Reflections on Windows Longhorn: A Cautionary Tale from a Retired Engineer
In a recent video on his YouTube channel, retired Microsoft engineer Dave Plummer revisited the ambitious yet tumultuous journey of the Windows Longhorn project, which began over two decades ago. As one of the last projects he worked on before his retirement, Plummer shared insights into the challenges and aspirations that defined Longhorn, a project intended to be the successor to Windows XP.
Plummer characterized Longhorn as a blend of “big ambitions, technical nightmares, and an extraordinary comeback.” However, he acknowledged that many users, particularly those who were satisfied with XP but disenchanted by Vista, might contest the notion of a comeback.
“Microsoft wanted Longhorn to reimagine what Windows could be,” Plummer explained. This vision encompassed a complete overhaul of the user experience, significant behind-the-scenes changes, and the introduction of WinFS, or Windows Future Storage. He described WinFS as one of the “crown jewels” of the new operating system, designed to allow users to search for files based on content tags and relationships rather than the traditional name and folder structure. “It was a bold plan,” he noted.
The project also aimed to embrace managed code with .NET, introduce a new presentation subsystem, and establish a fresh framework for communications and web services. Plummer remarked, “Windows XP’s colorful Luna interface was going to be yesterday’s news. Longhorn would be sleek, modern, and visually rich.” Yet, he cautioned that such ambitious goals often come with significant challenges.
As development progressed, Plummer observed the mounting difficulties. “One major problem was that with so many new features being developed simultaneously, the Windows codebase became fragile and bloated.” He identified WinFS as a key contributor to this instability, noting that the integration of various components became increasingly problematic. “We had a tradition at Microsoft called ‘Dog Fooding,’ meaning using our own daily builds of the OS to do our actual work. For Longhorn, dog fooding was tough. Builds were often too unstable to run for very long.”
He humorously remarked, “The degree to which eating dog food is tolerable can be measured in direct proportion to how good the dog food actually is. And this was not good dog food.” The challenges were compounded by the need for backward compatibility, leading to a precarious balancing act for the Longhorn team: innovate aggressively without breaking Windows.
The situation further deteriorated following a notable memo from Bill Gates in 2002, which prioritized security. While addressing security vulnerabilities in Windows XP was essential, it diverted resources and slowed Longhorn’s development. Plummer recalled the frustration of seeing the project’s timeline stretch as feature creep persisted. “It’s demoralizing as an engineer when you can see the light at the end of the tunnel getting further away and not closer.”
Ultimately, Plummer chose to take a sabbatical and later retire, feeling that the Longhorn debacle was only a small part of his decision. “I’m an incrementalist, not a revolutionary,” he stated. “I prefer to add things one solid feature at a time rather than reinventing everything all at once as part of some grand vision.”
The fate of Longhorn is well-documented. While the consumer team continued to push for new features, the server team adopted a more methodical approach to ensure stability. The turning point came when Dave Cutler, the architect behind Windows NT, suggested switching to the server team’s codebase. “It was never pleasant to consider throwing away years of work,” Plummer reflected, acknowledging the emotional toll on the developers involved.
The eventual reset in August 2004 marked a significant shift, as Microsoft announced the scrapping of the existing Longhorn codebase in favor of the Windows Server 2003 SP1 codebase, with select Longhorn features integrated. Plummer, who had retired before this pivotal moment, described the announcement as shocking yet oddly relieving for many. “It was devastating because nobody wants to see their hard work tossed out, but a relief because, by this point, everybody knew it wasn’t working.”
The outcome of this tumultuous journey was Windows Vista, which retained some features from Longhorn, such as translucent window effects, while discarding others, including WinFS. Plummer pondered, “Was the Longhorn project a failure? Well… yes and no.” He acknowledged that it failed to fulfill its original promises, with many radical ideas cut and a significant delay in the schedule. However, he also emphasized the positive legacy of Longhorn, noting that the reset and recovery shaped Microsoft’s future culture and engineering practices.
Plummer views the story of Longhorn as a cautionary tale, illustrating that even a company with vast resources can find itself overwhelmed. “The story of Longhorn is one of hubris and humility; Microsoft reached for the stars, stumbled, but then humbled itself to regroup and ultimately deliver something worthwhile.”
