Everything we knew about software has changed — Theo Browne, @t3dotgg ​

For the closing keynote of AIEWF2026, Theo provokes you to think wider, not just bigger.

In this keynote from the AI Engineer World's Fair, developer and YouTuber Theo Browne (@t3dotgg) argues that the rapid evolution of AI models—moving from tool-calling (Sonnet 3.5) to long-running task execution (Opus 4.5) and now orchestration (Mythos)—requires software engineers to fundamentally change how they build products.

Key Themes:
Rejecting Skeuomorphism: Browne compares the current state of software development to the design shift in iOS 7, urging developers to move away from legacy mental models and tools (like Git or terminal-centric workflows) that prioritize familiarity over actual utility (6:08 - 8:32).
The New Tier System: Traditional categorizations of "side project," "startup," and "too big" have shifted. He highlights that tasks once requiring a dedicated startup can now be managed by simple automated systems, such as a Markdown file running on a cron job (10:33 - 12:20).
Thinking Bigger: Rather than just building depth in a narrow feature set, Browne encourages builders to cover a wider spectrum of product functionality. Because AI agents can now handle significant parts of implementation, it is becoming viable for smaller teams to build products that compete with industry giants like AWS or Salesforce by architecting them for extensibility (13:12 - 15:30).

Takeaway: The barrier to entry for building complex, wide-reaching platforms has collapsed. Engineers should stop limiting themselves by legacy constraints and start building much more ambitious projects.

Timestamps
0:00 – Introduction and the "AI psychosis" experience
0:50 – Evolution of AI models: Sonnet 3.5, Opus 4.5, and Mythos
3:04 – The imperative to "go bigger" and push model capabilities
3:35 – Overcoming legacy constraints and developer habits
6:08 – Moving past our "skeuomorphic" phase in software development
9:30 – Personal project evolution: side projects, startups, and the "Markdown tier"
12:22 – Identifying the gap: What is "too big" anymore?
13:06 – Redefining the strategy: Building for a wider spectrum instead of just depth
14:50 – Scaling and architecting products to allow for user-driven extensibility