# DGR-063: Profile and optimize the critical seam - **Status / triage:** specification only; `ready-for-agent`; `passes: false` - **Execution mode:** `AFK` - **Milestone:** `M4` - **Dependencies:** `DGR-057`, `DGR-061` - **Blocks (derived):** `DGR-064` - **Labels:** `area:performance`, `type:optimization`, `priority:p1`, `ready-for-agent` - **Evidence class:** `real-hardware` - **Hardware:** `required` - **Model:** `generic` - **Upstream:** `conditional` ## Objective / description Fresh Ralph session: read `.scratch/distributed-gguf-runtime/RALPH-CONTEXT.md`, source issue `.scratch/distributed-gguf-runtime/issues/063-profile-and-optimize-the-critical-seam.md`, and evidence READMEs for dependencies (DGR-057, DGR-061) before changing code. Inspect live source/tests rather than trusting legacy pass states. Objective: Optimize only the measured dominant compute, serialization, copy, or transport bottleneck. ## Acceptance criteria - [ ] Profile worker compute, tensor conversion, copies, protobuf framing, compression, relay/direct transport, queueing, and synchronization. - [ ] Select one dominant bottleneck from evidence and lock its before/after benchmark. - [ ] Implement one bounded optimization without weakening correctness or protocol identity. - [ ] Report whether the optimization changes TTFT, prefill, decode, throughput, or memory and preserve raw data. - [ ] 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-063/README.md`. Until every criterion and applicable gate has real evidence, this story remains `passes: false`. Legacy evidence is provenance only, not completion credit.