mcp-injector

Compresses codebases with AST body folding before sending to Claude Code, Cursor, or VS Code — 57-89% token reduction with deterministic output for KV cache hits.

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mcp-injector

Claude Code reads raw files on demand, quickly exhausting your context window and budget. On a large codebase, this leads to slow responses and high API costs.

mcp-injector fixes this. It runs as a background daemon, pre-indexes your entire repository into a local SQLite catalog, and serves a compressed snapshot of your whole codebase to Claude on every query at roughly 1/5th the normal token cost.

I built this after my team's Claude API bill hit $400/month on a 500K line Spring Boot monorepo. After installing mcp-injector the same workflow costs ~$80/month. The difference is AST body folding (strips function bodies, keeps signatures) plus canonical determinism (byte-identical output every run so Anthropic's KV cache fires instead of miss).

No cloud. No telemetry. Runs entirely on your machine.--

Real-World Codebase Context Benchmarks

Estimate the impact of AST code compression on large open-source repositories (calculated at $3.00 / million input tokens for Claude 3.5 Sonnet):

RepositoryTotal FilesRaw Context TokensCompressed Context TokensToken ReductionCost Saved / Run
Django2,3595.6M0.6M89.3%$15.00
Spring Framework9,19315.0M5.2M65.3%$29.40
Next.js21,98524.0M10.2M57.5%$41.40

Numbers are reproducible. Run the open-source benchmark tool on any public repository:
mcp-benchmark repository

What It Looks Like

Run mcp-benchmark on your own project to see your exact savings before installing anything:

mcp-benchmark ./your-project

════════════════════════════════════════════════════════════════════════════════
  mcp-benchmark - context
  Tier 3 compression  |  $3.00/1M tokens  |  2026-07-06T12:00:00Z
════════════════════════════════════════════════════════════════════════════════

FILE                                          RAW TOKENS    COMPRESSED     SAVED   COST SAVED*
──────────────────────────────────────────────────────────────────────────────────────────
cmd/license-gen/main.go                            3,633           214     94.1%       $0.0103
main.go                                           17,555         1,917     89.1%       $0.0469
website/api/webhook.go                             2,682           295     89.0%       $0.0072
main_test.go                                       1,576           353     77.6%       $0.0037
──────────────────────────────────────────────────────────────────────────────────────────
TOTAL (4 files)                                   25,446         2,779     89.1%       $0.0680

  * Based on $3.00 / 1M input tokens

  Running this codebase through Claude 10x/day costs $0.76/day raw.
  With mcp-injector:  $0.08/day.  You save $0.68/day ($20/month).

Quick Install

Install the daemon locally and configure your IDEs:

curl -fsSL https://foldwork.dev/install | sh

Automatically configures Claude Desktop, Cursor IDE, and VS Code.

Getting Started

Step 1: Check if your project qualifies for the free tier

Run the benchmark CLI on your project to see your token savings and line count:

mcp-benchmark ./your-project

If your project is under 100,000 lines, mcp-injector is completely free. The benchmark output shows your exact line count.

Step 2: Install the daemon

curl -fsSL https://foldwork.dev/install | sh

The installer auto-detects Claude Desktop, Cursor, VS Code, and Devin Desktop and writes the MCP config automatically. You should see output like:

* mcp-injector v0.2.0 installed to /usr/local/bin/mcp-injector
* Claude Desktop configured
* Cursor configured
Restart your IDE and mcp-injector will be active.

Step 3: Restart your IDE

The MCP server starts automatically when your IDE launches. No separate daemon process to manage.

Step 4: Verify it is working

In Claude Code or Cursor, ask Claude:

"Use get_project_map to show me the structure of this project"

Claude will call the mcp-injector tool and return a compressed map of your entire codebase. If you see module names, entry points, and dependency information - it is working.

Step 5: Get the full source when needed

When Claude needs to see the complete implementation of a compressed function, it automatically calls injector_retrieve. You can also trigger this explicitly:

"Show me the full implementation of UserService.java"

Claude will fetch the uncompressed source from the local cache.

Step 6: Check your savings

injector_stats

Or ask Claude directly: "Call injector_stats and tell me my current token savings."

Advanced Usage

Inspecting specific files uncompressed

Sometimes you need Claude to see the exact implementation of a file while keeping the rest compressed. Use the unfolded_files parameter:

In your MCP call or by asking Claude:

"Get the project map but show me src/auth/handler.go at full resolution"

This passes "unfolded_files": ["src/auth/handler.go"] to get_project_map. That file is served raw; everything else stays compressed.

Glob patterns work too:

  • "**/*_test.go" - all test files uncompressed
  • "src/auth/*.go" - all files in a directory uncompressed

Switching branches

mcp-injector installs a post-checkout git hook when it first runs. Branch switching automatically triggers a full re-index. You will see this in the daemon logs:

[mcp-injector] Branch switched to feature/auth-refactor, re-indexing...
[mcp-injector] Re-index complete in 4.2s (47,293 lines indexed)

Security First: Zero-Leak Guarantee

Enterprise security teams often block AI coding tools because developers accidentally leak sensitive credentials in their context window.

mcp-injector solves this locally. The daemon includes a built-in Shannon entropy filter that analyzes all AST strings and comments in real-time. If it detects high-entropy strings (like AWS Access Keys, SSH private keys, or database passwords), it dynamically redacts them as [REDACTED: high entropy] before they ever leave your machine. Your API credentials are never sent to Anthropic.

If your codebase has a hardcoded API key or AWS credential, the get_project_map response will include:

"secrets_redacted": 2,
"files_with_redactions": ["config/db.go", "scripts/deploy.sh"]

The actual values are replaced with [REDACTED: high entropy]. Variable names are preserved so Claude still understands the code structure.

Manual MCP configuration

If the auto-installer does not detect your IDE, add this to your MCP config manually:

{
  "mcpServers": {
    "mcp-injector": {
      "command": "/usr/local/bin/mcp-injector",
      "env": {
        "MCP_WORKSPACE": "${workspaceFolder}"
      }
    }
  }
}

Config file locations:

  • Claude Desktop (Mac): ~/Library/Application Support/Claude/claude_desktop_config.json
  • Claude Desktop (Windows): %APPDATA%\Claude\claude_desktop_config.json
  • Claude Desktop (Linux): ~/.config/Claude/claude_desktop_config.json
  • Cursor: ~/.cursor/mcp.json
  • VS Code: .vscode/mcp.json
  • Devin Desktop: ~/.devin/mcp.json

How It Works

  • Persistent Local Daemon: Indexes your repository structure into a high-performance WAL-mode SQLite database catalog.
  • Smart File Watchers: Monitors files incrementally via OS notification hooks (inotify/FSEvents) and local git post-checkout / post-merge triggers.
  • Branch-Aware Re-indexing: Installs a post-checkout git hook on startup. Switching branches triggers automatic workspace re-indexing. get_project_map always reflects your current branch including uncommitted changes.
  • Canonical Output Determinism: Guarantees byte-identical outputs across runs, maximizing Claude's KV prompt caching hits.
  • Compress-Cache-Retrieve (CCR): Employs lossless AST compression. The LLM gets the high-level outline and calls injector_retrieve to fetch raw file bodies on-demand.
  • 100% Local & Offline: Running entirely on your local machine, keeping your intellectual property private and secure.

Supports: Go, Python, TypeScript, JavaScript, Java, C++, Rust.

Pricing Tiers

  • Free Tier: Workspaces under 100,000 total source lines (all tools and features fully active).
  • Pro Tier ($12/month or $99/year): Unlocks unlimited workspace sizes and high-speed incremental diff indexing.
    Activate Pro at foldwork.dev

Exposed MCP Tools

  • get_project_map - Generates a hierarchical outline of module exports, structures, and internal dependencies.

    • unfolded_files parameter: pass specific file paths or glob patterns to receive those files uncompressed while everything else stays folded.
    • git_context: always includes current branch, changed files, and recent commits in the response.
    • secrets_redacted: count of credentials automatically redacted before sending to Claude.

    Example call:

    {
  "tool": "get_project_map",
  "arguments": {
    "tier": 3,
    "unfolded_files": ["src/auth/handler.go", "**/*_test.go"]
  }
}

  • injector_retrieve - Retrieves the raw source code of any compressed symbol from the local cache. Supports start_line and end_line parameters for surgical snippet extraction.

  • injector_search - BM25 full-text search over indexed symbols. Returns line ranges, symbol types, and context snippets so you can skip redundant file retrievals.

  • injector_stats - Visualizes index status, current token savings, and CCR cache hit rates.

  • injector_sync - Synchronously waits for the daemon to finish indexing pending filesystem edits. Returns a list of exactly which files were reindexed to confirm changes.

Check your ROI (Savings Dashboard)

You can run mcp-injector status in your terminal at any time. This CLI dashboard visually proves your exact token savings and estimated dollars saved by comparing your raw codebase tokens against the AST-compressed tokens in real-time.

Security

mcp-injector automatically redacts secrets and credentials before they reach Claude's context window:

  • AWS access keys, GitHub PATs, Stripe secret keys
  • JWT tokens and bearer tokens
  • High-entropy strings detected via Shannon entropy analysis
  • Private key headers (-----BEGIN RSA PRIVATE KEY-----)
  • Air-Gapped Ready: Pro license validation uses strictly offline Ed25519 cryptography. The daemon never makes an outbound network request, even to verify your subscription.

Redacted content is replaced with [REDACTED BY MCP-INJECTOR]. A count of redactions is included in the get_project_map response so you always know what was protected.

Your code never leaves your machine. Redaction happens locally before compression, and is always-on - it cannot be disabled.

Uninstall

To remove mcp-injector completely:

# Remove binary
sudo rm /usr/local/bin/mcp-injector

# Remove index cache and logs
rm -rf ~/.mcp-injector/

# Remove from IDE MCP config (edit manually):
# Claude Desktop (Linux): ~/.config/Claude/claude_desktop_config.json
# Claude Desktop (macOS): ~/Library/Application Support/Claude/claude_desktop_config.json
# Cursor: ~/.cursor/mcp.json
# VS Code: .vscode/mcp.json
# Devin Desktop: ~/.devin/mcp.json
# (Remove the "mcp-injector" entry from mcpServers)

What Gets Redacted

mcp-injector automatically redacts the following before your code reaches Claude:

PatternExample Match
AWS access key IDsAKIAIOSFODNN7EXAMPLE
GitHub PATs (ghp_, ghs_)ghp_aBcDeFg...
Stripe secret keyssk_live_abc... / sk_test_abc...
JWT tokenseyJ...
PEM private key headers-----BEGIN RSA PRIVATE KEY-----
Generic high-entropy strings >20 charsDetected via Shannon entropy
Password / secret / token assignmentspassword = "abc123"

Redacted values are replaced with [REDACTED BY MCP-INJECTOR]. File paths and variable names are never redacted - only the values.

License

Commercial. Free tier available. Source code not public.
Support Contact: foldwork@proton.me