neuron-tai/.scratch/distributed-gguf-runtime/issues/031-introduce-the-project-owned-shardengine-interface.md

DGR-031: Introduce the project-owned ShardEngine interface

• Status / triage: specification only; ready-for-agent; passes: false
• Execution mode: AFK
• Milestone: M1
• Dependencies: DGR-021, DGR-025
• Blocks (derived): DGR-032, DGR-034, DGR-035, DGR-037
• Labels: area:engine, type:architecture, priority:p0, ready-for-agent
• Evidence class: model-free
• Hardware: none
• Model: generic
• Upstream: no

Objective / description

Fresh Ralph session: read .scratch/distributed-gguf-runtime/RALPH-CONTEXT.md, source issue .scratch/distributed-gguf-runtime/issues/031-introduce-the-project-owned-shardengine-interface.md, and evidence READMEs for dependencies (DGR-021, DGR-025) before changing code. Inspect live source/tests rather than trusting legacy pass states. Objective: Isolate worker/protocol code from llama.cpp internals behind a stable project-owned engine contract.

Acceptance criteria

• Define load, capabilities, prefill/decode, boundary/logits result, cancel, release, health, and metrics operations.
• Use project-owned request/result/state types; expose no ggml_tensor, llama context, scheduler, or ABI-owned structure.
• Reserve typed MTP and architecture auxiliary-state hooks without enabling them.
• Add contract tests proving fake and future llama implementations obey identical lifecycle semantics.
• Applicable shared quality gates in prd.json pass, and the evidence handoff records exact commands/results, changed files, limitations, and dependency handoff.

Shared quality gates

• Targeted deterministic tests pass; Python changes also pass python -m compileall packages tests.
• git diff --check passes.
• Default tests are model-download-free, API-credit-free, and GPU-free.
• Evidence README records exact changed files, commands/results, limitations, and dependency handoff; no fabricated evidence or inherited completion credit.
• Native changes pass focused out-of-tree CMake build and CTest; patch changes verify clean apply/check/reverse against the exact llama.cpp pin.
• Runs are opt-in and record exact artifact/split hashes, runtime/upstream pin, backend/driver, hardware, network, commands, and raw metrics. Model artifacts use configured mounted-drive storage and never /home.
• Preserve existing Transformers behavior and backend-agnostic Tracker routing/load balancing/billing/relay semantics unless an explicit versioned contract says otherwise. One scoped story commit is expected during execution, but this specification-materialization change is not committed.

Evidence handoff

Write and verify .scratch/distributed-gguf-runtime/evidence/DGR-031/README.md. Until every criterion and applicable gate has real evidence, this story remains passes: false. Legacy evidence is provenance only, not completion credit.