2. Toolchain versions and compiler settings

• Status: accepted
• Date: 2026-09-29

Context

The brief names pnpm workspaces, Turborepo, TypeScript strict with noUncheckedIndexedAccess, ESM only, Biome, Vitest, and Changesets, but not versions.

Decision

• TypeScript 7 (the native compiler, typescript@7.0.2). It's the current latest release, and typechecking speed matters across many packages. If a dependency's types or a tool we need only work with the JavaScript compiler, record that here and pin 6.x for the affected package.
• Compiler settings in tsconfig.base.json: strict, noUncheckedIndexedAccess, exactOptionalPropertyTypes, verbatimModuleSyntax, module/moduleResolution NodeNext. exactOptionalPropertyTypes goes beyond the brief. It stops undefined from being written into optional fields such as price and presence, which keeps "field absent" and "field present but empty" distinct in results. Drop it for a package only with an ADR.
• Default types: []. Each package opts in to ambient types it needs. See ADR 4 for core.
• Internal packages export source ("exports": { ".": "./src/index.ts" }) while everything is private. Packages published to npm get a build step and publishConfig when they're first published.
• Exact version pins for all dependencies, with Renovate grouping minor and patch updates weekly.
• Node 24 for development and CI (.nvmrc). The Node LTS test job uses lts/*.

Consequences

Contributors need Node 24 and pnpm 10. The TypeScript 7 choice should be revisited if the MCP SDK, Hono, or Tauri's JavaScript tooling has problems with it.