diff --git a/packages/kg-default-atoms/.gitignore b/packages/kg-default-atoms/.gitignore
new file mode 100644
index 0000000000..0264be4400
--- /dev/null
+++ b/packages/kg-default-atoms/.gitignore
@@ -0,0 +1,2 @@
+build/
+tsconfig.tsbuildinfo
diff --git a/packages/kg-default-atoms/eslint.config.mjs b/packages/kg-default-atoms/eslint.config.mjs
index d43dd6ed67..49b87a9339 100644
--- a/packages/kg-default-atoms/eslint.config.mjs
+++ b/packages/kg-default-atoms/eslint.config.mjs
@@ -1,42 +1,33 @@
-import {fixupPluginRules} from '@eslint/compat';
+import {defineConfig} from 'eslint/config';
 import eslint from '@eslint/js';
 import ghostPlugin from 'eslint-plugin-ghost';
-import globals from 'globals';
+import tseslint from 'typescript-eslint';
 
-const ghost = fixupPluginRules(ghostPlugin);
-
-export default [
+export default defineConfig([
     {ignores: ['build/**']},
-    eslint.configs.recommended,
     {
-        files: ['**/*.js'],
-        plugins: {ghost},
+        files: ['**/*.ts'],
+        extends: [
+            eslint.configs.recommended,
+            tseslint.configs.recommended
+        ],
         languageOptions: {
-            globals: globals.node
+            parserOptions: {ecmaVersion: 2022, sourceType: 'module'}
         },
+        plugins: {ghost: ghostPlugin},
         rules: {
-            ...ghostPlugin.configs.node.rules,
-            // match ESLint 8 behavior for catch clause variables
-            'no-unused-vars': ['error', {caughtErrors: 'none'}],
-            // disable rules incompatible with ESLint 9 flat config
-            'ghost/filenames/match-exported-class': 'off',
-            'ghost/filenames/match-exported': 'off',
-            'ghost/filenames/match-regex': 'off'
+            ...ghostPlugin.configs.ts.rules,
+            '@typescript-eslint/no-explicit-any': 'error'
         }
     },
     {
-        files: ['test/**/*.js'],
-        plugins: {ghost},
-        languageOptions: {
-            globals: {
-                ...globals.node,
-                ...globals.mocha,
-                should: true,
-                sinon: true
-            }
-        },
+        files: ['test/**/*.ts'],
         rules: {
-            ...ghostPlugin.configs.test.rules
+            ...ghostPlugin.configs['ts-test'].rules,
+            'ghost/mocha/no-global-tests': 'off',
+            'ghost/mocha/handle-done-callback': 'off',
+            'ghost/mocha/no-mocha-arrows': 'off',
+            'ghost/mocha/max-top-level-suites': 'off'
         }
     }
-];
+]);
diff --git a/packages/kg-default-atoms/index.js b/packages/kg-default-atoms/index.js
deleted file mode 100644
index d05c343b8d..0000000000
--- a/packages/kg-default-atoms/index.js
+++ /dev/null
@@ -1 +0,0 @@
-module.exports = require('./lib/atoms');
diff --git a/packages/kg-default-atoms/lib/atoms/index.js b/packages/kg-default-atoms/lib/atoms/index.js
deleted file mode 100644
index 380ec8c7c4..0000000000
--- a/packages/kg-default-atoms/lib/atoms/index.js
+++ /dev/null
@@ -1,3 +0,0 @@
-const softReturn = require('./soft-return');
-
-module.exports = [softReturn];
diff --git a/packages/kg-default-atoms/lib/atoms/soft-return.js b/packages/kg-default-atoms/lib/atoms/soft-return.js
deleted file mode 100644
index 3841940081..0000000000
--- a/packages/kg-default-atoms/lib/atoms/soft-return.js
+++ /dev/null
@@ -1,7 +0,0 @@
-module.exports = {
-    name: 'soft-return',
-    type: 'dom',
-    render(opts) {
-        return opts.env.dom.createElement('br');
-    }
-};
diff --git a/packages/kg-default-atoms/package.json b/packages/kg-default-atoms/package.json
index b4b6d5c8a6..9959f07b00 100644
--- a/packages/kg-default-atoms/package.json
+++ b/packages/kg-default-atoms/package.json
@@ -1,13 +1,25 @@
 {
   "name": "@tryghost/kg-default-atoms",
   "version": "5.1.7",
-  "repository": "https://github.com/TryGhost/Koenig/tree/master/packages/kg-default-atoms",
+  "repository": "https://github.com/TryGhost/Koenig/tree/main/packages/kg-default-atoms",
   "author": "Ghost Foundation",
   "license": "MIT",
-  "main": "index.js",
+  "main": "build/cjs/index.js",
+  "module": "build/esm/index.js",
+  "types": "build/esm/index.d.ts",
+  "exports": {
+    ".": {
+      "types": "./build/esm/index.d.ts",
+      "import": "./build/esm/index.js",
+      "require": "./build/cjs/index.js"
+    }
+  },
   "scripts": {
     "dev": "echo \"Implement me!\"",
-    "test": "NODE_ENV=testing c8 --all --reporter text --reporter cobertura mocha './test/**/*.test.js'",
+    "build": "tsc && tsc -p tsconfig.cjs.json && echo '{\"type\":\"module\"}' > build/esm/package.json",
+    "prepare": "tsc && tsc -p tsconfig.cjs.json && echo '{\"type\":\"module\"}' > build/esm/package.json",
+    "pretest": "tsc && tsc -p tsconfig.cjs.json && echo '{\"type\":\"module\"}' > build/esm/package.json && tsc -p tsconfig.test.json",
+    "test": "NODE_ENV=testing c8 --all --reporter text --reporter cobertura mocha --require tsx './test/**/*.test.ts'",
     "lint": "eslint . --cache",
     "posttest": "yarn lint"
   },
@@ -15,14 +27,24 @@
     "node": "^22.13.1 || ^24.0.0"
   },
   "files": [
-    "index.js",
-    "lib"
+    "build"
   ],
   "publishConfig": {
     "access": "public"
   },
   "devDependencies": {
+    "@eslint/js": "9.28.0",
+    "@types/mocha": "10.0.10",
+    "@types/node": "22.15.29",
+    "@types/should": "13.0.0",
+    "@types/sinon": "17.0.4",
     "c8": "11.0.0",
-    "simple-dom": "1.4.0"
+    "mocha": "11.7.5",
+    "should": "13.2.3",
+    "simple-dom": "1.4.0",
+    "sinon": "21.0.1",
+    "tsx": "4.19.4",
+    "typescript": "5.8.3",
+    "typescript-eslint": "8.33.1"
   }
 }
diff --git a/packages/kg-default-atoms/src/atoms/index.ts b/packages/kg-default-atoms/src/atoms/index.ts
new file mode 100644
index 0000000000..5f1b94f293
--- /dev/null
+++ b/packages/kg-default-atoms/src/atoms/index.ts
@@ -0,0 +1,3 @@
+import softReturn from './soft-return.js';
+
+export const atoms = [softReturn];
diff --git a/packages/kg-default-atoms/src/atoms/soft-return.ts b/packages/kg-default-atoms/src/atoms/soft-return.ts
new file mode 100644
index 0000000000..acd132a694
--- /dev/null
+++ b/packages/kg-default-atoms/src/atoms/soft-return.ts
@@ -0,0 +1,17 @@
+export interface AtomEnv {
+    dom: {
+        createElement(tag: string): unknown;
+    };
+}
+
+export interface AtomOpts {
+    env: AtomEnv;
+}
+
+export default {
+    name: 'soft-return',
+    type: 'dom',
+    render(opts: AtomOpts) {
+        return opts.env.dom.createElement('br');
+    }
+};
diff --git a/packages/kg-default-atoms/src/index.ts b/packages/kg-default-atoms/src/index.ts
new file mode 100644
index 0000000000..87a256d8d2
--- /dev/null
+++ b/packages/kg-default-atoms/src/index.ts
@@ -0,0 +1 @@
+export {atoms} from './atoms/index.js';
diff --git a/packages/kg-default-atoms/test/atoms/soft-return.test.js b/packages/kg-default-atoms/test/atoms/soft-return.test.js
deleted file mode 100644
index afe94b9443..0000000000
--- a/packages/kg-default-atoms/test/atoms/soft-return.test.js
+++ /dev/null
@@ -1,19 +0,0 @@
-// Switch these lines once there are useful utils
-// const testUtils = require('../utils');
-require('../utils');
-
-const atom = require('../../lib/atoms/soft-return');
-const SimpleDom = require('simple-dom');
-const serializer = new SimpleDom.HTMLSerializer(SimpleDom.voidMap);
-
-describe('Soft return atom', function () {
-    it('generates a `br` tag', function () {
-        let opts = {
-            env: {
-                dom: new SimpleDom.Document()
-            }
-        };
-
-        serializer.serialize(atom.render(opts)).should.match('<br>');
-    });
-});
diff --git a/packages/kg-default-atoms/test/atoms/soft-return.test.ts b/packages/kg-default-atoms/test/atoms/soft-return.test.ts
new file mode 100644
index 0000000000..6c2d839718
--- /dev/null
+++ b/packages/kg-default-atoms/test/atoms/soft-return.test.ts
@@ -0,0 +1,18 @@
+import '../utils/index.js';
+import atom from '../../src/atoms/soft-return.js';
+import {Document as SimpleDomDocument, HTMLSerializer, voidMap} from 'simple-dom';
+import type {SerializableNode} from '@simple-dom/interface';
+
+const serializer = new HTMLSerializer(voidMap);
+
+describe('Soft return atom', function () {
+    it('generates a `br` tag', function () {
+        const opts = {
+            env: {
+                dom: new SimpleDomDocument()
+            }
+        };
+
+        serializer.serialize(atom.render(opts) as SerializableNode).should.match('<br>');
+    });
+});
diff --git a/packages/kg-default-atoms/test/utils/assertions.js b/packages/kg-default-atoms/test/utils/assertions.ts
similarity index 100%
rename from packages/kg-default-atoms/test/utils/assertions.js
rename to packages/kg-default-atoms/test/utils/assertions.ts
diff --git a/packages/kg-default-atoms/test/utils/index.js b/packages/kg-default-atoms/test/utils/index.ts
similarity index 76%
rename from packages/kg-default-atoms/test/utils/index.js
rename to packages/kg-default-atoms/test/utils/index.ts
index 0d67d86ff8..f385b7bf56 100644
--- a/packages/kg-default-atoms/test/utils/index.js
+++ b/packages/kg-default-atoms/test/utils/index.ts
@@ -5,7 +5,7 @@
  */
 
 // Require overrides - these add globals for tests
-require('./overrides');
+import './overrides.js';
 
 // Require assertions - adds custom should assertions
-require('./assertions');
+import './assertions.js';
diff --git a/packages/kg-default-atoms/test/utils/overrides.js b/packages/kg-default-atoms/test/utils/overrides.js
deleted file mode 100644
index 90203424ee..0000000000
--- a/packages/kg-default-atoms/test/utils/overrides.js
+++ /dev/null
@@ -1,10 +0,0 @@
-// This file is required before any test is run
-
-// Taken from the should wiki, this is how to make should global
-// Should is a global in our eslint test config
-global.should = require('should').noConflict();
-should.extend();
-
-// Sinon is a simple case
-// Sinon is a global in our eslint test config
-global.sinon = require('sinon');
diff --git a/packages/kg-default-atoms/test/utils/overrides.ts b/packages/kg-default-atoms/test/utils/overrides.ts
new file mode 100644
index 0000000000..6138e929ff
--- /dev/null
+++ b/packages/kg-default-atoms/test/utils/overrides.ts
@@ -0,0 +1,15 @@
+// This file is required before any test is run
+
+// Taken from the should wiki, this is how to make should global
+// Should is a global in our eslint test config
+import should from 'should';
+import sinon from 'sinon';
+
+// @types/should is incomplete — noConflict and extend exist at runtime
+const shouldModule = should as unknown as {noConflict(): typeof should; extend(): void};
+Object.defineProperty(globalThis, 'should', {value: shouldModule.noConflict(), writable: true, configurable: true});
+shouldModule.extend();
+
+// Sinon is a simple case
+// Sinon is a global in our eslint test config
+Object.defineProperty(globalThis, 'sinon', {value: sinon, writable: true, configurable: true});
diff --git a/packages/kg-default-atoms/tsconfig.cjs.json b/packages/kg-default-atoms/tsconfig.cjs.json
new file mode 100644
index 0000000000..bd981491bc
--- /dev/null
+++ b/packages/kg-default-atoms/tsconfig.cjs.json
@@ -0,0 +1,13 @@
+{
+  "extends": "./tsconfig.json",
+  "compilerOptions": {
+    "module": "NodeNext",
+    "moduleResolution": "NodeNext",
+    "outDir": "build/cjs",
+    "verbatimModuleSyntax": false,
+    "declaration": false,
+    "declarationMap": false,
+    "sourceMap": false,
+    "incremental": false
+  }
+}
diff --git a/packages/kg-default-atoms/tsconfig.json b/packages/kg-default-atoms/tsconfig.json
new file mode 100644
index 0000000000..e2ebf36cde
--- /dev/null
+++ b/packages/kg-default-atoms/tsconfig.json
@@ -0,0 +1,22 @@
+{
+    "compilerOptions": {
+        "target": "es2022",
+        "module": "ES2022",
+        "moduleResolution": "bundler",
+        "rootDir": "src",
+        "outDir": "build/esm",
+        "strict": true,
+        "declaration": true,
+        "declarationMap": true,
+        "sourceMap": true,
+        "incremental": true,
+        "esModuleInterop": true,
+        "forceConsistentCasingInFileNames": true,
+        "skipLibCheck": true,
+        "resolveJsonModule": true,
+        "isolatedModules": true
+    },
+    "include": [
+        "src/**/*"
+    ]
+}
diff --git a/packages/kg-default-atoms/tsconfig.test.json b/packages/kg-default-atoms/tsconfig.test.json
new file mode 100644
index 0000000000..b092804ad8
--- /dev/null
+++ b/packages/kg-default-atoms/tsconfig.test.json
@@ -0,0 +1,16 @@
+{
+    "extends": "./tsconfig.json",
+    "compilerOptions": {
+        "rootDir": ".",
+        "outDir": null,
+        "noEmit": true,
+        "declaration": false,
+        "declarationMap": false,
+        "sourceMap": false,
+        "incremental": false
+    },
+    "include": [
+        "src/**/*",
+        "test/**/*"
+    ]
+}