diff --git a/nanobot/agent/loop.py b/nanobot/agent/loop.py
index e5a5183..1cd5730 100644
--- a/nanobot/agent/loop.py
+++ b/nanobot/agent/loop.py
@@ -206,7 +206,7 @@ class AgentLoop:
                         "type": "function",
                         "function": {
                             "name": tc.name,
-                            "arguments": json.dumps(tc.arguments)
+                            "arguments": json.dumps(tc.arguments, ensure_ascii=False)
                         }
                     }
                     for tc in response.tool_calls
@@ -388,6 +388,7 @@ class AgentLoop:
         )
         final_content, _ = await self._run_agent_loop(initial_messages)
 
+
         if final_content is None:
             final_content = "Background task completed."
         
diff --git a/nanobot/agent/subagent.py b/nanobot/agent/subagent.py
index 203836a..ffefc08 100644
--- a/nanobot/agent/subagent.py
+++ b/nanobot/agent/subagent.py
@@ -146,7 +146,7 @@ class SubagentManager:
                             "type": "function",
                             "function": {
                                 "name": tc.name,
-                                "arguments": json.dumps(tc.arguments),
+                                "arguments": json.dumps(tc.arguments, ensure_ascii=False),
                             },
                         }
                         for tc in response.tool_calls
@@ -159,7 +159,7 @@ class SubagentManager:
                     
                     # Execute tools
                     for tool_call in response.tool_calls:
-                        args_str = json.dumps(tool_call.arguments)
+                        args_str = json.dumps(tool_call.arguments, ensure_ascii=False)
                         logger.debug(f"Subagent [{task_id}] executing: {tool_call.name} with arguments: {args_str}")
                         result = await tools.execute(tool_call.name, tool_call.arguments)
                         messages.append({
diff --git a/nanobot/config/loader.py b/nanobot/config/loader.py
index 560c1f5..134e95f 100644
--- a/nanobot/config/loader.py
+++ b/nanobot/config/loader.py
@@ -31,7 +31,7 @@ def load_config(config_path: Path | None = None) -> Config:
 
     if path.exists():
         try:
-            with open(path) as f:
+            with open(path, encoding="utf-8") as f:
                 data = json.load(f)
             data = _migrate_config(data)
             return Config.model_validate(data)
diff --git a/nanobot/cron/service.py b/nanobot/cron/service.py
index 14666e8..3c77452 100644
--- a/nanobot/cron/service.py
+++ b/nanobot/cron/service.py
@@ -66,7 +66,7 @@ class CronService:
         
         if self.store_path.exists():
             try:
-                data = json.loads(self.store_path.read_text())
+                data = json.loads(self.store_path.read_text(encoding="utf-8"))
                 jobs = []
                 for j in data.get("jobs", []):
                     jobs.append(CronJob(
@@ -148,7 +148,7 @@ class CronService:
             ]
         }
         
-        self.store_path.write_text(json.dumps(data, indent=2))
+        self.store_path.write_text(json.dumps(data, indent=2, ensure_ascii=False), encoding="utf-8")
     
     async def start(self) -> None:
         """Start the cron service."""
diff --git a/nanobot/session/manager.py b/nanobot/session/manager.py
index 752fce4..42df1b1 100644
--- a/nanobot/session/manager.py
+++ b/nanobot/session/manager.py
@@ -121,7 +121,7 @@ class SessionManager:
             created_at = None
             last_consolidated = 0
 
-            with open(path) as f:
+            with open(path, encoding="utf-8") as f:
                 for line in f:
                     line = line.strip()
                     if not line:
@@ -151,7 +151,7 @@ class SessionManager:
         """Save a session to disk."""
         path = self._get_session_path(session.key)
 
-        with open(path, "w") as f:
+        with open(path, "w", encoding="utf-8") as f:
             metadata_line = {
                 "_type": "metadata",
                 "created_at": session.created_at.isoformat(),
@@ -159,9 +159,10 @@ class SessionManager:
                 "metadata": session.metadata,
                 "last_consolidated": session.last_consolidated
             }
-            f.write(json.dumps(metadata_line) + "\n")
+            f.write(json.dumps(metadata_line, ensure_ascii=False) + "\n")
             for msg in session.messages:
-                f.write(json.dumps(msg) + "\n")
+                f.write(json.dumps(msg, ensure_ascii=False) + "\n")
+
 
         self._cache[session.key] = session
     
@@ -181,7 +182,7 @@ class SessionManager:
         for path in self.sessions_dir.glob("*.jsonl"):
             try:
                 # Read just the metadata line
-                with open(path) as f:
+                with open(path, encoding="utf-8") as f:
                     first_line = f.readline().strip()
                     if first_line:
                         data = json.loads(first_line)