Shares of Zeta ripped higher today -- and they haven't stopped even after the bell rang thanks to a new partnership.

Starting the first full week of trading in 2026 on an auspicious note, Zeta Global Holdings Corp. climbed 8.8% during regular trading hours.

But the bulls' appetite for the advertising stock grew only larger after the bell rang. The company announced a collaboration with OpenAI, and investors are clearly thrilled. As of 8:34 p.m., Zeta Global stock was up 10% from where it ended after today's regular trading session.

The particulars of the new partnership

Zeta announced today that it will utilize OpenAI models to support Athena, Zeta's artificial intelligence (AI) agent, which integrates with its Zeta Marketing Platform. This integration provides marketing professionals with voice-activated answers and an adaptive interface.

Lauding the deal with OpenAI, Zeta Global CEO and co-founder David A. Steinberg, stated, "We've formed many partnerships throughout Zeta's history, but none will be more instrumental than the one we are embarking on with OpenAI."

In addition to its collaboration with OpenAI, Zeta announced that Athena's first two agentic applications, Insights and Advisor, have entered the beta phase of development. The company plans to launch Athena to all customers by the end of the first quarter of 2026.

Is it too late to buy Zeta Global stock now?

While Zeta Global's partnership with OpenAI is certain. Investors seeking to diversify their exposure to AI stocks should conduct thorough due diligence before clicking the buy button. Although OpenAI is a powerhouse in the burgeoning field of generative AI, savvy investors recognize that there's much more to a sound investment than a company deciding to partner with an industry leader.