diff --git a/apps/api-server/internal/middleware/redis_ratelimit_test.go b/apps/api-server/internal/middleware/redis_ratelimit_test.go
index 5c9744e..a4f39fb 100644
--- a/apps/api-server/internal/middleware/redis_ratelimit_test.go
+++ b/apps/api-server/internal/middleware/redis_ratelimit_test.go
@@ -64,8 +64,8 @@ func TestRedisRateLimiter_Allow(t *testing.T) {
 
 			cmd := redis.NewCmd(context.Background())
 			cmd.SetVal(mockResult)
-			// Match the actual call signature: script, key, now, window, limit
-			mockClient.On("Eval", mock.AnythingOfType("string"), mock.AnythingOfType("string"), mock.AnythingOfType("int64"), mock.AnythingOfType("int64"), mock.AnythingOfType("int64")).Return(cmd)
+			// Match the actual call signature: script, key, now (int64), window (float64), limit (int64)
+			mockClient.On("Eval", mock.AnythingOfType("string"), mock.AnythingOfType("string"), mock.AnythingOfType("int64"), mock.AnythingOfType("float64"), mock.AnythingOfType("int64")).Return(cmd)
 
 			// Create rate limiter with mock client
 			limiter := NewRedisRateLimiter(mockClient, "test", tt.limit, tt.window)
@@ -116,7 +116,7 @@ func TestRedisRateLimitMiddleware(t *testing.T) {
 			// Mock successful rate limit check
 			cmd := redis.NewCmd(context.Background())
 			cmd.SetVal([]any{int64(1), int64(4), int64(time.Now().Unix() + 60)})
-			mockClient.On("Eval", mock.AnythingOfType("string"), mock.AnythingOfType("string"), mock.AnythingOfType("int64"), mock.AnythingOfType("int64"), mock.AnythingOfType("int64")).Return(cmd)
+			mockClient.On("Eval", mock.AnythingOfType("string"), mock.AnythingOfType("string"), mock.AnythingOfType("int64"), mock.AnythingOfType("float64"), mock.AnythingOfType("int64")).Return(cmd)
 
 			// Create rate limiter with mock client
 			limiter := NewRedisRateLimiter(mockClient, "test", 5, time.Minute)
@@ -272,8 +272,8 @@ func TestMultiTierRateLimiter(t *testing.T) {
 	premiumCmd := redis.NewCmd(context.Background())
 	premiumCmd.SetVal([]any{int64(1), int64(99), int64(time.Now().Unix() + 60)})
 
-	mockClient.On("Eval", mock.AnythingOfType("string"), mock.AnythingOfType("string"), mock.AnythingOfType("int64"), mock.AnythingOfType("int64"), mock.AnythingOfType("int64")).Return(freeCmd).Once()
-	mockClient.On("Eval", mock.AnythingOfType("string"), mock.AnythingOfType("string"), mock.AnythingOfType("int64"), mock.AnythingOfType("int64"), mock.AnythingOfType("int64")).Return(premiumCmd).Once()
+	mockClient.On("Eval", mock.AnythingOfType("string"), mock.AnythingOfType("string"), mock.AnythingOfType("int64"), mock.AnythingOfType("float64"), mock.AnythingOfType("int64")).Return(freeCmd).Once()
+	mockClient.On("Eval", mock.AnythingOfType("string"), mock.AnythingOfType("string"), mock.AnythingOfType("int64"), mock.AnythingOfType("float64"), mock.AnythingOfType("int64")).Return(premiumCmd).Once()
 
 	// Create multi-tier rate limiter with mock client
 	tiers := map[string]struct {
diff --git a/apps/api-server/internal/services/chaos.go b/apps/api-server/internal/services/chaos.go
index 977248b..71cb431 100644
--- a/apps/api-server/internal/services/chaos.go
+++ b/apps/api-server/internal/services/chaos.go
@@ -30,6 +30,26 @@ type Experiment struct {
 	Error    string
 }
 
+// copy creates a deep copy of the experiment to avoid race conditions
+func (e *Experiment) copy() *Experiment {
+	var finished *time.Time
+	if e.Finished != nil {
+		fin := *e.Finished
+		finished = &fin
+	}
+	return &Experiment{
+		ID:       e.ID,
+		Name:     e.Name,
+		Target:   e.Target,
+		Type:     e.Type,
+		Config:   e.Config,
+		Status:   e.Status,
+		Started:  e.Started,
+		Finished: finished,
+		Error:    e.Error,
+	}
+}
+
 type ExperimentType string
 
 const (
@@ -90,7 +110,8 @@ func (cs *ChaosService) RunExperiment(ctx context.Context, expType ExperimentTyp
 	// Run experiment in background
 	go cs.executeExperiment(ctx, exp)
 
-	return exp, nil
+	// Return a copy to avoid race condition with JSON marshaling
+	return exp.copy(), nil
 }
 
 func (cs *ChaosService) executeExperiment(ctx context.Context, exp *Experiment) {