Docs/Core: Low-Resource Setups, SkyPilot Option, and No-Recompute (#45)

* docs: add SkyPilot template and instructions for running embeddings/index build on cloud GPU

* docs: add low-resource note in README; point to config guide; suggest OpenAI embeddings, SkyPilot remote build, and --no-recompute

* docs: consolidate low-resource guidance into config guide; README points to it

* cli: add --no-recompute and --no-recompute-embeddings flags; docs: clarify HNSW requires --no-compact when disabling recompute

* docs: dedupe recomputation guidance; keep single Low-resource setups section

* sky: expand leann-build.yaml with configurable params and flags (backend, recompute, compact, embedding options)

* hnsw: auto-disable compact when --no-recompute is used; docs: expand SkyPilot with -e overrides and copy-back example

* docs+sky: simplify SkyPilot flow (auto-build on launch, rsync copy-back); clarify HNSW auto non-compact when no-recompute

* feat: auto compact for hnsw when recompute

* reader: non-destructive portability (relative hints + fallback); fix comments; sky: refine yaml

* cli: unify flags to --recompute/--no-recompute for build/search/ask; docs: update references

* chore: remove

* hnsw: move pruned/no-recompute assertion into backend; api: drop global assertion; docs: will adjust after benchmarking

* cli: use argparse.BooleanOptionalAction for paired flags (--recompute/--compact) across build/search/ask

* docs: a real example on recompute

* benchmarks: fix and extend HNSW+DiskANN recompute vs no-recompute; docs: add fresh numbers and DiskANN notes

* benchmarks: unify HNSW & DiskANN into one clean script; isolate groups, fixed ports, warm-up, param complexity

* docs: diskann recompute

* core: auto-cleanup for LeannSearcher/LeannChat (__enter__/__exit__/__del__); ensure server terminate/kill robustness; benchmarks: use searcher.cleanup(); docs: suggest uv run

* fix: hang on warnings

* docs: boolean flags

* docs: leann help

packages/leann-backend-diskann/leann_backend_diskann/diskann_backend.py

@@ -441,9 +441,14 @@ class DiskannSearcher(BaseSearcher):
         else:  # "global"
             use_global_pruning = True
 
-        # Perform search with suppressed C++ output based on log level
-        use_deferred_fetch = kwargs.get("USE_DEFERRED_FETCH", True)
-        recompute_neighors = False
+        # Strategy:
+        # - Traversal always uses PQ distances
+        # - If recompute_embeddings=True, do a single final rerank via deferred fetch
+        #   (fetch embeddings for the final candidate set only)
+        # - Do not recompute neighbor distances along the path
+        use_deferred_fetch = True if recompute_embeddings else False
+        recompute_neighors = False  # Expected typo. For backward compatibility.
+
         with suppress_cpp_output_if_needed():
             labels, distances = self._index.batch_search(
                 query,

packages/leann-backend-hnsw/leann_backend_hnsw/hnsw_backend.py

@@ -54,12 +54,13 @@ class HNSWBuilder(LeannBackendBuilderInterface):
         self.efConstruction = self.build_params.setdefault("efConstruction", 200)
         self.distance_metric = self.build_params.setdefault("distance_metric", "mips")
         self.dimensions = self.build_params.get("dimensions")
-        if not self.is_recompute:
-            if self.is_compact:
-                # TODO: support this case @andy
-                raise ValueError(
-                    "is_recompute is False, but is_compact is True. This is not compatible now. change is compact to False and you can use the original HNSW index."
-                )
+        if not self.is_recompute and self.is_compact:
+            # Auto-correct: non-recompute requires non-compact storage for HNSW
+            logger.warning(
+                "is_recompute=False requires non-compact HNSW. Forcing is_compact=False."
+            )
+            self.is_compact = False
+            self.build_params["is_compact"] = False
 
     def build(self, data: np.ndarray, ids: list[str], index_path: str, **kwargs):
         from . import faiss  # type: ignore
@@ -184,9 +185,11 @@ class HNSWSearcher(BaseSearcher):
         """
         from . import faiss  # type: ignore
 
-        if not recompute_embeddings:
-            if self.is_pruned:
-                raise RuntimeError("Recompute is required for pruned index.")
+        if not recompute_embeddings and self.is_pruned:
+            raise RuntimeError(
+                "Recompute is required for pruned/compact HNSW index. "
+                "Re-run search with --recompute, or rebuild with --no-recompute and --no-compact."
+            )
         if recompute_embeddings:
             if zmq_port is None:
                 raise ValueError("zmq_port must be provided if recompute_embeddings is True")

packages/leann-core/src/leann/api.py

@@ -204,6 +204,18 @@ class LeannBuilder:
         **backend_kwargs,
     ):
         self.backend_name = backend_name
+        # Normalize incompatible combinations early (for consistent metadata)
+        if backend_name == "hnsw":
+            is_recompute = backend_kwargs.get("is_recompute", True)
+            is_compact = backend_kwargs.get("is_compact", True)
+            if is_recompute is False and is_compact is True:
+                warnings.warn(
+                    "HNSW with is_recompute=False requires non-compact storage. Forcing is_compact=False.",
+                    UserWarning,
+                    stacklevel=2,
+                )
+                backend_kwargs["is_compact"] = False
+
         backend_factory: Optional[LeannBackendFactoryInterface] = BACKEND_REGISTRY.get(backend_name)
         if backend_factory is None:
             raise ValueError(f"Backend '{backend_name}' not found or not registered.")
@@ -523,6 +535,7 @@ class LeannSearcher:
         self.embedding_model = self.meta_data["embedding_model"]
         # Support both old and new format
         self.embedding_mode = self.meta_data.get("embedding_mode", "sentence-transformers")
+        # Delegate portability handling to PassageManager
         self.passage_manager = PassageManager(
             self.meta_data.get("passage_sources", []), metadata_file_path=self.meta_path_str
         )
@@ -652,6 +665,23 @@ class LeannSearcher:
         if hasattr(self.backend_impl, "embedding_server_manager"):
             self.backend_impl.embedding_server_manager.stop_server()
 
+    # Enable automatic cleanup patterns
+    def __enter__(self):
+        return self
+
+    def __exit__(self, exc_type, exc, tb):
+        try:
+            self.cleanup()
+        except Exception:
+            pass
+
+    def __del__(self):
+        try:
+            self.cleanup()
+        except Exception:
+            # Avoid noisy errors during interpreter shutdown
+            pass
+
 
 class LeannChat:
     def __init__(
@@ -730,3 +760,19 @@ class LeannChat:
         """
         if hasattr(self.searcher, "cleanup"):
             self.searcher.cleanup()
+
+    # Enable automatic cleanup patterns
+    def __enter__(self):
+        return self
+
+    def __exit__(self, exc_type, exc, tb):
+        try:
+            self.cleanup()
+        except Exception:
+            pass
+
+    def __del__(self):
+        try:
+            self.cleanup()
+        except Exception:
+            pass

packages/leann-core/src/leann/chat.py

@@ -422,7 +422,6 @@ class LLMInterface(ABC):
                 top_k=10,
                 complexity=64,
                 beam_width=8,
-                USE_DEFERRED_FETCH=True,
                 skip_search_reorder=True,
                 recompute_beighbor_embeddings=True,
                 dedup_node_dis=True,
@@ -434,7 +433,6 @@ class LLMInterface(ABC):
         Supported kwargs:
             - complexity (int): Search complexity parameter (default: 32)
             - beam_width (int): Beam width for search (default: 4)
-            - USE_DEFERRED_FETCH (bool): Enable deferred fetch mode (default: False)
             - skip_search_reorder (bool): Skip search reorder step (default: False)
             - recompute_beighbor_embeddings (bool): Enable ZMQ embedding server for neighbor recomputation (default: False)
             - dedup_node_dis (bool): Deduplicate nodes by distance (default: False)

packages/leann-core/src/leann/cli.py

@@ -72,7 +72,7 @@ class LeannCLI:
     def create_parser(self) -> argparse.ArgumentParser:
         parser = argparse.ArgumentParser(
             prog="leann",
-            description="LEANN - Local Enhanced AI Navigation",
+            description="The smallest vector index in the world. RAG Everything with LEANN!",
             formatter_class=argparse.RawDescriptionHelpFormatter,
             epilog="""
 Examples:
@@ -102,9 +102,18 @@ Examples:
             help="Documents directories and/or files (default: current directory)",
         )
         build_parser.add_argument(
-            "--backend", type=str, default="hnsw", choices=["hnsw", "diskann"]
+            "--backend",
+            type=str,
+            default="hnsw",
+            choices=["hnsw", "diskann"],
+            help="Backend to use (default: hnsw)",
+        )
+        build_parser.add_argument(
+            "--embedding-model",
+            type=str,
+            default="facebook/contriever",
+            help="Embedding model (default: facebook/contriever)",
         )
-        build_parser.add_argument("--embedding-model", type=str, default="facebook/contriever")
         build_parser.add_argument(
             "--embedding-mode",
             type=str,
@@ -112,12 +121,28 @@ Examples:
             choices=["sentence-transformers", "openai", "mlx", "ollama"],
             help="Embedding backend mode (default: sentence-transformers)",
         )
-        build_parser.add_argument("--force", "-f", action="store_true", help="Force rebuild")
-        build_parser.add_argument("--graph-degree", type=int, default=32)
-        build_parser.add_argument("--complexity", type=int, default=64)
+        build_parser.add_argument(
+            "--force", "-f", action="store_true", help="Force rebuild existing index"
+        )
+        build_parser.add_argument(
+            "--graph-degree", type=int, default=32, help="Graph degree (default: 32)"
+        )
+        build_parser.add_argument(
+            "--complexity", type=int, default=64, help="Build complexity (default: 64)"
+        )
         build_parser.add_argument("--num-threads", type=int, default=1)
-        build_parser.add_argument("--compact", action="store_true", default=True)
-        build_parser.add_argument("--recompute", action="store_true", default=True)
+        build_parser.add_argument(
+            "--compact",
+            action=argparse.BooleanOptionalAction,
+            default=True,
+            help="Use compact storage (default: true). Must be `no-compact` for `no-recompute` build.",
+        )
+        build_parser.add_argument(
+            "--recompute",
+            action=argparse.BooleanOptionalAction,
+            default=True,
+            help="Enable recomputation (default: true)",
+        )
         build_parser.add_argument(
             "--file-types",
             type=str,
@@ -152,20 +177,26 @@ Examples:
         search_parser = subparsers.add_parser("search", help="Search documents")
         search_parser.add_argument("index_name", help="Index name")
         search_parser.add_argument("query", help="Search query")
-        search_parser.add_argument("--top-k", type=int, default=5)
-        search_parser.add_argument("--complexity", type=int, default=64)
+        search_parser.add_argument(
+            "--top-k", type=int, default=5, help="Number of results (default: 5)"
+        )
+        search_parser.add_argument(
+            "--complexity", type=int, default=64, help="Search complexity (default: 64)"
+        )
         search_parser.add_argument("--beam-width", type=int, default=1)
         search_parser.add_argument("--prune-ratio", type=float, default=0.0)
         search_parser.add_argument(
-            "--recompute-embeddings",
-            action="store_true",
+            "--recompute",
+            dest="recompute_embeddings",
+            action=argparse.BooleanOptionalAction,
             default=True,
-            help="Recompute embeddings (default: True)",
+            help="Enable/disable embedding recomputation (default: enabled). Should not do a `no-recompute` search in a `recompute` build.",
         )
         search_parser.add_argument(
             "--pruning-strategy",
             choices=["global", "local", "proportional"],
             default="global",
+            help="Pruning strategy (default: global)",
         )
 
         # Ask command
@@ -176,19 +207,27 @@ Examples:
             type=str,
             default="ollama",
             choices=["simulated", "ollama", "hf", "openai"],
+            help="LLM provider (default: ollama)",
+        )
+        ask_parser.add_argument(
+            "--model", type=str, default="qwen3:8b", help="Model name (default: qwen3:8b)"
         )
-        ask_parser.add_argument("--model", type=str, default="qwen3:8b")
         ask_parser.add_argument("--host", type=str, default="http://localhost:11434")
-        ask_parser.add_argument("--interactive", "-i", action="store_true")
-        ask_parser.add_argument("--top-k", type=int, default=20)
+        ask_parser.add_argument(
+            "--interactive", "-i", action="store_true", help="Interactive chat mode"
+        )
+        ask_parser.add_argument(
+            "--top-k", type=int, default=20, help="Retrieval count (default: 20)"
+        )
         ask_parser.add_argument("--complexity", type=int, default=32)
         ask_parser.add_argument("--beam-width", type=int, default=1)
         ask_parser.add_argument("--prune-ratio", type=float, default=0.0)
         ask_parser.add_argument(
-            "--recompute-embeddings",
-            action="store_true",
+            "--recompute",
+            dest="recompute_embeddings",
+            action=argparse.BooleanOptionalAction,
             default=True,
-            help="Recompute embeddings (default: True)",
+            help="Enable/disable embedding recomputation during ask (default: enabled)",
         )
         ask_parser.add_argument(
             "--pruning-strategy",

packages/leann-core/src/leann/embedding_server_manager.py

@@ -268,8 +268,12 @@ class EmbeddingServerManager:
             f"Terminating server process (PID: {self.server_process.pid}) for backend {self.backend_module_name}..."
         )
 
-        # Use simple termination - our improved server shutdown should handle this properly
-        self.server_process.terminate()
+        # Use simple termination first; if the server installed signal handlers,
+        # it will exit cleanly. Otherwise escalate to kill after a short wait.
+        try:
+            self.server_process.terminate()
+        except Exception:
+            pass
 
         try:
             self.server_process.wait(timeout=5)  # Give more time for graceful shutdown
@@ -278,7 +282,10 @@ class EmbeddingServerManager:
             logger.warning(
                 f"Server process {self.server_process.pid} did not terminate within 5 seconds, force killing..."
             )
-            self.server_process.kill()
+            try:
+                self.server_process.kill()
+            except Exception:
+                pass
             try:
                 self.server_process.wait(timeout=2)
                 logger.info(f"Server process {self.server_process.pid} killed successfully.")