diff --git a/src/rag/loaders.py b/src/rag/loaders.py
index 9dd2468..6aa25eb 100644
--- a/src/rag/loaders.py
+++ b/src/rag/loaders.py
@@ -29,9 +29,8 @@ def load_documents(directory: str | Path) -> list[Document]:
         raise FileNotFoundError(f"Document directory not found: {path}")
 
     documents: list[Document] = []
-    for file_path in sorted(path.iterdir(), key=lambda item: item.name):
-        if not file_path.is_file():
-            continue
+    files = [file_path for file_path in path.rglob("*") if file_path.is_file()]
+    for file_path in sorted(files, key=lambda item: item.relative_to(path).as_posix()):
         suffix = file_path.suffix.lower().lstrip(".")
         if suffix not in SUPPORTED_TEXT_EXTENSIONS:
             continue
diff --git a/tests/test_loaders.py b/tests/test_loaders.py
index 94c80c3..5b7ffcb 100644
--- a/tests/test_loaders.py
+++ b/tests/test_loaders.py
@@ -62,3 +62,118 @@ def test_workshop_corpus_is_a_markdown_collection() -> None:
     assert len(documents) == 6
     assert all(doc.filename.endswith(".md") for doc in documents)
     assert all(doc.metadata["source"].endswith(".md") for doc in documents)
+
+
+def test_load_documents_root_level_document(tmp_path: Path) -> None:
+    root_dir = tmp_path / "root"
+    root_dir.mkdir()
+    (root_dir / "document.txt").write_text("root content\n", encoding="utf-8")
+
+    documents = load_documents(root_dir)
+
+    assert len(documents) == 1
+    assert documents[0].filename == "document.txt"
+    assert documents[0].source == "document.txt"
+    assert documents[0].text == "root content\n"
+
+
+def test_load_documents_one_level_subdirectory(tmp_path: Path) -> None:
+    root_dir = tmp_path / "root"
+    docs_dir = root_dir / "docs"
+    docs_dir.mkdir(parents=True)
+    (docs_dir / "document.txt").write_text("nested content\n", encoding="utf-8")
+
+    documents = load_documents(root_dir)
+
+    assert len(documents) == 1
+    assert documents[0].filename == "document.txt"
+    assert documents[0].source == "docs/document.txt"
+
+
+def test_load_documents_multiple_nested_levels(tmp_path: Path) -> None:
+    root_dir = tmp_path / "root"
+    nested_dir = root_dir / "docs" / "java" / "oop"
+    nested_dir.mkdir(parents=True)
+    file_path = nested_dir / "inheritance.txt"
+    file_path.write_text("class Inheritance {}\n", encoding="utf-8")
+
+    documents = load_documents(root_dir)
+
+    assert len(documents) == 1
+    assert documents[0].filename == "inheritance.txt"
+    assert documents[0].source == "docs/java/oop/inheritance.txt"
+
+
+def test_load_documents_unsupported_extensions(tmp_path: Path) -> None:
+    root_dir = tmp_path / "root"
+    root_dir.mkdir()
+    (root_dir / "valid.txt").write_text("valid txt\n", encoding="utf-8")
+    (root_dir / "valid.md").write_text("valid md\n", encoding="utf-8")
+    (root_dir / "image.png").write_bytes(b"\x89PNG\r\n\x1a\n")
+    (root_dir / "random.xyz").write_text("random\n", encoding="utf-8")
+
+    documents = load_documents(root_dir)
+
+    assert [doc.filename for doc in documents] == ["valid.md", "valid.txt"]
+    assert [doc.source for doc in documents] == ["valid.md", "valid.txt"]
+
+
+def test_load_documents_mixed_root_and_nested_documents(tmp_path: Path) -> None:
+    root_dir = tmp_path / "root"
+    root_dir.mkdir()
+    (root_dir / "a.txt").write_text("a\n", encoding="utf-8")
+    (root_dir / "docs" / "java").mkdir(parents=True)
+    (root_dir / "docs" / "b.txt").write_text("b\n", encoding="utf-8")
+    (root_dir / "docs" / "java" / "c.txt").write_text("c\n", encoding="utf-8")
+    (root_dir / "notes").mkdir(parents=True)
+    (root_dir / "notes" / "d.md").write_text("d\n", encoding="utf-8")
+
+    documents = load_documents(root_dir)
+
+    sources = [doc.source for doc in documents]
+    assert sources == ["a.txt", "docs/b.txt", "docs/java/c.txt", "notes/d.md"]
+
+
+def test_load_documents_deterministic_ordering(tmp_path: Path) -> None:
+    root_dir = tmp_path / "root"
+    root_dir.mkdir()
+    (root_dir / "z_root.txt").write_text("z\n", encoding="utf-8")
+    (root_dir / "b_dir").mkdir()
+    (root_dir / "b_dir" / "a_file.txt").write_text("ba\n", encoding="utf-8")
+    (root_dir / "a_dir" / "sub_dir").mkdir(parents=True)
+    (root_dir / "a_dir" / "sub_dir" / "x_file.txt").write_text("ax\n", encoding="utf-8")
+
+    expected_sources = [
+        "a_dir/sub_dir/x_file.txt",
+        "b_dir/a_file.txt",
+        "z_root.txt",
+    ]
+
+    for _ in range(10):
+        documents = load_documents(root_dir)
+        assert [doc.source for doc in documents] == expected_sources
+
+
+def test_load_documents_empty_nested_directories(tmp_path: Path) -> None:
+    root_dir = tmp_path / "root"
+    (root_dir / "empty1" / "empty2").mkdir(parents=True)
+
+    documents = load_documents(root_dir)
+
+    assert documents == []
+
+
+def test_load_documents_unsupported_files_in_nested_directories(tmp_path: Path) -> None:
+    root_dir = tmp_path / "root"
+    docs_dir = root_dir / "docs"
+    docs_dir.mkdir(parents=True)
+    (docs_dir / "image.png").write_bytes(b"png data")
+    (docs_dir / "data.xyz").write_text("xyz data\n", encoding="utf-8")
+    (docs_dir / "valid.txt").write_text("valid content\n", encoding="utf-8")
+
+    documents = load_documents(root_dir)
+
+    assert len(documents) == 1
+    assert documents[0].filename == "valid.txt"
+    assert documents[0].source == "docs/valid.txt"
+