Wall Street’s hopes for a blockbuster IPO season are starting to fade as market volatility hits investor enthusiasm. Companies like SB Energy and Holtec delayed or withdrew plans due to rising bond yields. Shares of new firms, which were up 24% in June, now show gains of less than 1%.

Investors had been lining up for a parade of IPOs this fall, expected to be headlined by a gigantic and record-setting offering from Anthropic. But volatility in oil prices and rising bond yields, as well as an intensifying debate around AI safety, have dented investor enthusiasm and prompted many of the companies to revisit their listing plans.

SoftBank-backed data-center company SB Energy has delayed its IPO date after getting pushback on its potential valuation, according to people close to the deal. Many on Wall Street expected Nvidia-backed cloud startup NScale to launch its roadshow pitch to investors as early as next week, but some now anticipate the timing could change, other people familiar with the matter said. Nuclear-reactor company Holtec withdrew its IPO filing earlier this month, citing unfavorable market conditions.

Dunkin’ owner Inspire Brands originally considered a late 2026 or early 2027 IPO, other people familiar with the matter said. But it is now unlikely to go public this year unless shares in publicly traded restaurant rivals begin to trade better, they said.

AI giant Anthropic is weighing November for a potential listing after originally considering earlier in the fall, The Wall Street Journal has reported. Anthropic’s timing shifted as a debate over AI’s safety and the potential for AI agents going rogue gripped the world.

Its rival OpenAI, which filed for an IPO within days of Anthropic this spring, has pushed its own IPO off until at least next year, suggesting it wants to hold off until more safety-related work can be done in the industry.

The string of delayed offerings illustrates how quickly investors’ enthusiasm for shares of risky new companies can cool. Investors were clamoring for newly issued shares when SpaceX raised $86 billion in its seemingly goldilocks debut in June—and getting rewarded for it until recently.

At the end of June, shares in U.S. companies that had gone public this year were up 24% on average from their IPO prices, according to Dealogic. That premium by new issues has since evaporated; as of Tuesday morning, shares in U.S. companies that went public so far this year are up less than 1% on average from their IPO prices.

Fund managers say they are less eager to take risky bets as geopolitical events roil markets. Others say they are getting choosier when it comes to IPOs, with some reserving capital for Anthropic stock.

The IPO market is notoriously finicky and could yet bounce back this year if investor sentiment or market conditions improve. IPO volume surged in 2021 before going into a several-year freeze that began to thaw in 2025. If Anthropic proceeds with its offering this year, U.S. IPOs would likely break 2021’s annual record for money raised by new issues.

Write to Corrie Driebusch at corrie.driebusch@wsj.com