TypeScript 7 VS Code extension never activates for workspaces where only content-mapped files are opened

Start with packages/vscode-typescript/package.json and its activationEvents, then reproduce the workspace containing only a content-mapped file with js/ts.experimental.useTsgo and js/ts.contentMappers.enabled enabled. Compare the available activation strategies in the issue and verify that the extension activates and provides TypeScript 7 language features without opening a separate .ts or .js file.

🔎 Search Terms

• vscode-typescript activationEvents content mapper contentMappers
• TypeScript 7 extension does not activate
• onLanguage:typescript native-preview

🕗 Version & Regression Information

• The TypeScript 7 VS Code extension built from packages/vscode-typescript at f29aeb9 (main, 2026-09-16), running 7.1.0-dev.20260918.1 (@typescript/typescript-darwin-x64), VS Code 1.138.0, macOS 26.6 x64
• Same activationEvents in the published TypeScriptTeam.native-preview 0.20260708.2 and in current main, so not a regression

⏯ Playground Link

n/a (VS Code extension behaviour)

💻 Code

packages/vscode-typescript/package.json declares only

"activationEvents": [
  "onLanguage:javascript",
  "onLanguage:javascriptreact",
  "onLanguage:typescript",
  "onLanguage:typescriptreact"
]

A workspace whose tsconfig.json declares a content mapper for another extension:

{
  "contentMappers": [{ "package": "@tsrx/content-mapper", "extensions": [".tsrx"] }],
  "include": ["*.ts", "*.tsrx"]
}

Steps, with js/ts.experimental.useTsgo: true and js/ts.contentMappers.enabled: true:

1. Open the workspace and open a .tsrx file (or any file of a content-mapped language).
2. Observe: the extension is not activated (vscode.extensions.getExtension("TypeScriptTeam.native-preview").isActive === false), no language server starts, the file gets no diagnostics, hover or completions from TypeScript 7.
3. Open any .ts or .js file in the same window: the extension activates, the server starts, and the .tsrx file is served correctly from then on (its tsconfig mapper is picked up, diagnostics and hover appear).

🙁 Actual behavior

A workspace where the user only opens content-mapped files never gets TypeScript 7 features, with no indication why. From the user's point of view the mapped language's tooling looks broken; opening an unrelated .ts file "fixes" it.

🙂 Expected behavior

The extension should also activate when it may have work to do for content-mapped files, for example:

• workspaceContains:**/tsconfig.json (or **/jsconfig.json), or
• onStartupFinished when js/ts.experimental.useTsgo is on (it already reads the setting on activation and returns early when it is off), or
• an activation hook for extensions that declare a content mapper.

Additional information about the issue

Found while wiring the TSRX VS Code extension to TypeScript 7 content mappers (tsrx-org/tsrx#135). The built-in TypeScript extension does not have this gap in practice because VS Code activates it on other events as well (onLanguage:jsonc among them), so on TypeScript 5/6 the same workspace works.