feat: implement DGR-006 tensor bundle boundary

packages/node/native/proto/shard_runtime.proto

@@ -33,6 +33,16 @@ enum SchemaVersion {
   SCHEMA_VERSION_1 = 1;
 }
 
+// Certified transformer boundary family.  Names alone are not an adapter: a
+// Node must select an explicit architecture contract before interpreting a
+// TensorBundle.
+enum ArchitectureType {
+  ARCHITECTURE_TYPE_UNSPECIFIED = 0;
+  ARCHITECTURE_TYPE_DENSE = 1;
+  ARCHITECTURE_TYPE_MOE = 2;
+  ARCHITECTURE_TYPE_MLA = 3;
+}
+
 // ---------------------------------------------------------------------------
 // Tensor bundle — the public activation boundary
 // ---------------------------------------------------------------------------
@@ -142,6 +152,11 @@ message TensorBundle {
   // boundary payload can evolve without a whole-protocol version bump.
   uint32 bundle_version = 1;
   repeated NamedTensor tensors = 2;
+  // Explicit adapter selection; names are never interpreted through unchecked
+  // substitutions. UNSPECIFIED is accepted only for legacy DGR-002 bundles.
+  ArchitectureType architecture = 3;
+  // Adapter-owned semantic boundary, such as "pre_tail_residual".
+  string boundary_point = 4;
 }
 
 // ---------------------------------------------------------------------------
@@ -393,8 +408,9 @@ message ActivationChunk {
 // A decode step is one token: the envelope's identity fields are already fixed
 // for the life of the stream, so repeating them per token is pure overhead on
 // the hottest path. A DecodeStep carries only what changes — the step, the
-// position, and one tensor — and inherits the rest from the SessionOpen
-// handshake. A peer may always fall back to ActivationChunk with PHASE_DECODE.
+// position, and one compact boundary encoding — and inherits the rest from the
+// SessionOpen handshake.  A Node may always fall back to ActivationChunk with
+// PHASE_DECODE.
 message DecodeStep {
   // Idempotency step within the session; also orders the stream.
   uint64 idempotency_step = 1;
@@ -402,11 +418,50 @@ message DecodeStep {
   uint64 position = 2;
   // Tokens the receiver's cache must already hold. A mismatch is a CACHE_MISS.
   uint64 expected_past_len = 3;
-  // The single boundary tensor for this token, typically [1, 1, hidden].
+  // Legacy compact one-tensor boundary, typically [1, 1, hidden]. New readers
+  // accept it as a TensorBundle with one member; writers retain it where the
+  // selected architecture genuinely requires only one tensor.
   NamedTensor tensor = 4;
   // Work id for attribution; the session/epoch/fingerprint/range are inherited.
   string work_id = 5;
   int64 deadline_unix_nanos = 6;
+  // Versioned architecture boundary. This carries sidebands such as MoE router
+  // state or MLA/IndexShare state; when both fields are set, bundle is
+  // authoritative and tensor is retained only for older-Node forwarding.
+  TensorBundle bundle = 7;
+}
+
+// Exact request-level identity for a tail result. Runtime recipe identity is
+// deliberately repeated here: sampling the right logits with the wrong chat
+// template or reasoning mode is a different request, not a compatible result.
+message RequestRecipeIdentity {
+  string request_id = 1;
+  string runtime_recipe_digest = 2;
+  string chat_template_id = 3;
+  string chat_template_version = 4;
+  string reasoning_mode = 5;
+  ArchitectureType architecture = 6;
+}
+
+// Sampling is an explicit tail-only operation. A non-tail Shard never applies
+// final norm, LM head, row pruning, or sampling to its boundary output.
+message SamplingParameters {
+  float temperature = 1;
+  float top_p = 2;
+  uint32 top_k = 3;
+  uint64 seed = 4;
+  bool greedy = 5;
+}
+
+// Typed tail completion. The oneof keeps token id 0 unambiguous and prevents a
+// caller from treating an activation tensor as an inferred completion.
+message TailResult {
+  RequestRecipeIdentity identity = 1;
+  SamplingParameters sampling = 2;
+  oneof output {
+    TensorBundle logits = 3;
+    uint32 sampled_token_id = 4;
+  }
 }
 
 // Drop session state for a Route Session. Bounded memory does not depend on
@@ -471,7 +526,8 @@ message SessionResponse {
     ActivationChunk chunk = 2;
     Ack ack = 3;
     FlowControl flow_control = 4;
-    ShardStatus status = 5;
+  ShardStatus status = 5;
+  TailResult tail_result = 6;
   }
 }