feat(bench): publish release benchmark baselines

.github/workflows/benchmarks.yml

@@ -1,6 +1,6 @@
 name: Benchmarks
 
-# Detect performance regressions in exact-arithmetic benchmarks.
+# Detect performance regressions.
 # - Push to main: run benchmarks, save Criterion baseline, upload as artifact.
 # - PRs: find latest main baseline artifact, download, compare, report.
 # Regressions are warning-only — this workflow never fails on regression.

.github/workflows/release-benchmarks.yml

@@ -0,0 +1,87 @@
+name: Release Benchmarks
+
+# Archive full Criterion benchmark baselines for published releases.
+# Release jobs publish durable artifacts, so they intentionally do not restore
+# or save dependency caches.
+
+permissions:
+  contents: write
+
+on:
+  release:
+    types:
+      - published
+
+concurrency:
+  group: release-benchmarks-${{ github.event.release.tag_name }}
+  cancel-in-progress: false
+
+env:
+  CARGO_TERM_COLOR: always
+  RUST_BACKTRACE: 1
+
+jobs:
+  release-baseline:
+    runs-on: ubuntu-latest
+    timeout-minutes: 60
+
+    steps:
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+        with:
+          ref: ${{ github.event.release.tag_name }}
+          persist-credentials: false
+
+      - name: Install Rust toolchain
+        uses: actions-rust-lang/setup-rust-toolchain@46268bd060767258de96ed93c1251119784f2ab6 # v1.16.1
+        with:
+          cache: false
+
+      - name: Save release Criterion baseline
+        env:
+          RELEASE_TAG: ${{ github.event.release.tag_name }}
+        run: |
+          set -euo pipefail
+
+          cargo bench --features bench --bench vs_linalg -- --save-baseline "$RELEASE_TAG"
+          cargo bench --features bench,exact --bench exact -- --save-baseline "$RELEASE_TAG"
+
+      - name: Package release Criterion baseline
+        id: package-baseline
+        env:
+          RELEASE_TAG: ${{ github.event.release.tag_name }}
+        run: |
+          set -euo pipefail
+
+          asset="la-stack-${RELEASE_TAG}-criterion-baseline.tar.gz"
+          tar -C target -czf "$asset" criterion
+          echo "asset=$asset" >> "$GITHUB_OUTPUT"
+
+      - name: Upload temporary baseline artifact
+        uses: actions/upload-artifact@043fb46d1a93c77aae656e7c1c64a875d1fc6a0a # v7.0.1
+        with:
+          name: bench-baseline-${{ github.event.release.tag_name }}
+          path: ${{ steps.package-baseline.outputs.asset }}
+          retention-days: 30
+          if-no-files-found: error
+
+      - name: Attach baseline to GitHub Release
+        env:
+          GH_TOKEN: ${{ github.token }}
+          RELEASE_TAG: ${{ github.event.release.tag_name }}
+          RELEASE_ASSET: ${{ steps.package-baseline.outputs.asset }}
+        run: |
+          set -euo pipefail
+
+          gh release upload "$RELEASE_TAG" "$RELEASE_ASSET" --clobber
+
+      - name: Release baseline summary
+        env:
+          RELEASE_ASSET: ${{ steps.package-baseline.outputs.asset }}
+        run: |
+          set -euo pipefail
+
+          {
+            echo "### Release Benchmark Baseline"
+            echo ""
+            echo "Uploaded release asset: \`$RELEASE_ASSET\`"
+          } >> "$GITHUB_STEP_SUMMARY"

docs/BENCHMARKING.md

@@ -116,7 +116,9 @@ just bench-latest-vs-last
 ## Comparing performance across releases
 
 Criterion baselines are saved into `target/criterion/` and persist across
-`git checkout` but **not** across `cargo clean`.
+`git checkout` but **not** across `cargo clean`. Published releases also attach
+a compressed Criterion baseline to the GitHub Release so historical release
+baselines can be restored later.
 
 ### Latest vs last
 
@@ -158,6 +160,26 @@ just bench-compare v0.2.0
 
 You can save multiple baselines and compare against any of them.
 
+If the release baseline is already present in `target/criterion/`, skip the
+checkout step and compare directly. For example, to compare current code against
+the saved `v0.4.2` release baseline:
+
+```bash
+just bench-latest          # gather latest la-stack measurements
+just bench-compare v0.4.2  # compare latest measurements against v0.4.2
+```
+
+If the release baseline is not present locally, download and restore the release
+asset first:
+
+```bash
+gh release download v0.4.2 --pattern "la-stack-v0.4.2-criterion-baseline.tar.gz"  # fetch archived release baseline
+mkdir -p target                                                                    # ensure Criterion parent directory exists
+tar -C target -xzf la-stack-v0.4.2-criterion-baseline.tar.gz                       # restore target/criterion baseline data
+just bench-latest                                                                  # gather latest la-stack measurements
+just bench-compare v0.4.2                                                          # compare latest measurements against v0.4.2
+```
+
 ### Output
 
 `just bench-compare` writes `target/bench-reports/performance.md` by
@@ -187,11 +209,14 @@ See `scripts/criterion_dim_plot.py --help` for options.
 
 ## Release workflow
 
-At release time, save a baseline so future work can compare against it:
+At release time, save a local baseline so future work can compare against it:
 
 ```bash
 just bench-save-baseline $TAG
 just bench-save-last
 ```
 
+When the GitHub Release is published, `.github/workflows/release-benchmarks.yml`
+saves a full release baseline and attaches
+`la-stack-$TAG-criterion-baseline.tar.gz` to the release as the durable archive.
 See `docs/RELEASING.md` step 5 for where this fits in the release process.

docs/RELEASING.md

@@ -111,10 +111,18 @@ just bench-save-baseline $TAG
 just bench-save-last
 ```
 
-These baselines can be compared against in future optimization work. The
-default local report command, `just bench-compare`, compares latest
-measurements against `last` and writes `target/bench-reports/performance.md`;
-it does not update README benchmark tables or committed release artifacts.
+These baselines can be compared against in future optimization work on the
+release branch. The default local report command, `just bench-compare`, compares
+latest measurements against `last` and writes
+`target/bench-reports/performance.md`; it does not update README benchmark
+tables or committed release artifacts.
+
+After the GitHub Release is published, the `Release Benchmarks` workflow checks
+out the release tag, saves a full Criterion baseline, and attaches
+`la-stack-$TAG-criterion-baseline.tar.gz` to the release. That release asset is
+the durable archive for historical baseline comparisons; the workflow also
+uploads a short-lived Actions artifact for debugging the run.
+
 See `docs/BENCHMARKING.md` for the full comparison workflow.
 
 6. Validate the release branch