diff --git a/backend/app/modules/project/infrastructure/json_repository.py b/backend/app/modules/project/infrastructure/json_repository.py
index e69de29..810349f 100644
--- a/backend/app/modules/project/infrastructure/json_repository.py
+++ b/backend/app/modules/project/infrastructure/json_repository.py
@@ -0,0 +1,59 @@
+import json
+from datetime import datetime
+from pathlib import Path
+
+from app.modules.project.domain.entities import Project
+from app.modules.project.domain.repositories import ProjectRepository
+
+
+class JsonProjectRepository(ProjectRepository):
+    def __init__(self, path: Path) -> None:
+        self._path = path
+
+    def _load(self) -> list[dict]:
+        if not self._path.exists():
+            return []
+        return json.loads(self._path.read_text(encoding="utf-8"))
+
+    def _save(self, data: list[dict]) -> None:
+        self._path.parent.mkdir(parents=True, exist_ok=True)
+        self._path.write_text(json.dumps(data, ensure_ascii=False, indent=2), encoding="utf-8")
+
+    @staticmethod
+    def _to_dict(p: Project) -> dict:
+        return {
+            "id": p.id,
+            "name": p.name,
+            "design_dir": p.design_dir,
+            "code_dir": p.code_dir,
+            "created_at": p.created_at.isoformat(),
+        }
+
+    @staticmethod
+    def _from_dict(d: dict) -> Project:
+        return Project(
+            id=d["id"],
+            name=d["name"],
+            design_dir=d["design_dir"],
+            code_dir=d.get("code_dir"),
+            created_at=datetime.fromisoformat(d["created_at"]),
+        )
+
+    def list_all(self) -> list[Project]:
+        return [self._from_dict(d) for d in self._load()]
+
+    def get_by_id(self, project_id: str) -> Project | None:
+        for d in self._load():
+            if d["id"] == project_id:
+                return self._from_dict(d)
+        return None
+
+    def save(self, project: Project) -> None:
+        data = self._load()
+        data = [d for d in data if d["id"] != project.id]
+        data.append(self._to_dict(project))
+        self._save(data)
+
+    def delete(self, project_id: str) -> None:
+        data = [d for d in self._load() if d["id"] != project_id]
+        self._save(data)
diff --git a/backend/tests/test_project.py b/backend/tests/test_project.py
new file mode 100644
index 0000000..bc93340
--- /dev/null
+++ b/backend/tests/test_project.py
@@ -0,0 +1,44 @@
+import json
+from pathlib import Path
+
+import pytest
+from app.modules.project.domain.entities import Project
+from app.modules.project.infrastructure.json_repository import JsonProjectRepository
+
+
+@pytest.fixture
+def repo(tmp_path: Path) -> JsonProjectRepository:
+    return JsonProjectRepository(tmp_path / "projects.json")
+
+
+def test_empty_repo_returns_empty_list(repo: JsonProjectRepository):
+    assert repo.list_all() == []
+
+
+def test_save_and_get(repo: JsonProjectRepository):
+    from datetime import datetime
+    p = Project(id="id1", name="test", design_dir="/tmp/d", code_dir=None, created_at=datetime(2026, 1, 1))
+    repo.save(p)
+    assert repo.get_by_id("id1") is not None
+    assert repo.get_by_id("id1").name == "test"
+
+
+def test_list_all(repo: JsonProjectRepository):
+    from datetime import datetime
+    p1 = Project(id="id1", name="a", design_dir="/d1", code_dir=None, created_at=datetime(2026, 1, 1))
+    p2 = Project(id="id2", name="b", design_dir="/d2", code_dir=None, created_at=datetime(2026, 1, 2))
+    repo.save(p1)
+    repo.save(p2)
+    assert len(repo.list_all()) == 2
+
+
+def test_delete(repo: JsonProjectRepository):
+    from datetime import datetime
+    p = Project(id="id1", name="test", design_dir="/d", code_dir=None, created_at=datetime(2026, 1, 1))
+    repo.save(p)
+    repo.delete("id1")
+    assert repo.get_by_id("id1") is None
+
+
+def test_get_nonexistent_returns_none(repo: JsonProjectRepository):
+    assert repo.get_by_id("nope") is None