RizonAnthropic IPO: the date and the first-day market cap as forecasts
Anthropic filed its S-1 on Oct 26, 2026. On Oct 29 Polymarket priced a first trading day around Nov 19–20 and a first close near $1.93T. Both as one book.
Short answer: Anthropic, PBC publicly filed an S-1 with the SEC on Oct 26, 2026. On Oct 29, Polymarket's 12-date "Anthropic IPO by…?" ladder put the first trading day around Nov 19–20 (41.5¢ for trading by Nov 19, 61¢ by Nov 20), and its 10 market-cap buckets put the close on that day near $1.93T, if it lists. Rizon quotes each as one number: ANTH-IPO-DATE, a date market that Higher wins if there's no listing by Dec 31, 2026, and ANTH-IPO-CAP, in billions of dollars, void and refunded if there's no IPO by the end of 2027.
This post sets out what's known, what Polymarket and Kalshi priced on Oct 29, 2026, and how the two numbers trade as horizon contracts. It reports market prices; it isn't investment advice.
What's known
Verified: Anthropic, PBC (CIK 0002130357) publicly filed a registration statement on Form S-1 on Oct 26, 2026, on SEC EDGAR.
Reported, not verified against the filing: the ticker ANT on Nasdaq; no price range yet (no amended S-1 as of Oct 27); a roadshow from about Nov 10; a listing targeted for the week of Nov 16; a last private round of $65B, a Series H at $965B post-money, on May 28, 2026; and a $1.5–2T target reported by the Wall Street Journal. These come from secondary sources (Leverage Shares' IPO tracker, FutureSearch, Invezz).
When: the "IPO by" ladder
Polymarket's anthropic-ipo-by ($6.07M traded) pays $1 on each date if Anthropic's shares are listed on a public exchange and open for trading by 11:59 PM ET that day. An acquisition by an already-public company resolves No.
| By (2026) | Bid (¢) | Ask (¢) | Mid (¢) | Volume ($K) |
|---|---|---|---|---|
| Oct 31 | 0.1 | 0.05 | 1,523 | |
| Nov 15 | 1.5 | 1.9 | 1.7 | 313 |
| Nov 16 | 6.8 | 8.2 | 7.5 | 6 |
| Nov 17 | 12 | 13 | 12.5 | 7 |
| Nov 18 | 28 | 29 | 28.5 | 10 |
| Nov 19 | 41 | 42 | 41.5 | 4 |
| Nov 20 | 60 | 62 | 61 | 65 |
| Nov 23 | 62 | 64 | 63 | 6 |
| Nov 25 | 79 | 81 | 80 | 37 |
| Nov 30 | 87 | 88 | 87.5 | 552 |
| Dec 15 | 92 | 94 | 93 | 315 |
| Dec 31 | 94.6 | 94.7 | 94.65 | 1,449 |
The ladder crosses 50¢ between Nov 19 (a Thursday) and Nov 20 (a Friday): the median first trading day. It barely moves from Nov 20 to Nov 23 because Nov 21 and 22 are a weekend. The dates nearest the median had traded $4K–$65K each; the Oct 31 and Dec 31 dates, about $1.5M and $1.4M.
Other ladders agree: Polymarket's "In which month will Anthropic IPO?" had November at 88.35¢, and Kalshi's KXIPOANTHROPIC-DATE (where a listing counts as "confirmed" once the S-1 is effective, the IPO is priced or the exchange assigns a ticker) had "before Dec 1" at 86.5¢.
How big: the first-day market cap
Polymarket's anthropic-ipo-closing-market-cap-higher-strikes ($2.72M traded) resolves on shares outstanding times the closing price on the first trading day, from the primary exchange's listing page; a value exactly on a bucket edge counts in the higher bucket.
| Market cap ($T) | Bid (¢) | Ask (¢) | Mid (¢) | Volume ($K) |
|---|---|---|---|---|
| Under 1.25 | 3.0 | 3.1 | 3.05 | 211 |
| 1.25–1.5 | 6.2 | 6.3 | 6.25 | 212 |
| 1.5–1.75 | 15.6 | 15.8 | 15.7 | 257 |
| 1.75–2.0 | 32 | 33 | 32.5 | 491 |
| 2.0–2.25 | 22.8 | 23.9 | 23.35 | 670 |
| 2.25–2.5 | 11 | 12 | 11.5 | 360 |
| 2.5–2.75 | 2.4 | 2.5 | 2.45 | 161 |
| 2.75–3.0 | 1.3 | 1.4 | 1.35 | 100 |
| 3.0 or more | 0.8 | 0.9 | 0.85 | 118 |
| No IPO by Dec 31, 2027 | 3.6 | 3.7 | 3.65 | 138 |
Leave out "no IPO", normalise the mids, and the running total crosses one half inside 1.75–2.0, at about $1.93T. The "above" ladder agrees (above $1.75T at 70¢, above $2.0T at 41.5¢). A separate market on the valuation at pricing implies about $1.71T, so the buckets imply a first-day close about 13% above the IPO price.
| Quantity, as implied on Oct 29, 2026 | Median |
|---|---|
| First trading day | Nov 19–20 |
| Valuation at pricing ($T) | 1.71 |
| First-day closing market cap, if it lists ($T) | 1.93 |
The same two numbers on Rizon
| ANTH-IPO-DATE | ANTH-IPO-CAP | |
|---|---|---|
| The number | The ET date of the first day Anthropic shares trade on a public exchange | Shares outstanding × the official closing price that day, in $B |
| Kind | Date market (a Julian Day Number) | Fixed |
| Strikes | Midnights between days | Every $10B, written like $1.93T |
| Trading stops | When it lists (the market settles then), or at the deadline | When the first session closes (Rizon halts it) |
| If there's no IPO | Higher wins at every strike once Dec 31, 2026 passes | Void: everyone's size is refunded if there's none by Dec 31, 2027 |
| Source | The exchange listing and SEC filings | The primary exchange's close and the final prospectus's share count |
The date market works like the other date markets on Rizon: a strike is the midnight before a day, so "Higher than Nov 20" means the first trading day is Nov 20 or later, and "Lower" means Nov 19 or earlier. On Oct 29's prices, that strike was about 41.5% Lower and 58.5% Higher, and the next one, "Higher than Nov 21", about 39% Higher; the 50/50 point sat between them, where the book's best quotes would straddle it. The US–Iran post explains Julian Day Numbers with a worked example.
The market-cap market is conditional by design: if there's no IPO, there's no number, so it's void rather than settled. Polymarket prices that case as its own bucket (3.65¢); on Rizon the midpoint is a forecast of the close given a listing.
FAQ
When is Anthropic's IPO?
Anthropic publicly filed its S-1 on Oct 26, 2026. Reports, not verified, point to a Nasdaq listing as ANT in the week of Nov 16; on Oct 29 Polymarket priced trading by Nov 19 at 41.5¢ and by Nov 20 at 61¢.
What market cap do prediction markets expect for Anthropic's IPO?
On Oct 29, 2026, Polymarket's buckets implied a median first-day closing market cap of about $1.93T if it lists, against about $1.71T implied for the valuation at pricing.
What happens on Rizon if Anthropic doesn't list?
ANTH-IPO-DATE settles at its deadline: with no listing by Dec 31, 2026, Higher wins at every strike. ANTH-IPO-CAP is void if there's no IPO by Dec 31, 2027, and every position is refunded.
Was the S-1 filing verified?
Yes: the Oct 26, 2026 public S-1 filing is on SEC EDGAR under CIK 0002130357. The ticker, the exchange, the timetable, the last private round and the reported valuation target come from secondary reports.