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ADR 034 — Candle / QLoRA stack upgrades

Context

Section titled “Context”
  • Mens / Populi training paths depend on Candle, qlora-rs (vendored patch), peft-rs, and transitive stacks (zip, CUDA kernels).
  • The workspace dependency audit showed duplicate majors (e.g. zip) that cannot be collapsed without coordinated Candle + HF ecosystem bumps.
  • GPU builds (mens-candle-cuda, NVCC) require explicit CI coverage.

Decision

Section titled “Decision”
  • No ad-hoc Candle major bump inside manifest-normalization PRs.
  • Track one upgrade initiative with: MSRV check, CUDA release-build smoke, and lockfile diff review for zip / rand / half transitive shifts.
  • Keep using workspace pins + patches documented in root Cargo.toml.

Status

Section titled “Status”

Accepted (2026-10-01) — closed against measured repository state and a successful hosted CUDA-toolchain compile run.

Implementation (Phase 6, ML-01)

Section titled “Implementation (Phase 6, ML-01)”

The dedicated upgrade train found the stack already unified, so it made no speculative major bump:

  • Candle 0.10.2 (candle-core / candle-nn / candle-transformers pinned to 0.10 in [workspace.dependencies]; candle-metal-kernels patched from patches/candle-metal-kernels-0.10.2).
  • peft-rs 1.0.3 (patched from patches/peft-rs-1.0.3).
  • qlora-rs 1.0.5 (patched from patches/qlora-rs-1.0.5).

Evidence:

  • crates/vox-cli/tests/ml_dependency_health.rs reads locked cargo metadata and fails if more than one version of any of these crates resolves.
  • vox ci cuda-features / vox ci cuda-release-build were repaired to target the current owners, vox-plugin-speech and vox-ml-cli.
  • nightly.yml’s fail-closed ml-cuda-health job (ubuntu-latest, pinned CUDA 12.6.3 toolkit, CUDA_COMPUTE_CAP=80) passed: run 36821415478 at head SHA bc3214504f981e31817da3d9b4dbeae1b6cb0892.

Coverage limit. This evidence validates CUDA compilation and linkage only. It does not exercise a CUDA device or prove physical-GPU runtime behavior; that remains a local check (see runner contract).

Consequences

Section titled “Consequences”
  • Duplicate transitive versions outside this stack may persist; they are tracked in the workspace dependency audit.
  • A future Candle major bump is a new upgrade train under the same gates, not an incidental change.