diff --git a/pm3py/client.py b/pm3py/client.py
index 0d78e17..1285ec2 100644
--- a/pm3py/client.py
+++ b/pm3py/client.py
@@ -1,7 +1,9 @@
 """Main Proxmark3 client with nested API."""
 import asyncio
+import glob
 import inspect
 import logging
+import sys
 from dataclasses import dataclass, field
 
 from .transport import PM3Transport, PM3Response, PM3Error, ProgressCallback
@@ -26,21 +28,42 @@ class FirmwareInfo:
     warnings: list[str] = field(default_factory=list)
 
 
+def find_proxmark_port() -> str | None:
+    """Auto-detect the first available Proxmark3 serial port."""
+    if sys.platform == "darwin":
+        patterns = ["/dev/tty.usbmodem*"]
+    elif sys.platform == "win32":
+        # On Windows, we can't glob — caller should specify port
+        return None
+    else:
+        patterns = ["/dev/ttyACM*", "/dev/ttyUSB*"]
+
+    for pattern in patterns:
+        ports = sorted(glob.glob(pattern))
+        if ports:
+            return ports[0]
+    return None
+
+
 class Proxmark3:
     """Proxmark3 device client with structured Python API.
 
     Usage:
-        async with Proxmark3("/dev/ttyACM0") as pm3:
-            if not pm3.firmware.compatible:
-                print("Warnings:", pm3.firmware.warnings)
-            status = await pm3.hw.version()
-            print(status)
+        async with Proxmark3() as pm3:          # auto-detect port
+            print(await pm3.hw.ping())
 
-            # Raw access:
+        async with Proxmark3("/dev/ttyACM0") as pm3:  # explicit port
             resp = await pm3.send_ng(0x0108)
+
+        pm3 = Proxmark3.sync()                  # sync REPL, auto-detect
     """
 
-    def __init__(self, port: str, baudrate: int = 115200):
+    def __init__(self, port: str | None = None, baudrate: int = 115200):
+        if port is None:
+            port = find_proxmark_port()
+            if port is None:
+                raise PM3Error("No Proxmark3 device found")
+            log.info("pm3py: auto-detected %s", port)
         self._transport = PM3Transport(port, baudrate)
         self.hw = HWCommands(self._transport)
         self.lf = LFCommands(self._transport)
@@ -106,14 +129,14 @@ class Proxmark3:
         return await self._transport.send_mix(cmd, arg0, arg1, arg2, payload, timeout)
 
     @classmethod
-    def sync(cls, port: str, baudrate: int = 115200) -> "Proxmark3":
+    def sync(cls, port: str | None = None, baudrate: int = 115200) -> "Proxmark3":
         """Create a synchronous client for REPL / script usage.
 
         Usage:
-            pm3 = Proxmark3.sync("/dev/ttyACM0")
+            pm3 = Proxmark3.sync()              # auto-detect
+            pm3 = Proxmark3.sync("/dev/ttyACM0") # explicit
             print(pm3.firmware)
             print(pm3.hw.ping())
-            print(pm3.hf.mf.rdbl(block=0))
             pm3.close()
         """
         instance = cls(port, baudrate)