diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
new file mode 100644
index 0000000..b92d0e5
--- /dev/null
+++ b/.github/workflows/ci.yml
@@ -0,0 +1,87 @@
+name: CI
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+  workflow_dispatch:
+
+defaults:
+  run:
+    shell: bash
+
+permissions:
+  contents: read
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: ${{ github.event_name == 'pull_request' }}
+
+env:
+  # Both Go files are cgo wrappers over the vendored evmone/intx C++ sources.
+  CGO_ENABLED: "1"
+  # go.mod declares go 1.17 as the module minimum; build with a current toolchain.
+  GO_VERSION: "1.25"
+
+jobs:
+  lint:
+    runs-on: ubuntu-latest
+    timeout-minutes: 15
+    steps:
+      - uses: actions/checkout@v7
+        with:
+          persist-credentials: false
+
+      - uses: actions/setup-go@v7
+        with:
+          go-version: ${{ env.GO_VERSION }}
+          # The module has no dependencies and no go.sum, so there is nothing
+          # for the dependency cache to key on.
+          cache: false
+
+      - uses: golangci/golangci-lint-action@v9
+        with:
+          version: v2.12.2
+
+  build:
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest, macos-latest]
+    runs-on: ${{ matrix.os }}
+    timeout-minutes: 20
+    steps:
+      - uses: actions/checkout@v7
+        with:
+          persist-credentials: false
+
+      - uses: actions/setup-go@v7
+        with:
+          go-version: ${{ env.GO_VERSION }}
+          cache: false
+
+      - name: Compiler versions
+        run: |
+          go version
+          ${CXX:-c++} --version
+
+      - run: go build ./...
+
+      - run: go vet ./...
+
+      - run: go test ./...
+
+  actionlint:
+    runs-on: ubuntu-latest
+    timeout-minutes: 10
+    steps:
+      - uses: actions/checkout@v7
+        with:
+          persist-credentials: false
+
+      - name: actionlint
+        run: |
+          curl -sSfL \
+            "https://github.com/rhysd/actionlint/releases/download/v1.7.12/actionlint_1.7.12_linux_amd64.tar.gz" \
+            | tar -xz -C /usr/local/bin actionlint
+          actionlint
diff --git a/.golangci.yml b/.golangci.yml
new file mode 100644
index 0000000..1a346fa
--- /dev/null
+++ b/.golangci.yml
@@ -0,0 +1,22 @@
+version: "2"
+
+run:
+  # Every package here is cgo; without this the linter sees no Go code at all.
+  build-tags: []
+
+linters:
+  default: standard
+  enable:
+    - misspell
+    - unconvert
+    - usestdlibvars
+  settings:
+    govet:
+      enable:
+        # The whole package is unsafe.Pointer conversions into C++.
+        - unsafeptr
+
+formatters:
+  enable:
+    - gofmt
+    - goimports