neuron-tai/.scratch/distributed-gguf-runtime/issues/055-implement-compatible-continuous-decode-batching.md

DGR-055: Implement compatible continuous decode batching

• Status / triage: specification only; ready-for-agent; passes: false
• Execution mode: AFK
• Milestone: M4
• Dependencies: DGR-038, DGR-040, DGR-054
• Blocks (derived): DGR-056, DGR-057
• Labels: area:scheduler, area:batching, type:performance, priority:p1, ready-for-agent
• Evidence class: fixture
• 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/055-implement-compatible-continuous-decode-batching.md, and evidence READMEs for dependencies (DGR-038, DGR-040, DGR-054) before changing code. Inspect live source/tests rather than trusting legacy pass states. Objective: Batch compatible active sessions without violating route, recipe, position, or architecture state.

Acceptance criteria

• Batch only sessions with compatible engine, recipe, phase, boundary schema, and state layout.
• Preserve per-session positions, sequence IDs, outputs, cancellation, and accounting.
• Decode receives bounded service while prefill remains schedulable.
• Deterministic 1/2/4/8 concurrency tests show no cross-session corruption.
• 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-055/README.md. Until every criterion and applicable gate has real evidence, this story remains passes: false. Legacy evidence is provenance only, not completion credit.