Open Programs: goals and contracts

An Open Program owns goals, optional implementations, acceptance requirements, and dependencies. Humans and author Agents write the same .nx contract; the native frontend checks type boundaries, duplicate clauses, and dependencies.

A complete open goal

language "3.0"
program Sum {
    goal total() -> Int {
        intent "Sum every integer in inputs.get('values', []); return zero for an empty list."
        capabilities [sandbox.exec]
        ensure checks.sum
        review model("Handle all integers, including negatives, without hardcoded case outputs.")
        implementation open
    }
}

Save it as sum.nx and run uv run nexa check sum.nx --json. The report contains one open obligation, total. Execution requires checks.sum and an authorized model binding in the environment. This site's fixture provider executes the example with a solve(inputs) implementation that sums values and returns 0 for empty input. Frozen extra cases cover positive and negative integers, and a model review is recorded separately. Build uses one implementation request and one review request; locked replay uses zero requests.

Contract fields

Field	Meaning
goal name(arg: Type) -> Type	Parameters require types; results pass a type boundary before use
intent	Nonempty task intent; clarification creates a child revision
implementation open	Leaves a resolution obligation
implementation value <JSON>	Supplies an explicit JSON literal
implementation python "..."	Calls solve(inputs) inside OCI; requires sandbox.exec
ensure checks.name	Selects a fixed check with that environment name
review model("criterion")	Requests an independent structured boolean review
depends [name]	DAG dependency; results enter inputs["dependencies"]
stage runtime	Resolves in an activity; the default stage is build

Boundary types are Int, Float, String, Bool, Unit, Json, Patch, Repository, and ChangeRequest. A build goal cannot depend on a runtime goal. Each ensure/review must be unique within its kind; the automatic name typecheck is reserved.

A repository maintenance contract

The released examples/open_programs/maintain.nx declares a Repository parameter, a runtime goal from ChangeRequest to Patch, and an on change_request handler. The handler uses resolve, then propose repo.apply(result) requires human.approval. Candidate resolution, regression checks, authorization, and workspace application have separate records.

Named environment, sandbox, and acceptance declarations select reference bindings. Actual requirements come from goal clauses and environment configuration. Native compile_program dispatches explicit versions; existing compile_source/compile_file retain 2.4 Python lowering.

Continue with environments, evidence, and exact authorization.

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Source and validation · open_language / open_execution