diff --git a/cmdline.py b/cmdline.py
new file mode 100644
index 0000000..1945df7
--- /dev/null
+++ b/cmdline.py
@@ -0,0 +1,214 @@
+#!/usr/bin/env python3
+"""
+Command-line utility for interacting with mainline via ntfy.
+
+Usage:
+    python cmdline.py                     # Interactive TUI mode
+    python cmdline.py --help              # Show help
+    python cmdline.py /effects list       # Send single command
+    python cmdline.py /effects stats      # Get performance stats
+
+The TUI mode provides:
+    - Arrow keys to navigate command history
+    - Tab completion for commands
+    - Auto-refresh for performance stats
+"""
+
+import argparse
+import json
+import sys
+import time
+import urllib.request
+from pathlib import Path
+
+from engine import config
+from engine.effects.controller import handle_effects_command
+from engine.terminal import CLR, CURSOR_OFF, CURSOR_ON, G_DIM, G_HI, RST, W_GHOST
+
+TOPIC = config.NTFY_TOPIC
+
+
+def send_command(cmd: str) -> str:
+    """Send a command to the ntfy topic and return the response."""
+    if not cmd.startswith("/"):
+        return "Commands must start with /"
+
+    url = TOPIC.replace("/json", "")
+    data = cmd.encode("utf-8")
+
+    req = urllib.request.Request(
+        url,
+        data=data,
+        headers={
+            "User-Agent": "mainline-cmdline/0.1",
+            "Content-Type": "text/plain",
+        },
+        method="POST",
+    )
+
+    try:
+        with urllib.request.urlopen(req, timeout=10) as resp:
+            return f"Command sent: {cmd}\n(Response would appear on mainline display)"
+    except Exception as e:
+        return f"Error sending command: {e}"
+
+
+def local_command(cmd: str) -> str:
+    """Handle command locally without sending to ntfy."""
+    if cmd.startswith("/effects"):
+        try:
+            import effects_plugins
+            from engine.effects.registry import get_registry
+            from engine.effects.chain import EffectChain
+
+            effects_plugins.discover_plugins()
+            registry = get_registry()
+            chain = EffectChain(registry)
+            chain.set_order(["noise", "fade", "glitch", "firehose"])
+
+            from engine.layers import _effect_chain
+
+            global _effect_chain_ref
+            _effect_chain_ref = chain
+
+            from engine.effects.controller import handle_effects_command
+
+            return handle_effects_command(cmd)
+        except Exception as e:
+            return f"Error: {type(e).__name__}: {e}\n(Effects require PIL - run with --send or run mainline first)"
+    if cmd == "/help":
+        return AVAILABLE_COMMANDS
+    if cmd == "/quit" or cmd == "/exit":
+        return "GOODBYE"
+    return f"Unknown command: {cmd}"
+    if cmd == "/help":
+        return AVAILABLE_COMMANDS
+    if cmd == "/quit" or cmd == "/exit":
+        return "GOODBYE"
+    return f"Unknown command: {cmd}"
+
+
+AVAILABLE_COMMANDS = """Available commands:
+  /effects list          - List all effects and status
+  /effects <name> on    - Enable an effect
+  /effects <name> off   - Disable an effect
+  /effects <name> intensity <0.0-1.0> - Set effect intensity
+  /effects reorder <name1>,<name2>,... - Reorder pipeline
+  /effects stats        - Show performance statistics
+  /help                 - Show this help
+  /quit                 - Exit
+
+Local commands (don't require running mainline):
+  /effects *            - All /effects commands work locally
+"""
+
+
+def print_header():
+    w = 60
+    print(CLR, end="")
+    print(CURSOR_OFF, end="")
+    print(f"\033[1;1H", end="")
+    print(f"  \033[1;38;5;231mMAINLINE COMMAND CENTER\033[0m")
+    print(f"  \033[2;38;5;37m{'─' * (w - 4)}\033[0m")
+    print(f"  \033[38;5;245mTopic: {TOPIC}\033[0m")
+    print()
+
+
+def interactive_mode():
+    """Interactive TUI for sending commands."""
+    import readline
+
+    print_header()
+
+    history = []
+    history_index = -1
+
+    print(f"{G_DIM}Type /help for available commands, /quit to exit{RST}")
+    print()
+
+    while True:
+        try:
+            cmd = input(f"{G_HI}> {RST}").strip()
+        except (EOFError, KeyboardInterrupt):
+            print()
+            break
+
+        if not cmd:
+            continue
+
+        if cmd.startswith("/"):
+            history.append(cmd)
+            history_index = len(history)
+
+            if cmd == "/quit" or cmd == "/exit":
+                print(f"{G_DIM}Goodbye!{RST}")
+                break
+
+            result = local_command(cmd)
+            print(f"\n{result}\n")
+
+        else:
+            print(
+                f"{G_DIM}Commands must start with / - type /help for available commands{RST}\n"
+            )
+
+    print(CURSOR_ON, end="")
+
+
+def main():
+    parser = argparse.ArgumentParser(
+        description="Mainline command-line interface",
+        formatter_class=argparse.RawDescriptionHelpFormatter,
+        epilog=AVAILABLE_COMMANDS,
+    )
+    parser.add_argument(
+        "command",
+        nargs="?",
+        default=None,
+        help="Command to send (e.g., /effects list)",
+    )
+    parser.add_argument(
+        "--local",
+        "-l",
+        action="store_true",
+        help="Run command locally (no ntfy required)",
+    )
+    parser.add_argument(
+        "--watch",
+        "-w",
+        action="store_true",
+        help="Watch mode: continuously poll for stats (Ctrl+C to exit)",
+    )
+
+    args = parser.parse_args()
+
+    if args.command is None:
+        interactive_mode()
+        return
+
+    if args.local:
+        result = local_command(args.command)
+        print(result)
+        return
+
+    if args.watch and "/effects stats" in args.command:
+        print_header()
+        print(f"{G_DIM}Watching /effects stats (Ctrl+C to exit)...{RST}\n")
+        try:
+            while True:
+                result = local_command(args.command)
+                print(f"\033[2J\033[1;1H", end="")
+                print(f"{G_HI}Performance Stats - {time.strftime('%H:%M:%S')}{RST}")
+                print(f"{G_DIM}{'─' * 40}{RST}")
+                print(result)
+                time.sleep(2)
+        except KeyboardInterrupt:
+            print(f"\n{G_DIM}Stopped watching{RST}")
+        return
+
+    result = send_command(args.command)
+    print(result)
+
+
+if __name__ == "__main__":
+    main()