# 02 — Adopt the versioned gRPC Shard protocol

Status: done

## Mandatory fresh-session context

- Read [RALPH-CONTEXT.md](../RALPH-CONTEXT.md) completely before changing code.
- This issue is `DGR-002` in [prd.json](../prd.json).
- Read the evidence README for every dependency listed below.
- Inspect current code and `git status`; historical text and previous agent claims are not evidence.

## Description

As a node developer, I need a battle-proven streaming protocol so that Python and C++ Shards communicate without a custom socket protocol.

## Expected durable outputs

- packages/node/native/proto/shard_runtime.proto
- Reproducible Python/C++ schema generation and build wiring
- Protocol round-trip and compatibility tests
- evidence/DGR-002/README.md

## Acceptance criteria

- [x] Add a Protocol Buffers schema for capability, health, session stream, release, and cancellation operations.
- [x] Define one long-lived bidirectional gRPC stream per Route Session Activation Seam with deadlines, cancellation, flow control, and structured errors.
- [x] Define bounded chunking for prefill and a small decode fast path.
- [x] Carry schema version, request/work ID, Route Session ID, route epoch, artifact/recipe fingerprint, Shard range/effective start, phase, position, idempotency step, cache expectation, compression, and checksum.
- [x] Define a versioned named-tensor bundle with per-tensor name, shape, dtype, byte order, and payload fragments.
- [x] Add generated-schema round-trip and compatibility tests in Python and C++.
- [x] Targeted pytest tests pass
- [x] python -m compileall packages tests passes for Python changes
- [x] git diff --check passes
- [x] Default tests remain deterministic, model-download-free, API-credit-free, and GPU-free
- [x] Full deterministic pytest -q passes, or the exact pre-existing unrelated failure is recorded with a clean-tree reproduction
- [x] Read .scratch/distributed-gguf-runtime/RALPH-CONTEXT.md and this story issue completely before changing code
- [x] Read and verify every dependency evidence README before relying on dependency behavior
- [x] Preserve all pre-existing working-tree changes and stage only files belonging to this story
- [x] Write .scratch/distributed-gguf-runtime/evidence/DGR-002/README.md with files changed, exact commands and real results, limitations, compatibility notes, and dependent-story handoff
- [x] Update only this story issue to Status: done after every acceptance criterion and quality gate passes

## Dependency handoff

- None. This story may start immediately.

## Finish contract

- Create the task evidence directory and durable handoff required above.
- Preserve real failures and blockers; never fabricate benchmark, model, test or hardware output.
- Change this issue to `Status: done` only after all criteria pass.
- Emit `<promise>COMPLETE</promise>` only after the evidence handoff exists.

## References

- [Ralph execution context](../RALPH-CONTEXT.md)
- [PRD](../PRD.md)
- [Implementation strategy](../implementation-strategy.md)
- [Current architecture](../architecture.md)
- [Architecture decision](../ADR-0020-distributed-gguf-runtime.md)