diff --git a/agentrun/integration/langgraph/agent_converter.py b/agentrun/integration/langgraph/agent_converter.py
index f00a46b..8f1d069 100644
--- a/agentrun/integration/langgraph/agent_converter.py
+++ b/agentrun/integration/langgraph/agent_converter.py
@@ -30,6 +30,10 @@
 from typing import Any, Dict, Iterator, List, Optional, Union
 
 from agentrun.server.model import AgentResult, EventType
+from agentrun.utils.error_utils import (
+    build_error_event_data,
+    is_rate_limited_error,
+)
 from agentrun.utils.log import logger
 
 # 需要从工具输入中过滤掉的内部字段（LangGraph/MCP 注入的运行时对象）
@@ -952,10 +956,15 @@ def _convert_astream_events_event(
 
             yield AgentResult(
                 event=EventType.ERROR,
-                data={
-                    "message": f"LLM error: {error_message}",
-                    "code": "LLM_ERROR",
-                },
+                data=build_error_event_data(
+                    error,
+                    fallback_code="LLM_ERROR",
+                    fallback_message=(
+                        error_message
+                        if is_rate_limited_error(error)
+                        else f"LLM error: {error_message}"
+                    ),
+                ),
             )
 
         # 8. Chain 错误
diff --git a/agentrun/server/agui_protocol.py b/agentrun/server/agui_protocol.py
index 5e8ccb4..a9d6d43 100644
--- a/agentrun/server/agui_protocol.py
+++ b/agentrun/server/agui_protocol.py
@@ -53,6 +53,7 @@
 # ============================================================================
 
 DEFAULT_PREFIX = "/ag-ui/agent"
+RUN_ERROR_EXTRA_FIELDS = ("retryable", "retryAfterMs", "traceId")
 
 
 @dataclass
@@ -743,12 +744,18 @@ def _process_event_with_boundaries(
 
         # ERROR 事件
         if event.event == EventType.ERROR:
-            yield self._encoder.encode(
-                RunErrorEvent(
-                    message=event.data.get("message", ""),
-                    code=event.data.get("code"),
-                )
+            agui_event = RunErrorEvent(
+                message=event.data.get("message", ""),
+                code=event.data.get("code"),
             )
+            extra_fields = {
+                key: event.data[key]
+                for key in RUN_ERROR_EXTRA_FIELDS
+                if key in event.data
+            }
+            if extra_fields:
+                agui_event = agui_event.model_copy(update=extra_fields)
+            yield self._encoder.encode(agui_event)
             return
 
         # STATE 事件
diff --git a/agentrun/server/invoker.py b/agentrun/server/invoker.py
index 763e6a0..26f8956 100644
--- a/agentrun/server/invoker.py
+++ b/agentrun/server/invoker.py
@@ -24,6 +24,10 @@
 )
 import uuid
 
+from agentrun.utils.error_utils import (
+    build_error_event_data,
+    is_rate_limited_error,
+)
 from .model import AgentEvent, AgentRequest, EventType
 from .protocol import (
     AsyncInvokeAgentHandler,
@@ -117,10 +121,7 @@ async def invoke_stream(
                     if isinstance(item, str):
                         if not item:  # 跳过空字符串
                             continue
-                        yield AgentEvent(
-                            event=EventType.TEXT,
-                            data={"delta": item},
-                        )
+                        yield self._wrap_text(item)
 
                     elif isinstance(item, AgentEvent):
                         # 处理用户返回的事件
@@ -142,7 +143,11 @@ async def invoke_stream(
             logger.error(f"Agent 调用出错: {e}", exc_info=True)
             yield AgentEvent(
                 event=EventType.ERROR,
-                data={"message": str(e), "code": type(e).__name__},
+                data=build_error_event_data(
+                    e,
+                    fallback_code=type(e).__name__,
+                    fallback_message=str(e),
+                ),
             )
 
     def _process_user_event(
@@ -227,12 +232,7 @@ def _wrap_non_stream(self, result: Any) -> List[AgentEvent]:
             return results
 
         if isinstance(result, str):
-            results.append(
-                AgentEvent(
-                    event=EventType.TEXT,
-                    data={"delta": result},
-                )
-            )
+            results.append(self._wrap_text(result))
 
         elif isinstance(result, AgentEvent):
             # 处理可能的 TOOL_CALL 展开
@@ -243,12 +243,7 @@ def _wrap_non_stream(self, result: Any) -> List[AgentEvent]:
                 if isinstance(item, AgentEvent):
                     results.extend(self._process_user_event(item))
                 elif isinstance(item, str) and item:
-                    results.append(
-                        AgentEvent(
-                            event=EventType.TEXT,
-                            data={"delta": item},
-                        )
-                    )
+                    results.append(self._wrap_text(item))
                 else:
                     results.extend(self._wrap_model_chunk(item))
 
@@ -275,10 +270,7 @@ async def _wrap_stream(
             if isinstance(item, str):
                 if not item:
                     continue
-                yield AgentEvent(
-                    event=EventType.TEXT,
-                    data={"delta": item},
-                )
+                yield self._wrap_text(item)
 
             elif isinstance(item, AgentEvent):
                 for processed_event in self._process_user_event(item):
@@ -346,15 +338,25 @@ def _wrap_model_chunk(self, item: Any) -> List[AgentEvent]:
 
         content = self._read_attr_or_key(item, "content")
         if isinstance(content, str) and content:
-            events.append(
-                AgentEvent(
-                    event=EventType.TEXT,
-                    data={"delta": content},
-                )
-            )
+            events.append(self._wrap_text(content))
 
         return events
 
+    def _wrap_text(self, text: str) -> AgentEvent:
+        if is_rate_limited_error(text):
+            return AgentEvent(
+                event=EventType.ERROR,
+                data=build_error_event_data(
+                    text,
+                    fallback_code=type(text).__name__,
+                    fallback_message=text,
+                ),
+            )
+        return AgentEvent(
+            event=EventType.TEXT,
+            data={"delta": text},
+        )
+
     def _read_attr_or_key(self, obj: Any, key: str) -> Any:
         if isinstance(obj, dict):
             return obj.get(key)
diff --git a/agentrun/utils/error_utils.py b/agentrun/utils/error_utils.py
new file mode 100644
index 0000000..f7ebee6
--- /dev/null
+++ b/agentrun/utils/error_utils.py
@@ -0,0 +1,85 @@
+"""Small helpers for model rate-limit errors."""
+
+import re
+from typing import Any, Dict, Optional
+
+RATE_LIMITED_CODE = "RATE_LIMITED"
+RATE_LIMITED_RETRY_AFTER_MS = 2000
+_RATE_LIMIT_TEXT_RE = re.compile(
+    r"429|too[-_\s]*many[-_\s]*requests|rate[-_\s]*limit|throttl",
+    re.IGNORECASE,
+)
+_RATE_LIMIT_CODES = {
+    "ratelimitexceeded",
+    "ratelimited",
+    "throttling",
+    "toomanyrequests",
+}
+
+
+def build_error_event_data(
+    error: Any,
+    *,
+    fallback_code: str,
+    fallback_message: str,
+) -> Dict[str, Any]:
+    """Keep the original message; add rate-limit metadata only when matched."""
+    if not is_rate_limited_error(error):
+        return {"message": fallback_message, "code": fallback_code}
+
+    data: Dict[str, Any] = {
+        "message": fallback_message,
+        "code": RATE_LIMITED_CODE,
+        "retryable": True,
+        "retryAfterMs": RATE_LIMITED_RETRY_AFTER_MS,
+    }
+    trace_id = _get_value(error, "trace_id") or _get_value(error, "traceId")
+    if trace_id:
+        data["traceId"] = str(trace_id)
+    return data
+
+
+def is_rate_limited_error(error: Any) -> bool:
+    if error is None:
+        return False
+    if _status_code(error) == 429 or _status_code(_get_value(error, "response")) == 429:
+        return True
+    if _rate_limit_code(error) or _rate_limit_code(_get_value(error, "response")):
+        return True
+    return bool(_RATE_LIMIT_TEXT_RE.search(str(error)))
+
+
+def _status_code(obj: Any) -> Optional[int]:
+    for name in ("status_code", "status", "http_status", "statusCode"):
+        value = _get_value(obj, name)
+        if value is None:
+            continue
+        try:
+            return int(value)
+        except (TypeError, ValueError):
+            return None
+    return None
+
+
+def _rate_limit_code(obj: Any) -> bool:
+    for name in ("code", "error_code", "errorCode"):
+        code = _get_value(obj, name)
+        if code and _normalize_code(code) in _RATE_LIMIT_CODES:
+            return True
+    return False
+
+
+def _get_value(obj: Any, name: str) -> Optional[Any]:
+    if obj is None:
+        return None
+    if isinstance(obj, dict):
+        return obj.get(name)
+    return getattr(obj, name, None)
+
+
+def _normalize_code(code: Any) -> str:
+    value = "".join(ch for ch in str(code).lower() if ch.isalnum())
+    for suffix in ("exception", "error"):
+        if value.endswith(suffix):
+            return value[: -len(suffix)]
+    return value
diff --git a/tests/unittests/integration/test_langgraph_events.py b/tests/unittests/integration/test_langgraph_events.py
index 0e51714..7d88111 100644
--- a/tests/unittests/integration/test_langgraph_events.py
+++ b/tests/unittests/integration/test_langgraph_events.py
@@ -816,7 +816,7 @@ def test_on_llm_error(self):
             "event": "on_llm_error",
             "run_id": "run_llm",
             "data": {
-                "error": RuntimeError("API rate limit exceeded"),
+                "error": RuntimeError("Model backend failed"),
             },
         }
 
@@ -828,6 +828,25 @@ def test_on_llm_error(self):
         assert "RuntimeError" in results[0].data["message"]
         assert results[0].data["code"] == "LLM_ERROR"
 
+    def test_on_llm_error_rate_limited(self):
+        """测试 on_llm_error 限流错误归一化且 message 保留原始错误"""
+        event = {
+            "event": "on_llm_error",
+            "run_id": "run_llm",
+            "data": {
+                "error": RuntimeError("Error code: 429 - rate limit exceeded"),
+            },
+        }
+
+        results = list(AgentRunConverter().to_agui_events(event))
+
+        assert len(results) == 1
+        assert results[0].event == EventType.ERROR
+        assert results[0].data["message"] == "RuntimeError: Error code: 429 - rate limit exceeded"
+        assert results[0].data["code"] == "RATE_LIMITED"
+        assert results[0].data["retryable"] is True
+        assert results[0].data["retryAfterMs"] == 2000
+
     def test_on_chain_error(self):
         """测试 on_chain_error 事件
 
diff --git a/tests/unittests/integration/test_langgraph_to_agent_event.py b/tests/unittests/integration/test_langgraph_to_agent_event.py
index 74933d1..19bbdba 100644
--- a/tests/unittests/integration/test_langgraph_to_agent_event.py
+++ b/tests/unittests/integration/test_langgraph_to_agent_event.py
@@ -814,7 +814,7 @@ def test_on_llm_error(self):
             "event": "on_llm_error",
             "run_id": "run_llm",
             "data": {
-                "error": RuntimeError("API rate limit exceeded"),
+                "error": RuntimeError("Model backend failed"),
             },
         }
 
@@ -826,6 +826,25 @@ def test_on_llm_error(self):
         assert "RuntimeError" in results[0].data["message"]
         assert results[0].data["code"] == "LLM_ERROR"
 
+    def test_on_llm_error_rate_limited(self):
+        """测试 on_llm_error 限流错误归一化且 message 保留原始错误"""
+        event = {
+            "event": "on_llm_error",
+            "run_id": "run_llm",
+            "data": {
+                "error": RuntimeError("Error code: 429 - rate limit exceeded"),
+            },
+        }
+
+        results = list(AgentRunConverter().to_agui_events(event))
+
+        assert len(results) == 1
+        assert results[0].event == EventType.ERROR
+        assert results[0].data["message"] == "RuntimeError: Error code: 429 - rate limit exceeded"
+        assert results[0].data["code"] == "RATE_LIMITED"
+        assert results[0].data["retryable"] is True
+        assert results[0].data["retryAfterMs"] == 2000
+
     def test_on_chain_error(self):
         """测试 on_chain_error 事件
 
diff --git a/tests/unittests/server/test_agui_protocol.py b/tests/unittests/server/test_agui_protocol.py
index 0896a08..3188aab 100644
--- a/tests/unittests/server/test_agui_protocol.py
+++ b/tests/unittests/server/test_agui_protocol.py
@@ -101,6 +101,31 @@ def invoke_agent(request: AgentRequest):
 
         assert "RUN_ERROR" in types
 
+    @pytest.mark.asyncio
+    async def test_text_rate_limit_error_stream_payload(self):
+        """测试文本形式的 429 错误输出 RUN_ERROR 且无 RUN_FINISHED"""
+
+        def invoke_agent(request: AgentRequest):
+            return "Error code: 429 - rate limit exceeded"
+
+        client = self.get_client(invoke_agent)
+        response = client.post(
+            "/ag-ui/agent",
+            json={"messages": [{"role": "user", "content": "Hello"}]},
+        )
+
+        assert response.status_code == 200
+        events = _agui_sse_events(response)
+        types = [event.get("type") for event in events]
+        run_error = next(
+            event for event in events if event.get("type") == "RUN_ERROR"
+        )
+        assert "RUN_FINISHED" not in types
+        assert run_error["message"] == "Error code: 429 - rate limit exceeded"
+        assert run_error["code"] == "RATE_LIMITED"
+        assert run_error["retryable"] is True
+        assert run_error["retryAfterMs"] == 2000
+
     @pytest.mark.asyncio
     async def test_exception_in_parse_request(self):
         """测试 parse_request 中的异常处理（覆盖 155-156 行）
diff --git a/tests/unittests/server/test_error_utils.py b/tests/unittests/server/test_error_utils.py
new file mode 100644
index 0000000..0299fc1
--- /dev/null
+++ b/tests/unittests/server/test_error_utils.py
@@ -0,0 +1,36 @@
+"""Tests for model rate-limit helpers."""
+
+from agentrun.utils.error_utils import (
+    build_error_event_data,
+    is_rate_limited_error,
+)
+
+
+def test_text_429_rate_limit_is_rate_limited():
+    assert is_rate_limited_error("Error code: 429 - rate limit exceeded")
+
+
+def test_structured_status_429_is_rate_limited():
+    class RateLimitError(RuntimeError):
+        status_code = 429
+
+    assert is_rate_limited_error(RateLimitError("provider overloaded"))
+
+
+def test_non_rate_limit_text_is_not_rate_limited():
+    assert not is_rate_limited_error("normal response")
+
+
+def test_rate_limit_event_uses_original_message():
+    data = build_error_event_data(
+        "Error code: 429 - rate limit exceeded",
+        fallback_code="str",
+        fallback_message="Error code: 429 - rate limit exceeded",
+    )
+
+    assert data == {
+        "message": "Error code: 429 - rate limit exceeded",
+        "code": "RATE_LIMITED",
+        "retryable": True,
+        "retryAfterMs": 2000,
+    }
diff --git a/tests/unittests/server/test_invoker.py b/tests/unittests/server/test_invoker.py
index 76d8c65..8337db3 100644
--- a/tests/unittests/server/test_invoker.py
+++ b/tests/unittests/server/test_invoker.py
@@ -188,6 +188,26 @@ async def invoke_agent(req: AgentRequest) -> str:
         assert "Test error" in error_event.data["message"]
         assert error_event.data["code"] == "ValueError"
 
+    @pytest.mark.asyncio
+    async def test_invoke_stream_text_rate_limit_error(self, req):
+        """测试字符串形式的模型限流错误被转成 ERROR"""
+
+        async def invoke_agent(req: AgentRequest) -> str:
+            return "Error code: 429 - rate limit exceeded"
+
+        invoker = AgentInvoker(invoke_agent)
+
+        items: List[AgentEvent] = []
+        async for item in invoker.invoke_stream(req):
+            items.append(item)
+
+        assert len(items) == 1
+        assert items[0].event == EventType.ERROR
+        assert items[0].data["message"] == "Error code: 429 - rate limit exceeded"
+        assert items[0].data["code"] == "RATE_LIMITED"
+        assert items[0].data["retryable"] is True
+        assert items[0].data["retryAfterMs"] == 2000
+
 
 class TestInvokerSync:
     """同步调用测试"""