diff --git a/src/lib/categories.ts b/src/lib/categories.ts
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+++ b/src/lib/categories.ts
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+/**
+ * Category taxonomy for benchmark hubs.
+ *
+ * Mirrors the closed `Category` enum from `spec-schema.ts` (the source
+ * of truth that every YAML spec gets validated against). Centralised
+ * here so the `/benchmarks/category/<cat>` routes, the sitemap, the
+ * client filter and the meta-builders all share one slug ↔ label ↔
+ * description vocabulary. If a new category is added to the schema,
+ * adding it here is the only other touch-point needed to surface a
+ * dedicated hub URL.
+ *
+ * Slugs are lowercase, kebab-case, ASCII-only so they survive URL
+ * canonicalisation, RSS readers and JSON-LD @id fragments without
+ * needing encoding. Labels match the schema enum verbatim so the
+ * client filter can compare `b.category === entry.label` without an
+ * extra lookup.
+ *
+ * Descriptions are SEO copy that explains the category scope. They
+ * land in <meta description>, OG description, and the H1 sub-paragraph
+ * on the category hub page, so each must read as a standalone sentence
+ * (a) without the surrounding template and (b) with the category name
+ * substituted in. No em / en dashes per the project copy rules.
+ */
+
+export type Category =
+  | "Aggregators"
+  | "Bridges"
+  | "Blockchains"
+  | "Trading"
+  | "Wallets"
+  | "RPCs"
+  | "NFT APIs";
+
+export type CategoryEntry = {
+  /** URL slug. Lowercase, kebab-case, ASCII. */
+  slug: string;
+  /** Schema enum label, matches `Benchmark.category` exactly. */
+  label: Category;
+  /** Plural human heading used in H1 + breadcrumb. */
+  heading: string;
+  /** SEO copy under the H1 + <meta description>. */
+  description: string;
+};
+
+export const CATEGORIES: readonly CategoryEntry[] = [
+  {
+    slug: "aggregators",
+    label: "Aggregators",
+    heading: "Aggregator benchmarks",
+    description:
+      "Live OpenChainBench measurements for crypto data aggregators. Compare quote latency, market coverage, and freshness across the providers that fan out queries to multiple underlying sources.",
+  },
+  {
+    slug: "bridges",
+    label: "Bridges",
+    heading: "Bridge benchmarks",
+    description:
+      "Open, reproducible benchmarks for cross-chain bridges and intent layers. Compare quote latency, end-to-end fees, and route coverage across the bridges that move value between chains.",
+  },
+  {
+    slug: "blockchains",
+    label: "Blockchains",
+    heading: "Blockchain benchmarks",
+    description:
+      "Network-level measurements that compare blockchains head to head. Time to finality, block time, gas estimation accuracy, and validator economics on every L1 and L2 OpenChainBench tracks.",
+  },
+  {
+    slug: "trading",
+    label: "Trading",
+    heading: "Trading benchmarks",
+    description:
+      "Latency, fee, and freshness benchmarks for trading venues and execution providers. Perpetuals, spot DEX quotes, oracle deviation, and Polymarket data freshness measured continuously.",
+  },
+  {
+    slug: "wallets",
+    label: "Wallets",
+    heading: "Wallet benchmarks",
+    description:
+      "Benchmarks that compare wallet infrastructure providers on label coverage, address resolution, and the data layers that power production wallet UIs.",
+  },
+  {
+    slug: "rpcs",
+    label: "RPCs",
+    heading: "RPC benchmarks",
+    description:
+      "Live OpenChainBench measurements for RPC and node providers. Compare capability coverage, transaction landing latency, and reliability across the endpoints that power production dApps.",
+  },
+  {
+    slug: "nft-apis",
+    label: "NFT APIs",
+    heading: "NFT API benchmarks",
+    description:
+      "Benchmarks that compare NFT data API providers on collection metadata coverage, freshness, and the indexing depth that production NFT marketplaces and wallets depend on.",
+  },
+];
+
+export const CATEGORY_BY_SLUG: ReadonlyMap<string, CategoryEntry> = new Map(
+  CATEGORIES.map((c) => [c.slug, c]),
+);
+
+export const CATEGORY_SLUG_BY_LABEL: ReadonlyMap<Category, string> = new Map(
+  CATEGORIES.map((c) => [c.label, c.slug]),
+);
+
+/** Slug used in the `/benchmarks/category/<slug>` URL for a given
+ *  `Benchmark.category` value. Returns `null` for unknown labels so
+ *  call sites can degrade to the unscoped hub instead of a 404 link. */
+export function categorySlugFromLabel(label: string): string | null {
+  return CATEGORY_SLUG_BY_LABEL.get(label as Category) ?? null;
+}