TypeScript 7 is ~10× faster. Why your CI often only gets ~28%

The headline vs. the CI reality

TypeScript 7’s native compiler is a genuine leap. On a fast laptop, with type-heavy application code, teams report large speedups, sometimes approaching the “~10×” marketing number.

So why did one client’s CI only get about 28% faster?

Because CI is a different machine, with different constraints:

• Fewer or noisier cores than a developer laptop
• Cold or shared caches
• Full-program checks that still walk a large graph
• Workloads dominated by structure, not raw checker throughput

The native compiler is a gift. It does not rewrite a monorepo that re-checks everything on every PR.

What the real numbers look like

A useful way to talk about TypeScript 7:

Treat “10×” as best-case local type-check throughput, not a promise for every tsc invocation in every pipeline.

What actually moves build times

With or without TypeScript 7, the same patterns show up in audits:

1. Barrel files, index.ts re-exports that pull huge module graphs into every check
2. Giant unions & deep conditionals, type instantiations explode across call sites
3. skipLibCheck off, re-checking .d.ts from node_modules every run
4. No incremental builds, no .tsbuildinfo cache locally or in CI
5. Monorepos without project references, one giant program instead of tsc -b

Often the highest-ROI change is a one-line import fix:

// Before, pulls the whole components barrel into the check
import { Button } from "@/components";
 
// After, keeps the graph small
import { Button } from "@/components/Button";

How to evaluate TypeScript 7 on your repo

1. Record a baseline: npx tsc --noEmit --extendedDiagnostics
2. Upgrade on a branch; keep the same tsconfig shape first
3. Re-run the same command locally and in CI
4. Compare wall-clock and check time, don’t only look at laptop numbers
5. Only then invest in structural fixes (references, barrels, type complexity)

If CI barely moves but local feels transformed, you learned something useful: your bottleneck is environment + graph, not “TypeScript is slow.”

Bottom line

TypeScript 7 can make the checker dramatically faster. It will not rescue a build that is slow for structural reasons. Measure both environments, then fix config, types, and CI so the native compiler’s gains stick.

Want the short version? Your config. Your types. Your CI. Those still decide most of the bill.