fix(tools): split concatenated streamed tool-call args

agent/chat_completion_helpers.py

@@ -39,6 +39,42 @@
 logger = logging.getLogger(__name__)
 
 
+
+def _split_concatenated_tool_call_arguments(raw_args: str) -> list[str] | None:
+    """Split ``{"..."}{"..."}`` tool-call payloads into separate JSON objects.
+
+    Some providers can concatenate multiple complete top-level argument
+    objects without delimiters when emitting parallel tool calls in a single
+    streaming chunk. Only return a split when the entire payload can be
+    losslessly decoded as 2+ complete dict objects; otherwise return None so
+    existing truncation handling stays in control.
+    """
+    if not isinstance(raw_args, str):
+        return None
+
+    raw_stripped = raw_args.strip()
+    if not raw_stripped:
+        return None
+
+    decoder = json.JSONDecoder()
+    pos = 0
+    decoded: list[str] = []
+    while pos < len(raw_stripped):
+        while pos < len(raw_stripped) and raw_stripped[pos].isspace():
+            pos += 1
+        if pos >= len(raw_stripped):
+            break
+        try:
+            parsed, end = decoder.raw_decode(raw_stripped, pos)
+        except json.JSONDecodeError:
+            return None
+        if not isinstance(parsed, dict):
+            return None
+        decoded.append(json.dumps(parsed, separators=(",", ":")))
+        pos = end
+
+    return decoded if len(decoded) > 1 else None
+
 def _ra():
     """Lazy ``run_agent`` reference.
 
@@ -1907,6 +1943,26 @@ def _call_chat_completions():
                 tc = tool_calls_acc[idx]
                 arguments = tc["function"]["arguments"]
                 tool_name = tc["function"]["name"] or "?"
+                split_arguments = _split_concatenated_tool_call_arguments(arguments)
+                if split_arguments:
+                    logger.warning(
+                        "Split concatenated tool_call arguments for %s into %d calls",
+                        tool_name,
+                        len(split_arguments),
+                    )
+                    base_id = tc["id"] or f"call_{idx}"
+                    for split_idx, split_arg in enumerate(split_arguments):
+                        split_id = base_id if split_idx == 0 else f"{base_id}_split_{split_idx}"
+                        mock_tool_calls.append(SimpleNamespace(
+                            id=split_id,
+                            type=tc["type"],
+                            extra_content=tc.get("extra_content"),
+                            function=SimpleNamespace(
+                                name=tc["function"]["name"],
+                                arguments=split_arg,
+                            ),
+                        ))
+                    continue
                 if arguments and arguments.strip():
                     try:
                         json.loads(arguments)

tests/test_model_tools_tool_call_payload_repair.py

@@ -0,0 +1,32 @@
+from __future__ import annotations
+
+import json
+from pathlib import Path
+
+from agent import chat_completion_helpers as helper
+
+
+def test_split_concatenated_tool_call_arguments_returns_complete_dict_json_objects():
+    result = helper._split_concatenated_tool_call_arguments(
+        '{"path":"README.md"}{"query":"tool calls"}'
+    )
+    assert result == ['{"path":"README.md"}', '{"query":"tool calls"}']
+    assert [json.loads(item) for item in result] == [
+        {"path": "README.md"},
+        {"query": "tool calls"},
+    ]
+
+
+def test_split_concatenated_tool_call_arguments_rejects_single_partial_or_non_dict_payloads():
+    assert helper._split_concatenated_tool_call_arguments('{"path":"README.md"}') is None
+    assert helper._split_concatenated_tool_call_arguments('{"path":"README.md"}{"query":') is None
+    assert helper._split_concatenated_tool_call_arguments('[1,2]{"path":"README.md"}') is None
+    assert helper._split_concatenated_tool_call_arguments('') is None
+
+
+def test_streaming_reconstruction_wires_concatenated_argument_splitter():
+    source = Path(helper.__file__).read_text(encoding="utf-8")
+    assert "split_arguments = _split_concatenated_tool_call_arguments(arguments)" in source
+    assert "mock_tool_calls.append(SimpleNamespace(" in source
+    assert "split_idx" in source
+    assert "continue" in source