diff --git a/src/genesis/rag/impact_rag.py b/src/genesis/rag/impact_rag.py
index fa10be8..ab14a2d 100644
--- a/src/genesis/rag/impact_rag.py
+++ b/src/genesis/rag/impact_rag.py
@@ -36,12 +36,14 @@ class ImpactRAG:
         chunks = []
         for name, text in sources:
             for piece in _split(text):
-                chunks.append(f"[{name}]\n{piece}")
+                # 跳过空片段，避免产生空向量噪声 chunk
+                if piece.strip():
+                    chunks.append(f"[{name}]\n{piece}")
         embs = self.embedder.embed(chunks)
         self.store.add(scope, chunks, embs)
 
     def index_dir(self, scope: str, root: str) -> int:
-        """D1：索引目录内文本源文件（既有系统源码）。返回索引的片段数。"""
+        """D1：索引目录内文本源文件（既有系统源码）。返回索引的文件数。"""
         root_path = Path(root)
         sources: List[Tuple[str, str]] = []
         if root_path.is_dir():
@@ -50,9 +52,15 @@ class ImpactRAG:
                     try:
                         text = p.read_text(encoding="utf-8", errors="ignore")
                     except Exception:
+                        # 读取异常的文件跳过，不中断整体索引
                         continue
-                    if text.strip():
-                        sources.append((str(p.relative_to(root_path)), text))
+                    # 空内容文件跳过
+                    if not text.strip():
+                        continue
+                    # 含 NUL 字节的疑似二进制文件（误带白名单扩展名）跳过
+                    if "\x00" in text:
+                        continue
+                    sources.append((str(p.relative_to(root_path)), text))
         if sources:
             self.index(scope, sources)
         return len(sources)
diff --git a/tests/test_impact_rag.py b/tests/test_impact_rag.py
index e6deabd..dfab69c 100644
--- a/tests/test_impact_rag.py
+++ b/tests/test_impact_rag.py
@@ -33,3 +33,124 @@ def test_index_dir_reads_text_files(tmp_path):
         assert res and "OrderController" in res[0]
     finally:
         store.close()
+
+
+def test_retrieve_empty_query_returns_empty():
+    # 空 query（仅空白）直接返回空列表，不调用向量检索
+    store = RagStore(":memory:")
+    try:
+        rag = ImpactRAG(store, FakeEmbedder())
+        rag.index("p1", [("a.java", "创建订单")])
+        assert rag.retrieve("p1", "   ", k=3) == []
+    finally:
+        store.close()
+
+
+def test_index_empty_text_source_not_indexed():
+    # 空文本源：_split 回退为空片段，过滤后无 chunk
+    store = RagStore(":memory:")
+    try:
+        rag = ImpactRAG(store, FakeEmbedder())
+        rag.index("p", [("empty.txt", "")])
+        assert rag.retrieve("p", "x", k=3) == []
+    finally:
+        store.close()
+
+
+def test_index_dir_non_dir_root_returns_zero():
+    # 非目录 root：is_dir() 为 False，返回 0
+    store = RagStore(":memory:")
+    try:
+        rag = ImpactRAG(store, FakeEmbedder())
+        assert rag.index_dir("p", "不存在的路径") == 0
+    finally:
+        store.close()
+
+
+def test_index_dir_skips_empty_file(tmp_path):
+    # 空内容 .txt 文件不应被索引
+    (tmp_path / "empty.txt").write_text("", encoding="utf-8")
+    store = RagStore(":memory:")
+    try:
+        rag = ImpactRAG(store, FakeEmbedder())
+        assert rag.index_dir("p", str(tmp_path)) == 0
+    finally:
+        store.close()
+
+
+def test_index_dir_skips_read_error(tmp_path, monkeypatch):
+    # 读取异常的文件被 except 跳过，整体不崩
+    (tmp_path / "a.txt").write_text("创建订单", encoding="utf-8")
+    monkeypatch.setattr(
+        __import__("pathlib").Path,
+        "read_text",
+        lambda *a, **k: (_ for _ in ()).throw(Exception),
+    )
+    store = RagStore(":memory:")
+    try:
+        rag = ImpactRAG(store, FakeEmbedder())
+        assert rag.index_dir("p", str(tmp_path)) == 0
+    finally:
+        store.close()
+
+
+def test_index_dir_uppercase_ext_indexed(tmp_path):
+    # 大写扩展名（.JAVA）应经 .lower() 命中白名单并被索引
+    (tmp_path / "Foo.JAVA").write_text(
+        "public class Foo { 创建订单 }", encoding="utf-8"
+    )
+    store = RagStore(":memory:")
+    try:
+        rag = ImpactRAG(store, FakeEmbedder())
+        n = rag.index_dir("p", str(tmp_path))
+        assert n == 1
+        res = rag.retrieve("p", "创建订单", k=1)
+        assert res and "Foo" in res[0]
+    finally:
+        store.close()
+
+
+def test_index_dir_empty_dir_returns_zero(tmp_path):
+    # 目录内无文本文件（sources 为空）返回 0
+    store = RagStore(":memory:")
+    try:
+        rag = ImpactRAG(store, FakeEmbedder())
+        assert rag.index_dir("p", str(tmp_path)) == 0
+    finally:
+        store.close()
+
+
+def test_index_dir_skips_nul_binary_text(tmp_path):
+    # 含 NUL 字节的 .txt 视为二进制误带扩展名，应跳过
+    (tmp_path / "bad.txt").write_bytes(b"hello\x00world")
+    store = RagStore(":memory:")
+    try:
+        rag = ImpactRAG(store, FakeEmbedder())
+        assert rag.index_dir("p", str(tmp_path)) == 0
+    finally:
+        store.close()
+
+
+def test_index_splits_long_single_paragraph():
+    # 单段落超长：触发 len(buf)+len(p) > size 且 buf 为空分支 -> 整体作为 1 个 chunk
+    store = RagStore(":memory:")
+    try:
+        rag = ImpactRAG(store, FakeEmbedder())
+        rag.index("p", [("long.txt", "丙" * 900)])
+        chunks = rag.retrieve("p", "丙", k=5)
+        assert len(chunks) == 1
+    finally:
+        store.close()
+
+
+def test_index_splits_multiple_paragraphs():
+    # 多段落（含空行）：触发拆行、空白行过滤、and buf 真分支 -> 2 个 chunk
+    store = RagStore(":memory:")
+    try:
+        rag = ImpactRAG(store, FakeEmbedder())
+        text = "甲" * 500 + "\n\n" + "乙" * 500
+        rag.index("p", [("multi.txt", text)])
+        chunks = rag.retrieve("p", "甲", k=5)
+        assert len(chunks) == 2
+    finally:
+        store.close()