Fluent in VC.Fluent in LLMs.

Virtus Opus is an independent iOS app studio and startup advisory practice. We design and ship consumer iOS applications — eight are live on the App Store — and we provide fractional CFO services, COO advisory, fundraising strategy, and startup advisory to early-stage founders. The combination is deliberate: the same person who understands your cap table also runs operations and understands what it costs to build and ship the product.

Erdem Gülen. His background spans corporate finance (KPMG, Turkcell) and startup executive roles (V-Count, Scotty), and from November 2026 is COO at Buyutech, an Ankara-based automotive camera and perception technology company. He has co-founded four ventures — three failures and one exit — angel invests, and mentors founders across seven accelerator programs. After years advising startups he learned to build software directly, and still writes the code as well as the financial models. Virtus Opus and its apps continue alongside the Buyutech role.

A fractional CFO is a part-time chief financial officer — senior financial leadership without the cost of a full-time executive hire. It typically makes sense when you have real revenue or an upcoming raise, but the finance work does not yet justify a full-time CFO salary. Common triggers: preparing for a seed or Series A round, a cap table that has become hard to reason about, investors asking for reporting you cannot currently produce, or a founder spending too many hours in spreadsheets instead of on the product.

Comprehensive CFO advisory, controlling and reporting, investment readiness and round closure support, and business strategy and implementation. In practice this means financial modeling, investor-ready reporting, data room preparation, budget and runway management, and sitting in on the conversations where the numbers matter.

Both. The portfolio on this site is our own — every app was designed, built, and shipped in-house, which is also the proof of what we can do for a client. We take on client application development covering iOS and web applications, AI and prompt engineering, UI/UX design, and databases and APIs.

Mostly early-stage — pre-seed through Series A — where a founder needs financial rigor, a product shipped, or both, and cannot yet justify senior full-time hires for either. We work with founders worldwide and are comfortable operating fully remotely.

It depends on scope. Engagements range from a focused one-off piece of work — a financial model, an investment readiness review — to an ongoing monthly fractional CFO retainer. Get in touch at hello@virtusop.us with a short description of where you are and we will tell you what it would realistically take.

Most of our apps are deliberately privacy-first and process data on-device. OpusCam analyses your photo library entirely on your iPhone, B-Roll AI tags your camera roll locally, and Okumaca works fully offline with no account required. Where an app does use a cloud service, its own privacy policy — linked from each app page — says so explicitly. For example, ChronoCast AI and VisuCraft send the photo you choose to AI providers, including Anthropic's Claude, to generate your result; B-Roll AI uses Claude only on our server, on public audio metadata — never on your photos or personal data.

Istanbul, Turkey — working with founders and companies worldwide. Advisory and development engagements run remotely as a matter of course, across time zones.

Email hello@virtusop.us or use the contact form on virtusop.us. Tell us roughly where you are — stage, what you are building, and what is currently in your way. Advisory work is taken on selectively alongside Erdem's role at Buyutech, so the first conversation is also an honest check on fit — a conversation, not a pitch.