diff --git a/docs/integration/calibration-appliance-integration.md b/docs/integration/calibration-appliance-integration.md
index a7c32588..00e9dcdb 100644
--- a/docs/integration/calibration-appliance-integration.md
+++ b/docs/integration/calibration-appliance-integration.md
@@ -88,7 +88,7 @@ UUID (`calibration_uuid()`) is the `baseline_id` referenced by enrollments and b
   "session": { "room_id": "...", "baseline_id": "...", "events": [ /* event-sourced audit log */ ] }
 }
 ```
-Anchor labels (fixed sequence): `empty, stand_still, sit, lie_down, breathe_slow, breathe_normal, small_move, sleep_posture`.
+Anchor labels (fixed sequence, **JSON wire = snake_case**, test-enforced): `empty, stand_still, sit, lie_down, breathe_slow, breathe_normal, small_move, sleep_posture`.
 
 ### 3.4 Specialist bank — JSON (`train-room` → `room-watch` / runtime)
 
@@ -136,6 +136,7 @@ Anchor labels (fixed sequence): `empty, stand_still, sit, lie_down, breathe_slow
 | GET | `/api/v1/calibration/result` | last finalized baseline summary |
 | GET | `/api/v1/calibration/baselines` | list persisted `.bin` baselines |
 | GET | `/api/v1/room/state?bank=<name>` | **live RoomState** (mixture-of-specialists over the CSI window; bank resolved as a sanitized name under `output_dir`) |
+| POST | `/api/v1/room/train` | `{ room_id, baseline_id, anchors[] }` → train + persist a specialist bank as `<output_dir>/<room_id>.json` (read back via `/room/state?bank=<room_id>`) |
 
 A single background task owns the UDP socket + recorder (handlers talk to it over an mpsc channel +
 shared status snapshot), so the API is non-blocking. Enrollment/train/room-state are CLI today
diff --git a/v2/crates/wifi-densepose-calibration/src/anchor.rs b/v2/crates/wifi-densepose-calibration/src/anchor.rs
index 868fc8e8..ae91ecfb 100644
--- a/v2/crates/wifi-densepose-calibration/src/anchor.rs
+++ b/v2/crates/wifi-densepose-calibration/src/anchor.rs
@@ -20,7 +20,11 @@ pub enum Posture {
 }
 
 /// The fixed guided-anchor sequence (ADR-151 §2.2).
+///
+/// Serializes as snake_case (`empty`, `stand_still`, …) to match
+/// [`AnchorLabel::as_str`] and the documented JSON contract.
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, Serialize, Deserialize)]
+#[serde(rename_all = "snake_case")]
 pub enum AnchorLabel {
     /// Empty room reference (reuses the ADR-135 baseline).
     Empty,
@@ -284,6 +288,17 @@ mod tests {
         assert_eq!(AnchorLabel::from_str("nope"), None);
     }
 
+    #[test]
+    fn label_serde_is_snake_case_matching_as_str() {
+        // The JSON wire format must equal as_str() (the documented contract).
+        for l in AnchorLabel::SEQUENCE {
+            let json = serde_json::to_string(&l).unwrap();
+            assert_eq!(json, format!("\"{}\"", l.as_str()));
+            let back: AnchorLabel = serde_json::from_str(&json).unwrap();
+            assert_eq!(back, l);
+        }
+    }
+
     #[test]
     fn sequence_order_and_next() {
         let mut s = EnrollmentSession::new("living-room", "base-1", 0);
diff --git a/v2/crates/wifi-densepose-cli/src/calibrate_api.rs b/v2/crates/wifi-densepose-cli/src/calibrate_api.rs
index 5522e91f..43034a3d 100644
--- a/v2/crates/wifi-densepose-cli/src/calibrate_api.rs
+++ b/v2/crates/wifi-densepose-cli/src/calibrate_api.rs
@@ -37,7 +37,7 @@ use serde::{Deserialize, Serialize};
 use tokio::net::UdpSocket;
 use tokio::sync::{mpsc, oneshot, RwLock};
 use tower_http::cors::CorsLayer;
-use wifi_densepose_calibration::extract::Features;
+use wifi_densepose_calibration::extract::{AnchorFeature, Features};
 use wifi_densepose_calibration::{MixtureOfSpecialists, SpecialistBank};
 use wifi_densepose_core::types::CsiFrame;
 use wifi_densepose_signal::{BaselineCalibration, CalibrationRecorder};
@@ -274,6 +274,7 @@ pub async fn execute(args: CalibrateServeArgs) -> Result<()> {
         .route("/api/v1/calibration/result", get(result))
         .route("/api/v1/calibration/baselines", get(baselines))
         .route("/api/v1/room/state", get(room_state))
+        .route("/api/v1/room/train", post(train_room))
         .layer(CorsLayer::permissive())
         .with_state(state);
 
@@ -528,7 +529,8 @@ async fn descriptor() -> impl IntoResponse {
             "POST /api/v1/calibration/stop": "finalize current session early",
             "GET  /api/v1/calibration/result": "last finalized baseline summary",
             "GET  /api/v1/calibration/baselines": "list persisted baseline files",
-            "GET  /api/v1/room/state?bank=<name>": "live mixture-of-specialists RoomState over the CSI window"
+            "GET  /api/v1/room/state?bank=<name>": "live mixture-of-specialists RoomState over the CSI window",
+            "POST /api/v1/room/train": "{ room_id, baseline_id, anchors[] } → train + persist a specialist bank"
         }
     }))
 }
@@ -588,6 +590,47 @@ async fn result(State(st): State<ApiState>) -> impl IntoResponse {
     }
 }
 
+/// Body for `POST /api/v1/room/train` — an enrollment (CLI `enroll` output or
+/// any client that gathered labelled anchor features).
+#[derive(Deserialize)]
+struct TrainRequest {
+    room_id: String,
+    baseline_id: String,
+    #[serde(default)]
+    anchors: Vec<AnchorFeature>,
+}
+
+/// Train a per-room specialist bank from posted anchors and persist it as
+/// `<output_dir>/<room_id>.json` (the name `room-state` reads back).
+async fn train_room(State(st): State<ApiState>, Json(req): Json<TrainRequest>) -> impl IntoResponse {
+    if req.anchors.is_empty() {
+        return (StatusCode::BAD_REQUEST, Json(serde_json::json!({"error":"no anchors in request"}))).into_response();
+    }
+    let at = (unix_ms() / 1000) as i64;
+    let bank = match SpecialistBank::train(&req.room_id, &req.baseline_id, &req.anchors, at) {
+        Ok(b) => b,
+        Err(e) => return (StatusCode::BAD_REQUEST, Json(serde_json::json!({"error": format!("training failed: {e}")}))).into_response(),
+    };
+    let name = sanitize_room_id(&req.room_id);
+    let dir = { st.status.read().await.output_dir.clone() };
+    let path = format!("{dir}/{name}.json");
+    let json = match bank.to_json() {
+        Ok(j) => j,
+        Err(e) => return (StatusCode::INTERNAL_SERVER_ERROR, Json(serde_json::json!({"error": format!("serialize: {e}")}))).into_response(),
+    };
+    if let Err(e) = tokio::fs::write(&path, json).await {
+        return (StatusCode::INTERNAL_SERVER_ERROR, Json(serde_json::json!({"error": format!("cannot write {path}: {e}")}))).into_response();
+    }
+    let kinds: Vec<String> = bank.trained_kinds().iter().map(|k| format!("{k:?}")).collect();
+    (StatusCode::OK, Json(serde_json::json!({
+        "room_id": bank.room_id,
+        "bank": name,                  // pass as ?bank=<name> to /room/state
+        "anchor_count": bank.anchor_count,
+        "specialists": kinds,
+        "path": path,
+    }))).into_response()
+}
+
 /// Query for `GET /api/v1/room/state`.
 #[derive(Deserialize)]
 struct RoomStateQuery {