With Anthropic's mega-IPO imminent, a "rush to launch" has swept through the US IPO market.

AI unicorn Anthropic is about to launch a historic IPO comparable in size to SpaceX, reshaping the rhythm of the entire US IPO market. Multiple companies are vying to complete their listings before this mega-deal, but the window of opportunity is limited—the Federal Reserve's interest rate meeting, the midterm elections, and inflationary pressures are all looming, making the scheduling game between underwriters and issuers unprecedentedly complex.

According to Bloomberg, Anthropic is preparing to file for an IPO, with the fundraising expected to match or even surpass SpaceX's record $86.2 billion. The impending mega-deal has left some companies and their investors struggling to attract long-term investors and sovereign wealth funds.

"This will be a very busy September and continue into October," said Rob Stowe, head of equity capital markets for the Americas at Barclays. He anticipates a highly concentrated window of IPOs from Labor Day until the election.

The market consequences have already served as a cautionary tale: a month before SpaceX's IPO, 14 sizable companies rushed to list, but these hastily listed companies suffered a weighted average loss of 9.5% after listing.

The overall performance of the US market is also unsatisfactory – the weighted average return of US IPOs this year is only 5.6%, far behind the 13% increase of the S&P 500 and the 17% increase of the Nasdaq 100.

The window for scrambling to get ahead has been drastically compressed, and the competition for scheduling has become fierce.

The window of opportunity between Labor Day and the midterm elections in November was already limited, and the Federal Reserve's mid-September policy meeting further squeezed issuers' room for maneuver. Meanwhile, higher-than-expected inflation data is exacerbating uncertainty, prompting more companies to enter the market earlier than to wait and see.

Doug Adams, co-head of global equity capital markets at Citigroup, predicts that six or more companies will each raise more than $1 billion between Labor Day and the election. He stated that many large companies are assessing market timing, "focusing not only on what the market is doing, but also on when is the right time for the company to go public."

The queue of companies waiting to go public is impressive. Cloud computing company Nscale has joined Anthropic in the IPO queue; smart health ring maker Ora Health Oy may launch a multi-billion dollar IPO as early as next month; privately backed temporary power service provider Aggreko Plc and solar and energy storage company CoVolt Power Inc. both filed for IPOs in August and are expected to list before Anthropic.

In addition, SoftBank Group's digital infrastructure company SB Energy plans to raise more than $5 billion, and Roark Capital's Inspire Brands Inc. may also test the market before the election. Switch Inc. secretly filed for an IPO earlier this month and raised nearly $50 billion in a new round of funding in July.

AI-themed companies enjoy exclusive traffic, while non-themed companies are neglected.

With AI becoming a "monthly theme" in the market, funds are highly concentrated in specific sectors, making it increasingly difficult for non-themed companies to go public.

Eddie Molloy, co-head of global equity capital markets at Morgan Stanley, bluntly stated: "Non-thematic IPOs are more difficult to pursue. The amount of capital tied up in broad themes like the AI infrastructure ecosystem and aerospace and defense is enormous. If you're a small to medium-sized issuer unrelated to these trends, attracting buyer attention is even more challenging."

The clustering of large deals has also suppressed the visibility of smaller financing rounds. JD Moriarty, Vice Chairman and Head of Global Technology Equity Capital Markets at Bank of America, stated, "If a company is relatively small, we would advise caution. The market is very likely to ignore them because there are too many large deals to choose from."

The overall performance of major IPOs this year has also been disappointing. According to data compiled by Bloomberg, the 16 companies that raised more than $1 billion saw a weighted average post-IPO share price increase of only 4.2%, and six of the top ten IPOs still have share prices below their offering price.

SpaceX's post-IPO gains were less than 5%, and SK Hynix Inc.'s record-breaking post-IPO stock price also experienced dramatic fluctuations, both closely related to the repeated shifts in investor sentiment towards AI trading.

Market sentiment has improved, providing a brief window for entry.

Despite significant pressures, the recent market stabilization provides some support for issuers. The S&P 500 has rebounded 5.4% from its July lows, and the Nasdaq 100 has risen more than 8% over the same period, helping companies to justify their entry into the market now.

Positive signs are emerging in the biotechnology sector. According to Bloomberg Intelligence analysts Sam Fazeli and Cindy Wu, the average fundraising size for US biotechnology IPOs in 2026 will reach $329 million, the highest level since 2018, far exceeding recent performance, with 30 listings expected throughout the year, demonstrating strong year-end momentum.

Overall, market participants generally expect a surge in IPOs from September to October before Anthropic's official launch. However, the issuance window is highly concentrated and competition is fierce, and the timing of the IPOs by issuers and underwriters will directly affect the success or failure of the transactions.

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