diff --git a/app/api/v1/plugins.py b/app/api/v1/plugins.py
index 587ed35..eaaf3f6 100644
--- a/app/api/v1/plugins.py
+++ b/app/api/v1/plugins.py
@@ -1181,7 +1181,20 @@ def render_project(
     output_path = os.path.join(settings.PROCESSED_DIR, safe_name)
     try:
         result_path = engine.render_project(req.project_json, output_path)
-        return {"url": f"/static/audio/processed/{os.path.basename(result_path)}", "path": result_path}
+        # EBU R128 loudness + true peak (D1) — trả kèm response để mastering
+        # panel hiển thị LUFS/dBTP ngay sau export mà không cần đọc lại file.
+        data, _sr = sf.read(result_path, dtype="float32", always_2d=True)
+        audio = data.T
+        from app.core import loudness
+        resp = {
+            "url": f"/static/audio/processed/{os.path.basename(result_path)}",
+            "path": result_path,
+        }
+        _lufs = loudness.integrated_lufs(audio, _sr)
+        _tp = loudness.true_peak_db(audio, _sr)
+        resp["lufs"] = round(_lufs, 2) if np.isfinite(_lufs) else None
+        resp["true_peak_db"] = round(_tp, 2) if np.isfinite(_tp) else None
+        return resp
     except Exception as e:
         raise HTTPException(status_code=500, detail=f"Render failed: {str(e)}")
 
diff --git a/app/core/loudness.py b/app/core/loudness.py
new file mode 100644
index 0000000..3979fbc
--- /dev/null
+++ b/app/core/loudness.py
@@ -0,0 +1,92 @@
+"""EBU R128 loudness + true peak (D1).
+
+- integrated_lufs: K-weighting (BS.1770) + 400 ms windows, 100 ms hop,
+  absolute (-70 LUFS) + relative (-10 LU) gating -> LUFS.
+- true_peak_db: 4x oversample (Kaiser-16) -> max |x| in dBTP.
+
+Stereo-only (channel weight 1.0 L/R); mono broadcast to 2 ch = same result.
+"""
+import numpy as np
+from scipy.signal import lfilter, resample_poly
+
+
+def _k_weighting_coeffs(sr: float):
+    """Two biquad stages per ITU-R BS.1770-4 (RBJ cookbook form)."""
+    # Stage 1: high shelf +4 dB, f0=1681.97 Hz, Q=0.7072
+    G = 3.999843853973347
+    f0 = 1681.974450955533
+    Q = 0.7071752369554196
+    A = 10 ** (G / 40.0)
+    w0 = 2 * np.pi * f0 / sr
+    alpha = np.sin(w0) / (2 * Q)
+    cosw = np.cos(w0)
+    b = np.array([
+        A * ((A + 1) + (A - 1) * cosw + 2 * np.sqrt(A) * alpha),
+        -2 * A * ((A - 1) + (A + 1) * cosw),
+        A * ((A + 1) + (A - 1) * cosw - 2 * np.sqrt(A) * alpha),
+    ])
+    a = np.array([
+        (A + 1) - (A - 1) * cosw + 2 * np.sqrt(A) * alpha,
+        2 * ((A - 1) - (A + 1) * cosw),
+        (A + 1) - (A - 1) * cosw - 2 * np.sqrt(A) * alpha,
+    ])
+    # Stage 2: high-pass f0=38.14 Hz, Q=0.5003
+    f1 = 38.13547087602444
+    Q1 = 0.5003270373238773
+    w1 = 2 * np.pi * f1 / sr
+    alpha1 = np.sin(w1) / (2 * Q1)
+    cosw1 = np.cos(w1)
+    hp_b = np.array([(1 + cosw1) / 2, -(1 + cosw1), (1 + cosw1) / 2])
+    hp_a = np.array([1 + alpha1, -2 * cosw1, 1 - alpha1])
+    return b / a[0], a / a[0], hp_b, hp_a
+
+
+def _k_weighted(audio: np.ndarray, sr: float) -> np.ndarray:
+    b1, a1, b2, a2 = _k_weighting_coeffs(sr)
+    out = np.empty_like(audio)
+    for c in range(audio.shape[0]):
+        out[c] = lfilter(b2, a2, lfilter(b1, a1, audio[c]))
+    return out
+
+
+def integrated_lufs(audio: np.ndarray, sr: float) -> float:
+    """Integrated loudness in LUFS (EBU R128 / BS.1770-4). -inf for silence."""
+    audio = np.asarray(audio, dtype=np.float64)
+    if audio.ndim == 1:
+        audio = audio[np.newaxis, :]
+    if audio.shape[1] == 0:
+        return -np.inf
+    k = _k_weighted(audio, sr)
+    block = int(round(0.4 * sr))
+    hop = int(round(0.1 * sr))
+    n = max(1, (k.shape[1] - block) // hop + 1)
+    powers = np.empty(n)
+    for i in range(n):
+        seg = k[:, i * hop:i * hop + block]
+        powers[i] = np.mean(seg ** 2)
+    # Absolute gate: -70 LUFS -> power = 10^((-70 + 0.691)/10)
+    abs_gate = 10 ** ((-70.0 + 0.691) / 10.0)
+    above_abs = powers[powers > abs_gate]
+    if above_abs.size == 0:
+        return -np.inf
+    abs_loud = -0.691 + 10.0 * np.log10(np.mean(above_abs))
+    # Relative gate: abs_loud - 10 LU
+    rel_gate = 10 ** ((abs_loud - 10.0 + 0.691) / 10.0)
+    gated = above_abs[above_abs > rel_gate]
+    if gated.size == 0:
+        gated = above_abs
+    return float(-0.691 + 10.0 * np.log10(np.mean(gated)))
+
+
+def true_peak_db(audio: np.ndarray, sr: float, oversample: int = 4) -> float:
+    """True peak in dBTP (4x oversample). -inf for digital silence."""
+    audio = np.asarray(audio, dtype=np.float64)
+    if audio.ndim == 1:
+        audio = audio[np.newaxis, :]
+    if audio.shape[1] == 0:
+        return -np.inf
+    up = resample_poly(audio, oversample, 1, axis=1, window=("kaiser", 16))
+    peak = float(np.max(np.abs(up)))
+    if peak <= 1e-12:
+        return -np.inf
+    return 20.0 * np.log10(peak)
diff --git a/tests/test_loudness.py b/tests/test_loudness.py
new file mode 100644
index 0000000..cde3cb0
--- /dev/null
+++ b/tests/test_loudness.py
@@ -0,0 +1,43 @@
+"""D1: EBU R128 loudness + true peak metrics (app/core/loudness.py)."""
+import numpy as np
+
+from app.core import loudness
+
+
+def _sine(dbfs, sr=44100, sec=3.0, freq=1000.0):
+    t = np.arange(int(sr * sec)) / sr
+    x = (10 ** (dbfs / 20.0)) * np.sin(2 * np.pi * freq * t)
+    return np.stack([x, x])
+
+
+def test_sine_minus20_lufs():
+    # 1 kHz sine @ -20 dBFS: RMS -23.01 dB + K-weight +0.44 dB - 0.691 offset
+    # => ~ -23.3 LUFS (0 dBFS sine ~ -3.7 LUFS per EBU R128).
+    audio = _sine(-20.0)
+    lufs = loudness.integrated_lufs(audio, 44100)
+    assert -24.5 < lufs < -22.0, lufs
+    tp = loudness.true_peak_db(audio, 44100)
+    assert abs(tp - (-20.0)) < 0.2, tp
+
+
+def test_true_peak_inter_sample_overshoot():
+    # Square-ish: sample peak 0 dBFS, oversampled true peak > 0 dBTP.
+    sr = 44100
+    x = np.repeat([1.0, 1.0, -1.0, -1.0], int(sr * 0.125))
+    audio = np.stack([x, x])
+    assert loudness.true_peak_db(audio, sr) > 0.05
+
+
+def test_silence_inf():
+    audio = np.zeros((2, 44100))
+    assert loudness.integrated_lufs(audio, 44100) == -np.inf
+    assert loudness.true_peak_db(audio, 44100) == -np.inf
+
+
+def test_mono_and_stereo_same():
+    sr = 44100
+    t = np.arange(sr * 2) / sr
+    x = 0.2 * np.sin(2 * np.pi * 440 * t)
+    mono = loudness.integrated_lufs(x, sr)
+    stereo = loudness.integrated_lufs(np.stack([x, x]), sr)
+    assert abs(mono - stereo) < 1e-6