diff --git a/app/(admin)/settings/agent-workflow/agent-workflow-settings-client.tsx b/app/(admin)/settings/agent-workflow/agent-workflow-settings-client.tsx
index 28dc60e8c..42bfbaddb 100644
--- a/app/(admin)/settings/agent-workflow/agent-workflow-settings-client.tsx
+++ b/app/(admin)/settings/agent-workflow/agent-workflow-settings-client.tsx
@@ -31,6 +31,7 @@ import {
   Video,
 } from "lucide-react";
 import {
+  AGENT_WORKFLOW_PROMPT_FRAGMENT_MAX_LENGTH,
   defaultAgentWorkflowConstraintSettings,
   AGENT_WORKFLOW_MAX_OPTION_DEPTH,
   AGENT_WORKFLOW_MAX_TREE_DEPTH,
@@ -3222,9 +3223,16 @@ export function AgentWorkflowSettingsClient({
                     />
                   </div>
                   <div className="space-y-1">
-                    <Label className="text-xs">Prompt 片段</Label>
+                    <div className="flex items-center justify-between gap-2">
+                      <Label className="text-xs">Prompt 片段</Label>
+                      <span className="text-[10px] text-muted-foreground">
+                        {(option.promptFragment || "").length} /{" "}
+                        {AGENT_WORKFLOW_PROMPT_FRAGMENT_MAX_LENGTH}
+                      </span>
+                    </div>
                     <Textarea
                       value={option.promptFragment || ""}
+                      maxLength={AGENT_WORKFLOW_PROMPT_FRAGMENT_MAX_LENGTH}
                       onChange={(e) =>
                         updateOption(step.key, option.key, (currentOption) => ({
                           ...currentOption,
diff --git a/app/api/site-settings/route.ts b/app/api/site-settings/route.ts
index b5f9f5d3f..bf4bec891 100644
--- a/app/api/site-settings/route.ts
+++ b/app/api/site-settings/route.ts
@@ -32,6 +32,7 @@ import {
 } from "@/lib/agents/secondary-type-config";
 import {
   AGENT_WORKFLOW_UI_CONFIG_KEY,
+  AGENT_WORKFLOW_PROMPT_FRAGMENT_MAX_LENGTH,
   defaultAgentWorkflowUiConfig,
   normalizeAgentWorkflowUiConfig,
 } from "@/lib/agents/workflow-ui-config";
@@ -709,7 +710,12 @@ const agentWorkflowOptionSchema: z.ZodTypeAny = z.lazy(() =>
     previewImageUrl: z.string().trim().max(1000).nullable().optional(),
     enabled: z.boolean().optional(),
     sortOrder: z.number().min(0).max(999).optional(),
-    promptFragment: z.string().trim().max(1000).nullable().optional(),
+    promptFragment: z
+      .string()
+      .trim()
+      .max(AGENT_WORKFLOW_PROMPT_FRAGMENT_MAX_LENGTH)
+      .nullable()
+      .optional(),
     blockedOptionKeys: z.array(z.string().trim().min(1).max(64)).max(100).optional(),
     children: z.array(agentWorkflowOptionSchema).max(100).optional(),
   })
diff --git a/lib/agents/workflow-ui-config.ts b/lib/agents/workflow-ui-config.ts
index 9897a0130..3b6ff8ae5 100644
--- a/lib/agents/workflow-ui-config.ts
+++ b/lib/agents/workflow-ui-config.ts
@@ -14,6 +14,7 @@ import type {
 export const AGENT_WORKFLOW_UI_CONFIG_KEY = "agent_workflow_ui_config";
 export const AGENT_WORKFLOW_MAX_TREE_DEPTH = 8;
 export const AGENT_WORKFLOW_MAX_OPTION_DEPTH = 8;
+export const AGENT_WORKFLOW_PROMPT_FRAGMENT_MAX_LENGTH = 20_000;
 export const defaultAgentWorkflowCategoryLabels: AgentWorkflowCategoryLabels = {
   firstCategory: "品牌",
   secondCategory: "店铺",
@@ -855,7 +856,7 @@ export function normalizeAgentWorkflowUiConfig(value: unknown): AgentWorkflowUiC
       defaultOption?.buttonName ||
       `选项${optionIndex + 1}`;
     const promptFragment =
-      normalizeText(optionRecord.promptFragment, 1000) ||
+      normalizeText(optionRecord.promptFragment, AGENT_WORKFLOW_PROMPT_FRAGMENT_MAX_LENGTH) ||
       defaultOption?.promptFragment ||
       buttonName;
     const hasRawBlockedOptionKeys = Array.isArray(optionRecord.blockedOptionKeys);