diff --git a/OpticalChannelTester/App.cpp b/OpticalChannelTester/App.cpp
index 29f5c12..393ab23 100644
--- a/OpticalChannelTester/App.cpp
+++ b/OpticalChannelTester/App.cpp
@@ -123,13 +123,16 @@ void formatMenuLine(const char *label, const char *value, char *out, size_t size
   snprintf(out, size, "%s%*s%s", label, padding, "", value);
 }
 
-uint32_t overallProgress(uint32_t stageIndex, uint8_t step) {
-  if (step > MEASUREMENT_PROGRESS_STEPS) step = MEASUREMENT_PROGRESS_STEPS;
-  return stageIndex * MEASUREMENT_PROGRESS_STEPS + step;
+uint32_t overallProgress(uint32_t stageIndex, uint8_t step,
+                         uint8_t stepsPerStage = MEASUREMENT_PROGRESS_STEPS) {
+  if (step > stepsPerStage) step = stepsPerStage;
+  return stageIndex * stepsPerStage + step;
 }
 
-uint32_t overallProgressTotal(uint32_t stageCount) {
-  return stageCount * MEASUREMENT_PROGRESS_STEPS;
+uint32_t overallProgressTotal(
+    uint32_t stageCount,
+    uint8_t stepsPerStage = MEASUREMENT_PROGRESS_STEPS) {
+  return stageCount * stepsPerStage;
 }
 
 uint32_t stageWallTimeMs(uint32_t testTimeMs, uint32_t frequencyHz) {
@@ -1536,10 +1539,13 @@ void App::showDriverResult(const DriverStats &s, bool testPassed) {
     snprintf(two, sizeof(two), UiText::DRIVER_MEASUREMENT_FORMAT,
       delay, response);
   }
+  const bool finished = testPassed || s.reason != FailReason::NONE;
+  const uint8_t progressSteps = driverTest_.progressSteps();
   display_.show(one, two,
-    overallProgress(stageIndex_, driverTest_.progressStep()),
-    overallProgressTotal(stageCount_), s.reason == FailReason::NONE ? nullptr :
-      roleCorner(Role::SOLO));
+    finished ? 0U : overallProgress(
+      stageIndex_, driverTest_.progressStep(), progressSteps),
+    finished ? 0U : overallProgressTotal(stageCount_, progressSteps),
+    s.reason == FailReason::NONE ? nullptr : roleCorner(Role::SOLO));
 }
 
 void App::showRemoteResult(const ProtocolPacket &packet) {
diff --git a/OpticalChannelTester/Config.h b/OpticalChannelTester/Config.h
index a4d0037..c2efc6b 100644
--- a/OpticalChannelTester/Config.h
+++ b/OpticalChannelTester/Config.h
@@ -109,6 +109,8 @@ static_assert(MEASUREMENT_AVERAGING_PERIODS > 0,
   "Averaging window must contain at least one period");
 constexpr uint8_t MEASUREMENT_PROGRESS_STEPS = 10;
 constexpr uint32_t OLED_PROGRESS_UPDATE_MS = 15;
+constexpr uint8_t DRIVER_SHORT_SAMPLE_PROGRESS_STEPS = 10;
+constexpr uint32_t DRIVER_PROGRESS_INTERVAL_MS = 100;
 
 constexpr uint32_t IDLE_POWER_SAVE_TIMEOUT_MS = 60000;
 // usb_serial_jtag_is_connected() needs no open COM port or CDC traffic, but a
@@ -162,10 +164,10 @@ constexpr uint32_t DRIVER_RESPONSE_TIMEOUT_NS = 10000;
 // the selected maximum down to the selected minimum. Widths are stored in
 // nanoseconds so sub-microsecond pulses remain representable without floats.
 constexpr uint32_t PWM_FREQUENCY_OPTIONS_HZ[] = {
-  500, 1000, 2000, 5000, 10000, 25000,
+  500, 1000, 2000, 5000, 10000,
 };
 constexpr uint32_t MAX_PULSE_OPTIONS_NS[] = {
-  2000, 5000, 10000, 20000, 50000, 100000, 200000, 500000
+  2000, 5000, 10000, 50000, 100000, 500000
 };
 constexpr uint32_t MIN_PULSE_OPTIONS_NS[] = {
   250, 500, 1000, 2000, 5000, 10000, 50000
@@ -175,6 +177,6 @@ constexpr uint32_t TEST_PULSE_WIDTHS_NS[] = {
   100000, 200000, 500000, 1000000
 };
 constexpr float ACCURACY_OPTIONS_PCT[] = {1.0f, 2.0f, 5.0f, 10.0f};
-constexpr uint32_t TEST_TIME_OPTIONS_MS[] = {100, 250, 500, 1000, 2000, 5000};
+constexpr uint32_t TEST_TIME_OPTIONS_MS[] = {100, 250, 500, 1000, 2000, 5000, 60000};
 
 template <typename T, size_t N> constexpr size_t countOf(const T (&)[N]) { return N; }
diff --git a/OpticalChannelTester/DriverTest.cpp b/OpticalChannelTester/DriverTest.cpp
index c02a109..0d46b83 100644
--- a/OpticalChannelTester/DriverTest.cpp
+++ b/OpticalChannelTester/DriverTest.cpp
@@ -5,11 +5,22 @@
 
 #include <driver/gpio.h>
 #include <esp_cpu.h>
+#include <esp_task_wdt.h>
 #include <esp_timer.h>
 #include <esp32-hal-cpu.h>
 #include <soc/gpio_struct.h>
 #include <string.h>
 
+static inline uint32_t IRAM_ATTR maskAllInterrupts() {
+  uint32_t state;
+  asm volatile("rsil %0, 15" : "=a"(state) :: "memory");
+  return state;
+}
+
+static inline void IRAM_ATTR restoreInterrupts(uint32_t state) {
+  asm volatile("wsr %0, ps\nrsync" :: "a"(state) : "memory");
+}
+
 void DriverEdgeStats::reset() {
   memset(this, 0, sizeof(*this));
   minDelayTicks = minResponseTicks = UINT32_MAX;
@@ -78,7 +89,13 @@ bool DriverTest::start(uint32_t frequencyHz, uint32_t pulseNs,
   faultLongTicks_ = nsToTicks(DRIVER_FAULT_MIN_NS);
   stuckTicks_ = nsToTicks(DRIVER_RX_STUCK_MIN_NS);
   testTicks_ = static_cast<uint64_t>(captureHz_) * testTimeMs / 1000ULL;
-  subsampleTicks_ = testTicks_ / SUBSAMPLE_COUNT;
+  const uint32_t requestedSubsamples = testTimeMs < 1000U ?
+    DRIVER_SHORT_SAMPLE_PROGRESS_STEPS :
+    (testTimeMs + DRIVER_PROGRESS_INTERVAL_MS - 1U) /
+      DRIVER_PROGRESS_INTERVAL_MS;
+  subsampleCount_ = static_cast<uint8_t>(
+    requestedSubsamples > UINT8_MAX ? UINT8_MAX : requestedSubsamples);
+  subsampleTicks_ = testTicks_ / subsampleCount_;
   if (!pollPeriodCycles_ || !pollWindowAfterCycles_ ||
       !ackStartMaxTicks_ || !faultLongTicks_ || !stuckTicks_ ||
       !testTicks_ || !subsampleTicks_)
@@ -117,14 +134,14 @@ bool DriverTest::start(uint32_t frequencyHz, uint32_t pulseNs,
 }
 
 bool DriverTest::armCapture() {
-  Serial.flush();
+  // Never wait for USB/Serial here: a disconnected or slow host must not
+  // delay a subsample or consume the test's global timeout.
   if (!__atomic_load_n(&core0WdtDisabled_, __ATOMIC_ACQUIRE)) {
-    const bool disabled = disableCore0WDT();
+    TaskHandle_t idle0 = xTaskGetIdleTaskHandleForCore(0);
+    const bool watched = idle0 && esp_task_wdt_status(idle0) == ESP_OK;
+    const bool disabled = watched && disableCore0WDT();
     __atomic_store_n(&core0WdtDisabled_, disabled, __ATOMIC_RELEASE);
-    if (!disabled) {
-      state_ = DriverState::IDLE;
-      return false;
-    }
+    // If IDLE0 is not watched there is nothing to remove or restore.
   }
   __atomic_store_n(&captureReady_, false, __ATOMIC_RELEASE);
   __atomic_store_n(&captureActive_, true, __ATOMIC_RELEASE);
@@ -184,6 +201,8 @@ void IRAM_ATTR DriverTest::pollTaskLoop() {
     uint8_t hotCount = 0;
     bool sawTxStart = false;
     bool critical = false;
+    bool allInterruptsMasked = false;
+    uint32_t interruptState = 0;
 
     auto sampleOnce = [&]() {
       const uint32_t current = GPIO.in & PIN_MASK;
@@ -218,12 +237,18 @@ void IRAM_ATTR DriverTest::pollTaskLoop() {
       for (uint8_t i = 0; i < 16U; ++i) sampleOnce();
     if (sawTxStart) windowEnd = lastTxStart + pollWindowAfterCycles_;
     const bool synchronized = sawTxStart;
+    if (synchronized) {
+      interruptState = maskAllInterrupts();
+      allInterruptsMasked = true;
+    }
 
     while (__atomic_load_n(&captureActive_, __ATOMIC_ACQUIRE) && synchronized) {
       while (__atomic_load_n(&captureActive_, __ATOMIC_ACQUIRE) &&
              static_cast<int32_t>(esp_cpu_get_cycle_count() - windowEnd) < 0)
         for (uint8_t i = 0; i < 16U; ++i) sampleOnce();
 
+      restoreInterrupts(interruptState);
+      allInterruptsMasked = false;
       portEXIT_CRITICAL(&pollMux_);
       critical = false;
       flushHot();
@@ -249,8 +274,11 @@ void IRAM_ATTR DriverTest::pollTaskLoop() {
 
       portENTER_CRITICAL(&pollMux_);
       critical = true;
+      interruptState = maskAllInterrupts();
+      allInterruptsMasked = true;
       windowEnd = nextStart + pollWindowAfterCycles_;
     }
+    if (allInterruptsMasked) restoreInterrupts(interruptState);
     if (critical) portEXIT_CRITICAL(&pollMux_);
     flushHot();
     if (__atomic_exchange_n(&core0WdtDisabled_, false,
@@ -325,7 +353,7 @@ void DriverTest::processSettling(const TimedEvent &event) {
   const uint64_t measuredBefore =
     static_cast<uint64_t>(completedSubsamples_) * subsampleTicks_;
   const uint64_t thisSubsampleTicks =
-    completedSubsamples_ + 1U == SUBSAMPLE_COUNT ?
+    completedSubsamples_ + 1U == subsampleCount_ ?
       testTicks_ - measuredBefore : subsampleTicks_;
   deadlineTick_ = event.tick + thisSubsampleTicks;
   processTx(event, lightOn);
@@ -509,7 +537,7 @@ void DriverTest::completeIfPossible(uint64_t now) {
     fail(FailReason::DATA_LOSS, lastEventTick_);
     return;
   }
-  if (completedSubsamples_ >= SUBSAMPLE_COUNT) {
+  if (completedSubsamples_ >= subsampleCount_) {
     __atomic_store_n(&progressUpdatePending_, false, __ATOMIC_RELEASE);
     state_ = DriverState::PASS;
   } else {
diff --git a/OpticalChannelTester/DriverTest.h b/OpticalChannelTester/DriverTest.h
index fca035e..c2533a2 100644
--- a/OpticalChannelTester/DriverTest.h
+++ b/OpticalChannelTester/DriverTest.h
@@ -57,6 +57,7 @@ class DriverTest {
   void printSummary() const;
   void printTrace() const;
   uint8_t progressStep() const { return currentStep_; }
+  uint8_t progressSteps() const { return subsampleCount_; }
   uint32_t tickHz() const { return captureHz_; }
   const DriverStats &stats() const { return publishedStats_; }
 
@@ -113,7 +114,6 @@ class DriverTest {
   uint64_t ticksToNs(uint64_t ticks) const;
 
   static constexpr uint8_t MAX_PENDING = 8;
-  static constexpr uint8_t SUBSAMPLE_COUNT = 10;
   static constexpr uint16_t RING_CAPACITY = 2048;
   static constexpr uint8_t TRACE_CAPACITY = 32;
   static_assert((RING_CAPACITY & (RING_CAPACITY - 1U)) == 0,
@@ -161,6 +161,7 @@ class DriverTest {
   uint64_t lastActiveTxTick_ = 0;
   uint8_t settleCycles_ = 0;
   uint8_t settledCycles_ = 0;
+  uint8_t subsampleCount_ = DRIVER_SHORT_SAMPLE_PROGRESS_STEPS;
   uint8_t completedSubsamples_ = 0;
   bool rxActiveRawHigh_ = true;
   bool txPulseLightOn_ = true;