[Bugfix] Fix Gemma4 streaming tool call corruption for split boolean/number values (#39114)

Signed-off-by: sfeng33 <4florafeng@gmail.com>

tests/tool_parsers/test_gemma4_tool_parser.py

@@ -491,6 +491,51 @@ class TestStreamingExtraction:
             assert parsed_args["count"] == 42
             assert parsed_args["active"] is True
 
+    def test_streaming_boolean_split_across_chunks(self, parser, mock_request):
+        """Boolean value split across token boundaries must not corrupt JSON."""
+        chunks = [
+            "<|tool_call>",
+            "call:search{input:{all:" + "true"[:3],
+            "e}}",
+            "<tool_call|>",
+        ]
+
+        results = self._simulate_streaming(parser, mock_request, chunks)
+        args_text = self._collect_arguments(results)
+        assert args_text, "No arguments were streamed"
+        parsed_args = json.loads(args_text)
+        assert parsed_args["input"]["all"] is True
+
+    def test_streaming_false_split_across_chunks(self, parser, mock_request):
+        """Boolean false split across chunks."""
+        chunks = [
+            "<|tool_call>",
+            "call:set{flag:" + "false"[:4],
+            "e}",
+            "<tool_call|>",
+        ]
+
+        results = self._simulate_streaming(parser, mock_request, chunks)
+        args_text = self._collect_arguments(results)
+        assert args_text, "No arguments were streamed"
+        parsed_args = json.loads(args_text)
+        assert parsed_args["flag"] is False
+
+    def test_streaming_number_split_across_chunks(self, parser, mock_request):
+        """Number split across chunks must not change type."""
+        chunks = [
+            "<|tool_call>",
+            "call:set{count:4",
+            "2}",
+            "<tool_call|>",
+        ]
+
+        results = self._simulate_streaming(parser, mock_request, chunks)
+        args_text = self._collect_arguments(results)
+        assert args_text, "No arguments were streamed"
+        parsed_args = json.loads(args_text)
+        assert parsed_args["count"] == 42
+
     def test_streaming_empty_args(self, parser, mock_request):
         """Tool call with no arguments."""
         chunks = [

vllm/tool_parsers/gemma4_tool_parser.py

@@ -78,7 +78,7 @@ def _parse_gemma4_value(value_str: str) -> object:
     return value_str
 
 
-def _parse_gemma4_args(args_str: str) -> dict:
+def _parse_gemma4_args(args_str: str, *, partial: bool = False) -> dict:
     """Parse Gemma4's custom key:value format into a Python dict.
 
     Format examples::
@@ -89,6 +89,12 @@ def _parse_gemma4_args(args_str: str) -> dict:
         nested:{inner_key:<|"|>val<|"|>}
         items:[<|"|>a<|"|>,<|"|>b<|"|>]
 
+    Args:
+        args_str: The raw Gemma4 argument string.
+        partial: When True (streaming), bare values at end of string are
+            omitted because they may be incomplete and type-unstable
+            (e.g. partial boolean parsed as bare string).
+
     Returns a dict ready for ``json.dumps()``.
     """
     if not args_str or not args_str.strip():
@@ -155,7 +161,12 @@ def _parse_gemma4_args(args_str: str) -> dict:
                 elif args_str[i] == "}":
                     depth -= 1
                 i += 1
-            result[key] = _parse_gemma4_args(args_str[obj_start : i - 1])
+            if depth > 0:
+                # Incomplete nested object — use i (not i-1) to avoid
+                # dropping the last char, and recurse as partial.
+                result[key] = _parse_gemma4_args(args_str[obj_start:i], partial=True)
+            else:
+                result[key] = _parse_gemma4_args(args_str[obj_start : i - 1])
 
         # Array: [...]
         elif args_str[i] == "[":
@@ -173,20 +184,26 @@ def _parse_gemma4_args(args_str: str) -> dict:
                 elif args_str[i] == "]":
                     depth -= 1
                 i += 1
-            arr_content = args_str[arr_start : i - 1]
-            result[key] = _parse_gemma4_array(arr_content)
+            if depth > 0:
+                result[key] = _parse_gemma4_array(args_str[arr_start:i], partial=True)
+            else:
+                result[key] = _parse_gemma4_array(args_str[arr_start : i - 1])
 
         # Bare value (number, boolean, etc.)
         else:
             val_start = i
             while i < n and args_str[i] not in (",", "}", "]"):
                 i += 1
+            if partial and i >= n:
+                # Value may be incomplete (e.g. partial boolean) —
+                # withhold to avoid type instability during streaming.
+                break
             result[key] = _parse_gemma4_value(args_str[val_start:i])
 
     return result
 
 
-def _parse_gemma4_array(arr_str: str) -> list:
+def _parse_gemma4_array(arr_str: str, *, partial: bool = False) -> list:
     """Parse a Gemma4 array content string into a Python list."""
     items: list = []
     i = 0
@@ -224,7 +241,10 @@ def _parse_gemma4_array(arr_str: str) -> list:
                 elif arr_str[i] == "}":
                     depth -= 1
                 i += 1
-            items.append(_parse_gemma4_args(arr_str[obj_start : i - 1]))
+            if depth > 0:
+                items.append(_parse_gemma4_args(arr_str[obj_start:i], partial=True))
+            else:
+                items.append(_parse_gemma4_args(arr_str[obj_start : i - 1]))
 
         # Nested array
         elif arr_str[i] == "[":
@@ -237,13 +257,18 @@ def _parse_gemma4_array(arr_str: str) -> list:
                 elif arr_str[i] == "]":
                     depth -= 1
                 i += 1
-            items.append(_parse_gemma4_array(arr_str[sub_start : i - 1]))
+            if depth > 0:
+                items.append(_parse_gemma4_array(arr_str[sub_start:i], partial=True))
+            else:
+                items.append(_parse_gemma4_array(arr_str[sub_start : i - 1]))
 
         # Bare value
         else:
             val_start = i
             while i < n and arr_str[i] not in (",", "]"):
                 i += 1
+            if partial and i >= n:
+                break
             items.append(_parse_gemma4_value(arr_str[val_start:i]))
 
     return items
@@ -663,7 +688,7 @@ class Gemma4ToolParser(ToolParser):
             DeltaMessage with the argument diff, or None if no new content.
         """
         try:
-            current_args = _parse_gemma4_args(raw_args_str)
+            current_args = _parse_gemma4_args(raw_args_str, partial=True)
         except Exception:
             logger.debug(
                 "Could not parse partial Gemma4 args yet: %s",