Adding AGENTS.md

AGENTS.md

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+# Cloud Agent Instructions for kpt
+
+For Copilot, Cursor, Codex, Gemini Code Assist or any agents generating code or review Pull Requests
+in this repository. 
+
+## Generic rules
+
+### Coding
+
+* Never commit directly to this repository, always aim for a pull request
+* Always ask for a final review of a human before commiting
+* Make sure that AI agent usage is attributed in the correct way
+
+### Reviewing PRs
+
+* When comitting suggested changes add a signoff of the approving human and add the `Assisted-by`
+  tag to the commit message
+* If a comment was not accepted and the Conversation was resolved do not make the same comment again
+
+
+## Repository Overview
+
+**kpt** is a package-centric toolchain that automates Kubernetes configuration editing and management. It enables declarative configuration authoring, automation, and delivery at scale through a "Configuration as Data" approach, supporting Kubernetes platforms and KRM-driven infrastructure (e.g., Config Connector, Crossplane).
+
+- **Language**: Go 1.26.3
+- **Repository Size**: ~78 MB
+- **License**: Apache 2.0
+- **Key Topics**: Kubernetes, configuration management, CLI tooling, GitOps, policy-as-code, KRM (Kubernetes Resource Model)
+
+## Quick Build & Test Commands
+
+**Trust these instructions first.** Only perform searches if you find this information incomplete or inaccurate.
+
+### Prerequisites
+- Go 1.26.3 (specified in `go.mod`)
+- Git (required and checked at runtime)
+- Docker or Podman (for `test-docker` and function runtime tests)
+- Kind v0.30.0 (for e2e live apply tests with Kubernetes 1.33 and 1.34)
+
+### Build
+
+```bash
+make build
+```
+This compiles kpt to `$(go env GOPATH)/bin/kpt` using LDFLAGS with git commit SHA.
+
+### Run All Checks (Build, Test, Lint)
+
+```bash
+make all
+```
+
+Runs: `fix vet fmt lint test build tidy` in sequence. *Always* run this before committing.
+
+### Unit Tests
+
+```bash
+make test
+```
+
+Runs Go tests with coverage. Set `KRM_FN_RUNTIME` to select function runtime (docker/podman, default uses system default).
+
+### Docker/Podman Runtime Tests
+
+```bash
+make test-docker
+```
+
+Requires Docker or Podman. Tests that need container runtime (e.g., pipeline tests). Respects `KRM_FN_RUNTIME` environment variable.
+
+### E2E Function Tests
+
+#### Render tests
+
+```bash
+make make test-fn-render T=".*"
+```
+#### Eval tests
+
+```bash
+make make test-fn-eval T=".*"
+```
+
+Use `T` parameter to filter tests by regex (e.g., `T=fnconfig` for function config tests). Set `KRM_FN_RUNTIME` to select runtime.
+
+### E2E Live Apply Tests
+
+```bash
+make test-live-apply
+```
+
+Requires KinD with Kubernetes 1.33.4 and 1.34.0 (specific SHAs pinned in CI). These tests use Kind internally. Timeout is 20 minutes.
+
+### Linting
+
+```bash
+make lint
+```
+
+Runs golangci-lint v2.11.4. If already installed locally with matching version, uses it; otherwise downloads and runs via `go run`.
+
+### Code Generation & Formatting
+
+```bash
+make fmt        # Run gofmt and goimports
+make fix        # Run go fix
+make vet        # Run go vet
+make tidy       # Run go mod tidy
+make generate   # Generate code from templates (mdtogo, copyright headers)
+make schema     # Generate schema
+```
+
+### Setting Up Git Config (Required for Tests)
+
+Many tests require git configuration:
+
+```bash
+git config --global user.email "you@example.com"
+git config --global user.name "Your Name"
+```
+
+## Project Layout
+
+### Root Level Files & Directories
+
+* **main.go**: CLI entry point; contains //go:generate directives for CLI documentation
+* **Makefile**: Primary build orchestration
+* **.golangci.yml**: Linting configuration (golangci-lint v2.11.4)
+* **go.mod / go.sum**: Dependency management (Go 1.26.3)
+* **CONTRIBUTING.md**: Contribution guidelines and code review requirements
+* **CODEOWNERS**: Default reviewers
+
+### Key Source Directories
+
+* **cmd/**: CLI command implementations using Cobra framework
+* **run/**: Main CLI setup; contains GetMain() that initializes Cobra commands with environment setup
+* **pkg/**: Core library packages (business logic, utilities)
+* **internal/**: Internal packages; includes internal/docs/generated/ (generated from Markdown via mdtogo)
+* **mdtogo/**: Code generator tool that converts CLI documentation Markdown files to Go variables
+
+### Build & CI Configuration
+
+* **.github/workflows/go.yml**: Main CI workflow
+  * Runs on Linux (docker/podman matrix) and macOS
+  * Executes: `make all` + `make test-docker`
+  * Triggered on PRs and pushes (excludes dependabot branches)
+* **.github/workflows/verifyContent.yml**: Verifies CLI examples
+  * Runs `make build`, installs mdrip/kind, runs `make site-verify-examples`
+  * Triggered on changes to `commands/`, `internal/` paths
+* **.github/workflows/e2eEnvironment.yml**: KinD-based e2e tests
+  * Tests Kubernetes 1.33 and 1.34 with KinD v0.30.0
+  * Runs `./e2e/live/end-to-end-test.sh -k <K8S_VERSION>`
+* **.github/workflows/live-e2e.yml**: Live apply e2e tests
+  * Tests with pinned Kubernetes image SHAs
+  * Runs `make test-live-apply` with `K8S_VERSION` environment variable
+
+### Documentation & Tests
+
+* **documentation/**: Hugo-based website published to kpt.dev
+  * Run `make serve` from root (serves docs locally)
+  * Requires `npm install` first
+
+* **e2e/**: End-to-end test suites
+  * Contains testdata directories for function render/eval tests
+  * Live tests in `e2e/live/end-to-end-test.sh`
+
+### Other Notable Directories
+
+* **release/**: Release automation (GoReleaser config, Homebrew formula generation)
+* **hack/**: Miscellaneous development utilities
+* **healthcheck/**: Separate module for health checking (Go 1.26.3, local Makefile)
+* **thirdparty/**: Third-party code (excluded from linting)
+* **Formula/**: Homebrew package definition (generated by `go run ./release/formula/main.go VERSION`)
+
+## Linting Rules & Style
+
+### Linter Configuration
+
+* **Enabled Linters**: bodyclose, copyloopvar, dogsled, dupl, errcheck, gochecknoinits, goconst, gocritic, gocyclo, govet, ineffassign, lll, misspell, nakedret, revive, staticcheck, unconvert, unparam, unused, whitespace
+* **Duplication Threshold**: 400 lines
+* **Cyclomatic Complexity**: max 30
+* **Line Length**: max 170 characters
+* **Revive Confidence**: 0.85
+* **Excluded Paths**: thirdparty/, third_party, builtin, examples
+* **Test Files**: Further relaxed rules (gosec, funlen disabled for *_test.go files)
+
+### Code Style Requirements (from CONTRIBUTING.md)
+
+* **Copyright Headers**: All files must have Apache 2.0 license header
+  * Use format: // Copyright YEAR The kpt Authors (or year range if modified)
+   * Year should match creation year, or creation-to-modification year range
+* **Developer Certificate of Origin (DCO)**: Commits must be signed with -s flag
+* **Large Features**: Require reviewed and merged design document (use /docs/design-docs/00-template.md as template)
+* **AI Usage**: Must declare AI usage in PR description and commit messages with `Assisted-by: AGENT_NAME:MODEL_VERSION` format
+
+## Validation Checklist for PRs
+
+Before submitting a PR, verify:
+
+1. ✅ All tests pass: make all
+1. ✅ All linting passes: make lint
+1. ✅ Code formatted: make fmt
+1. ✅ Dependencies tidied: make tidy
+1. ✅ Copyright headers added/updated per CONTRIBUTING.md
+1. ✅ DCO sign-off: use git commit -s
+1. ✅ For CLI/API changes: design document reviewed and merged
+1. ✅ AI usage declared in PR description (if applicable)
+
+## Common Build Issues & Workarounds
+
+### Docker/Podman Not Available
+
+If `make test-docker` fails due to missing Docker/Podman:
+
+* Install Docker Desktop or Podman
+* For Podman: ensure it's on PATH and `podman version` runs successfully
+* Set `KRM_FN_RUNTIME=podman` if using Podman
+
+### KinD Setup Issues
+
+For e2e live tests (`make test-live-apply`):
+
+* KinD v0.30.0 is auto-installed by CI workflow
+* Requires Docker running in background
+* Tests use specific Kubernetes image SHAs (see live-e2e.yml matrix)
+* Timeout is 20 minutes; allow sufficient time
+
+### Git Configuration
+
+Tests fail silently if git user not configured. Always run:
+
+```bash
+git config --global user.email "you@example.com"
+git config --global user.name "Your Name"
+```
+
+### Module Generation
+
+If changes modify CLI documentation in documentation/content/en/reference/cli/:
+
+* Run `make generate` to regenerate `internal/docs/generated/`
+* Commit generated files
+
+### Known CI Skips
+
+* Windows build currently disabled (see `.github/workflows/go.yml` line 88-104, issue #3463)
+* Some linters disabled: `funlen`, `gosec` (marked TODO in .`golangci.yml`)
+
+## Environment Variables
+
+* **KRM_FN_RUNTIME**: Select function runtime for tests: `docker`,  `podman` or `nerdctl`
+* **K8S_VERSION**: Kubernetes version for e2e live tests (used in CI with pinned SHAs)
+* **KPT_NO_PAGER_HELP**: Set to 1 to disable pager for help output
+PAGER: Custom pager command (default: less -R)
+* **KPT_FN_WASM_RUNTIME**: WASM function runtime selection
+* **GOPATH**: Go workspace path (used in CI workflows)
+* **GOBIN**: Go binary installation directory
+
+## Key Dependencies
+
+* **Cobra**: CLI framework
+* **Kubernetes libraries (k8s.io/*)**: For Kubernetes resource handling
+* **sigs.k8s.io/cli-utils**: CLI utilities
+* **sigs.k8s.io/kustomize/kyaml**: YAML handling for Kubernetes
+* **sigs.k8s.io/controller-runtime**: Controller and reconciliation patterns
+* **wasmtime-go**: WebAssembly function runtime
+* **go-containerregistry**: Container image handling
+
+## Testing Strategy
+
+* **Unit Tests**: Run with `make test` (standard Go tests)
+* **Docker-based Tests**: Run with `make test-docker` (requires container runtime)
+* **Function E2E Tests**: Run with make `test-fn-render` / `make test-fn-eval` (testdata-driven)
+* **Live Apply E2E**: Run with `make test-live-apply` (KinD-based, 20-minute timeout)
+* **Example Verification**: Run with `make site-verify-examples` (verifies CLI examples in docs)
+
+## Implementation Notes for Code Changes
+
+* **CLI Commands**: Add to `commands/` directory; use Cobra; update `documentation/cli` for documentation
+* **Library Code**: Place in `pkg/` for public APIs; use `internal/` for internal utilities
+* **Tests**: Colocate `*_test.go` files with source; use testdata directories for fixtures
+* **Generated Code**: Run `make generate` after modifying templates
+* **Linting Issues**: Address all `golangci-lint` findings; consult `.golangci.yml` for thresholds
+* **Git Flow**: Always create feature branches; use squash-merge preferred per repository settings
+* **Documentation**: Update Markdown in documentation/; run `make serve` to make sure that there are no errors
+
+Trust these instructions. They have been validated against the Makefile, GitHub workflows, go.mod,
+and contributing guidelines. Only search for additional details if:
+
+* Build or test commands fail with unexpected errors
+* Instructions reference non-existent paths or commands
+* New tool versions are released and compatibility is unclear