diff --git a/runner.go b/runner.go
index 72e23f0..9ff5835 100644
--- a/runner.go
+++ b/runner.go
@@ -19,6 +19,9 @@ 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)
 
+// ErrRunnerInvalidDependencyName is returned when a RunSpec dependency name is empty, duplicated, or self-referential.
+var ErrRunnerInvalidDependencyName = coreerr.E("", "runner dependency names must be non-empty, unique, and not self-referential", nil)
+
 // ErrRunnerContextRequired is returned when a runner method is called without a context.
 var ErrRunnerContextRequired = coreerr.E("", "runner context is required", nil)
 
@@ -399,6 +402,20 @@ func validateSpecs(specs []RunSpec) error {
 			return coreerr.E("Runner.validateSpecs", "runner spec name is duplicated", ErrRunnerInvalidSpecName)
 		}
 		seen[spec.Name] = struct{}{}
+
+		deps := make(map[string]struct{}, len(spec.After))
+		for _, dep := range spec.After {
+			if dep == "" {
+				return coreerr.E("Runner.validateSpecs", "runner dependency name is required", ErrRunnerInvalidDependencyName)
+			}
+			if dep == spec.Name {
+				return coreerr.E("Runner.validateSpecs", "runner dependency cannot reference itself", ErrRunnerInvalidDependencyName)
+			}
+			if _, ok := deps[dep]; ok {
+				return coreerr.E("Runner.validateSpecs", "runner dependency name is duplicated", ErrRunnerInvalidDependencyName)
+			}
+			deps[dep] = struct{}{}
+		}
 	}
 	return nil
 }
diff --git a/runner_test.go b/runner_test.go
index 84b85b5..f27e078 100644
--- a/runner_test.go
+++ b/runner_test.go
@@ -327,6 +327,30 @@ func TestRunner_InvalidSpecNames(t *testing.T) {
 		assert.ErrorIs(t, err, ErrRunnerInvalidSpecName)
 	})
 
+	t.Run("rejects empty dependency names", func(t *testing.T) {
+		_, err := runner.RunAll(context.Background(), []RunSpec{
+			{Name: "one", Command: "echo", Args: []string{"a"}, After: []string{""}},
+		})
+		require.Error(t, err)
+		assert.ErrorIs(t, err, ErrRunnerInvalidDependencyName)
+	})
+
+	t.Run("rejects duplicated dependency names", func(t *testing.T) {
+		_, err := runner.RunAll(context.Background(), []RunSpec{
+			{Name: "one", Command: "echo", Args: []string{"a"}, After: []string{"two", "two"}},
+		})
+		require.Error(t, err)
+		assert.ErrorIs(t, err, ErrRunnerInvalidDependencyName)
+	})
+
+	t.Run("rejects self dependency", func(t *testing.T) {
+		_, err := runner.RunAll(context.Background(), []RunSpec{
+			{Name: "one", Command: "echo", Args: []string{"a"}, After: []string{"one"}},
+		})
+		require.Error(t, err)
+		assert.ErrorIs(t, err, ErrRunnerInvalidDependencyName)
+	})
+
 	t.Run("rejects duplicate names", func(t *testing.T) {
 		_, err := runner.RunAll(context.Background(), []RunSpec{
 			{Name: "same", Command: "echo", Args: []string{"a"}},