The initial build used **dumble**, the cordiverse zero-config esbuild wrapper that upstream Cordis itself builds with — maximum alignment with the vendored packages' conventions (it reads each package.json and infers entries/formats from the `exports` field). But dumble is a liability as a load-bearing tool in this repo: v0.2.x, ~530 npm downloads/week, effectively one maintainer, and we were invoking it through a custom orchestration script (`scripts/build.ts`) because it has no workspace mode.
Build output currently matters only for `pnpm run build` + publint (nothing publishes yet; dev/test/demo run unbuilt via tsx), so the switching cost is at its lowest now and only grows once packages publish.
- Root `tsdown.config.ts` with `workspace: ['vendor/*', 'packages/*']` (explicit globs, not `workspace: true`, which would also pick up `examples/*` — they have package.json files but are not pnpm workspaces).
- Two per-package overrides in vendor/ (ours, like the regenerated tsconfigs; logged in vendor/README.md): schemastery (dual `.mjs`/`.cjs` via `outExtensions`), logger-console (two single-entry passes so the shared base class is inlined into each entry instead of a hash-named chunk, matching upstream's published shape).
Output file lists are byte-for-byte-list identical to dumble's (verified by snapshot diff at migration time); externals still come from each package's dependencies/peerDependencies. We give up dumble's exports-field inference — new packages with non-default shapes need a per-package `tsdown.config.ts` instead of just package.json fields. Future option: tsdown could also absorb declaration bundling (isolatedDeclarations) if `tsc -b` ever becomes the bottleneck; that would be a new RFC.
