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AGENTS.md

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+# AGENTS.md - heat-operator
+
+For project description, deployment, configuration examples, and contributing
+guidelines, see [README.md](README.md).
+
+## Tech stack
+
+| Layer | Technology |
+|-------|------------|
+| Language | Go (modules, multi-module workspace via `go.work` — local dev file, not committed to the repo) |
+| Scaffolding | [Kubebuilder v4](https://book.kubebuilder.io/) + [Operator SDK](https://sdk.operatorframework.io/) |
+| CRD generation | controller-gen (DeepCopy, CRDs, RBAC, webhooks) |
+| Config management | Kustomize |
+| Packaging | OLM bundle |
+| Testing | Ginkgo/Gomega + envtest (functional), KUTTL (integration) |
+| Linting | golangci-lint (`.golangci.yaml`) |
+| CI | Zuul (`zuul.d/`), Prow (`.ci-operator.yaml`), GitHub Actions |
+
+## Custom Resources
+
+| Kind | Purpose |
+|------|---------|
+| `Heat` | Top-level CR. Owns the database, keystone service, transport URL, and spawns sub-CRs for each service component. |
+| `HeatAPI` | Manages the Heat API deployment (httpd/WSGI). |
+| `HeatCfnAPI` | Manages the Heat CloudFormation-compatible API deployment. |
+| `HeatEngine` | Manages the engine service deployment (stack operations). |
+
+The `Heat` CR has defaulting and validating admission webhooks.
+Sub-CRs are created and owned by the `Heat` controller -- not intended to
+be created directly by users.
+
+## Directory structure
+
+**Maintenance rule:** when directories are added, removed, or renamed, or when
+their purpose changes, update this table to match.
+
+| Directory | Contents |
+|-----------|----------|
+| `api/v1beta1/` | CRD types (`heat_types.go`, `heatapi_types.go`, `heatcfnapi_types.go`, `heatengine_types.go`), conditions, webhook markers |
+| `cmd/` | `main.go` entry point |
+| `internal/controller/` | Reconcilers: `heat_controller.go`, `heatapi_controller.go`, `heatcfnapi_controller.go`, `heatengine_controller.go` |
+| `internal/heat/` | Heat-level resource builders (db-sync, common helpers) |
+| `internal/heatapi/` | HeatAPI resource builders |
+| `internal/heatcfnapi/` | HeatCfnAPI resource builders |
+| `internal/heatengine/` | HeatEngine resource builders |
+| `internal/webhook/` | Webhook implementation |
+| `templates/` | Config files and scripts mounted into pods via `OPERATOR_TEMPLATES` env var |
+| `config/crd,rbac,manager,webhook/` | Generated Kubernetes manifests (CRDs, RBAC, deployment, webhooks) |
+| `config/samples/` | Example CRs (Kustomize overlays). Includes TLS and topology variants. |
+| `test/functional/` | envtest-based Ginkgo/Gomega tests |
+| `test/kuttl/` | KUTTL integration tests |
+| `hack/` | Helper scripts (CRD schema checker, local webhook runner) |
+| `ci/` | CI job definitions |
+
+## Build commands
+
+After modifying Go code, always run: `make generate manifests fmt vet`.
+
+Do not hand-edit files under `zz_generated*` or `config/crd/bases/` — they are
+generated by controller-gen.
+
+## Code style guidelines
+
+- Follow standard openstack-k8s-operators conventions and lib-common patterns.
+- Use `lib-common` modules for conditions, endpoints, TLS, storage, and other
+  cross-cutting concerns rather than re-implementing them.
+- CRD types go in `api/v1beta1/`. Controller logic goes in
+  `internal/controller/`. Resource-building helpers go in `internal/heat*`
+  packages matching the CR they support.
+- Config templates are plain files in `templates/` -- they are mounted at
+  runtime via the `OPERATOR_TEMPLATES` environment variable.
+- Webhook logic is split between the kubebuilder markers in `api/v1beta1/` and
+  the implementation in `internal/webhook/`.
+
+## Testing
+
+- Functional tests use the envtest framework with Ginkgo/Gomega and live in
+  `test/functional/`.
+- KUTTL integration tests live in `test/kuttl/`.
+- Run all functional tests: `make test`.
+- When adding a new field or feature, add corresponding test cases in
+  `test/functional/` and update fixture data accordingly.
+
+## Key dependencies
+
+- [lib-common](https://github.com/openstack-k8s-operators/lib-common): shared modules for conditions, endpoints, database, TLS, secrets, etc.
+- [infra-operator](https://github.com/openstack-k8s-operators/infra-operator): RabbitMQ and topology APIs.
+- [mariadb-operator](https://github.com/openstack-k8s-operators/mariadb-operator): database provisioning.
+- [keystone-operator](https://github.com/openstack-k8s-operators/keystone-operator): identity service registration.
+- [Developer guide](https://github.com/openstack-k8s-operators/dev-docs/blob/main/developer.md): local development setup, building, running, and debugging the operator.