ADR-0018 · accepted

The kit is one package with entries

Since ADR-0020: the package has twenty-one entries. game, game/browser and game/scenario (a game's declarations, its engine and its scenarios) are a tenth group, which may import core and runtime.

Since ADR-0019: the package has eighteen entries. net/worker (the signalling worker, for Cloudflare) and net/testing (test helpers for a Co-op game) joined the sixteen below. Both are in the net group, so the graph has no new arrow. net/worker may import cloudflare:workers, with @cloudflare/workers-types as an optional peer for its types; tsconfig.worker.json checks it with Workers types and no DOM.

ADR-0016 published the kit as nine packages under @arcadekit, on one shared version. This replaces that layout with one package. ADR-0016's other decisions stand: the name, the licence, the build, the source condition, what users need, the checks, and releasing with Changesets and trusted publishing.

Why

Nine packages cost more than they gave.

• They never released apart. One version covered all nine, so every release was nine publishes, nine changelogs with the same lines and nine trusted publishers.
• A user installed several of them and had to keep their versions equal by hand. A game on the kit listed up to nine dependencies that only work together.
• Each package had its own package.json, tsconfig, build config and peer ranges to keep in step.
• What the split did enforce, that core and input carry no Effect and that a lower layer doesn't import a higher one, can be enforced by lint and a test.

Decision

One package. The kit publishes as the unscoped arcadekit, from packages/arcadekit. It starts at 0.3.0, the minor after the nine packages' 0.2.3, and its changelog keeps their entries.

Sixteen entries, carried over. Each entry of the nine packages is a subpath export of the same name, with the same exports: @arcadekit/core is arcadekit/core, and @arcadekit/net/browser is arcadekit/net/browser. The entries are core, input, content, content/browser, save, save/browser, audio, audio/browser, render-three, runtime, runtime/browser, runtime/testing, net, net/browser, net/signalling and foldkit. The package has no root export, so an import always names an entry. Each entry's source is packages/arcadekit/src/<entry>/, with its README beside it.

No shims. The nine @arcadekit/* packages stay on npm at 0.2.3 and get no further release. They are deprecated with a message naming arcadekit once the games that use them have moved.

Peer dependencies. effect is the one required peer: every entry but core and input imports it. three, @types/three, foldkit and @effect/platform-browser are optional peers, so a game installs only what the entries it imports need. The ranges are ADR-0016's.

Lint and a test replace the package boundaries.

• oxlint.config.ts lists which entry may import which: the graph the nine packages had. core, input, content, save, audio and render-three import no other entry; runtime imports core; net imports core and runtime; foldkit imports runtime, which only its tests use. The rule entry-direction/allowed (tools/lint/entry-direction.ts) fails any other import between entries. It also fails an import that reaches into another entry's files instead of its public file, and one that names the package itself (arcadekit/core from inside the package), since a relative import says the same thing without going through exports. Adding an arrow to the graph is a design decision, made in the PR that adds it.
• core and input stay free of Effect (ADR-0017), and each optional peer stays in the entry it is for. Lint bans effect in the files of core and input, and packages/arcadekit/test/entry-packages.test.ts lists the packages each entry may import: none for core and input; effect for the rest, with three for render-three, foldkit for foldkit and @effect/platform-browser for save/browser. It follows every import from each entry, in src/ and in the built dist/ (the JavaScript and the type files), and fails if any reaches another package. The built check matters because the build shares chunks between entries. Inside the package a dynamic import names its module in a plain string, so lint and the test can read it.
• packages/arcadekit/tsconfig.root.json compiles core and the root entries of content, save, audio, runtime and net, with net/signalling, without DOM types, as each package's own config did.

One build. tsdown builds every entry in one pass, sharing chunks, so a module two entries use exists once: arcadekit/runtime and arcadekit/net step the same GameLoop.

When to split again

Either of these would justify a second package:

• someone outside this repository needs a subset, for example core without the effect peer;
• an entry needs a dependency that can't be an optional peer, such as one with a native build or one that every install would have to download.

Until then, a new part of the kit is a new entry.

Consequences

• Every import of the kit changes, from @arcadekit/<entry> to arcadekit/<entry>. The genre packages and the demo apps changed with it; a game outside the workspace changes its imports and replaces its @arcadekit/* dependencies with arcadekit.
• The keys of the Effect services follow the names: @arcadekit/audio/Audio is arcadekit/audio/Audio, and @arcadekit/net/PeerConnector is arcadekit/net/PeerConnector. Only a program that had both the old and the new package would notice.
• A package manager warns about nothing when an optional peer is missing. A game that imports arcadekit/render-three without three fails when it resolves the import, so each entry's README names its peers.
• The genre packages keep their names (@arcadekit/survivors, @arcadekit/push-puzzle) and stay private.
• Earlier ADRs and findings keep their wording: where they say @arcadekit/runtime or packages/net/src, read arcadekit/runtime and packages/arcadekit/src/net.
• Changesets has one package to version, so its fixed group is gone.
• npm needs the package to exist before it can trust the release workflow. The maintainer publishes a 0.0.0 placeholder once (scripts/npm-setup.sh), and the workflow publishes every real version.