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 the dedicated skill for your CMS)

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 project ID, dataset, API version, and CDN preference. Always set apiVersion to a dated string and useCdn explicitly.

import { createClient } from "@sanity/client";

export const client = createClient({
  projectId: process.env.SANITY_PROJECT_ID!,
  dataset: process.env.SANITY_DATASET!,
  apiVersion: "2025-02-19", // Pin to a specific API version date
  useCdn: true, // true for public reads, false for authenticated/fresh data
});

For dual client setup (public + preview with token), see examples/core.md.

---

Pattern 2: GROQ Queries with Filters and Projections

GROQ queries combine filters, projections, ordering, and slicing. Always use defineQuery() for TypeGen and $param for dynamic values.

import { defineQuery } from "groq";

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

Never interpolate user input into GROQ strings -- always use $param parameters to prevent GROQ injection. For advanced queries (combined queries, conditional projections), see examples/core.md.

---

Pattern 3: Schema Definitions with defineType and defineField

Define content structure with defineType, defineField, and defineArrayMember from "sanity" for type safety and Studio UI.

import { defineType, defineField } from "sanity";

export const postType = defineType({
  name: "post",
  type: "document",
  fields: [
    defineField({
      name: "title",
      type: "string",
      validation: (r) => r.required(),
    }),
    defineField({ name: "slug", type: "slug", options: { source: "title" } }),
  ],
});

For complete schemas (images with hotspot, arrays, references, previews, object types), see examples/schemas.md.

---

Pattern 4: Portable Text Rendering

Render block content with @portabletext/react. Define custom PortableTextComponents for non-standard blocks (images, code) and marks (links, highlights).

import { PortableText } from "@portabletext/react";
<PortableText value={body} components={components} />;

Do not use the deprecated @sanity/block-content-to-react package. For full component examples, see examples/rich-content.md.

---

Pattern 5: Image URL Builder

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

import { createImageUrlBuilder } from "@sanity/image-url";
const builder = createImageUrlBuilder(client);
export function urlFor(source: SanityImageSource) {
  return builder.image(source);
}
// Usage: urlFor(image).width(800).auto("format").url()

For responsive srcSet patterns and image transformations, see examples/rich-content.md.

---

Pattern 6: Mutations (Create, Patch, Delete)

Use @sanity/client methods for document mutations. Always call .commit() on patches and transactions.

await client.create({ _type: "post", title: "New Post" });
await client.patch("post-123").set({ title: "Updated" }).commit();
await client.delete("post-123");

For createOrReplace, createIfNotExists, transactions, array inserts, and visibility options, see examples/mutations.md.

---

Pattern 7: Real-Time Listeners

Subscribe to document changes with client.listen(). The listener only uses the filter portion of GROQ -- projections and ordering are ignored.

const subscription = client.listen(`*[_type == "post"]`).subscribe({
  next: (update) => {
    /* update.transition: 'update' | 'appear' | 'disappear' */
  },
  error: (err) => console.error(err),
});
subscription.unsubscribe(); // Cleanup when done

For production frontends, evaluate the newer Live Content API as a simpler alternative. For listener options and caveats, see examples/mutations.md.

---

Pattern 8: TypeGen for Type-Safe GROQ

Configure TypeGen in sanity.cli.ts with overloadClientMethods: true for typed client.fetch results. Use defineQuery() from "groq" to make queries discoverable by TypeGen.

// sanity.cli.ts — set typegen.overloadClientMethods: true
// queries/post-queries.ts — wrap queries with defineQuery()
// sanity.types.ts — auto-generated result types
const posts = await client.fetch(allPostsQuery); // Typed result

Inline query strings without defineQuery() produce untyped (any) results. For full TypeGen configuration and workflow, see examples/core.md.

---

<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>