diff --git a/docker_agent_sandbox/sandbox.py b/docker_agent_sandbox/sandbox.py
index 60a3ab3..014ca64 100644
--- a/docker_agent_sandbox/sandbox.py
+++ b/docker_agent_sandbox/sandbox.py
@@ -248,53 +248,28 @@ class DockerSandbox:
     # ------------------------------------------------------------------
 
     def exec(self, command: str, timeout: int = 120, kill_grace: int = 5) -> tuple[int, str]:
-        """
-        Run *command* inside the container via the low-level exec API.
-
-        Returns ``(exit_code, combined_stdout_stderr)``.
-
-        Exit code 124 indicates a timeout (137 if escalation to SIGKILL was
-        needed). *command* is passed as a single argv element to ``bash -c``,
-        so shell metacharacters within it need no extra escaping.
-        """
         if self._container is None:
             return 1, "Sandbox container is not running."
 
-        create_kwargs: dict = {}
-        if self._working_dir is not None:
-            create_kwargs["workdir"] = self._working_dir
-
         wrapped = [
-            "timeout",
-            "--kill-after",
-            f"{kill_grace}s",
-            f"{timeout}s",
-            "bash",
-            "-c",
-            command,
+            "timeout", "--kill-after", f"{kill_grace}s", f"{timeout}s",
+            "bash", "-c", command,
         ]
+        kwargs = {}
+        if self._working_dir is not None:
+            kwargs["workdir"] = self._working_dir
 
         try:
-            exec_id = self._client.api.exec_create(
-                self._container.id,
+            exit_code, output = self._container.exec_run(
                 wrapped,
                 stdout=True,
                 stderr=True,
-                **create_kwargs,
+                demux=False,
+                **kwargs,
             )
-            sock = self._client.api.exec_start(exec_id["Id"], socket=True)
-
-            gen = (demux_adaptor(*frame) for frame in frames_iter(sock, tty=False))
-            stdout, stderr = consume_socket_output(gen, demux=True)
-
-            exit_code = self._client.api.exec_inspect(exec_id["Id"])["ExitCode"]
-            if exit_code is None:
-                exit_code = 0
-
-            output = ((stdout or b"") + (stderr or b"")).decode("utf-8", errors="replace")
-
+            text = (output or b"").decode("utf-8", errors="replace")
             if exit_code in (124, 137):
-                return exit_code, output + f"\n[command timed out after {timeout}s]"
-            return exit_code, output
+                return exit_code, text + f"\n[command timed out after {timeout}s]"
+            return exit_code, text
         except Exception as exc:
             return 1, f"Error running command in container: {exc}"