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ADR 0027: Single-tenant DB and instance metadata marker

Date: 2026-01-22

Status: Accepted

Decision

  • Each experiment uses its own Postgres database and its own scheduler/worker processes.
  • EXPERIMENT_ID is required only for process attachment and external naming (Redis namespace/queue, job branch prefix, logs/artifacts paths).
  • The database stores a single-row InstanceMetadata marker with the expected experiment identity and root commit.
  • Scheduler/worker startup must fail fast if the marker is missing or mismatched; the upgrade path is a destructive reset (uv run loreley reset-db --yes).