Jev Shopper

Jev Shopper shop design

Jev Shopper runs a live shop window: a few products stream price ticks and Jev (TypeSafe's System One model) reads the window each tick and calls the best buy — the product furthest below its own usual price — showing confidence and spending on paper when the signal is strong. The agent shapes shopper.json — the products, the price noise, the budget and the deal bar. The shop and its prices are made up.

The loop

1. Update shopper.json (title, products with price/drift, vol, tickMs, and a style line that tells Jev a buying strategy). The viewer watches it and Jev adapts live — no restart, no second server.
2. node "$JEV_DSH/toolchain/check.mjs" verifies the workspace's shopper.json is valid. Run it before you call a shop done.
3. Watch the board. The top bar shows the share of deal calls Jev got right and what its buys saved against the usual price. Does Jev buy real sales, or wobbles (little saved), or nothing (dull)? That observation is the finding.

Reading the shop

The viewer shows each product as a price card with a live chart, a spotlight on Jev's "best buy", a probability bar per product, purchase stamps, the budget left and receipts. Every product has a hidden fair price (list price, slow drift, now and then a real sale). Jev reads that price plus noise. vol is the noise and the difficulty dial: at 0.01 Jev's deal calls are right almost every time and buys save about 16%; at 0.15 wobbles pass for deals, calls are right about half the time and buys save about 3%.

Verifying a shop

node "$JEV_DSH/toolchain/check.mjs" returns non-zero when shopper.json is invalid (no title, fewer than two products, a non-positive price, duplicate names, out-of-range vol, tickMs, cash, minDeal or drift, more than 8 products). It doesn't replace watching the calls: confirm Jev buys during real sales (tick "show the hidden fair price" in the pane to see them), and that turning vol up makes it buy wobbles instead.

Driving Jev yourself

toolchain/jev.mjs exports a small client. Example (from the workspace) — ask Jev's read on a window before you commit to it:

node --input-type=module -e '
import { evaluate, jev } from "$JEV_DSH/toolchain/jev.mjs";
const res = await evaluate({
  state: "Pick the best value. Prices tick live: Espresso Machine: 240.62 (+2.1% over 6 ticks) vol 8% — Hiking Boots: 119.50 (-4.2% over 6 ticks) vol 8% — Desk Lamp: 45.00 (-3.1% over 6 ticks) vol 8%. Which is the best buy to act on now?",
  questions: {
    buy: jev.choice(["Espresso Machine", "Hiking Boots", "Desk Lamp"], "Which product is the best buy to act on right now?"),
  },
});
console.log(JSON.stringify(res.answers, null, 2));
'

Without TYPESAFE_API_KEY this uses the deterministic mock; set the key to hit live Jev.