Initial Update: Monday, 27 July 2015 18:00 UTC
We are actively investigating issues with TypeScript errors on Visual Studio Online hosted build service. Some customers may experience an error about “…TypeScript\1.4\1.4\tsc.exe" is invalid. This webpage gives more information of this issue: https://github.com/Microsoft/TypeScript/issues/3493
We are applying the workaround to the targets file on the VM and it will be updated in next few hours.
We sincerely apologize for any inconvenience this may be causing you.
Sincerely,
VS Online Service Delivery Team