plans + specs

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+# Sync Engine, Scheduler, and Operational UI Implementation Plan
+
+> **For agentic workers:** REQUIRED SUB-SKILL: Use superpowers:subagent-driven-development (recommended) or superpowers:executing-plans to implement this plan task-by-task. Steps use checkbox (`- [ ]`) syntax for tracking.
+
+**Goal:** Integrate the database, MyWhoosh client, FIT rewriter, Garmin importer, scheduler, MFA workflow, retry behavior, and operational admin pages into a resilient multi-user sync service.
+
+**Architecture:** A `SyncManager` owns per-user `asyncio.Lock` instances and executes a durable activity state machine. External clients are injected via factories for tests. A lightweight FastAPI lifespan scheduler triggers syncs at the configured interval; different users run concurrently, while each user's pipeline is serialized.
+
+**Tech Stack:** Python 3.12, asyncio, FastAPI lifespan, SQLAlchemy, HTMX, Jinja2, pytest/pytest-asyncio.
+
+## Global Constraints
+
+- Multiple users sync independently and may run concurrently.
+- At most one sync may run for a given user at a time.
+- Manual sync and scheduled sync use the same pipeline and lock.
+- Durable activity stages are `discovered`, `downloaded`, `converted`, `imported`, `duplicate`, `failed` with `last_completed_stage` retained on failure.
+- `imported` and `duplicate` are terminal.
+- Transient network/server failures retry at most once in a run; later attempts occur on future scheduler ticks.
+- Invalid MyWhoosh/Garmin credentials and Garmin MFA set `action_required`.
+- Corrupt/unsupported FIT is non-retryable per activity.
+- Failure of one user or one activity must never stop other users.
+- Original and converted FIT files remain on disk in v1.
+- MFA codes are never persisted or logged.
+
+---
+
+## File Structure
+
+```text
+app/sync/
+  __init__.py
+  states.py
+  manager.py
+  scheduler.py
+app/web/
+  operations.py
+  templates/
+    dashboard.html
+    users/detail.html
+    system.html
+    fragments/user_card.html
+    fragments/sync_result.html
+    fragments/mfa_form.html
+app/db/
+  repositories.py
+tests/sync/
+  fakes.py
+  test_manager.py
+  test_concurrency.py
+  test_scheduler.py
+tests/web/
+  test_operations.py
+  test_mfa.py
+```
+
+## Task 1: Add durable activity/sync-run repository operations
+
+**Files:**
+- Modify: `app/db/repositories.py`
+- Create: `tests/db/test_sync_state.py`
+
+**Interfaces:**
+- Produces methods to advance activity stages, mark failures without losing `last_completed_stage`, list pending activities, and create/finalize sync runs.
+
+- [ ] **Step 1: Write failing state-transition tests**
+
+```python
+# tests/db/test_sync_state.py
+from app.db.models import ActivityStatus
+
+
+def test_failure_retains_last_completed_stage(activity_repository, seeded_activity) -> None:
+    activity_repository.mark_downloaded(seeded_activity.id, "/data/activities/1/a/source.fit")
+    activity_repository.mark_failed(seeded_activity.id, "Garmin timeout", retryable=True)
+    activity = activity_repository.get(seeded_activity.id)
+
+    assert activity.status == ActivityStatus.FAILED
+    assert activity.last_completed_stage == ActivityStatus.DOWNLOADED
+    assert activity.retryable is True
+
+
+def test_converted_activity_is_pending_until_terminal(activity_repository, seeded_activity) -> None:
+    activity_repository.mark_converted(seeded_activity.id, "/data/activities/1/a/converted.fit")
+    ids = [item.id for item in activity_repository.list_pending_for_user(seeded_activity.user_id)]
+    assert seeded_activity.id in ids
+```
+
+- [ ] **Step 2: Run and verify failure**
+
+Run: `pytest tests/db/test_sync_state.py -v`
+
+Expected: missing repository methods.
+
+- [ ] **Step 3: Implement explicit transition methods**
+
+Add methods with these exact effects:
+
+```python
+def mark_downloaded(self, activity_id: int, path: str) -> Activity:
+    activity = self._require(activity_id)
+    activity.source_fit_path = path
+    activity.status = ActivityStatus.DOWNLOADED
+    activity.last_completed_stage = ActivityStatus.DOWNLOADED
+    activity.last_error = None
+    activity.retryable = True
+    self.session.commit()
+    return activity
+
+
+def mark_converted(self, activity_id: int, path: str) -> Activity:
+    activity = self._require(activity_id)
+    activity.converted_fit_path = path
+    activity.status = ActivityStatus.CONVERTED
+    activity.last_completed_stage = ActivityStatus.CONVERTED
+    activity.last_error = None
+    activity.retryable = True
+    self.session.commit()
+    return activity
+
+
+def mark_imported(self, activity_id: int, garmin_activity_id: str | None) -> Activity:
+    activity = self._require(activity_id)
+    activity.status = ActivityStatus.IMPORTED
+    activity.last_completed_stage = ActivityStatus.IMPORTED
+    activity.garmin_activity_id = garmin_activity_id
+    activity.last_error = None
+    activity.retryable = False
+    self.session.commit()
+    return activity
+
+
+def mark_duplicate(self, activity_id: int) -> Activity:
+    activity = self._require(activity_id)
+    activity.status = ActivityStatus.DUPLICATE
+    activity.last_completed_stage = ActivityStatus.DUPLICATE
+    activity.last_error = None
+    activity.retryable = False
+    self.session.commit()
+    return activity
+
+
+def mark_failed(self, activity_id: int, error: str, *, retryable: bool) -> Activity:
+    activity = self._require(activity_id)
+    activity.status = ActivityStatus.FAILED
+    activity.last_error = error[:2000]
+    activity.retryable = retryable
+    self.session.commit()
+    return activity
+```
+
+`list_pending_for_user()` must exclude terminal states and include failed rows only when `retryable=True`.
+
+- [ ] **Step 4: Add `SyncRunRepository` create/finalize methods**
+
+`start(user_id)` creates `RUNNING`; `finish(...)` sets counts, `finished_at`, status, and optional summary error. Do not store exception tracebacks in SQLite.
+
+- [ ] **Step 5: Run DB state tests**
+
+Run: `pytest tests/db/test_sync_state.py -v`
+
+Expected: PASS.
+
+- [ ] **Step 6: Commit**
+
+```bash
+git add app/db/repositories.py tests/db/test_sync_state.py
+git commit -m "feat: add durable sync state transitions"
+```
+
+## Task 2: Implement the single-user sync state machine
+
+**Files:**
+- Create: `app/sync/states.py`
+- Create: `app/sync/manager.py`
+- Create: `tests/sync/fakes.py`
+- Create: `tests/sync/test_manager.py`
+
+**Interfaces:**
+- Produces `SyncManager.sync_user(user_id: int, mfa_code: str | None = None) -> SyncOutcome`.
+- Constructor receives `session_factory`, `credential_cipher`, `settings`, `mywhoosh_factory`, `garmin_factory`, and `fit_converter`.
+- `mywhoosh_factory(token_store: MyWhooshTokenStore) -> MyWhooshClient`.
+- `garmin_factory(email: str, password: str, tokenstore: Path) -> GarminUploader`.
+- `fit_converter(source_path: Path, output_path: Path) -> FitConversionResult`.
+
+- [ ] **Step 1: Define result models and fake integration factories**
+
+```python
+# app/sync/states.py
+from dataclasses import dataclass
+
+
+@dataclass(frozen=True)
+class SyncOutcome:
+    user_id: int
+    status: str
+    discovered: int
+    imported: int
+    skipped: int
+    failed: int
+    message: str | None = None
+```
+
+Implement concrete fakes:
+
+```python
+# tests/sync/fakes.py
+from app.garmin.uploader import UploadResult
+
+
+class FakeMyWhooshClient:
+    def __init__(self, activities, fit_bytes: bytes) -> None:
+        self.activities = activities
+        self.fit_bytes = fit_bytes
+        self.list_calls = 0
+        self.download_calls = 0
+
+    async def list_activities(self, email: str, password: str):
+        self.list_calls += 1
+        return list(self.activities)
+
+    async def download_fit(self, activity_file_id: str, email: str, password: str) -> bytes:
+        self.download_calls += 1
+        return self.fit_bytes
+
+
+class FakeGarminUploader:
+    def __init__(self, result: UploadResult | None = None, error: Exception | None = None) -> None:
+        self.result = result or UploadResult("imported", False, "g-1", {"activityId": "g-1"})
+        self.error = error
+        self.calls = 0
+
+    def import_fit(self, fit_path, mfa_code=None):
+        self.calls += 1
+        if self.error is not None:
+            raise self.error
+        return self.result
+```
+
+- [ ] **Step 2: Write the happy-path test**
+
+```python
+@pytest.mark.asyncio
+async def test_new_activity_downloads_converts_and_imports(manager, seeded_user, tmp_path) -> None:
+    outcome = await manager.sync_user(seeded_user.id)
+
+    assert outcome.discovered == 1
+    assert outcome.imported == 1
+    assert outcome.failed == 0
+    activity = load_only_activity(seeded_user.id)
+    assert activity.status == ActivityStatus.IMPORTED
+    assert Path(activity.source_fit_path).exists()
+    assert Path(activity.converted_fit_path).exists()
+```
+
+- [ ] **Step 3: Write resume tests before implementation**
+
+```python
+@pytest.mark.asyncio
+@pytest.mark.parametrize(
+    ("status", "last_stage", "expected_downloads", "expected_conversions", "expected_imports"),
+    [
+        (ActivityStatus.DOWNLOADED, ActivityStatus.DOWNLOADED, 0, 1, 1),
+        (ActivityStatus.CONVERTED, ActivityStatus.CONVERTED, 0, 0, 1),
+        (ActivityStatus.IMPORTED, ActivityStatus.IMPORTED, 0, 0, 0),
+        (ActivityStatus.FAILED, ActivityStatus.CONVERTED, 0, 0, 1),
+    ],
+)
+async def test_resume_from_durable_stage(
+    manager_factory, seeded_activity_factory, status, last_stage,
+    expected_downloads, expected_conversions, expected_imports,
+) -> None:
+    activity = seeded_activity_factory(status=status, last_completed_stage=last_stage, retryable=True)
+    manager, mywhoosh, converter, garmin = manager_factory(activity)
+    await manager.sync_user(activity.user_id)
+    assert mywhoosh.download_calls == expected_downloads
+    assert converter.calls == expected_conversions
+    assert garmin.calls == expected_imports
+```
+
+- [ ] **Step 4: Run and verify failure**
+
+Run: `pytest tests/sync/test_manager.py -v`
+
+Expected: missing manager.
+
+- [ ] **Step 5: Implement per-activity filesystem layout and state machine**
+
+Use paths:
+
+```python
+activity_dir = settings.activities_dir / str(user.id) / activity.mywhoosh_activity_id
+source_path = activity_dir / "source.fit"
+converted_path = activity_dir / "edge-1030-plus.fit"
+```
+
+Create per-user integration instances from decrypted credentials and isolated token paths:
+
+```python
+mw_email = self.credential_cipher.decrypt(user.mywhoosh_email_enc)
+mw_password = self.credential_cipher.decrypt(user.mywhoosh_password_enc)
+garmin_email = self.credential_cipher.decrypt(user.garmin_email_enc)
+garmin_password = self.credential_cipher.decrypt(user.garmin_password_enc)
+
+token_dir = self.settings.tokens_dir / str(user.id)
+mywhoosh = self.mywhoosh_factory(MyWhooshTokenStore(token_dir / "mywhoosh.json"))
+garmin = self.garmin_factory(garmin_email, garmin_password, token_dir / "garmin")
+remote_activities = await mywhoosh.list_activities(mw_email, mw_password)
+```
+
+For each remote activity, call `get_or_create_discovered(...)`, then resume from `activity.last_completed_stage` when `activity.status == FAILED`; otherwise use `activity.status`.
+
+Core sequence:
+
+```python
+if stage == ActivityStatus.DISCOVERED:
+    fit_bytes = await mywhoosh.download_fit(remote.activity_file_id, mw_email, mw_password)
+    activity_dir.mkdir(parents=True, exist_ok=True)
+    source_path.write_bytes(fit_bytes)
+    repo.mark_downloaded(activity.id, str(source_path))
+
+if stage in {ActivityStatus.DOWNLOADED}:
+    fit_converter(source_path, converted_path)
+    repo.mark_converted(activity.id, str(converted_path))
+
+if stage in {ActivityStatus.CONVERTED}:
+    upload = await asyncio.to_thread(garmin.import_fit, converted_path, mfa_code)
+    if upload.duplicate:
+        repo.mark_duplicate(activity.id)
+    else:
+        repo.mark_imported(activity.id, upload.garmin_activity_id)
+```
+
+After each repository transition, update the local `stage` variable from the returned record so resume behavior is deterministic.
+
+- [ ] **Step 6: Implement exception mapping**
+
+Map exceptions with explicit user connection-state updates:
+
+```python
+except MyWhooshTransientError as exc:
+    user.health_state = HealthState.DEGRADED
+    user.mywhoosh_state = "error"
+    repo.mark_failed(activity.id, str(exc), retryable=True)
+except MyWhooshAuthError as exc:
+    user.health_state = HealthState.ACTION_REQUIRED
+    user.mywhoosh_state = "auth_required"
+    user.action_reason = "mywhoosh_auth_required"
+    stop_user_run = True
+except MyWhooshIntegrationError as exc:
+    user.health_state = HealthState.ACTION_REQUIRED
+    user.mywhoosh_state = "integration_error"
+    user.action_reason = "mywhoosh_integration_changed"
+    stop_user_run = True
+except GarminUploadBlocked:
+    user.health_state = HealthState.ACTION_REQUIRED
+    user.garmin_state = "mfa_required"
+    user.action_reason = "garmin_mfa_required"
+    stop_user_run = True
+except GarminAuthError as exc:
+    user.health_state = HealthState.ACTION_REQUIRED
+    user.garmin_state = "auth_required"
+    user.action_reason = "garmin_auth_required"
+    stop_user_run = True
+except GarminTransientError as exc:
+    user.health_state = HealthState.DEGRADED
+    user.garmin_state = "error"
+    repo.mark_failed(activity.id, str(exc), retryable=True)
+except FitFormatError as exc:
+    repo.mark_failed(activity.id, str(exc), retryable=False)
+```
+
+On successful MyWhoosh listing set `mywhoosh_state="connected"`; on successful Garmin import set `garmin_state="connected"`. Persist the user after each connection-state change. Unexpected exceptions mark the run/user `degraded` and log only exception class plus sanitized message.
+
+- [ ] **Step 7: Run manager tests**
+
+Run: `pytest tests/sync/test_manager.py -v`
+
+Expected: PASS.
+
+- [ ] **Step 8: Commit**
+
+```bash
+git add app/sync/states.py app/sync/manager.py tests/sync
+git commit -m "feat: add resumable per-user sync pipeline"
+```
+
+## Task 3: Add per-user locks and cross-user isolation
+
+**Files:**
+- Modify: `app/sync/manager.py`
+- Create: `tests/sync/test_concurrency.py`
+
+**Interfaces:**
+- Produces `SyncAlreadyRunning` and ensures only one active `sync_user()` call per user.
+
+- [ ] **Step 1: Write concurrency tests**
+
+```python
+@pytest.mark.asyncio
+async def test_same_user_cannot_run_twice(manager, seeded_user) -> None:
+    first_started = asyncio.Event()
+    release_first = asyncio.Event()
+    manager.test_hooks = SyncTestHooks(first_started=first_started, release=release_first)
+
+    first = asyncio.create_task(manager.sync_user(seeded_user.id))
+    await first_started.wait()
+
+    with pytest.raises(SyncAlreadyRunning):
+        await manager.sync_user(seeded_user.id)
+
+    release_first.set()
+    await first
+
+
+@pytest.mark.asyncio
+async def test_different_users_can_run_concurrently(manager, user_a, user_b) -> None:
+    results = await asyncio.gather(manager.sync_user(user_a.id), manager.sync_user(user_b.id))
+    assert {result.user_id for result in results} == {user_a.id, user_b.id}
+```
+
+Do not leave production-only `test_hooks`; instead inject a fake MyWhoosh client whose `list_activities()` blocks on test events.
+
+- [ ] **Step 2: Run and verify failure**
+
+Run: `pytest tests/sync/test_concurrency.py -v`
+
+Expected: same-user duplicate execution is not yet blocked.
+
+- [ ] **Step 3: Implement lock registry**
+
+```python
+class SyncAlreadyRunning(RuntimeError):
+    pass
+
+
+class SyncManager:
+    def __init__(...):
+        self._locks: dict[int, asyncio.Lock] = {}
+        self._locks_guard = asyncio.Lock()
+
+    async def _lock_for(self, user_id: int) -> asyncio.Lock:
+        async with self._locks_guard:
+            return self._locks.setdefault(user_id, asyncio.Lock())
+
+    async def sync_user(self, user_id: int, mfa_code: str | None = None) -> SyncOutcome:
+        lock = await self._lock_for(user_id)
+        if lock.locked():
+            raise SyncAlreadyRunning(f"sync already running for user {user_id}")
+        async with lock:
+            return await self._sync_user_locked(user_id, mfa_code)
+```
+
+- [ ] **Step 4: Add a `sync_all_enabled()` isolation method**
+
+```python
+async def sync_all_enabled(self) -> list[SyncOutcome | Exception]:
+    user_ids = self._load_enabled_user_ids()
+    return await asyncio.gather(
+        *(self.sync_user(user_id) for user_id in user_ids),
+        return_exceptions=True,
+    )
+```
+
+A failure for one user must appear as one list element and must not cancel sibling jobs.
+
+- [ ] **Step 5: Run concurrency tests**
+
+Run: `pytest tests/sync/test_concurrency.py -v`
+
+Expected: PASS.
+
+- [ ] **Step 6: Commit**
+
+```bash
+git add app/sync/manager.py tests/sync/test_concurrency.py
+git commit -m "feat: isolate concurrent user syncs"
+```
+
+## Task 4: Add the periodic scheduler through FastAPI lifespan
+
+**Files:**
+- Create: `app/sync/scheduler.py`
+- Modify: `app/main.py`
+- Create: `tests/sync/test_scheduler.py`
+
+**Interfaces:**
+- Produces `SyncScheduler.start()`, `stop()`, `run_once()`, `last_tick`, `next_tick`.
+- Scheduler interval is `Settings.sync_interval_minutes`.
+
+- [ ] **Step 1: Write scheduler test with a short injected interval**
+
+```python
+@pytest.mark.asyncio
+async def test_scheduler_calls_sync_all_and_survives_failure() -> None:
+    fake = FakeSyncManager(results=[RuntimeError("one user failed")])
+    scheduler = SyncScheduler(fake, interval_seconds=0.01)
+    await scheduler.start()
+    await asyncio.sleep(0.035)
+    await scheduler.stop()
+    assert fake.calls >= 2
+    assert scheduler.last_tick is not None
+```
+
+- [ ] **Step 2: Run and verify failure**
+
+Run: `pytest tests/sync/test_scheduler.py -v`
+
+Expected: missing scheduler.
+
+- [ ] **Step 3: Implement scheduler loop**
+
+```python
+class SyncScheduler:
+    def __init__(self, manager, *, interval_seconds: float) -> None:
+        self.manager = manager
+        self.interval_seconds = interval_seconds
+        self._task: asyncio.Task | None = None
+        self._stop = asyncio.Event()
+        self.last_tick = None
+        self.next_tick = None
+
+    async def run_once(self) -> None:
+        self.last_tick = datetime.now(timezone.utc)
+        await self.manager.sync_all_enabled()
+        self.next_tick = datetime.now(timezone.utc) + timedelta(seconds=self.interval_seconds)
+
+    async def _run(self) -> None:
+        while not self._stop.is_set():
+            await self.run_once()
+            try:
+                await asyncio.wait_for(self._stop.wait(), timeout=self.interval_seconds)
+            except TimeoutError:
+                pass
+```
+
+`stop()` sets the event and awaits the task. Never allow one `sync_all_enabled()` exception to kill the loop; log it and continue.
+
+- [ ] **Step 4: Wire into FastAPI lifespan**
+
+Build the concrete `SyncManager` once during app startup, store it on `app.state.sync_manager`, create `SyncScheduler(... interval_minutes * 60)`, start it, and stop it during lifespan shutdown.
+
+- [ ] **Step 5: Run scheduler tests**
+
+Run: `pytest tests/sync/test_scheduler.py -v`
+
+Expected: PASS.
+
+- [ ] **Step 6: Commit**
+
+```bash
+git add app/sync/scheduler.py app/main.py tests/sync/test_scheduler.py
+git commit -m "feat: schedule periodic user synchronization"
+```
+
+## Task 5: Add dashboard/manual sync/system operational routes
+
+**Files:**
+- Create: `app/web/operations.py`
+- Modify: `app/web/routes.py`
+- Modify: `app/web/templates/dashboard.html`
+- Create: `app/web/templates/system.html`
+- Create: `app/web/templates/fragments/sync_result.html`
+- Create: `tests/web/test_operations.py`
+
+**Interfaces:**
+- Routes: `POST /users/{id}/sync`, `POST /sync-all`, `GET /system`.
+- Manual actions use the same `SyncManager` instance and lock as the scheduler.
+
+- [ ] **Step 1: Write manual-sync tests**
+
+```python
+def test_manual_sync_calls_shared_manager(authenticated_client, fake_sync_manager) -> None:
+    response = authenticated_client.post(
+        "/users/1/sync",
+        data={"csrf_token": authenticated_client.csrf_token},
+    )
+    assert response.status_code == 200
+    assert fake_sync_manager.user_calls == [1]
+
+
+def test_manual_sync_reports_already_running(authenticated_client, fake_sync_manager) -> None:
+    fake_sync_manager.raise_already_running = True
+    response = authenticated_client.post(
+        "/users/1/sync",
+        data={"csrf_token": authenticated_client.csrf_token},
+    )
+    assert response.status_code == 409
+    assert "already running" in response.text.lower()
+```
+
+- [ ] **Step 2: Run and verify failure**
+
+Run: `pytest tests/web/test_operations.py -v`
+
+Expected: routes missing.
+
+- [ ] **Step 3: Implement routes with admin and CSRF checks**
+
+Each state-changing route must execute in this order:
+
+```python
+require_admin(request)
+validate_csrf(request, csrf_token)
+```
+
+Then call `await request.app.state.sync_manager.sync_user(user_id)` or `sync_all_enabled()`.
+
+- [ ] **Step 4: Expand dashboard data**
+
+Add a repository projection that contains only safe display fields:
+
+```python
+@dataclass(frozen=True)
+class UserDashboardRow:
+    id: int
+    name: str
+    enabled: bool
+    health_state: str
+    action_reason: str | None
+    last_sync_at: datetime | None
+    last_activity_name: str | None
+    last_activity_status: str | None
+
+
+def dashboard_rows(self) -> list[UserDashboardRow]:
+    users = self.list_all()
+    rows = []
+    for user in users:
+        last_run = self.session.scalar(
+            select(SyncRun).where(SyncRun.user_id == user.id).order_by(SyncRun.started_at.desc()).limit(1)
+        )
+        last_activity = self.session.scalar(
+            select(Activity).where(Activity.user_id == user.id).order_by(Activity.created_at.desc()).limit(1)
+        )
+        rows.append(UserDashboardRow(
+            id=user.id,
+            name=user.name,
+            enabled=user.enabled,
+            health_state=user.health_state.value,
+            action_reason=user.action_reason,
+            last_sync_at=last_run.finished_at if last_run else None,
+            last_activity_name=last_activity.activity_name if last_activity else None,
+            last_activity_status=last_activity.status.value if last_activity else None,
+        ))
+    return rows
+```
+
+Pass only these rows to `dashboard.html`. Render the MFA action only when `row.action_reason == "garmin_mfa_required"`. No decrypted credential is part of this projection.
+
+- [ ] **Step 5: Implement read-only system page**
+
+Expose application version, configured interval, scheduler `last_tick` and `next_tick`, user count, and activity count. The only action is a CSRF-protected `sync all now` POST.
+
+- [ ] **Step 6: Run tests**
+
+Run: `pytest tests/web/test_operations.py -v`
+
+Expected: PASS.
+
+- [ ] **Step 7: Commit**
+
+```bash
+git add app/web tests/web/test_operations.py
+git commit -m "feat: add operational sync controls"
+```
+
+## Task 6: Add Garmin MFA lifecycle and failed-activity retry
+
+**Files:**
+- Modify: `app/web/routes.py`
+- Modify: `app/web/templates/users/detail.html`
+- Create: `app/web/templates/fragments/mfa_form.html`
+- Create: `tests/web/test_mfa.py`
+- Modify: `app/sync/manager.py`
+
+**Interfaces:**
+- Route: `POST /users/{id}/garmin-mfa` with one-time `code`.
+- Route: `POST /activities/{id}/retry`.
+- MFA code exists only in request memory and the immediate `sync_user(user_id, mfa_code=code)` call.
+
+- [ ] **Step 1: Write MFA lifecycle test**
+
+```python
+def test_mfa_code_is_used_once_and_not_persisted(authenticated_client, fake_sync_manager, db_session) -> None:
+    response = authenticated_client.post(
+        "/users/1/garmin-mfa",
+        data={"csrf_token": authenticated_client.csrf_token, "code": "123456"},
+    )
+    assert response.status_code == 200
+    assert fake_sync_manager.mfa_calls == [(1, "123456")]
+
+    persisted_text = " ".join(str(row) for row in db_session.execute(text("select * from sync_runs")).all())
+    assert "123456" not in persisted_text
+```
+
+- [ ] **Step 2: Write retry test for non-terminal failed activity**
+
+Assert the route changes a retryable failed activity back to `status=last_completed_stage`, clears `last_error`, then calls the user's normal sync. Reject retry for `retryable=False` with HTTP 409.
+
+- [ ] **Step 3: Implement MFA route**
+
+Validate code as a non-empty short string, never log it, and call:
+
+```python
+outcome = await request.app.state.sync_manager.sync_user(user_id, mfa_code=code.strip())
+```
+
+After a successful Garmin login/import, clear `action_reason` and restore health to `healthy` or `degraded` according to the resulting sync outcome.
+
+- [ ] **Step 4: Implement failed-activity reset operation**
+
+Repository method:
+
+```python
+def reset_retryable_failure(self, activity_id: int) -> Activity:
+    activity = self._require(activity_id)
+    if activity.status != ActivityStatus.FAILED or not activity.retryable:
+        raise ValueError("activity is not retryable")
+    activity.status = activity.last_completed_stage
+    activity.last_error = None
+    self.session.commit()
+    return activity
+```
+
+- [ ] **Step 5: Run MFA/retry tests**
+
+Run: `pytest tests/web/test_mfa.py tests/web/test_operations.py -v`
+
+Expected: PASS.
+
+- [ ] **Step 6: Commit**
+
+```bash
+git add app/web app/sync/manager.py app/db/repositories.py tests/web/test_mfa.py
+git commit -m "feat: handle Garmin MFA and activity retries"
+```
+
+## Task 7: End-to-end regression and Docker acceptance
+
+**Files:**
+- Modify: `docker-compose.example.yml` only if integration exposes a missing runtime configuration
+- Create: `tests/test_acceptance.py`
+
+**Interfaces:**
+- No new interface; verifies the v1 acceptance criteria with fake external services.
+
+- [ ] **Step 1: Add an application-level acceptance test with two users**
+
+Build the app with temporary SQLite/data directories and injected fake MyWhoosh/Garmin factories. Seed two enabled users, give each one distinct remote activity IDs, run `sync_all_enabled()`, and assert:
+
+```python
+assert all(result.status == "success" for result in results)
+assert count_terminal_activities(user_a.id) == 1
+assert count_terminal_activities(user_b.id) == 1
+assert user_a_source_path.parent != user_b_source_path.parent
+assert user_a_garmin_factory.tokenstore != user_b_garmin_factory.tokenstore
+```
+
+- [ ] **Step 2: Add isolation acceptance test**
+
+Configure User B to raise `GarminUploadBlocked`; assert User A still imports and User B ends `action_required` with no impact on User A.
+
+- [ ] **Step 3: Run the full suite**
+
+Run: `pytest -v`
+
+Expected: PASS.
+
+- [ ] **Step 4: Build Docker image again**
+
+Run: `docker build -t mywhoosh-garmin-sync:test .`
+
+Expected: successful build with the complete dependency set.
+
+- [ ] **Step 5: Start local container and exercise smoke paths**
+
+Start with a temporary bind-mounted `/data`, then verify:
+
+```bash
+curl -fsS http://127.0.0.1:18080/healthz
+curl -I http://127.0.0.1:18080/
+```
+
+Expected: health JSON and dashboard redirect to `/login` when unauthenticated.
+
+- [ ] **Step 6: Verify secrets are absent from captured test logs**
+
+Run:
+
+```bash
+pytest -v 2>&1 | tee /tmp/mywhoosh-garmin-test.log
+! grep -F "mw-secret" /tmp/mywhoosh-garmin-test.log
+! grep -F "garmin-secret" /tmp/mywhoosh-garmin-test.log
+! grep -F "123456" /tmp/mywhoosh-garmin-test.log
+```
+
+Expected: all three negated `grep` commands succeed.
+
+- [ ] **Step 7: Commit**
+
+```bash
+git add tests/test_acceptance.py docker-compose.example.yml
+git commit -m "test: cover multi-user sync acceptance"
+```