Link to the code that reproduces this issue

https://github.com/Thakisis/cache-components

To Reproduce

Prerequisites

• A Turso database (free tier works). Create a database and get your TURSO_DATABASE_URL and TURSO_AUTH_TOKEN.
• Bun installed
• A Vercel account

Setup

git clone https://github.com/Thakisis/cache-components
cd cache-components
bun install

Create a .env.local file:

TURSO_DATABASE_URL=your_turso_url
TURSO_AUTH_TOKEN=your_turso_token

Run migrations and seed the database:

bun run db:migrate
bun run db:seed

Local (works correctly)

bun run dev

1. Open the app — 10 product cards are displayed
2. Click Edit Product on any card
3. Change a single field (e.g. name) and click Save Changes
4. ✅ Only the edited field shows the update highlight

Vercel (broken)

Deploy to Vercel setting the same env vars (TURSO_DATABASE_URL, TURSO_AUTH_TOKEN).

1. Open the deployed app
2. Click Edit Product on any card
3. Change a single field (e.g. name) and click Save Changes
4. ❌ All fields of that product show the update highlight — all cacheTag entries for that product id are invalidated

Relevant code

Each field component uses a unique tag per field+id:

// getProductField in server/queries/products.ts
export async function getProductField(id, field) {
  "use cache";
  cacheTag(`${field}-${id}`);
  // ...
}

The server action only invalidates the changed field's tag:

// Only the changed field tag is added
const FIELD_CACHE_TAGS = {
  name: (id) => `name-${id}`,
  description: (id) => `description-${id}`,
  // ...
};
 
for (const field of changedFields) {
  const tagFn = FIELD_CACHE_TAGS[field];
  if (tagFn) tagsToRevalidate.add(tagFn(original.id));
}
 
for (const tag of tagsToRevalidate) {
  updateTag(tag); // only one tag, e.g. "name-5"
}

Current vs. Expected behavior

Expected behavior (local build)

Only the component whose cacheTag matches the invalidated tag should re-render. For example, calling updateTag('name-5') should only revalidate ProductName for product id 5.

Actual behavior (Vercel only)

All cached field components for the edited product re-render (ProductName, ProductDescription, ProductBadge, ProductBrand, ProductRating, Price). This is confirmed by the updatedAt tooltip changing on all fields and wrapper component show blue outline, which only happens when the component re-executes and returns a new date value from the database.

Provide environment information

- **Next.js:** 16.1.6
- **Runtime:** Vercel (production) vs local (Windows, Bun)
- **Database:** Turso (LibSQL) + Drizzle ORM
- **Build:** performed on Windows with Bun

Which area(s) are affected? (Select all that apply)

cacheComponents

Which stage(s) are affected? (Select all that apply)

Vercel (Deployed)

Additional context

• Related issues from October 2025 mention similar behavior but do not identify Vercel as the specific environment where it fails
• The issue does not reproduce locally, suggesting it is specific to Vercel's Data Cache implementation rather than the Next.js compiler
• It is worth noting that in very rare occasions, all fields being revalidated can also happen in a local production build (bun run build && bun run start) on the first data mutation.