[Feature] Gigachat 3.5 support (#29189)

Co-authored-by: Stanislav Petrov <stapetrov@sberbank.ru>
Co-authored-by: Viacheslav Barinov <vvadbarinov@sberbank.ru>
Co-authored-by: Viacheslav <viacheslav.teh@gmail.com>
Co-authored-by: Xinyuan Tong <xinyuantong.cs@gmail.com>
Co-authored-by: Xinyuan Tong <115166877+JustinTong0323@users.noreply.github.com>

test/registered/unit/parser/test_template_manager.py

@@ -67,6 +67,22 @@ class TestTemplateManagerReasoningDetection(CustomTestCase):
         )
         return force, config, parser
 
+    def test_gigachat35_gcml_template_wins_over_generic_think_tags(self):
+        """The GCML marker must map both parsers to gigachat35; the template also
+        carries <think>, so the rule has to outrank the generic deepseek-r1
+        think-tags fallback."""
+        template = """
+        {{- 'assistant<|role_sep|>\\n<think>' -}}
+        <｜GCML｜tool_calls>
+        """
+        vocab = ["<think>", "</think>", "<|role_sep|>\n"]
+        force, config, parser = self._detect(template, vocab)
+        self.assertEqual(parser, "gigachat35")
+        self.assertEqual(
+            detect_tool_call_parser(template, _DummyTokenizer(vocab), config, force),
+            "gigachat35",
+        )
+
     def test_qwen3_template_not_misclassified_as_glm45(self):
         template = """
         {% set enable_thinking = enable_thinking if enable_thinking is defined else true %}