diff --git a/.github/workflows/unittest.yml b/.github/workflows/unittest.yml
new file mode 100644
index 00000000..e4100b82
--- /dev/null
+++ b/.github/workflows/unittest.yml
@@ -0,0 +1,55 @@
+name: Tests (reme)
+
+on:
+  push:
+    branches: [main, master, dev, develop, 'dev/**']
+    paths:
+      - 'reme4/**'
+      - 'reme/reme2/**'
+      - 'tests4/**'
+      - 'pyproject.toml'
+      - '.github/workflows/tests4.yml'
+  pull_request:
+    branches: [main, master, dev, develop]
+    paths:
+      - 'reme4/**'
+      - 'reme/reme2/**'
+      - 'tests4/**'
+      - 'pyproject.toml'
+      - '.github/workflows/tests4.yml'
+  workflow_dispatch:
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  unit-tests:
+    name: Unit Tests - py${{ matrix.python-version }}
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        python-version: ["3.10", "3.13"]
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Set up Python ${{ matrix.python-version }}
+        uses: actions/setup-python@v5
+        with:
+          python-version: ${{ matrix.python-version }}
+          cache: 'pip'
+
+      - name: Install dependencies
+        run: |
+          python -m pip install --upgrade pip setuptools wheel
+          pip install -e ".[dev]"
+
+      - name: Run tests4 unit tests
+        run: |
+          pytest tests4/unittest \
+            -v \
+            --tb=long \
+            -s \
+            --log-cli-level=WARNING
diff --git a/reme4/__init__.py b/reme4/__init__.py
index 76b34dcf..8dba02ec 100644
--- a/reme4/__init__.py
+++ b/reme4/__init__.py
@@ -22,3 +22,5 @@ __all__ = [
     "steps",
     "utils",
 ]
+
+__version__ = "0.4.0.0"
diff --git a/reme4/components/service/http_service.py b/reme4/components/service/http_service.py
index 6c7b9272..64806114 100644
--- a/reme4/components/service/http_service.py
+++ b/reme4/components/service/http_service.py
@@ -3,6 +3,7 @@
 import asyncio
 import json
 import os
+import warnings
 from collections.abc import AsyncGenerator
 from contextlib import asynccontextmanager
 from typing import TYPE_CHECKING
@@ -84,4 +85,16 @@ class HttpService(BaseService):
         self.service.post("/health")(lambda: {"status": "healthy"})
 
     def start_service(self, app: "Application") -> None:
+        # uvicorn 0.41 still imports websockets.legacy / WebSocketServerProtocol
+        # on startup; silence those specific lines since we don't use WebSocket.
+        warnings.filterwarnings(
+            "ignore",
+            category=DeprecationWarning,
+            message=r".*websockets\.legacy is deprecated.*",
+        )
+        warnings.filterwarnings(
+            "ignore",
+            category=DeprecationWarning,
+            message=r".*WebSocketServerProtocol is deprecated.*",
+        )
         uvicorn.run(self.service, host=self.host, port=self.port, **self.kwargs)
diff --git a/reme4/config/default.yaml b/reme4/config/default.yaml
new file mode 100644
index 00000000..5eb447cf
--- /dev/null
+++ b/reme4/config/default.yaml
@@ -0,0 +1,12 @@
+service:
+  backend: http
+  host: 127.0.0.1
+  port: 2333
+
+jobs:
+  - name: demo
+    backend: base
+    description: "Echo back the incoming query (smoke test)."
+    steps:
+      - backend: demo_echo
+
diff --git a/reme4/schema/application_config.py b/reme4/schema/application_config.py
index b71e6d21..a6cdf018 100644
--- a/reme4/schema/application_config.py
+++ b/reme4/schema/application_config.py
@@ -29,7 +29,7 @@ class ApplicationConfig(BaseModel):
 
     app_name: str = Field(default=os.getenv("APP_NAME", "ReMe"), description="Application display name")
     working_dir: str = Field(default=".reme", description="Working directory for runtime files")
-    enable_logo: bool = Field(default=False, description="Show ASCII logo on startup")
+    enable_logo: bool = Field(default=True, description="Show ASCII logo on startup")
     language: str = Field(default="", description="Default language for LLM interactions")
     log_to_console: bool = Field(default=True, description="Log to console")
     log_to_file: bool = Field(default=True, description="Log to file")
diff --git a/reme4/steps/__init__.py b/reme4/steps/__init__.py
index 2fde5b11..76f8c3a7 100644
--- a/reme4/steps/__init__.py
+++ b/reme4/steps/__init__.py
@@ -1,7 +1,9 @@
 """steps"""
 
+from . import demo
 from .base_step import BaseStep
 
 __all__ = [
     "BaseStep",
+    "demo",
 ]
diff --git a/reme4/steps/base_step.py b/reme4/steps/base_step.py
index c79d5f5e..7cd45b55 100644
--- a/reme4/steps/base_step.py
+++ b/reme4/steps/base_step.py
@@ -25,6 +25,8 @@ T = TypeVar("T")
 class BaseStep(ABC):
     """Composable unit of an LLM workflow."""
 
+    component_type = ComponentEnum.STEP
+
     def __new__(cls, *args, **kwargs):
         # Snapshot init args so copy() can rebuild an equivalent instance later.
         instance = object.__new__(cls)
diff --git a/reme4/steps/demo/__init__.py b/reme4/steps/demo/__init__.py
new file mode 100644
index 00000000..057484a3
--- /dev/null
+++ b/reme4/steps/demo/__init__.py
@@ -0,0 +1,19 @@
+"""Demo steps for smoke-testing the application stack."""
+
+from ..base_step import BaseStep
+from ...components.component_registry import R
+
+
+@R.register("demo_echo")
+class DemoEchoStep(BaseStep):
+    """Echo back the incoming `query` field into `response.answer`."""
+
+    async def execute(self):
+        assert self.context is not None
+        query = self.context.get("query", "")
+        self.context.response.answer = f"echo: {query}"
+        self.context.response.metadata["step"] = self.name
+        return self.context.response
+
+
+__all__ = ["DemoEchoStep"]
diff --git a/tests4/unittest/test_bm25_index_perf.py b/tests4/unittest/test_bm25_index_perf.py
new file mode 100644
index 00000000..b6ba0f34
--- /dev/null
+++ b/tests4/unittest/test_bm25_index_perf.py
@@ -0,0 +1,337 @@
+"""BM25Index performance tests for add_docs and retrieve."""
+
+import asyncio
+import os
+import random
+import tempfile
+import time
+
+from reme4.components.keyword_index import BM25Index
+from reme4.components.tokenizer import RegexTokenizer
+
+# A small vocab of realistic-looking words for generating random text
+_VOCAB = [
+    "algorithm",
+    "data",
+    "machine",
+    "learning",
+    "model",
+    "network",
+    "neural",
+    "training",
+    "optimization",
+    "gradient",
+    "loss",
+    "function",
+    "parameter",
+    "weight",
+    "bias",
+    "layer",
+    "activation",
+    "relu",
+    "sigmoid",
+    "softmax",
+    "backpropagation",
+    "forward",
+    "pass",
+    "batch",
+    "epoch",
+    "iteration",
+    "convergence",
+    "divergence",
+    "regularization",
+    "dropout",
+    "attention",
+    "transformer",
+    "encoder",
+    "decoder",
+    "embedding",
+    "token",
+    "vector",
+    "matrix",
+    "tensor",
+    "computation",
+    "graph",
+    "node",
+    "edge",
+    "vertex",
+    "path",
+    "search",
+    "retrieval",
+    "index",
+    "query",
+    "document",
+    "corpus",
+    "term",
+    "frequency",
+    "inverse",
+    "score",
+    "rank",
+    "relevance",
+    "precision",
+    "recall",
+    "f1",
+    "metric",
+    "evaluation",
+    "benchmark",
+    "dataset",
+    "sample",
+    "feature",
+    "label",
+    "class",
+    "predict",
+    "classification",
+    "regression",
+    "clustering",
+    "dimension",
+    "reduction",
+    "pca",
+    "tsne",
+    "visualization",
+    "matplotlib",
+    "plot",
+    "chart",
+    "histogram",
+    "scatter",
+    "line",
+    "bar",
+    "database",
+    "sql",
+    "query",
+    "table",
+    "row",
+    "column",
+    "index",
+    "primary",
+    "foreign",
+    "key",
+    "constraint",
+    "schema",
+    "migration",
+    "version",
+    "control",
+    "git",
+    "commit",
+    "branch",
+    "merge",
+    "conflict",
+    "resolution",
+    "review",
+    "approve",
+    "reject",
+    "pull",
+    "request",
+    "issue",
+    "bug",
+    "fix",
+    "feature",
+    "enhancement",
+    "refactor",
+    "test",
+    "deploy",
+    "production",
+    "staging",
+    "development",
+    "environment",
+    "configuration",
+    "setting",
+    "variable",
+    "constant",
+    "global",
+    "local",
+    "scope",
+    "closure",
+    "callback",
+    "promise",
+    "async",
+    "await",
+    "synchronous",
+    "asynchronous",
+    "concurrent",
+    "parallel",
+    "thread",
+    "process",
+    "memory",
+    "cache",
+    "buffer",
+    "queue",
+    "stack",
+    "heap",
+    "pool",
+]
+
+
+class temp_chdir:
+    """Context manager to temporarily chdir into a path and restore on exit."""
+
+    def __init__(self, path):
+        self.path = path
+        self.old = None
+
+    def __enter__(self):
+        self.old = os.getcwd()
+        os.chdir(self.path)
+        return self
+
+    def __exit__(self, *exc):
+        os.chdir(self.old)
+
+
+def _gen_random_text(n_tokens: int) -> str:
+    """Generate random text with approximately n_tokens words."""
+    words = random.choices(_VOCAB, k=n_tokens)
+    return " ".join(words)
+
+
+def _gen_random_query(n_words: int) -> str:
+    """Generate a random query with n_words words."""
+    words = random.choices(_VOCAB, k=n_words)
+    return " ".join(words)
+
+
+async def _make_index() -> BM25Index:
+    """Create and start a BM25Index using cwd as working dir, with non-filtering tokenizer."""
+    index = BM25Index()
+    tokenizer = RegexTokenizer(filter_stopwords=False)
+    index.tokenizer = tokenizer
+    index._owned.append(tokenizer)  # pylint: disable=protected-access
+    await index.start()
+    return index
+
+
+async def _setup_index_for_retrieve(n_docs: int = 100, doc_tokens: int = 1000) -> BM25Index:
+    """Build an index with n_docs medium-sized docs in cwd."""
+    index = await _make_index()
+    docs = {f"doc_{i}": _gen_random_text(doc_tokens) for i in range(n_docs)}
+    await index.add_docs(docs)
+    return index
+
+
+def test_add_docs_small():
+    """Add 100 small docs (~100 tokens each)."""
+
+    async def run():
+        docs = {f"doc_{i}": _gen_random_text(100) for i in range(100)}
+        with tempfile.TemporaryDirectory() as tmp, temp_chdir(tmp):
+            index = await _make_index()
+            t0 = time.perf_counter()
+            await index.add_docs(docs)
+            elapsed = time.perf_counter() - t0
+            print(f"  add_docs (100 docs x ~100 tokens): {elapsed:.4f}s")
+            await index.close()
+
+    asyncio.run(run())
+
+
+def test_add_docs_medium():
+    """Add 100 medium docs (~1000 tokens each)."""
+
+    async def run():
+        docs = {f"doc_{i}": _gen_random_text(1000) for i in range(100)}
+        with tempfile.TemporaryDirectory() as tmp, temp_chdir(tmp):
+            index = await _make_index()
+            t0 = time.perf_counter()
+            await index.add_docs(docs)
+            elapsed = time.perf_counter() - t0
+            print(f"  add_docs (100 docs x ~1000 tokens): {elapsed:.4f}s")
+            await index.close()
+
+    asyncio.run(run())
+
+
+def test_add_docs_large():
+    """Add 100 large docs (~10000 tokens each)."""
+
+    async def run():
+        docs = {f"doc_{i}": _gen_random_text(10000) for i in range(100)}
+        with tempfile.TemporaryDirectory() as tmp, temp_chdir(tmp):
+            index = await _make_index()
+            t0 = time.perf_counter()
+            await index.add_docs(docs)
+            elapsed = time.perf_counter() - t0
+            print(f"  add_docs (100 docs x ~10000 tokens): {elapsed:.4f}s")
+            await index.close()
+
+    asyncio.run(run())
+
+
+def test_retrieve_short_query():
+    """Retrieve with 1-word query."""
+
+    async def run():
+        with tempfile.TemporaryDirectory() as tmp, temp_chdir(tmp):
+            index = await _setup_index_for_retrieve()
+            query = _gen_random_query(1)
+            t0 = time.perf_counter()
+            await index.retrieve(query, limit=10)
+            elapsed = time.perf_counter() - t0
+            print(f"  retrieve (1-word query, 100 docs): {elapsed:.6f}s")
+            await index.close()
+
+    asyncio.run(run())
+
+
+def test_retrieve_medium_query():
+    """Retrieve with 5-word query."""
+
+    async def run():
+        with tempfile.TemporaryDirectory() as tmp, temp_chdir(tmp):
+            index = await _setup_index_for_retrieve()
+            query = _gen_random_query(5)
+            t0 = time.perf_counter()
+            await index.retrieve(query, limit=10)
+            elapsed = time.perf_counter() - t0
+            print(f"  retrieve (5-word query, 100 docs): {elapsed:.6f}s")
+            await index.close()
+
+    asyncio.run(run())
+
+
+def test_retrieve_long_query():
+    """Retrieve with 20-word query."""
+
+    async def run():
+        with tempfile.TemporaryDirectory() as tmp, temp_chdir(tmp):
+            index = await _setup_index_for_retrieve()
+            query = _gen_random_query(20)
+            t0 = time.perf_counter()
+            await index.retrieve(query, limit=10)
+            elapsed = time.perf_counter() - t0
+            print(f"  retrieve (20-word query, 100 docs): {elapsed:.6f}s")
+            await index.close()
+
+    asyncio.run(run())
+
+
+def test_retrieve_very_long_query():
+    """Retrieve with 100-word query."""
+
+    async def run():
+        with tempfile.TemporaryDirectory() as tmp, temp_chdir(tmp):
+            index = await _setup_index_for_retrieve()
+            query = _gen_random_query(100)
+            t0 = time.perf_counter()
+            await index.retrieve(query, limit=10)
+            elapsed = time.perf_counter() - t0
+            print(f"  retrieve (100-word query, 100 docs): {elapsed:.6f}s")
+            await index.close()
+
+    asyncio.run(run())
+
+
+if __name__ == "__main__":
+    random.seed(42)
+    print("=== BM25Index Performance Tests ===\n")
+
+    print("[add_docs]")
+    test_add_docs_small()
+    test_add_docs_medium()
+    test_add_docs_large()
+
+    print("\n[retrieve]")
+    test_retrieve_short_query()
+    test_retrieve_medium_query()
+    test_retrieve_long_query()
+    test_retrieve_very_long_query()
+
+    print("\nDone.")
diff --git a/tests4/unittest/test_bm25_lite.py b/tests4/unittest/test_bm25_lite.py
new file mode 100644
index 00000000..75865797
--- /dev/null
+++ b/tests4/unittest/test_bm25_lite.py
@@ -0,0 +1,586 @@
+"""Tests for BM25Index search engine."""
+
+# pylint: disable=protected-access
+
+import asyncio
+import os
+import tempfile
+import warnings
+
+from reme4.components.keyword_index import BM25Index
+from reme4.components.tokenizer import RegexTokenizer
+
+# Filter jieba/pkg_resources deprecation warnings
+warnings.filterwarnings("ignore", category=DeprecationWarning, module="jieba")
+warnings.filterwarnings("ignore", category=DeprecationWarning, module="pkg_resources")
+
+
+class temp_chdir:
+    """Context manager to temporarily chdir into a path and restore on exit."""
+
+    def __init__(self, path):
+        self.path = path
+        self.old = None
+
+    def __enter__(self):
+        self.old = os.getcwd()
+        os.chdir(self.path)
+        return self
+
+    def __exit__(self, *exc):
+        os.chdir(self.old)
+
+
+async def create_bm25(k1: float = 1.5, b: float = 0.75) -> BM25Index:
+    """Create and start a BM25Index in cwd with a non-filtering tokenizer.
+
+    The non-filtering tokenizer keeps short test texts (e.g. "hello world") visible,
+    since several common test words ("hello", "我", "的") are in the default stopwords.
+    """
+    bm25 = BM25Index(k1=k1, b=b)
+    # Replace the unresolved Dependency placeholder with a real tokenizer instance.
+    tokenizer = RegexTokenizer(filter_stopwords=False)
+    bm25.tokenizer = tokenizer
+    bm25._owned.append(tokenizer)
+    await bm25.start()
+    return bm25
+
+
+def test_basic_init():
+    """Test BM25Index initialization."""
+
+    async def run():
+        with tempfile.TemporaryDirectory() as tmpdir, temp_chdir(tmpdir):
+            bm25 = BM25Index()
+            assert bm25.k1 == 1.5
+            assert bm25.b == 0.75
+            assert bm25.vocab == {}
+            assert bm25.inverted_index == {}
+            assert bm25.doc_meta == {}
+            assert bm25.n_docs == 0
+            assert bm25.avg_len == 0.0
+            print("✓ test_basic_init passed")
+
+    asyncio.run(run())
+
+
+def test_start_with_tokenizer():
+    """Test BM25Index starts and initializes tokenizer."""
+
+    async def run():
+        with tempfile.TemporaryDirectory() as tmpdir, temp_chdir(tmpdir):
+            bm25 = await create_bm25()
+            assert bm25.tokenizer is not None
+            assert bm25.is_started
+
+            await bm25.close()
+            assert not bm25.is_started
+            print("✓ test_start_with_tokenizer passed")
+
+    asyncio.run(run())
+
+
+def test_add_single_doc():
+    """Test adding a single document."""
+
+    async def run():
+        with tempfile.TemporaryDirectory() as tmpdir, temp_chdir(tmpdir):
+            bm25 = await create_bm25()
+
+            await bm25.add_docs({"doc1": "hello world"})
+
+            assert bm25.n_docs == 1
+            assert bm25.total_len > 0
+            assert "doc1" in bm25.doc_meta
+
+            await bm25.close()
+            print("✓ test_add_single_doc passed")
+
+    asyncio.run(run())
+
+
+def test_add_multiple_docs():
+    """Test adding multiple documents."""
+
+    async def run():
+        with tempfile.TemporaryDirectory() as tmpdir, temp_chdir(tmpdir):
+            bm25 = await create_bm25()
+
+            docs = {
+                "doc1": "hello world",
+                "doc2": "hello python",
+                "doc3": "world python",
+            }
+            await bm25.add_docs(docs)
+
+            assert bm25.n_docs == 3
+            assert len(bm25.vocab) > 0
+            assert len(bm25.inverted_index) > 0
+
+            await bm25.close()
+            print("✓ test_add_multiple_docs passed")
+
+    asyncio.run(run())
+
+
+def test_retrieve_basic():
+    """Test basic retrieval functionality."""
+
+    async def run():
+        with tempfile.TemporaryDirectory() as tmpdir, temp_chdir(tmpdir):
+            bm25 = await create_bm25()
+
+            docs = {
+                "doc1": "python programming language",
+                "doc2": "java programming language",
+                "doc3": "python data analysis",
+            }
+            await bm25.add_docs(docs)
+
+            results = await bm25.retrieve("python", limit=3)
+            assert len(results) <= 3
+            assert "doc1" in results or "doc3" in results
+
+            await bm25.close()
+            print("✓ test_retrieve_basic passed")
+
+    asyncio.run(run())
+
+
+def test_retrieve_with_limit():
+    """Test retrieval with result limit."""
+
+    async def run():
+        with tempfile.TemporaryDirectory() as tmpdir, temp_chdir(tmpdir):
+            bm25 = await create_bm25()
+
+            docs = {f"doc{i}": f"python programming {i}" for i in range(10)}
+            await bm25.add_docs(docs)
+
+            results = await bm25.retrieve("python", limit=3)
+            assert len(results) == 3
+
+            results = await bm25.retrieve("python", limit=5)
+            assert len(results) == 5
+
+            await bm25.close()
+            print("✓ test_retrieve_with_limit passed")
+
+    asyncio.run(run())
+
+
+def test_retrieve_empty_query():
+    """Test retrieval with empty or unknown query."""
+
+    async def run():
+        with tempfile.TemporaryDirectory() as tmpdir, temp_chdir(tmpdir):
+            bm25 = await create_bm25()
+
+            docs = {"doc1": "hello world"}
+            await bm25.add_docs(docs)
+
+            results = await bm25.retrieve("", limit=3)
+            assert results == {}
+
+            results = await bm25.retrieve("unknownxyz", limit=3)
+            assert results == {}
+
+            await bm25.close()
+            print("✓ test_retrieve_empty_query passed")
+
+    asyncio.run(run())
+
+
+def test_retrieve_empty_index():
+    """Test retrieval from empty index."""
+
+    async def run():
+        with tempfile.TemporaryDirectory() as tmpdir, temp_chdir(tmpdir):
+            bm25 = await create_bm25()
+
+            results = await bm25.retrieve("python", limit=3)
+            assert results == {}
+
+            await bm25.close()
+            print("✓ test_retrieve_empty_index passed")
+
+    asyncio.run(run())
+
+
+def test_update_doc():
+    """Test updating an existing document."""
+
+    async def run():
+        with tempfile.TemporaryDirectory() as tmpdir, temp_chdir(tmpdir):
+            bm25 = await create_bm25()
+
+            await bm25.add_docs({"doc1": "hello world python"})
+            old_len = bm25.total_len
+
+            await bm25.add_docs({"doc1": "java"})
+            assert bm25.n_docs == 1
+            assert bm25.total_len != old_len
+
+            results = await bm25.retrieve("java", limit=1)
+            assert "doc1" in results
+
+            await bm25.close()
+            print("✓ test_update_doc passed")
+
+    asyncio.run(run())
+
+
+def test_remove_doc():
+    """Test removing a document."""
+
+    async def run():
+        with tempfile.TemporaryDirectory() as tmpdir, temp_chdir(tmpdir):
+            bm25 = await create_bm25()
+
+            docs = {
+                "doc1": "hello world",
+                "doc2": "hello python",
+            }
+            await bm25.add_docs(docs)
+            assert bm25.n_docs == 2
+
+            bm25._remove_doc("doc1")
+            assert bm25.n_docs == 1
+            assert "doc1" not in bm25.doc_meta
+
+            results = await bm25.retrieve("hello", limit=2)
+            assert "doc1" not in results
+            assert "doc2" in results
+
+            await bm25.close()
+            print("✓ test_remove_doc passed")
+
+    asyncio.run(run())
+
+
+def test_remove_nonexistent_doc():
+    """Test removing a nonexistent document (should be no-op)."""
+
+    async def run():
+        with tempfile.TemporaryDirectory() as tmpdir, temp_chdir(tmpdir):
+            bm25 = await create_bm25()
+
+            await bm25.add_docs({"doc1": "hello world"})
+            bm25._remove_doc("nonexistent")
+            assert bm25.n_docs == 1
+
+            await bm25.close()
+            print("✓ test_remove_nonexistent_doc passed")
+
+    asyncio.run(run())
+
+
+def test_clear():
+    """Test clearing the index."""
+
+    async def run():
+        with tempfile.TemporaryDirectory() as tmpdir, temp_chdir(tmpdir):
+            bm25 = await create_bm25()
+
+            await bm25.add_docs(
+                {
+                    "doc1": "hello world",
+                    "doc2": "hello python",
+                },
+            )
+            assert bm25.n_docs == 2
+
+            await bm25.clear()
+            assert bm25.n_docs == 0
+            assert bm25.vocab == {}
+            assert bm25.inverted_index == {}
+            assert bm25.doc_meta == {}
+            assert bm25.total_len == 0
+            assert bm25._idf_cache == {}
+
+            await bm25.close()
+            print("✓ test_clear passed")
+
+    asyncio.run(run())
+
+
+def test_optimize_index():
+    """Test optimize_index functionality to compact vocab."""
+
+    async def run():
+        with tempfile.TemporaryDirectory() as tmpdir, temp_chdir(tmpdir):
+            bm25 = await create_bm25()
+
+            await bm25.add_docs({"doc1": "hello world"})
+            bm25._remove_doc("doc1")
+
+            assert bm25.n_docs == 0
+            assert len(bm25.vocab) > 0
+
+            await bm25.optimize_index()
+            assert bm25.vocab == {}
+            assert bm25.inverted_index == {}
+
+            await bm25.close()
+            print("✓ test_optimize_index passed")
+
+    asyncio.run(run())
+
+
+def test_optimize_index_with_docs():
+    """Test optimize_index with remaining documents."""
+
+    async def run():
+        with tempfile.TemporaryDirectory() as tmpdir, temp_chdir(tmpdir):
+            bm25 = await create_bm25()
+
+            await bm25.add_docs(
+                {
+                    "doc1": "hello world",
+                    "doc2": "hello python",
+                },
+            )
+
+            old_vocab = bm25.vocab.copy()
+            bm25._remove_doc("doc1")
+
+            await bm25.optimize_index()
+
+            assert bm25.n_docs == 1
+            assert "doc2" in bm25.doc_meta
+            assert len(bm25.vocab) < len(old_vocab)
+
+            results = await bm25.retrieve("hello", limit=1)
+            assert "doc2" in results
+
+            await bm25.close()
+            print("✓ test_optimize_index_with_docs passed")
+
+    asyncio.run(run())
+
+
+def test_persistence():
+    """Test dump and load persistence."""
+
+    async def run():
+        with tempfile.TemporaryDirectory() as tmpdir, temp_chdir(tmpdir):
+            bm25 = await create_bm25()
+            docs = {
+                "doc1": "hello world",
+                "doc2": "hello python",
+                "doc3": "programming language",
+            }
+            await bm25.add_docs(docs)
+
+            old_vocab = bm25.vocab.copy()
+            old_doc_meta = {k: dict(v) for k, v in bm25.doc_meta.items()}
+
+            await bm25.dump()
+            await bm25.close()
+
+            bm25_new = await create_bm25()
+
+            assert bm25_new.vocab == old_vocab
+            assert bm25_new.n_docs == 3
+            for doc_id in old_doc_meta:
+                assert doc_id in bm25_new.doc_meta
+
+            results = await bm25_new.retrieve("hello", limit=2)
+            assert "doc1" in results or "doc2" in results
+
+            await bm25_new.close()
+            print("✓ test_persistence passed")
+
+    asyncio.run(run())
+
+
+def test_custom_params():
+    """Test custom k1 and b parameters."""
+
+    async def run():
+        with tempfile.TemporaryDirectory() as tmpdir, temp_chdir(tmpdir):
+            bm25 = await create_bm25(k1=2.0, b=0.5)
+
+            assert bm25.k1 == 2.0
+            assert bm25.b == 0.5
+
+            await bm25.add_docs({"doc1": "test document"})
+            results = await bm25.retrieve("test", limit=1)
+            assert "doc1" in results
+
+            await bm25.close()
+            print("✓ test_custom_params passed")
+
+    asyncio.run(run())
+
+
+def test_chinese_text():
+    """Test with Chinese text."""
+
+    async def run():
+        with tempfile.TemporaryDirectory() as tmpdir, temp_chdir(tmpdir):
+            bm25 = await create_bm25()
+
+            docs = {
+                "doc1": "我爱北京天安门",
+                "doc2": "北京是中国的首都",
+                "doc3": "上海的天气很好",
+            }
+            await bm25.add_docs(docs)
+
+            results = await bm25.retrieve("北", limit=2)
+            assert len(results) <= 2
+            assert "doc1" in results or "doc2" in results
+
+            await bm25.close()
+            print("✓ test_chinese_text passed")
+
+    asyncio.run(run())
+
+
+def test_mixed_chinese_english():
+    """Test with mixed Chinese and English text."""
+
+    async def run():
+        with tempfile.TemporaryDirectory() as tmpdir, temp_chdir(tmpdir):
+            bm25 = await create_bm25()
+
+            docs = {
+                "doc1": "Python 是一种编程语言",
+                "doc2": "Java 编程语言",
+                "doc3": "Python 数据分析",
+            }
+            await bm25.add_docs(docs)
+
+            results = await bm25.retrieve("Python", limit=3)
+            assert len(results) > 0
+
+            results = await bm25.retrieve("编", limit=2)
+            assert len(results) > 0
+
+            await bm25.close()
+            print("✓ test_mixed_chinese_english passed")
+
+    asyncio.run(run())
+
+
+def test_idf_cache():
+    """Test IDF cache functionality."""
+
+    async def run():
+        with tempfile.TemporaryDirectory() as tmpdir, temp_chdir(tmpdir):
+            bm25 = await create_bm25()
+
+            await bm25.add_docs(
+                {
+                    "doc1": "hello world",
+                    "doc2": "hello python",
+                },
+            )
+
+            token = "hello"
+            if token in bm25.vocab:
+                tid = bm25.vocab[token]
+                idf1 = bm25._get_idf(tid)
+                assert tid in bm25._idf_cache
+                idf2 = bm25._get_idf(tid)
+                assert idf1 == idf2
+
+            await bm25.close()
+            print("✓ test_idf_cache passed")
+
+    asyncio.run(run())
+
+
+def test_avg_len():
+    """Test average document length calculation."""
+
+    async def run():
+        with tempfile.TemporaryDirectory() as tmpdir, temp_chdir(tmpdir):
+            bm25 = await create_bm25()
+
+            assert bm25.avg_len == 0.0
+
+            await bm25.add_docs({"doc1": "hello world python"})
+            assert bm25.avg_len > 0
+
+            await bm25.add_docs({"doc2": "test"})
+            new_avg = bm25.avg_len
+            assert new_avg > 0
+
+            await bm25.close()
+            print("✓ test_avg_len passed")
+
+    asyncio.run(run())
+
+
+def test_score_ordering():
+    """Test that results are ordered by score descending."""
+
+    async def run():
+        with tempfile.TemporaryDirectory() as tmpdir, temp_chdir(tmpdir):
+            bm25 = await create_bm25()
+
+            docs = {
+                "doc1": "python python python",
+                "doc2": "python python",
+                "doc3": "python",
+            }
+            await bm25.add_docs(docs)
+
+            results = await bm25.retrieve("python", limit=3)
+            scores = list(results.values())
+
+            for i in range(len(scores) - 1):
+                assert scores[i] >= scores[i + 1]
+
+            await bm25.close()
+            print("✓ test_score_ordering passed")
+
+    asyncio.run(run())
+
+
+def test_empty_doc():
+    """Test adding empty document."""
+
+    async def run():
+        with tempfile.TemporaryDirectory() as tmpdir, temp_chdir(tmpdir):
+            bm25 = await create_bm25()
+
+            await bm25.add_docs({"doc1": ""})
+            assert bm25.n_docs == 0
+
+            await bm25.add_docs({"doc2": "   "})
+            assert bm25.n_docs == 0
+
+            await bm25.close()
+            print("✓ test_empty_doc passed")
+
+    asyncio.run(run())
+
+
+if __name__ == "__main__":
+    print("\n=== BM25Index Tests ===")
+    test_basic_init()
+    test_start_with_tokenizer()
+    test_add_single_doc()
+    test_add_multiple_docs()
+    test_retrieve_basic()
+    test_retrieve_with_limit()
+    test_retrieve_empty_query()
+    test_retrieve_empty_index()
+    test_update_doc()
+    test_remove_doc()
+    test_remove_nonexistent_doc()
+    test_clear()
+    test_optimize_index()
+    test_optimize_index_with_docs()
+    test_persistence()
+    test_custom_params()
+    test_chinese_text()
+    test_mixed_chinese_english()
+    test_idf_cache()
+    test_avg_len()
+    test_score_ordering()
+    test_empty_doc()
+    print("\n所有测试通过!")
diff --git a/tests4/unittest/test_default_file_parser.py b/tests4/unittest/test_default_file_parser.py
new file mode 100644
index 00000000..75f68ba5
--- /dev/null
+++ b/tests4/unittest/test_default_file_parser.py
@@ -0,0 +1,205 @@
+"""Tests for DefaultFileParser."""
+
+import asyncio
+import os
+import tempfile
+
+from reme4.components.file_parser import DefaultFileParser
+
+
+# Add parent path for import
+
+
+def test_parse_empty_file():
+    """Test parsing an empty file."""
+
+    async def run():
+        with tempfile.NamedTemporaryFile(mode="w", delete=False, suffix=".txt") as f:
+            temp_path = f.name
+
+        try:
+            parser = DefaultFileParser()
+            file_node, chunks = await parser.parse(temp_path)
+            assert file_node.path == temp_path
+            assert len(chunks) == 0
+            print("✓ test_parse_empty_file passed")
+        finally:
+            os.unlink(temp_path)
+
+    asyncio.run(run())
+
+
+def test_parse_small_file():
+    """Test parsing a file smaller than chunk size."""
+
+    async def run():
+        content = "Hello World\nThis is a test\nLine 3"
+        with tempfile.NamedTemporaryFile(mode="w", delete=False, suffix=".txt") as f:
+            f.write(content)
+            temp_path = f.name
+
+        try:
+            parser = DefaultFileParser(chunk_byte_size=10000)
+            _, chunks = await parser.parse(temp_path)
+            assert len(chunks) == 1
+            assert chunks[0].start_line == 1
+            assert chunks[0].end_line == 3
+            assert chunks[0].text == content
+            print("✓ test_parse_small_file passed")
+        finally:
+            os.unlink(temp_path)
+
+    asyncio.run(run())
+
+
+def test_parse_multiline_file():
+    """Test parsing a file with multiple lines."""
+
+    async def run():
+        lines = ["Line 1", "Line 2", "Line 3", "Line 4", "Line 5"]
+        content = "\n".join(lines)
+        with tempfile.NamedTemporaryFile(mode="w", delete=False, suffix=".txt") as f:
+            f.write(content)
+            temp_path = f.name
+
+        try:
+            parser = DefaultFileParser(chunk_byte_size=10000)
+            _, chunks = await parser.parse(temp_path)
+            assert len(chunks) == 1
+            assert chunks[0].start_line == 1
+            assert chunks[0].end_line == 5
+            print("✓ test_parse_multiline_file passed")
+        finally:
+            os.unlink(temp_path)
+
+    asyncio.run(run())
+
+
+def test_parse_chunked_file():
+    """Test parsing a file that requires multiple chunks."""
+
+    async def run():
+        # Create content larger than chunk size
+        lines = ["A" * 100 for _ in range(200)]  # ~20200 bytes
+        content = "\n".join(lines)
+        with tempfile.NamedTemporaryFile(mode="w", delete=False, suffix=".txt") as f:
+            f.write(content)
+            temp_path = f.name
+
+        try:
+            parser = DefaultFileParser(chunk_byte_size=5000, overlap_byte_size=100)
+            _, chunks = await parser.parse(temp_path)
+            assert len(chunks) > 1, f"Expected multiple chunks, got {len(chunks)}"
+            # Verify overlap by checking that consecutive chunks share some content
+            print(f"  Created {len(chunks)} chunks")
+            print("✓ test_parse_chunked_file passed")
+        finally:
+            os.unlink(temp_path)
+
+    asyncio.run(run())
+
+
+def test_parse_with_custom_encoding():
+    """Test parsing a file with different encodings."""
+
+    async def run():
+        content = "你好世界\n测试内容"
+        with tempfile.NamedTemporaryFile(mode="w", delete=False, suffix=".txt", encoding="utf-8") as f:
+            f.write(content)
+            temp_path = f.name
+
+        try:
+            parser = DefaultFileParser(encoding="utf-8")
+            _, chunks = await parser.parse(temp_path)
+            assert len(chunks) >= 1
+            assert "你好世界" in chunks[0].text
+            print("✓ test_parse_with_custom_encoding passed")
+        finally:
+            os.unlink(temp_path)
+
+    asyncio.run(run())
+
+
+def test_file_node_properties():
+    """Test FileNode has correct properties."""
+
+    async def run():
+        content = "test content"
+        with tempfile.NamedTemporaryFile(mode="w", delete=False, suffix=".txt") as f:
+            f.write(content)
+            temp_path = f.name
+
+        try:
+            parser = DefaultFileParser()
+            file_node, _ = await parser.parse(temp_path)
+            assert hasattr(file_node, "path")
+            assert hasattr(file_node, "st_mtime")
+            assert file_node.st_mtime > 0
+            print("✓ test_file_node_properties passed")
+        finally:
+            os.unlink(temp_path)
+
+    asyncio.run(run())
+
+
+def test_file_chunk_properties():
+    """Test FileChunk has correct properties."""
+
+    async def run():
+        content = "test content for chunk"
+        with tempfile.NamedTemporaryFile(mode="w", delete=False, suffix=".txt") as f:
+            f.write(content)
+            temp_path = f.name
+
+        try:
+            parser = DefaultFileParser()
+            _, chunks = await parser.parse(temp_path)
+            chunk = chunks[0]
+            assert hasattr(chunk, "path")
+            assert hasattr(chunk, "start_line")
+            assert hasattr(chunk, "end_line")
+            assert hasattr(chunk, "text")
+            assert hasattr(chunk, "id")
+            assert chunk.start_line >= 1
+            assert chunk.end_line >= chunk.start_line
+            print("✓ test_file_chunk_properties passed")
+        finally:
+            os.unlink(temp_path)
+
+    asyncio.run(run())
+
+
+def test_min_chunk_and_overlap_size():
+    """Test that minimum chunk and overlap sizes are enforced."""
+
+    async def run():
+        # These values should be clamped to minimums
+        parser = DefaultFileParser(chunk_byte_size=1, overlap_byte_size=0)
+        assert parser.chunk_byte_size == 100  # minimum
+        assert parser.overlap_byte_size == 4  # minimum
+
+        content = "test"
+        with tempfile.NamedTemporaryFile(mode="w", delete=False, suffix=".txt") as f:
+            f.write(content)
+            temp_path = f.name
+
+        try:
+            _, chunks = await parser.parse(temp_path)
+            assert len(chunks) == 1
+            print("✓ test_min_chunk_and_overlap_size passed")
+        finally:
+            os.unlink(temp_path)
+
+    asyncio.run(run())
+
+
+if __name__ == "__main__":
+    test_parse_empty_file()
+    test_parse_small_file()
+    test_parse_multiline_file()
+    test_parse_chunked_file()
+    test_parse_with_custom_encoding()
+    test_file_node_properties()
+    test_file_chunk_properties()
+    test_min_chunk_and_overlap_size()
+    print("\n所有测试通过!")
diff --git a/tests4/unittest/test_tokenizer.py b/tests4/unittest/test_tokenizer.py
new file mode 100644
index 00000000..5dc99308
--- /dev/null
+++ b/tests4/unittest/test_tokenizer.py
@@ -0,0 +1,169 @@
+"""Tests for Tokenizers."""
+
+import asyncio
+
+from reme4.components.tokenizer import JiebaTokenizer, RegexTokenizer
+
+
+async def compare_tokenizers(texts: list[str], filter_stopwords: bool = False, name: str = ""):
+    """Compare both tokenizers on same input."""
+    jieba = JiebaTokenizer(filter_stopwords=filter_stopwords)
+    regex = RegexTokenizer(filter_stopwords=filter_stopwords)
+
+    await jieba.start()
+    await regex.start()
+
+    jieba_result = jieba.tokenize(texts)
+    regex_result = regex.tokenize(texts)
+
+    print(f"\n--- {name} ---")
+    print(f"输入: {texts}")
+    print(f"Jieba: {jieba_result}")
+    print(f"Regex: {regex_result}")
+
+    await jieba.close()
+    await regex.close()
+
+    return jieba_result, regex_result
+
+
+def test_basic_chinese():
+    """Test basic Chinese text."""
+
+    async def run():
+        jieba_result, regex_result = await compare_tokenizers(
+            ["我爱北京天安门", "今天天气很好"],
+            name="纯中文",
+        )
+
+        assert "北京" in jieba_result[0] or "天安门" in jieba_result[0]
+        assert "我" in regex_result[0]
+        print("✓ test_basic_chinese passed")
+
+    asyncio.run(run())
+
+
+def test_basic_english():
+    """Test basic English text."""
+
+    async def run():
+        _, regex_result = await compare_tokenizers(
+            ["I love Beijing very much"],
+            name="英文",
+        )
+
+        assert "love" in regex_result[0]
+        assert "beijing" in regex_result[0]
+        print("✓ test_basic_english passed")
+
+    asyncio.run(run())
+
+
+def test_mixed_chinese_english():
+    """Test mixed Chinese-English text."""
+
+    async def run():
+        jieba_result, regex_result = await compare_tokenizers(
+            ["我用 Python 学习 machine learning 和 iPhone15 Pro。"],
+            name="中英混合",
+        )
+
+        assert "python" in jieba_result[0]
+        assert "python" in regex_result[0]
+        print("✓ test_mixed_chinese_english passed")
+
+    asyncio.run(run())
+
+
+def test_open_example():
+    """Test the 'open' example."""
+
+    async def run():
+        jieba_result, regex_result = await compare_tokenizers(
+            ["我觉得open很好呀，能分好次吗？"],
+            name="'open' 案例",
+        )
+
+        # open 保持完整
+        assert "open" in jieba_result[0]
+        assert "open" in regex_result[0]
+
+        # Regex 中文按字拆分
+        assert "我" in regex_result[0]
+        assert "很" in regex_result[0]
+
+        print("✓ test_open_example passed")
+
+    asyncio.run(run())
+
+
+def test_with_stopwords():
+    """Test with stopwords filtering."""
+
+    async def run():
+        jieba_result, regex_result = await compare_tokenizers(
+            ["我觉得open很好呀，能分好次吗？"],
+            filter_stopwords=True,
+            name="停用词过滤",
+        )
+
+        # 停用词被过滤
+        assert "吗" not in jieba_result[0]
+        assert "吗" not in regex_result[0]
+        assert "的" not in jieba_result[0]
+
+        print("✓ test_with_stopwords passed")
+
+    asyncio.run(run())
+
+
+def test_multiple_texts():
+    """Test multiple texts at once."""
+
+    async def run():
+        texts = [
+            "我爱北京天安门",
+            "I love Python programming",
+            "今天学习 machine learning",
+        ]
+        jieba_result, regex_result = await compare_tokenizers(texts, name="多个文本")
+
+        assert len(jieba_result) == 3
+        assert len(regex_result) == 3
+        print("✓ test_multiple_texts passed")
+
+    asyncio.run(run())
+
+
+def test_tokenizer_lifecycle():
+    """Test tokenizer start/close lifecycle."""
+
+    async def run():
+        tokenizer = JiebaTokenizer(filter_stopwords=True)
+
+        assert not tokenizer.is_started
+        assert len(tokenizer.stopwords) == 0
+
+        await tokenizer.start()
+        assert tokenizer.is_started
+        assert len(tokenizer.stopwords) > 0
+
+        await tokenizer.close()
+        assert not tokenizer.is_started
+        assert len(tokenizer.stopwords) == 0
+
+        print("✓ test_tokenizer_lifecycle passed")
+
+    asyncio.run(run())
+
+
+if __name__ == "__main__":
+    print("\n=== Tokenizer Tests ===")
+    test_basic_chinese()
+    test_basic_english()
+    test_mixed_chinese_english()
+    test_open_example()
+    test_with_stopwords()
+    test_multiple_texts()
+    test_tokenizer_lifecycle()
+    print("\n所有测试通过!")