Broadcom shareholders got a brutal lesson this week in what happens when your biggest customer starts shopping around. Shares of the AI chip giant tumbled as much as 5.9% on Wednesday and finished the session down 4.61% at $362.48, wiping out roughly $87 billion in market capitalization in a single day. By Thursday's close the stock was still down nearly 13% for the week and sitting more than 20% below its 52-week high, even as the broader market got hammered by rising bond yields and a grim Walmart forecast.

The trigger: Alphabet's Google disclosed in an SEC filing that it has broadened its custom-chip alliance with Marvell Technology, handing Marvell a warrant to buy up to 58.97 million Marvell shares at $206.58 apiece — a stake worth up to $12.2 billion if fully exercised. The warrant vests over time and is tied to as much as $120 billion in qualifying product revenue through fiscal 2033. In exchange, Marvell will build custom silicon for Google covering AI inference accelerators, storage controllers, networking chips, memory interface controllers and near-memory computing — territory Broadcom has dominated for years as the lead outside designer of Google's Tensor Processing Units.

Marvell shares, unsurprisingly, went the other way, jumping roughly 9.8% to close at $237.27 and adding about $17 billion in value — a far smaller gain than Broadcom's loss, underscoring how jumpy investors have become about any crack in the AI-chip pecking order.

Wall Street Reacts

Broadcom's own agreement with Google, struck in 2025, technically runs through 2031 and remains intact. But the Marvell news confirmed what Broadcom's own chief executive had flagged months earlier. On the company's fiscal second-quarter earnings call, CEO Hock Tan told analysts a customer of Google's size was never going to stick with one supplier forever.

WE FULLY EXPECT THAT THERE WILL BE SOME DIVERSITY OF SOURCES FOR THEM.

That diversification arrived on schedule. Macquarie moved fastest, cutting its rating on Broadcom to Neutral from Outperform and slicing its price target 15% to $437 from $513, per a note reported by Investing.com. The bank now projects Broadcom's share of Google's TPU-related chip revenue sliding from roughly 95% this year to 80% in 2027 and 65% in 2028 as both Marvell and MediaTek carve out bigger roles.

Not every analyst is convinced Broadcom is actually losing ground. Morningstar called the Marvell pact "another endorsement of Marvell's custom silicon strategy as it lands a brand new blue-chip customer," framing it as evidence the overall AI chip market is expanding rather than proof Broadcom is being displaced. The bull case leans on Broadcom's own numbers: AI semiconductor revenue hit $10.8 billion last quarter, up 143% year-over-year, and the company has guided for more than 200% growth to $16 billion in the current quarter, with management pointing to a path toward $100 billion in annual AI chip revenue by 2027.

The next real test comes fast. Marvell reports earnings on August 27, followed by Broadcom on September 2, when investors will get their first hard look at whether the Google deal is already showing up in either company's order books — or whether Wednesday's selloff was an overreaction to a threat that's still mostly theoretical.