[Responses API] Sanitize leaked Harmony control tokens in tool names and recipients

tests/entrypoints/openai/parser/test_harmony_utils.py

@@ -8,10 +8,13 @@
 from vllm.entrypoints.openai.parser.harmony_utils import (
     auto_drop_analysis_messages,
     get_encoding,
+    get_streamable_parser_for_assistant,
     get_system_message,
     has_custom_tools,
     parse_chat_input_to_harmony_message,
     parse_chat_output,
+    sanitize_harmony_name,
+    sanitize_harmony_recipient,
 )
 from vllm.entrypoints.openai.responses.harmony import (
     response_previous_input_to_harmony,
@@ -841,3 +844,191 @@ def test_all_standard_channels_present(self) -> None:
                 assert channel in valid_channels, (
                     f"{channel} missing when with_custom_tools={with_tools}"
                 )
+
+
+class TestSanitizeHarmonyName:
+    """Tests for sanitize_harmony_name()."""
+
+    def test_clean_name_unchanged(self) -> None:
+        assert sanitize_harmony_name("get_weather") == "get_weather"
+
+    def test_strip_channel_token(self) -> None:
+        assert (
+            sanitize_harmony_name("manage_cart<|channel|>commentary") == "manage_cart"
+        )
+
+    def test_strip_constrain_token(self) -> None:
+        assert sanitize_harmony_name("<|constrain|>json") == ""
+
+    def test_pure_control_token_returns_empty(self) -> None:
+        assert sanitize_harmony_name("<|start|>") == ""
+
+    def test_multiple_tokens_earliest_wins(self) -> None:
+        assert sanitize_harmony_name("foo<|channel|>bar<|constrain|>baz") == "foo"
+
+    def test_empty_string(self) -> None:
+        assert sanitize_harmony_name("") == ""
+
+    def test_trailing_whitespace_stripped(self) -> None:
+        assert sanitize_harmony_name("tool_name  <|end|>") == "tool_name"
+
+
+class TestSanitizeHarmonyRecipient:
+    """Tests for sanitize_harmony_recipient()."""
+
+    def test_clean_dotted_name_unchanged(self) -> None:
+        assert sanitize_harmony_recipient("browser.search") == "browser.search"
+
+    def test_clean_simple_name_unchanged(self) -> None:
+        assert sanitize_harmony_recipient("python") == "python"
+
+    def test_contaminated_first_part_preserved_structure(self) -> None:
+        """browser<|channel|>.search → browser.search"""
+        assert (
+            sanitize_harmony_recipient("browser<|channel|>.search") == "browser.search"
+        )
+
+    def test_contaminated_second_part(self) -> None:
+        """browser.search<|end|>garbage → browser.search"""
+        assert (
+            sanitize_harmony_recipient("browser.search<|end|>garbage")
+            == "browser.search"
+        )
+
+    def test_pure_control_token_returns_empty(self) -> None:
+        assert sanitize_harmony_recipient("<|constrain|>json") == ""
+
+    def test_functions_dotted_contaminated(self) -> None:
+        """functions.get_weather<|channel|>commentary → functions.get_weather"""
+        assert (
+            sanitize_harmony_recipient("functions.get_weather<|channel|>commentary")
+            == "functions.get_weather"
+        )
+
+    def test_empty_string(self) -> None:
+        assert sanitize_harmony_recipient("") == ""
+
+    def test_container_dotted_contaminated(self) -> None:
+        """container<|channel|>.exec → container.exec"""
+        assert (
+            sanitize_harmony_recipient("container<|channel|>.exec") == "container.exec"
+        )
+
+
+class TestResilientStreamableParser:
+    """Tests for ResilientStreamableParser error recovery."""
+
+    def test_normal_sequence_unchanged(self) -> None:
+        """Normal token sequence should produce same results as raw parser."""
+        encoding = get_encoding()
+        harmony_str = "<|channel|>final<|message|>Hello world<|end|>"
+        token_ids = encoding.encode(harmony_str, allowed_special="all")
+
+        parser = get_streamable_parser_for_assistant()
+        for tok in token_ids:
+            parser.process(tok)
+
+        assert len(parser.messages) == 1
+        assert parser.messages[0].content[0].text == "Hello world"
+        assert parser.messages[0].channel == "final"
+
+    def test_missing_start_recovery(self) -> None:
+        """Parser should recover when <|start|> is missing between messages."""
+        encoding = get_encoding()
+        # First message completes normally, second is missing <|start|>
+        first_msg = "<|channel|>final<|message|>First.<|end|>"
+        second_msg = "<|channel|>final<|message|>Second.<|end|>"
+        first_tokens = encoding.encode(first_msg, allowed_special="all")
+        second_tokens = encoding.encode(second_msg, allowed_special="all")
+
+        parser = get_streamable_parser_for_assistant()
+        for tok in first_tokens:
+            parser.process(tok)
+        # Feed second message tokens directly (missing <|start|>assistant)
+        for tok in second_tokens:
+            parser.process(tok)
+
+        assert len(parser.messages) == 2
+        assert parser.messages[0].content[0].text == "First."
+        assert parser.messages[1].content[0].text == "Second."
+
+    def test_constrain_in_header_skipped(self) -> None:
+        """<|constrain|> in HEADER state should be skipped gracefully."""
+        encoding = get_encoding()
+        # First, complete a normal message so parser goes to EXPECT_START
+        first_msg = "<|channel|>final<|message|>First.<|end|>"
+        first_tokens = encoding.encode(first_msg, allowed_special="all")
+
+        # Build a second message where <|constrain|> appears in the header
+        # after <|start|>assistant, before <|channel|>
+        start_tok = encoding.encode("<|start|>", allowed_special="all")
+        role_toks = encoding.encode("assistant", allowed_special="all")
+        constrain_tok = encoding.encode("<|constrain|>", allowed_special="all")
+        # Garbage tokens that should be skipped
+        json_toks = encoding.encode("json", allowed_special="all")
+        message_tok = encoding.encode("<|message|>", allowed_special="all")
+        text_toks = encoding.encode("Second.", allowed_special="all")
+        end_tok = encoding.encode("<|end|>", allowed_special="all")
+
+        parser = get_streamable_parser_for_assistant()
+        # Complete first message
+        for tok in first_tokens:
+            parser.process(tok)
+        assert len(parser.messages) == 1
+
+        # Feed: <|start|>assistant → puts parser in HEADER state
+        for tok in start_tok:
+            parser.process(tok)
+        for tok in role_toks:
+            parser.process(tok)
+        # Feed: <|constrain|> → should enter skip mode
+        for tok in constrain_tok:
+            parser.process(tok)
+        # Feed: json tokens → should be discarded in skip mode
+        for tok in json_toks:
+            parser.process(tok)
+        # Feed: <|message|> → should exit skip mode and resume
+        for tok in message_tok:
+            parser.process(tok)
+        # Feed: text + <|end|>
+        for tok in text_toks:
+            parser.process(tok)
+        for tok in end_tok:
+            parser.process(tok)
+
+        # Should have produced two messages despite the malformed sequence
+        assert len(parser.messages) == 2
+        assert parser.messages[0].content[0].text == "First."
+
+    def test_messages_recipients_sanitized(self) -> None:
+        """Messages returned by .messages should have sanitized recipients,
+        preventing contaminated history in multi-turn interactions."""
+        encoding = get_encoding()
+        # Build a tool call message with a contaminated recipient
+        harmony_str = (
+            "<|channel|>commentary"
+            "<|message|>Let me search.<|end|>"
+            "<|start|>assistant to=functions.get_weather<|channel|>commentary"
+            '<|constrain|>json<|message|>{"loc": "SF"}<|end|>'
+        )
+        token_ids = encoding.encode(harmony_str, allowed_special="all")
+
+        parser = get_streamable_parser_for_assistant()
+        for tok in token_ids:
+            parser.process(tok)
+
+        msgs = parser.messages
+        # All recipients should be clean (no control tokens)
+        for msg in msgs:
+            if msg.recipient is not None:
+                for tok_str in (
+                    "<|channel|>",
+                    "<|constrain|>",
+                    "<|start|>",
+                    "<|end|>",
+                    "<|message|>",
+                ):
+                    assert tok_str not in msg.recipient, (
+                        f"Leaked control token {tok_str!r} "
+                        f"in message recipient: {msg.recipient!r}"
+                    )

tests/entrypoints/openai/responses/test_harmony_utils.py

@@ -461,3 +461,34 @@ def test_parser_state_to_response_output_analysis_channel() -> None:
     assert len(builtin_items) == 1
     assert not isinstance(builtin_items[0], McpCall)
     assert builtin_items[0].type == "reasoning"
+
+
+class TestHarmonyOutputSanitization:
+    """Tests that leaked Harmony control tokens are sanitized in output."""
+
+    def test_constrain_recipient_treated_as_no_recipient(self):
+        """<|constrain|>json as recipient should be sanitized to empty,
+        falling through to _parse_message_no_recipient (produces message)."""
+        message = Message.from_role_and_content(Role.ASSISTANT, "Some output text")
+        message = message.with_channel("commentary")
+        message = message.with_recipient("<|constrain|>json")
+
+        output_items = harmony_to_response_output(message)
+
+        # Should produce a message (preamble), not an MCP call
+        assert len(output_items) == 1
+        assert isinstance(output_items[0], ResponseOutputMessage)
+        assert output_items[0].type == "message"
+
+    def test_contaminated_tool_name_cleaned_in_function_call(self):
+        """Function name with leaked <|channel|> should be sanitized."""
+        message = Message.from_role_and_content(Role.ASSISTANT, '{"location": "SF"}')
+        message = message.with_channel("commentary")
+        message = message.with_recipient("functions.get_weather<|channel|>commentary")
+
+        output_items = harmony_to_response_output(message)
+
+        assert len(output_items) == 1
+        assert isinstance(output_items[0], ResponseFunctionToolCall)
+        assert output_items[0].name == "get_weather"
+        assert "<|" not in output_items[0].name

vllm/entrypoints/openai/chat_completion/stream_harmony.py

@@ -17,6 +17,7 @@
     DeltaMessage,
     DeltaToolCall,
 )
+from vllm.entrypoints.openai.parser.harmony_utils import sanitize_harmony_name
 
 
 class TokenState(NamedTuple):
@@ -109,7 +110,9 @@ def extract_harmony_streaming_delta(
             opened_new_call = False
             if prev_recipient != group.recipient:
                 # New tool call - emit the opening message
-                tool_name = group.recipient.split("functions.", 1)[1]
+                tool_name = sanitize_harmony_name(
+                    group.recipient.split("functions.", 1)[1]
+                )
                 tool_messages.append(
                     DeltaToolCall(
                         id=make_tool_call_id(),