diff --git a/.gitignore b/.gitignore
index 2ebd082b17d..f80e9cb45af 100644
--- a/.gitignore
+++ b/.gitignore
@@ -135,6 +135,7 @@ src/go-landing
 
 **/dist
 **/dist/
+**/dist-esm/
 **/dist-measure/
 **/dist-prod/
 **/dist-prod-measure/
diff --git a/src/packages/api-client/package.json b/src/packages/api-client/package.json
index 71791c9d163..e08c6a1d3e0 100644
--- a/src/packages/api-client/package.json
+++ b/src/packages/api-client/package.json
@@ -3,12 +3,30 @@
   "version": "0.1.2",
   "description": "CoCalc api client - use cocalc from nodejs",
   "main": "./dist/index.js",
+  "exports": {
+    ".": {
+      "types": "./dist/index.d.ts",
+      "import": "./dist-esm/index.js",
+      "default": "./dist/index.js"
+    },
+    "./*": {
+      "types": "./dist/*.d.ts",
+      "import": "./dist-esm/*.js",
+      "default": "./dist/*.js"
+    },
+    "./src/*": {
+      "types": "./dist/src/*.d.ts",
+      "import": "./dist-esm/src/*.js",
+      "default": "./dist/src/*.js"
+    }
+  },
+  "files": ["dist/**", "dist-esm/**", "bin/**", "README.md", "package.json"],
   "scripts": {
     "preinstall": "npx only-allow pnpm",
-    "build": "../node_modules/.bin/tsc --build",
+    "build": "pnpm exec tsc --build && pnpm exec tsc -p tsconfig-esm.json && echo '{\"type\":\"module\"}' > dist-esm/package.json",
+    "clean": "rm -rf node_modules dist dist-esm",
     "depcheck": "pnpx depcheck --ignores @cocalc/api-client "
   },
-  "files": ["dist/**", "bin/**", "README.md", "package.json"],
   "author": "SageMath, Inc.",
   "keywords": ["cocalc", "jupyter"],
   "license": "SEE LICENSE.md",
diff --git a/src/packages/api-client/tsconfig-esm.json b/src/packages/api-client/tsconfig-esm.json
new file mode 100644
index 00000000000..a78c78ec542
--- /dev/null
+++ b/src/packages/api-client/tsconfig-esm.json
@@ -0,0 +1,15 @@
+{
+  "extends": "../tsconfig.json",
+  "compilerOptions": {
+    "rootDir": "./",
+    "outDir": "dist-esm",
+    "module": "ESNext",
+    "moduleResolution": "bundler",
+    "declaration": false,
+    "declarationMap": false,
+    "composite": false,
+    "incremental": false,
+    "sourceMap": true
+  },
+  "exclude": ["node_modules", "../node_modules", "dist", "dist-esm", "test"]
+}
diff --git a/src/packages/api-client/tsconfig.json b/src/packages/api-client/tsconfig.json
index cacab0cc85c..6591776d9cc 100644
--- a/src/packages/api-client/tsconfig.json
+++ b/src/packages/api-client/tsconfig.json
@@ -4,6 +4,6 @@
     "rootDir": "./",
     "outDir": "dist"
   },
-  "exclude": ["node_modules", "dist", "test"],
+  "exclude": ["node_modules", "dist", "dist-esm", "test"],
   "references": [{ "path": "../backend" }]
 }
diff --git a/src/packages/backend/package.json b/src/packages/backend/package.json
index 7b3addadf33..a28f3975e70 100644
--- a/src/packages/backend/package.json
+++ b/src/packages/backend/package.json
@@ -3,12 +3,36 @@
   "version": "1.22.2",
   "description": "CoCalc backend functionality: functionality used by either the hub, the next.js server or the project.",
   "exports": {
-    "./*": "./dist/*.js",
-    "./database": "./dist/database/index.js",
-    "./conat": "./dist/conat/index.js",
-    "./server-settings": "./dist/server-settings/index.js",
-    "./auth/*": "./dist/auth/*.js",
-    "./auth/tokens/*": "./dist/auth/tokens/*.js"
+    "./*": {
+      "types": "./dist/*.d.ts",
+      "import": "./dist-esm/*.js",
+      "default": "./dist/*.js"
+    },
+    "./database": {
+      "types": "./dist/database/index.d.ts",
+      "import": "./dist-esm/database/index.js",
+      "default": "./dist/database/index.js"
+    },
+    "./conat": {
+      "types": "./dist/conat/index.d.ts",
+      "import": "./dist-esm/conat/index.js",
+      "default": "./dist/conat/index.js"
+    },
+    "./server-settings": {
+      "types": "./dist/server-settings/index.d.ts",
+      "import": "./dist-esm/server-settings/index.js",
+      "default": "./dist/server-settings/index.js"
+    },
+    "./auth/*": {
+      "types": "./dist/auth/*.d.ts",
+      "import": "./dist-esm/auth/*.js",
+      "default": "./dist/auth/*.js"
+    },
+    "./auth/tokens/*": {
+      "types": "./dist/auth/tokens/*.d.ts",
+      "import": "./dist-esm/auth/tokens/*.js",
+      "default": "./dist/auth/tokens/*.js"
+    }
   },
   "keywords": [
     "utilities",
@@ -16,8 +40,8 @@
   ],
   "scripts": {
     "preinstall": "npx only-allow pnpm",
-    "clean": "rm -rf dist node_modules",
-    "build": "pnpm exec tsc --build",
+    "clean": "rm -rf dist dist-esm node_modules",
+    "build": "pnpm exec tsc --build && pnpm exec tsc -p tsconfig-esm.json && echo '{\"type\":\"module\"}' > dist-esm/package.json",
     "test": "pnpm exec jest --forceExit",
     "test-conat": " pnpm exec jest --forceExit conat",
     "testp": "pnpm exec jest --forceExit",
@@ -32,6 +56,7 @@
   },
   "files": [
     "dist/**",
+    "dist-esm/**",
     "bin/**",
     "README.md",
     "package.json"
diff --git a/src/packages/backend/tsconfig-esm.json b/src/packages/backend/tsconfig-esm.json
new file mode 100644
index 00000000000..3f30680a9a1
--- /dev/null
+++ b/src/packages/backend/tsconfig-esm.json
@@ -0,0 +1,18 @@
+{
+  "extends": "../tsconfig.json",
+  "compilerOptions": {
+    "rootDir": "./",
+    "outDir": "dist-esm",
+    "module": "ESNext",
+    "moduleResolution": "bundler",
+    "declaration": false,
+    "declarationMap": false,
+    "composite": false,
+    "incremental": false,
+    "sourceMap": true,
+    "paths": {
+      "@cocalc/backend/*": ["./*"]
+    }
+  },
+  "exclude": ["node_modules", "../node_modules", "dist", "dist-esm", "test"]
+}
diff --git a/src/packages/backend/tsconfig.json b/src/packages/backend/tsconfig.json
index 148fecfd626..288674f56d4 100644
--- a/src/packages/backend/tsconfig.json
+++ b/src/packages/backend/tsconfig.json
@@ -6,6 +6,6 @@
     "rootDir": "./",
     "outDir": "dist"
   },
-  "exclude": ["node_modules", "dist", "test"],
+  "exclude": ["node_modules", "dist", "dist-esm", "test"],
   "references": [{ "path": "../util", "path": "../conat" }]
 }
diff --git a/src/packages/comm/package.json b/src/packages/comm/package.json
index 0d2f9e6ef32..5e746cca097 100644
--- a/src/packages/comm/package.json
+++ b/src/packages/comm/package.json
@@ -3,20 +3,38 @@
   "version": "0.1.0",
   "description": "Communication between project and frontend app support",
   "exports": {
-    "./*": "./dist/*.js",
-    "./websocket/*": "./dist/websocket/*.js",
-    "./project-status/*": "./dist/project-status/*.js",
-    "./project-info/*": "./dist/project-info/*.js"
+    "./*": {
+      "types": "./dist/*.d.ts",
+      "import": "./dist-esm/*.js",
+      "default": "./dist/*.js"
+    },
+    "./websocket/*": {
+      "types": "./dist/websocket/*.d.ts",
+      "import": "./dist-esm/websocket/*.js",
+      "default": "./dist/websocket/*.js"
+    },
+    "./project-status/*": {
+      "types": "./dist/project-status/*.d.ts",
+      "import": "./dist-esm/project-status/*.js",
+      "default": "./dist/project-status/*.js"
+    },
+    "./project-info/*": {
+      "types": "./dist/project-info/*.d.ts",
+      "import": "./dist-esm/project-info/*.js",
+      "default": "./dist/project-info/*.js"
+    }
   },
   "files": [
     "dist/**",
+    "dist-esm/**",
     "README.md",
     "package.json",
     "tsconfig.json"
   ],
   "scripts": {
     "preinstall": "npx only-allow pnpm",
-    "build": "../node_modules/.bin/tsc --build",
+    "build": "pnpm exec tsc --build && pnpm exec tsc -p tsconfig-esm.json && echo '{\"type\":\"module\"}' > dist-esm/package.json",
+    "clean": "rm -rf node_modules dist dist-esm",
     "depcheck": "pnpx depcheck --ignores @types/node"
   },
   "author": "SageMath, Inc.",
diff --git a/src/packages/comm/tsconfig-esm.json b/src/packages/comm/tsconfig-esm.json
new file mode 100644
index 00000000000..a78c78ec542
--- /dev/null
+++ b/src/packages/comm/tsconfig-esm.json
@@ -0,0 +1,15 @@
+{
+  "extends": "../tsconfig.json",
+  "compilerOptions": {
+    "rootDir": "./",
+    "outDir": "dist-esm",
+    "module": "ESNext",
+    "moduleResolution": "bundler",
+    "declaration": false,
+    "declarationMap": false,
+    "composite": false,
+    "incremental": false,
+    "sourceMap": true
+  },
+  "exclude": ["node_modules", "../node_modules", "dist", "dist-esm", "test"]
+}
diff --git a/src/packages/comm/tsconfig.json b/src/packages/comm/tsconfig.json
index 33d0246c7a0..d76904054d8 100644
--- a/src/packages/comm/tsconfig.json
+++ b/src/packages/comm/tsconfig.json
@@ -4,7 +4,7 @@
     "rootDir": "./",
     "outDir": "dist"
   },
-  "exclude": ["node_modules", "dist", "test"],
+  "exclude": ["node_modules", "dist", "dist-esm", "test"],
   "references": [
     { "path": "../sync" },
     { "path": "../jupyter" },
diff --git a/src/packages/conat/package.json b/src/packages/conat/package.json
index 60baba51b37..9ed2ad4c8e1 100644
--- a/src/packages/conat/package.json
+++ b/src/packages/conat/package.json
@@ -3,28 +3,77 @@
   "version": "1.0.0",
   "description": "Conat -- pub/sub framework.  Usable by both nodejs and browser.",
   "exports": {
-    "./sync/*": "./dist/sync/*.js",
-    "./llm/*": "./dist/llm/*.js",
-    "./socket": "./dist/socket/index.js",
-    "./socket/*": "./dist/socket/*.js",
-    "./hub/changefeeds": "./dist/hub/changefeeds/index.js",
-    "./hub/api": "./dist/hub/api/index.js",
-    "./hub/api/*": "./dist/hub/api/*.js",
-    "./compute/*": "./dist/compute/*.js",
-    "./service": "./dist/service/index.js",
-    "./project/api": "./dist/project/api/index.js",
-    "./browser-api": "./dist/browser-api/index.js",
-    "./*": "./dist/*.js"
+    "./sync/*": {
+      "types": "./dist/sync/*.d.ts",
+      "import": "./dist-esm/sync/*.js",
+      "default": "./dist/sync/*.js"
+    },
+    "./llm/*": {
+      "types": "./dist/llm/*.d.ts",
+      "import": "./dist-esm/llm/*.js",
+      "default": "./dist/llm/*.js"
+    },
+    "./socket": {
+      "types": "./dist/socket/index.d.ts",
+      "import": "./dist-esm/socket/index.js",
+      "default": "./dist/socket/index.js"
+    },
+    "./socket/*": {
+      "types": "./dist/socket/*.d.ts",
+      "import": "./dist-esm/socket/*.js",
+      "default": "./dist/socket/*.js"
+    },
+    "./hub/changefeeds": {
+      "types": "./dist/hub/changefeeds/index.d.ts",
+      "import": "./dist-esm/hub/changefeeds/index.js",
+      "default": "./dist/hub/changefeeds/index.js"
+    },
+    "./hub/api": {
+      "types": "./dist/hub/api/index.d.ts",
+      "import": "./dist-esm/hub/api/index.js",
+      "default": "./dist/hub/api/index.js"
+    },
+    "./hub/api/*": {
+      "types": "./dist/hub/api/*.d.ts",
+      "import": "./dist-esm/hub/api/*.js",
+      "default": "./dist/hub/api/*.js"
+    },
+    "./compute/*": {
+      "types": "./dist/compute/*.d.ts",
+      "import": "./dist-esm/compute/*.js",
+      "default": "./dist/compute/*.js"
+    },
+    "./service": {
+      "types": "./dist/service/index.d.ts",
+      "import": "./dist-esm/service/index.js",
+      "default": "./dist/service/index.js"
+    },
+    "./project/api": {
+      "types": "./dist/project/api/index.d.ts",
+      "import": "./dist-esm/project/api/index.js",
+      "default": "./dist/project/api/index.js"
+    },
+    "./browser-api": {
+      "types": "./dist/browser-api/index.d.ts",
+      "import": "./dist-esm/browser-api/index.js",
+      "default": "./dist/browser-api/index.js"
+    },
+    "./*": {
+      "types": "./dist/*.d.ts",
+      "import": "./dist-esm/*.js",
+      "default": "./dist/*.js"
+    }
   },
   "scripts": {
     "preinstall": "npx only-allow pnpm",
-    "build": "pnpm exec tsc --build",
-    "clean": "rm -rf dist node_modules",
+    "build": "pnpm exec tsc --build && pnpm exec tsc -p tsconfig-esm.json && echo '{\"type\":\"module\"}' > dist-esm/package.json",
+    "clean": "rm -rf dist dist-esm node_modules",
     "test": "pnpm exec jest",
     "depcheck": "pnpx depcheck --ignores events,bufferutil,utf-8-validate"
   },
   "files": [
     "dist/**",
+    "dist-esm/**",
     "README.md",
     "package.json"
   ],
diff --git a/src/packages/conat/tsconfig-esm.json b/src/packages/conat/tsconfig-esm.json
new file mode 100644
index 00000000000..3d3cafccc3b
--- /dev/null
+++ b/src/packages/conat/tsconfig-esm.json
@@ -0,0 +1,18 @@
+{
+  "extends": "../tsconfig.json",
+  "compilerOptions": {
+    "rootDir": "./",
+    "outDir": "dist-esm",
+    "module": "ESNext",
+    "moduleResolution": "bundler",
+    "declaration": false,
+    "declarationMap": false,
+    "composite": false,
+    "incremental": false,
+    "sourceMap": true,
+    "paths": {
+      "@cocalc/conat/*": ["./*"]
+    }
+  },
+  "exclude": ["node_modules", "../node_modules", "dist", "dist-esm", "test"]
+}
diff --git a/src/packages/conat/tsconfig.json b/src/packages/conat/tsconfig.json
index 687201523d0..3df517e77b4 100644
--- a/src/packages/conat/tsconfig.json
+++ b/src/packages/conat/tsconfig.json
@@ -4,7 +4,7 @@
     "rootDir": "./",
     "outDir": "dist"
   },
-  "exclude": ["node_modules", "dist", "test"],
+  "exclude": ["node_modules", "dist", "dist-esm", "test"],
   "references_comment": "Do not define path:../comm because that causes a circular references.",
   "references": [{ "path": "../util" }]
 }
diff --git a/src/packages/pnpm-lock.yaml b/src/packages/pnpm-lock.yaml
index 3f75997cf66..fa3ef7f9e8a 100644
--- a/src/packages/pnpm-lock.yaml
+++ b/src/packages/pnpm-lock.yaml
@@ -75,6 +75,8 @@ importers:
         specifier: ^18.16.14
         version: 18.19.122
 
+  api-client/dist-esm: {}
+
   assets:
     dependencies:
       jquery:
@@ -152,6 +154,8 @@ importers:
         specifier: ^18.16.14
         version: 18.19.122
 
+  backend/dist-esm: {}
+
   cdn:
     devDependencies:
       codemirror:
@@ -177,6 +181,8 @@ importers:
         specifier: ^18.16.14
         version: 18.19.122
 
+  comm/dist-esm: {}
+
   conat:
     dependencies:
       '@cocalc/comm':
@@ -244,6 +250,8 @@ importers:
         specifier: ^18.16.14
         version: 18.19.122
 
+  conat/dist-esm: {}
+
   database:
     dependencies:
       '@cocalc/backend':
@@ -1764,6 +1772,8 @@ importers:
         specifier: ^7.3.9
         version: 7.3.9
 
+  sync-client/dist-esm: {}
+
   sync-fs:
     dependencies:
       '@cocalc/api-client':
@@ -1798,6 +1808,10 @@ importers:
         specifier: ^18.16.14
         version: 18.19.122
 
+  sync-fs/dist-esm: {}
+
+  sync/dist-esm: {}
+
   util:
     dependencies:
       '@ant-design/colors':
@@ -1866,9 +1880,6 @@ importers:
       sha1:
         specifier: ^1.1.1
         version: 1.1.1
-      underscore:
-        specifier: ^1.12.1
-        version: 1.13.7
       utility-types:
         specifier: ^3.10.0
         version: 3.11.0
@@ -1904,6 +1915,8 @@ importers:
         specifier: ^0.22.0
         version: 0.22.0
 
+  util/dist-esm: {}
+
 packages:
 
   '@adobe/css-tools@4.4.3':
diff --git a/src/packages/project/servers/hub/handle-message.ts b/src/packages/project/servers/hub/handle-message.ts
index f9c13c23d7f..07dfae7c3cf 100644
--- a/src/packages/project/servers/hub/handle-message.ts
+++ b/src/packages/project/servers/hub/handle-message.ts
@@ -153,7 +153,7 @@ export default async function handleMessage(
       }
       if (mesg.id != null) {
         // send back confirmation that a signal was sent
-        socket.write_mesg("json", message.signal_sent({ id: mesg.id }));
+        socket.write_mesg("json", message.success({ id: mesg.id }));
       }
       return;
 
diff --git a/src/packages/static/src/module-rules.ts b/src/packages/static/src/module-rules.ts
index 2231b3c7c72..b18696f8ccd 100644
--- a/src/packages/static/src/module-rules.ts
+++ b/src/packages/static/src/module-rules.ts
@@ -18,6 +18,14 @@ export default function moduleRules(
 ): Configuration["module"] {
   return {
     rules: [
+      {
+        // TypeScript emits ESM without .js extensions in import specifiers,
+        // but dist-esm/package.json declares "type":"module" which makes
+        // rspack enforce fully-specified imports. Disable that requirement.
+        test: /\.js$/,
+        include: /dist-esm/,
+        resolve: { fullySpecified: false },
+      },
       {
         test: /\.(js|jsx|ts|tsx|mjs|cjs)$/,
         // the swc-loader absolutely mangles some upstream libraries so they
diff --git a/src/packages/sync-client/package.json b/src/packages/sync-client/package.json
index b7352febacd..913db8c286b 100644
--- a/src/packages/sync-client/package.json
+++ b/src/packages/sync-client/package.json
@@ -4,19 +4,40 @@
   "description": "CoCalc Lightweight Nodejs Sync Client",
   "main": "./dist/lib/index.js",
   "exports": {
-    ".": "./dist/lib/index.js",
-    "./*": "./dist/*.js",
-    "./lib/*": "./dist/lib/*.js"
+    ".": {
+      "types": "./dist/lib/index.d.ts",
+      "import": "./dist-esm/lib/index.js",
+      "default": "./dist/lib/index.js"
+    },
+    "./*": {
+      "types": "./dist/*.d.ts",
+      "import": "./dist-esm/*.js",
+      "default": "./dist/*.js"
+    },
+    "./lib/*": {
+      "types": "./dist/lib/*.d.ts",
+      "import": "./dist-esm/lib/*.js",
+      "default": "./dist/lib/*.js"
+    }
   },
-  "files": ["dist/**", "bin/**", "README.md", "package.json"],
+  "files": [
+    "dist/**",
+    "dist-esm/**",
+    "bin/**",
+    "README.md",
+    "package.json"
+  ],
   "scripts": {
     "preinstall": "npx only-allow pnpm",
-    "build": "../node_modules/.bin/tsc --build",
-    "clean": "rm -rf node_modules dist",
+    "build": "pnpm exec tsc --build && pnpm exec tsc -p tsconfig-esm.json && echo '{\"type\":\"module\"}' > dist-esm/package.json",
+    "clean": "rm -rf node_modules dist dist-esm",
     "depcheck": "pnpx depcheck"
   },
   "author": "SageMath, Inc.",
-  "keywords": ["cocalc", "jupyter"],
+  "keywords": [
+    "cocalc",
+    "jupyter"
+  ],
   "license": "SEE LICENSE.md",
   "dependencies": {
     "@cocalc/api-client": "workspace:*",
diff --git a/src/packages/sync-client/tsconfig-esm.json b/src/packages/sync-client/tsconfig-esm.json
new file mode 100644
index 00000000000..a78c78ec542
--- /dev/null
+++ b/src/packages/sync-client/tsconfig-esm.json
@@ -0,0 +1,15 @@
+{
+  "extends": "../tsconfig.json",
+  "compilerOptions": {
+    "rootDir": "./",
+    "outDir": "dist-esm",
+    "module": "ESNext",
+    "moduleResolution": "bundler",
+    "declaration": false,
+    "declarationMap": false,
+    "composite": false,
+    "incremental": false,
+    "sourceMap": true
+  },
+  "exclude": ["node_modules", "../node_modules", "dist", "dist-esm", "test"]
+}
diff --git a/src/packages/sync-client/tsconfig.json b/src/packages/sync-client/tsconfig.json
index 25705765cef..7c8ba4e1eaa 100644
--- a/src/packages/sync-client/tsconfig.json
+++ b/src/packages/sync-client/tsconfig.json
@@ -5,7 +5,7 @@
     "rootDir": "./",
     "outDir": "dist"
   },
-  "exclude": ["node_modules", "dist", "test"],
+  "exclude": ["node_modules", "dist", "dist-esm", "test"],
   "references": [
     { "path": "../sync" },
     { "path": "../api-client" },
diff --git a/src/packages/sync-fs/package.json b/src/packages/sync-fs/package.json
index 909eccaf63a..ee28321dd79 100644
--- a/src/packages/sync-fs/package.json
+++ b/src/packages/sync-fs/package.json
@@ -4,20 +4,33 @@
   "description": "CoCalc Filesystem Sync",
   "main": "./dist/lib/index.js",
   "exports": {
-    ".": "./dist/lib/index.js",
-    "./*": "./dist/*.js",
-    "./lib/*": "./dist/lib/*.js"
+    ".": {
+      "types": "./dist/lib/index.d.ts",
+      "import": "./dist-esm/lib/index.js",
+      "default": "./dist/lib/index.js"
+    },
+    "./*": {
+      "types": "./dist/*.d.ts",
+      "import": "./dist-esm/*.js",
+      "default": "./dist/*.js"
+    },
+    "./lib/*": {
+      "types": "./dist/lib/*.d.ts",
+      "import": "./dist-esm/lib/*.js",
+      "default": "./dist/lib/*.js"
+    }
   },
   "files": [
     "dist/**",
+    "dist-esm/**",
     "bin/**",
     "README.md",
     "package.json"
   ],
   "scripts": {
     "preinstall": "npx only-allow pnpm",
-    "build": "../node_modules/.bin/tsc --build",
-    "clean": "rm -rf node_modules dist",
+    "build": "pnpm exec tsc --build && pnpm exec tsc -p tsconfig-esm.json && echo '{\"type\":\"module\"}' > dist-esm/package.json",
+    "clean": "rm -rf node_modules dist dist-esm",
     "test": "pnpm exec jest --forceExit --runInBand",
     "depcheck": "pnpx depcheck"
   },
diff --git a/src/packages/sync-fs/tsconfig-esm.json b/src/packages/sync-fs/tsconfig-esm.json
new file mode 100644
index 00000000000..a78c78ec542
--- /dev/null
+++ b/src/packages/sync-fs/tsconfig-esm.json
@@ -0,0 +1,15 @@
+{
+  "extends": "../tsconfig.json",
+  "compilerOptions": {
+    "rootDir": "./",
+    "outDir": "dist-esm",
+    "module": "ESNext",
+    "moduleResolution": "bundler",
+    "declaration": false,
+    "declarationMap": false,
+    "composite": false,
+    "incremental": false,
+    "sourceMap": true
+  },
+  "exclude": ["node_modules", "../node_modules", "dist", "dist-esm", "test"]
+}
diff --git a/src/packages/sync-fs/tsconfig.json b/src/packages/sync-fs/tsconfig.json
index 2290a242a58..c700fa3faa7 100644
--- a/src/packages/sync-fs/tsconfig.json
+++ b/src/packages/sync-fs/tsconfig.json
@@ -4,7 +4,7 @@
     "rootDir": "./",
     "outDir": "dist"
   },
-  "exclude": ["node_modules", "dist", "test"],
+  "exclude": ["node_modules", "dist", "dist-esm", "test"],
   "references": [
     { "path": "../api-client" },
     { "path": "../sync-client" },
diff --git a/src/packages/sync/package.json b/src/packages/sync/package.json
index fbe9669a4cd..f0937901f89 100644
--- a/src/packages/sync/package.json
+++ b/src/packages/sync/package.json
@@ -3,20 +3,37 @@
   "version": "0.11.2",
   "description": "CoCalc realtime synchronization framework",
   "exports": {
-    "./*": "./dist/*.js",
-    "./table": "./dist/table/index.js",
-    "./listings": "./dist/listings/index.js",
-    "./editor/db": "./dist/editor/db/index.js"
+    "./*": {
+      "types": "./dist/*.d.ts",
+      "import": "./dist-esm/*.js",
+      "default": "./dist/*.js"
+    },
+    "./table": {
+      "types": "./dist/table/index.d.ts",
+      "import": "./dist-esm/table/index.js",
+      "default": "./dist/table/index.js"
+    },
+    "./listings": {
+      "types": "./dist/listings/index.d.ts",
+      "import": "./dist-esm/listings/index.js",
+      "default": "./dist/listings/index.js"
+    },
+    "./editor/db": {
+      "types": "./dist/editor/db/index.d.ts",
+      "import": "./dist-esm/editor/db/index.js",
+      "default": "./dist/editor/db/index.js"
+    }
   },
   "scripts": {
     "preinstall": "npx only-allow pnpm",
-    "build": "../node_modules/.bin/tsc --build",
+    "build": "pnpm exec tsc --build && pnpm exec tsc -p tsconfig-esm.json && echo '{\"type\":\"module\"}' > dist-esm/package.json",
     "test": "pnpm exec jest --forceExit",
     "depcheck": "pnpx depcheck --ignores events",
     "prepublishOnly": "pnpm test"
   },
   "files": [
     "dist/**",
+    "dist-esm/**",
     "bin/**",
     "README.md",
     "package.json"
diff --git a/src/packages/sync/tsconfig-esm.json b/src/packages/sync/tsconfig-esm.json
new file mode 100644
index 00000000000..0f19e5a2d51
--- /dev/null
+++ b/src/packages/sync/tsconfig-esm.json
@@ -0,0 +1,18 @@
+{
+  "extends": "../tsconfig.json",
+  "compilerOptions": {
+    "rootDir": "./",
+    "outDir": "dist-esm",
+    "module": "ESNext",
+    "moduleResolution": "bundler",
+    "declaration": false,
+    "declarationMap": false,
+    "composite": false,
+    "incremental": false,
+    "sourceMap": true,
+    "paths": {
+      "@cocalc/sync/*": ["./*"]
+    }
+  },
+  "exclude": ["node_modules", "../node_modules", "dist", "dist-esm", "test"]
+}
diff --git a/src/packages/sync/tsconfig.json b/src/packages/sync/tsconfig.json
index 0bdfd8b3a42..9692649d113 100644
--- a/src/packages/sync/tsconfig.json
+++ b/src/packages/sync/tsconfig.json
@@ -4,6 +4,6 @@
     "rootDir": "./",
     "outDir": "dist"
   },
-  "exclude": ["node_modules", "dist", "test"],
+  "exclude": ["node_modules", "dist", "dist-esm", "test"],
   "references": [{ "path": "../util" }, { "path": "../conat" }]
 }
diff --git a/src/packages/util/heartbeat.js b/src/packages/util/heartbeat.js
deleted file mode 100644
index 835ad533942..00000000000
--- a/src/packages/util/heartbeat.js
+++ /dev/null
@@ -1,6 +0,0 @@
-/*
- *  This file is part of CoCalc: Copyright © 2020 Sagemath, Inc.
- *  License: MS-RSL – see LICENSE.md for details
- */
-
-exports.PROJECT_HUB_HEARTBEAT_INTERVAL_S = 30;
diff --git a/src/packages/util/heartbeat.ts b/src/packages/util/heartbeat.ts
new file mode 100644
index 00000000000..58a0d987991
--- /dev/null
+++ b/src/packages/util/heartbeat.ts
@@ -0,0 +1,6 @@
+/*
+ *  This file is part of CoCalc: Copyright © 2020–2026 Sagemath, Inc.
+ *  License: MS-RSL – see LICENSE.md for details
+ */
+
+export const PROJECT_HUB_HEARTBEAT_INTERVAL_S = 30;
diff --git a/src/packages/util/immutable-types.js b/src/packages/util/immutable-types.ts
similarity index 78%
rename from src/packages/util/immutable-types.js
rename to src/packages/util/immutable-types.ts
index bdadc2f8f42..9f0d4f88d1c 100644
--- a/src/packages/util/immutable-types.js
+++ b/src/packages/util/immutable-types.ts
@@ -1,20 +1,9 @@
 /*
- *  This file is part of CoCalc: Copyright © 2020 Sagemath, Inc.
+ *  This file is part of CoCalc: Copyright © 2020–2026 Sagemath, Inc.
  *  License: MS-RSL – see LICENSE.md for details
  */
 
-/*
- * decaffeinate suggestions:
- * DS207: Consider shorter variations of null checks
- * Full docs: https://github.com/decaffeinate/decaffeinate/blob/master/docs/suggestions.md
- */
-//##############################################################################
-//
-// CoCalc: Collaborative web-based calculation
-// Copyright (C) 2017, Sagemath Inc.
-// MS-RSL
-//
-//##############################################################################
+import * as Immutable from "immutable";
 
 /*
 Custom Prop Validation for immutable.js types, so they work just like other
@@ -48,8 +37,8 @@ const check_is_immutable = function (
   props,
   propName,
   componentName,
-  location,
-  propFullName
+  _location?,
+  _propFullName?,
 ) {
   if (componentName == null) {
     componentName = "ANONYMOUS";
@@ -61,7 +50,7 @@ const check_is_immutable = function (
     return new Error(
       `Invalid prop \`${propName}\` of` +
         ` type ${type} supplied to` +
-        ` \`${componentName}\`, expected an immutable collection or frozen object.`
+        ` \`${componentName}\`, expected an immutable collection or frozen object.`,
     );
   }
 };
@@ -72,14 +61,14 @@ const allow_isRequired = function (validate) {
     props,
     propName,
     componentName,
-    location
+    location,
   ) {
     if (componentName == null) {
       componentName = "ANONYMOUS";
     }
     if (props[propName] == null && isRequired) {
       return new Error(
-        `Required prop \`${propName}\` was not specified in \`${componentName}\``
+        `Required prop \`${propName}\` was not specified in \`${componentName}\``,
       );
     }
     return validate(props, propName, componentName, location);
@@ -98,7 +87,7 @@ const create_immutable_type_required_chain = function (validate) {
     immutable_type_name,
     props,
     propName,
-    componentName
+    componentName,
   ) {
     if (componentName == null) {
       componentName = "ANONYMOUS";
@@ -107,16 +96,16 @@ const create_immutable_type_required_chain = function (validate) {
       const T = immutable_type_name;
       if (props[propName].toJS == null) {
         return new Error(
-          `NOT EVEN IMMUTABLE, wanted immutable.${T} ${props}, ${propName}`
+          `NOT EVEN IMMUTABLE, wanted immutable.${T} ${props}, ${propName}`,
         );
       }
-      if (require("immutable")[`${T}`][`is${T}`](props[propName])) {
+      if (Immutable[`${T}`][`is${T}`](props[propName])) {
         return null;
       } else {
         return new Error(
           `Component \`${componentName}\`` +
             ` expected ${propName} to be an immutable.${T}` +
-            ` but was supplied ${props[propName]}`
+            ` but was supplied ${props[propName]}`,
         );
       }
     } else {
@@ -126,17 +115,18 @@ const create_immutable_type_required_chain = function (validate) {
 
   // To add more immutable.js types, mimic code below.
   const check_immutable_chain = allow_isRequired(
-    check_type.bind(null, undefined)
+    check_type.bind(null, undefined),
   );
   check_immutable_chain.Map = allow_isRequired(check_type.bind(null, "Map"));
   check_immutable_chain.List = allow_isRequired(check_type.bind(null, "List"));
   check_immutable_chain.Set = allow_isRequired(check_type.bind(null, "Set"));
   check_immutable_chain.Stack = allow_isRequired(
-    check_type.bind(null, "Stack")
+    check_type.bind(null, "Stack"),
   );
   check_immutable_chain.category = "IMMUTABLE";
 
   return check_immutable_chain;
 };
 
-exports.immutable = create_immutable_type_required_chain(check_is_immutable);
+export const immutable =
+  create_immutable_type_required_chain(check_is_immutable);
diff --git a/src/packages/util/mathjax-config.js b/src/packages/util/mathjax-config.ts
similarity index 96%
rename from src/packages/util/mathjax-config.js
rename to src/packages/util/mathjax-config.ts
index 487cd673dd2..1e97f52c022 100644
--- a/src/packages/util/mathjax-config.js
+++ b/src/packages/util/mathjax-config.ts
@@ -1,12 +1,12 @@
 /*
- *  This file is part of CoCalc: Copyright © 2020 Sagemath, Inc.
+ *  This file is part of CoCalc: Copyright © 2020–2026 Sagemath, Inc.
  *  License: MS-RSL – see LICENSE.md for details
  */
 
 // mathjax configuration: this could be cleaned up further or even parameterized with some code during startup
 // ATTN: do not use "xypic.js", frequently causes crash!
 
-exports.MathJaxConfig = {
+export const MathJaxConfig = {
   skipStartupTypeset: true,
   extensions: ["tex2jax.js", "asciimath2jax.js", "Safe.js"], // "static/mathjax_extensions/xypic.js"
   // NOTE: "output/CommonHTML" is the output default: http://docs.mathjax.org/en/latest/output.html
diff --git a/src/packages/util/mathjax-utils-2.js b/src/packages/util/mathjax-utils-2.ts
similarity index 88%
rename from src/packages/util/mathjax-utils-2.js
rename to src/packages/util/mathjax-utils-2.ts
index eaded15324d..8af099c7dc7 100644
--- a/src/packages/util/mathjax-utils-2.js
+++ b/src/packages/util/mathjax-utils-2.ts
@@ -1,5 +1,5 @@
 /*
- *  This file is part of CoCalc: Copyright © 2020 Sagemath, Inc.
+ *  This file is part of CoCalc: Copyright © 2020–2026 Sagemath, Inc.
  *  License: MS-RSL – see LICENSE.md for details
  */
 
diff --git a/src/packages/util/mathjax-utils.d.ts b/src/packages/util/mathjax-utils.d.ts
deleted file mode 100644
index 06e5f458d8f..00000000000
--- a/src/packages/util/mathjax-utils.d.ts
+++ /dev/null
@@ -1,2 +0,0 @@
-export const replace_math: Function;
-export const remove_math: Function;
diff --git a/src/packages/util/mathjax-utils.js b/src/packages/util/mathjax-utils.ts
similarity index 89%
rename from src/packages/util/mathjax-utils.js
rename to src/packages/util/mathjax-utils.ts
index a631e961a41..942222a8d2b 100644
--- a/src/packages/util/mathjax-utils.js
+++ b/src/packages/util/mathjax-utils.ts
@@ -1,5 +1,5 @@
 /*
- *  This file is part of CoCalc: Copyright © 2020 Sagemath, Inc.
+ *  This file is part of CoCalc: Copyright © 2020–2026 Sagemath, Inc.
  *  License: MS-RSL – see LICENSE.md for details
  */
 
@@ -21,8 +21,7 @@ const MATHSPLIT = /(\$\$?|\\(?:begin|end)\{[a-z]*\*?\}|(?:\n\s*)+)/i;
 // Jupyter classic doesn't and it conflicts too much with markdown.  Use $'s and e.g., \begin{equation}.
 // const MATHSPLIT = /(\$\$?|\\(?:begin|end)\{[a-z]*\*?\}|(?:\n\s*)+|\\(?:\(|\)|\[|\]))/i;
 
-// This runs under node.js and is js (not ts) so can't use import.
-const { regex_split } = require("./regex-split");
+import { regex_split } from "./regex-split";
 
 //  The math is in blocks i through j, so
 //    collect it into one block and clear the others.
@@ -56,8 +55,7 @@ function process_math(i, j, pre_process, math, blocks, tags) {
 //
 
 // Do *NOT* conflict with the ones used in ./markdown-utils.ts
-const MATH_ESCAPE = "\uFE32\uFE33"; // unused unicode -- hardcoded below too
-exports.MATH_ESCAPE = MATH_ESCAPE;
+export const MATH_ESCAPE = "\uFE32\uFE33"; // unused unicode -- hardcoded below too
 
 const DEFAULT_TAGS = {
   open: MATH_ESCAPE,
@@ -66,12 +64,12 @@ const DEFAULT_TAGS = {
   display_close: MATH_ESCAPE,
 };
 
-function remove_math(text, tags = DEFAULT_TAGS) {
-  let math = []; // stores math strings for later
-  let start;
-  let end;
-  let last;
-  let braces;
+export function remove_math(text: string, tags = DEFAULT_TAGS) {
+  let math: string[] = []; // stores math strings for later
+  let start: number | null = null;
+  let end: string | null = null;
+  let last: number | null = null;
+  let braces: number = 0;
 
   // Except for extreme edge cases, this should catch precisely those pieces of the markdown
   // source that will later be turned into code spans. While MathJax will not TeXify code spans,
@@ -88,7 +86,7 @@ function remove_math(text, tags = DEFAULT_TAGS) {
         return wholematch.replace(/\$/g, "~D");
       });
     de_tilde = function (text) {
-      return text.replace(/~([TD])/g, function (wholematch, character) {
+      return text.replace(/~([TD])/g, function (_wholematch, character) {
         return { T: "~", D: "$" }[character];
       });
     };
@@ -101,7 +99,7 @@ function remove_math(text, tags = DEFAULT_TAGS) {
   let blocks = regex_split(text.replace(/\r\n?/g, "\n"), MATHSPLIT);
 
   for (let i = 1, m = blocks.length; i < m; i += 2) {
-    const block = blocks[i];
+    const block = blocks[i] as string;
     if (start) {
       //
       //  If we are in math, look for the end delimiter,
@@ -159,17 +157,16 @@ function remove_math(text, tags = DEFAULT_TAGS) {
   }
   return [de_tilde(blocks.join("")), math];
 }
-exports.remove_math = remove_math;
 
 //
 //  Put back the math strings that were saved.
 //
-function replace_math(text, math, tags) {
+export function replace_math(text, math, tags?) {
   // Replace all the math group placeholders in the text
   // with the saved strings.
   if (tags == null) {
     // Easy to do with a regexp
-    return text.replace(/\uFE32\uFE33(\d+)\uFE32\uFE33/g, function (match, n) {
+    return text.replace(/\uFE32\uFE33(\d+)\uFE32\uFE33/g, function (_match, n) {
       return math[n];
     });
   } else {
@@ -197,5 +194,3 @@ function replace_math(text, math, tags) {
     return text;
   }
 }
-
-exports.replace_math = replace_math;
diff --git a/src/packages/util/message.d.ts b/src/packages/util/message.d.ts
deleted file mode 100644
index 2682106b9ac..00000000000
--- a/src/packages/util/message.d.ts
+++ /dev/null
@@ -1,105 +0,0 @@
-export const start_session: any;
-export const session_started: any;
-export const output: any;
-export const execute_javascript: any;
-export const usernames: any;
-export const create_account: any;
-export const account_created: any;
-export const account_creation_failed: any;
-export const delete_account: any;
-export const account_deleted: any;
-export const sign_in: any;
-export const remember_me_failed: any;
-export const sign_in_failed: any;
-export const signed_in: any;
-export const sign_out: any;
-export const signed_out: any;
-export const error: any;
-export const success: any;
-export const reconnect: any;
-export const cookies: any;
-export const open_project: any;
-export const project_opened: any;
-export const project_exec: any;
-export const project_exec_output: any;
-export const named_server_port: any;
-export const read_file_from_project: any;
-export const file_read_from_project: any;
-export const read_text_file_from_project: any;
-export const text_file_read_from_project: any;
-export const write_file_to_project: any;
-export const write_text_file_to_project: any;
-export const file_written_to_project: any;
-export const project_users: any;
-export const version: any;
-export const save_blob: any;
-export const storage: any;
-export const projects_running_on_server: any;
-export const local_hub: any;
-export const copy_path_between_projects: any;
-export const copy_path_between_projects_response: any;
-export const copy_path_status: any;
-export const copy_path_status_response: any;
-export const copy_path_delete: any;
-export const print_to_pdf: any;
-export const printed_to_pdf: any;
-export const heartbeat: any;
-export const ping: any;
-export const pong: any;
-export const log_client_error: any;
-export const webapp_error: any;
-export const stripe_get_customer: any;
-export const stripe_customer: any;
-export const stripe_create_source: any;
-export const stripe_delete_source: any;
-export const stripe_set_default_source: any;
-export const stripe_update_source: any;
-export const stripe_plans: any;
-export const stripe_create_subscription: any;
-export const stripe_cancel_subscription: any;
-export const stripe_update_subscription: any;
-export const stripe_get_subscriptions: any;
-export const stripe_subscriptions: any;
-export const stripe_get_coupon: any;
-export const stripe_coupon: any;
-export const stripe_get_charges: any;
-export const stripe_charges: any;
-export const stripe_get_invoices: any;
-export const stripe_invoices: any;
-export const stripe_admin_create_invoice_item: any;
-export const query: any;
-export const uuid: any;
-export const uuid: any;
-export const query_cancel: any;
-export const api_key: any;
-export const api_key_info: any;
-export const api_keys: any;
-export const api_keys_response: any;
-export const user_auth: any;
-export const user_auth_token: any;
-export const get_available_upgrades: any;
-export const disconnect_from_project: any;
-export const available_upgrades: any;
-export const remove_all_upgrades: any;
-export const sagews_execute_code: any;
-export const sagews_output: any;
-export const sagews_output_ack: any;
-export const sagews_interrupt: any;
-export const sagews_quit: any;
-export const sagews_start: any;
-export const user_tracking: any;
-export const purchase_license: any;
-export const purchase_license_resp: any;
-export const chatgpt: any;
-export const chatgpt_response: any;
-export const openai_embeddings_search: any;
-export const openai_embeddings_search_response: any;
-export const openai_embeddings_save: any;
-export const openai_embeddings_save_response: any;
-export const openai_embeddings_remove: any;
-export const openai_embeddings_remove_response: any;
-export const jupyter_execute: any;
-export const jupyter_execute_response: any;
-export const jupyter_kernels: any;
-export const jupyter_start_pool: any;
-export const signal_sent: any;
diff --git a/src/packages/util/message.js b/src/packages/util/message.ts
similarity index 94%
rename from src/packages/util/message.js
rename to src/packages/util/message.ts
index 5aea5143a8e..2ca78039486 100644
--- a/src/packages/util/message.js
+++ b/src/packages/util/message.ts
@@ -1,5 +1,5 @@
 /*
- *  This file is part of CoCalc: Copyright © 2020 Sagemath, Inc.
+ *  This file is part of CoCalc: Copyright © 2020-2026 Sagemath, Inc.
  *  License: MS-RSL – see LICENSE.md for details
  */
 
@@ -96,19 +96,17 @@ If id is not provided in the API message, a random id will be
 generated and returned in the response.\
 `;
 
-const misc = require("./misc");
-const { defaults } = misc;
+import { defaults, to_json } from "./misc";
+import mapValues from "lodash/mapValues";
+
 const { required } = defaults;
-const _ = require("underscore");
 
-function message(obj) {
-  exports[obj.event] = function (opts, strict) {
-    if (opts == null) {
-      opts = {};
-    }
-    if (strict == null) {
-      strict = false;
-    }
+// All message factories are collected here at runtime.
+// IMPORTANT: these are unpacked as named exports at the bottom of this file.
+const messages: Record<string, any> = {};
+
+function message(obj: any) {
+  messages[obj.event] = function (opts: any = {}, strict = false) {
     if (opts.event != null) {
       throw Error(
         `ValueError: must not define 'event' when calling message creation function (opts=${JSON.stringify(
@@ -121,50 +119,50 @@ function message(obj) {
   return obj;
 }
 
+// messages that can be used by the HTTP api.   {'event':true, ...}
+export const api_messages: Record<string, boolean> = {};
+
+// this holds the documentation for the message protocol
+export const documentation: { intro: string; events: Record<string, any> } = {
+  intro: doc_intro,
+  events: {},
+};
+
+// holds all the examples: list of expected in/out objects for each message
+export const examples: Record<string, any> = {};
+
 // message2 for "version 2" of the message definitions
 // TODO document it, for now just search for "message2" to see examples
-function message2(obj) {
-  function mk_desc(val) {
+function message2(obj: any) {
+  function mk_desc(val: any) {
     let { desc } = val;
     if (val.init === required) {
       desc += " (required)";
     } else if (val.init != null) {
-      desc += ` (default: ${misc.to_json(val.init)})`;
+      desc += ` (default: ${to_json(val.init)})`;
     }
     return desc;
   }
 
   // reassembling a version 1 message from a version 2 message
-  const mesg_v1 = _.mapObject(obj.fields, (val) => val.init);
+  const mesg_v1: any = mapValues(obj.fields, (val: any) => val.init);
   mesg_v1.event = obj.event;
   // extracting description for the documentation
-  const fdesc = _.mapObject(obj.fields, mk_desc);
-  exports.documentation.events[obj.event] = {
+  const fdesc = mapValues(obj.fields, mk_desc);
+  documentation.events[obj.event] = {
     description: obj.desc != null ? obj.desc : "",
     fields: fdesc,
   };
   // ... and the examples
-  exports.examples[obj.event] = obj.examples;
+  examples[obj.event] = obj.examples;
   // wrapped version 1 message
   message(mesg_v1);
   return obj;
 }
 
-// messages that can be used by the HTTP api.   {'event':true, ...}
-exports.api_messages = {};
-
-// this holds the documentation for the message protocol
-exports.documentation = {
-  intro: doc_intro,
-  events: {},
-};
-
-// holds all the examples: list of expected in/out objects for each message
-exports.examples = {};
-
-const API = (obj) =>
+const API = (obj: any) =>
   // obj could be message version 1 or 2!
-  (exports.api_messages[obj.event] = true);
+  (api_messages[obj.event] = true);
 
 //###########################################
 // Sage session management; executing code
@@ -2038,3 +2036,120 @@ API(
     kernels: undefined, // response is same message but with this filled in with array of data giving available kernels
   }),
 );
+
+// Named exports for all message factories registered above.
+// When adding a new message() call, also add its event name here.
+export const {
+  account_created,
+  account_creation_failed,
+  account_deleted,
+  api_key,
+  api_key_info,
+  api_keys,
+  api_keys_response,
+  available_upgrades,
+  chatgpt,
+  chatgpt_response,
+  cookies,
+  copy_path_between_projects,
+  copy_path_between_projects_response,
+  copy_path_delete,
+  copy_path_status,
+  copy_path_status_response,
+  create_account,
+  delete_account,
+  disconnect_from_project,
+  error,
+  execute_javascript,
+  file_read_from_project,
+  file_written_to_project,
+  get_available_upgrades,
+  heartbeat,
+  jupyter_execute,
+  jupyter_execute_response,
+  jupyter_kernels,
+  jupyter_start_pool,
+  local_hub,
+  log_client_error,
+  named_server_port,
+  openai_embeddings_remove,
+  openai_embeddings_remove_response,
+  openai_embeddings_save,
+  openai_embeddings_save_response,
+  openai_embeddings_search,
+  openai_embeddings_search_response,
+  open_project,
+  output,
+  ping,
+  pong,
+  print_to_pdf,
+  printed_to_pdf,
+  project_exec,
+  project_exec_output,
+  project_opened,
+  project_users,
+  projects_running_on_server,
+  purchase_license,
+  purchase_license_resp,
+  query,
+  query_cancel,
+  read_file_from_project,
+  read_text_file_from_project,
+  reconnect,
+  remember_me_failed,
+  remove_all_upgrades,
+  sagews_execute_code,
+  sagews_interrupt,
+  sagews_output,
+  sagews_output_ack,
+  sagews_quit,
+  sagews_start,
+  save_blob,
+  session_started,
+  sign_in,
+  sign_in_failed,
+  sign_out,
+  signed_in,
+  signed_out,
+  start_session,
+  stripe_admin_create_invoice_item,
+  stripe_cancel_subscription,
+  stripe_charges,
+  stripe_coupon,
+  stripe_create_source,
+  stripe_create_subscription,
+  stripe_customer,
+  stripe_delete_source,
+  stripe_get_charges,
+  stripe_get_coupon,
+  stripe_get_customer,
+  stripe_get_invoices,
+  stripe_get_subscriptions,
+  stripe_invoices,
+  stripe_plans,
+  stripe_set_default_source,
+  stripe_subscriptions,
+  stripe_update_source,
+  stripe_update_subscription,
+  success,
+  text_file_read_from_project,
+  user_auth,
+  user_search_results,
+  user_tracking,
+  version,
+  webapp_error,
+  write_file_to_project,
+  write_text_file_to_project,
+} = messages;
+
+// Safeguard: fail at load time if a message() call was added above
+// but its event name was not added to the export list.
+// In CJS, tsc compiles named exports to properties on `exports`.
+for (const key of Object.keys(messages)) {
+  // @ts-ignore -- accessing CJS exports object directly for runtime check
+  if (typeof exports[key] !== "function") {
+    throw Error(
+      `message.ts: "${key}" is registered via message() but missing from the named export list at the bottom of this file. Add it there.`,
+    );
+  }
+}
diff --git a/src/packages/util/package.json b/src/packages/util/package.json
index f7d21c4d8ea..c94bed17a7c 100644
--- a/src/packages/util/package.json
+++ b/src/packages/util/package.json
@@ -3,27 +3,68 @@
   "version": "1.77.2",
   "description": "CoCalc code shared between the frontend and the backend",
   "exports": {
-    "./*": "./dist/*.js",
-    "./db-schema": "./dist/db-schema/index.js",
-    "./fill": "./dist/fill/index.js",
-    "./types": "./dist/types/index.js",
-    "./consts": "./dist/consts/index.js",
-    "./i18n": "./dist/i18n/index.js",
-    "./sync/table": "./dist/sync/table/index.js",
-    "./sync/editor/db": "./dist/sync/editor/db/index.js",
-    "./licenses/purchase/*": "./dist/licenses/purchase/*.js",
-    "./redux/*": "./dist/redux/*.js"
+    "./*": {
+      "types": "./dist/*.d.ts",
+      "import": "./dist-esm/*.js",
+      "default": "./dist/*.js"
+    },
+    "./db-schema": {
+      "types": "./dist/db-schema/index.d.ts",
+      "import": "./dist-esm/db-schema/index.js",
+      "default": "./dist/db-schema/index.js"
+    },
+    "./fill": {
+      "types": "./dist/fill/index.d.ts",
+      "import": "./dist-esm/fill/index.js",
+      "default": "./dist/fill/index.js"
+    },
+    "./types": {
+      "types": "./dist/types/index.d.ts",
+      "import": "./dist-esm/types/index.js",
+      "default": "./dist/types/index.js"
+    },
+    "./consts": {
+      "types": "./dist/consts/index.d.ts",
+      "import": "./dist-esm/consts/index.js",
+      "default": "./dist/consts/index.js"
+    },
+    "./i18n": {
+      "types": "./dist/i18n/index.d.ts",
+      "import": "./dist-esm/i18n/index.js",
+      "default": "./dist/i18n/index.js"
+    },
+    "./sync/table": {
+      "types": "./dist/sync/table/index.d.ts",
+      "import": "./dist-esm/sync/table/index.js",
+      "default": "./dist/sync/table/index.js"
+    },
+    "./sync/editor/db": {
+      "types": "./dist/sync/editor/db/index.d.ts",
+      "import": "./dist-esm/sync/editor/db/index.js",
+      "default": "./dist/sync/editor/db/index.js"
+    },
+    "./licenses/purchase/*": {
+      "types": "./dist/licenses/purchase/*.d.ts",
+      "import": "./dist-esm/licenses/purchase/*.js",
+      "default": "./dist/licenses/purchase/*.js"
+    },
+    "./redux/*": {
+      "types": "./dist/redux/*.d.ts",
+      "import": "./dist-esm/redux/*.js",
+      "default": "./dist/redux/*.js"
+    }
   },
   "scripts": {
     "preinstall": "npx only-allow pnpm",
-    "clean": "rm -rf node_modules dist",
-    "build": "pnpm exec tsc --build",
+    "clean": "rm -rf node_modules dist dist-esm",
+    "build": "pnpm exec tsc --build && pnpm exec tsc -p tsconfig-esm.json && echo '{\"type\":\"module\"}' > dist-esm/package.json",
     "test": "pnpm exec jest",
     "depcheck": "pnpx depcheck --ignores events",
     "prepublishOnly": "pnpm test"
   },
   "files": [
     "dist/**",
+    "dist-esm/**",
     "bin/**",
     "README.md",
     "package.json"
@@ -60,7 +101,6 @@
     "request-ip": "^3.3.0",
     "reselect": "^4.1.8",
     "sha1": "^1.1.1",
-    "underscore": "^1.12.1",
     "utility-types": "^3.10.0",
     "uuid": "^8.3.2",
     "voucher-code-generator": "^1.3.0"
diff --git a/src/packages/util/quota.test.ts b/src/packages/util/quota.test.ts
index fe9b29082c4..014d1bfd39a 100644
--- a/src/packages/util/quota.test.ts
+++ b/src/packages/util/quota.test.ts
@@ -13,7 +13,7 @@ extend it to test whatever you changed too.  In one terminal:
 
 and in another:
 
-.../packages/util$ ../node_modules/.bin/jest dist/quota.test.js  [--watch]
+.../packages/util$ pnpm exec jest dist/quota.test.js  [--watch]
 
 
 Also generally do this:
diff --git a/src/packages/util/regex-split.js b/src/packages/util/regex-split.js
deleted file mode 100644
index 352affbbfb8..00000000000
--- a/src/packages/util/regex-split.js
+++ /dev/null
@@ -1,120 +0,0 @@
-/*
- *  This file is part of CoCalc: Copyright © 2020 Sagemath, Inc.
- *  License: MS-RSL – see LICENSE.md for details
- */
-
-//============================================================================
-// Cross-browser RegEx Split
-//============================================================================
-
-// This code has been MODIFIED from the code licensed below to not replace the
-// default browser split.  The license is reproduced here.
-
-// see http://blog.stevenlevithan.com/archives/cross-browser-split for more info:
-/*!
- * Cross-Browser Split 1.1.1
- * Copyright 2007-2012 Steven Levithan <stevenlevithan.com>
- * Available under the MIT License
- * ECMAScript compliant, uniform cross-browser split method
- */
-
-/**
- * Splits a string into an array of strings using a regex or string
- * separator. Matches of the separator are not included in the result array.
- * However, if `separator` is a regex that contains capturing groups,
- * backreferences are spliced into the result each time `separator` is
- * matched. Fixes browser bugs compared to the native
- * `String.prototype.split` and can be used reliably cross-browser.
- * @param {String} str String to split.
- * @param {RegExp} separator Regex to use for separating
- *     the string.
- * @param {Number} [limit] Maximum number of items to include in the result
- *     array.
- * @returns {Array} Array of substrings.
- * @example
- *
- * // Basic use
- * regex_split('a b c d', ' ');
- * // -> ['a', 'b', 'c', 'd']
- *
- * // With limit
- * regex_split('a b c d', ' ', 2);
- * // -> ['a', 'b']
- *
- * // Backreferences in result array
- * regex_split('..word1 word2..', /([a-z]+)(\d+)/i);
- * // -> ['..', 'word', '1', ' ', 'word', '2', '..']
- */
-exports.regex_split = function (str, separator, limit) {
-  var output = [],
-    flags =
-      (separator.ignoreCase ? "i" : "") +
-      (separator.multiline ? "m" : "") +
-      (separator.extended ? "x" : "") + // Proposed for ES6
-      (separator.sticky ? "y" : ""), // Firefox 3+
-    lastLastIndex = 0,
-    separator2,
-    match,
-    lastIndex,
-    lastLength;
-  // Make `global` and avoid `lastIndex` issues by working with a copy
-  separator = new RegExp(separator.source, flags + "g");
-
-  var compliantExecNpcg = typeof /()??/.exec("")[1] === "undefined";
-  if (!compliantExecNpcg) {
-    // Doesn't need flags gy, but they don't hurt
-    separator2 = new RegExp("^" + separator.source + "$(?!\\s)", flags);
-  }
-  /* Values for `limit`, per the spec:
-   * If undefined: 4294967295 // Math.pow(2, 32) - 1
-   * If 0, Infinity, or NaN: 0
-   * If positive number: limit = Math.floor(limit); if (limit > 4294967295) limit -= 4294967296;
-   * If negative number: 4294967296 - Math.floor(Math.abs(limit))
-   * If other: Type-convert, then use the above rules
-   */
-  limit =
-    typeof limit === "undefined"
-      ? -1 >>> 0 // Math.pow(2, 32) - 1
-      : limit >>> 0; // ToUint32(limit)
-  for (match = separator.exec(str); match; match = separator.exec(str)) {
-    // `separator.lastIndex` is not reliable cross-browser
-    lastIndex = match.index + match[0].length;
-    if (lastIndex > lastLastIndex) {
-      output.push(str.slice(lastLastIndex, match.index));
-      // Fix browsers whose `exec` methods don't consistently return `undefined` for
-      // nonparticipating capturing groups
-      if (!compliantExecNpcg && match.length > 1) {
-        match[0].replace(separator2, function () {
-          for (var i = 1; i < arguments.length - 2; i++) {
-            if (typeof arguments[i] === "undefined") {
-              match[i] = undefined;
-            }
-          }
-        });
-      }
-      if (match.length > 1 && match.index < str.length) {
-        Array.prototype.push.apply(output, match.slice(1));
-      }
-      lastLength = match[0].length;
-      lastLastIndex = lastIndex;
-      if (output.length >= limit) {
-        break;
-      }
-    }
-    if (separator.lastIndex === match.index) {
-      separator.lastIndex++; // Avoid an infinite loop
-    }
-  }
-  if (lastLastIndex === str.length) {
-    if (lastLength || !separator.test("")) {
-      output.push("");
-    }
-  } else {
-    output.push(str.slice(lastLastIndex));
-  }
-  return output.length > limit ? output.slice(0, limit) : output;
-};
-
-//============================================================================
-// End contributed Cross-browser RegEx Split
-//============================================================================
diff --git a/src/packages/util/regex-split.test.ts b/src/packages/util/regex-split.test.ts
new file mode 100644
index 00000000000..8e967a0c85b
--- /dev/null
+++ b/src/packages/util/regex-split.test.ts
@@ -0,0 +1,96 @@
+/*
+ *  This file is part of CoCalc: Copyright © 2026 Sagemath, Inc.
+ *  License: MS-RSL – see LICENSE.md for details
+ */
+
+import { regex_split } from "./regex-split";
+
+describe("regex_split", () => {
+  test("basic split on space", () => {
+    expect(regex_split("a b c d", / /)).toEqual(["a", "b", "c", "d"]);
+  });
+
+  test("split with limit", () => {
+    expect(regex_split("a b c d", / /, 2)).toEqual(["a", "b"]);
+  });
+
+  test("split with capturing groups includes backreferences", () => {
+    expect(regex_split("..word1 word2..", /([a-z]+)(\d+)/i)).toEqual([
+      "..",
+      "word",
+      "1",
+      " ",
+      "word",
+      "2",
+      "..",
+    ]);
+  });
+
+  test("empty string returns array with empty string", () => {
+    expect(regex_split("", /,/)).toEqual([""]);
+  });
+
+  test("no match returns original string in array", () => {
+    expect(regex_split("hello", /,/)).toEqual(["hello"]);
+  });
+
+  test("consecutive separators produce empty strings", () => {
+    expect(regex_split("a,,b", /,/)).toEqual(["a", "", "b"]);
+  });
+
+  test("separator at start", () => {
+    expect(regex_split(",a,b", /,/)).toEqual(["", "a", "b"]);
+  });
+
+  test("separator at end", () => {
+    expect(regex_split("a,b,", /,/)).toEqual(["a", "b", ""]);
+  });
+
+  test("case-insensitive flag is preserved", () => {
+    expect(regex_split("aXbXc", /x/i)).toEqual(["a", "b", "c"]);
+  });
+
+  test("multiline flag is preserved", () => {
+    const result = regex_split("a\nb\nc", /^/m);
+    expect(result).toEqual(["a\n", "b\n", "c"]);
+  });
+
+  test("limit of 0 returns empty array", () => {
+    expect(regex_split("a,b,c", /,/, 0)).toEqual([]);
+  });
+
+  test("limit of 1 returns first part", () => {
+    expect(regex_split("a,b,c", /,/, 1)).toEqual(["a"]);
+  });
+
+  test("limit larger than splits returns all parts", () => {
+    expect(regex_split("a,b", /,/, 100)).toEqual(["a", "b"]);
+  });
+
+  test("split on alternation (MATHSPLIT-like pattern)", () => {
+    // Mimics the MathJax MATHSPLIT pattern for $ delimiters
+    const MATHSPLIT = /(\$\$?)/;
+    expect(regex_split("text $math$ more", MATHSPLIT)).toEqual([
+      "text ",
+      "$",
+      "math",
+      "$",
+      " more",
+    ]);
+  });
+
+  test("split with \\begin/\\end pattern", () => {
+    const MATHSPLIT = /(\$\$?|\\(?:begin|end)\{[a-z]*\*?\})/i;
+    const result = regex_split(
+      "before\\begin{align}x=1\\end{align}after",
+      MATHSPLIT,
+    );
+    expect(result).toEqual([
+      "before",
+      "\\begin{align}",
+      "x=1",
+      "\\end{align}",
+      "after",
+    ]);
+  });
+});
diff --git a/src/packages/util/regex-split.ts b/src/packages/util/regex-split.ts
new file mode 100644
index 00000000000..250b4638d4b
--- /dev/null
+++ b/src/packages/util/regex-split.ts
@@ -0,0 +1,128 @@
+/*
+ *  This file is part of CoCalc: Copyright © 2020–2026 Sagemath, Inc.
+ *  License: MS-RSL – see LICENSE.md for details
+ */
+
+//============================================================================
+// Cross-browser RegEx Split
+//============================================================================
+
+// This code has been MODIFIED from the code licensed below to not replace the
+// default browser split.  The license is reproduced here.
+
+// see http://blog.stevenlevithan.com/archives/cross-browser-split for more info:
+/*!
+ * Cross-Browser Split 1.1.1
+ * Copyright 2007-2012 Steven Levithan <stevenlevithan.com>
+ * Available under the MIT License
+ * ECMAScript compliant, uniform cross-browser split method
+ */
+
+/**
+ * Splits a string into an array of strings using a regex separator.
+ * Matches of the separator are not included in the result array.
+ * However, if `separator` is a regex that contains capturing groups,
+ * backreferences are spliced into the result each time `separator` is
+ * matched. Fixes browser bugs compared to the native
+ * `String.prototype.split` and can be used reliably cross-browser.
+ *
+ * @example
+ * regex_split('a b c d', / /);
+ * // -> ['a', 'b', 'c', 'd']
+ *
+ * @example
+ * regex_split('a b c d', / /, 2);
+ * // -> ['a', 'b']
+ *
+ * @example
+ * regex_split('..word1 word2..', /([a-z]+)(\d+)/i);
+ * // -> ['..', 'word', '1', ' ', 'word', '2', '..']
+ */
+export function regex_split(
+  str: string,
+  separator: RegExp,
+  limit?: number,
+): (string | undefined)[] {
+  const output: (string | undefined)[] = [];
+
+  const flags =
+    (separator.ignoreCase ? "i" : "") +
+    (separator.multiline ? "m" : "") +
+    ((separator as any).extended ? "x" : "") + // Proposed for ES6
+    (separator.sticky ? "y" : ""); // Firefox 3+
+
+  // Make `global` and avoid `lastIndex` issues by working with a copy
+  const globalSeparator = new RegExp(separator.source, flags + "g");
+
+  let lastLastIndex = 0;
+  let lastLength: number | undefined;
+
+  // For non-compliant browsers that don't return `undefined` for
+  // nonparticipating capturing groups.
+  const compliantExecNpcg = typeof /()??/.exec("")![1] === "undefined";
+  let separator2: RegExp | undefined;
+  if (!compliantExecNpcg) {
+    separator2 = new RegExp("^" + globalSeparator.source + "$(?!\\s)", flags);
+  }
+
+  // Values for `limit`, per the spec:
+  //  If undefined: 4294967295 // Math.pow(2, 32) - 1
+  //  If 0, Infinity, or NaN: 0
+  //  If positive number: limit = Math.floor(limit); ...
+  //  If negative number: 4294967296 - Math.floor(Math.abs(limit))
+  //  If other: Type-convert, then use the above rules
+  const effectiveLimit: number =
+    typeof limit === "undefined"
+      ? -1 >>> 0 // Math.pow(2, 32) - 1
+      : limit >>> 0; // ToUint32(limit)
+
+  let match: RegExpExecArray | null;
+  for (
+    match = globalSeparator.exec(str);
+    match;
+    match = globalSeparator.exec(str)
+  ) {
+    // `separator.lastIndex` is not reliable cross-browser
+    const lastIndex = match.index + match[0].length;
+    if (lastIndex > lastLastIndex) {
+      output.push(str.slice(lastLastIndex, match.index));
+      // Fix browsers whose `exec` methods don't consistently return `undefined`
+      // for nonparticipating capturing groups
+      if (!compliantExecNpcg && match.length > 1) {
+        match[0].replace(separator2!, function (...args: any[]): string {
+          for (let i = 1; i < args.length - 2; i++) {
+            if (typeof args[i] === "undefined") {
+              match![i] = undefined as any;
+            }
+          }
+          return "";
+        });
+      }
+      if (match.length > 1 && match.index < str.length) {
+        Array.prototype.push.apply(output, match.slice(1));
+      }
+      lastLength = match[0].length;
+      lastLastIndex = lastIndex;
+      if (output.length >= effectiveLimit) {
+        break;
+      }
+    }
+    if (globalSeparator.lastIndex === match.index) {
+      globalSeparator.lastIndex++; // Avoid an infinite loop
+    }
+  }
+  if (lastLastIndex === str.length) {
+    if (lastLength || !globalSeparator.test("")) {
+      output.push("");
+    }
+  } else {
+    output.push(str.slice(lastLastIndex));
+  }
+  return output.length > effectiveLimit
+    ? output.slice(0, effectiveLimit)
+    : output;
+}
+
+//============================================================================
+// End contributed Cross-browser RegEx Split
+//============================================================================
diff --git a/src/packages/util/smc-version.js b/src/packages/util/smc-version.ts
similarity index 58%
rename from src/packages/util/smc-version.js
rename to src/packages/util/smc-version.ts
index 44ef81468b6..3c42cd09b65 100644
--- a/src/packages/util/smc-version.js
+++ b/src/packages/util/smc-version.ts
@@ -1,2 +1,2 @@
 /* autogenerated by the update_version script */
-exports.version=1763609578;
+export const version = 1771527616;
diff --git a/src/packages/util/tsconfig-esm.json b/src/packages/util/tsconfig-esm.json
new file mode 100644
index 00000000000..32df14142bf
--- /dev/null
+++ b/src/packages/util/tsconfig-esm.json
@@ -0,0 +1,18 @@
+{
+  "extends": "../tsconfig.json",
+  "compilerOptions": {
+    "rootDir": "./",
+    "outDir": "dist-esm",
+    "module": "ESNext",
+    "moduleResolution": "bundler",
+    "declaration": false,
+    "declarationMap": false,
+    "composite": false,
+    "incremental": false,
+    "sourceMap": true,
+    "paths": {
+      "@cocalc/util/*": ["./*"]
+    }
+  },
+  "exclude": ["node_modules", "../node_modules", "dist", "dist-esm", "test"]
+}
diff --git a/src/packages/util/tsconfig.json b/src/packages/util/tsconfig.json
index 95a218962f3..7870d144938 100644
--- a/src/packages/util/tsconfig.json
+++ b/src/packages/util/tsconfig.json
@@ -4,5 +4,5 @@
     "rootDir": "./",
     "outDir": "dist"
   },
-  "exclude": ["node_modules", "../node_modules", "dist", "test"]
+  "exclude": ["node_modules", "../node_modules", "dist", "dist-esm", "test"]
 }
diff --git a/src/packages/util/upgrades.js b/src/packages/util/upgrades.ts
similarity index 79%
rename from src/packages/util/upgrades.js
rename to src/packages/util/upgrades.ts
index 1d98ecd5594..0bab6544dd3 100644
--- a/src/packages/util/upgrades.js
+++ b/src/packages/util/upgrades.ts
@@ -1,16 +1,15 @@
 /*
- *  This file is part of CoCalc: Copyright © 2020 Sagemath, Inc.
+ *  This file is part of CoCalc: Copyright © 2020–2026 Sagemath, Inc.
  *  License: MS-RSL – see LICENSE.md for details
  */
 
-const { PROJECT_UPGRADES } = require("./schema");
-
-const misc = require("./misc");
+import { PROJECT_UPGRADES } from "./schema";
+import { cmp, map_sum } from "./misc";
 
 // This is used by the frontend in r_account.  It's also used by the backend
 // to double check the claims of the frontend.
 // stripe_subscriptions_data = stripe_customer?.subscriptions?.data
-function get_total_upgrades(stripe_subscriptions_data, DEBUG = false) {
+export function get_total_upgrades(stripe_subscriptions_data, DEBUG = false) {
   if (DEBUG) {
     return PROJECT_UPGRADES.subscription.professional.benefits;
   }
@@ -22,7 +21,7 @@ function get_total_upgrades(stripe_subscriptions_data, DEBUG = false) {
   // always running isn't in any of the subscriptions and I don't want to edit benefits
   // for all of them, so just put a zero 0 (since this whole old upgrades thing
   // will eventually go away). https://github.com/sagemathinc/cocalc/issues/4802
-  let total = { always_running: 0 };
+  let total: Record<string, number> = { always_running: 0 };
   for (let sub of subs) {
     if (sub.status != "active" && sub.status != "trialing") {
       // not yet paid for or no longer available.
@@ -35,14 +34,12 @@ function get_total_upgrades(stripe_subscriptions_data, DEBUG = false) {
     }
     const benefits = info.benefits;
     for (let q = 0; q < sub.quantity; q++) {
-      total = misc.map_sum(total, benefits);
+      total = map_sum(total, benefits);
     }
   }
   return total;
 }
 
-exports.get_total_upgrades = get_total_upgrades;
-
 //
 // INPUT:
 //    subscriptions = {standard:2, premium:1, course:2, ...}
@@ -51,17 +48,17 @@ exports.get_total_upgrades = get_total_upgrades;
 // OUTPUT:
 //     {available:{cores:10, network:3, ...},   excess:{project_id:{cores:2, ...}}  }
 //
-function available_upgrades(stripe_subscriptions_data, projects) {
+export function available_upgrades(stripe_subscriptions_data, projects) {
   let project_id, upgrades;
   const available = get_total_upgrades(stripe_subscriptions_data); // start with amount available being your quota
-  const excess = {}; // nothing exceeds quota
+  const excess: Record<string, Record<string, number>> = {}; // nothing exceeds quota
   // sort projects by project_id so that excess will be well defined
-  const v = [];
+  const v: { project_id: string; upgrades: any }[] = [];
   for (project_id in projects) {
     upgrades = projects[project_id];
     v.push({ project_id, upgrades });
   }
-  v.sort((a, b) => misc.cmp(a.project_id, b.project_id));
+  v.sort((a, b) => cmp(a.project_id, b.project_id));
   for ({ project_id, upgrades } of v) {
     for (let prop in upgrades) {
       const curval = upgrades[prop];
@@ -83,7 +80,6 @@ function available_upgrades(stripe_subscriptions_data, projects) {
   }
   return { available, excess };
 }
-exports.available_upgrades = available_upgrades;
 
 // INPUT: same as above, but also a single project_id
 //
@@ -93,13 +89,10 @@ exports.available_upgrades = available_upgrades;
 //      {cores:2, network:1, disk_quota:2000, memory:1000}
 //
 //
-function upgrade_maxes(stripe_subscriptions_data, projects, project_id) {
-  const { available, excess } = available_upgrades(
-    stripe_subscriptions_data,
-    projects,
-  );
+export function upgrade_maxes(stripe_subscriptions_data, projects, project_id) {
+  const { available } = available_upgrades(stripe_subscriptions_data, projects);
   const allocated = projects[project_id];
-  const maxes = {};
+  const maxes: Record<string, number> = {};
   for (let param in available) {
     const avail = available[param];
     const max = PROJECT_UPGRADES.max_per_project[param]; // the maximum allowed for this param for any project
@@ -108,5 +101,3 @@ function upgrade_maxes(stripe_subscriptions_data, projects, project_id) {
   }
   return maxes;
 }
-
-exports.upgrade_maxes = upgrade_maxes;
diff --git a/src/scripts/add-esm-extensions.py b/src/scripts/add-esm-extensions.py
new file mode 100755
index 00000000000..0b2dad81e44
--- /dev/null
+++ b/src/scripts/add-esm-extensions.py
@@ -0,0 +1,187 @@
+#!/usr/bin/env python3
+"""
+Add .js extensions to relative TypeScript imports for NodeNext/ESM compatibility.
+
+For each .ts/.tsx file, finds relative imports without file extensions and
+adds the correct .js suffix:
+
+  import { x } from "./foo"       -> import { x } from "./foo.js"
+  import { x } from "../bar"      -> import { x } from "../bar.js"
+  export { x } from "./foo"       -> export { x } from "./foo.js"
+  import("./foo")                 -> import("./foo.js")
+
+  Directory imports (./dir where dir/index.ts exists):
+  import { x } from "./dir"       -> import { x } from "./dir/index.js"
+
+Imports that already have an extension (e.g. "./style.css", "./data.json")
+are left unchanged.
+
+Usage:
+  python3 scripts/add-esm-extensions.py packages/util
+  python3 scripts/add-esm-extensions.py packages/util packages/comm
+  python3 scripts/add-esm-extensions.py --dry-run packages/util
+"""
+
+import re
+import sys
+from pathlib import Path
+
+# Matches: from "./path" or from '../path' (relative, no extension)
+# Captures: (quote)(path)(quote)
+FROM_PATTERN = re.compile(
+    r"""(?<!\w)(from\s+)(["'])(\.\.?/[^"']+)(["'])""",
+)
+
+# Matches: import("./path") — dynamic imports
+DYNAMIC_PATTERN = re.compile(
+    r"""((?<!\w)import\s*\(\s*)(["'])(\.\.?/[^"']+)(["'])""",
+)
+
+# Matches: import "./path" — side-effect-only imports (no `from`)
+SIDEEFFECT_PATTERN = re.compile(
+    r"""((?<!\w)import\s+)(["'])(\.\.?/[^"']+)(["'])""",
+)
+
+
+def has_extension(path: str) -> bool:
+    """Return True if the last path segment has a file extension."""
+    return bool(Path(path).suffix)
+
+
+def resolve_esm_path(import_path: str, source_file: Path) -> str:
+    """
+    Given a relative import path and the source file it appears in,
+    return the correct ESM path with .js extension.
+    Returns the original path unchanged if it already has an extension
+    or if the target cannot be resolved.
+    """
+    if has_extension(import_path):
+        return import_path  # already has .css, .json, .js, etc.
+
+    source_dir = source_file.parent
+    target_base = source_dir / import_path
+
+    # Check: is there a .ts or .tsx source file at this path?
+    for ext in (".ts", ".tsx"):
+        if target_base.with_suffix(ext).exists():
+            return import_path + ".js"
+
+    # Check: is it a directory with an index.ts or index.tsx?
+    if target_base.is_dir():
+        for index_name in ("index.ts", "index.tsx"):
+            if (target_base / index_name).exists():
+                return import_path + "/index.js"
+
+    # Check: pre-compiled .d.ts declaration file (treat as .js at runtime)
+    if target_base.with_suffix(".d.ts").exists():
+        return import_path + ".js"
+
+    # Check: already a .js file (e.g. hand-written JS utility)
+    if target_base.with_suffix(".js").exists():
+        return import_path + ".js"
+
+    # Could not resolve — warn and leave unchanged
+    print(
+        f"  WARN: cannot resolve '{import_path}' from {source_file.name}",
+        file=sys.stderr,
+    )
+    return import_path
+
+
+def fix_file(filepath: Path, dry_run: bool = False) -> bool:
+    """
+    Fix all extensionless relative imports in a single file.
+    Returns True if the file was (or would be) changed.
+    """
+    try:
+        content = filepath.read_text(encoding="utf-8")
+    except Exception as e:
+        print(f"  ERROR reading {filepath}: {e}", file=sys.stderr)
+        return False
+
+    changed = False
+
+    def make_replacer(filepath: Path):
+        def replacer(m: re.Match) -> str:
+            nonlocal changed
+            prefix, q1, path, q2 = m.group(1), m.group(2), m.group(3), m.group(4)
+            new_path = resolve_esm_path(path, filepath)
+            if new_path != path:
+                changed = True
+                return f"{prefix}{q1}{new_path}{q2}"
+            return m.group(0)
+
+        return replacer
+
+    replacer = make_replacer(filepath)
+    new_content = FROM_PATTERN.sub(replacer, content)
+    new_content = DYNAMIC_PATTERN.sub(replacer, new_content)
+    new_content = SIDEEFFECT_PATTERN.sub(replacer, new_content)
+
+    if changed and not dry_run:
+        filepath.write_text(new_content, encoding="utf-8")
+
+    return changed
+
+
+EXCLUDE_DIRS = {"node_modules", "dist", "dist-esm", ".git", "__pycache__"}
+
+
+def fix_package(package_dir: Path, dry_run: bool = False) -> int:
+    """
+    Fix all .ts/.tsx source files in a package directory.
+    Returns the count of files changed (or that would be changed in dry-run).
+    """
+    count = 0
+    source_files = sorted(
+        [
+            p
+            for p in package_dir.rglob("*.[tj]s")
+            if p.suffix in (".ts", ".tsx")
+            and not any(part in EXCLUDE_DIRS for part in p.parts)
+        ]
+    )
+
+    for filepath in source_files:
+        if fix_file(filepath, dry_run):
+            rel = filepath.relative_to(package_dir)
+            print(f"  {'[dry] ' if dry_run else ''}fixed: {rel}")
+            count += 1
+
+    return count
+
+
+def main() -> None:
+    import argparse
+
+    parser = argparse.ArgumentParser(
+        description="Add .js extensions to TypeScript imports for NodeNext ESM"
+    )
+    parser.add_argument(
+        "packages",
+        nargs="+",
+        help="Package directories to process (e.g. packages/util)",
+    )
+    parser.add_argument(
+        "--dry-run",
+        action="store_true",
+        help="Print what would change without writing files",
+    )
+    args = parser.parse_args()
+
+    total = 0
+    for pkg in args.packages:
+        pkg_path = Path(pkg)
+        if not pkg_path.is_dir():
+            print(f"ERROR: '{pkg}' is not a directory", file=sys.stderr)
+            sys.exit(1)
+        print(f"\nProcessing {pkg_path.resolve().name}...")
+        count = fix_package(pkg_path, args.dry_run)
+        print(f"  {'Would change' if args.dry_run else 'Changed'} {count} files")
+        total += count
+
+    print(f"\nTotal: {total} files {'affected' if args.dry_run else 'updated'}")
+
+
+if __name__ == "__main__":
+    main()
diff --git a/src/update_version b/src/update_version
index 8308d2f1f06..05c8bcbc28c 100755
--- a/src/update_version
+++ b/src/update_version
@@ -12,14 +12,14 @@ Goto account -> admin site settings -> required browser version
 import argparse, os, time
 
 ROOT = os.path.dirname(os.path.realpath(__file__))
-TARGET = os.path.join(ROOT, "packages/util/smc-version.js")
+TARGET = os.path.join(ROOT, "packages/util/smc-version.ts")
 
 def write_version_file():
     # Create version file, based on the current time
     now = int(time.time())
     v = []
     v.append("/* autogenerated by the update_version script */")
-    v.append("exports.version=%s;"%now)
+    v.append("export const version = %s;"%now)
     open(TARGET,'w').write('\n'.join(v) + '\n')
     os.chdir(os.path.join(ROOT, "packages/util"))
     os.system("npm run build")
diff --git a/src/workspaces.py b/src/workspaces.py
index 707edf20bc1..96f2c1a7219 100755
--- a/src/workspaces.py
+++ b/src/workspaces.py
@@ -375,11 +375,11 @@ def clean(args) -> None:
     v = packages(args)
 
     if args.dist_only:
-        folders = ['dist']
+        folders = ['dist', 'dist-esm']
     elif args.node_modules_only:
         folders = ['node_modules']
     else:
-        folders = ['node_modules', 'dist', SUCCESSFUL_BUILD]
+        folders = ['node_modules', 'dist', 'dist-esm', SUCCESSFUL_BUILD]
 
     paths = []
     for path in v: