feat(core,clients): one rumble policy engine for every platform (rumble root fix D)

punktfunk-core client/rumble.rs: a per-connection policy engine consumes seq-gated wire
updates and emits EFFECTIVE actuator commands — re-emits on renewals (duration APIs stay
re-armed), self-silences at the v2 lease, a UNIFORM 1 s legacy-host staleness replacing the
per-platform zoo (Apple 1.6 s / Android 60 s / SDL 1.5 s / Deck 1 s), quirk-declared
actuator keepalives (Deck 40 ms + LSB dedupe-defeat jitter), and one stop per buzzing pad
on connection close. Per-pad mailbox semantics: a stalled embedder wakes to ONE current
command, and a stop can structurally never be the update an overflowing queue drops.

New API/ABI: NativeClient::{next_rumble_command,set_rumble_quirks} +
punktfunk_connection_next_rumble_cmd/_set_rumble_quirks (next_rumble/next_rumble2 stay for
un-migrated embedders; both consumers are fed). Migrations DELETE the platform forks:
pf-client-core loses RumbleState + the Deck keepalive loop + LEGACY_RUMBLE_CEILING_MS and
physically silences a slot at close; Android loses the 60 s legacy one-shot (backstop
repack, cancel-on-zero); Apple loses envelopeDeadline + sessionStaleSeconds + both tick
watchdogs (CoreHaptics realization untouched; mac xcframework rebuilt locally).

design/rumble-root-fix.md par. D. Engine 10/10 unit tests; core tests 176 Linux / 175
Windows + clippy -D warnings; swift build + RumbleTuningTests; Kotlin + android-native
compile green.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

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

@@ -52,9 +52,6 @@ class GamepadFeedback(
         const val TAG_PLAYER_LEDS: Byte = 0x02
         const val TAG_TRIGGER: Byte = 0x03
         const val TAG_HID_RAW: Byte = 0x05
-        // Fallback one-shot duration against a legacy host (no v2 TTL lease): the prior fixed value.
-        // A new host renews far below this, so it never actually holds this long there.
-        const val LEGACY_RUMBLE_MS = 60_000L
     }
 
     /** One controller's rumble binding — VibratorManager (API 31+) OR the legacy single Vibrator (API 28–30). */
@@ -95,19 +92,19 @@ class GamepadFeedback(
             while (running) {
                 val ev = NativeBridge.nativeNextRumble(handle)
                 if (ev < 0L) continue // timeout / closed
-                // ev bits 49..52 = wire pad index; bit 48 = has a v2 lease; bits 32..47 = ttl_ms;
-                // 16..31 = low; 0..15 = high. The lease flag is out-of-band, so any ttl_ms (incl.
-                // 0xFFFF) is a real lease — no in-band sentinel. No lease (legacy host) → the prior
-                // long one-shot.
+                // ev bits 49..52 = wire pad index; bits 32..47 = backstop duration (ms);
+                // 16..31 = low; 0..15 = high. These are EFFECTIVE commands from the core's shared
+                // rumble policy engine — it owns every lease/staleness/close decision (uniform
+                // across all clients; the old 60 s legacy-host exposure is gone) and emits
+                // explicit zeros, so apply verbatim: (0, 0) = cancel, non-zero = one-shot for
+                // the backstop (the hardware net under a stalled poll thread).
                 val pad = ((ev ushr 49) and 0xFL).toInt()
-                val hasLease = ((ev ushr 48) and 0x1L) == 0x1L
-                val ttl = ((ev ushr 32) and 0xFFFF).toInt()
-                val durationMs = if (hasLease) ttl.toLong() else LEGACY_RUMBLE_MS
+                val backstopMs = ((ev ushr 32) and 0xFFFF)
                 renderRumble(
                     pad,
                     ((ev ushr 16) and 0xFFFF).toInt(),
                     (ev and 0xFFFF).toInt(),
-                    durationMs,
+                    backstopMs,
                 )
             }
         }, "pf-rumble").apply { isDaemon = true; start() }
@@ -212,12 +209,13 @@ class GamepadFeedback(
 
     /**
      * low = heavy/left motor, high = light/right motor; both 0..0xFFFF (the host's u16 amplitudes),
-     * addressed to wire pad [pad]. `durationMs` is the host's v2 envelope TTL — the one-shot self-
-     * terminates after it unless the host renews, so a lost stop (or a dead host) silences at the
-     * lease instead of the old fixed 60 s. Against a legacy host it is [LEGACY_RUMBLE_MS].
+     * addressed to wire pad [pad]. `durationMs` is the engine command's backstop — the one-shot's
+     * self-termination net under a stalled poll thread; the engine emits explicit zero commands at
+     * every policy stop (lease expiry, legacy staleness, session close), so cancel-on-zero is the
+     * real stop mechanism.
      */
     private fun renderRumble(pad: Int, low: Int, high: Int, durationMs: Long) {
-        Log.i(TAG, "rumble pad=$pad low=$low high=$high ttlMs=$durationMs") // verification line — BEFORE any no-op return
+        Log.i(TAG, "rumble pad=$pad low=$low high=$high backstopMs=$durationMs") // verification line — BEFORE any no-op return
         // Opt-in phone mirror, BEFORE the controller-bind early-return: the exact pads this
         // serves have no vibrator of their own, so their bind below is null. It follows
         // controller 1 unconditionally rather than only motor-less pads — capability probing

clients/android/native/src/feedback.rs

@@ -24,14 +24,19 @@ const TAG_PLAYER_LEDS: u8 = 0x02;
 const TAG_TRIGGER: u8 = 0x03;
 const TAG_HID_RAW: u8 = 0x05;
 
-/// `NativeBridge.nativeNextRumble(handle): Long` — block up to ~100 ms for the next rumble update.
-/// Returns a packed positive long: bits 49..52 = wire `pad` index (0..15), bit 48 = "has a v2 lease",
-/// bits 32..47 = `ttl_ms`, bits 16..31 = `low`, bits 0..15 = `high` (`low`/`high` 0..=0xFFFF, `0/0` =
-/// stop). The lease flag is out-of-band so ANY 16-bit `ttl_ms` — including 0xFFFF — is unambiguous (no
-/// in-band sentinel to collide with a real 65535 ms lease). No lease (legacy host) → bit 48 clear, and
-/// Kotlin falls back to its long one-shot. `-1` on timeout / session closed (all packed values are
-/// positive, so `-1` stays unambiguous). Kotlin routes the update back to the controller holding that
-/// wire `pad` index (multi-pad rumble). Run from a Kotlin poll thread.
+/// `NativeBridge.nativeNextRumble(handle): Long` — block up to ~100 ms for the next EFFECTIVE
+/// rumble command from the core's shared policy engine (`design/rumble-root-fix.md` §D). The
+/// engine owns ALL rumble policy — v2 lease expiry, legacy-host staleness (a uniform 1 s, ending
+/// the old 60 s Android exposure), connection-close drain zeros — so Kotlin applies commands
+/// verbatim: `(0, 0)` = cancel now, non-zero = one-shot at this level.
+///
+/// Returns a packed positive long: bits 49..52 = wire `pad` index (0..15), bits 32..47 = the
+/// command's `backstop_ms` (≤ 5000 — the one-shot duration, i.e. the hardware net under a stalled
+/// poll thread; the engine emits explicit zeros at every policy stop, so it is never the stop
+/// mechanism), bits 16..31 = `low`, bits 0..15 = `high` (0..=0xFFFF). `-1` on timeout / session
+/// closed (all packed values are positive, so `-1` stays unambiguous). Kotlin routes the command
+/// back to the controller holding that wire `pad` index (multi-pad rumble). Run from a Kotlin
+/// poll thread.
 #[no_mangle]
 pub extern "system" fn Java_io_unom_punktfunk_kit_NativeBridge_nativeNextRumble(
     _env: JNIEnv,
@@ -43,24 +48,17 @@ pub extern "system" fn Java_io_unom_punktfunk_kit_NativeBridge_nativeNextRumble(
         if handle == 0 {
             return -1;
         }
-        // SAFETY: live handle per the nativeConnect/nativeClose contract; next_rumble_ttl is &self on
-        // the Sync connector — safe alongside the decode/audio/input threads. Kotlin stops these poll
-        // threads (and joins them — unbounded) before nativeClose frees the handle.
+        // SAFETY: live handle per the nativeConnect/nativeClose contract; next_rumble_command is
+        // &self on the Sync connector — safe alongside the decode/audio/input threads. Kotlin
+        // stops these poll threads (and joins them — unbounded) before nativeClose frees the
+        // handle.
         let h = unsafe { &*(handle as *const SessionHandle) };
-        match h.client.next_rumble_ttl(PULL_TIMEOUT) {
-            Ok((pad, low, high, ttl)) => {
-                // The reorder gate already ran in the core, so this update is fresh. Encode the
-                // Option out-of-band: a real lease sets bit 48 and carries ttl_ms verbatim. The pad
-                // index rides above the lease flag (bits 49..52), keeping the whole word positive.
-                let (lease_flag, ttl_bits) = match ttl {
-                    Some(ms) => (1i64 << 48, jlong::from(ms) << 32),
-                    None => (0, 0),
-                };
-                (jlong::from(pad & 0xF) << 49)
-                    | lease_flag
-                    | ttl_bits
-                    | (jlong::from(low) << 16)
-                    | jlong::from(high)
+        match h.client.next_rumble_command(PULL_TIMEOUT) {
+            Ok(cmd) => {
+                (jlong::from(cmd.pad & 0xF) << 49)
+                    | (jlong::from(cmd.backstop_ms.min(0xFFFF) as u16) << 32)
+                    | (jlong::from(cmd.low) << 16)
+                    | jlong::from(cmd.high)
             }
             Err(_) => -1, // NoFrame (timeout) or Closed — Kotlin loops on its running flag
         }

clients/apple/Sources/PunktfunkKit/Connection/PunktfunkConnection.swift

@@ -777,6 +777,34 @@ public final class PunktfunkConnection {
         }
     }
 
+    /// Pull the next EFFECTIVE rumble command from the core's shared rumble policy engine — the
+    /// uniform replacement for per-platform rumble policy. The engine owns every decision
+    /// (v2 lease expiry, legacy-host staleness at a uniform 1 s, connection-close drain zeros),
+    /// so apply commands verbatim: `(0, 0)` = stop now, non-zero = run at this level.
+    /// `backstopMs` is a safety-net duration for duration-parameterized platform APIs — the
+    /// CoreHaptics renderer ignores it (its finite segment ceiling is the equivalent net).
+    /// Drain from the (single) feedback thread, alongside `nextHidOutput`.
+    public func nextRumbleCommand(timeoutMs: UInt32 = 0) throws
+        -> (pad: UInt16, low: UInt16, high: UInt16, backstopMs: UInt32)?
+    {
+        feedbackLock.lock()
+        defer { feedbackLock.unlock() }
+        guard let h = liveHandle() else { throw PunktfunkClientError.closed }
+
+        var pad: UInt16 = 0, low: UInt16 = 0, high: UInt16 = 0, backstop: UInt32 = 0
+        let rc = punktfunk_connection_next_rumble_cmd(h, &pad, &low, &high, &backstop, timeoutMs)
+        switch rc {
+        case statusOK:
+            return (pad, low, high, backstop)
+        case statusNoFrame:
+            return nil
+        case statusClosed:
+            throw PunktfunkClientError.closed
+        default:
+            throw PunktfunkClientError.status(rc)
+        }
+    }
+
     /// One DualSense feedback event a game wrote to the host's virtual pad — replay it on
     /// the real controller (GCDeviceLight, GCControllerPlayerIndex,
     /// GCDualSenseAdaptiveTrigger). Only a `.dualSense` session emits these.

clients/apple/Sources/PunktfunkKit/Gamepad/GamepadFeedback.swift

@@ -155,21 +155,18 @@ public final class GamepadFeedback {
                     // meta, was unaffected). Pacing with a short sleep OUTSIDE the lock (below) keeps
                     // rumble/HID latency low while leaving the lock free between polls.
                     //
-                    // Rumble is idempotent state, so drain the plane DRY and apply only the newest
-                    // level PER PAD. The old one-datagram-per-cycle shape let a burst outpace the
-                    // ~125 Hz drain: levels rendered up to ~130 ms late through the core's 16-deep
-                    // queue, and its drop-newest overflow could shed a stop while stale nonzero
-                    // states queued ahead of it — buzzing until the host's next 500 ms refresh.
-                    var newestByPad: [UInt8: (low: UInt16, high: UInt16, ttl: UInt32)] = [:]
+                    // Rumble arrives as EFFECTIVE commands from the core's shared policy engine
+                    // (design/rumble-root-fix.md §D): the engine owns leases, legacy staleness,
+                    // and close-drain zeros, and its per-pad mailbox already coalesces — a
+                    // stalled drain wakes to ONE current-level command per pad, and a stop can
+                    // never be shed by a queue. Apply verbatim, in order.
                     var rumbleBurst = 0
                     while rumbleBurst < 64, !flag.isStopped,
-                          let r = try connection.nextRumble2(timeoutMs: 0) {
-                        newestByPad[UInt8(truncatingIfNeeded: r.pad)] = (r.low, r.high, r.ttlMs)
+                          let c = try connection.nextRumbleCommand(timeoutMs: 0) {
+                        self?.routeRumble(
+                            pad: UInt8(truncatingIfNeeded: c.pad), low: c.low, high: c.high)
                         rumbleBurst += 1
                     }
-                    for (pad, n) in newestByPad {
-                        self?.routeRumble(pad: pad, low: n.low, high: n.high, ttlMs: n.ttl)
-                    }
                     // Drain a BOUNDED burst of hidout events so sustained 0xCD traffic (a game writing
                     // per-frame LED/trigger reports) can't spin here or block stop() past one cycle.
                     var burst = 0
@@ -218,15 +215,15 @@ public final class GamepadFeedback {
         }
     }
 
-    /// Route one rumble envelope to its pad's renderer (drain thread). An update for a pad with no
+    /// Route one engine command to its pad's renderer (drain thread). A command for a pad with no
     /// live renderer — one that just left the forwarded set — is dropped.
-    private func routeRumble(pad: UInt8, low: UInt16, high: UInt16, ttlMs: UInt32) {
+    private func routeRumble(pad: UInt8, low: UInt16, high: UInt16) {
         let renderer = withRouting { rumbleByPad[pad] }
-        renderer?.apply(low: low, high: high, ttlMs: ttlMs)
+        renderer?.apply(low: low, high: high)
         // The opt-in device mirror follows controller 1 unconditionally — the pads it exists for
         // have no motors (their renderer above no-ops), and mirroring deliberately isn't gated on
         // that: capability probing can't see a motor-less MFi pad, and the user opted in.
-        if pad == 0 { deviceRumble?.apply(low: low, high: high, ttlMs: ttlMs) }
+        if pad == 0 { deviceRumble?.apply(low: low, high: high) }
     }
 
     private func withRouting<R>(_ body: () -> R) -> R {

clients/apple/Sources/PunktfunkKit/Gamepad/RumbleRenderer.swift

@@ -23,23 +23,6 @@ enum RumbleTuning {
     /// the churn that lost stops inside CoreHaptics. Newest level wins when the window opens;
     /// zero is never throttled.
     static let minRebakeSeconds: TimeInterval = 0.025
-    /// Session watchdog: silence the motors when no wire command arrived for this long. This is
-    /// the **legacy-host fallback only** — an old host sends no self-termination lease, so its
-    /// periodic re-send (every 500 ms) is the sole liveness signal and 3 vanished refreshes means
-    /// the channel or host died while audible. A v2 host instead supplies a per-command TTL (see
-    /// [`leaseSeconds`]); that deadline supersedes this watchdog.
-    static let sessionStaleSeconds: TimeInterval = 1.6
-
-    /// The legacy no-lease sentinel a v2 `ttl_ms` carries for an old host (mirrors the C ABI's
-    /// `PUNKTFUNK_RUMBLE_NO_TTL`). `UInt32.max` by construction.
-    static let noTTL: UInt32 = .max
-
-    /// Interpret a wire TTL (ms) from a rumble update: `nil` for the legacy no-lease sentinel
-    /// ([`noTTL`]) — the renderer falls back to [`sessionStaleSeconds`] — else the self-termination
-    /// lease in seconds (render the level for at most this long unless the host renews it).
-    static func leaseSeconds(ttlMs: UInt32) -> TimeInterval? {
-        ttlMs == noTTL ? nil : TimeInterval(ttlMs) / 1000
-    }
     /// Levels closer than this (≈0.4 % of full scale) are the same level — an identical host
     /// refresh must never rebuild a player.
     static let levelEpsilon: Float = 1.0 / 256.0
@@ -110,13 +93,15 @@ enum RumbleTuning {
 /// `@unchecked Sendable` is sound because every property is read and written only inside
 /// `queue` closures — the serial queue is the synchronization.
 final class RumbleRenderer: @unchecked Sendable {
-    /// What an un-refreshed nonzero target means. A live session ties motor life to wire
-    /// liveness (the host refreshes state every 500 ms); the controller test panel holds a
-    /// slider level indefinitely.
+    /// Who ends an un-refreshed nonzero target. Session mode applies the core policy engine's
+    /// commands verbatim — the engine (punktfunk-core `client/rumble.rs`) owns every lease,
+    /// staleness, and close decision and emits explicit zeros, so the renderer keeps NO
+    /// staleness policy of its own anymore. The controller test panel (`manual`) holds a slider
+    /// level indefinitely; both are identical renderer-side today, the distinction is kept for
+    /// the call sites' intent.
     struct Policy {
-        let staleAfter: TimeInterval?
-        static let session = Policy(staleAfter: RumbleTuning.sessionStaleSeconds)
-        static let manual = Policy(staleAfter: nil)
+        static let session = Policy()
+        static let manual = Policy()
     }
 
     /// Which physical actuator this renderer drives: the forwarded controller's haptics engine
@@ -160,13 +145,9 @@ final class RumbleRenderer: @unchecked Sendable {
     private var controller: GCController?
     private var low: Motor?
     private var high: Motor?
-    /// Wire-truth target (raw wire units) and when it was last confirmed by any command.
+    /// Wire-truth target (raw wire units) — the engine command's level, applied verbatim; the
+    /// core policy engine owns when it ends (explicit zero commands), so no deadline lives here.
     private var target: (low: UInt16, high: UInt16) = (0, 0)
-    private var lastCommand = DispatchTime(uptimeNanoseconds: 0)
-    /// The v2 envelope lease: the active level is authorized until here unless the host renews it
-    /// (`tick` silences at the deadline). `nil` against a legacy host (no lease — the
-    /// `sessionStaleSeconds` watchdog is the backstop) and while silent.
-    private var envelopeDeadline: DispatchTime?
     /// Runs while anything is (or should be) audible: staleness watchdog, segment re-arm,
     /// throttled-level catch-up, engine rebuild after a reset, HID keepalive. Nil while silent,
     /// so an idle controller costs no timer wakeups and no radio traffic.
@@ -247,17 +228,9 @@ final class RumbleRenderer: @unchecked Sendable {
     /// against a legacy host (no lease → the staleness watchdog is the backstop). Renewals at an
     /// unchanged level extend the deadline before the idempotence guard, so a held rumble never
     /// lapses mid-effect.
-    func apply(low lowAmp: UInt16, high highAmp: UInt16, ttlMs: UInt32 = RumbleTuning.noTTL) {
+    func apply(low lowAmp: UInt16, high highAmp: UInt16) {
         queue.async {
-            self.lastCommand = .now()
             let active = lowAmp != 0 || highAmp != 0
-            // v2 lease: a nonzero level gets an explicit deadline; a stop or a legacy update clears
-            // it. Set BEFORE the idempotence guard so an identical renewal still extends the lease.
-            if let lease = RumbleTuning.leaseSeconds(ttlMs: ttlMs), active {
-                self.envelopeDeadline = .now() + lease
-            } else {
-                self.envelopeDeadline = nil
-            }
             if active != self.wasActive {
                 self.wasActive = active
                 log.debug(
@@ -275,7 +248,6 @@ final class RumbleRenderer: @unchecked Sendable {
             self.ticker?.cancel()
             self.ticker = nil
             self.target = (0, 0)
-            self.envelopeDeadline = nil
             self.wasActive = false
             self.teardown()
             self.closeHID()
@@ -331,25 +303,11 @@ final class RumbleRenderer: @unchecked Sendable {
         healthSink?(problem)
     }
 
-    /// Watchdog + housekeeping heartbeat while audible.
+    /// Housekeeping heartbeat while audible: segment re-arm, HID keepalive, backoff retries.
+    /// Every liveness decision (lease expiry, legacy-host staleness, session close) lives in the
+    /// core policy engine now — it emits explicit zero commands, so the renderer never guesses
+    /// when a level should end.
     private func tick() {
-        if let deadline = envelopeDeadline {
-            // v2 host lease: silence the moment it lapses unrenewed. This firing in the wild is the
-            // observable signature of a host that stopped renewing (a dropped stop, or a dead host)
-            // — the whole point of the envelope model: the motor can't outlive the host's intent.
-            if target != (0, 0), DispatchTime.now() >= deadline {
-                log.warning("rumble: envelope expired unrenewed — silencing")
-                target = (0, 0)
-                envelopeDeadline = nil
-            }
-        } else if let after = policy.staleAfter, target != (0, 0), seconds(since: lastCommand) > after {
-            // Legacy host (no lease): it re-sends state every 500 ms, so this much silence means the
-            // channel (or host) died while a motor was on. A direct-connected pad would have been
-            // stopped by its game long ago — force the same outcome.
-            log.warning(
-                "rumble: no wire refresh for \(after, format: .fixed(precision: 1), privacy: .public)s — auto-silencing")
-            target = (0, 0)
-        }
         render()
     }
 

clients/apple/Tests/PunktfunkKitTests/RumbleTuningTests.swift

@@ -52,13 +52,6 @@ final class RumbleTuningTests: XCTestCase {
         XCTAssertEqual(RumbleTuning.handoffStart(endsAt: 100, now: 100.5), 100.5)
     }
 
-    func testPolicies() {
-        // The session policy ties motor life to wire liveness; the manual (test-panel) policy
-        // holds a level indefinitely.
-        XCTAssertNotNil(RumbleRenderer.Policy.session.staleAfter)
-        XCTAssertNil(RumbleRenderer.Policy.manual.staleAfter)
-    }
-
     /// Exercise the renderer's queue/ticker machinery without a physical pad: a wire-rate call
     /// storm, an audible target left to the ticker (watchdog path), then `stop()` — which runs
     /// `queue.sync` against the same serial queue the ticker fires on and must not deadlock.
@@ -75,45 +68,22 @@ final class RumbleTuningTests: XCTestCase {
         renderer.stop()
     }
 
-    func testLeaseSecondsInterpretsWireTTL() {
-        // The legacy no-lease sentinel → nil (fall back to the staleness watchdog).
-        XCTAssertNil(RumbleTuning.leaseSeconds(ttlMs: RumbleTuning.noTTL))
-        XCTAssertEqual(RumbleTuning.noTTL, UInt32.max)
-        // A real lease → its duration in seconds (non-nil for any ttl != noTTL).
-        XCTAssertEqual(RumbleTuning.leaseSeconds(ttlMs: 400) ?? .nan, 0.4, accuracy: 1e-9)
-        XCTAssertEqual(RumbleTuning.leaseSeconds(ttlMs: 0) ?? .nan, 0, accuracy: 1e-9)
-        XCTAssertEqual(RumbleTuning.leaseSeconds(ttlMs: 150) ?? .nan, 0.15, accuracy: 1e-9)
-    }
-
-    func testEnvelopeLeaseBoundsMotorLifeTighterThanTheLegacyWatchdog() {
-        // The whole point of v2: a host-supplied lease silences the motor faster than the
-        // legacy staleness watchdog ever could (which needs sessionStaleSeconds of silence). The
-        // default 400 ms TTL is well under that, on every platform.
-        let defaultTTL = RumbleTuning.leaseSeconds(ttlMs: 400)
-        XCTAssertNotNil(defaultTTL)
-        XCTAssertLessThan(defaultTTL!, RumbleTuning.sessionStaleSeconds)
-        // The ticker must be able to observe an expired lease promptly (well within one TTL).
-        XCTAssertLessThan(RumbleTuning.tickSeconds, defaultTTL!)
-    }
-
-    /// A v2 envelope with a short TTL, left unrenewed, must self-silence — the renderer's core
-    /// promise. Drive the real queue/ticker (no physical pad) and confirm it doesn't wedge.
-    func testEnvelopeExpiresWhenUnrenewed() {
+    /// A zero command must silence promptly — the engine (punktfunk-core) emits explicit zeros at
+    /// every policy stop (lease expiry, legacy staleness, session close), and the renderer's only
+    /// job is to apply them. Drive the real queue/ticker (no physical pad) and confirm no wedge.
+    func testZeroCommandSilencesAndTeardownDoesNotDeadlock() {
         let renderer = RumbleRenderer(policy: .session)
         renderer.retarget(nil)
-        // A 100 ms lease, then no renewal — the ticker (50 ms) must silence it on its own.
-        renderer.apply(low: 0x8000, high: 0x8000, ttlMs: 100)
-        Thread.sleep(forTimeInterval: 0.3)
-        // No assertion on private state; this exercises the expiry path + serial-queue teardown
+        renderer.apply(low: 0x8000, high: 0x8000)
+        Thread.sleep(forTimeInterval: 0.1)
+        renderer.apply(low: 0, high: 0)
+        Thread.sleep(forTimeInterval: 0.1)
+        // No assertion on private state; this exercises the stop path + serial-queue teardown
         // without deadlock (the ticker fires on the same queue stop() sync-hops onto).
         renderer.stop()
     }
 
     func testTuningRelationsTheDesignDependsOn() {
-        // The watchdog must tolerate a couple of lost 500 ms host refreshes (heals, not gaps)
-        // but trip well before a stuck rumble reads as "still going".
-        XCTAssertGreaterThan(RumbleTuning.sessionStaleSeconds, 2 * 0.5)
-        XCTAssertLessThanOrEqual(RumbleTuning.sessionStaleSeconds, 2.5)
         // Re-arm headroom must clear several ticker periods, or a steady rumble could miss the
         // segment boundary and gap.
         XCTAssertGreaterThanOrEqual(
@@ -123,9 +93,8 @@ final class RumbleTuningTests: XCTestCase {
         // The rebake throttle must be far under the host refresh period, or refreshed level
         // changes would queue behind it; and under a frame at 30 fps so ramps stay smooth.
         XCTAssertLessThan(RumbleTuning.minRebakeSeconds, 1.0 / 30)
-        // The ticker (which lands throttled levels) must outpace the HID keepalive and the
-        // watchdog, or those deadlines could be overshot by a full period.
+        // The ticker (which lands throttled levels) must outpace the HID keepalive, or its
+        // deadline could be overshot by a full period.
         XCTAssertLessThan(RumbleTuning.tickSeconds, RumbleTuning.hidKeepaliveSeconds)
-        XCTAssertLessThan(RumbleTuning.tickSeconds, RumbleTuning.sessionStaleSeconds)
     }
 }