werkator/docs/adrs/0009-2026-09-01.multi-repo-instance.md

One Werkator Instance Serves a Set of Repositories

Status:

• proposed: 2026-09-01
• accepted: 2026-09-01
• rejected: -
• superseded: -

Decision [accepted]: The founding tenet "one instance per repository" is revised to "one instance per repository set": a Werkator instance aggregates self-contained repositories listed in an instance registry, sharing one service, one port, one UI, one watcher schedule, and one global executor cap. Implementation is planned as docs/plan/22-multi-repo.md; this ADR records the decision and its shape, not the code.

Context and Problem Statement

"One instance per repository" (docs/Werkator-Konzept.md) does not scale even to two repositories on a Hostsharing Managed Webspace: building Werkbaum next to Werkator on mih34 would need a second service, a second assigned port, a second tunnel or domain, a second UI and metrics page. Every repository multiplies operations while the instance-level resources could be shared.

Technical Background

Everything repository-specific already lives inside the repository or is keyed by it: machine config with secrets, build results, auto-build slots, worktrees, and buildenvs under .git/werkator/; the artifact store under a per-repo key. An instance can therefore aggregate repositories without absorbing their state — adding or removing a repository is a registry entry, never a data migration, and single-repo mode stays the degenerate case (a registry of one, implicitly the current working directory).

Considered Options

• One instance per repository set (registry + aggregation) — chosen
• A federation dashboard proxying several single-repo instances
• Status quo: one instance, one repository

One Instance per Repository Set

Good:

• One service, port, UI, tunnel/domain, metrics page for any number of repositories.
• Repositories stay self-contained; per-repo secrets, history, and pinning semantics are untouched.
• Global concurrency control across all repositories.

Bad:

• The repo dimension must be threaded through executor pools, watcher cycle, routes, and UI — the largest refactor since the rewrite (mitigated by a behavior-preserving RepoContext session first).
• Instance-level and repo-level configuration must be split cleanly (see below).

Federation Dashboard over Single-Repo Instances

Rejected: less invasive, but it keeps N services, N ports, and N tunnels — it solves only the UI aggregation, not the operations burden that motivated the change.

Status Quo

Rejected: on a webspace, ports and domains are the scarce, manually assigned resource; per-repository services do not scale there.

Decision Outcome

One instance per repository set, with the configuration split decided 2026-09-01:

• Instance config lives in ~/.werkator.yml in the home directory of the user running the instance — one instance per OS user, matching the platform model. It carries server.* (port, domain/public base URL, nginx), the repository registry, the control token, the global executor.maxConcurrent, and the watcher schedule. The file name stays .werkator.yml in all three locations; the location carries the meaning.
• Repo defaults may live in the home file, but only in an explicit defaults: block, merged below every repository's own layers (home defaults → committed project config → repo machine config → branch layer); pinning semantics are unchanged. Accepted cost: secrets may then live in two places.
• Repo config stays in each repository: the committed .werkator.yml and the machine config in its .git/werkator/.
• Instance keys found in a repo's machine config are ignored with a warning naming both files once a home config exists — never merged silently.
• When a home config with a registry exists, werkator server serves the registry regardless of the current directory; without one it serves the current directory exactly as before.
• Repository names (routes, UI) default to the directory basename, are overridable per registry entry, and duplicates abort the start loudly.

Consequences: docs/Werkator-Konzept.md and AGENTS.md change their wording when the implementation lands (plan step 22 sessions B–D); until then this ADR documents the target and the existing behavior remains accurate.