diff --git a/ui/raw.html b/ui/raw.html
index f91dbd22..fe6f6a3a 100644
--- a/ui/raw.html
+++ b/ui/raw.html
@@ -48,22 +48,25 @@
   <span class="pill" id="lastTs">last: --</span>
   <span class="badge absent" id="globalBadge" style="font-size:13px;padding:4px 12px;">absent</span>
   <span class="pill" id="globalCV">CV 0%</span>
-  <!-- ADR-021: WiFi-CSI vital signs — breathing + heart rate (computed server-side).
-       Norm tags: adult-at-rest reference ranges shown next to the live value so
-       the operator can tell healthy vs. anomalous at a glance. -->
+  <!-- ADR-021 + ADR-121: dual-source vital signs.
+       Each pill shows WiFi-CSI (📶) and mmWave (📡) side-by-side so
+       the operator can spot disagreement between modalities. Norms
+       are adult-at-rest ranges. -->
   <span class="pill" id="brPill"
         style="background:rgba(63,185,80,0.18); color:rgb(63,185,80); border:1px solid rgb(63,185,80);"
-        title="WiFi-CSI breathing rate (bandpass 0.1-0.5 Hz, ADR-021). Adult-at-rest norm: 12-20 BPM. Below 12 = bradypnea, above 20 = tachypnea.">
-    🫁 <b id="brBpm">— BPM</b>
-    <span style="opacity:0.55;font-size:11px">норма 12–20</span>
-    <span id="brConf" style="opacity:0.7;font-size:11px">·</span>
+        title="Breathing rate, two sources: 📶 = WiFi-CSI bandpass 0.1-0.5 Hz (ADR-021). 📡 = HLK-LD2402 mmWave distance bandpass (ADR-121). Adult-at-rest norm: 12-20 BPM. Below 12 = bradypnea, above 20 = tachypnea.">
+    🫁 <span style="opacity:0.6;font-size:11px">📶</span><b id="brBpm">— BPM</b><span id="brConf" style="opacity:0.7;font-size:11px">·</span>
+    <span style="opacity:0.4">|</span>
+    <span style="opacity:0.6;font-size:11px">📡</span><b id="brBpmMm">— BPM</b><span id="brConfMm" style="opacity:0.7;font-size:11px">·</span>
+    <span style="opacity:0.55;font-size:11px;margin-left:6px">норма 12–20</span>
   </span>
   <span class="pill" id="hrPill"
         style="background:rgba(248,81,73,0.18); color:rgb(248,81,73); border:1px solid rgb(248,81,73);"
-        title="WiFi-CSI heart rate (bandpass 0.8-2.0 Hz, ADR-021). Adult-at-rest norm: 60-100 BPM. Below 60 = bradycardia, above 100 = tachycardia.">
-    💓 <b id="hrBpm">— BPM</b>
-    <span style="opacity:0.55;font-size:11px">норма 60–100</span>
-    <span id="hrConf" style="opacity:0.7;font-size:11px">·</span>
+        title="Heart rate, two sources: 📶 = WiFi-CSI bandpass 0.8-2.0 Hz (ADR-021). 📡 = HLK-LD2402 mmWave (cm precision and 6 Hz cadence put heartbeat below the noise floor — value shown for transparency, expect low confidence). Adult-at-rest norm: 60-100 BPM.">
+    💓 <span style="opacity:0.6;font-size:11px">📶</span><b id="hrBpm">— BPM</b><span id="hrConf" style="opacity:0.7;font-size:11px">·</span>
+    <span style="opacity:0.4">|</span>
+    <span style="opacity:0.6;font-size:11px">📡</span><b id="hrBpmMm">— BPM</b><span id="hrConfMm" style="opacity:0.7;font-size:11px">·</span>
+    <span style="opacity:0.55;font-size:11px;margin-left:6px">норма 60–100</span>
   </span>
   <!-- ADR-121: HLK-LD2402 24 GHz mmWave radar pill — hidden until first reading. -->
   <span class="pill" id="mmwavePill" style="display:none; background:rgba(33,150,243,0.18);
@@ -600,5 +603,57 @@ async function pollMmwave() {
 }
 pollMmwave();
 setInterval(pollMmwave, 200);
+
+// ── ADR-121 follow-up: poll mmWave-derived vital signs @ 1 Hz ────────
+// Slower than the distance poll (5 Hz) — BPM only meaningfully updates
+// once per breath cycle, and the FFT runs on a 30-s buffer so faster
+// polling just wastes cycles.
+const brBpmMm   = document.getElementById('brBpmMm');
+const brConfMm  = document.getElementById('brConfMm');
+const hrBpmMm   = document.getElementById('hrBpmMm');
+const hrConfMm  = document.getElementById('hrConfMm');
+let mmVitalsBusy = false;
+async function pollMmwaveVitals() {
+  if (mmVitalsBusy) return; mmVitalsBusy = true;
+  try {
+    const r = await fetch('/api/v1/mmwave/vitals', { cache: 'no-store' });
+    if (!r.ok) throw new Error('http ' + r.status);
+    const j = await r.json();
+    const vs = (j && j.available) ? (j.vital_signs || {}) : {};
+    const BR_MIN = 12, BR_MAX = 20, HR_MIN = 60, HR_MAX = 100;
+    if (typeof vs.breathing_rate_bpm === 'number' && Number.isFinite(vs.breathing_rate_bpm) && vs.breathing_rate_bpm > 0) {
+      const v = vs.breathing_rate_bpm;
+      const out = v < BR_MIN || v > BR_MAX;
+      brBpmMm.textContent = ' ' + v.toFixed(1) + ' BPM ';
+      brBpmMm.style.color = out ? '#f0a020' : '';
+      brConfMm.textContent = '· ' + ((vs.breathing_confidence || 0) * 100).toFixed(0) + '%';
+    } else {
+      brBpmMm.textContent = ' — BPM ';
+      brBpmMm.style.color = '';
+      // Buffer-fill hint: at 6 Hz × 30 s = 180 samples needed.
+      const fill = j && j.buffer_status ? j.buffer_status.breathing_samples : 0;
+      const cap  = j && j.buffer_status ? j.buffer_status.breathing_capacity : 180;
+      brConfMm.textContent = cap > 0 ? '· ' + fill + '/' + cap : '·';
+    }
+    if (typeof vs.heart_rate_bpm === 'number' && Number.isFinite(vs.heart_rate_bpm) && vs.heart_rate_bpm > 0) {
+      const v = vs.heart_rate_bpm;
+      const out = v < HR_MIN || v > HR_MAX;
+      hrBpmMm.textContent = ' ' + v.toFixed(0) + ' BPM ';
+      hrBpmMm.style.color = out ? '#f0a020' : '';
+      hrConfMm.textContent = '· ' + ((vs.heartbeat_confidence || 0) * 100).toFixed(0) + '%';
+    } else {
+      // mmWave at 6 Hz / cm precision can't resolve heartbeat —
+      // expect this to stay "n/a" in practice.
+      hrBpmMm.textContent = ' n/a ';
+      hrBpmMm.style.color = '';
+      hrConfMm.textContent = '·';
+    }
+  } catch (_) {
+    brBpmMm.textContent = ' — BPM '; brConfMm.textContent = '·';
+    hrBpmMm.textContent = ' n/a ';   hrConfMm.textContent = '·';
+  } finally { mmVitalsBusy = false; }
+}
+pollMmwaveVitals();
+setInterval(pollMmwaveVitals, 1000);
 </script>
 </body></html>
diff --git a/v2/crates/wifi-densepose-sensing-server/src/main.rs b/v2/crates/wifi-densepose-sensing-server/src/main.rs
index 6601c48c..71c2f15a 100644
--- a/v2/crates/wifi-densepose-sensing-server/src/main.rs
+++ b/v2/crates/wifi-densepose-sensing-server/src/main.rs
@@ -5100,6 +5100,36 @@ async fn mmwave_latest() -> Json<serde_json::Value> {
     }
 }
 
+/// ADR-121 follow-up: GET /api/v1/mmwave/vitals — breathing + (best-
+/// effort) heart-rate computed from the mmWave distance time-series.
+/// Returns `{ available: false }` if no recent reading or if the
+/// detector buffer is still warming up.
+///
+/// Same shape as `/api/v1/vital-signs` so the UI can render both
+/// sources with a single code path.
+async fn mmwave_vitals() -> Json<serde_json::Value> {
+    use wifi_densepose_sensing_server::mmwave;
+    let stale = std::time::Duration::from_secs(2);
+    match mmwave::current_vitals(stale) {
+        Some(vs) => {
+            let (br_samples, br_cap) = mmwave::buffer_status();
+            Json(serde_json::json!({
+                "available": true,
+                "source": "mmwave:hlk-ld2402",
+                "vital_signs": vs,
+                "buffer_status": {
+                    "breathing_samples": br_samples,
+                    "breathing_capacity": br_cap,
+                },
+            }))
+        }
+        None => Json(serde_json::json!({
+            "available": false,
+            "source": "mmwave:offline",
+        })),
+    }
+}
+
 /// POST /api/v1/adaptive/unload — unload the adaptive model (revert to thresholds).
 async fn adaptive_unload(State(state): State<SharedState>) -> Json<serde_json::Value> {
     let mut s = state.write().await;
@@ -7685,6 +7715,7 @@ async fn main() {
         .route("/api/v1/adaptive/status", get(adaptive_status))
         .route("/api/v1/adaptive/debug", get(adaptive_debug))
         .route("/api/v1/mmwave/latest", get(mmwave_latest))
+        .route("/api/v1/mmwave/vitals", get(mmwave_vitals))
         .route("/api/v1/adaptive/unload", post(adaptive_unload))
         // Field model calibration (eigenvalue-based person counting)
         .route("/api/v1/calibration/start", post(calibration_start))
diff --git a/v2/crates/wifi-densepose-sensing-server/src/mmwave.rs b/v2/crates/wifi-densepose-sensing-server/src/mmwave.rs
index 4e1d614e..f0a727de 100644
--- a/v2/crates/wifi-densepose-sensing-server/src/mmwave.rs
+++ b/v2/crates/wifi-densepose-sensing-server/src/mmwave.rs
@@ -18,6 +18,13 @@ use std::io::Read;
 use std::sync::{Mutex, OnceLock};
 use std::time::{Duration, Instant};
 
+use crate::vital_signs::{VitalSignDetector, VitalSigns};
+
+/// HLK-LD2402 Normal-Mode cadence: factory firmware emits ~6 distance
+/// lines/sec. We pick 6.0 Hz as the detector's nominal sample_rate so
+/// the breathing band (0.1–0.5 Hz) sits comfortably inside Nyquist.
+const MMWAVE_SAMPLE_RATE_HZ: f64 = 6.0;
+
 /// Latest mmWave reading + when it landed.
 #[derive(Debug, Clone, Copy)]
 pub struct MmwaveReading {
@@ -26,11 +33,21 @@ pub struct MmwaveReading {
 }
 
 static LATEST: OnceLock<Mutex<Option<MmwaveReading>>> = OnceLock::new();
+static VITALS: OnceLock<Mutex<Option<VitalSigns>>> = OnceLock::new();
+static DETECTOR: OnceLock<Mutex<VitalSignDetector>> = OnceLock::new();
 
 fn latest() -> &'static Mutex<Option<MmwaveReading>> {
     LATEST.get_or_init(|| Mutex::new(None))
 }
 
+fn vitals_slot() -> &'static Mutex<Option<VitalSigns>> {
+    VITALS.get_or_init(|| Mutex::new(None))
+}
+
+fn detector_slot() -> &'static Mutex<VitalSignDetector> {
+    DETECTOR.get_or_init(|| Mutex::new(VitalSignDetector::new(MMWAVE_SAMPLE_RATE_HZ)))
+}
+
 /// Returns the most recent reading if it landed within `staleness`.
 pub fn current(staleness: Duration) -> Option<MmwaveReading> {
     let g = latest().lock().unwrap();
@@ -38,6 +55,28 @@ pub fn current(staleness: Duration) -> Option<MmwaveReading> {
     if r.at.elapsed() <= staleness { Some(r) } else { None }
 }
 
+/// Returns the latest mmWave-derived VitalSigns. Breathing is
+/// computed from a 30-s buffer of distance samples (chest movement
+/// modulates range by 5–10 mm — visible as flicker between adjacent
+/// cm bins). Heart rate at 6 Hz / cm precision is essentially below
+/// the noise floor; we surface it but expect very low confidence.
+///
+/// Returns `None` if no recent mmWave reading exists within
+/// `staleness` (so the UI can show "—" when the radar is unplugged).
+pub fn current_vitals(staleness: Duration) -> Option<VitalSigns> {
+    // Gate on data freshness: if no recent distance reading, vitals
+    // are stale — return None rather than the last cached estimate.
+    current(staleness)?;
+    vitals_slot().lock().unwrap().clone()
+}
+
+/// Buffer fill stats for UI ("12/180 samples").
+pub fn buffer_status() -> (usize, usize) {
+    let det = detector_slot().lock().unwrap();
+    let (br_samples, br_cap, _hr_samples, _hr_cap) = det.buffer_status();
+    (br_samples, br_cap)
+}
+
 /// Spawn the blocking serial reader thread. Returns immediately.
 /// `port` example: `/dev/cu.usbserial-1140` (macOS) or `/dev/ttyUSB0`
 /// (Linux). `baud` should be 115200 for HLK-LD2402 default firmware.
@@ -84,6 +123,19 @@ fn run(port: String, baud: u32) {
                     distance_cm: cm,
                     at: Instant::now(),
                 });
+                // Feed the same value into a VitalSignDetector tuned for
+                // mmWave's 6 Hz cadence so we can publish a
+                // breathing-rate estimate from chest-induced cm
+                // flicker. Phase is empty (radar gives no phase here)
+                // — extract_heartbeat falls back to amplitude residual
+                // which is mostly noise at cm precision, but we
+                // surface it anyway for transparency.
+                let cm_f = cm as f64;
+                let vs = detector_slot()
+                    .lock()
+                    .unwrap()
+                    .process_frame(&[cm_f], &[]);
+                *vitals_slot().lock().unwrap() = Some(vs);
             } else if !line.is_empty() {
                 tracing::trace!("mmwave non-distance line: {line:?}");
             }
diff --git a/v2/crates/wifi-densepose-sensing-server/static/raw.html b/v2/crates/wifi-densepose-sensing-server/static/raw.html
index f91dbd22..fe6f6a3a 100644
--- a/v2/crates/wifi-densepose-sensing-server/static/raw.html
+++ b/v2/crates/wifi-densepose-sensing-server/static/raw.html
@@ -48,22 +48,25 @@
   <span class="pill" id="lastTs">last: --</span>
   <span class="badge absent" id="globalBadge" style="font-size:13px;padding:4px 12px;">absent</span>
   <span class="pill" id="globalCV">CV 0%</span>
-  <!-- ADR-021: WiFi-CSI vital signs — breathing + heart rate (computed server-side).
-       Norm tags: adult-at-rest reference ranges shown next to the live value so
-       the operator can tell healthy vs. anomalous at a glance. -->
+  <!-- ADR-021 + ADR-121: dual-source vital signs.
+       Each pill shows WiFi-CSI (📶) and mmWave (📡) side-by-side so
+       the operator can spot disagreement between modalities. Norms
+       are adult-at-rest ranges. -->
   <span class="pill" id="brPill"
         style="background:rgba(63,185,80,0.18); color:rgb(63,185,80); border:1px solid rgb(63,185,80);"
-        title="WiFi-CSI breathing rate (bandpass 0.1-0.5 Hz, ADR-021). Adult-at-rest norm: 12-20 BPM. Below 12 = bradypnea, above 20 = tachypnea.">
-    🫁 <b id="brBpm">— BPM</b>
-    <span style="opacity:0.55;font-size:11px">норма 12–20</span>
-    <span id="brConf" style="opacity:0.7;font-size:11px">·</span>
+        title="Breathing rate, two sources: 📶 = WiFi-CSI bandpass 0.1-0.5 Hz (ADR-021). 📡 = HLK-LD2402 mmWave distance bandpass (ADR-121). Adult-at-rest norm: 12-20 BPM. Below 12 = bradypnea, above 20 = tachypnea.">
+    🫁 <span style="opacity:0.6;font-size:11px">📶</span><b id="brBpm">— BPM</b><span id="brConf" style="opacity:0.7;font-size:11px">·</span>
+    <span style="opacity:0.4">|</span>
+    <span style="opacity:0.6;font-size:11px">📡</span><b id="brBpmMm">— BPM</b><span id="brConfMm" style="opacity:0.7;font-size:11px">·</span>
+    <span style="opacity:0.55;font-size:11px;margin-left:6px">норма 12–20</span>
   </span>
   <span class="pill" id="hrPill"
         style="background:rgba(248,81,73,0.18); color:rgb(248,81,73); border:1px solid rgb(248,81,73);"
-        title="WiFi-CSI heart rate (bandpass 0.8-2.0 Hz, ADR-021). Adult-at-rest norm: 60-100 BPM. Below 60 = bradycardia, above 100 = tachycardia.">
-    💓 <b id="hrBpm">— BPM</b>
-    <span style="opacity:0.55;font-size:11px">норма 60–100</span>
-    <span id="hrConf" style="opacity:0.7;font-size:11px">·</span>
+        title="Heart rate, two sources: 📶 = WiFi-CSI bandpass 0.8-2.0 Hz (ADR-021). 📡 = HLK-LD2402 mmWave (cm precision and 6 Hz cadence put heartbeat below the noise floor — value shown for transparency, expect low confidence). Adult-at-rest norm: 60-100 BPM.">
+    💓 <span style="opacity:0.6;font-size:11px">📶</span><b id="hrBpm">— BPM</b><span id="hrConf" style="opacity:0.7;font-size:11px">·</span>
+    <span style="opacity:0.4">|</span>
+    <span style="opacity:0.6;font-size:11px">📡</span><b id="hrBpmMm">— BPM</b><span id="hrConfMm" style="opacity:0.7;font-size:11px">·</span>
+    <span style="opacity:0.55;font-size:11px;margin-left:6px">норма 60–100</span>
   </span>
   <!-- ADR-121: HLK-LD2402 24 GHz mmWave radar pill — hidden until first reading. -->
   <span class="pill" id="mmwavePill" style="display:none; background:rgba(33,150,243,0.18);
@@ -600,5 +603,57 @@ async function pollMmwave() {
 }
 pollMmwave();
 setInterval(pollMmwave, 200);
+
+// ── ADR-121 follow-up: poll mmWave-derived vital signs @ 1 Hz ────────
+// Slower than the distance poll (5 Hz) — BPM only meaningfully updates
+// once per breath cycle, and the FFT runs on a 30-s buffer so faster
+// polling just wastes cycles.
+const brBpmMm   = document.getElementById('brBpmMm');
+const brConfMm  = document.getElementById('brConfMm');
+const hrBpmMm   = document.getElementById('hrBpmMm');
+const hrConfMm  = document.getElementById('hrConfMm');
+let mmVitalsBusy = false;
+async function pollMmwaveVitals() {
+  if (mmVitalsBusy) return; mmVitalsBusy = true;
+  try {
+    const r = await fetch('/api/v1/mmwave/vitals', { cache: 'no-store' });
+    if (!r.ok) throw new Error('http ' + r.status);
+    const j = await r.json();
+    const vs = (j && j.available) ? (j.vital_signs || {}) : {};
+    const BR_MIN = 12, BR_MAX = 20, HR_MIN = 60, HR_MAX = 100;
+    if (typeof vs.breathing_rate_bpm === 'number' && Number.isFinite(vs.breathing_rate_bpm) && vs.breathing_rate_bpm > 0) {
+      const v = vs.breathing_rate_bpm;
+      const out = v < BR_MIN || v > BR_MAX;
+      brBpmMm.textContent = ' ' + v.toFixed(1) + ' BPM ';
+      brBpmMm.style.color = out ? '#f0a020' : '';
+      brConfMm.textContent = '· ' + ((vs.breathing_confidence || 0) * 100).toFixed(0) + '%';
+    } else {
+      brBpmMm.textContent = ' — BPM ';
+      brBpmMm.style.color = '';
+      // Buffer-fill hint: at 6 Hz × 30 s = 180 samples needed.
+      const fill = j && j.buffer_status ? j.buffer_status.breathing_samples : 0;
+      const cap  = j && j.buffer_status ? j.buffer_status.breathing_capacity : 180;
+      brConfMm.textContent = cap > 0 ? '· ' + fill + '/' + cap : '·';
+    }
+    if (typeof vs.heart_rate_bpm === 'number' && Number.isFinite(vs.heart_rate_bpm) && vs.heart_rate_bpm > 0) {
+      const v = vs.heart_rate_bpm;
+      const out = v < HR_MIN || v > HR_MAX;
+      hrBpmMm.textContent = ' ' + v.toFixed(0) + ' BPM ';
+      hrBpmMm.style.color = out ? '#f0a020' : '';
+      hrConfMm.textContent = '· ' + ((vs.heartbeat_confidence || 0) * 100).toFixed(0) + '%';
+    } else {
+      // mmWave at 6 Hz / cm precision can't resolve heartbeat —
+      // expect this to stay "n/a" in practice.
+      hrBpmMm.textContent = ' n/a ';
+      hrBpmMm.style.color = '';
+      hrConfMm.textContent = '·';
+    }
+  } catch (_) {
+    brBpmMm.textContent = ' — BPM '; brConfMm.textContent = '·';
+    hrBpmMm.textContent = ' n/a ';   hrConfMm.textContent = '·';
+  } finally { mmVitalsBusy = false; }
+}
+pollMmwaveVitals();
+setInterval(pollMmwaveVitals, 1000);
 </script>
 </body></html>