diff --git a/backend/internal/app/cloud_agent_pi_image_references.go b/backend/internal/app/cloud_agent_pi_image_references.go
new file mode 100644
index 000000000..9130dc8d2
--- /dev/null
+++ b/backend/internal/app/cloud_agent_pi_image_references.go
@@ -0,0 +1,15 @@
+package app
+
+// 独立 Agent 运行时（Pi）的模型步骤带上获准图片清单。
+//
+// canvas_inspect_image 看图后，服务端的规范历史里会多一条带 resource: 图片占位的 user 消息。
+// 旧的 Go 执行循环在发请求前调用 cloudAgentImageReferences，把这些占位对应的资源写进
+// input.referenceImages，供应商层据此读取真实图片；Pi 路径（runCloudAgentModelStep）漏了这一步，
+// 预检发现占位不在获准清单里，整轮以「模型协议引用了未获准的图片」失败。
+//
+// 这里复用同一个函数：校验资源归属与大小、按模型的图片数量上限移出多余图片，并返回清单。
+// 它会改写传入的 canonical（只影响本次请求的副本），所以必须在组装任务输入之前调用，
+// 且在 state.Canonical 已经保存完整历史之后调用。
+func (s *Service) cloudAgentPiStepImageReferences(userID string, req CloudAgentRequest, canonical *canonicalAgentRequest) ([]providerMedia, error) {
+	return s.cloudAgentImageReferences(userID, req, canonical)
+}
diff --git a/backend/internal/app/cloud_agent_pi_image_references_test.go b/backend/internal/app/cloud_agent_pi_image_references_test.go
new file mode 100644
index 000000000..670fead51
--- /dev/null
+++ b/backend/internal/app/cloud_agent_pi_image_references_test.go
@@ -0,0 +1,44 @@
+package app
+
+import "testing"
+
+// 复现：canvas_inspect_image 看图后下一次模型调用报「模型协议引用了未获准的图片」。
+func TestCloudAgentPiStepImageReferencesSatisfyPlaceholderPreflight(t *testing.T) {
+	s, _, _ := cloudAgentVisionFixture(t)
+	state := cloudAgentRuntime{Request: agentTestRequest()}
+	state.Request.VisionEnabled = true
+	call := cloudAgentStoryboardCall(t, "canvas_inspect_image", "inspect-cat", map[string]any{"nodeId": "cat"})
+	result, err := s.prepareCloudAgentImageInspection("user", "agent-canvas", &state, call)
+	if err != nil {
+		t.Fatal(err)
+	}
+	history := []map[string]any{
+		{"role": "user", "content": "参考左侧素材"},
+		{"role": "user", "content": cloudAgentImageContentParts(result.(cloudAgentImageInspection))},
+	}
+
+	// 不带清单时预检拒绝，复现修复前的失败。
+	bare := canonicalAgentRequest{ToolChoice: "auto", Messages: history}
+	if err := validateAgentResourcePlaceholders(canvasGenerationInput{Mode: "text", AgentRequests: &agentToolRequests{Canonical: &bare}}); err == nil {
+		t.Fatal("placeholder without approved references passed preflight")
+	}
+
+	canonical := canonicalAgentRequest{ToolChoice: "auto", Messages: history}
+	references, err := s.cloudAgentPiStepImageReferences("user", state.Request, &canonical)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(references) != 1 {
+		t.Fatalf("references = %#v, want the inspected image", references)
+	}
+	input := canvasGenerationInput{Mode: "text", ReferenceImages: references, AgentRequests: &agentToolRequests{Canonical: &canonical}}
+	if err := validateAgentResourcePlaceholders(input); err != nil {
+		t.Fatalf("preflight still rejects the inspected image: %v", err)
+	}
+
+	// 没有图片的历史不产生清单，也不报错。
+	plain := canonicalAgentRequest{ToolChoice: "auto", Messages: history[:1]}
+	if refs, err := s.cloudAgentPiStepImageReferences("user", state.Request, &plain); err != nil || len(refs) != 0 {
+		t.Fatalf("text-only history: refs=%#v err=%v", refs, err)
+	}
+}
diff --git a/backend/internal/app/cloud_agent_pi_model.go b/backend/internal/app/cloud_agent_pi_model.go
index f2e6b7048..177ba8035 100644
--- a/backend/internal/app/cloud_agent_pi_model.go
+++ b/backend/internal/app/cloud_agent_pi_model.go
@@ -229,6 +229,12 @@ func (s *Service) runCloudAgentModelStep(ctx context.Context, userID, runID stri
 			// 纠偏上下文只用于这一次请求，不写回运行状态，避免下一步重复出现。
 			canonical.Messages = append(append([]map[string]any(nil), canonical.Messages...), correction...)
 		}
+		// 看图后的历史里有 resource: 图片占位，必须随请求带上获准图片清单，
+		// 否则预检以「模型协议引用了未获准的图片」拒绝（见 cloud_agent_pi_image_references.go）。
+		references, refErr := s.cloudAgentPiStepImageReferences(userID, state.Request, &canonical)
+		if refErr != nil {
+			return nil, false, refErr
+		}
 		input := map[string]any{
 			"mode":          "text",
 			"prompt":        state.Request.Prompt,
@@ -244,6 +250,9 @@ func (s *Service) runCloudAgentModelStep(ctx context.Context, userID, runID stri
 				"maxOutputTokens": cloudAgentStepOutputBudget(state.StepLimits, state.BoostStepOutputBudget),
 			},
 		}
+		if len(references) > 0 {
+			input["referenceImages"] = references
+		}
 		req := CreateTaskRequest{
 			ProjectID: state.Request.CanvasID,
 			Type:      "canvas_text",