From 42e1589db4a5760ab9257ac5a5c8162325788d0d Mon Sep 17 00:00:00 2001
From: Mikhail Kostryukov <mike@triptrack.net>
Date: Tue, 21 Jul 2026 00:51:18 +0300
Subject: [PATCH] [Bugfix] glm47 parser: tolerate missing opening <arg_value>
 tag

Under concurrent load, GLM-4.7-family models occasionally skip the
opening <arg_value> tag when emitting tool calls, producing
<arg_key>key</arg_key>value</arg_value> with the value fully intact.
The argument regexes required the opening tag, so such calls were
silently parsed as empty arguments ({}), failing downstream tool
validation. Make the opening tag optional in both the full and
partial argument regexes; the closing </arg_value> still delimits
the value. Streaming is unaffected for well-formed output: the
incremental lexer buffers ambiguous tag prefixes, so a partially
streamed <arg_value> tag never leaks into the value.

Signed-off-by: Mikhail Kostryukov <mike@triptrack.net>
---
 .../test_glm47_moe_tool_parser.py             | 63 +++++++++++++++++++
 vllm/parser/glm47_moe.py                      |  8 ++-
 2 files changed, 69 insertions(+), 2 deletions(-)

diff --git a/tests/tool_parsers/test_glm47_moe_tool_parser.py b/tests/tool_parsers/test_glm47_moe_tool_parser.py
index dc4b726a5383..d2aa072b8111 100644
--- a/tests/tool_parsers/test_glm47_moe_tool_parser.py
+++ b/tests/tool_parsers/test_glm47_moe_tool_parser.py
@@ -163,6 +163,34 @@ def test_whitespace_preserved_in_arg_values(self, glm47_tool_parser, mock_reques
         assert r.tools_called
         assert json.loads(r.tool_calls[0].function.arguments) == {"city": "  Beijing  "}
 
+    def test_missing_arg_value_open_tag(self, glm47_tool_parser, mock_request):
+        # Under load GLM-4.7-family models occasionally skip the opening
+        # <arg_value> tag while still emitting the value and closing tag.
+        out = (
+            "<tool_call>get_weather<arg_key>city</arg_key>"
+            "Beijing</arg_value></tool_call>"
+        )
+        r = glm47_tool_parser.extract_tool_calls(out, request=mock_request)
+        assert r.tools_called
+        assert r.tool_calls[0].function.name == "get_weather"
+        assert json.loads(r.tool_calls[0].function.arguments) == {"city": "Beijing"}
+
+    def test_missing_arg_value_open_tag_multiple_args(
+        self, glm47_tool_parser, mock_request
+    ):
+        out = (
+            "<tool_call>get_weather"
+            "<arg_key>city</arg_key>Beijing</arg_value>"
+            "<arg_key>date</arg_key><arg_value>2026-07-21</arg_value>"
+            "</tool_call>"
+        )
+        r = glm47_tool_parser.extract_tool_calls(out, request=mock_request)
+        assert r.tools_called
+        assert json.loads(r.tool_calls[0].function.arguments) == {
+            "city": "Beijing",
+            "date": "2026-07-21",
+        }
+
     def test_content_before(self, glm47_tool_parser, mock_request):
         out = "Checking.<tool_call>get_current_date</tool_call>"
         r = glm47_tool_parser.extract_tool_calls(out, request=mock_request)
@@ -266,3 +294,38 @@ def test_with_args(self, glm47_tool_parser, mock_request):
         ]
         args = json.loads("".join(arguments))
         assert args["city"] == "Beijing"
+
+    def test_missing_arg_value_open_tag(self, glm47_tool_parser, mock_request):
+        _reset(glm47_tool_parser)
+        chunks = [
+            "<tool_call>",
+            "get_weather\n",
+            "<arg_key>city</arg_key>",
+            "Bei",
+            "jing",
+            "</arg_value>",
+            "</tool_call>",
+        ]
+        current_text = ""
+        deltas = []
+        for chunk in chunks:
+            current_text += chunk
+            delta = glm47_tool_parser.extract_tool_calls_streaming(
+                previous_text="",
+                current_text=current_text,
+                delta_text=chunk,
+                previous_token_ids=[],
+                current_token_ids=[],
+                delta_token_ids=[],
+                request=mock_request,
+            )
+            if delta:
+                deltas.append(delta)
+        arguments = [
+            tool_call.function.arguments
+            for delta in deltas
+            for tool_call in (delta.tool_calls or [])
+            if tool_call.function and tool_call.function.arguments
+        ]
+        args = json.loads("".join(arguments))
+        assert args["city"] == "Beijing"
diff --git a/vllm/parser/glm47_moe.py b/vllm/parser/glm47_moe.py
index 00e517f2ea68..1afabbfef312 100644
--- a/vllm/parser/glm47_moe.py
+++ b/vllm/parser/glm47_moe.py
@@ -48,14 +48,18 @@
     ("<|system|>", "<|user|>", "<|assistant|>", "<|observation|>")
 )
 
+# The opening <arg_value> tag is optional: under load GLM-4.7-family models
+# occasionally skip it, emitting
+# ``<arg_key>key</arg_key>value</arg_value>`` with the value fully intact.
+# Requiring the tag would silently drop such arguments (yielding ``{}``).
 _ARG_RE = re.compile(
     r"<arg_key>(?P<key>.*?)</arg_key>\s*"
-    r"<arg_value>(?P<value>.*?)</arg_value>",
+    r"(?:<arg_value>)?(?P<value>.*?)</arg_value>",
     re.DOTALL,
 )
 _PARTIAL_ARG_RE = re.compile(
     r"<arg_key>(?P<key>.*?)</arg_key>\s*"
-    r"<arg_value>(?P<value>.*)$",
+    r"(?:<arg_value>)?(?P<value>.*)$",
     re.DOTALL,
 )