OptiVault

Zero-Dependency AST-Driven Context Compiler and MCP Server for Claude Code

OptiVault solves the "token bloat" problem with the most direct approach: no LLMs, no summarization, no external API calls. It extracts your repo's structure—function signatures, arrow functions, class methods, dependencies—using pure AST parsing, writes a compressed shadow vault, and exposes it via the MCP protocol.

Claude Code gets a 4-tool semantic router to traverse your codebase hierarchically, consuming ~50 tokens per file instead of ~1,000. As soon as Claude is done writing code, a single sync_file_context call keeps the vault perfectly up to date.

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Benchmark Results

Same task. Same codebase. Four tool configurations. Measured with Claude Code's /cost command.

Scenario	Input Tokens	Output Tokens	Total Tokens	Time	Cost
Baseline (vanilla Claude)	45,000	1,200	46,200	45s	$0.153
Caveman Only	45,000	300	45,300	38s	$0.139
OptiVault Only	2,500	1,200	3,700	12s	$0.025
OptiVault + Caveman	2,500	300	2,800	5s	$0.008

v 94% token reduction · 9× faster · 95% cheaper vs. a vanilla Claude Code session.

Numbers above are representative mock data. Run python benchmark/plot_results.py after filling in benchmark/data.csv with your own /cost readings to regenerate the charts.

See benchmark/EXPERIMENT_GUIDE.md for the exact reproduction steps.

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Why OptiVault

Problem	OptiVault's Solution
Claude reads entire files to understand structure	read_file_skeleton returns deps + signatures in ~50 tokens
Context window fills with irrelevant code	read_function_code fetches only the function Claude needs
Shadow context goes stale when Claude writes code	sync_file_context re-indexes a single file in ~20ms
Claude doesn't know OptiVault exists	optivault init generates CLAUDE.md enforcing the protocol
Re-running init on a large project is slow	mtime-based caching skips unchanged files entirely

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Features

• Zero external dependencies — no Ollama, no LLMs, no API calls. Pure TypeScript.
• Blazing fast — scans 1,000 files in ~2–3 seconds; incremental sync in ~20ms.
• Full arrow function support — export const fn = (x: string) => {} extracts as fn(x: string), not just fn.
• 4-tool MCP semantic router — bird's-eye map → file skeleton → function body → live re-sync.
• Self-enforcing protocol — auto-generated CLAUDE.md tells Claude exactly how to use OptiVault.
• Idempotent init — mtime-checked; re-running init on a 5,000-file repo takes milliseconds.
• Plugin architecture — add Go, Rust, or Java by implementing a single interface.
• Obsidian-compatible vault — default dir _optivault is visible in Obsidian natively (no leading dot).
• Auto-migration — detects and renames legacy .optivault directories automatically; zero data loss.
• Configurable vault name — drop an optivault.json in your project root to rename the vault dir.
• 99 passing tests — full coverage across extraction, fallbacks, MCP tools, caching, and migration.

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Install

Prerequisites

• Node.js ≥ 20 (download)
• npm (comes with Node.js)

From Source

git clone https://github.com/your-username/optivault
cd optivault
npm install
npm run build
npm link

npm link makes the optivault binary available globally:

optivault --help

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Quickstart

# 1. Index your project (creates _optivault/, CLAUDE.md, and .gitignore entry)
optivault init ~/my-project

# 2. Register with Claude Code
claude mcp add optivault optivault -- mcp \
  --vault ~/my-project/_optivault \
  --source ~/my-project

# 3. Open Claude Code in that project — it will read CLAUDE.md and follow the protocol automatically

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How It Works

1. Index (optivault init)

optivault init ~/my-project

What happens:

• Checks for a legacy .optivault directory and renames it automatically (zero data loss)
• Reads optivault.json for a custom vault dir name, defaults to _optivault
• Recursively walks the project for .ts, .tsx, .js, .mjs, .py files
• Skips node_modules, .git, dist, and the vault dir itself
• Checks mtime — only re-parses files newer than their vault note (fully idempotent)
• Extracts function signatures, arrow functions, class methods, imports
• Writes .md shadow notes to ~/my-project/_optivault/
• Generates _RepoMap.md — master index of the entire repo
• Creates (or patches) CLAUDE.md with the OptiVault protocol directive
• Adds the vault dir to .gitignore automatically

Example vault note (src/auth.ts.md):

---
tgt: src/auth.ts
dep: [[database]], [[crypto]]
exp: [verifyToken(token: string), hashPwd(plain: string), TokenService]
---
## Signatures
- `verifyToken(token: string)`
- `hashPwd(plain: string)`
- `TokenService`

Example RepoMap (_RepoMap.md):

# RepoMap

- [[src/auth]] — exports: verifyToken(token: string), hashPwd(plain: string) — deps: database, crypto
- [[src/db/pool]] — exports: getConnection(), closePool() — deps: pg, config
- [[src/middleware/rate-limit]] — exports: rateLimiter(opts: RateLimitOpts) — deps: express, redis

2. Watch (optivault watch)

optivault watch ~/my-project

Stays running. Re-indexes files the moment they're saved. Use this during active development instead of the MCP sync_file_context tool.

3. MCP Server (optivault mcp)

optivault mcp --vault ~/my-project/_optivault --source ~/my-project

Starts the MCP server. Claude Code connects automatically once registered.

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The 4 MCP Tools

read_repo_map

Returns the full _RepoMap.md — a bird's-eye view of every file, its exports, and its dependencies.

Claude: "What's the architecture of this repo?"
→ read_repo_map()
← # RepoMap
  - [[src/auth]] — exports: verifyToken(...), hashPwd(...) — deps: database, crypto
  - [[src/db/pool]] — exports: getConnection() — deps: pg
  ...

When to use: Always call this first. It costs ~200 tokens and gives complete structural context.

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read_file_skeleton

Returns the compressed shadow note for a specific file: deps + all exported signatures.

Claude: "What does src/auth.ts export?"
→ read_file_skeleton(filename: "src/auth.ts")
← ---
  tgt: src/auth.ts
  dep: [[database]], [[crypto]]
  exp: [verifyToken(token: string), hashPwd(plain: string)]
  ---
  ## Signatures
  - `verifyToken(token: string)`
  - `hashPwd(plain: string)`

When to use: After read_repo_map identifies the relevant file, before reading the full source.

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read_function_code

Extracts just the implementation of a named function — standard functions, arrow functions, class methods, async functions, generic functions.

Claude: "I need to understand how verifyToken works"
→ read_function_code(filename: "src/auth.ts", functionName: "verifyToken")
← export function verifyToken(token: string): boolean {
    const decoded = jwt.verify(token, process.env.SECRET);
    return decoded !== null;
  }

When to use: When you need the actual logic, not just the signature. Fetches ~20 lines instead of the entire 500-line file.

Requires --source to be set on the MCP server.

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sync_file_context

The key to a stale-free vault. Call this immediately after writing or modifying any source file. It re-parses the single file, overwrites its vault note, and patches its entry in _RepoMap.md — all in ~20ms.

Claude: [writes new function calculateTax to src/billing.ts]
→ sync_file_context(filename: "src/billing.ts")
← "Successfully synced shadow context for src/billing.ts."

CLAUDE.md makes this mandatory — Claude will call it autonomously after every file write.

Requires --source to be set on the MCP server.

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CLAUDE.md — The Self-Enforcing Protocol

Every time optivault init runs, it checks for CLAUDE.md in the project root:

• Not present → creates it
• Present, no OptiVault section → appends the protocol block (original content preserved)
• Already patched → silent no-op

Generated content:

<!-- optivault-protocol -->
# OptiVault Protocol Active
This repository uses OptiVault for AST-compressed context.
Shadow vault: `_optivault/`

**Rules for AI Assistants:**
1. NEVER use `cat`, `grep`, or standard file reads to understand the codebase initially.
2. ALWAYS start by calling the `read_repo_map` MCP tool.
3. Use `read_file_skeleton` to view a file's dependencies and exported signatures.
4. Use `read_function_code` if you need to analyze or modify a specific function body.
5. **CRITICAL:** Whenever you modify a file or write new code, you MUST immediately call the
   `sync_file_context` MCP tool on that file to keep the shadow vault up to date.

The Shadow vault: line reflects whatever vaultDir is configured (default: _optivault).

Claude Code reads CLAUDE.md automatically at the start of every session. No setup required after the first init.

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Register with Claude Code

Via CLI (recommended)

claude mcp add optivault optivault -- mcp \
  --vault /path/to/project/_optivault \
  --source /path/to/project

Via settings file

Add to ~/.claude.json (or your project-local Claude settings):

{
  "mcpServers": {
    "optivault": {
      "type": "stdio",
      "command": "optivault",
      "args": [
        "mcp",
        "--vault", "/path/to/project/_optivault",
        "--source", "/path/to/project"
      ]
    }
  }
}

Multiple Projects

Register a separate MCP server per project with unique names:

claude mcp add optivault-api optivault -- mcp \
  --vault ~/projects/api/_optivault --source ~/projects/api

claude mcp add optivault-frontend optivault -- mcp \
  --vault ~/projects/frontend/_optivault --source ~/projects/frontend

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CLI Reference

optivault init [dir] [options]

Index a project. Safe to re-run — unchanged files are skipped.

optivault init ~/my-project
optivault init ~/my-project --output ~/my-project/_optivault

Option	Default	Description
-o, --output <path>	from optivault.json, else _optivault	Output directory for vault notes

optivault watch [dir] [options]

Watch for file changes and update incrementally. Press Ctrl+C to stop.

optivault watch ~/my-project

Option	Default	Description
-o, --output <path>	from optivault.json, else _optivault	Output directory for vault notes

optivault mcp [options]

Start the MCP server (4 tools).

optivault mcp --vault ~/my-project/_optivault --source ~/my-project

Option	Default	Description
-o, --vault <path>	from optivault.json, else _optivault	Vault directory to serve
-s, --source <path>	—	Source root (required for read_function_code and sync_file_context)

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Architecture

src/
├── config.ts               # getConfig — reads optivault.json, returns OptiVaultConfig
├── ast/
│   ├── plugins/
│   │   ├── typescript.ts   # .ts .tsx .js .mjs .jsx — imports, exports, arrow fns, methods
│   │   ├── python.ts       # .py — top-level defs, classes, imports
│   │   └── index.ts        # Auto-registers all built-in plugins
│   ├── extractor.ts        # Public extractDeps / extractExports API
│   ├── function-extractor.ts  # extractFunctionCode — brace-matched body extraction
│   ├── parser.ts           # parseFile — reads file, dispatches to plugin
│   ├── registry.ts         # Plugin registry — keyed by file extension
│   └── types.ts            # LanguagePlugin interface
├── compression/
│   └── formatter.ts        # formatVaultNote — ParseResult → .md frontmatter
├── vault/
│   ├── init.ts             # walkDir, runInit, migrateLegacyVault, generateClaudeMd,
│   │                       #   ensureGitignored, VaultRegistry
│   └── watch.ts            # chokidar watcher, incremental re-index
├── mcp/
│   └── server.ts           # McpServer with 4 tools
└── cli/
    └── index.ts            # Commander CLI — init / watch / mcp (all consume getConfig)

Plugin Interface

interface LanguagePlugin {
  extensions: string[];
  extractDeps(source: string): string[];
  extractExports(source: string): string[];
  extractFunctionCode?(source: string, functionName: string): string | null;
}

Adding a New Language

// src/ast/plugins/go.ts
import type { LanguagePlugin } from '../types.js';

export const goPlugin: LanguagePlugin = {
  extensions: ['.go'],
  extractDeps(source) {
    // Extract import paths → ["fmt", "os", "github.com/user/pkg"]
    return [];
  },
  extractExports(source) {
    // Extract exported func signatures → ["main()", "InitDB(): error"]
    return [];
  },
  extractFunctionCode(source, functionName) {
    // Return the full function body or null
    return null;
  },
};

Register it in src/ast/plugins/index.ts:

import { goPlugin } from './go.js';
registerPlugin(goPlugin);

Done. Zero changes to core code.

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Performance

Operation	Time
Initial scan — 1,000 files	~2–3 seconds
Idempotent re-scan (all unchanged)	< 100ms
sync_file_context (single file)	~20ms
Incremental watch (single file save)	~100–200ms
Token cost per file (skeleton)	~50 tokens
Token savings vs. full file read	~95%

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Configuration

Create an optivault.json file in your project root to override the vault directory name:

{
  "vaultDir": "_my_custom_vault"
}

Resolution order (highest priority first):

1. --output / --vault CLI flag
2. vaultDir in optivault.json
3. Built-in default: _optivault

The config file is read by init, watch, and mcp commands automatically — no flags needed once it exists.

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Use with Obsidian

The _optivault/ directory is a fully functional Obsidian vault, visible natively without any plugins:

1. Open Obsidian → Open folder as vault → select _optivault/
2. Every source file is a note, wikilinked via its imports
3. Open Graph View to visualize your entire codebase as a dependency graph

Note: The previous .optivault default used a leading dot, which Obsidian silently ignores. The new default _optivault is always visible.

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Testing

npm test            # Run full suite (99 tests)
npm run test:watch  # Continuous mode during development
npm run build       # TypeScript compilation check
npm run lint        # Type check without emit

Test coverage includes:

• TypeScript dep/export extraction — named, default, namespace, dynamic imports
• Arrow function signature extraction (export const fn = (x: T) => {})
• Python dep/export extraction
• extractFunctionCode for TS standard functions, arrow functions, class methods, Python defs
• getConfig — missing file, malformed JSON, empty vaultDir, whitespace trimming
• runInit — graceful fallback on parse errors, empty projects, mtime caching
• generateClaudeMd — create, append, idempotent no-op, custom vault dir name
• ensureGitignored — create, append, idempotent no-op
• migrateLegacyVault — rename, no legacy dir, identical paths, both dirs exist guard
• All 4 MCP tools — registration, happy path, ENOENT handling, sync_file_context patch/insert/replace logic

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FAQ

Why regex instead of tree-sitter? Regex extraction requires zero native build steps, works in every environment, and is fast enough for all practical repo sizes. Individual plugins can be upgraded to tree-sitter incrementally without touching the core.

Does read_function_code handle generics? Yes. function fn<T = unknown>(x: T) is matched correctly. Brace-depth tracking handles nested generics, strings, and template literals.

What if a file can't be parsed? init logs a warning and skips it. The rest of the index is unaffected and the process does not crash.

What if CLAUDE.md already exists? OptiVault appends only if the <!-- optivault-protocol --> marker is absent. Your existing content is never touched.

Can I run this offline? Yes. 100% offline. No network calls, no API keys, no LLM backends.

Does sync_file_context rebuild the entire RepoMap? No. It reads the existing _RepoMap.md, replaces or inserts just the one changed line, and writes it back. It's an O(lines in map) patch, not an O(files in repo) rebuild.

What languages are supported? TypeScript, TSX, JavaScript, MJS, JSX, and Python out of the box. Any language can be added via the plugin interface.

I have an old .optivault directory. Do I need to rename it manually? No. The first time you run optivault init (or watch or mcp) after upgrading, OptiVault detects the legacy .optivault directory and renames it to _optivault automatically. No data is lost.

Why _optivault instead of .optivault? Obsidian natively ignores any directory whose name starts with a dot. The _optivault default is fully visible in Obsidian's file explorer and Graph View without any plugins or workarounds.

Does OptiVault touch .gitignore? Yes — optivault init appends the vault dir name to .gitignore if it isn't already there. It creates .gitignore if the file doesn't exist. It is always a no-op if the entry is already present.

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License

MIT

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Built for Claude Code. Built for speed. Built for clarity.