6.0.20260203 -> 6.0.20260205 breaks TS default setting

When updating JavaScript and TypeScript Nightly from version 6.0.20260203 to 6.0.20260205, VSCode starts complaining about strict errors even though we don't have strict check enabled. We do have some sub options of strict enabled, but not all.

It might be two separate errors, but I'm writing them both as I noticed them both in the same project with the same configs..
If needed, I can separate it out into two issues.

On 6.0.20260205 it's having issues, unable to parse @types/jest, even though it's installed (though as a dep, not devDep):

Cannot find name 'beforeEach'. Do you need to install type definitions for a test runner? Try `npm i --save-dev @types/jest` or `npm i --save-dev @types/mocha` and then add 'jest' or 'mocha' to the types field in your tsconfig.

and

Unable to resolve signature of parameter decorator when called as an expression.
  Argument of type 'undefined' is not assignable to parameter of type 'string'. ts(1239)

So I downgraded to 6.0.20260204, the jest issue was no more, but the other things were. Setting strict: false, even though it should be default false, solves the ts(1239) issue, but the jest types issue remains on 6.0.20260205 even if I have strict: false.

We are using an old version of node and TS though, dunno if it's relevant or not:

package.json

...
"engines": {
    "node": "^14.19.0",
    "npm": "^6.14.18"
  },
...
"dependencies": {
    "@types/jest": "29.5.14",
   "jest": "29.7.0",
...
},
"devDependencies": {
    "typescript": "4.9.5",
...
}

main parent project tsconfig

{
  "compileOnSave": false,
  "compilerOptions": {
    "module": "commonjs",
    "moduleResolution": "node",
    "target": "ES2020",
    "sourceMap": true,
    "experimentalDecorators": true,
    "noImplicitAny": true,
    "preserveConstEnums": true,
    "noEmitOnError": true,
    "outDir": "./src",
    "noImplicitThis": true,
    "importHelpers": true,
    "alwaysStrict": true,
    "strictBindCallApply": true
  },
  "include": [
    "ts/**/*.ts"
  ],
  "exclude": [
    "node_modules"
  ]
}

{
  "extends": "./node_modules/<parent-module>/tsconfig.json",
  "compilerOptions": {
    "declaration": true,
    "outDir": "./",
    "rootDirs": [
      "node_modules/<another-module>/"
    ]
  },
  "include": [
    "ts/**/*.ts"
  ],
  "exclude": [
    "node_modules"
  ]
}

Node version

$ node --version
v14.21.3

VSCode about info

Version: 1.108.2
Commit: c9d77990917f3102ada88be140d28b038d1dd7c7
Date: 2026-01-21T13:52:09.270Z
Electron: 39.2.7
ElectronBuildId: 12953945
Chromium: 142.0.7444.235
Node.js: 22.21.1
V8: 14.2.231.21-electron.0
OS: Linux x64 6.14.0-37-generic

Reproduce the report in VS Code using TypeScript Nightly 6.0.20260203 through 6.0.20260205, the supplied tsconfig files, and the listed Node, Jest, and @types/jest versions. Compare the strict-default and decorator diagnostics and the @types/jest resolution; done means the regression is isolated and both diagnostics behave as expected without explicit strict settings.