Starting with TypeScript 7, a compiler port using native code will unlock “better raw performance, memory usage, and parallelism.”
For years, the TypeScript compiler has been the heartbeat of modern web development, yet its reliance on JavaScript has created a performance ceiling for massive codebases. That ceiling is about to be shattered.
This initiative, codenamed Project Corsa, is a complete re-platforming of the ecosystem’s core. For engineering leads, this shift from the legacy ‘Strada’ codebase to a native binary represents a pivotal change in how development cycles are managed and promises to slash build times while reducing the hardware footprint of CI/CD pipelines.
Efficiency drives this overhaul. As projects scale, single-threaded compilation becomes a costly bottleneck. By moving to native code, TypeScript 7 leverages shared-memory parallelism, meaning it can “build up multiple projects in parallel” rather than churning through them sequentially.
The early data suggests the returns are massive.
In benchmarks shared by the team, the build time for the sentry project collapsed from 133.08 seconds using the current compiler to just 16.25 seconds with the native port—an 8.19x speedup. The vscode codebase saw similar gains, dropping from 89.11 seconds to 8.74 seconds. Even without incremental build settings, “TypeScript 7 often sees close to a 10x speedup over the 6.0 compiler on full builds.”
For organisations paying for compute by the minute, or developers losing hours to local compile cycles, these are direct operational savings.
Rewrite projects are notorious. They often stall, break, or remain stuck in “beta” limbo for years. Microsoft argues this one is different. “For a lot of developers, a project rewrite might feel entirely theoretical until it’s finally released. That’s not the case here,” asserts Daniel Rosenwasser, Product Manager of the TypeScript team.
The native language service is already functional and many core features are reimplemented and stable. While earlier iterations were reportedly “crashy,” the re-architected service is “more robust, and should be able to handle codebases, both big and small, without issues.”
Reliability figures back this up. Of roughly 20,000 compiler test cases, the native build matches the error reporting of the legacy version in all but 74 instances. The team notes that the remaining gaps are largely “known incomplete work” or intentional changes, meaning engineering teams “can confidently use TypeScript 7 today to type-check your project for errors.”
Navigating the upgrade to TypeScript 7
Of course, speed has a price. To streamline the new architecture, TypeScript 7 will jettison legacy baggage.
This release is opinionated. The –strict flag will be enabled by default, enforcing tighter type safety across the board. Support for older environments is also shrinking: –target es5 is being removed, making es2015 the absolute floor for compilation targets.
Teams relying on complex JSDoc patterns for type-checking will also face friction. The team has “stripped down some of our support for complex and some less-used patterns,” meaning tags like @enum and @constructor are no longer recognised.
Perhaps the biggest operational hurdle transitioning to TypeScript 7 is toolchain fragmentation. The new native compiler does not support the existing API used by the current JavaScript compiler. This breaks compatibility for third-party tools – linters, formatters, and plugins – that depend on the old architecture.
The workaround? Run them side-by-side. The team suggests using the standard package for tooling and the native preview (tsgo) for raw build speed. To help with configuration migration, they are experimenting with a tool called ts5to6 to automate updates to tsconfig.json files.
Microsoft is clear: there is no turning back. There will be no TypeScript 6.1.
“TypeScript 6.0 will be our last release based on the existing TypeScript/JavaScript codebase,” Rosenwasser declared.
The 6.0 release serves solely as a bridge to the native future. Once released, the legacy codebase enters strict maintenance mode, receiving patches only for security issues or high-severity regressions. The team is “very unlikely to merge pull requests into 6.0,” focusing their entire velocity on bringing the native TypeScript 7 port to parity.
See also: How agentic AI coding tools change software development
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