neuron-tai/.scratch/distributed-gguf-runtime/evidence/DGR-005/DECOMPOSITION.md

DGR-005 decomposition — 2026-07-14

Verified starting point

• The mandated environment is present: project Python 3.14.6, CMake 4.4.0, and protobuf 7.35.1.
• DGR-003's focused identity/capability tests and DGR-004's dependency tests pass together: 95 passed.
• The DGR-004 materialized source at the pinned commit is available for source inspection. It contains only the DGR-004 CMake-marker patch.

Why this chain cannot safely claim DGR-005 yet

At the locked llama.cpp revision, llama_model_base::load_tensors():

1. sizes layers to hparams.n_layer_all;
2. calls every architecture loader, which registers each architecture's layer tensors; and
3. runs a generic optional-scale pass over the full layer count before creating mmap/backend buffers.

Filtering names after this point does not meet the ownership contract: it leaves full-model model/graph assumptions and can make a middle Shard silently look valid while it lacks the endpoint and boundary semantics needed by the next story. A generic blk.N.* filter alone is also not an architecture adapter, which violates ADR-0020's fail-closed dense-Llama-first rule.

Required child slices

1. DGR-005A — native dense-Llama ownership API and loader

   • Add an explicit end-exclusive owned range to the project-owned native interface and validate it against immutable GGUF layer metadata.
   • Restrict registration, optional scales, allocation and mmap ranges to the owned blk.N.* tensors.
   • Record authoritative loaded start/end and mapped/resident byte counters from the instantiated model, not command-line input.
   • Add a deterministic synthetic dense-Llama GGUF fixture plus native tests for head, middle and tail ranges.

2. DGR-005B — endpoint ownership and graph guard

   • Load token embeddings only for the head, and final norm/output head only for the tail, including tied embeddings.
   • Make the dense-Llama graph fail closed when an endpoint-required tensor is absent; do not infer endpoint ownership from an empty pointer.
   • Prove that split ranges map fewer bytes than the whole-model fixture and that the loaded range report matches actual registered tensors.

3. DGR-003-emission follow-up

   • Expose the resulting immutable native loaded-artifact report to a native worker/backend adapter.
   • Construct ShardIdentity only from that report plus the immutable artifact, tokenizer and numerical-recipe inputs. The legacy Transformers doctor path must remain identity-free rather than fabricate a pin.
   • Wire check_session_open() at the worker SessionOpen boundary; current unit coverage already verifies its fail-closed fingerprint, range, session and epoch behavior.

Handoff and non-claims

No DGR-005 source patch, identity-emission code, issue status, or prd.json pass state was changed. No model was loaded, downloaded, benchmarked, or certified. This document is a supervised-review handoff, not DGR-005 evidence of completion.