275 lines
13 KiB
Python
275 lines
13 KiB
Python
#!/usr/bin/env python3
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"""Local MCP semantic search backed by Qwen3 embedding and reranking."""
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from __future__ import annotations
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import argparse
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import ast
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import hashlib
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import heapq
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import json
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import os
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from pathlib import Path
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import re
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import sqlite3
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import threading
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MODEL = "Qwen/Qwen3-Embedding-0.6B"
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RERANKER_MODEL = "Qwen/Qwen3-Reranker-0.6B"
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EMBEDDING_DIMENSIONS = 1024
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CHUNK_TOKENS = 400
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OVERLAP_TOKENS = 64
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DENSE_CANDIDATES = 50
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LEXICAL_CANDIDATES = 50
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RERANK_CANDIDATES = 20
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FINAL_RESULTS = 20
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RRF_K = 60
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INDEX_VERSION = 2
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RETRIEVAL_INSTRUCTION = "Given a codebase question, retrieve relevant code and documentation that answer the question."
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TEXT_EXTENSIONS = {".c", ".cpp", ".cs", ".go", ".java", ".js", ".json", ".md", ".py", ".ps1", ".rs", ".sh", ".toml", ".ts", ".tsx", ".txt", ".yaml", ".yml"}
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def sections(text: str, path: str):
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lines = text.splitlines(keepends=True)
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boundaries = {0: "<module>", len(lines): "<module>"}
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suffix = Path(path).suffix.lower()
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if suffix == ".py":
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try:
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tree = ast.parse(text)
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except (SyntaxError, ValueError):
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tree = None
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def visit(node, parent):
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symbol = parent
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if isinstance(node, (ast.FunctionDef, ast.AsyncFunctionDef, ast.ClassDef)):
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symbol = f"{parent}.{node.name}" if parent != "<module>" else node.name
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start = min([node.lineno, *(item.lineno for item in node.decorator_list)]) - 1
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boundaries[start] = symbol
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boundaries.setdefault(node.end_lineno, parent)
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for child in ast.iter_child_nodes(node):
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visit(child, symbol)
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if tree is not None:
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visit(tree, "<module>")
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else:
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fence = None
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headings = []
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for number, line in enumerate(lines):
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if suffix == ".md":
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marker = re.match(r"^\s{0,3}(`{3,}|~{3,})", line)
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if marker:
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value = marker[1]
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if fence is None:
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fence = value
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elif value[0] == fence[0] and len(value) >= len(fence):
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fence = None
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continue
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heading = re.match(r"^\s{0,3}(#{1,6})\s+(.+?)\s*#*\s*$", line)
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if heading and fence is None:
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level = len(heading[1])
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headings = [(depth, title) for depth, title in headings if depth < level]
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headings.append((level, heading[2]))
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boundaries[number] = " / ".join(title for _, title in headings)
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elif suffix == ".toml":
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heading = re.match(r"^\s*\[\[?([^\]]+)\]\]?\s*(?:#.*)?$", line)
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if heading:
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boundaries[number] = heading[1]
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elif suffix in {".js", ".ts", ".tsx", ".cs", ".java", ".go", ".rs", ".c", ".cpp", ".ps1", ".sh"}:
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symbol = re.match(
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r"^\s*(?:(?:export|default|public|private|protected|internal|static|abstract|async|sealed|partial|pub)\s+)*"
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r"(?:(?:class|interface|struct|enum|record|function|fn|def)\s+([\w$-]+)"
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r"|func\s+(?:\([^)]*\)\s*)?([\w]+)"
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r"|(?:const|let|var)\s+([\w$]+)\s*=.*=>"
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r"|([\w$-]+)\s*\([^;]*\)\s*\{"
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r"|[\w<>\[\],?]+\s+([\w]+)\s*\([^;]*\)\s*(?:\{|=>|$))", line)
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if symbol:
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name = next(value for value in symbol.groups() if value)
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if name not in {"if", "for", "foreach", "while", "switch", "catch", "using", "lock"}:
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boundaries[number] = name
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positions = sorted(boundaries)
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for start, end in zip(positions, positions[1:]):
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content = "".join(lines[start:end])
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if content.strip():
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yield boundaries[start], content
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def chunks(text: str, path: str, tokenizer):
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for symbol, content in sections(text, path):
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offsets = tokenizer(content, add_special_tokens=False, return_offsets_mapping=True)["offset_mapping"]
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start = 0
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while start < len(offsets):
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end = min(start + CHUNK_TOKENS, len(offsets))
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first = 0 if start == 0 else offsets[start][0]
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while end > start:
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last = len(content) if end == len(offsets) else offsets[end][0]
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value = content[first:last].strip()
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if len(tokenizer(value, add_special_tokens=False)["input_ids"]) <= CHUNK_TOKENS:
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break
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end -= 1
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if value:
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yield symbol, value
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if end == len(offsets):
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break
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start = max(start + 1, end - OVERLAP_TOKENS)
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def document_text(path: str, symbol: str, content: str):
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return f"Path: {path}\nSymbol: {symbol}\n\n{content}"
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def reciprocal_rank_fusion(*rankings):
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scores = {}
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for ranking in rankings:
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for rank, identifier in enumerate(ranking, 1):
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scores[identifier] = scores.get(identifier, 0.0) + 1.0 / (RRF_K + rank)
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return sorted(scores, key=lambda identifier: (-scores[identifier], identifier))
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class Index:
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def __init__(self, root: Path, data: Path):
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self.root = root.resolve()
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self.data = data.resolve()
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self.data.mkdir(parents=True, exist_ok=True)
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identity = json.dumps([os.path.normcase(str(self.root)), MODEL, EMBEDDING_DIMENSIONS,
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INDEX_VERSION, CHUNK_TOKENS, OVERLAP_TOKENS])
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database = hashlib.sha256(identity.encode()).hexdigest() + ".sqlite3"
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self.db = sqlite3.connect(self.data / database, check_same_thread=False, timeout=30)
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self.db.execute("create table if not exists chunks (path text, symbol text, text text, vector blob)")
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self.db.execute("create index if not exists chunks_path on chunks (path)")
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self.db.execute("create virtual table if not exists lexical using fts5(document)")
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self.db.execute("create table if not exists files (path text primary key, digest text)")
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self.db.commit()
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self.lock = threading.RLock()
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self.model = None
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self.reranker_model = None
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def files(self):
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ignored = {".git", ".venv", "generated", "node_modules", ".my-ai-configuration"}
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result = []
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for directory, directories, filenames in os.walk(self.root):
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directories[:] = sorted(name for name in directories if name not in ignored
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and not (Path(directory) / name).is_symlink()
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and (Path(directory) / name).resolve().is_relative_to(self.root)
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and (Path(directory) / name).resolve() != self.data)
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for name in sorted(filenames):
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path = Path(directory) / name
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if path.is_symlink() or path.suffix.lower() not in TEXT_EXTENSIONS or not path.is_file() or path.stat().st_size > 524288:
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continue
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result.append(path)
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if len(result) == 2000:
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return result
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return result
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def encoder(self):
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if self.model is None:
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from sentence_transformers import SentenceTransformer
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self.model = SentenceTransformer(MODEL, truncate_dim=EMBEDDING_DIMENSIONS,
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prompts={"query": f"Instruct: {RETRIEVAL_INSTRUCTION}\nQuery: "})
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return self.model
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def reranker(self):
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if self.reranker_model is None:
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from sentence_transformers import CrossEncoder
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self.reranker_model = CrossEncoder(RERANKER_MODEL, prompts={"query": RETRIEVAL_INSTRUCTION}, default_prompt_name="query")
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return self.reranker_model
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def rerank(self, query: str, rows: list[dict], limit: int):
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candidates = rows[:RERANK_CANDIDATES]
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scores = self.reranker().predict([(query, document_text(item["path"], item["symbol"], item["text"]))
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for item in candidates], batch_size=8)
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for item, score in zip(candidates, scores):
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item["score"] = round(float(score), 6)
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return sorted(candidates, key=lambda item: item["score"], reverse=True)[:min(limit, FINAL_RESULTS)]
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def delete_path(self, path):
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self.db.execute("delete from lexical where rowid in (select rowid from chunks where path = ?)", (path,))
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self.db.execute("delete from chunks where path = ?", (path,))
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def rebuild(self):
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with self.lock:
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self.refresh(force=True)
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return self.db.execute("select count(*) from chunks").fetchone()[0]
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def refresh(self, force=False):
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previous = dict(self.db.execute("select path, digest from files"))
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with self.db:
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for path in self.files():
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relative = path.relative_to(self.root).as_posix()
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content = path.read_bytes()
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digest = hashlib.sha256(content).hexdigest()
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old_digest = previous.pop(relative, None)
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if not force and digest == old_digest:
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continue
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values = list(chunks(content.decode("utf-8", errors="ignore"), relative, self.encoder().tokenizer))
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documents = [document_text(relative, symbol, value) for symbol, value in values]
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vectors = self.encoder().encode(documents, normalize_embeddings=True) if documents else []
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self.delete_path(relative)
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for (symbol, value), document, vector in zip(values, documents, vectors):
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if len(vector) != EMBEDDING_DIMENSIONS:
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raise ValueError("Embedding must have 1024 dimensions")
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cursor = self.db.execute("insert into chunks values (?, ?, ?, ?)",
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(relative, symbol, value, vector.tobytes()))
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self.db.execute("insert into lexical(rowid, document) values (?, ?)", (cursor.lastrowid, document))
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self.db.execute("insert or replace into files values (?, ?)", (relative, digest))
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for relative in previous:
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self.delete_path(relative)
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self.db.execute("delete from files where path = ?", (relative,))
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def search(self, query: str, top_k: int = 5):
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if not query.strip():
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raise ValueError("query must not be empty")
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with self.lock:
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self.refresh()
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if not self.db.execute("select 1 from chunks limit 1").fetchone():
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return []
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import numpy as np
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vector = self.encoder().encode([query], prompt_name="query", normalize_embeddings=True)[0]
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if len(vector) != EMBEDDING_DIMENSIONS:
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raise ValueError("Embedding must have 1024 dimensions")
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scores = ((identifier, float(np.dot(vector, np.frombuffer(blob, dtype=np.float32))))
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for identifier, blob in self.db.execute("select rowid, vector from chunks"))
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dense = [identifier for identifier, _ in heapq.nlargest(DENSE_CANDIDATES, scores, key=lambda item: item[1])]
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terms = list(dict.fromkeys(re.findall(r"[^\W_]+", query)))[:128]
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expression = " OR ".join(f'"{term}"' for term in terms)
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lexical = [row[0] for row in self.db.execute(
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"select rowid from lexical where lexical match ? order by bm25(lexical), rowid limit ?",
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(expression, LEXICAL_CANDIDATES))] if terms else []
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identifiers = reciprocal_rank_fusion(dense, lexical)[:RERANK_CANDIDATES]
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placeholders = ",".join("?" for _ in identifiers)
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rows = {identifier: {"path": path, "symbol": symbol, "text": text}
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for identifier, path, symbol, text in self.db.execute(
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f"select rowid, path, symbol, text from chunks where rowid in ({placeholders})", identifiers)}
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candidates = [rows[identifier] for identifier in identifiers]
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return self.rerank(query, candidates, max(1, min(top_k, FINAL_RESULTS)))
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def main():
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parser = argparse.ArgumentParser()
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parser.add_argument("--root", default=os.getcwd(), type=Path)
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parser.add_argument("--data-dir", required=True, type=Path)
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parser.add_argument("--model-cache", required=True, type=Path)
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args = parser.parse_args()
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args.model_cache.mkdir(parents=True, exist_ok=True)
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os.environ.setdefault("HF_HOME", str(args.model_cache.resolve()))
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from mcp.server.fastmcp import FastMCP
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index = Index(args.root, args.data_dir)
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mcp = FastMCP("my-ai-qwen3-retrieval")
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@mcp.tool()
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def semantic_search(query: str, top_k: int = 5) -> list[dict]:
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"""Search repository concepts, behavior, and implementation patterns first with Qwen3 embedding and reranking. Verify returned passages against current files; use direct reads for known paths."""
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return index.search(query, top_k)
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@mcp.tool()
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def rebuild_index() -> str:
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"""Rebuild the local repository embedding index."""
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return json.dumps({"chunks": index.rebuild()})
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mcp.run()
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if __name__ == "__main__":
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main()
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