library

OPM kernel

The reference implementation of the Open Platform Model runtime, packaged as a Go library. Every OPM front-end — the opm CLI, the opm-operator controller, the planned Crossplane composition function, and any future runtime — embeds this kernel and inherits its behaviour.

The kernel owns:

• Loading OPM artifacts (modules, platforms, releases) from CUE module directories and .cue files.
• Resolving CUE module references through the native CUE module system (OCI registries, cue.mod).
• Validating user-supplied values against #config schemas with grouped, position-aware diagnostics.
• Matching component requirements against the active Platform's #matchers index.
• Executing matched transformers (resolved by FQN against Platform.#composedTransformers) and emitting platform-neutral rendered values with full provenance.

The kernel does not own:

• Process model, command flags, exit codes, stdout/stderr formatting (lives in CLI / controller).
• Logging output (loggers are passed in by the caller).
• Cluster reconciliation, status reporting, GitOps wiring (lives in opm-operator).
• Platform-native identity beyond the core.Identity tuple — adapters wrap rendered values into platform-specific resources.
• Debug-overlay policy. #ModuleDebug is not a kernel artifact; the kernel accepts only Module, ModuleInstance, and Platform (see "Artifact types" below). Debug values live as a debugValues field on Module itself; whether the frontend layers them into the values stack is policy that lives in the helper layer (CLI / operator / XR fn).

Artifact types

The kernel accepts exactly three artifact types — every input ultimately resolves to one of them:

#ModuleDebug was previously contemplated as a fourth top-level artifact and has been retired; debugValues is now a field on Module. The migration is one line: read mod.Package.LookupPath(schema.DebugValues) and feed the result into the helper-side values stack at the layer your frontend prefers. The kernel itself never observes the distinction.

See CONSTITUTION.md for the full set of principles.

Layout

opm/
  core/                   Platform-neutral primitives — Compiled, Resource, Identity
  errors/                 Structured errors, grouped CUE diagnostics
  schema/                 OPM core schema loader (OCILoader, Cache), CUE path inventory, metadata decoders
  kernel/                 Public Kernel struct — single entry point for the OPM runtime
  module/                 Module / Instance model and value-validation accessors
  platform/               Platform artifact model — kernel's sole input for matching and execution
  compile/                match -> execute -> emit pipeline
  materialize/            Resolve a Platform's #registry subscriptions into a sealed MaterializedPlatform
  helper/                 Opt-in frontend convenience layer (a frontend MAY skip these)
    loader/file/          Filesystem loading (modules, releases, platforms)
    loader/registry/      Load a published module from an OCI registry by path@version
    loader/internal/shape Shared artifact shape gate (single-sourced across loaders)
    synth/                Instance / Platform synthesis from typed inputs (no file / no bytes)
  internal/               Test-only cross-package internals (schematest, registrytest)
adr/                      Architecture decision records
enhancements/             Long-form design proposals (umbrella + slices)
openspec/                 OpenSpec proposals, specs, archives
modules/                  Test-only OPM modules used by integration tests
testdata/                 CUE module fixtures consumed by package tests
Taskfile.yml              fmt / vet / lint / test entry points

The OPM core schema is no longer vendored or embedded — it is fetched at runtime from CUE_REGISTRY via opm/schema (the apis/ tree and the old opm/api / opm/apiversion packages were removed). The opm/loader/ deprecation shim is also gone; the canonical import path is opm/helper/loader/file (or opm/helper/loader/registry for published modules). A standalone opm/validate/ package was contemplated but never landed — validation primitives live on *kernel.Kernel (ValidateConfig, ValidateConfigPartial, ValidateConfigDetailed), composed with the ConfigSchema() accessors on *module.Module / *module.Instance.

Compile pipeline

loaderfile.LoadInstancePackage  ->  cue.Value (release artifact)
Kernel.ProcessModuleInstance    ->  *module.Instance          (validated, concrete)
Kernel.Compile                 ->  *kernel.CompileResult    (rendered + provenance)
        |
        +-- compile.Match           component <-> transformer pairing (paired output)
        +-- compile.Module.Execute  per-pair transformer execution
                |
                +-- FillPath #moduleInstance with the whole evaluated instance (0019 D3)
                +-- FillPath #component with the evaluated component (definitions intact; 0019 D1)
                +-- FillPath #context.{moduleInstanceMetadata, componentMetadata, runtimeName}
                +-- decode `output` (kind-based dispatch: ListKind | StructKind)
                +-- emit []*core.Compiled carrying Instance/Component/Transformer FQN provenance

The kernel exposes two phase-explicit methods that map onto frontend subcommands: Kernel.Match (match) and Kernel.Compile (apply / render). Values are validated where they are applied — Kernel.ProcessModuleInstance is the validated entry point, and Compile renders the instance as processed. The old free-function entry points (compile.CompileModuleInstance, compile.ProcessModuleInstance, module.ParseModuleInstance) have been removed — construct a Kernel and call its methods directly.

*core.Compiled is the kernel's terminal output. Adapters in downstream implementations wrap each Compiled with a platform-specific core.Resource that fills core.Identity.

Quick start

See docs/getting-started.md for an end-to-end walkthrough — constructing a Kernel, loading a Module, layered values validation, Platform composition, and compiling a Instance into rendered *core.Compiled values.

API stability

The library follows SemVer 2.0.0. The public surface is everything under opm/. Two distinct compatibility tracks coexist and must not be confused:

• Go module SemVer governs the Go types and function signatures consumed by downstream binaries. A breaking change here is a major bump of the library.
• OPM schema versioning governs the CUE shapes consumed at runtime — #Module, #ModuleInstance, #Platform, #Component, transformer contracts. The kernel MUST be able to load and render older schema versions seamlessly so that downstream implementations inherit multi-version support without per-implementation effort.

The two tracks are independent: within an OPM schema major, additive shape changes are absorbed by floating-major resolution and require no Go-side bump; a shape break in the schema is itself a coordinated library-breaking event.

OPM schema resolution

The library does NOT vendor or embed the OPM core schema. At runtime the kernel resolves opmodel.dev/core@v2 through CUE's module system against CUE_REGISTRY, then memoizes the built cue.Value in a per-Kernel *schema.Cache.

Key pieces:

• opm/schema — schema loader (Loader interface, OCILoader sole public implementation), per-instance memoization (Cache), CUE path inventory, metadata decoders, and the PublicRegistry const (opmodel.dev=ghcr.io/open-platform-model,registry.cue.works).
• opm/kernel — kernel.WithSchemaLoader(schema.Loader) configures which Loader the Kernel's cache wraps; (*Kernel).SchemaCache() exposes the cache to release-synthesis and other callers.

Frontends (CLI, operator, future Crossplane fn) set CUE_REGISTRY (typically to schema.PublicRegistry) before constructing the Kernel. The library auto-applies no default; this keeps Principle I (kernel neutrality) intact and avoids hidden lookups. See docs/getting-started.md for the deployment pattern, including the warm-cache pre-seeding pattern for restricted environments.

Helper boundary (opm/helper/)

Anything under opm/helper/ is opt-in convenience for embedding the kernel; a frontend MAY skip it and call the kernel directly. Anything outside opm/helper/ is part of the kernel contract.

Today this layer holds:

• opm/helper/loader/file — filesystem-coupled loaders: LoadModulePackage, LoadInstancePackage, LoadPlatformFile. Modules and releases both load as CUE packages (unified in commit 7c435f2); only platforms still load from a single .cue file.
• opm/helper/platform — Platform composition (Compose): takes a shell Platform plus a slice of *module.Module and FillPath-injects each into #registry so the schema's computed views resolve.
• opm/helper/synth — Instance synthesis (Instance): build a ModuleInstance CUE value from typed inputs (name, namespace, module reference, values, labels, annotations) without round-tripping through a file. Pairs with Kernel.SynthesizeInstance, which chains synth + validate in one call.

Layered values validation lives on the kernel itself — see Kernel.ValidateConfigDetailed and the Source type in opm/kernel. See enhancements/001-kernel-redesign-around-platform/02-design.md.

The previous opm/loader/ deprecation shim has been removed (commit 3a9a9bd); the canonical import path is opm/helper/loader/file.

Quality gates

task fmt
task vet
task lint
task test
# or all four
task check

Further reading

• CONSTITUTION.md — design principles (kernel neutrality, type safety, separation of concerns, SemVer discipline, small batches).
• openspec/config.yaml — normative constitution source.
• opmodel.dev/core@v2 — current OPM schema, published as an OCI CUE module (sources live in the workspace core/ repo).
• docs/getting-started.md — end-to-end embedding walkthrough.
• docs/design/ — flow diagrams and pipeline notes (compile-pipeline-known-gaps.md).
• enhancements/ — long-form design proposals (kernel redesign, compiler/runtime split, platform construct, module context, claims).
• adr/ — architecture decision records.
• CHANGELOG.md — released-version history (generated by release-please).
• migrations/README.md — migration-documentation policy: per-change fragments, dormant until GA (pre-GA breaking changes are recorded in CHANGELOG.md and the OpenSpec archive).