Agile's dominance in software development is waning as teams embrace Spec-Driven Development powered by large language models. The manifesto's vague principles and commercialization through certifications failed to deliver on promises, leaving developers questioning what Agile truly meant. Meanwhile, LLMs excel at processing detailed specifications, making comprehensive documentation valuable again.

Critics argue Agile's core concepts weren't revolutionary. The 1970 Royce paper outlined iterative development, customer collaboration, and prototyping—practices later marketed as Agile innovations. The 1976 Bell and Thayer study showed iterative approaches existed decades before the manifesto. Waterfall wasn't the industry standard it's often portrayed as, and Winston W. Royce himself recommended moving away from rigid sequential processes.

As AI transforms programming workflows, the pendulum swings back to documentation-first approaches. LLMs struggle with ambiguity but thrive on clear specifications, validating Royce's insight that documentation, specification, and design are fundamentally linked. The industry's shift toward Spec-Driven Development represents not a new trend but a return to engineering fundamentals that worked before Agile's commercialization. This evolution suggests Agile's legacy may be more about marketing than methodology.