diff --git a/tools/flash_app_only.jlink b/tools/flash_app_only.jlink
new file mode 100644
index 0000000..8e707cf
--- /dev/null
+++ b/tools/flash_app_only.jlink
@@ -0,0 +1,10 @@
+HideDeviceSelection 1
+si SWD
+speed 4000
+device AT32F403AC
+connect
+halt
+loadbin project/IAR_V7.4/YNGJ-GT1-M/Exe/YNGJ-GT1-M.bin, 0x08008000
+r
+g
+exit
diff --git a/tools/flash_mcu_and_extflash.py b/tools/flash_mcu_and_extflash.py
new file mode 100644
index 0000000..c2c16e0
--- /dev/null
+++ b/tools/flash_mcu_and_extflash.py
@@ -0,0 +1,289 @@
+# -*- coding: utf-8 -*-
+"""Flash K1 MCU APP (J-Link) + ExtFlash ALL.res (RTT flash all).
+
+Usage:
+  python tools/flash_mcu_and_extflash.py
+  python tools/flash_mcu_and_extflash.py --mcu PATH.bin --all PATH.res
+"""
+from __future__ import annotations
+
+import argparse
+import shutil
+import subprocess
+import time
+from pathlib import Path
+
+PROJ = Path(__file__).resolve().parents[1]
+REPO = PROJ.parents[1]
+STAGE = Path(r"C:\Temp\k1flash")
+JLINK = Path(r"C:\Program Files\SEGGER\JLink_V818\JLink.exe")
+DEFAULT_DEVICES = ("AT32F403AC", "Cortex-M4", "AT32F403A")
+
+DEFAULT_MCU = (
+    REPO
+    / "tools"
+    / "out"
+    / "K1_MCU_v0.2.11_toneRes_v0914_20260914_d06e44b"
+    / "YNGJ-GT1-M_MCU_v0.2.11_20260914.bin"
+)
+FALLBACK_MCU = PROJ / "project" / "IAR_V7.4" / "YNGJ-GT1-M" / "Exe" / "YNGJ-GT1-M.bin"
+
+DEFAULT_ALL = REPO / "tools" / "out" / "extflash_ALL_tone0914_ui0902.res"
+FALLBACK_ALL = (
+    REPO
+    / "tools"
+    / "out"
+    / "K1_MCU_v0.2.11_toneRes_v0914_20260914_d06e44b"
+    / "extflash_ALL_tone0914_ui0902_20260914.res"
+)
+
+
+def kill_debuggers() -> None:
+    for n in (
+        "cspybat.exe",
+        "CSpyBat.exe",
+        "JLink.exe",
+        "JLinkGUIServer.exe",
+        "JLinkRTTClient.exe",
+        "JFlash.exe",
+    ):
+        subprocess.run(["taskkill", "/F", "/IM", n], capture_output=True)
+    time.sleep(0.8)
+
+
+def resolve_path(primary: Path, fallback: Path) -> Path:
+    if primary.is_file():
+        return primary
+    if fallback.is_file():
+        return fallback
+    raise SystemExit(f"missing file:\n  {primary}\n  {fallback}")
+
+
+def flash_mcu_jlink(mcu_bin: Path) -> None:
+    STAGE.mkdir(parents=True, exist_ok=True)
+    staged = STAGE / "YNGJ-GT1-M.bin"
+    shutil.copy2(mcu_bin, staged)
+    cmdfile = STAGE / "flash_app.jlink"
+    cmdfile.write_text(
+        "\n".join(
+            [
+                "HideDeviceSelection 1",
+                "si SWD",
+                "speed 4000",
+                "device AT32F403AC",
+                "connect",
+                "halt",
+                f"loadbin {staged}, 0x08008000",
+                "r",
+                "g",
+                "exit",
+                "",
+            ]
+        ),
+        encoding="ascii",
+    )
+    if not JLINK.is_file():
+        raise SystemExit(f"missing JLink.exe: {JLINK}")
+    print(f"[1/3] J-Link flash MCU → 0x08008000 ({staged.name}, {staged.stat().st_size} bytes)")
+    r = subprocess.run(
+        [
+            str(JLINK),
+            "-Device",
+            "AT32F403AC",
+            "-If",
+            "SWD",
+            "-Speed",
+            "4000",
+            "-AutoConnect",
+            "1",
+            "-CommandFile",
+            str(cmdfile),
+        ],
+        capture_output=True,
+        text=True,
+        encoding="utf-8",
+        errors="replace",
+        timeout=120,
+    )
+    out = (r.stdout or "") + (r.stderr or "")
+    print(out[-1200:] if out else f"rc={r.returncode}")
+    if r.returncode != 0:
+        raise SystemExit(f"J-Link MCU flash failed rc={r.returncode}")
+    if "Failed" in out and "O.K." not in out:
+        raise SystemExit("J-Link MCU flash reported failure")
+    time.sleep(2.5)
+
+
+def connect_jlink(device: str):
+    import pylink
+
+    jlink = pylink.JLink()
+    jlink.open()
+    try:
+        jlink.exec_command("HideDeviceSelection = 1")
+    except Exception:
+        pass
+    jlink.set_tif(pylink.enums.JLinkInterfaces.SWD)
+    last = None
+    for candidate in (device, *DEFAULT_DEVICES):
+        try:
+            try:
+                jlink.exec_command(f"Device = {candidate}")
+            except Exception:
+                pass
+            jlink.connect(candidate)
+            print(f"Connected as {candidate}")
+            return jlink
+        except Exception as exc:
+            last = exc
+    jlink.close()
+    raise SystemExit(f"J-Link connect failed: {last}")
+
+
+def find_rtt_cb(jlink, ram_base: int = 0x20000000, ram_size: int = 0x18000):
+    needle = b"SEGGER RTT"
+    chunk = 0x1000
+    was_halted = jlink.halted()
+    if not was_halted:
+        jlink.halt()
+    try:
+        for off in range(0, ram_size, chunk):
+            data = bytes(jlink.memory_read8(ram_base + off, min(chunk, ram_size - off)))
+            idx = data.find(needle)
+            if idx >= 0:
+                return ram_base + off + idx
+    finally:
+        if not was_halted:
+            if hasattr(jlink, "restart"):
+                jlink.restart()
+            else:
+                jlink.go()
+            time.sleep(0.1)
+    return None
+
+
+def rtt_read_text(jlink, timeout_s: float = 0.2) -> str:
+    deadline = time.time() + timeout_s
+    chunks: list[bytes] = []
+    while time.time() < deadline:
+        try:
+            data = bytes(jlink.rtt_read(0, 512) or [])
+        except Exception:
+            data = b""
+        if data:
+            chunks.append(data)
+            deadline = time.time() + timeout_s
+        else:
+            time.sleep(0.02)
+    return b"".join(chunks).decode("ascii", errors="replace")
+
+
+def wait_for(jlink, marker: str, timeout_s: float) -> str:
+    deadline = time.time() + timeout_s
+    buf = ""
+    while time.time() < deadline:
+        buf += rtt_read_text(jlink, 0.15)
+        if marker in buf:
+            return buf
+    raise SystemExit(f"Timeout waiting for {marker!r}\n--- RTT ---\n{buf[-1000:]}")
+
+
+def send_bytes(jlink, payload: bytes) -> None:
+    off = 0
+    while off < len(payload):
+        try:
+            n = jlink.rtt_write(0, list(payload[off : off + 64]))
+        except Exception:
+            time.sleep(0.05)
+            continue
+        if n is None or n <= 0:
+            time.sleep(0.02)
+            continue
+        off += n
+
+
+def flash_all_rtt(all_res: Path, device: str) -> None:
+    data = all_res.read_bytes()
+    size = len(data)
+    print(f"[2/3] RTT flash ALL.res @ 0x0 ({all_res.name}, {size} bytes)")
+
+    jlink = connect_jlink(device)
+    try:
+        print("hardware reset...")
+        jlink.reset(halt=False)
+        time.sleep(4.0)
+        cb = find_rtt_cb(jlink)
+        if cb is None:
+            raise SystemExit("RTT CB not found — is MCU running 0.2.11+ with APP_LOG?")
+        print(f"RTT CB @ 0x{cb:08X}")
+        jlink.rtt_start(cb)
+        time.sleep(0.5)
+        _ = rtt_read_text(jlink, 0.5)
+
+        send_bytes(jlink, f"flash all {size}\n".encode("ascii"))
+        log = wait_for(jlink, "FLASH_ALL_GO", 20.0)
+        print(log.strip().splitlines()[-1])
+        time.sleep(0.2)
+
+        chunk = 256
+        sent = 0
+        t0 = time.time()
+        while sent < size:
+            end = min(sent + chunk, size)
+            send_bytes(jlink, data[sent:end])
+            sent = end
+            log = wait_for(jlink, "FLASH_ACK", 90.0)
+            if "FLASH_ALL_OK" in log:
+                print(log.strip().splitlines()[-1])
+                print(f"ALL.res done in {time.time() - t0:.1f}s")
+                break
+            if sent % (128 * 1024) == 0 or sent == size:
+                print(f"  {sent}/{size} ({100.0 * sent / size:.1f}%) {time.time() - t0:.1f}s")
+        else:
+            log = wait_for(jlink, "FLASH_ALL_OK", 90.0)
+            print(log.strip().splitlines()[-1])
+
+        print("[3/3] verify BIN3 via tone status")
+        send_bytes(jlink, b"tone status\n")
+        log = wait_for(jlink, "TONE @BIN3", 10.0)
+        for line in log.strip().splitlines():
+            if "BIN3" in line or "TONE @" in line or "loaded" in line:
+                print(line)
+        if "magic=AB444142" in log.replace(" ", "") or "magic=AB" in log:
+            # formats like magic=AB444142 or magic=AB44...
+            pass
+        if "magic=00000000" in log:
+            raise SystemExit("BIN3 still empty after flash — verify failed")
+        print("Verify OK (BIN3 not empty).")
+    finally:
+        try:
+            jlink.rtt_stop()
+        except Exception:
+            pass
+        jlink.close()
+
+
+def main() -> None:
+    ap = argparse.ArgumentParser()
+    ap.add_argument("--mcu", type=Path, default=DEFAULT_MCU)
+    ap.add_argument("--all", dest="all_res", type=Path, default=DEFAULT_ALL)
+    ap.add_argument("--device", default="AT32F403AC")
+    ap.add_argument("--skip-mcu", action="store_true")
+    args = ap.parse_args()
+
+    mcu = resolve_path(args.mcu, FALLBACK_MCU)
+    all_res = resolve_path(args.all_res, FALLBACK_ALL)
+    print(f"MCU : {mcu}")
+    print(f"ALL : {all_res}")
+
+    kill_debuggers()
+    if not args.skip_mcu:
+        flash_mcu_jlink(mcu)
+    else:
+        print("[1/3] skip MCU flash")
+    flash_all_rtt(all_res, args.device)
+    print("Done. Please power-cycle / long-press power and test universal pick.")
+
+
+if __name__ == "__main__":
+    main()