fix: tool-call-parser validation when using SGLang tokenizer

Signed-off-by: Krishnan Prashanth <[email protected]>

Author: KrishnanPrash

components/src/dynamo/sglang/args.py

@@ -45,14 +45,12 @@
         "flags": ["--dyn-tool-call-parser"],
         "type": str,
         "default": None,
-        "choices": get_tool_parser_names(),
         "help": "Tool call parser name for the model.",
     },
     "reasoning-parser": {
         "flags": ["--dyn-reasoning-parser"],
         "type": str,
         "default": None,
-        "choices": get_reasoning_parser_names(),
         "help": "Reasoning parser name for the model. If not specified, no reasoning parsing is performed.",
     },
     "custom-jinja-template": {
@@ -228,30 +226,14 @@ def _set_parser(
 
     Returns:
         Resolved parser name, preferring Dynamo's value if both set.
-
-    Raises:
-        ValueError: If parser name is not valid.
     """
-    # If both are present, give preference to dynamo_str
     if sglang_str is not None and dynamo_str is not None:
         logging.warning(
             f"--dyn-{arg_name} and --{arg_name} are both set. Giving preference to --dyn-{arg_name}"
         )
         return dynamo_str
-    # If dynamo_str is not set, use try to use sglang_str if it matches with the allowed parsers
     elif sglang_str is not None:
         logging.warning(f"--dyn-{arg_name} is not set. Using --{arg_name}.")
-        if arg_name == "tool-call-parser" and sglang_str not in get_tool_parser_names():
-            raise ValueError(
-                f"--{arg_name} is not a valid tool call parser. Valid parsers are: {get_tool_parser_names()}"
-            )
-        elif (
-            arg_name == "reasoning-parser"
-            and sglang_str not in get_reasoning_parser_names()
-        ):
-            raise ValueError(
-                f"--{arg_name} is not a valid reasoning parser. Valid parsers are: {get_reasoning_parser_names()}"
-            )
         return sglang_str
     else:
         return dynamo_str
@@ -482,6 +464,23 @@ async def parse_args(args: list[str]) -> Config:
         "reasoning-parser",
     )
 
+    # Validate parser names when using Dynamo's tokenizer (not SGLang's)
+    if not parsed_args.use_sglang_tokenizer:
+        if tool_call_parser and tool_call_parser not in get_tool_parser_names():
+            logging.error(
+                f"Tool call parser '{tool_call_parser}' is not valid when using Dynamo's tokenizer. "
+                f"Valid parsers are: {get_tool_parser_names()}. "
+                f"Use --use-sglang-tokenizer to delegate tool parsing to SGLang."
+            )
+            sys.exit(1)
+        if reasoning_parser and reasoning_parser not in get_reasoning_parser_names():
+            logging.error(
+                f"Reasoning parser '{reasoning_parser}' is not valid when using Dynamo's tokenizer. "
+                f"Valid parsers are: {get_reasoning_parser_names()}. "
+                f"Use --use-sglang-tokenizer to delegate reasoning parsing to SGLang."
+            )
+            sys.exit(1)
+
     if parsed_args.custom_jinja_template and parsed_args.use_sglang_tokenizer:
         logging.error(
             "Cannot use --custom-jinja-template and --use-sglang-tokenizer together. "

components/src/dynamo/sglang/tests/test_sglang_unit.py

@@ -75,3 +75,49 @@ async def test_custom_jinja_template_env_var_expansion(monkeypatch, mock_sglang_
         f"Expected custom_jinja_template value to be {JINJA_TEMPLATE_PATH}, "
         f"got {config.dynamo_args.custom_jinja_template}"
     )
+
+
+# --- Tool Call Parser Validation Tests ---
+
+
+@pytest.mark.asyncio
+async def test_tool_call_parser_valid_with_dynamo_tokenizer(mock_sglang_cli):
+    """Valid parser name works when using Dynamo's tokenizer."""
+    mock_sglang_cli(
+        "--model",
+        "Qwen/Qwen3-0.6B",
+        "--dyn-tool-call-parser",
+        "hermes",  # supported by Dynamo
+    )
+
+    config = await parse_args(sys.argv[1:])
+
+    assert config.dynamo_args.tool_call_parser == "hermes"
+
+
+@pytest.mark.asyncio
+async def test_tool_call_parser_invalid_with_dynamo_tokenizer(mock_sglang_cli):
+    """Invalid parser name exits when using Dynamo's tokenizer."""
+    mock_sglang_cli(
+        "--model", "Qwen/Qwen3-0.6B", "--dyn-tool-call-parser", "nonexistent_parser"
+    )
+
+    with pytest.raises(SystemExit):
+        await parse_args(sys.argv[1:])
+
+
+@pytest.mark.asyncio
+async def test_tool_call_parser_invalid_with_sglang_tokenizer(mock_sglang_cli):
+    """Invalid Dynamo parser name is allowed when using SGLang's tokenizer."""
+    mock_sglang_cli(
+        "--model",
+        "Qwen/Qwen3-0.6B",
+        "--dyn-tool-call-parser",
+        "sglang_only_parser",
+        "--use-sglang-tokenizer",
+    )
+
+    config = await parse_args(sys.argv[1:])
+
+    assert config.dynamo_args.tool_call_parser == "sglang_only_parser"
+    assert config.dynamo_args.use_sglang_tokenizer is True