🎯 Changes

I'm using TanStack Form for a large-scale form application. The project manages user-addable table rows (each row containing multiple inputs) along with 20-30 additional fields on a single page. During form submission, UI blocking of 2.7 seconds, and in some cases 8-10 seconds, was occurring.

After profiling, I identified that the __flush_internals function in @tanstack/store was causing a performance bottleneck due to excessive recursive calls.

Change the data structure of __depsThatHaveWrittenThisTick from Array to Set, replacing O(n) includes() with O(1) has() for duplicate checking.

- current: [] as Array<Derived<unknown> | Store<unknown>>,
+ current: new Set<Derived<unknown> | Store<unknown>>(),

- if (__depsThatHaveWrittenThisTick.current.includes(derived)) {
+ if (__depsThatHaveWrittenThisTick.current.has(derived)) {

- __depsThatHaveWrittenThisTick.current.push(derived)
+ __depsThatHaveWrittenThisTick.current.add(derived)

- __depsThatHaveWrittenThisTick.current = []
+ __depsThatHaveWrittenThisTick.current.clear()

Benchmark

✅ Checklist

• I have followed the steps in the Contributing guide.
• I have tested this code locally with pnpm test:pr.

🚀 Release Impact

• This change affects published code, and I have generated a changeset.
• This change is docs/CI/dev-only (no release).