diff --git a/ios/App/CoachWatch/WorkoutManager.swift b/ios/App/CoachWatch/WorkoutManager.swift
index a86556f..13c5a03 100644
--- a/ios/App/CoachWatch/WorkoutManager.swift
+++ b/ios/App/CoachWatch/WorkoutManager.swift
@@ -2,6 +2,9 @@ import Foundation
 import HealthKit
 
 /// Pilote la séance via HKLiveWorkoutBuilder et pousse les metrics vers l'iPhone.
+/// `@MainActor` (donc Sendable) : l'état observable vit sur le main ; les callbacks
+/// HealthKit, livrés hors-main, sont `nonisolated` et hoppent vers le main.
+@MainActor
 final class WorkoutManager: NSObject, ObservableObject {
     static let shared = WorkoutManager()
 
@@ -15,12 +18,7 @@ final class WorkoutManager: NSObject, ObservableObject {
     private let healthStore = HKHealthStore()
     private var session: HKWorkoutSession?
     private var builder: HKLiveWorkoutBuilder?
-    private var distanceType = HKQuantityType(.distanceWalkingRunning)
 
-    // Valeurs de travail, mutées uniquement dans les callbacks HealthKit (livrés sérialisés).
-    private var bHeartRate = 0.0
-    private var bEnergy = 0.0
-    private var bDistance = 0.0
     private var lastSentAt = Date.distantPast
     private let sendInterval: TimeInterval = 2
 
@@ -29,11 +27,10 @@ final class WorkoutManager: NSObject, ObservableObject {
     func startWorkout(activityType: HKWorkoutActivityType,
                       locationType: HKWorkoutSessionLocationType) async {
         guard HKHealthStore.isHealthDataAvailable() else {
-            setStatus("HealthKit indisponible sur cet appareil")
+            statusMessage = "HealthKit indisponible sur cet appareil"
             return
         }
-        distanceType = Self.distanceType(for: activityType)
-
+        let distanceType = Self.distanceType(for: activityType)
         let hr = HKQuantityType(.heartRate)
         let energy = HKQuantityType(.activeEnergyBurned)
         let read: Set<HKObjectType> = [hr, energy, distanceType]
@@ -42,7 +39,7 @@ final class WorkoutManager: NSObject, ObservableObject {
         do {
             try await healthStore.requestAuthorization(toShare: share, read: read)
         } catch {
-            setStatus("Autorisation Santé refusée : \(error.localizedDescription)")
+            statusMessage = "Autorisation Santé refusée : \(error.localizedDescription)"
             return
         }
 
@@ -63,12 +60,10 @@ final class WorkoutManager: NSObject, ObservableObject {
             let start = Date()
             session.startActivity(with: start)
             try await builder.beginCollection(at: start)
-            await MainActor.run {
-                self.isRunning = true
-                self.statusMessage = nil
-            }
+            isRunning = true
+            statusMessage = nil
         } catch {
-            setStatus("Démarrage séance impossible : \(error.localizedDescription)")
+            statusMessage = "Démarrage séance impossible : \(error.localizedDescription)"
         }
     }
 
@@ -76,8 +71,23 @@ final class WorkoutManager: NSObject, ObservableObject {
     func resume() { session?.resume() }
     func end() { session?.end() }
 
-    private func setStatus(_ message: String) {
-        DispatchQueue.main.async { [weak self] in self?.statusMessage = message }
+    /// Appelé sur le main depuis le callback de collecte (hors-main).
+    private func ingest(hr: Double?, kcal: Double?, dist: Double?, elapsed: TimeInterval) {
+        if let hr { heartRate = hr }
+        if let kcal { activeEnergyKcal = kcal }
+        if let dist { distanceMeters = dist }
+        elapsedSec = elapsed
+
+        let now = Date()
+        guard now.timeIntervalSince(lastSentAt) >= sendInterval else { return }
+        lastSentAt = now
+        ConnectivityManager.shared.sendSample([
+            "heartRate": heartRate,
+            "activeEnergyKcal": activeEnergyKcal,
+            "distanceMeters": distanceMeters,
+            "elapsedSec": elapsed,
+            "ts": now.timeIntervalSince1970
+        ])
     }
 
     private static func distanceType(for activity: HKWorkoutActivityType) -> HKQuantityType {
@@ -88,70 +98,58 @@ final class WorkoutManager: NSObject, ObservableObject {
 }
 
 extension WorkoutManager: HKLiveWorkoutBuilderDelegate {
-    func workoutBuilder(_ workoutBuilder: HKLiveWorkoutBuilder,
-                        didCollectDataOf collectedTypes: Set<HKSampleType>) {
+    nonisolated func workoutBuilder(_ workoutBuilder: HKLiveWorkoutBuilder,
+                                    didCollectDataOf collectedTypes: Set<HKSampleType>) {
         let hrType = HKQuantityType(.heartRate)
         let energyType = HKQuantityType(.activeEnergyBurned)
+        let walkRun = HKQuantityType(.distanceWalkingRunning)
+        let cycling = HKQuantityType(.distanceCycling)
+
+        var hr: Double?
+        var kcal: Double?
+        var dist: Double?
 
         for type in collectedTypes {
             guard let qType = type as? HKQuantityType,
                   let stats = workoutBuilder.statistics(for: qType) else { continue }
             if qType == hrType {
                 let bpm = HKUnit.count().unitDivided(by: .minute())
-                if let v = stats.mostRecentQuantity()?.doubleValue(for: bpm) { bHeartRate = v }
+                hr = stats.mostRecentQuantity()?.doubleValue(for: bpm)
             } else if qType == energyType {
-                if let v = stats.sumQuantity()?.doubleValue(for: .kilocalorie()) { bEnergy = v }
-            } else if qType == distanceType {
-                if let v = stats.sumQuantity()?.doubleValue(for: .meter()) { bDistance = v }
+                kcal = stats.sumQuantity()?.doubleValue(for: .kilocalorie())
+            } else if qType == walkRun || qType == cycling {
+                dist = stats.sumQuantity()?.doubleValue(for: .meter())
             }
         }
         let elapsed = workoutBuilder.elapsedTime
-        publish(elapsed: elapsed)
-        maybeSend(elapsed: elapsed)
-    }
-
-    func workoutBuilderDidCollectEvent(_ workoutBuilder: HKLiveWorkoutBuilder) {}
-
-    private func publish(elapsed: TimeInterval) {
-        let hr = bHeartRate, kcal = bEnergy, dist = bDistance
-        DispatchQueue.main.async { [weak self] in
-            guard let self else { return }
-            self.heartRate = hr
-            self.activeEnergyKcal = kcal
-            self.distanceMeters = dist
-            self.elapsedSec = elapsed
+        Task { @MainActor in
+            self.ingest(hr: hr, kcal: kcal, dist: dist, elapsed: elapsed)
         }
     }
 
-    private func maybeSend(elapsed: TimeInterval) {
-        let now = Date()
-        guard now.timeIntervalSince(lastSentAt) >= sendInterval else { return }
-        lastSentAt = now
-        ConnectivityManager.shared.sendSample([
-            "heartRate": bHeartRate,
-            "activeEnergyKcal": bEnergy,
-            "distanceMeters": bDistance,
-            "elapsedSec": elapsed,
-            "ts": now.timeIntervalSince1970
-        ])
-    }
+    nonisolated func workoutBuilderDidCollectEvent(_ workoutBuilder: HKLiveWorkoutBuilder) {}
 }
 
 extension WorkoutManager: HKWorkoutSessionDelegate {
-    func workoutSession(_ workoutSession: HKWorkoutSession,
-                        didChangeTo toState: HKWorkoutSessionState,
-                        from fromState: HKWorkoutSessionState,
-                        date: Date) {
-        guard toState == .ended, let builder else { return }
-        Task { [weak self] in
+    nonisolated func workoutSession(_ workoutSession: HKWorkoutSession,
+                                    didChangeTo toState: HKWorkoutSessionState,
+                                    from fromState: HKWorkoutSessionState,
+                                    date: Date) {
+        guard toState == .ended else { return }
+        let builder = workoutSession.associatedWorkoutBuilder()
+        Task {
             try? await builder.endCollection(at: date)
             _ = try? await builder.finishWorkout()
-            await MainActor.run { self?.isRunning = false }
         }
+        Task { @MainActor in self.isRunning = false }
     }
 
-    func workoutSession(_ workoutSession: HKWorkoutSession, didFailWithError error: Error) {
-        setStatus("Erreur séance : \(error.localizedDescription)")
-        DispatchQueue.main.async { [weak self] in self?.isRunning = false }
+    nonisolated func workoutSession(_ workoutSession: HKWorkoutSession,
+                                    didFailWithError error: Error) {
+        let message = error.localizedDescription
+        Task { @MainActor in
+            self.statusMessage = "Erreur séance : \(message)"
+            self.isRunning = false
+        }
     }
 }