diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 8db8dde..41a231c 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -81,22 +81,3 @@ jobs:
       run: ./script/bootstrap
     - name: Lint
       run: ./script/lint
-
-  thirdparty:
-    strategy:
-      matrix:
-        go-version: [1.15.x, 1.16.x]
-        platform: [ubuntu-latest]
-    runs-on: ${{ matrix.platform }}
-    steps:
-    - name: Install Go
-      uses: actions/setup-go@37335c7bb261b353407cff977110895fa0b4f7d8 # v2.1.3
-      with:
-        go-version: ${{ matrix.go-version }}
-    - name: Checkout code
-      uses: actions/checkout@5a4ac9002d0be2fb38bd78e4b4dbde5606d7042f # v2.3.4
-      with:
-        persist-credentials: false
-    - name: Run Third-Party Tests
-      working-directory: ./tests/thirdparty
-      run: go test -pkgs packages.json
diff --git a/.github/workflows/packages.yml b/.github/workflows/packages.yml
new file mode 100644
index 0000000..1e75781
--- /dev/null
+++ b/.github/workflows/packages.yml
@@ -0,0 +1,558 @@
+# Code generated by make_workflow.go. DO NOT EDIT.
+
+name: packages
+permissions:
+  contents: read
+on:
+  push:
+    branches:
+      - master
+  pull_request:
+
+jobs:
+  zeebo-xxh3:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Install Go
+        uses: actions/setup-go@37335c7bb261b353407cff977110895fa0b4f7d8 # v2.1.3
+        with:
+          go-version: 1.17.x
+      - name: Checkout avo
+        uses: actions/checkout@5a4ac9002d0be2fb38bd78e4b4dbde5606d7042f # v2.3.4
+        with:
+          path: avo
+          persist-credentials: false
+      - name: Checkout zeebo/xxh3
+        uses: actions/checkout@5a4ac9002d0be2fb38bd78e4b4dbde5606d7042f # v2.3.4
+        with:
+          repository: zeebo/xxh3
+          ref: v1.0.0-rc1
+          path: xxh3
+          persist-credentials: false
+      - name: Avo Module Replacement
+        working-directory: xxh3/avo
+        run: |
+          go mod edit -modfile=go.mod -require=github.com/mmcloughlin/avo@v0.0.0-00010101000000-000000000000
+          go mod edit -modfile=go.mod -replace=github.com/mmcloughlin/avo=${{ github.workspace }}/avo
+          go mod tidy -modfile=go.mod
+      - name: Generate
+        working-directory: xxh3/avo
+        run: |
+          go run . -avx -out ../accum_vector_avx_amd64.s
+          go run . -sse -out ../accum_vector_sse_amd64.s
+      - name: Diff
+        working-directory: xxh3
+        run: git diff
+      - name: Test
+        working-directory: xxh3
+        run: go test ./...
+  dgryski-go-sip13:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Install Go
+        uses: actions/setup-go@37335c7bb261b353407cff977110895fa0b4f7d8 # v2.1.3
+        with:
+          go-version: 1.17.x
+      - name: Checkout avo
+        uses: actions/checkout@5a4ac9002d0be2fb38bd78e4b4dbde5606d7042f # v2.3.4
+        with:
+          path: avo
+          persist-credentials: false
+      - name: Checkout dgryski/go-sip13
+        uses: actions/checkout@5a4ac9002d0be2fb38bd78e4b4dbde5606d7042f # v2.3.4
+        with:
+          repository: dgryski/go-sip13
+          ref: 62edffca92457b3a66125c686137cc5f0fe81672
+          path: go-sip13
+          persist-credentials: false
+      - name: Setup Root Module
+        working-directory: go-sip13
+        run: go mod init github.com/dgryski/go-sip13
+      - name: Setup Generator Module
+        working-directory: go-sip13/_avo
+        run: |
+          sed -i.bak '/+build ignore/d' asm.go
+          go mod init github.com/dgryski/go-sip13/_avo
+      - name: Avo Module Replacement
+        working-directory: go-sip13/_avo
+        run: |
+          go mod edit -modfile=go.mod -require=github.com/mmcloughlin/avo@v0.0.0-00010101000000-000000000000
+          go mod edit -modfile=go.mod -replace=github.com/mmcloughlin/avo=${{ github.workspace }}/avo
+          go mod tidy -modfile=go.mod
+      - name: Generate
+        working-directory: go-sip13/_avo
+        run: |
+          go mod edit -modfile=go.mod -require=github.com/dgryski/go-sip13@v0.0.0-00010101000000-000000000000
+          go mod edit -modfile=go.mod -replace=github.com/dgryski/go-sip13=../
+          go run . -out ../sip13_amd64.s
+      - name: Diff
+        working-directory: go-sip13
+        run: git diff
+      - name: Test
+        working-directory: go-sip13
+        run: go test ./...
+  phoreproject-bls:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Install Go
+        uses: actions/setup-go@37335c7bb261b353407cff977110895fa0b4f7d8 # v2.1.3
+        with:
+          go-version: 1.17.x
+      - name: Checkout avo
+        uses: actions/checkout@5a4ac9002d0be2fb38bd78e4b4dbde5606d7042f # v2.3.4
+        with:
+          path: avo
+          persist-credentials: false
+      - name: Checkout phoreproject/bls
+        uses: actions/checkout@5a4ac9002d0be2fb38bd78e4b4dbde5606d7042f # v2.3.4
+        with:
+          repository: phoreproject/bls
+          ref: a88a5ae26844d7293359422888d7c7f69f43c845
+          path: bls
+          persist-credentials: false
+      - name: Setup
+        working-directory: bls/asm
+        run: |
+          sed -i.bak '/+build ignore/d' asm.go
+          go mod init github.com/phoreproject/bls/asm
+      - name: Avo Module Replacement
+        working-directory: bls/asm
+        run: |
+          go mod edit -modfile=go.mod -require=github.com/mmcloughlin/avo@v0.0.0-00010101000000-000000000000
+          go mod edit -modfile=go.mod -replace=github.com/mmcloughlin/avo=${{ github.workspace }}/avo
+          go mod tidy -modfile=go.mod
+      - name: Generate
+        working-directory: bls/asm
+        run: |
+          go mod edit -modfile=go.mod -require=github.com/phoreproject/bls@v0.0.0-00010101000000-000000000000
+          go mod edit -modfile=go.mod -replace=github.com/phoreproject/bls=../
+          go mod download
+          go run . -out ../primitivefuncs_amd64.s
+      - name: Diff
+        working-directory: bls
+        run: git diff
+      - name: Test
+        working-directory: bls
+        run: go test ./...
+  minio-md5-simd:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Install Go
+        uses: actions/setup-go@37335c7bb261b353407cff977110895fa0b4f7d8 # v2.1.3
+        with:
+          go-version: 1.17.x
+      - name: Checkout avo
+        uses: actions/checkout@5a4ac9002d0be2fb38bd78e4b4dbde5606d7042f # v2.3.4
+        with:
+          path: avo
+          persist-credentials: false
+      - name: Checkout minio/md5-simd
+        uses: actions/checkout@5a4ac9002d0be2fb38bd78e4b4dbde5606d7042f # v2.3.4
+        with:
+          repository: minio/md5-simd
+          ref: 30ad8af83f6868c2a30c615f3edf1a9366bf3f89
+          path: md5-simd
+          persist-credentials: false
+      - name: Avo Module Replacement
+        working-directory: md5-simd/_gen
+        run: |
+          go mod edit -modfile=go.mod -require=github.com/mmcloughlin/avo@v0.0.0-00010101000000-000000000000
+          go mod edit -modfile=go.mod -replace=github.com/mmcloughlin/avo=${{ github.workspace }}/avo
+          go mod tidy -modfile=go.mod
+      - name: Generate
+        working-directory: md5-simd/_gen
+        run: go run gen.go -out ../md5block_amd64.s -stubs ../md5block_amd64.go -pkg md5simd
+      - name: Diff
+        working-directory: md5-simd
+        run: git diff
+      - name: Test
+        working-directory: md5-simd
+        run: go test ./...
+  zeebo-blake3:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Install Go
+        uses: actions/setup-go@37335c7bb261b353407cff977110895fa0b4f7d8 # v2.1.3
+        with:
+          go-version: 1.17.x
+      - name: Checkout avo
+        uses: actions/checkout@5a4ac9002d0be2fb38bd78e4b4dbde5606d7042f # v2.3.4
+        with:
+          path: avo
+          persist-credentials: false
+      - name: Checkout zeebo/blake3
+        uses: actions/checkout@5a4ac9002d0be2fb38bd78e4b4dbde5606d7042f # v2.3.4
+        with:
+          repository: zeebo/blake3
+          ref: 25dba572f0e78ec108f0dd79c9c15288f542d7d9
+          path: blake3
+          persist-credentials: false
+      - name: Avo Module Replacement
+        working-directory: blake3/avo
+        run: |
+          go mod edit -modfile=go.mod -require=github.com/mmcloughlin/avo@v0.0.0-00010101000000-000000000000
+          go mod edit -modfile=go.mod -replace=github.com/mmcloughlin/avo=${{ github.workspace }}/avo
+          go mod tidy -modfile=go.mod
+      - name: Generate
+        working-directory: blake3/avo
+        run: |
+          go run ./avx2 -out ../avx2/impl.s
+          go run ./sse41 -out ../sse41/impl.s
+      - name: Diff
+        working-directory: blake3
+        run: git diff
+      - name: Test
+        working-directory: blake3
+        run: go test ./...
+  klauspost-reedsolomon:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Install Go
+        uses: actions/setup-go@37335c7bb261b353407cff977110895fa0b4f7d8 # v2.1.3
+        with:
+          go-version: 1.17.x
+      - name: Checkout avo
+        uses: actions/checkout@5a4ac9002d0be2fb38bd78e4b4dbde5606d7042f # v2.3.4
+        with:
+          path: avo
+          persist-credentials: false
+      - name: Checkout klauspost/reedsolomon
+        uses: actions/checkout@5a4ac9002d0be2fb38bd78e4b4dbde5606d7042f # v2.3.4
+        with:
+          repository: klauspost/reedsolomon
+          ref: 922778284547557265cff0f903ab5f4c27e40ae9
+          path: reedsolomon
+          persist-credentials: false
+      - name: Avo Module Replacement
+        working-directory: reedsolomon/_gen
+        run: |
+          go mod edit -modfile=go.mod -require=github.com/mmcloughlin/avo@v0.0.0-00010101000000-000000000000
+          go mod edit -modfile=go.mod -replace=github.com/mmcloughlin/avo=${{ github.workspace }}/avo
+          go mod tidy -modfile=go.mod
+      - name: Generate
+        working-directory: reedsolomon/_gen
+        run: go run gen.go -out ../galois_gen_amd64.s -stubs ../galois_gen_amd64.go -pkg reedsolomon
+      - name: Diff
+        working-directory: reedsolomon
+        run: git diff
+      - name: Test
+        working-directory: reedsolomon
+        run: go test ./...
+  orisano-wyhash:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Install Go
+        uses: actions/setup-go@37335c7bb261b353407cff977110895fa0b4f7d8 # v2.1.3
+        with:
+          go-version: 1.17.x
+      - name: Checkout avo
+        uses: actions/checkout@5a4ac9002d0be2fb38bd78e4b4dbde5606d7042f # v2.3.4
+        with:
+          path: avo
+          persist-credentials: false
+      - name: Checkout orisano/wyhash
+        uses: actions/checkout@5a4ac9002d0be2fb38bd78e4b4dbde5606d7042f # v2.3.4
+        with:
+          repository: orisano/wyhash
+          ref: 32a3f7f6ba4797e2d87dab2969cc9dd63d39cce9
+          path: wyhash
+          persist-credentials: false
+      - name: Setup Generator Module
+        working-directory: wyhash/avo
+        run: go mod init github.com/orisano/wyhash/avo
+      - name: Avo Module Replacement
+        working-directory: wyhash/avo
+        run: |
+          go mod edit -modfile=go.mod -require=github.com/mmcloughlin/avo@v0.0.0-00010101000000-000000000000
+          go mod edit -modfile=go.mod -replace=github.com/mmcloughlin/avo=${{ github.workspace }}/avo
+          go mod tidy -modfile=go.mod
+      - name: Generate
+        working-directory: wyhash/avo
+        run: go run gen.go -out ../blocks_amd64.s -stubs ../blocks_amd64.go -pkg wyhash
+      - name: Diff
+        working-directory: wyhash
+        run: git diff
+      - name: Test
+        working-directory: wyhash
+        run: go test ./...
+  klauspost-compress-s2:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Install Go
+        uses: actions/setup-go@37335c7bb261b353407cff977110895fa0b4f7d8 # v2.1.3
+        with:
+          go-version: 1.17.x
+      - name: Checkout avo
+        uses: actions/checkout@5a4ac9002d0be2fb38bd78e4b4dbde5606d7042f # v2.3.4
+        with:
+          path: avo
+          persist-credentials: false
+      - name: Checkout klauspost/compress
+        uses: actions/checkout@5a4ac9002d0be2fb38bd78e4b4dbde5606d7042f # v2.3.4
+        with:
+          repository: klauspost/compress
+          ref: 2adf487b3e02f95ce7efd6e4953fda0ae7ecd080
+          path: compress
+          persist-credentials: false
+      - name: Avo Module Replacement
+        working-directory: compress/s2/_generate
+        run: |
+          go mod edit -modfile=go.mod -require=github.com/mmcloughlin/avo@v0.0.0-00010101000000-000000000000
+          go mod edit -modfile=go.mod -replace=github.com/mmcloughlin/avo=${{ github.workspace }}/avo
+          go mod tidy -modfile=go.mod
+      - name: Generate
+        working-directory: compress/s2/_generate
+        run: go run gen.go -out ../encodeblock_amd64.s -stubs ../encodeblock_amd64.go -pkg s2
+      - name: Diff
+        working-directory: compress/s2
+        run: git diff
+      - name: Test
+        working-directory: compress/s2
+        run: go test ./...
+  dgryski-go-bloomindex:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Install Go
+        uses: actions/setup-go@37335c7bb261b353407cff977110895fa0b4f7d8 # v2.1.3
+        with:
+          go-version: 1.17.x
+      - name: Checkout avo
+        uses: actions/checkout@5a4ac9002d0be2fb38bd78e4b4dbde5606d7042f # v2.3.4
+        with:
+          path: avo
+          persist-credentials: false
+      - name: Checkout dgryski/go-bloomindex
+        uses: actions/checkout@5a4ac9002d0be2fb38bd78e4b4dbde5606d7042f # v2.3.4
+        with:
+          repository: dgryski/go-bloomindex
+          ref: 0902316dce158c154b958ee5cfc706c62af29a42
+          path: go-bloomindex
+          persist-credentials: false
+      - name: Setup Root Module
+        working-directory: go-bloomindex
+        run: |
+          go mod init github.com/dgryski/go-bloomindex
+          go get github.com/dgryski/go-bits@v0.0.0-20180113010104-bd8a69a71dc2
+      - name: Create Generator Module
+        working-directory: go-bloomindex
+        run: |
+          mkdir avo
+          git mv asm.go avo
+      - name: Setup Generator Module
+        working-directory: go-bloomindex/avo
+        run: |
+          sed -i.bak '/+build ignore/d' asm.go
+          go mod init github.com/dgryski/go-bloomindex/avo
+      - name: Avo Module Replacement
+        working-directory: go-bloomindex/avo
+        run: |
+          go mod edit -modfile=go.mod -require=github.com/mmcloughlin/avo@v0.0.0-00010101000000-000000000000
+          go mod edit -modfile=go.mod -replace=github.com/mmcloughlin/avo=${{ github.workspace }}/avo
+          go mod tidy -modfile=go.mod
+      - name: Generate
+        working-directory: go-bloomindex/avo
+        run: go run asm.go -out ../query_amd64.s
+      - name: Diff
+        working-directory: go-bloomindex
+        run: git diff
+      - name: Test
+        working-directory: go-bloomindex
+        run: go test ./...
+  dgryski-go-marvin32:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Install Go
+        uses: actions/setup-go@37335c7bb261b353407cff977110895fa0b4f7d8 # v2.1.3
+        with:
+          go-version: 1.17.x
+      - name: Checkout avo
+        uses: actions/checkout@5a4ac9002d0be2fb38bd78e4b4dbde5606d7042f # v2.3.4
+        with:
+          path: avo
+          persist-credentials: false
+      - name: Checkout dgryski/go-marvin32
+        uses: actions/checkout@5a4ac9002d0be2fb38bd78e4b4dbde5606d7042f # v2.3.4
+        with:
+          repository: dgryski/go-marvin32
+          ref: 7d18f4c6ea7c24b29d1c7a670f8ae40b0812f2e3
+          path: go-marvin32
+          persist-credentials: false
+      - name: Setup Root Module
+        working-directory: go-marvin32
+        run: go mod init github.com/dgryski/go-marvin32
+      - name: Create Generator Module
+        working-directory: go-marvin32
+        run: |
+          mkdir avo
+          git mv asm.go avo
+      - name: Setup Generator Module
+        working-directory: go-marvin32/avo
+        run: |
+          sed -i.bak '/+build ignore/d' asm.go
+          go mod init github.com/dgryski/go-marvin32/avo
+      - name: Avo Module Replacement
+        working-directory: go-marvin32/avo
+        run: |
+          go mod edit -modfile=go.mod -require=github.com/mmcloughlin/avo@v0.0.0-00010101000000-000000000000
+          go mod edit -modfile=go.mod -replace=github.com/mmcloughlin/avo=${{ github.workspace }}/avo
+          go mod tidy -modfile=go.mod
+      - name: Generate
+        working-directory: go-marvin32/avo
+        run: |
+          go mod edit -modfile=go.mod -require=github.com/dgryski/go-marvin32@v0.0.0-00010101000000-000000000000
+          go mod edit -modfile=go.mod -replace=github.com/dgryski/go-marvin32=../
+          go run asm.go -out ../marvin_amd64.s
+      - name: Diff
+        working-directory: go-marvin32
+        run: git diff
+      - name: Test
+        working-directory: go-marvin32
+        run: go test ./...
+  dgryski-go-speck:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Install Go
+        uses: actions/setup-go@37335c7bb261b353407cff977110895fa0b4f7d8 # v2.1.3
+        with:
+          go-version: 1.17.x
+      - name: Checkout avo
+        uses: actions/checkout@5a4ac9002d0be2fb38bd78e4b4dbde5606d7042f # v2.3.4
+        with:
+          path: avo
+          persist-credentials: false
+      - name: Checkout dgryski/go-speck
+        uses: actions/checkout@5a4ac9002d0be2fb38bd78e4b4dbde5606d7042f # v2.3.4
+        with:
+          repository: dgryski/go-speck
+          ref: 5b36d4c08d8840c352a153bf37281434ad550ec0
+          path: go-speck
+          persist-credentials: false
+      - name: Setup Root Module
+        working-directory: go-speck
+        run: |
+          go mod init github.com/dgryski/go-speck
+          go get github.com/dgryski/go-skipjack@v0.0.0-20150401095227-f3a984a142ab
+      - name: Create Generator Module
+        working-directory: go-speck
+        run: |
+          mkdir avo
+          git mv asm.go avo
+      - name: Setup Generator Module
+        working-directory: go-speck/avo
+        run: |
+          sed -i.bak '/+build ignore/d' asm.go
+          go mod init github.com/dgryski/go-speck/avo
+      - name: Avo Module Replacement
+        working-directory: go-speck/avo
+        run: |
+          go mod edit -modfile=go.mod -require=github.com/mmcloughlin/avo@v0.0.0-00010101000000-000000000000
+          go mod edit -modfile=go.mod -replace=github.com/mmcloughlin/avo=${{ github.workspace }}/avo
+          go mod tidy -modfile=go.mod
+      - name: Generate
+        working-directory: go-speck/avo
+        run: |
+          go mod edit -modfile=go.mod -require=github.com/dgryski/go-speck@v0.0.0-00010101000000-000000000000
+          go mod edit -modfile=go.mod -replace=github.com/dgryski/go-speck=../
+          go run asm.go -out ../speck_amd64.s
+      - name: Diff
+        working-directory: go-speck
+        run: git diff
+      - name: Test
+        working-directory: go-speck
+        run: go test ./...
+  dgryski-go-chaskey:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Install Go
+        uses: actions/setup-go@37335c7bb261b353407cff977110895fa0b4f7d8 # v2.1.3
+        with:
+          go-version: 1.17.x
+      - name: Checkout avo
+        uses: actions/checkout@5a4ac9002d0be2fb38bd78e4b4dbde5606d7042f # v2.3.4
+        with:
+          path: avo
+          persist-credentials: false
+      - name: Checkout dgryski/go-chaskey
+        uses: actions/checkout@5a4ac9002d0be2fb38bd78e4b4dbde5606d7042f # v2.3.4
+        with:
+          repository: dgryski/go-chaskey
+          ref: ba454392bc5ab6daae103e15147185f8f4a27dcc
+          path: go-chaskey
+          persist-credentials: false
+      - name: Setup Root Module
+        working-directory: go-chaskey
+        run: |
+          go mod init github.com/dgryski/go-chaskey
+          go get github.com/dchest/siphash@v1.2.2
+      - name: Create Generator Module
+        working-directory: go-chaskey
+        run: |
+          mkdir avo
+          git mv asm.go avo
+      - name: Setup Generator Module
+        working-directory: go-chaskey/avo
+        run: |
+          sed -i.bak '/+build ignore/d' asm.go
+          go mod init github.com/dgryski/go-chaskey/avo
+      - name: Avo Module Replacement
+        working-directory: go-chaskey/avo
+        run: |
+          go mod edit -modfile=go.mod -require=github.com/mmcloughlin/avo@v0.0.0-00010101000000-000000000000
+          go mod edit -modfile=go.mod -replace=github.com/mmcloughlin/avo=${{ github.workspace }}/avo
+          go mod tidy -modfile=go.mod
+      - name: Generate
+        working-directory: go-chaskey/avo
+        run: |
+          go mod edit -modfile=go.mod -require=github.com/dgryski/go-chaskey@v0.0.0-00010101000000-000000000000
+          go mod edit -modfile=go.mod -replace=github.com/dgryski/go-chaskey=../
+          go run asm.go -out ../core_amd64.s
+      - name: Diff
+        working-directory: go-chaskey
+        run: git diff
+      - name: Test
+        working-directory: go-chaskey
+        run: go test ./...
+  lukechampine-us-merkle-blake2b:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Install Go
+        uses: actions/setup-go@37335c7bb261b353407cff977110895fa0b4f7d8 # v2.1.3
+        with:
+          go-version: 1.17.x
+      - name: Checkout avo
+        uses: actions/checkout@5a4ac9002d0be2fb38bd78e4b4dbde5606d7042f # v2.3.4
+        with:
+          path: avo
+          persist-credentials: false
+      - name: Checkout lukechampine/us
+        uses: actions/checkout@5a4ac9002d0be2fb38bd78e4b4dbde5606d7042f # v2.3.4
+        with:
+          repository: lukechampine/us
+          ref: dff56a80f83653cb14eeeb57ba6ba3c3e942c412
+          path: us
+          persist-credentials: false
+      - name: Create Generator Module
+        working-directory: us/merkle/blake2b
+        run: |
+          mkdir avo
+          git mv gen.go avo
+      - name: Setup Generator Module
+        working-directory: us/merkle/blake2b/avo
+        run: |
+          sed -i.bak '/+build ignore/d' gen.go
+          go mod init github.com/lukechampine/us/merkle/blake2b/avo
+      - name: Avo Module Replacement
+        working-directory: us/merkle/blake2b/avo
+        run: |
+          go mod edit -modfile=go.mod -require=github.com/mmcloughlin/avo@v0.0.0-00010101000000-000000000000
+          go mod edit -modfile=go.mod -replace=github.com/mmcloughlin/avo=${{ github.workspace }}/avo
+          go mod tidy -modfile=go.mod
+      - name: Generate
+        working-directory: us/merkle/blake2b/avo
+        run: go run gen.go -out ../blake2b_amd64.s
+      - name: Diff
+        working-directory: us/merkle/blake2b
+        run: git diff
+      - name: Test
+        working-directory: us/merkle/blake2b
+        run: go test ./...
diff --git a/.github/workflows/thirdparty.yml b/.github/workflows/thirdparty.yml
new file mode 100644
index 0000000..2e773c3
--- /dev/null
+++ b/.github/workflows/thirdparty.yml
@@ -0,0 +1,34 @@
+name: thirdparty
+
+permissions:
+  contents: read
+
+on:
+  push:
+    branches:
+      - master
+    paths:
+      - "tests/thirdparty/**"
+  pull_request:
+    paths:
+      - "tests/thirdparty/**"
+
+jobs:
+  test:
+    strategy:
+      matrix:
+        go-version: [1.17.x]
+        platform: [ubuntu-latest]
+    runs-on: ${{ matrix.platform }}
+    steps:
+      - name: Install Go
+        uses: actions/setup-go@37335c7bb261b353407cff977110895fa0b4f7d8 # v2.1.3
+        with:
+          go-version: ${{ matrix.go-version }}
+      - name: Checkout code
+        uses: actions/checkout@5a4ac9002d0be2fb38bd78e4b4dbde5606d7042f # v2.3.4
+        with:
+          persist-credentials: false
+      - name: Run Third-Party Tests
+        working-directory: tests/thirdparty
+        run: go test -pkgs packages.json
diff --git a/internal/prnt/printer.go b/internal/prnt/printer.go
index 410895c..904d1b2 100644
--- a/internal/prnt/printer.go
+++ b/internal/prnt/printer.go
@@ -13,8 +13,11 @@ import (
 // any errors to be stored so they can be checked at the end, rather than having
 // error checks obscuring the code generation.
 type Generator struct {
-	buf bytes.Buffer
-	err error
+	buf     bytes.Buffer
+	level   int    // current indentation level
+	indent  string // indentation string
+	pending bool   // if there's a pending indentation
+	err     error  // saved error from printing
 }
 
 // Raw provides direct access to the underlying output stream.
@@ -22,11 +25,38 @@ func (g *Generator) Raw() io.Writer {
 	return &g.buf
 }
 
+// SetIndentString sets the string used for one level of indentation. Use
+// Indent() and Dedent() to control indent level.
+func (g *Generator) SetIndentString(indent string) {
+	g.indent = indent
+}
+
+// Indent increments the indent level.
+func (g *Generator) Indent() {
+	g.level++
+}
+
+// Dedent decrements the indent level.
+func (g *Generator) Dedent() {
+	g.level--
+}
+
+// Linef prints formatted output terminated with a new line.
+func (g *Generator) Linef(format string, args ...interface{}) {
+	g.Printf(format, args...)
+	g.NL()
+}
+
 // Printf prints to the internal buffer.
 func (g *Generator) Printf(format string, args ...interface{}) {
 	if g.err != nil {
 		return
 	}
+	if g.pending {
+		indent := strings.Repeat(g.indent, g.level)
+		format = indent + format
+		g.pending = false
+	}
 	_, err := fmt.Fprintf(&g.buf, format, args...)
 	g.AddError(err)
 }
@@ -34,6 +64,7 @@ func (g *Generator) Printf(format string, args ...interface{}) {
 // NL prints a new line.
 func (g *Generator) NL() {
 	g.Printf("\n")
+	g.pending = true
 }
 
 // Comment writes comment lines prefixed with "// ".
diff --git a/tests/thirdparty/config.go b/tests/thirdparty/config.go
index d857a32..1e7d0a5 100644
--- a/tests/thirdparty/config.go
+++ b/tests/thirdparty/config.go
@@ -3,51 +3,226 @@ package thirdparty
 
 import (
 	"encoding/json"
+	"errors"
+	"fmt"
 	"io"
 	"os"
+	"path"
 	"path/filepath"
+	"strings"
 )
 
-// Package defines an integration test based on a third-party package using avo.
-type Package struct {
-	ImportPath string     `json:"import_path"` // package import path
-	Version    string     `json:"version"`     // git sha, tag or branch
-	Generate   [][]string `json:"generate"`    // generate commands to run
-	Dir        string     `json:"dir"`         // working directory for generate commands
-	Test       string     `json:"test"`        // test path relative to repo root (if empty defaults to ./...)
+// GithubRepository specifies a repository on github.
+type GithubRepository struct {
+	Owner string `json:"owner"`
+	Name  string `json:"name"`
 }
 
-// Name returns the package name.
-func (p Package) Name() string {
-	return filepath.Base(p.ImportPath)
+func (r GithubRepository) String() string {
+	return path.Join(r.Owner, r.Name)
 }
 
 // CloneURL returns the git clone URL.
-func (p Package) CloneURL() string {
-	return "https://" + p.ImportPath + ".git"
+func (r GithubRepository) CloneURL() string {
+	return fmt.Sprintf("https://github.com/%s.git", r)
 }
 
-// TestPath returns the paths to run "go test" on, relative to the repository root.
-func (p Package) TestPath() string {
-	if p.Test == "" {
-		return "./..."
+// Step represents a set of commands to run as part of the testing plan for a
+// third-party package.
+type Step struct {
+	Name             string   `json:"name"`
+	WorkingDirectory string   `json:"dir"`
+	Commands         []string `json:"commands"`
+}
+
+// Validate step parameters.
+func (s *Step) Validate() error {
+	if s.Name == "" {
+		return errors.New("missing name")
 	}
-	return p.Test
+	if len(s.Commands) == 0 {
+		return errors.New("missing commands")
+	}
+	return nil
+}
+
+// Package defines an integration test based on a third-party package using avo.
+type Package struct {
+	// Repository the package belongs to. At the moment, all packages are
+	// available on github.
+	Repository GithubRepository `json:"repository"`
+
+	// Version as a git sha, tag or branch.
+	Version string `json:"version"`
+
+	// Sub-package within the repository under test. All file path references
+	// will be relative to this directory. If empty the root of the repository
+	// is used.
+	SubPackage string `json:"pkg"`
+
+	// Path to the module file for the avo generator package. This is necessary
+	// so the integration test can insert replace directives to point at the avo
+	// version under test.
+	Module string `json:"module"`
+
+	// Setup steps. These run prior to the insertion of avo replace directives,
+	// therefore should be used if it's necessary to initialize new go modules
+	// within the repository.
+	Setup []*Step `json:"setup"`
+
+	// Steps to run the avo code generator.
+	Generate []*Step `json:"generate"` // generate commands to run
+
+	// Test steps. If empty, defaults to "go test ./...".
+	Test []*Step `json:"test"`
+}
+
+// ID returns an identifier for the package.
+func (p *Package) ID() string {
+	pkgpath := path.Join(p.Repository.String(), p.SubPackage)
+	return strings.ReplaceAll(pkgpath, "/", "-")
+}
+
+// setdefaults fills in missing parameters to help make the input package
+// descriptions less verbose.
+func (p *Package) setdefaults() {
+	for _, stage := range []struct {
+		Steps       []*Step
+		DefaultName string
+	}{
+		{p.Setup, "Setup"},
+		{p.Generate, "Generate"},
+		{p.Test, "Test"},
+	} {
+		if len(stage.Steps) == 1 && stage.Steps[0].Name == "" {
+			stage.Steps[0].Name = stage.DefaultName
+		}
+	}
+}
+
+// Validate package definition.
+func (p *Package) Validate() error {
+	if p.Version == "" {
+		return errors.New("missing version")
+	}
+	if p.Module == "" {
+		return errors.New("missing module")
+	}
+	if len(p.Generate) == 0 {
+		return errors.New("no generate commands")
+	}
+
+	stages := map[string][]*Step{
+		"setup":    p.Setup,
+		"generate": p.Generate,
+		"test":     p.Test,
+	}
+	for name, steps := range stages {
+		for _, s := range steps {
+			if err := s.Validate(); err != nil {
+				return fmt.Errorf("%s step: %w", name, err)
+			}
+		}
+	}
+
+	return nil
+}
+
+// Context specifies execution environment parameters for a third-party test.
+type Context struct {
+	// Path to the avo version under test.
+	AvoDirectory string
+
+	// Path to the checked out third-party repository.
+	RepositoryDirectory string
+}
+
+// Steps generates the list of steps required to execute the integration test
+// for this package. Context specifies execution environment parameters.
+func (p *Package) Steps(c *Context) []*Step {
+	var steps []*Step
+
+	// Optional setup.
+	steps = append(steps, p.Setup...)
+
+	// Replace avo dependency.
+	const invalid = "v0.0.0-00010101000000-000000000000"
+	moddir := filepath.Dir(p.Module)
+	modfile := filepath.Base(p.Module)
+	steps = append(steps, &Step{
+		Name:             "Avo Module Replacement",
+		WorkingDirectory: moddir,
+		Commands: []string{
+			"go mod edit -modfile=" + modfile + " -require=github.com/mmcloughlin/avo@" + invalid,
+			"go mod edit -modfile=" + modfile + " -replace=github.com/mmcloughlin/avo=" + c.AvoDirectory,
+			"go mod tidy -modfile=" + modfile,
+		},
+	})
+
+	// Run generation.
+	steps = append(steps, p.Generate...)
+
+	// Display changes.
+	steps = append(steps, &Step{
+		Name:     "Diff",
+		Commands: []string{"git diff"},
+	})
+
+	// Tests.
+	if len(p.Test) > 0 {
+		steps = append(steps, p.Test...)
+	} else {
+		steps = append(steps, &Step{
+			Name: "Test",
+			Commands: []string{
+				"go test ./...",
+			},
+		})
+	}
+
+	// Prepend sub-directory to every step.
+	if p.SubPackage != "" {
+		for _, s := range steps {
+			s.WorkingDirectory = filepath.Join(p.SubPackage, s.WorkingDirectory)
+		}
+	}
+
+	return steps
+}
+
+// Packages is a collection of third-party integration tests.
+type Packages []*Package
+
+func (p Packages) setdefaults() {
+	for _, pkg := range p {
+		pkg.setdefaults()
+	}
+}
+
+// Validate the package collection.
+func (p Packages) Validate() error {
+	for _, pkg := range p {
+		if err := pkg.Validate(); err != nil {
+			return fmt.Errorf("package %s: %w", pkg.ID(), err)
+		}
+	}
+	return nil
 }
 
 // LoadPackages loads a list of package configurations from JSON format.
-func LoadPackages(r io.Reader) ([]Package, error) {
-	var pkgs []Package
+func LoadPackages(r io.Reader) (Packages, error) {
+	var pkgs Packages
 	d := json.NewDecoder(r)
 	d.DisallowUnknownFields()
 	if err := d.Decode(&pkgs); err != nil {
 		return nil, err
 	}
+	pkgs.setdefaults()
 	return pkgs, nil
 }
 
 // LoadPackagesFile loads a list of package configurations from a JSON file.
-func LoadPackagesFile(filename string) ([]Package, error) {
+func LoadPackagesFile(filename string) (Packages, error) {
 	f, err := os.Open(filename)
 	if err != nil {
 		return nil, err
diff --git a/tests/thirdparty/config_test.go b/tests/thirdparty/config_test.go
index 88bd8a8..81cc399 100644
--- a/tests/thirdparty/config_test.go
+++ b/tests/thirdparty/config_test.go
@@ -5,33 +5,85 @@ import (
 	"testing"
 )
 
-func TestPackageName(t *testing.T) {
-	p := Package{ImportPath: "github.com/username/repo"}
-	if p.Name() != "repo" {
-		t.Fail()
+func TestValidateErrors(t *testing.T) {
+	cases := []struct {
+		Name           string
+		Item           interface{ Validate() error }
+		ErrorSubstring string
+	}{
+		{
+			Name:           "step_missing_name",
+			Item:           &Step{},
+			ErrorSubstring: "missing name",
+		},
+		{
+			Name: "step_missing_commands",
+			Item: &Step{
+				Name: "Setup",
+			},
+			ErrorSubstring: "missing commands",
+		},
+		{
+			Name: "package_missing_version",
+			Item: &Package{
+				Repository: GithubRepository{Owner: "octocat", Name: "hello-world"},
+			},
+			ErrorSubstring: "missing version",
+		},
+		{
+			Name: "package_missing_module",
+			Item: &Package{
+				Repository: GithubRepository{Owner: "octocat", Name: "hello-world"},
+				Version:    "v1.0.1",
+			},
+			ErrorSubstring: "missing module",
+		},
+		{
+			Name: "package_no_generate_commands",
+			Item: &Package{
+				Repository: GithubRepository{Owner: "octocat", Name: "hello-world"},
+				Version:    "v1.0.1",
+				Module:     "avo/go.mod",
+			},
+			ErrorSubstring: "no generate commands",
+		},
+		{
+			Name: "package_invalid_generate_commands",
+			Item: &Package{
+				Repository: GithubRepository{Owner: "octocat", Name: "hello-world"},
+				Version:    "v1.0.1",
+				Module:     "avo/go.mod",
+				Generate: []*Step{
+					{},
+				},
+			},
+			ErrorSubstring: "generate step: missing name",
+		},
+		{
+			Name: "packages_invalid_package",
+			Item: Packages{
+				{
+					Repository: GithubRepository{Owner: "octocat", Name: "hello-world"},
+				},
+			},
+			ErrorSubstring: "missing version",
+		},
+	}
+	for _, c := range cases {
+		c := c // scopelint
+		t.Run(c.Name, func(t *testing.T) {
+			err := c.Item.Validate()
+			if err == nil {
+				t.Fatal("expected error; got nil")
+			}
+			if !strings.Contains(err.Error(), c.ErrorSubstring) {
+				t.Fatalf("expected error message to contain %q; got %q", c.ErrorSubstring, err)
+			}
+		})
 	}
 }
 
-func TestPackageCloneURL(t *testing.T) {
-	p := Package{ImportPath: "github.com/username/repo"}
-	if p.CloneURL() != "https://github.com/username/repo.git" {
-		t.Fail()
-	}
-}
-
-func TestPackagesTestPath(t *testing.T) {
-	p := Package{}
-	if p.TestPath() != "./..." {
-		t.Fail()
-	}
-
-	p.Test = "./sub"
-	if p.TestPath() != "./sub" {
-		t.Fail()
-	}
-}
-
-func TestLoadPackages(t *testing.T) {
+func TestLoadPackagesBad(t *testing.T) {
 	r := strings.NewReader(`[{"unknown_field": "value"}]`)
 	_, err := LoadPackages(r)
 	if err == nil {
@@ -39,19 +91,6 @@ func TestLoadPackages(t *testing.T) {
 	}
 }
 
-func TestLoadPackagesFile(t *testing.T) {
-	pkgs, err := LoadPackagesFile("packages.json")
-	if err != nil {
-		t.Fatal(err)
-	}
-	for _, pkg := range pkgs {
-		t.Log(pkg.ImportPath)
-	}
-	if len(pkgs) == 0 {
-		t.Fatal("no packages loaded")
-	}
-}
-
 func TestLoadPackagesFileNotExist(t *testing.T) {
 	pkgs, err := LoadPackagesFile("does_not_exist")
 	if pkgs != nil {
@@ -61,3 +100,37 @@ func TestLoadPackagesFileNotExist(t *testing.T) {
 		t.Fatal("expected non-nil error")
 	}
 }
+
+func TestPackagesFileValid(t *testing.T) {
+	pkgs, err := LoadPackagesFile("packages.json")
+	if err != nil {
+		t.Fatal(err)
+	}
+	for _, pkg := range pkgs {
+		t.Logf("read: %s", pkg.ID())
+	}
+	if len(pkgs) == 0 {
+		t.Fatal("no packages loaded")
+	}
+	if err := pkgs.Validate(); err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestPackagesFileStepsValid(t *testing.T) {
+	pkgs, err := LoadPackagesFile("packages.json")
+	if err != nil {
+		t.Fatal(err)
+	}
+	c := &Context{
+		AvoDirectory:        "avo",
+		RepositoryDirectory: "repo",
+	}
+	for _, pkg := range pkgs {
+		for _, s := range pkg.Steps(c) {
+			if err := s.Validate(); err != nil {
+				t.Errorf("package %s: %s", pkg.ID(), err)
+			}
+		}
+	}
+}
diff --git a/tests/thirdparty/make_workflow.go b/tests/thirdparty/make_workflow.go
new file mode 100644
index 0000000..f46f019
--- /dev/null
+++ b/tests/thirdparty/make_workflow.go
@@ -0,0 +1,148 @@
+//go:build ignore
+// +build ignore
+
+package main
+
+import (
+	"flag"
+	"log"
+	"os"
+	"path"
+	"path/filepath"
+	"runtime"
+
+	"github.com/mmcloughlin/avo/internal/prnt"
+	"github.com/mmcloughlin/avo/tests/thirdparty"
+)
+
+var (
+	pkgsfilename = flag.String("pkgs", "", "packages configuration")
+	output       = flag.String("output", "", "path to output file (default stdout)")
+)
+
+func main() {
+	if err := mainerr(); err != nil {
+		log.Fatal(err)
+	}
+}
+
+func mainerr() error {
+	flag.Parse()
+
+	// Read packages.
+	pkgs, err := thirdparty.LoadPackagesFile(*pkgsfilename)
+	if err != nil {
+		return err
+	}
+
+	if err := pkgs.Validate(); err != nil {
+		return err
+	}
+
+	// Determine output.
+	w := os.Stdout
+	if *output != "" {
+		f, err := os.Create(*output)
+		if err != nil {
+			return err
+		}
+		defer f.Close()
+		w = f
+	}
+
+	// Generate workflow file.
+	b, err := GenerateWorkflow(pkgs)
+	if err != nil {
+		return err
+	}
+
+	// Write output.
+	if _, err := w.Write(b); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func GenerateWorkflow(pkgs thirdparty.Packages) ([]byte, error) {
+	g := &prnt.Generator{}
+	g.SetIndentString("  ")
+
+	_, self, _, _ := runtime.Caller(0)
+	g.Linef("# Code generated by %s. DO NOT EDIT.", filepath.Base(self))
+	g.NL()
+
+	// Header.
+	g.Linef("name: packages")
+
+	g.Linef("permissions:")
+	g.Linef("  contents: read")
+
+	g.Linef("on:")
+	g.Linef("  push:")
+	g.Linef("    branches:")
+	g.Linef("      - master")
+	g.Linef("  pull_request:")
+
+	// One job per package.
+	g.NL()
+	g.Linef("jobs:")
+	g.Indent()
+	for _, pkg := range pkgs {
+		g.Linef("%s:", pkg.ID())
+		g.Indent()
+
+		g.Linef("runs-on: ubuntu-latest")
+		g.Linef("steps:")
+		g.Indent()
+
+		// Install Go.
+		g.Linef("- name: Install Go")
+		g.Linef("  uses: actions/setup-go@37335c7bb261b353407cff977110895fa0b4f7d8 # v2.1.3")
+		g.Linef("  with:")
+		g.Linef("    go-version: 1.17.x")
+
+		// Checkout avo.
+		avodir := "avo"
+		g.Linef("- name: Checkout avo")
+		g.Linef("  uses: actions/checkout@5a4ac9002d0be2fb38bd78e4b4dbde5606d7042f # v2.3.4")
+		g.Linef("  with:")
+		g.Linef("    path: %s", avodir)
+		g.Linef("    persist-credentials: false")
+
+		// Checkout the third-party package.
+		pkgdir := pkg.Repository.Name
+		g.Linef("- name: Checkout %s", pkg.Repository)
+		g.Linef("  uses: actions/checkout@5a4ac9002d0be2fb38bd78e4b4dbde5606d7042f # v2.3.4")
+		g.Linef("  with:")
+		g.Linef("    repository: %s", pkg.Repository)
+		g.Linef("    ref: %s", pkg.Version)
+		g.Linef("    path: %s", pkgdir)
+		g.Linef("    persist-credentials: false")
+
+		// Build steps.
+		c := &thirdparty.Context{
+			AvoDirectory:        path.Join("${{ github.workspace }}", avodir),
+			RepositoryDirectory: path.Join("${{ github.workspace }}", pkgdir),
+		}
+
+		for _, step := range pkg.Steps(c) {
+			g.Linef("- name: %s", step.Name)
+			g.Linef("  working-directory: %s", path.Join(pkgdir, step.WorkingDirectory))
+			if len(step.Commands) == 1 {
+				g.Linef("  run: %s", step.Commands[0])
+			} else {
+				g.Linef("  run: |")
+				for _, cmd := range step.Commands {
+					g.Linef("    %s", cmd)
+				}
+			}
+		}
+
+		g.Dedent()
+		g.Dedent()
+	}
+	g.Dedent()
+
+	return g.Result()
+}
diff --git a/tests/thirdparty/packages.json b/tests/thirdparty/packages.json
index 19e6b3c..5f3e19f 100644
--- a/tests/thirdparty/packages.json
+++ b/tests/thirdparty/packages.json
@@ -1,234 +1,371 @@
 [
     {
-        "import_path": "github.com/zeebo/xxh3",
-        "version": "65f423c10688c362d2a2ce6987b665c72ee7bddd",
-        "dir": "avo",
+        "repository": {
+            "owner": "zeebo",
+            "name": "xxh3"
+        },
+        "version": "v1.0.0-rc1",
+        "module": "avo/go.mod",
         "generate": [
-            [
-                "go",
-                "run",
-                "-mod=mod",
-                ".",
-                "-avx",
-                "-out",
-                "../vector_avx_amd64.s"
-            ],
-            [
-                "go",
-                "run",
-                ".",
-                "-sse",
-                "-out",
-                "../vector_sse_amd64.s"
-            ]
+            {
+                "dir": "avo",
+                "commands": [
+                    "go run . -avx -out ../accum_vector_avx_amd64.s",
+                    "go run . -sse -out ../accum_vector_sse_amd64.s"
+                ]
+            }
         ]
     },
     {
-        "import_path": "github.com/dgryski/go-sip13",
-        "version": "25c5027a8c7bfa6dab4b577e53e5c9068f6e2152",
-        "generate": [
-            [
-                "go",
-                "run",
-                "-mod=mod",
-                "_avo/asm.go",
-                "-out",
-                "sip13_amd64.s"
-            ]
-        ]
-    },
-    {
-        "import_path": "github.com/orisano/wyhash",
-        "version": "32a3f7f6ba4797e2d87dab2969cc9dd63d39cce9",
-        "generate": [
-            [
-                "go",
-                "run",
-                "-mod=mod",
-                "avo/gen.go",
-                "-out",
-                "blocks_amd64.s",
-                "-stubs",
-                "blocks_amd64.go"
-            ]
-        ]
-    },
-    {
-        "import_path": "github.com/dgryski/go-bloomindex",
-        "version": "0902316dce158c154b958ee5cfc706c62af29a42",
-        "generate": [
-            [
-                "go",
-                "run",
-                "asm.go",
-                "-out",
-                "query_amd64.s"
-            ]
-        ]
-    },
-    {
-        "import_path": "github.com/dgryski/go-marvin32",
-        "version": "7d18f4c6ea7c24b29d1c7a670f8ae40b0812f2e3",
-        "generate": [
-            [
-                "go",
-                "run",
-                "-mod=mod",
-                "asm.go",
-                "-out",
-                "marvin_amd64.s"
-            ]
-        ]
-    },
-    {
-        "import_path": "github.com/dgryski/go-speck",
-        "version": "5b36d4c08d8840c352a153bf37281434ad550ec0",
-        "generate": [
-            [
-                "go",
-                "run",
-                "asm.go",
-                "-out",
-                "speck_amd64.s"
-            ]
-        ]
-    },
-    {
-        "import_path": "github.com/dgryski/go-chaskey",
-        "version": "ba454392bc5ab6daae103e15147185f8f4a27dcc",
-        "generate": [
-            [
-                "go",
-                "run",
-                "asm.go",
-                "-out",
-                "core_amd64.s"
-            ]
-        ]
-    },
-    {
-        "import_path": "github.com/mkevac/gopherconrussia2019",
-        "version": "235b8b0156a20b4e078b88462e669730f99caeb1",
-        "dir": "simplesimd",
-        "generate": [
-            [
-                "go",
-                "run",
-                "asm.go",
-                "-out",
-                "simd.s",
-                "-stubs",
-                "stub.go"
-            ]
-        ]
-    },
-    {
-        "import_path": "github.com/phoreproject/bls",
-        "version": "9d5f85bf4a9badf491a1b9b27fb3344b489bd2c4",
-        "generate": [
-            [
-                "go",
-                "run",
-                "-mod=mod",
-                "asm/asm.go",
-                "-out",
-                "primitivefuncs_amd64.s"
-            ]
-        ]
-    },
-    {
-        "import_path": "github.com/klauspost/compress",
-        "version": "2adf487b3e02f95ce7efd6e4953fda0ae7ecd080",
-        "dir": "s2/_generate",
-        "generate": [
-            [
-                "go",
-                "run",
-                "-mod=mod",
-                "gen.go",
-                "-out",
-                "../encodeblock_amd64.s",
-                "-stubs",
-                "../encodeblock_amd64.go",
-                "-pkg",
-                "s2"
-            ]
+        "repository": {
+            "owner": "dgryski",
+            "name": "go-sip13"
+        },
+        "version": "62edffca92457b3a66125c686137cc5f0fe81672",
+        "module": "_avo/go.mod",
+        "setup": [
+            {
+                "name": "Setup Root Module",
+                "commands": [
+                    "go mod init github.com/dgryski/go-sip13"
+                ]
+            },
+            {
+                "name": "Setup Generator Module",
+                "dir": "_avo",
+                "commands": [
+                    "sed -i.bak '/+build ignore/d' asm.go",
+                    "go mod init github.com/dgryski/go-sip13/_avo"
+                ]
+            }
         ],
-        "test": "./s2"
-    },
-    {
-        "import_path": "github.com/klauspost/reedsolomon",
-        "version": "922778284547557265cff0f903ab5f4c27e40ae9",
-        "dir": "_gen",
         "generate": [
-            [
-                "go",
-                "run",
-                "-mod=mod",
-                "gen.go",
-                "-out",
-                "../galois_gen_amd64.s",
-                "-stubs",
-                "../galois_gen_amd64.go",
-                "-pkg",
-                "reedsolomon"
-            ]
+            {
+                "dir": "_avo",
+                "commands": [
+                    "go mod edit -modfile=go.mod -require=github.com/dgryski/go-sip13@v0.0.0-00010101000000-000000000000",
+                    "go mod edit -modfile=go.mod -replace=github.com/dgryski/go-sip13=../",
+                    "go run . -out ../sip13_amd64.s"
+                ]
+            }
         ]
     },
     {
-        "import_path": "github.com/minio/md5-simd",
+        "repository": {
+            "owner": "phoreproject",
+            "name": "bls"
+        },
+        "version": "a88a5ae26844d7293359422888d7c7f69f43c845",
+        "module": "asm/go.mod",
+        "setup": [
+            {
+                "dir": "asm",
+                "commands": [
+                    "sed -i.bak '/+build ignore/d' asm.go",
+                    "go mod init github.com/phoreproject/bls/asm"
+                ]
+            }
+        ],
+        "generate": [
+            {
+                "dir": "asm",
+                "commands": [
+                    "go mod edit -modfile=go.mod -require=github.com/phoreproject/bls@v0.0.0-00010101000000-000000000000",
+                    "go mod edit -modfile=go.mod -replace=github.com/phoreproject/bls=../",
+                    "go mod download",
+                    "go run . -out ../primitivefuncs_amd64.s"
+                ]
+            }
+        ]
+    },
+    {
+        "repository": {
+            "owner": "minio",
+            "name": "md5-simd"
+        },
         "version": "30ad8af83f6868c2a30c615f3edf1a9366bf3f89",
-        "dir": "_gen",
+        "module": "_gen/go.mod",
         "generate": [
-            [
-                "go",
-                "run",
-                "-mod=mod",
-                "gen.go",
-                "-out",
-                "../md5block_amd64.s",
-                "-stubs",
-                "../md5block_amd64.go",
-                "-pkg",
-                "md5simd"
-            ]
+            {
+                "dir": "_gen",
+                "commands": [
+                    "go run gen.go -out ../md5block_amd64.s -stubs ../md5block_amd64.go -pkg md5simd"
+                ]
+            }
         ]
     },
     {
-        "import_path": "github.com/zeebo/blake3",
+        "repository": {
+            "owner": "zeebo",
+            "name": "blake3"
+        },
         "version": "25dba572f0e78ec108f0dd79c9c15288f542d7d9",
-        "dir": "avo",
+        "module": "avo/go.mod",
         "generate": [
-            [
-                "go",
-                "run",
-                "-mod=mod",
-                "./avx2",
-                "-out",
-                "../avx2/impl.s"
-            ],
-            [
-                "go",
-                "run",
-                "./sse41",
-                "-out",
-                "../sse41/impl.s"
-            ]
+            {
+                "dir": "avo",
+                "commands": [
+                    "go run ./avx2 -out ../avx2/impl.s",
+                    "go run ./sse41 -out ../sse41/impl.s"
+                ]
+            }
         ]
     },
     {
-        "import_path": "github.com/lukechampine/us",
-        "version": "dff56a80f83653cb14eeeb57ba6ba3c3e942c412",
-        "dir": "merkle/blake2b",
+        "repository": {
+            "owner": "klauspost",
+            "name": "reedsolomon"
+        },
+        "version": "922778284547557265cff0f903ab5f4c27e40ae9",
+        "module": "_gen/go.mod",
         "generate": [
-            [
-                "go",
-                "run",
-                "gen.go",
-                "-out",
-                "blake2b_amd64.s"
-            ]
+            {
+                "dir": "_gen",
+                "commands": [
+                    "go run gen.go -out ../galois_gen_amd64.s -stubs ../galois_gen_amd64.go -pkg reedsolomon"
+                ]
+            }
+        ]
+    },
+    {
+        "repository": {
+            "owner": "orisano",
+            "name": "wyhash"
+        },
+        "version": "32a3f7f6ba4797e2d87dab2969cc9dd63d39cce9",
+        "module": "avo/go.mod",
+        "setup": [
+            {
+                "name": "Setup Generator Module",
+                "dir": "avo",
+                "commands": [
+                    "go mod init github.com/orisano/wyhash/avo"
+                ]
+            }
         ],
-        "test": "./merkle/..."
+        "generate": [
+            {
+                "dir": "avo",
+                "commands": [
+                    "go run gen.go -out ../blocks_amd64.s -stubs ../blocks_amd64.go -pkg wyhash"
+                ]
+            }
+        ]
+    },
+    {
+        "repository": {
+            "owner": "klauspost",
+            "name": "compress"
+        },
+        "version": "2adf487b3e02f95ce7efd6e4953fda0ae7ecd080",
+        "pkg": "s2",
+        "module": "_generate/go.mod",
+        "generate": [
+            {
+                "dir": "_generate",
+                "commands": [
+                    "go run gen.go -out ../encodeblock_amd64.s -stubs ../encodeblock_amd64.go -pkg s2"
+                ]
+            }
+        ]
+    },
+    {
+        "repository": {
+            "owner": "dgryski",
+            "name": "go-bloomindex"
+        },
+        "version": "0902316dce158c154b958ee5cfc706c62af29a42",
+        "module": "avo/go.mod",
+        "setup": [
+            {
+                "name": "Setup Root Module",
+                "commands": [
+                    "go mod init github.com/dgryski/go-bloomindex",
+                    "go get github.com/dgryski/go-bits@v0.0.0-20180113010104-bd8a69a71dc2"
+                ]
+            },
+            {
+                "name": "Create Generator Module",
+                "commands": [
+                    "mkdir avo",
+                    "git mv asm.go avo"
+                ]
+            },
+            {
+                "name": "Setup Generator Module",
+                "dir": "avo",
+                "commands": [
+                    "sed -i.bak '/+build ignore/d' asm.go",
+                    "go mod init github.com/dgryski/go-bloomindex/avo"
+                ]
+            }
+        ],
+        "generate": [
+            {
+                "dir": "avo",
+                "commands": [
+                    "go run asm.go -out ../query_amd64.s"
+                ]
+            }
+        ]
+    },
+    {
+        "repository": {
+            "owner": "dgryski",
+            "name": "go-marvin32"
+        },
+        "version": "7d18f4c6ea7c24b29d1c7a670f8ae40b0812f2e3",
+        "module": "avo/go.mod",
+        "setup": [
+            {
+                "name": "Setup Root Module",
+                "commands": [
+                    "go mod init github.com/dgryski/go-marvin32"
+                ]
+            },
+            {
+                "name": "Create Generator Module",
+                "commands": [
+                    "mkdir avo",
+                    "git mv asm.go avo"
+                ]
+            },
+            {
+                "name": "Setup Generator Module",
+                "dir": "avo",
+                "commands": [
+                    "sed -i.bak '/+build ignore/d' asm.go",
+                    "go mod init github.com/dgryski/go-marvin32/avo"
+                ]
+            }
+        ],
+        "generate": [
+            {
+                "dir": "avo",
+                "commands": [
+                    "go mod edit -modfile=go.mod -require=github.com/dgryski/go-marvin32@v0.0.0-00010101000000-000000000000",
+                    "go mod edit -modfile=go.mod -replace=github.com/dgryski/go-marvin32=../",
+                    "go run asm.go -out ../marvin_amd64.s"
+                ]
+            }
+        ]
+    },
+    {
+        "repository": {
+            "owner": "dgryski",
+            "name": "go-speck"
+        },
+        "version": "5b36d4c08d8840c352a153bf37281434ad550ec0",
+        "module": "avo/go.mod",
+        "setup": [
+            {
+                "name": "Setup Root Module",
+                "commands": [
+                    "go mod init github.com/dgryski/go-speck",
+                    "go get github.com/dgryski/go-skipjack@v0.0.0-20150401095227-f3a984a142ab"
+                ]
+            },
+            {
+                "name": "Create Generator Module",
+                "commands": [
+                    "mkdir avo",
+                    "git mv asm.go avo"
+                ]
+            },
+            {
+                "name": "Setup Generator Module",
+                "dir": "avo",
+                "commands": [
+                    "sed -i.bak '/+build ignore/d' asm.go",
+                    "go mod init github.com/dgryski/go-speck/avo"
+                ]
+            }
+        ],
+        "generate": [
+            {
+                "dir": "avo",
+                "commands": [
+                    "go mod edit -modfile=go.mod -require=github.com/dgryski/go-speck@v0.0.0-00010101000000-000000000000",
+                    "go mod edit -modfile=go.mod -replace=github.com/dgryski/go-speck=../",
+                    "go run asm.go -out ../speck_amd64.s"
+                ]
+            }
+        ]
+    },
+    {
+        "repository": {
+            "owner": "dgryski",
+            "name": "go-chaskey"
+        },
+        "version": "ba454392bc5ab6daae103e15147185f8f4a27dcc",
+        "module": "avo/go.mod",
+        "setup": [
+            {
+                "name": "Setup Root Module",
+                "commands": [
+                    "go mod init github.com/dgryski/go-chaskey",
+                    "go get github.com/dchest/siphash@v1.2.2"
+                ]
+            },
+            {
+                "name": "Create Generator Module",
+                "commands": [
+                    "mkdir avo",
+                    "git mv asm.go avo"
+                ]
+            },
+            {
+                "name": "Setup Generator Module",
+                "dir": "avo",
+                "commands": [
+                    "sed -i.bak '/+build ignore/d' asm.go",
+                    "go mod init github.com/dgryski/go-chaskey/avo"
+                ]
+            }
+        ],
+        "generate": [
+            {
+                "dir": "avo",
+                "commands": [
+                    "go mod edit -modfile=go.mod -require=github.com/dgryski/go-chaskey@v0.0.0-00010101000000-000000000000",
+                    "go mod edit -modfile=go.mod -replace=github.com/dgryski/go-chaskey=../",
+                    "go run asm.go -out ../core_amd64.s"
+                ]
+            }
+        ]
+    },
+    {
+        "repository": {
+            "owner": "lukechampine",
+            "name": "us"
+        },
+        "version": "dff56a80f83653cb14eeeb57ba6ba3c3e942c412",
+        "pkg": "merkle/blake2b",
+        "module": "avo/go.mod",
+        "setup": [
+            {
+                "name": "Create Generator Module",
+                "commands": [
+                    "mkdir avo",
+                    "git mv gen.go avo"
+                ]
+            },
+            {
+                "name": "Setup Generator Module",
+                "dir": "avo",
+                "commands": [
+                    "sed -i.bak '/+build ignore/d' gen.go",
+                    "go mod init github.com/lukechampine/us/merkle/blake2b/avo"
+                ]
+            }
+        ],
+        "generate": [
+            {
+                "dir": "avo",
+                "commands": [
+                    "go run gen.go -out ../blake2b_amd64.s"
+                ]
+            }
+        ]
     }
 ]
diff --git a/tests/thirdparty/packages_test.go b/tests/thirdparty/packages_test.go
index 25dabb3..3f43419 100644
--- a/tests/thirdparty/packages_test.go
+++ b/tests/thirdparty/packages_test.go
@@ -2,7 +2,6 @@ package thirdparty
 
 import (
 	"flag"
-	"os"
 	"os/exec"
 	"path/filepath"
 	"runtime"
@@ -11,6 +10,8 @@ import (
 	"github.com/mmcloughlin/avo/internal/test"
 )
 
+//go:generate go run make_workflow.go -pkgs packages.json -output ../../.github/workflows/packages.yml
+
 // Custom flags.
 var (
 	pkgsfilename = flag.String("pkgs", "", "packages configuration")
@@ -33,7 +34,7 @@ func TestPackages(t *testing.T) {
 
 	for _, pkg := range pkgs {
 		pkg := pkg // scopelint
-		t.Run(pkg.Name(), func(t *testing.T) {
+		t.Run(pkg.ID(), func(t *testing.T) {
 			dir, clean := test.TempDir(t)
 			if !*preserve {
 				defer clean()
@@ -54,57 +55,36 @@ func TestPackages(t *testing.T) {
 // PackageTest executes an integration test based on a given third-party package.
 type PackageTest struct {
 	*testing.T
-	Package
+	*Package
 
 	WorkDir string // working directory for the test
 	Latest  bool   // use latest version of the package
 
 	repopath string // path the repo is cloned to
-	cwd      string // working directory to execute commands in
 }
 
 // Run the test.
 func (t *PackageTest) Run() {
 	t.checkout()
-	t.modinit()
-	t.replaceavo()
-	t.diff()
-	t.generate()
-	t.diff()
-	t.test()
+	t.steps()
 }
 
 // checkout the code at the specified version.
 func (t *PackageTest) checkout() {
 	// Clone repo.
 	dst := filepath.Join(t.WorkDir, t.Name())
-	t.git("clone", "--quiet", t.CloneURL(), dst)
+	test.Exec(t.T, "git", "clone", "--quiet", t.Repository.CloneURL(), dst)
 	t.repopath = dst
-	t.cd(t.repopath)
 
 	// Checkout specific version.
 	if t.Latest {
 		t.Log("using latest version")
 		return
 	}
-	t.git("-C", t.repopath, "checkout", "--quiet", t.Version)
+	test.Exec(t.T, "git", "-C", t.repopath, "checkout", "--quiet", t.Version)
 }
 
-// modinit initializes the repo as a go module if it isn't one already.
-func (t *PackageTest) modinit() {
-	// Check if module path already exists.
-	gomod := filepath.Join(t.repopath, "go.mod")
-	if _, err := os.Stat(gomod); err == nil {
-		t.Logf("already a module")
-		return
-	}
-
-	// Initialize the module.
-	t.gotool("mod", "init", t.ImportPath)
-}
-
-// replaceavo points all avo dependencies to the local version.
-func (t *PackageTest) replaceavo() {
+func (t *PackageTest) steps() {
 	// Determine the path to avo.
 	_, self, _, ok := runtime.Caller(1)
 	if !ok {
@@ -112,64 +92,17 @@ func (t *PackageTest) replaceavo() {
 	}
 	avodir := filepath.Join(filepath.Dir(self), "..", "..")
 
-	// Edit all go.mod files in the repo.
-	err := filepath.Walk(t.repopath, func(path string, info os.FileInfo, err error) error {
-		if err != nil {
-			return err
+	// Run steps.
+	c := &Context{
+		AvoDirectory:        avodir,
+		RepositoryDirectory: t.repopath,
+	}
+
+	for _, s := range t.Steps(c) {
+		for _, command := range s.Commands {
+			cmd := exec.Command("sh", "-c", command)
+			cmd.Dir = filepath.Join(t.repopath, s.WorkingDirectory)
+			test.ExecCommand(t.T, cmd)
 		}
-		dir, base := filepath.Split(path)
-		if base != "go.mod" {
-			return nil
-		}
-		t.cd(dir)
-		t.gotool("mod", "tidy")
-		t.gotool("get", "github.com/mmcloughlin/avo")
-		t.gotool("mod", "edit", "-replace=github.com/mmcloughlin/avo="+avodir)
-		t.gotool("mod", "download")
-		return nil
-	})
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	t.cd(t.repopath)
-}
-
-// generate runs generate commands.
-func (t *PackageTest) generate() {
-	if len(t.Generate) == 0 {
-		t.Fatal("no commands specified")
-	}
-	for _, args := range t.Generate {
-		cmd := exec.Command(args[0], args[1:]...)
-		cmd.Dir = filepath.Join(t.repopath, t.Dir)
-		test.ExecCommand(t.T, cmd)
 	}
 }
-
-// diff runs git diff on the repository.
-func (t *PackageTest) diff() {
-	t.git("-C", t.repopath, "diff")
-}
-
-// test runs go test.
-func (t *PackageTest) test() {
-	t.gotool("test", t.TestPath())
-}
-
-// git runs a git command.
-func (t *PackageTest) git(arg ...string) {
-	test.Exec(t.T, "git", arg...)
-}
-
-// gotool runs a go command.
-func (t *PackageTest) gotool(arg ...string) {
-	cmd := exec.Command(test.GoTool(), arg...)
-	cmd.Dir = t.cwd
-	test.ExecCommand(t.T, cmd)
-}
-
-// cd sets the working directory.
-func (t *PackageTest) cd(dir string) {
-	t.cwd = dir
-}