fix: preserve cleared preview state

Author: Vaibhaav

backend/internal/preview/entry.go

@@ -11,7 +11,7 @@ import (
 	"github.com/aoagents/agent-orchestrator/backend/internal/domain"
 )
 
-var entryCandidates = []string{"index.html", "dist/index.html", "build/index.html", "public/index.html"}
+var entryCandidates = []string{"index.html", "public/index.html", "dist/index.html", "build/index.html"}
 
 // Entry is a workspace-local static frontend entrypoint.
 type Entry struct {

backend/internal/preview/poller.go

@@ -12,6 +12,7 @@ import (
 	"github.com/aoagents/agent-orchestrator/backend/internal/domain"
 )
 
+// DefaultPollInterval is the preview poller's scan interval when none is configured.
 const DefaultPollInterval = 250 * time.Millisecond
 
 type sessionPreviewSource interface {
@@ -22,6 +23,7 @@ type previewSetter interface {
 	SetPreview(ctx context.Context, id domain.SessionID, previewURL string) (domain.Session, error)
 }
 
+// PollerConfig configures preview poller timing and logging.
 type PollerConfig struct {
 	Interval time.Duration
 	Logger   *slog.Logger
@@ -44,6 +46,7 @@ type entryState struct {
 	size    int64
 }
 
+// NewPoller constructs a preview poller over the supplied session source and setter.
 func NewPoller(source sessionPreviewSource, setter previewSetter, baseURL string, cfg PollerConfig) *Poller {
 	p := &Poller{
 		source:   source,
@@ -137,7 +140,7 @@ func (p *Poller) Poll(ctx context.Context) error {
 func (p *Poller) shouldRefresh(sess domain.SessionRecord, target string, seenBefore bool) bool {
 	current := strings.TrimSpace(sess.Metadata.PreviewURL)
 	if current == "" {
-		return !seenBefore
+		return !seenBefore && sess.Metadata.PreviewRevision == 0
 	}
 	if current == target || isWorkspacePreviewURL(current, sess.ID) {
 		return true

backend/internal/preview/poller_test.go

@@ -70,6 +70,23 @@ func TestPollerUsesFirstExistingEntrypoint(t *testing.T) {
 	})
 }
 
+func TestPollerPreservesEntrypointPriority(t *testing.T) {
+	workspace := t.TempDir()
+	writeFile(t, filepath.Join(workspace, "public", "index.html"), "<main>public</main>")
+	writeFile(t, filepath.Join(workspace, "dist", "index.html"), "<main>dist</main>")
+	svc := &fakePreviewSessions{sessions: []domain.SessionRecord{workerSession("ao-1", workspace, "")}}
+	poller := NewPoller(svc, svc, "http://127.0.0.1:3001", PollerConfig{Logger: discardLogger()})
+
+	if err := poller.Poll(context.Background()); err != nil {
+		t.Fatalf("Poll: %v", err)
+	}
+
+	assertSets(t, svc.sets, previewSet{
+		id:  "ao-1",
+		url: "http://127.0.0.1:3001/api/v1/sessions/ao-1/preview/files/public/index.html",
+	})
+}
+
 func TestPollerRefreshesOnlyWhenEntrypointChanges(t *testing.T) {
 	workspace := t.TempDir()
 	entry := filepath.Join(workspace, "index.html")
@@ -101,6 +118,23 @@ func TestPollerRefreshesOnlyWhenEntrypointChanges(t *testing.T) {
 	}
 }
 
+func TestPollerDoesNotRestoreClearedPreviewAfterRestart(t *testing.T) {
+	workspace := t.TempDir()
+	writeFile(t, filepath.Join(workspace, "index.html"), "<main>hello</main>")
+	sess := workerSession("ao-1", workspace, "")
+	sess.Metadata.PreviewRevision = 2
+	svc := &fakePreviewSessions{sessions: []domain.SessionRecord{sess}}
+	poller := NewPoller(svc, svc, "http://127.0.0.1:3001", PollerConfig{Logger: discardLogger()})
+
+	if err := poller.Poll(context.Background()); err != nil {
+		t.Fatalf("Poll: %v", err)
+	}
+
+	if len(svc.sets) != 0 {
+		t.Fatalf("sets = %#v, want cleared preview to remain empty after restart", svc.sets)
+	}
+}
+
 func TestPollerDoesNotOverrideExplicitPreviewTarget(t *testing.T) {
 	workspace := t.TempDir()
 	writeFile(t, filepath.Join(workspace, "index.html"), "<main>hello</main>")