diff --git a/backend/internal/library/knowledge/quality.go b/backend/internal/library/knowledge/quality.go
index 23a6150..e028a82 100644
--- a/backend/internal/library/knowledge/quality.go
+++ b/backend/internal/library/knowledge/quality.go
@@ -45,6 +45,13 @@ func MinBreadthGraphNodes() int {
 	return minBreadthNodes
 }
 
+func KnowledgeGraphJSONOnlyRetryPrompt() string {
+	return strings.TrimSpace(`上次回覆沒有包含可解析的 JSON。請**只**輸出一個 JSON 物件：
+- 直接以 { 開頭、以 } 結尾，不要任何思考過程、說明文字或 markdown 圍欄
+- 結構需含 nodes 與 edges 陣列，欄位齊全
+- 不要使用 ... 省略，也不要加註解或尾端逗號`)
+}
+
 func KnowledgeGraphRetryUserPrompt() string {
 	return strings.TrimSpace(`上次產出過於簡略或節點不足。請重新產出完整 TKG JSON：
 - 節點總數 **24～32 個**，L1≥8、L2≥12（廣度優先，多方向觸及）
diff --git a/backend/internal/library/placement/research_map.go b/backend/internal/library/placement/research_map.go
index c2cff1d..fbc258b 100644
--- a/backend/internal/library/placement/research_map.go
+++ b/backend/internal/library/placement/research_map.go
@@ -206,6 +206,13 @@ func BuildResearchMapUserPrompt(in ResearchMapInput) string {
 	return BuildResearchMapFinalizeUserPrompt(in, "")
 }
 
+func ResearchMapJSONOnlyRetryPrompt() string {
+	return strings.TrimSpace(`上次回覆沒有包含可解析的 JSON。請**只**輸出一個 JSON 物件：
+- 直接以 { 開頭、以 } 結尾，不要任何思考過程、說明文字或 markdown 圍欄
+- 需含 audienceSummary、contentGoal、questions、pillars、exclusions、patrolKeywords 欄位
+- 不要使用 ... 省略，也不要加註解或尾端逗號`)
+}
+
 func ResearchMapRetryUserPrompt() string {
 	return strings.TrimSpace(`上次產出過於簡略或項目不足。請重新產出完整 JSON，密度對齊系統 prompt 優秀範例：
 - 必須緊扣【輸入資料】中的品牌、產品與主題目標，不可照搬範例用字
diff --git a/backend/internal/worker/job/expand_graph.go b/backend/internal/worker/job/expand_graph.go
index 4ea3d4b..d6ec2da 100644
--- a/backend/internal/worker/job/expand_graph.go
+++ b/backend/internal/worker/job/expand_graph.go
@@ -265,13 +265,38 @@ func runExpandGraph(ctx context.Context, step StepContext, deps ExpandGraphDeps)
 		return err
 	}
 
-	graph, err := libkg.ParseSynthOutput(result.Text, libkg.SynthInput{
+	synthIn := libkg.SynthInput{
 		Seed:           seed,
 		ProductBrief:   productBrief,
 		TargetAudience: brand.TargetAudience,
-	}, braveSources)
+	}
+	graph, err := libkg.ParseSynthOutput(result.Text, synthIn, braveSources)
 	if err != nil {
-		return app.For(code.AI).SvcThirdParty("延伸知識產生失敗，請重試：" + err.Error())
+		// The model occasionally replies with reasoning/prose and no JSON
+		// object. Retry once, explicitly demanding a raw JSON object.
+		jsonOnlyReq := placement.ResearchGenerateRequest(domai.GenerateRequest{
+			Provider: providerID,
+			Model:    credential.Model,
+			Credential: domai.Credential{
+				APIKey: credential.APIKey,
+			},
+			System: systemPrompt,
+			Messages: []domai.Message{
+				{Role: "user", Content: userPrompt},
+				{Role: "assistant", Content: result.Text},
+				{Role: "user", Content: libkg.KnowledgeGraphJSONOnlyRetryPrompt()},
+			},
+		})
+		retryResult, retryErr := deps.AI.GenerateText(ctx, jsonOnlyReq)
+		if retryErr != nil {
+			return app.For(code.AI).SvcThirdParty("延伸知識產生失敗，請重試：" + err.Error())
+		}
+		retryGraph, retryParseErr := libkg.ParseSynthOutput(retryResult.Text, synthIn, braveSources)
+		if retryParseErr != nil {
+			return app.For(code.AI).SvcThirdParty("延伸知識產生失敗，請重試：" + retryParseErr.Error())
+		}
+		graph = retryGraph
+		result = retryResult
 	}
 	if libkg.GraphTooThin(graph) {
 		retryReq := placement.ResearchGenerateRequest(domai.GenerateRequest{
@@ -288,11 +313,7 @@ func runExpandGraph(ctx context.Context, step StepContext, deps ExpandGraphDeps)
 			},
 		})
 		if retryResult, retryErr := deps.AI.GenerateText(ctx, retryReq); retryErr == nil {
-			if retryGraph, parseErr := libkg.ParseSynthOutput(retryResult.Text, libkg.SynthInput{
-				Seed:           seed,
-				ProductBrief:   productBrief,
-				TargetAudience: brand.TargetAudience,
-			}, braveSources); parseErr == nil && !libkg.GraphTooThin(retryGraph) {
+			if retryGraph, parseErr := libkg.ParseSynthOutput(retryResult.Text, synthIn, braveSources); parseErr == nil && !libkg.GraphTooThin(retryGraph) {
 				graph = retryGraph
 			}
 		}
@@ -724,7 +745,29 @@ func ensureResearchMap(
 
 	parsed, err := placement.ParseResearchMapOutput(result.Text)
 	if err != nil {
-		return app.For(code.AI).SvcThirdParty("研究地圖產生失敗，請重試：" + err.Error())
+		// Model sometimes replies with reasoning/prose and no JSON object.
+		// Retry once, explicitly demanding a raw JSON object.
+		jsonOnlyResult, retryErr := deps.AI.GenerateText(ctx, placement.ResearchGenerateRequest(domai.GenerateRequest{
+			Provider: providerID,
+			Model:    credential.Model,
+			Credential: domai.Credential{
+				APIKey: credential.APIKey,
+			},
+			System: placement.BuildResearchMapSystemPrompt(),
+			Messages: []domai.Message{
+				{Role: "user", Content: finalPrompt},
+				{Role: "assistant", Content: result.Text},
+				{Role: "user", Content: placement.ResearchMapJSONOnlyRetryPrompt()},
+			},
+		}))
+		if retryErr != nil {
+			return app.For(code.AI).SvcThirdParty("研究地圖產生失敗，請重試：" + err.Error())
+		}
+		parsed, err = placement.ParseResearchMapOutput(jsonOnlyResult.Text)
+		if err != nil {
+			return app.For(code.AI).SvcThirdParty("研究地圖產生失敗，請重試：" + err.Error())
+		}
+		result = jsonOnlyResult
 	}
 	if placement.ResearchMapTooThin(parsed) {
 		if retryResult, retryErr := deps.AI.GenerateText(ctx, placement.ResearchGenerateRequest(domai.GenerateRequest{