# Provider Execution Runtime Contract

## Contract metadata

- id: `iop.execution-runtime`
- boundary: inner
- status: active
- source evidence:
  - `packages/go/execution/types.go`
  - `packages/go/execution/registry.go`
  - `packages/go/execution/emitter.go`
  - `packages/go/execution/failure.go`
  - `apps/node/internal/node/runtime_bridge.go`

## Scope

The execution package defines host-neutral provider primitives. It owns provider registration, lifecycle, execution events, typed failures, cancellation, token usage, and the three provider commands `capabilities`, `transport_status`, and `ollama_api`.

`session_id` is an opaque correlation value. It does not select, create, resume, or terminate a process. Repeated requests with the same value are independent executions. Cancellation targets a non-empty `run_id` only.

## Requirements

- Providers implement the narrow `Provider` interface and may expose optional lifecycle, command, or tunnel capabilities.
- Event emitters preserve order and publish exactly one terminal event.
- Registry lookup uses provider identity and returns typed failures for missing or unavailable providers.
- Callers must reject commands outside the closed provider-command allowlist before provider lookup.
- Token usage remains observation data attached to execution or tunnel results.

## Prohibited ownership

The package must not own interactive shells, persistent processes, terminal emulation, working-directory mutation, resumable conversations, local quota probing, or arbitrary host command execution. It must not import application-internal packages or generated transport types.

## Verification

- `go test -count=1 ./packages/go/execution`
- `go test -race -count=1 ./packages/go/execution`
- `go vet ./packages/go/execution`