diff --git a/pkg/agent/subturn_test.go b/pkg/agent/subturn_test.go
index a2d7120dd..e690fa544 100644
--- a/pkg/agent/subturn_test.go
+++ b/pkg/agent/subturn_test.go
@@ -1813,3 +1813,196 @@ func TestSpawnDuringAbort_RaceCondition(t *testing.T) {
 	// The important thing is that it doesn't panic or deadlock
 	t.Log("Race condition handled gracefully - no panic or deadlock")
 }
+
+// ====================== Slow SubTurn Cancellation Test ======================
+
+// slowMockProvider simulates a slow LLM call that takes a long time to complete.
+// This is used to test the scenario where a parent turn finishes before the child SubTurn.
+type slowMockProvider struct {
+	delay time.Duration
+}
+
+func (m *slowMockProvider) Chat(
+	ctx context.Context,
+	messages []providers.Message,
+	toolDefs []providers.ToolDefinition,
+	model string,
+	options map[string]any,
+) (*providers.LLMResponse, error) {
+	select {
+	case <-time.After(m.delay):
+		// Completed normally after delay
+		return &providers.LLMResponse{
+			Content: "slow response completed",
+		}, nil
+	case <-ctx.Done():
+		// Context was cancelled while waiting
+		return nil, ctx.Err()
+	}
+}
+
+func (m *slowMockProvider) GetDefaultModel() string {
+	return "slow-model"
+}
+
+// TestAsyncSubTurn_ParentFinishesEarly simulates the scenario where:
+// 1. Parent spawns an async SubTurn that takes a long time
+// 2. Parent finishes quickly
+// 3. SubTurn should be cancelled with context canceled error
+func TestAsyncSubTurn_ParentFinishesEarly(t *testing.T) {
+	// Save original MockEventBus.Emit to capture events
+	originalEmit := MockEventBus.Emit
+	defer func() {
+		MockEventBus.Emit = originalEmit
+	}()
+
+	var mu sync.Mutex
+	var events []any
+	MockEventBus.Emit = func(e any) {
+		mu.Lock()
+		defer mu.Unlock()
+		events = append(events, e)
+	}
+
+	cfg := &config.Config{
+		Agents: config.AgentsConfig{
+			Defaults: config.AgentDefaults{
+				Provider: "mock",
+			},
+		},
+	}
+	msgBus := bus.NewMessageBus()
+	provider := &slowMockProvider{delay: 5 * time.Second} // SubTurn takes 5 seconds
+	al := NewAgentLoop(cfg, msgBus, provider)
+
+	ctx := context.Background()
+	parentTS := &turnState{
+		ctx:            ctx,
+		turnID:         "parent-fast",
+		depth:          0,
+		session:        newEphemeralSession(nil),
+		pendingResults: make(chan *tools.ToolResult, 16),
+		concurrencySem: make(chan struct{}, maxConcurrentSubTurns),
+	}
+	parentTS.ctx, parentTS.cancelFunc = context.WithCancel(ctx)
+
+	var subTurnErr error
+	var subTurnResult *tools.ToolResult
+	var wg sync.WaitGroup
+
+	// Spawn async SubTurn in a goroutine (it will be slow)
+	wg.Add(1)
+	go func() {
+		defer wg.Done()
+		subTurnCfg := SubTurnConfig{
+			Model: "slow-model",
+			Async: true, // Asynchronous SubTurn
+		}
+		subTurnResult, subTurnErr = spawnSubTurn(parentTS.ctx, al, parentTS, subTurnCfg)
+	}()
+
+	// Parent finishes quickly (after 100ms), while SubTurn is still running
+	time.Sleep(100 * time.Millisecond)
+	t.Log("Parent finishing early...")
+	parentTS.Finish()
+
+	// Wait for SubTurn to complete (or be cancelled)
+	wg.Wait()
+
+	// Check the result
+	t.Logf("SubTurn error: %v", subTurnErr)
+	t.Logf("SubTurn result: %v", subTurnResult)
+
+	if subTurnErr != nil {
+		if errors.Is(subTurnErr, context.Canceled) {
+			t.Log("✓ SubTurn was cancelled as expected (context canceled)")
+		} else {
+			t.Logf("SubTurn failed with other error: %v", subTurnErr)
+		}
+	} else {
+		t.Log("SubTurn completed before parent finished (unlikely but possible)")
+	}
+
+	// Log captured events
+	mu.Lock()
+	t.Logf("Captured %d events:", len(events))
+	for i, e := range events {
+		t.Logf("  Event %d: %T", i+1, e)
+	}
+	mu.Unlock()
+}
+
+// TestAsyncSubTurn_ParentWaitsForChild simulates the scenario where:
+// 1. Parent spawns an async SubTurn that takes some time
+// 2. Parent WAITS for SubTurn to complete before finishing
+// 3. Both should complete successfully
+func TestAsyncSubTurn_ParentWaitsForChild(t *testing.T) {
+	cfg := &config.Config{
+		Agents: config.AgentsConfig{
+			Defaults: config.AgentDefaults{
+				Provider: "mock",
+			},
+		},
+	}
+	msgBus := bus.NewMessageBus()
+	provider := &slowMockProvider{delay: 200 * time.Millisecond} // SubTurn takes 200ms
+	al := NewAgentLoop(cfg, msgBus, provider)
+
+	ctx := context.Background()
+	parentTS := &turnState{
+		ctx:            ctx,
+		turnID:         "parent-wait",
+		depth:          0,
+		session:        newEphemeralSession(nil),
+		pendingResults: make(chan *tools.ToolResult, 16),
+		concurrencySem: make(chan struct{}, maxConcurrentSubTurns),
+	}
+	parentTS.ctx, parentTS.cancelFunc = context.WithCancel(ctx)
+
+	var subTurnErr error
+	var subTurnResult *tools.ToolResult
+	var wg sync.WaitGroup
+
+	// Spawn async SubTurn in a goroutine
+	wg.Add(1)
+	go func() {
+		defer wg.Done()
+		subTurnCfg := SubTurnConfig{
+			Model: "slow-model",
+			Async: true,
+		}
+		subTurnResult, subTurnErr = spawnSubTurn(parentTS.ctx, al, parentTS, subTurnCfg)
+	}()
+
+	// Parent WAITS for SubTurn to complete
+	t.Log("Parent waiting for SubTurn...")
+	wg.Wait()
+	t.Log("SubTurn completed, parent now finishing")
+
+	// Now parent can finish safely
+	parentTS.Finish()
+
+	// Check the result
+	if subTurnErr != nil {
+		if errors.Is(subTurnErr, context.Canceled) {
+			t.Errorf("SubTurn should NOT have been cancelled: %v", subTurnErr)
+		} else {
+			t.Logf("SubTurn failed with error: %v", subTurnErr)
+		}
+	} else {
+		t.Log("✓ SubTurn completed successfully")
+		if subTurnResult != nil {
+			t.Logf("SubTurn result: %s", subTurnResult.ForLLM)
+		}
+	}
+
+	// Check channel delivery
+	select {
+	case r := <-parentTS.pendingResults:
+		if r != nil {
+			t.Logf("✓ Result delivered to channel: %s", r.ForLLM)
+		}
+	case <-time.After(100 * time.Millisecond):
+		t.Log("No result in channel (expected since we waited)")
+	}
+}