chore: add prettier for markdown and astro formatting

.prettierignore

@@ -0,0 +1,14 @@
+# Dependencies and build output (prettier ignores node_modules by default; listed for clarity)
+node_modules
+dist
+build
+.next
+.astro
+.ponder
+generated
+
+# Lockfiles
+pnpm-lock.yaml
+
+# Generated changelogs — owned by changesets, do not reformat
+**/CHANGELOG.md

.prettierrc.json

@@ -0,0 +1,15 @@
+{
+  "printWidth": 100,
+  "proseWrap": "preserve",
+  "plugins": ["prettier-plugin-astro"],
+  "overrides": [
+    {
+      "files": "*.astro",
+      "options": {
+        "parser": "astro",
+        "bracketSameLine": true,
+        "astroSkipFrontmatter": true
+      }
+    }
+  ]
+}

docs/ensnode.io/config/integrations/starlight/sidebar-topics/reference.ts

@@ -22,6 +22,7 @@ export const referenceSidebarTopic = {
           link: "/docs/reference/contributing/building",
         },
         { label: "Creating a Release", link: "/docs/reference/contributing/releases" },
+        { label: "Format & Lint", link: "/docs/reference/contributing/formatting" },
         {
           label: "REST API Documentation",
           link: "/docs/reference/contributing/rest-api-docs",

docs/ensnode.io/package.json

@@ -13,6 +13,8 @@
     "astro": "astro",
     "lint": "biome check --write",
     "lint:ci": "biome ci",
+    "lint:prettier": "prettier --write \"**/*.astro\"",
+    "lint:prettier:ci": "prettier --check \"**/*.astro\"",
     "omnigraph-examples:refresh-responses": "tsx --tsconfig tsconfig.json scripts/fetch-omnigraph-example-responses.mts",
     "omnigraph:snapshot": "tsx --tsconfig tsconfig.json scripts/snapshot-omnigraph-version.mts",
     "test": "vitest",
@@ -57,6 +59,8 @@
   "devDependencies": {
     "@types/react": "catalog:",
     "@types/react-dom": "catalog:",
+    "prettier": "catalog:",
+    "prettier-plugin-astro": "catalog:",
     "tsx": "^4.19.3",
     "vitest": "catalog:"
   }

docs/ensnode.io/src/content/docs/docs/reference/contributing/formatting.mdx

@@ -0,0 +1,30 @@
+---
+title: Formatting with Biome and Prettier
+sidebar:
+  label: Formatting
+  order: 6
+---
+
+We use Biome to format most of the codebase, and Prettier to cover the rest:
+
+- Biome handles JS, TS, JSON, CSS, and the frontmatter of `.astro` files.
+- Prettier handles Markdown (`.md` and `.mdx`) across the repo, and the template portion of `.astro` files in `docs/ensnode.io` and `docs/ensrainbow.io` via [`prettier-plugin-astro`](https://github.com/withastro/prettier-plugin-astro). The `astroSkipFrontmatter: true` option keeps the frontmatter under Biome's ownership.
+
+## Running the formatters
+
+From the monorepo root:
+
+```bash
+pnpm lint
+```
+
+CI runs `pnpm lint:ci` (check-only) on every PR.
+
+## Windows: line-ending diffs
+
+Git on Windows checks files out with CRLF (`\r\n`) line endings by default. Biome and Prettier write LF (`\n`). After `pnpm lint`, files may appear modified, but Git normalizes the endings back to LF when staging, so nothing changes in the resulting commit.
+
+To clear the noise from your working tree:
+
+- One-off: run `git add --all`. The index normalizes the endings and the files drop out of `git status`.
+- Permanent: run `git config --global core.autocrlf input`, then `git checkout -- .`. Your working tree converts to LF and future checkouts keep it that way.

docs/ensrainbow.io/package.json

@@ -12,7 +12,9 @@
     "preview": "astro preview",
     "astro": "astro",
     "lint": "biome check --write .",
-    "lint:ci": "biome ci"
+    "lint:ci": "biome ci",
+    "lint:prettier": "prettier --write \"**/*.astro\"",
+    "lint:prettier:ci": "prettier --check \"**/*.astro\""
   },
   "dependencies": {
     "@astrojs/react": "catalog:",
@@ -30,6 +32,8 @@
   },
   "devDependencies": {
     "@types/react": "catalog:",
-    "@types/react-dom": "catalog:"
+    "@types/react-dom": "catalog:",
+    "prettier": "catalog:",
+    "prettier-plugin-astro": "catalog:"
   }
 }

package.json

@@ -4,8 +4,12 @@
   "private": true,
   "packageManager": "pnpm@10.33.0",
   "scripts": {
-    "lint": "biome check --write .",
-    "lint:ci": "biome ci",
+    "lint": "pnpm run lint:biome && pnpm run lint:prettier",
+    "lint:ci": "pnpm run lint:biome:ci && pnpm run lint:prettier:ci",
+    "lint:prettier": "pnpm exec prettier --write \"**/*.{md,mdx}\" && pnpm -r lint:prettier",
+    "lint:prettier:ci": "pnpm exec prettier --check \"**/*.{md,mdx}\" && pnpm -r lint:prettier:ci",
+    "lint:biome": "biome check --write .",
+    "lint:biome:ci": "biome ci",
     "test": "vitest --silent passed-only",
     "test:integration": "vitest --config vitest.integration.config.ts --silent passed-only",
     "test:integration:ci": "pnpm -F @ensnode/integration-test-env start:ci",
@@ -36,6 +40,8 @@
     "@changesets/cli": "^2.29.8",
     "@typescript/native-preview": "7.0.0-dev.20260128.1",
     "jsdom": "^27.0.1",
+    "prettier": "catalog:",
+    "prettier-plugin-astro": "catalog:",
     "tsup": "catalog:",
     "typescript": "catalog:",
     "vitest": "catalog:"

pnpm-workspace.yaml

@@ -27,6 +27,8 @@ catalog:
   pino: 10.1.0
   ponder: 0.16.6
   postcss: 8.5.12
+  prettier: 3.6.2
+  prettier-plugin-astro: 0.14.1
   react: 19.2.1
   react-dom: 19.2.1
   tailwind-merge: ^3.4.0