Anthony Levandowski, the former Google engineer at the center of a battle between the tech giant and Uber Technologies Inc., was never a typical employee. And for years, Google was fine with that.

Weeks after Google hired him in 2007 to work on a global photo database called Street View, Mr. Levandowski, then 27 years old, registered a startup to sell a sensor system to Google for the same project, according to public records and former employees of both companies.

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