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A week ago, Polymarket traders thought Anthropic had close to a coin flip’s chance of pulling off 2026’s largest IPO. That optimism has cooled.
The AI company’s odds of claiming the title now sit at 31.7%, down from about 46% one week earlier. Traders are increasingly betting that SpaceX, which already went public this year, will keep the crown.
The numbers behind the slide
The Polymarket contract asks a simple question: which company will have the largest IPO by market cap in 2026? More than $7.4 million has been traded on it so far.
SpaceX holds a commanding lead, priced at a 65% to 66.5% probability as of Nov. 4, 2026. Anthropic’s odds have moved within a range of 27.8% to 31.7%, depending on the snapshot.
The decline lines up with Anthropic’s public paperwork. The company filed its Form S-1 with the SEC on Oct. 26, 2026, for a Nasdaq debut under the ticker ANT.
What the S-1 revealed
Anthropic reported $16.3 billion in revenue for the first half of 2026. The bottom line looks very different. Anthropic posted a net loss of $80.7 billion for the same period, a figure driven by non-cash adjustments.
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The listing is targeting mid-November 2026, with an expected valuation of $1.5 trillion to $2 trillion. Traders appear fairly confident on timing, with a separate Polymarket contract pricing an 85% chance that Anthropic lists in November 2026.
So the market is not doubting that the IPO will happen. It is doubting whether it will be big enough to beat SpaceX.
The SpaceX benchmark
SpaceX set a very high bar. Its IPO on June 12, 2026, raised approximately $75 billion and valued the company at between $1.77 trillion and $1.8 trillion.
That puts the comparison in sharp focus. Anthropic’s expected range of $1.5 trillion to $2 trillion overlaps with SpaceX’s valuation, but only the upper portion of that range clears it.
What this means
The roughly 14-point drop in a week suggests traders recalibrated after seeing Anthropic’s financials and valuation expectations in writing.
The contract is narrow. It only asks whether Anthropic beats SpaceX, and SpaceX already locked in its result back in June.
SpaceX’s number is fixed, while Anthropic’s depends on how the deal is priced and how the stock trades out of the gate. With an 85% chance of a November listing priced in, the answer to the bigger question may arrive within weeks rather than months.
