diff --git a/components/canvas/CanvasChatPanel.tsx b/components/canvas/CanvasChatPanel.tsx
index d243ecf34..79fd78151 100644
--- a/components/canvas/CanvasChatPanel.tsx
+++ b/components/canvas/CanvasChatPanel.tsx
@@ -3506,6 +3506,19 @@ export function CanvasChatPanel({
     activeComposerModeRef.current = activeComposerMode;
   }, [activeComposerMode]);
 
+  useEffect(() => {
+    if (composerModeOverride !== "agent") return;
+    if (agentEnabled && hasSelectedAgentPreset) return;
+
+    activeComposerModeRef.current = computedComposerMode;
+    setComposerModeOverride(null);
+  }, [
+    agentEnabled,
+    composerModeOverride,
+    computedComposerMode,
+    hasSelectedAgentPreset,
+  ]);
+
   useEffect(() => {
     if (!selectedModelId && siteSettings) {
       const nextModelId = agentEnabled ? "auto" : firstImageModelId || firstVideoModelId || "";
@@ -7637,6 +7650,12 @@ export function CanvasChatPanel({
       textContent = `请基于当前工作流设定生成方案：${workflowContext.summaryText}`;
     }
     const effectiveComposerMode = activeComposerModeRef.current || activeComposerMode;
+    if (effectiveComposerMode === "agent" && !selectedAgentPresetId) {
+      toast.error("智能体模式缺少生图模式配置，请先选择智能体后再发送");
+      activeComposerModeRef.current = computedComposerMode;
+      setComposerModeOverride(null);
+      return;
+    }
 
     if (!textContent && hasAgentUploadSlots && selectedAgentPreset) {
       textContent = `请按「${selectedAgentPreset.name}」智能体配置顺序处理产品图1、产品图2和模特图。`;
@@ -7791,6 +7810,7 @@ export function CanvasChatPanel({
     ensureImagePointsBeforeSend,
     getSendGuard,
     clearStreamImageGenerationStateForChat,
+    computedComposerMode,
     releaseSendGuard,
     setSendGuard,
     shouldBlockDuplicateSend,
diff --git a/lib/utils.ts b/lib/utils.ts
index 685969e81..8b328c83a 100644
--- a/lib/utils.ts
+++ b/lib/utils.ts
@@ -19,8 +19,12 @@ export const fetcher = async (url: string) => {
   const response = await fetch(url);
 
   if (!response.ok) {
-    const { code, cause } = await response.json();
-    throw new ChatSDKError(code as ErrorCode, cause);
+    const { code, cause, message } = await response.json();
+    const error = new ChatSDKError(code as ErrorCode, cause);
+    if (typeof message === "string" && message.trim()) {
+      error.message = message;
+    }
+    throw error;
   }
 
   return response.json();
@@ -48,7 +52,11 @@ export async function fetchWithErrorHandlers(
       const cause = typeof payload?.cause === "string" ? payload.cause : undefined;
 
       if (code) {
-        throw new ChatSDKError(code, cause);
+        const error = new ChatSDKError(code, cause);
+        if (typeof payload?.message === "string" && payload.message.trim()) {
+          error.message = payload.message;
+        }
+        throw error;
       }
 
       const fallbackMessage =