Carry optional prompt labels through results

json_contract_test.go

@@ -12,6 +12,10 @@ import (
 	"gitea.maximumdirect.net/eric/promptkit"
 )
 
+func stringPointerForTest(value string) *string {
+	return &value
+}
+
 func TestGenerateResponseUsagePresenceJSON(t *testing.T) {
 	value := promptkit.GenerateResponse{
 		Content: "ok",
@@ -42,6 +46,45 @@ func TestGenerateResponseUsagePresenceJSON(t *testing.T) {
 	}
 }
 
+func TestPromptVersionJSONDistinguishesAbsenceAndDeclaredEmpty(t *testing.T) {
+	tests := []struct {
+		name        string
+		value       *string
+		wantPresent bool
+		wantValue   string
+	}{
+		{name: "absent"},
+		{name: "declared empty", value: stringPointerForTest(""), wantPresent: true},
+		{name: "declared text", value: stringPointerForTest("release/v1"), wantPresent: true, wantValue: "release/v1"},
+	}
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			check := func(label string, marshal func() ([]byte, error)) {
+				t.Helper()
+				payload, err := marshal()
+				if err != nil {
+					t.Fatal(err)
+				}
+				object := decodeJSONObject(t, payload)
+				value, present := object["prompt_version"]
+				if present != test.wantPresent {
+					t.Errorf("%s prompt_version present=%t, want %t: %s", label, present, test.wantPresent, payload)
+				}
+				var decoded string
+				if test.wantPresent && (json.Unmarshal(value, &decoded) != nil || decoded != test.wantValue) {
+					t.Errorf("%s prompt_version=%#v, want %q", label, value, test.wantValue)
+				}
+			}
+			check("prepared", func() ([]byte, error) {
+				return json.Marshal(promptkit.PreparedRun{PromptVersion: test.value})
+			})
+			check("result", func() ([]byte, error) {
+				return json.Marshal(promptkit.RunResult{PromptVersion: test.value})
+			})
+		})
+	}
+}
+
 func TestPreparedRunJSONContractRoundTripsAllFields(t *testing.T) {
 	value := fullyPopulatedPreparedRun()
 	payload, err := json.Marshal(value)
@@ -216,7 +259,7 @@ func fullyPopulatedPreparedRun() promptkit.PreparedRun {
 	start := time.Date(2026, time.August, 11, 12, 13, 14, 150_000_000, time.UTC)
 	return promptkit.PreparedRun{
 		PromptID:             "prompt.prepared",
-		PromptVersion:        "2.1.0",
+		PromptVersion:        stringPointerForTest("2.1.0"),
 		PromptHash:           "prompt-hash",
 		SelectedProfileID:    "profile-prepared",
 		SelectedBackendID:    "backend-prepared",
@@ -283,7 +326,7 @@ func fullyPopulatedRunResult() promptkit.RunResult {
 			IsValid:        false,
 		},
 		PromptID:             "prompt.result",
-		PromptVersion:        "3.2.1",
+		PromptVersion:        stringPointerForTest("3.2.1"),
 		PromptHash:           "result-prompt-hash",
 		SessionID:            "session-result",
 		RenderedPromptHash:   "result-rendered-hash",