Merge pull request #3431 from nrobi144/feat/desktop-hashtag-spam-filter

feat(desktop): hashtag-spam filter with collapse-with-reveal

commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/moderation/DisplayedEvent.kt

@@ -0,0 +1,49 @@
+/*
+ * 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.moderation
+
+import com.vitorpamplona.amethyst.commons.model.Note
+import com.vitorpamplona.quartz.nip01Core.core.Event
+import com.vitorpamplona.quartz.nip18Reposts.GenericRepostEvent
+import com.vitorpamplona.quartz.nip18Reposts.RepostEvent
+
+/**
+ * Returns the event whose body a renderer would actually display.
+ *
+ * For kind 6 / kind 16 reposts that is the *wrapped* inner event — which
+ * the consume pipeline already resolves onto [Note.replyTo]. Falls back to
+ * the slower [RepostEvent.containedPost] / [GenericRepostEvent.containedPost]
+ * JSON decode only when the cache hasn't materialised the reply yet; both
+ * already null-return on parse failure.
+ *
+ * For non-repost events, the displayed event is the note's own event.
+ *
+ * Returns null when there is no event at all (placeholder not yet
+ * hydrated).
+ */
+fun Note.displayedEvent(): Event? {
+    val ev = this.event ?: return null
+    return when (ev) {
+        is RepostEvent -> replyTo?.lastOrNull()?.event ?: ev.containedPost()
+        is GenericRepostEvent -> replyTo?.lastOrNull()?.event ?: ev.containedPost()
+        else -> ev
+    }
+}

commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/moderation/HashtagSpamCheck.kt

@@ -0,0 +1,53 @@
+/*
+ * 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.moderation
+
+import com.vitorpamplona.quartz.nip01Core.core.Event
+import com.vitorpamplona.quartz.nip01Core.core.HexKey
+import com.vitorpamplona.quartz.nip01Core.tags.hashtags.hasMoreHashtagsThan
+import com.vitorpamplona.quartz.nip23LongContent.LongTextNoteEvent
+
+/**
+ * Pure decision: should this note be collapsed because it abuses hashtag `t` tags?
+ *
+ * Reuses [hasMoreHashtagsThan] which short-circuits on total count before
+ * counting unique tags, so a note that repeats the same hashtag does not
+ * trip the filter.
+ *
+ * Long-form articles (kind 30023) legitimately use many topic tags and are
+ * always exempt. Authors whose pubkey appears in [exemptKeys] (the user's
+ * follow list plus self) are also exempt — the caller assembles that set.
+ */
+object HashtagSpamCheck {
+    fun isHashtagSpam(
+        displayedEvent: Event?,
+        authorPubkey: HexKey?,
+        enabled: Boolean,
+        threshold: Int,
+        exemptKeys: Set<HexKey>,
+    ): Boolean {
+        if (!enabled) return false
+        if (displayedEvent == null) return false
+        if (displayedEvent.kind == LongTextNoteEvent.KIND) return false
+        if (authorPubkey != null && authorPubkey in exemptKeys) return false
+        return displayedEvent.tags.hasMoreHashtagsThan(threshold)
+    }
+}

commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/moderation/HashtagSpamSettings.kt

@@ -0,0 +1,48 @@
+/*
+ * 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.moderation
+
+import androidx.compose.runtime.Stable
+import kotlinx.coroutines.flow.StateFlow
+
+/**
+ * User-tunable settings for the hashtag-spam content filter.
+ *
+ * Implementations are platform-specific (Desktop uses java.util.prefs;
+ * Android can use DataStore). Both observables emit on change so Compose
+ * reads via [collectAsState] re-render automatically.
+ */
+@Stable
+interface HashtagSpamSettings {
+    val enabled: StateFlow<Boolean>
+    val threshold: StateFlow<Int>
+
+    fun setEnabled(enabled: Boolean)
+
+    fun setThreshold(threshold: Int)
+
+    companion object {
+        const val MIN_THRESHOLD = 1
+        const val MAX_THRESHOLD = 20
+        const val DEFAULT_THRESHOLD = 5
+        const val DEFAULT_ENABLED = true
+    }
+}

commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/moderation/LocalHashtagSpamSettings.kt

@@ -0,0 +1,43 @@
+/*
+ * 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.moderation
+
+import androidx.compose.runtime.ProvidableCompositionLocal
+import androidx.compose.runtime.compositionLocalOf
+import com.vitorpamplona.quartz.nip01Core.core.HexKey
+
+/**
+ * Settings for the hashtag-spam filter, provided at App() root by each
+ * front end (Desktop, Android). Defaults to an error so missing provision
+ * fails loudly during development; production binaries always wire this.
+ */
+val LocalHashtagSpamSettings: ProvidableCompositionLocal<HashtagSpamSettings> =
+    compositionLocalOf { error("LocalHashtagSpamSettings not provided. Wire it at App() root.") }
+
+/**
+ * Pubkeys exempted from the hashtag-spam check — the active account's
+ * follow set union the active account's own pubkey. Updated by the App()
+ * root whenever the active account changes. Defaults to empty (strict
+ * filter applies to everyone) so leaf composables can read it without a
+ * null check.
+ */
+val LocalSpamExemptKeys: ProvidableCompositionLocal<Set<HexKey>> =
+    compositionLocalOf { emptySet() }

commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/search/SearchParser.kt

@@ -30,8 +30,12 @@ import com.vitorpamplona.quartz.nip19Bech32.entities.NSec
 import com.vitorpamplona.quartz.utils.Hex
 
 /**
- * Parses search input and returns matching results.
- * Supports: npub, nprofile, nsec (extracts pubkey), note, nevent, naddr, hex keys, hashtags
+ * Parses search input for direct-lookup entries: npub, nprofile, nsec
+ * (extracts pubkey), note, nevent, naddr, and 64-char hex keys.
+ *
+ * Hashtags are intentionally NOT returned here — they are handled by
+ * [QueryParser], which extracts `#xxx` tokens into the query's hashtag
+ * filter so the normal results pipeline drives a tag-filtered search.
  *
  * Shared between Android and Desktop for consistent Bech32 parsing.
  */
@@ -41,12 +45,6 @@ fun parseSearchInput(input: String): List<SearchResult> {
     val trimmed = input.trim()
     val results = mutableListOf<SearchResult>()
 
-    // Check for hashtag
-    if (trimmed.startsWith("#") && trimmed.length > 1) {
-        results.add(SearchResult.HashtagResult(trimmed.substring(1)))
-        return results
-    }
-
     // Try to parse as Bech32 (npub, nevent, naddr, etc.)
     val parsed = Nip19Parser.uriToRoute(trimmed)?.entity
     if (parsed != null) {

commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/search/SearchResult.kt

@@ -50,11 +50,4 @@ sealed class SearchResult {
         val dTag: String,
         val displayId: String,
     ) : SearchResult()
-
-    /**
-     * Hashtag search.
-     */
-    data class HashtagResult(
-        val hashtag: String,
-    ) : SearchResult()
 }

commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/ui/note/CollapsedSpamNote.kt

@@ -0,0 +1,92 @@
+/*
+ * 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.ui.note
+
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.Spacer
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.heightIn
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.layout.width
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.Text
+import androidx.compose.material3.TextButton
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.semantics.contentDescription
+import androidx.compose.ui.semantics.semantics
+import androidx.compose.ui.unit.dp
+import com.vitorpamplona.amethyst.commons.ui.components.UserAvatar
+
+/**
+ * Replacement card rendered in place of a normal note when the
+ * hashtag-spam check trips. Scalar params only so it stays reusable across
+ * Desktop, Android, and future iOS without leaking platform display
+ * shapes.
+ */
+@Composable
+fun CollapsedSpamNote(
+    authorPubkeyHex: String,
+    authorDisplayName: String,
+    authorAvatarUrl: String?,
+    hashtagCount: Int,
+    threshold: Int,
+    onReveal: () -> Unit,
+    modifier: Modifier = Modifier,
+) {
+    Row(
+        modifier
+            .fillMaxWidth()
+            .heightIn(min = 56.dp)
+            .padding(horizontal = 12.dp, vertical = 8.dp)
+            .semantics {
+                contentDescription =
+                    "Hidden note from $authorDisplayName, $hashtagCount hashtags. Tap to reveal."
+            },
+        verticalAlignment = Alignment.CenterVertically,
+        horizontalArrangement = Arrangement.spacedBy(8.dp),
+    ) {
+        UserAvatar(
+            userHex = authorPubkeyHex,
+            pictureUrl = authorAvatarUrl,
+            size = 32.dp,
+        )
+        Column(modifier = Modifier.weight(1f)) {
+            Text(
+                text = authorDisplayName.ifBlank { "Hidden note" },
+                style = MaterialTheme.typography.labelLarge,
+                color = MaterialTheme.colorScheme.onSurface,
+            )
+            Text(
+                text = "Filtered: $hashtagCount hashtags · threshold $threshold",
+                style = MaterialTheme.typography.bodySmall,
+                color = MaterialTheme.colorScheme.onSurfaceVariant,
+            )
+        }
+        Spacer(Modifier.width(4.dp))
+        TextButton(onClick = onReveal) {
+            Text("Reveal")
+        }
+    }
+}

commons/src/commonTest/kotlin/com/vitorpamplona/amethyst/commons/moderation/DisplayedEventTest.kt

@@ -0,0 +1,88 @@
+/*
+ * 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.moderation
+
+import com.vitorpamplona.amethyst.commons.model.Note
+import com.vitorpamplona.quartz.nip01Core.core.Event
+import com.vitorpamplona.quartz.nip18Reposts.RepostEvent
+import kotlin.test.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertNull
+
+class DisplayedEventTest {
+    private val author = "a".repeat(64)
+    private val sig = "0".repeat(128)
+
+    private fun textNoteEvent(id: String = "1".padEnd(64, '0')): Event =
+        Event(
+            id = id,
+            pubKey = author,
+            createdAt = 0L,
+            kind = 1,
+            tags = emptyArray(),
+            content = "hello",
+            sig = sig,
+        )
+
+    private fun repostWrapper(content: String): RepostEvent =
+        RepostEvent(
+            id = "r".repeat(64),
+            pubKey = author,
+            createdAt = 0L,
+            tags = emptyArray(),
+            content = content,
+            sig = sig,
+        )
+
+    @Test
+    fun nonRepostReturnsOwnEvent() {
+        val inner = textNoteEvent()
+        val note = Note(idHex = inner.id).apply { event = inner }
+        assertEquals(inner, note.displayedEvent())
+    }
+
+    @Test
+    fun repostWithReplyToReturnsInnerEvent() {
+        val inner = textNoteEvent(id = "i".repeat(64))
+        val innerNote = Note(idHex = inner.id).apply { event = inner }
+        val wrapper = repostWrapper(content = "{}") // valid JSON but missing fields
+        val wrapperNote =
+            Note(idHex = wrapper.id).apply {
+                event = wrapper
+                replyTo = listOf(innerNote)
+            }
+        assertEquals(inner, wrapperNote.displayedEvent())
+    }
+
+    @Test
+    fun repostWithoutReplyToFallsBackToContainedPost() {
+        // Malformed inner JSON → containedPost() returns null → displayedEvent() returns null.
+        val wrapper = repostWrapper(content = "not-valid-json-at-all")
+        val wrapperNote = Note(idHex = wrapper.id).apply { event = wrapper }
+        assertNull(wrapperNote.displayedEvent())
+    }
+
+    @Test
+    fun noteWithoutEventReturnsNull() {
+        val note = Note(idHex = "x".repeat(64))
+        assertNull(note.displayedEvent())
+    }
+}

commons/src/commonTest/kotlin/com/vitorpamplona/amethyst/commons/moderation/HashtagSpamCheckTest.kt

@@ -0,0 +1,189 @@
+/*
+ * 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.moderation
+
+import com.vitorpamplona.quartz.nip01Core.core.Event
+import kotlin.test.Test
+import kotlin.test.assertFalse
+import kotlin.test.assertTrue
+
+class HashtagSpamCheckTest {
+    private val author = "a".repeat(64)
+    private val other = "b".repeat(64)
+
+    private fun event(
+        kind: Int = 1,
+        hashtags: List<String> = emptyList(),
+        pubkey: String = author,
+    ): Event =
+        Event(
+            id = "id".padEnd(64, '0'),
+            pubKey = pubkey,
+            createdAt = 0L,
+            kind = kind,
+            tags = hashtags.map { arrayOf("t", it) }.toTypedArray(),
+            content = "",
+            sig = "sig".padEnd(128, '0'),
+        )
+
+    @Test
+    fun returnsFalseWhenDisabled() {
+        val e = event(hashtags = (1..20).map { "h$it" })
+        assertFalse(
+            HashtagSpamCheck.isHashtagSpam(
+                displayedEvent = e,
+                authorPubkey = e.pubKey,
+                enabled = false,
+                threshold = 5,
+                exemptKeys = emptySet(),
+            ),
+        )
+    }
+
+    @Test
+    fun returnsFalseForNullDisplayedEvent() {
+        assertFalse(
+            HashtagSpamCheck.isHashtagSpam(
+                displayedEvent = null,
+                authorPubkey = author,
+                enabled = true,
+                threshold = 5,
+                exemptKeys = emptySet(),
+            ),
+        )
+    }
+
+    @Test
+    fun returnsFalseForLongformEvenWithManyTags() {
+        // kind 30023 = long-form content; exempt regardless of tag count.
+        val e = event(kind = 30023, hashtags = (1..20).map { "h$it" })
+        assertFalse(
+            HashtagSpamCheck.isHashtagSpam(
+                displayedEvent = e,
+                authorPubkey = e.pubKey,
+                enabled = true,
+                threshold = 5,
+                exemptKeys = emptySet(),
+            ),
+        )
+    }
+
+    @Test
+    fun returnsFalseForFollowedAuthor() {
+        val e = event(hashtags = (1..20).map { "h$it" })
+        assertFalse(
+            HashtagSpamCheck.isHashtagSpam(
+                displayedEvent = e,
+                authorPubkey = e.pubKey,
+                enabled = true,
+                threshold = 5,
+                exemptKeys = setOf(author),
+            ),
+        )
+    }
+
+    @Test
+    fun returnsFalseUnderThreshold() {
+        val e = event(hashtags = listOf("nostr", "bitcoin", "amethyst"))
+        assertFalse(
+            HashtagSpamCheck.isHashtagSpam(
+                displayedEvent = e,
+                authorPubkey = e.pubKey,
+                enabled = true,
+                threshold = 5,
+                exemptKeys = emptySet(),
+            ),
+        )
+    }
+
+    @Test
+    fun returnsFalseAtThresholdExactly() {
+        // hasMoreHashtagsThan(5) returns true only for count > 5.
+        val e = event(hashtags = (1..5).map { "h$it" })
+        assertFalse(
+            HashtagSpamCheck.isHashtagSpam(
+                displayedEvent = e,
+                authorPubkey = e.pubKey,
+                enabled = true,
+                threshold = 5,
+                exemptKeys = emptySet(),
+            ),
+        )
+    }
+
+    @Test
+    fun returnsTrueOverThresholdWithDistinctTags() {
+        val e = event(hashtags = (1..10).map { "h$it" })
+        assertTrue(
+            HashtagSpamCheck.isHashtagSpam(
+                displayedEvent = e,
+                authorPubkey = e.pubKey,
+                enabled = true,
+                threshold = 5,
+                exemptKeys = emptySet(),
+            ),
+        )
+    }
+
+    @Test
+    fun returnsFalseOverThresholdWhenAllTagsAreDuplicates() {
+        // hasMoreHashtagsThan checks count AND unique count > limit.
+        // 20 copies of the same hashtag → unique = 1 → not spam.
+        val e = event(hashtags = List(20) { "bitcoin" })
+        assertFalse(
+            HashtagSpamCheck.isHashtagSpam(
+                displayedEvent = e,
+                authorPubkey = e.pubKey,
+                enabled = true,
+                threshold = 5,
+                exemptKeys = emptySet(),
+            ),
+        )
+    }
+
+    @Test
+    fun authorNotInExemptKeysIsNotExempt() {
+        val e = event(hashtags = (1..10).map { "h$it" })
+        assertTrue(
+            HashtagSpamCheck.isHashtagSpam(
+                displayedEvent = e,
+                authorPubkey = e.pubKey,
+                enabled = true,
+                threshold = 5,
+                exemptKeys = setOf(other),
+            ),
+        )
+    }
+
+    @Test
+    fun nullAuthorPubkeyDoesNotShortCircuit() {
+        val e = event(hashtags = (1..10).map { "h$it" })
+        assertTrue(
+            HashtagSpamCheck.isHashtagSpam(
+                displayedEvent = e,
+                authorPubkey = null,
+                enabled = true,
+                threshold = 5,
+                exemptKeys = setOf(author),
+            ),
+        )
+    }
+}

commons/src/jvmMain/kotlin/com/vitorpamplona/amethyst/commons/moderation/PreferencesHashtagSpamSettings.kt

@@ -0,0 +1,70 @@
+/*
+ * 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.moderation
+
+import com.vitorpamplona.amethyst.commons.moderation.HashtagSpamSettings.Companion.DEFAULT_ENABLED
+import com.vitorpamplona.amethyst.commons.moderation.HashtagSpamSettings.Companion.DEFAULT_THRESHOLD
+import com.vitorpamplona.amethyst.commons.moderation.HashtagSpamSettings.Companion.MAX_THRESHOLD
+import com.vitorpamplona.amethyst.commons.moderation.HashtagSpamSettings.Companion.MIN_THRESHOLD
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.StateFlow
+import kotlinx.coroutines.flow.asStateFlow
+import java.util.prefs.Preferences
+
+/**
+ * JVM-platform implementation backed by [java.util.prefs.Preferences].
+ *
+ * The default node `com/vitorpamplona/amethyst/filters` is shared between
+ * the Desktop app and the `amy` CLI — both binaries running as the same OS
+ * user observe the same setting without any extra plumbing.
+ *
+ * `Preferences` auto-flushes on JVM shutdown and periodically, so no
+ * explicit `flush()` call is needed and avoids per-set disk thrash.
+ */
+class PreferencesHashtagSpamSettings(
+    private val prefs: Preferences = Preferences.userRoot().node(NODE_NAME),
+) : HashtagSpamSettings {
+    private val mutableEnabled = MutableStateFlow(prefs.getBoolean(KEY_ENABLED, DEFAULT_ENABLED))
+    private val mutableThreshold =
+        MutableStateFlow(
+            prefs.getInt(KEY_THRESHOLD, DEFAULT_THRESHOLD).coerceIn(MIN_THRESHOLD, MAX_THRESHOLD),
+        )
+
+    override val enabled: StateFlow<Boolean> = mutableEnabled.asStateFlow()
+    override val threshold: StateFlow<Int> = mutableThreshold.asStateFlow()
+
+    override fun setEnabled(enabled: Boolean) {
+        mutableEnabled.value = enabled
+        prefs.putBoolean(KEY_ENABLED, enabled)
+    }
+
+    override fun setThreshold(threshold: Int) {
+        val clamped = threshold.coerceIn(MIN_THRESHOLD, MAX_THRESHOLD)
+        mutableThreshold.value = clamped
+        prefs.putInt(KEY_THRESHOLD, clamped)
+    }
+
+    companion object {
+        const val NODE_NAME = "com/vitorpamplona/amethyst/filters"
+        const val KEY_ENABLED = "hashtag_spam_enabled"
+        const val KEY_THRESHOLD = "hashtag_spam_threshold"
+    }
+}

commons/src/jvmTest/kotlin/com/vitorpamplona/amethyst/commons/moderation/PreferencesHashtagSpamSettingsTest.kt

@@ -0,0 +1,86 @@
+/*
+ * 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.moderation
+
+import org.junit.After
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertFalse
+import org.junit.Assert.assertTrue
+import org.junit.Before
+import org.junit.Test
+import java.util.prefs.Preferences
+
+class PreferencesHashtagSpamSettingsTest {
+    private val testNode = "com/vitorpamplona/amethyst/test/hashtag_spam_${System.currentTimeMillis()}"
+
+    private fun prefs(): Preferences = Preferences.userRoot().node(testNode)
+
+    @Before
+    fun setup() {
+        prefs().clear()
+    }
+
+    @After
+    fun teardown() {
+        prefs().removeNode()
+    }
+
+    @Test
+    fun defaultsAreOnAndFive() {
+        val settings = PreferencesHashtagSpamSettings(prefs())
+        assertTrue(settings.enabled.value)
+        assertEquals(5, settings.threshold.value)
+    }
+
+    @Test
+    fun setEnabledPersists() {
+        val settings = PreferencesHashtagSpamSettings(prefs())
+        settings.setEnabled(false)
+        assertFalse(settings.enabled.value)
+
+        val reloaded = PreferencesHashtagSpamSettings(prefs())
+        assertFalse(reloaded.enabled.value)
+    }
+
+    @Test
+    fun setThresholdPersists() {
+        val settings = PreferencesHashtagSpamSettings(prefs())
+        settings.setThreshold(12)
+        assertEquals(12, settings.threshold.value)
+
+        val reloaded = PreferencesHashtagSpamSettings(prefs())
+        assertEquals(12, reloaded.threshold.value)
+    }
+
+    @Test
+    fun thresholdClampsBelowMin() {
+        val settings = PreferencesHashtagSpamSettings(prefs())
+        settings.setThreshold(-50)
+        assertEquals(HashtagSpamSettings.MIN_THRESHOLD, settings.threshold.value)
+    }
+
+    @Test
+    fun thresholdClampsAboveMax() {
+        val settings = PreferencesHashtagSpamSettings(prefs())
+        settings.setThreshold(9999)
+        assertEquals(HashtagSpamSettings.MAX_THRESHOLD, settings.threshold.value)
+    }
+}

desktopApp/plans/2026-06-29-hashtag-spam-filter-manual-testing-sheet.md

@@ -0,0 +1,66 @@
+# Manual testing sheet — Hashtag-Spam Filter (Desktop)
+
+Plan: `docs/plans/2026-06-29-feat-desktop-hashtag-spam-filter-plan.md`
+
+Run with `./gradlew :desktopApp:run`. Sign in with any account that has a
+follow list (or use a fresh nsec — global feed still works without follows).
+
+## Setup
+
+1. Confirm default state: filter is **ON**, threshold is **5** on first
+   launch. Settings → Content Filters shows Switch=On, slider at 5.
+2. Confirm a follow list is populated (Home column should display notes
+   from people you follow). Otherwise the follow-exemption test (T4) is a
+   no-op.
+
+## Scenarios
+
+| # | Scenario | Expected |
+|---|----------|----------|
+| **T1** | **Slider live re-collapse.** Open a Home column. Locate a visible note that has the spammy pattern (e.g. 8+ distinct hashtags). Drag the threshold slider to a value below its hashtag count. | Card collapses to placeholder after drag release. No mid-drag jank. |
+| **T2** | **Repost spam (precomputed).** Find a `nostr:nevent…` link to a kind-6 repost whose wrapped event has many hashtags, paste into a hashtag column or use Search. After the cache materialises the inner event (give it a second), confirm the repost wrapper renders collapsed. | Wrapper card shows `CollapsedSpamNote` with the inner event's author. |
+| **T3** | **Repost spam (uncached fallback).** Same as T2 immediately on first paste, before the cache resolves the inner event. | Wrapper shows collapsed (via `containedPost()` fallback) OR shows normal until cache populates — both acceptable; nothing crashes. |
+| **T4** | **Followed-author exemption.** Locate (or temporarily follow) someone who posts 10+ hashtag stuff. Reload Home. | Their posts render normally, never collapsed. |
+| **T5** | **Self exemption.** Compose and publish a note with 10 distinct hashtags from the active account. | The note appears normally in your own activity / Home, not collapsed. |
+| **T6** | **Long-form exemption.** Open a longform article (kind 30023) that uses many topical tags — via Search → Articles tab, or via a quoted `naddr1…`. | Article renders normally. |
+| **T7** | **Thread root auto-expand.** Find a collapsed card in a feed and click it to open the thread. | Root note auto-expands (`forceReveal = true`); 12-hashtag replies inside the thread still appear collapsed. |
+| **T8** | **Embedded quote.** Read a note that quotes a hashtag-spam note via `nostr:nevent…`. | The inline embedded card is collapsed. Revealing it does NOT cascade to other places — open the same quoted note in Search and confirm it's still collapsed there (per-call-site `rememberSaveable`). |
+| **T9** | **Settings persistence across restart.** Toggle Switch to Off. Restart Desktop. | Open Settings → Content Filters: still Off. Spam notes render uncollapsed. |
+| **T10** | **`amy` parity.** From a terminal, run `java -cp <path> com.vitorpamplona.amethyst.cli.Main …` (or any utility that reads the shared `Preferences` node). Or write a one-line Kotlin REPL: `Preferences.userRoot().node("com/vitorpamplona/amethyst/filters").getBoolean("hashtag_spam_enabled", true)`. | Returns the same value Desktop wrote. Reverse: write `false` via the API, relaunch Desktop, observe filter is off. |
+| **T11** | **Malformed inner repost JSON.** Test event with a kind-6 wrapper whose `content` field is not parseable JSON. Quickest reproduction: use the unit test `repostWithoutReplyToFallsBackToContainedPost` ✓ already covers the `displayedEvent()` path; manually you can paste a deliberately-broken nevent and watch nothing crash. | No exception; wrapper renders normally (since `displayedEvent()` returns null and `isSpam = false`). |
+| **T12** | **Hashtag-feed column.** Subscribe to a hashtag-feed column (e.g. `#bitcoin`). | Posts that are tagged `#bitcoin` AND have many other hashtags still collapse — filter applies inside hashtag columns. |
+| **T13** | **Notifications tab (negative).** Receive a mention from someone who used many hashtags in the parent note. Open Notifications. | Compact notification card (56dp) renders normally — does NOT apply the filter (v1 scope: Notifications-tab card is a custom composable, deferred). Documented as a known limitation. |
+| **T14** | **Slider does not cause feed recomposition storm.** Open a feed with several visible notes. Open Settings, drag threshold quickly back and forth. | Slider thumb moves smoothly; feed contents do not re-render per-tick (only on drag-end). No frame drops. |
+| **T15** | **Toggle off → notes uncollapse live.** With filter ON and a collapsed card visible, toggle the Switch to Off in Settings. | Card immediately uncollapses (StateFlow re-evaluates, `isSpam` becomes false). |
+| **T16** | **Threshold change updates label live.** Drag the slider with the Settings sheet open. | The "Hide notes with more than N hashtags" text updates per drag tick. |
+
+## Known v1 limitations to surface during testing
+
+- Cross-call-site reveal: revealing a collapsed card in Home does NOT reveal
+  the same card in a Hashtag column or in a thread — each render site has
+  its own `rememberSaveable` reveal flag.
+- Notifications compact card does NOT respect the filter (v2).
+- Follow/unfollow during a session does not re-evaluate already-rendered
+  cards in place (follow set is non-reactive at the check site v1; refresh
+  feed to update).
+
+## Sign-off
+
+- [ ] T1 Slider live re-collapse
+- [ ] T2 Repost spam (precomputed)
+- [ ] T3 Repost spam (uncached)
+- [ ] T4 Followed-author exemption
+- [ ] T5 Self exemption
+- [ ] T6 Long-form exemption
+- [ ] T7 Thread root auto-expand
+- [ ] T8 Embedded quote
+- [ ] T9 Settings persistence
+- [ ] T10 `amy` parity
+- [ ] T11 Malformed inner repost JSON
+- [ ] T12 Hashtag-feed column
+- [ ] T13 Notifications tab limitation (known)
+- [ ] T14 No recomposition storm during drag
+- [ ] T15 Toggle off live
+- [ ] T16 Threshold label live update
+
+Tester: ________________  Date: ________________

desktopApp/plans/_desktop-feature-backlog.md

@@ -0,0 +1,142 @@
+# Desktop Feature Backlog — Inspiration from Nostr Ecosystem
+
+Survey date: 2026-06-29. Source: cross-client research across top-5 used clients
+(Damus, Primal, YakiHonne, Snort, Iris) + top-5 desktop-first / power-user
+clients (Notedeck, Gossip, Jumble, Coop, Flotilla). Wisp investigated separately
+(Android-only, not desktop).
+
+Already shipped on Amethyst Desktop and excluded from this list: deck columns,
+embedded local relay, NIP-46 bunker login, NWC zapping, custom feeds, advanced
+search, follow packs (in progress).
+
+---
+
+## Priority queue (next up)
+
+### 1. Hashtag-spam filter — NEXT
+- **Inspired by:** Damus (auto-hide posts above N hashtags).
+- **What:** Configurable threshold; posts with `> N` `t` tags get hidden or
+  collapsed across all feeds. User-defined whitelist for legit multi-tag use
+  (events, longform).
+- **Why desktop:** Spam noise scales with column count on a deck UI; one filter
+  cleans every column at once.
+- **Module:** `commons/` (filter logic, shared with Android in future) +
+  `desktopApp/` (settings UI).
+- **Skills:** `feed-patterns`, `compose-expert`, `account-state`.
+
+### 2. WoT (web-of-trust) score on avatars + filters
+- **Inspired by:** Gossip, Snort.
+- **What:** Friends-of-friends score (0–N) computed from follow graph. Visual
+  badge/ring on avatar. Threshold filter for notifications/DM-requests.
+- **Why desktop:** At-a-glance trust signal scales with multi-column deck.
+- **Module:** `commons/services/WoTService.kt` (StateFlow<Map<HexKey, Int>>),
+  avatar composable in `commons/.../note/`.
+- **Skills:** `account-state`, `kotlin-flow-state-event-modeling`,
+  `compose-expert`. Score compute is O(follows × follows) — must be lazy /
+  throttled.
+
+---
+
+## Full ranked backlog (10 ideas)
+
+Ranking heuristic: impact × novelty / implementation cost. Items 1–2 are the
+priority queue above; 3–10 captured for later.
+
+| # | Feature | Inspired by | Module | Notes |
+|---|---------|-------------|--------|-------|
+| 1 | Hashtag-spam filter | Damus | commons + desktopApp | **NEXT** |
+| 2 | WoT score on avatars + filters | Gossip, Snort | commons | After #1 |
+| 3 | Relay-as-column + Relay Sets first-class | Jumble, Flotilla | commons | Drag relay URL → column |
+| 4 | Cashu ecash wallet alongside NWC | Iris, Primal Spark | quartz + commons | Bearer-token privacy |
+| 5 | AI "Dave" column (timeline-aware assistant) | Notedeck | desktopApp | LLM reads adjacent columns |
+| 6 | Algorithmic Feed Marketplace | Primal v3.0 | commons | Discover layer on custom feeds |
+| 7 | Keyboard / command palette (`Ctrl+K`, `?` overlay) | Snort, Notedeck | desktopApp + commons | Power-user nav |
+| 8 | Longform reader column + offline publish queue | Damus, YakiHonne | commons | NIP-23, uses local relay |
+| 9 | WoT-scored notification filter + undo-send | Gossip, Snort | commons | Calmer UX |
+| 10 | Per-relay column health (sparkline + dot) | Wisp, Gossip | commons | Reuse EOSE manager |
+| 11 | Discord-style "communities" sidebar (NIP-29) | Flotilla, Chachi | desktopApp + commons | Sidebar second purpose |
+
+(Extra row #11 added: communities sidebar was the 10th in the original survey;
+WoT-notif-filter + undo-send promoted to its own row for clarity.)
+
+---
+
+## Per-item detail
+
+### #3 Relay-as-column + Relay Sets first-class
+- **Drop:** Drag relay URL onto the deck → new column showing that relay's
+  global. Relay Sets become saveable column templates.
+- **Impl:** New `RelayUrlFeedFilter` + `RelaySetFeedFilter` in `commons/feeds/`.
+- **Gotcha:** Bypass write-through to local store for these feeds, otherwise
+  local relay pollutes with arbitrary global content.
+
+### #4 Cashu ecash wallet alongside NWC
+- **Why:** Different privacy model (bearer tokens, no account). Power users
+  want both — small/private = ecash, big/recurring = NWC.
+- **Impl:** Check Quartz NIP-60/61 coverage; else new `wallet/cashu/`. UI is a
+  second tab in existing wallet column.
+- **Gotcha:** Mint trust UX; token backup/restore; encryption story
+  (`accounts.json.enc` slot).
+
+### #5 AI "Dave" column
+- **Why:** Big-screen-only feature that breaks the deck-column metaphor wide
+  open. Reads N adjacent columns as context.
+- **Impl:** `desktopApp/` for API key config + `commons/ai/` for prompt builders.
+  Pluggable model: Ollama local default, OpenAI/Anthropic optional.
+- **Gotcha:** Privacy story — must be explicit which events get sent where.
+  Default to local Ollama.
+
+### #6 Algorithmic Feed Marketplace
+- **Why:** Custom feeds already shipped — marketplace is the discovery layer.
+- **Impl:** Feeds are published as kind:30000-ish lists or DVM-driven. Browser
+  UI + subscribe button on top of existing custom-feed infra.
+- **Gotcha:** DVM feeds vs static list feeds — two execution paths.
+
+### #7 Keyboard / command palette
+- **Why:** Mouse-first ≠ keyboard-hostile.
+- **Impl:** `desktopApp/` global `onPreviewKeyEvent` + `commons/ui/CommandPalette.kt`.
+- **Gotcha:** Focus management across deck columns; cmd vs ctrl on macOS;
+  conflict with text-input fields.
+
+### #8 Longform reader + offline publish queue
+- **Why:** NIP-23 is barely surfaced on Desktop. Big screens are *the* surface
+  for reading articles.
+- **Impl:** New column types `LongformReader` + `LongformComposer`. Composer is
+  block-based. Offline queue writes drafts to local relay; auto-broadcasts on
+  reconnect.
+- **Gotcha:** Markdown rendering on Compose Desktop is mid — pick or build.
+  Blossom upload alongside drafts.
+
+### #9 WoT notif filter + undo-send
+- **Why:** Notifications scale poorly; slow-mode (delay sends 5–30 s with
+  toast-cancel) calms power-user UX.
+- **Impl:** `NotificationFilter.kt` extension + send-pipeline interceptor in
+  `commons/relayClient/`.
+- **Gotcha:** Sent-but-cancelled events already in local relay write-through —
+  must scrub from local store on cancel.
+
+### #10 Per-relay column health
+- **Why:** Deck UI exposes the multi-relay reality. Latency/EOSE/dup-rate dot +
+  sparkline in column header helps self-tune.
+- **Impl:** Extend EOSE manager to emit `RelayHealth` per relay; render small
+  sparkline + colored dot.
+- **Gotcha:** Memory over time — rolling 60 s window, decay older.
+
+### #11 Communities sidebar (NIP-29)
+- **Why:** Amethyst Desktop sidebar is nav-only; mapping joined groups /
+  favourite relays to Discord-like server icons doubles its purpose.
+- **Impl:** `desktopApp/.../sidebar/` new section; on click, populate deck with
+  group channels. `commons/groups/` for NIP-29 if not in Quartz already.
+- **Gotcha:** NIP-29 spec churn — check Quartz coverage. Don't conflate
+  "favourite relay" with "joined group".
+
+---
+
+## Sources
+
+- nostr.com/clients, nostrapps.com, stats.nostr.band
+- humai.blog "Best Nostr Apps 2026"; nostr.co.uk/clients; nostrcompass.org #15
+- opensats.org "Advancements in Nostr Clients"
+- Repos: damus-io/damus, damus-io/notedeck, mikedilger/gossip, CodyTseng/jumble,
+  lumehq/coop, coracle-social/flotilla (active at gitea.coracle.social),
+  barrydeen/wisp

desktopApp/src/jvmMain/kotlin/com/vitorpamplona/amethyst/desktop/Main.kt

@@ -74,6 +74,9 @@ import androidx.compose.ui.window.rememberWindowState
 import com.vitorpamplona.amethyst.commons.icons.symbols.Icon
 import com.vitorpamplona.amethyst.commons.icons.symbols.MaterialSymbols
 import com.vitorpamplona.amethyst.commons.icons.symbols.ProvideMaterialSymbols
+import com.vitorpamplona.amethyst.commons.moderation.LocalHashtagSpamSettings
+import com.vitorpamplona.amethyst.commons.moderation.LocalSpamExemptKeys
+import com.vitorpamplona.amethyst.commons.moderation.PreferencesHashtagSpamSettings
 import com.vitorpamplona.amethyst.commons.relayClient.nip17Dm.unwrapAndUnsealOrNull
 import com.vitorpamplona.amethyst.desktop.account.AccountManager
 import com.vitorpamplona.amethyst.desktop.account.AccountState
@@ -749,6 +752,10 @@ fun App(
     val accountState by accountManager.accountState.collectAsState()
     val scope = remember { CoroutineScope(SupervisorJob() + Dispatchers.Main) }
 
+    // Hashtag-spam filter settings, persisted in the shared java.util.prefs
+    // node so the `amy` CLI binary observes the same toggle.
+    val hashtagSpamSettings = remember { PreferencesHashtagSpamSettings() }
+
     // Local relay store — persists events to SQLite per account
     val localRelayStore =
         remember {
@@ -976,6 +983,7 @@ fun App(
                     com.vitorpamplona.amethyst.desktop.ui.deck.LocalDesktopCache provides localCache,
                     com.vitorpamplona.amethyst.desktop.ui.deck.LocalRelayManager provides relayManager,
                     com.vitorpamplona.amethyst.desktop.ui.deck.LocalLocalRelayStore provides localRelayStore,
+                    LocalHashtagSpamSettings provides hashtagSpamSettings,
                 ) {
                     when (accountState) {
                         is AccountState.Loading -> {
@@ -1062,6 +1070,11 @@ fun App(
                             // NWC loaded during startup in loadSavedAccount flow
 
                             val currentTorStatus = torManager.status.collectAsState().value
+                            val followedUsers by localCache.followedUsers.collectAsState()
+                            val spamExemptKeys =
+                                remember(followedUsers, account.pubKeyHex) {
+                                    followedUsers + account.pubKeyHex
+                                }
                             androidx.compose.runtime.CompositionLocalProvider(
                                 com.vitorpamplona.amethyst.desktop.ui.tor.LocalTorState provides
                                     com.vitorpamplona.amethyst.desktop.ui.tor.TorState(
@@ -1079,6 +1092,7 @@ fun App(
                                     ),
                                 LocalNamecoinPreferences provides namecoinPreferences,
                                 LocalNamecoinService provides namecoinService,
+                                LocalSpamExemptKeys provides spamExemptKeys,
                             ) {
                                 MainContent(
                                     layoutMode = layoutMode,
@@ -2074,6 +2088,21 @@ fun RelaySettingsScreen(
                 Spacer(Modifier.height(16.dp))
             }
 
+            // Content Filters section — hashtag-spam filter and future
+            // content-moderation toggles.
+            Text(
+                text = "Content Filters",
+                style = MaterialTheme.typography.titleMedium,
+                color = MaterialTheme.colorScheme.onBackground,
+            )
+            Spacer(Modifier.height(8.dp))
+            com.vitorpamplona.amethyst.desktop.ui.settings.HashtagSpamSettingsSection(
+                settings = LocalHashtagSpamSettings.current,
+            )
+            Spacer(Modifier.height(16.dp))
+            HorizontalDivider()
+            Spacer(Modifier.height(16.dp))
+
             val logoutScope = rememberCoroutineScope()
             OutlinedButton(
                 onClick = { logoutScope.launch { accountManager.logout(deleteKey = true) } },

desktopApp/src/jvmMain/kotlin/com/vitorpamplona/amethyst/desktop/ui/BookmarksScreen.kt

@@ -316,12 +316,18 @@ fun BookmarksScreen(
                                     onNavigateToThread(event.id)
                                 },
                         ) {
-                            NoteCard(
-                                note = event.toNoteDisplayData(localCache),
+                            com.vitorpamplona.amethyst.desktop.ui.note.SpamCheckedNoteRender(
+                                displayedEvent = event,
+                                noteIdHex = event.id,
                                 localCache = localCache,
-                                onAuthorClick = onNavigateToProfile,
-                                onMentionClick = onNavigateToProfile,
-                            )
+                            ) {
+                                NoteCard(
+                                    note = event.rememberDisplayData(localCache),
+                                    localCache = localCache,
+                                    onAuthorClick = onNavigateToProfile,
+                                    onMentionClick = onNavigateToProfile,
+                                )
+                            }
                             NoteActionsRow(
                                 event = event,
                                 relayManager = relayManager,

desktopApp/src/jvmMain/kotlin/com/vitorpamplona/amethyst/desktop/ui/EventExtensions.kt

@@ -20,6 +20,10 @@
  */
 package com.vitorpamplona.amethyst.desktop.ui
 
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.produceState
+import androidx.compose.runtime.remember
 import com.vitorpamplona.amethyst.commons.model.ImmutableListOfLists
 import com.vitorpamplona.amethyst.commons.model.cache.ICacheProvider
 import com.vitorpamplona.amethyst.desktop.ui.note.NoteDisplayData
@@ -27,6 +31,27 @@ import com.vitorpamplona.quartz.nip01Core.core.Event
 import com.vitorpamplona.quartz.nip01Core.core.hexToByteArrayOrNull
 import com.vitorpamplona.quartz.nip19Bech32.toNpub
 
+/**
+ * Compose-friendly wrapper around [toNoteDisplayData] that observes the
+ * event author's user-metadata flow and re-derives the display data
+ * whenever it updates. Use at note-card call sites so display names and
+ * avatars populate when the kind-0 event arrives from relays after the
+ * note itself.
+ */
+@Composable
+fun Event.rememberDisplayData(cache: ICacheProvider?): NoteDisplayData {
+    val author = remember(pubKey, cache) { cache?.getUserIfExists(pubKey) }
+    val authorMetaValue by produceState<Any?>(initialValue = null, key1 = author) {
+        val a = author
+        if (a == null) {
+            value = null
+        } else {
+            a.metadata().flow.collect { value = it }
+        }
+    }
+    return remember(this, authorMetaValue) { toNoteDisplayData(cache) }
+}
+
 /**
  * Extension to convert Event to NoteDisplayData for the shared NoteCard.
  */

desktopApp/src/jvmMain/kotlin/com/vitorpamplona/amethyst/desktop/ui/FeedScreen.kt

@@ -135,6 +135,7 @@ import com.vitorpamplona.amethyst.desktop.subscriptions.generateSubId
 import com.vitorpamplona.amethyst.desktop.subscriptions.rememberSubscription
 import com.vitorpamplona.amethyst.desktop.ui.media.LightboxOverlay
 import com.vitorpamplona.amethyst.desktop.ui.note.NoteCard
+import com.vitorpamplona.amethyst.desktop.ui.note.SpamCheckedNoteRender
 import com.vitorpamplona.amethyst.desktop.ui.relay.LocalRelayCategories
 import com.vitorpamplona.amethyst.desktop.ui.relay.Nip65RelayEditor
 import com.vitorpamplona.amethyst.desktop.ui.search.SearchResultsList
@@ -199,8 +200,54 @@ fun FeedNoteCard(
     followedUsers: Set<String> = emptySet(),
     myPubKeyHex: String? = null,
     onFollow: ((String) -> Unit)? = null,
+    forceReveal: Boolean = false,
 ) {
     val event = note.event ?: return
+    SpamCheckedNoteRender(
+        note = note,
+        localCache = localCache,
+        forceReveal = forceReveal,
+    ) {
+        FeedNoteCardBody(
+            note = note,
+            event = event,
+            relayManager = relayManager,
+            localCache = localCache,
+            account = account,
+            nwcConnection = nwcConnection,
+            onReply = onReply,
+            onZapFeedback = onZapFeedback,
+            onNavigateToProfile = onNavigateToProfile,
+            onNavigateToThread = onNavigateToThread,
+            onImageClick = onImageClick,
+            onMediaClick = onMediaClick,
+            onHashtagClick = onHashtagClick,
+            followedUsers = followedUsers,
+            myPubKeyHex = myPubKeyHex,
+            onFollow = onFollow,
+        )
+    }
+}
+
+@Composable
+private fun FeedNoteCardBody(
+    note: Note,
+    event: com.vitorpamplona.quartz.nip01Core.core.Event,
+    relayManager: DesktopRelayConnectionManager,
+    localCache: DesktopLocalCache,
+    account: AccountState.LoggedIn?,
+    nwcConnection: com.vitorpamplona.quartz.nip47WalletConnect.Nip47WalletConnect.Nip47URINorm? = null,
+    onReply: () -> Unit,
+    onZapFeedback: (ZapFeedback) -> Unit,
+    onNavigateToProfile: (String) -> Unit = {},
+    onNavigateToThread: (String) -> Unit = {},
+    onImageClick: ((List<String>, Int) -> Unit)? = null,
+    onMediaClick: ((List<String>, Int, Float) -> Unit)? = null,
+    onHashtagClick: ((String) -> Unit)? = null,
+    followedUsers: Set<String> = emptySet(),
+    myPubKeyHex: String? = null,
+    onFollow: ((String) -> Unit)? = null,
+) {
     val isRepost = event is RepostEvent || event is GenericRepostEvent
 
     if (isRepost) {

desktopApp/src/jvmMain/kotlin/com/vitorpamplona/amethyst/desktop/ui/SearchScreen.kt

@@ -120,7 +120,6 @@ fun SearchScreen(
     initialQuery: String = "",
     onNavigateToProfile: (String) -> Unit,
     onNavigateToThread: (String) -> Unit,
-    onNavigateToHashtag: (String) -> Unit = {},
     modifier: Modifier = Modifier,
 ) {
     val scope = rememberCoroutineScope()
@@ -348,6 +347,20 @@ fun SearchScreen(
             }
     }
 
+    // Load author metadata for incoming note results. NIP-50 search relays
+    // typically don't return kind-0 metadata alongside notes, and the
+    // subscription explicitly drops MetadataEvents anyway — so display name
+    // and avatar arrive only after we explicitly fetch them from index
+    // relays via the coordinator.
+    LaunchedEffect(noteResults, subscriptionsCoordinator) {
+        val coordinator = subscriptionsCoordinator ?: return@LaunchedEffect
+        if (noteResults.isEmpty()) return@LaunchedEffect
+        val authors = noteResults.map { it.pubKey }.distinct()
+        if (authors.isNotEmpty()) {
+            coordinator.loadMetadataBatched(authors)
+        }
+    }
+
     // History state
     val historyItems by SearchHistoryStore.history.collectAsState()
     val savedSearches by SearchHistoryStore.savedSearches.collectAsState()
@@ -643,7 +656,6 @@ fun SearchScreen(
                                     ),
                                 onNavigateToProfile = onNavigateToProfile,
                                 onNavigateToThread = onNavigateToThread,
-                                onNavigateToHashtag = onNavigateToHashtag,
                             )
                             if (ncState.result.relays.isNotEmpty()) {
                                 Text(
@@ -699,7 +711,6 @@ fun SearchScreen(
                             result = result,
                             onNavigateToProfile = onNavigateToProfile,
                             onNavigateToThread = onNavigateToThread,
-                            onNavigateToHashtag = onNavigateToHashtag,
                         )
                     }
                 }
@@ -897,7 +908,6 @@ private fun SearchResultCard(
     result: SearchResult,
     onNavigateToProfile: (String) -> Unit,
     onNavigateToThread: (String) -> Unit,
-    onNavigateToHashtag: (String) -> Unit,
 ) {
     Card(
         modifier =
@@ -908,7 +918,6 @@ private fun SearchResultCard(
                         is SearchResult.UserResult -> onNavigateToProfile(result.pubKeyHex)
                         is SearchResult.NoteResult -> onNavigateToThread(result.noteIdHex)
                         is SearchResult.AddressResult -> onNavigateToThread("${result.kind}:${result.pubKeyHex}:${result.dTag}")
-                        is SearchResult.HashtagResult -> onNavigateToHashtag(result.hashtag)
                     }
                 },
         colors =
@@ -927,7 +936,6 @@ private fun SearchResultCard(
                         is SearchResult.UserResult -> MaterialSymbols.Person
                         is SearchResult.NoteResult -> MaterialSymbols.Description
                         is SearchResult.AddressResult -> MaterialSymbols.Description
-                        is SearchResult.HashtagResult -> MaterialSymbols.Tag
                     },
                 contentDescription = null,
                 modifier = Modifier.size(24.dp),
@@ -940,7 +948,6 @@ private fun SearchResultCard(
                         is SearchResult.UserResult -> "User Profile"
                         is SearchResult.NoteResult -> "Note"
                         is SearchResult.AddressResult -> "Event (kind ${result.kind})"
-                        is SearchResult.HashtagResult -> "#${result.hashtag}"
                     },
                     style = MaterialTheme.typography.titleSmall,
                     color = MaterialTheme.colorScheme.onSurface,
@@ -950,10 +957,9 @@ private fun SearchResultCard(
                         is SearchResult.UserResult -> result.displayId
                         is SearchResult.NoteResult -> result.displayId
                         is SearchResult.AddressResult -> result.displayId
-                        is SearchResult.HashtagResult -> "Search posts with this hashtag"
                     },
                     style = MaterialTheme.typography.bodySmall,
-                    fontFamily = if (result is SearchResult.HashtagResult) null else FontFamily.Monospace,
+                    fontFamily = FontFamily.Monospace,
                     color = MaterialTheme.colorScheme.onSurfaceVariant,
                 )
             }

desktopApp/src/jvmMain/kotlin/com/vitorpamplona/amethyst/desktop/ui/ThreadScreen.kt

@@ -318,6 +318,8 @@ fun ThreadScreen(
                                             com.vitorpamplona.amethyst.desktop.service.media.GlobalMediaPlayer
                                                 .toggleFullscreen()
                                         },
+                                        // Root of an explicitly-opened thread — user opted in, skip spam collapse.
+                                        forceReveal = true,
                                     )
                                 }
                                 HorizontalDivider(thickness = 1.dp)

desktopApp/src/jvmMain/kotlin/com/vitorpamplona/amethyst/desktop/ui/note/NoteCard.kt

@@ -530,13 +530,18 @@ fun QuotedNoteEmbed(
         authorMetaValue
         val displayData = event.toNoteDisplayData(localCache)
 
-        NoteCard(
-            note = displayData,
+        SpamCheckedNoteRender(
+            note = note,
             localCache = localCache,
-            onClick = onNavigateToThread?.let { nav -> { nav(event.id) } },
-            onAuthorClick = onMentionClick,
-            onMentionClick = onMentionClick,
-        )
+        ) {
+            NoteCard(
+                note = displayData,
+                localCache = localCache,
+                onClick = onNavigateToThread?.let { nav -> { nav(event.id) } },
+                onAuthorClick = onMentionClick,
+                onMentionClick = onMentionClick,
+            )
+        }
     } else {
         Card(
             modifier = Modifier.fillMaxWidth(),

desktopApp/src/jvmMain/kotlin/com/vitorpamplona/amethyst/desktop/ui/note/SpamCheckedNoteRender.kt

@@ -0,0 +1,123 @@
+/*
+ * 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.desktop.ui.note
+
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.collectAsState
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.saveable.rememberSaveable
+import androidx.compose.runtime.setValue
+import com.vitorpamplona.amethyst.commons.model.Note
+import com.vitorpamplona.amethyst.commons.moderation.HashtagSpamCheck
+import com.vitorpamplona.amethyst.commons.moderation.LocalHashtagSpamSettings
+import com.vitorpamplona.amethyst.commons.moderation.LocalSpamExemptKeys
+import com.vitorpamplona.amethyst.commons.moderation.displayedEvent
+import com.vitorpamplona.amethyst.commons.ui.note.CollapsedSpamNote
+import com.vitorpamplona.amethyst.desktop.cache.DesktopLocalCache
+import com.vitorpamplona.quartz.nip01Core.core.Event
+import com.vitorpamplona.quartz.nip01Core.tags.hashtags.countHashtags
+
+/**
+ * Wraps a note render in the hashtag-spam check.
+ *
+ * Reads [LocalHashtagSpamSettings] and [LocalSpamExemptKeys] from
+ * composition. If the check trips and the user hasn't revealed this
+ * specific note (per-note [rememberSaveable] keyed by id), renders
+ * [CollapsedSpamNote] with author info pulled from [localCache];
+ * otherwise calls [normal].
+ *
+ * @param displayedEvent The event whose body the [normal] block renders.
+ *   For repost wrappers, callers should pass the *inner* event (via
+ *   [Note.displayedEvent]). For search results that already hold an
+ *   [Event] directly, pass it as-is.
+ * @param noteIdHex Stable id used as the [rememberSaveable] key for the
+ *   reveal flag — must match the id of whatever the [normal] block renders.
+ * @param forceReveal When `true`, skips the check entirely and always
+ *   renders [normal]. Used by thread-detail screens where the user
+ *   explicitly opted into the root note.
+ */
+@Composable
+fun SpamCheckedNoteRender(
+    displayedEvent: Event?,
+    noteIdHex: String,
+    localCache: DesktopLocalCache?,
+    forceReveal: Boolean = false,
+    normal: @Composable () -> Unit,
+) {
+    val settings = LocalHashtagSpamSettings.current
+    val enabled by settings.enabled.collectAsState()
+    val threshold by settings.threshold.collectAsState()
+    val exemptKeys = LocalSpamExemptKeys.current
+
+    val isSpam =
+        remember(noteIdHex, displayedEvent, enabled, threshold, exemptKeys) {
+            HashtagSpamCheck.isHashtagSpam(
+                displayedEvent = displayedEvent,
+                authorPubkey = displayedEvent?.pubKey,
+                enabled = enabled,
+                threshold = threshold,
+                exemptKeys = exemptKeys,
+            )
+        }
+
+    var revealed by rememberSaveable(noteIdHex) { mutableStateOf(false) }
+
+    if (!forceReveal && isSpam && !revealed && displayedEvent != null) {
+        val authorPubkey = displayedEvent.pubKey
+        val author = localCache?.getUserIfExists(authorPubkey)
+        val displayName = author?.toBestDisplayName() ?: authorPubkey.take(8)
+        val avatarUrl = author?.profilePicture()
+        val hashtagCount = displayedEvent.tags.countHashtags()
+        CollapsedSpamNote(
+            authorPubkeyHex = authorPubkey,
+            authorDisplayName = displayName,
+            authorAvatarUrl = avatarUrl,
+            hashtagCount = hashtagCount,
+            threshold = threshold,
+            onReveal = { revealed = true },
+        )
+    } else {
+        normal()
+    }
+}
+
+/**
+ * [Note]-shaped convenience overload — resolves the displayed event
+ * (unwrapping kind 6 / 16 reposts) and delegates to the primary helper.
+ */
+@Composable
+fun SpamCheckedNoteRender(
+    note: Note,
+    localCache: DesktopLocalCache?,
+    forceReveal: Boolean = false,
+    normal: @Composable () -> Unit,
+) {
+    val displayedEvent = remember(note, note.event) { note.displayedEvent() }
+    SpamCheckedNoteRender(
+        displayedEvent = displayedEvent,
+        noteIdHex = note.idHex,
+        localCache = localCache,
+        forceReveal = forceReveal,
+        normal = normal,
+    )
+}

desktopApp/src/jvmMain/kotlin/com/vitorpamplona/amethyst/desktop/ui/search/SearchResultsList.kt

@@ -60,7 +60,8 @@ import com.vitorpamplona.amethyst.commons.search.SearchSortOrder
 import com.vitorpamplona.amethyst.commons.ui.components.UserSearchCard
 import com.vitorpamplona.amethyst.desktop.cache.DesktopLocalCache
 import com.vitorpamplona.amethyst.desktop.ui.note.NoteCard
-import com.vitorpamplona.amethyst.desktop.ui.toNoteDisplayData
+import com.vitorpamplona.amethyst.desktop.ui.note.SpamCheckedNoteRender
+import com.vitorpamplona.amethyst.desktop.ui.rememberDisplayData
 import com.vitorpamplona.quartz.nip23LongContent.LongTextNoteEvent
 
 @Composable
@@ -153,24 +154,36 @@ fun SearchResultsList(
             if (!collapsed) {
                 val displayNotes = textNotes.take(5)
                 items(displayNotes, key = { "note-${it.id}" }) { event ->
-                    NoteCard(
-                        note = event.toNoteDisplayData(localCache),
+                    SpamCheckedNoteRender(
+                        displayedEvent = event,
+                        noteIdHex = event.id,
                         localCache = localCache,
-                        onClick = { onNavigateToThread(event.id) },
-                        onAuthorClick = onNavigateToProfile,
-                        onMentionClick = onNavigateToProfile,
-                    )
+                    ) {
+                        NoteCard(
+                            note = event.rememberDisplayData(localCache),
+                            localCache = localCache,
+                            onClick = { onNavigateToThread(event.id) },
+                            onAuthorClick = onNavigateToProfile,
+                            onMentionClick = onNavigateToProfile,
+                        )
+                    }
                 }
                 if (textNotes.size > 5) {
                     item(key = "notes-expand") {
                         ExpandableSection(
                             remaining = textNotes.drop(5),
                         ) { event ->
-                            NoteCard(
-                                note = event.toNoteDisplayData(localCache),
-                                onClick = { onNavigateToThread(event.id) },
-                                onAuthorClick = onNavigateToProfile,
-                            )
+                            SpamCheckedNoteRender(
+                                displayedEvent = event,
+                                noteIdHex = event.id,
+                                localCache = localCache,
+                            ) {
+                                NoteCard(
+                                    note = event.rememberDisplayData(localCache),
+                                    onClick = { onNavigateToThread(event.id) },
+                                    onAuthorClick = onNavigateToProfile,
+                                )
+                            }
                         }
                     }
                 }
@@ -197,24 +210,36 @@ fun SearchResultsList(
             }
             if (!collapsed) {
                 items(articles.take(5), key = { "article-${it.id}" }) { event ->
-                    NoteCard(
-                        note = event.toNoteDisplayData(localCache),
+                    SpamCheckedNoteRender(
+                        displayedEvent = event,
+                        noteIdHex = event.id,
                         localCache = localCache,
-                        onClick = { onNavigateToThread(event.id) },
-                        onAuthorClick = onNavigateToProfile,
-                        onMentionClick = onNavigateToProfile,
-                    )
+                    ) {
+                        NoteCard(
+                            note = event.rememberDisplayData(localCache),
+                            localCache = localCache,
+                            onClick = { onNavigateToThread(event.id) },
+                            onAuthorClick = onNavigateToProfile,
+                            onMentionClick = onNavigateToProfile,
+                        )
+                    }
                 }
                 if (articles.size > 5) {
                     item(key = "articles-expand") {
                         ExpandableSection(
                             remaining = articles.drop(5),
                         ) { event ->
-                            NoteCard(
-                                note = event.toNoteDisplayData(localCache),
-                                onClick = { onNavigateToThread(event.id) },
-                                onAuthorClick = onNavigateToProfile,
-                            )
+                            SpamCheckedNoteRender(
+                                displayedEvent = event,
+                                noteIdHex = event.id,
+                                localCache = localCache,
+                            ) {
+                                NoteCard(
+                                    note = event.rememberDisplayData(localCache),
+                                    onClick = { onNavigateToThread(event.id) },
+                                    onAuthorClick = onNavigateToProfile,
+                                )
+                            }
                         }
                     }
                 }
@@ -239,13 +264,19 @@ fun SearchResultsList(
             }
             if (!collapsed) {
                 items(otherNotes.take(5), key = { "other-${it.id}" }) { event ->
-                    NoteCard(
-                        note = event.toNoteDisplayData(localCache),
+                    SpamCheckedNoteRender(
+                        displayedEvent = event,
+                        noteIdHex = event.id,
                         localCache = localCache,
-                        onClick = { onNavigateToThread(event.id) },
-                        onAuthorClick = onNavigateToProfile,
-                        onMentionClick = onNavigateToProfile,
-                    )
+                    ) {
+                        NoteCard(
+                            note = event.rememberDisplayData(localCache),
+                            localCache = localCache,
+                            onClick = { onNavigateToThread(event.id) },
+                            onAuthorClick = onNavigateToProfile,
+                            onMentionClick = onNavigateToProfile,
+                        )
+                    }
                 }
             }
         }

desktopApp/src/jvmMain/kotlin/com/vitorpamplona/amethyst/desktop/ui/settings/HashtagSpamSettingsSection.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.desktop.ui.settings
+
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.Spacer
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.height
+import androidx.compose.foundation.layout.width
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.Slider
+import androidx.compose.material3.Switch
+import androidx.compose.material3.Text
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.LaunchedEffect
+import androidx.compose.runtime.collectAsState
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableFloatStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.unit.dp
+import com.vitorpamplona.amethyst.commons.moderation.HashtagSpamSettings
+import kotlin.math.roundToInt
+
+/**
+ * Settings UI for the hashtag-spam content filter.
+ *
+ * Decoupled-thumb pattern: a local [Float] state drives the [Slider] thumb,
+ * the [StateFlow] only sees the committed [Int] on [onValueChangeFinished].
+ * Prevents per-tick recomposition storms in the feed while the user drags.
+ */
+@Composable
+fun HashtagSpamSettingsSection(
+    settings: HashtagSpamSettings,
+    modifier: Modifier = Modifier,
+) {
+    val enabled by settings.enabled.collectAsState()
+    val committed by settings.threshold.collectAsState()
+
+    var live by remember { mutableFloatStateOf(committed.toFloat()) }
+    LaunchedEffect(committed) { live = committed.toFloat() }
+
+    Column(modifier = modifier.fillMaxWidth()) {
+        Text(
+            text = "Hashtag-spam filter",
+            style = MaterialTheme.typography.titleSmall,
+            color = MaterialTheme.colorScheme.onBackground,
+        )
+        Spacer(Modifier.height(8.dp))
+        Row(verticalAlignment = Alignment.CenterVertically) {
+            Switch(checked = enabled, onCheckedChange = settings::setEnabled)
+            Spacer(Modifier.width(8.dp))
+            Text(
+                text = if (enabled) "On" else "Off",
+                style = MaterialTheme.typography.bodyMedium,
+            )
+        }
+        if (enabled) {
+            Spacer(Modifier.height(8.dp))
+            Text(
+                text = "Hide notes with more than ${live.roundToInt()} hashtags",
+                style = MaterialTheme.typography.bodyMedium,
+            )
+            Slider(
+                value = live,
+                onValueChange = { live = it },
+                onValueChangeFinished = { settings.setThreshold(live.roundToInt()) },
+                valueRange =
+                    HashtagSpamSettings.MIN_THRESHOLD
+                        .toFloat()..HashtagSpamSettings.MAX_THRESHOLD.toFloat(),
+                steps = HashtagSpamSettings.MAX_THRESHOLD - HashtagSpamSettings.MIN_THRESHOLD - 1,
+            )
+            Text(
+                text = "Long-form articles and posts from people you follow are always shown.",
+                style = MaterialTheme.typography.bodySmall,
+                color = MaterialTheme.colorScheme.onSurfaceVariant,
+            )
+        }
+    }
+}

docs/plans/2026-06-29-feat-desktop-hashtag-spam-filter-plan.md

@@ -0,0 +1,867 @@
+---
+title: Desktop Hashtag-Spam Filter
+type: feat
+status: active
+date: 2026-06-29
+origin: docs/brainstorms/2026-06-29-feat-hashtag-spam-filter-brainstorm.md
+deepened: 2026-06-29
+---
+
+# Desktop Hashtag-Spam Filter
+
+## Enhancement Summary
+
+**Deepened on:** 2026-06-29 (same day as plan write).
+
+**Review agents used:** architecture-strategist, code-simplicity-reviewer,
+pattern-recognition-specialist, performance-oracle, agent-native-reviewer,
+security-sentinel · plus best-practices research (Compose collapse-UX + Slider
+patterns) and a Quartz/NoteCard-variant verification sweep.
+
+### Key corrections vs initial plan
+
+1. **Repost unwrap uses `note.replyTo`, not `containedPost()`.** Desktop's
+   `DesktopLocalCache.consumeRepost()` already resolves the boosted event into
+   `note.replyTo` at consume time — a pointer chase, not a JSON parse per render.
+2. **NoteCard signature mismatch.** Desktop `NoteCard` takes `NoteDisplayData`,
+   not `Note`. Spam check is hoisted to the **caller** (`FeedScreen`,
+   `QuotedNoteEmbed`, thread renderer); `NoteCard` itself stays untouched, the
+   caller chooses between `NoteCard(...)` and `CollapsedSpamNote(...)`.
+3. **Persistence moves to `commons/jvmMain/`** with a stable
+   `java.util.prefs` node name shared between Desktop and the `amy` CLI —
+   closes the agent-native parity gap from day one.
+4. **Settings UI gets its own "Content Filters" section** in `Main.kt`'s
+   settings screen, not under `RelaySettingsScreen` (this isn't a relay
+   concern).
+5. **Reveal state simplifies to `rememberSaveable(note.idHex)`** — drop the
+   `LocalRevealedSpamState` CompositionLocal + `SnapshotStateMap`. Trade-off:
+   the same spam note revealed in column A stays collapsed in column B —
+   accepted as v1 limitation.
+6. **Slider commits on `onValueChangeFinished`** with a local `Float` state
+   driving the thumb. Live label reads the local float. No `debounce`, no
+   `prefs.flush()` thrash, no recomposition storm during drag.
+7. **`collectAsState` hoisted to column scope** (or higher) and scalars
+   pushed down to leaf items — not collected per-card.
+8. **`HashtagSpamCheck` placed in `commons/.../hashtags/`** (existing
+   package), not a new `filters/` package.
+9. **Self + follow exemption** merged into a single `exemptKeys: Set<HexKey>`
+   parameter.
+10. **`NoOpHashtagSpamSettings` dropped.** Always provide
+    `PreferencesHashtagSpamSettings` at App root via
+    `compositionLocalOf { error("Provide LocalHashtagSpamSettings") }`.
+11. **Notifications-tab compact card is out of scope v1** — uses a custom
+    56 dp composable that doesn't funnel through `NoteCard`. All other
+    Desktop note-render surfaces (Home/Hashtag/Profile/Search/Thread
+    replies/Embedded quotes) DO funnel through `NoteCard` and pick up the
+    filter for free.
+12. **Quartz API name correction:** `containedPost()`, not
+    `containedNote()`.
+
+### New considerations discovered
+
+- `note.replyTo` is precomputed by `DesktopLocalCache.consumeRepost`
+  (`desktopApp/.../cache/DesktopLocalCache.kt:401-416`). Use it.
+- `Kind3Follows.authors` is a `val` on an `@Immutable` data class
+  (`commons/.../nip02FollowList/Kind3FollowListState.kt:100-104`), so
+  `account.followingKeySet()` returns a stable reference — no extra caching
+  needed. The plan's earlier reactivity hedge was unnecessary.
+- `containedPost()` already returns `null` on parse failure
+  (`quartz/.../nip18Reposts/RepostEvent.kt:87-92`) — no extra try/catch.
+- Embedded quotes (`QuotedNoteEmbed`) and search results both call
+  `NoteCard()` directly, so the caller-side check handles them naturally
+  when we patch those call sites.
+
+---
+
+## Overview
+
+Detect notes that abuse `t` (hashtag) tags as a visibility trick and render
+them as a compact reveal-on-click placeholder instead of the normal note
+card. Logic in `commons/` (callable by Desktop, future Android, and the
+`amy` CLI). UI + settings shipped on Desktop first. Reuses Quartz's
+`hasMoreHashtagsThan` primitive.
+
+**Carried forward from brainstorm**
+(`docs/brainstorms/2026-06-29-feat-hashtag-spam-filter-brainstorm.md`):
+collapse-with-reveal · single global threshold · default 5 (slider 1–20,
+with off-switch) · auto-exempt long-form articles (kind 30023) + followed
+authors · persisted via `java.util.prefs.Preferences`.
+
+**Resolved during planning + deepening:** default ON · repost wrapper
+checks the inner wrapped event's tags (via pre-resolved `note.replyTo`) ·
+thread root auto-expands but replies stay collapsed · hashtag-feed columns
+still filter · reveal state is session-scoped via `rememberSaveable` keyed
+by note id · settings persisted under a `commons/jvmMain` `java.util.prefs`
+node shared with `amy`.
+
+## Problem Statement
+
+Hashtag-spam — posts with 10–30 `t` tags chosen to maximize cross-feed
+visibility — pollutes every multi-column deck view. The cost scales with
+column count: Desktop's TweetDeck-style UI exposes the problem more than
+Android. Existing `AntiSpamFilter` only catches duplicate content, not
+visibility-bombs.
+
+## Proposed Solution
+
+### High-level approach
+
+A pure check function in `commons/` (`HashtagSpamCheck.isHashtagSpam(...)`)
+called by the **callers** of each note-card composable (feed `LazyColumn`
+item lambdas, embedded-quote renderer, thread item renderer). When the check
+returns `true`, the caller renders a `CollapsedSpamNote` placeholder
+instead of the normal note card. The placeholder takes primitive scalars
+so the same composable is reusable across Desktop and (later) Android.
+
+Settings (enabled flag + integer threshold) live behind a
+`HashtagSpamSettings` interface in `commons/`, with a
+`PreferencesHashtagSpamSettings` JVM implementation backing
+`java.util.prefs.Preferences.userRoot().node("com/vitorpamplona/amethyst/filters")`
+— shared with `amy` CLI for agent-native parity.
+
+### Why **not** a FeedFilter
+
+`commons/.../ui/feeds/AdditiveFeedFilter.kt` is **exclusionary** —
+`applyFilter()` returns a `Set<Note>` and items not in the set vanish.
+Collapse-with-reveal needs to keep the item and render it differently, so
+the decision belongs at render time, not in the feed pipeline. The
+brainstorm doc named the unit `HashtagSpamFilter`; renamed to
+`HashtagSpamCheck`.
+
+### Architecture
+
+```
+┌──────────────────────────────────────────────────────────────────┐
+│ commons/  (platform-agnostic, callable by Desktop / amy / Android)│
+│ ┌──────────────────────────────────────────────────────────────┐ │
+│ │ commonMain/                                                  │ │
+│ │   hashtags/HashtagSpamCheck.kt        (pure function)        │ │
+│ │   hashtags/HashtagSpamSettings.kt     (interface, @Stable)   │ │
+│ │   hashtags/displayedEvent.kt          (Note → Event? helper) │ │
+│ │   ui/note/CollapsedSpamNote.kt        (scalar-param card)    │ │
+│ │   ui/LocalHashtagSpamSettings.kt      (CompositionLocal,     │ │
+│ │                                        error-on-default)     │ │
+│ │ jvmMain/                                                     │ │
+│ │   hashtags/PreferencesHashtagSpamSettings.kt                 │ │
+│ │     (java.util.prefs-backed impl, shared node name)          │ │
+│ └──────────────────────────────────────────────────────────────┘ │
+└──────────────────────────────────────────────────────────────────┘
+                              ▲
+                              │
+┌─────────────────────────────┴────────────────────────────────────┐
+│ desktopApp/  (only the UI wire-up + caller-side check)           │
+│   Main.kt                                                        │
+│     CompositionLocalProvider(LocalHashtagSpamSettings provides   │
+│                              PreferencesHashtagSpamSettings()) { │
+│       App() …                                                    │
+│     }                                                            │
+│   ui/settings/HashtagSpamSettingsSection.kt                      │
+│     (Switch + Slider; local Float thumb; commit on              │
+│      onValueChangeFinished)                                      │
+│   feeds/FeedScreen.kt (and QuotedNoteEmbed, ThreadScreen replies)│
+│     LazyColumn { items(notes, key = { it.idHex }) { note ->      │
+│       if (isHashtagSpam(...)) CollapsedSpamNote(...)             │
+│       else NoteCard(NoteDisplayData(note), …)                    │
+│     }}                                                           │
+└──────────────────────────────────────────────────────────────────┘
+
+┌──────────────────────────────────────────────────────────────────┐
+│ cli/  (amy — v2 subcommands, plan-out only)                      │
+│   amy filter hashtag-spam get / set                              │
+│   amy notes is-spam <neventid|hex>                               │
+│   amy notes feed --include-spam=false (default)                  │
+└──────────────────────────────────────────────────────────────────┘
+```
+
+### Pure check function
+
+`commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/hashtags/HashtagSpamCheck.kt`:
+
+```kotlin
+object HashtagSpamCheck {
+    /**
+     * Pure: no side effects, no IO. Caller passes plain scalars so this
+     * stays Compose-friendly for `remember(...)` keys and unit-testable
+     * without setting up a CompositionLocal.
+     *
+     * `displayedEvent` is the event whose body the note card actually
+     * renders — for kind 6/16 reposts that means the wrapped inner event
+     * resolved through `Note.displayedEvent()`.
+     *
+     * `exemptKeys` should already include the user's self pubkey plus
+     * every pubkey in the current follow list; merged at the call site so
+     * this function stays single-purpose.
+     */
+    fun isHashtagSpam(
+        displayedEvent: Event?,
+        authorPubkey: HexKey?,
+        enabled: Boolean,
+        threshold: Int,
+        exemptKeys: Set<HexKey>,
+    ): Boolean {
+        if (!enabled) return false
+        if (displayedEvent == null) return false
+        if (displayedEvent.kind == LongFormContentEvent.KIND) return false      // 30023
+        if (authorPubkey != null && authorPubkey in exemptKeys) return false
+        return displayedEvent.tags.hasMoreHashtagsThan(threshold)
+    }
+}
+```
+
+### Displayed-event resolver
+
+`commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/hashtags/displayedEvent.kt`:
+
+```kotlin
+/**
+ * For reposts (kind 6) and generic reposts (kind 16), the "displayed
+ * event" is the wrapped inner event already resolved on `note.replyTo`
+ * by the consume pipeline. Falls back to `containedPost()` only if the
+ * cache hasn't materialised the reply yet; that path JSON-parses and
+ * returns null on bad content (Quartz API already handles try/catch).
+ */
+fun Note.displayedEvent(): Event? {
+    val e = this.event ?: return null
+    return when (e) {
+        is RepostEvent -> replyTo?.lastOrNull()?.event ?: e.containedPost()
+        is GenericRepostEvent -> replyTo?.lastOrNull()?.event ?: e.containedPost()
+        else -> e
+    }
+}
+```
+
+`containedPost()` (not `containedNote()` — corrected) lives at
+`quartz/.../nip18Reposts/RepostEvent.kt:87` and
+`.../GenericRepostEvent.kt:87`. Both already wrap `fromJson(content)` in
+try/catch returning null.
+
+### Settings interface
+
+`commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/hashtags/HashtagSpamSettings.kt`:
+
+```kotlin
+@Stable
+interface HashtagSpamSettings {
+    val enabled: StateFlow<Boolean>
+    val threshold: StateFlow<Int>
+    fun setEnabled(enabled: Boolean)
+    fun setThreshold(threshold: Int)
+}
+```
+
+`LocalHashtagSpamSettings`:
+
+```kotlin
+val LocalHashtagSpamSettings: ProvidableCompositionLocal<HashtagSpamSettings> =
+    compositionLocalOf { error("LocalHashtagSpamSettings not provided") }
+```
+
+No `NoOpHashtagSpamSettings` — caller (`Main.kt` `App()`) is always required
+to provide the real impl. Compose idiom for "must provide" via `error { ... }`
+default, mirroring how Material3 enforces theme provision.
+
+### Persistence (commons/jvmMain — shared with `amy`)
+
+`commons/src/jvmMain/kotlin/com/vitorpamplona/amethyst/commons/hashtags/PreferencesHashtagSpamSettings.kt`:
+
+```kotlin
+class PreferencesHashtagSpamSettings(
+    prefs: Preferences = Preferences.userRoot().node("com/vitorpamplona/amethyst/filters"),
+) : HashtagSpamSettings {
+    private val _enabled = MutableStateFlow(prefs.getBoolean(KEY_ENABLED, true))
+    private val _threshold = MutableStateFlow(prefs.getInt(KEY_THRESHOLD, 5))
+    override val enabled = _enabled.asStateFlow()
+    override val threshold = _threshold.asStateFlow()
+
+    override fun setEnabled(v: Boolean) {
+        _enabled.value = v
+        prefs.putBoolean(KEY_ENABLED, v)
+    }
+
+    override fun setThreshold(v: Int) {
+        val clamped = v.coerceIn(MIN, MAX)
+        _threshold.value = clamped
+        prefs.putInt(KEY_THRESHOLD, clamped)
+    }
+
+    companion object {
+        const val KEY_ENABLED = "hashtag_spam_enabled"
+        const val KEY_THRESHOLD = "hashtag_spam_threshold"
+        const val MIN = 1
+        const val MAX = 20
+    }
+}
+```
+
+- Shared `java.util.prefs` node `com/vitorpamplona/amethyst/filters` (not
+  per-class) so `amy` constructing the same impl observes the same node.
+- No `prefs.flush()` — `java.util.prefs` auto-flushes on JVM shutdown and
+  periodically; explicit flush thrashes disk.
+- Defaults: enabled = `true`, threshold = `5`. New installs and existing
+  users (absent keys) both get the defaults. No migration code.
+
+### Collapsed-note placeholder
+
+`commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/ui/note/CollapsedSpamNote.kt`:
+
+```kotlin
+@Composable
+fun CollapsedSpamNote(
+    authorDisplayName: String,
+    authorAvatarUrl: String?,
+    createdAtSeconds: Long,
+    hashtagCount: Int,
+    threshold: Int,
+    onReveal: () -> Unit,
+    modifier: Modifier = Modifier,
+) {
+    Row(
+        modifier
+            .fillMaxWidth()
+            .heightIn(min = 56.dp)
+            .padding(horizontal = 12.dp, vertical = 8.dp)
+            .semantics {
+                contentDescription =
+                    "Hidden note from $authorDisplayName, $hashtagCount hashtags. Tap to reveal."
+            },
+        verticalAlignment = Alignment.CenterVertically,
+    ) {
+        Avatar(url = authorAvatarUrl, size = 32.dp)
+        Spacer(Modifier.width(8.dp))
+        Column(Modifier.weight(1f)) {
+            Text(authorDisplayName, style = MaterialTheme.typography.labelLarge)
+            Text(
+                "Filtered: $hashtagCount hashtags · threshold $threshold",
+                style = MaterialTheme.typography.bodySmall,
+                color = MaterialTheme.colorScheme.onSurfaceVariant,
+            )
+        }
+        Text(relativeTimeShort(createdAtSeconds), style = MaterialTheme.typography.bodySmall)
+        TextButton(onClick = onReveal) { Text("Reveal") }
+    }
+}
+```
+
+Parameters are **scalars only** — no `Note`, no `NoteDisplayData`, no
+`Event`. This is the single shareable surface; Android, Desktop, and any
+future front-end render it from their own data shape by mapping at the call
+site.
+
+Always visible: avatar, display name, timestamp, hashtag count, reason
+chip, Reveal button. Hidden: body, media, link previews. Convergent with
+Mastodon/Tusky/Bluesky CW-card conventions (research: best-practices).
+
+### Caller-side integration
+
+The check happens **outside** `NoteCard` because Desktop's `NoteCard` takes
+a `NoteDisplayData` that doesn't carry the raw `Note`/`Event` we need. Each
+caller resolves `Note → displayed event → spam decision` and renders
+`CollapsedSpamNote` or `NoteCard`.
+
+`desktopApp/.../ui/FeedScreen.kt` (representative):
+
+```kotlin
+@Composable
+fun FeedScreen(notes: List<Note>, account: IAccount) {
+    val settings = LocalHashtagSpamSettings.current
+    val enabled by settings.enabled.collectAsState()
+    val threshold by settings.threshold.collectAsState()
+    val exemptKeys = remember(account) {
+        // Stable: Kind3Follows.authors is @Immutable, selfPubkey is a String
+        account.followingKeySet() + account.userProfile().pubkeyHex
+    }
+
+    LazyColumn {
+        items(notes, key = { it.idHex }) { note ->
+            val displayedEvent = note.displayedEvent()
+            val isSpam = remember(note.idHex, displayedEvent, enabled, threshold, exemptKeys) {
+                HashtagSpamCheck.isHashtagSpam(
+                    displayedEvent = displayedEvent,
+                    authorPubkey = displayedEvent?.pubKey,
+                    enabled = enabled,
+                    threshold = threshold,
+                    exemptKeys = exemptKeys,
+                )
+            }
+            var revealed by rememberSaveable(note.idHex) { mutableStateOf(false) }
+
+            Box(Modifier.animateItem()) {                                  // smooth resize
+                if (isSpam && !revealed) {
+                    CollapsedSpamNote(
+                        authorDisplayName = note.author?.bestDisplayName() ?: "",
+                        authorAvatarUrl = note.author?.profilePicture(),
+                        createdAtSeconds = displayedEvent?.createdAt ?: 0L,
+                        hashtagCount = displayedEvent?.tags?.countHashtags() ?: 0,
+                        threshold = threshold,
+                        onReveal = { revealed = true },
+                    )
+                } else {
+                    NoteCard(NoteDisplayData(note), /* … */)
+                }
+            }
+        }
+    }
+}
+```
+
+Important specifics from research:
+
+- `collectAsState()` is called **once at column scope**, not once per note —
+  prevents 60–360 redundant collectors per visible viewport (perf-oracle).
+- `key = { it.idHex }` on `items(...)` is required for `Modifier.animateItem()`
+  to animate the size change correctly.
+- `rememberSaveable(note.idHex)` survives `LazyColumn` recycling on scroll.
+- Trade-off: the same spam note shown simultaneously in Home + Hashtag
+  columns has independent reveal state per column. Acceptable v1.
+
+#### Other caller sites that need the same pattern
+
+1. **`QuotedNoteEmbed`** at `desktopApp/.../ui/note/NoteCard.kt:470-535` — when
+   a note body contains `nostr:nevent…` and the rich-text renderer recurses
+   into `NoteCard`. Patch this entry to apply the same check.
+2. **Thread replies** in `desktopApp/.../ui/ThreadScreen.kt` — replies use
+   `NoteCard` too. The **root** note auto-expands (caller passes
+   `forceReveal = true`); replies use the normal collapse rule.
+3. **Search results** at `desktopApp/.../ui/search/SearchResultsList.kt:156+`
+   — same call-site change.
+4. **Notifications-tab compact 56 dp card** at `NotificationsScreen.kt:271-366`
+   does NOT funnel through `NoteCard` (it's a bespoke compact composable).
+   Verified by Quartz/NoteCard-variant sweep. **Deferred to v2** — the
+   notification's snippet text isn't a full note body so the impact is
+   lower.
+
+#### Thread root auto-expand
+
+Thread screen owns its caller and simply passes `forceReveal = true` to
+the root note's `revealed` state initialization, while replies keep
+`rememberSaveable(note.idHex) { mutableStateOf(false) }`. No `ReplyContext`
+plumbing through `NoteCard` (that didn't exist anyway — corrected from the
+draft).
+
+### Settings UI (Desktop)
+
+`desktopApp/src/jvmMain/kotlin/com/vitorpamplona/amethyst/desktop/ui/settings/HashtagSpamSettingsSection.kt`:
+
+```kotlin
+@Composable
+fun HashtagSpamSettingsSection(
+    settings: HashtagSpamSettings,
+    modifier: Modifier = Modifier,
+) {
+    val enabled by settings.enabled.collectAsState()
+    val committed by settings.threshold.collectAsState()
+
+    // Local slider state — decouples drag from StateFlow churn.
+    // LaunchedEffect resyncs if a different surface changes the threshold.
+    var live by remember { mutableFloatStateOf(committed.toFloat()) }
+    LaunchedEffect(committed) { live = committed.toFloat() }
+
+    Column(modifier.padding(16.dp)) {
+        Text("Hashtag-spam filter", style = MaterialTheme.typography.titleMedium)
+        Row(verticalAlignment = Alignment.CenterVertically) {
+            Switch(checked = enabled, onCheckedChange = settings::setEnabled)
+            Spacer(Modifier.width(8.dp))
+            Text(if (enabled) "On" else "Off")
+        }
+        if (enabled) {
+            Text("Hide notes with more than ${live.roundToInt()} hashtags",
+                 style = MaterialTheme.typography.bodyMedium)
+            Slider(
+                value = live,
+                onValueChange = { live = it },                            // local only — no recompose storm
+                onValueChangeFinished = { settings.setThreshold(live.roundToInt()) },
+                valueRange = 1f..20f,
+                steps = 18,
+            )
+            Text("Long-form articles and posts from people you follow are always shown.",
+                 style = MaterialTheme.typography.bodySmall,
+                 color = MaterialTheme.colorScheme.onSurfaceVariant)
+        }
+    }
+}
+```
+
+Wired into `Main.kt` settings screen as a dedicated **Content Filters**
+section (sibling to Wallet Connect, Media Server, Namecoin, Local Relay),
+not under `RelaySettingsScreen`'s relay-specific entries. Section header
+spans the screen so users searching "spam" or "hashtag" find it.
+
+The settings impl is provided at App root:
+
+```kotlin
+// Main.kt App()
+val hashtagSpamSettings = remember { PreferencesHashtagSpamSettings() }
+CompositionLocalProvider(
+    LocalHashtagSpamSettings provides hashtagSpamSettings,
+    // existing CompositionLocals …
+) {
+    App(…)
+}
+```
+
+## Technical Considerations
+
+### Performance
+
+- Quartz `hasMoreHashtagsThan` is O(n) over the note's tag array (n ≈ 5–30
+  worst case) with short-circuit on total count before any hashset
+  allocation. Sub-microsecond per note.
+- `note.displayedEvent()` is a pointer chase via the precomputed
+  `note.replyTo` for reposts — no JSON parse on the hot path. Falls back
+  to `containedPost()` (which itself has try/catch + null return) only
+  for the rare unconsumed-repost case.
+- `isHashtagSpam` is `remember(...)`-memoized against
+  `(noteId, displayedEvent, enabled, threshold, exemptKeys)`. The
+  `exemptKeys` set is `remember(account)`-cached at column scope so
+  references stay stable across recompositions.
+- Settings StateFlows are `collectAsState`d **once per column**, not per
+  note — prevents O(visible notes) flow collectors per deck.
+- `Slider` uses local `Float` state; downstream collectors only see the
+  committed `Int` on drag-end → zero feed recompositions while the user
+  drags the thumb.
+- `rememberSaveable(note.idHex)` for reveal flag survives LazyColumn
+  recycling on scroll without any external state container.
+
+### Stability annotations
+
+- `HashtagSpamSettings` interface: `@Stable` — public observable surface
+  (`StateFlow` instances) changes only via `setEnabled`/`setThreshold`,
+  honest stability contract.
+- `PreferencesHashtagSpamSettings` class: omit annotation — `@Stable` would
+  be redundant on a class implementing a `@Stable` interface, and
+  `@Immutable` is wrong (it holds `MutableStateFlow`s).
+- `HashtagSpamCheck` is `object` — implicitly `@Immutable`.
+
+### Threshold reactivity
+
+`enabled` and `threshold` are exposed as `StateFlow` and read via
+`collectAsState()` at column scope. Setting changes → StateFlow emit →
+column recomposes → all visible cards re-evaluate `isSpam` and
+re-collapse/re-reveal accordingly. Project pattern memory:
+`?.collectAsState()?.value` does NOT work for tracking — use `by … .collectAsState()`.
+
+### Follow-set reactivity
+
+`account.followingKeySet()` returns
+`kind3FollowList.flow.value.authors`. `Kind3Follows` is `@Immutable`, so
+the returned `Set<HexKey>` reference is stable until the follow list
+mutates upstream. Currently no `StateFlow<Set<HexKey>>` accessor exists —
+follow/unfollow during a session won't reactively re-evaluate cards in
+place. Acceptable for v1 (follow churn is low). A future refactor to expose
+`kind3FollowList.flow` directly on `IAccount` closes the gap.
+
+### Reposts and the displayed event
+
+| `note.event` kind | `note.displayedEvent()` |
+|-------------------|--------------------------|
+| 6 (`RepostEvent`) | `replyTo.last().event` (precomputed) ?: `containedPost()` |
+| 16 (`GenericRepostEvent`) | `replyTo.last().event` (precomputed) ?: `containedPost()` |
+| anything else | `note.event` |
+
+The wrapped event is **already materialised on `note.replyTo`** by
+`DesktopLocalCache.consumeRepost()` — no JSON parsing on render.
+
+### Inside threads
+
+Thread screen owns the caller; for the **root** note it initialises
+`revealed = true` (auto-expand on opt-in click-through). Replies use
+the default collapsed/`rememberSaveable` path. No special threading types.
+
+### Inside embedded/quoted notes
+
+`QuotedNoteEmbed` (the entry that recurses into `NoteCard` for inline
+`nostr:nevent…` references) gets the same check at its call site.
+Independent `rememberSaveable` per quote location.
+
+### Security / privacy
+
+- Pure client-side: no network IO, no relay filter derivation, no telemetry.
+- App-global persistence (not per-account) intentionally avoids leaking
+  per-Nostr-identity behavioural fingerprints to anyone with filesystem
+  access — the OS-account boundary is the trust boundary.
+- Malformed inner repost events: `containedPost()` already returns null,
+  `isHashtagSpam` returns false (does not collapse, does not throw).
+- Censorship-resistance smell test: content is **collapsed, not dropped**;
+  one click reveals; settings live in a top-level "Content Filters" section
+  (not buried under relays).
+
+## System-Wide Impact
+
+### Interaction graph
+
+```
+PreferencesHashtagSpamSettings (java.util.prefs node)
+    │
+    ▼ CompositionLocalProvider in Main.kt App()
+LocalHashtagSpamSettings
+    │
+    ▼ collectAsState() at column scope
+(enabled, threshold) as scalars
+    │
+    ▼ per-note remember(...) at LazyColumn item
+HashtagSpamCheck.isHashtagSpam(displayedEvent, …)
+    │
+    ▼ if true & !revealed
+CollapsedSpamNote(scalars, onReveal)
+    │
+    └─ onReveal → rememberSaveable(note.idHex) flips → recomposes this row only
+```
+
+### Error & failure propagation
+
+- `note.displayedEvent()`: fallback chain `replyTo → containedPost → null`.
+  Null displayed event → `isHashtagSpam = false` → normal NoteCard renders.
+  Never throws.
+- `Preferences.put*` may throw `BackingStoreException`. Wrap in try/catch
+  inside `setEnabled`/`setThreshold`; log and continue (in-memory state
+  already updated; persistence is best-effort).
+- Settings UI: `LocalHashtagSpamSettings` default `error("...")` only fires
+  if App root forgot the provider. Caught at first launch, never in prod.
+
+### State lifecycle risks
+
+- Reveal state is `rememberSaveable` per LazyColumn item. Survives scroll
+  recycling; lost on screen close (intentional).
+- Settings keys absent on first launch → defaults (`true`, `5`). No
+  partial-state risk; `java.util.prefs` is atomic per key.
+- Slider local-Float state is column-instance scoped; lost on settings
+  screen close. Re-derived from committed `Int` on next open.
+
+### API surface parity
+
+- **commons:** `HashtagSpamCheck` (pure), `HashtagSpamSettings` (interface),
+  `Note.displayedEvent()` extension, `CollapsedSpamNote` (scalar
+  composable), `LocalHashtagSpamSettings` (CompositionLocal),
+  `PreferencesHashtagSpamSettings` (`jvmMain` impl, shared `java.util.prefs`
+  node with `amy`).
+- **desktopApp:** App-root provider, `HashtagSpamSettingsSection` Compose
+  UI, caller-side check in `FeedScreen` / `QuotedNoteEmbed` / `ThreadScreen`
+  / `SearchResultsList`.
+- **amethyst (Android):** no changes v1. Future adoption is a single
+  `AndroidHashtagSpamSettings` (DataStore-backed) + `LocalHashtagSpamSettings`
+  provider + the same caller-side pattern. Commons does not leak Desktop
+  types so the path is clean.
+- **cli (amy):** day-1 picks up the shared `java.util.prefs` node — agents
+  using `amy` see the same setting users configured in Desktop. v2 adds
+  `amy filter hashtag-spam {get|set}` and `amy notes is-spam <ref>`
+  subcommands; v2 also adds `amy notes feed --include-spam` (default
+  respects setting).
+
+### Integration test scenarios
+
+1. **Slider live re-collapse.** Open a Home column with a known spammy
+   visible (revealed). Drag threshold down past its tag count.
+   `onValueChangeFinished` commits → all visible cards re-evaluate → that
+   card collapses. No mid-drag visual jank.
+2. **Repost spam (precomputed).** A kind:6 wrapping a 12-hashtag kind:1
+   already consumed → `replyTo` materialised → check trips on inner →
+   wrapper collapses.
+3. **Repost spam (unconsumed).** Same scenario but the inner event hasn't
+   been cached → fallback to `containedPost()` succeeds → same outcome.
+4. **Followed-author exemption.** 15-hashtag note from a key in follow set
+   → does NOT collapse.
+5. **Self exemption.** 15-hashtag note from the active account → does NOT
+   collapse for self.
+6. **Long-form exemption.** kind:30023 with 12 topic tags → no collapse.
+7. **Thread root auto-expand.** Tap a collapsed card → thread screen → root
+   shows full content; a 12-hashtag reply in the thread stays collapsed.
+8. **Embedded quote.** A note quotes a 15-hashtag note via `nostr:nevent…`
+   → the inline embedded card renders as collapsed; revealing it does NOT
+   reveal the same note in the parent feed column (independent
+   `rememberSaveable` per call site).
+9. **Settings persistence.** Toggle off, restart Desktop app → off-state
+   restored from `java.util.prefs` node.
+10. **amy parity.** From command line, write enabled=false to the shared
+    prefs node via plain `java.util.prefs` API → relaunch Desktop →
+    Desktop reads the same node → filter is off.
+11. **Malformed inner repost.** `containedPost()` returns null on bad
+    inner JSON → `isHashtagSpam` returns false → renders normal NoteCard
+    of the wrapper (which itself has 0 hashtags). No crash.
+
+## Acceptance Criteria
+
+### Functional
+
+- [x] `HashtagSpamCheck.isHashtagSpam` in
+      `commons/commonMain/.../moderation/HashtagSpamCheck.kt`. Compiles for
+      `:commons:compileKotlinJvm`. *(Note: filed under `moderation/` not
+      `hashtags/` — `hashtags/` is the existing icon-only package.)*
+- [x] `HashtagSpamSettings` (`@Stable` interface) in
+      `commons/commonMain/.../moderation/HashtagSpamSettings.kt`.
+- [x] `LocalHashtagSpamSettings` CompositionLocal with `error(...)`
+      default. `LocalSpamExemptKeys` CompositionLocal added for the
+      account-derived exempt set.
+- [x] `PreferencesHashtagSpamSettings` JVM impl in `commons/jvmMain`
+      bound to `Preferences.userRoot().node("com/vitorpamplona/amethyst/filters")`
+      with keys `hashtag_spam_enabled` (default `true`) and
+      `hashtag_spam_threshold` (default `5`, range 1–20).
+- [x] `CollapsedSpamNote` composable in
+      `commons/commonMain/.../ui/note/CollapsedSpamNote.kt` taking scalar
+      params only (no `Note`, no `NoteDisplayData`, no `Event`); includes
+      a11y `contentDescription`.
+- [x] `Note.displayedEvent()` extension in
+      `commons/commonMain/.../moderation/DisplayedEvent.kt` returning the
+      wrapped event for kind 6 / 16 via `replyTo` (precomputed), falling
+      back to `containedPost()` and finally null.
+- [x] Desktop `FeedNoteCard` (covers FeedScreen + ThreadScreen +
+      UserProfileScreen), `QuotedNoteEmbed`, `BookmarksScreen`, and
+      `SearchResultsList` (5 sites) all branch on the spam check
+      caller-side via the shared `SpamCheckedNoteRender` helper and render
+      either `CollapsedSpamNote` or `NoteCard`.
+- [x] `FeedNoteCard` exposes `forceReveal: Boolean = false`; ThreadScreen
+      passes `forceReveal = true` for the root note. Replies inside the
+      thread use default `rememberSaveable` collapsed.
+- [x] `Main.kt` provides `LocalHashtagSpamSettings` at App root (always-on)
+      and `LocalSpamExemptKeys` inside the LoggedIn branch (account-aware);
+      adds a **Content Filters** settings section containing
+      `HashtagSpamSettingsSection`.
+- [x] `HashtagSpamSettingsSection`: Switch + Slider with local `Float`
+      state, commit on `onValueChangeFinished`, live label, exemption
+      footnote.
+- [x] Notifications-tab compact card explicitly **out of scope v1** —
+      documented in the deferred section + manual testing sheet T13.
+- [x] `collectAsState` for settings called once inside
+      `SpamCheckedNoteRender` (per visible card, but with cheap stable
+      `StateFlow` references); slider settings UI also collects once.
+
+### Non-functional
+
+- [ ] No measurable frame-time regression in profiler runs of a 200-note
+      column (manual smoke test pending — see T14 in testing sheet).
+- [x] Spotless clean: `./gradlew spotlessApply` produces no diff.
+- [x] Compiles cleanly: `./gradlew :commons:compileKotlinJvm
+      :desktopApp:compileKotlin`.
+- [x] No `Preferences.flush()` calls; rely on JVM auto-flush.
+
+### Quality gates
+
+- [x] Unit tests for `HashtagSpamCheck` (commons) — disabled, longform
+      exempt, self exempt, follow exempt, under threshold, equal threshold,
+      over threshold with duplicates only (helper short-circuits on
+      uniques), over threshold with uniques, null displayedEvent, null
+      authorPubkey. **10 tests, all green.**
+- [x] Unit test for `Note.displayedEvent()` — repost with materialised
+      `replyTo`, repost with null `replyTo` (fallback returns null on
+      malformed JSON), non-repost (returns own event), null event.
+      **4 tests, all green.**
+- [x] Unit test for `PreferencesHashtagSpamSettings` — read default, read
+      after set, threshold clamps to 1..20, both keys persist across
+      instance recreation (test-specific node suffix). **5 tests, all
+      green.**
+- [x] Manual testing sheet at
+      `desktopApp/plans/2026-06-29-hashtag-spam-filter-manual-testing-sheet.md`
+      covering 16 integration scenarios.
+
+## Success Metrics
+
+- Subjective deck-feed cleanliness on default ON / threshold 5 (no
+  collapsed legit follow content, visible spam collapsed).
+- No frame drops > 16 ms during slider drag or feed scroll in a heavy
+  column.
+- Settings persist across app restarts and across the Desktop ↔ `amy`
+  boundary.
+
+## Dependencies & Risks
+
+| Risk | Likelihood | Mitigation |
+|------|------------|------------|
+| `replyTo` unset for very fresh reposts | low | Fall back to `containedPost()`; both already null-safe |
+| Embedded `NoteCard` recursion misses a call site | medium | Audit every site that constructs `NoteCard(NoteDisplayData(note), …)` during impl; integration scenario #8 catches misses |
+| Follow-set non-reactive during a session | low | Acceptable v1; track for a future `IAccount.followingFlow()` accessor |
+| Default-on surprises power users | medium | Settings entry is in a top-level **Content Filters** section and easy to find; no toast (per simplicity review) |
+| amy and Desktop diverge on settings node name | low | Use a constant `Preferences` node name in commons and reference it from both binaries |
+| `Modifier.animateItem()` on an alpha API surface | low | Compose Foundation 1.7+ stable; project already uses it elsewhere — verify during impl |
+
+## Out of Scope (deferred)
+
+- User-curated hashtag allowlist (waiting for false-positive feedback).
+- Per-column threshold override.
+- Aggregated "N filtered today" badge.
+- Account-synced setting via NIP-78/NIP-51.
+- Android UI (commons logic ready; Android wires later).
+- **`amy` subcommands** for the filter (`amy filter hashtag-spam …`,
+  `amy notes is-spam`, `amy notes feed --include-spam`) — v2; v1 ships the
+  shared `java.util.prefs` node so the data is already accessible.
+- Banner when feed is 100 % collapsed.
+- Cross-column shared reveal state (each column's reveal flag is
+  independent in v1 — `rememberSaveable` per call site).
+- Notifications-tab compact 56 dp card spam check (custom composable that
+  doesn't go through `NoteCard`).
+- Persistent "permanently revealed" notes across sessions.
+
+## Sources & References
+
+### Origin
+
+- **Brainstorm:** `docs/brainstorms/2026-06-29-feat-hashtag-spam-filter-brainstorm.md`
+  — collapse-with-reveal · global threshold · default 5 · longform +
+  followed exemptions · `Preferences` persistence.
+
+### Internal references
+
+- `quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nip01Core/tags/hashtags/TagArrayExt.kt:41`
+  — `hasMoreHashtagsThan(limit)` primitive.
+- `quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nip18Reposts/RepostEvent.kt:87`
+  + `.../GenericRepostEvent.kt:87` — `containedPost()` (null-safe).
+- `desktopApp/src/jvmMain/kotlin/com/vitorpamplona/amethyst/desktop/cache/DesktopLocalCache.kt:401-416`
+  — `consumeRepost()` precomputes `note.replyTo` (use this, not JSON
+  decode).
+- `commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/model/nip02FollowList/Kind3FollowListState.kt:100-104`
+  — `@Immutable Kind3Follows.authors: Set<HexKey>` (stable ref).
+- `commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/model/IAccount.kt:101`
+  — `followingKeySet(): Set<String>`.
+- `desktopApp/src/jvmMain/kotlin/com/vitorpamplona/amethyst/desktop/ui/note/NoteCard.kt:96-112`
+  — `NoteCard(note: NoteDisplayData, …)` signature (caller-side check).
+- `desktopApp/src/jvmMain/kotlin/com/vitorpamplona/amethyst/desktop/ui/note/NoteCard.kt:470-535`
+  — `QuotedNoteEmbed` recursion site (also needs caller-side check).
+- `desktopApp/src/jvmMain/kotlin/com/vitorpamplona/amethyst/desktop/ui/search/SearchResultsList.kt:156+`
+  — search-result call sites.
+- `desktopApp/src/jvmMain/kotlin/com/vitorpamplona/amethyst/desktop/DesktopPreferences.kt`
+  — existing `java.util.prefs` pattern (referenced; settings live in
+  commons/jvmMain instead).
+- `desktopApp/src/jvmMain/kotlin/com/vitorpamplona/amethyst/desktop/ui/settings/LocalRelaySettingsScreen.kt`
+  — Switch + Slider settings UI pattern.
+- `desktopApp/src/jvmMain/kotlin/com/vitorpamplona/amethyst/desktop/ui/deck/LocalFeedProvider.kt:64-87`
+  — existing `Local*` CompositionLocal pattern.
+- `commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/ui/feeds/AdditiveFeedFilter.kt`
+  — why we don't extend `FeedFilter` (exclusionary contract).
+- `commons/ARCHITECTURE.md` — module taxonomy / `commons/jvmMain` placement
+  for JVM-only helpers.
+
+### External references
+
+- [Android Developers — Lazy lists and lazy grids](https://developer.android.com/develop/ui/compose/lists)
+  — stable `key`, `Modifier.animateItem()`.
+- [Android Developers — Where to hoist state](https://developer.android.com/develop/ui/compose/state-hoisting).
+- [JetBrains compose-multiplatform #4366 — Slider draggable state](https://github.com/JetBrains/compose-multiplatform/issues/4366)
+  — why local `Float` + `onValueChangeFinished` is needed.
+- [issuetracker #240599812 — AnimatedVisibility in LazyColumn](https://issuetracker.google.com/issues/240599812)
+  — pitfalls with collapsed-item layout.
+- [Mastodon moderating docs](https://docs.joinmastodon.org/user/moderating/)
+  + [Bluesky moderation docs](https://docs.bsky.app/docs/advanced-guides/moderation)
+  — convergent "always show author, gate body" convention.
+
+### Skill references
+
+- `feed-patterns` — confirmed `FeedFilter` is exclusionary; not used here.
+- `compose-expert` — note-card composition + state hoisting.
+- `compose-side-effects` — `LaunchedEffect(committed) { live = … }` to
+  resync slider local state on upstream change.
+- `compose-recomposition-performance` — hoist `collectAsState` to column
+  scope; `rememberSaveable` survives recycling; local `Float` thumb.
+- `compose-stability-diagnostics` — `@Stable` on the settings interface.
+- `kotlin-flow-state-event-modeling` — StateFlow + collectAsState
+  reactivity.
+- `account-state` — `IAccount.followingKeySet()`; `Kind3Follows`
+  immutability.
+- `nostr-expert` — repost event unwrap via `replyTo`; `containedPost()`
+  semantics.
+- `amy-expert` — shared `java.util.prefs` node so `amy` reads the same
+  setting users configure in Desktop.
+- `kotlin-multiplatform` — `commons/jvmMain` placement for JVM-only
+  persistence impls.
+
+### Backlog reference
+
+- `desktopApp/plans/_desktop-feature-backlog.md` priority item #1; WoT
+  score on avatars is the next item.