Compatibility

tsz is close to tsc compatibility across diagnostics, emit, and editor behavior. The remaining work is concentrated in real-project compile readiness and the last release-gate gaps tracked below.

Currently tracking TypeScript 6.0.3.

Type Checking

The conformance suite compares tsz diagnostics with tsc on TypeScript's own compiler tests. This is the main signal for whether tsz agrees with tsc about types and errors.

Type checking
100.0%

12,583 of 12,585 compiler tests match tsc.

Emit

Emit compatibility means the generated output matches what TypeScript users expect from tsc. JavaScript emit and declaration emit are tracked separately because they fail for different reasons and matter to different users.

JavaScript emit
100.0%
Declaration emit
100.0%

JavaScript emit is at 100.0% (1 skipped). Declaration emit is at 100.0% (11,862 skipped).

Language Service

The language-service suite checks editor-facing behavior: completions, hover, go-to-definition, diagnostics, and related workflows that developers feel in an IDE.

Editor behavior
99.9%

6,556 of 6,562 editor tests match the TypeScript suite.

Project compatibility

These rows track real project fixtures that tsc accepts. A green row means tsz completed the same project check; red or yellow rows identify the current compatibility blocker.
utility-types green exit success check 5 files 34 MiB peak
ts-essentials green exit success check 95 files 35 MiB peak
RxJS green exit success check 240 files 39 MiB peak
type-fest green exit success check 206 files 42 MiB peak
ts-toolbelt yellow nonzero exit check 242 files 232 MiB peak
Zod yellow nonzero exit check 8 files 268 MiB peak
Kysely yellow nonzero exit check 272 files 798 MiB peak
type-challenges solutions green exit success check 78 files 20 MiB peak
generated Vite app green exit success check 4 files 78 MiB peak
generated Next app green exit success check 7 files 89 MiB peak
large-ts-repo red timeout timing 6,061 files —
Next.js full project green exit success check 1,396 files 222 MiB peak
Valibot red timeout check 1,083 files 1,623 MiB peak
MSW yellow nonzero exit check 156 files 244 MiB peak
Comlink yellow nonzero exit check 3 files 122 MiB peak
Effect red timeout check 363 files 785 MiB peak
Drizzle ORM red timeout check 448 files 1,378 MiB peak
ts-rest yellow nonzero exit check 30 files 174 MiB peak
ofetch yellow nonzero exit check 7 files 51 MiB peak
ts-pattern yellow nonzero exit check 18 files 181 MiB peak
tRPC yellow nonzero exit check 107 files 263 MiB peak
TanStack Query yellow nonzero exit check 49 files 213 MiB peak
TanStack Router yellow nonzero exit check 62 files 301 MiB peak
Zustand yellow nonzero exit check 16 files 59 MiB peak
Jotai yellow nonzero exit check 37 files 215 MiB peak
fp-ts yellow nonzero exit check 123 files 869 MiB peak
io-ts yellow nonzero exit check 16 files 192 MiB peak
Immer yellow nonzero exit check 17 files 47 MiB peak
Remeda red timeout check 522 files 697 MiB peak
ts-morph red timeout check 1,007 files 1,316 MiB peak
ArkType yellow nonzero exit check 154 files 255 MiB peak
Superstruct yellow nonzero exit check 8 files 35 MiB peak
Runtypes yellow nonzero exit check 76 files 218 MiB peak
HotScript yellow nonzero exit check 39 files 61 MiB peak
TypeBox red timeout check 709 files 767 MiB peak
class-transformer yellow nonzero exit check 35 files 38 MiB peak
TypeGraphQL yellow nonzero exit check 116 files 251 MiB peak
neverthrow yellow nonzero exit check 5 files 219 MiB peak
XState yellow nonzero exit check 72 files 275 MiB peak
MobX red crash check 58 files 218 MiB peak