diff --git a/.changeset/jolly-dingos-spend.md b/.changeset/jolly-dingos-spend.md
new file mode 100644
index 0000000..a845151
--- /dev/null
+++ b/.changeset/jolly-dingos-spend.md
@@ -0,0 +1,2 @@
+---
+---
diff --git a/package.json b/package.json
index 0d85ec2..a8c7bc3 100644
--- a/package.json
+++ b/package.json
@@ -86,7 +86,8 @@
     "changeset:status": "changeset status",
     "release:version": "changeset version",
     "typecheck": "tsc --noEmit && tsc -p tsconfig.workers.json --noEmit && tsc -p tsconfig.viewer.json --noEmit",
-    "build": "tsc -p tsconfig.build.json && npm run build:viewer && npm run build:embed",
+    "clean:dist": "node scripts/clean-dist.ts",
+    "build": "npm run clean:dist && tsc -p tsconfig.build.json && npm run build:viewer && npm run build:embed",
     "deploy": "npm run build:viewer && wrangler deploy",
     "dev:cloud": "npm run build:viewer && wrangler dev",
     "prepack": "npm run build",
diff --git a/scripts/clean-dist.ts b/scripts/clean-dist.ts
new file mode 100644
index 0000000..06c7fa2
--- /dev/null
+++ b/scripts/clean-dist.ts
@@ -0,0 +1,14 @@
+#!/usr/bin/env node
+
+// Removes the tsc output tree before a package build. TypeScript only writes
+// files, it never deletes output for sources that were renamed or removed, so a
+// long-lived checkout accumulates stale modules that `npm pack` happily ships
+// (and the "./*" export makes importable). The vite builds already self-clean
+// via emptyOutDir, so this is the one output tree that needed it.
+//
+// Anchored to the package root rather than the process CWD so it cannot delete
+// a `dist` belonging to whatever directory the script was invoked from.
+
+import { rmSync } from "node:fs";
+
+rmSync(new URL("../dist", import.meta.url), { recursive: true, force: true });