diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0a6868a..f4bf927 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,16 @@
 # Changelog
 
+## v14.0.0-SNAPSHOT - unreleased
+
+### 💥 Breaking Changes
+
+* Requires `hoist-react >= 85.0`.
+* Flipped `@babel/plugin-proposal-decorators` from `{version: 'legacy'}` to `{version: '2023-05'}`
+  to align with hoist-react v85's migration to TC39 Stage 3 modern decorators. Consuming apps must
+  upgrade `@xh/hoist` and `@xh/hoist-dev-utils` together — mixing a legacy-decorator app with this
+  build of dev-utils will silently break all `@observable` and `@bindable` fields. See the
+  hoist-react v85 upgrade notes for the codemod required in app code.
+
 ## v13.0.0-SNAPSHOT - unreleased
 
 ## v12.0.0 - 2026-03-31
diff --git a/configureWebpack.js b/configureWebpack.js
index 01d5d03..67e6e49 100644
--- a/configureWebpack.js
+++ b/configureWebpack.js
@@ -442,6 +442,7 @@ async function configureWebpack(env) {
                                                 // (Note these plugins are all generally bundled with preset-env.)
                                                 include: [
                                                     'transform-class-properties',
+                                                    'transform-class-static-block',
                                                     'transform-nullish-coalescing-operator',
                                                     'transform-optional-chaining',
                                                     'transform-private-methods',
@@ -462,10 +463,14 @@ async function configureWebpack(env) {
                                             {allowDeclareFields: true, isTSX: true}
                                         ],
 
-                                        // Support our current decorator syntax, for MobX and Hoist decorators.
-                                        // See notes @ https://babeljs.io/docs/en/babel-plugin-proposal-decorators#legacy
-                                        // and https://mobx.js.org/enabling-decorators.html#babel-7
-                                        ['@babel/plugin-proposal-decorators', {version: 'legacy'}],
+                                        // Support TC39 Stage 3 (2023-05 / 2022.3) decorators, used by hoist-react
+                                        // v85+ and compatible apps. See:
+                                        //   https://babeljs.io/docs/babel-plugin-proposal-decorators
+                                        //   https://mobx.js.org/enabling-decorators.html
+                                        // Apps upgrading from hoist-react < 85 must also add the `accessor`
+                                        // keyword to `@observable` / `@bindable` fields and remove
+                                        // `makeObservable(this)` calls — see the v85 upgrade notes.
+                                        ['@babel/plugin-proposal-decorators', {version: '2023-05'}],
 
                                         // Avoid importing every FA icon ever made.
                                         // See https://github.com/FortAwesome/react-fontawesome/issues/70
diff --git a/package.json b/package.json
index fe9278d..570666a 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
     "name": "@xh/hoist-dev-utils",
-    "version": "13.0.0-SNAPSHOT",
+    "version": "14.0.0-SNAPSHOT",
     "description": "Utilities for configuring builds of Hoist-React client applications.",
     "repository": {
         "type": "git",