diff --git a/c/set-protocol/docs/GUI_PLOT.md b/c/set-protocol/docs/GUI_PLOT.md
index d57233b..97f9eda 100644
--- a/c/set-protocol/docs/GUI_PLOT.md
+++ b/c/set-protocol/docs/GUI_PLOT.md
@@ -3,7 +3,7 @@
 Численная логика находится в `include/set_plot.h` и `src/set_plot.c`.
 Это модуль C99 без Qt, Android, транспорта, динамической памяти и глобального
 состояния. Он собирается в существующую библиотеку SETProtocol; отдельная DLL
-для графиков не требуется. Версия ABI графиков — `set_plot_abi_version() == 1`.
+для графиков не требуется. Версия ABI графиков — `set_plot_abi_version() == 2`.
 
 | Общее в templates | Адаптер приложения |
 |---|---|
@@ -13,6 +13,7 @@
 | Перевод значения в долю экрана и обратно, инверсия Y | Canvas/QPainter и оформление шкал |
 | Перемещение маркера от начальной координаты, ограничение видимой областью | Захват линии пальцем/мышью, редактор положения |
 | Разность B−A, D−C и множитель единиц, шаги шкалы 1/2/5 | Подписи, цвета, миллисекунды/герцы/единицы сигнала |
+| Проверка абсолютных границ X/Y для фиксации осей | Диалог ввода и хранение отдельных границ времени/FFT |
 | Модели маркеров и их размещение в Kotlin/Python-портах | Жизненный цикл экрана, очистка и выбор источника |
 
 Модель маркеров: A/B — координаты X и вертикальные линии во всю высоту поля;
@@ -59,8 +60,9 @@ SETGUI: `ui/plot_interaction.py` адаптирует общий модуль к
 используются исходные метки приёма. Дискретные дорожки имеют общую X-шкалу,
 а маркеры уровня Y относятся к аналоговому полю.
 
-Расчёт FFT не является частью этого модуля. Android вычисляет спектр через
-`set_spectrum.c`; вкладка спектра SETGUI получает готовые уровни в дБмВ от
+Расчёт FFT не является частью этого модуля. Android и SETGUI вычисляют спектр через
+`set_spectrum.c`; там же находится общий поиск доминирующего узкополосного пика,
+а трёхсекундный таймер его отображения остаётся состоянием GUI. Вкладка спектра SETGUI получает готовые уровни в дБмВ от
 прибора. Общая интерактивная часть не меняет эти данные или единицы.
 
 ## Проверка и сборка
diff --git a/c/set-protocol/docs/GUI_TRENDS.md b/c/set-protocol/docs/GUI_TRENDS.md
index 6a3819b..2898b89 100644
--- a/c/set-protocol/docs/GUI_TRENDS.md
+++ b/c/set-protocol/docs/GUI_TRENDS.md
@@ -12,7 +12,7 @@
 | `include/set_trends.h`, `src/set_trends.c` | C99: фильтрация GAS/raw CAN, signed/unsigned word, payload подписки SET GUI; использует `pcan_id` и ABI export macro |
 | `ports/android/kotlin/ru/setcorp/setprotocol/trends/` | Модель, валидация JSON, ограниченная история, GAS_WATCH; JVM + org.json, без Android/Compose |
 | `ports/android/setprotocol_jni.c` | Только преобразование JNI-аргументов |
-| `python/protocan/trends.py` | Модель, JSON, история и `NativeTrends`; Python 3.9+, stdlib, без Qt |
+| `python/protocan/trends.py` | Модель, JSON, история и `NativeTrends` (word/CAN/GAS request/ack/data); Python 3.9+, stdlib, без Qt |
 | `tests/fixtures/trends-v1.json` | Один образец для тестов обоих GUI и обмена настройками |
 
 ## Формат файла
@@ -44,6 +44,8 @@ UTF-8 JSON: `format = "setflash-trends"`, `version = 1`, `profiles` — слов
 
 CAN — пассивный приём, без записи GAS и автоматической отправки запросов.
 GAS принимает только входящие FROM_DEVICE; TX/RTR/ошибки исключены.
+Полный `GAS_WATCH_DATA`, включая 32-битную метку прибора, разбирается функцией
+`set_trend_watch_decode`; UI не знает смещений полей и endian.
 SET GUI оформляет подписку в порядке адресов. ACK должен подтвердить весь
 список: при частичном принятии нельзя определить пропущенные адреса, поэтому
 строить график по смещённым индексам запрещено. При паузе порт приложения
diff --git a/c/set-protocol/include/set_plot.h b/c/set-protocol/include/set_plot.h
index 2ae6847..df7cc60 100644
--- a/c/set-protocol/include/set_plot.h
+++ b/c/set-protocol/include/set_plot.h
@@ -17,10 +17,11 @@ enum set_plot_operation {
     SET_PLOT_DRAG = 4,      /* initial,deltaPixels,length,low,high,inverted -> clamped value */
     SET_PLOT_TICK_STEP = 5, /* range,lengthPixels -> nice step */
     SET_PLOT_DELTA = 6,     /* A,B,multiplier -> (B-A)*multiplier */
-    SET_PLOT_DB_DELTA = 7   /* A,B -> 20*log10(abs(B/A)); zero is invalid */
+    SET_PLOT_DB_DELTA = 7,  /* A,B -> 20*log10(abs(B/A)); zero is invalid */
+    SET_PLOT_LIMITS = 8     /* xMin,xMax,yMin,yMax -> validated unchanged limits */
 };
 
-/** Version of this plot ABI, independently of the transport ABI. */
+/** Version of this plot ABI, independently of the transport ABI (currently 2). */
 PCAN_ABI_API uint32_t set_plot_abi_version(void);
 /** Evaluates one operation. Returns output count, or 0 for invalid arguments.
  * TRANSFORM rejects malformed viewports; invalid gesture values return the
diff --git a/c/set-protocol/include/set_spectrum.h b/c/set-protocol/include/set_spectrum.h
index 554c1a5..8747924 100644
--- a/c/set-protocol/include/set_spectrum.h
+++ b/c/set-protocol/include/set_spectrum.h
@@ -28,6 +28,15 @@ PCAN_ABI_API int set_spectrum_analyze(const double *times, const double *values,
     size_t max_size, int window, int filter, double low_hz, double high_hz, int remove_mean,
     double *amplitudes, size_t capacity, double *meta);
 
+/** Find the strongest non-DC local maximum above both the absolute floor and
+ * relative_threshold * median(non-DC amplitudes). The caller supplies scratch
+ * storage of at least count-1 doubles. peak = {frequency_hz, amplitude}.
+ * Returns 1 when found, 0 when no narrow-band peak exists, -1 on invalid input.
+ */
+PCAN_ABI_API int set_spectrum_dominant_peak(const double *amplitudes, size_t count,
+    double bin_hz, double relative_threshold, double absolute_floor,
+    double *scratch, size_t scratch_capacity, double *peak, size_t peak_capacity);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/c/set-protocol/include/set_trends.h b/c/set-protocol/include/set_trends.h
index 1693d4a..b187f0c 100644
--- a/c/set-protocol/include/set_trends.h
+++ b/c/set-protocol/include/set_trends.h
@@ -48,6 +48,13 @@ PCAN_ABI_API int set_trend_watch_ack(
 PCAN_ABI_API int set_trend_watch_values(
     const uint8_t *payload, size_t size, uint16_t *words, size_t capacity);
 
+/** Decode the complete GAS_WATCH_DATA payload including its device timestamp.
+ * This is the preferred ABI for GUI ports; the older values-only symbol remains
+ * available for binary compatibility.
+ */
+PCAN_ABI_API int set_trend_watch_decode(const uint8_t *payload, size_t size,
+    uint32_t *timestamp_ms, uint16_t *words, size_t capacity);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/c/set-protocol/ports/android/kotlin/ru/setcorp/setprotocol/NativeSetProtocol.kt b/c/set-protocol/ports/android/kotlin/ru/setcorp/setprotocol/NativeSetProtocol.kt
index 8aa7255..bc11653 100644
--- a/c/set-protocol/ports/android/kotlin/ru/setcorp/setprotocol/NativeSetProtocol.kt
+++ b/c/set-protocol/ports/android/kotlin/ru/setcorp/setprotocol/NativeSetProtocol.kt
@@ -16,12 +16,18 @@ object NativeSetProtocol {
     /** {status, N, Fs, jitter, amplitudes...}; status != 0 has no amplitudes. */
     external fun nativeSpectrum(times: DoubleArray, values: DoubleArray, maxSize: Int,
         window: Int, filter: Int, lowHz: Double, highHz: Double, removeMean: Boolean): DoubleArray?
+    /** {frequencyHz, amplitude}, empty when no narrow-band peak is present. */
+    external fun nativeSpectrumPeak(amplitudes: DoubleArray, binHz: Double,
+        relativeThreshold: Double, absoluteFloor: Double): DoubleArray?
     external fun nativeTrendCanValue(
         source: Int, address: Long, deviceType: Int, device: Int, byteOffset: Int,
         extended: Boolean, signed: Boolean, canId: Long, flags: Int, input: ByteArray,
     ): Int
     external fun nativeTrendWatchRequest(period: Int, addresses: IntArray): ByteArray?
+    external fun nativeTrendWatchAck(input: ByteArray, period: Int, count: Int): Boolean
     external fun nativeTrendWatchValues(input: ByteArray): IntArray?
+    /** {unsigned timestampMs, word0, ...}. */
+    external fun nativeTrendWatchDecode(input: ByteArray): LongArray?
     external fun nativePackId(
         priority: Int,
         route: Int,
diff --git a/c/set-protocol/ports/android/kotlin/ru/setcorp/setprotocol/trends/GuiGasWatch.kt b/c/set-protocol/ports/android/kotlin/ru/setcorp/setprotocol/trends/GuiGasWatch.kt
index 5a814ad..924ed9c 100644
--- a/c/set-protocol/ports/android/kotlin/ru/setcorp/setprotocol/trends/GuiGasWatch.kt
+++ b/c/set-protocol/ports/android/kotlin/ru/setcorp/setprotocol/trends/GuiGasWatch.kt
@@ -10,37 +10,28 @@ object GuiGasWatch {
 
     fun request(periodMs: Int, addresses: List<Int>): ByteArray {
         require(periodMs in 0..65535 && addresses.size <= 64 && addresses.all { it in 0..65535 })
-        if (NativeSetProtocol.available) return requireNotNull(NativeSetProtocol.nativeTrendWatchRequest(periodMs, addresses.toIntArray()))
-        return ByteArray(4 + addresses.size * 2).also { output ->
-            put16(output, 0, periodMs)
-            put16(output, 2, addresses.size)
-            addresses.forEachIndexed { index, address -> put16(output, 4 + index * 2, address) }
-        }
+        check(NativeSetProtocol.available) { "Общая библиотека SETProtocol недоступна" }
+        return requireNotNull(NativeSetProtocol.nativeTrendWatchRequest(periodMs, addresses.toIntArray()))
     }
 
     fun validateAck(payload: ByteArray, periodMs: Int, count: Int) {
-        require(payload.size == 4 && read16(payload, 0) == periodMs && read16(payload, 2) == count) {
+        require(NativeSetProtocol.available && NativeSetProtocol.nativeTrendWatchAck(payload, periodMs, count)) {
             "Прибор принял не все адреса GAS. Проверьте карту регистров; отображение по неполной подписке невозможно"
         }
     }
 
     fun values(payload: ByteArray, expectedCount: Int): List<Int> {
-        val values = if (NativeSetProtocol.available) {
-            requireNotNull(NativeSetProtocol.nativeTrendWatchValues(payload)) { "Повреждён GAS_WATCH_DATA" }.toList()
-        } else {
-            require(payload.size >= 6) { "GAS_WATCH_DATA короче заголовка" }
-            val count = read16(payload, 4)
-            require(count <= 64 && payload.size == 6 + count * 2) { "Неверная длина GAS_WATCH_DATA" }
-            List(count) { read16(payload, 6 + it * 2) }
-        }
+        check(NativeSetProtocol.available) { "Общая библиотека SETProtocol недоступна" }
+        val values = requireNotNull(NativeSetProtocol.nativeTrendWatchValues(payload)) { "Повреждён GAS_WATCH_DATA" }.toList()
         require(values.size == expectedCount) { "Число значений GAS не соответствует подписке" }
         return values
     }
 
-    private fun read16(data: ByteArray, offset: Int): Int =
-        (data[offset].toInt() and 0xFF) or ((data[offset + 1].toInt() and 0xFF) shl 8)
-    private fun put16(data: ByteArray, offset: Int, value: Int) {
-        data[offset] = value.toByte()
-        data[offset + 1] = (value ushr 8).toByte()
+    data class Sample(val timestampMs: Long, val values: List<Int>)
+    fun decode(payload: ByteArray, expectedCount: Int): Sample {
+        check(NativeSetProtocol.available) { "Общая библиотека SETProtocol недоступна" }
+        val decoded = requireNotNull(NativeSetProtocol.nativeTrendWatchDecode(payload)) { "Повреждён GAS_WATCH_DATA" }
+        require(decoded.size == expectedCount + 1) { "Число значений GAS не соответствует подписке" }
+        return Sample(decoded[0], decoded.drop(1).map(Long::toInt))
     }
 }
diff --git a/c/set-protocol/ports/android/kotlin/ru/setcorp/setprotocol/trends/NativePlot.kt b/c/set-protocol/ports/android/kotlin/ru/setcorp/setprotocol/trends/NativePlot.kt
index 92f264b..1ce5a53 100644
--- a/c/set-protocol/ports/android/kotlin/ru/setcorp/setprotocol/trends/NativePlot.kt
+++ b/c/set-protocol/ports/android/kotlin/ru/setcorp/setprotocol/trends/NativePlot.kt
@@ -32,3 +32,10 @@ fun plotTickStep(range: Double, pixels: Double): Double = NativePlot.call(5, ran
 fun plotDelta(a: Double, b: Double, multiplier: Double = 1.0): Double = NativePlot.call(6, a, b, multiplier)[0]
 fun plotDbDelta(a: Double, b: Double): Double? =
     runCatching { NativePlot.call(7, a, b)[0] }.getOrNull()
+
+data class PlotLimits(val xMin: Double, val xMax: Double, val yMin: Double, val yMax: Double) {
+    fun validated(): PlotLimits {
+        val values = NativePlot.call(8, xMin, xMax, yMin, yMax)
+        return PlotLimits(values[0], values[1], values[2], values[3])
+    }
+}
diff --git a/c/set-protocol/ports/android/kotlin/ru/setcorp/setprotocol/trends/TrendSpectrum.kt b/c/set-protocol/ports/android/kotlin/ru/setcorp/setprotocol/trends/TrendSpectrum.kt
index 5f02bd3..cf8679c 100644
--- a/c/set-protocol/ports/android/kotlin/ru/setcorp/setprotocol/trends/TrendSpectrum.kt
+++ b/c/set-protocol/ports/android/kotlin/ru/setcorp/setprotocol/trends/TrendSpectrum.kt
@@ -34,6 +34,8 @@ data class TrendSpectrum(
     val binHz: Double get() = if (size > 0) sampleRate / size else 0.0
 }
 
+data class SpectrumPeak(val frequencyHz: Double, val amplitude: Double)
+
 /** Math is implemented once in C and used unchanged by JNI and ctypes. */
 object SpectrumAnalyzer {
     fun analyze(points: List<TrendPoint>, options: SpectrumOptions): TrendSpectrum {
@@ -64,4 +66,12 @@ object SpectrumAnalyzer {
         return TrendSpectrum(output[1].toInt(), output[2], output[3],
             if (error == null) output.drop(4) else emptyList(), error)
     }
+
+    fun dominantPeak(spectrum: TrendSpectrum, relativeThreshold: Double = 3.0,
+                     absoluteFloor: Double = 1e-6): SpectrumPeak? {
+        if (spectrum.error != null || spectrum.size <= 0 || spectrum.amplitudes.size < 3) return null
+        val result = NativeSetProtocol.nativeSpectrumPeak(spectrum.amplitudes.toDoubleArray(),
+            spectrum.binHz, relativeThreshold, absoluteFloor) ?: return null
+        return result.takeIf { it.size == 2 }?.let { SpectrumPeak(it[0], it[1]) }
+    }
 }
diff --git a/c/set-protocol/ports/android/setprotocol_jni.c b/c/set-protocol/ports/android/setprotocol_jni.c
index 7f916f7..57da780 100644
--- a/c/set-protocol/ports/android/setprotocol_jni.c
+++ b/c/set-protocol/ports/android/setprotocol_jni.c
@@ -276,6 +276,30 @@ Java_ru_setcorp_setprotocol_NativeSetProtocol_nativeTrendCanValue(
         (uint8_t)flags, (const uint8_t *)data, (size_t)size);
 }
 
+JNIEXPORT jdoubleArray JNICALL
+Java_ru_setcorp_setprotocol_NativeSetProtocol_nativeSpectrumPeak(
+    JNIEnv *env, jobject self, jdoubleArray input, jdouble bin_hz,
+    jdouble relative_threshold, jdouble absolute_floor)
+{
+    (void)self;
+    jsize count = input == NULL ? 0 : (*env)->GetArrayLength(env, input);
+    if (count < 3 || count > (jsize)(SET_SPECTRUM_MAX / 2U + 1U)) return NULL;
+    double *buffer = (double *)malloc(sizeof(double) * (size_t)(count * 2 - 1));
+    if (buffer == NULL) return NULL;
+    double *amplitudes = buffer, *scratch = buffer + count, peak[2];
+    (*env)->GetDoubleArrayRegion(env, input, 0, count, amplitudes);
+    int status = (*env)->ExceptionCheck(env) ? -1 : set_spectrum_dominant_peak(
+        amplitudes, (size_t)count, bin_hz, relative_threshold, absolute_floor,
+        scratch, (size_t)count - 1U, peak, 2U);
+    jdoubleArray result = NULL;
+    if (status >= 0) {
+        result = (*env)->NewDoubleArray(env, status == 1 ? 2 : 0);
+        if (result != NULL && status == 1) (*env)->SetDoubleArrayRegion(env, result, 0, 2, peak);
+    }
+    free(buffer);
+    return result;
+}
+
 JNIEXPORT jbyteArray JNICALL
 Java_ru_setcorp_setprotocol_NativeSetProtocol_nativeTrendWatchRequest(
     JNIEnv *env, jobject self, jint period, jintArray input)
@@ -298,6 +322,20 @@ Java_ru_setcorp_setprotocol_NativeSetProtocol_nativeTrendWatchRequest(
     return result;
 }
 
+JNIEXPORT jboolean JNICALL
+Java_ru_setcorp_setprotocol_NativeSetProtocol_nativeTrendWatchAck(
+    JNIEnv *env, jobject self, jbyteArray input, jint period, jint count)
+{
+    (void)self;
+    if (input == NULL || period < 0 || period > 65535 || count < 0) return JNI_FALSE;
+    jsize size = (*env)->GetArrayLength(env, input);
+    if (size != 4) return JNI_FALSE;
+    jbyte payload[4];
+    (*env)->GetByteArrayRegion(env, input, 0, size, payload);
+    return set_trend_watch_ack((const uint8_t *)payload, (size_t)size,
+        (uint16_t)period, (size_t)count) ? JNI_TRUE : JNI_FALSE;
+}
+
 JNIEXPORT jintArray JNICALL
 Java_ru_setcorp_setprotocol_NativeSetProtocol_nativeTrendWatchValues(
     JNIEnv *env, jobject self, jbyteArray input)
@@ -317,6 +355,28 @@ Java_ru_setcorp_setprotocol_NativeSetProtocol_nativeTrendWatchValues(
     return result;
 }
 
+JNIEXPORT jlongArray JNICALL
+Java_ru_setcorp_setprotocol_NativeSetProtocol_nativeTrendWatchDecode(
+    JNIEnv *env, jobject self, jbyteArray input)
+{
+    (void)self;
+    jsize size = input == NULL ? 0 : (*env)->GetArrayLength(env, input);
+    if (size < 6 || size > (jsize)(6U + 2U * SET_TREND_WATCH_MAX)) return NULL;
+    jbyte payload[6U + 2U * SET_TREND_WATCH_MAX];
+    uint16_t words[SET_TREND_WATCH_MAX];
+    uint32_t timestamp = 0U;
+    jlong values[1U + SET_TREND_WATCH_MAX];
+    (*env)->GetByteArrayRegion(env, input, 0, size, payload);
+    int count = set_trend_watch_decode((const uint8_t *)payload, (size_t)size,
+        &timestamp, words, SET_TREND_WATCH_MAX);
+    if (count < 0) return NULL;
+    values[0] = (jlong)timestamp;
+    for (int i = 0; i < count; ++i) values[i + 1] = (jlong)words[i];
+    jlongArray result = (*env)->NewLongArray(env, count + 1);
+    if (result != NULL) (*env)->SetLongArrayRegion(env, result, 0, count + 1, values);
+    return result;
+}
+
 typedef struct {
     uint8_t *storage;
     size_t storage_size;
diff --git a/c/set-protocol/ports/android/tests/ru/setcorp/setprotocol/trends/PlotViewportTest.kt b/c/set-protocol/ports/android/tests/ru/setcorp/setprotocol/trends/PlotViewportTest.kt
index d9918d2..af6962b 100644
--- a/c/set-protocol/ports/android/tests/ru/setcorp/setprotocol/trends/PlotViewportTest.kt
+++ b/c/set-protocol/ports/android/tests/ru/setcorp/setprotocol/trends/PlotViewportTest.kt
@@ -36,4 +36,12 @@ class PlotViewportTest {
         }
         SpectrumOptions().validate()
     }
+    @Test fun absoluteLimitsAndDominantPeakUseNativeCore() {
+        assertEquals(PlotLimits(0.0, 500.0, -1.0, 1.0),
+            PlotLimits(0.0, 500.0, -1.0, 1.0).validated())
+        assertTrue(runCatching { PlotLimits(1.0, 1.0, -1.0, 1.0).validated() }.isFailure)
+        val spectrum = TrendSpectrum(12, 60.0, 0.0,
+            listOf(10.0, .01, .02, .8, .03, .4, .02))
+        assertEquals(15.0, SpectrumAnalyzer.dominantPeak(spectrum)!!.frequencyHz, 0.0)
+    }
 }
diff --git a/c/set-protocol/src/set_plot.c b/c/set-protocol/src/set_plot.c
index 66ed13c..368275b 100644
--- a/c/set-protocol/src/set_plot.c
+++ b/c/set-protocol/src/set_plot.c
@@ -8,13 +8,13 @@ static int finite_values(const double *v, size_t n) {
     return 1;
 }
 
-uint32_t set_plot_abi_version(void) { return 1U; }
+uint32_t set_plot_abi_version(void) { return 2U; }
 
 size_t set_plot_eval(uint32_t op, const double *v, size_t n, double *out, size_t cap) {
-    static const size_t sizes[] = {10, 3, 4, 4, 6, 2, 3, 2};
+    static const size_t sizes[] = {10, 3, 4, 4, 6, 2, 3, 2, 4};
     double span, fraction;
-    if (op > SET_PLOT_DB_DELTA || !v || !out || n != sizes[op] ||
-        cap < (op == SET_PLOT_TRANSFORM ? 4U : 1U)) return 0;
+    if (op > SET_PLOT_LIMITS || !v || !out || n != sizes[op] ||
+        cap < (op == SET_PLOT_TRANSFORM || op == SET_PLOT_LIMITS ? 4U : 1U)) return 0;
     if (op == SET_PLOT_TRANSFORM) {
         double w, h, fx, fy;
         if (!finite_values(v, 4) || v[2] < 1.0/128 || v[2] > 1 ||
@@ -69,6 +69,10 @@ size_t set_plot_eval(uint32_t op, const double *v, size_t n, double *out, size_t
         if (v[0] == 0 || v[1] == 0) return 0;
         out[0] = 20 * log10(fabs(v[1] / v[0]));
         break;
+    case SET_PLOT_LIMITS:
+        if (v[0] >= v[1] || v[2] >= v[3]) return 0;
+        out[0] = v[0]; out[1] = v[1]; out[2] = v[2]; out[3] = v[3];
+        return 4;
     default: return 0;
     }
     return isfinite(out[0]) ? 1 : 0;
diff --git a/c/set-protocol/src/set_spectrum.c b/c/set-protocol/src/set_spectrum.c
index a73003e..259f0ec 100644
--- a/c/set-protocol/src/set_spectrum.c
+++ b/c/set-protocol/src/set_spectrum.c
@@ -4,6 +4,13 @@
 
 #define PI 3.14159265358979323846
 
+static int compare_double(const void *left, const void *right)
+{
+    const double a = *(const double *)left;
+    const double b = *(const double *)right;
+    return (a > b) - (a < b);
+}
+
 static double window_value(int window, size_t index, size_t n)
 {
     double phase = 2.0 * PI * (double)index / (double)n;
@@ -124,3 +131,35 @@ int set_spectrum_analyze(const double *times, const double *values, size_t count
     free(scratch);
     return result;
 }
+
+int set_spectrum_dominant_peak(const double *amplitudes, size_t count,
+    double bin_hz, double relative_threshold, double absolute_floor,
+    double *scratch, size_t scratch_capacity, double *peak, size_t peak_capacity)
+{
+    size_t i, usable = 0U, peak_bin = 0U;
+    double peak_amplitude = -1.0, median, threshold;
+    if (amplitudes == NULL || scratch == NULL || peak == NULL || count < 3U ||
+        scratch_capacity < count - 1U || peak_capacity < 2U || !isfinite(bin_hz) ||
+        bin_hz <= 0.0 || !isfinite(relative_threshold) || relative_threshold <= 0.0 ||
+        !isfinite(absolute_floor) || absolute_floor < 0.0) return -1;
+    for (i = 1U; i < count; ++i) {
+        if (isfinite(amplitudes[i]) && amplitudes[i] >= 0.0)
+            scratch[usable++] = amplitudes[i];
+    }
+    if (usable < 2U) return 0;
+    qsort(scratch, usable, sizeof(double), compare_double);
+    median = scratch[usable / 2U];
+    for (i = 1U; i + 1U < count; ++i) {
+        const double value = amplitudes[i];
+        if (isfinite(value) && isfinite(amplitudes[i - 1U]) && isfinite(amplitudes[i + 1U]) &&
+            value >= amplitudes[i - 1U] && value > amplitudes[i + 1U] && value > peak_amplitude) {
+            peak_bin = i;
+            peak_amplitude = value;
+        }
+    }
+    threshold = fmax(absolute_floor, median * relative_threshold);
+    if (peak_bin == 0U || peak_amplitude < threshold) return 0;
+    peak[0] = (double)peak_bin * bin_hz;
+    peak[1] = peak_amplitude;
+    return 1;
+}
diff --git a/c/set-protocol/src/set_trends.c b/c/set-protocol/src/set_trends.c
index c1c2203..4c3da43 100644
--- a/c/set-protocol/src/set_trends.c
+++ b/c/set-protocol/src/set_trends.c
@@ -6,6 +6,12 @@ static uint16_t get16(const uint8_t *p)
     return (uint16_t)((uint16_t)p[0] | ((uint16_t)p[1] << 8));
 }
 
+static uint32_t get32(const uint8_t *p)
+{
+    return (uint32_t)p[0] | ((uint32_t)p[1] << 8) |
+        ((uint32_t)p[2] << 16) | ((uint32_t)p[3] << 24);
+}
+
 static void put16(uint8_t *p, uint16_t value)
 {
     p[0] = (uint8_t)value;
@@ -63,6 +69,12 @@ int set_trend_watch_ack(const uint8_t *payload, size_t size, uint16_t period_ms,
 }
 
 int set_trend_watch_values(const uint8_t *payload, size_t size, uint16_t *words, size_t capacity)
+{
+    return set_trend_watch_decode(payload, size, NULL, words, capacity);
+}
+
+int set_trend_watch_decode(const uint8_t *payload, size_t size, uint32_t *timestamp_ms,
+    uint16_t *words, size_t capacity)
 {
     size_t i, count;
     if (payload == NULL || size < 6U) return -1;
@@ -70,5 +82,6 @@ int set_trend_watch_values(const uint8_t *payload, size_t size, uint16_t *words,
     if (count > SET_TREND_WATCH_MAX || size != 6U + count * 2U || count > capacity ||
         (count > 0U && words == NULL)) return -1;
     for (i = 0U; i < count; ++i) words[i] = get16(payload + 6U + i * 2U);
+    if (timestamp_ms != NULL) *timestamp_ms = get32(payload);
     return (int)count;
 }
diff --git a/c/set-protocol/tests/test_plot.c b/c/set-protocol/tests/test_plot.c
index e606956..6615548 100644
--- a/c/set-protocol/tests/test_plot.c
+++ b/c/set-protocol/tests/test_plot.c
@@ -9,7 +9,7 @@ int main(void) {
     const double y[] = {15, 10, 30, 1};
     const double drag[] = {0, 100, 500, -10, 10, 1};
     double back[4], bad[] = {NAN, 10, 8};
-    assert(set_plot_abi_version() == 1);
+    assert(set_plot_abi_version() == 2);
     assert(set_plot_eval(SET_PLOT_TRANSFORM, zoom, 10, output, 4) == 4);
     assert(output[0] == .125 && output[1] == 0 && output[2] == .5 && output[3] == 1);
     assert(output[4] == 12345);
@@ -26,6 +26,13 @@ int main(void) {
     assert(output[0] == y[0]);
     assert(set_plot_eval(SET_PLOT_DRAG, drag, 6, output, 4) == 1);
     assert(output[0] == -4);
+    {
+        const double limits[] = {0, 500, -2, 2};
+        const double reversed[] = {1, 1, -2, 2};
+        assert(set_plot_eval(SET_PLOT_LIMITS, limits, 4, output, 4) == 4);
+        assert(output[0] == 0 && output[1] == 500 && output[2] == -2 && output[3] == 2);
+        assert(set_plot_eval(SET_PLOT_LIMITS, reversed, 4, output, 4) == 0);
+    }
     puts("shared plot: OK");
     return 0;
 }
diff --git a/c/set-protocol/tests/test_spectrum.c b/c/set-protocol/tests/test_spectrum.c
index 0de2e94..64a36b7 100644
--- a/c/set-protocol/tests/test_spectrum.c
+++ b/c/set-protocol/tests/test_spectrum.c
@@ -17,6 +17,15 @@ int main(void)
     assert(set_spectrum_analyze(times, values, 32, 32, 0, SET_FILTER_LOW_PASS, 0, 16, 1, output, 17, meta) == SET_SPECTRUM_CUTOFF);
     times[12] = times[11];
     assert(set_spectrum_analyze(times, values, 32, 32, 0, 0, 0, 0, 1, output, 17, meta) == SET_SPECTRUM_TIMING);
+    {
+        const double amplitudes[] = {10.0, .01, .02, .8, .03, .4, .02};
+        const double noise[] = {0, .10, .12, .11, .09, .10};
+        double scratch[6], peak[2];
+        assert(set_spectrum_dominant_peak(amplitudes, 7, 5, 3, 1e-6, scratch, 6, peak, 2) == 1);
+        assert(peak[0] == 15 && peak[1] == .8);
+        assert(set_spectrum_dominant_peak(noise, 6, 1, 3, 1e-6, scratch, 6, peak, 2) == 0);
+        assert(set_spectrum_dominant_peak(amplitudes, 7, 0, 3, 1e-6, scratch, 6, peak, 2) == -1);
+    }
     puts("shared spectrum: OK");
     return 0;
 }
diff --git a/c/set-protocol/tests/test_trends.c b/c/set-protocol/tests/test_trends.c
index 97f10ee..f357bd2 100644
--- a/c/set-protocol/tests/test_trends.c
+++ b/c/set-protocol/tests/test_trends.c
@@ -34,8 +34,11 @@ int main(void)
     assert(!set_trend_watch_ack(expected, 4, 1000, 3));
     const uint8_t packet[] = {1, 2, 3, 4, 2, 0, 52, 18, 255, 255};
     uint16_t words[64];
+    uint32_t timestamp = 0;
     assert(set_trend_watch_values(packet, sizeof(packet), words, 64) == 2);
     assert(words[0] == 0x1234 && words[1] == 0xFFFF);
+    assert(set_trend_watch_decode(packet, sizeof(packet), &timestamp, words, 64) == 2);
+    assert(timestamp == 0x04030201UL);
     assert(set_trend_watch_values(packet, sizeof(packet) - 1, words, 64) == -1);
     assert(set_trend_watch_values(packet, sizeof(packet), words, 1) == -1);
     puts("Shared trend tests passed");
diff --git a/python/protocan/plot.py b/python/protocan/plot.py
index 67248f5..967638d 100644
--- a/python/protocan/plot.py
+++ b/python/protocan/plot.py
@@ -37,7 +37,7 @@ class PlotMath:
         self.library = library
         library.set_plot_abi_version.restype = ctypes.c_uint32
         library.set_plot_abi_version.argtypes = []
-        if library.set_plot_abi_version() != 1:
+        if library.set_plot_abi_version() != 2:
             raise RuntimeError("Unsupported plot ABI")
         library.set_plot_eval.argtypes = [ctypes.c_uint32, ctypes.POINTER(ctypes.c_double),
             ctypes.c_size_t, ctypes.POINTER(ctypes.c_double), ctypes.c_size_t]
@@ -67,6 +67,10 @@ class PlotMath:
         except ValueError:
             return None
 
+    def limits(self, left: float, right: float, bottom: float, top: float) -> "Bounds":
+        """Validate absolute axis limits in the shared core."""
+        return Bounds(*self.call(8, left, right, bottom, top))
+
 
 @dataclass(frozen=True)
 class Viewport:
@@ -92,6 +96,9 @@ class Bounds:
     bottom: float
     top: float
 
+    def validated(self, core: PlotMath) -> "Bounds":
+        return core.limits(self.left, self.right, self.bottom, self.top)
+
     def fraction(self, core: PlotMath, value: float, horizontal: bool) -> float:
         return core.call(2, value, self.bottom if horizontal else self.left,
             self.top if horizontal else self.right, int(horizontal))[0]
diff --git a/python/protocan/spectrum.py b/python/protocan/spectrum.py
index 1ce87ec..07b1eb5 100644
--- a/python/protocan/spectrum.py
+++ b/python/protocan/spectrum.py
@@ -37,6 +37,12 @@ class Spectrum:
         return tuple(i * self.sample_rate / self.size for i in range(len(self.amplitudes)))
 
 
+@dataclass(frozen=True)
+class SpectrumPeak:
+    frequency_hz: float
+    amplitude: float
+
+
 class NativeSpectrum:
     def __init__(self, library: ctypes.CDLL):
         self.lib = library
@@ -46,6 +52,11 @@ class NativeSpectrum:
             ctypes.c_int, ctypes.c_int, ctypes.c_double, ctypes.c_double, ctypes.c_int,
             pointer, ctypes.c_size_t, pointer]
         self._analyze.restype = ctypes.c_int
+        self._peak = library.set_spectrum_dominant_peak
+        self._peak.argtypes = [pointer, ctypes.c_size_t, ctypes.c_double,
+            ctypes.c_double, ctypes.c_double, pointer, ctypes.c_size_t,
+            pointer, ctypes.c_size_t]
+        self._peak.restype = ctypes.c_int
 
     def analyze(self, times, values, *, max_size=4096, window=Window.HANN, filter=Filter.NONE,
                 low_hz=10.0, high_hz=100.0, remove_mean=True) -> Spectrum:
@@ -69,3 +80,15 @@ class NativeSpectrum:
             raise ValueError(message.get(status, "FFT failed"))
         n = int(meta[0])
         return Spectrum(n, meta[1], meta[2], tuple(output[:n // 2 + 1]))
+
+    def dominant_peak(self, spectrum: Spectrum, *, relative_threshold: float = 3.0,
+                      absolute_floor: float = 1e-6) -> SpectrumPeak | None:
+        amplitudes = (ctypes.c_double * len(spectrum.amplitudes))(*spectrum.amplitudes)
+        scratch = (ctypes.c_double * max(1, len(spectrum.amplitudes) - 1))()
+        output = (ctypes.c_double * 2)()
+        status = self._peak(amplitudes, len(spectrum.amplitudes),
+            spectrum.sample_rate / spectrum.size, relative_threshold, absolute_floor,
+            scratch, len(scratch), output, 2)
+        if status < 0:
+            raise ValueError("Invalid spectrum peak input")
+        return SpectrumPeak(output[0], output[1]) if status else None
diff --git a/python/protocan/trends.py b/python/protocan/trends.py
index e047e1b..94c67fa 100644
--- a/python/protocan/trends.py
+++ b/python/protocan/trends.py
@@ -99,12 +99,6 @@ class TrendSignal:
         if self.source == "CAN_RAW" and not 0 <= self.byteOffset <= 6:
             raise ValueError("Word offset must be 0..6")
 
-    def word_value(self, word: int) -> float:
-        if not 0 <= word <= 65535:
-            raise ValueError("Not a 16-bit word")
-        return float(word - 65536 if self.valueType == "INT16" and word >= 32768 else word)
-
-
 def validate_settings(settings: Mapping[str, list[TrendSignal]]) -> None:
     ids = set()
     for profile, signals in settings.items():
@@ -178,6 +172,20 @@ class NativeTrends:
             ctypes.c_uint8, ctypes.c_uint8, ctypes.c_uint8, ctypes.c_uint8,
             ctypes.c_uint32, ctypes.c_uint8, ctypes.c_void_p, ctypes.c_size_t]
         self.decode.restype = ctypes.c_int32
+        self._word = library.set_trend_word_value
+        self._word.argtypes = [ctypes.c_uint16, ctypes.c_uint8]
+        self._word.restype = ctypes.c_int32
+        self._watch_request = library.set_trend_watch_request
+        self._watch_request.argtypes = [ctypes.c_uint16, ctypes.POINTER(ctypes.c_uint16),
+            ctypes.c_size_t, ctypes.c_void_p, ctypes.c_size_t]
+        self._watch_request.restype = ctypes.c_size_t
+        self._watch_ack = library.set_trend_watch_ack
+        self._watch_ack.argtypes = [ctypes.c_void_p, ctypes.c_size_t, ctypes.c_uint16, ctypes.c_size_t]
+        self._watch_ack.restype = ctypes.c_int
+        self._watch_decode = library.set_trend_watch_decode
+        self._watch_decode.argtypes = [ctypes.c_void_p, ctypes.c_size_t,
+            ctypes.POINTER(ctypes.c_uint32), ctypes.POINTER(ctypes.c_uint16), ctypes.c_size_t]
+        self._watch_decode.restype = ctypes.c_int
 
     def can_value(self, signal: TrendSignal, can_id: int, flags: int, data: bytes) -> float | None:
         if signal.source not in ("CAN_GAS", "CAN_RAW"):
@@ -191,3 +199,33 @@ class NativeTrends:
             signal.byteOffset, signal.extended, signal.valueType == "INT16", can_id, flags,
             payload, len(data))
         return None if value == -2147483648 else float(value)
+
+    def word_value(self, signal: TrendSignal, word: int) -> float:
+        if not 0 <= word <= 65535:
+            raise ValueError("Not a 16-bit word")
+        return float(self._word(word, signal.valueType == "INT16"))
+
+    def watch_request(self, period_ms: int, addresses: list[int]) -> bytes:
+        if not 0 <= period_ms <= 65535 or len(addresses) > MAX_SIGNALS or any(
+                type(address) is not int or not 0 <= address <= 65535 for address in addresses):
+            raise ValueError("Invalid GAS watch request")
+        source = (ctypes.c_uint16 * len(addresses))(*addresses)
+        output = (ctypes.c_uint8 * (4 + len(addresses) * 2))()
+        size = self._watch_request(period_ms, source, len(addresses), output, len(output))
+        if not size:
+            raise ValueError("Invalid GAS watch request")
+        return bytes(output[:size])
+
+    def validate_watch_ack(self, payload: bytes, period_ms: int, count: int) -> None:
+        data = (ctypes.c_uint8 * len(payload)).from_buffer_copy(payload)
+        if not self._watch_ack(data, len(payload), period_ms, count):
+            raise ValueError("Device did not accept the complete GAS subscription")
+
+    def watch_values(self, payload: bytes, expected_count: int | None = None) -> tuple[int, list[int]]:
+        data = (ctypes.c_uint8 * len(payload)).from_buffer_copy(payload)
+        timestamp = ctypes.c_uint32()
+        words = (ctypes.c_uint16 * MAX_SIGNALS)()
+        count = self._watch_decode(data, len(payload), ctypes.byref(timestamp), words, MAX_SIGNALS)
+        if count < 0 or expected_count is not None and count != expected_count:
+            raise ValueError("Invalid GAS watch data")
+        return timestamp.value, list(words[:count])
diff --git a/python/tests/test_spectrum.py b/python/tests/test_spectrum.py
index febddd0..60be5ac 100644
--- a/python/tests/test_spectrum.py
+++ b/python/tests/test_spectrum.py
@@ -35,6 +35,9 @@ class SpectrumTests(unittest.TestCase):
                 peak = max(range(len(result.amplitudes)), key=result.amplitudes.__getitem__)
                 self.assertEqual(64, result.frequencies[peak])
                 self.assertAlmostEqual(3.25, result.amplitudes[peak], places=9)
+                detected = self.core.dominant_peak(result)
+                self.assertAlmostEqual(64, detected.frequency_hz, places=9)
+                self.assertAlmostEqual(3.25, detected.amplitude, places=9)
 
     def test_dc_and_nyquist_are_not_doubled(self):
         times, _ = self.sample()
diff --git a/python/tests/test_trends.py b/python/tests/test_trends.py
index b18474b..9a82963 100644
--- a/python/tests/test_trends.py
+++ b/python/tests/test_trends.py
@@ -57,7 +57,6 @@ class TrendTests(unittest.TestCase):
         for value in ("-1", "+1", "FF", "0x", "1.0", "256"):
             with self.assertRaises(ValueError):
                 parse_address(value, 255)
-        self.assertEqual(-2.0, TrendSignal("s", valueType="INT16").word_value(65534))
 
     def test_bounded_history(self):
         history = TrendHistory()
@@ -81,6 +80,13 @@ class TrendTests(unittest.TestCase):
         self.assertIsNone(core.can_value(signal, frame_id ^ 0x08000000, 1, data))
         raw = replace(signal, source="CAN_RAW", address="0x321", extended=False, byteOffset=2)
         self.assertEqual(-2.0, core.can_value(raw, 0x321, 0, data))
+        self.assertEqual(-2.0, core.word_value(TrendSignal("s", valueType="INT16"), 65534))
+        self.assertEqual(bytes([232, 3, 2, 0, 52, 18, 255, 255]),
+                         core.watch_request(1000, [0x1234, 0xFFFF]))
+        core.validate_watch_ack(bytes([232, 3, 2, 0]), 1000, 2)
+        timestamp, words = core.watch_values(bytes([1, 2, 3, 4, 2, 0, 52, 18, 255, 255]), 2)
+        self.assertEqual(0x04030201, timestamp)
+        self.assertEqual([0x1234, 0xFFFF], words)
 
 
 if __name__ == "__main__":