<!-- GENERATED FROM prd.json — DO NOT EDIT AS AN INDEPENDENT SOURCE. prd.json IS AUTHORITATIVE. -->
# DGR-032: Implement deterministic fake `ShardEngine`

- **Status / triage:** completed; `passes: true`
- **Execution mode:** `AFK`
- **Milestone:** `M1`
- **Dependencies:** `DGR-031`
- **Blocks (derived):** `DGR-033`
- **Labels:** `area:engine`, `area:testing`, `type:fixture`, `priority:p0`, `ready-for-agent`
- **Evidence class:** `fixture`
- **Hardware:** `none`
- **Model:** `fake`
- **Upstream:** `no`

## Objective / description

Fresh Ralph session: read `.scratch/distributed-gguf-runtime/RALPH-CONTEXT.md`, source issue `.scratch/distributed-gguf-runtime/issues/032-implement-deterministic-fake-shardengine.md`, and evidence READMEs for dependencies (DGR-031) before changing code. Inspect live source/tests rather than trusting legacy pass states. Objective: Provide an engine fixture that deterministically transforms typed boundary bundles and session state.

## Acceptance criteria

- [x] Support head, middle, tail, prefill, decode, cancellation, and release with deterministic outputs.
- [x] Model isolated session/epoch state and deterministic cache-miss/stale-epoch failures.
- [x] Support configurable delay, memory pressure, malformed output, and crash injection.
- [x] Contract tests distinguish fixture evidence from real-model certification.
- [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.

## Evidence handoff

Verified evidence: `.scratch/distributed-gguf-runtime/evidence/DGR-032/README.md`. Legacy evidence remains provenance only and grants no implementation completion credit.
