diff --git a/tests/test_acceptance.py b/tests/test_acceptance.py
new file mode 100644
index 0000000..2db5b65
--- /dev/null
+++ b/tests/test_acceptance.py
@@ -0,0 +1,250 @@
+"""Application-level, multi-user acceptance tests for the full MyWhoosh -> Garmin
+sync pipeline (Task 7 of the sync-scheduler-web plan).
+
+These tests build a real `SyncManager` wired to a real SQLite database and a
+real `CredentialCipher`, but with fake MyWhoosh/Garmin factories, so they
+exercise the whole state machine end-to-end for two independent users without
+touching any real external service.
+"""
+
+from __future__ import annotations
+
+from pathlib import Path
+
+import pytest
+from cryptography.fernet import Fernet
+from sqlalchemy import func, select
+from sqlalchemy.orm import sessionmaker
+
+from app.db.models import Activity, ActivityStatus, HealthState, SyncUser
+from app.db.repositories import UserRepository
+from app.db.session import create_db_engine, create_session_factory, initialize_schema
+from app.garmin.uploader import GarminUploadBlocked, UploadResult
+from app.mywhoosh.models import MyWhooshActivity
+from app.security.credentials import CredentialCipher
+from app.sync.manager import SyncManager
+
+
+class StubSettings:
+    """Minimal stand-in for app.config.Settings exposing only the two
+    properties SyncManager needs."""
+
+    def __init__(self, tmp_path: Path) -> None:
+        self.tokens_dir = tmp_path / "tokens"
+        self.activities_dir = tmp_path / "activities"
+
+
+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, password):
+        self.list_calls += 1
+        return list(self.activities)
+
+    async def download_fit(self, activity_file_id, email, password):
+        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
+
+
+def fake_fit_converter(source_path: Path, output_path: Path) -> None:
+    output_path.parent.mkdir(parents=True, exist_ok=True)
+    output_path.write_bytes(b"fake-converted-fit-bytes")
+
+
+def count_terminal_activities(session_factory: sessionmaker, user_id: int) -> int:
+    with session_factory() as session:
+        return session.scalar(
+            select(func.count())
+            .select_from(Activity)
+            .where(
+                Activity.user_id == user_id,
+                Activity.status.in_([ActivityStatus.IMPORTED, ActivityStatus.DUPLICATE]),
+            )
+        )
+
+
+def _create_user(session, cipher: CredentialCipher, *, name: str) -> SyncUser:
+    return UserRepository(session).create(
+        name=name,
+        enabled=True,
+        mywhoosh_email_enc=cipher.encrypt(f"{name.lower()}-mywhoosh@example.com"),
+        mywhoosh_password_enc=cipher.encrypt("mw-secret"),
+        garmin_email_enc=cipher.encrypt(f"{name.lower()}-garmin@example.com"),
+        garmin_password_enc=cipher.encrypt("garmin-secret"),
+    )
+
+
+@pytest.fixture
+def session_factory(tmp_path: Path):
+    db_path = tmp_path / "acceptance.db"
+    engine = create_db_engine(f"sqlite:///{db_path}")
+    initialize_schema(engine)
+    factory = create_session_factory(engine)
+    try:
+        yield factory
+    finally:
+        engine.dispose()
+
+
+@pytest.fixture
+def cipher() -> CredentialCipher:
+    return CredentialCipher(Fernet.generate_key().decode("ascii"))
+
+
+@pytest.fixture
+def settings(tmp_path: Path) -> StubSettings:
+    return StubSettings(tmp_path)
+
+
+@pytest.fixture
+def two_users(session_factory, cipher: CredentialCipher):
+    with session_factory() as session:
+        user_a = _create_user(session, cipher, name="Alice")
+        user_b = _create_user(session, cipher, name="Bob")
+        return user_a, user_b
+
+
+def _build_manager(
+    *,
+    session_factory,
+    cipher: CredentialCipher,
+    settings: StubSettings,
+    user_a: SyncUser,
+    user_b: SyncUser,
+    fake_mw_a: FakeMyWhooshClient,
+    fake_mw_b: FakeMyWhooshClient,
+    fake_garmin_a: FakeGarminUploader,
+    fake_garmin_b: FakeGarminUploader,
+):
+    mywhoosh_fakes = {str(user_a.id): fake_mw_a, str(user_b.id): fake_mw_b}
+    garmin_fakes = {str(user_a.id): fake_garmin_a, str(user_b.id): fake_garmin_b}
+    garmin_factory_calls: list[tuple[str, str, Path]] = []
+
+    def mywhoosh_factory(token_store):
+        user_key = token_store.path.parent.name
+        return mywhoosh_fakes[user_key]
+
+    def garmin_factory(email, password, tokenstore):
+        garmin_factory_calls.append((email, password, tokenstore))
+        user_key = tokenstore.parent.name
+        return garmin_fakes[user_key]
+
+    manager = SyncManager(
+        session_factory=session_factory,
+        credential_cipher=cipher,
+        settings=settings,
+        mywhoosh_factory=mywhoosh_factory,
+        garmin_factory=garmin_factory,
+        fit_converter=fake_fit_converter,
+    )
+    return manager, garmin_factory_calls
+
+
+@pytest.mark.asyncio
+async def test_two_user_happy_path(session_factory, cipher, settings, two_users):
+    user_a, user_b = two_users
+
+    remote_a = MyWhooshActivity(
+        id="remote-a-1", title="Alice Ride", activity_file_id="file-a-1", started_at=None
+    )
+    remote_b = MyWhooshActivity(
+        id="remote-b-1", title="Bob Ride", activity_file_id="file-b-1", started_at=None
+    )
+    fake_mw_a = FakeMyWhooshClient(activities=[remote_a], fit_bytes=b"alice-source-bytes")
+    fake_mw_b = FakeMyWhooshClient(activities=[remote_b], fit_bytes=b"bob-source-bytes")
+    fake_garmin_a = FakeGarminUploader()
+    fake_garmin_b = FakeGarminUploader()
+
+    manager, garmin_factory_calls = _build_manager(
+        session_factory=session_factory,
+        cipher=cipher,
+        settings=settings,
+        user_a=user_a,
+        user_b=user_b,
+        fake_mw_a=fake_mw_a,
+        fake_mw_b=fake_mw_b,
+        fake_garmin_a=fake_garmin_a,
+        fake_garmin_b=fake_garmin_b,
+    )
+
+    results = await manager.sync_all_enabled()
+
+    assert all(result.status == "success" for result in results)
+    assert count_terminal_activities(session_factory, user_a.id) == 1
+    assert count_terminal_activities(session_factory, user_b.id) == 1
+
+    with session_factory() as session:
+        activity_a = session.scalar(select(Activity).where(Activity.user_id == user_a.id))
+        activity_b = session.scalar(select(Activity).where(Activity.user_id == user_b.id))
+        assert Path(activity_a.source_fit_path).exists()
+        assert Path(activity_b.source_fit_path).exists()
+        assert Path(activity_a.source_fit_path).parent != Path(activity_b.source_fit_path).parent
+
+    tokenstores = {str(call[2]) for call in garmin_factory_calls}
+    assert len(tokenstores) == 2
+
+
+@pytest.mark.asyncio
+async def test_isolation_when_one_user_requires_mfa(session_factory, cipher, settings, two_users):
+    user_a, user_b = two_users
+
+    remote_a = MyWhooshActivity(
+        id="remote-a-1", title="Alice Ride", activity_file_id="file-a-1", started_at=None
+    )
+    remote_b = MyWhooshActivity(
+        id="remote-b-1", title="Bob Ride", activity_file_id="file-b-1", started_at=None
+    )
+    fake_mw_a = FakeMyWhooshClient(activities=[remote_a], fit_bytes=b"alice-source-bytes")
+    fake_mw_b = FakeMyWhooshClient(activities=[remote_b], fit_bytes=b"bob-source-bytes")
+    fake_garmin_a = FakeGarminUploader()
+    fake_garmin_b = FakeGarminUploader(error=GarminUploadBlocked("Garmin requested MFA"))
+
+    manager, garmin_factory_calls = _build_manager(
+        session_factory=session_factory,
+        cipher=cipher,
+        settings=settings,
+        user_a=user_a,
+        user_b=user_b,
+        fake_mw_a=fake_mw_a,
+        fake_mw_b=fake_mw_b,
+        fake_garmin_a=fake_garmin_a,
+        fake_garmin_b=fake_garmin_b,
+    )
+
+    results = await manager.sync_all_enabled()
+
+    results_by_user = {result.user_id: result for result in results}
+    assert results_by_user[user_a.id].status == "success"
+    assert results_by_user[user_b.id].status != "success"
+    assert results_by_user[user_b.id].status == "failed"
+
+    assert count_terminal_activities(session_factory, user_a.id) == 1
+
+    with session_factory() as session:
+        reloaded_b = UserRepository(session).get(user_b.id)
+        assert reloaded_b.health_state == HealthState.ACTION_REQUIRED
+        assert reloaded_b.action_reason == "garmin_mfa_required"
+
+        reloaded_a = UserRepository(session).get(user_a.id)
+        assert reloaded_a.health_state == HealthState.HEALTHY
+        assert reloaded_a.action_reason is None
+
+        activity_a = session.scalar(select(Activity).where(Activity.user_id == user_a.id))
+        assert activity_a.status in (ActivityStatus.IMPORTED, ActivityStatus.DUPLICATE)