docs: establish ADR framework with template and agent guidelines

.claude/CLAUDE.md

@@ -3,3 +3,7 @@
 See @../AGENTS.md for project guidelines.
 
 See @../redhat-compliance-and-responsible-ai.md for Red Hat compliance and responsible AI rules.
+
+## Architecture Decision Records
+
+Before marking work complete, check: did you reject an alternative or accept a trade-off? If yes, suggest creating an ADR in `adr/`. Before proposing changes, check existing ADRs for prior decisions that might be affected. See [adr/README.md](../adr/README.md) for conventions.

AGENTS.md

@@ -748,11 +748,33 @@ Use this to trigger a reconciliation without changing the spec.
 kubectl patch dw <name> --type merge -p "{\"metadata\": {\"annotations\": {\"force-update\": \"$(date +%s)\"}}}"
 ```
 
+## Architecture Decision Records (ADRs)
+
+ADRs live in the [`adr/`](adr/) directory. They capture the **why** behind non-trivial design decisions — information that is lost in code and PR descriptions over time.
+
+### When to Create an ADR
+
+Before marking work complete, ask: **did I reject an alternative or accept a trade-off?** If yes, create an ADR.
+
+Specifically, write an ADR when your change involves any of these:
+
+1. **You rejected an alternative** — There were 2+ reasonable approaches and you picked one
+2. **You accepted a trade-off** — Something got worse in exchange for something more important
+3. **You changed a resource lifecycle or ownership model** — Who creates, owns, or cleans up a Kubernetes resource
+4. **You changed an external contract** — API shape, CRD fields, Secret/ConfigMap naming, image paths
+
+**Don't** write an ADR for: bug fixes, dependency bumps, refactors preserving behavior, test additions, docs, or performance optimizations with no trade-offs.
+
+### How to Create an ADR
+
+Copy [`adr/TEMPLATE.md`](adr/TEMPLATE.md) to `adr/YYYY-MM-DD-short-slug.md` and fill in all sections. See [`adr/AGENTS.md`](adr/AGENTS.md) for maintenance conventions.
+
 ## See Also
 
 - **[README.md](README.md)** - Project overview, installation, what is DevWorkspace Operator
 - **[CONTRIBUTING.md](CONTRIBUTING.md)** - Development setup, debugging, testing, contribution guidelines
 - **[redhat-compliance-and-responsible-ai.md](redhat-compliance-and-responsible-ai.md)** - Red Hat compliance & responsible AI rules
+- **[adr/](adr/)** - Architecture Decision Records
 - **[docs/additional-configuration.adoc](docs/additional-configuration.adoc)** - DevWorkspace configuration options
 - **[docs/unsupported-devfile-api.adoc](docs/unsupported-devfile-api.adoc)** - Unsupported Devfile API features
 - **[Devfile Documentation](https://devfile.io/)** - Devfile specification

adr/2026-05-11-backup-auth-secret-lifecycle.md

@@ -0,0 +1,97 @@
+# Backup Auth Secret Must Not Be Owned by Any Workspace
+
+**Status**: Accepted
+**Date**: 2026-05-11
+**Deciders**: DevWorkspace Operator maintainers
+**Related Issue**: [CRW-10760](https://redhat.atlassian.net/browse/CRW-10760)
+
+## Context
+
+The backup system copies the registry authentication secret (e.g., quay.io credentials) from the operator namespace into each workspace namespace as `devworkspace-backup-registry-auth`. The original implementation set a Kubernetes controller ownerReference from this secret to the DevWorkspace that triggered the copy:
+
+```go
+controllerutil.SetControllerReference(workspace, desiredSecret, scheme)
+```
+
+This was likely intended to clean up the secret when no workspaces need it anymore — standard Kubernetes garbage collection pattern.
+
+However, two properties of this secret make ownerReference-based lifecycle management incorrect:
+
+1. **The secret is a namespace singleton**: All workspaces in a namespace share the same `devworkspace-backup-registry-auth` secret, but a Kubernetes object can have only one controller owner. Whichever workspace's backup job ran last "wins" ownership.
+
+2. **The secret is needed after all workspaces are deleted**: The primary restore use case is creating a new workspace from a backup of a deleted one. If the auth secret is garbage-collected when the last workspace is deleted, the user cannot authenticate to the private registry to pull the backup image.
+
+**Bug observed (CRW-10760)**: When using quay.io (private registry) for backups, deleting a workspace caused backup entries to disappear from the Dashboard backup list for ALL workspaces in the namespace. The auth secret was garbage-collected, and the Dashboard could no longer query the registry.
+
+**Validated on CRC cluster** (DWO 0.40.1, quay.io/okurinny):
+- The `devworkspace-backup-registry-auth` secret was confirmed to have ownerReference to a single workspace (`nodejs`)
+- Deleting that workspace triggered K8s GC, removing the secret
+- The secret was not re-created by subsequent backup cycles (remaining workspaces already had recent backups)
+- Backup listing in the Dashboard failed for all workspaces
+
+## Decision
+
+**Remove the ownerReference from the backup registry auth secret.** The secret becomes a namespace-scoped resource with no ownership tie to any workspace.
+
+### What Changes
+
+- `pkg/secrets/backup.go`: Remove the `controllerutil.SetControllerReference()` call in `CopySecret()`
+- The secret is still created via `c.Create()` with `AlreadyExists` handling, just without an ownerReference
+- The restore path now resolves the operator namespace via `infrastructure.GetNamespace()` to copy the secret on demand when it is missing
+
+### What Doesn't Change
+
+- Per-workspace resources (job runner ServiceAccount, image-builder RoleBinding) retain their ownerReferences — their GC on workspace deletion is correct and expected
+- The backup Job itself retains its ownerReference (short-lived, TTL-cleaned)
+- The `CopySecret` function signature stays the same
+
+## Considered Alternatives
+
+### Alternative 1: Multi-owner references (non-controller)
+
+Add each workspace as a non-controller owner of the secret. K8s GC would only delete the secret when ALL owning workspaces are gone.
+
+**Rejected because**:
+- The secret must survive deletion of ALL workspaces (for restore)
+- Adds complexity to track and merge owner lists
+- Non-controller ownerReferences have subtle GC semantics
+
+### Alternative 2: Finalizer-based cleanup
+
+Remove ownerReference but add a cleanup mechanism (e.g., a controller that deletes the secret when the namespace has zero DevWorkspaces).
+
+**Rejected because**:
+- Adds complexity for a marginal benefit (one small secret in an otherwise-empty namespace)
+- Could race with restore operations (user creates a workspace from backup right after the last one is deleted)
+- Namespace deletion already cleans up all resources
+
+### Alternative 3: Per-workspace auth secrets
+
+Create a unique auth secret per workspace (e.g., `devworkspace-backup-registry-auth-{workspace-id}`).
+
+**Rejected because**:
+- Multiplies secrets unnecessarily (all contain the same credentials)
+- The restore path expects the predefined name `devworkspace-backup-registry-auth`
+- Still wouldn't survive workspace deletion for restore use case
+
+## Consequences
+
+### Positive
+
+1. **Backups survive workspace deletion**: Users can delete all workspaces and still restore from backups
+2. **No cross-workspace interference**: Deleting one workspace no longer affects other workspaces' backup capabilities
+3. **Simpler lifecycle**: No ownership tracking needed for a namespace-scoped singleton
+
+### Negative
+
+1. **Secret persists in empty namespaces**: If all workspaces are deleted and the user never restores, the auth secret remains until the namespace is deleted. This is a minor leak — one small secret per namespace.
+
+### Neutral
+
+1. **Existing secrets on upgraded clusters**: Secrets created by older DWO versions will retain their stale ownerReference until the next `CopySecret` call overwrites them (via `SyncObjectWithCluster`). In the worst case, one more GC event occurs before the fix takes effect.
+
+## References
+
+- `pkg/secrets/backup.go` — `CopySecret()` function
+- `controllers/backupcronjob/rbac.go` — Per-workspace SA/RoleBinding (unchanged)
+- `pkg/constants/metadata.go:204` — `DevWorkspaceBackupAuthSecretName`

adr/AGENTS.md

@@ -0,0 +1,32 @@
+# ADR Maintenance Guide for AI Agents
+
+This guide covers how to create and maintain ADRs. For when to create an ADR, see the root [AGENTS.md](../AGENTS.md).
+
+## Creating a New ADR
+
+1. Copy [TEMPLATE.md](TEMPLATE.md) to a new file named `YYYY-MM-DD-short-slug.md`
+2. Use today's date and a descriptive lowercase slug with hyphens
+3. Fill in all sections — the "Considered Alternatives" section is the most valuable part
+4. Set status to **Proposed** if seeking feedback, or **Accepted** if the decision is final
+
+## Naming Convention
+
+`YYYY-MM-DD-short-description.md`
+
+- Date prefix for chronological ordering
+- Lowercase, hyphens only, no special characters
+- Keep the slug short but descriptive
+
+## Superseding an ADR
+
+When a decision is replaced:
+
+1. Update the old ADR's status line: `**Status**: Superseded by [New Title](YYYY-MM-DD-new-slug.md)`
+2. Create the new ADR with its own context explaining why the previous decision changed
+3. Reference the old ADR in the new one's Context section
+
+## Format Rules
+
+- Follow the structure in [TEMPLATE.md](TEMPLATE.md)
+- End every file with a trailing newline
+- Use the existing ADRs as examples for tone and level of detail

adr/README.md

@@ -0,0 +1,39 @@
+# Architecture Decision Records (ADRs)
+
+This directory contains Architecture Decision Records for the DevWorkspace Operator.
+
+## What is an ADR?
+
+An ADR captures a significant design decision along with its context, alternatives considered, and trade-offs accepted. ADRs preserve the **why** behind decisions — information that is lost in code, commit messages, and PR descriptions over time.
+
+## When to Write an ADR
+
+Write an ADR when your change involves any of these:
+
+1. **You rejected an alternative** — There were 2+ reasonable approaches and you picked one. The code shows what you chose but not what you didn't.
+2. **You accepted a trade-off** — Something got worse (performance, complexity, a minor leak) in exchange for something more important.
+3. **You changed a resource lifecycle or ownership model** — Who creates, owns, or cleans up a Kubernetes resource.
+4. **You changed an external contract** — API shape, CRD fields, Secret/ConfigMap naming conventions, image paths.
+
+**Don't** write an ADR for: bug fixes, dependency bumps, refactors preserving behavior, test additions, docs updates, or performance optimizations with no trade-offs.
+
+## Lifecycle
+
+| Status | Meaning |
+|--------|---------|
+| **Proposed** | Under discussion, not yet accepted |
+| **Accepted** | Decision is in effect |
+| **Deprecated** | Decision is outdated but not yet replaced |
+| **Superseded** | Replaced by a newer ADR (link to it in the status line) |
+
+To supersede an ADR, update its status to `Superseded by [new ADR title](new-adr-file.md)` and create a new ADR.
+
+## Naming Convention
+
+Files use date-prefixed slugs: `YYYY-MM-DD-short-description.md`
+
+Example: `2026-05-11-backup-auth-secret-lifecycle.md`
+
+## Creating a New ADR
+
+Copy [TEMPLATE.md](TEMPLATE.md) and fill in the sections. See existing ADRs for examples.

adr/TEMPLATE.md

@@ -0,0 +1,51 @@
+# [Title of Decision]
+
+**Status**: Proposed | Accepted | Deprecated | Superseded by [title](link)
+**Date**: YYYY-MM-DD
+**Deciders**: DevWorkspace Operator maintainers
+**Related Issue**: [ISSUE-ID](link) *(optional)*
+
+## Context
+
+What is the problem or need that prompted this decision? Include enough background for someone unfamiliar with the issue to understand why a decision was needed.
+
+## Decision
+
+What did we decide to do? Be specific about what changes and what stays the same.
+
+## Considered Alternatives
+
+### Alternative 1: [Name]
+
+Brief description.
+
+**Rejected because**:
+- Reason 1
+- Reason 2
+
+### Alternative 2: [Name]
+
+Brief description.
+
+**Rejected because**:
+- Reason 1
+- Reason 2
+
+## Consequences
+
+### Positive
+
+1. Benefit 1
+2. Benefit 2
+
+### Negative
+
+1. Downside or accepted trade-off
+
+### Neutral
+
+1. Side effects that are neither positive nor negative
+
+## References
+
+- Links to relevant code, docs, PRs, or external resources