Kernel and hosts
One sp-eval-kernel owns workflow semantics (resolve, outer FrameworkAttempt, evidence commit, gates). Frameworks own assertion/scorer semantics inside the runner. Hosts supply execution primitives — they never synthesize Softprobe orchestration decisions.
Responsibility split
sp-eval-kernel
One statically linked Rust binary implements validation, outer DAG planning, idempotent FrameworkAttempt execution, state transitions, and event emission.
| Transport | Use |
|---|---|
| stdin/stdout framed Protobuf | One-shot local/CI |
| Unix socket or gRPC | Long-lived managed/federated daemon |
Same crate, same semantics — verified by shared conformance corpus.
Hosts
| Host | Owns | Does not own |
|---|---|---|
| Local/CI CLI | Process launch, local CAS artifact dir, collecting framework JUnit/Markdown | Workflow IDs, gate logic |
| Managed worker | Queues, sandboxes, quotas, tenancy, object storage upload | Whether retries are legal (asks kernel) |
| Federated worker | Private data residency, hardware placement | Authoritative state without signed ingestion |
Hosts feed every lease outcome back through kernel commands; they do not append raw events from public clients.
SDK layers
| Layer | Audience |
|---|---|
| Public Python/TS SDK | Ergonomic workflow clients, REST clients |
| Internal host client | Framed Protobuf state-machine commands (trusted only) |
Public SDKs never export kernel event append or transition APIs.
Distribution
sp-eval-kernel ships with Softprobe CLI releases: pinned protocol compatibility, checksum/signature, platform matrix (linux/darwin, amd64/arm64). Upgrade/downgrade refusal when WorkflowVersion requires unsupported capabilities.