WhoOwnsWhat is a shared ledger application designed for two-person side projects, such as indie hacker collaborations or hackathon teams. Its primary function is to track and split costs for SaaS subscriptions, domains, and other project expenses, while also maintaining a record of who controls each account and billing method. The tool addresses the common problem of informal cost sharing and ownership ambiguity in small partnerships by providing a structured, transparent system to log payments, see balances, and settle debts. Key features include the ability to log a cost and automatically calculate the split among up to eight people, with settle-up links to facilitate repayment. The ownership list records who administers each service (for example, domain registrar, Vercel, Notion, Slack, Claude) and indicates risks such as a single admin who could cause renewal problems if unavailable. The app also provides alerts for access and renewal risks, a breakup simulator to test project dissolution scenarios, and a handover checklist to transfer control cleanly. Additional capabilities include a founder record that all participants confirm, weekly email summaries of who owes whom, and an MCP (Model Context Protocol) integration for use with Claude Code and Cursor. Typical use cases involve two people building a side project together. They log expenses for services like Supabase Pro, domains, and hosting, and the ledger updates balances instantly. Users can view a project overview from a single prompt, connect a client using a project token, and access a free hackathon kit with checklists. The workflow is straightforward: one person pays for a service and records the cost, the split is computed, and either party can use the settle-up links to even out. The ownership list helps identify potential single points of failure, and the handover tool ensures a clean exit when the project ends or changes hands. Technically, WhoOwnsWhat operates as a web application at whoownswhat.xyz. Payments and provider permissions are handled externally; the app only tracks logs and splits. It is designed for simple, two-person projects but can accommodate up to eight people. The app includes a demo illustrating how cost logging, balance tracking, and admin risk alerts work, though all example data is illustrative. No installation or technical setup is required beyond creating an account and adding a project.