nnrp-1-preview2 Capability Catalog
Always-on cases
Preview2 currently has one mandatory protocol-floor feature with no capability token: header.fixed_shape. It comes from l0.header.fixed_shape.golden, and because required_capabilities is empty, every implementation is checked against the fixed 40-byte common-header round-trip contract.
Capability overview table
| Token | Layers | Status reach | Combination rule | Description |
|---|---|---|---|---|
body_region.prelude | L0 | mandatory | none | Stable encoding layout for the body-region prelude. |
cache.lifecycle | L1 | mandatory | none | Cache-object allocation, acknowledgement, invalidation, and namespace handling. |
control.client_hello | L0 | mandatory | none | CLIENT_HELLO fixed metadata block. |
control.session_patch_ack | L0 | mandatory | none | SESSION_PATCH_ACK fixed metadata block. |
flow_update | L0 / L1 | mandatory | none | FLOW_UPDATE at both wire and semantic layers. |
frame_submit.mixed | L0 / L1 | mandatory | must also claim payload.tensor | The mixed-submit FRAME_SUBMIT hot path. |
object_reference.cache | L0 / L1 | mandatory + optional | the L1 optional case also needs result_push.partial | Cache object-reference blocks and result-body reference resolution. |
payload.tensor | L0 / L1 | mandatory dependency | usually paired with frame_submit.mixed, result_push.partial, and result_push.stale_reuse | Dependency token for the tensor-profile main path. |
payload.typed | L0 / L1 | mandatory + optional | none | Non-tensor typed payload descriptors and region packing. |
result_hint | L0 / L1 | mandatory | none | RESULT_HINT wire shape and metadata semantics. |
result_push.degraded | L1 | experimental | none | Degraded / fallback result path, currently informational only. |
result_push.partial | L0 / L1 | mandatory + optional | the mandatory result path also needs result_push.stale_reuse and payload.tensor | Partial-delivery results. |
result_push.stale_reuse | L0 / L1 | mandatory | must also claim result_push.partial and payload.tensor | Stale-frame reuse semantics. |
transport.probe | L1 / L3 | optional | none | Probe metadata and transport-selection logic. |
transport.quic | L3 | optional | none | QUIC smoke interoperability. |
transport.tcp | L3 | optional | none | TCP smoke interoperability. |
Detailed explanations
body_region.prelude
Claiming this token means the implementation is ready to publicly guarantee the wire layout of the body-region prelude. Preview2 requires the inline, reference, and typed-payload region prefixes to preserve field order, length encoding, and flag layout without local variation.
cache.lifecycle
This token covers the cache-object lifecycle rather than a single cache message in isolation. Once claimed, the repository accepts the mandatory CACHE_PUT → CACHE_ACK → CACHE_INVALIDATE semantic path together with namespace and object-state handling.
control.client_hello
This token covers the fixed CLIENT_HELLO metadata block. The point is not business-level negotiation policy; the point is a frozen pack / parse contract for version range, bitmaps, cache parameters, target cadence, and related fixed-width fields.
control.session_patch_ack
This token covers the SESSION_PATCH_ACK fixed metadata block, including patch masks, reject reasons, retry timing, and effective configuration fields. The implementation must both parse and re-emit the canonical wire shape.
flow_update
flow_update spans both the L0 and L1 contract surface. L0 freezes the packet shape; L1 additionally validates scope, retry-after semantics, credit epoch handling, flags, and framed round-trip behavior.
frame_submit.mixed
This is one of the core Preview2 submit-path tokens, but it never stands alone. The mandatory FRAME_SUBMIT cases only enter selected once payload.tensor is also claimed, because the path implicitly depends on the tensor descriptor / schema / body layout.
object_reference.cache
This token has two layers. The first is the mandatory L0 object-reference block round-trip. The second is an optional L1 result-body resolution check. Claiming object_reference.cache alone selects the L0 mandatory case; claiming it together with result_push.partial also opts into the optional composite-body reference-resolution case.
payload.tensor
payload.tensor is a dependency capability for the Preview2 hot path rather than a standalone vector page. In the current baseline it mainly exists to complete the frame_submit.mixed and result_push.partial / result_push.stale_reuse combinations, meaning the implementation accepts responsibility for the frozen tensor descriptor, schema, and body layout.
payload.typed
This token covers non-tensor typed payload descriptor and region packing. Preview2 uses it for both mandatory L0 descriptor vectors and optional L1 region/frame preservation checks, which makes it suitable for implementations gradually adding token/audio/video/event style payload paths.
result_hint
This token covers the full RESULT_HINT surface. L0 checks the fixed wire vector; L1 requires reason codes, fixed-width fields, and framed round-trip behavior to remain valid instead of merely surviving a happy-path parser.
result_push.degraded
This is still experimental in Preview2. Claiming it does not create a mandatory gate, but it does move degraded / fallback result behavior into the informational report so SDKs can converge before the public surface is frozen.
result_push.partial
This token means the implementation supports partial-delivery results. In the current baseline, however, the mandatory result path still needs result_push.stale_reuse and payload.tensor together with it. It also combines with object_reference.cache to decide whether the optional composite-body reference-resolution case becomes active.
result_push.stale_reuse
This token isolates stale-frame reuse semantics. The current mandatory case binds it to result_push.partial and payload.tensor because Preview2's canonical result vector covers the combined partial + stale-reuse path rather than independent result sub-features.
transport.probe
This token shows up in both L1 control-metadata validation and L3 transport-selection smoke logic. Claiming it means the implementation accepts the probe-message wire shape and the selection contract that ranks paths by success, throughput, and RTT.
transport.quic
This token only affects an L3 optional smoke case. Once claimed, the repository is expected to bring up a minimal QUIC path and complete the shortest control plus submit/result interoperability loop.
transport.tcp
This token is parallel to transport.quic, but targets TCP. Once claimed, the repository accepts the minimum TCP session bring-up, frame-boundary handling, and smoke-path interoperability checks.