Improve runtime error messages

backend/handlers/api.go

@@ -196,13 +196,13 @@ func (a *App) previewDownload(c *gin.Context) {
 	cmd := exec.Command("python3", a.WorkerScript, "--mode", "probe", "--url", req.URL)
 	output, err := cmd.CombinedOutput()
 	if err != nil {
-		c.JSON(http.StatusBadGateway, gin.H{"error": strings.TrimSpace(string(output))})
+		c.JSON(http.StatusBadGateway, gin.H{"error": summarizeOutput("download preview probe failed", output, err)})
 		return
 	}
 
 	var preview PreviewResponse
 	if err := json.Unmarshal(output, &preview); err != nil {
-		c.JSON(http.StatusBadGateway, gin.H{"error": "invalid probe response"})
+		c.JSON(http.StatusBadGateway, gin.H{"error": summarizeOutput("download preview returned invalid JSON", output, err)})
 		return
 	}
 	c.JSON(http.StatusOK, preview)
@@ -272,7 +272,7 @@ func (a *App) searchMedia(c *gin.Context) {
 	if len(results) == 0 {
 		warning := "SearXNG returned no renderable results."
 		if expandErr != nil {
-			warning += " Query expansion fallback was used."
+			warning += " Query expansion failed: " + expandErr.Error()
 		}
 		c.JSON(http.StatusOK, gin.H{"results": []services.AIRecommendation{}, "warning": warning})
 		return
@@ -295,7 +295,7 @@ func (a *App) searchMedia(c *gin.Context) {
 		}
 		warning := err.Error()
 		if expandErr != nil {
-			warning = warning + " Query expansion fallback was used."
+			warning = warning + " Query expansion failed: " + expandErr.Error()
 		}
 		c.JSON(http.StatusOK, gin.H{"results": fallback, "warning": warning, "queries": queryVariants})
 		return
@@ -303,7 +303,7 @@ func (a *App) searchMedia(c *gin.Context) {
 
 	response := gin.H{"results": mergeRecommendations(recommended, scored, 20), "queries": queryVariants}
 	if expandErr != nil {
-		response["warning"] = "Gemini query expansion failed, using the original query only."
+		response["warning"] = "Gemini query expansion failed: " + expandErr.Error() + ". Using the original query only."
 	}
 	c.JSON(http.StatusOK, response)
 }
@@ -423,3 +423,17 @@ func EnsurePaths(downloadsDir, workerScript string) error {
 	}
 	return nil
 }
+
+func summarizeOutput(prefix string, output []byte, err error) string {
+	trimmed := strings.TrimSpace(string(output))
+	if trimmed == "" && err != nil {
+		return prefix + ": " + err.Error()
+	}
+	if trimmed == "" {
+		return prefix
+	}
+	if len(trimmed) > 1200 {
+		trimmed = trimmed[:1200] + "..."
+	}
+	return prefix + ": " + trimmed
+}