Xgrep

xgrep

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Ultra-fast indexed code search engine with MCP server for AI coding tools.

Pre-builds a trigram inverted index, then searches in milliseconds. Designed for repeated searches on large codebases — by humans and AI agents alike.

Features

• Indexed search — trigram inverted index makes repeated searches 2-46x faster than ripgrep
• File discovery — --find mode locates files 2-15x faster than fd
• MCP server — built-in Model Context Protocol server for AI coding tools (Claude Code, Cursor, etc.)
• LLM-optimized output — --format llm produces Markdown with language tags, context lines, and token-aware truncation
• Git-aware — search only changed files (--changed), recent commits (--since 1h), respects .gitignore
• Zero config — install via cargo/npm/pip, then xg "pattern". Index builds automatically on first search
• Hybrid search — serves results from index instantly while rebuilding in the background

Why xgrep?

| | ripgrep | zoekt | xgrep | |---|---------|-------|-------| | Setup | None | Server required | None (cargo/npm/pip) | | First search | Instant | After server start | Auto-builds index | | Repeated search (Linux kernel) | 1,687ms | 170ms (server) | 37ms | | File discovery (next.js, 26K files) | N/A | N/A | 9ms (fd: 191ms) | | Index size | N/A | 155% of source | 8% of source | | AI agent integration | None | None | MCP server built-in | | Memory (search) | 11MB | 288MB | 208MB |

xgrep is not a ripgrep replacement. Use ripgrep for one-off searches. Use xgrep when you search the same codebase repeatedly — the index pays for itself after ~2 searches.

Installation

Choose your package manager:

# Rust (recommended — native binary, no runtime)
cargo install xgrep-search    # Requires Rust 1.85+

# npm (Node.js 18+)
npm install -g xgrep

# pip (Python 3.8+)
pip install xgrep-search

Prebuilt binaries are also available on the Releases page.

Quick Start

xg "pattern"                  # Search (auto-builds index on first run)

Build from source

git clone https://github.com/momokun7/xgrep.git
cd xgrep/rust
cargo build --release
cp target/release/xg ~/.local/bin/

Usage

xg "pattern"                  # Smart-case search (all-lowercase = case-insensitive)
xg "Pattern"                  # Mixed/upper case in pattern = case-sensitive
xg "pattern" -i               # Force case-insensitive
xg "pattern" -s               # Force case-sensitive (disable smart-case)
xg "pattern" /path/to/repo    # Search a specific directory
xg -e "handle_\w+"            # Regex search
xg "pattern" -w               # Match whole words only
xg "pattern" -t rs            # Filter by file type
xg "pattern" -C 3             # Context lines (symmetric)
xg "pattern" -A 2 -B 1        # 2 lines after, 1 line before
xg "pattern" -g "*.rs"        # Include only paths matching glob (repeatable)
xg "pattern" -g "!*_test.rs"  # Exclude paths matching glob (! prefix)
xg "pattern" --format llm     # Markdown output for LLMs
xg "pattern" --changed        # Only git changed files
xg "pattern" --exclude vendor  # Exclude paths containing "vendor"
xg "pattern" --absolute-paths # Show absolute paths
xg "pattern" --no-hints       # Suppress regex pattern hints
xg --find "*.rs"              # Find files by glob pattern
xg --list-types               # Show supported file types
xg status                     # Show index status
xg init                       # Explicitly rebuild index

Search is smart-case by default: an all-lowercase pattern matches case-insensitively, while any uppercase letter makes the search case-sensitive. Use -i or -s to override (priority: -i > -s > smart-case).

Environment Variables

| Variable | Description | Default | |----------|-------------|---------| | XGREP_LLM_CONTEXT | Default context lines for --format llm | 3 | | XGREP_ABSOLUTE_PATHS | Set to 1 to always use absolute paths | unset | | XGREP_NO_HINTS | Set to 1 to suppress regex pattern hints | unset |

Run xg --help for all options.

MCP Server

xgrep runs as an MCP server, giving AI coding tools fast indexed search.

xg serve                        # Start MCP server
xg serve --root /path/to/repo   # Specific directory

Claude Code

{
  "mcpServers": {
    "xgrep": {
      "command": "xg",
      "args": ["serve"]
    }
  }
}

Available tools: search, find_definitions, read_file, index_status, build_index

See [docs/agents.md](docs/agents.md) for agent-oriented usage patterns.

Performance

> Measurement environment (tables below): Apple M4, 32GB RAM, NVMe SSD, macOS 15. > Warm filesystem cache, hyperfine --warmup 5 --runs 20. Results on other hardware — especially > shared Linux machines or HDD — will differ; see [Reproducibility](#reproducibility) below.

Search: Linux kernel (92,947 files, 2.0GB)

| Query | xg | ripgrep | vs ripgrep | Pattern type | |-------|-----|---------|------------|--------------| | struct file_operations | 37ms | 1,687ms | 46x faster | focused | | printk | 52ms | 1,756ms | 34x faster | focused | | EXPORT_SYMBOL | 66ms | 1,773ms | 27x faster | focused |

The queries above were selected for xgrep's sweet spot (trigram index filters well). For distributed patterns that appear across most files, xgrep approaches ripgrep speed — see the [Reproducibility](#reproducibility) section for honest numbers.

File discovery: next.js (27,332 files)

| Query | xg --find | fd | vs fd | |-------|-----------|-----|-------| | *.ts (4,838 files) | 20.8ms | 187.3ms | 9x faster | | config (substring) | 12.7ms | 188.1ms | 15x faster |

Index cost

| Metric | xgrep | zoekt | |--------|-------|-------| | Build time (Linux kernel) | 6s | 46s | | Index size | 175MB (8% of source) | 3.0GB (155%) | | Breakeven | ~2 searches | — |

> First run includes a one-time index build. See [docs/benchmarks.md](docs/benchmarks.md) for full results including medium/small repos.

Reproducibility

The numbers above were measured on the author's Apple M4 with a warm filesystem cache. Third-party benchmarks on shared Linux machines (different CPU, spinning disk, cold cache) show a different picture depending on pattern type:

| Query | hits | M4 result | Third-party Linux (example) | |-------|------|-----------|------------------------------| | CONFIG_PREEMPT_RT | ~300 | xg wins big | xg wins big (cache fits in L3) | | EXPORT_SYMBOL_GPL | ~21k | xg wins | xg faster, but gap narrows | | raw_spin_lock_irqsave | ~1.2k | xg wins | xg ≈ ripgrep (互角) | | devm_kzalloc | ~7.4k | xg wins | xg slower than ripgrep |

The pattern: when trigram intersection leaves many candidate files (widely-used symbols), xgrep must scan nearly the whole codebase — the index overhead then outweighs the savings. This is a known limitation being investigated. Use bench/fair-bench.sh to measure on your own hardware; the script runs both focused and distributed queries for a complete picture.

Limitations

• Short queries (< 3 chars) bypass the index — no speed advantage over ripgrep
• Tiny files (< 3 bytes) hold no trigrams and are invisible to indexed content search — a deliberate trade-off of the trigram index
• Index staleness — background rebuild runs every ~30s. Use --fresh for up-to-date results
• find_definitions uses regex heuristics, not AST analysis — false positives expected

When to use ripgrep instead: one-off searches, very small codebases (< 100 files), or queries shorter than 3 characters.

How It Works

1. Index Build: Walks the codebase, extracts 3-byte trigrams from each file, builds an inverted index with delta+varint compression
2. Search: Extracts trigrams from query, intersects posting lists to find candidate files, verifies matches
3. Hybrid Mode: Combines index results with direct scanning of changed files when index is stale
4. MCP Server: Exposes search via JSON-RPC over stdio, with token-aware truncation

Contributing

See [CONTRIBUTING.md](CONTRIBUTING.md) for development setup and guidelines.

License

MIT

Source & license

This open-source MCP server is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: momokun7
• Source: momokun7/xgrep
• License: MIT
• Homepage: https://crates.io/crates/xgrep-search

Install and usage instructions live in the source repository linked above.