fix: prevent canvas agent requests without preset

app/canvas/[id]/page.tsx

@@ -1983,7 +1983,7 @@ export default function CanvasEditorPage({ params }: PageProps) {
                     chatId={`canvas-${id}`} 
                     onClose={() => setIsPanelOpen(false)} 
                     onOpenFileList={() => setPanelMode('fileList')}
-                    selectedAgentPresetId={null}
+                    selectedAgentPresetId={isCanvasAgentModeEnabled ? selectedAgentPresetId : null}
                     chatScope="canvas"
                     agentEnabled={isCanvasAgentModeEnabled}
                   />

components/canvas/CanvasChatPanel.tsx

@@ -3116,8 +3116,10 @@ export function CanvasChatPanel({
   const isConversationModel = Boolean(
     currentModel && isCanvasConversationOnlyModel(currentModel)
   );
+  const hasSelectedAgentPreset = Boolean(String(selectedAgentPresetId || "").trim());
   const isAgentModel =
     agentEnabled &&
+    hasSelectedAgentPreset &&
     !isDetailGenerationMode &&
     (!selectedModelId || selectedModelId === "auto" || isConversationModel);
   const computedComposerMode = useMemo<"agent" | "image" | "video" | "detail">(() => {
@@ -3660,6 +3662,11 @@ export function CanvasChatPanel({
         if (!agentEnabled) {
           return;
         }
+        if (!hasSelectedAgentPreset) {
+          toast.error("请先选择生图模式后再使用 Agent 模式");
+          activeComposerModeRef.current = computedComposerMode;
+          return;
+        }
         const preferredAgentModelId =
           allModels.find(
             (model) =>
@@ -3721,8 +3728,10 @@ export function CanvasChatPanel({
       aiDetailGenerationEnabled,
       agentEnabled,
       allModels,
+      computedComposerMode,
       firstImageModelId,
       firstVideoModelId,
+      hasSelectedAgentPreset,
       lastConversationModelId,
       lastImageModelId,
       isCanvasConversationOnlyModel,
@@ -8176,7 +8185,9 @@ export function CanvasChatPanel({
       : 0;
   const canSend = isDetailGenerationMode
     ? detailValidationIssues.length === 0 && !isDetailGenerating
-    : hasInputOrAttachments && hasEnoughAgentUploads;
+    : hasInputOrAttachments &&
+      hasEnoughAgentUploads &&
+      (activeComposerMode !== "agent" || hasSelectedAgentPreset);
   const currentVideoImageLimit = isVideoModel
     ? getVideoImageLimit(videoParams, currentModel?.providerType, currentModel?.videoToolCapability)
     : null;