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@@ -1,7 +1,8 @@
 # ADR-002 — Repository Boundary: railiance-hosts vs railiance-bootstrap
 
-**Status:** Accepted
+**Status:** Superseded by ADR-003
 **Date:** 2026-03-09
+**Superseded:** 2026-03-10 — see `ADR-003-railiance-5repo-stack-architecture.md`
 **Deciders:** Bernd Worsch
 
 ---
diff --git a/docs/adr/ADR-003-railiance-5repo-stack-architecture.md b/docs/adr/ADR-003-railiance-5repo-stack-architecture.md
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@@ -0,0 +1,103 @@
+# ADR-003 — Railiance 5-Repo Stack Architecture
+
+**Status:** Accepted
+**Date:** 2026-03-10
+**Deciders:** Bernd Worsch
+**Supersedes:** ADR-002 (repo-boundary-hosts-vs-bootstrap)
+
+---
+
+## Context
+
+ADR-002 defined a two-repo boundary between `railiance-hosts` (OS baseline)
+and `railiance-bootstrap` (Kubernetes layer). As the railiance tooling expands
+to cover platform services, developer enablement, and application deployments,
+a two-repo model is insufficient and the naming no longer signals stack position.
+
+The **Orthogonal Architecture Standard** (OAS v1.0,
+`canon/standards/orthogonal-architecture_v1.0.md`) defines six canonical
+dimensions. The Stack dimension (S1–S5) provides a natural, self-documenting
+structure for the railiance tooling.
+
+---
+
+## Decision
+
+### One repo per Stack level
+
+The railiance toolset is structured as five repositories, each owning exactly
+one OAS Stack level:
+
+| OAS Level | Repository | Responsibility |
+|-----------|------------|----------------|
+| S1 Infrastructure Substrate | `railiance-infra` | OS provisioning, security hardening, Ansible roles, Goss spec + test suite, Terraform, inventory, secrets |
+| S2 Cluster Runtime | `railiance-cluster` | k3s, Helm, ingress, CNI, admission controllers, operators, kubeconfig management |
+| S3 Platform Services | `railiance-platform` | PostgreSQL HA, object storage, secret management, identity, message brokers, caches |
+| S4 Developer Enablement | `railiance-enablement` | CI/CD pipelines, developer portal, platform templates, SDKs, buildpacks |
+| S5 Workloads & Experience | `railiance-apps` | Application Helm releases, Kubernetes manifests for user-facing services (Gitea, coulomb apps) |
+
+### Naming rationale
+
+The name of each repo encodes its OAS Stack level. A reader seeing the repo
+list immediately knows the stack position without reading documentation.
+`railiance-enablement` is preferred over `railiance-dev` to avoid ambiguity
+with "development environment."
+
+### Boundary rule
+
+> **Every file, playbook, and configuration belongs in exactly one repo,
+> determined by the OAS Stack level of the concern it addresses.**
+
+The authoritative reference for whether a concern belongs at a given Stack
+level is `canon/standards/orthogonal-architecture_v1.0.md` §5 (Stack
+Dimension Specification).
+
+### Pre-condition chain
+
+Each layer depends on the layer below being converged and verified:
+
+```
+railiance-infra (make converge + make verify)
+  → railiance-cluster (k3s install + smoke test)
+    → railiance-platform (platform services deployed)
+      → railiance-enablement (CI/CD and tooling active)
+        → railiance-apps (application deployments)
+```
+
+No layer may re-configure concerns owned by a lower layer.
+
+---
+
+## Content relocations from railiance-cluster
+
+The following items existed in `railiance-bootstrap` (now `railiance-cluster`)
+but belong at other Stack levels and are relocated as part of this ADR:
+
+| Item | Relocated to | OAS Level | Reason |
+|------|-------------|-----------|--------|
+| `cloudinit/user-data.yaml` | `railiance-infra` | S1 | Cloud-init is node provisioning |
+| `tools/cmd/railiance-plan-host` | `railiance-infra` | S1 | Host planning is infrastructure scope |
+| `tools/cmd/railiance-backup` | `railiance-platform` | S3 | Backup is a platform service concern |
+
+---
+
+## Consequences
+
+- `railiance-infra` and `railiance-cluster` are renames; git history is
+  preserved.
+- `railiance-platform`, `railiance-enablement`, and `railiance-apps` are new
+  repos, initially containing only scaffolding (CLAUDE.md, Makefile, workplans/).
+- State Hub `ManagedRepo` slugs are updated from the old names to the new ones.
+- All CLAUDE.md, Makefile, and workplan files in the renamed repos are updated
+  to reflect the new names.
+- ADR-002 is superseded and should not be used as an authoritative reference.
+  Its boundary table is incorporated and extended here.
+
+---
+
+## Superseded ADR
+
+ADR-002 (`ADR-002-repo-boundary-hosts-vs-bootstrap.md`) is superseded by
+this document. Its core rule — that items defined in `spec/server-baseline.yaml`
+must not be managed by `railiance-cluster` — remains in force and is
+generalised here: no layer may manage concerns owned by a layer below it.