Merge pull request 'fix(client/android): rumble survives a vibrator fault, and an unplug stops leaking' (#35) from worktree-haptics-m5-android into main

.gitea/workflows/android.yml

@@ -160,6 +160,14 @@ jobs:
           key: gradle-${{ hashFiles('clients/android/**/*.gradle.kts', 'clients/android/gradle/wrapper/gradle-wrapper.properties') }}
           restore-keys: gradle-
 
+      # The kit's JVM unit tests — the pure parsers, migrations and feedback policies. They were
+      # running nowhere: this workflow only assembled, and android-screenshots.yml runs the :app
+      # module's tests, so nothing enforced :kit's. Cheap (a couple of seconds against an already
+      # built module) and it is the only automated cover those behaviours have.
+      - name: kit unit tests
+        working-directory: clients/android
+        run: ./gradlew :kit:testDebugUnitTest --stacktrace
+
       - name: assembleDebug (cargo-ndk → jniLibs → APK)
         working-directory: clients/android
         env:

clients/android/kit/src/main/kotlin/io/unom/punktfunk/kit/DsCapture.kt

@@ -116,7 +116,9 @@ class DsCapture(
             // The interfaces are about to release with the kernel driver still detached — a
             // mid-rumble teardown would leave the motors running with nobody to stop them.
             // EP0-direct (the reader thread is stopping; the queue would never drain).
-            usb.writeControl(stopReport(m))
+            // Nothing can retry after this point, so a failure is worth saying out loud: it is
+            // the difference between a quiet pad and one that buzzes until it is unplugged.
+            if (!usb.writeControl(stopReport(m))) Log.w(TAG, "teardown rumble stop was not written")
         }
         disarmBackstop()
         usb.stop()
@@ -145,6 +147,9 @@ class DsCapture(
         val wasActive = model != null
         model = null
         releaseSlot()
+        // Release the transport too: the link only *signals* the drop, so without this an unplug
+        // left its connection open, its interfaces claimed and its detach receiver registered.
+        usb.stop()
         if (wasActive) onActiveChanged?.invoke(false)
     }
 
@@ -216,17 +221,20 @@ class DsCapture(
 
     override fun rumble(pad: Int, low: Int, high: Int, backstopMs: Long) {
         val m = model ?: return
-        if (low == 0 && high == 0) {
-            disarmBackstop()
-        } else {
-            armBackstop(backstopMs)
-        }
-        if (m == DsDevice.Model.DUALSHOCK4) {
+        val stop = low == 0 && high == 0
+        if (!stop) armBackstop(backstopMs)
+        val sent = if (m == DsDevice.Model.DUALSHOCK4) {
             ds4Low = low
             ds4High = high
             writeDs4()
         } else {
-            usb.writeRaw(0, DsDevice.ds5RumbleReport(m, low, high))
+            usb.writeRaw(0, DsDevice.ds5RumbleReport(m, low, high), OutReportQueue.KEY_RUMBLE)
+        }
+        if (stop) {
+            // Disarm only once the stop is actually on its way. Dropping the net *before* the
+            // write — as this used to — meant a discarded stop left the motors running with
+            // nothing scheduled to try again; a USB pad holds its last level until told zero.
+            if (sent) disarmBackstop() else armBackstop(STOP_RETRY_MS)
         }
     }
 
@@ -252,6 +260,9 @@ class DsCapture(
         usb.writeRaw(0, DsDevice.ds5TriggerReport(m, which, effect))
     }
 
+    // Coalescable: the DS4's write is full-state (motors AND lightbar, rebuilt from the current
+    // fields on every call), so a newer one supersedes an older one wholesale — nothing is lost by
+    // collapsing a backlog of them down to the last.
     private fun writeDs4() = usb.writeRaw(
         0,
         DsDevice.ds4Report(
@@ -261,6 +272,7 @@ class DsCapture(
             (ds4Rgb shr 8) and 0xFF,
             ds4Rgb and 0xFF,
         ),
+        OutReportQueue.KEY_RUMBLE,
     )
 
     /** The report that stops the motors. The DS4's is a full-state write, so it zeroes the
@@ -284,7 +296,12 @@ class DsCapture(
         backstop?.let { mainHandler.removeCallbacks(it) }
         val r = Runnable {
             backstop = null
-            model?.let { usb.writeRaw(0, stopReport(it)) }
+            val m = model ?: return@Runnable
+            // The net itself can be refused (a full queue, a connection going away). Re-arm rather
+            // than give up: this is the last thing between a stalled poll thread and a pad that
+            // buzzes until it is unplugged. It stops re-arming as soon as the link closes, which
+            // clears `model` and disarms.
+            if (!usb.writeRaw(0, stopReport(m), OutReportQueue.KEY_RUMBLE)) armBackstop(STOP_RETRY_MS)
         }
         backstop = r
         mainHandler.postDelayed(r, ms.coerceAtLeast(1))
@@ -297,5 +314,9 @@ class DsCapture(
 
     private companion object {
         const val TAG = "DsCapture"
+
+        /** How soon to retry a rumble stop whose write was rejected. Short: the motors are running
+         *  and the host has already moved on, so nothing else is coming to silence them. */
+        const val STOP_RETRY_MS = 100L
     }
 }

clients/android/kit/src/main/kotlin/io/unom/punktfunk/kit/GamepadFeedback.kt

@@ -88,6 +88,9 @@ class GamepadFeedback(
         const val TAG_PLAYER_LEDS: Byte = 0x02
         const val TAG_TRIGGER: Byte = 0x03
         const val TAG_HID_RAW: Byte = 0x05
+
+        /** Sparse-log cadence for swallowed render failures — see [noteRenderFailure]. */
+        const val LOG_EVERY = 128L
     }
 
     /** One controller's rumble binding — VibratorManager (API 31+) OR the legacy single Vibrator (API 28–30). */
@@ -125,6 +128,7 @@ class GamepadFeedback(
     fun start() {
         running = true
         rumbleThread = Thread({
+            var failures = 0L
             while (running) {
                 val ev = NativeBridge.nativeNextRumble(handle)
                 if (ev < 0L) continue // timeout / closed
@@ -136,26 +140,50 @@ class GamepadFeedback(
                 // the backstop (the hardware net under a stalled poll thread).
                 val pad = ((ev ushr 49) and 0xFL).toInt()
                 val backstopMs = ((ev ushr 32) and 0xFFFF)
-                renderRumble(
-                    pad,
-                    ((ev ushr 16) and 0xFFFF).toInt(),
-                    (ev and 0xFFFF).toInt(),
-                    backstopMs,
-                )
+                // Rendering is binder calls into the vibrator service, and every one of them can
+                // throw unchecked — DeadSystemRuntimeException when system_server goes down, and
+                // the ordinary RuntimeException a dying service wraps its RemoteException in.
+                // Unguarded, ONE of those killed this thread outright: `running` stayed true, so
+                // nothing noticed and nothing restarted it, and rumble was gone for the rest of
+                // the session. Losing a single command is recoverable; losing the loop is not.
+                runCatching {
+                    renderRumble(
+                        pad,
+                        ((ev ushr 16) and 0xFFFF).toInt(),
+                        (ev and 0xFFFF).toInt(),
+                        backstopMs,
+                    )
+                }.onFailure { failures = noteRenderFailure("rumble", it, failures) }
             }
         }, "pf-rumble").apply { isDaemon = true; start() }
 
         hidoutThread = Thread({
             // 128: the raw as-is passthrough events are [pad][kind tag][report kind][≤64 bytes].
             val buf = ByteBuffer.allocateDirect(128)
+            var failures = 0L
             while (running) {
                 val n = NativeBridge.nativeNextHidout(handle, buf)
                 if (n < 0) continue // timeout / closed
-                dispatchHidout(buf, n)
+                // Same hazard as the rumble loop above: lights/trigger rendering is binder and USB
+                // calls, and an unchecked throw here would silently end the rich-feedback plane.
+                runCatching { dispatchHidout(buf, n) }
+                    .onFailure { failures = noteRenderFailure("hidout", it, failures) }
             }
         }, "pf-hidout").apply { isDaemon = true; start() }
     }
 
+    /**
+     * Record a render failure the poll loop swallowed, and return the updated count. Logged on the
+     * first occurrence and sparsely after: a genuinely dead vibrator service fails on *every*
+     * command, which at a rumble plane's rate would bury the log.
+     */
+    private fun noteRenderFailure(plane: String, t: Throwable, seen: Long): Long {
+        if (seen == 0L || seen % LOG_EVERY == 0L) {
+            Log.w(TAG, "$plane render failed (#${seen + 1}) — command dropped, poll loop alive", t)
+        }
+        return seen + 1
+    }
+
     /** Idempotent. Stops + joins the poll threads (must complete before the router is released / handle freed). */
     fun stop() {
         running = false
@@ -269,7 +297,7 @@ class GamepadFeedback(
         val m = bind.vm
         if (m != null) {
             if (lo == 0 && hi == 0) {
-                m.cancel() // (0,0) = stop
+                runCatching { m.cancel() } // (0,0) = stop
                 return
             }
             val combo = CombinedVibration.startParallel()
@@ -294,7 +322,7 @@ class GamepadFeedback(
         // API 28–30 legacy single-motor path: blend both motors into one effect.
         val lv = bind.legacy ?: return
         if (lo == 0 && hi == 0) {
-            lv.cancel() // (0,0) = stop
+            runCatching { lv.cancel() } // (0,0) = stop
             return
         }
         val a = (lo * 0.8 + hi * 0.33).toInt().coerceIn(1, 255)

clients/android/kit/src/main/kotlin/io/unom/punktfunk/kit/HidUsbLink.kt

@@ -14,8 +14,8 @@ import android.hardware.usb.UsbRequest
 import android.os.Build
 import android.util.Log
 import java.nio.ByteBuffer
-import java.util.concurrent.ConcurrentLinkedQueue
 import java.util.concurrent.TimeoutException
+import java.util.concurrent.atomic.AtomicBoolean
 
 /**
  * Generic USB transport for a client-captured HID controller — the device-agnostic half of what
@@ -81,14 +81,20 @@ class HidUsbLink(
 
     /** Pending OUT reports, submitted by the reader thread — only one thread may drive a
      *  connection's [UsbRequest]s ([UsbDeviceConnection.requestWait] returns ANY completed
-     *  request; a second waiter would steal the reader's completions). */
-    private val outQueue = ConcurrentLinkedQueue<ByteArray>()
+     *  request; a second waiter would steal the reader's completions). See [OutReportQueue] for
+     *  what gets discarded when it fills, and why that is not simply "the oldest". */
+    private val outQueue = OutReportQueue()
 
     private var reader: Thread? = null
     private var detachReceiver: BroadcastReceiver? = null
 
     @Volatile private var running = false
 
+    /** Latches on the first "this link is down" signal so [onClosed] fires exactly once, however
+     *  many of the racing detectors (detach broadcast, reader error streak, failed re-queue) see
+     *  it. Reset by [start]. */
+    private val down = AtomicBoolean(false)
+
     /** First attached matching device, or null. Does not need USB permission to enumerate. */
     fun findDevice(): UsbDevice? = usb.deviceList.values.firstOrNull(config.deviceMatch)
 
@@ -114,6 +120,7 @@ class HidUsbLink(
         connection = conn
         device = dev
         claims = claimed
+        down.set(false)
         running = true
         Log.i(
             config.tag,
@@ -134,10 +141,7 @@ class HidUsbLink(
                 val gone: UsbDevice? = intent.getParcelableExtra(UsbManager.EXTRA_DEVICE)
                 if (gone?.deviceName == dev.deviceName) {
                     Log.i(config.tag, "USB detached (${dev.deviceName})")
-                    if (running) {
-                        running = false
-                        onClosed()
-                    }
+                    linkDown()
                 }
             }
         }
@@ -221,6 +225,9 @@ class HidUsbLink(
         if (live.isEmpty()) {
             Log.e(config.tag, "no IN request could be queued")
             finishReader(claims)
+            // `start` already returned true, so without this the owner would sit waiting on a
+            // capture that never streams and never reports itself dead.
+            linkDown()
             return
         }
         val scratch = ByteArray(64)
@@ -295,10 +302,23 @@ class HidUsbLink(
         } finally {
             finishReader(claims)
         }
-        if (running) {
-            running = false
-            onClosed()
-        }
+        linkDown()
+    }
+
+    /**
+     * Report the link down, exactly once, from whichever detector noticed first — the detach
+     * broadcast (main thread) or the reader thread on its way out.
+     *
+     * This only *signals*; releasing the connection and the interfaces stays the owner's job, via
+     * the [stop] its `onClosed` handler calls. Previously nothing released them on this path: the
+     * detach receiver flipped a flag and fired the callback, so an unplug left the connection open,
+     * the interfaces claimed (the pad could not return to Android's own input stack) and the
+     * receiver still registered — and a re-plug overwrote the field holding it, leaking a receiver
+     * that stayed live for the process's lifetime.
+     */
+    private fun linkDown() {
+        running = false
+        if (down.compareAndSet(false, true)) onClosed()
     }
 
     private fun finishReader(claims: List<Claim>) {
@@ -314,28 +334,35 @@ class HidUsbLink(
      * Write one raw report to the device: kind 0 = output report (the active interface's
      * interrupt-OUT, else a `SET_REPORT(Output)` control transfer), kind 1 = feature report
      * (`SET_REPORT(Feature)`). [data] is the full report, id byte first, hidapi framing.
+     *
+     * [coalesce] tells the pending-OUT queue whether a newer report of the same kind may replace
+     * this one — [OutReportQueue.KEY_RUMBLE] for motor levels, the default [OutReportQueue.NO_COALESCE]
+     * for one-shots (lightbar, player LEDs, trigger effects) the sender will not repeat.
+     *
+     * Returns whether the report reached the device or is queued for it. A caller that is writing
+     * a **stop** needs this: a discarded stop has nothing behind it, so it must not be mistaken
+     * for one that landed.
      */
-    fun writeRaw(kind: Int, data: ByteArray) {
-        if (data.isEmpty()) return
-        when (kind) {
+    fun writeRaw(kind: Int, data: ByteArray, coalesce: Int = OutReportQueue.NO_COALESCE): Boolean {
+        if (data.isEmpty()) return false
+        return when (kind) {
             0 -> {
                 if ((activeClaim ?: claims.firstOrNull())?.outReq != null) {
-                    // Interrupt-OUT rides UsbRequests submitted by the reader thread. Bounded,
-                    // newest-wins: these are level-styled commands the sender re-sends anyway.
-                    while (outQueue.size >= 32) outQueue.poll()
-                    outQueue.offer(data)
+                    // Interrupt-OUT rides UsbRequests submitted by the reader thread.
+                    outQueue.offer(data, coalesce)
                 } else {
                     setReport(REPORT_TYPE_OUTPUT, data)
                 }
             }
             1 -> setReport(REPORT_TYPE_FEATURE, data)
+            else -> false
         }
     }
 
-    private fun setReport(type: Int, data: ByteArray) {
-        val conn = connection ?: return
-        val ifId = (activeClaim ?: claims.firstOrNull())?.iface?.id ?: return
-        sendReport(conn, ifId, type, data)
+    private fun setReport(type: Int, data: ByteArray): Boolean {
+        val conn = connection ?: return false
+        val ifId = (activeClaim ?: claims.firstOrNull())?.iface?.id ?: return false
+        return sendReport(conn, ifId, type, data)
     }
 
     /**
@@ -344,9 +371,8 @@ class HidUsbLink(
      * queue would never drain (e.g. a rumble stop before the interfaces release). Safe from any
      * thread: EP0 control transfers are independent of the reader's `requestWait`.
      */
-    fun writeControl(data: ByteArray) {
-        if (data.isNotEmpty()) setReport(REPORT_TYPE_OUTPUT, data)
-    }
+    fun writeControl(data: ByteArray): Boolean =
+        data.isNotEmpty() && setReport(REPORT_TYPE_OUTPUT, data)
 
     private fun sendKeepAlive(conn: UsbDeviceConnection, ifaceId: Int) {
         for (f in config.keepAliveFeatures) sendReport(conn, ifaceId, REPORT_TYPE_FEATURE, f)
@@ -358,27 +384,48 @@ class HidUsbLink(
      * "unnumbered" (id 0 in wValue, id byte stripped from the payload). EP0 is independent of
      * the interrupt endpoints, so this is safe alongside the reader thread's requestWait.
      */
-    private fun sendReport(conn: UsbDeviceConnection, ifaceId: Int, type: Int, data: ByteArray) {
+    private fun sendReport(
+        conn: UsbDeviceConnection,
+        ifaceId: Int,
+        type: Int,
+        data: ByteArray,
+    ): Boolean {
         val id = data[0].toInt() and 0xFF
         val payload = if (id == 0) data.copyOfRange(1, data.size) else data
-        conn.controlTransfer(
-            0x21, // host→device, class, interface
-            0x09, // SET_REPORT
-            (type shl 8) or id,
-            ifaceId,
-            payload,
-            payload.size,
-            WRITE_TIMEOUT_MS,
-        )
+        // controlTransfer returns the byte count, or a negative value on failure — a failed write
+        // must be reported as such, not swallowed (a dropped rumble stop has nothing behind it).
+        val n = runCatching {
+            conn.controlTransfer(
+                0x21, // host→device, class, interface
+                0x09, // SET_REPORT
+                (type shl 8) or id,
+                ifaceId,
+                payload,
+                payload.size,
+                WRITE_TIMEOUT_MS,
+            )
+        }.getOrDefault(-1)
+        return n >= 0
     }
 
-    /** Stop the read loop and release the interfaces. Idempotent; does not fire [onClosed]. */
+    /**
+     * Stop the read loop and release the interfaces. Idempotent; does not fire [onClosed].
+     *
+     * Safe to call from the `onClosed` handler itself — that is how an unplug now gets cleaned up,
+     * and it arrives on the reader thread, which must not try to join itself.
+     */
     fun stop() {
         running = false
+        // Claim the down-latch so the reader's own exit does not report a close the owner asked for.
+        down.set(true)
         detachReceiver?.let { runCatching { context.unregisterReceiver(it) } }
         detachReceiver = null
-        runCatching { reader?.join(1000) }
-        reader = null
+        if (reader !== Thread.currentThread()) {
+            runCatching { reader?.join(1000) }
+            // Only forget the thread once it is actually gone: clearing it while it still runs
+            // would let a later stop() skip the join and free the connection under it.
+            reader = null
+        }
         outQueue.clear()
         activeClaim = null
         for (c in claims) runCatching { connection?.releaseInterface(c.iface) }

clients/android/kit/src/main/kotlin/io/unom/punktfunk/kit/OutReportQueue.kt

@@ -0,0 +1,89 @@
+package io.unom.punktfunk.kit
+
+/**
+ * The pending interrupt-OUT reports for a captured controller: a bounded FIFO whose overflow
+ * policy knows which reports may be thrown away and which may not.
+ *
+ * The queue exists because only one thread may drive a connection's `UsbRequest`s, so writes from
+ * the feedback threads are handed to the reader thread rather than submitted directly. It has to
+ * be bounded — a stalled or unplugged device would otherwise grow it without limit — and the
+ * question is what to discard when it fills.
+ *
+ * The old policy was "newest wins": drop from the head until there is room. That is right for
+ * rumble, which is *level-styled* — the host re-sends it continuously, so a dropped frame is
+ * replaced milliseconds later and nothing is permanently lost. It is wrong for everything else.
+ * A lightbar colour, a player-LED mask and an adaptive-trigger effect are **one-shots**: the host
+ * sends them on change and never repeats them. Dropping one leaves the pad wrong until the next
+ * time that value happens to change, which may be never.
+ *
+ * So eviction is driven by an explicit [key] supplied by the caller, not by inspecting the bytes.
+ * That distinction cannot be recovered from the report itself: every DualSense output report
+ * carries the *same* report id and differs only in its `valid_flag` bytes, so an id-keyed policy
+ * would happily let a rumble supersede a lightbar — the very bug this replaces, relocated.
+ *
+ * Two rules:
+ *  - A report offered with a coalescing key **replaces** the pending report with that key, in
+ *    place. A burst of rumble collapses to its latest value and never displaces anything else.
+ *  - Only when the queue is full does anything get dropped, and then the oldest *coalescable*
+ *    report goes first. A one-shot is discarded only if the queue is full of nothing but
+ *    one-shots — which needs [cap] distinct one-shots outstanding, far beyond what a real pad
+ *    produces.
+ *
+ * Thread-safe: offered by the feedback threads, drained by the reader thread.
+ */
+internal class OutReportQueue(private val cap: Int = CAP) {
+    private class Entry(val key: Int, val data: ByteArray)
+
+    private val items = ArrayDeque<Entry>()
+
+    /**
+     * Queue [data] for submission. [key] is [NO_COALESCE] for a one-shot, or a caller-chosen
+     * constant identifying a level-styled stream whose newer values supersede older ones.
+     *
+     * Returns false only if the report had to be dropped outright — the caller can then treat the
+     * write as failed rather than assuming it is on its way.
+     */
+    fun offer(data: ByteArray, key: Int = NO_COALESCE): Boolean = synchronized(items) {
+        if (key != NO_COALESCE) {
+            val at = items.indexOfFirst { it.key == key }
+            if (at >= 0) {
+                // Supersede in place: keeping the queue position stops a fast rumble stream from
+                // repeatedly jumping the one-shots queued ahead of it.
+                items[at] = Entry(key, data)
+                return true
+            }
+        }
+        if (items.size >= cap) {
+            val victim = items.indexOfFirst { it.key != NO_COALESCE }
+            if (victim >= 0) {
+                items.removeAt(victim)
+            } else if (key != NO_COALESCE) {
+                // Nothing coalescable to sacrifice and this report is itself replaceable — drop it
+                // rather than a one-shot that will never come again.
+                return false
+            } else {
+                items.removeFirst()
+            }
+        }
+        items.addLast(Entry(key, data))
+        return true
+    }
+
+    /** The next report to submit, or null when nothing is pending. */
+    fun poll(): ByteArray? = synchronized(items) { items.removeFirstOrNull()?.data }
+
+    fun clear() = synchronized(items) { items.clear() }
+
+    val size: Int get() = synchronized(items) { items.size }
+
+    companion object {
+        /** This report is a one-shot: never superseded, evicted only as a last resort. */
+        const val NO_COALESCE = 0
+
+        /** Motor levels — re-sent continuously, so only the newest is worth keeping. */
+        const val KEY_RUMBLE = 1
+
+        /** Deep enough to absorb a burst, small enough that a stalled device cannot bloat us. */
+        const val CAP = 32
+    }
+}

clients/android/kit/src/main/kotlin/io/unom/punktfunk/kit/Sc2Capture.kt

@@ -273,10 +273,20 @@ class Sc2Capture(
 
     private fun onLinkClosed() {
         Log.i(TAG, "SC2 link closed (unplug / power-off)")
+        // Both transports share this callback, so read which one was live BEFORE clearing it —
+        // releasing the other would tear down a link that never dropped.
+        val dropped = activeLink
         activeLink = LINK_NONE
         dongleLink = false
         releaseSlot()
         releaseUiKeys()
+        // Release the transport too — see the note in DsCapture.onLinkClosed. The Puck makes this
+        // worse than a single leak: it is the pad that gets power-cycled, so the same process can
+        // round-trip a link many times in one session.
+        when (dropped) {
+            LINK_USB -> usb.stop()
+            LINK_BLE -> ble.stop()
+        }
         onActiveChanged?.invoke(false)
     }
 

clients/android/kit/src/test/kotlin/io/unom/punktfunk/kit/OutReportQueueTest.kt

@@ -0,0 +1,102 @@
+package io.unom.punktfunk.kit
+
+import org.junit.Assert.assertArrayEquals
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertFalse
+import org.junit.Assert.assertNull
+import org.junit.Assert.assertTrue
+import org.junit.Test
+
+/**
+ * The pending-OUT queue's overflow policy. What is being pinned here is the distinction the old
+ * "drop from the head until there is room" policy did not make: rumble is re-sent continuously and
+ * may be thrown away, while a lightbar/player-LED/trigger report is sent once and never repeated.
+ */
+class OutReportQueueTest {
+    /** A report carrying a 0..255 marker so a test can tell which one came back out. */
+    private fun report(marker: Int) = byteArrayOf(0x02, marker.toByte())
+
+    // Masked: the marker rides in a Byte, and Byte.toInt() sign-extends.
+    private fun drain(q: OutReportQueue): List<Int> =
+        generateSequence { q.poll() }.map { it[1].toInt() and 0xFF }.toList()
+
+    @Test
+    fun `rumble supersedes the pending rumble instead of queueing another`() {
+        val q = OutReportQueue()
+        assertTrue(q.offer(report(1), OutReportQueue.KEY_RUMBLE))
+        assertTrue(q.offer(report(2), OutReportQueue.KEY_RUMBLE))
+        assertTrue(q.offer(report(3), OutReportQueue.KEY_RUMBLE))
+        assertEquals("a rumble burst must collapse to one entry", 1, q.size)
+        assertArrayEquals(report(3), q.poll())
+        assertNull(q.poll())
+    }
+
+    @Test
+    fun `superseding keeps the queue position so a rumble stream cannot jump one-shots`() {
+        val q = OutReportQueue()
+        q.offer(report(1), OutReportQueue.KEY_RUMBLE)
+        q.offer(report(10)) // a one-shot queued behind it
+        q.offer(report(2), OutReportQueue.KEY_RUMBLE)
+        // The newer rumble takes the OLD rumble's slot, so the one-shot does not get starved
+        // behind an endlessly-renewed entry.
+        assertEquals(listOf(2, 10), drain(q))
+    }
+
+    @Test
+    fun `a full queue sacrifices rumble, never a one-shot`() {
+        val q = OutReportQueue(cap = 4)
+        q.offer(report(1), OutReportQueue.KEY_RUMBLE)
+        q.offer(report(10))
+        q.offer(report(11))
+        q.offer(report(12))
+        assertEquals(4, q.size)
+        // Full. The old policy dropped the head — here that is a rumble, but only by luck of
+        // ordering; what matters is that the one-shots all survive.
+        assertTrue(q.offer(report(13)))
+        assertEquals(listOf(10, 11, 12, 13), drain(q))
+    }
+
+    @Test
+    fun `the one-shot the host never repeats survives a rumble storm`() {
+        val q = OutReportQueue(cap = 4)
+        // The exact regression: a lightbar colour queued once, then a flood of rumble. Under the
+        // old newest-wins eviction the colour was dropped from the head and never came back,
+        // leaving the pad lit wrong until the value next happened to change.
+        q.offer(report(200)) // lightbar
+        repeat(50) { q.offer(report(it), OutReportQueue.KEY_RUMBLE) }
+        val out = drain(q)
+        assertTrue("the lightbar report must still be queued, got $out", out.contains(200))
+        assertEquals("rumble must not have accumulated", listOf(200, 49), out)
+    }
+
+    @Test
+    fun `a queue full of one-shots refuses a rumble rather than dropping one`() {
+        val q = OutReportQueue(cap = 2)
+        q.offer(report(10))
+        q.offer(report(11))
+        assertFalse(
+            "with nothing coalescable to sacrifice, the replaceable report yields",
+            q.offer(report(1), OutReportQueue.KEY_RUMBLE),
+        )
+        assertEquals(listOf(10, 11), drain(q))
+    }
+
+    @Test
+    fun `only a queue of nothing but one-shots drops one, and it is the oldest`() {
+        val q = OutReportQueue(cap = 2)
+        q.offer(report(10))
+        q.offer(report(11))
+        assertTrue(q.offer(report(12)))
+        assertEquals(listOf(11, 12), drain(q))
+    }
+
+    @Test
+    fun `clear empties the queue`() {
+        val q = OutReportQueue()
+        q.offer(report(1), OutReportQueue.KEY_RUMBLE)
+        q.offer(report(10))
+        q.clear()
+        assertEquals(0, q.size)
+        assertNull(q.poll())
+    }
+}