diff --git a/rfd-ts/package-lock.json b/rfd-ts/package-lock.json
index 7f443e1c..47717943 100644
--- a/rfd-ts/package-lock.json
+++ b/rfd-ts/package-lock.json
@@ -1,22 +1,22 @@
 {
   "name": "@oxide/rfd.ts",
-  "version": "0.15.3",
+  "version": "0.15.4",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "@oxide/rfd.ts",
-      "version": "0.15.3",
+      "version": "0.15.4",
       "license": "MPL-2.0",
       "devDependencies": {
-        "tsup": "^8.0.2",
-        "typescript": "^5.7.2"
+        "tsup": "^8.5.1",
+        "typescript": "^6.0.3"
       },
       "engines": {
         "node": ">=18"
       },
       "peerDependencies": {
-        "zod": "^3.23.8 || ^4.0.0"
+        "zod": "^4.0.0"
       }
     },
     "node_modules/@esbuild/aix-ppc64": {
@@ -1790,9 +1790,9 @@
       }
     },
     "node_modules/typescript": {
-      "version": "5.9.3",
-      "resolved": "https://registry.npmjs.org/typescript/-/typescript-5.9.3.tgz",
-      "integrity": "sha512-jl1vZzPDinLr9eUt3J/t7V6FgNEw9QjvBPdysz9KfQDD41fQrC2Y4vKQdiaUpFT4bXlb1RHhLpp8wtm6M5TgSw==",
+      "version": "6.0.3",
+      "resolved": "https://registry.npmjs.org/typescript/-/typescript-6.0.3.tgz",
+      "integrity": "sha512-y2TvuxSZPDyQakkFRPZHKFm+KKVqIisdg9/CZwm9ftvKXLP8NRWj38/ODjNbr43SsoXqNuAisEf1GdCxqWcdBw==",
       "dev": true,
       "license": "Apache-2.0",
       "bin": {
@@ -1925,9 +1925,9 @@
       }
     },
     "node_modules/zod": {
-      "version": "4.0.13",
-      "resolved": "https://registry.npmjs.org/zod/-/zod-4.0.13.tgz",
-      "integrity": "sha512-jv+zRxuZQxTrFHzxZ46ezL2FtnE+M4HIJHJEwLsZ7UjrXHltdG6HrxvqM0twoVCWxJiYf8WqKjAcjztegpkB+Q==",
+      "version": "4.4.3",
+      "resolved": "https://registry.npmjs.org/zod/-/zod-4.4.3.tgz",
+      "integrity": "sha512-ytENFjIJFl2UwYglde2jchW2Hwm4GJFLDiSXWdTrJQBIN9Fcyp7n4DhxJEiWNAJMV1/BqWfW/kkg71UDcHJyTQ==",
       "license": "MIT",
       "peer": true,
       "funding": {
diff --git a/rfd-ts/package.json b/rfd-ts/package.json
index 55d8b533..67a0cd39 100644
--- a/rfd-ts/package.json
+++ b/rfd-ts/package.json
@@ -5,8 +5,8 @@
   },
   "description": "TypeScript client for the RFD API",
   "devDependencies": {
-    "tsup": "^8.0.2",
-    "typescript": "^5.7.2"
+    "tsup": "^8.5.1",
+    "typescript": "^6.0.3"
   },
   "engines": {
     "node": ">=18"
@@ -30,31 +30,18 @@
   "license": "MPL-2.0",
   "name": "@oxide/rfd.ts",
   "peerDependencies": {
-    "zod": "^3.23.8 || ^4.0.0"
+    "zod": "^4.0.0"
   },
   "repository": {
     "type": "git",
     "url": "git+https://github.com/oxidecomputer/rfd-api.git"
   },
   "scripts": {
-    "build": "tsup --dts",
+    "build": "tsup",
     "prepublishOnly": "npm run build",
     "test": "echo \"Error: no test specified\" && exit 1",
     "tsc": "tsc"
   },
-  "tsup": {
-    "clean": true,
-    "entry": [
-      "src/Api.ts",
-      "src/retry.ts",
-      "src/validate.ts"
-    ],
-    "format": [
-      "cjs",
-      "esm"
-    ],
-    "splitting": false
-  },
   "type": "module",
   "typesVersions": {
     "*": {
diff --git a/rfd-ts/tsup.config.ts b/rfd-ts/tsup.config.ts
new file mode 100644
index 00000000..44c81c7d
--- /dev/null
+++ b/rfd-ts/tsup.config.ts
@@ -0,0 +1,15 @@
+import { defineConfig } from 'tsup'
+
+export default defineConfig({
+  clean: true,
+  entry: ['src/Api.ts', 'src/retry.ts', 'src/validate.ts'],
+  format: ['cjs', 'esm'],
+  splitting: false,
+  // tsup unconditionally injects `baseUrl: '.'` into the DTS build, which TS 6 flags as deprecated.
+  // https://github.com/egoist/tsup/issues/1388
+  dts: {
+    compilerOptions: {
+      ignoreDeprecations: '6.0',
+    },
+  },
+})