diff --git a/app/src/test/kotlin/io/flamenet/messenger/app/GroupPinResolvesTest.kt b/app/src/test/kotlin/io/flamenet/messenger/app/GroupPinResolvesTest.kt
new file mode 100644
index 0000000..39f071c
--- /dev/null
+++ b/app/src/test/kotlin/io/flamenet/messenger/app/GroupPinResolvesTest.kt
@@ -0,0 +1,128 @@
+package io.flamenet.messenger.app
+
+import io.flamenet.client.MessengerApi
+import io.flamenet.client.RelayClient
+import io.flamenet.e2e.DeviceIdentity
+import io.flamenet.e2e.Vault
+import javax.crypto.KeyGenerator
+import javax.crypto.SecretKey
+import kotlin.test.AfterTest
+import kotlin.test.BeforeTest
+import kotlin.test.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertNotNull
+import kotlin.test.assertNull
+import okhttp3.mockwebserver.MockWebServer
+import org.junit.runner.RunWith
+import org.robolectric.RobolectricTestRunner
+import org.robolectric.annotation.Config
+
+/**
+ * A pin in a GROUP resolves to the message it names (§6.19).
+ *
+ * 🔴 **Written to settle a published claim.** The spec says a group pin *"is
+ * carried correctly on the wire but cannot resolve yet, because a group
+ * transcript does not record"* a message id. `Session.sendGroup` mints a `mid`
+ * and passes it to `record(...)`, so the stated reason is already false — but
+ * relay#46's rule is that a claim is flipped by a run, not by reading the code,
+ * and nothing exercised the group case.
+ *
+ * ⚠️ The 1:1 case was never in doubt. This is specifically about a group
+ * thread, because that is what the spec singles out.
+ */
+@RunWith(RobolectricTestRunner::class)
+@Config(sdk = [34])
+class GroupPinResolvesTest {
+
+    private lateinit var server: MockWebServer
+
+    @BeforeTest fun start() { server = MockWebServer().also { it.start() } }
+    @AfterTest fun stop() { server.shutdown() }
+
+    private class MapStorage : Vault.Storage {
+        private val records = mutableMapOf<String, ByteArray>()
+        override fun read(name: String) = records[name]
+        override fun write(name: String, bytes: ByteArray) { records[name] = bytes }
+        override fun delete(name: String) { records.remove(name) }
+        override fun names() = records.keys.toList()
+    }
+
+    private fun key(): SecretKey =
+        KeyGenerator.getInstance("AES").apply { init(256) }.generateKey()
+
+    private val gid = "abc123"
+    private val thread = Vault.threadForGroup("abc123")
+
+    private fun session(): Session {
+        val identity = DeviceIdentity.create()
+        val vault = Vault(MapStorage(), key()).also { it.saveIdentity(identity) }
+        val base = server.url("/").toString()
+        return Session("alice", 1, identity, vault,
+            RelayClient(base, "alice", "app pass word"),
+            MessengerApi(base, "alice", "app pass word"))
+    }
+
+    @Test
+    fun `a group transcript records a message id`() {
+        val s = session()
+        s.record(thread, "in a group", mine = true, author = 1L, messageId = "gm1")
+        assertEquals("gm1", s.history(thread).single().id,
+            "a group line carries no id — the spec's stated reason would hold")
+    }
+
+    @Test
+    fun `a pin in a group thread resolves to the message it names`() {
+        val s = session()
+        s.record(thread, "worth keeping", mine = true, author = 1L, messageId = "gm1")
+        s.record(thread, "ordinary", mine = false, author = 2L, messageId = "gm2")
+
+        s.applyPin(thread, "gm1")
+        val pinned = assertNotNull(s.pinnedMessage(thread), "nothing was pinned")
+        assertEquals("gm1", pinned)
+
+        // 🔴 The resolve: the banner needs the MESSAGE, not just its id.
+        val target = s.history(thread).firstOrNull { it.id == pinned }
+        assertEquals("worth keeping", assertNotNull(target).text,
+            "the pin named a message the group transcript could not find")
+    }
+
+    /**
+     * ⚠️ An id, never a copy. A stored copy would go stale the moment the
+     * message was edited and would survive it being deleted — a banner quoting
+     * words no longer in the conversation.
+     */
+    @Test
+    fun `the pin follows an edit rather than quoting the old words`() {
+        val s = session()
+        s.record(thread, "before", mine = false, author = 2L, messageId = "gm1")
+        s.applyPin(thread, "gm1")
+        s.applyEdit(thread, "gm1", author = 2L, newText = "after")
+
+        val pinned = assertNotNull(s.pinnedMessage(thread))
+        val target = s.history(thread).firstOrNull { it.id == pinned }
+        assertEquals("after", assertNotNull(target).text,
+            "the banner is quoting words that are no longer in the conversation")
+    }
+
+    @Test
+    fun `taking the pin down leaves nothing pinned`() {
+        val s = session()
+        s.record(thread, "x", mine = true, author = 1L, messageId = "gm1")
+        s.applyPin(thread, "gm1")
+        s.applyPin(thread, "")
+        assertNull(s.pinnedMessage(thread))
+    }
+
+    /** A group's pin and a person's pin are separate threads, separately pinned. */
+    @Test
+    fun `a group pin does not leak into a one-to-one thread`() {
+        val s = session()
+        val dm = Vault.threadForUser(2L)
+        s.record(thread, "group message", mine = true, author = 1L, messageId = "gm1")
+        s.record(dm, "direct message", mine = true, author = 1L, messageId = "dm1")
+
+        s.applyPin(thread, "gm1")
+        assertEquals("gm1", s.pinnedMessage(thread))
+        assertNull(s.pinnedMessage(dm), "pinning in a group pinned something in a DM")
+    }
+}