diff --git a/.github/workflows/build-awkward-cpp.yml b/.github/workflows/build-awkward-cpp.yml
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+# SPDX-FileCopyrightText: 2026 The RISE Project
+# SPDX-License-Identifier: MIT
+---
+# This workflow is based on the `make_sdist`/`build_wheels` jobs of
+# https://github.com/scikit-hep/awkward/blob/cef1a524fb52896b86ef505526f2fe4689f5e217/.github/workflows/reusable-build-wheels.yml
+name: Build awkward-cpp wheels (riscv64)
+
+on:
+  workflow_dispatch:
+    inputs:
+      version:
+        description: 'awkward-cpp version to build (e.g. 56)'
+        required: true
+        default: '56'
+  pull_request:
+    paths:
+      - '.github/workflows/build-awkward-cpp.yml'
+
+concurrency:
+  group: ${{ github.workflow }}-${{ inputs.version || '56' }}-${{ github.head_ref || github.run_id }}
+  cancel-in-progress: true
+
+permissions:
+  contents: read  # to fetch code (actions/checkout)
+
+env:
+  # `inputs.version` is empty on pull_request events; default to 56 there.
+  AWKWARD_CPP_VERSION: ${{ inputs.version || '56' }}
+  # awkward-cpp is released from the scikit-hep/awkward monorepo by a
+  # workflow_dispatch-only job (deploy-cpp.yml) that never pushes a git tag
+  # (gotcha 103). This is the version-bump commit ("awkward 2.13.0 and
+  # awkward-cpp 56"), verified byte-identical to the PyPI sdist. Update
+  # alongside AWKWARD_CPP_VERSION.
+  AWKWARD_CPP_REF: cef1a524fb52896b86ef505526f2fe4689f5e217
+  MANYLINUX_RISCV64_IMAGE: quay.io/pypa/manylinux_2_39_riscv64
+
+jobs:
+  setup:
+    uses: $/.github/workflows/_setup.yml
+
+  build_sdist:
+    needs: [setup]
+    # The sdist is architecture-independent; build it once on x86 instead of
+    # burning a scarce riscv runner (CLAUDE.md gotcha 4).
+    name: Build awkward-cpp ${{ inputs.version || '56' }} sdist
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+    outputs:
+      sdist_name: ${{ steps.sdist.outputs.sdist_name }}
+    steps:
+      - name: Checkout scikit-hep/awkward ${{ env.AWKWARD_CPP_REF }}
+        uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1  # v7.0.1
+        with:
+          repository: scikit-hep/awkward
+          ref: ${{ env.AWKWARD_CPP_REF }}
+          # rapidjson is a submodule of awkward-cpp/, and its LICENSE is one of
+          # the project's declared license-files.
+          submodules: true
+          persist-credentials: false
+
+      - name: Prepare build files
+        run: pipx run nox -s prepare
+
+      - name: Build awkward-cpp sdist
+        id: sdist
+        run: |
+          pipx run build --sdist awkward-cpp
+          pipx run twine check awkward-cpp/dist/*
+          sdists=(awkward-cpp/dist/*.tar.gz)
+          echo "sdist_name=$(basename "${sdists[0]}")" >> "$GITHUB_OUTPUT"
+
+      - name: Upload sdist artifact
+        uses: actions/upload-artifact@043fb46d1a93c77aae656e7c1c64a875d1fc6a0a  # v7.0.1
+        with:
+          name: awkward-cpp-${{ env.AWKWARD_CPP_VERSION }}-sdist
+          path: awkward-cpp/dist/*.tar.gz
+          if-no-files-found: error
+
+  build_wheels:
+    needs: [setup, build_sdist]
+    name: Build awkward-cpp ${{ inputs.version || '56' }} ${{ matrix.python }}-manylinux_riscv64
+    runs-on: ubuntu-24.04-riscv
+    timeout-minutes: 180
+    permissions:
+      contents: read
+    strategy:
+      fail-fast: false
+      matrix:
+        python: [cp312, cp313, cp314, cp314t]
+    steps:
+      - name: Download sdist
+        uses: actions/download-artifact@3e5f45b2cfb9172054b4087a40e8e0b5a5461e7c  # v8.0.1
+        with:
+          name: awkward-cpp-${{ env.AWKWARD_CPP_VERSION }}-sdist
+          path: dist/
+
+      - name: Build wheels
+        uses: pypa/cibuildwheel@1828c10ab37f080699c7b81cea34097c684a7074  # v4.2.0
+        with:
+          package-dir: dist/${{ needs.build_sdist.outputs.sdist_name }}
+        env:
+          CIBW_BUILD: ${{ matrix.python }}-manylinux_riscv64
+          CIBW_MANYLINUX_RISCV64_IMAGE: ${{ env.MANYLINUX_RISCV64_IMAGE }}
+          # Override upstream's build-frontend = "build[uv]": cibuildwheel's
+          # audit step makes a venv on the host and asserts a host `uv`
+          # exists, which this self-hosted runner has none of (gotcha 13).
+          CIBW_BUILD_FRONTEND: build
+          CIBW_ENVIRONMENT: >-
+            PIP_EXTRA_INDEX_URL=https://pypi.riseproject.dev/simple/
+            PIP_ONLY_BINARY=cmake,numpy
+          CIBW_TEST_REQUIRES: pytest>=6
+          CIBW_TEST_SOURCES: >-
+            tests-cpu-kernels tests-cpu-kernels-explicit
+            tests-spec tests-spec-explicit
+          # Upstream's own test-command also runs {project}/tests, which is
+          # the parent `awkward` package's suite (imports `awkward`, not
+          # awkward_cpp) - out of scope here since we only build awkward-cpp
+          # and `awkward` has no riscv64 wheel of its own.
+          CIBW_TEST_COMMAND: >-
+            pytest {package}/tests-cpu-kernels {package}/tests-cpu-kernels-explicit
+            {package}/tests-spec {package}/tests-spec-explicit
+
+      - uses: actions/upload-artifact@043fb46d1a93c77aae656e7c1c64a875d1fc6a0a  # v7.0.1
+        with:
+          name: awkward-cpp-${{ env.AWKWARD_CPP_VERSION }}-${{ matrix.python }}-manylinux_riscv64
+          path: ./wheelhouse/*.whl
+          if-no-files-found: error
+
+  publish:
+    name: Publish awkward-cpp ${{ inputs.version || '56' }}
+    needs: [setup, build_wheels]
+    permissions:
+      contents: write
+      pull-requests: write
+    uses: $/.github/workflows/_publish-wheel.yml
+    with:
+      artifact-pattern: awkward-cpp-${{ inputs.version || '56' }}-*-manylinux_riscv64