Cambio

A news-aware market maker for LatAm stablecoins on Celo. Cambio quotes USDT↔wARS and USDT↔wBRL on Textile FX, and pays other agents over x402 to read the news — widening its spread or stepping back before a peso shock, instead of being picked off by it.

Built for the Agents on Open Rails hackathon (Loops House × Celo): Open Corridors: Textile FX and Build with buy.

Where we are and what is left: docs/ROADMAP.md.

The problem

Pesos and reais move on news — central-bank announcements, capital-control rumours, a devaluation. A maker quoting these thin corridors loses money when the news lands before its price does: traders fill the stale quote and resell into a pool that has already moved. That is the main way a small maker loses, and the reason few quote these corridors.

It is not hypothetical. The first Textile fill we inspected on Celo (0x059102b0…151c) was a taker buying a maker's 321,016 wARS for 199.98 USDT and selling them into the Uniswap pool for 200.15 USDT in the same transaction: $0.17 straight out of the maker, measured by src/ledger.ts as −$0.18 of edge against the pool.

The user is the maker operator — a small treasury quoting LatAm stablecoins on Celo with its own capital.

How it works

                 ┌──────────── buy gateway (x402, USA₮) ────────────┐
                 │  X search: devaluación, cepo, Copom…  $0.005/call │
                 └───────────────────────┬──────────────────────────┘
                                         │ posts
                                  src/news.ts ── regime: calm | elevated | shock
                                         │            │
                         rewrites stitch.toml     state/regime.json
                         (spread ×3, size ½)          │
                                         │            ▼
  Uniswap pool ┐                         │      src/feed.ts ──► /feed/wars-usdt
  Textile tick ├─► fair value ─► skew ───┴──►   {price, timestamp}   (503 = stop)
  dólar cripto │   (median, outliers out,                 │
  CCL / PTAX  ┘     refuse if they disagree)              ▼
                                               Stitch (Textile's maker bot)
                                                          │ fills on the reactor
                                                          ▼
                                                 src/ledger.ts → state/pnl.json
                                                 (edge vs pool per fill, equity,
                                                  data cost, daily loss halt)

1. Fair value — src/fairvalue.ts, src/sources.ts

• Pesos are anchored on the crypto/CCL dollar, not the official rate. Measured 2026-10-12: wARS on Celo at ~1,602–1,606 per dollar; dólar cripto 1,605, contado con liqui 1,606; the official wholesale rate 1,512. Pricing off the official rate would be 6% wrong on every fill.
• Sources per corridor, fetched in parallel, each optional:
  • wARS: Uniswap USDT/wARS pool on Celo · Textile ticker · dolarapi cripto · dolarapi contadoconliqui
  • wBRL: Uniswap USDT/wBRL pool on Celo · Textile ticker · AwesomeAPI USD/BRL · Banco Central PTAX
• Median of fresh sources; any source more than 150 bps from it is dropped; no price at all if fewer than two remain or they span more than 120 bps.
• Inventory skew: up to 25 bps toward unloading whichever side we hold too much of.
• Stitch reads the price as debt per collateral — USDT per wARS (≈ 0.000623), not wARS per USDT. Inverting it "makes the bot post wildly mispriced orders" (Stitch's docs). One conversion, toStitchPrice, pinned by a test.

2. The off switch is the feed — src/feed.ts

The feed answers 503 instead of a price when the sources disagree, when the regime is shock, or when the daily loss limit has been hit. Stitch's staleness_secs = 20 then pulls every quote on its own — no restart, and no second process has to be alive for quoting to stop.

3. News risk agent — src/news.ts (the buy integration)

• Pays x.posts.search on the buy gateway (gateway.usebuy.ai) over x402 on Celo — USA₮ by default, USDT or USDC configurable — one search per corridor per poll, within_time:1h.
• Scores posts with a weighted term list (Spanish for Argentina, Portuguese for Brazil), each post counted once so reposts cannot fake a crisis → calm (score < 12), elevated (≥ 12), shock (≥ 30).
• elevated: spread ×3, size ½ (stitch.toml rewritten, Stitch restarted). shock: the feed withholds the price.
• Up is immediate; down only after an hour with no reading at that level.
• Polls every 20 minutes when calm, every 5 when not. Every call is checked against NEWS_MAX_PER_CALL before signing and against NEWS_DAILY_BUDGET before calling, and logged to state/spend.jsonl with its receipt (tx hash), the score, the top matching posts and whether it changed quoting.
• A failed read never relaxes the regime: no news is not good news.

4. Ledger — src/ledger.ts

• Finds our fills as UniswapX Fill(orderHash, filler, swapper, nonce) events on Textile's reactor 0xa9AA…35b3 with swapper = our maker.
• Edge per fill against the Uniswap pool's price at that block; equity at fair value against a baseline; data cost from the spend log. totalPnlUsd = equity change − data cost.
• Writes state/halt.json when the day's P&L passes −$15: the feed stops publishing until the next UTC midnight.

Running it

Requirements: Deno 2, Stitch, a VPS that can stay up.

cp .env.example .env            # fill MAKER_ADDRESS, NEWS_PAYER_KEY, budgets
deno task check                 # typecheck + tests

deno task feed                  # :8787 — /feed/wars-usdt, /feed/wbrl-usdt, /status
deno task news                  # pays buy, sets the regime, writes stitch/stitch.toml
deno task ledger --watch        # P&L every 2 minutes

# Stitch, pointed at the generated stitch/stitch.toml — install and run it
# per its README (Permit2 approvals first: `stitch approve`, needs a little CELO).

Deploying to a server: follow deploy/RUNBOOK.md, step by step.

Dry runs that spend nothing:

deno task news --once --fixture test/fixtures/shock.json   # sample posts, no payment
curl localhost:8787/status                                  # what the feed believes and why

stitch/stitch.celo.example.toml is the generated config in calm conditions.

Wallets — three, never shared

Wallet	Holds	Key lives in
Maker (Stitch operator)	the inventory: USDT + wARS/wBRL, ~0.5 CELO for approvals	stitch/stitch.env only
News payer	a few dollars of USA₮ for x402 calls	.env (NEWS_PAYER_KEY)
—	Cambio never holds anyone else's money	—

Start with roughly $300 (half USDT, half wARS) and the caps in src/config.ts (75 USDT / 120,000 wARS per side), which are deliberately below the balance — Textile's own advice is "start wide and small".

Before going live — verify

• The Celo wARS and wBRL corridors accept a new maker (ask Textile).
• Stitch's TOML keys match src/stitchconf.ts for the version installed (a misspelt key is silently ignored).
• Run Stitch in lean shadow first and compare its quotes to /status.
• STITCH_RESTART_CMD restarts Stitch (e.g. systemctl restart stitch): Stitch reads its config only at startup.
• ERC-8004 identity registered for the maker wallet.
• Attribution: this project's own Loops tag (never Remesso's). Note what can and cannot carry it — x402 payments are submitted by the facilitator and Stitch sends its own approvals, so neither is tagged by Cambio; tag any transaction Cambio sends itself, and ask Textile how fills are credited.

Honest limits

• The corridors are thin: Textile's 24h ticker showed ~$1,900 of USDT/wARS and ~$4,400 of USDT/wBRL. P&L will be dollars, not hundreds.
• Professional makers are already there (the fill above came from a wallet holding ~$113k).
• The keyword scorer is v1: readable and auditable, not clever. Tune the weights and thresholds from state/spend.jsonl against the fills that followed.
• Data is a cost against the spread: at ~$1.50/day it must earn its keep. The adaptive polling exists for that reason, and the ledger reports P&L net of it.
• Live on mainnet with real money. It can lose it.

Layout

src/config.ts       corridors, addresses, risk limits
src/sources.ts      price sources
src/fairvalue.ts    blend, outlier rejection, skew, Stitch orientation  (pure)
src/regime.ts       posts → score → regime → effects                    (pure)
src/feed.ts         the HTTP feed Stitch polls; the off switch
src/news.ts         pays buy over x402, sets the regime, rewrites stitch.toml
src/stitchconf.ts   renders stitch.toml
src/ledger.ts       fills, edge, equity, data cost, daily loss halt
src/state.ts        shared JSON state under state/
src/alerts.ts       Telegram / webhook alerts, sent once per change
src/dashboard.ts    the public evidence page (/dashboard, /api/dashboard)
src/attribution.ts  ERC-8021 suffix for this project's own code
scripts/register-8004.ts   ERC-8004 identity for the maker wallet
deploy/             systemd units, installer, config-swap script, RUNBOOK.md
docs/ROADMAP.md     status and what is left · docs/journal.md  daily trading notes
test/               20 tests