Phase0 is an AI-first, cloud-based operating system for small architecture and engineering firms, unifying the workflows that sit between project planning and project profitability. The platform brings AVA (tendering, awarding, billing), HOAI fee management and site management together in a single browser-based solution covering the full project lifecycle. Built on construction-specific data rather than a general-purpose model, its AI agents take over the administrative work that consumes the most time in these firms, from bills of quantities and site diaries to invoice verification, giving them continuous cost and margin transparency. More than 1,000 firms across the DACH region already use Phase0 as their central project platform.