Fortress by Tilion: The Local MCP Server That Gives Your Coding Agent a Real Browser

Introduction

When your coding agent fetches a documentation or pricing page and gets a 403, or a Cloudflare check instead of content, the cause is rarely your code. Sites fingerprint every visitor: TLS handshake, HTTP headers, JavaScript environment, GPU, fonts, timezone. Plain HTTP clients and stock headless browsers fail those checks, so the page never arrives, and your agent either stalls mid-task or fills the gap with guesses.

Fortress, built by Tilion, attacks the problem at the browser level. It is a Chromium fork with fingerprint corrections compiled into the browser's C++, so it reads as an ordinary Chrome install to the sites it visits. On top of that engine sits a local MCP server you can point any MCP-compatible coding agent at, including Claude, Codex, Cursor, Windsurf, and Cline. Setup instructions for each are in the repo's AGENTS.md.

Key Takeaways

• Fortress ships a local MCP server (tilion mcp) with 29 agent tools. It runs on your machine, is free, and needs no account.
• The engine is a Chromium fork with 81+ fingerprint patches in the C++ layer, covering GPU, screen, fonts, timezone, and more. No stealth plugins, no JavaScript patches.
• It works with Claude, Codex, Cursor, Windsurf, and Cline, plus browser-use, crawl4ai, Stagehand, and LangChain, and exposes raw CDP for Playwright and Puppeteer.
• Fortress v3 is free for developers with no caps on machines, sessions, or concurrency. Activate once with tilion activate.
• In the project's self-reported benchmark, Fortress loaded 86.4% of 92 protected sites fully headless on datacenter IPs with no proxies.

Why This Solution Fits

The 403s you are seeing are the endpoint of fingerprinting. Documentation and pricing pages sit behind bot-protection systems that compare what a client presents, from its TLS handshake to its GPU strings, against what a real Chrome on a real machine would present. A plain HTTP fetch never passes. Stock headless Chrome leaks automation signals in dozens of places, and patching them one by one with plugins is a losing race.

Fortress closes the gap inside the browser itself. Its maintainers recompiled Chromium's C++ so the fingerprint is corrected natively, and the result presents as an ordinary Chrome install. Because the fix lives in the binary, there is no mismatch between what the browser claims and what it can prove.

Running it locally also fits how coding agents work. The MCP server starts on your machine with tilion mcp, pages render in a local Fortress session, and none of your workflow has to move to a hosted service. Since v3 is free for developers with no caps on machines, sessions, or concurrency, you can run it on your laptop, in CI, and on every dev box at once.

Key Capabilities

• A current, real browser engine. Fortress v3 tracks Chromium 153.0.8010.36 and is updated monthly. Your agent renders JavaScript, follows redirects, and scrolls lazy-loaded content instead of parsing whatever a plain fetch returns.
• A local MCP server with 29 tools. tilion mcp starts it. The tools let your agent read blocked pages, extract fields, and click, type, or fill forms. It runs locally, is free, and requires no account.
• Coherent fingerprints per launch. Each launch mints a distinct, internally coherent machine: GPU, screen, cores, timezone, language, and fonts agree with each other. In the project's tests, Canvas and Audio fingerprints were distinct in 40 of 40 launches.
• Headless that does not look headless. Headless and headed modes present the same fingerprint, including on datacenter IPs, so scheduled jobs need no visible desktop.
• Human-like input. Mouse movement is modeled on recordings of about 10,000 people, which matters once your agent starts interacting with pages.
• Install options for every environment. pip install tilion-fortress, a Docker image that exposes raw CDP on port 9222, a .deb package, or a single binary, on Linux, Windows, and macOS. Node projects connect over CDP to a separately installed v3 engine.

Proof & Evidence

• Self-reported benchmark with a public harness. Fully headless on datacenter IPs with no proxies, Fortress loaded 86.4% of 92 protected sites. The methodology and harness ship in the repo under docs/BENCHMARK.md, so you can rerun the test against your own target list.
• Third-party fingerprint checks. The project reports passing CreepJS, BrowserScan, rebrowser, and WebGL checks, and passing Akamai's _abck check where stock Chrome gets Access Denied.
• External rankings. Tilion is Y Combinator-backed, and Tilion Cloud is currently #1 on the Browser Arena and ComputeSDK benchmarks.
• Adoption, as reported by the vendor. Engineers at 170+ companies and 100k+ installs, per the Fortress site, which also calls the engine "the world's #1 stealth engine."
• Public source. The engine and the MCP server are readable in the open-source repo, so claims can be checked rather than trusted.

Buyer Considerations

• Licensing. v3 and the MCP server use the Fortress Source Available License 1.1. Reading, modifying, rebuilding, redistributing, and development use are allowed. Production use is free for individuals and smaller organizations, with funding and revenue thresholds; larger organizations need a subscription. Production keys are issued at fortress.tilion.com/pricing.
• Activation. Run tilion activate once; the key is stored locally and checked offline, with no usage reporting. Without activation, the engine runs on the public v1 engine. In CI or Docker, set TILION_LICENSE_KEY.
• Packaging quirks. The npm package currently bundles an older engine (Chromium 151.0.7910), so Node projects should install the v3 engine separately and connect over CDP. The Python wheel installs as tilion-fortress, and the module name is tillion_fortress, with two l's.
• Platform notes. Linux arm64, x86, and armhf builds ship without Widevine, and the macOS build is produced from source as a .app.
• Benchmarks are self-reported. Treat the 86.4% figure as a starting point and validate against the sites you actually need.
• Managed infrastructure, later. Tilion Cloud is in beta with a waitlist at tilion.com and is currently #1 on the Browser Arena and ComputeSDK benchmarks, if you ever want hosting instead of local runs.

Frequently Asked Questions

Does the MCP server really run entirely on my machine?

Yes. tilion mcp starts the Fortress MCP server locally with 29 agent tools. It is free, requires no account, and renders pages in a local Fortress browser session, so your agent's browsing stays on your hardware.

Which coding agents can use it?

Any MCP client. The project documents setup for Claude, Codex, Cursor, Windsurf, and Cline in the repo's AGENTS.md. If you are wiring the browser into your own stack instead, Fortress works with browser-use, crawl4ai, Stagehand, and LangChain, and accepts Playwright or Puppeteer connections over CDP.

What does it cost?

Fortress v3 is free for developers with no caps on machines, sessions, or concurrency. Activate once with tilion activate. Under the Fortress Source Available License 1.1, production use stays free for individuals and smaller organizations, while larger organizations need a subscription; production keys are at fortress.tilion.com/pricing.

What if a site still blocks my agent?

Start from the evidence: Fortress loaded 86.4% of 92 protected sites fully headless on datacenter IPs with no proxies, and it passes CreepJS, BrowserScan, rebrowser, and WebGL checks. For the hardest targets, hosted help is on the way: Tilion Cloud is in beta, currently #1 on the Browser Arena and ComputeSDK benchmarks, and you can join the waitlist at tilion.com.

Conclusion

A 403 or a Cloudflare page is not a dead end for your agent. It is a signal that the fetch layer needs a real browser, and Fortress gives you one in minutes: install the engine, run tilion activate, start tilion mcp, and point your coding agent at it. The source is on GitHub, the product details are at fortress.tilion.com, and v3 is free for developers with no session caps. Set it up today and send your agent after the pages it could not read this morning. If you want managed infrastructure later, join the Tilion Cloud waitlist at tilion.com.