Meta Platforms shares have finally delivered the breakout that bulls had long been waiting for.

With the launch of its personal AI assistant Muse, which quickly climbed to the top of app rankings, Meta shares have risen 36% since the start of September, easing market concerns that its massive AI spending would fail to generate returns.

The stock is on track for its best monthly performance since July 2013 and is only about 1% away from joining the ranks of companies with a market value of at least $2 trillion.

Rob Biederman, co-founder and managing partner of Asymmetric Capital Partners, said: "Muse clearly validates Meta's AI strategy and market position. Over the past year and a half, the stock was essentially range-bound because investors did not know whether AI was a positive or a negative for the company." He also said AI agents are expected to become the main gateway for many people to access the internet, which would put Meta in a more favorable competitive position.

Meta shares rose as much as 0.4% in premarket trading on Friday and are poised for a third straight session of gains.

This month's rally marks a sharp reversal for Meta shares. For most of this year, the stock was weighed down by high AI spending and litigation risks related to its social media business. Less than six weeks ago, after releasing a disappointing revenue outlook in late July, Meta's year-to-date decline reached 18%; as of August 18, the stock was among the 50 worst performers in the S&P 500.

But since then, Meta has gained 43% cumulatively, making it the third-best performer in the S&P 500 over the same period. The rebound began after Meta agreed late last month to pay up to $18 billion to settle a social media lawsuit, removing a major source of pressure on the stock.

Still, the biggest driver of the share price increase remains investor expectations for Meta's new AI products and their potential revenue contribution. That has also led investors such as Biederman to believe that Meta shares still have room to rise further.