diff --git a/condor/acp/pydantic_ai_client.py b/condor/acp/pydantic_ai_client.py
index bdd09937..a2697f5c 100644
--- a/condor/acp/pydantic_ai_client.py
+++ b/condor/acp/pydantic_ai_client.py
@@ -701,17 +701,20 @@ async def start(self) -> None:
         toolsets = []
         for srv_config in self.mcp_server_configs:
             command = srv_config["command"]
-            args = srv_config.get("args", [])
+            # StdioServerParameters requires list[str]; YAML/config may yield ints
+            # (e.g. numeric hummingbot passwords) that only surface with pydantic-ai
+            # backends (lmstudio:/ollama:/openrouter:), not ACP agents.
+            args = [str(a) for a in srv_config.get("args", [])]
 
             # Inherit the parent process env (same as ACPClient) so cloud keys
             # loaded via dotenv — e.g. OPENROUTER_API_KEY — reach MCP tools like
             # get_available_models. extra_env / per-server env overlay on top.
-            env = dict(os.environ)
+            env = {k: str(v) for k, v in os.environ.items()}
             if self.extra_env:
-                env.update(self.extra_env)
+                env.update({k: str(v) for k, v in self.extra_env.items()})
             for env_entry in srv_config.get("env", []):
                 if isinstance(env_entry, dict):
-                    env[env_entry["name"]] = env_entry["value"]
+                    env[str(env_entry["name"])] = str(env_entry["value"])
 
             mcp_server = MCPServerStdio(
                 command,
diff --git a/handlers/agents/_shared.py b/handlers/agents/_shared.py
index fa93c135..5fbddc89 100644
--- a/handlers/agents/_shared.py
+++ b/handlers/agents/_shared.py
@@ -232,14 +232,38 @@ def _condor_mcp_args(
         os.environ.get("TELEGRAM_TOKEN", ""),
     ]
     if agent_slug:
-        args.extend(["--agent-slug", agent_slug])
+        args.extend(["--agent-slug", str(agent_slug)])
     if server_name:
-        args.extend(["--server-name", server_name])
+        args.extend(["--server-name", str(server_name)])
     if delegate_worker:
         args.append("--delegate-worker")
     return args
 
 
+def _hummingbot_mcp_args(server: dict[str, Any], server_name: str) -> list[str]:
+    """Build CLI args for the hummingbot MCP subprocess.
+
+    Username/password must be strings — YAML loads unquoted numerics as int
+    (e.g. ``password: 123``), and pydantic-ai's StdioServerParameters rejects
+    non-string args when starting LM Studio / other local-model sessions.
+    """
+    api_url = f"http://{server['host']}:{server['port']}"
+    return [
+        "run",
+        "python",
+        "-m",
+        "mcp_servers.hummingbot_api",
+        "--url",
+        api_url,
+        "--username",
+        str(server["username"]),
+        "--password",
+        str(server["password"]),
+        "--server-name",
+        str(server_name),
+    ]
+
+
 def build_mcp_servers_for_session(
     user_id: int,
     chat_id: int | str,
@@ -314,25 +338,10 @@ def build_mcp_servers_for_session(
         )
         return [condor]
 
-    api_url = f"http://{server['host']}:{server['port']}"
-
     mcp_hummingbot = {
         "name": "mcp-hummingbot",
         "command": "uv",
-        "args": [
-            "run",
-            "python",
-            "-m",
-            "mcp_servers.hummingbot_api",
-            "--url",
-            api_url,
-            "--username",
-            server["username"],
-            "--password",
-            server["password"],
-            "--server-name",
-            server_name,
-        ],
+        "args": _hummingbot_mcp_args(server, server_name),
         "env": [],
     }
 
diff --git a/tests/test_agents.py b/tests/test_agents.py
index c9d667bc..cb8764b8 100644
--- a/tests/test_agents.py
+++ b/tests/test_agents.py
@@ -721,3 +721,34 @@ def get_server(self, name):
     servers = build_mcp_servers_for_session(42, 42)
     condor = next(s for s in servers if s["name"] == "condor")
     assert "--agent-slug" not in condor["args"]
+
+
+def test_hummingbot_mcp_args_stringify_numeric_credentials(monkeypatch):
+    """YAML ``password: 123`` loads as int; StdioServerParameters requires str."""
+    import config_manager
+
+    from handlers.agents._shared import build_mcp_servers_for_session
+
+    class _NumericPasswordServer:
+        def get_accessible_servers(self, user_id):
+            return ["local"]
+
+        def get_server(self, name):
+            return {
+                "host": "localhost",
+                "port": 8000,
+                "username": 999,
+                "password": 123,
+            }
+
+    monkeypatch.setattr(
+        config_manager, "get_config_manager", lambda: _NumericPasswordServer()
+    )
+    monkeypatch.setattr(config_manager, "get_effective_server", lambda *a, **k: "local")
+
+    servers = build_mcp_servers_for_session(42, 42)
+    hb = next(s for s in servers if s["name"] == "mcp-hummingbot")
+    args = hb["args"]
+    assert all(isinstance(a, str) for a in args)
+    assert args[args.index("--password") + 1] == "123"
+    assert args[args.index("--username") + 1] == "999"