diff --git a/tier2/gen-worker/service/bootstrap.py b/tier2/gen-worker/service/bootstrap.py
index 3ec6b804..b0c7fbfe 100644
--- a/tier2/gen-worker/service/bootstrap.py
+++ b/tier2/gen-worker/service/bootstrap.py
@@ -48,6 +48,17 @@ WRITER_KICK_TEXT = (
 )
 
 
+def _user_input(text: str) -> dict[str, Any]:
+    """组装 POST /chat/ 的 input(一条 user Msg)。
+
+    ChatRequest.input 是 agentscope.message.Msg;Msg.content 必须是【内容块列表】而非裸字符串
+    (2026-06-24 活服务 smoke 实证:发裸字符串 content 返 422「Input should be a valid list」——
+    Python 端 UserMsg(content=str) 的字符串自动包块只发生在构造器内,经 REST 传 JSON 不走那条,
+    故须显式发 [TextBlock])。TextBlock JSON 形状 = {type:"text", text:...}(源码 message/_block.py:11)。
+    """
+    return {"name": "user", "role": "user", "content": [{"type": "text", "text": text}]}
+
+
 def _resolve_m3_credential_payload(model_name: str = "MiniMax-M3") -> dict[str, Any]:
     """组装注册 M3 凭据(POST /credential/)的请求体——base_url/key 经 worker.client 解析,绝不硬编码。
 
@@ -163,7 +174,7 @@ async def start_new_game(
         chat_body = {
             "agent_id": agent_id,
             "session_id": session_id,
-            "input": {"name": "user", "role": "user", "content": WRITER_KICK_TEXT},
+            "input": _user_input(WRITER_KICK_TEXT),
         }
         chat = await _post(http, base_url, "/chat/", chat_body, user_header=user_id)
 
@@ -197,7 +208,7 @@ async def resume_session(
     chat_body = {
         "agent_id": agent_id,
         "session_id": session_id,
-        "input": {"name": "user", "role": "user", "content": text},
+        "input": _user_input(text),
     }
     async with httpx.AsyncClient() as http:
         chat = await _post(http, base_url, "/chat/", chat_body, user_header=user_id)
@@ -259,7 +270,7 @@ async def iterate_existing_project(
         chat_body = {
             "agent_id": agent_id,
             "session_id": session_id,
-            "input": {"name": "user", "role": "user", "content": text},
+            "input": _user_input(text),
         }
         chat = await _post(http, base_url, "/chat/", chat_body, user_header=user_id)