4. Keep packages/core runtime-agnostic through its compiler settings

• Status: accepted
• Date: 2026-09-29

Context

Core must run unchanged on Node, Bun, Cloudflare Workers, and in the Tauri webview's sidecar. It may use only fetch, Web Crypto, URL, and injected interfaces.

Decision

packages/core/tsconfig.json sets "lib": ["ES2023", "WebWorker"] and "types": [].

• The WebWorker lib provides fetch, Request, Response, URL, crypto.subtle, TextEncoder, AbortSignal, and timers without document, window, or other DOM-only APIs that don't exist on servers.
• types: [] means @types/node is never loaded, even if it's hoisted into node_modules, so a Node API doesn't typecheck in core.

scripts/check-invariants.mjs fails if either setting changes, or if core gains a dependency other than zod. The Biome rules in ADR 3 catch Node, Bun, and Workers imports and globals.

Consequences

The WebWorker lib declares a few globals (self, postMessage) that don't exist on every runtime. Core shouldn't use them, and the fetch lint rule already rejects self.fetch.