Cursor Agent Window: AI SDK v5 Migration First Try

Put off a dependency migration for 2 months because they usually break everything. Cursor shipped Agent Window and Plan Mode, so I tested if it could handle a real AISDK v4 to v5 refactor on my production app. The result? Migration completed first try. No errors. No context loss. No chat restarts. Here's what actually made the difference: - Agent Window's real-time diff view (vs the old chat sidebar) - Plan Mode forcing clarification before code changes - Two MCPs (ref.tools and exa.ai) pulling live AISDK v5 docs - Vercel AI Gateway integration handled in one shot This was VibeStamps.com - a Next.js app using AISDK for timestamp generation. The refactor touched package dependencies, API routes, and migrated to Gemini 2.5 Pro through the new gateway. Without the MCPs, Cursor would have been guessing about v5 patterns since it just launched. Without Plan Mode, it probably would have YOLO migrated and broken half the app. The Agent Window layout let me catch potential issues in real-time instead of cleaning up afterwards. That said - this was a focused refactor on one app. I'm testing if this holds up for larger projects and multiple agents working in parallel. Tools tested: - Cursor 2.0 with Agent Window - Plan Mode (pre-flight clarification) - ref.tools MCP (documentation) - exa.ai MCP (semantic search) - AISDK v5 - Vercel AI Gateway - Gemini 2.5 Pro 🕒 Timestamps 00:00 Putting Cursor's new Agent to a real-world test 01:04 Defining the refactor: AISDK v5 and Vercel AI Gateway 02:09 Explaining the new Agent Window UI vs the chat sidebar 04:08 How Plan Mode forces the AI to think before coding 06:01 Explaining the critical role of MCPs (ref.tools & exa.ai) 07:23 The live refactor begins with the AI agent driving 08:46 Migration completes successfully in a single attempt 09:54 Recap: Why the Agent Window, Plan Mode, and MCPs worked 11:06 Final thoughts and preview of managing multiple agents MCP setup guide: https://youtu.be/W4aLlxapvr4 VibeStamps source code: https://github.com/RayFernando1337/vibestamps Tired of AI giving you garbage code? I'll be your senior dev for 5 days. → The AI Architect Intensive: https://rfer.me/1337 What you get: ✅ 5 days of 1-on-1 senior guidance (same time daily) ✅ Fix your broken prompting permanently ✅ Ship real features by Day 5 ✅ Your money back if you don't ship working code Only $1,337 • 3 spots per week • US/Europe/Asia welcome SUPPORT THE CHANNEL Join 200+ builders in our private Discord where we ship AI apps together: https://rfer.me/discord