feat: show approximate EUR/USD value next to reward amounts

[zaibon]

What

The reward amount input (Balance.svelte, used in simple mode, the expert-mode single reward and each multi-reward contributor card) now shows a small line under it:

≈ 22.23 €                                   Balance ≈ 106.70 €

It updates live as the amount or token changes. A tooltip says the value is approximate and names the price source.

Price source

• CoinGecko's keyless API wasn't an option. Since its recent limits, /simple/token_price without a key returns error 10012: "exceeds the allowed limit of 1 contract address". That means one request per token. Mapping contracts to IDs instead needs /coins/list?include_platform=true, which is about 3.9 MB.
• DefiLlama coins.llama.fi/prices/current/... needs no key, accepts many coins in one request (contract addresses per chain plus coingecko:<id> for native coins) and returns confidence. Prices are in USD, so EURC (coingecko:euro-coin) is added to the same request and used as the USD→EUR rate. That's close enough for "≈". Cross-check: ETH came out at 2,398 € via DefiLlama/EURC and 2,394 € from CoinGecko's simple/price?vs_currencies=eur.

Browser vs server route

The app calls the API directly from the browser:

• DefiLlama sends Access-Control-Allow-Origin: *.
• Rate limits then apply to each user's IP instead of shared Vercel IPs. Keyless public APIs often return 429 to shared serverless IPs, so this is the more robust choice.
• It adds no server hop or cold start, which suits a client-only (ssr = false) app.
• The shared runes store already prevents duplicate requests within a tab.

Caching / degradation

• src/lib/services/prices.svelte.ts: a shared store. While a wallet is connected, one refresh loop fetches all Peanut-listed tokens of the current chain in one request, cached for 5 min and deduplicated while a request is in flight. Many contributor cards only read the store.
• No € value when: the chain is a testnet (Sepolia and anything not mapped), the token is unpriced or DefiLlama's confidence is below 0.9, or the request fails or hits a rate limit. After a failure, prices up to 15 min old are kept, then dropped.
• Nothing in the reward flow depends on prices.

Testing

• pnpm run check, pnpm run lint and pnpm run build pass.
• In headless Chrome (dev server), /, /dashboard and /badges render with no console errors.
• Live lookup through the service module: Base, Optimism and mainnet ETH, USDC and WETH return € values. Sepolia returns nothing.
• With a Base balance injected into the store: the € line updates on amount and token changes and is hidden for an unpriced token (Ed).
• With the chain set to Base while 20 readers read the store: 1 request. Switching to Sepolia sends no request, and switching back within the TTL uses the cache.
• With a simulated 429, the € value is hidden and there are no page errors.
• Not tested: a real wallet connection, and a visual check of the multi-reward cards.

🤖 Generated with Claude Code

[vercel]

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Project	Deployment	Actions	Updated
commitkudos	Ready	Preview	Oct 4, 2026 3:09pm UTC

[zaibon]

Added a €/$ toggle in the header (next to the light/dark switch). It switches every reward input between euros and US dollars, and the choice is saved in localStorage. The store now keeps DefiLlama's USD prices plus the EURC rate, so switching sends no new request, and USD values still show if the EUR rate is missing. Tested in headless Chrome: 0.002 ETH on Base shows ≈ 4.80 € and ≈ $5.40, the choice persists across reloads, there are no console errors, and check/lint/build pass.