Fix: handle non-string tool call arguments in memory consolidation

Fixes #1042. When the LLM returns tool call arguments as a dict or
JSON string instead of parsed values, memory consolidation would fail
with "TypeError: data must be str, not dict".

Changes:
- Add type guard in MemoryStore.consolidate() to parse string arguments
  and reject unexpected types gracefully
- Add regression tests covering dict args, string args, and edge cases

nanobot/agent/memory.py

@@ -125,6 +125,13 @@ class MemoryStore:
                 return False
 
             args = response.tool_calls[0].arguments
+            # Some providers return arguments as a JSON string instead of dict
+            if isinstance(args, str):
+                args = json.loads(args)
+            if not isinstance(args, dict):
+                logger.warning("Memory consolidation: unexpected arguments type %s", type(args).__name__)
+                return False
+
             if entry := args.get("history_entry"):
                 if not isinstance(entry, str):
                     entry = json.dumps(entry, ensure_ascii=False)

tests/test_memory_consolidation_types.py

@@ -0,0 +1,147 @@
+"""Test MemoryStore.consolidate() handles non-string tool call arguments.
+
+Regression test for https://github.com/HKUDS/nanobot/issues/1042
+When memory consolidation receives dict values instead of strings from the LLM
+tool call response, it should serialize them to JSON instead of raising TypeError.
+"""
+
+import json
+from pathlib import Path
+from unittest.mock import AsyncMock, MagicMock
+
+import pytest
+
+from nanobot.agent.memory import MemoryStore
+from nanobot.providers.base import LLMResponse, ToolCallRequest
+
+
+def _make_session(message_count: int = 30, memory_window: int = 50):
+    """Create a mock session with messages."""
+    session = MagicMock()
+    session.messages = [
+        {"role": "user", "content": f"msg{i}", "timestamp": "2026-01-01 00:00"}
+        for i in range(message_count)
+    ]
+    session.last_consolidated = 0
+    return session
+
+
+def _make_tool_response(history_entry, memory_update):
+    """Create an LLMResponse with a save_memory tool call."""
+    return LLMResponse(
+        content=None,
+        tool_calls=[
+            ToolCallRequest(
+                id="call_1",
+                name="save_memory",
+                arguments={
+                    "history_entry": history_entry,
+                    "memory_update": memory_update,
+                },
+            )
+        ],
+    )
+
+
+class TestMemoryConsolidationTypeHandling:
+    """Test that consolidation handles various argument types correctly."""
+
+    @pytest.mark.asyncio
+    async def test_string_arguments_work(self, tmp_path: Path) -> None:
+        """Normal case: LLM returns string arguments."""
+        store = MemoryStore(tmp_path)
+        provider = AsyncMock()
+        provider.chat = AsyncMock(
+            return_value=_make_tool_response(
+                history_entry="[2026-01-01] User discussed testing.",
+                memory_update="# Memory\nUser likes testing.",
+            )
+        )
+        session = _make_session(message_count=60)
+
+        result = await store.consolidate(session, provider, "test-model", memory_window=50)
+
+        assert result is True
+        assert store.history_file.exists()
+        assert "[2026-01-01] User discussed testing." in store.history_file.read_text()
+        assert "User likes testing." in store.memory_file.read_text()
+
+    @pytest.mark.asyncio
+    async def test_dict_arguments_serialized_to_json(self, tmp_path: Path) -> None:
+        """Issue #1042: LLM returns dict instead of string — must not raise TypeError."""
+        store = MemoryStore(tmp_path)
+        provider = AsyncMock()
+        provider.chat = AsyncMock(
+            return_value=_make_tool_response(
+                history_entry={"timestamp": "2026-01-01", "summary": "User discussed testing."},
+                memory_update={"facts": ["User likes testing"], "topics": ["testing"]},
+            )
+        )
+        session = _make_session(message_count=60)
+
+        result = await store.consolidate(session, provider, "test-model", memory_window=50)
+
+        assert result is True
+        assert store.history_file.exists()
+        history_content = store.history_file.read_text()
+        parsed = json.loads(history_content.strip())
+        assert parsed["summary"] == "User discussed testing."
+
+        memory_content = store.memory_file.read_text()
+        parsed_mem = json.loads(memory_content)
+        assert "User likes testing" in parsed_mem["facts"]
+
+    @pytest.mark.asyncio
+    async def test_string_arguments_as_raw_json(self, tmp_path: Path) -> None:
+        """Some providers return arguments as a JSON string instead of parsed dict."""
+        store = MemoryStore(tmp_path)
+        provider = AsyncMock()
+
+        # Simulate arguments being a JSON string (not yet parsed)
+        response = LLMResponse(
+            content=None,
+            tool_calls=[
+                ToolCallRequest(
+                    id="call_1",
+                    name="save_memory",
+                    arguments=json.dumps({
+                        "history_entry": "[2026-01-01] User discussed testing.",
+                        "memory_update": "# Memory\nUser likes testing.",
+                    }),
+                )
+            ],
+        )
+        provider.chat = AsyncMock(return_value=response)
+        session = _make_session(message_count=60)
+
+        result = await store.consolidate(session, provider, "test-model", memory_window=50)
+
+        assert result is True
+        assert "User discussed testing." in store.history_file.read_text()
+
+    @pytest.mark.asyncio
+    async def test_no_tool_call_returns_false(self, tmp_path: Path) -> None:
+        """When LLM doesn't use the save_memory tool, return False."""
+        store = MemoryStore(tmp_path)
+        provider = AsyncMock()
+        provider.chat = AsyncMock(
+            return_value=LLMResponse(content="I summarized the conversation.", tool_calls=[])
+        )
+        session = _make_session(message_count=60)
+
+        result = await store.consolidate(session, provider, "test-model", memory_window=50)
+
+        assert result is False
+        assert not store.history_file.exists()
+
+    @pytest.mark.asyncio
+    async def test_skips_when_few_messages(self, tmp_path: Path) -> None:
+        """Consolidation should be a no-op when messages < keep_count."""
+        store = MemoryStore(tmp_path)
+        provider = AsyncMock()
+        session = _make_session(message_count=10)
+
+        result = await store.consolidate(session, provider, "test-model", memory_window=50)
+
+        assert result is True
+        provider.chat.assert_not_called()