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@@ -5,6 +5,7 @@ These docs walk through how to migrate our JavaScript SDKs through different maj
 - Upgrading from [SDK 4.x to 5.x/6.x](./docs/migration/v4-to-v5_v6.md)
 - Upgrading from [SDK 6.x to 7.x](./docs/migration/v6-to-v7.md)
 - Upgrading from [SDK 7.x to 8.x](./MIGRATION.md#upgrading-from-7x-to-8x)
+- Upgrading from [SDK 8.x to 9.x](./docs/migration/v8-to-v9.md) (Work in Progress - v9 is not released yet)
 
 # Upgrading from 7.x to 8.x
 
diff --git a/docs/migration/v8-to-v9.md b/docs/migration/v8-to-v9.md
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@@ -0,0 +1,159 @@
+# Upgrading from 8.x to 9.x
+
+**DISCLAIMER: THIS MIGRATION GUIDE IS WORK IN PROGRESS**
+
+Version 9 of the Sentry SDK concerns itself with API cleanup and compatibility updates.
+This update contains behavioral changes that will not be caught by TypeScript or linters, so we recommend carefully reading the section on [Behavioral Changes](#2-behavior-changes).
+
+Before updating to version `9.x` of the SDK, we recommend upgrading to the latest version of `8.x`.
+You can then go through the [Deprecations in 8.x](#deprecations-in-8x) and remove and migrate usages of deprecated APIs in your code before upgrading to `9.x`.
+
+Version 9 of the JavaScript SDK is compatible with Sentry self-hosted versions 24.4.2 or higher (unchanged from last major).
+Lower versions may continue to work, but may not support all features.
+
+## 1. Version Support Changes:
+
+Version 9 of the Sentry SDK has new compatibility ranges for runtimes and frameworks.
+We periodically update the compatibility ranges in major versions to increase reliability and quality of APIs and instrumentation data.
+
+### General Runtime Support Changes
+
+**ECMAScript Version:** All of the JavaScript code in the Sentry SDK packages may now contain ECMAScript 2020 features.
+This includes features like Nullish Coalescing (`??`), Optional Chaining (`?.`), `String.matchAll()`, Logical Assignment Operators (`&&=`, `||=`, `??=`), and `Promise.allSettled()`.
+
+If you observe failures due to syntax or features listed above, it may be an indicator that your current runtime does not support ES2020.
+If your runtime does not support ES2020, we recommend transpiling the SDK using Babel or similar tooling.
+
+**Node.js:** The minimum supported Node.js versions are TBD, TBD, and TBD.
+We no longer test against Node TBD, TBD, or TBD and cannot guarantee that the SDK will work as expected on these versions.
+
+**Browsers:** Due to SDK code now including ES2020 features, the minimum supported browser list now looks as follows:
+
+- Chrome 80
+- Edge 80
+- Safari 14, iOS Safari 14.4
+- Firefox 74
+- Opera 67
+- Samsung Internet 13.0
+
+If you need to support older browsers, we recommend transpiling your code using Babel or similar tooling.
+
+### Framework Support Changes
+
+**Angular:** TBD
+
+**Ember:** TBD
+
+**Next.js:** TBD
+
+**Nuxt:** TBD
+
+**React:** TBD
+
+**Vue:** TBD
+
+**Astro:** TBD
+
+**Gatsby:** TBD
+
+**NestJS:** TBD
+
+**Svelte:** TBD
+
+**SvelteKit:** TBD
+
+**Bun:** TBD
+
+**Cloudflare Workers:** TBD
+
+**Deno:** TBD
+
+**Solid:** TBD
+
+**SolidStart:** TBD
+
+**GCP Functions:** TBD
+
+**AWS Lambda:** TBD
+
+## 2. Behavior Changes
+
+- Next.js withSentryConfig returning Promise
+- `request` on sdk processing metadata will be ignored going forward
+- respect sourcemap generation settings
+- SDK init options undefined
+- no more polyfills
+- no more update spans in vue component tracking by default
+- new propagation context
+- Client & Scope renaming
+
+## 3. Package Removals
+
+As part of an architectural cleanup we deprecated the following packages:
+
+- `@sentry/utils`
+- `@sentry/types`
+
+All of these packages exports and APIs have been moved into the `@sentry/core` package.
+
+The `@sentry/utils` package will no longer be published.
+
+The `@sentry/types` package will continue to be published but it is deprecated and we don't plan on extending its APi.
+You may experience slight compatibility issues in the future by using it.
+We decided to keep this package around to temporarily lessen the upgrade burden.
+It will be removed in a future major version.
+
+## 4. Removal of Deprecated APIs
+
+- [General](#general)
+- [Server-side SDKs (Node, Deno, Bun, ...)](#server-side-sdks-node-deno-bun-)
+- [Next.js SDK](#nextjs-sdk)
+- [Vue/Nuxt SDK](#vuenuxt-sdk)
+
+### General
+
+- sessionTimingIntegration
+- debugIntegration
+- `Request` type
+- spanid on propagation context
+- makeFifoCache in utils
+
+### Server-side SDKs (Node, Deno, Bun, ...)
+
+- processThreadBreadcrumbIntegration
+- NestJS stuff in Node sdk
+- various NestJS APIs
+- NestJS `@WithSentry`
+- `AddRequestDataToEventOptions.transaction`
+
+### Next.js SDK
+
+- `experimental_captureRequestError`
+
+### Vue/Nuxt SDK
+
+- vueComponent tracking options
+
+## 5. Build Changes
+
+Previously the CJS versions of the SDK code (wrongfully) contained compatibility statements for default exports in ESM:
+
+```js
+Object.defineProperty(exports, '__esModule', { value: true });
+```
+
+The SDK no longer contains these statements.
+Let us know if this is causing issues in your setup by opening an issue on GitHub.
+
+# Deprecations in 8.x
+
+TBD (Copy over from migrations list we collected)
+
+# No Version Support Timeline
+
+Version support timelines are stressful for anybody using the SDK, so we won't be defining one.
+Instead, we will be applying bug fixes and features to older versions as long as there is demand for them.
+We also hold ourselves to high standards security-wise, meaning that if any vulnerabilities are found, we will in almost all cases backport them.
+
+Note, that we will decide on a case-per-case basis, what gets backported or not.
+If you need a fix or feature in a previous version of the SDK, feel free to reach out via a GitHub issue.