diff --git a/apps/ai-game-creator-shell/src-tauri/src/agent/direct_tool_bridge.rs b/apps/ai-game-creator-shell/src-tauri/src/agent/direct_tool_bridge.rs
index bfff40a20..254ebd93e 100644
--- a/apps/ai-game-creator-shell/src-tauri/src/agent/direct_tool_bridge.rs
+++ b/apps/ai-game-creator-shell/src-tauri/src/agent/direct_tool_bridge.rs
@@ -4965,6 +4965,29 @@ mod tests {
         );
         assert!(!prompt_not_text.contains("不能为空"), "{prompt_not_text}");
 
+        let oversized_not_text = match resource_generation_input(&json!({
+            "kind": "video",
+            "mode": "create",
+            "prompt": vec!["需要回显但必须截断的字段内容"; 40],
+            "assetName": "开场"
+        })) {
+            Ok(_) => panic!("prompt 不是字符串时必须被拒绝"),
+            Err(error) => error.to_user_msg(),
+        };
+        assert!(
+            oversized_not_text.contains("prompt 必须是字符串"),
+            "{oversized_not_text}"
+        );
+        assert!(
+            oversized_not_text.contains('…'),
+            "超长回显必须带截断标记：{oversized_not_text}"
+        );
+        assert!(
+            oversized_not_text.chars().count() < 200,
+            "超长回显必须被截断：{}",
+            oversized_not_text.chars().count()
+        );
+
         let brief_not_text = required_text(&json!({ "brief": 5 }), PrepareGameArtTextField::Brief)
             .expect_err("brief 不是字符串时必须被拒绝")
             .to_user_msg();
diff --git a/apps/ai-game-creator-shell/src-tauri/src/agent/tool/arguments.rs b/apps/ai-game-creator-shell/src-tauri/src/agent/tool/arguments.rs
index 961fee811..8b49b1f30 100644
--- a/apps/ai-game-creator-shell/src-tauri/src/agent/tool/arguments.rs
+++ b/apps/ai-game-creator-shell/src-tauri/src/agent/tool/arguments.rs
@@ -6,6 +6,13 @@
 use serde_json::Value;
 
 use super::error::ToolPageRejection;
+use crate::agent::runtime_state::truncate_agent_runtime_text;
+
+/// 字段给了非字符串值时，回显进诊断的那个值最多保留多少字符。
+///
+/// 类型错只需要让模型看出「传进来的是什么」，不必把整个对象或数组原样带进工具结果与
+/// 诊断 sidecar；`got` 会同时出现在 `to_user_msg` 和序列化后的 `error` 里。
+const NOT_TEXT_GOT_MAX_CHARS: usize = 120;
 
 /// 一个会被边界校验的文本字段。
 pub(crate) trait ToolTextField<E>: Copy {
@@ -35,7 +42,10 @@ pub(crate) fn optional_text<F: ToolTextField<E>, E>(
         return Ok(None);
     };
     let Some(value) = value.as_str() else {
-        return Err(field.not_text(value.to_string()));
+        return Err(field.not_text(truncate_agent_runtime_text(
+            &value.to_string(),
+            NOT_TEXT_GOT_MAX_CHARS,
+        )));
     };
     let value = value.trim();
     if value.is_empty() {