diff --git a/app/Livewire/ProgramEditor.php b/app/Livewire/ProgramEditor.php
index 76559d8..0690d91 100644
--- a/app/Livewire/ProgramEditor.php
+++ b/app/Livewire/ProgramEditor.php
@@ -217,7 +217,11 @@ public function formattedDuration(): string
 
     public function totalDuration(): int
     {
-        return array_reduce(
+        if (empty($this->phases)) {
+            return 0;
+        }
+
+        $total = array_reduce(
             $this->phases,
             static function (int $carry, array $p): int {
                 $repTime = $p['duration'] * $p['repetitions'];
@@ -226,6 +230,9 @@ static function (int $carry, array $p): int {
             },
             0,
         );
+
+        // The last phase's cooldown is never executed (timer goes straight to COMPLETED).
+        return $total - (int) ($this->phases[array_key_last($this->phases)]['cooldown'] ?? 0);
     }
 
     /**
diff --git a/app/Livewire/TimerScreen.php b/app/Livewire/TimerScreen.php
index abb7958..3ee5e5f 100644
--- a/app/Livewire/TimerScreen.php
+++ b/app/Livewire/TimerScreen.php
@@ -126,6 +126,10 @@ public function start(): void
         $runner  = app(TimerRunner::class);
         $program = Program::with('phases')->findOrFail($this->programId);
 
+        if ($program->phases->isEmpty()) {
+            return;
+        }
+
         $this->programTotalDuration = $program->totalDuration();
         $runner->load($program);
         $runner->start();
diff --git a/resources/views/livewire/timer-screen.blade.php b/resources/views/livewire/timer-screen.blade.php
index b405b1f..87cb252 100644
--- a/resources/views/livewire/timer-screen.blade.php
+++ b/resources/views/livewire/timer-screen.blade.php
@@ -259,13 +259,20 @@ class="text-gray-800 text-xs mt-2 select-none"
 
             {{-- Primary action --}}
             @if($state === StateMachine::idle)
-                <button
-                    wire:click="start"
-                    class="w-full bg-blue-600 hover:bg-blue-500 active:bg-blue-700 text-white font-bold
-                   text-xl py-5 rounded-3xl transition-colors shadow-lg shadow-blue-900/40"
-                >
-                    Start
-                </button>
+                @if(count($phases) === 0)
+                    <div class="w-full text-center text-amber-400 text-sm font-medium py-4 px-4
+                                bg-amber-950/40 border border-amber-800/40 rounded-3xl">
+                        No phases — edit this program to add at least one phase before starting.
+                    </div>
+                @else
+                    <button
+                        wire:click="start"
+                        class="w-full bg-blue-600 hover:bg-blue-500 active:bg-blue-700 text-white font-bold
+                       text-xl py-5 rounded-3xl transition-colors shadow-lg shadow-blue-900/40"
+                    >
+                        Start
+                    </button>
+                @endif
 
             @elseif($state === StateMachine::prepare)
                 {{-- No primary action during prepare — user just waits --}}