Anthropic’s IPO filing shows that post-listing selling restrictions will not expire on a single date. Instead, the company set out a staggered lock-up schedule with 23 separate timing points, and the release path differs for employees, certain shareholders, and the founders. The biggest open question in the filing is a separate one: whether the charity-related 5% stake held through a public benefit fund is subject to any lock-up at all.
According to the prospectus, employees are positioned to sell first after the IPO. Non-founder directors, executive officers, and certain current and former employees and advisers may sell 10% of their locked-up shares on the first trading day after the listing. Some shareholders begin phased releases on day 27. Founders and shareholders holding more than 0.5% of fully diluted shares face the longest timeline, with full release delayed until as late as day 365 after the IPO.
Lock-up schedule is split into 23 release points
The filing describes the lock-up as the standard agreement between pre-IPO holders, underwriters, and the company that restricts share sales for a set period after listing. Anthropic did not choose a one-time unlock. It divided the process into 23 separate points tied to trading days and earnings releases.
The prospectus still leaves the IPO price, share count, and tranche-by-tranche allocations blank. That means the rules can be mapped out, but the actual number of shares that may hit the market at each point cannot yet be calculated from the filing.
Three groups, three different release paths
The prospectus divides restricted holders into three groups.
Group one: employees, non-founder directors, and executives
The first group includes employees, non-founder directors, and executives. They may sell 10% on the first trading day after the IPO. Another 35% becomes available on the second full trading day after Anthropic reports full-year 2026 results. The remainder unlocks on the earlier of the second full trading day after the company reports first-quarter 2027 results or day 180 after the IPO.
Group two: certain unnamed shareholders
The second group consists of certain shareholders whose ownership percentages are left blank and who are not named in the filing. Their shares are also fully released by the day-180 threshold.
Before that point, 26% is released across four tranches on days 27, 48, 62, and 76. Another 12.5% is released after the company reports full-year 2026 results. Five later tranches each release 9.5%. BlockTempo’s calculation puts the cumulative amount at as much as 86%, with the remaining 14% released at day 180.
Group three: holders above 0.5% and the seven co-founders
The third group covers shareholders who own more than 0.5% of fully diluted shares and Anthropic’s seven co-founders. Their final release comes on the earlier of the second full trading day after the company reports third-quarter 2027 results or day 365 after the IPO.
For holders above the 0.5% threshold, the early tranches are roughly 30% of the size of group two’s corresponding tranches. By day 180, the cumulative release reaches as much as 30%. After the tranches tied to second-quarter 2027 results, the cumulative figure rises to about 90.9%, leaving the final 9.1% for the last release point.
The founders remain almost entirely locked up. The filing provides one opening: starting at the day-180 threshold, each founder may transfer up to 29% of his or her holdings. The prospectus also lists five founders, including Tom Brown, as selling shareholders. Shares they sell in the IPO itself are not subject to the lock-up, although the filing leaves the share count blank.
Early release depends on filing dates or underwriter discretion
The filing points to two kinds of early-release triggers. One is the set of dates and earnings-report milestones written into the prospectus. The other is the discretion of Goldman Sachs and Morgan Stanley.
The document does not include a clause that would accelerate unlocks if the stock reaches a certain price. It does say the two underwriters may waive the lock-up in whole or in part at any time.
After the lock-up period ends, holders of at least 60% of registrable securities may require Anthropic to register a block sale beginning six months after the registration statement becomes effective, so long as the offering size is at least $200 million. The company is required to do this only twice. Google and Broadcom have separate registration rights agreements.
Employee stock is the clearest source of supply
Among the possible sources of post-IPO supply, employee equity is the most clearly defined.
The filing says restricted stock units, or RSUs, vest only after both service-based and performance-based conditions are met. The performance condition is typically the effectiveness of the IPO registration statement. Once that happens, RSUs for employees who have already satisfied the service condition vest at once. Anthropic will withhold part of the shares for taxes and use a portion of IPO proceeds to cover those tax payments, although the amount is not disclosed.
That structure means employees do not need to sell shares immediately after the IPO just to pay taxes. Even so, more supply is coming. After June 30, the board approved about 91 million additional RSUs with a grant-date fair value of $5.8 billion. Anthropic said it expects to file an S-8 registration statement right after the IPO so those shares can become tradable, subject to lock-up and vesting restrictions.
The 5% public benefit fund stake is the least certain piece
The filing leaves the public benefit fund as the most uncertain part of the supply picture. Anthropic donated 846,840,960 Class N shares to its wholly owned subsidiary, Anthropic Public Benefit Fund. The filing says that stake represented about 5% of fully diluted shares as of June 30, 2026, assuming full conversion of Amazon notes.
Class N shares are non-voting common stock. If they are sold in the market or transferred to an unrelated third party, they automatically convert into voting Class A shares.
The prospectus says the fund may transfer the shares, donate them to third parties, or sell them through public offerings or private placements. What it does not say is whether those shares are bound by the lock-up, or whether the fund has any near-term plan not to sell. In practical terms, that makes the fund a potential source of supply, but not one that is clearly built into the published release schedule.
The filing also says Anthropic’s board may issue up to another 2% to the fund each time the stock rises 50% from a milestone level, with the first milestone measured from the IPO price. The language is discretionary rather than mandatory. For shareholders, that is dilution first.
Founders’ 80% donation pledge is also unresolved
The same uncertainty applies to the founders’ pledge to donate 80% of their holdings. The prospectus says the pledge is voluntary, revocable, and not legally binding. It does not specify timing, amount, or recipients.
During the lock-up period, a donation does not bypass the restrictions. If shares are transferred to a charity or given as a bona fide gift, the recipient must sign a lock-up agreement and cannot provide consideration.
The larger question comes after the lock-up expires. The filing itself says later sales by recipients could result in a substantial number of shares entering the market.
Key dates investors may want to track
The IPO date has not been set, so all timing in the filing is relative.
- First trading day after the IPO: employees may sell 10%.
- Days 27, 48, 62, and 76: group two shareholders and holders above 0.5% begin phased releases.
- Second full trading day after full-year 2026 results: employees get another 35% release.
- Days 13, 27, 41, 55, and 69 after that earnings milestone: groups two and three each have five more release tranches.
- Day 180: employees and group two are fully unlocked, and founders may begin transferring up to 29%.
- Days 34 to 76 after first-quarter 2027 results: holders above 0.5% get four more tranches.
- After second-quarter 2027 results: six additional tranches are released.
- Second full trading day after third-quarter 2027 results, or day 365: all remaining restricted shares are released.
BlockTempo said the filing points to supply entering the market from the first day of trading, while leaving three questions unanswered: the actual share count in each tranche, whether the public benefit fund will sell, and when founders might donate shares.
This report is based on Anthropic’s S-1 filing and BlockTempo’s review of the document.
