diff --git a/adapters/__init__.py b/adapters/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/adapters/storage/__init__.py b/adapters/storage/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/adapters/storage/json_file.py b/adapters/storage/json_file.py
new file mode 100644
index 0000000..f2f8de0
--- /dev/null
+++ b/adapters/storage/json_file.py
@@ -0,0 +1,202 @@
+"""JSON file storage adapter for JIGAIDO.
+
+Implements RoomStorage and TrackingStorage ports using JSON file persistence.
+Data stored at:
+- Rooms: ~/.jigaido/data/<room_id>.json
+- Tracking: ~/.jigaido/tracking/<room_id>_<user_id>.json
+"""
+
+import json
+import os
+from pathlib import Path
+
+from core.models import Bounty, RoomData, TrackingData, TrackedBounty
+from core.ports import RoomStorage, TrackingStorage
+
+
+class JsonFileRoomStorage:
+    """RoomStorage implementation using JSON files.
+
+    Stores room data at ~/.jigaido/data/<room_id>.json
+    """
+
+    def __init__(self, data_dir: Path | None = None):
+        if data_dir is None:
+            data_dir = Path.home() / ".jigaido" / "data"
+        self._data_dir = data_dir
+        self._data_dir.mkdir(parents=True, exist_ok=True)
+
+    def _get_file_path(self, room_id: int) -> Path:
+        return self._data_dir / f"{room_id}.json"
+
+    def load(self, room_id: int) -> RoomData | None:
+        """Load room data from JSON file. Returns None if not found."""
+        file_path = self._get_file_path(room_id)
+        if not file_path.exists():
+            return None
+
+        with open(file_path, "r") as f:
+            data = json.load(f)
+
+        bounties = [
+            Bounty(
+                id=b["id"],
+                text=b.get("text"),
+                link=b.get("link"),
+                due_date_ts=b.get("due_date_ts"),
+                created_at=b["created_at"],
+                created_by_user_id=b["created_by_user_id"],
+            )
+            for b in data.get("bounties", [])
+        ]
+
+        return RoomData(
+            room_id=data["room_id"],
+            bounties=bounties,
+            next_id=data["next_id"],
+        )
+
+    def save(self, room_data: RoomData) -> None:
+        """Save room data to JSON file."""
+        data = {
+            "room_id": room_data.room_id,
+            "next_id": room_data.next_id,
+            "bounties": [
+                {
+                    "id": b.id,
+                    "text": b.text,
+                    "link": b.link,
+                    "due_date_ts": b.due_date_ts,
+                    "created_at": b.created_at,
+                    "created_by_user_id": b.created_by_user_id,
+                }
+                for b in room_data.bounties
+            ],
+        }
+
+        with open(self._get_file_path(room_data.room_id), "w") as f:
+            json.dump(data, f)
+
+    def add_bounty(self, room_id: int, bounty: Bounty) -> None:
+        """Add a bounty to a room, creating the room if necessary."""
+        room_data = self.load(room_id)
+        if room_data is None:
+            room_data = RoomData(room_id=room_id, bounties=[], next_id=1)
+
+        room_data.bounties.append(bounty)
+        if bounty.id >= room_data.next_id:
+            room_data.next_id = bounty.id + 1
+
+        self.save(room_data)
+
+    def update_bounty(self, room_id: int, bounty: Bounty) -> None:
+        """Update an existing bounty in a room."""
+        room_data = self.load(room_id)
+        if room_data is None:
+            return
+
+        for i, b in enumerate(room_data.bounties):
+            if b.id == bounty.id:
+                room_data.bounties[i] = bounty
+                break
+
+        self.save(room_data)
+
+    def delete_bounty(self, room_id: int, bounty_id: int) -> None:
+        """Delete a bounty from a room."""
+        room_data = self.load(room_id)
+        if room_data is None:
+            return
+
+        room_data.bounties = [b for b in room_data.bounties if b.id != bounty_id]
+        self.save(room_data)
+
+    def get_bounty(self, room_id: int, bounty_id: int) -> Bounty | None:
+        """Get a specific bounty from a room by ID."""
+        room_data = self.load(room_id)
+        if room_data is None:
+            return None
+
+        for b in room_data.bounties:
+            if b.id == bounty_id:
+                return b
+
+        return None
+
+
+class JsonFileTrackingStorage:
+    """TrackingStorage implementation using JSON files.
+
+    Stores tracking data at ~/.jigaido/tracking/<room_id>_<user_id>.json
+    """
+
+    def __init__(self, tracking_dir: Path | None = None):
+        if tracking_dir is None:
+            tracking_dir = Path.home() / ".jigaido" / "tracking"
+        self._tracking_dir = tracking_dir
+        self._tracking_dir.mkdir(parents=True, exist_ok=True)
+
+    def _get_file_path(self, room_id: int, user_id: int) -> Path:
+        return self._tracking_dir / f"{room_id}_{user_id}.json"
+
+    def load(self, room_id: int, user_id: int) -> TrackingData | None:
+        """Load tracking data from JSON file. Returns None if not found."""
+        file_path = self._get_file_path(room_id, user_id)
+        if not file_path.exists():
+            return None
+
+        with open(file_path, "r") as f:
+            data = json.load(f)
+
+        tracked = [
+            TrackedBounty(
+                bounty_id=t["bounty_id"],
+                created_at=t["created_at"],
+            )
+            for t in data.get("tracked", [])
+        ]
+
+        return TrackingData(
+            room_id=data["room_id"],
+            user_id=data["user_id"],
+            tracked=tracked,
+        )
+
+    def save(self, tracking_data: TrackingData) -> None:
+        """Save tracking data to JSON file."""
+        data = {
+            "room_id": tracking_data.room_id,
+            "user_id": tracking_data.user_id,
+            "tracked": [
+                {
+                    "bounty_id": t.bounty_id,
+                    "created_at": t.created_at,
+                }
+                for t in tracking_data.tracked
+            ],
+        }
+
+        with open(
+            self._get_file_path(tracking_data.room_id, tracking_data.user_id), "w"
+        ) as f:
+            json.dump(data, f)
+
+    def track_bounty(self, room_id: int, user_id: int, tracked: TrackedBounty) -> None:
+        """Add a bounty to a user's tracking list, creating the tracking entry if needed."""
+        tracking_data = self.load(room_id, user_id)
+        if tracking_data is None:
+            tracking_data = TrackingData(room_id=room_id, user_id=user_id, tracked=[])
+
+        tracking_data.tracked.append(tracked)
+        self.save(tracking_data)
+
+    def untrack_bounty(self, room_id: int, user_id: int, bounty_id: int) -> None:
+        """Remove a bounty from a user's tracking list."""
+        tracking_data = self.load(room_id, user_id)
+        if tracking_data is None:
+            return
+
+        tracking_data.tracked = [
+            t for t in tracking_data.tracked if t.bounty_id != bounty_id
+        ]
+        self.save(tracking_data)
diff --git a/tests/test_json_file_adapter.py b/tests/test_json_file_adapter.py
new file mode 100644
index 0000000..068d2f8
--- /dev/null
+++ b/tests/test_json_file_adapter.py
@@ -0,0 +1,269 @@
+"""Tests for adapters/storage/json_file.py — JSON file storage adapter."""
+
+import pytest
+import tempfile
+import shutil
+from pathlib import Path
+
+from core.models import Bounty, RoomData, TrackingData, TrackedBounty
+from core.ports import RoomStorage, TrackingStorage
+from adapters.storage.json_file import JsonFileRoomStorage, JsonFileTrackingStorage
+
+
+class TestJsonFileRoomStorage:
+    """Tests for JsonFileRoomStorage adapter."""
+
+    @pytest.fixture
+    def temp_dir(self):
+        """Create a temporary directory for test files."""
+        tmp = tempfile.mkdtemp()
+        yield Path(tmp)
+        shutil.rmtree(tmp)
+
+    @pytest.fixture
+    def storage(self, temp_dir):
+        """Create a JsonFileRoomStorage instance with temp directory."""
+        return JsonFileRoomStorage(data_dir=temp_dir)
+
+    def test_implements_room_storage_protocol(self, storage):
+        """Verify JsonFileRoomStorage implements RoomStorage protocol."""
+        assert isinstance(storage, RoomStorage)
+
+    def test_load_returns_none_for_nonexistent_room(self, storage):
+        """Load returns None if room doesn't exist."""
+        result = storage.load(-1001)
+        assert result is None
+
+    def test_save_and_load_room(self, storage):
+        """Test saving and loading room data."""
+        room = RoomData(room_id=-1001, bounties=[], next_id=1)
+        storage.save(room)
+
+        loaded = storage.load(-1001)
+        assert loaded is not None
+        assert loaded.room_id == -1001
+        assert loaded.next_id == 1
+        assert loaded.bounties == []
+
+    def test_add_bounty_creates_room(self, storage):
+        """Test add_bounty creates room if it doesn't exist."""
+        bounty = Bounty(
+            id=1,
+            text="Test bounty",
+            link=None,
+            due_date_ts=None,
+            created_at=1000,
+            created_by_user_id=123,
+        )
+        storage.add_bounty(-1001, bounty)
+
+        room = storage.load(-1001)
+        assert room is not None
+        assert len(room.bounties) == 1
+        assert room.bounties[0].text == "Test bounty"
+        assert room.next_id == 2
+
+    def test_add_bounty_appends_to_existing_room(self, storage):
+        """Test add_bounty appends to existing room."""
+        bounty1 = Bounty(
+            id=1,
+            text="First",
+            link=None,
+            due_date_ts=None,
+            created_at=1000,
+            created_by_user_id=123,
+        )
+        bounty2 = Bounty(
+            id=2,
+            text="Second",
+            link=None,
+            due_date_ts=None,
+            created_at=1001,
+            created_by_user_id=123,
+        )
+        storage.add_bounty(-1001, bounty1)
+        storage.add_bounty(-1001, bounty2)
+
+        room = storage.load(-1001)
+        assert len(room.bounties) == 2
+        assert room.next_id == 3
+
+    def test_update_bounty(self, storage):
+        """Test updating an existing bounty."""
+        bounty = Bounty(
+            id=1,
+            text="Original",
+            link=None,
+            due_date_ts=None,
+            created_at=1000,
+            created_by_user_id=123,
+        )
+        storage.add_bounty(-1001, bounty)
+
+        updated = Bounty(
+            id=1,
+            text="Updated",
+            link="https://example.com",
+            due_date_ts=2000,
+            created_at=1000,
+            created_by_user_id=123,
+        )
+        storage.update_bounty(-1001, updated)
+
+        result = storage.get_bounty(-1001, 1)
+        assert result is not None
+        assert result.text == "Updated"
+        assert result.link == "https://example.com"
+
+    def test_delete_bounty(self, storage):
+        """Test deleting a bounty."""
+        bounty = Bounty(
+            id=1,
+            text="To delete",
+            link=None,
+            due_date_ts=None,
+            created_at=1000,
+            created_by_user_id=123,
+        )
+        storage.add_bounty(-1001, bounty)
+        storage.delete_bounty(-1001, 1)
+
+        result = storage.get_bounty(-1001, 1)
+        assert result is None
+
+    def test_get_bounty_returns_none_for_nonexistent(self, storage):
+        """Test get_bounty returns None for non-existent bounty."""
+        result = storage.get_bounty(-1001, 999)
+        assert result is None
+
+    def test_update_bounty_for_nonexistent_room(self, storage):
+        """Test update_bounty does nothing for non-existent room."""
+        bounty = Bounty(
+            id=1,
+            text="Test",
+            link=None,
+            due_date_ts=None,
+            created_at=1000,
+            created_by_user_id=123,
+        )
+        result = storage.update_bounty(-1001, bounty)
+        # Should not raise, should just return
+
+
+class TestJsonFileTrackingStorage:
+    """Tests for JsonFileTrackingStorage adapter."""
+
+    @pytest.fixture
+    def temp_dir(self):
+        """Create a temporary directory for test files."""
+        tmp = tempfile.mkdtemp()
+        yield Path(tmp)
+        shutil.rmtree(tmp)
+
+    @pytest.fixture
+    def storage(self, temp_dir):
+        """Create a JsonFileTrackingStorage instance with temp directory."""
+        return JsonFileTrackingStorage(tracking_dir=temp_dir)
+
+    def test_implements_tracking_storage_protocol(self, storage):
+        """Verify JsonFileTrackingStorage implements TrackingStorage protocol."""
+        assert isinstance(storage, TrackingStorage)
+
+    def test_load_returns_none_for_nonexistent_tracking(self, storage):
+        """Load returns None if tracking doesn't exist."""
+        result = storage.load(-1001, 123456)
+        assert result is None
+
+    def test_save_and_load_tracking(self, storage):
+        """Test saving and loading tracking data."""
+        tracking = TrackingData(
+            room_id=-1001,
+            user_id=123456,
+            tracked=[
+                TrackedBounty(bounty_id=1, created_at=1000),
+            ],
+        )
+        storage.save(tracking)
+
+        loaded = storage.load(-1001, 123456)
+        assert loaded is not None
+        assert loaded.room_id == -1001
+        assert loaded.user_id == 123456
+        assert len(loaded.tracked) == 1
+
+    def test_track_bounty_creates_tracking(self, storage):
+        """Test track_bounty creates tracking if it doesn't exist."""
+        tracked = TrackedBounty(bounty_id=5, created_at=1000)
+        storage.track_bounty(-1001, 123456, tracked)
+
+        result = storage.load(-1001, 123456)
+        assert result is not None
+        assert len(result.tracked) == 1
+        assert result.tracked[0].bounty_id == 5
+
+    def test_track_bounty_appends_to_existing(self, storage):
+        """Test track_bounty appends to existing tracking."""
+        tracked1 = TrackedBounty(bounty_id=1, created_at=1000)
+        tracked2 = TrackedBounty(bounty_id=2, created_at=1001)
+        storage.track_bounty(-1001, 123456, tracked1)
+        storage.track_bounty(-1001, 123456, tracked2)
+
+        result = storage.load(-1001, 123456)
+        assert len(result.tracked) == 2
+
+    def test_untrack_bounty(self, storage):
+        """Test untracking a bounty."""
+        tracked = TrackedBounty(bounty_id=5, created_at=1000)
+        storage.track_bounty(-1001, 123456, tracked)
+        storage.untrack_bounty(-1001, 123456, 5)
+
+        result = storage.load(-1001, 123456)
+        assert len(result.tracked) == 0
+
+    def test_untrack_nonexistent_does_not_raise(self, storage):
+        """Test untracking non-existent bounty doesn't raise."""
+        # Should not raise
+        storage.untrack_bounty(-1001, 123456, 999)
+
+    def test_tracking_persists_across_storage_instances(self, temp_dir):
+        """Test that tracking data persists when using different storage instances."""
+        storage1 = JsonFileTrackingStorage(tracking_dir=temp_dir)
+        tracked = TrackedBounty(bounty_id=5, created_at=1000)
+        storage1.track_bounty(-1001, 123456, tracked)
+
+        # Create a new storage instance pointing to the same directory
+        storage2 = JsonFileTrackingStorage(tracking_dir=temp_dir)
+        result = storage2.load(-1001, 123456)
+        assert result is not None
+        assert len(result.tracked) == 1
+
+
+class TestJsonFileRoomStoragePersistence:
+    """Test that room data persists across storage instances."""
+
+    @pytest.fixture
+    def temp_dir(self):
+        """Create a temporary directory for test files."""
+        tmp = tempfile.mkdtemp()
+        yield Path(tmp)
+        shutil.rmtree(tmp)
+
+    def test_room_persists_across_storage_instances(self, temp_dir):
+        """Test room data persists when using different storage instances."""
+        storage1 = JsonFileRoomStorage(data_dir=temp_dir)
+        bounty = Bounty(
+            id=1,
+            text="Persisted bounty",
+            link=None,
+            due_date_ts=None,
+            created_at=1000,
+            created_by_user_id=123,
+        )
+        storage1.add_bounty(-1001, bounty)
+
+        # Create a new storage instance pointing to the same directory
+        storage2 = JsonFileRoomStorage(data_dir=temp_dir)
+        room = storage2.load(-1001)
+        assert room is not None
+        assert len(room.bounties) == 1
+        assert room.bounties[0].text == "Persisted bounty"