fix: make Linux OpenBLAS an explicit backend choice

.github/workflows/ci.yml

@@ -36,6 +36,9 @@ jobs:
     runs-on: ${{ matrix.os }}
     steps:
       - uses: actions/checkout@v4
+      - name: Install optional OpenBLAS backend
+        if: runner.os == 'Linux' && contains(matrix.flags, '--all-features')
+        run: sudo apt-get update -qq && sudo apt-get install -y libopenblas-dev pkg-config
       # Pin a complete, present Xcode on macOS: the floating `macos-latest`
       # image intermittently leaves a default selection whose clang runtime
       # (`libclang_rt.osx.a`) is missing, breaking the link with
@@ -93,6 +96,9 @@ jobs:
     runs-on: ${{ matrix.os }}
     steps:
       - uses: actions/checkout@v4
+      - name: Install optional OpenBLAS backend
+        if: runner.os == 'Linux' && contains(matrix.flags, '--all-features')
+        run: sudo apt-get update -qq && sudo apt-get install -y libopenblas-dev pkg-config
       # See the `check` job: deterministic Xcode so macOS linking is stable.
       - if: runner.os == 'macOS'
         id: xcode
@@ -133,6 +139,9 @@ jobs:
     runs-on: ${{ matrix.os }}
     steps:
       - uses: actions/checkout@v4
+      - name: Install optional OpenBLAS backend
+        if: runner.os == 'Linux' && contains(matrix.flags, '--all-features')
+        run: sudo apt-get update -qq && sudo apt-get install -y libopenblas-dev pkg-config
       # See the `check` job: deterministic Xcode so macOS linking is stable.
       - if: runner.os == 'macOS'
         id: xcode
@@ -212,6 +221,8 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
+      - name: Install optional OpenBLAS backend
+        run: sudo apt-get update -qq && sudo apt-get install -y libopenblas-dev pkg-config
       - uses: dtolnay/rust-toolchain@stable
       - uses: Swatinem/rust-cache@v2
       - run: cargo doc --no-deps --all-features
@@ -230,6 +241,8 @@ jobs:
       contents: read
     steps:
       - uses: actions/checkout@v4
+      - name: Install optional OpenBLAS backend
+        run: sudo apt-get update -qq && sudo apt-get install -y libopenblas-dev pkg-config
       - uses: dtolnay/rust-toolchain@stable
         with:
           components: llvm-tools-preview
@@ -325,6 +338,8 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
+      # cargo-semver-checks enables public features, including system-openblas.
+      - run: sudo apt-get update -qq && sudo apt-get install -y libopenblas-dev pkg-config
       - uses: dtolnay/rust-toolchain@stable
       - uses: Swatinem/rust-cache@v2
       - uses: taiki-e/install-action@v2
@@ -365,6 +380,8 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
+      - name: Install optional OpenBLAS backend
+        run: sudo apt-get update -qq && sudo apt-get install -y libopenblas-dev pkg-config
       - uses: dtolnay/rust-toolchain@stable
       - uses: Swatinem/rust-cache@v2
       - uses: taiki-e/install-action@v2
@@ -524,3 +541,13 @@ jobs:
       - run: |
           sudo apt-get update && sudo apt-get install -y minisign
       - run: ./scripts/sign-models.sh --dry-run
+
+  linux-blas:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: dtolnay/rust-toolchain@stable
+      - uses: Swatinem/rust-cache@v2
+      - run: sudo apt-get update -qq && sudo apt-get install -y libopenblas-dev pkg-config
+      - name: Verify Rust default and explicit OpenBLAS artifacts
+        run: bash scripts/check-linux-blas.sh

.github/workflows/linux-cpu-der.yml

@@ -79,15 +79,14 @@ jobs:
         env:
           OUT: benchmarks/results/linux-cpu-native-der-ci
           EP: cpu
-          FEATURES: cli
+          # Match release assets: Rust kernels, no system-openblas.
+          FEATURES: cli-native
           POLYVOICE_POWERSET_BATCH_SIZE: "8"
           POLYVOICE_VBX_PLDA_DIR: ${{ github.workspace }}/fixtures/vbx-plda
           ASSERT_BASELINE: "1"
           BASELINE_JSON: ${{ github.workspace }}/tests/der_baseline.json
         run: |
           set -euo pipefail
-          sudo apt-get update -qq
-          sudo apt-get install -y -qq libopenblas-dev pkg-config
           if [ "$MODE" = "full" ]; then
             export MAX_VOX=0 MAX_AMI=0
           else

.github/workflows/mutants.yml

@@ -25,6 +25,7 @@ jobs:
       - uses: taiki-e/install-action@v2
         with:
           tool: cargo-mutants
+      - run: sudo apt-get update -qq && sudo apt-get install -y libopenblas-dev pkg-config
       - run: cargo mutants --all-features --timeout 300
       - if: always()
         uses: actions/upload-artifact@v4

.github/workflows/release.yml

@@ -53,6 +53,8 @@ jobs:
       - run: bash scripts/download-ami-test-single.sh
       - run: bash scripts/download-voxconverse-test.sh
       - run: cargo run --features cli --bin polyvoice -- download-models --profile balanced
+      - name: Install OpenBLAS for all-features validation
+        run: sudo apt-get update -qq && sudo apt-get install -y libopenblas-dev pkg-config
       - run: bash scripts/release-check.sh
 
   cli-binaries:
@@ -105,6 +107,7 @@ jobs:
             ~/Library/Caches/ort.pyke.io
             ~/AppData/Local/ort.pyke.io
           key: ort-dfbin-${{ runner.os }}-${{ hashFiles('Cargo.lock') }}
+      # Release assets use Rust Linux kernels; system-openblas is not enabled.
       - run: cargo build --release --features cli --target ${{ matrix.target }}
       - name: Rename binary (unix)
         if: runner.os != 'Windows'

CHANGELOG.md

@@ -42,6 +42,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Changed
 
+- Linux native builds now use Rust kernels regardless of installed BLAS.
+  Enable `system-openblas` for the optional LP64 OpenBLAS backend; missing
+  development files fail clearly instead of silently selecting a fallback.
+  `--all-features` includes this opt-in. Darwin remains unchanged.
+
 - `PipelineBuilder::validate` rejects out-of-range public settings (NaN,
   infinity, `max_speakers == 0`, `min_cluster_size == 0`, non-positive
   embed windows, AHC thresholds outside [-1, 1], AS-norm `top_n < 2`,

CONTRIBUTING.md

@@ -113,3 +113,8 @@ Library docs: [docs/API.md](docs/API.md).
 ## License
 
 By contributing, you agree that your contributions will be licensed under MIT.
+
+On Linux, `--all-features` and the release checks require LP64 OpenBLAS
+development files and `pkg-config` because they enable `system-openblas`.
+Ordinary `--features cli` builds use Rust kernels without BLAS. See the
+[backend contract](docs/strategy/zero-deps.md#linux-backend-selection).

Cargo.toml

@@ -68,6 +68,8 @@ crate-type = ["cdylib", "rlib"]
 
 [features]
 default = []
+# Opt-in Linux LP64 OpenBLAS for enabled native kernels; no effect on Darwin.
+system-openblas = ["polyvoice-kernels?/system-openblas"]
 # InferenceRuntime surface (tensors, factory, session trait). No native dylib.
 # Enabled by `backend-tract`. Stages that load ONNX *files* via tract depend
 # on this, not on a concrete engine. The product CLI does not enable `infer`.

PRODUCTION-READINESS.md

@@ -42,8 +42,8 @@ mean no C/C++ code, no system libraries, or zero Rust crates.
 
 - Empty default features provide the BYO core with normal Rust dependencies.
 - Native Darwin inference compiles C shims and links Accelerate/BNNS.
-- Native Linux uses Rust kernels and currently auto-detects installed BLAS.
-  Making that choice explicit and reproducible remains a release requirement.
+- Native Linux uses Rust kernels by default; `system-openblas` explicitly
+  enables the optional LP64 OpenBLAS backend.
 - Download-enabled builds pull TLS dependencies, including `ring` native
   code. `pipeline-local` omits the downloader and its TLS graph.
 - Python also depends on the Python runtime/ABI.

benchmarks/results/linux-blas-selection-2026-09-24/NOTES.md

@@ -0,0 +1,97 @@
+# Explicit Linux OpenBLAS selection: before/after evidence
+
+Host: AMD Ryzen AI 9 HX 370, Linux x86_64, 24 logical CPUs, performance
+CPU governor. Date: 2026-09-24. Release profile, balanced INT8, v2 + VBx,
+CPU, powerset batch 8, collar 0, overlap included, checked-in PLDA fixtures.
+
+## Revisions and artifacts
+
+- `baseline`: master `a8461d42f7793f2f21409b41f7619e881b4c5a43`, `--features cli`.
+  Its auto-detection found no BLAS; the saved binary has no BLAS imports.
+- `rust`: `64f13c8433c684b6ff73f8cc5e5f5597baa278ec`, `--features cli`.
+  Default Rust backend even with OpenBLAS available to pkg-config.
+- `openblas`: same implementation revision, `--features cli,system-openblas`.
+  Ubuntu LP64 pthread OpenBLAS 0.3.32, extracted locally with its Fortran
+  runtime dependencies; no system installation changes. pkg-config points
+  to that prefix and the runtime loader path points to its shared libraries.
+
+[Measurements](measurements.json) include binary SHA-256, source revision,
+DER, wall RTFx and process peak RSS for every completed run. Source revision
+is recorded explicitly: the bench program itself queries the current checkout
+at runtime, which cannot identify a saved baseline executable.
+
+Model pair unchanged, **8,414,314 bytes**:
+
+- powerset_int8: `175896d26f639933cd86906d2dd3e6796eddb23c1f719925a3949052da76183b`
+- resnet34_int8: `24b58559fefb2af624a5d371c43ebae891a9a8ca363b2f9e7c31fd8e440a36b3`
+
+## Scope and results
+
+Vox-3 is euqef/fuzfh/msbyq. Vox-10 is the first ten filenames in sorted
+VoxConverse-test order; AMI-1 is the first sorted AMI-test recording.
+The exact filenames and all per-file quality fields are in
+[quality.json](quality.json). These are fixed diagnostic subsets, not the
+published full-split Vox/AMI reference scores.
+
+Vox-3 runs alternate baseline/rust/openblas five times for each jobs setting.
+Vox-10 has one run per backend; AMI-1 repeats baseline/rust three times and
+OpenBLAS once. Table timing/RSS values are medians, **not release floors**.
+
+| Dataset | Jobs | Backend | Runs | DER₀ micro % | Wall RTFx | Peak RSS MiB |
+|---------|------|---------|------|--------------|-----------|--------------|
+| vox3 | 1 | baseline | 5 | 7.0295 | 91.7 | 316.5 |
+| vox3 | 1 | rust | 5 | 7.0295 | 89.4 | 314.8 |
+| vox3 | 1 | openblas | 5 | 7.0295 | 93.0 | 321.2 |
+| vox3 | 3 | baseline | 5 | 7.0295 | 117.0 | 469.5 |
+| vox3 | 3 | rust | 5 | 7.0295 | 127.7 | 480.4 |
+| vox3 | 3 | openblas | 5 | 7.0295 | 132.3 | 480.5 |
+| vox10 | 3 | baseline | 1 | 16.4243 | 134.8 | 2283.0 |
+| vox10 | 3 | rust | 1 | 16.4243 | 95.6 | 2224.9 |
+| vox10 | 3 | openblas | 1 | 15.6938 | 165.1 | 2242.2 |
+| ami1 | 3 | baseline | 3 | 32.5584 | 144.7 | 1263.9 |
+| ami1 | 3 | rust | 3 | 32.5584 | 150.0 | 1292.6 |
+| ami1 | 3 | openblas | 1 | 31.7272 | 163.5 | 1299.3 |
+
+Default Rust matches the baseline on every recorded per-file quality field,
+including speaker counts and turn counts. OpenBLAS matches Vox-3 quality but
+changes clustering on Vox-10/AMI-1; its lower DER here is subset evidence,
+not a universal improvement or numerical-equivalence claim.
+
+**Performance limitation:** unrelated builds and CPU-heavy tests were active
+on the host. Throughput fluctuated substantially, including between repeated
+runs of the same binary. Full-corpus comparisons were stopped after detecting
+that contention; no incomplete full-corpus result is included. These runs
+measure before/after behavior but do not certify isolated performance parity
+or establish new speed/RSS baselines. Default median AMI RSS is slightly
+higher than baseline, with overlapping observed ranges; no memory improvement
+is claimed. Re-run on an idle reference host for performance qualification.
+
+Darwin implementation and all five locked scoreboard limits are unchanged.
+Darwin scoreboard CI passed; its shared-runner result does not substitute for
+an isolated Darwin RTF/RSS measurement. Linux subset RSS is not the Darwin
+Vox-3 memory protocol.
+
+## Reproduction and verification
+
+Save a release `polyvoice-bench` from each revision/feature selection. Prepare
+subset directories with `audio/` and `rttm/` symlinks for the recorded filenames.
+For each binary and dataset:
+
+```bash
+POLYVOICE_VBX_PLDA_DIR="$PWD/fixtures/vbx-plda" POLYVOICE_POWERSET_BATCH_SIZE=8 \
+  /usr/bin/time -v ./saved-polyvoice-bench DATASET \
+  --profile balanced --pipeline v2 --clusterer vbx --execution-provider cpu \
+  --collar 0 --jobs 3 --output result.json
+```
+
+For the OpenBLAS binary, install the runtime or set `LD_LIBRARY_PATH` to its
+local prefix. Read process RSS from `/usr/bin/time -v`, not summed workers.
+
+Validation:
+
+- `scripts/check-linux-blas.sh`: passes for both artifacts with OpenBLAS
+  available, including missing-prerequisite failure and `readelf`/`ldd` checks.
+- Kernel tests: 58 Rust / 59 OpenBLAS passed; three manual tests ignored each.
+- Product CLI/FFI/OpenBLAS library tests: 943 passed; local-only library: 875.
+- Clippy: product CLI/FFI and all-features with `-D warnings` passed.
+- Dependency invariants, standalone lockfiles, formatting and doc links passed.