diff --git a/.github/workflows/npm-publish.yml b/.github/workflows/npm-publish.yml
index 449d04f..46f08a8 100644
--- a/.github/workflows/npm-publish.yml
+++ b/.github/workflows/npm-publish.yml
@@ -1,6 +1,5 @@
-# Publishes to npm when a GitHub release is created.
-# `npm publish` gates itself: prepack runs the build, prepublishOnly runs lint + tests.
-# For more information see: https://docs.github.com/en/actions/publishing-packages/publishing-nodejs-packages
+# Builds and verifies the release without npm credentials, then gives the
+# publish command the token only after it receives the finished tarball.
 
 name: Node.js Package
 
@@ -9,20 +8,82 @@ on:
     types: [created]
 
 jobs:
-  publish-npm:
+  build:
     runs-on: ubuntu-latest
     permissions:
       contents: read
-      id-token: write
+    outputs:
+      package-sha: ${{ steps.package.outputs.sha }}
     steps:
       - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7
+        with:
+          fetch-depth: 0
+          persist-credentials: false
+          ref: main
+      - name: Verify release source
+        env:
+          RELEASE_BODY: ${{ github.event.release.body }}
+          RELEASE_REF: ${{ github.ref }}
+          RELEASE_SHA: ${{ github.sha }}
+          RELEASE_TAG: ${{ github.event.release.tag_name }}
+        run: |
+          node tools/publish-check.mjs
+          release_commit=$(git rev-parse "refs/tags/${RELEASE_TAG}^{commit}")
+          git switch --detach "$release_commit"
       - uses: pnpm/action-setup@0977fd99725f1db4007ccb2928dbb4e90d06cc86 # v6
       - uses: actions/setup-node@820762786026740c76f36085b0efc47a31fe5020 # v7
         with:
           node-version: 24
           cache: pnpm
-          registry-url: https://registry.npmjs.org/
       - run: pnpm install --frozen-lockfile
-      - run: npm publish --access public --provenance
+      - name: Test and pack
+        run: |
+          pnpm exec safe-publish-latest --force-in-publish
+          pnpm run lint
+          pnpm run format
+          pnpm run typecheck
+          pnpm run test
+          pnpm run build
+          mkdir release-artifact
+          npm pack --ignore-scripts --pack-destination release-artifact
+      - name: Record package digest
+        id: package
+        run: |
+          shopt -s nullglob
+          packages=(release-artifact/*.tgz)
+          test "${#packages[@]}" -eq 1
+          echo "sha=$(sha256sum "${packages[0]}" | cut -d ' ' -f 1)" >> "$GITHUB_OUTPUT"
+      - uses: actions/upload-artifact@043fb46d1a93c77aae656e7c1c64a875d1fc6a0a # v7.0.1
+        with:
+          name: npm-package
+          path: release-artifact/*.tgz
+          if-no-files-found: error
+          retention-days: 1
+
+  publish-npm:
+    needs: build
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      id-token: write
+    steps:
+      - uses: actions/download-artifact@3e5f45b2cfb9172054b4087a40e8e0b5a5461e7c # v8.0.1
+        with:
+          name: npm-package
+          path: release-artifact
+      - uses: actions/setup-node@820762786026740c76f36085b0efc47a31fe5020 # v7
+        with:
+          node-version: 24
+          registry-url: https://registry.npmjs.org/
+      - name: Verify package digest
+        env:
+          EXPECTED_SHA: ${{ needs.build.outputs.package-sha }}
+        run: |
+          shopt -s nullglob
+          packages=(release-artifact/*.tgz)
+          test "${#packages[@]}" -eq 1
+          echo "$EXPECTED_SHA  ${packages[0]}" | sha256sum --check --strict
+      - name: Publish to npm
+        run: npm publish ./release-artifact/*.tgz --access public --provenance --ignore-scripts
         env:
           NODE_AUTH_TOKEN: ${{ secrets.npm_token }}
diff --git a/tools/publish-check.mjs b/tools/publish-check.mjs
new file mode 100644
index 0000000..698799e
--- /dev/null
+++ b/tools/publish-check.mjs
@@ -0,0 +1,113 @@
+// Run this from main before checking out the release. It inspects the tag as
+// data, so a bad tag cannot replace the checks that decide whether it ships.
+import { execFileSync, spawnSync } from "node:child_process";
+import { env } from "node:process";
+
+/**
+ * @param {string} message
+ * @returns {never}
+ */
+const fail = (message) => {
+  console.error(message);
+  process.exit(1);
+};
+
+/** @param {...string} args */
+const git = (...args) =>
+  execFileSync("git", args, {
+    encoding: "utf8",
+    stdio: ["pipe", "pipe", "pipe"],
+  }).trim();
+
+const releaseTag = env.RELEASE_TAG;
+if (!releaseTag) fail("RELEASE_TAG is missing, refusing to publish");
+
+const tagRef = `refs/tags/${releaseTag}`;
+if (env.RELEASE_REF !== tagRef) {
+  fail(`release ref is ${env.RELEASE_REF ?? "missing"} instead of ${tagRef}`);
+}
+
+let tagType;
+try {
+  tagType = git("cat-file", "-t", tagRef);
+} catch {
+  fail(`${releaseTag} is missing from the checkout`);
+}
+if (tagType !== "tag") {
+  fail(`${releaseTag} is not annotated, refusing to publish`);
+}
+
+const tagTarget = git("rev-parse", `${tagRef}^{commit}`);
+if (!env.RELEASE_SHA) fail("RELEASE_SHA is missing, refusing to publish");
+if (tagTarget !== env.RELEASE_SHA) {
+  fail(`${releaseTag} moved after the release event, refusing to publish`);
+}
+
+let packageJson;
+let changelog;
+try {
+  packageJson = JSON.parse(git("show", `${tagTarget}:package.json`));
+  changelog = git("show", `${tagTarget}:CHANGELOG.md`);
+} catch {
+  fail(`${releaseTag} has invalid release files`);
+}
+
+const { version } = packageJson;
+if (typeof version !== "string" || version.length === 0) {
+  fail(`${releaseTag} has no package version, refusing to publish`);
+}
+
+const expectedTag = `v${version}`;
+if (releaseTag !== expectedTag) {
+  fail(`release tag is ${releaseTag} instead of ${expectedTag}`);
+}
+
+const releaseHeading = `## [${version}]`;
+const releaseStart = changelog.search(/^## \[/mu);
+const nextRelease = changelog.indexOf("\n## [", releaseStart + 1);
+if (
+  releaseStart === -1 ||
+  !changelog.startsWith(releaseHeading, releaseStart)
+) {
+  fail(`the newest CHANGELOG.md release is not ${version}`);
+}
+const releaseNotes = `${changelog
+  .slice(releaseStart, nextRelease === -1 ? undefined : nextRelease)
+  .trim()}\n`;
+
+const tagObject = git("cat-file", "-p", tagRef);
+const annotationStart = tagObject.indexOf("\n\n");
+const annotation =
+  annotationStart === -1
+    ? ""
+    : `${tagObject.slice(annotationStart + 2).trim()}\n`;
+if (annotation !== releaseNotes) {
+  fail(`${releaseTag} annotation does not match CHANGELOG.md`);
+}
+
+const releaseBody = env.RELEASE_BODY;
+if (releaseBody === undefined) {
+  fail("RELEASE_BODY is missing, refusing to publish");
+}
+if (`${releaseBody.trimEnd()}\n` !== releaseNotes) {
+  fail("GitHub release notes do not match CHANGELOG.md");
+}
+
+const mainRef = env.RELEASE_MAIN_REF ?? "origin/main";
+const ancestry = spawnSync(
+  "git",
+  ["merge-base", "--is-ancestor", tagTarget, mainRef],
+  { encoding: "utf8" },
+);
+if (ancestry.error) throw ancestry.error;
+if (ancestry.status !== 0 && ancestry.status !== 1) {
+  process.stderr.write(ancestry.stderr);
+  fail(`could not verify ${mainRef}`);
+}
+if (ancestry.status === 1) {
+  fail(`${releaseTag} is not reachable from ${mainRef}`);
+}
+
+console.log(
+  `${releaseTag} is annotated, documented, and reachable from ${mainRef}`,
+);
diff --git a/tools/release-check.mjs b/tools/release-check.mjs
index 2cc24da..d197939 100644
--- a/tools/release-check.mjs
+++ b/tools/release-check.mjs
@@ -19,6 +19,7 @@ const here = import.meta.dirname;
 const root = dirname(here);
 const changelogPath = join(here, "changelog.mjs");
 const changelogPresetPath = join(here, "changelog-preset.mjs");
+const publishCheckPath = join(here, "publish-check.mjs");
 const tagReleasePath = join(here, "tag-release.mjs");
 
 /**
@@ -55,6 +56,39 @@ const runTagRelease = (repo) =>
     timeout: 30_000,
   });
 
+/**
+ * @param {string} repo
+ * @param {string} releaseTag
+ * @param {string} [mainRef]
+ * @param {string} [releaseBody]
+ * @param {string} [releaseSha]
+ */
+const runPublishCheck = (
+  repo,
+  releaseTag,
+  mainRef = "refs/heads/main",
+  releaseBody = "## [1.3.9] (2026-08-17)\n\n* secure the release tools\n",
+  releaseSha = git(
+    repo,
+    "rev-parse",
+    `refs/tags/${releaseTag}^{commit}`,
+  ).trim(),
+) => {
+  return spawnSync(process.execPath, [publishCheckPath], {
+    cwd: repo,
+    encoding: "utf8",
+    env: {
+      ...env,
+      RELEASE_BODY: releaseBody,
+      RELEASE_MAIN_REF: mainRef,
+      RELEASE_REF: `refs/tags/${releaseTag}`,
+      RELEASE_SHA: releaseSha,
+      RELEASE_TAG: releaseTag,
+    },
+    timeout: 30_000,
+  });
+};
+
 /**
  * @param {string} repo
  * @param {string} tagName
@@ -257,6 +291,119 @@ const checks = [
         assert.equal(tagObject(repo, "v1.3.9"), originalObject);
       }),
   ],
+  [
+    "publish accepts the matching annotated tag on main",
+    () =>
+      inTempDir((directory) => {
+        const repo = initReleaseRepo(directory);
+        const tagResult = runTagRelease(repo);
+        assert.equal(tagResult.status, 0, tagResult.stderr);
+
+        const result = runPublishCheck(repo, "v1.3.9");
+        assert.equal(result.status, 0, result.stderr);
+        assert.match(result.stdout, /annotated, documented/u);
+      }),
+  ],
+  [
+    "publish rejects a tag that does not match package.json",
+    () =>
+      inTempDir((directory) => {
+        const repo = initReleaseRepo(directory);
+        git(repo, "tag", "-a", "v1.3.8", "-m", "old name, new files");
+        const result = runPublishCheck(repo, "v1.3.8");
+        assert.notEqual(result.status, 0);
+        assert.match(result.stderr, /instead of v1\.3\.9/u);
+      }),
+  ],
+  [
+    "publish rejects a tag moved after the release event",
+    () =>
+      inTempDir((directory) => {
+        const repo = initReleaseRepo(directory);
+        const tagResult = runTagRelease(repo);
+        assert.equal(tagResult.status, 0, tagResult.stderr);
+        const releaseSha = tagTarget(repo, "v1.3.9");
+
+        git(repo, "tag", "--delete", "v1.3.9");
+        git(repo, "commit", "--quiet", "--allow-empty", "-m", "fix: later");
+        git(
+          repo,
+          "tag",
+          "-a",
+          "v1.3.9",
+          "-m",
+          "## [1.3.9] (2026-08-17)\n\n* secure the release tools",
+        );
+
+        const result = runPublishCheck(
+          repo,
+          "v1.3.9",
+          "refs/heads/main",
+          undefined,
+          releaseSha,
+        );
+        assert.notEqual(result.status, 0);
+        assert.match(result.stderr, /moved after the release event/u);
+      }),
+  ],
+  [
+    "publish rejects release notes that drift from the changelog",
+    () =>
+      inTempDir((directory) => {
+        const repo = initReleaseRepo(directory);
+        const tagResult = runTagRelease(repo);
+        assert.equal(tagResult.status, 0, tagResult.stderr);
+
+        const result = runPublishCheck(
+          repo,
+          "v1.3.9",
+          "refs/heads/main",
+          "## [1.3.9] (2026-08-17)\n\n* different notes\n",
+        );
+        assert.notEqual(result.status, 0);
+        assert.match(result.stderr, /release notes do not match/u);
+      }),
+  ],
+  [
+    "publish rejects a lightweight release tag",
+    () =>
+      inTempDir((directory) => {
+        const repo = initReleaseRepo(directory);
+        git(repo, "tag", "v1.3.9");
+
+        const result = runPublishCheck(repo, "v1.3.9");
+        assert.notEqual(result.status, 0);
+        assert.match(result.stderr, /not annotated/u);
+      }),
+  ],
+  [
+    "publish rejects a release tag outside main",
+    () =>
+      inTempDir((directory) => {
+        const repo = initReleaseRepo(directory);
+        const tagResult = runTagRelease(repo);
+        assert.equal(tagResult.status, 0, tagResult.stderr);
+        git(repo, "checkout", "--quiet", "--detach");
+        git(repo, "branch", "--force", "main", "HEAD^");
+
+        const result = runPublishCheck(repo, "v1.3.9");
+        assert.notEqual(result.status, 0);
+        assert.match(result.stderr, /not reachable/u);
+      }),
+  ],
+  [
+    "publish accepts a main checkout past the release tag",
+    () =>
+      inTempDir((directory) => {
+        const repo = initReleaseRepo(directory);
+        const tagResult = runTagRelease(repo);
+        assert.equal(tagResult.status, 0, tagResult.stderr);
+        git(repo, "commit", "--quiet", "--allow-empty", "-m", "fix: later");
+
+        const result = runPublishCheck(repo, "v1.3.9");
+        assert.equal(result.status, 0, result.stderr);
+      }),
+  ],
 ];
 
 for (const [name, check] of checks) {