diff --git a/runner.go b/runner.go
index 3687369..53da9b2 100644
--- a/runner.go
+++ b/runner.go
@@ -16,6 +16,9 @@ type Runner struct {
 // ErrRunnerNoService is returned when a runner was created without a service.
 var ErrRunnerNoService = coreerr.E("", "runner service is nil", nil)
 
+// ErrRunnerInvalidSpecName is returned when a RunSpec name is empty or duplicated.
+var ErrRunnerInvalidSpecName = coreerr.E("", "runner spec names must be non-empty and unique", nil)
+
 // NewRunner creates a runner for the given service.
 func NewRunner(svc *Service) *Runner {
 	return &Runner{service: svc}
@@ -74,6 +77,9 @@ func (r *Runner) RunAll(ctx context.Context, specs []RunSpec) (*RunAllResult, er
 	if err := r.ensureService(); err != nil {
 		return nil, err
 	}
+	if err := validateSpecs(specs); err != nil {
+		return nil, err
+	}
 	start := time.Now()
 
 	// Build dependency graph
@@ -239,6 +245,9 @@ func (r *Runner) RunSequential(ctx context.Context, specs []RunSpec) (*RunAllRes
 	if err := r.ensureService(); err != nil {
 		return nil, err
 	}
+	if err := validateSpecs(specs); err != nil {
+		return nil, err
+	}
 	start := time.Now()
 	results := make([]RunResult, 0, len(specs))
 
@@ -282,6 +291,9 @@ func (r *Runner) RunParallel(ctx context.Context, specs []RunSpec) (*RunAllResul
 	if err := r.ensureService(); err != nil {
 		return nil, err
 	}
+	if err := validateSpecs(specs); err != nil {
+		return nil, err
+	}
 	start := time.Now()
 	results := make([]RunResult, len(specs))
 
@@ -312,3 +324,17 @@ func (r *Runner) RunParallel(ctx context.Context, specs []RunSpec) (*RunAllResul
 
 	return aggResult, nil
 }
+
+func validateSpecs(specs []RunSpec) error {
+	seen := make(map[string]struct{}, len(specs))
+	for _, spec := range specs {
+		if spec.Name == "" {
+			return coreerr.E("Runner.validateSpecs", "runner spec name is required", ErrRunnerInvalidSpecName)
+		}
+		if _, ok := seen[spec.Name]; ok {
+			return coreerr.E("Runner.validateSpecs", "runner spec name is duplicated", ErrRunnerInvalidSpecName)
+		}
+		seen[spec.Name] = struct{}{}
+	}
+	return nil
+}
diff --git a/runner_test.go b/runner_test.go
index 1f160db..a6081ca 100644
--- a/runner_test.go
+++ b/runner_test.go
@@ -243,3 +243,33 @@ func TestRunner_NilService(t *testing.T) {
 	require.Error(t, err)
 	assert.ErrorIs(t, err, ErrRunnerNoService)
 }
+
+func TestRunner_InvalidSpecNames(t *testing.T) {
+	runner := newTestRunner(t)
+
+	t.Run("rejects empty names", func(t *testing.T) {
+		_, err := runner.RunSequential(context.Background(), []RunSpec{
+			{Name: "", Command: "echo", Args: []string{"a"}},
+		})
+		require.Error(t, err)
+		assert.ErrorIs(t, err, ErrRunnerInvalidSpecName)
+	})
+
+	t.Run("rejects duplicate names", func(t *testing.T) {
+		_, err := runner.RunAll(context.Background(), []RunSpec{
+			{Name: "same", Command: "echo", Args: []string{"a"}},
+			{Name: "same", Command: "echo", Args: []string{"b"}},
+		})
+		require.Error(t, err)
+		assert.ErrorIs(t, err, ErrRunnerInvalidSpecName)
+	})
+
+	t.Run("rejects duplicate names in parallel mode", func(t *testing.T) {
+		_, err := runner.RunParallel(context.Background(), []RunSpec{
+			{Name: "one", Command: "echo", Args: []string{"a"}},
+			{Name: "one", Command: "echo", Args: []string{"b"}},
+		})
+		require.Error(t, err)
+		assert.ErrorIs(t, err, ErrRunnerInvalidSpecName)
+	})
+}