Fix gemini candidate starvation

TODO.md

@@ -655,6 +655,30 @@
 - If behavior in the browser does not match the latest backend/frontend code, the first assumption should be stale frontend assets until proven otherwise
 
 ## Recent Change Log
+- Date: `2026-03-17`
+- What changed:
+  - Fixed a search-budget regression where source collection could consume the full `SearchService` deadline and leave no time for Envato / Artgrid enrichment, causing Gemini to see only missing or low-value visuals.
+  - Split the search-service deadline into:
+    - collector deadline
+    - enrichment deadline with an explicit reserved window
+  - Added unit coverage for the new deadline split behavior.
+  - Stopped frontend preview-probe fallback from calling `/api/download/preview` for Artgrid items that do not already have a provider preview URL, so unsupported `yt-dlp` Artgrid probe errors no longer fire just from opening or hovering those results.
+- Why it changed:
+  - The user-provided log `ai-media-hub-2026-03-17T07-01-21-282Z.log` showed:
+    - `search_service:deadline_reached`
+    - immediate `search_service:enrich_start` -> `search_service:enrich_complete`
+    - `withPreview: 0`
+    - `withLowValueThumbnail: 12`
+    - repeated `candidate has no thumbnail or preview video`
+    - final warning `gemini vision returned no candidate evaluations`
+  - The same log also showed Artgrid preview probe failures from `yt-dlp` returning `Unsupported URL`, which were not helping user-facing preview behavior.
+- How it was verified:
+  - `pwsh -NoProfile -File scripts/selftest.ps1`
+  - added Go tests for the search/enrichment deadline split helper
+- What is still risky or incomplete:
+  - This preserves time for enrichment, but it does not guarantee that every live Envato / Artgrid page yields a usable preview URL.
+  - Artgrid still depends on backend-enriched provider preview URLs for true video preview; if no provider preview is discovered, the UI will still fall back to thumbnail-only rendering.
+
 - Date: `2026-03-17`
 - What changed:
   - Added repo-local Windows 11 PowerShell workflows:

backend/services/cse.go

@@ -53,6 +53,8 @@ type SearchExecutionMeta struct {
 	PartialDueToDeadline bool `json:"partialDueToDeadline"`
 }
 
+const searchEnrichmentReserve = 4 * time.Second
+
 func NewSearchService(baseURL, googleVideoEngine, webEngine string) *SearchService {
 	if googleVideoEngine == "" {
 		googleVideoEngine = "google videos"
@@ -84,9 +86,11 @@ func (s *SearchService) SearchMediaWithDeadline(queries []string, enabledPlatfor
 	if s.BaseURL == "" {
 		return nil, meta, fmt.Errorf("searxng base url is not configured")
 	}
+	collectionDeadline, enrichmentDeadline := splitSearchDeadlines(deadline)
 	s.debug("search_service:start", map[string]any{
 		"queries":          queries,
 		"enabledPlatforms": enabledPlatforms,
+		"deadlineSet":      !deadline.IsZero(),
 	})
 
 	seen := map[string]bool{}
@@ -99,7 +103,7 @@ func (s *SearchService) SearchMediaWithDeadline(queries []string, enabledPlatfor
 	primaryQueries := baseQueries[:minInt(len(baseQueries), 4)]
 	runSearchPass := func(bases []string, onlyMissing bool) {
 		for _, base := range bases {
-			if !deadline.IsZero() && time.Now().After(deadline) {
+			if !collectionDeadline.IsZero() && time.Now().After(collectionDeadline) {
 				meta.PartialDueToDeadline = true
 				s.debug("search_service:deadline_reached", map[string]any{"stage": "runSearchPass", "base": base})
 				return
@@ -109,7 +113,7 @@ func (s *SearchService) SearchMediaWithDeadline(queries []string, enabledPlatfor
 				continue
 			}
 			for _, collector := range s.collectors {
-				if !deadline.IsZero() && time.Now().After(deadline) {
+				if !collectionDeadline.IsZero() && time.Now().After(collectionDeadline) {
 					meta.PartialDueToDeadline = true
 					s.debug("search_service:deadline_reached", map[string]any{"stage": "collectorLoop", "collector": collector.Name()})
 					return
@@ -133,7 +137,7 @@ func (s *SearchService) SearchMediaWithDeadline(queries []string, enabledPlatfor
 					"searchQueries": searchQueries,
 				})
 				for _, searchQuery := range searchQueries {
-					if !deadline.IsZero() && time.Now().After(deadline) {
+					if !collectionDeadline.IsZero() && time.Now().After(collectionDeadline) {
 						meta.PartialDueToDeadline = true
 						s.debug("search_service:deadline_reached", map[string]any{"stage": "queryLoop", "collector": collector.Name(), "query": searchQuery})
 						return
@@ -192,11 +196,22 @@ func (s *SearchService) SearchMediaWithDeadline(queries []string, enabledPlatfor
 		"hadError":             lastErr != nil,
 		"partialDueToDeadline": meta.PartialDueToDeadline,
 	})
-	enriched, enrichMeta := s.EnrichResultsWithDeadline(results, deadline)
+	enriched, enrichMeta := s.EnrichResultsWithDeadline(results, enrichmentDeadline)
 	meta.PartialDueToDeadline = meta.PartialDueToDeadline || enrichMeta.PartialDueToDeadline
 	return enriched, meta, nil
 }
 
+func splitSearchDeadlines(deadline time.Time) (time.Time, time.Time) {
+	if deadline.IsZero() {
+		return time.Time{}, time.Time{}
+	}
+	remaining := time.Until(deadline)
+	if remaining <= searchEnrichmentReserve {
+		return deadline, deadline
+	}
+	return deadline.Add(-searchEnrichmentReserve), deadline
+}
+
 func (s *SearchService) EnrichResults(results []SearchResult) []SearchResult {
 	enriched, _ := s.EnrichResultsWithDeadline(results, time.Time{})
 	return enriched

backend/services/cse_test.go

@@ -182,6 +182,30 @@ func TestSearchServiceFetchCacheRoundTrip(t *testing.T) {
 	}
 }
 
+func TestSplitSearchDeadlinesReservesEnrichmentWindow(t *testing.T) {
+	deadline := time.Now().Add(20 * time.Second)
+	collectionDeadline, enrichmentDeadline := splitSearchDeadlines(deadline)
+
+	if enrichmentDeadline.IsZero() {
+		t.Fatal("expected enrichment deadline to be preserved")
+	}
+	if !collectionDeadline.Before(enrichmentDeadline) {
+		t.Fatalf("expected collection deadline before enrichment deadline, got %v >= %v", collectionDeadline, enrichmentDeadline)
+	}
+	if gap := enrichmentDeadline.Sub(collectionDeadline); gap < searchEnrichmentReserve-500*time.Millisecond {
+		t.Fatalf("expected reserve close to %v, got %v", searchEnrichmentReserve, gap)
+	}
+}
+
+func TestSplitSearchDeadlinesDoesNotReserveWhenDeadlineIsTooClose(t *testing.T) {
+	deadline := time.Now().Add(2 * time.Second)
+	collectionDeadline, enrichmentDeadline := splitSearchDeadlines(deadline)
+
+	if !collectionDeadline.Equal(enrichmentDeadline) {
+		t.Fatalf("expected identical deadlines when budget is too tight, got %v and %v", collectionDeadline, enrichmentDeadline)
+	}
+}
+
 func TestSearchServiceSkipsArtgridAPIAfter403(t *testing.T) {
 	var apiRequests atomic.Int32
 	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {

frontend/app.js

@@ -691,10 +691,10 @@ function renderResults(results) {
     node.addEventListener("click", () => openResultModal(item));
     previewVideo.poster = usableThumbnail ? item.thumbnailUrl : "";
     const mediaArea = node.querySelector(".relative");
-    if (item.previewVideoUrl || item.source === "Google Video" || item.source === "Artgrid") {
+    if (item.previewVideoUrl || item.source === "Google Video") {
       mediaArea.addEventListener("mouseenter", async () => {
         let previewURL = item.previewVideoUrl || "";
-        if (!previewURL && (item.source === "Google Video" || item.source === "Artgrid")) {
+        if (!previewURL && item.source === "Google Video") {
           const preview = await fetchResultPreview(item);
           previewURL = preview?.previewStreamUrl || "";
         }
@@ -769,7 +769,7 @@ async function openResultModal(item) {
   const embedURL = buildResultModalEmbedURL(item);
   const fallbackReason = item.previewBlockedReason || "Embedded view was unavailable, switched to fallback preview.";
   let resolvedPreviewURL = item.previewVideoUrl || "";
-  if (!resolvedPreviewURL && (item.source === "Google Video" || item.source === "Artgrid")) {
+  if (!resolvedPreviewURL && item.source === "Google Video") {
     const preview = await fetchResultPreview(item);
     resolvedPreviewURL = preview?.previewStreamUrl || "";
   }