Using Windsurf Flow to refactor a legacy React codebase with Context API

Context API sprawl is the silent killer of React performance; once you hit that tipping point where every state change triggers a full-tree re-render, you're basically fighting the framework. I spent the last few days using Windsurf's "Flow" mode to migrate a legacy dashboard from a monolithic GlobalContext to a more granular, sliced architecture, and the difference in agentic behavior compared to standard Copilot is night and day.

The biggest hurdle with legacy refactors is context. Standard LLMs often hallucinate the shape of your state because they only see the open file. Windsurf's Flow actually indexes the dependency graph, so when I told it to "split the UserContext and ThemeContext into separate providers," it didn't just write the code—it proactively searched for every single useContext(GlobalContext) call across 40 different files to update the imports.

Here is the workflow that actually worked without breaking the build:

Step 1: The Mapping Prompt
I didn't start by coding. I started by making the agent audit the state. I used a prompt in the Flow console:

Analyze GlobalContext.tsx and find all state slices that are accessed by less than 20% of the components. List them as candidates for splitting to avoid unnecessary re-renders.

This gave me a concrete list of what to decouple instead of guessing.

Step 2: The Atomic Migration
Instead of a "do it all" prompt, I used a loop. For each slice (e.g., UserSettings), I commanded:

Extract UserSettings state from GlobalContext into a new UserSettingsContext. 
1. Create UserSettingsContext.tsx.
2. Update GlobalContext.tsx to remove these fields.
3. Update all consuming components to use UserSettingsContext.
4. Ensure the Provider wrapping order in App.tsx maintains the correct dependency hierarchy.

Step 3: Handling the "Gotchas"
The agent initially struggled with the Provider nesting. It tried to put the new providers inside the old one, which didn't make sense. I had to intervene and explicitly tell it to flatten the provider tree in App.tsx.

One technical tip: if you're using TypeScript, the agent occasionally loses track of the Context type definitions during the split. I found that keeping the types.ts file open in a pinned tab helped the Flow agent maintain type safety across the refactor.

The productivity gain was massive. Manually updating 40+ files for a context split is tedious and error-prone. With Flow, the "thinking" phase (where it maps the file references) takes about 10 seconds, and the execution takes another 30. I spent more time reviewing diffs than actually typing.

Performance Result:
Bundle size: Slightly increased due to more provider wrappers (negligible).
Renders: Using the React DevTools profiler, I saw a 60% reduction in wasted renders on the main dashboard because the ThemeContext updates no longer trigger a re-render of the UserAccount components.

If you're still using Cursor's Composer for this, try Windsurf's Flow for deep refactors. The way it handles the "context" of the codebase (pun intended) feels more like a pair programmer who has actually read the whole repo rather than a smart autocomplete.