Kalshi Puts Anthropic First at 91 Cents After OpenAI Ruled Out a 2026 Listing

Kalshi's event market on which AI lab goes public first now prices Anthropic ahead of OpenAI at 93 cents on the Anthropic contract as of September 25, up from a range of 88 to 92 cents in the week before September 12. The OpenAI side of the same event, KXOAIANTH-40, has fallen to a 9 to 12 cent spread, and the two contracts together have traded 397,708 contracts since the market opened. The repricing is not a slow drift. It followed two dated events: Sam Altman's September 12 statement that taking OpenAI public now would come at an "ill-advised moment," and September 18 reporting from The Wall Street Journal and The New York Times that Anthropic pushed its own listing window from October to November 2026.

What the two venues are actually pricing

The Kalshi event asks a comparative question: will OpenAI or Anthropic IPO first, with the market closing January 1, 2040. Anthropic's contract last traded at 95 cents with a 91 to 95 cent bid-ask spread in September 25 trading, against open interest of 52,131 contracts. OpenAI's contract last traded at 9 cents on 195,223 contracts of volume. Because the two contracts are complements, the market is effectively saying there is a 4 to 9 percent chance neither company lists first within the window, or that some third path (a withdrawal by both, or an outside company neither contract contemplates) takes the title.

Polymarket runs the question differently. Its "Anthropic IPO before 2027?" market, open since November 12, 2025, traded at 77.5 percent on September 25 against a $583,024 lifetime volume and thin 24-hour turnover of $486. That is a 15 point gap to Kalshi's Anthropic-side price, and the gap is mostly definition. Kalshi asks who is first; Polymarket asks whether Anthropic lists at all before January 1, 2027. A November 2026 listing satisfies both, but a delayed or withdrawn OpenAI filing lifts Kalshi's Anthropic price without moving Polymarket's calendar question at all. Reporting both numbers side by side is the only honest way to describe the divergence.

The price path on the Polymarket contract shows how much of the repricing came from the OpenAI news. The contract closed at 87.5 percent on September 11, dropped to 73.5 percent by September 16, then recovered to 80.5 percent on September 17 and has traded between 75.5 and 77.5 since. Kalshi's Anthropic contract shows the same shape: a dip to 86 cents on September 21, then a recovery through 92 cents by September 24. The dip-and-recover pattern tracks the reporting cycle around Anthropic's own timeline, not any change in OpenAI's status.

The dated events behind the repricing

Three filings and statements carry the story. Anthropic confidentially filed its S-1 with the SEC on June 1, 2026, per the company's own statement and CNBC's report that day, which quoted the company saying the filing "gives us the option to go public after the SEC completes its review." OpenAI filed confidentially a week later, on June 8, 2026, per Reuters and the AP. Both filings were, at the time, priced by Kalshi as a genuine race: the OpenAI contract traded as high as 14 cents on August 27 and 23 cents on September 16.

The September 12 Altman statement changed the comparison. Reporting by Fortune and others that day has Altman ruling out a 2026 listing outright, which converts the Kalshi event from a race into a countdown on a single company's calendar. The OpenAI contract fell from 10 cents to 8 cents in the following week's trading and sits at 9 cents now.

Anthropic's own window also moved. Reuters reported on September 4 that the IPO launch had shifted toward mid-October, and WSJ and NYT reporting on September 18 moved the target listing to November, with the company reportedly wanting a full quarter of third-quarter financials before the roadshow. Forbes carried the November angle on September 23. The crypto and markets press has cited a potential valuation around $2 trillion and proceeds near $100 billion, which would exceed SpaceX's June 2026 listing as the largest IPO on record. Those figures are reporting, not filings; the public prospectus has not yet landed, and the market's 91 to 95 cent range prices a November or December listing as likely but not certain.

Resolutions

The desk's track-record ledger shows no covered markets past their expected resolution date as of September 25, so nothing settled this week. The next dated markers on this story are the public S-1 filing, expected in the coming weeks per Reuters' September 4 report, and the mid-October roadshow start. The desk will file both Kalshi contracts on this event to the ledger with this piece, so the 93 and 9 cent prints are on record against whatever the listing calendar actually delivers.

Elsewhere on the desk's beat, the Fed October hike contracts continue to dominate volume and were covered in the September 23 and 24 pieces on Kalshi putting the October Fed hike at two thirds on its December ladder and on the October hike odds jumping 14 points on the Barr speech; nothing in this week's data changes that picture. The structural story worth watching on this AI-IPO market is liquidity rather than price. A 4 cent spread on a contract that closes in 2040 is a functioning two-sided market. The 1.5 point spread Polymarket quotes on its calendar question, with $486 of daily volume, is a market that moves on little and says less, the same lesson October's Fed meeting coin toss on prediction markets already showed. When a venue's price moves, check the volume behind it first.

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