diff --git a/ms_agent/utils/rate_limiter.py b/ms_agent/utils/rate_limiter.py
index 3bb94ec52..20ce91d82 100644
--- a/ms_agent/utils/rate_limiter.py
+++ b/ms_agent/utils/rate_limiter.py
@@ -66,20 +66,20 @@ async def __aexit__(self, exc_type, exc_val, exc_tb):
 
     async def _wait_if_needed(self):
         """Check and wait to satisfy rate limits"""
-        now = time.time()
-
-        # 1. Check minimum request interval
-        if self._last_request_time > 0:
-            elapsed = now - self._last_request_time
-            if elapsed < self.min_request_interval:
-                wait_time = self.min_request_interval - elapsed
-                logger.debug(
-                    f'Enforcing min interval: waiting {wait_time:.3f}s')
-                await asyncio.sleep(wait_time)
-                now = time.time()
-
-        # 2. Check requests per second limit
         async with self._lock:
+            now = time.time()
+
+            # 1. Check minimum request interval
+            if self._last_request_time > 0:
+                elapsed = now - self._last_request_time
+                if elapsed < self.min_request_interval:
+                    wait_time = self.min_request_interval - elapsed
+                    logger.debug(
+                        f'Enforcing min interval: waiting {wait_time:.3f}s')
+                    await asyncio.sleep(wait_time)
+                    now = time.time()
+
+            # 2. Check requests per second limit
             # Clean up expired request records (older than 1 second)
             cutoff_time = now - 1.0
             while self._request_times and self._request_times[0] < cutoff_time:
diff --git a/tests/utils/test_rate_limiter_pacing.py b/tests/utils/test_rate_limiter_pacing.py
new file mode 100644
index 000000000..bac027611
--- /dev/null
+++ b/tests/utils/test_rate_limiter_pacing.py
@@ -0,0 +1,75 @@
+# Copyright (c) ModelScope Contributors. All rights reserved.
+"""Concurrent callers must observe the same request-start spacing."""
+import asyncio
+import time
+
+import pytest
+from ms_agent.utils.rate_limiter import RateLimiter
+
+
+@pytest.mark.parametrize('max_concurrent', [1, 4])
+def test_minimum_interval_between_concurrent_requests(max_concurrent):
+    async def run():
+        limiter = RateLimiter(
+            max_requests_per_second=100,
+            min_request_interval=0.05,
+            max_concurrent=max_concurrent,
+        )
+        starts = []
+
+        async def request():
+            async with limiter:
+                starts.append(time.monotonic())
+
+        await asyncio.wait_for(
+            asyncio.gather(*(request() for _ in range(4))), timeout=3)
+        gaps = [later - earlier for earlier, later in zip(starts, starts[1:])]
+        assert all(gap >= 0.045 for gap in gaps), gaps
+
+    asyncio.run(run())
+
+
+def test_spacing_does_not_serialize_request_bodies():
+    async def run():
+        limiter = RateLimiter(
+            max_requests_per_second=100,
+            min_request_interval=0.05,
+            max_concurrent=3,
+        )
+        starts = []
+        all_entered = asyncio.Event()
+
+        async def request():
+            async with limiter:
+                starts.append(time.monotonic())
+                if len(starts) == 3:
+                    all_entered.set()
+                await all_entered.wait()
+
+        await asyncio.wait_for(
+            asyncio.gather(*(request() for _ in range(3))), timeout=3)
+        gaps = [later - earlier for earlier, later in zip(starts, starts[1:])]
+        assert all(gap >= 0.045 for gap in gaps), gaps
+
+    asyncio.run(run())
+
+
+def test_requests_per_second_still_limits_concurrent_requests():
+    async def run():
+        limiter = RateLimiter(
+            max_requests_per_second=2,
+            min_request_interval=0.05,
+            max_concurrent=3,
+        )
+        starts = []
+
+        async def request():
+            async with limiter:
+                starts.append(time.monotonic())
+
+        await asyncio.wait_for(
+            asyncio.gather(*(request() for _ in range(3))), timeout=3)
+        assert starts[1] - starts[0] >= 0.045
+        assert starts[2] - starts[0] >= 1.0
+
+    asyncio.run(run())