Fixing software bug is part of the daily work routine in software engineering which requires collaboration and thus has been explored as a core CSCW domain, since the early inception of the research field. In this paper, we explore the use of chat technology in software engineering by analyzing the coordination between client and vendor in a large government software project in Brazil (Gov-IT). We collected our empirical material through face-to-face and online interviews, site and chat forums observations. Looking closely at the bug fixing activities within Gov-IT, we find that the client and the vendor use chat technology to coordinate their cooperative work by enabling the participants to monitor the availability of developers and the urgency of detecting bugs synchronously. This way, the chat technology made it possible for the client to report bugs and developers to resolve bugs in a timely manner. Moreover, the chat technology enabled the participants to request and share artefacts synchronously, making it possible to analyze and understand the contextual nature surrounding bugs faster than using the bug tracking system. Finally, the chat technology enabled participants in enacting commitment and interdependence across vendor and client, creating cooperative situations of mutual dependence. Our results suggest that we, as CSCW designers, must rethink the design of bug tracking systems and find new ways to re-configure systems, so they support the coordinative practices involved in detecting, analyzing, and resolving critical and severe software bugs synchronously.