[Bugfix][Frontend] Emit non-ASCII tool-call arguments without \uXXXX escapes (#46308)

Signed-off-by: EazyReal <8047065+EazyReal@users.noreply.github.com>
Co-authored-by: EazyReal <8047065+EazyReal@users.noreply.github.com>

tests/tool_parsers/test_hunyuan_a13b_tool_parser.py

@@ -177,3 +177,15 @@ def test_hunyuan_a13b_tool_parser_streaming(model_deltas, expected_tool_calls):
         reconstructor.tool_calls[idx].id = expected_tool_calls[idx].id
 
     assert reconstructor.tool_calls == expected_tool_calls
+
+
+def test_hunyuan_a13b_tool_parser_non_ascii():
+    mock_tokenizer = MagicMock()
+    tool_parser: ToolParser = ToolParserManager.get_tool_parser("hunyuan_a13b")(
+        mock_tokenizer
+    )
+    model_output = '<tool_calls>[{"name": "get_weather", "arguments": {"city": "北京"}}]</tool_calls>'
+    _, tool_calls = run_tool_extraction(tool_parser, model_output, streaming=False)
+    args = tool_calls[0].function.arguments
+    assert "北京" in args
+    assert "\\u" not in args

tests/tool_parsers/test_seed_oss_tool_parser.py

@@ -495,3 +495,28 @@ def test_streaming_tool_calls(
         actual_args = json.loads(arguments_str)
         expected_args = json.loads(expected_tool.function.arguments)
         assert actual_args == expected_args
+
+
+def test_streaming_tool_calls_non_ascii(
+    seed_oss_tool_parser, seed_oss_tokenizer, sample_tools
+):
+    request = ChatCompletionRequest(model=MODEL, messages=[], tools=sample_tools)
+    model_output = (
+        """<seed:think>\n</seed:cot_budget_reflect>\n</seed:cot_budget_reflect>\n"""
+        """The current thinking budget is 0, so I will directly start answering the question.\n</seed:think>\n"""
+        """<seed:tool_call>\n<function=get_weather>\n"""
+        """<parameter=location>北京</parameter>\n</function>\n</seed:tool_call>"""
+    )
+
+    args = "".join(
+        tool_call.function.arguments
+        for delta_message in stream_delta_message_generator(
+            seed_oss_tool_parser, seed_oss_tokenizer, model_output, request
+        )
+        if delta_message.tool_calls
+        for tool_call in delta_message.tool_calls
+        if tool_call.function and tool_call.function.arguments is not None
+    )
+
+    assert "北京" in args
+    assert "\\u" not in args

tests/tool_parsers/test_xlam_tool_parser.py

@@ -532,3 +532,26 @@ def test_extract_tool_calls_streaming_incremental(
     parsed_args = json.loads(full_args)
     expected_args = json.loads(expected_first_tool.function.arguments)
     assert parsed_args == expected_args
+
+
+@pytest.mark.parametrize("streaming", [False, True])
+def test_extract_tool_calls_non_ascii(xlam_tool_parser, xlam_tokenizer, streaming):
+    # Use parallel tool calls so the streaming path re-serializes arguments
+    # (the ensure_ascii fix only runs when tool_count > 1).
+    model_output = """[{"name": "get_current_weather", "arguments": {"city": "北京"}}, {"name": "get_current_weather", "arguments": {"city": "上海"}}]"""  # noqa: E501
+
+    if streaming:
+        request = ChatCompletionRequest(model=MODEL, messages=[])
+        args = "".join(
+            delta.tool_calls[0].function.arguments
+            for delta in stream_delta_message_generator(
+                xlam_tool_parser, xlam_tokenizer, model_output, request
+            )
+            if delta.tool_calls and delta.tool_calls[0].function.arguments
+        )
+    else:
+        extracted = xlam_tool_parser.extract_tool_calls(model_output, request=None)  # type: ignore[arg-type]
+        args = "".join(tc.function.arguments for tc in extracted.tool_calls)
+
+    assert "北京" in args
+    assert "\\u" not in args

vllm/tool_parsers/hunyuan_a13b_tool_parser.py

@@ -144,7 +144,7 @@ class HunyuanA13BToolParser(ToolParser):
                     function=FunctionCall(
                         name=call["name"],
                         arguments=(
-                            json.dumps(call["arguments"])
+                            json.dumps(call["arguments"], ensure_ascii=False)
                             if isinstance(call["arguments"], dict)
                             else call["arguments"]
                         ),

vllm/tool_parsers/seed_oss_tool_parser.py

@@ -528,7 +528,7 @@ class SeedOssToolParser(ToolParser):
                                     '"'
                                     + self.current_param_name
                                     + '": "'
-                                    + json.dumps(param_value)[1:-1]
+                                    + json.dumps(param_value, ensure_ascii=False)[1:-1]
                                     + '"'
                                 )
                             else:
@@ -536,7 +536,7 @@ class SeedOssToolParser(ToolParser):
                                     ', "'
                                     + self.current_param_name
                                     + '": "'
-                                    + json.dumps(param_value)[1:-1]
+                                    + json.dumps(param_value, ensure_ascii=False)[1:-1]
                                     + '"'
                                 )
 
@@ -571,11 +571,11 @@ class SeedOssToolParser(ToolParser):
                     # Calculate incremental JSON
                     full_value = self.current_param_value + value_chunk
                     prev_escaped = (
-                        json.dumps(self.current_param_value)[1:-1]
+                        json.dumps(self.current_param_value, ensure_ascii=False)[1:-1]
                         if self.current_param_value
                         else ""
                     )
-                    full_escaped = json.dumps(full_value)[1:-1]
+                    full_escaped = json.dumps(full_value, ensure_ascii=False)[1:-1]
                     delta_escaped = full_escaped[len(prev_escaped) :]
 
                     self.in_param = False
@@ -606,12 +606,16 @@ class SeedOssToolParser(ToolParser):
                     if value_chunk:
                         # Stream the escaped delta
                         prev_escaped = (
-                            json.dumps(self.current_param_value)[1:-1]
+                            json.dumps(self.current_param_value, ensure_ascii=False)[
+                                1:-1
+                            ]
                             if self.current_param_value
                             else ""
                         )
                         self.current_param_value += value_chunk
-                        full_escaped = json.dumps(self.current_param_value)[1:-1]
+                        full_escaped = json.dumps(
+                            self.current_param_value, ensure_ascii=False
+                        )[1:-1]
                         delta_escaped = full_escaped[len(prev_escaped) :]
 
                         if delta_escaped:

vllm/tool_parsers/xlam_tool_parser.py

@@ -165,7 +165,7 @@ class xLAMToolParser(ToolParser):
                     function=FunctionCall(
                         name=call["name"],
                         arguments=(
-                            json.dumps(call["arguments"])
+                            json.dumps(call["arguments"], ensure_ascii=False)
                             if isinstance(call["arguments"], dict)
                             else call["arguments"]
                         ),
@@ -473,7 +473,9 @@ class xLAMToolParser(ToolParser):
                             ):
                                 current_tool = parsed_tools[current_idx]
                                 if isinstance(current_tool.get("arguments"), dict):
-                                    args_text = json.dumps(current_tool["arguments"])
+                                    args_text = json.dumps(
+                                        current_tool["arguments"], ensure_ascii=False
+                                    )
                                 else:
                                     args_text = str(current_tool.get("arguments", "{}"))
                         except (json.JSONDecodeError, KeyError, IndexError):