0014. Adopt commodity components, build where we have an edge

Status

Accepted. Date: 2026-11-04.

Context

Hephaestus keeps its full scope, but a solo operator cannot write every commodity component. Rule 8 requires checking the Adopt-or-build table before building one.

Decision

We adopt, behind our own interfaces so each can be swapped: Keycloak (Apache 2.0) or a managed OIDC provider for login, passwords, MFA and SSO; the open-source Svix server for outbound webhooks; Restate or Temporal for long multi-step workflows; Dapr pub/sub for event brokers, conditional on a two-day spike holding up in Compose and on deploy targets, else native EventBus adapters; Inspect as the LLM eval runner; moonrepo with proto for polyglot builds; and Atlas for relational migrations across every language. We build in-house where we have an edge: money and ledger, idempotency, the spec and conformance suites, provenance and reproducibility, causal and statistics tooling, the UI registry, templates and the heph CLI.

Consequences

Less code to own and review, and mature tools for the commodity parts. Each adopted tool is a dependency to track, and the Dapr choice is deferred to a spike in the adapters phase. Commodity components must not be hand-built without first checking this table.