diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index d1c44ff..dd6d67a 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -17,6 +17,11 @@ name: Release
 #      build cannot forge, and the registries are configured to require it.
 #   6. No third-party actions in the publish path. Only actions/* and pypa/*.
 #
+# The npm tarball goes to two registries. npm resolves registries per scope with no per-package
+# override, and `@matchory/ui` lives on GitHub Packages, so a repository consuming both must point
+# the whole scope at one place. Publishing identical bytes to npmjs and GitHub Packages makes either
+# mapping work. npmjs is canonical and is the copy that carries provenance.
+#
 # Packagist is absent on purpose: it reads tags from this repository and builds nothing, so there is
 # no artefact to attest. Composer has no provenance mechanism, which makes the signed tag and the
 # repository's branch protection the whole of its supply-chain story. See SECURITY.md.
@@ -344,7 +349,7 @@ jobs:
         env:
           NPM_TOKEN: ${{ secrets.NPM_TOKEN }}
         run: |
-          if npm view @matchory/coding-style version --registry https://registry.npmjs.org > /dev/null 2>&1; then
+          if npm view @matchory/coding-style version --@matchory:registry=https://registry.npmjs.org > /dev/null 2>&1; then
             exists=true
           else
             exists=false
@@ -366,18 +371,30 @@ jobs:
             echo 'Publishing via OIDC trusted publishing'
           fi
 
-      # `publishConfig.registry` in package.json does NOT win over an `@scope:registry` entry in an
-      # .npmrc, and npm's provenance code does not validate which registry it is publishing to. So a
-      # stray scope mapping — a developer's ~/.npmrc, a repository .npmrc added later, setup-node's
-      # registry wiring — could redirect a provenance-signed release to another registry entirely.
-      # Pinning --registry on the command line removes that vector, and this asserts it took effect.
-      - name: The resolved publish registry is npmjs
+      # For a SCOPED package npm resolves the registry from `@scope:registry`, and only falls back to
+      # the generic `registry` key. `--registry` sets the generic key, so it loses to any
+      # `@matchory:registry` entry — in a developer .npmrc, a repository .npmrc, or setup-node's
+      # config. This was verified the hard way: a publish with `--registry https://registry.npmjs.org`
+      # went to GitHub Packages instead, because a scope mapping outranked it.
+      #
+      # `--@matchory:registry=` sets the key that actually wins. npm's provenance code does not
+      # validate the destination registry at all, so without this a provenance-signed release could
+      # land somewhere unintended.
+      - name: Confirm the publish target is npmjs
         run: |
-          resolved="$(npm config get @matchory:registry)"
+          target="$(npm publish ./dist/*.tgz \
+            --dry-run \
+            --@matchory:registry=https://registry.npmjs.org \
+            --access public \
+            --tag '${{ needs.verify.outputs.dist_tag }}' 2>&1 \
+            | grep -oE 'Publishing to [^ ]+' | head -1)"
 
-          if [ "${resolved}" != 'undefined' ] && [ "${resolved#https://registry.npmjs.org}" = "${resolved}" ]; then
-            echo "::warning::@matchory:registry resolves to ${resolved}; --registry overrides it for this publish"
-          fi
+          echo "${target:-<no target reported>}"
+
+          case "${target}" in
+            *'https://registry.npmjs.org'*) echo 'Target confirmed: npmjs' ;;
+            *) echo "::error::resolved publish target is not npmjs (${target:-unknown}); refusing to publish"; exit 1 ;;
+          esac
 
       - name: Publish
         env:
@@ -389,7 +406,7 @@ jobs:
           fi
 
           npm publish ./dist/*.tgz \
-            --registry https://registry.npmjs.org \
+            --@matchory:registry=https://registry.npmjs.org \
             --provenance \
             --access public \
             --tag '${{ needs.verify.outputs.dist_tag }}'
@@ -397,6 +414,57 @@ jobs:
           # Leave nothing behind on the runner even though it is ephemeral.
           npm config delete '//registry.npmjs.org/:_authToken' || true
 
+  publish-github-packages:
+    name: Publish to GitHub Packages
+    needs: [verify, build-npm, publish-npm]
+    runs-on: ubuntu-latest
+    environment: release
+    permissions:
+      contents: read
+      packages: write
+    steps:
+      - name: Set up Node
+        uses: actions/setup-node@249970729cb0ef3589644e2896645e5dc5ba9c38 # v6
+        with:
+          node-version: 24
+
+      - name: Pin npm
+        run: npm install -g "npm@${NPM_VERSION}"
+
+      - name: Download the attested tarball
+        uses: actions/download-artifact@018cc2cf5baa6db3ef3c5f8a56943fffe632ef53 # v6
+        with:
+          name: npm-tarball
+          path: dist
+
+      # Byte-identical to what npmjs received, and to what was attested.
+      - name: Checksum matches what was attested
+        run: |
+          cd dist
+          sha256sum --check ./*.sha256
+
+      # npm resolves a registry per SCOPE, with no per-package override. `@matchory/ui` is published
+      # here because it is proprietary, so any repository consuming it maps the whole `@matchory` scope
+      # to GitHub Packages — and would therefore never find this package on npmjs. Publishing the same
+      # tarball to both registries is what makes the scope work either way.
+      #
+      # npmjs remains canonical: it is public, carries the provenance statement, and is what external
+      # consumers and the README point at.
+      - name: Publish
+        env:
+          GH_PACKAGES_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        run: |
+          npm config set '//npm.pkg.github.com/:_authToken' "${GH_PACKAGES_TOKEN}"
+
+          # --provenance is deliberately omitted. GitHub Packages neither displays nor verifies npm
+          # provenance statements, and the same bytes already carry one on npmjs plus a GitHub artefact
+          # attestation. Generating a second statement here would add a claim nobody can check.
+          npm publish ./dist/*.tgz \
+            --@matchory:registry=https://npm.pkg.github.com \
+            --tag '${{ needs.verify.outputs.dist_tag }}'
+
+          npm config delete '//npm.pkg.github.com/:_authToken' || true
+
   publish-pypi:
     name: Publish to PyPI
     needs: [verify, build-python]
@@ -428,7 +496,7 @@ jobs:
 
   github-release:
     name: Publish the GitHub release
-    needs: [verify, publish-npm, publish-pypi]
+    needs: [verify, publish-npm, publish-github-packages, publish-pypi]
     runs-on: ubuntu-latest
     permissions:
       contents: write
diff --git a/CHANGELOG.md b/CHANGELOG.md
index b511553..202fb7d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -65,6 +65,10 @@ ecosystems, so a malicious version would run in our CI and on developer machines
 
 - OIDC **trusted publishing** on both npm and PyPI. No long-lived registry credential exists in this
   repository.
+- The npm package is published to **npmjs and GitHub Packages** from the same attested tarball. npm
+  resolves registries per scope with no per-package override, and `@matchory/ui` is on GitHub Packages,
+  so a repository consuming both has to point the whole scope at one registry. npmjs is canonical and
+  carries the provenance statement.
 - npm artefacts carry [provenance](https://docs.npmjs.com/generating-provenance-statements); PyPI
   artefacts carry [PEP 740](https://peps.python.org/pep-0740/) attestations. Both also get GitHub
   artefact attestations, verifiable with `gh attestation verify <file> --repo matchory/coding-style`.
diff --git a/README.md b/README.md
index 34c8f98..a29d79c 100644
--- a/README.md
+++ b/README.md
@@ -238,8 +238,16 @@ repository, like not using Rector at all.
 pnpm add -D @matchory/coding-style
 ```
 
-Published to GitHub Packages. Consumers need `@matchory:registry=https://npm.pkg.github.com` in
-`.npmrc`, same as `@matchory/ui`.
+Published to **both npmjs and GitHub Packages**, as identical bytes from the same attested tarball, so
+it resolves whichever way your `.npmrc` points the `@matchory` scope.
+
+That is not redundancy for its own sake. npm resolves a registry per *scope* and has no per-package
+override, and `@matchory/ui` is proprietary so it lives on GitHub Packages. A repository consuming both
+must therefore point the whole scope at one registry. Publishing to both is what lets it.
+
+npmjs is canonical: it is public, and it is the copy that carries
+[provenance](https://docs.npmjs.com/generating-provenance-statements). Prefer it unless you already map
+the scope to GitHub Packages for `@matchory/ui`.
 
 ESLint plugins are regular `dependencies` so their versions are pinned centrally — that is the point
 of the package. The tools themselves (`eslint`, `oxlint`, `oxfmt`, `typescript`) are optional peer
diff --git a/SECURITY.md b/SECURITY.md
index 2850fab..7bf03b5 100644
--- a/SECURITY.md
+++ b/SECURITY.md
@@ -27,6 +27,12 @@ npm audit signatures
 **PyPI** — published with [PEP 740](https://peps.python.org/pep-0740/) attestations, visible under
 the file's details on PyPI.
 
+The npm package is published to **npmjs and GitHub Packages** from the same attested tarball, because
+npm resolves registries per scope and `@matchory/ui` lives on GitHub Packages. The two copies are
+byte-identical, verified by SHA-256 before each upload. Only the npmjs copy carries an npm provenance
+statement: GitHub Packages neither displays nor verifies them, so generating a second statement there
+would add a claim nobody can check. The GitHub artefact attestation below covers both.
+
 **GitHub artefact attestations** — both the npm tarball and the Python distributions are attested and
 attached to the release:
 
@@ -99,6 +105,9 @@ Stated explicitly rather than left for someone to discover:
 
 - **Composer has no artefact provenance.** See above. The mitigation is repository protection plus
   signed tags.
+- **The GitHub Packages copy has no npm provenance statement**, only the shared GitHub artefact
+  attestation. It is byte-identical to the npmjs copy, which does carry provenance, and the checksum is
+  verified before upload. Verify against npmjs if you need the provenance chain.
 - **`@matchory/coding-style@0.0.0` was published from a maintainer machine and has no provenance.** npm
   cannot configure a trusted publisher for a package that does not exist, so something had to be
   published first. The placeholder contains only a README and the licence, is deprecated, and is not
diff --git a/js/README.md b/js/README.md
index 9dbf9da..289cfba 100644
--- a/js/README.md
+++ b/js/README.md
@@ -10,6 +10,9 @@ ruff presets for Python. All three share one version number.
 pnpm add -D @matchory/coding-style
 ```
 
+Published to both npmjs and GitHub Packages as identical bytes, so it resolves whichever registry your
+`.npmrc` maps the `@matchory` scope to. npmjs is canonical and carries provenance.
+
 ```ts
 // oxfmt.config.ts
 import { oxfmtBase } from '@matchory/coding-style/oxfmt';