Anthropic's shot at 2026's biggest IPO tumbles as SpaceX keeps the lead

Anthropic's dream of the year's biggest IPO is slipping. Prediction markets now put just a 28% chance on the AI company being 2026's largest listing by market cap, according to Kobeissi Letter. That's down from a peak of 62%.

The crown stays with SpaceX and its $SPCX ticker. Traders who once saw Anthropic vaulting past Elon Musk's rocket company have flipped the script, and the gap between the two is now the market's working assumption.

Two pieces of news are dragging on sentiment. Reports suggest Anthropic could land a 'high junk' credit rating, a label normally reserved for borrowers with shaky balance sheets. Meanwhile, OpenAI has trimmed its fundraising valuation target by $150 billion — a huge haircut from the sector's biggest name.

The timing stings. Anthropic is expected to hit public markets this month, meaning it will price into a mood that has cooled fast. A month ago the AI lab looked like the marquee debut of the year; now it's the underdog in its own story.

Nothing is final until the shares price and trade, and SpaceX's own listing plans carry their own risk. But for now, the race for 2026's biggest IPO has a clear frontrunner — and it isn't the Claude maker.