`, favicon, and body of `Root()` to\nmatch your app's existing `index.html`, and stamp anything else your shell\nreferences directly (images, css) with `immutableFileUrl()`.\n\n1. Create `frontend/root.tsx`:\n\n```tsx\n/** @jsxImportSource npm:hono@4/jsx */\nimport { raw } from \"npm:hono@4/html\";\nimport { immutableFileUrl } from \"https://esm.town/v/std/utils/index.ts\";\n\n// The HTML shell for the app. It is never cached, so immutableFileUrl can stamp\n// the current val version into each asset URL — the browser caches those\n// immutably, and publishing the val changes the URLs, refetching exactly once.\nexport function Root() {\n return (\n <>\n {raw(\"<!DOCTYPE html>\")}\n <html lang=\"en\">\n <head>\n <meta charSet=\"UTF-8\" />\n <meta name=\"viewport\" content=\"width=device-width, initial-scale=1.0\" />\n <title>React Hono Val Town Starter

[{"_1":2,"_3":-5,"_4":-5},"loaderData",{"_5":6,"_7":8,"_9":10},"actionData","errors","root",{"_179":180,"_181":182},"routes/_app.x.$handle.$name",{"_11":12,"_13":14,"_15":16,"_18":19,"_17":-7,"_136":-5,"_20":137,"_22":138,"_139":140,"_141":142,"_26":143,"_24":144,"_145":-5,"_146":-5,"_147":52,"_148":149,"_150":43,"_151":-5,"_152":-5,"_153":154},"routes/_app.x.$handle.$name.branch.$branch.code.$",{"_11":12,"_13":14,"_15":16,"_17":-7,"_18":19,"_20":21,"_22":23,"_24":25,"_26":27,"_28":-5,"_29":-5,"_30":-5,"_31":-5,"_32":-5},"handle","shark1","name","crypto-prices","branchName","main","version","path","index.ts","project",{"_33":77,"_13":14,"_44":78,"_79":-5,"_80":52,"_81":82,"_83":82,"_84":85,"_86":-5,"_87":88,"_89":36,"_90":43,"_91":-5,"_92":-5,"_93":66,"_94":95,"_96":97,"_98":99,"_100":101,"_102":-5,"_103":104,"_105":104,"_106":107,"_108":107,"_109":107,"_110":104,"_111":104,"_112":113,"_114":115,"_116":117,"_118":52},"tree",[55,56,57],"file",{"_33":34,"_13":19,"_35":36,"_37":-5,"_38":39,"_40":41,"_42":43,"_44":45,"_17":46,"_47":48,"_49":50,"_51":52,"_53":-5,"_18":54},"contents",[],"upstream","pull","ahead","behind","envVars","id","84455730-4a45-453d-bd94-02ca7775ad60","fileId","01a07568-ca00-74ac-b535-b23c9547b261","parentId","branchId","cd221a1a-99d4-4998-8f31-307310e36f0d","branchVersion",2,"latest",true,"createdAt",["D",1788676276361],1,"fileType","http","content","// Live crypto prices and sparklines for the Revolut clone.\n//\n// The app drew its charts from a sine wave keyed off the ticker's hash, so\n// every coin traced the same shape and the numbers meant nothing. This proxies\n// CoinGecko's free market endpoint, which returns the price, the 24h change\n// and a 7-day sparkline in a single call.\n//\n// Responses are cached in blob storage for a minute. CoinGecko rate-limits\n// anonymous callers hard, and a phone that refreshes on every tab switch would\n// burn the budget in seconds.\nimport { Hono } from \"npm:hono\";\nimport { blob } from \"https://esm.town/v/std/blob\";\nimport { parseVal } from \"https://esm.town/v/std/utils/index.ts\";\n\nconst app = new Hono();\n\n/** Ticker → CoinGecko id. Their ids are names, not symbols. */\nconst IDS: Record = {\n BTC: \"bitcoin\", ETH: \"ethereum\", USDT: \"tether\", BNB: \"binancecoin\",\n SOL: \"solana\", XRP: \"ripple\", ADA: \"cardano\", DOGE: \"dogecoin\",\n TRX: \"tron\", TON: \"the-open-network\", MATIC: \"matic-network\",\n DOT: \"polkadot\", LTC: \"litecoin\", SHIB: \"shiba-inu\", AVAX: \"avalanche-2\",\n LINK: \"chainlink\", ATOM: \"cosmos\", UNI: \"uniswap\", XLM: \"stellar\",\n NEAR: \"near\", ALGO: \"algorand\", FIL: \"filecoin\", ARB: \"arbitrum\",\n OP: \"optimism\", AAVE: \"aave\", SUSHI: \"sushi\", DASH: \"dash\",\n ETC: \"ethereum-classic\", BCH: \"bitcoin-cash\", XMR: \"monero\",\n};\n\nconst CACHE_SECONDS = 60;\n\ntype Quote = {\n symbol: string;\n price: number;\n changePercent24h: number;\n /** Oldest → newest, roughly hourly over the last week. */\n sparkline: number[];\n};\n\nasync function fetchQuotes(symbols: string[], currency: string): Promise {\n const wanted = symbols.filter((s) => IDS[s]);\n if (wanted.length === 0) return [];\n\n const url = new URL(\"https://api.coingecko.com/api/v3/coins/markets\");\n url.searchParams.set(\"vs_currency\", currency.toLowerCase());\n url.searchParams.set(\"ids\", wanted.map((s) => IDS[s]).join(\",\"));\n url.searchParams.set(\"sparkline\", \"true\");\n url.searchParams.set(\"price_change_percentage\", \"24h\");\n url.searchParams.set(\"per_page\", \"250\");\n\n const response = await fetch(url, {\n headers: { accept: \"application/json\", \"user-agent\": \"revolut-clone-study\" },\n });\n if (!response.ok) throw new Error(`coingecko ${response.status}`);\n\n const rows = await response.json();\n const bySymbol = new Map(\n Object.entries(IDS).map(([symbol, id]) => [id, symbol]),\n );\n\n return rows.map((row: any): Quote => ({\n symbol: bySymbol.get(row.id) ?? row.symbol?.toUpperCase() ?? \"\",\n price: row.current_price ?? 0,\n changePercent24h: row.price_change_percentage_24h_in_currency\n ?? row.price_change_percentage_24h ?? 0,\n // Thin the 168-point week to 48 — a 90pt-wide sparkline cannot show more,\n // and the payload is what the phone pays for.\n sparkline: thin(row.sparkline_in_7d?.price ?? [], 48),\n }));\n}\n\nfunction thin(series: number[], count: number): number[] {\n if (series.length <= count) return series;\n const step = series.length / count;\n return Array.from({ length: count }, (_, i) => series[Math.floor(i * step)]);\n}\n\napp.get(\"/prices\", async (c) => {\n const currency = (c.req.query(\"currency\") ?? \"usd\").toLowerCase();\n const symbols = (c.req.query(\"symbols\") ?? \"BTC,ETH\")\n .split(\",\").map((s) => s.trim().toUpperCase()).filter(Boolean);\n\n const key = `quotes:${currency}:${symbols.slice().sort().join(\",\")}`;\n\n // Serve the cached copy while it is fresh.\n try {\n const cached = await blob.getJSON(key) as\n { at: number; quotes: Quote[] } | undefined;\n if (cached && Date.now() - cached.at < CACHE_SECONDS * 1000) {\n return c.json({ currency, quotes: cached.quotes, cached: true });\n }\n } catch { /* a cold or evicted cache is not an error */ }\n\n try {\n const quotes = await fetchQuotes(symbols, currency);\n await blob.setJSON(key, { at: Date.now(), quotes });\n return c.json({ currency, quotes, cached: false });\n } catch (error) {\n // Upstream is down or rate-limiting. Hand back the stale copy if there is\n // one — a minute-old price beats an error on a screen that is mostly\n // decorative.\n try {\n const stale = await blob.getJSON(key) as\n { quotes: Quote[] } | undefined;\n if (stale) return c.json({ currency, quotes: stale.quotes, stale: true });\n } catch { /* nothing cached */ }\n return c.json({ error: String(error), quotes: [] }, 502);\n }\n});\n\napp.get(\"/\", (c) =>\n c.json({\n service: \"crypto-prices\",\n usage: \"/prices?symbols=BTC,ETH,SOL¤cy=gbp\",\n supported: Object.keys(IDS),\n }));\n\napp.get(\"/source\", (c) => c.redirect(parseVal().links.self.val));\n\napp.onError((err) => Promise.reject(err));\n\nexport default app.fetch;\n","deleted",false,"label",[19],{"_33":70,"_13":71,"_35":72,"_37":-5,"_38":39,"_40":46,"_42":43,"_44":73,"_17":66,"_47":24,"_49":74,"_51":52,"_53":-5,"_59":75,"_18":76},{"_33":62,"_13":63,"_35":64,"_37":-5,"_38":39,"_40":46,"_42":43,"_44":65,"_17":66,"_47":24,"_49":67,"_51":52,"_53":-5,"_59":68,"_18":69},{"_33":34,"_13":19,"_35":36,"_37":-5,"_38":39,"_40":41,"_42":43,"_44":58,"_17":46,"_47":48,"_49":50,"_51":52,"_53":-5,"_59":60,"_18":61},["D",1788676276361],"children",[],[19],"138ad373-5b92-4832-96b2-f70669d97168","README.md","01a07568-ca00-74ac-b535-ad5f1b066384",["D",1788676196622],0,"# React + Hono Starter\n\nA minimal starter template for building client-side React apps with a Hono\nbackend on Val Town. Click **Remix** to get your own copy.\n\n## Picking a starter\n\n| Starter | When to pick it |\n| --- | --- |\n| [`basic-html-starter`](https://www.val.town/x/templates/basic-html-starter) | Static HTML pages. Sprinkle of vanilla JS. No server-side rendering. |\n| [`hono-jsx-starter`](https://www.val.town/x/templates/hono-jsx-starter) | Dynamic server-rendered HTML with JSX. API routes. No React, no SPA. |\n| **[`react-hono-starter`](https://www.val.town/x/templates/react-hono-starter)** *(you're here)* | Client-side React SPA with a Hono API backend. |\n\n**Want to build UI?** Start writing React components in\n[`frontend/components/`](/frontend/components/). Import them into `App.tsx` and\nyou're good to go. Styling is [Twind](https://twind.style/) — just use Tailwind\nutility classes, zero config.\n\n**Want to add an API?** Add routes in [`index.ts`](/index.ts) (there's a\ncommented-out example). Fetch them from your React components.\n\n## Architecture\n\n```mermaid\ngraph LR\n Browser -->|\"GET /\"| Hono[\"index.ts
(Hono server)\"]\n Hono -->|serves| HTML[\"root.tsx\"]\n HTML -->|loads| Entry[\"index.tsx\"]\n Entry -->|renders| App[\"App.tsx\"]\n App -->|renders| Counter[\"Counter.tsx\"]\n```\n\n## File structure\n\n```\nindex.ts ← Hono backend (serves frontend + API routes)\nfrontend/\n root.tsx ← HTML shell (stamps immutable asset URLs)\n index.tsx ← React entrypoint (mounts )\n favicon.svg ← App icon\n components/\n App.tsx ← Root component (layout + view source link)\n Counter.tsx ← Example component with state\n```\n\n## How it works\n\n1. **`index.ts`** is the HTTP entrypoint — a Hono server that serves the\n frontend and any API routes you add.\n2. **`frontend/root.tsx`** is the HTML shell — it loads Twind and stamps\n immutable asset URLs for the favicon and React entrypoint.\n3. **`frontend/index.tsx`** mounts the React app.\n4. **`frontend/components/App.tsx`** is the root layout — add new components\n alongside it.\n5. **`frontend/components/Counter.tsx`** is an example stateful component —\n replace it with your own!\n\n## Next steps\n\n- Add API routes in `index.ts`\n- Add new components in `frontend/components/`\n- Add a SQLite database — see the\n [React Hono Example](https://www.val.town/x/stevekrouse/reactHonoExample) for\n a full-stack example with database, queries, and shared types\n\nTemplate updates and upgrade paths for existing remixes: [CHANGELOG.md](/CHANGELOG.md)\n",[],[63],"891067ab-3909-4d1c-8676-4fc76d006e7a","CHANGELOG.md","01a07568-ca00-74ac-b535-aa0dd82fd353",["D",1788676196622],"# Changelog\n\n## 2026-07-30 — Immutable asset caching\n\nFrontend files are now served at version-addressed URLs\n(`/__immutable/45/frontend/index.tsx`) with\n`Cache-Control: public, max-age=31536000, immutable`, so repeat visits load the\nwhole client graph from the browser cache — roughly 3× faster (~665ms → ~157ms\nmeasured). Publishing your val bumps its version, which changes every URL, so\ncaches invalidate automatically. Old-version URLs return 404 after a publish\n(like Next.js build assets); a reload picks up the new version.\n\nWhat changed in the template:\n\n- `frontend/index.html` → [`frontend/root.tsx`](/frontend/root.tsx): the HTML\n shell is now JSX and stamps asset URLs with `immutableFileUrl()`\n- [`index.ts`](/index.ts): serves `Root()` at `/`, and one\n `app.get(\"/__immutable/*\", (c) => serveImmutableFile(c.req.path))` route\n serves all frontend files\n\n### Upgrading an existing remix\n\nYour copy of this template doesn't update automatically. Two options:\n\n**Minimal (most of the benefit):** point both routes at `serveImmutableFile` —\nyour existing bare URLs redirect into versioned space, the new route serves\nthem, and the whole module graph gets cached (costs one redirect per page view):\n\n```ts\nimport { serveImmutableFile } from \"https://esm.town/v/std/utils/index.ts\";\n\napp.get(\"/__immutable/*\", (c) => serveImmutableFile(c.req.path));\napp.get(\"/frontend/**/*\", (c) => serveImmutableFile(c.req.path)); // was serveFile\n```\n\n**Full upgrade (also removes the redirect):** three self-contained steps —\nno other files needed. Adjust the ``, favicon, and body of `Root()` to\nmatch your app's existing `index.html`, and stamp anything else your shell\nreferences directly (images, css) with `immutableFileUrl()`.\n\n1. Create `frontend/root.tsx`:\n\n```tsx\n/** @jsxImportSource npm:hono@4/jsx */\nimport { raw } from \"npm:hono@4/html\";\nimport { immutableFileUrl } from \"https://esm.town/v/std/utils/index.ts\";\n\n// The HTML shell for the app. It is never cached, so immutableFileUrl can stamp\n// the current val version into each asset URL — the browser caches those\n// immutably, and publishing the val changes the URLs, refetching exactly once.\nexport function Root() {\n return (\n <>\n {raw(\"<!DOCTYPE html>\")}\n <html lang=\"en\">\n <head>\n <meta charSet=\"UTF-8\" />\n <meta name=\"viewport\" content=\"width=device-width, initial-scale=1.0\" />\n <title>React Hono Val Town Starter\n