"However, there were several major caveats to the arrangement that persisted until 1912: [...] and reserved the right to in any case to retain a free hand in sending the bulk of its forces against either Germany or Austria-Hungary. St. Petersburg had contended with Vienna for Balkan advantage, and the Romanovs had scores to settle with the Habsburgs that dated to the Crimean War. Whatever, the interpretation of alliance obligations, Russian planners always remained uncertain whether Germany might turn east or west at the onset of a European war. For Russia, the difference was significant. It was plus or minus roughly thirteen German corps, or perhaps as many as six field armies."
From: HAMILTON R.F. and HERWIG H.H. eds., War Planning 1914, Cambridge, 2010, pp. 82-83.
So let's say Russia stuck with the pre-1912 arrangement and then witnesses how the Germans in 1914 deploy the bulk of their forces westward. Rather than upholding alliance commitments to attack Germany, the Romanovs get overjoyed at a chance to crush the Habsburgs. So Russia stays on the defensive against the Germans and focuses all its forces on Austria-Hungary to relieve Serbia. The Tenth Army stays as a defending forces while the First and Second Armies, earmarked for operations in East Prussia IOTL, go to Galicia. What happens? Would the Russians break out beyond Galicia with these additional forces before Germany can come to Austria-Hungary's aid? How is the Western Front affected?