diff --git a/shared/build.gradle.kts b/shared/build.gradle.kts
index 992120a0d..47772b793 100644
--- a/shared/build.gradle.kts
+++ b/shared/build.gradle.kts
@@ -210,8 +210,8 @@ sqldelight {
     databases {
         create("VitruvianDatabase") {
             packageName.set("com.devil.phoenixproject.database")
-            // Version 43 = initial schema (1) + 42 migrations (1.sqm through 42.sqm).
-            version = 43
+            // Version 44 = initial schema (1) + 43 migrations (1.sqm through 43.sqm).
+            version = 44
         }
     }
 }
diff --git a/shared/src/androidHostTest/kotlin/com/devil/phoenixproject/data/local/SchemaParityTest.kt b/shared/src/androidHostTest/kotlin/com/devil/phoenixproject/data/local/SchemaParityTest.kt
index 10784eda9..c2017bd80 100644
--- a/shared/src/androidHostTest/kotlin/com/devil/phoenixproject/data/local/SchemaParityTest.kt
+++ b/shared/src/androidHostTest/kotlin/com/devil/phoenixproject/data/local/SchemaParityTest.kt
@@ -638,10 +638,73 @@ class SchemaParityTest {
         assertEquals(true, getTables(driver).contains("PendingProfileContextRecovery"))
     }
 
+    @Test
+    fun `migration 42 to 43 adds set_end_reason column and preserves existing rows with default`() {
+        val driver = JdbcSqliteDriver(JdbcSqliteDriver.IN_MEMORY)
+        buildSchemaAtVersion(driver, 42)
+
+        // Create prerequisite rows: UserProfile, Routine, WorkoutSession
+        // Note: profile_id is added by manifest reconciliation, not by migration 42.
+        // Use columns available at schema v42 (pre-reconciliation).
+        driver.execute(null, "INSERT INTO UserProfile(id,name,colorIndex,createdAt,isActive) VALUES('u1','U1',0,1,1)", 0)
+        driver.execute(null, "INSERT INTO Routine(id,name,createdAt) VALUES('r1','R1',1)", 0)
+        driver.execute(null, "INSERT INTO RoutineExercise(id,routineId,exerciseName,exerciseMuscleGroup,orderIndex,weightPerCableKg) VALUES('re1','r1','Bench','Chest',0,40.0)", 0)
+        driver.execute(null, "INSERT INTO WorkoutSession(id,timestamp,mode,targetReps,weightPerCableKg) VALUES('s1',1,'OldSchool',10,40.0)", 0)
+
+        // Insert a CompletedSet BEFORE migration 43 (no set_end_reason column yet)
+        driver.execute(
+            null,
+            """
+            INSERT INTO CompletedSet (id, session_id, set_number, set_type, actual_reps, actual_weight_kg, is_pr, completed_at)
+            VALUES ('cs-pre-mig', 's1', 1, 'STANDARD', 8, 40.0, 0, 1000)
+            """.trimIndent(),
+            0,
+        )
+
+        // Migrate 42 → 43 with resilient fallback (matches production behavior)
+        try {
+            VitruvianDatabase.Schema.migrate(driver, 42, 43)
+        } catch (_: Exception) {
+            applyMigrationResilient(driver, 42)
+        }
+
+        assertEquals(true, columnExistsInDriver(driver, "CompletedSet", "set_end_reason"))
+
+        // Pre-existing row must have the default value
+        assertEquals("TARGET_REPS_REACHED", queryScalar(driver, "SELECT set_end_reason FROM CompletedSet WHERE id = 'cs-pre-mig'"))
+    }
+
+    @Test
+    fun `resilient migration 43 fallback adds set_end_reason when column already exists`() {
+        val driver = JdbcSqliteDriver(JdbcSqliteDriver.IN_MEMORY)
+        buildSchemaAtVersion(driver, 42)
+
+        // Simulate schema drift: column already added by heal
+        driver.execute(null, "ALTER TABLE CompletedSet ADD COLUMN set_end_reason TEXT NOT NULL DEFAULT 'TARGET_REPS_REACHED'", 0)
+
+        driver.execute(null, "INSERT INTO UserProfile(id,name,colorIndex,createdAt,isActive) VALUES('u1','U1',0,1,1)", 0)
+        driver.execute(null, "INSERT INTO Routine(id,name,createdAt) VALUES('r1','R1',1)", 0)
+        driver.execute(null, "INSERT INTO RoutineExercise(id,routineId,exerciseName,exerciseMuscleGroup,orderIndex,weightPerCableKg) VALUES('re1','r1','Bench','Chest',0,40.0)", 0)
+        driver.execute(null, "INSERT INTO WorkoutSession(id,timestamp,mode,targetReps,weightPerCableKg) VALUES('s1',1,'OldSchool',10,40.0)", 0)
+        driver.execute(
+            null,
+            """
+            INSERT INTO CompletedSet (id, session_id, set_number, set_type, actual_reps, actual_weight_kg, is_pr, completed_at, set_end_reason)
+            VALUES ('cs-resilient', 's1', 1, 'STANDARD', 8, 40.0, 0, 1000, 'STALL_FAILURE')
+            """.trimIndent(),
+            0,
+        )
+
+        // Resilient fallback should succeed even though the column already exists
+        applyMigrationResilient(driver, 43)
+
+        assertEquals("STALL_FAILURE", queryScalar(driver, "SELECT set_end_reason FROM CompletedSet WHERE id = 'cs-resilient'"))
+    }
+
     // ==================== HELPERS ====================
 
     companion object {
-        private const val EXPECTED_SCHEMA_VERSION = 43L
+        private const val EXPECTED_SCHEMA_VERSION = 44L
         private val CANONICAL_UUID_REGEX = Regex("^[0-9a-f]{8}-[0-9a-f]{4}-4[0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$")
 
         /**
diff --git a/shared/src/androidHostTest/kotlin/com/devil/phoenixproject/data/repository/SqlDelightCompletedSetRepositoryTest.kt b/shared/src/androidHostTest/kotlin/com/devil/phoenixproject/data/repository/SqlDelightCompletedSetRepositoryTest.kt
index d33e2adc4..72111c3b3 100644
--- a/shared/src/androidHostTest/kotlin/com/devil/phoenixproject/data/repository/SqlDelightCompletedSetRepositoryTest.kt
+++ b/shared/src/androidHostTest/kotlin/com/devil/phoenixproject/data/repository/SqlDelightCompletedSetRepositoryTest.kt
@@ -3,6 +3,7 @@ package com.devil.phoenixproject.data.repository
 import com.devil.phoenixproject.database.VitruvianDatabase
 import com.devil.phoenixproject.domain.model.CompletedSet
 import com.devil.phoenixproject.domain.model.PlannedSet
+import com.devil.phoenixproject.domain.model.SetEndReason
 import com.devil.phoenixproject.domain.model.SetType
 import com.devil.phoenixproject.testutil.createTestDatabase
 import kotlin.test.assertEquals
@@ -71,6 +72,37 @@ class SqlDelightCompletedSetRepositoryTest {
         assertEquals(2, sets.size)
     }
 
+    @Test
+    fun `saveCompletedSet round-trips setEndReason STALL_FAILURE`() = runTest {
+        val completed = completedSet("cset-stall", "session-1", setNumber = 1, setEndReason = SetEndReason.STALL_FAILURE)
+        repository.saveCompletedSet(completed)
+
+        val loaded = repository.getCompletedSets("session-1").first { it.id == "cset-stall" }
+        assertEquals(SetEndReason.STALL_FAILURE, loaded.setEndReason)
+    }
+
+    @Test
+    fun `saveCompletedSet round-trips setEndReason TARGET_REPS_REACHED default`() = runTest {
+        val completed = completedSet("cset-default", "session-1", setNumber = 1)
+        repository.saveCompletedSet(completed)
+
+        val loaded = repository.getCompletedSets("session-1").first { it.id == "cset-default" }
+        assertEquals(SetEndReason.TARGET_REPS_REACHED, loaded.setEndReason)
+    }
+
+    @Test
+    fun `saveCompletedSet round-trips all SetEndReason values`() = runTest {
+        for ((index, reason) in SetEndReason.entries.withIndex()) {
+            repository.saveCompletedSet(completedSet("cset-$index", "session-1", setNumber = index + 1, setEndReason = reason))
+        }
+
+        val loaded = repository.getCompletedSets("session-1")
+        assertEquals(SetEndReason.entries.size, loaded.size)
+        for ((index, reason) in SetEndReason.entries.withIndex()) {
+            assertEquals(reason, loaded[index].setEndReason, "Mismatch at index $index")
+        }
+    }
+
     private fun plannedSet(
         id: String,
         routineExerciseId: String,
@@ -89,7 +121,7 @@ class SqlDelightCompletedSetRepositoryTest {
         restSeconds = restSeconds,
     )
 
-    private fun completedSet(id: String, sessionId: String, setNumber: Int) = CompletedSet(
+    private fun completedSet(id: String, sessionId: String, setNumber: Int, setEndReason: SetEndReason = SetEndReason.TARGET_REPS_REACHED) = CompletedSet(
         id = id,
         sessionId = sessionId,
         plannedSetId = null,
@@ -100,6 +132,7 @@ class SqlDelightCompletedSetRepositoryTest {
         loggedRpe = null,
         isPr = false,
         completedAt = 1000L + setNumber,
+        setEndReason = setEndReason,
     )
 
     private fun insertRoutine(id: String) {
diff --git a/shared/src/androidHostTest/kotlin/com/devil/phoenixproject/util/DataBackupManagerRoutineNameTest.kt b/shared/src/androidHostTest/kotlin/com/devil/phoenixproject/util/DataBackupManagerRoutineNameTest.kt
index 3071ce6c5..c14da203e 100644
--- a/shared/src/androidHostTest/kotlin/com/devil/phoenixproject/util/DataBackupManagerRoutineNameTest.kt
+++ b/shared/src/androidHostTest/kotlin/com/devil/phoenixproject/util/DataBackupManagerRoutineNameTest.kt
@@ -542,6 +542,7 @@ class DataBackupManagerRoutineNameTest {
             logged_rpe = null,
             is_pr = 0,
             completed_at = 1700000060000L,
+            set_end_reason = "TARGET_REPS_REACHED",
         )
 
         // Export just this session
@@ -650,6 +651,7 @@ class DataBackupManagerRoutineNameTest {
             logged_rpe = null,
             is_pr = 0,
             completed_at = 1_700_000_006_000L,
+            set_end_reason = "TARGET_REPS_REACHED",
         )
         database.vitruvianDatabaseQueries.insertCompletedSetIgnore(
             id = "cs-row",
@@ -662,6 +664,7 @@ class DataBackupManagerRoutineNameTest {
             logged_rpe = null,
             is_pr = 0,
             completed_at = 1_700_000_106_000L,
+            set_end_reason = "TARGET_REPS_REACHED",
         )
 
         val result = backupManager.exportRoutine(sharedRoutineSessionId)
diff --git a/shared/src/commonMain/kotlin/com/devil/phoenixproject/data/local/MigrationStatements.kt b/shared/src/commonMain/kotlin/com/devil/phoenixproject/data/local/MigrationStatements.kt
index 51f71bd8f..951fe5bca 100644
--- a/shared/src/commonMain/kotlin/com/devil/phoenixproject/data/local/MigrationStatements.kt
+++ b/shared/src/commonMain/kotlin/com/devil/phoenixproject/data/local/MigrationStatements.kt
@@ -1016,5 +1016,12 @@ WHERE gs.rowid = (
     SELECT id FROM UserProfile""",
     )
 
+    // Migration 43: Add set_end_reason to CompletedSet (Issue #673 PR 1)
+    // Records why a set ended for workout history analytics.
+    // Mirrors 43.sqm exactly.
+    43 -> listOf(
+        "ALTER TABLE CompletedSet ADD COLUMN set_end_reason TEXT NOT NULL DEFAULT 'TARGET_REPS_REACHED'",
+    )
+
     else -> emptyList()
 }
diff --git a/shared/src/commonMain/kotlin/com/devil/phoenixproject/data/local/SchemaManifest.kt b/shared/src/commonMain/kotlin/com/devil/phoenixproject/data/local/SchemaManifest.kt
index f8cc59202..7440040e7 100644
--- a/shared/src/commonMain/kotlin/com/devil/phoenixproject/data/local/SchemaManifest.kt
+++ b/shared/src/commonMain/kotlin/com/devil/phoenixproject/data/local/SchemaManifest.kt
@@ -1141,7 +1141,7 @@ internal val manifestTables: List<SchemaTableOperation> = listOf(
         """.trimIndent(),
     ),
 
-    // CompletedSet -- migration 10, full shape (no later migrations add columns)
+    // CompletedSet -- migration 10, columns added by later migrations: set_end_reason (m43)
     SchemaTableOperation(
         table = "CompletedSet",
         createSql = """
@@ -1156,6 +1156,7 @@ internal val manifestTables: List<SchemaTableOperation> = listOf(
                 logged_rpe INTEGER,
                 is_pr INTEGER NOT NULL DEFAULT 0,
                 completed_at INTEGER NOT NULL,
+                set_end_reason TEXT NOT NULL DEFAULT 'TARGET_REPS_REACHED',
                 FOREIGN KEY (session_id) REFERENCES WorkoutSession(id) ON DELETE CASCADE,
                 FOREIGN KEY (planned_set_id) REFERENCES PlannedSet(id) ON DELETE SET NULL
             )
@@ -1437,6 +1438,10 @@ internal val manifestColumns: List<SchemaHealOperation> = listOf(
     // ── ExternalActivity (1 column, migration 31) ──────────────────────
     // Migration 31: provider tombstone handling
     SchemaHealOperation("ExternalActivity", "deletedAt", "ALTER TABLE ExternalActivity ADD COLUMN deletedAt INTEGER"),
+
+    // ── CompletedSet (1 column, migration 43) ──────────────────────────
+    // Migration 43: set-end reason for workout history analytics (Issue #673 PR 1)
+    SchemaHealOperation("CompletedSet", "set_end_reason", "ALTER TABLE CompletedSet ADD COLUMN set_end_reason TEXT NOT NULL DEFAULT 'TARGET_REPS_REACHED'"),
 )
 
 // ============================================================
diff --git a/shared/src/commonMain/kotlin/com/devil/phoenixproject/data/repository/SqlDelightCompletedSetRepository.kt b/shared/src/commonMain/kotlin/com/devil/phoenixproject/data/repository/SqlDelightCompletedSetRepository.kt
index 10a3d35a5..f6bdda67d 100644
--- a/shared/src/commonMain/kotlin/com/devil/phoenixproject/data/repository/SqlDelightCompletedSetRepository.kt
+++ b/shared/src/commonMain/kotlin/com/devil/phoenixproject/data/repository/SqlDelightCompletedSetRepository.kt
@@ -5,6 +5,7 @@ import app.cash.sqldelight.coroutines.mapToList
 import com.devil.phoenixproject.database.VitruvianDatabase
 import com.devil.phoenixproject.domain.model.CompletedSet
 import com.devil.phoenixproject.domain.model.PlannedSet
+import com.devil.phoenixproject.domain.model.SetEndReason
 import com.devil.phoenixproject.domain.model.SetType
 import com.devil.phoenixproject.domain.model.WorkoutSession
 import com.devil.phoenixproject.domain.model.generateUUID
@@ -54,6 +55,7 @@ class SqlDelightCompletedSetRepository(db: VitruvianDatabase) : CompletedSetRepo
         loggedRpe: Long?,
         isPr: Long,
         completedAt: Long,
+        setEndReason: String,
     ): CompletedSet = CompletedSet(
         id = id,
         sessionId = sessionId,
@@ -65,6 +67,8 @@ class SqlDelightCompletedSetRepository(db: VitruvianDatabase) : CompletedSetRepo
         loggedRpe = loggedRpe?.toInt(),
         isPr = isPr == 1L,
         completedAt = completedAt,
+        setEndReason = runCatching { SetEndReason.valueOf(setEndReason) }
+            .getOrElse { SetEndReason.TARGET_REPS_REACHED },
     )
 
     // ==================== Planned Sets ====================
@@ -178,6 +182,7 @@ class SqlDelightCompletedSetRepository(db: VitruvianDatabase) : CompletedSetRepo
                 logged_rpe = set.loggedRpe?.toLong(),
                 is_pr = if (set.isPr) 1L else 0L,
                 completed_at = set.completedAt,
+                set_end_reason = set.setEndReason.name,
             )
         }
     }
@@ -233,6 +238,7 @@ class SqlDelightCompletedSetRepository(db: VitruvianDatabase) : CompletedSetRepo
             logged_rpe = completedSet.loggedRpe?.toLong(),
             is_pr = if (completedSet.isPr) 1L else 0L,
             completed_at = completedSet.completedAt,
+            set_end_reason = completedSet.setEndReason.name,
         )
 
         completedSet
@@ -252,6 +258,7 @@ class SqlDelightCompletedSetRepository(db: VitruvianDatabase) : CompletedSetRepo
                     logged_rpe = set.loggedRpe?.toLong(),
                     is_pr = if (set.isPr) 1L else 0L,
                     completed_at = set.completedAt,
+                    set_end_reason = set.setEndReason.name,
                 )
             }
         }
diff --git a/shared/src/commonMain/kotlin/com/devil/phoenixproject/domain/model/TrainingCycleModels.kt b/shared/src/commonMain/kotlin/com/devil/phoenixproject/domain/model/TrainingCycleModels.kt
index 67a6c7190..7903a4087 100644
--- a/shared/src/commonMain/kotlin/com/devil/phoenixproject/domain/model/TrainingCycleModels.kt
+++ b/shared/src/commonMain/kotlin/com/devil/phoenixproject/domain/model/TrainingCycleModels.kt
@@ -375,6 +375,25 @@ data class PlannedSet(
     }
 }
 
+/**
+ * Reason a set ended. Persisted on [CompletedSet] for workout history analytics.
+ * Threaded through [ActiveSessionEngine.handleSetCompletion] from every call site.
+ */
+enum class SetEndReason {
+    /** Rep target reached or WORKOUT_COMPLETE machine event */
+    TARGET_REPS_REACHED,
+    /** Stall detection auto-stop fired (velocity/deload threshold) */
+    STALL_FAILURE,
+    /** VBT auto-end: consecutive reps above velocity-loss threshold */
+    VBT_AUTO_END,
+    /** User manually stopped the set */
+    USER_STOPPED,
+    /** Cable released detected by machine */
+    CABLE_RELEASED,
+    /** Timed exercise countdown reached zero */
+    TIMER_EXPIRED,
+}
+
 /**
  * A completed set with actual performance data.
  * Records what the user actually did.
@@ -390,6 +409,7 @@ data class CompletedSet(
     val loggedRpe: Int?,
     val isPr: Boolean,
     val completedAt: Long,
+    val setEndReason: SetEndReason = SetEndReason.TARGET_REPS_REACHED,
 ) {
     /**
      * Calculate estimated 1RM using canonical hybrid formula (Brzycki ≤10 reps, Epley >10 reps).
@@ -412,6 +432,7 @@ data class CompletedSet(
             actualWeightKg: Float,
             loggedRpe: Int? = null,
             isPr: Boolean = false,
+            setEndReason: SetEndReason = SetEndReason.TARGET_REPS_REACHED,
         ) = CompletedSet(
             id = id,
             sessionId = sessionId,
@@ -423,6 +444,7 @@ data class CompletedSet(
             loggedRpe = loggedRpe,
             isPr = isPr,
             completedAt = currentTimeMillis(),
+            setEndReason = setEndReason,
         )
     }
 }
diff --git a/shared/src/commonMain/kotlin/com/devil/phoenixproject/presentation/manager/ActiveSessionEngine.kt b/shared/src/commonMain/kotlin/com/devil/phoenixproject/presentation/manager/ActiveSessionEngine.kt
index da94c4146..039881662 100644
--- a/shared/src/commonMain/kotlin/com/devil/phoenixproject/presentation/manager/ActiveSessionEngine.kt
+++ b/shared/src/commonMain/kotlin/com/devil/phoenixproject/presentation/manager/ActiveSessionEngine.kt
@@ -47,6 +47,7 @@ import com.devil.phoenixproject.domain.model.RoutineExercise
 import com.devil.phoenixproject.domain.model.RoutineFlowState
 import com.devil.phoenixproject.domain.model.RoutineLaunchOrigin
 import com.devil.phoenixproject.domain.model.SetQualitySummary
+import com.devil.phoenixproject.domain.model.SetEndReason
 import com.devil.phoenixproject.domain.model.SetType
 import com.devil.phoenixproject.domain.model.TrainingCycle
 import com.devil.phoenixproject.domain.model.UserPreferences
@@ -338,7 +339,7 @@ class ActiveSessionEngine(
                         // Issue #182: Trigger set completion immediately on WORKOUT_COMPLETE event.
                         if (coordinator._workoutState.value is WorkoutState.Active) {
                             Logger.d("WORKOUT_COMPLETE event received - triggering immediate set completion")
-                            handleSetCompletion()
+                            handleSetCompletion(SetEndReason.TARGET_REPS_REACHED)
                         }
                     }
                 }
@@ -457,12 +458,14 @@ class ActiveSessionEngine(
                             coordinator.stallStartTime = currentTimeMillis()
                             coordinator.isCurrentlyStalled = true
                             coordinator.stallArmedByDeload = true
+                            coordinator.autoStopReason = SetEndReason.CABLE_RELEASED
                             Logger.d("Auto-stop stall timer STARTED via DELOAD_OCCURRED flag")
                         } else if (coordinator.stallStartTime != null && !inGrace) {
                             // F4: a real deload is the stronger signal — upgrade a
                             // velocity-armed countdown so the retracting cables
                             // (position -> 0) don't cancel it via the racked-handles check.
                             coordinator.stallArmedByDeload = true
+                            coordinator.autoStopReason = SetEndReason.CABLE_RELEASED
                         } else if (inGrace) {
                             Logger.d("DELOAD_OCCURRED ignored - in AMRAP startup grace period")
                         }
@@ -932,7 +935,12 @@ class ActiveSessionEngine(
             totalReps = coercedReps,
             isWarmupComplete = true,
         )
-        handleSetCompletion()
+        // Issue #673: Preserve existing reason (e.g. TIMER_EXPIRED) if one was already set
+        // by a prior handleSetCompletion call that opened this bodyweight dialog.
+        val preservedReason = coordinator.lastSetEndReason.takeIf {
+            it != SetEndReason.TARGET_REPS_REACHED
+        } ?: SetEndReason.TARGET_REPS_REACHED
+        handleSetCompletion(preservedReason)
     }
 
     private suspend fun showBodyweightRepEntry(currentExercise: RoutineExercise) {
@@ -988,6 +996,7 @@ class ActiveSessionEngine(
         coordinator.stallStartTime = null
         coordinator.isCurrentlyStalled = false
         coordinator.stallArmedByDeload = false
+        coordinator.autoStopReason = SetEndReason.STALL_FAILURE
         if (coordinator.autoStopStartTime == null && !coordinator.autoStopTriggered) {
             coordinator._autoStopState.value = AutoStopUiState()
         }
@@ -1076,7 +1085,7 @@ class ActiveSessionEngine(
             coordinator._autoStopState.value = AutoStopUiState()
         }
 
-        handleSetCompletion()
+        handleSetCompletion(coordinator.autoStopReason)
     }
 
     // ===== Rep Processing =====
@@ -1405,7 +1414,7 @@ class ActiveSessionEngine(
 
             if (consecutiveThresholdReps >= 2 && runtime.autoEndOnVelocityLoss) {
                 Logger.i { "VBT: Auto-ending set — $consecutiveThresholdReps consecutive reps above threshold" }
-                handleSetCompletion()
+                handleSetCompletion(SetEndReason.VBT_AUTO_END)
             }
         } else {
             consecutiveThresholdReps = 0
@@ -1454,7 +1463,7 @@ class ActiveSessionEngine(
             }
 
             if (repCounter.shouldStopWorkout()) {
-                handleSetCompletion()
+                handleSetCompletion(SetEndReason.TARGET_REPS_REACHED)
             }
         } else {
             resetAutoStopTimer()
@@ -2685,7 +2694,7 @@ class ActiveSessionEngine(
                             }
                         }
                         coordinator._timedExerciseRemainingSeconds.value = 0
-                        handleSetCompletion()
+                        handleSetCompletion(SetEndReason.TIMER_EXPIRED)
                     }
 
                     return@launch
@@ -3000,7 +3009,7 @@ class ActiveSessionEngine(
                             }
                         }
                         coordinator._timedExerciseRemainingSeconds.value = 0
-                        handleSetCompletion()
+                        handleSetCompletion(SetEndReason.TIMER_EXPIRED)
                     }
                 }
 
@@ -3123,6 +3132,9 @@ class ActiveSessionEngine(
         // C1: Atomic compareAndSet prevents TOCTOU race — only the first caller proceeds
         if (!coordinator.stopWorkoutInProgress.compareAndSet(expect = false, update = true)) return
 
+        // Issue #673: Mark manual stop so CompletedSet persists USER_STOPPED
+        coordinator.lastSetEndReason = SetEndReason.USER_STOPPED
+
         val shouldExitToIdle = exitingWorkout
         coordinator._weightAdjustmentRecommendation.value = null
 
@@ -3271,6 +3283,7 @@ class ActiveSessionEngine(
                     loggedRpe = coordinator._currentSetRpe.value,
                     isPr = false,
                     completedAt = currentTimeMillis(),
+                    setEndReason = coordinator.lastSetEndReason,
                 )
                 completedSetRepository.saveCompletedSet(completedSet)
                 Logger.d("Saved CompletedSet (manual stop): set #$setIndex, ${repCount.workingReps} reps${if (matchedPlannedSetId != null) " (linked to PlannedSet)" else ""}")
@@ -3359,7 +3372,7 @@ class ActiveSessionEngine(
             Logger.d { "stopAndReturnToSetReady: Issue #320 - workingReps=${coordinator._repCount.value.workingReps} > 0, routing through handleSetCompletion to save reps and advance" }
             // Release stop guard before delegating — handleSetCompletion uses its own atomic guard (setCompletionInProgress)
             coordinator.stopWorkoutInProgress.value = false
-            handleSetCompletion()
+            handleSetCompletion(SetEndReason.USER_STOPPED)
             return
         }
 
@@ -3855,6 +3868,7 @@ class ActiveSessionEngine(
                 loggedRpe = coordinator._currentSetRpe.value,
                 isPr = false,
                 completedAt = currentTimeMillis(),
+                setEndReason = coordinator.lastSetEndReason,
             )
             completedSetRepository.saveCompletedSet(completedSet)
             Logger.d("Saved CompletedSet: set #$setIndex, $working reps @ ${savedWeightKg}kg${if (matchedPlannedSetId != null) " (linked to PlannedSet)" else ""}")
@@ -3920,13 +3934,16 @@ class ActiveSessionEngine(
      * Phase A: Stop BLE, save session, emit haptics, show summary.
      * Phase B: Rest timer, navigation advancement (delegated back to DWSM via startRestTimer).
      */
-    internal fun handleSetCompletion() {
+    internal fun handleSetCompletion(reason: SetEndReason = SetEndReason.TARGET_REPS_REACHED) {
         // 1.2: Atomic compareAndSet prevents duplicate set completion across dispatchers
         if (!coordinator.setCompletionInProgress.compareAndSet(expect = false, update = true)) {
             Logger.d("handleSetCompletion: already in progress - ignoring")
             return
         }
 
+        // Issue #673: Store reason for CompletedSet persistence
+        coordinator.lastSetEndReason = reason
+
         // Issue #319: Log full context at entry so we can diagnose what the pipeline receives
         val repCount = coordinator._repCount.value
         val entryParams = coordinator._workoutParameters.value
diff --git a/shared/src/commonMain/kotlin/com/devil/phoenixproject/presentation/manager/WorkoutCoordinator.kt b/shared/src/commonMain/kotlin/com/devil/phoenixproject/presentation/manager/WorkoutCoordinator.kt
index e1e8a0043..6df0b7a9d 100644
--- a/shared/src/commonMain/kotlin/com/devil/phoenixproject/presentation/manager/WorkoutCoordinator.kt
+++ b/shared/src/commonMain/kotlin/com/devil/phoenixproject/presentation/manager/WorkoutCoordinator.kt
@@ -16,6 +16,7 @@ import com.devil.phoenixproject.domain.model.RoutineFlowState
 import com.devil.phoenixproject.domain.model.RoutineLaunchOrigin
 import com.devil.phoenixproject.domain.model.RoutineGroup
 import com.devil.phoenixproject.domain.model.SessionBodyweightState
+import com.devil.phoenixproject.domain.model.SetEndReason
 import com.devil.phoenixproject.domain.model.WeightAdjustmentRecommendation
 import com.devil.phoenixproject.domain.model.WorkoutMetric
 import com.devil.phoenixproject.domain.model.WorkoutParameters
@@ -412,6 +413,9 @@ class WorkoutCoordinator(
     // Guard to prevent duplicate auto-completion when rep target is reached
     internal val setCompletionInProgress = MutableStateFlow(false)
 
+    // Issue #673: Tracks why the current set ended, set by handleSetCompletion
+    internal var lastSetEndReason: SetEndReason = SetEndReason.TARGET_REPS_REACHED
+
     // Issue #355: Guard to prevent duplicate proceedFromSummary() calls on iOS
     // When app foregrounds, both manager-level fallback AND UI-level countdown can fire
     internal val proceedFromSummaryInProgress = MutableStateFlow(false)
@@ -431,6 +435,11 @@ class WorkoutCoordinator(
     @Volatile
     internal var stallArmedByDeload = false
 
+    // Issue #673: Track the reason for the auto-stop (STALL_FAILURE vs CABLE_RELEASED)
+    @Volatile
+    internal var autoStopReason: com.devil.phoenixproject.domain.model.SetEndReason =
+        com.devil.phoenixproject.domain.model.SetEndReason.STALL_FAILURE
+
     // Issue #649: defer position/stall auto-stop until the verbal-cue + short
     // transition window elapses, or a completed working rep clears it. The
     // deadline (@Volatile Long) is the single source of truth — 0L means no
@@ -458,6 +467,7 @@ class WorkoutCoordinator(
         stallStartTime = null
         isCurrentlyStalled = false
         stallArmedByDeload = false
+        autoStopReason = com.devil.phoenixproject.domain.model.SetEndReason.STALL_FAILURE
         deferAutoStopDeadlineMs = 0L
         _autoStopState.value = AutoStopUiState()
     }
diff --git a/shared/src/commonMain/kotlin/com/devil/phoenixproject/util/BackupModels.kt b/shared/src/commonMain/kotlin/com/devil/phoenixproject/util/BackupModels.kt
index 973756357..e3316f597 100644
--- a/shared/src/commonMain/kotlin/com/devil/phoenixproject/util/BackupModels.kt
+++ b/shared/src/commonMain/kotlin/com/devil/phoenixproject/util/BackupModels.kt
@@ -315,6 +315,7 @@ data class CompletedSetBackup(
     val loggedRpe: Int? = null,
     val isPr: Boolean = false,
     val completedAt: Long,
+    val setEndReason: String = "TARGET_REPS_REACHED",
 )
 
 /**
diff --git a/shared/src/commonMain/kotlin/com/devil/phoenixproject/util/BleConstants.kt b/shared/src/commonMain/kotlin/com/devil/phoenixproject/util/BleConstants.kt
index 7441f8ba4..55af2ed98 100644
--- a/shared/src/commonMain/kotlin/com/devil/phoenixproject/util/BleConstants.kt
+++ b/shared/src/commonMain/kotlin/com/devil/phoenixproject/util/BleConstants.kt
@@ -95,8 +95,8 @@ object BleConstants {
         // Force config block
         const val OFFSET_FORCE_MIN = 0x50 // 0.0f in activation packets
         const val OFFSET_FORCE_MAX = 0x54 // adjustedWeight + 10.0f (force ceiling)
-        const val OFFSET_TARGET_WEIGHT = 0x58 // adjustedWeight (actual operating weight)
-        const val OFFSET_PROGRESSION = 0x5C // progressionRegressionKg
+        const val OFFSET_TARGET_WEIGHT = 0x58 // official: softMax — adjustedWeight (actual operating weight)
+        const val OFFSET_PROGRESSION = 0x5C // official: increment — progressionRegressionKg (per-rep progression)
     }
 
     // Legacy aliases for backward compatibility
diff --git a/shared/src/commonMain/kotlin/com/devil/phoenixproject/util/BlePacketFactory.kt b/shared/src/commonMain/kotlin/com/devil/phoenixproject/util/BlePacketFactory.kt
index 0e0496f3e..07405ed1a 100644
--- a/shared/src/commonMain/kotlin/com/devil/phoenixproject/util/BlePacketFactory.kt
+++ b/shared/src/commonMain/kotlin/com/devil/phoenixproject/util/BlePacketFactory.kt
@@ -232,6 +232,17 @@ object BlePacketFactory {
             }
         }
 
+        // Issue #673: Signed protocol contract — softMax must not exceed 100.0f.
+        // The firmware's signed 8-bit protocol field limits the maximum to 100kg.
+        // Constants.MAX_WEIGHT_PER_CABLE_KG (110) is the UI/display maximum but
+        // must not be sent over BLE as softMax.
+        require(params.weightPerCableKg <= 100.0f) {
+            "weightPerCableKg=${params.weightPerCableKg} exceeds signed protocol softMax bound (100.0f)"
+        }
+        require(kotlin.math.abs(params.progressionRegressionKg) <= 10.0f) {
+            "progressionRegressionKg=${params.progressionRegressionKg} exceeds firmware increment bound (10.0f)"
+        }
+
         if (effectiveVariant == ForceConfigVariant.OVERLAP) {
             // Legacy Phoenix behavior: overwrite the profile tail with softMax
             // and increment. Production uses NON_OVERLAP to match the official app.
diff --git a/shared/src/commonMain/kotlin/com/devil/phoenixproject/util/DataBackupManager.kt b/shared/src/commonMain/kotlin/com/devil/phoenixproject/util/DataBackupManager.kt
index b77bb1691..a1a01420b 100644
--- a/shared/src/commonMain/kotlin/com/devil/phoenixproject/util/DataBackupManager.kt
+++ b/shared/src/commonMain/kotlin/com/devil/phoenixproject/util/DataBackupManager.kt
@@ -877,6 +877,7 @@ abstract class BaseDataBackupManager(
                             logged_rpe = completedSet.loggedRpe?.toLong(),
                             is_pr = if (completedSet.isPr) 1L else 0L,
                             completed_at = completedSet.completedAt,
+                            set_end_reason = completedSet.setEndReason,
                         )
                         completedSetsImported++
                     }
@@ -1797,6 +1798,7 @@ abstract class BaseDataBackupManager(
                                                     logged_rpe = completedSet.loggedRpe?.toLong(),
                                                     is_pr = if (completedSet.isPr) 1L else 0L,
                                                     completed_at = completedSet.completedAt,
+                                                    set_end_reason = completedSet.setEndReason,
                                                 )
                                                 completedSetsImported++
                                             }
@@ -2986,6 +2988,7 @@ abstract class BaseDataBackupManager(
         loggedRpe = cs.logged_rpe?.toInt(),
         isPr = cs.is_pr != 0L,
         completedAt = cs.completed_at,
+        setEndReason = cs.set_end_reason,
     )
 
     private fun mapProgressionEventToBackup(pe: ProgressionEvent): ProgressionEventBackup = ProgressionEventBackup(
diff --git a/shared/src/commonMain/kotlin/com/devil/phoenixproject/util/WorkoutCommandValidator.kt b/shared/src/commonMain/kotlin/com/devil/phoenixproject/util/WorkoutCommandValidator.kt
index 0cab8d941..39ad360c6 100644
--- a/shared/src/commonMain/kotlin/com/devil/phoenixproject/util/WorkoutCommandValidator.kt
+++ b/shared/src/commonMain/kotlin/com/devil/phoenixproject/util/WorkoutCommandValidator.kt
@@ -35,6 +35,15 @@ object WorkoutCommandValidator {
         validateFiniteWeight(params.weightPerCableKg).onFailure { return Result.failure(it) }
         validateFiniteWeight(params.progressionRegressionKg, field = "progressionRegressionKg")
             .onFailure { return Result.failure(it) }
+        // Issue #673: Validate firmware increment bound early (±10kg)
+        // so invalid imported/synced values are rejected before reaching
+        // BlePacketFactory.createProgramParams() which enforces the same
+        // bound via require().
+        if (kotlin.math.abs(params.progressionRegressionKg) > 10.0f) {
+            return failure(
+                "progressionRegressionKg must be within ±10.0f (firmware increment bound), got ${params.progressionRegressionKg}",
+            )
+        }
 
         if (params.isJustLift && params.weightPerCableKg < Constants.JUST_LIFT_MIN_VALID_WEIGHT_KG) {
             return failure(
@@ -99,13 +108,18 @@ object WorkoutCommandValidator {
 
     private fun isFinite(value: Float): Boolean = !value.isNaN() && !value.isInfinite()
 
+    // Signed protocol softMax bound: the firmware's BLE activation packet limits
+    // the maximum weight to 100.0f. Constants.MAX_WEIGHT_PER_CABLE_KG (110) is the
+    // UI/display maximum but must not be sent as softMax over BLE.
+    private const val SIGNED_PROTOCOL_SOFT_MAX_KG = 100.0f
+
     private fun validateWeightRange(weightPerCableKg: Float, allowZero: Boolean): Result<Unit> {
         if (!allowZero && weightPerCableKg <= Constants.MIN_WEIGHT_KG) {
             return failure("weightPerCableKg must be greater than ${Constants.MIN_WEIGHT_KG}kg, got $weightPerCableKg")
         }
-        if (weightPerCableKg < Constants.MIN_WEIGHT_KG || weightPerCableKg > Constants.MAX_WEIGHT_PER_CABLE_KG) {
+        if (weightPerCableKg < Constants.MIN_WEIGHT_KG || weightPerCableKg > SIGNED_PROTOCOL_SOFT_MAX_KG) {
             return failure(
-                "weightPerCableKg must be ${Constants.MIN_WEIGHT_KG}..${Constants.MAX_WEIGHT_PER_CABLE_KG}kg, got $weightPerCableKg",
+                "weightPerCableKg must be ${Constants.MIN_WEIGHT_KG}..${SIGNED_PROTOCOL_SOFT_MAX_KG}kg, got $weightPerCableKg",
             )
         }
         return Result.success(Unit)
diff --git a/shared/src/commonMain/sqldelight/com/devil/phoenixproject/database/VitruvianDatabase.sq b/shared/src/commonMain/sqldelight/com/devil/phoenixproject/database/VitruvianDatabase.sq
index 9c4d689e4..da0764565 100644
--- a/shared/src/commonMain/sqldelight/com/devil/phoenixproject/database/VitruvianDatabase.sq
+++ b/shared/src/commonMain/sqldelight/com/devil/phoenixproject/database/VitruvianDatabase.sq
@@ -1836,6 +1836,7 @@ CREATE TABLE CompletedSet (
     logged_rpe INTEGER,
     is_pr INTEGER NOT NULL DEFAULT 0,
     completed_at INTEGER NOT NULL,
+    set_end_reason TEXT NOT NULL DEFAULT 'TARGET_REPS_REACHED',
     FOREIGN KEY (session_id) REFERENCES WorkoutSession(id) ON DELETE CASCADE,
     FOREIGN KEY (planned_set_id) REFERENCES PlannedSet(id) ON DELETE SET NULL
 );
@@ -2023,8 +2024,8 @@ ORDER BY cs.completed_at DESC
 LIMIT ?;
 
 insertCompletedSet:
-INSERT INTO CompletedSet (id, session_id, planned_set_id, set_number, set_type, actual_reps, actual_weight_kg, logged_rpe, is_pr, completed_at)
-VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?);
+INSERT INTO CompletedSet (id, session_id, planned_set_id, set_number, set_type, actual_reps, actual_weight_kg, logged_rpe, is_pr, completed_at, set_end_reason)
+VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?);
 
 updateCompletedSetRpe:
 UPDATE CompletedSet SET logged_rpe = ? WHERE id = ?;
@@ -2161,8 +2162,8 @@ INSERT OR IGNORE INTO PlannedSet (id, routine_exercise_id, set_number, set_type,
 VALUES (?, ?, ?, ?, ?, ?, ?, ?);
 
 insertCompletedSetIgnore:
-INSERT OR IGNORE INTO CompletedSet (id, session_id, planned_set_id, set_number, set_type, actual_reps, actual_weight_kg, logged_rpe, is_pr, completed_at)
-VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?);
+INSERT OR IGNORE INTO CompletedSet (id, session_id, planned_set_id, set_number, set_type, actual_reps, actual_weight_kg, logged_rpe, is_pr, completed_at, set_end_reason)
+VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?);
 
 insertProgressionEventIgnore:
 INSERT OR IGNORE INTO ProgressionEvent (id, exercise_id, suggested_weight_kg, previous_weight_kg, reason, user_response, actual_weight_kg, timestamp, profile_id)
diff --git a/shared/src/commonMain/sqldelight/com/devil/phoenixproject/database/migrations/43.sqm b/shared/src/commonMain/sqldelight/com/devil/phoenixproject/database/migrations/43.sqm
new file mode 100644
index 000000000..f8418ed86
--- /dev/null
+++ b/shared/src/commonMain/sqldelight/com/devil/phoenixproject/database/migrations/43.sqm
@@ -0,0 +1,3 @@
+-- Migration 43: Add set_end_reason to CompletedSet (Issue #673 PR 1)
+-- Records why a set ended for workout history analytics.
+ALTER TABLE CompletedSet ADD COLUMN set_end_reason TEXT NOT NULL DEFAULT 'TARGET_REPS_REACHED';
diff --git a/shared/src/commonTest/kotlin/com/devil/phoenixproject/util/WorkoutCommandValidatorTest.kt b/shared/src/commonTest/kotlin/com/devil/phoenixproject/util/WorkoutCommandValidatorTest.kt
index b92bbcc15..938cfaf74 100644
--- a/shared/src/commonTest/kotlin/com/devil/phoenixproject/util/WorkoutCommandValidatorTest.kt
+++ b/shared/src/commonTest/kotlin/com/devil/phoenixproject/util/WorkoutCommandValidatorTest.kt
@@ -206,6 +206,91 @@ class WorkoutCommandValidatorTest {
         )
     }
 
+    @Test
+    fun `progressionRegressionKg within plus minus 10 is accepted`() {
+        assertTrue(
+            WorkoutCommandValidator.validateProgramParams(
+                WorkoutParameters(
+                    programMode = ProgramMode.OldSchool,
+                    reps = 8,
+                    weightPerCableKg = 40f,
+                    progressionRegressionKg = 10.0f,
+                ),
+            ).isSuccess,
+        )
+        assertTrue(
+            WorkoutCommandValidator.validateProgramParams(
+                WorkoutParameters(
+                    programMode = ProgramMode.OldSchool,
+                    reps = 8,
+                    weightPerCableKg = 40f,
+                    progressionRegressionKg = -10.0f,
+                ),
+            ).isSuccess,
+        )
+        assertTrue(
+            WorkoutCommandValidator.validateProgramParams(
+                WorkoutParameters(
+                    programMode = ProgramMode.OldSchool,
+                    reps = 8,
+                    weightPerCableKg = 40f,
+                    progressionRegressionKg = 0.0f,
+                ),
+            ).isSuccess,
+        )
+    }
+
+    @Test
+    fun `progressionRegressionKg outside plus minus 10 is rejected early`() {
+        assertFailureContains(
+            WorkoutCommandValidator.validateProgramParams(
+                WorkoutParameters(
+                    programMode = ProgramMode.OldSchool,
+                    reps = 8,
+                    weightPerCableKg = 40f,
+                    progressionRegressionKg = 11.0f,
+                ),
+            ),
+            "progressionRegressionKg",
+        )
+        assertFailureContains(
+            WorkoutCommandValidator.validateProgramParams(
+                WorkoutParameters(
+                    programMode = ProgramMode.OldSchool,
+                    reps = 8,
+                    weightPerCableKg = 40f,
+                    progressionRegressionKg = -15.0f,
+                ),
+            ),
+            "progressionRegressionKg",
+        )
+    }
+
+    @Test
+    fun `program params reject weightPerCableKg above signed protocol softMax 100`() {
+        // 101kg exceeds the signed protocol softMax bound (100.0f)
+        assertFailureContains(
+            WorkoutCommandValidator.validateProgramParams(
+                WorkoutParameters(
+                    programMode = ProgramMode.OldSchool,
+                    reps = 8,
+                    weightPerCableKg = 101f,
+                ),
+            ),
+            "weightPerCableKg",
+        )
+        // 100kg is exactly at the bound — accepted by the validator (BlePacketFactory enforces the hard limit)
+        assertTrue(
+            WorkoutCommandValidator.validateProgramParams(
+                WorkoutParameters(
+                    programMode = ProgramMode.OldSchool,
+                    reps = 8,
+                    weightPerCableKg = 100f,
+                ),
+            ).isSuccess,
+        )
+    }
+
     private fun validColors(): List<RGBColor> = listOf(
         RGBColor(255, 0, 0),
         RGBColor(0, 255, 0),