Clean up MVP output handling

internal/cli/run_test.go

@@ -773,6 +773,40 @@ func TestRunPipelineRejectsUnsafeOutputFileName(t *testing.T) {
 	if got := string(readFile(t, filepath.Join(runDir, diagnostics.ArtifactErrorLog))); !strings.Contains(got, "output file name") {
 		t.Fatalf("error log = %q, want unsafe output file error", got)
 	}
+	if _, err := os.Stat(filepath.Join(runDir, diagnostics.ArtifactRunManifest)); err != nil {
+		t.Fatalf("expected diagnostics manifest after unsafe output file failure: %v", err)
+	}
+}
+
+func TestRunPipelineWritesDiagnosticsArtifactsWhenDurableOutputWriteFails(t *testing.T) {
+	diagnosticsDir := t.TempDir()
+	configPath := writeTestConfig(t, mvpConfigYAMLWithDiagnostics("dnd-session", diagnosticsDir, "always"))
+	inputPath := writeSeriatimInput(t)
+	outputRootFile := writeFile(t, "not-a-directory", "occupied")
+	var stdout bytes.Buffer
+	var stderr bytes.Buffer
+
+	code := RunWithOptions([]string{"run", "dnd-session", "--config", configPath, "--input", inputPath, "--output-dir", outputRootFile}, &stdout, &stderr, Options{
+		LLMClientFactory: fakeLLMFactory(newFakeRunLLMClient(false), nil),
+	})
+
+	if code != 1 {
+		t.Fatalf("RunWithOptions() code = %d, want 1", code)
+	}
+	if !strings.Contains(stderr.String(), "create output directory") {
+		t.Fatalf("stderr = %q, want output directory error", stderr.String())
+	}
+	runDir := onlyChildDir(t, diagnosticsDir)
+	for _, name := range []string{
+		diagnostics.ArtifactRunManifest,
+		diagnostics.ArtifactWarnings,
+		diagnostics.ArtifactRunReport,
+		diagnostics.ArtifactErrorLog,
+	} {
+		if _, err := os.Stat(filepath.Join(runDir, name)); err != nil {
+			t.Fatalf("expected diagnostics artifact %q after durable output write failure: %v", name, err)
+		}
+	}
 }
 
 func TestRunPipelineWritesDiagnosticsArtifactsOnSuccess(t *testing.T) {