# PRD: Performant Concurrent Distributed GGUF Runtime

## Overview

Build one lean native GGUF execution path that lets an Inference Route combine consumer machines to serve models larger than any one node can hold. Reuse the existing Meshnet control plane and llama.cpp/GGML execution engine. Adopt gRPC/HTTP2 and Protocol Buffers for the native Shard worker data plane rather than inventing a transport.

The program is benchmark-gated. GGUF is not assumed faster merely because it is quantized or uses a different file format. The first story compares the current Transformers/safetensors backend against whole-model llama.cpp on controlled model/hardware/quality lanes and locks a performance contract. Native distributed work proceeds only when GGUF provides a meaningful speed or fit benefit.

## Goals

- Execute one GGUF model across independently addressable contiguous Shards.
- Retain Hot KV State locally for each Shard and isolate concurrent Route Sessions.
- Batch compatible decode steps across active sessions for aggregate throughput.
- Use consumer CPU, AMD, NVIDIA, Vulkan, Metal, and mixed routes only where a real certified forward passes.
- Beat the current distributed safetensors route under a controlled performance contract or enable a larger otherwise-unroutable model at useful measured speed.
- Keep the critical path to Meshnet plus a small pinned llama.cpp fork and standalone C++ worker.
- Produce narrow upstream collaboration material for llama.cpp without placing Meshnet networking or economics inside upstream.

## Quality Gates

Every story must:

- Run its targeted `pytest` tests.
- Run `python -m compileall packages tests` for Python changes.
- Run `git diff --check`.
- Keep default tests deterministic, model-download-free, API-credit-free, and GPU-free.
- Preserve existing Transformers/safetensors behavior unless the story explicitly changes a versioned compatibility contract.

Stories touching the native worker must also:

- Build the pinned C++ target with CMake.
- Run focused C++/protocol tests through CTest or the documented equivalent.
- Verify the llama.cpp patch stack applies cleanly to the exact pinned commit.

Real-model/hardware stories must:

- Require `MESHNET_ENABLE_REAL_INFERENCE_TESTS=1`.
- Use the machine-specific mounted-drive model path and the certified runtime environment; never place model artifacts under `/home`.
- Record exact model revision, artifact hash, runtime recipe, hardware, driver/backend, commands, raw JSON metrics, and output-quality result.
- Label synthetic tests as unit coverage rather than distributed acceptance.

Before a story is marked complete, run the full deterministic `pytest -q` suite or record the exact pre-existing unrelated failure with a clean-tree reproduction.

## User Stories

### DGR-001: Lock the safetensors-versus-GGUF performance contract
**Description:** As a runtime engineer, I need a controlled baseline so that GGUF work proceeds from measured speed, memory, and quality rather than reputation.

**Acceptance Criteria:**
- [ ] Benchmark the same model architecture/revision, machine, prompts, context lengths, output lengths, sampling policy, and concurrency across the current Transformers/safetensors recipe and whole-model llama.cpp recipes.
- [ ] Separate correctness/quality lanes from quantized performance/fit lanes instead of claiming BF16 and Q4 are numerically equivalent.
- [ ] Report TTFT, prefill tok/s, decode tok/s, p50/p95 latency, aggregate throughput, RSS, VRAM, artifact size, failures, and output drift in machine-readable JSON.
- [ ] Add concurrency levels 1 and 4 where memory permits.
- [ ] Write a versioned performance contract consumed by later release gates, including an explicit stop condition when llama.cpp/GGUF has no meaningful speed or fit benefit.

### DGR-002: Adopt the versioned gRPC Shard protocol
**Description:** As a node developer, I need a battle-proven streaming protocol so that Python and C++ Shards communicate without a custom socket protocol.

**Acceptance Criteria:**
- [ ] Add a Protocol Buffers schema for capability, health, session stream, release, and cancellation operations.
- [ ] Define one long-lived bidirectional gRPC stream per Route Session Activation Seam with deadlines, cancellation, flow control, and structured errors.
- [ ] Define bounded chunking for prefill and a small decode fast path.
- [ ] 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.
- [ ] Define a versioned named-tensor bundle with per-tensor name, shape, dtype, byte order, and payload fragments.
- [ ] Add generated-schema round-trip and compatibility tests in Python and C++.

### DGR-003: Define exact Artifact and runtime recipe identity
**Description:** As the Tracker, I need exact compatibility identity so that only numerically and operationally compatible Shards form an Inference Route.

**Acceptance Criteria:**
- [ ] Separate weight quantization, activation dtype, compute dtype, KV dtype/layout, tokenizer revision, architecture adapter, backend, and runtime version.
- [ ] Bind derivative or split artifacts to an exact source Model Artifact hash and Shard range.
- [ ] Produce a stable compatibility fingerprint used by capability admission and the gRPC handshake.
- [ ] Fail closed on mismatched artifact, tokenizer, architecture, range, boundary schema, activation recipe, or cache layout.
- [ ] Keep unsupported recipes registered-but-dark until a real distributed forward certifies them.

### DGR-004: Create the reproducible pinned llama.cpp patch stack
**Description:** As a maintainer, I need a small auditable fork boundary so that upstream updates do not turn the runtime into an unmaintainable stitched codebase.

**Acceptance Criteria:**
- [ ] Pin one exact llama.cpp commit through a reproducible source dependency mechanism.
- [ ] Store a numbered minimal patch stack separately from Meshnet networking code.
- [ ] Add a build script that applies/checks patches and builds the standalone worker without manual source copying.
- [ ] Record upstream file/ABI assumptions and fail clearly when the pin changes.
- [ ] Preserve upstream license and attribution notices.
- [ ] Add a clean rebuild smoke test that does not download a model.

### DGR-005: Implement dense-Llama range-aware GGUF ownership
**Description:** As a node, I need to map only my assigned dense-Llama Shard so that aggregate consumer memory can hold a model larger than one node.

**Acceptance Criteria:**
- [ ] Register and allocate only `blk.N.*` tensors in the assigned range.
- [ ] Load embeddings only for the head and final norm/LM head only for the tail, including tied embeddings.
- [ ] Prefer range-aware mapping from one exact source GGUF; if derivative sub-GGUFs are used temporarily, verify source/slice hashes and avoid claiming final artifact semantics.
- [ ] Report authoritative loaded range and endpoint ownership from the model, not operator CLI claims.
- [ ] Demonstrate mapped/resident memory scales with owned tensors rather than full model size.

### DGR-006: Implement architecture-defined boundary input/output
**Description:** As a Shard, I need to consume and emit the correct transformer boundary state so that disjoint processes reproduce whole-model execution.

**Acceptance Criteria:**
- [ ] Head accepts token IDs and owns token embedding.
- [ ] Middle/tail bypass token embedding and accept the named boundary bundle.
- [ ] Non-tail emits the unnormalized architecture-defined residual/boundary before final norm/head and before tail-only row pruning.
- [ ] Tail emits logits or token output through an explicit sampling contract.
- [ ] Dense-Llama whole-model versus two-range prefill and greedy-decode parity passes the documented tolerance.
- [ ] The adapter interface fails closed for uncertified architectures.

### DGR-007: Add isolated concurrent local Hot KV State
**Description:** As a client, I need concurrent Route Sessions to retain independent per-Shard cache so that one request cannot clear or corrupt another.

**Acceptance Criteria:**
- [ ] Map `(Route Session ID, route epoch)` to an isolated llama sequence or bounded context.
- [ ] Allocate KV only for owned layers.
- [ ] Support prefill append, decode append, truncate, release, TTL/LRU eviction, and explicit cache-miss response.
- [ ] Reject stale epochs and incompatible cache recipes.
- [ ] At least four concurrent sessions on a small model complete without token or KV cross-talk.
- [ ] Cancellation/release of one session leaves other sessions intact and memory returns to the configured budget.

### DGR-008: Build the standalone C++ gRPC Shard worker
**Description:** As a node runtime, I need one supervised native process so that llama.cpp internals remain behind a stable project-owned protocol.

**Acceptance Criteria:**
- [ ] Worker exposes capability, health, session stream, release, cancellation, and metrics services from DGR-002.
- [ ] Worker loads one exact Artifact/recipe/Shard identity and refuses mismatched requests.
- [ ] Streaming path enforces bounded messages, flow control, deadlines, idempotency, and independent session cancellation.
- [ ] Worker does not expose raw llama.cpp RPC or arbitrary GGML graph execution.
- [ ] Graceful shutdown releases sessions; crash behavior is bounded and observable.
- [ ] Python integration tests run against a fake model mode without model downloads.

### DGR-009: Integrate the native worker with Meshnet
**Description:** As the existing node service, I need a GGUF Shard backend adapter so that the Tracker, relay, billing, telemetry, and capability admission remain the sole control plane.

**Acceptance Criteria:**
- [ ] Implement the existing model-backend surface without changing Transformers behavior.
- [ ] Registration carries exact validated GGUF recipe, Shard, backend and concurrency/KV capacity.
- [ ] Tracker forms only complete compatible routes and keeps uncertified recipes dark.
- [ ] Direct routes use gRPC streams; relayed routes carry the same versioned protobuf frames as opaque binary through the existing relay seam.
- [ ] Existing request/work IDs, cancellation, Generation Telemetry, billing, and per-node attribution remain correlated.
- [ ] No vLLM, Nakshatra, prima.cpp, or custom-engine control plane becomes a core dependency.

### DGR-010: Pass local real-model two-process acceptance
**Description:** As a release engineer, I need real local distributed parity before involving network variability.

**Acceptance Criteria:**
- [ ] Two local worker processes open disjoint dense-Llama ranges from the certified Artifact.
- [ ] Prefill and at least 32 greedy decode tokens match whole-model llama.cpp within the certified tolerance.
- [ ] Each worker retains only its own tensors and Hot KV State.
- [ ] Four concurrent Route Sessions pass isolation and cleanup checks.
- [ ] Report TTFT, prefill/decode throughput, seam bytes/latency, worker RSS/VRAM, KV memory, batch size, and queue time.
- [ ] Killing one worker produces a bounded structured failure rather than a deadlock.

### DGR-011: Pass a real heterogeneous two-machine route
**Description:** As a consumer-hardware operator, I need two physical machines to execute one GGUF model so that the distributed claim is real.

**Acceptance Criteria:**
- [ ] Tracker selects two physical nodes with disjoint Shards and one exact certified recipe/compatibility class.
- [ ] Actual CPU/GPU execution occurs on both nodes; synthetic workers do not satisfy acceptance.
- [ ] Prefill/decode, concurrent-session isolation, telemetry, cancellation, and cleanup pass over the real transport/relay path.
- [ ] Exact hardware, network, backend, model hash, route, commands, and raw metrics are recorded.
- [ ] A model or recipe larger than one participating node's admitted memory is exercised when available.
- [ ] Output drift is measured and incompatible mixed backends fail closed.

### DGR-012: Implement continuous batching and bounded admission
**Description:** As a node operator, I need active sessions batched safely so that concurrency increases aggregate throughput rather than serializing every request.

**Acceptance Criteria:**
- [ ] Node scheduler admits sessions against weight, KV, scratch, and queue budgets.
- [ ] Compatible decode steps from multiple sessions form llama.cpp batches while preserving per-session positions and outputs.
- [ ] Prefill does not starve decode; scheduling policy and bounds are explicit.
- [ ] Backpressure prevents unbounded queued activations or KV growth.
- [ ] Capability telemetry reports active sessions, queue depth, batch occupancy, KV pressure, prefill/decode rates, and rejected admissions.
- [ ] Concurrency 1/2/4/8 benchmark identifies saturation and shows no cross-session corruption.

### DGR-013: Harden failure, cancellation, and restart semantics
**Description:** As a client, I need failures to be bounded and explicit so that distributed speed does not come with hanging or corrupted generations.

**Acceptance Criteria:**
- [ ] Deadlines and heartbeat/health loss terminate blocked stream operations.
- [ ] Cancellation propagates across every Shard and releases local KV and queued buffers.
- [ ] Duplicate steps are idempotent; uncertain mutations are never replayed silently.
- [ ] Alpha failover restarts from token zero on a newly compatible route rather than importing unverified KV.
- [ ] Worker death, stream reset, malformed bundle, stale epoch, and cache miss tests pass.
- [ ] Billing/work records distinguish completed, cancelled, failed, and unverified work.

### DGR-014: Enforce the GGUF-versus-safetensors release gate
**Description:** As the product owner, I need an end-to-end comparison so that the native runtime ships only if it advances model access or performance.

**Acceptance Criteria:**
- [ ] Run current distributed safetensors and distributed GGUF routes on the same certified model/hardware/network scenario where technically comparable.
- [ ] Report quality, TTFT, prefill/decode throughput, aggregate concurrency throughput, p95 latency, seam cost, memory, KV pressure, failures, and cleanup.
- [ ] Evaluate against the DGR-001 performance contract without changing thresholds after seeing results.
- [ ] Ship recommendation is one of: promote GGUF, optimize a measured bottleneck with a new bounded task, or stop the native track.
- [ ] Results clearly separate quantization gains from transport/runtime gains.

### DGR-015: Add and certify a Qwen3/Qwen3-MoE adapter
**Description:** As a client seeking top models, I need a separately certified MoE-capable architecture after the dense runtime proves stable.

**Acceptance Criteria:**
- [ ] Implement explicit tensor ownership, router/top-k, expert/shared-expert, Q/K normalization, boundary bundle, and cache semantics for the selected Qwen3 family recipe.
- [ ] Do not reuse the dense-Llama adapter through unchecked name substitutions.
- [ ] Whole-model versus distributed prefill/decode parity passes the architecture-specific tolerance.
- [ ] Expert memory ownership and communication are measured.
- [ ] Real consumer-hardware acceptance and capability admission pass before the recipe becomes routable.

### DGR-016: Produce the upstream llama.cpp collaboration package
**Description:** As a maintainer, I need narrow upstreamable proposals so that our patch burden can shrink without asking llama.cpp to own Meshnet networking.

**Acceptance Criteria:**
- [ ] Separate generic llama.cpp hooks from Meshnet protocol/control-plane code.
- [ ] Prepare minimal reproducible examples and tests for range-aware loading, boundary input/output, and layer-filtered KV.
- [ ] Compare the proposal with Nakshatra and prima.cpp evidence and explain why the API is generally useful.
- [ ] Preserve one scoped commit/patch per concern against the exact upstream pin.
- [ ] Produce an outreach document suitable for Georgi/llama.cpp maintainers; actual sending remains a human action.

## Functional Requirements

1. The public distributed primitive is an ordered Inference Route of contiguous Shards.
2. The native runtime uses llama.cpp/GGML; vLLM remains optional as a complete managed provider.
3. Native worker communication uses gRPC/HTTP2 and Protocol Buffers with one stable stream per Route Session Activation Seam.
4. Artifact identity, runtime recipe, boundary schema, activation dtype and cache layout must match exactly before routing.
5. Hot KV State remains local to the node serving the Shard.
6. Multiple Route Sessions must execute concurrently without shared-cache corruption.
7. Nodes batch compatible active decode steps and enforce bounded admission/backpressure.
8. Unsupported architectures and hardware recipes remain non-routable until real certification passes.
9. Default tests never download models or require GPUs; real tests are explicit and preserve artifacts off `/home`.
10. The release decision is based on measured performance, fit, quality, concurrency, and reliability relative to the safetensors baseline.

## Non-Goals

- Forking vLLM or importing its PagedAttention/Torch distributed runtime.
- Adopting Nakshatra, prima.cpp, llama-gguf, LiGGUF, or GPUStack as the control plane.
- Public WAN tensor/expert parallel collectives.
- QUIC, WebRTC, or a custom socket protocol.
- Automatic KV migration or mid-generation route repair in the first release.
- Speculative decoding or disaggregated prefill before the core release gate.
- Supporting every GGUF architecture before dense Llama and Qwen3-family certification.
- A marketing-scale model demo that bypasses parity, concurrency, admission, or performance gates.

## Success Metrics

- A real model larger than one admitted node can execute across consumer machines when suitable hardware/artifacts are available.
- Four or more concurrent sessions complete without cross-talk; hardware-specific saturation is measured.
- Distributed GGUF passes the locked performance/fit contract against the existing safetensors route.
- Worker and Tracker recover all resources after completion, cancellation, malformed input, and node failure.
- The critical runtime remains Meshnet plus one standalone worker and a small auditable llama.cpp patch stack.

## Open Questions

- Exact benchmark model and quantization lanes are selected by DGR-001 from currently supported, legally redistributable artifacts.
- Final hardware-specific concurrency and useful-speed thresholds are locked by measured baselines rather than guessed globally.
- Upstream llama.cpp acceptance is desirable but not a prerequisite for the first narrow pinned fork.