Keep checkpoints aligned with PromptKit profiles

internal/framework/llm/promptkit_client_test.go

@@ -6,6 +6,8 @@ import (
 	"errors"
 	"io"
 	"net/http"
+	"os"
+	"path/filepath"
 	"strings"
 	"sync"
 	"sync/atomic"
@@ -119,6 +121,63 @@ func TestNewPromptKitClientReportsAssetAndEngineConstructionFailures(t *testing.
 	})
 }
 
+func TestPromptKitClientCheckpointFingerprintTracksProfileSource(t *testing.T) {
+	profilePath := filepath.Join(t.TempDir(), "profiles.yml")
+	writeProfile := func(model string) {
+		t.Helper()
+		content := "id: checkpoint-profile\nendpoint: http://promptkit.test/v1\nmodel: " + model + "\n"
+		if err := os.WriteFile(profilePath, []byte(content), 0o600); err != nil {
+			t.Fatal(err)
+		}
+	}
+	fingerprintFor := func() CheckpointFingerprint {
+		t.Helper()
+		client, err := NewPromptKitClient(PromptKitClientConfig{
+			Assets:      newTestPromptKitAssets(t),
+			ProfileFile: profilePath,
+		})
+		if err != nil {
+			t.Fatal(err)
+		}
+		values, err := client.LLMCheckpointFingerprints()
+		if err != nil {
+			t.Fatal(err)
+		}
+		if len(values) != 1 || values[0].Name != promptKitProfileFingerprintName {
+			t.Fatalf("checkpoint fingerprints = %#v, want one profile-source identity", values)
+		}
+		return values[0]
+	}
+
+	writeProfile("model-one")
+	first := fingerprintFor()
+	writeProfile("model-two")
+	second := fingerprintFor()
+	if first == second {
+		t.Fatalf("profile-source fingerprint = %#v for both profile models", first)
+	}
+	if strings.Contains(first.Value, profilePath) || strings.Contains(first.Value, "model-one") {
+		t.Fatalf("profile-source fingerprint exposes source details: %#v", first)
+	}
+
+	client, err := NewPromptKitClient(PromptKitClientConfig{Assets: newTestPromptKitAssets(t)})
+	if err != nil {
+		t.Fatal(err)
+	}
+	copy, err := client.LLMCheckpointFingerprints()
+	if err != nil {
+		t.Fatal(err)
+	}
+	copy[0].Value = "mutated"
+	fresh, err := client.LLMCheckpointFingerprints()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if fresh[0].Value == "mutated" {
+		t.Fatal("LLMCheckpointFingerprints exposed mutable backing storage")
+	}
+}
+
 func TestPromptKitClientUsesPromptDefaultProfileWhenRequestProfileEmpty(t *testing.T) {
 	fake := &fakePromptKitLLM{content: `{"ok":true}`}
 	client := newTestPromptKitClient(t, fake)