api-cms-sanity

name	api-cms-sanity
description	Structured content platform — GROQ queries, schema definitions, @sanity/client, Portable Text, image handling, real-time listeners, mutations, TypeGen

Sanity Patterns

Quick Guide: Use Sanity for structured content management with GROQ queries, typed schemas via defineType/defineField, and @sanity/client for data fetching. Always set apiVersion to a dated string, use useCdn: true for public reads, handle draft documents explicitly, use @sanity/image-url for image transformations, and render rich text with @portabletext/react. Generate TypeScript types with sanity typegen generate.

---

<critical_requirements>

CRITICAL: Before Using This Skill

All code must follow project conventions in CLAUDE.md (kebab-case, named exports, import ordering, import type, named constants)

(You MUST always set apiVersion on createClient to a dated string like '2025-02-19' — omitting it uses a legacy API that may break)

(You MUST use useCdn: true for public read queries and useCdn: false when using a token or needing fresh data)

(You MUST use parameterized GROQ queries ($param) for any dynamic values — never interpolate user input into GROQ strings)

(You MUST handle drafts explicitly — draft documents have _id prefixed with drafts. and are not returned by default with perspective: 'published')

(You MUST use defineQuery() from groq and assign queries to named variables for TypeGen type generation)

</critical_requirements>

---

Auto-detection: Sanity, sanity, @sanity/client, createClient, GROQ, groq, defineType, defineField, defineArrayMember, @sanity/image-url, urlFor, @portabletext/react, PortableText, portable text, block content, sanity.config, sanity.cli, typegen, sanity studio, content lake

When to use:

• Setting up @sanity/client with createClient for data fetching
• Writing GROQ queries (filters, projections, joins, ordering, slicing)
• Defining content schemas with defineType, defineField, defineArrayMember
• Rendering Portable Text (block content) with @portabletext/react
• Generating image URLs with @sanity/image-url (responsive images, crops, hotspots)
• Performing mutations (create, patch, delete, transactions)
• Setting up real-time listeners with client.listen()
• Generating TypeScript types with Sanity TypeGen

Key patterns covered:

• Client setup with createClient and apiVersion configuration
• GROQ query language: filters, projections, ordering, slicing, joins, references
• Schema definitions: document types, object types, arrays, references, images
• Portable Text rendering with custom components
• Image URL builder with responsive images and transformations
• Mutations: create, createOrReplace, patch, delete, transactions
• Real-time listeners via client.listen()
• TypeGen for type-safe GROQ queries with defineQuery()

When NOT to use:

• GraphQL-only APIs (Sanity supports GROQ primarily; use GraphQL skill if needed)
• Direct database access (Sanity is a hosted content lake, not a database)
• Non-Sanity CMS platforms (use dedicated skills for Contentful, Strapi, etc.)

Detailed Resources:

• For decision frameworks and quick-reference tables, see reference.md

Client & GROQ:

• examples/core.md — Client setup, GROQ queries, error handling, TypeGen

Schemas:

• examples/schemas.md — defineType, defineField, document types, object types, references, images

Rich Content:

• examples/rich-content.md — Portable Text rendering, image URL builder, responsive images

Mutations & Real-time:

• examples/mutations.md — Create, patch, delete, transactions, real-time listeners

---

Philosophy

Sanity is a structured content platform built around a real-time content lake, GROQ (Graph-Relational Object Queries) as its query language, and Sanity Studio as a customizable editing environment.

Core principles:

1. Structured content — Content is defined by schemas (defineType, defineField) that describe shape, validation, and editorial UI. Schemas are code, not configuration files.
2. GROQ-first querying — GROQ lets you filter, project, join, and reshape data in a single query. Unlike REST or GraphQL, GROQ queries return exactly the shape you define in the projection.
3. Content as data — Rich text is stored as Portable Text (a JSON-based specification), making it renderable in any frontend framework without vendor lock-in.
4. API versioning — Every client must specify an apiVersion date string. This pins your code to a specific API behavior, preventing breaking changes from affecting production.
5. CDN caching — Public read queries use useCdn: true for edge-cached responses. Mutations and authenticated reads use useCdn: false for fresh data.
6. Type generation — Sanity TypeGen generates TypeScript types from both your schemas and GROQ queries, enabling end-to-end type safety from content model to frontend.

When to use Sanity:

• Content-driven websites and applications (blogs, marketing sites, documentation)
• Projects needing real-time collaborative editing in a customizable studio
• Multi-channel content delivery (web, mobile, IoT) from a single content source
• Teams wanting type-safe content queries with GROQ and TypeGen

When NOT to use:

• Transactional data requiring ACID guarantees (use a database)
• User-generated content at massive scale (Sanity is optimized for editorial content)
• Projects needing a self-hosted CMS (Sanity's content lake is hosted, though the Studio is open source)

---

Core Patterns

Pattern 1: Client Setup with createClient

Configure @sanity/client with your project ID, dataset, API version, and CDN preference.

// lib/sanity-client.ts
import { createClient } from "@sanity/client";

const PROJECT_ID = process.env.SANITY_PROJECT_ID!;
const DATASET = process.env.SANITY_DATASET!;
const API_VERSION = "2025-02-19";

export const client = createClient({
  projectId: PROJECT_ID,
  dataset: DATASET,
  apiVersion: API_VERSION,
  useCdn: true, // true for public reads, false for authenticated/fresh data
});

Why good: apiVersion pins API behavior, useCdn: true for cached reads, named constants for environment variables, no hardcoded credentials

// BAD: Missing apiVersion, hardcoded credentials
import { createClient } from "@sanity/client";

const client = createClient({
  projectId: "abc123",
  dataset: "production",
  // No apiVersion — uses legacy API behavior
});

Why bad: No apiVersion causes unpredictable API behavior across deployments, hardcoded project ID belongs in environment variables, no useCdn specified

---

Pattern 2: GROQ Queries with Filters and Projections

GROQ queries combine filters (what to fetch), projections (what shape to return), and ordering/slicing (how to sort and paginate).

Basic Query Structure

import { defineQuery } from "groq";

// Filter → Projection → Order → Slice
const POSTS_QUERY = defineQuery(`
  *[_type == "post" && published == true]{
    _id,
    title,
    slug,
    "authorName": author->name,
    "categoryTitle": category->title,
    publishedAt
  } | order(publishedAt desc) [0...10]
`);

Parameterized Queries

const POST_BY_SLUG_QUERY = defineQuery(`
  *[_type == "post" && slug.current == $slug][0]{
    _id,
    title,
    body,
    "author": author->{name, image},
    "categories": categories[]->title
  }
`);

// Always pass dynamic values as parameters
const post = await client.fetch(POST_BY_SLUG_QUERY, { slug: "my-post" });

Why good: defineQuery() enables TypeGen type inference, parameters prevent GROQ injection, projection returns only needed fields, [0] returns a single object instead of an array, reference joins via -> operator

// BAD: String interpolation in GROQ
const query = `*[_type == "post" && slug.current == "${userInput}"]`;
// GROQ injection vulnerability!

Why bad: String interpolation allows GROQ injection attacks — always use $param parameters

---

Pattern 3: Schema Definitions with defineType and defineField

Schemas define content structure, validation, and Studio UI. Use defineType, defineField, and defineArrayMember for type safety.

Document Type

// schemas/post.ts
import { defineType, defineField, defineArrayMember } from "sanity";

export const postType = defineType({
  name: "post",
  title: "Post",
  type: "document",
  fields: [
    defineField({
      name: "title",
      title: "Title",
      type: "string",
      validation: (rule) => rule.required().min(5).max(100),
    }),
    defineField({
      name: "slug",
      title: "Slug",
      type: "slug",
      options: { source: "title", maxLength: 96 },
      validation: (rule) => rule.required(),
    }),
    defineField({
      name: "author",
      title: "Author",
      type: "reference",
      to: [{ :  }],
    }),
    ({
      : ,
      : ,
      : ,
      : [
        ({ :  }),
        ({ : , : { :  } }),
      ],
    }),
    ({
      : ,
      : ,
      : ,
    }),
  ],
  : {
    : { : , : , :  },
    () {
       { author } = selection;
       { ...selection, : author ?  :  };
    },
  },
});

Why good: defineType/defineField provide IDE autocomplete and type checking, validation rules enforce content quality, slug generated from title, hotspot: true enables focal point cropping, preview customizes Studio list appearance

---

Pattern 4: Portable Text Rendering

Render Sanity's block content (Portable Text) using @portabletext/react with custom components for non-standard blocks and marks.

import { PortableText } from "@portabletext/react";
import type { PortableTextComponents } from "@portabletext/react";

const components: PortableTextComponents = {
  types: {
    image: ({ value }) => {
      if (!value?.asset?._ref) return null;
      return (
        <figure>
          <img src={urlFor(value).width(800).url()} alt={value.alt || ""} />
          {value.caption && <figcaption>{value.caption}</figcaption>}
        </figure>
      );
    },
    code: ({ value }) => (
      <pre data-language={value.language}>
        <code>{value.code}</code>
      </pre>
    ),
  },
  marks: {
    link: ({ children, value }) => {
      const rel = value.?.()
        ? 
        : ;
       target = value.?.() ?  : ;
       (
        
      );
    },
    :  ,
  },
  : {
    :  ,
    :  ,
  },
};


 () {
   ;
}
 {  };

Why good: Custom components for image, code, link, and heading blocks; external links get noopener noreferrer; images use urlFor for optimized URLs; fallback for missing assets; named export

---

Pattern 5: Image URL Builder

Use @sanity/image-url to generate optimized, responsive image URLs with automatic crop and hotspot support.

// lib/sanity-image.ts
import { createImageUrlBuilder } from "@sanity/image-url";
import type { SanityImageSource } from "@sanity/image-url";
import { client } from "./sanity-client";

const builder = createImageUrlBuilder(client);

export function urlFor(source: SanityImageSource) {
  return builder.image(source);
}

Responsive Images

const WIDTHS = [400, 800, 1200] as const;

function ResponsiveImage({
  image,
  alt,
}: {
  image: SanityImageSource;
  alt: string;
}) {
  return (
    <img
      src={urlFor(image).width(800).auto("format").url()}
      srcSet={WIDTHS.map(
        (w) => `${urlFor(image).width(w).auto("format").url()} ${w}w`,
      ).join(", ")}
      sizes="(max-width: 600px) 400px, (max-width: 1200px) 800px, 1200px"
      alt={alt}
      loading="lazy"
    />
  );
}
export { ResponsiveImage };

Why good: createImageUrlBuilder initializes from client config, urlFor helper is reusable, .auto("format") serves WebP/AVIF when supported, responsive srcSet with named width constants, lazy loading for performance, crop/hotspot applied automatically from the full image field

---

Pattern 6: Mutations (Create, Patch, Delete)

Use @sanity/client methods for creating, updating, and deleting documents.

Create

const newPost = await client.create({
  _type: "post",
  title: "New Post",
  slug: { _type: "slug", current: "new-post" },
  publishedAt: new Date().toISOString(),
});

Create or Replace

// Overwrites entirely if document exists, creates if it doesn't
await client.createOrReplace({
  _id: "singleton-settings",
  _type: "siteSettings",
  title: "My Site",
  description: "Site description",
});

Patch

// Set fields
await client.patch("post-123").set({ title: "Updated Title" }).commit();

// Increment a number field
await client.patch("post-123").inc({ viewCount: 1 }).commit();

// Unset (remove) a field
await client.patch("post-123").unset(["temporaryField"]).commit();

// Insert into an array at a specific position
await client
  .patch("post-123")
  .insert("after", "tags[-1]", [{ _key: "abc", label: "new-tag" }])
  .commit();

Delete

await client.delete("post-123");

Transaction (Atomic Multi-Mutation)

await client
  .transaction()
  .create({ _type: "log", message: "Post archived" })
  .patch("post-123", (p) => p.set({ archived: true }))
  .commit();

Why good: .commit() required on patches and transactions, createOrReplace for singletons, _key required for array items, transactions group related mutations atomically

---

Pattern 7: Real-Time Listeners

Subscribe to document changes with client.listen() using a GROQ filter.

// Listen for new/updated published posts
const LISTENER_QUERY = `*[_type == "post" && published == true]`;

const subscription = client.listen(LISTENER_QUERY).subscribe({
  next: (update) => {
    if (update.type === "mutation") {
      console.log(`Document ${update.documentId} was ${update.transition}`);
      // update.transition: 'update' | 'appear' | 'disappear'
      // update.result contains the document if it matched the filter
    }
  },
  error: (err) => {
    console.error("Listener error:", err.message);
  },
});

// Cleanup: unsubscribe when done
subscription.unsubscribe();

Why good: GROQ filter scopes to relevant documents, observable-based subscription with error handling, cleanup via unsubscribe(), transition field indicates what happened to the document

When to use: Preview mode, live dashboards, collaborative editing indicators. For production frontends, evaluate the newer Live Content API as a simpler alternative.

---

Pattern 8: TypeGen for Type-Safe GROQ

Use Sanity TypeGen to generate TypeScript types from schemas and GROQ queries.

Configuration

// sanity.cli.ts
import { defineCliConfig } from "sanity/cli";

// NOTE: default export required by Sanity CLI tooling
export default defineCliConfig({
  api: {
    projectId: "your-project-id",
    dataset: "production",
  },
  typegen: {
    enabled: true,
    path: "./src/**/*.{ts,tsx}",
    schema: "schema.json",
    generates: "./sanity.types.ts",
    overloadClientMethods: true,
  },
});

Query with defineQuery

// queries/post-queries.ts
import { defineQuery } from "groq";

export const allPostsQuery = defineQuery(`
  *[_type == "post" && published == true]{
    _id,
    title,
    slug,
    publishedAt
  } | order(publishedAt desc)
`);

export const postBySlugQuery = defineQuery(`
  *[_type == "post" && slug.current == $slug][0]{
    _id,
    title,
    body,
    "author": author->{name, image}
  }
`);

Using Generated Types

import type {
  AllPostsQueryResult,
  PostBySlugQueryResult,
} from "./sanity.types";
import { allPostsQuery, postBySlugQuery } from "./queries/post-queries";

// Return type is automatically inferred when overloadClientMethods is true
const posts = await client.fetch(allPostsQuery);
// posts: AllPostsQueryResult

const post = await client.fetch(postBySlugQuery, { slug: "my-post" });
// post: PostBySlugQueryResult

Why good: defineQuery() enables TypeGen to find and type queries, overloadClientMethods: true makes client.fetch return typed results, queries in dedicated files for organization, generated types update automatically during sanity dev

// BAD: Inline query without defineQuery
const posts = await client.fetch(`*[_type == "post"]{ title }`);
// TypeGen cannot generate types for inline queries
// posts is typed as 'any'

Why bad: TypeGen requires queries assigned to variables using defineQuery() or the groq template literal — inline strings produce untyped results

---

<decision_framework>

Decision Framework

useCdn: true vs false

Is the data public and non-personalized?
├─ YES → useCdn: true (edge-cached, fast)
└─ NO →
    ├─ Using a token for authenticated reads? → useCdn: false
    ├─ Need real-time fresh data (preview)? → useCdn: false
    └─ Performing mutations? → useCdn: false

Draft Handling

Do you need draft documents?
├─ YES → Use perspective: 'previewDrafts' (requires token)
├─ NO → Use perspective: 'published' (default since API v2025-02-19)
└─ Mixed (preview mode toggle)?
    └─ Create two clients: one public (useCdn: true), one preview (token + useCdn: false)

GROQ Query Return Shape

How many documents do you expect?
├─ One (by ID, slug, singleton) → Add [0] at end (returns object or null)
├─ Many (list, feed) → No slice suffix (returns array)
└─ Paginated → Add [start...end] slice

Image Handling

How should images be delivered?
├─ Fixed size (thumbnails, avatars) → urlFor(img).width(W).height(H).url()
├─ Responsive (article images) → srcSet with multiple widths
├─ Format optimization → .auto('format') for WebP/AVIF
└─ Cropped to aspect ratio → .width(W).height(H).fit('crop')

Mutation Method Selection

What operation do you need?
├─ Create new document → client.create()
├─ Create or fully replace → client.createOrReplace() (for singletons)
├─ Create only if missing → client.createIfNotExists()
├─ Update specific fields → client.patch(id).set({...}).commit()
├─ Remove fields → client.patch(id).unset([...]).commit()
├─ Multiple related changes → client.transaction()...commit()
└─ Delete document → client.delete(id)

</decision_framework>

---

<red_flags>

RED FLAGS

High Priority Issues:

• Missing apiVersion on client — Omitting apiVersion uses legacy API behavior that may change without notice. Always pin to a date string.
• String interpolation in GROQ queries — Interpolating user input into GROQ strings enables GROQ injection. Always use $param parameters.
• Using useCdn: true with a token — CDN-cached responses ignore authentication tokens. Authenticated queries must use useCdn: false.
• Accessing draft documents without a token — Drafts (drafts.* documents) require an API token and perspective: 'previewDrafts'. Without a token, drafts are invisible.

Medium Priority Issues:

• Fetching all fields with {...} when only a few are needed — Over-fetching wastes bandwidth and CDN cache efficiency. Project only the fields you need.
• Missing .commit() on patches — client.patch(id).set({...}) without .commit() does nothing — the mutation is never sent.
• Not using defineQuery() for GROQ queries — TypeGen cannot generate types for queries that aren't wrapped in defineQuery() or assigned to named variables.
• Hardcoded project ID or dataset — Use environment variables; hardcoded values prevent environment switching and leak project details.
• Using deprecated @sanity/block-content-to-react — Replaced by @portabletext/react. The old package is unmaintained.

Common Mistakes:

• Forgetting _key on array items in mutations — Every item in a Sanity array must have a unique _key field. Mutations without _key will fail.
• Using _id with client.create() — create() generates a random _id. If you specify _id and the document exists, it errors. Use createOrReplace() or createIfNotExists() for idempotent operations.
• Not handling the case where [0] returns null — A GROQ query ending in [0] returns null if no documents match, not an empty object.
• Expecting client.listen() to work with projections — The listener only uses the filter portion of a GROQ query. Projections, ordering, and slicing are ignored.

Gotchas & Edge Cases:

• API version 2025-02-19 changed default perspective — Before this version, the default perspective was raw (includes drafts). After, it defaults to published. Existing code may break if you update apiVersion without accounting for this.
• CDN cache is eventual — After a mutation, CDN-cached queries (useCdn: true) may return stale data for a few seconds. Use useCdn: false or add a small delay for consistency-critical reads after writes.
• Slug fields store value in .current — Query slug.current, not slug directly. *[slug == "my-slug"] will never match.
• Image fields require the full object for crop/hotspot — Passing only asset._ref to urlFor() works for basic URLs but loses crop and hotspot metadata. Pass the entire image field object.
• Portable Text arrays need _key on every block — When creating Portable Text content programmatically, every block and inline object needs a unique _key.
• client.listen() reconnects automatically — But there's no built-in guarantee against missed events during reconnection. For critical use cases, combine with periodic re-fetching.
• TypeGen requires schema.json extraction first — Run npx sanity schema extract before npx sanity typegen generate. The extract step reads your Studio schemas and outputs a JSON representation.

</red_flags>

---

<critical_reminders>

CRITICAL REMINDERS

All code must follow project conventions in CLAUDE.md (kebab-case, named exports, import ordering, import type, named constants)

(You MUST always set apiVersion on createClient to a dated string like '2025-02-19' — omitting it uses a legacy API that may break)

(You MUST use useCdn: true for public read queries and useCdn: false when using a token or needing fresh data)

(You MUST use parameterized GROQ queries ($param) for any dynamic values — never interpolate user input into GROQ strings)

(You MUST handle drafts explicitly — draft documents have _id prefixed with drafts. and are not returned by default with perspective: 'published')

(You MUST use defineQuery() from groq and assign queries to named variables for TypeGen type generation)

Failure to follow these rules will cause unpredictable API behavior, GROQ injection vulnerabilities, and untyped query results.

</critical_reminders>