Detect stale tsx versions when launching TypeScript AppHosts in VS Code

Summary

TypeScript AppHosts can show a runtime warning when VS Code launches the project's installed tsx and the lockfile still resolves tsx 4.21.0 or older.

The immediate workaround is:

npm install --save-dev tsx@latest

VS Code must then be reloaded before the warning disappears.

Reproduction

1. Open an existing TypeScript AppHost whose package lock resolves tsx 4.21.0 or older.
2. Start or debug the AppHost from VS Code using the Aspire extension.
3. Observe the tsx warning.
4. Upgrade tsx to the latest version and reload VS Code.
5. Start or debug the AppHost again; the warning no longer appears.

Current behavior

• The current TypeScript starter references tsx ^4.22.3, so newly installed projects normally avoid this.
• Existing projects can retain the stale version in their lockfile.
• The brownfield TypeScript setup in TypeScriptLanguageSupport still ensures only tsx ^4.21.0, which does not prevent the affected version.
• Aspire launches the app's locally installed tsx, but does not detect this condition or explain the corrective action.

Expected behavior

Aspire should prevent or diagnose this condition rather than relying on users to recognize a tsx warning. Possible approaches:

• raise the minimum tsx version used by TypeScript AppHost setup;
• detect the resolved installed version during tooling validation and provide an actionable message; or
• add a focused troubleshooting note until existing projects are covered by product diagnostics.

The diagnostic should account for npm, pnpm, Yarn, and Bun projects and should tell VS Code users to reload the window after updating the dependency when necessary.

Created from a Microsoft Teams conversation.