fix(frontend): bound stop strings and regex patterns (#37029)

test/registered/unit/sampling/test_sampling_params.py

@@ -14,6 +14,9 @@ import msgspec
 
 from sglang.srt.sampling.sampling_params import (
     MAX_LEN,
+    MAX_STOP_COUNT,
+    MAX_STOP_REGEX_COUNT,
+    MAX_STOP_REGEX_LEN,
     TOP_K_ALL,
     SamplingParams,
     get_max_seq_length,
@@ -344,6 +347,17 @@ class TestSamplingParamsNormalize(CustomTestCase):
         sp.normalize(tokenizer=tokenizer)
         self.assertEqual(sp.stop_strs, ["stop1", "stop2"])
 
+    def test_stop_count_limit(self):
+        tokenizer = self._mock_tokenizer()
+        SamplingParams(stop=["x"] * MAX_STOP_COUNT).normalize(tokenizer)
+
+        with self.assertRaises(ValueError) as cm:
+            SamplingParams(stop=["x"] * (MAX_STOP_COUNT + 1)).normalize(tokenizer)
+        self.assertEqual(
+            str(cm.exception),
+            f"at most {MAX_STOP_COUNT} stop strings are allowed, got {MAX_STOP_COUNT + 1}",
+        )
+
     def test_stop_str_max_len_uses_encoded_length(self):
         """Test that max_len is based on encoded token count, not character count."""
         # "ab" encodes to 1 token, "cdef" encodes to 2 tokens
@@ -385,6 +399,33 @@ class TestSamplingParamsNormalize(CustomTestCase):
         sp.normalize(tokenizer=tokenizer)
         self.assertEqual(sp.stop_regex_max_len, 3)
 
+    def test_stop_regex_count_limit(self):
+        tokenizer = self._mock_tokenizer()
+        SamplingParams(stop_regex=["x"] * MAX_STOP_REGEX_COUNT).normalize(tokenizer)
+
+        with self.assertRaises(ValueError) as cm:
+            SamplingParams(stop_regex=["x"] * (MAX_STOP_REGEX_COUNT + 1)).normalize(
+                tokenizer
+            )
+        self.assertEqual(
+            str(cm.exception),
+            f"at most {MAX_STOP_REGEX_COUNT} stop_regex patterns are allowed, "
+            f"got {MAX_STOP_REGEX_COUNT + 1}",
+        )
+
+    def test_stop_regex_byte_length_limit(self):
+        tokenizer = self._mock_tokenizer()
+        pattern = "é" * (MAX_STOP_REGEX_LEN // 2)
+        SamplingParams(stop_regex=pattern).normalize(tokenizer)
+
+        with self.assertRaises(ValueError) as cm:
+            SamplingParams(stop_regex=pattern + "a").normalize(tokenizer)
+        self.assertEqual(
+            str(cm.exception),
+            f"stop_regex is {MAX_STOP_REGEX_LEN + 1} bytes, over the "
+            f"{MAX_STOP_REGEX_LEN}-byte limit",
+        )
+
 
 class TestSamplingParamsMsgspecStruct(CustomTestCase):