[heft] `The TypeScript compiler version 5.9.3 is newer than the latest version that was tested with Heft (5.8); it may not work correctly.`

[eliw00d]

Summary

The NEWEST_SUPPORTED_TS_MINOR_VERSION constant is still set to 8. TypeScript 5.9 was released on Aug 1, 2025. Despite this and the warnings emitted, everything seems to be working as expected.

Repro steps

1. Install TypeScript 5.9.3 and run rush commands.
2. See: The TypeScript compiler version 5.9.3 is newer than the latest version that was tested with Heft (5.8); it may not work correctly.

Expected result: No warnings about TypeScript 5.9.3 being incompatible.

Actual result: Warnings about TypeScript 5.9.3 being incompatible.

Details

Standard questions

Please answer these questions to help us investigate your issue more quickly:

Question	Answer
@rushstack/heft version?	1.1.7
Operating system?	Mac
Would you consider contributing a PR?	Yes
Node.js version (node -v)?	24.11.1