diff --git a/lib/canvas/agent-explicit-operations.ts b/lib/canvas/agent-explicit-operations.ts
index 03c51e669..af97867d1 100644
--- a/lib/canvas/agent-explicit-operations.ts
+++ b/lib/canvas/agent-explicit-operations.ts
@@ -8,6 +8,7 @@ import {
 } from "@/lib/canvas/agent-model-planner";
 
 type ExplicitOperationKind =
+  | "add_annotation"
   | "create_agent_slot"
   | "create_text_node"
   | "rename_node"
@@ -332,6 +333,59 @@ function buildUpdateNoteOperation(params: {
   };
 }
 
+function buildAddAnnotationOperation(params: {
+  context: CanvasAgentContext;
+  projectId: string;
+  messageId: string;
+  chatId: string;
+  userText: string;
+  requestedNodeIds?: string[];
+}): CanvasAgentExplicitOperationPlan | null {
+  const text = params.userText.trim();
+  if (!/批注|标注|箭头|框选/i.test(text)) return null;
+  if (/按.*(?:批注|标注|箭头|框选).*(?:修改|编辑|改图|改主图|生成|出图|修图)/i.test(text)) {
+    return null;
+  }
+  if (hasMediaMutationIntent(text)) return null;
+
+  const annotationText = extractContentFromPatterns(
+    text,
+    [
+      /(?:添加批注|加批注|写批注|批注为|批注成|批注|添加标注|加标注|写标注|标注为|标注成|标注|箭头说明|框选说明)\s*[:：]?\s*([\s\S]+)$/i,
+      /[:：]\s*([\s\S]+)$/i,
+    ],
+    1000
+  );
+  if (!annotationText) return null;
+
+  const targetNodeIds = getTargetNodeIds({
+    context: params.context,
+    requestedNodeIds: params.requestedNodeIds,
+    allowedTypes: ["image", "video"],
+  }).slice(0, 10);
+  if (targetNodeIds.length === 0) return null;
+
+  return {
+    operationPlan: {
+      ...buildPlanBase({ ...params, operation: "add_annotation" }),
+      targetNodeIds,
+      textContent: annotationText,
+      annotations: [
+        {
+          type: "text-note",
+          text: annotationText,
+          color: "#f59e0b",
+        },
+      ],
+    },
+    reply: "已给选中图片添加批注。",
+    progressTitle: "正在添加画布批注",
+    progressMessage: "我会把批注保存到选中的图片或视频节点。",
+    completedTitle: "画布批注已添加",
+    failedTitle: "画布批注添加失败",
+  };
+}
+
 export function buildCanvasAgentExplicitOperationPlan(params: {
   context: CanvasAgentContext;
   projectId: string;
@@ -354,6 +408,7 @@ export function buildCanvasAgentExplicitOperationPlan(params: {
     buildCreateAgentSlotOperation(commonParams) ||
     buildCreateTextOperation(commonParams) ||
     buildRenameOperation(commonParams) ||
-    buildUpdateNoteOperation(commonParams)
+    buildUpdateNoteOperation(commonParams) ||
+    buildAddAnnotationOperation(commonParams)
   );
 }
diff --git a/tests/routes/canvas-chat-helpers.test.ts b/tests/routes/canvas-chat-helpers.test.ts
index 1699b4488..da3030343 100644
--- a/tests/routes/canvas-chat-helpers.test.ts
+++ b/tests/routes/canvas-chat-helpers.test.ts
@@ -1020,6 +1020,34 @@ test.describe("canvas chat pure helpers", () => {
     });
   });
 
+  test("builds deterministic annotation additions for selected media nodes only", () => {
+    const outcome = buildCanvasAgentExplicitOperationPlan({
+      context: plannerContext,
+      projectId: plannerContext.projectId || "",
+      messageId: "message-1",
+      chatId: "chat-1",
+      userText: "给选中图片加批注：这里需要重点保留产品轮廓",
+    });
+
+    expect(outcome?.operationPlan).toMatchObject({
+      operation: "add_annotation",
+      targetNodeIds: ["image-1"],
+      textContent: "这里需要重点保留产品轮廓",
+      annotations: [
+        {
+          type: "text-note",
+          text: "这里需要重点保留产品轮廓",
+          color: "#f59e0b",
+        },
+      ],
+      metadata: {
+        messageId: "message-1",
+        chatId: "chat-1",
+        planner: "deterministic",
+      },
+    });
+  });
+
   test("does not route media generation or note-driven image edits as explicit canvas operations", () => {
     expect(
       buildCanvasAgentExplicitOperationPlan({
@@ -1050,6 +1078,16 @@ test.describe("canvas chat pure helpers", () => {
         userText: "新建一个视频槽位并生成片头",
       })
     ).toBeNull();
+
+    expect(
+      buildCanvasAgentExplicitOperationPlan({
+        context: plannerContext,
+        projectId: plannerContext.projectId || "",
+        messageId: "message-1",
+        chatId: "chat-1",
+        userText: "按这张图上的批注修改",
+      })
+    ).toBeNull();
   });
 
   test("normalizes model-planned annotations to selected media nodes", () => {