diff --git a/internal/application/service/chat_pipeline/rerank.go b/internal/application/service/chat_pipeline/rerank.go
index 20ff2348..d33fe831 100644
--- a/internal/application/service/chat_pipeline/rerank.go
+++ b/internal/application/service/chat_pipeline/rerank.go
@@ -10,6 +10,7 @@ import (
 
 	"github.com/Tencent/WeKnora/internal/models/rerank"
 	"github.com/Tencent/WeKnora/internal/searchutil"
+	"github.com/Tencent/WeKnora/internal/tracing/langfuse"
 	"github.com/Tencent/WeKnora/internal/types"
 	"github.com/Tencent/WeKnora/internal/types/interfaces"
 )
@@ -83,9 +84,7 @@ func (p *PluginRerank) OnEvent(ctx context.Context,
 			})
 			continue
 		}
-		// 合并Content和ImageInfo的文本内容
 		passage := getEnrichedPassage(ctx, result)
-		// Skip passages that become empty after cleaning
 		if strings.TrimSpace(passage) == "" {
 			pipelineInfo(ctx, "Rerank", "empty_passage_skip", map[string]interface{}{
 				"chunk_id": result.ID,
@@ -96,6 +95,31 @@ func (p *PluginRerank) OnEvent(ctx context.Context,
 		candidatesToRerank = append(candidatesToRerank, result)
 	}
 
+	passagesPreview := langfuse.SummarizePassagePreviews(candidatesToRerank, passages, 25)
+	rerankCtx, rerankSpan := langfuse.GetManager().StartSpan(ctx, langfuse.SpanOptions{
+		Name: "rerank",
+		Input: map[string]interface{}{
+			"query":             chatManage.RewriteQuery,
+			"candidate_count":   len(candidatesToRerank),
+			"direct_load_count": len(directLoadResults),
+			"rerank_model_id":   chatManage.RerankModelID,
+			"threshold":         chatManage.RerankThreshold,
+			"rerank_top_k":      chatManage.RerankTopK,
+			"faq_priority":      chatManage.FAQPriorityEnabled,
+			"faq_score_boost":   chatManage.FAQScoreBoost,
+			"passages_preview":  passagesPreview,
+		},
+		Metadata: map[string]interface{}{
+			"session_id": chatManage.SessionID,
+		},
+	})
+	ctx = rerankCtx
+	spanOutput := map[string]interface{}{}
+	var spanErr error
+	defer func() {
+		rerankSpan.Finish(spanOutput, nil, spanErr)
+	}()
+
 	pipelineInfo(ctx, "Rerank", "build_passages", map[string]interface{}{
 		"total_cnt":     len(chatManage.SearchResult),
 		"candidate_cnt": len(candidatesToRerank),
@@ -103,6 +127,8 @@ func (p *PluginRerank) OnEvent(ctx context.Context,
 	})
 
 	var rerankResp []rerank.RankResult
+	var rawRerankResp []rerank.RankResult
+	thresholdDegraded := false
 
 	// Only call rerank model if there are candidates
 	if len(candidatesToRerank) > 0 {
@@ -119,11 +145,18 @@ func (p *PluginRerank) OnEvent(ctx context.Context,
 				"candidate_cnt": len(candidatesToRerank),
 			})
 			chatManage.SearchResult = append(directLoadResults, candidatesToRerank...)
+			spanOutput = map[string]interface{}{
+				"stage":           "api_error_fallback",
+				"candidate_count": len(candidatesToRerank),
+				"error":           rerankErr.Error(),
+			}
 			return next()
 		}
+		rawRerankResp = append([]rerank.RankResult(nil), rerankResp...)
 
 		// If no results and threshold is high enough, try with lower threshold
 		if len(rerankResp) == 0 && originalThreshold > 0.3 {
+			thresholdDegraded = true
 			degradedThreshold := originalThreshold * 0.7
 			if degradedThreshold < 0.3 {
 				degradedThreshold = 0.3
@@ -144,8 +177,15 @@ func (p *PluginRerank) OnEvent(ctx context.Context,
 					"candidate_cnt": len(candidatesToRerank),
 				})
 				chatManage.SearchResult = append(directLoadResults, candidatesToRerank...)
+				spanOutput = map[string]interface{}{
+					"stage":              "api_error_fallback",
+					"candidate_count":    len(candidatesToRerank),
+					"threshold_degraded": thresholdDegraded,
+					"error":              rerankErr.Error(),
+				}
 				return next()
 			}
+			rawRerankResp = append([]rerank.RankResult(nil), rerankResp...)
 		}
 	}
 
@@ -169,6 +209,7 @@ func (p *PluginRerank) OnEvent(ctx context.Context,
 		base := sr.Score
 		sr.Metadata["base_score"] = fmt.Sprintf("%.4f", base)
 		modelScore := rr.RelevanceScore
+		sr.Metadata["model_score"] = fmt.Sprintf("%.4f", modelScore)
 		sr.Score = compositeScore(sr, modelScore, base)
 
 		// Apply FAQ score boost if enabled
@@ -193,8 +234,9 @@ func (p *PluginRerank) OnEvent(ctx context.Context,
 	for _, sr := range directLoadResults {
 		base := sr.Score
 		sr.Metadata["base_score"] = fmt.Sprintf("%.4f", base)
-		// Assign high model score for direct load items
 		modelScore := 1.0
+		sr.Metadata["model_score"] = fmt.Sprintf("%.4f", modelScore)
+		// Assign high model score for direct load items
 		sr.Score = compositeScore(sr, modelScore, base)
 		reranked = append(reranked, sr)
 	}
@@ -216,15 +258,84 @@ func (p *PluginRerank) OnEvent(ctx context.Context,
 		pipelineWarn(ctx, "Rerank", "output", map[string]interface{}{
 			"filtered_cnt": 0,
 		})
+		spanOutput = buildRerankSpanOutput(
+			candidatesToRerank,
+			passages,
+			directLoadResults,
+			rawRerankResp,
+			reranked,
+			nil,
+			chatManage,
+			thresholdDegraded,
+		)
 		return ErrSearchNothing
 	}
 
+	spanOutput = buildRerankSpanOutput(
+		candidatesToRerank,
+		passages,
+		directLoadResults,
+		rawRerankResp,
+		reranked,
+		chatManage.RerankResult,
+		chatManage,
+		thresholdDegraded,
+	)
 	pipelineInfo(ctx, "Rerank", "output", map[string]interface{}{
 		"filtered_cnt": len(chatManage.RerankResult),
 	})
 	return next()
 }
 
+func buildRerankSpanOutput(
+	candidates []*types.SearchResult,
+	passages []string,
+	directLoad []*types.SearchResult,
+	modelScores []rerank.RankResult,
+	composite []*types.SearchResult,
+	final []*types.SearchResult,
+	chatManage *types.ChatManage,
+	thresholdDegraded bool,
+) map[string]interface{} {
+	modelRows := make([]map[string]interface{}, 0, len(modelScores))
+	for i, rr := range modelScores {
+		row := map[string]interface{}{
+			"rank":        i + 1,
+			"index":       rr.Index,
+			"model_score": rr.RelevanceScore,
+		}
+		if rr.Index >= 0 && rr.Index < len(candidates) {
+			row["chunk_id"] = candidates[rr.Index].ID
+			row["knowledge_id"] = candidates[rr.Index].KnowledgeID
+			row["knowledge_title"] = candidates[rr.Index].KnowledgeTitle
+			row["match_type"] = candidates[rr.Index].MatchType
+			row["retrieval_score"] = candidates[rr.Index].Score
+			if rr.Index < len(passages) {
+				row["preview"] = langfuse.TruncateRunes(passages[rr.Index], 160)
+			}
+		}
+		modelRows = append(modelRows, row)
+	}
+
+	out := map[string]interface{}{
+		"candidate_count":    len(candidates),
+		"direct_load_count":  len(directLoad),
+		"model_result_count": len(modelScores),
+		"composite_count":    len(composite),
+		"final_count":        len(final),
+		"threshold":          chatManage.RerankThreshold,
+		"rerank_top_k":       chatManage.RerankTopK,
+		"threshold_degraded": thresholdDegraded,
+		"model_scores":       langfuse.SummarizeRankScores(modelRows, 50),
+		"composite_results":  langfuse.SummarizeSearchResults(composite, 25),
+		"final_results":      langfuse.SummarizeSearchResults(final, 25),
+	}
+	if len(modelScores) > 50 {
+		out["model_scores_truncated"] = len(modelScores) - 50
+	}
+	return out
+}
+
 // rerank performs the actual reranking operation with given query and passages
 func (p *PluginRerank) rerank(ctx context.Context,
 	chatManage *types.ChatManage, rerankModel rerank.Reranker, query string, passages []string,
diff --git a/internal/application/service/knowledgebase_search.go b/internal/application/service/knowledgebase_search.go
index 605b442f..a2a42d5e 100644
--- a/internal/application/service/knowledgebase_search.go
+++ b/internal/application/service/knowledgebase_search.go
@@ -191,15 +191,26 @@ func (s *knowledgeBaseService) HybridSearch(ctx context.Context,
 	retrieveCtx, retrieveSpan := langfuse.GetManager().StartSpan(ctx, langfuse.SpanOptions{
 		Name: "retrieve",
 		Input: map[string]interface{}{
-			"kb_ids":      searchKBIDs,
-			"group_count": len(groups),
-			"match_count": matchCount,
+			"query_text":             params.QueryText,
+			"kb_ids":                 searchKBIDs,
+			"knowledge_ids":          params.KnowledgeIDs,
+			"tag_ids":                params.TagIDs,
+			"match_count":            matchCount,
+			"vector_threshold":       params.VectorThreshold,
+			"keyword_threshold":      params.KeywordThreshold,
+			"disable_vector_match":   params.DisableVectorMatch,
+			"disable_keywords_match": params.DisableKeywordsMatch,
+			"group_count":            len(groups),
+		},
+		Metadata: map[string]interface{}{
+			"primary_kb_id":      kb.ID,
+			"primary_kb_type":    string(kb.Type),
+			"embedding_model_id": kb.EmbeddingModelID,
+			"has_query_embedding": len(params.QueryEmbedding) > 0,
 		},
 	})
 	retrieveResults, err := s.retrieveFromStores(retrieveCtx, groups, retriever.EngineAwareNormalizer{})
-	retrieveSpan.Finish(map[string]interface{}{
-		"result_count": totalHits(retrieveResults),
-	}, nil, err)
+	retrieveSpan.Finish(langfuse.SummarizeRetrieveOutput(retrieveResults), nil, err)
 	if err != nil {
 		logger.ErrorWithFields(ctx, err, map[string]interface{}{
 			"knowledge_base_ids": searchKBIDs,
@@ -278,7 +289,7 @@ func allBaseParamsEmpty(groups []*storeGroup) bool {
 }
 
 // totalHits counts the IndexWithScore entries across a slice of retrieve
-// results. Used only for langfuse span metadata.
+// results.
 func totalHits(rrs []*types.RetrieveResult) int {
 	n := 0
 	for _, r := range rrs {
diff --git a/internal/models/rerank/langfuse_wrapper.go b/internal/models/rerank/langfuse_wrapper.go
index ba8fa78c..f62e7856 100644
--- a/internal/models/rerank/langfuse_wrapper.go
+++ b/internal/models/rerank/langfuse_wrapper.go
@@ -6,6 +6,9 @@ import (
 	"github.com/Tencent/WeKnora/internal/tracing/langfuse"
 )
 
+const langfuseRerankPreviewDocs = 8
+const langfuseRerankMaxScores = 50
+
 // langfuseReranker wraps a Reranker and reports each rerank call as a
 // Langfuse generation observation. Rerankers don't return token usage, but
 // the call still incurs cost (billed per 1K documents by most vendors); we
@@ -24,32 +27,75 @@ func (l *langfuseReranker) Rerank(ctx context.Context, query string, documents [
 		return l.inner.Rerank(ctx, query, documents)
 	}
 
+	totalChars := len([]rune(query))
+	for _, doc := range documents {
+		totalChars += len([]rune(doc))
+	}
+
 	genCtx, gen := mgr.StartGeneration(ctx, langfuse.GenerationOptions{
 		Name:  "rerank",
 		Model: l.inner.GetModelName(),
 		Input: map[string]interface{}{
-			"query":          query,
-			"document_count": len(documents),
-			// Only send short previews — reranker inputs can be hundreds of
-			// passages totalling hundreds of KB, which would bloat traces.
-			"documents_preview": previewDocs(documents, 5),
+			"query":             query,
+			"document_count":    len(documents),
+			"documents_preview": previewDocs(documents, langfuseRerankPreviewDocs),
 		},
 		Metadata: map[string]interface{}{
-			"model_id":    l.inner.GetModelID(),
-			"num_queries": 1,
+			"model_id":        l.inner.GetModelID(),
+			"num_queries":     1,
+			"total_chars":     totalChars,
+			"avg_doc_chars":   avgDocChars(documents),
 		},
 	})
 
 	results, err := l.inner.Rerank(genCtx, query, documents)
 
 	output := map[string]interface{}{
-		"results":     summarizeResults(results, 10),
+		"results":     summarizeResults(results, documents, langfuseRerankMaxScores),
 		"total_count": len(results),
+		"score_stats": scoreStats(results),
+	}
+	if len(results) > langfuseRerankMaxScores {
+		output["truncated"] = len(results) - langfuseRerankMaxScores
 	}
 	gen.Finish(output, approxRerankUsage(query, documents), err)
 	return results, err
 }
 
+func avgDocChars(documents []string) int {
+	if len(documents) == 0 {
+		return 0
+	}
+	total := 0
+	for _, doc := range documents {
+		total += len([]rune(doc))
+	}
+	return total / len(documents)
+}
+
+func scoreStats(results []RankResult) map[string]interface{} {
+	if len(results) == 0 {
+		return nil
+	}
+	minScore := results[0].RelevanceScore
+	maxScore := results[0].RelevanceScore
+	sum := 0.0
+	for _, r := range results {
+		if r.RelevanceScore < minScore {
+			minScore = r.RelevanceScore
+		}
+		if r.RelevanceScore > maxScore {
+			maxScore = r.RelevanceScore
+		}
+		sum += r.RelevanceScore
+	}
+	return map[string]interface{}{
+		"min": minScore,
+		"max": maxScore,
+		"avg": sum / float64(len(results)),
+	}
+}
+
 func approxRerankUsage(query string, documents []string) *langfuse.TokenUsage {
 	total := len([]rune(query))/4 + 1
 	for _, d := range documents {
@@ -80,16 +126,22 @@ func previewDocs(docs []string, n int) []map[string]interface{} {
 	return out
 }
 
-func summarizeResults(results []RankResult, n int) []map[string]interface{} {
+func summarizeResults(results []RankResult, documents []string, n int) []map[string]interface{} {
 	if len(results) < n {
 		n = len(results)
 	}
 	out := make([]map[string]interface{}, 0, n)
 	for i := 0; i < n; i++ {
-		out = append(out, map[string]interface{}{
-			"index": results[i].Index,
-			"score": results[i].RelevanceScore,
-		})
+		row := map[string]interface{}{
+			"rank":        i + 1,
+			"index":       results[i].Index,
+			"model_score": results[i].RelevanceScore,
+		}
+		idx := results[i].Index
+		if idx >= 0 && idx < len(documents) {
+			row["preview"] = truncateRunes(documents[idx], 160)
+		}
+		out = append(out, row)
 	}
 	return out
 }
diff --git a/internal/tracing/langfuse/retrieval_obs.go b/internal/tracing/langfuse/retrieval_obs.go
new file mode 100644
index 00000000..cfe38b33
--- /dev/null
+++ b/internal/tracing/langfuse/retrieval_obs.go
@@ -0,0 +1,204 @@
+package langfuse
+
+import (
+	"fmt"
+	"sort"
+
+	"github.com/Tencent/WeKnora/internal/types"
+)
+
+const defaultHitPreviewLimit = 25
+
+// TruncateRunes shortens s to at most maxRunes runes for trace payloads.
+func TruncateRunes(s string, maxRunes int) string {
+	if maxRunes <= 0 {
+		return ""
+	}
+	r := []rune(s)
+	if len(r) <= maxRunes {
+		return s
+	}
+	return string(r[:maxRunes]) + "..."
+}
+
+// SummarizeRetrieveOutput builds Langfuse output for the retrieve span.
+func SummarizeRetrieveOutput(results []*types.RetrieveResult) map[string]interface{} {
+	out := map[string]interface{}{
+		"total_hits":   0,
+		"vector_hits":  0,
+		"keyword_hits": 0,
+		"group_count":  len(results),
+		"by_retriever": []map[string]interface{}{},
+		"top_hits":     []map[string]interface{}{},
+	}
+	if len(results) == 0 {
+		return out
+	}
+
+	byRetriever := make([]map[string]interface{}, 0, len(results))
+	var all []*types.IndexWithScore
+	for _, rr := range results {
+		if rr == nil {
+			continue
+		}
+		count := len(rr.Results)
+		out["total_hits"] = out["total_hits"].(int) + count
+		if rr.RetrieverType == types.VectorRetrieverType {
+			out["vector_hits"] = out["vector_hits"].(int) + count
+		} else {
+			out["keyword_hits"] = out["keyword_hits"].(int) + count
+		}
+		byRetriever = append(byRetriever, map[string]interface{}{
+			"engine":    string(rr.RetrieverEngineType),
+			"retriever": string(rr.RetrieverType),
+			"count":     count,
+		})
+		all = append(all, rr.Results...)
+	}
+	out["by_retriever"] = byRetriever
+	out["top_hits"] = summarizeIndexHits(all, defaultHitPreviewLimit)
+	return out
+}
+
+// SummarizeSearchResults builds a compact ranked preview for rerank spans.
+func SummarizeSearchResults(results []*types.SearchResult, limit int) map[string]interface{} {
+	if limit <= 0 {
+		limit = defaultHitPreviewLimit
+	}
+	out := map[string]interface{}{
+		"count":    len(results),
+		"top_hits": []map[string]interface{}{},
+	}
+	if len(results) == 0 {
+		return out
+	}
+
+	sorted := append([]*types.SearchResult(nil), results...)
+	sort.Slice(sorted, func(i, j int) bool {
+		if sorted[i].Score != sorted[j].Score {
+			return sorted[i].Score > sorted[j].Score
+		}
+		return sorted[i].ID < sorted[j].ID
+	})
+
+	hits := make([]map[string]interface{}, 0, minInt(limit, len(sorted)))
+	for i, sr := range sorted {
+		if i >= limit {
+			break
+		}
+		item := map[string]interface{}{
+			"rank":            i + 1,
+			"chunk_id":        sr.ID,
+			"knowledge_id":    sr.KnowledgeID,
+			"knowledge_title": sr.KnowledgeTitle,
+			"composite_score": fmt.Sprintf("%.4f", sr.Score),
+			"match_type":      sr.MatchType,
+			"chunk_type":      sr.ChunkType,
+			"preview":         TruncateRunes(sr.Content, 160),
+		}
+		if sr.Metadata != nil {
+			if base, ok := sr.Metadata["base_score"]; ok {
+				item["retrieval_score"] = base
+			}
+			if model, ok := sr.Metadata["model_score"]; ok {
+				item["model_score"] = model
+			}
+			if boosted, ok := sr.Metadata["faq_boosted"]; ok {
+				item["faq_boosted"] = boosted
+			}
+			if orig, ok := sr.Metadata["faq_original_score"]; ok {
+				item["faq_original_score"] = orig
+			}
+		}
+		hits = append(hits, item)
+	}
+	out["top_hits"] = hits
+	if len(sorted) > limit {
+		out["truncated"] = len(sorted) - limit
+	}
+	return out
+}
+
+// SummarizeRankScores builds rerank model score rows for Langfuse output.
+func SummarizeRankScores(
+	results []map[string]interface{},
+	limit int,
+) []map[string]interface{} {
+	if limit <= 0 {
+		limit = defaultHitPreviewLimit
+	}
+	if len(results) <= limit {
+		return results
+	}
+	out := make([]map[string]interface{}, limit)
+	copy(out, results[:limit])
+	return out
+}
+
+func summarizeIndexHits(hits []*types.IndexWithScore, limit int) []map[string]interface{} {
+	if len(hits) == 0 {
+		return nil
+	}
+	sorted := append([]*types.IndexWithScore(nil), hits...)
+	sort.Slice(sorted, func(i, j int) bool {
+		if sorted[i].Score != sorted[j].Score {
+			return sorted[i].Score > sorted[j].Score
+		}
+		return sorted[i].ChunkID < sorted[j].ChunkID
+	})
+
+	n := minInt(limit, len(sorted))
+	out := make([]map[string]interface{}, 0, n)
+	for i := 0; i < n; i++ {
+		hit := sorted[i]
+		out = append(out, map[string]interface{}{
+			"rank":              i + 1,
+			"chunk_id":          hit.ChunkID,
+			"knowledge_id":      hit.KnowledgeID,
+			"knowledge_base_id": hit.KnowledgeBaseID,
+			"score":             fmt.Sprintf("%.4f", hit.Score),
+			"match_type":        hit.MatchType,
+			"preview":           TruncateRunes(hit.Content, 160),
+		})
+	}
+	return out
+}
+
+// SummarizePassagePreviews builds rerank passage previews aligned with candidates.
+func SummarizePassagePreviews(
+	candidates []*types.SearchResult,
+	passages []string,
+	limit int,
+) []map[string]interface{} {
+	if limit <= 0 {
+		limit = defaultHitPreviewLimit
+	}
+	n := len(candidates)
+	if len(passages) < n {
+		n = len(passages)
+	}
+	if limit < n {
+		n = limit
+	}
+	out := make([]map[string]interface{}, 0, n)
+	for i := 0; i < n; i++ {
+		sr := candidates[i]
+		out = append(out, map[string]interface{}{
+			"index":             i,
+			"chunk_id":          sr.ID,
+			"knowledge_id":      sr.KnowledgeID,
+			"knowledge_title":   sr.KnowledgeTitle,
+			"retrieval_score":   fmt.Sprintf("%.4f", sr.Score),
+			"match_type":        sr.MatchType,
+			"preview":           TruncateRunes(passages[i], 160),
+		})
+	}
+	return out
+}
+
+func minInt(a, b int) int {
+	if a < b {
+		return a
+	}
+	return b
+}
diff --git a/internal/tracing/langfuse/retrieval_obs_test.go b/internal/tracing/langfuse/retrieval_obs_test.go
new file mode 100644
index 00000000..a9e2913f
--- /dev/null
+++ b/internal/tracing/langfuse/retrieval_obs_test.go
@@ -0,0 +1,49 @@
+package langfuse
+
+import (
+	"testing"
+
+	"github.com/Tencent/WeKnora/internal/types"
+)
+
+func TestSummarizeRetrieveOutput_countsAndPreviews(t *testing.T) {
+	out := SummarizeRetrieveOutput([]*types.RetrieveResult{
+		{
+			RetrieverEngineType: types.PostgresRetrieverEngineType,
+			RetrieverType:       types.VectorRetrieverType,
+			Results: []*types.IndexWithScore{
+				{ChunkID: "c1", KnowledgeID: "k1", Score: 0.9, Content: "alpha"},
+				{ChunkID: "c2", KnowledgeID: "k1", Score: 0.5, Content: "beta"},
+			},
+		},
+		{
+			RetrieverEngineType: types.PostgresRetrieverEngineType,
+			RetrieverType:       types.KeywordsRetrieverType,
+			Results: []*types.IndexWithScore{
+				{ChunkID: "c3", KnowledgeID: "k2", Score: 0.7, Content: "gamma"},
+			},
+		},
+	})
+
+	if out["total_hits"] != 3 {
+		t.Fatalf("total_hits = %v, want 3", out["total_hits"])
+	}
+	if out["vector_hits"] != 2 || out["keyword_hits"] != 1 {
+		t.Fatalf("vector/keyword hits = %v/%v", out["vector_hits"], out["keyword_hits"])
+	}
+	hits := out["top_hits"].([]map[string]interface{})
+	if len(hits) != 3 || hits[0]["chunk_id"] != "c1" {
+		t.Fatalf("unexpected top_hits: %#v", hits)
+	}
+}
+
+func TestSummarizeSearchResults_sortsByScore(t *testing.T) {
+	out := SummarizeSearchResults([]*types.SearchResult{
+		{ID: "low", Score: 0.2, Content: "low"},
+		{ID: "high", Score: 0.9, Content: "high"},
+	}, 10)
+	hits := out["top_hits"].([]map[string]interface{})
+	if len(hits) != 2 || hits[0]["chunk_id"] != "high" {
+		t.Fatalf("unexpected hits: %#v", hits)
+	}
+}