fix(agents): pair null call IDs with empty result IDs (#7837)

* fix(agents): pair null call IDs with empty result IDs

* fix(agents): treat producer sentinel IDs as absent when pairing

Middleware producers spell a missing provider ID three ways: "" is canonical,
str(tool_call.get("id", "")) yields "None" once the key is present with a
null value, and the artifact/deferred/knowledge middlewares fall back to
"missing_tool_call_id". Only "" reached the pairing pass, so a result carrying
either sentinel was dropped as an orphan and the middleware's guidance was
replaced by the interrupted placeholder — the exact outcome this PR set out to
avoid, just through a different spelling.

Route every absent spelling through one canonicalisation used by the pairing
gate, the candidate comparison and the turn-completeness count.

---------

Co-authored-by: huyengiang101086-spec <270684046+huyengiang101086-spec@users.noreply.github.com>
Co-authored-by: Willem Jiang <willem.jiang@gmail.com>

README.md

@@ -224,6 +224,10 @@ For Google's official Gemini OpenAI-compatible endpoint, use the
 
 For MindIE XML tool calls, see the
 [argument parsing and newline compatibility guide](backend/docs/CONFIGURATION.md#mindie-xml-tool-arguments).
+Tool-result recovery treats null and empty call IDs alike — including the
+`"None"` and `"missing_tool_call_id"` spellings middleware producers use when a
+provider call had no ID — preserving middleware guidance when a result can be
+uniquely paired; ambiguous partial results remain rejected.
 Both synchronous and asynchronous streams retain this compatibility: tool-enabled
 streams simulate chunks from a non-streaming response, while no-tool streams stay native.
 Newline compatibility preserves literal escapes inside backtick and tilde code

backend/packages/harness/deerflow/agents/middlewares/dangling_tool_call_middleware.py

@@ -39,6 +39,28 @@ _UNKNOWN_TOOL_NAME = "unknown_tool"
 _EMPTY_TOOL_NAME_ERROR = "Tool call could not be executed because its name was missing or empty."
 _SYNTHETIC_TOOL_CALL_ID_PREFIX = "deerflow_synthetic_tool_call_"
 
+# Middleware producers spell an absent provider ID differently: "" is the canonical
+# spelling, but ``str(tool_call.get("id", ""))`` yields "None" once the key is present
+# with a null value, and the artifact/deferred/knowledge middlewares fall back to
+# "missing_tool_call_id". They all answer the same call, so pairing treats them alike.
+_ABSENT_TOOL_CALL_ID_SPELLINGS = frozenset({"None", "missing_tool_call_id"})
+
+
+def _canonical_tool_call_id(tool_call_id: object) -> object:
+    """Return one value for every spelling middleware uses for "this call had no ID"."""
+    return "" if _absent_tool_call_id(tool_call_id) else tool_call_id
+
+
+def _absent_tool_call_id(tool_call_id: object) -> bool:
+    """Whether an ID is missing in any spelling: null, blank, or a producer sentinel."""
+    if not _valid_tool_call_id(tool_call_id):
+        return True
+    return isinstance(tool_call_id, str) and tool_call_id in _ABSENT_TOOL_CALL_ID_SPELLINGS
+
+
+def _same_tool_call_id(left: object, right: object) -> bool:
+    return _canonical_tool_call_id(left) == _canonical_tool_call_id(right)
+
 
 def _valid_tool_name(name: object) -> bool:
     return isinstance(name, str) and bool(name.strip())
@@ -93,12 +115,12 @@ def _relabel_tool_call_ids(tool_calls: list, msg_index: int, source: str) -> tup
 
 
 def _turn_malformed_result_count(messages: list, start: int) -> int:
-    """Count the malformed results issued by the turn opened at ``start``."""
+    """Count the unpaired results issued by the turn opened at ``start``."""
     count = 0
     for msg in messages[start + 1 :]:
         if getattr(msg, "type", None) == "ai":
             break
-        if isinstance(msg, ToolMessage) and not _valid_tool_call_id(msg.tool_call_id):
+        if isinstance(msg, ToolMessage) and _absent_tool_call_id(msg.tool_call_id):
             count += 1
     return count
 
@@ -123,7 +145,7 @@ def _claim_synthetic_id(open_calls: list[dict], result: ToolMessage, positional:
     Returning ``None`` leaves the result malformed for the orphan pass to drop, which is
     what an unattributable result gets today — better than inventing a pairing.
     """
-    candidates = [position for position, entry in enumerate(open_calls) if entry["original"] == result.tool_call_id and _names_can_pair(entry["name"], result.name)]
+    candidates = [position for position, entry in enumerate(open_calls) if _same_tool_call_id(entry["original"], result.tool_call_id) and _names_can_pair(entry["name"], result.name)]
     if not candidates or (len(candidates) > 1 and not positional):
         return None
     return open_calls.pop(candidates[0])["synthetic"]
@@ -415,8 +437,9 @@ class DanglingToolCallMiddleware(AgentMiddleware[AgentState]):
                 continue
 
             # Re-point an already-paired result at its call's new id so the pairing
-            # below keeps it instead of dropping it as an orphan.
+            # below keeps it instead of dropping it as an orphan. Results carrying a
-            if not isinstance(msg, ToolMessage) or _valid_tool_call_id(msg.tool_call_id):
+            # producer sentinel are still unpaired — the sentinel is not the call's id.
+            if not isinstance(msg, ToolMessage) or not _absent_tool_call_id(msg.tool_call_id):
                 continue
             synthetic = _claim_synthetic_id(open_calls, msg, positional)
             if synthetic is not None:

backend/tests/AGENTS.md

@@ -1,5 +1,8 @@
 # Backend Tests
 
+`test_null_tool_result_pairing.py` pins null/empty/sentinel ID equivalence, provider-wire
+pairing, and ambiguity rejection for incomplete parallel results.
+
 `test_lark_broker_image.py` stages Python files from the broker Dockerfile's
 final-stage COPY instructions. Run shim installation and the health endpoint
 under `-I -S`, adding only the staged script directory to the import path;

backend/tests/test_null_tool_result_pairing.py

@@ -0,0 +1,94 @@
+"""Missing call IDs must not swallow middleware-generated tool guidance."""
+
+import pytest
+from langchain_core.messages import AIMessage, ToolMessage
+from langchain_openai.chat_models.base import _convert_message_to_dict
+
+from deerflow.agents.middlewares.dangling_tool_call_middleware import DanglingToolCallMiddleware
+
+
+@pytest.mark.parametrize("call_id,result_id", [(None, ""), ("", None), (None, None), ("", "")])
+def test_missing_ids_preserve_result_and_provider_pairing(call_id, result_id):
+    call = AIMessage(content="", tool_calls=[{"name": "write_file", "id": call_id, "args": {"path": "a.md"}}])
+    # Normal middleware replies use ""; model_construct also covers old None-ID history.
+    constructor = ToolMessage.model_construct if result_id is None else ToolMessage
+    result = constructor(content="Error: read the file before writing it", tool_call_id=result_id, name="write_file", status="error")
+    patched = DanglingToolCallMiddleware()._build_patched_messages([call, result])
+
+    assert patched is not None
+    assert len(patched) == 2
+    assert patched[1].content == result.content
+    assert patched[1].status == "error"
+    wire_call, wire_result = map(_convert_message_to_dict, patched)
+    assert wire_call["tool_calls"][0]["id"] == wire_result["tool_call_id"]
+    assert wire_result["tool_call_id"]
+    assert call.tool_calls[0]["id"] == call_id
+    assert result.tool_call_id == result_id
+
+
+def test_mixed_missing_ids_keep_partial_same_name_results_ambiguous():
+    call = AIMessage(content="", tool_calls=[{"name": "bash", "id": call_id, "args": {}} for call_id in (None, "")])
+    result = ToolMessage(content="UNATTRIBUTABLE", tool_call_id="", name="bash")
+    patched = DanglingToolCallMiddleware()._build_patched_messages([call, result])
+
+    assert patched is not None
+    assert all(message.content != "UNATTRIBUTABLE" for message in patched[1:])
+    assert len(patched[1:]) == 2
+    assert all(message.status == "error" for message in patched[1:])
+
+
+def test_missing_id_does_not_override_a_different_tool_name():
+    call = AIMessage(content="", tool_calls=[{"name": "write_file", "id": None, "args": {}}])
+    result = ToolMessage(content="UNRELATED", tool_call_id="", name="bash")
+    patched = DanglingToolCallMiddleware()._build_patched_messages([call, result])
+
+    assert patched is not None
+    assert patched[1].content != "UNRELATED"
+    assert patched[1].status == "error"
+
+
+def test_mixed_missing_ids_complete_parallel_turn_keeps_input_order():
+    call = AIMessage(content="", tool_calls=[{"name": "bash", "id": call_id, "args": {}} for call_id in (None, "")])
+    replies = [ToolMessage(content=text, tool_call_id="", name="bash") for text in ("FIRST", "SECOND")]
+    patched = DanglingToolCallMiddleware()._build_patched_messages([call, *replies])
+
+    assert patched is not None
+    assert [message.content for message in patched[1:]] == ["FIRST", "SECOND"]
+    assert [message.tool_call_id for message in patched[1:]] == [tc["id"] for tc in patched[0].tool_calls]
+
+
+@pytest.mark.parametrize("sentinel", ["None", "missing_tool_call_id"])
+def test_producer_sentinel_ids_pair_with_a_null_call_id(sentinel):
+    """Producers spell a missing ID as "None" or "missing_tool_call_id", not ""."""
+    call = AIMessage(content="", tool_calls=[{"name": "write_file", "id": None, "args": {"path": "a.md"}}])
+    result = ToolMessage(content="Error: read the file before writing it", tool_call_id=sentinel, name="write_file", status="error")
+    patched = DanglingToolCallMiddleware()._build_patched_messages([call, result])
+
+    assert patched is not None
+    assert len(patched) == 2
+    assert patched[1].content == result.content
+    assert patched[1].status == "error"
+    wire_call, wire_result = map(_convert_message_to_dict, patched)
+    assert wire_call["tool_calls"][0]["id"] == wire_result["tool_call_id"]
+
+
+def test_producer_sentinel_pairing_does_not_invent_one_for_a_valid_id():
+    """A sentinel result must not steal the slot of a call that does have an ID."""
+    call = AIMessage(content="", tool_calls=[{"name": "write_file", "id": "call_1", "args": {}}])
+    result = ToolMessage(content="UNRELATED", tool_call_id="missing_tool_call_id", name="write_file")
+    patched = DanglingToolCallMiddleware()._build_patched_messages([call, result])
+
+    assert patched is not None
+    assert patched[1].content != "UNRELATED"
+    assert patched[1].status == "error"
+
+
+def test_producer_sentinels_complete_a_parallel_turn_in_input_order():
+    """Mixed call spellings plus sentinel results: order still identifies the calls."""
+    call = AIMessage(content="", tool_calls=[{"name": "bash", "id": call_id, "args": {}} for call_id in (None, "")])
+    replies = [ToolMessage(content=text, tool_call_id="missing_tool_call_id", name="bash") for text in ("FIRST", "SECOND")]
+    patched = DanglingToolCallMiddleware()._build_patched_messages([call, *replies])
+
+    assert patched is not None
+    assert [message.content for message in patched[1:]] == ["FIRST", "SECOND"]
+    assert [message.tool_call_id for message in patched[1:]] == [tc["id"] for tc in patched[0].tool_calls]