What it watches
Two things, continuously. Whale flow — large single trades across every market on each venue, deduplicated. On Polymarket, each whale carries the trader's pseudonym and a link to the on-chain Polygon transaction you can verify yourself; Kalshi trades come straight from Kalshi's public trade feed — real, but not settled on a public chain. And cross-venue gaps — the same outcome priced differently on the two venues, tracked on human-confirmed equivalent market pairs.
How it works
A Python engine polls both venues' public market feeds, computes every signal with deterministic math on real trades — no models, no guessing — and logs it all to Postgres. The terminal reads from that same pipeline. Trades are simulated on paper with real fees, so the engine can measure honestly whether an apparent edge survives contact with reality.
What it is not
Harpoon is not a tip service, and whale-following is not a trading strategy. Our own backtests of blindly copying large trades come out negative — and we'd rather tell you that than sell you a signal. We didn't assume arbitrage was dead, either: we built cross-venue arb detection, measured whether it actually pays, and found it doesn't. The same measurement shows equivalent markets usually price within about a cent of each other, so by the time a gap is real it's already been arbed out — durable arbitrage is vanishingly rare. That's a deliberate research finding, not a missing feature. What's left that's genuinely worth watching is the whale flow itself, so that's all this terminal shows: where big money moves, as it moves, for you to form your own view.
Who's building it
Harpoon is built in the open by Sanath Boddhula — the whale is the target, the archer is the strike. Follow the build on X, or ask for early access.