Code review:

- only parse commonName when the alt tag has the Birdstar prefix
- summary() on both Birdstar events now uses the canonical NIP-31
  tags.alt() helper instead of a raw firstTagValue("alt") lookup
- speciesReference() only returns http(s) URLs since UIs render it as
  a clickable link (rejects e.g. javascript: schemes), with a test
- Detection card: parse tags once into a single remember slot, drop
  the near-dead '?: summary' title fallback, stop rebuilding the
  italic TextStyle every recomposition
- Hoist the duplicated bird-emoji literal into a shared BIRD_PREFIX
- Trim the redundant factory test to the assertIs idiom

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/note/types/Birdex.kt

@@ -45,6 +45,9 @@ import com.vitorpamplona.quartz.experimental.birdstar.BirdexEvent
 /** How many species names to list before collapsing into a "+N more" suffix. */
 private const val SPECIES_PREVIEW_LIMIT = 6
 
+/** Bird emoji prefix shared by both Birdstar card titles. */
+private const val BIRD_PREFIX = "\uD83D\uDC26 "
+
 /**
  * Minimal, fixed-size summary card for a Birdstar "Birdex" (kind 12473).
  *
@@ -65,7 +68,7 @@ fun RenderBirdex(baseNote: Note) {
 
     Column(MaterialTheme.colorScheme.replyModifier.padding(10.dp)) {
         Text(
-            text = "\uD83D\uDC26 " + pluralStringResource(R.plurals.birdex_species_count, names.size, names.size),
+            text = BIRD_PREFIX + pluralStringResource(R.plurals.birdex_species_count, names.size, names.size),
             style = MaterialTheme.typography.titleMedium,
         )
 
@@ -91,41 +94,47 @@ fun RenderBirdex(baseNote: Note) {
  * Minimal card for a single Birdstar bird detection (kind 2473).
  *
  * The event has no body and no images. The title is the common name parsed from
- * the publisher's `alt` tag (falling back to the raw `alt`, then a generic
- * label), and the scientific name renders as an italic link to the Wikidata
- * species entry from the `i` tag when one is present. The `g` geohash is
- * surfaced by the generic note-location UI, not here.
+ * the publisher's `alt` tag (a generic label when absent), and the scientific
+ * name renders as an italic link to the Wikidata species entry from the `i` tag
+ * when one is present. The `g` geohash is surfaced by the generic note-location
+ * UI, not here.
  */
 @Composable
 fun RenderBirdDetection(baseNote: Note) {
     val noteEvent = baseNote.event as? BirdDetectionEvent ?: return
 
-    val commonName = remember(noteEvent) { noteEvent.commonName() }
-    val summary = remember(noteEvent) { noteEvent.summary() }
-    val species = remember(noteEvent) { noteEvent.speciesName() }
-    val reference = remember(noteEvent) { noteEvent.speciesReference() }
+    val detection =
+        remember(noteEvent) {
+            BirdDetectionInfo(
+                commonName = noteEvent.commonName(),
+                species = noteEvent.speciesName(),
+                reference = noteEvent.speciesReference(),
+            )
+        }
 
     Column(MaterialTheme.colorScheme.replyModifier.padding(10.dp)) {
         Text(
-            text = "\uD83D\uDC26 " + (commonName ?: summary ?: stringResource(R.string.bird_detection_title)),
+            text = BIRD_PREFIX + (detection.commonName ?: stringResource(R.string.bird_detection_title)),
             style = MaterialTheme.typography.titleMedium,
             maxLines = 2,
             overflow = TextOverflow.Ellipsis,
         )
 
-        if (species != null) {
+        if (detection.species != null) {
             Spacer(Modifier.height(6.dp))
-            val speciesStyle = MaterialTheme.typography.bodyMedium.copy(fontStyle = FontStyle.Italic)
-            if (reference != null) {
+            if (detection.reference != null) {
+                val typography = MaterialTheme.typography
+                val speciesStyle = remember(typography) { typography.bodyMedium.copy(fontStyle = FontStyle.Italic) }
                 ClickableUrl(
-                    urlText = species,
-                    url = reference,
+                    urlText = detection.species,
+                    url = detection.reference,
                     style = speciesStyle,
                 )
             } else {
                 Text(
-                    text = species,
-                    style = speciesStyle,
+                    text = detection.species,
+                    style = MaterialTheme.typography.bodyMedium,
+                    fontStyle = FontStyle.Italic,
                     color = MaterialTheme.colorScheme.placeholderText,
                     maxLines = 1,
                     overflow = TextOverflow.Ellipsis,
@@ -134,3 +143,10 @@ fun RenderBirdDetection(baseNote: Note) {
         }
     }
 }
+
+/** Tag values parsed once per event for the detection card. */
+private class BirdDetectionInfo(
+    val commonName: String?,
+    val species: String?,
+    val reference: String?,
+)

quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/experimental/birdstar/BirdDetectionEvent.kt

@@ -24,6 +24,7 @@ import androidx.compose.runtime.Immutable
 import com.vitorpamplona.quartz.nip01Core.core.Event
 import com.vitorpamplona.quartz.nip01Core.core.HexKey
 import com.vitorpamplona.quartz.nip01Core.core.firstTagValue
+import com.vitorpamplona.quartz.nip31Alts.alt
 import com.vitorpamplona.quartz.nip50Search.SearchableEvent
 
 /**
@@ -59,20 +60,26 @@ class BirdDetectionEvent(
     /** Scientific name of the detected species, from the `n` tag (may be null). */
     fun speciesName() = tags.firstTagValue("n")
 
-    /** External species reference (Wikidata entity URL), from the `i` tag (may be null). */
-    fun speciesReference() = tags.firstTagValue("i")
+    /**
+     * External species reference (Wikidata entity URL), from the `i` tag.
+     * Only http(s) URLs are returned — UIs render this as a clickable link,
+     * so other schemes are rejected here rather than at every call site.
+     */
+    fun speciesReference() = tags.firstTagValue("i")?.takeIf { it.startsWith("https://") || it.startsWith("http://") }
 
-    /** Publisher-provided human-readable summary, from the `alt` tag (may be null). */
-    fun summary() = tags.firstTagValue("alt")
+    /** Publisher-provided human-readable summary, from the NIP-31 `alt` tag (may be null). */
+    fun summary() = tags.alt()
 
     /**
      * Common (vernacular) species name, parsed out of the `alt` tag. Birdstar
-     * writes `Bird detection: <Common name> (<Scientific name>)`; this strips the
-     * fixed prefix and the trailing parenthetical. Null when the `alt` tag is
-     * missing or nothing is left after stripping.
+     * currently writes `Bird detection: <Common name> (<Scientific name>)` (in
+     * English); this strips the fixed prefix and the trailing parenthetical.
+     * Null when the `alt` tag is missing or nothing is left after stripping —
+     * including if a future Birdstar release rewords the alt text.
      */
     fun commonName(): String? {
         val alt = summary() ?: return null
+        if (!alt.startsWith(ALT_PREFIX)) return null
         return alt
             .removePrefix(ALT_PREFIX)
             .substringBeforeLast(" (")

quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/experimental/birdstar/BirdexEvent.kt

@@ -23,8 +23,8 @@ package com.vitorpamplona.quartz.experimental.birdstar
 import androidx.compose.runtime.Immutable
 import com.vitorpamplona.quartz.nip01Core.core.BaseReplaceableEvent
 import com.vitorpamplona.quartz.nip01Core.core.HexKey
-import com.vitorpamplona.quartz.nip01Core.core.firstTagValue
 import com.vitorpamplona.quartz.nip01Core.core.mapValueTagged
+import com.vitorpamplona.quartz.nip31Alts.alt
 import com.vitorpamplona.quartz.nip50Search.SearchableEvent
 
 /**
@@ -65,8 +65,8 @@ class BirdexEvent(
     /** Number of collected species (one `n` tag per species). */
     fun speciesCount() = speciesNames().size
 
-    /** Publisher-provided human-readable summary, from the `alt` tag (may be null). */
-    fun summary() = tags.firstTagValue("alt")
+    /** Publisher-provided human-readable summary, from the NIP-31 `alt` tag (may be null). */
+    fun summary() = tags.alt()
 
     companion object {
         const val KIND = 12473

quartz/src/commonTest/kotlin/com/vitorpamplona/quartz/experimental/birdstar/BirdDetectionEventTest.kt

@@ -52,11 +52,24 @@ class BirdDetectionEventTest {
 
     @Test
     fun factoryBuildsBirdDetectionForKind2473() {
-        val event = sampleEvent()
-        assertTrue(
-            event is BirdDetectionEvent,
-            "Expected a BirdDetectionEvent but got ${event::class.simpleName}",
-        )
+        assertIs<BirdDetectionEvent>(sampleEvent())
+    }
+
+    @Test
+    fun speciesReferenceRejectsNonHttpValues() {
+        val event: Event =
+            EventFactory.create(
+                id = "00".repeat(32),
+                pubKey = "00".repeat(32),
+                createdAt = 1_783_089_908L,
+                kind = BirdDetectionEvent.KIND,
+                tags = arrayOf(arrayOf("i", "javascript:alert(1)")),
+                content = "",
+                sig = "00".repeat(64),
+            )
+        assertIs<BirdDetectionEvent>(event)
+
+        assertEquals(null, event.speciesReference())
     }
 
     @Test
@@ -89,6 +102,23 @@ class BirdDetectionEventTest {
         assertEquals(null, event.commonName())
     }
 
+    @Test
+    fun commonNameIsNullWhenAltLacksTheBirdstarPrefix() {
+        val event: Event =
+            EventFactory.create(
+                id = "00".repeat(32),
+                pubKey = "00".repeat(32),
+                createdAt = 1_783_089_908L,
+                kind = BirdDetectionEvent.KIND,
+                tags = arrayOf(arrayOf("alt", "Arbitrary attacker-controlled title (spoof)")),
+                content = "",
+                sig = "00".repeat(64),
+            )
+        assertIs<BirdDetectionEvent>(event)
+
+        assertEquals(null, event.commonName())
+    }
+
     @Test
     fun commonNameHandlesAltWithoutParenthetical() {
         val event: Event =