0024, Bun as runtime for app services

Status: Accepted Date: 2026-02 Stakeholders: Bobby Nannier

Context

The TypeScript-first Olympus apps (Athena, Hera, Site) and the CLI (Octl) need a JavaScript runtime.

Node 20+, ubiquitous, mature, widest module compatibility.
Deno, TypeScript-first, secure by default, smaller ecosystem.
Bun, TypeScript-first, fast startup, Node-compatible module resolution, modern primitives (Bun.spawn, Bun.serve, Bun.password).

Bun for all app containers.

Fast startup. Container cold start is ~200ms instead of ~600ms (Node). Compounds across the 12+ containers in a deploy.
TypeScript without a compile step. Bun runs .ts directly. No tsc build in the app images for app source (Next.js still bundles its own production build).
Native modules are tested. Bun's Node compatibility is excellent at this point; we've hit only minor edge cases.
bun install is fast. Per-repo install times are ~3× faster than npm install.
Some Node-only modules occasionally need a workaround. Documented per-repo when they arise.

Octl ships as an npm package consumed by npx. The runtime is whatever Node or Bun the user has. The code is Bun-compatible but invoked under either.
GitHub Actions runners use Node by default. Bun is installed via oven-sh/setup-bun in workflows that need it.