feat: add NIP-89 client tag to all signed events via NostrSignerWithClientTag decorator

Introduces a signer decorator that automatically appends the NIP-89
client tag to every event before signing, ensuring all events carry
client identification without modifying individual event creation sites.
Works transparently with internal, external (NIP-55), and remote (NIP-46) signers.

https://claude.ai/code/session_01WRtuk1ySCfqXzfFrieKsDs

amethyst/src/main/java/com/vitorpamplona/amethyst/model/accountsCache/AccountCacheState.kt

@@ -33,6 +33,7 @@ import com.vitorpamplona.quartz.nip01Core.signers.NostrSigner
 import com.vitorpamplona.quartz.nip01Core.signers.NostrSignerInternal
 import com.vitorpamplona.quartz.nip03Timestamp.OtsResolverBuilder
 import com.vitorpamplona.quartz.nip55AndroidSigner.client.NostrSignerExternal
+import com.vitorpamplona.quartz.nip89AppHandlers.clientTag.NostrSignerWithClientTag
 import com.vitorpamplona.quartz.utils.Log
 import kotlinx.coroutines.CoroutineExceptionHandler
 import kotlinx.coroutines.CoroutineScope
@@ -91,9 +92,11 @@ class AccountCacheState(
         val cached = accounts.value[signer.pubKey]
         if (cached != null) return cached
 
+        val signerWithClientTag = NostrSignerWithClientTag(signer, CLIENT_TAG_NAME)
+
         return Account(
             settings = accountSettings,
-            signer = signer,
+            signer = signerWithClientTag,
             geolocationFlow = geolocationFlow,
             nwcFilterAssembler = nwcFilterAssembler,
             otsResolverBuilder = otsResolverBuilder,
@@ -122,4 +125,8 @@ class AccountCacheState(
             emptyMap()
         }
     }
+
+    companion object {
+        const val CLIENT_TAG_NAME = "Amethyst"
+    }
 }

desktopApp/src/jvmMain/kotlin/com/vitorpamplona/amethyst/desktop/model/DesktopIAccount.kt

@@ -31,6 +31,7 @@ import com.vitorpamplona.amethyst.desktop.network.RelayConnectionManager
 import com.vitorpamplona.amethyst.desktop.ui.chats.DmSendTracker
 import com.vitorpamplona.quartz.nip01Core.signers.EventTemplate
 import com.vitorpamplona.quartz.nip01Core.signers.NostrSigner
+import com.vitorpamplona.quartz.nip89AppHandlers.clientTag.NostrSignerWithClientTag
 import com.vitorpamplona.quartz.nip04Dm.messages.PrivateDmEvent
 import com.vitorpamplona.quartz.nip17Dm.NIP17Factory
 import com.vitorpamplona.quartz.nip17Dm.files.ChatMessageEncryptedFileHeaderEvent
@@ -62,7 +63,7 @@ class DesktopIAccount(
     val dmSendTracker: DmSendTracker,
     private val scope: CoroutineScope,
 ) : IAccount {
-    override val signer: NostrSigner = accountState.signer
+    override val signer: NostrSigner = NostrSignerWithClientTag(accountState.signer, CLIENT_TAG_NAME)
 
     override val pubKey: String = accountState.pubKeyHex
 
@@ -221,4 +222,8 @@ class DesktopIAccount(
         }
         chatroomList.addMessage(roomKey, note)
     }
+
+    companion object {
+        const val CLIENT_TAG_NAME = "Amethyst"
+    }
 }

quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nip89AppHandlers/clientTag/NostrSignerWithClientTag.kt

@@ -0,0 +1,97 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.quartz.nip89AppHandlers.clientTag
+
+import com.vitorpamplona.quartz.nip01Core.core.Event
+import com.vitorpamplona.quartz.nip01Core.core.HexKey
+import com.vitorpamplona.quartz.nip01Core.relay.normalizer.NormalizedRelayUrl
+import com.vitorpamplona.quartz.nip01Core.signers.NostrSigner
+import com.vitorpamplona.quartz.nip57Zaps.LnZapPrivateEvent
+import com.vitorpamplona.quartz.nip57Zaps.LnZapRequestEvent
+
+/**
+ * A [NostrSigner] decorator that automatically appends a NIP-89 client tag
+ * to every event before delegating signing to the wrapped [inner] signer.
+ *
+ * This ensures all events produced by the application carry the client
+ * identification tag without requiring each call site to add it manually.
+ *
+ * Works with any signer implementation: internal, external (NIP-55/Amber),
+ * or remote (NIP-46/Bunker).
+ */
+class NostrSignerWithClientTag(
+    val inner: NostrSigner,
+    val clientTag: Array<String>,
+) : NostrSigner(inner.pubKey) {
+    constructor(
+        inner: NostrSigner,
+        clientName: String,
+    ) : this(inner, ClientTag.assemble(clientName))
+
+    constructor(
+        inner: NostrSigner,
+        clientName: String,
+        addressId: String?,
+        relayHint: NormalizedRelayUrl?,
+    ) : this(inner, ClientTag.assemble(clientName, addressId, relayHint))
+
+    override fun isWriteable(): Boolean = inner.isWriteable()
+
+    override suspend fun <T : Event> sign(
+        createdAt: Long,
+        kind: Int,
+        tags: Array<Array<String>>,
+        content: String,
+    ): T = inner.sign(createdAt, kind, appendClientTag(tags), content)
+
+    override suspend fun nip04Encrypt(
+        plaintext: String,
+        toPublicKey: HexKey,
+    ): String = inner.nip04Encrypt(plaintext, toPublicKey)
+
+    override suspend fun nip04Decrypt(
+        ciphertext: String,
+        fromPublicKey: HexKey,
+    ): String = inner.nip04Decrypt(ciphertext, fromPublicKey)
+
+    override suspend fun nip44Encrypt(
+        plaintext: String,
+        toPublicKey: HexKey,
+    ): String = inner.nip44Encrypt(plaintext, toPublicKey)
+
+    override suspend fun nip44Decrypt(
+        ciphertext: String,
+        fromPublicKey: HexKey,
+    ): String = inner.nip44Decrypt(ciphertext, fromPublicKey)
+
+    override suspend fun decryptZapEvent(event: LnZapRequestEvent): LnZapPrivateEvent = inner.decryptZapEvent(event)
+
+    override suspend fun deriveKey(nonce: HexKey): HexKey = inner.deriveKey(nonce)
+
+    override fun hasForegroundSupport(): Boolean = inner.hasForegroundSupport()
+
+    private fun appendClientTag(tags: Array<Array<String>>): Array<Array<String>> {
+        // Don't add if a client tag already exists
+        if (tags.any { it.size >= 2 && it[0] == ClientTag.TAG_NAME }) return tags
+
+        return tags + arrayOf(clientTag)
+    }
+}

quartz/src/commonTest/kotlin/com/vitorpamplona/quartz/nip89AppHandlers/clientTag/NostrSignerWithClientTagTest.kt

@@ -0,0 +1,117 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.quartz.nip89AppHandlers.clientTag
+
+import com.vitorpamplona.quartz.nip01Core.crypto.KeyPair
+import com.vitorpamplona.quartz.nip01Core.crypto.verify
+import com.vitorpamplona.quartz.nip01Core.signers.NostrSignerInternal
+import com.vitorpamplona.quartz.nip01Core.signers.eventTemplate
+import com.vitorpamplona.quartz.nip10Notes.TextNoteEvent
+import kotlinx.coroutines.test.runTest
+import kotlin.test.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertTrue
+
+class NostrSignerWithClientTagTest {
+    private val keyPair = KeyPair()
+    private val innerSigner = NostrSignerInternal(keyPair)
+
+    @Test
+    fun addsClientTagToSignedEvent() =
+        runTest {
+            val signer = NostrSignerWithClientTag(innerSigner, "Amethyst")
+
+            val template =
+                eventTemplate<TextNoteEvent>(
+                    kind = TextNoteEvent.KIND,
+                    description = "Hello Nostr",
+                )
+
+            val event = signer.sign<TextNoteEvent>(template)
+
+            assertTrue(event.verify())
+
+            val clientTags = event.tags.filter { it.size >= 2 && it[0] == "client" }
+            assertEquals(1, clientTags.size)
+            assertEquals("Amethyst", clientTags[0][1])
+        }
+
+    @Test
+    fun doesNotDuplicateExistingClientTag() =
+        runTest {
+            val signer = NostrSignerWithClientTag(innerSigner, "Amethyst")
+
+            val template =
+                eventTemplate<TextNoteEvent>(
+                    kind = TextNoteEvent.KIND,
+                    description = "Hello Nostr",
+                ) {
+                    client("OtherClient")
+                }
+
+            val event = signer.sign<TextNoteEvent>(template)
+
+            assertTrue(event.verify())
+
+            val clientTags = event.tags.filter { it.size >= 2 && it[0] == "client" }
+            assertEquals(1, clientTags.size)
+            assertEquals("OtherClient", clientTags[0][1])
+        }
+
+    @Test
+    fun addsClientTagWithAddressAndRelay() =
+        runTest {
+            val signer =
+                NostrSignerWithClientTag(
+                    innerSigner,
+                    "Amethyst",
+                    "31990:abc123:amethyst",
+                    null,
+                )
+
+            val template =
+                eventTemplate<TextNoteEvent>(
+                    kind = TextNoteEvent.KIND,
+                    description = "Hello Nostr",
+                )
+
+            val event = signer.sign<TextNoteEvent>(template)
+
+            assertTrue(event.verify())
+
+            val clientTags = event.tags.filter { it.size >= 2 && it[0] == "client" }
+            assertEquals(1, clientTags.size)
+            assertEquals("Amethyst", clientTags[0][1])
+            assertEquals("31990:abc123:amethyst", clientTags[0][2])
+        }
+
+    @Test
+    fun preservesSamePubKey() {
+        val signer = NostrSignerWithClientTag(innerSigner, "Amethyst")
+        assertEquals(innerSigner.pubKey, signer.pubKey)
+    }
+
+    @Test
+    fun delegatesIsWriteable() {
+        val signer = NostrSignerWithClientTag(innerSigner, "Amethyst")
+        assertEquals(innerSigner.isWriteable(), signer.isWriteable())
+    }
+}