Context: JSS is officially in maintenance mode with EOL June 2026, but the npm packages carry no deprecation signal. Developers running `npm install @sitecore-jss/sitecore-jss-nextjs` receive no warning that JSS is deprecated or that Content SDK is the successor. The npm `deprecated` flag is the standard mechanism for communicating this — every major ecosystem package uses it (e.g., `request`, `istanbul`). Without it, new projects will continue to adopt JSS past its EOL.
Steps:
1. For packages with direct Content SDK equivalents, run:
```
npm deprecate @sitecore-jss/sitecore-jss "JSS is deprecated and reaches EOL June 2026. Migrate to @sitecore-content-sdk/core. See https://doc.sitecore.com/sai/en/developers/content-sdk/10/upgrade-jss-22-8-next-js-apps-to-content-sdk-1-0.html"
```
2. Repeat for `@sitecore-jss/sitecore-jss-nextjs` (-> `@sitecore-content-sdk/nextjs`), `@sitecore-jss/sitecore-jss-react` (-> `@sitecore-content-sdk/react`), `@sitecore-jss/sitecore-jss-cli` (-> `@sitecore-content-sdk/cli`)
3. For packages with no equivalent (Angular, Vue, Forms, React Native, Rendering Host), use: "JSS is deprecated and reaches EOL June 2026. This package has no Content SDK equivalent and will not be maintained."
4. Update `README.md` at the repo root with a deprecation banner at the top
5. Add a `MIGRATION.md` linking to the official Sitecore migration documentation
Acceptance criteria:
All 14 JSS packages carry an npm deprecation message
Each deprecation message names the specific Content SDK replacement (or states no equivalent)
Repository README has a prominent deprecation banner
Migration documentation link included
Risks: Deprecation notices may cause alarm among teams not yet ready to migrate. Pair with clear messaging that JSS 22.12 will receive security fixes through EOL and that migration guides are available.