<!-- GENERATED FROM prd.json — DO NOT EDIT AS AN INDEPENDENT SOURCE. prd.json IS AUTHORITATIVE. -->
# DGR-025: Define exact artifact and runtime recipe identity

- **Status / triage:** completed; `passes: true`
- **Execution mode:** `AFK`
- **Milestone:** `M1`
- **Dependencies:** `DGR-018`, `DGR-021`
- **Blocks (derived):** `DGR-026`, `DGR-031`, `DGR-041`, `DGR-044`
- **Labels:** `area:identity`, `area:admission`, `type:domain`, `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/025-define-exact-artifact-and-runtime-recipe-identity.md`, and evidence READMEs for dependencies (DGR-018, DGR-021) before changing code. Inspect live source/tests rather than trusting legacy pass states. Objective: Ensure the tracker and worker only combine numerically and operationally compatible shards.

## Acceptance criteria

- [x] Fingerprint source artifact SHA, tokenizer revision, architecture adapter/version, boundary schema, runtime pin/patch stack, backend, quant, activation/compute dtype, and KV/state layout.
- [x] Bind each shard to an exact half-open range without hardcoding a topology or quant.
- [x] Fail closed on any artifact, adapter, boundary, cache, backend, or runtime mismatch.
- [x] Unsupported recipes remain registered-but-dark until real-hardware evidence certifies them.
- [x] 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

Verified evidence: `.scratch/distributed-gguf-runtime/evidence/DGR-025/README.md`. Legacy evidence remains provenance only and grants no implementation completion credit.
