Reduce noisy Gemini partial failure counts

TODO.md

@@ -235,6 +235,7 @@
 - Artgrid preview playback now has a server-side ffmpeg transcode path for `.m3u8` style preview URLs, but this trades storage savings for runtime CPU cost.
 - The provided Artgrid HTML sample still does not expose a direct preview `m3u8` or `mp4` URL by itself, and `yt-dlp` probe on the sample clip URL returned `Unsupported URL`, so fully reliable Artgrid playback still depends on live-page/runtime preview discovery succeeding elsewhere in the pipeline.
 - Docker CLI is not installed in this environment, so container-image build verification still cannot be performed locally from this machine.
+- Gemini batch warnings can still mix true model/output failures with harmless candidate-skip cases unless the recovery path filters those error classes before surfacing them.
 - The local self-test script is better than before, but it is still a smoke test, not full integration coverage.
 
 ## Current Risks Around Search Quality
@@ -557,6 +558,7 @@
 - [ ] Reduce `/api/search` latency further without collapsing result count
 - [ ] Rebuild the reverted search-expansion work from the previous stable baseline, but only after measuring where candidate quality collapses between ranked pool and final merge
 - [ ] Validate the reopened `5ca7aef` search-breadth direction against real proxy timeouts and visible result count before widening it any further
+- [ ] Continue hardening Gemini batch parsing so truncated JSON and ignorable low-visual candidate failures do not inflate user-facing warning counts
 - [ ] Build a repeatable repo-local bootstrap script or documented setup command set for non-root machines so fresh PC setup does not depend on shell history
 - [ ] Improve Envato / Artgrid preview acquisition reliability so Gemini Vision sees real frames more often
 - [ ] Browser-verify the new result modal at multiple viewport heights and confirm translated Source Summary readability on real long descriptions
@@ -628,6 +630,24 @@
 - 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:
+  - Restored hard/ignorable Gemini batch error filtering so low-value thumbnail skips and no-visual candidate skips do not count as user-facing partial batch failures when useful recommendations were still recovered.
+  - Added unit coverage for the Gemini batch error filtering behavior.
+- Why it changed:
+  - The user reported the warning `gemini vision partially failed on 3 of 4 batches`.
+  - The provided log `ai-media-hub-2026-03-17T06-06-04-447Z.log` showed three different batch-failure classes mixed together:
+    - real Gemini JSON extraction failures
+    - low-value thumbnail skips
+    - no-visual candidate skips
+  - Only the first class should strongly influence the user-facing partial-failure warning.
+- How it was verified:
+  - `go test ./...`
+  - `bash scripts/selftest.sh`
+- What is still risky or incomplete:
+  - This reduces noisy partial-failure warnings, but it does not eliminate genuine Gemini JSON truncation or provider-side preview problems.
+  - If the model starts returning different malformed JSON patterns, the parser and warning logic may still need further hardening.
+
 - Date: `2026-03-17`
 - What changed:
   - Reapplied the broader-search / modal-fitting codepath from `5ca7aef` as requested by the user.

backend/services/gemini_test.go

@@ -213,3 +213,18 @@ func TestMergeRecommendationsExcludesIrrelevantAndPendingFiller(t *testing.T) {
 		t.Fatalf("unexpected merged result: %#v", merged)
 	}
 }
+
+func TestFilterHardGeminiErrorsIgnoresLowValueVisualFailures(t *testing.T) {
+	errs := []string{
+		"candidate thumbnail is low value",
+		"no candidate thumbnails or preview frames could be fetched for gemini vision",
+		"gemini vision JSON extraction failed: no complete JSON object found",
+	}
+	filtered := filterHardGeminiErrors(errs)
+	if len(filtered) != 1 {
+		t.Fatalf("expected only hard errors to remain, got %#v", filtered)
+	}
+	if !strings.Contains(filtered[0], "JSON extraction failed") {
+		t.Fatalf("unexpected filtered errors: %#v", filtered)
+	}
+}

backend/services/ranker.go

@@ -187,6 +187,7 @@ func EvaluateAllCandidatesWithGeminiWithDeadline(service *GeminiService, query s
 				})
 			}
 			recovered, recoveredErrs := recoverGeminiBatchSequentially(service, query, ranked, batch.index*chunkSize, chunkSize, deadline)
+			hardErrs := filterHardGeminiErrors(recoveredErrs)
 			if len(recovered) > 0 {
 				stats.SequentialRetried++
 				stats.Succeeded++
@@ -197,9 +198,9 @@ func EvaluateAllCandidatesWithGeminiWithDeadline(service *GeminiService, query s
 					seen[item.Link] = true
 					merged = append(merged, item)
 				}
-				if len(recoveredErrs) > 0 {
+				if len(hardErrs) > 0 {
 					stats.Failed++
-					for _, recoveredErr := range recoveredErrs {
+					for _, recoveredErr := range hardErrs {
 						if len(stats.Errors) < 5 {
 							stats.Errors = append(stats.Errors, recoveredErr)
 						}
@@ -207,6 +208,9 @@ func EvaluateAllCandidatesWithGeminiWithDeadline(service *GeminiService, query s
 				}
 				continue
 			}
+			if len(hardErrs) == 0 {
+				continue
+			}
 			stats.Failed++
 			if len(stats.Errors) < 5 {
 				stats.Errors = append(stats.Errors, batch.err.Error())
@@ -345,6 +349,35 @@ func MergeGeminiBatchStats(base, extra GeminiBatchStats) GeminiBatchStats {
 	return merged
 }
 
+func filterHardGeminiErrors(errs []string) []string {
+	filtered := make([]string, 0, len(errs))
+	for _, item := range errs {
+		if isIgnorableGeminiError(item) {
+			continue
+		}
+		filtered = append(filtered, item)
+	}
+	return filtered
+}
+
+func isIgnorableGeminiError(message string) bool {
+	lower := strings.ToLower(strings.TrimSpace(message))
+	if lower == "" {
+		return false
+	}
+	for _, token := range []string{
+		"no candidate thumbnails or preview frames could be fetched for gemini vision",
+		"candidate thumbnail is low value",
+		"candidate has no thumbnail or preview video",
+		"image url is empty",
+	} {
+		if strings.Contains(lower, token) {
+			return true
+		}
+	}
+	return false
+}
+
 func recoverGeminiBatchSequentially(service *GeminiService, query string, ranked []SearchResult, startIndex, chunkSize int, deadline time.Time) ([]AIRecommendation, []string) {
 	recovered := make([]AIRecommendation, 0, chunkSize)
 	errs := make([]string, 0, 4)