Add AGENTS.md (#3678)

* Add AGENTS.md

Signed-off-by: Per Goncalves da Silva <pegoncal@redhat.com>

* Add AGENTS.md

Signed-off-by: Per Goncalves da Silva <pegoncal@redhat.com>

---------

Signed-off-by: Per Goncalves da Silva <pegoncal@redhat.com>
Co-authored-by: Per Goncalves da Silva <pegoncal@redhat.com>

Author: perdasilva

AGENTS.md

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+# AGENTS.md
+
+This file provides AI agents with comprehensive context about the Operator Lifecycle Manager (OLM) v0 codebase to enable effective navigation, understanding, and contribution.
+
+## Project Status
+
+**CRITICAL**: This repository is in **maintenance mode**. OLM v0 accepts only critical bug fixes and security updates. For new development, use [operator-controller](https://github.com/operator-framework/operator-controller) (OLM v1).
+
+## Project Overview
+
+Operator Lifecycle Manager (OLM) extends Kubernetes to provide declarative installation, upgrade, and lifecycle management for Kubernetes operators. It's part of the [Operator Framework](https://github.com/operator-framework) ecosystem.
+
+### Core Capabilities
+- **Over-the-Air Updates**: Automatic operator updates via catalog channels
+- **Dependency Resolution**: Automatic resolution and installation of operator dependencies
+- **Multi-tenancy**: Namespace-scoped operator management via OperatorGroups
+- **Discovery**: Catalog-based operator discovery and installation
+- **Stability**: Prevents conflicting operators from owning the same APIs
+
+## Architecture
+
+OLM consists of two main operators working together:
+
+### 1. OLM Operator (`cmd/olm`)
+**Responsibility**: Manages the installation and lifecycle of operators defined by ClusterServiceVersions (CSVs)
+
+**Key Functions**:
+- Creates Deployments, ServiceAccounts, Roles, and RoleBindings from CSV specifications
+- Manages CSV lifecycle states: None → Pending → InstallReady → Installing → Succeeded/Failed
+- Monitors installed operator health and rotates certificates
+- Enforces OperatorGroup namespace scoping
+
+**Primary Controllers**:
+- CSV Controller (pkg/controller/operators/olm)
+- OperatorGroup Controller
+
+### 2. Catalog Operator (`cmd/catalog`)
+**Responsibility**: Manages operator catalogs, subscriptions, and dependency resolution
+
+**Key Functions**:
+- Monitors CatalogSources and builds operator catalogs
+- Processes Subscriptions to track operator updates
+- Generates InstallPlans with resolved dependencies
+- Creates CRDs and CSVs from catalog content
+
+**Primary Controllers**:
+- Subscription Controller
+- InstallPlan Controller
+- CatalogSource Controller
+- Registry Reconciler
+
+## Custom Resource Definitions (CRDs)
+
+| Resource | API Group | Owner | Description |
+|----------|-----------|-------|-------------|
+| **ClusterServiceVersion (CSV)** | operators.coreos.com/v1alpha1 | OLM | Defines operator metadata, installation strategy, permissions, and owned/required CRDs |
+| **Subscription** | operators.coreos.com/v1alpha1 | Catalog | Tracks operator updates from a catalog channel; drives automatic upgrades |
+| **InstallPlan** | operators.coreos.com/v1alpha1 | Catalog | Calculated list of resources to install/upgrade; requires approval (manual or automatic) |
+| **CatalogSource** | operators.coreos.com/v1alpha1 | Catalog | Repository of operators and metadata; served via grpc from operator-registry |
+| **OperatorGroup** | operators.coreos.com/v1 | OLM | Groups namespaces for operator installation scope; enables multi-tenancy |
+| **OperatorCondition** | operators.coreos.com/v2 | OLM | Tracks operator health status and conditions |
+
+## Directory Structure
+
+```
+operator-lifecycle-manager/
+├── cmd/                          # Entry point binaries
+│   ├── catalog/                  # Catalog Operator main
+│   ├── olm/                      # OLM Operator main
+│   ├── package-server/           # Package API server
+│   └── copy-content/             # Content copy utility
+│
+├── pkg/                          # Core implementation
+│   ├── api/                      # API client and wrappers
+│   │   ├── client/               # Generated Kubernetes clients
+│   │   └── wrappers/             # Client wrapper utilities
+│   │
+│   ├── controller/               # Main controllers
+│   │   ├── bundle/               # Bundle lifecycle controller
+│   │   ├── install/              # Installation controller
+│   │   ├── operators/            # Operator/CSV controllers (OLM Operator)
+│   │   └── registry/             # Catalog/registry controllers (Catalog Operator)
+│   │
+│   ├── lib/                      # Shared libraries and utilities
+│   │   ├── catalogsource/        # CatalogSource utilities
+│   │   ├── csv/                  # CSV manipulation utilities
+│   │   ├── operatorclient/       # Operator client abstractions
+│   │   ├── operatorlister/       # Informer-based listers
+│   │   ├── operatorstatus/       # Status management
+│   │   ├── ownerutil/            # Owner reference utilities
+│   │   ├── queueinformer/        # Queue-based informers
+│   │   ├── scoped/               # Scoped client for multi-tenancy
+│   │   └── [other utilities]
+│   │
+│   ├── metrics/                  # Prometheus metrics
+│   └── package-server/           # Package server implementation
+│
+├── test/                         # Testing infrastructure
+│   ├── e2e/                      # End-to-end tests
+│   └── images/                   # Test container images
+│
+├── doc/                          # Documentation
+│   ├── design/                   # Architecture and design docs
+│   └── contributors/             # Contributor guides
+│
+└── vendor/                       # Vendored dependencies
+```
+
+## Key Packages and Their Responsibilities
+
+### Controllers (`pkg/controller/`)
+
+#### `pkg/controller/operators/`
+The heart of the OLM Operator. Contains the CSV controller that manages the complete operator lifecycle.
+
+**Key files**:
+- `olm/operator.go` - Main OLM operator reconciler
+- `olm/csv.go` - CSV reconciliation logic
+- `catalog/operator.go` - Catalog operator reconciler
+
+#### `pkg/controller/registry/`
+Registry and catalog management for the Catalog Operator.
+
+**Key files**:
+- `reconciler/reconciler.go` - CatalogSource reconciliation
+- `grpc/source.go` - gRPC catalog source handling
+
+#### `pkg/controller/install/`
+Manages the installation of resources defined in InstallPlans.
+
+### Libraries (`pkg/lib/`)
+
+#### `pkg/lib/operatorclient/`
+Abstraction layer over Kubernetes clients providing OLM-specific operations.
+
+#### `pkg/lib/operatorlister/`
+Informer-based listers for efficient caching and querying of OLM resources.
+
+#### `pkg/lib/queueinformer/`
+Queue-based informer pattern used throughout OLM controllers for event-driven reconciliation.
+
+#### `pkg/lib/ownerutil/`
+Owner reference management ensuring proper garbage collection of OLM-managed resources.
+
+#### `pkg/lib/scoped/`
+Scoped clients that respect OperatorGroup namespace boundaries for multi-tenancy.
+
+## Development Workflow
+
+### Building
+```bash
+make build              # Build all binaries
+make image              # Build container image
+make local-build        # Build with 'local' tag
+```
+
+### Testing
+```bash
+make unit               # Unit tests with setup-envtest
+make e2e                # E2E tests (requires cluster)
+make e2e-local          # Build + deploy + e2e locally
+make coverage           # Unit tests with coverage
+```
+
+### Code Generation
+```bash
+make gen-all            # Generate all code (clients, mocks, manifests)
+make codegen            # Generate K8s clients and deep-copy methods
+make mockgen            # Generate test mocks
+make manifests          # Copy CRD manifests from operator-framework/api
+```
+
+### Local Development
+```bash
+make run-local          # Complete local setup
+# OR step-by-step:
+make kind-create        # Create kind cluster (kind-olmv0)
+make cert-manager-install
+make deploy             # Deploy OLM to cluster
+```
+
+## Key Design Patterns
+
+### Control Loop State Machines
+
+**CSV Lifecycle**:
+```
+None → Pending → InstallReady → Installing → Succeeded
+                     ↑                          ↓
+                     ←----------←------←-------Failed
+```
+
+**InstallPlan Lifecycle**:
+```
+None → Planning → RequiresApproval → Installing → Complete
+                         ↓                ↓
+                         ←-------←-------Failed
+```
+
+**Subscription Lifecycle**:
+```
+None → UpgradeAvailable → UpgradePending → AtLatestKnown
+         ↑                                      ↓
+         ←-----------←-----------←-------------←
+```
+
+### Dependency Resolution
+- CSVs declare owned CRDs (what they provide) and required CRDs (what they need)
+- Catalog Operator resolves transitive dependencies via graph traversal
+- InstallPlans capture the complete dependency closure
+- Resolution is based on (Group, Version, Kind) - no version pinning
+
+### Catalog and Channel Model
+```
+Package (e.g., "etcd")
+  ├── Channel: "stable" → CSV v0.9.4 → CSV v0.9.3 → CSV v0.9.2
+  ├── Channel: "alpha"  → CSV v0.10.0
+  └── Channel: "beta"   → CSV v0.9.4
+```
+
+Subscriptions track a channel; OLM follows the replacement chain to upgrade operators.
+
+## Testing Strategy
+
+### Unit Tests
+- Use `setup-envtest` for real Kubernetes API behavior
+- Race detection enabled by default (`CGO_ENABLED=1`)
+- Mock generation via `counterfeiter` and `gomock`
+
+### E2E Tests
+- Full cluster testing with Ginkgo/Gomega BDD framework
+- Test images in `test/images/` hosted on quay.io/olmtest
+- Default timeout: 90 minutes (configurable via `E2E_TIMEOUT`)
+- Uses kind cluster named `kind-olmv0`
+
+### Integration Tests
+- Bundle and catalog integration testing
+- Upgrade path validation
+- Multi-tenant scenario testing
+
+## Important Dependencies
+
+| Dependency | Version | Purpose |
+|------------|---------|---------|
+| kubernetes | v0.34.1 | Core K8s libraries |
+| controller-runtime | v0.22.2 | Controller framework |
+| operator-framework/api | v0.35.0 | OLM API definitions |
+| operator-registry | v1.60.0 | Catalog/bundle tooling |
+| ginkgo/gomega | v2.26.0 / v1.38.2 | BDD testing |
+
+## Common Tasks for AI Agents
+
+### Understanding Operator Installation Flow
+1. User creates Subscription pointing to catalog/package/channel
+2. Catalog Operator queries catalog for latest CSV in channel
+3. Catalog Operator creates InstallPlan with resolved dependencies
+4. Upon approval, Catalog Operator creates CRDs and CSV
+5. OLM Operator detects CSV, validates requirements, creates Deployment/RBAC
+6. CSV transitions through: Pending → InstallReady → Installing → Succeeded
+
+### Debugging Installation Issues
+- Check CSV status and conditions: `kubectl get csv -o yaml`
+- Examine InstallPlan: `kubectl get ip -o yaml`
+- Review operator logs: OLM Operator and Catalog Operator pods in `olm` namespace
+- Verify OperatorGroup configuration for namespace scoping
+
+### Adding New Functionality
+**REMINDER**: This repository is in maintenance mode - only critical fixes accepted!
+
+For understanding existing code:
+1. Controllers follow controller-runtime patterns with Reconcile() methods
+2. Use informers and listers from `pkg/lib/operatorlister`
+3. Queue-based event handling via `pkg/lib/queueinformer`
+4. Always respect OperatorGroup namespace scoping
+
+### Code Generation
+Most code is generated - don't hand-edit:
+- Client code: Generated from CRDs using k8s.io/code-generator
+- Deep-copy methods: Auto-generated for all API types
+- Mocks: Generated via counterfeiter/gomock
+- CRD manifests: Copied from operator-framework/api repository
+
+Always run `make gen-all` after API changes.
+
+## Navigation Tips
+
+### Finding Controllers
+- OLM Operator controllers: `pkg/controller/operators/`
+- Catalog Operator controllers: `pkg/controller/registry/`, subscription/installplan logic in `pkg/controller/operators/catalog/`
+
+### Finding API Definitions
+- CRDs are defined in operator-framework/api (external dependency)
+- Clients are in `pkg/api/client/`
+- Listers are in `pkg/lib/operatorlister/`
+
+### Finding Business Logic
+- CSV installation: `pkg/controller/operators/olm/`
+- Dependency resolution: `pkg/controller/registry/resolver/`
+- Catalog management: `pkg/controller/registry/reconciler/`
+- InstallPlan execution: `pkg/controller/install/`
+
+### Finding Utilities
+- Owner references: `pkg/lib/ownerutil/`
+- Scoped clients: `pkg/lib/scoped/`
+- Operator clients: `pkg/lib/operatorclient/`
+- Queue informers: `pkg/lib/queueinformer/`
+
+## Anti-Patterns to Avoid
+
+1. **Don't bypass OperatorGroup scoping** - Always use scoped clients for multi-tenancy
+2. **Don't modify generated code** - Edit source (CRDs, annotations) and regenerate
+3. **Don't skip approval for InstallPlans** - Respect manual approval settings
+4. **Don't create CSVs directly** - Use Subscriptions/Catalogs for proper lifecycle
+5. **Don't ignore owner references** - Critical for garbage collection
+
+## Resources and Links
+
+- [OLM Documentation](https://olm.operatorframework.io/)
+- [Architecture Doc](doc/design/architecture.md)
+- [Philosophy](doc/design/philosophy.md)
+- [Design Proposals](doc/contributors/design-proposals/)
+- [Operator Framework Community](https://github.com/operator-framework/community)
+- [OperatorHub.io](https://operatorhub.io/) - Public operator catalog
+
+## Quick Reference
+
+### Resource Short Names
+```bash
+kubectl get csv          # ClusterServiceVersions
+kubectl get sub          # Subscriptions
+kubectl get ip           # InstallPlans
+kubectl get catsrc       # CatalogSources
+kubectl get og           # OperatorGroups
+```
+
+### Common Build Targets
+```bash
+make build build-utils   # Build all binaries
+make test unit e2e       # Run tests
+make lint verify         # Code quality
+make gen-all             # Generate everything
+make run-local           # Full local dev environment
+```
+
+### Tool Management
+Tools are managed via **bingo** (`.bingo/Variables.mk`) for reproducible builds. All tools are version-pinned.
+
+## Contributing
+
+See [CONTRIBUTING.md](CONTRIBUTING.md) and [CLAUDE.md](CLAUDE.md) for detailed guidelines.
+
+**Remember**: OLM v0 is in maintenance mode - only critical security fixes and outage issues are accepted!