diff --git a/tools/chatgui-android/app/src/main/java/com/utun/chat/data/CallOutputRecovery.kt b/tools/chatgui-android/app/src/main/java/com/utun/chat/data/CallOutputRecovery.kt
new file mode 100644
index 00000000..bff7e344
--- /dev/null
+++ b/tools/chatgui-android/app/src/main/java/com/utun/chat/data/CallOutputRecovery.kt
@@ -0,0 +1,36 @@
+package com.utun.chat.data
+
+/** Только playback worker. Ошибка ограничивает повтор в текущем маршруте, не в следующем. */
+internal class CallOutputRecovery {
+    var deviceId = Int.MIN_VALUE
+        private set
+    var failures = 0
+        private set
+
+    fun route(id: Int): Boolean {
+        if (id == deviceId) return false
+        deviceId = id; failures = 0
+        return true
+    }
+
+    fun failed(): Boolean { failures++; return failures <= 2 }
+    val tryFast: Boolean get() = failures == 0
+}
+
+/** Локальный счётчик нового устройства начинается с нуля; общий PCM-счётчик не сбрасывается. */
+internal class CallOutputPosition {
+    var base = 0L
+        private set
+    private var head = CallPlaybackHead()
+
+    fun reset() { base = 0; head = CallPlaybackHead() }
+
+    fun reopen(written: Long) {
+        require(written >= base)
+        base = written
+        head = CallPlaybackHead()
+    }
+
+    fun played(raw: Int, written: Long): Long? = head.update(raw, written - base)?.let { base + it }
+    fun timestamp(local: Long): Long = if (local < 0) -1 else base + local
+}
diff --git a/tools/chatgui-android/app/src/test/java/com/utun/chat/data/CallOutputRecoveryTest.kt b/tools/chatgui-android/app/src/test/java/com/utun/chat/data/CallOutputRecoveryTest.kt
new file mode 100644
index 00000000..f256d52d
--- /dev/null
+++ b/tools/chatgui-android/app/src/test/java/com/utun/chat/data/CallOutputRecoveryTest.kt
@@ -0,0 +1,31 @@
+package com.utun.chat.data
+
+import org.junit.Assert.*
+import org.junit.Test
+
+class CallOutputRecoveryTest {
+    @Test fun routeChangeRestoresFastAttemptButDuplicateConfirmationDoesNot() {
+        val p = CallOutputRecovery()
+        assertTrue(p.route(3)); assertTrue(p.tryFast)
+        assertTrue(p.failed()); assertFalse(p.tryFast)
+        assertFalse(p.route(3)); assertFalse(p.tryFast)
+        assertTrue(p.failed()); assertFalse(p.failed())
+        assertTrue(p.route(2)); assertTrue(p.tryFast); assertEquals(0, p.failures)
+        assertTrue(p.route(3)); assertTrue(p.tryFast)
+    }
+
+    @Test fun replacementKeepsAcceptedPcmPositionAndPartialBlockRemainder() {
+        val p = CallOutputPosition()
+        assertEquals(480L, p.played(480, 960))
+        // 288 сэмплов следующего блока успели записаться; остаток 672 ещё принадлежит worker.
+        val accepted = 960L + 288
+        p.reopen(accepted)
+        assertEquals(accepted, p.played(0, accepted))
+        assertEquals(accepted + 96, p.played(96, accepted + 672))
+        assertEquals(accepted + 48, p.timestamp(48))
+        assertEquals(-1L, p.timestamp(-1))
+        assertNull(p.played(1000, accepted + 672))
+        p.reopen(1920)
+        assertEquals(1920L, p.played(0, 1920))
+    }
+}