feat(sync): split FillPendingDetails into activities/workouts phases

Progress becomes phase-aware ({Phase, Done, Total} instead of a flat
{Done, Total}), with FullSync reporting an indeterminate "discovering"
phase during backfill/incremental sync (there's no meaningful total
before those calls have already happened), then FillPendingDetails
reporting a real Done/Total for its activities pass, then its new,
independent workouts pass.

alignWorkoutTargets now takes a lap count instead of a []garmin.Lap
slice, since it never used lap content, only length -- this lets the
new workouts pass call it against laps read back from the DB rather
than needing the original Garmin lap data again.

Splitting the passes also fixes a latent bug: an activity whose
details were fetched successfully but whose workout fetch failed in
that same run previously had no way to ever retry the workout fetch,
since ActivitiesMissingDetails stops returning it once
details_fetched_at/splits_fetched_at are set. ActivitiesMissingWorkout
queries workout_id/workout_raw_json independently, so it keeps
surfacing that activity until its workout is actually fetched.

backend/internal/garmin/mock/mock.go

@@ -10,11 +10,17 @@ import (
 
 // Client is a fake garmin.Client returning data supplied by the test/caller.
 type Client struct {
-	AuthResults        []garmin.AuthResult // consumed in order by Authenticate/CompleteMFA calls
+	AuthResults []garmin.AuthResult // consumed in order by Authenticate/CompleteMFA calls
-	Activities         []garmin.Activity
+	Activities  []garmin.Activity
-	Splits             map[int64]garmin.ActivitySplits
+	Splits      map[int64]garmin.ActivitySplits
-	Details            map[int64]garmin.ActivityDetails
+	Details     map[int64]garmin.ActivityDetails
-	Workouts           map[int64]garmin.Workout
+	Workouts    map[int64]garmin.Workout
+	// WorkoutErrByID, if set for a given workout ID, makes GetWorkoutByID
+	// return that error for that ID specifically -- independent of the
+	// all-calls-fail Err field below -- so a test can simulate one
+	// activity's workout fetch failing while others in the same batch
+	// succeed.
+	WorkoutErrByID     map[int64]error
 	Err                error // if set, every call returns this error
 	authResultCursor   int
 	ClosedCalled       bool
@@ -79,6 +85,9 @@ func (c *Client) GetWorkoutByID(ctx context.Context, workoutID int64) (garmin.Wo
 	if c.Err != nil {
 		return garmin.Workout{}, c.Err
 	}
+	if err, ok := c.WorkoutErrByID[workoutID]; ok {
+		return garmin.Workout{}, err
+	}
 	return c.Workouts[workoutID], nil
 }
 

backend/internal/sync/mapping.go

@@ -94,9 +94,9 @@ func toLapRows(laps []garmin.Lap, samples []garmin.Sample, targets []*garmin.Wor
 	return rows
 }
 
-// alignWorkoutTargets zips an activity's recorded laps against its
+// alignWorkoutTargets zips an activity's lap count against its structured
-// structured workout's flattened steps, returning one *garmin.WorkoutStep
+// workout's flattened steps, returning one *garmin.WorkoutStep per lap (nil
-// per lap (nil where unavailable).
+// where unavailable).
 //
 // Confirmed against a real activity (via Garmin Connect's own workout view)
 // that recording sometimes continues one lap past the end of the workout's
@@ -110,11 +110,11 @@ func toLapRows(laps []garmin.Lap, samples []garmin.Sample, targets []*garmin.Wor
 // Any other mismatch (extra manual laps, auto-lap-by-distance also firing,
 // etc.) can't be trusted at all, so every entry comes back nil rather than
 // risk showing a target against the wrong lap.
-func alignWorkoutTargets(laps []garmin.Lap, workout garmin.Workout) []*garmin.WorkoutStep {
+func alignWorkoutTargets(lapCount int, workout garmin.Workout) []*garmin.WorkoutStep {
 	steps := workout.FlattenSteps()
-	out := make([]*garmin.WorkoutStep, len(laps))
+	out := make([]*garmin.WorkoutStep, lapCount)
 
-	switch len(laps) - len(steps) {
+	switch lapCount - len(steps) {
 	case 0, 1:
 		for i := range steps {
 			s := steps[i]

backend/internal/sync/service.go

@@ -54,9 +54,23 @@ func (c Config) withDefaults() Config {
 	return c
 }
 
-// Progress reports how far a currently-running (or just-finished)
+// Phase values reported by Progress.Phase.
-// FillPendingDetails pass has gotten, for a status banner to poll.
+const (
+	PhaseIdle        = "idle"
+	PhaseDiscovering = "discovering"
+	PhaseActivities  = "activities"
+	PhaseWorkouts    = "workouts"
+)
+
+// Progress reports how far a currently-running (or just-finished) FullSync
+// has gotten, for a status modal to poll. PhaseDiscovering (backfillCore/
+// incrementalSyncCore) has no meaningful Total -- discovering how many
+// activities exist IS the act of fetching them, so it's reported as an
+// indeterminate step (Done/Total both 0) rather than a fake percentage.
+// PhaseActivities/PhaseWorkouts do have a real Total, taken once from a
+// local DB count at the start of each pass (see FillPendingDetails).
 type Progress struct {
+	Phase string
 	Done  int
 	Total int
 }
@@ -80,19 +94,20 @@ func NewService(g garmin.Client, db *store.DB, userID int64, cfg Config, now fun
 	if now == nil {
 		now = time.Now
 	}
-	return &Service{garmin: g, db: db, userID: userID, cfg: cfg.withDefaults(), now: now}
+	return &Service{garmin: g, db: db, userID: userID, cfg: cfg.withDefaults(), now: now, progress: Progress{Phase: PhaseIdle}}
 }
 
-// Progress returns the current detail-fill progress (0/0 when idle).
+// Progress returns the current sync progress (phase idle, 0/0 when nothing
+// is running).
 func (s *Service) Progress() Progress {
 	s.progressMu.Lock()
 	defer s.progressMu.Unlock()
 	return s.progress
 }
 
-func (s *Service) setProgress(done, total int) {
+func (s *Service) setProgress(phase string, done, total int) {
 	s.progressMu.Lock()
-	s.progress = Progress{Done: done, Total: total}
+	s.progress = Progress{Phase: phase, Done: done, Total: total}
 	s.progressMu.Unlock()
 }
 
@@ -199,6 +214,11 @@ func (s *Service) FullSync(ctx context.Context, detailFillLimit int) error {
 	if err != nil {
 		return err
 	}
+	// Reset to idle on every return path, including an early error return
+	// from backfillCore/incrementalSyncCore before FillPendingDetails (which
+	// otherwise owns its own idle-reset) ever runs.
+	s.setProgress(PhaseDiscovering, 0, 0)
+	defer s.setProgress(PhaseIdle, 0, 0)
 
 	backfillCount, err := s.backfillCore(ctx)
 	if err != nil {
@@ -270,11 +290,22 @@ func (s *Service) fetchAndStoreWindow(ctx context.Context, startDate, endDate st
 	return len(activities), newCount, nil
 }
 
-// FillPendingDetails fetches get_activity_splits/get_activity_details for up
+// FillPendingDetails fetches activity details/splits for up to limit
-// to limit activities that don't have them yet, then (re)classifies each one.
+// activities missing them, then fetches workouts for up to limit activities
-// Calls are made sequentially with Config.InterCallDelay between them to
+// missing those (independently -- see ActivitiesMissingWorkout), then
+// (re)classifies every activity touched by the first pass. Each pass makes
+// its Garmin calls sequentially with Config.InterCallDelay between them to
 // avoid Garmin/Cloudflare rate limiting.
 func (s *Service) FillPendingDetails(ctx context.Context, limit int) error {
+	defer s.setProgress(PhaseIdle, 0, 0)
+
+	if err := s.fillPendingActivityDetails(ctx, limit); err != nil {
+		return err
+	}
+	return s.fillPendingWorkouts(ctx, limit)
+}
+
+func (s *Service) fillPendingActivityDetails(ctx context.Context, limit int) error {
 	pending, err := s.db.ActivitiesMissingDetails(ctx, s.userID, limit)
 	if err != nil {
 		return err
@@ -284,8 +315,7 @@ func (s *Service) FillPendingDetails(ctx context.Context, limit int) error {
 		return fmt.Errorf("load profile: %w", err)
 	}
 
-	s.setProgress(0, len(pending))
+	s.setProgress(PhaseActivities, 0, len(pending))
-	defer s.setProgress(0, 0)
 
 	for i, a := range pending {
 		if i > 0 {
@@ -301,7 +331,41 @@ func (s *Service) FillPendingDetails(ctx context.Context, limit int) error {
 		if err := s.ClassifyActivity(ctx, a.ID); err != nil {
 			return fmt.Errorf("classify activity %d: %w", a.GarminActivityID, err)
 		}
-		s.setProgress(i+1, len(pending))
+		s.setProgress(PhaseActivities, i+1, len(pending))
+	}
+	return nil
+}
+
+// fillPendingWorkouts fetches get_workout_by_id for up to limit activities
+// missing it. Unlike fillPendingActivityDetails, one activity's workout
+// fetch failing is non-fatal (logged, loop continues) -- workout target
+// bands are enrichment, not core activity data, and workout_raw_json
+// staying NULL means ActivitiesMissingWorkout will naturally retry it on
+// the next sync.
+func (s *Service) fillPendingWorkouts(ctx context.Context, limit int) error {
+	pending, err := s.db.ActivitiesMissingWorkout(ctx, s.userID, limit)
+	if err != nil {
+		return err
+	}
+	profile, err := s.db.GetProfile(ctx, s.userID)
+	if err != nil {
+		return fmt.Errorf("load profile: %w", err)
+	}
+
+	s.setProgress(PhaseWorkouts, 0, len(pending))
+
+	for i, a := range pending {
+		if i > 0 {
+			select {
+			case <-ctx.Done():
+				return ctx.Err()
+			case <-time.After(s.cfg.InterCallDelay):
+			}
+		}
+		if err := s.fillActivityWorkout(ctx, a, profile); err != nil {
+			log.Printf("sync: fill workout for activity %d failed, will retry next sync: %v", a.GarminActivityID, err)
+		}
+		s.setProgress(PhaseWorkouts, i+1, len(pending))
 	}
 	return nil
 }
@@ -316,23 +380,14 @@ func (s *Service) fillActivityDetails(ctx context.Context, a store.Activity, pro
 		return fmt.Errorf("get_activity_details: %w", err)
 	}
 
-	targets := make([]*garmin.WorkoutStep, len(splits.Laps))
-	if a.WorkoutID != nil {
-		workout, err := s.garmin.GetWorkoutByID(ctx, *a.WorkoutID)
-		if err != nil {
-			log.Printf("sync: get_workout_by_id(%d) for activity %d failed, continuing without target zones: %v", *a.WorkoutID, a.GarminActivityID, err)
-		} else {
-			targets = alignWorkoutTargets(splits.Laps, workout)
-			if err := s.db.SetActivityWorkout(ctx, s.userID, a.ID, string(workout.Raw)); err != nil {
-				return err
-			}
-		}
-	}
-
 	samples := garmin.ExtractSamples(details)
 	if err := s.db.ReplaceActivitySamples(ctx, s.userID, a.ID, toSampleRows(samples)); err != nil {
 		return err
 	}
+	// No workout-target alignment here -- that's fillActivityWorkout's job,
+	// run as its own later pass (see fillPendingWorkouts). targets is an
+	// all-nil placeholder the same length as splits.Laps.
+	targets := make([]*garmin.WorkoutStep, len(splits.Laps))
 	if err := s.db.ReplaceLaps(ctx, s.userID, a.ID, toLapRows(splits.Laps, samples, targets, profile)); err != nil {
 		return err
 	}
@@ -342,6 +397,35 @@ func (s *Service) fillActivityDetails(ctx context.Context, a store.Activity, pro
 	return s.db.SetActivitySplitsFetched(ctx, s.userID, a.ID)
 }
 
+// fillActivityWorkout fetches a's structured workout and re-derives its
+// laps' target pace/HR bands from it. Requires a.WorkoutID to be set --
+// only ever called for activities ActivitiesMissingWorkout returned, which
+// already filters on that. Reads laps back from the DB (already written by
+// fillActivityDetails, in some earlier pass or run) rather than needing the
+// original garmin.Lap data again, since alignWorkoutTargets only needs a
+// count.
+func (s *Service) fillActivityWorkout(ctx context.Context, a store.Activity, profile store.Profile) error {
+	workout, err := s.garmin.GetWorkoutByID(ctx, *a.WorkoutID)
+	if err != nil {
+		return fmt.Errorf("get_workout_by_id: %w", err)
+	}
+	laps, err := s.db.LapsForActivity(ctx, s.userID, a.ID)
+	if err != nil {
+		return err
+	}
+	targets := alignWorkoutTargets(len(laps), workout)
+	for i := range laps {
+		if i < len(targets) && targets[i] != nil {
+			laps[i].TargetPaceLowMps, laps[i].TargetPaceHighMps = targetPaceRange(*targets[i])
+			laps[i].TargetHRLowBpm, laps[i].TargetHRHighBpm = targetHRRange(*targets[i], profile)
+		}
+	}
+	if err := s.db.ReplaceLaps(ctx, s.userID, a.ID, laps); err != nil {
+		return err
+	}
+	return s.db.SetActivityWorkout(ctx, s.userID, a.ID, string(workout.Raw))
+}
+
 // ClassifyActivity (re)runs the rule engine for one activity against the
 // currently active workout kinds and appends a new kind_assignments row.
 // Safe to call repeatedly (e.g. after editing a workout kind's rule).

backend/internal/sync/service_test.go

@@ -2,6 +2,7 @@ package sync
 
 import (
 	"context"
+	"fmt"
 	"path/filepath"
 	"testing"
 	"time"
@@ -92,7 +93,7 @@ func TestAlignWorkoutTargets_MatchesLapsToFlattenedSteps(t *testing.T) {
 		}},
 	}}
 
-	targets := alignWorkoutTargets(laps, workout)
+	targets := alignWorkoutTargets(len(laps), workout)
 	if len(targets) != 2 {
 		t.Fatalf("expected 2 aligned targets, got %d", len(targets))
 	}
@@ -118,7 +119,7 @@ func TestAlignWorkoutTargets_OneExtraTrailingLapKeepsOtherTargets(t *testing.T)
 		}},
 	}}
 
-	targets := alignWorkoutTargets(laps, workout)
+	targets := alignWorkoutTargets(len(laps), workout)
 	if len(targets) != 3 {
 		t.Fatalf("expected 3 slots (one per lap), got %d", len(targets))
 	}
@@ -141,7 +142,7 @@ func TestAlignWorkoutTargets_MismatchedCountYieldsAllNil(t *testing.T) {
 		}},
 	}}
 
-	targets := alignWorkoutTargets(laps, workout)
+	targets := alignWorkoutTargets(len(laps), workout)
 	if len(targets) != 3 {
 		t.Fatalf("expected 3 slots (one per lap), got %d", len(targets))
 	}
@@ -629,24 +630,27 @@ func TestFullSync_RecordsOneCombinedSyncRun(t *testing.T) {
 	}
 }
 
-func TestFillPendingDetails_ReportsLiveProgress(t *testing.T) {
+func TestFillPendingDetails_ReportsPhaseAwareProgressThroughActivitiesAndWorkoutsPhases(t *testing.T) {
 	db := openTestDB(t)
 	ctx := context.Background()
 	userID := provisionTestUser(t, db)
 
+	const n = 2
 	m := &mock.Client{
 		Activities: []garmin.Activity{},
 		Splits:     map[int64]garmin.ActivitySplits{},
 		Details:    map[int64]garmin.ActivityDetails{},
+		Workouts:   map[int64]garmin.Workout{},
 	}
-	const n = 3
 	for i := int64(1); i <= n; i++ {
+		workoutID := i + 100
 		m.Activities = append(m.Activities, garmin.Activity{
-			ActivityID: i, ActivityType: garmin.ActivityType{TypeKey: "running"},
+			ActivityID: i, ActivityType: garmin.ActivityType{TypeKey: "running"}, WorkoutID: &workoutID,
 			StartTimeGMT: "2026-07-0" + string(rune('0'+i)) + " 06:00:00", Distance: 5000, Duration: 1500,
 		})
 		m.Splits[i] = garmin.ActivitySplits{ActivityID: i}
 		m.Details[i] = garmin.ActivityDetails{ActivityID: i}
+		m.Workouts[workoutID] = garmin.Workout{}
 	}
 
 	svc := NewService(m, db, userID, Config{InterCallDelay: 150 * time.Millisecond},
@@ -655,27 +659,171 @@ func TestFillPendingDetails_ReportsLiveProgress(t *testing.T) {
 		t.Fatalf("backfillCore: %v", err)
 	}
 
-	if p := svc.Progress(); p.Total != 0 {
+	if p := svc.Progress(); p.Phase != PhaseIdle {
-		t.Fatalf("Progress before FillPendingDetails = %+v, want zero value", p)
+		t.Fatalf("Progress before FillPendingDetails = %+v, want PhaseIdle", p)
 	}
 
 	done := make(chan error, 1)
 	go func() { done <- svc.FillPendingDetails(ctx, n) }()
 
-	time.Sleep(200 * time.Millisecond) // into the delay before the 2nd or 3rd item
+	// Timeline with InterCallDelay=150ms and n=2 per phase: activities pass
-	mid := svc.Progress()
+	// does item0 (instant), delays ~150ms, does item1 -- landing here around
-	if mid.Total != n {
+	// t=75ms should be mid-delay in the activities phase.
-		t.Errorf("mid-flight Progress().Total = %d, want %d", mid.Total, n)
+	time.Sleep(75 * time.Millisecond)
+	midActivities := svc.Progress()
+	if midActivities.Phase != PhaseActivities {
+		t.Errorf("mid-activities Progress().Phase = %q, want %q", midActivities.Phase, PhaseActivities)
 	}
-	if mid.Done <= 0 || mid.Done >= n {
+	if midActivities.Total != n {
-		t.Errorf("mid-flight Progress().Done = %d, want strictly between 0 and %d (i.e. actually in progress)", mid.Done, n)
+		t.Errorf("mid-activities Progress().Total = %d, want %d", midActivities.Total, n)
+	}
+	if midActivities.Done != 1 {
+		t.Errorf("mid-activities Progress().Done = %d, want 1", midActivities.Done)
+	}
+
+	// The activities phase finishes its own delay+item1 around t=150ms, then
+	// the workouts phase starts: item0 (instant), delay ~150ms, item1.
+	// Landing around t=150+75=225ms should be mid-delay in the workouts phase.
+	time.Sleep(150 * time.Millisecond)
+	midWorkouts := svc.Progress()
+	if midWorkouts.Phase != PhaseWorkouts {
+		t.Errorf("mid-workouts Progress().Phase = %q, want %q", midWorkouts.Phase, PhaseWorkouts)
+	}
+	if midWorkouts.Total != n {
+		t.Errorf("mid-workouts Progress().Total = %d, want %d", midWorkouts.Total, n)
+	}
+	if midWorkouts.Done != 1 {
+		t.Errorf("mid-workouts Progress().Done = %d, want 1", midWorkouts.Done)
 	}
 
 	if err := <-done; err != nil {
 		t.Fatalf("FillPendingDetails: %v", err)
 	}
-	if final := svc.Progress(); final.Total != 0 || final.Done != 0 {
+	if final := svc.Progress(); final.Phase != PhaseIdle || final.Total != 0 || final.Done != 0 {
-		t.Errorf("Progress after completion = %+v, want zero value (idle)", final)
+		t.Errorf("Progress after completion = %+v, want zero-value PhaseIdle", final)
+	}
+}
+
+func TestFillPendingDetails_RetriesWorkoutFetchForActivityWithDetailsAlreadyFetched(t *testing.T) {
+	db := openTestDB(t)
+	ctx := context.Background()
+	userID := provisionTestUser(t, db)
+
+	const garminActivityID = 77
+	const workoutID = 888
+	workoutIDPtr := int64(workoutID)
+	id, err := db.UpsertActivity(ctx, userID, store.Activity{
+		GarminActivityID: garminActivityID, WorkoutID: &workoutIDPtr,
+		StartTimeUTC: "2026-07-01 06:00:00", RawJSON: "{}",
+	})
+	if err != nil {
+		t.Fatalf("UpsertActivity: %v", err)
+	}
+	// Simulate a prior run that successfully fetched details/splits but
+	// whose workout fetch failed (workout_raw_json stays NULL).
+	if err := db.SetActivityDetails(ctx, userID, id, "{}"); err != nil {
+		t.Fatalf("SetActivityDetails: %v", err)
+	}
+	if err := db.SetActivitySplitsFetched(ctx, userID, id); err != nil {
+		t.Fatalf("SetActivitySplitsFetched: %v", err)
+	}
+	if err := db.ReplaceLaps(ctx, userID, id, []store.Lap{{LapIndex: 1, IntensityType: "ACTIVE"}}); err != nil {
+		t.Fatalf("ReplaceLaps: %v", err)
+	}
+
+	m := &mock.Client{
+		Workouts: map[int64]garmin.Workout{
+			workoutID: {Segments: []garmin.WorkoutSegment{
+				{Steps: []garmin.WorkoutStep{
+					{Type: "ExecutableStepDTO", TargetType: garmin.WorkoutTargetType{TypeKey: "pace.zone"}, TargetValueOne: f(3.0), TargetValueTwo: f(3.5)},
+				}},
+			}},
+		},
+	}
+	svc := NewService(m, db, userID, Config{}, fixedNow(time.Date(2026, 7, 11, 0, 0, 0, 0, time.UTC)))
+
+	// A prior FillPendingDetails call (which had ActivitiesMissingDetails
+	// return nothing, since details are already fetched) still reaches this
+	// activity via ActivitiesMissingWorkout.
+	if err := svc.FillPendingDetails(ctx, 10); err != nil {
+		t.Fatalf("FillPendingDetails: %v", err)
+	}
+
+	laps, err := db.LapsForActivity(ctx, userID, id)
+	if err != nil || len(laps) != 1 {
+		t.Fatalf("LapsForActivity: %v, %+v", err, laps)
+	}
+	if laps[0].TargetPaceLowMps == nil || *laps[0].TargetPaceLowMps != 3.0 {
+		t.Errorf("TargetPaceLowMps = %v, want 3.0 (workout fetch should have been retried)", laps[0].TargetPaceLowMps)
+	}
+}
+
+func TestFillPendingDetails_OneWorkoutFetchFailureDoesNotAbortTheWorkoutsPass(t *testing.T) {
+	db := openTestDB(t)
+	ctx := context.Background()
+	userID := provisionTestUser(t, db)
+
+	const failingWorkoutID = 200
+	const okWorkoutID = 201
+	failingPtr, okPtr := int64(failingWorkoutID), int64(okWorkoutID)
+	m := &mock.Client{
+		Activities: []garmin.Activity{
+			{ActivityID: 1, ActivityType: garmin.ActivityType{TypeKey: "running"}, WorkoutID: &failingPtr,
+				StartTimeGMT: "2026-07-01 06:00:00", Distance: 5000, Duration: 1500},
+			{ActivityID: 2, ActivityType: garmin.ActivityType{TypeKey: "running"}, WorkoutID: &okPtr,
+				StartTimeGMT: "2026-07-02 06:00:00", Distance: 5000, Duration: 1500},
+		},
+		Splits: map[int64]garmin.ActivitySplits{
+			1: {ActivityID: 1, Laps: []garmin.Lap{{LapIndex: 1, IntensityType: "ACTIVE"}}},
+			2: {ActivityID: 2, Laps: []garmin.Lap{{LapIndex: 1, IntensityType: "ACTIVE"}}},
+		},
+		Details: map[int64]garmin.ActivityDetails{1: {ActivityID: 1}, 2: {ActivityID: 2}},
+		Workouts: map[int64]garmin.Workout{
+			okWorkoutID: {Segments: []garmin.WorkoutSegment{
+				{Steps: []garmin.WorkoutStep{
+					{Type: "ExecutableStepDTO", TargetType: garmin.WorkoutTargetType{TypeKey: "pace.zone"}, TargetValueOne: f(3.0), TargetValueTwo: f(3.5)},
+				}},
+			}},
+		},
+		WorkoutErrByID: map[int64]error{failingWorkoutID: fmt.Errorf("garmin says no")},
+	}
+	// Not timing-sensitive -- keep InterCallDelay negligible so the 2
+	// activities/2 workouts here don't cost real wall-clock seconds
+	// (Config{}'s default is 1s per gap).
+	svc := NewService(m, db, userID, Config{InterCallDelay: time.Millisecond},
+		fixedNow(time.Date(2026, 7, 11, 0, 0, 0, 0, time.UTC)))
+
+	if _, err := svc.backfillCore(ctx); err != nil {
+		t.Fatalf("backfillCore: %v", err)
+	}
+	if err := svc.FillPendingDetails(ctx, 10); err != nil {
+		t.Fatalf("FillPendingDetails should not return an error for a per-activity workout fetch failure: %v", err)
+	}
+
+	remaining, err := db.CountActivitiesMissingWorkout(ctx, userID)
+	if err != nil {
+		t.Fatalf("CountActivitiesMissingWorkout: %v", err)
+	}
+	if remaining != 1 {
+		t.Errorf("CountActivitiesMissingWorkout = %d, want 1 (the failing activity stays pending, retryable next sync)", remaining)
+	}
+
+	activities, err := db.ListActivities(ctx, userID, store.ActivityFilter{})
+	if err != nil {
+		t.Fatalf("ListActivities: %v", err)
+	}
+	var okActivity store.Activity
+	for _, a := range activities {
+		if a.GarminActivityID == 2 {
+			okActivity = a
+		}
+	}
+	laps, err := db.LapsForActivity(ctx, userID, okActivity.ID)
+	if err != nil || len(laps) != 1 {
+		t.Fatalf("LapsForActivity: %v, %+v", err, laps)
+	}
+	if laps[0].TargetPaceLowMps == nil || *laps[0].TargetPaceLowMps != 3.0 {
+		t.Errorf("the succeeding activity's TargetPaceLowMps = %v, want 3.0 (should not be affected by the other activity's failure)", laps[0].TargetPaceLowMps)
 	}
 }