Cognition's rebuild of Devin for Claude Sonnet 4.5 reveals fascinating new AI behaviors that could transform how we approach vibe coding. Discover what these changes mean for your creative development workflow.
Cognition rebuilt Devin for Claude Sonnet 4.5, achieving 2x faster performance and12% better results on Junior Developer evaluations. But the real story isn't just the performance gains—it's the completely new AI behaviors that emerged.
These behaviors could fundamentally change how we approach vibe coding, making AI assistants more intuitive and context-aware than ever before.
Sonnet 4.5 is the first model that's aware of its own context window. As it approaches limits, it proactively summarizes progress and becomes more decisive about implementing fixes.
This "context anxiety" could actually enhance your creative flow:
However, this awareness can backfire. The model sometimes takes shortcuts or leaves tasks incomplete when it believes it's near the end of its window, even when it has plenty of room left.
Solution: Cognition discovered that enabling the 1M token beta but capping usage at 200k gives the model confidence to work normally without anxiety-driven shortcuts.
Sonnet 4.5 actively builds knowledge about the problem space through documentation and experimentation. It treats the file system as its memory, frequently writing summaries and notes for both you and its own future reference.
This behavior aligns perfectly with vibe coding principles:
# Project Summary - React Dashboard ## What We Built Today - User authentication system with JWT tokens - Dashboard layout with responsive design - Data visualization components using Chart.js - API integration for real-time data ## Key Decisions Made - Chose Material-UI for consistent design system - Implemented Redux for state management - Used React Query for server state caching ## Next Steps - Add user role management - Implement data export functionality - Add unit tests for authentication flow
The model is notably more proactive about writing and executing short scripts and tests to create feedback loops, showing good judgment about when to use this capability.
This is a game-changer for vibe coding because:
When editing a React app, the model gets the HTML of the page to check its work along the way, ensuring behavior is correct. This creates a natural feedback loop that maintains your creative momentum.
Sonnet 4.5 efficiently maximizes actions per context window through parallel tool execution—running multiple bash commands at once, reading several files simultaneously, and overlapping work where possible.
Parallel execution means:
These new AI behaviors could fundamentally enhance vibe coding by:
Cognition is exploring several exciting directions that could further enhance vibe coding:
The model's improved judgment about when to externalize state suggests it might handle subagent delegation more effectively, creating specialized AI assistants for different aspects of your project.
Early experiments suggest the model works well with verification systems, letting it reason about its own development process rather than just executing tasks.
The evolution of AI coding agents like Devin represents a fundamental shift toward more context-aware, proactive, and efficient development workflows. For vibe coders, this means AI assistants that better understand and support your creative process.
These new behaviors—context awareness, proactive documentation, automatic testing, and parallel execution—could make AI-assisted development feel more natural and supportive of your creative flow than ever before.
The future of vibe coding isn't just about better AI—it's about AI that understands and enhances your creative process, making you more productive while preserving the joy and flow that makes coding feel like art.
This blog post is based on insights from Cognition's technical blog about rebuilding Devin for Claude Sonnet 4.5.
Original source:Rebuilding Devin for Claude Sonnet 4.5: Lessons and Challenges
This post analyzes the technical insights from a vibe coding perspective, exploring how these new AI behaviors could enhance creative development workflows.