diff --git a/internal/struktly/audit/types_test.go b/internal/struktly/audit/types_test.go
new file mode 100644
index 0000000..7403f99
--- /dev/null
+++ b/internal/struktly/audit/types_test.go
@@ -0,0 +1,74 @@
+package audit
+
+import (
+	"encoding/json"
+	"os"
+	"path/filepath"
+	"reflect"
+	"strings"
+	"testing"
+	"time"
+)
+
+// TestAuditLog_JSONFileRoundTrip writes an AuditLog the way orchestrator.writeJSON
+// does and checks the file content and that it decodes back to the same value.
+func TestAuditLog_JSONFileRoundTrip(t *testing.T) {
+	want := AuditLog{
+		Timestamp: time.Date(2026, 9, 21, 12, 30, 45, 123456789, time.UTC),
+		Inputs: InputHashes{
+			SpecHash:   "spec-sha256",
+			PolicyHash: "policy-sha256",
+		},
+		Policy: PolicyResult{Passed: true, Reason: "within limits"},
+		Generation: GenerationResult{
+			Prompts: []string{"first prompt", "second prompt"},
+			Model:   "test-model",
+		},
+		Verification: VerificationResult{Passed: true, Output: "ok"},
+		Outcome:      "SUCCESS",
+	}
+
+	path := filepath.Join(t.TempDir(), "audit.json")
+	f, err := os.Create(path)
+	if err != nil {
+		t.Fatalf("create %s: %v", path, err)
+	}
+	enc := json.NewEncoder(f)
+	enc.SetIndent("", "  ")
+	if err := enc.Encode(want); err != nil {
+		_ = f.Close()
+		t.Fatalf("encode: %v", err)
+	}
+	if err := f.Close(); err != nil {
+		t.Fatalf("close %s: %v", path, err)
+	}
+
+	data, err := os.ReadFile(path)
+	if err != nil {
+		t.Fatalf("read %s: %v", path, err)
+	}
+	content := string(data)
+	for _, fragment := range []string{
+		`"spec_hash": "spec-sha256"`,
+		`"policy_hash": "policy-sha256"`,
+		"\"prompts\": [\n      \"first prompt\",\n      \"second prompt\"\n    ]",
+		`"model": "test-model"`,
+		`"outcome": "SUCCESS"`,
+	} {
+		if !strings.Contains(content, fragment) {
+			t.Errorf("file content missing %q:\n%s", fragment, content)
+		}
+	}
+
+	var got AuditLog
+	if err := json.Unmarshal(data, &got); err != nil {
+		t.Fatalf("unmarshal: %v", err)
+	}
+	if !got.Timestamp.Equal(want.Timestamp) {
+		t.Errorf("Timestamp = %v, want %v", got.Timestamp, want.Timestamp)
+	}
+	got.Timestamp = want.Timestamp
+	if !reflect.DeepEqual(got, want) {
+		t.Errorf("decoded AuditLog = %+v, want %+v", got, want)
+	}
+}