China's CXMT (memory manufacturing giant) surges 466% to $489 billion market cap on IPO debut, signaling geopolitical shift in semiconductor supply.

Stocks on Wall Street were mixed as Nvidia and other chip companies weighed on the tech-heavy Nasdaq. The concerns were revived by reports that Nvidia was providing a US$250 billion backstop to help finance an OpenAI data centre project in Ohio. In contrast, software firms Salesforce and Microsoft were among those helping to buoy the blue-chip Dow Jones Industrial Average.

Meanwhile, Chinese memory chip maker CXMT soared in its debut to become the most valuable listed company in Mainland China, surging 465% on the Shanghai Stock Exchange's Star Market to reach a valuation of about 3.28 trillion yuan. Separately, Dutch chipmaking equipment manufacturer ASML declined after reports that a state-backed Chinese company had begun mass production of lithography machines that have been dominated by the European firm.

"Reports that Nvidia could provide a roughly US$250 billion backstop for an OpenAI-related data centre project have raised fresh questions about circular financing within the AI ecosystem and how much future demand is being supported by suppliers financing their own customers," said Moomoo market strategy consultant Greg Boland. "The concern comes at an important time, with Microsoft and Meta reporting Wednesday followed by Apple and Amazon Thursday, putting AI spending, orders and returns on that investment firmly in focus."

The Nasdaq Composite fell 0.4% in late trading with Nvidia down 4.5%. The Dow was up 0.4% and the S&P 500 was marginally higher in late trading. Across the Atlantic, markets were stronger with the UK's FTSE 100 up 0.4%, Germany's DAX climbing 1%, and France's CAC 40 advancing 0.4%.

Space company Rocket Lab climbed 3% to US$65.81 after winning a US$266 million contract from the US Space Force to deliver 12 suborbital launches with the potential for six more. SpaceX fell 3.2% to US$111.44.

Oil prices tumbled as the US and Iran returned to negotiations to de-escalate Middle East tensions, with President Donald Trump indicating there was a good chance of a deal. Brent crude futures fell 8.9% to US$88.20 a barrel. Meanwhile, luxury heavyweight LVMH met expectations as second-quarter sales rose 3% with strong demand in the US, while fast-fashion company Shein posted a loss on slowing sales as it prepares for a Hong Kong listing.

Australian futures were pointing to a 0.4% decline for the S&P/ASX 200 when trading opens, while the New Zealand dollar fell to 57.75 US cents from 57.97 cents. Statistics New Zealand is expected to release monthly employment figures and the June quarter household living-costs price index.