diff --git a/ios/App/CoachWatch/WorkoutManager.swift b/ios/App/CoachWatch/WorkoutManager.swift
index 029f1bf..91affb9 100644
--- a/ios/App/CoachWatch/WorkoutManager.swift
+++ b/ios/App/CoachWatch/WorkoutManager.swift
@@ -1,5 +1,8 @@
 import Foundation
 import HealthKit
+import os
+
+private let workoutLog = Logger(subsystem: "ch.hypnotruck.coach.watchkitapp", category: "workout")
 
 /// Pilote la séance via HKLiveWorkoutBuilder et pousse les metrics vers l'iPhone.
 /// `@MainActor` (donc Sendable) : l'état observable vit sur le main ; les callbacks
@@ -39,7 +42,10 @@ final class WorkoutManager: NSObject, ObservableObject {
 
         do {
             try await healthStore.requestAuthorization(toShare: share, read: read)
+            let woStatus = healthStore.authorizationStatus(for: HKQuantityType.workoutType())
+            workoutLog.info("requestAuthorization OK; workoutType share status=\(woStatus.rawValue)")
         } catch {
+            workoutLog.error("requestAuthorization threw: \(error.localizedDescription)")
             statusMessage = "Autorisation Santé refusée : \(error.localizedDescription)"
             return
         }
@@ -60,12 +66,16 @@ final class WorkoutManager: NSObject, ObservableObject {
 
             let start = Date()
             session.startActivity(with: start)
+            workoutLog.info("startActivity called, beginning collection…")
             try await builder.beginCollection(at: start)
             isRunning = true
             statusMessage = nil
+            workoutLog.info("beginCollection OK, isRunning=true")
         } catch {
             self.session = nil
             self.builder = nil
+            let ns = error as NSError
+            workoutLog.error("start failed domain=\(ns.domain) code=\(ns.code): \(error.localizedDescription)")
             statusMessage = "Démarrage séance impossible : \(error.localizedDescription)"
         }
     }
@@ -138,6 +148,7 @@ extension WorkoutManager: HKWorkoutSessionDelegate {
                                     didChangeTo toState: HKWorkoutSessionState,
                                     from fromState: HKWorkoutSessionState,
                                     date: Date) {
+        workoutLog.info("session didChangeTo state=\(toState.rawValue) from=\(fromState.rawValue)")
         guard toState == .ended else { return }
         let builder = workoutSession.associatedWorkoutBuilder()
         Task {
@@ -154,6 +165,8 @@ extension WorkoutManager: HKWorkoutSessionDelegate {
     nonisolated func workoutSession(_ workoutSession: HKWorkoutSession,
                                     didFailWithError error: Error) {
         let message = error.localizedDescription
+        let ns = error as NSError
+        workoutLog.error("session didFailWithError domain=\(ns.domain) code=\(ns.code): \(message)")
         Task { @MainActor in
             self.statusMessage = "Erreur séance : \(message)"
             self.isRunning = false