diff --git a/backend/cpp/audio-cpp/Makefile b/backend/cpp/audio-cpp/Makefile
index d66d53628..a281ccce1 100644
--- a/backend/cpp/audio-cpp/Makefile
+++ b/backend/cpp/audio-cpp/Makefile
@@ -9,7 +9,7 @@
 # recipe is a make target (not a prepare.sh) so 'make purge && make' is a clean
 # rebuild and so the bump bot can see the pin.
 
-AUDIO_CPP_VERSION?=9a02e61326aaaf9d462b584ca5e0daba22c0abfc
+AUDIO_CPP_VERSION?=cf124a67cc55d8f65a9a15eec69edbff0fb212c8
 AUDIO_CPP_REPO?=https://github.com/0xShug0/audio.cpp
 
 CURRENT_MAKEFILE_DIR := $(dir $(abspath $(lastword $(MAKEFILE_LIST))))
diff --git a/backend/cpp/audio-cpp/capability_routing.cpp b/backend/cpp/audio-cpp/capability_routing.cpp
index 9cd5b9b32..df597ef37 100644
--- a/backend/cpp/audio-cpp/capability_routing.cpp
+++ b/backend/cpp/audio-cpp/capability_routing.cpp
@@ -13,7 +13,7 @@ struct NamedTask {
 // Short names are exactly the strings audio.cpp prints and parses in
 // framework/runtime/session.cpp, so a name pinned here survives conversion at
 // the engine boundary and a name copied out of audio.cpp is accepted here. All
-// thirteen have an upstream name; only "spk" is absent from the --task table in
+// tasks have an upstream name; only "spk" is absent from the --task table in
 // docs/usage.md.
 const NamedTask kTaskNames[] = {
     {Task::Vad, "vad"},
@@ -30,6 +30,7 @@ const NamedTask kTaskNames[] = {
     {Task::SpeakerRecognition, "spk"},
     {Task::Svc, "svc"},
     {Task::Midi, "midi"},
+    {Task::TurnDetection, "turn"},
 };
 
 // Accepted on input but never emitted. "spkrec" was this backend's own earlier
diff --git a/backend/cpp/audio-cpp/capability_routing.h b/backend/cpp/audio-cpp/capability_routing.h
index 6b0a9098b..1624b9d2e 100644
--- a/backend/cpp/audio-cpp/capability_routing.h
+++ b/backend/cpp/audio-cpp/capability_routing.h
@@ -26,6 +26,7 @@ enum class Task {
     SpeakerRecognition,
     Svc,
     Midi,
+    TurnDetection,
 };
 
 // Mirrors engine::runtime::RunMode.
@@ -78,7 +79,7 @@ struct Route {
 Route resolve_route(Rpc rpc, const RequestShape &shape, const Capabilities &caps);
 
 // Canonical audio.cpp short names: gen, tts, clon, vc, svc, s2s, asr, align,
-// vad, diar, sep, vdes, spk. parse_task_name additionally accepts "spkrec" as
+// vad, diar, sep, vdes, spk, midi, turn. parse_task_name additionally accepts "spkrec" as
 // a legacy alias; task_name only ever emits "spk".
 const char *task_name(Task task);
 const char *mode_name(Mode mode);
diff --git a/backend/cpp/audio-cpp/capability_routing_test.cpp b/backend/cpp/audio-cpp/capability_routing_test.cpp
index 9163d4ba3..d149b84f3 100644
--- a/backend/cpp/audio-cpp/capability_routing_test.cpp
+++ b/backend/cpp/audio-cpp/capability_routing_test.cpp
@@ -361,7 +361,8 @@ static void test_names_round_trip() {
                         Task::SourceSeparation, Task::AudioGeneration, Task::Tts,
                         Task::VoiceCloning, Task::VoiceConversion,
                         Task::SpeechToSpeech, Task::Alignment, Task::VoiceDesign,
-                        Task::SpeakerRecognition, Task::Svc, Task::Midi};
+                        Task::SpeakerRecognition, Task::Svc, Task::Midi,
+                        Task::TurnDetection};
     for (const Task t : all) {
         Task parsed = Task::Vad;
         const bool ok = parse_task_name(task_name(t), parsed);
@@ -567,7 +568,28 @@ static void test_unsupported_surface_message_with_empty_capabilities() {
           "empty-capability message says the family supports nothing");
 }
 
+static void test_turn_detection_is_not_vad() {
+    Task turn = Task::Vad;
+    check(parse_task_name("turn", turn), "upstream turn task parses");
+    check(std::string(task_name(turn)) == "turn", "turn task name round-trips");
+    Capabilities caps{"smart_turn", {{turn, {Mode::Offline}}}};
+    const Rpc all[] = {Rpc::Tts, Rpc::TtsStream, Rpc::AudioTranscription,
+                      Rpc::AudioTranscriptionStream, Rpc::AudioTranscriptionLive,
+                      Rpc::Vad, Rpc::Diarize, Rpc::SoundGeneration, Rpc::AudioTransform};
+    for (const auto rpc : all) {
+        check(!resolve_route(rpc, RequestShape{}, caps).ok,
+              "turn detection cannot serve an existing RPC");
+        RequestShape pinned;
+        pinned.pinned_task = "turn";
+        check(!resolve_route(rpc, pinned, caps).ok,
+              "pinning turn detection cannot bypass RPC admission");
+    }
+    check(describe_capabilities(caps).find("turn/offline") != std::string::npos,
+          "turn detection has an accurate capability diagnostic");
+}
+
 int main() {
+    test_turn_detection_is_not_vad();
     test_plain_tts();
     test_tts_with_voice_reference_prefers_cloning();
     test_tts_voice_reference_falls_back_to_tts();
diff --git a/backend/cpp/audio-cpp/loaded_model.cpp b/backend/cpp/audio-cpp/loaded_model.cpp
index 28bed59b3..15e2e758f 100644
--- a/backend/cpp/audio-cpp/loaded_model.cpp
+++ b/backend/cpp/audio-cpp/loaded_model.cpp
@@ -67,10 +67,9 @@ static_assert(kEngine(engine::runtime::VoiceTaskKind::SpeechToSpeech) == 8, "Voi
 static_assert(kEngine(engine::runtime::VoiceTaskKind::Alignment) == 9, "VoiceTaskKind drifted");
 static_assert(kEngine(engine::runtime::VoiceTaskKind::VoiceDesign) == 10, "VoiceTaskKind drifted");
 static_assert(kEngine(engine::runtime::VoiceTaskKind::SpeakerRecognition) == 11, "VoiceTaskKind drifted");
-// The last member. Pinning it pins the member count too, as long as the
-// enumerators stay contiguous and unassigned, which upstream's declaration is.
 static_assert(kEngine(engine::runtime::VoiceTaskKind::Svc) == 12, "VoiceTaskKind drifted");
-static_assert(kEngine(engine::runtime::VoiceTaskKind::Midi) == 13,
+static_assert(kEngine(engine::runtime::VoiceTaskKind::Midi) == 13, "VoiceTaskKind drifted");
+static_assert(kEngine(engine::runtime::VoiceTaskKind::TurnDetection) == 14,
               "engine::runtime::VoiceTaskKind gained, lost or reordered a member. "
               "audiocpp_backend::Task mirrors it positionally: update capability_routing.h, "
               "to_engine_task and from_engine_task together, then move this pin.");
@@ -89,6 +88,7 @@ static_assert(kMirror(Task::VoiceDesign) == 10, "Task drifted from VoiceTaskKind
 static_assert(kMirror(Task::SpeakerRecognition) == 11, "Task drifted from VoiceTaskKind");
 static_assert(kMirror(Task::Svc) == 12, "Task drifted from VoiceTaskKind");
 static_assert(kMirror(Task::Midi) == 13, "Task drifted from VoiceTaskKind");
+static_assert(kMirror(Task::TurnDetection) == 14, "Task drifted from VoiceTaskKind");
 
 static_assert(static_cast<int>(engine::runtime::RunMode::Offline) == 0, "RunMode drifted");
 static_assert(static_cast<int>(engine::runtime::RunMode::Streaming) == 1,
@@ -247,6 +247,7 @@ engine::runtime::VoiceTaskKind to_engine_task(Task task) {
     case Task::SpeakerRecognition: return K::SpeakerRecognition;
     case Task::Svc:                return K::Svc;
     case Task::Midi:               return K::Midi;
+    case Task::TurnDetection:      return K::TurnDetection;
     }
     // Unreachable for any valid enumerator. No `default:` label, so -Wswitch
     // still reports a member this switch stops covering.
@@ -270,6 +271,7 @@ Task from_engine_task(engine::runtime::VoiceTaskKind kind) {
     case K::SpeakerRecognition: return Task::SpeakerRecognition;
     case K::Svc:                return Task::Svc;
     case K::Midi:               return Task::Midi;
+    case K::TurnDetection:      return Task::TurnDetection;
     }
     return Task::Vad;
 }
diff --git a/docs/content/features/audio-cpp.md b/docs/content/features/audio-cpp.md
index 59013ea5d..e77d68559 100644
--- a/docs/content/features/audio-cpp.md
+++ b/docs/content/features/audio-cpp.md
@@ -221,6 +221,10 @@ unaffected.
 
 ## Pinned tasks
 
+The upstream `turn` task performs turn detection. LocalAI has no RPC for this
+task, so requests to a model that only advertises `turn` are refused. It is not
+routed through voice activity detection (`vad`).
+
 Two routes are unreachable by auto-routing and need `task:` in the model config, because
 nothing in a request distinguishes them from a task the same family also advertises: