Second-hand buyers have no protection outside big marketplaces. A private sale ends with cash in a car park, and if the gears fail on day three there is nobody to call and no proof of what the item was like at handover. Honest sellers suffer too, because buyers discount for that risk or walk away.
What exists and what is new
Closest: buyer protection inside eBay and PayPal, and advice articles for Facebook Marketplace. Platform protection only works inside one platform, and advice articles leave you on your own. New: protection that works for any private sale, with a guided video condition check at handover, a short hold on part of the payment, and an AI comparison of the two videos when something goes wrong.
The data it runs on
The handover video and the buyer's claim evidence: a guided 30-second recording both people watch being made, the agreed test written in plain words, the claim video shot from the same angles, and repair quotes. The serial number is read from the video to check public stolen-goods registers.
1. The mission
Every private sale as safe as a shop. Any two strangers, any item, any classifieds site: a video, a hold and a fair test, so more things get reused and fewer get bought new.
2. Why people can't resist it
Relief at the risky moment. The handover is when buyers feel most exposed; one tap removes the fear.
Sellers get paid faster. "Holdback ready" listings sell in a third of the time and for a bit more, so sellers ask for it.
No arguing. The video settles "it was fine when I sold it", which most people dread more than losing money.
3. How it works for real
Accounts: phone or email login with a passkey smart wallet (Privy or Coinbase Smart Wallet). The seller needs only a link. Payment by card, BLIK or bank in, payout to bank, held as USDC on Base with gas sponsored.
Escrow: a per-deal contract that pays the first share instantly and holds the rest with a release time; release, refund or split need either the timer, both signatures, or a reviewer's signature.
Guided video: the app overlays a shot list per category (bikes, phones, laptops). A vision model (Gemini 2.5 Flash or GPT-4o mini via OpenRouter) reads serials, counts shifts or checks screens, and flags damage frame by frame.
Claim comparison: the same vision model compares matched frames from both videos; a frontier LLM (Claude) writes the plain-language finding and proposes an outcome from repair quotes, within rules fixed in advance.
Repair quotes: a shop directory with simple quote requests sent as Holdback, never as the user.
Reputation: a seller record that counts sales, claims and how they were settled, attached to a verified phone and optional ID.
4. Cost per use
Handover video analysis (about 30 frames to a Flash-class vision model): about $0.02. Stolen-register lookups: free to $0.01. A claim comparison with a summary: about $0.05. Gas on Base for lock and release: under $0.02. Payment processing is the real cost (card fees about 1.5%), passed into the fee.
Pricing: 0.5% of the price, minimum 12 PLN (about $3), buyer pays. Free for sellers. Paid seller plan ($4 a month) adds the verified badge, ID check and faster payouts.
5. Growth loop
Every deal has two people, and the one who didn't start it experiences the product at its best moment. Sellers paste "Holdback ready" into their next listings; buyers send a Holdback link to their next seller. Claim stories ("380 PLN back in 6 hours") spread in local buy-and-sell groups.
Each week a seller's completed holds, zero-claim rate and repeat buyers add up in a Deal Record that ranks their listings, so every clean sale makes the next one faster and sellers keep coming back to log the next deal.
6. Risks and guardrails
Fake claims: claims must use the same guided angles; crash or misuse signs are checked; repeat claimers are limited.
Stolen goods: serial checks on public registers where available, ID checks above a value threshold; the app never certifies legal ownership.
Privacy: videos show the item, not faces, and are deleted 30 days after the hold ends.
Legal: consumer rules and escrow licensing differ by country; work through licensed payment partners. This is general information, not legal advice.
7. MVP build order
Deal link with price, hold percent and days, accepted by the seller in a browser.
Card in, bank out, with a timed escrow on Base Sepolia.
Guided video capture for bikes and phones with a vision check summary.
Claim flow with video comparison and a proposed split both must accept.