code-explorer

Rust MCP server giving LLMs IDE-grade code intelligence.

The Problem

LLMs waste most of their context window on code navigation. grep returns walls of text. cat dumps entire files when you need one function. There's no way to ask "who calls this?" or "what changed here last?" — the tools are blind to code structure.

The result: shallow understanding, hallucinated edits, constant human course-correction.

The Solution

code-explorer is an MCP server that gives your AI coding agent the same navigation tools a human developer uses in an IDE — but optimized for token efficiency.

Four pillars:

Pillar	What it does	Tools
LSP Navigation	Go-to-definition, find references, rename — via real language servers	7 tools, 9 languages
Semantic Search	Find code by concept, not just text match — via embeddings	4 tools
Git Integration	Blame, history, diffs — context no other tool provides	3 tools
Persistent Memory	Remember project knowledge across sessions	4 tools

Plus file operations (7 tools), AST analysis (2 tools), workflow (3 tools), config (2 tools), and library navigation (2 tools) — 33 tools total.

Recent additions:

• Library Search — navigate third-party dependency source code via LSP-inferred discovery, symbol navigation, and semantic search. Libraries auto-register when goto_definition returns paths outside the project root.
• Incremental Index Rebuilding — smart change detection for the embedding index. Uses git diff → mtime → SHA-256 fallback chain to skip unchanged files, with staleness warnings when the index falls behind HEAD.
• Semantic Drift Detection — detects how much code changed in meaning after re-indexing, not just that bytes changed. Useful for filtering doc staleness and understanding the scope of a refactor. Opt out with drift_detection_enabled = false in [embeddings].

Platform Support

Tested on Linux. macOS and Windows may work but have not been verified. Contributions welcome.

Installation

This is a Claude Code tool. code-explorer is built for Claude Code and currently requires it as the host agent. Other MCP-capable agents may work but are not tested.

The easiest way to get started: clone the repo and let Claude do the installation for you. It has access to the full documentation, your system, and the install scripts — it will handle everything from building the binary to registering the MCP server and installing LSP servers for your languages.

git clone https://github.com/mareurs/code-explorer.git
cd code-explorer
claude
# Then ask: "Help me install and set up code-explorer"

If you prefer to install manually, follow the steps below.

---

code-explorer has two components that work together:

1. MCP Server — provides the 33 tools (symbol navigation, semantic search, git, etc.)
2. Routing Plugin — ensures Claude always uses the right tool, across all sessions and subagents

Both are recommended. The MCP server gives Claude the capability; the plugin ensures that capability is always used correctly. Without the plugin, Claude will occasionally fall back to grep/cat/read out of habit — especially in subagents that start with a blank slate.

Step 1: Install the MCP server

cargo install code-explorer

Register it globally so it's available in every Claude Code session:

claude mcp add --global code-explorer -- code-explorer start --project .

Or per-project (add to your project's .mcp.json):

claude mcp add code-explorer -- code-explorer start --project /path/to/your/project

Step 2: Install the routing plugin

claude /plugin install code-explorer-routing@sdd-misc-plugins

Or add to your user settings (~/.claude/settings.json) for all sessions:

{
  "enabledPlugins": {
    "code-explorer-routing@sdd-misc-plugins": true
  }
}

The plugin is available from the claude-plugins marketplace.

Step 3: Verify

claude mcp list
# Should show: code-explorer with 33 tools

How They Interact

┌─────────────────────────────────────────────────────┐
│                   Claude Code                        │
│                                                      │
│  ┌─────────────────────────────────────────────┐    │
│  │  code-explorer-routing plugin (hooks)        │    │
│  │                                              │    │
│  │  SessionStart  → inject tool selection guide │    │
│  │  SubagentStart → propagate to all subagents  │    │
│  │  PreToolUse    → redirect grep/cat/read to   │    │
│  │                  code-explorer equivalents    │    │
│  └──────────────────────┬──────────────────────┘    │
│                         │ routes to                   │
│  ┌──────────────────────▼──────────────────────┐    │
│  │  code-explorer MCP server (33 tools)         │    │
│  │                                              │    │
│  │  LSP · Semantic · Git · AST · Memory · ...   │    │
│  └──────────────────────────────────────────────┘    │
└─────────────────────────────────────────────────────┘

Without the plugin: Claude has access to the tools but may not use them optimally — it might read whole files instead of using find_symbol, or grep instead of semantic_search.

With the plugin: Every session and subagent gets automatic guidance on which tool to use for each situation. The PreToolUse hook actively intercepts suboptimal tool calls and redirects them before they execute.

Tools (33)

Category	Count	Highlights
Symbol Navigation	7	find_symbol, get_symbols_overview, find_referencing_symbols, rename_symbol
File Operations	7	read_file, list_dir, search_for_pattern, create_text_file
Semantic Search	4	semantic_search, index_project, index_status, check_drift
Library Navigation	2	list_libraries, index_library
Git	3	git_blame, git_log, git_diff
AST Analysis	2	list_functions, extract_docstrings (offline, instant)
Memory	4	write_memory, read_memory, list_memories, delete_memory
Workflow & Config	4	onboarding, execute_shell_command, activate_project

Every tool defaults to compact output (exploring mode) and supports detail_level: "full" with pagination for when you need the complete picture.

See the full tool reference for parameters, examples, and usage guidance.

Supported Languages

	Languages
Full (LSP + tree-sitter)	Rust, Python, TypeScript, TSX, Go, Java, Kotlin
LSP only	JavaScript, JSX, C, C++, C#, Ruby
Detection only	PHP, Swift, Scala, Elixir, Haskell, Lua, Bash, Markdown

Install LSP servers with the bundled script:

./scripts/install-lsp.sh --check          # see what's installed / missing
./scripts/install-lsp.sh --all            # install everything
./scripts/install-lsp.sh rust python go   # install specific languages

See Language Support for manual install commands and known quirks.

Contributing

See CONTRIBUTING.md for how to get started. PRs from Claude Code are welcome!

License

MIT