tl;dr: River Markets raised an $8.5M seed led by Haun Ventures. Attestable raised a $20M seed co-led by Altimeter and TLV Partners. both announced august 11 2026. frontrun flagged them on april 14 and april 3, which is 119 days and 130 days of lead.
who led River Markets' $8.5M seed?
River Markets is building the prime broker for prediction markets: unified execution and risk across venues, aimed at professional trading firms rather than retail.
that is a real gap. prediction markets have fragmented into a dozen venues with separate margin, separate settlement and separate risk, which is precisely the problem prime brokerage solved for equities and then for crypto. River is running the same play one layer up.
the $8.5M seed was led by Haun Ventures, with Y Combinator and CB Ventures. their write-up.
Today, River Markets announced an $8.5M seed round led by @HaunVentures.
— River Markets (@river_markets) August 11, 2026
We're building the prime broker for prediction markets, giving professional trading firms unified execution and risk across venues.
who led Attestable's $20M seed?
Attestable describes itself in six words: AI integrity, signed by a universal truth. the $20M seed was co-led by Jamin Ball at Altimeter and Yonatan Mandelbaum at TLV Partners.
the company came out of stealth on announcement day. CEO Yogi framed it as solving a problem that was considered impossible: practical zero-knowledge proofs, aimed at making AI verifiable.
The world has identified verifiable AI as a missing civilization-scale primitive. The core technical obstacle, practical zero-knowledge proofs, was considered impossible.
— Yogi (@Yogi_Brn) August 11, 2026
We solved it.
Today, we are launching @attestablecom, the AI Integrity Company, and announcing a $20M seed
$20M is a large seed by any standard, and it is the kind of round that arrives fully formed in the press with no public build-up at all. Attestable has 884 followers on X today, the day after announcing it.
how early did frontrun flag them?
River Markets: flagged april 14 2026, announced august 11 2026. 119 days.
Attestable: flagged april 3 2026, announced august 11 2026. 130 days.
River Markets is the receipt we would point at first, and the reason is a date that has nothing to do with us. the @river_markets account was created on april 3 2026. we flagged the company on april 14, eleven days later.
there was no product launch to react to, no funding rumour, no press. there was an X account that was under two weeks old and a set of tracked accounts that had already found it. 30 tracked accounts are on River today; 12 of them were there before the round was announced.
Attestable followed the same curve on a longer runway. 19 tracked accounts today, 6 of them in place before the news, with the first arriving on the day we flagged the company back in april.
both raises clear our receipt ledger's 7-day minimum lead with room to spare, so they join the permanent record with their flag dates, a source link and no rounded numbers.
eleven days is the whole argument
most sourcing tools are reactive by construction. they wait for a filing, a launch, a job posting, a press mention, and then they tell you. every one of those events is downstream of a company already existing in public.
a follow is upstream of all of it. the people closest to a deal follow the company while they are looking at it, which is before there is anything to react to. on River Markets there was literally nothing else to find in april: an eleven-day-old account and a graph that had already moved.
that is a 119-day head start on a round Haun Ventures ended up leading, and it cost one line in a report.
see the list before the round
River Markets and Attestable already raised. the useful list is the one where the round has not happened yet.
frontrun watches the follow graphs of 2,000+ tracked venture investors on X and flags the companies they converge on, with a date, the morning it happens.
read next: Preview and Alloy Robotics, flagged 174 and 180 days early · startups flagged before they raised · the fundraise receipt ledger
open source deal flow
companies and founders surfaced on frontrun. curated, every week.
