
 }

commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/model/topNavFeeds/hashtag/HashtagTopNavPerRelayFilterSet.kt

@@ -27,4 +27,6 @@ class HashtagTopNavPerRelayFilterSet(
     val set: Map<NormalizedRelayUrl, HashtagTopNavPerRelayFilter>,
 ) : IFeedTopNavPerRelayFilterSet {
     override fun scopeFor(relay: NormalizedRelayUrl) = set[relay]
+
+    override fun relays() = set.keys
 }

commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/model/topNavFeeds/noteBased/allcommunities/AllCommunitiesTopNavPerRelayFilterSet.kt

@@ -27,4 +27,6 @@ class AllCommunitiesTopNavPerRelayFilterSet(
     val set: Map<NormalizedRelayUrl, AllCommunitiesTopNavPerRelayFilter>,
 ) : IFeedTopNavPerRelayFilterSet {
     override fun scopeFor(relay: NormalizedRelayUrl) = set[relay]
+
+    override fun relays() = set.keys
 }

commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/model/topNavFeeds/noteBased/author/AuthorsTopNavPerRelayFilterSet.kt

@@ -27,4 +27,6 @@ class AuthorsTopNavPerRelayFilterSet(
     val set: Map<NormalizedRelayUrl, AuthorsTopNavPerRelayFilter>,
 ) : IFeedTopNavPerRelayFilterSet {
     override fun scopeFor(relay: NormalizedRelayUrl) = set[relay]
+
+    override fun relays() = set.keys
 }

commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/model/topNavFeeds/noteBased/community/SingleCommunityTopNavPerRelayFilterSet.kt

@@ -27,4 +27,6 @@ class SingleCommunityTopNavPerRelayFilterSet(
     val set: Map<NormalizedRelayUrl, SingleCommunityTopNavPerRelayFilter>,
 ) : IFeedTopNavPerRelayFilterSet {
     override fun scopeFor(relay: NormalizedRelayUrl) = set[relay]
+
+    override fun relays() = set.keys
 }

commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/model/topNavFeeds/noteBased/muted/MutedAuthorsTopNavPerRelayFilterSet.kt

@@ -27,4 +27,6 @@ class MutedAuthorsTopNavPerRelayFilterSet(
     val set: Map<NormalizedRelayUrl, MutedAuthorsTopNavPerRelayFilter>,
 ) : IFeedTopNavPerRelayFilterSet {
     override fun scopeFor(relay: NormalizedRelayUrl) = set[relay]
+
+    override fun relays() = set.keys
 }

commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/model/topNavFeeds/relay/RelayTopNavPerRelayFilterSet.kt

@@ -30,4 +30,6 @@ class RelayTopNavPerRelayFilterSet(
     // The relay *is* the whole selection here, so there is nothing per-relay left to say — the
     // filter's own relay already carries it.
     override fun scopeFor(relay: NormalizedRelayUrl): IFeedTopNavPerRelayFilter? = null
+
+    override fun relays() = setOf(relayUrl)
 }

commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/model/topNavFeeds/unknown/UnknownTopNavPerRelayFilterSet.kt

@@ -26,4 +26,6 @@ import com.vitorpamplona.quartz.nip01Core.relay.normalizer.NormalizedRelayUrl
 
 object UnknownTopNavPerRelayFilterSet : IFeedTopNavPerRelayFilterSet {
     override fun scopeFor(relay: NormalizedRelayUrl): IFeedTopNavPerRelayFilter? = null
+
+    override fun relays() = emptySet<NormalizedRelayUrl>()
 }

commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/relayClient/discover/DiscoveryFilterAssembler.kt

@@ -23,6 +23,8 @@ package com.vitorpamplona.amethyst.commons.relayClient.discover
 import com.vitorpamplona.amethyst.commons.model.IAccount
 import com.vitorpamplona.amethyst.commons.model.topNavFeeds.IFeedTopNavPerRelayFilterSet
 import com.vitorpamplona.amethyst.commons.model.topNavFeeds.TopFilter
+import com.vitorpamplona.amethyst.commons.relayClient.discover.nip90DVMs.DiscoveryDvmHeartbeatSubAssembler
+import com.vitorpamplona.amethyst.commons.relayClient.discover.nip90DVMs.DvmHeartbeatSources
 import com.vitorpamplona.amethyst.commons.relayClient.topNavFeeds.TopNavFeedFilterAssembler
 import com.vitorpamplona.amethyst.commons.relayClient.topNavFeeds.TopNavFeedQueryState
 import com.vitorpamplona.amethyst.commons.ui.feeds.FeedContentState
@@ -56,10 +58,12 @@ class DiscoveryQueryState(
 
 class DiscoveryFilterAssembler(
     client: INostrClient,
+    dvmHeartbeat: DvmHeartbeatSources,
 ) : TopNavFeedFilterAssembler<DiscoveryQueryState>({ keys ->
         listOf(
             DiscoveryLongFormClassifiedsAndDVMSubAssembler1(client, keys),
             DiscoveryFollowsSetsAndLiveStreamsSubAssembler2(client, keys),
             DiscoveryPublicChatsAndCommunitiesSubAssembler3(client, keys),
+            DiscoveryDvmHeartbeatSubAssembler(client, keys, dvmHeartbeat),
         )
     })

commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/relayClient/discover/nip90DVMs/DvmHeartbeatOutboxSubAssembler.kt

@@ -0,0 +1,138 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.commons.relayClient.discover.nip90DVMs
+
+import com.vitorpamplona.amethyst.commons.relayClient.discover.DiscoveryQueryState
+import com.vitorpamplona.amethyst.commons.relayClient.subscriptions.ExplainedFilter
+import com.vitorpamplona.amethyst.commons.relayClient.subscriptions.SubPurpose
+import com.vitorpamplona.amethyst.commons.relayClient.topNavFeeds.TopNavFeedSubAssembler
+import com.vitorpamplona.amethyst.commons.relays.SincePerRelayMap
+import com.vitorpamplona.quartz.nip01Core.core.HexKey
+import com.vitorpamplona.quartz.nip01Core.relay.client.INostrClient
+import com.vitorpamplona.quartz.nip01Core.relay.client.pool.RelayBasedFilter
+import com.vitorpamplona.quartz.nip01Core.relay.normalizer.NormalizedRelayUrl
+import com.vitorpamplona.quartz.nip89AppHandlers.definition.AppDefinitionEvent
+import com.vitorpamplona.quartz.nip90Dvms.dvmHeartbeat.DvmHeartbeatEvent
+import com.vitorpamplona.quartz.utils.TimeUtils
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.StateFlow
+
+/** How many DVM outbox relays the fetcher may open at once; coverage-ranked, so the top relays carry most authors. */
+private const val MAX_OUTBOX_RELAYS = 12
+
+/**
+ * Batches the announcement authors per DVM outbox relay so the freshness gate sees the beats the
+ * DVMs actually publish. DVMs send heartbeats to their own write relays, which need not overlap
+ * the user's discovery relays — the global heartbeat REQ (issued on the selection's relays) alone
+ * leaves alive DVMs invisible. Their beats exist on the outbox; this fetcher brings them into the
+ * same cache slots the gate reads.
+ *
+ * Authors with no known outbox are skipped, not blocked: the global REQ is their fallback.
+ * Relays are coverage-ranked and capped at [maxRelays] so browsing Discover cannot open dozens
+ * of sockets; deterministic tie-breaking keeps the chosen set stable across re-issues.
+ */
+fun dvmHeartbeatOutboxFilters(
+    announcements: List<AppDefinitionEvent>,
+    outboxRelaysFor: (HexKey) -> Collection<NormalizedRelayUrl>,
+    now: Long,
+    maxRelays: Int = MAX_OUTBOX_RELAYS,
+): List<RelayBasedFilter> {
+    if (announcements.isEmpty()) return emptyList()
+
+    val authorsByRelay = mutableMapOf<NormalizedRelayUrl, MutableList<HexKey>>()
+    announcements.forEach { app ->
+        outboxRelaysFor(app.pubKey).forEach { relay ->
+            authorsByRelay.getOrPut(relay) { mutableListOf() }.add(app.pubKey)
+        }
+    }
+    if (authorsByRelay.isEmpty()) return emptyList()
+
+    val since = now - DvmHeartbeatEvent.MAX_AGE_SECONDS
+    return authorsByRelay
+        .entries
+        .sortedWith(
+            compareByDescending<MutableMap.MutableEntry<NormalizedRelayUrl, MutableList<HexKey>>> { it.value.size }
+                .thenBy { it.key.url },
+        ).take(maxRelays)
+        .map { (relay, authors) ->
+            val covered = authors.distinct().sorted()
+            RelayBasedFilter(
+                relay = relay,
+                filter =
+                    ExplainedFilter(
+                        purpose = SubPurpose.DISCOVER_FEED,
+                        kinds = listOf(DvmHeartbeatEvent.KIND),
+                        authors = covered,
+                        limit = covered.size,
+                        since = since,
+                    ),
+            )
+        }
+}
+
+/**
+ * Cache-backed inputs the outbox fetcher needs, provided by the front end (the cache query and
+ * relay-hint surface are platform caches, not commons).
+ *
+ * [announcements] MUST be the ungated announcement set (every cached content-discovery DVM). The
+ * gated feed list would turn any transient staleness into a permanent drop: a DVM leaves the
+ * gated list the moment its beat ages out, the fetcher would stop covering it, and no beat would
+ * ever arrive to bring it back.
+ *
+ * [outboxRelaysFor] resolves where a DVM publishes its beats — NIP-65 outbox relays plus any
+ * relay hints for the author (the same mix the event finder uses).
+ *
+ * [changes] drive re-issues: when the cached announcement set or the outbox data moves, the
+ * batches are recomputed.
+ */
+class DvmHeartbeatSources(
+    val announcements: () -> List<AppDefinitionEvent>,
+    val outboxRelaysFor: (HexKey) -> Collection<NormalizedRelayUrl>,
+    val changes: List<Flow<*>>,
+)
+
+/**
+ * The discovery-side subscription that runs [dvmHeartbeatOutboxFilters] for the cached
+ * announcement set, alive while the Discover screen is composed (it joins the same assembler
+ * group and lifecycle as the other discovery sub-assemblers).
+ *
+ * No floor collectors ([floors] is empty) — the announcement set and outbox data ([changes]) are
+ * the drivers, not note timestamps.
+ */
+class DiscoveryDvmHeartbeatSubAssembler(
+    client: INostrClient,
+    allKeys: () -> Set<DiscoveryQueryState>,
+    private val sources: DvmHeartbeatSources,
+) : TopNavFeedSubAssembler<DiscoveryQueryState>(client, allKeys) {
+    override fun updateFilter(
+        key: DiscoveryQueryState,
+        since: SincePerRelayMap?,
+    ): List<RelayBasedFilter> =
+        dvmHeartbeatOutboxFilters(
+            sources.announcements(),
+            outboxRelaysFor = sources.outboxRelaysFor,
+            now = TimeUtils.now(),
+        )
+
+    override fun floors(key: DiscoveryQueryState): List<StateFlow<Long?>> = emptyList()
+
+    override fun extraInvalidators(key: DiscoveryQueryState): List<Flow<*>> = sources.changes
+}

commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/relayClient/discover/nip90DVMs/SubAssemblyHelper.kt

@@ -36,9 +36,13 @@ import com.vitorpamplona.amethyst.commons.relayClient.discover.nip90DVMs.filterC
 import com.vitorpamplona.amethyst.commons.relayClient.discover.nip90DVMs.filterContentDVMsByGeohash
 import com.vitorpamplona.amethyst.commons.relayClient.discover.nip90DVMs.filterContentDVMsByHashtag
 import com.vitorpamplona.amethyst.commons.relayClient.discover.nip90DVMs.filterContentDVMsGlobal
+import com.vitorpamplona.amethyst.commons.relayClient.subscriptions.ExplainedFilter
+import com.vitorpamplona.amethyst.commons.relayClient.subscriptions.SubPurpose
 import com.vitorpamplona.amethyst.commons.relayClient.subscriptions.scopedTo
 import com.vitorpamplona.amethyst.commons.relays.SincePerRelayMap
 import com.vitorpamplona.quartz.nip01Core.relay.client.pool.RelayBasedFilter
+import com.vitorpamplona.quartz.nip90Dvms.dvmHeartbeat.DvmHeartbeatEvent
+import com.vitorpamplona.quartz.utils.TimeUtils
 
 fun makeContentDVMsFilter(
     feedSettings: IFeedTopNavPerRelayFilterSet,
@@ -55,4 +59,34 @@ fun makeContentDVMsFilter(
         is MutedAuthorsTopNavPerRelayFilterSet -> filterContentDVMsByAuthors(feedSettings, since, defaultSince)
         is SingleCommunityTopNavPerRelayFilterSet -> filterContentDVMsByCommunity(feedSettings, since, defaultSince)
         else -> emptyList()
+    }.let { contentDvmFilters ->
+        plusHeartbeatFilter(feedSettings, contentDvmFilters)
     }.scopedTo(feedSettings)
+
+/**
+ * The 31990 announcements say what a DVM advertises; kind-11998 heartbeats say whether it is
+ * still alive (amethyst/plans/2026-09-10-dvm-heartbeat-liveness.md). Ask on the selection's own
+ * relays — NOT the 31990 filters' relays, which skip relays whose per-relay slice is empty and
+ * whole selections (the Relay variant) that dispatch no 31990 filters at all; there the cached
+ * DVM list would lose its beat stream and the staleness timer would drop every DVM within ~7
+ * minutes. Rolling window instead of the announcement cursor: beats expire (NIP-40) every 5
+ * minutes, so a stored `since` would miss beats on re-opened tabs.
+ */
+private fun plusHeartbeatFilter(
+    feedSettings: IFeedTopNavPerRelayFilterSet,
+    contentDvmFilters: List<RelayBasedFilter>,
+): List<RelayBasedFilter> {
+    val relays = feedSettings.relays()
+    if (relays.isEmpty()) return contentDvmFilters
+    val heartbeatFilter =
+        ExplainedFilter(
+            purpose = SubPurpose.DISCOVER_FEED,
+            kinds = listOf(DvmHeartbeatEvent.KIND),
+            limit = 100,
+            since = TimeUtils.now() - DvmHeartbeatEvent.MAX_AGE_SECONDS,
+        )
+    return contentDvmFilters +
+        relays.map { relay ->
+            RelayBasedFilter(relay = relay, filter = heartbeatFilter)
+        }
+}

commons/src/commonTest/kotlin/com/vitorpamplona/amethyst/commons/relayClient/discover/nip90DVMs/DvmHeartbeatOutboxFiltersTest.kt

@@ -0,0 +1,120 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.commons.relayClient.discover.nip90DVMs
+
+import com.vitorpamplona.quartz.nip01Core.core.HexKey
+import com.vitorpamplona.quartz.nip01Core.relay.normalizer.NormalizedRelayUrl
+import com.vitorpamplona.quartz.nip01Core.relay.normalizer.RelayUrlNormalizer
+import com.vitorpamplona.quartz.nip89AppHandlers.definition.AppDefinitionEvent
+import com.vitorpamplona.quartz.nip90Dvms.dvmHeartbeat.DvmHeartbeatEvent
+import kotlin.test.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertTrue
+
+/**
+ * DVMs publish heartbeats to their own outbox relays, which may not overlap the user's discovery
+ * relays at all — so the global heartbeat REQ alone leaves alive DVMs invisible (their beats never
+ * reach the cache the freshness gate reads). The outbox fetcher batches the announcement authors
+ * per DVM outbox relay so the gate sees the beats the DVMs actually publish.
+ */
+class DvmHeartbeatOutboxFiltersTest {
+    private val r1 = RelayUrlNormalizer.normalizeOrNull("wss://r1.example/")!!
+    private val r2 = RelayUrlNormalizer.normalizeOrNull("wss://r2.example/")!!
+    private val r3 = RelayUrlNormalizer.normalizeOrNull("wss://r3.example/")!!
+
+    private fun announcement(pubKey: HexKey) =
+        AppDefinitionEvent(
+            id = pubKey.take(16) + "a".repeat(48),
+            pubKey = pubKey,
+            createdAt = 1_760_000_000L,
+            tags = arrayOf(arrayOf("d", "dvm"), arrayOf("k", "5300")),
+            content = """{"name":"DVM"}""",
+            sig = "b".repeat(128),
+        )
+
+    private val authorA = "aa".repeat(32)
+    private val authorB = "bb".repeat(32)
+    private val authorC = "cc".repeat(32)
+
+    private val outboxes: (HexKey) -> Set<NormalizedRelayUrl> =
+        {
+            when (it) {
+                authorA -> setOf(r1, r2)
+                authorB -> setOf(r1, r3)
+                else -> emptySet()
+            }
+        }
+
+    @Test
+    fun batchesAnnouncementAuthorsPerOutboxRelay() {
+        val filters =
+            dvmHeartbeatOutboxFilters(
+                announcements = listOf(announcement(authorA), announcement(authorB), announcement(authorC)),
+                outboxRelaysFor = outboxes,
+                now = 1_760_000_420L,
+            )
+
+        assertEquals(3, filters.size, "r1 carries A+B, r2 carries A, r3 carries B; author C has no outbox")
+
+        val authorsOn = { relay: String -> filters.first { it.relay.url == relay }.filter.authors }
+
+        assertEquals(setOf(authorA, authorB), authorsOn(r1.url)?.toSet())
+        assertEquals(setOf(authorA), authorsOn(r2.url)?.toSet())
+        assertEquals(setOf(authorB), authorsOn(r3.url)?.toSet())
+
+        filters.forEach {
+            assertEquals(listOf(DvmHeartbeatEvent.KIND), it.filter.kinds)
+            assertEquals(1_759_999_520L, it.filter.since, "rolling window: now - MAX_AGE_SECONDS")
+        }
+    }
+
+    @Test
+    fun anAuthorWithNoKnownOutboxIsSkippedNotBlocked() {
+        val filters =
+            dvmHeartbeatOutboxFilters(
+                announcements = listOf(announcement(authorC)),
+                outboxRelaysFor = outboxes,
+                now = 1_760_000_420L,
+            )
+
+        assertTrue(filters.isEmpty(), "no outbox known — the global REQ is that DVM's fallback")
+    }
+
+    @Test
+    fun relayCapKeepsTheMostCoveringRelays() {
+        val filters =
+            dvmHeartbeatOutboxFilters(
+                announcements = listOf(announcement(authorA), announcement(authorB)),
+                outboxRelaysFor = outboxes,
+                now = 1_760_000_420L,
+                maxRelays = 2,
+            )
+
+        assertEquals(setOf(r1.url, r2.url), filters.map { it.relay.url }.toSet(), "r1 covers 2, r2 and r3 tie at 1 — tie broken deterministically")
+    }
+
+    @Test
+    fun noAnnouncementsMeansNoRequests() {
+        assertTrue(
+            dvmHeartbeatOutboxFilters(emptyList(), outboxRelaysFor = outboxes, now = 1_760_000_420L).isEmpty(),
+        )
+    }
+}

commons/src/commonTest/kotlin/com/vitorpamplona/amethyst/commons/relayClient/discover/nip90DVMs/MakeContentDVMsFilterTest.kt

@@ -0,0 +1,101 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.commons.relayClient.discover.nip90DVMs
+
+import com.vitorpamplona.amethyst.commons.model.topNavFeeds.global.GlobalTopNavPerRelayFilter
+import com.vitorpamplona.amethyst.commons.model.topNavFeeds.global.GlobalTopNavPerRelayFilterSet
+import com.vitorpamplona.amethyst.commons.model.topNavFeeds.noteBased.author.AuthorsTopNavPerRelayFilter
+import com.vitorpamplona.amethyst.commons.model.topNavFeeds.noteBased.author.AuthorsTopNavPerRelayFilterSet
+import com.vitorpamplona.amethyst.commons.model.topNavFeeds.relay.RelayTopNavPerRelayFilterSet
+import com.vitorpamplona.amethyst.commons.relayClient.subscriptions.ExplainedFilter
+import com.vitorpamplona.quartz.nip01Core.relay.normalizer.RelayUrlNormalizer
+import com.vitorpamplona.quartz.nip89AppHandlers.definition.AppDefinitionEvent
+import com.vitorpamplona.quartz.nip90Dvms.dvmHeartbeat.DvmHeartbeatEvent
+import kotlin.test.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertTrue
+
+/**
+ * The DVM discovery list renders cached kind-31990 announcements on EVERY top-nav selection, and
+ * its freshness gate needs kind-11998 heartbeats to keep flowing. A selection whose per-relay set
+ * dispatches to no 31990 filter (the Relay variant; a relay whose author set is momentarily empty)
+ * must still issue the heartbeat REQ — otherwise cached beats age out and the 60s staleness timer
+ * drops every DVM within ~7 minutes (the "DVMs disappear after a while" bug).
+ */
+class MakeContentDVMsFilterTest {
+    private val relay = RelayUrlNormalizer.normalizeOrNull("wss://relay.example/")!!
+    private val otherRelay = RelayUrlNormalizer.normalizeOrNull("wss://other.example/")!!
+
+    @Test
+    fun relayVariantIssuesTheHeartbeatFilterEvenWithoutAnnouncementFilters() {
+        val filters = makeContentDVMsFilter(RelayTopNavPerRelayFilterSet(relay), null, null)
+
+        assertEquals(1, filters.size, "the Relay variant has no 31990 filter but must get the heartbeat REQ")
+        assertEquals(relay, filters.first().relay)
+        assertEquals(listOf(DvmHeartbeatEvent.KIND), (filters.first().filter as? ExplainedFilter)?.kinds)
+    }
+
+    @Test
+    fun globalVariantKeepsAnnouncementFiltersAndGainsTheHeartbeatFilter() {
+        val filters =
+            makeContentDVMsFilter(
+                GlobalTopNavPerRelayFilterSet(mapOf(relay to GlobalTopNavPerRelayFilter)),
+                null,
+                null,
+            )
+
+        val byKind =
+            filters
+                .groupBy { it.filter.kinds }
+                .mapValues { entry -> entry.value.map { it.relay } }
+
+        assertEquals(listOf(relay), byKind[listOf(AppDefinitionEvent.KIND)], "31990 REQ unchanged")
+        assertEquals(listOf(relay), byKind[listOf(DvmHeartbeatEvent.KIND)], "heartbeat REQ rides the same relay")
+    }
+
+    @Test
+    fun authorVariantRelayWithNoAuthorsStillGetsTheHeartbeatFilter() {
+        val filters =
+            makeContentDVMsFilter(
+                AuthorsTopNavPerRelayFilterSet(
+                    mapOf(
+                        relay to AuthorsTopNavPerRelayFilter(emptySet()),
+                        otherRelay to AuthorsTopNavPerRelayFilter(setOf("a".repeat(64))),
+                    ),
+                ),
+                null,
+                null,
+            )
+
+        val heartbeatRelays =
+            filters
+                .filter { it.filter.kinds == listOf(DvmHeartbeatEvent.KIND) }
+                .map { it.relay }
+                .sortedBy { it.url }
+
+        assertEquals(
+            listOf(otherRelay, relay).sortedBy { it.url },
+            heartbeatRelays,
+            "a relay whose author set is empty skips the 31990 REQ but must not skip the heartbeat REQ",
+        )
+        assertTrue(filters.any { it.filter.kinds == listOf(AppDefinitionEvent.KIND) && it.relay == otherRelay })
+    }
+}

quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nip90Dvms/dvmHeartbeat/DvmHeartbeatEvent.kt

@@ -0,0 +1,84 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.quartz.nip90Dvms.dvmHeartbeat
+
+import androidx.compose.runtime.Immutable
+import androidx.compose.runtime.Stable
+import com.vitorpamplona.quartz.nip01Core.core.BaseAddressableEvent
+import com.vitorpamplona.quartz.nip01Core.core.HexKey
+import com.vitorpamplona.quartz.nip01Core.signers.EventTemplate
+import com.vitorpamplona.quartz.nip01Core.signers.eventTemplate
+import com.vitorpamplona.quartz.nip40Expiration.expiration
+import com.vitorpamplona.quartz.utils.TimeUtils
+
+/**
+ * DVM heartbeat (kind 11998, experimental — no NIP yet): a beat a DVM publishes every 300s to
+ * prove it is alive. The operator contract is plain-text content with `d` (the DVM's NIP-89
+ * DTAG), `status` (free text) and `expiration` (createdAt + 300, NIP-40) tags.
+ *
+ * The kind sits in the replaceable range (10000–19999), so relays keep only the latest beat
+ * per author. The `d` tag participates in the client-side address so each announced DVM has
+ * its own cache slot: `Address(11998, dvmPubKey, dTag)` mirrors the announcement's
+ * `Address(31990, dvmPubKey, dTag)`.
+ */
+@Stable
+@Immutable
+class DvmHeartbeatEvent(
+    id: HexKey,
+    pubKey: HexKey,
+    createdAt: Long,
+    tags: Array<Array<String>>,
+    content: String,
+    sig: HexKey,
+) : BaseAddressableEvent(id, pubKey, createdAt, KIND, tags, content, sig) {
+    fun status(): String? = tags.firstOrNull { it.size > 1 && it[0] == STATUS_TAG }?.get(1)
+
+    fun expiration(): Long? = tags.expiration()
+
+    /** True while this beat still proves liveness at [now]. */
+    fun isFreshAt(now: Long = TimeUtils.now()): Boolean = createdAt >= now - MAX_AGE_SECONDS
+
+    companion object {
+        const val KIND = 11998
+        const val STATUS_TAG = "status"
+        const val CONTENT = "Alive and kicking"
+
+        /**
+         * A beat older than this no longer proves liveness. Beats arrive every 300s, so this
+         * window deliberately tolerates several missed deliveries (relay reconnects, REQ churn)
+         * before a DVM is dropped — hysteresis against transient delivery gaps, at the cost of a
+         * dead DVM lingering this long before disappearing.
+         */
+        const val MAX_AGE_SECONDS = 900
+
+        fun build(
+            dTag: String,
+            status: String,
+            expiration: Long,
+            createdAt: Long = TimeUtils.now(),
+        ): EventTemplate<DvmHeartbeatEvent> =
+            eventTemplate(KIND, CONTENT, createdAt) {
+                add(arrayOf("d", dTag))
+                add(arrayOf(STATUS_TAG, status))
+                add(arrayOf("expiration", expiration.toString()))
+            }
+    }
+}

quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/utils/EventFactory.kt

@@ -358,6 +358,7 @@ import com.vitorpamplona.quartz.nip90Dvms.contentDiscoveryRequest.NIP90ContentDi
 import com.vitorpamplona.quartz.nip90Dvms.contentDiscoveryResponse.NIP90ContentDiscoveryResponseEvent
 import com.vitorpamplona.quartz.nip90Dvms.contentSearch.NIP90ContentSearchRequestEvent
 import com.vitorpamplona.quartz.nip90Dvms.contentSearch.NIP90ContentSearchResponseEvent
+import com.vitorpamplona.quartz.nip90Dvms.dvmHeartbeat.DvmHeartbeatEvent
 import com.vitorpamplona.quartz.nip90Dvms.eventCount.NIP90EventCountRequestEvent
 import com.vitorpamplona.quartz.nip90Dvms.eventCount.NIP90EventCountResponseEvent
 import com.vitorpamplona.quartz.nip90Dvms.eventPowDelegation.NIP90EventPowDelegationRequestEvent
@@ -734,6 +735,7 @@ class EventFactory {
                 NutzapRedemptionEvent.KIND -> NutzapRedemptionEvent(id, pubKey, createdAt, tags, content, sig)
                 NostrConnectEvent.KIND -> NostrConnectEvent(id, pubKey, createdAt, tags, content, sig)
                 NIP90StatusEvent.KIND -> NIP90StatusEvent(id, pubKey, createdAt, tags, content, sig)
+                DvmHeartbeatEvent.KIND -> DvmHeartbeatEvent(id, pubKey, createdAt, tags, content, sig)
                 NIP90TextExtractionRequestEvent.KIND -> NIP90TextExtractionRequestEvent(id, pubKey, createdAt, tags, content, sig)
                 NIP90TextExtractionResponseEvent.KIND -> NIP90TextExtractionResponseEvent(id, pubKey, createdAt, tags, content, sig)
                 NIP90SummarizationRequestEvent.KIND -> NIP90SummarizationRequestEvent(id, pubKey, createdAt, tags, content, sig)

quartz/src/commonTest/kotlin/com/vitorpamplona/quartz/nip90Dvms/dvmHeartbeat/DvmHeartbeatEventTest.kt

@@ -0,0 +1,133 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.quartz.nip90Dvms.dvmHeartbeat
+
+import com.vitorpamplona.quartz.nip01Core.core.Address
+import com.vitorpamplona.quartz.nip01Core.core.Event
+import com.vitorpamplona.quartz.utils.EventFactory
+import kotlin.test.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertFalse
+import kotlin.test.assertIs
+import kotlin.test.assertNull
+import kotlin.test.assertTrue
+
+class DvmHeartbeatEventTest {
+    private val pubKey = "11".repeat(32)
+    private val dTag = "my-dvm"
+    private val beatTime = 1_760_000_000L
+
+    private fun heartbeat(createdAt: Long = beatTime) =
+        DvmHeartbeatEvent(
+            id = "00".repeat(32),
+            pubKey = pubKey,
+            createdAt = createdAt,
+            tags =
+                arrayOf(
+                    arrayOf("d", dTag),
+                    arrayOf("status", "My heart keeps beating like a hammer"),
+                    arrayOf("expiration", (createdAt + 300).toString()),
+                ),
+            content = "Alive and kicking",
+            sig = "22".repeat(64),
+        )
+
+    @Test
+    fun addressIncludesTheDTag() {
+        val event = heartbeat()
+        assertEquals(dTag, event.dTag())
+        assertEquals(Address(11998, pubKey, dTag), event.address())
+        assertEquals("11998:$pubKey:$dTag", event.addressTag())
+    }
+
+    @Test
+    fun missingDTagFallsBackToEmptyAddress() {
+        val event =
+            DvmHeartbeatEvent(
+                id = "00".repeat(32),
+                pubKey = pubKey,
+                createdAt = beatTime,
+                tags = emptyArray(),
+                content = "Alive and kicking",
+                sig = "22".repeat(64),
+            )
+        assertEquals("", event.dTag())
+        assertEquals(Address(11998, pubKey, ""), event.address())
+    }
+
+    @Test
+    fun readsStatusAndExpiration() {
+        val event = heartbeat()
+        assertEquals("My heart keeps beating like a hammer", event.status())
+        assertEquals(beatTime + 300, event.expiration())
+    }
+
+    @Test
+    fun statusIsOptional() {
+        val event = DvmHeartbeatEvent("00".repeat(32), pubKey, beatTime, arrayOf(arrayOf("d", dTag)), "", "22".repeat(64))
+        assertNull(event.status())
+        assertNull(event.expiration())
+    }
+
+    @Test
+    fun freshnessBoundary() {
+        val event = heartbeat()
+        assertTrue(event.isFreshAt(beatTime + 900))
+        assertFalse(event.isFreshAt(beatTime + 901))
+    }
+
+    @Test
+    fun buildWritesAllTags() {
+        val template =
+            DvmHeartbeatEvent.build(
+                dTag = dTag,
+                status = "My heart keeps beating like a hammer",
+                expiration = beatTime + 300,
+                createdAt = beatTime,
+            )
+        assertEquals(11998, template.kind)
+        assertEquals("Alive and kicking", template.content)
+        assertEquals(
+            listOf(
+                listOf("d", dTag),
+                listOf("status", "My heart keeps beating like a hammer"),
+                listOf("expiration", (beatTime + 300).toString()),
+            ),
+            template.tags.map { it.toList() },
+        )
+    }
+
+    @Test
+    fun factoryBuildsDvmHeartbeatForKind11998() {
+        val event: Event =
+            EventFactory.create(
+                id = "00".repeat(32),
+                pubKey = pubKey,
+                createdAt = beatTime,
+                kind = DvmHeartbeatEvent.KIND,
+                tags = arrayOf(arrayOf("d", dTag)),
+                content = "",
+                sig = "22".repeat(64),
+            )
+        assertIs<DvmHeartbeatEvent>(event)
+        assertTrue(EventFactory.isKnownKind(DvmHeartbeatEvent.KIND), "kind 11998 should be a known kind")
+    }
+}

quartz/src/commonTest/kotlin/com/vitorpamplona/quartz/utils/EventFactoryKindRangeTest.kt

@@ -73,6 +73,9 @@ class EventFactoryKindRangeTest {
             10090,
             10101,
             10102,
+            // DVM heartbeat: the d tag is the DVM's NIP-89 DTAG and keys its client-side
+            // cache address (relay storage stays plain-replaceable per the kind range).
+            11998,
         )
 
     private val probeDTag = "probe-d-tag"

quartz/src/jvmTest/kotlin/com/vitorpamplona/quartz/nip50Search/IndexableContentGoldenTest.kt

@@ -107,7 +107,9 @@ class IndexableContentGoldenTest {
             "a kind's indexed text changed. If deliberate: rerun with -Dgolden=write, update " +
                 "references/searchable-kinds.md in the same commit, and schedule a reindex " +
                 "(IEventStore.reindexFullTextSearch) — existing databases keep their old text.",
-            golden.readText().trim(),
+            // Normalize CRLF: Windows checkouts (autocrlf) would otherwise fail this comparison
+            // on invisible line endings alone.
+            golden.readText().replace("\r\n", "\n").trim(),
             actual.trim(),
         )
     }
@@ -211,6 +213,7 @@ class IndexableContentGoldenTest {
                 10100,
                 10154,
                 11871,
+                11998,
                 12473,
                 15128,
                 15129,

quartz/src/jvmTest/resources/indexable-content.golden

@@ -52,6 +52,7 @@
 10100	
 10154	The Title\nThe Description
 11871	The content body.
+11998	<not searchable>
 12473	The Alt
 15128	The Title\nThe Description
 15129	The Title\nThe Description