diff --git a/.github/workflows/deploy-site.yml b/.github/workflows/deploy-site.yml
new file mode 100644
index 0000000000..ca65980e84
--- /dev/null
+++ b/.github/workflows/deploy-site.yml
@@ -0,0 +1,99 @@
+# Build apps/website and publish it to the repo that serves t27.ai.
+#
+# anomaly-register A51: four PRs merged, every check green, and the live site
+# changed nothing for a week. This app deploys from gHashTag/ghashtag.github.io,
+# which holds build output only, and a human copied dist/ into it. Nothing in
+# the pipeline noticed, because every other check reads the source.
+#
+# The deploy needs write access to a second repository, which a workflow token
+# does not have. It requires a secret named GHIO_TOKEN -- a fine-grained PAT
+# with Contents: write on gHashTag/ghashtag.github.io and nothing else. Until
+# that secret exists this workflow does not run, and check:deployed keeps
+# reporting the gap on every PR.
+#
+# Manual only, on purpose. Publishing to the live domain on every push to main
+# would mean any merge broadcasts, and this project's rule is that content is
+# approved before it goes out.
+name: Deploy site to t27.ai
+
+on:
+  workflow_dispatch:
+    inputs:
+      reason:
+        description: 'What is being published (goes in the commit message)'
+        required: true
+
+jobs:
+  deploy:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-node@v4
+        with:
+          node-version: '22'
+          cache: npm
+          cache-dependency-path: apps/website/package-lock.json
+
+      - name: Build
+        working-directory: apps/website
+        run: |
+          npm ci
+          npx vite build
+
+      # The same three checks the PR runs, against the tree being published.
+      # A deploy that skips them is how a broken build reaches the domain.
+      - name: Checks
+        working-directory: apps/website
+        run: |
+          npm run typecheck:ratchet
+          npm run check:api
+
+      - name: Checkout the deploy repo
+        uses: actions/checkout@v4
+        with:
+          repository: gHashTag/ghashtag.github.io
+          token: ${{ secrets.GHIO_TOKEN }}
+          path: ghio
+
+      # Copy the build, then delete bundles the new index.html cannot reach.
+      # Skipping that step is how 74 orphans accumulated once, keeping
+      # withdrawn claims greppable for weeks after the components were fixed.
+      - name: Copy the build and drop unreachable bundles
+        run: |
+          cp -R apps/website/dist/assets/. ghio/assets/
+          cp apps/website/dist/index.html ghio/index.html
+          cp apps/website/dist/manifest.json ghio/manifest.json
+          node - <<'EOF'
+          const {readFileSync, readdirSync, unlinkSync} = require('node:fs');
+          const {join} = require('node:path');
+          const A = 'ghio/assets';
+          const entry = [...readFileSync('ghio/index.html','utf8')
+            .matchAll(/assets\/([\w.-]+\.(?:js|css))/g)].map(m => m[1]);
+          const seen = new Set(); const stack = [...entry];
+          while (stack.length) {
+            const f = stack.pop();
+            if (seen.has(f)) continue;
+            seen.add(f);
+            try {
+              for (const m of readFileSync(join(A,f),'utf8').matchAll(/["']\.\/([\w.-]+\.(?:js|css))["']/g))
+                if (!seen.has(m[1])) stack.push(m[1]);
+            } catch {}
+          }
+          let n = 0;
+          for (const f of readdirSync(A))
+            if (/\.(js|css)$/.test(f) && !seen.has(f)) { unlinkSync(join(A,f)); n++; }
+          console.log(`  ${seen.size} reachable, ${n} orphan(s) removed`);
+          EOF
+
+      - name: Commit and push
+        working-directory: ghio
+        run: |
+          git config user.name gHashTag
+          git config user.email admin@t27.ai
+          git add -A
+          git diff --cached --quiet && { echo "  nothing changed — the live site is already this build"; exit 0; }
+          git commit -m "Deploy: ${{ inputs.reason }}
+
+          Built from gHashTag/trinity@${{ github.sha }} by the deploy workflow.
+          See anomaly-register A51 for why this exists."
+          git push
diff --git a/.github/workflows/website-checks.yml b/.github/workflows/website-checks.yml
index dd9995fcf5..725b962480 100644
--- a/.github/workflows/website-checks.yml
+++ b/.github/workflows/website-checks.yml
@@ -78,3 +78,16 @@ jobs:
         env:
           CHROME_PATH: ${{ steps.chrome.outputs.chrome-path }}
         run: npm run check:render -- --no-build
+
+      # A51: four PRs merged, every check green, and the live site changed
+      # nothing -- this app deploys from a second repository that holds build
+      # output only, copied there by hand. Every check above runs against the
+      # source, so all of them pass on a tree whose output nobody published.
+      #
+      # This one fetches t27.ai and compares the entry bundle. It never fails
+      # the job: a merge is not a deploy, and blocking one on the other
+      # inverts the order. It is here so the gap is visible in the log rather
+      # than discovered a week later in the site's <head>.
+      - name: Is the live site this build?
+        continue-on-error: true
+        run: npm run check:deployed
diff --git a/apps/website/package.json b/apps/website/package.json
index c6d409dca5..02d5cfe053 100644
--- a/apps/website/package.json
+++ b/apps/website/package.json
@@ -13,6 +13,7 @@
     "typecheck:ratchet": "node scripts/typecheck-ratchet.mjs",
     "check:api": "node scripts/api-contract-check.mjs",
     "check:render": "node scripts/render-check.mjs",
+    "check:deployed": "node scripts/deployed-check.mjs",
     "check:aria": "node scripts/aria-refs-check.mjs",
     "typecheck:update": "node scripts/typecheck-ratchet.mjs --update"
   },
diff --git a/apps/website/scripts/deployed-check.mjs b/apps/website/scripts/deployed-check.mjs
new file mode 100644
index 0000000000..fd577df3eb
--- /dev/null
+++ b/apps/website/scripts/deployed-check.mjs
@@ -0,0 +1,62 @@
+// Is what t27.ai serves the same thing this tree builds?
+//
+// anomaly-register A51: four PRs merged, every check green, and the live site
+// changed nothing. The SPA deploys from a second repository that holds build
+// output only, and nothing copies a build into it. The site kept serving
+// "First chip with native SU(3) Unitary Core" for a week after the tree that
+// produces it stopped saying that.
+//
+// A51 concluded no test in the source repo could see this. That was wrong by
+// one assumption: a test that FETCHES THE LIVE SITE can. This is that test.
+//
+//   npm run check:deployed
+//
+// It compares what the deployed index.html loads against what dist/index.html
+// loads. Vite hashes bundle names by content, so equal names mean equal
+// bundles and a different name means the deploy is behind -- or ahead, which
+// is worth knowing too.
+//
+// What it cannot tell you: WHICH direction, or whether the difference matters.
+// A whitespace change moves the hash. So this warns; it does not fail a build.
+// A gate that blocks a merge because someone has not deployed yet inverts the
+// order of operations.
+import { readFileSync, existsSync } from 'node:fs';
+
+const SITE = process.env.DEPLOY_URL ?? 'https://t27.ai/';
+const entryOf = (html) => (html.match(/assets\/(index-[\w-]+\.js)/) ?? [])[1];
+
+if (!existsSync('dist/index.html')) {
+  console.log('  no dist/ — run `npx vite build` first (nothing to compare)');
+  process.exit(0);
+}
+const local = entryOf(readFileSync('dist/index.html', 'utf8'));
+if (!local) {
+  console.error('  no entry bundle in dist/index.html. That is a build problem, not a deploy one.');
+  process.exit(1);
+}
+
+let live;
+try {
+  const res = await fetch(SITE, { headers: { 'User-Agent': 'deployed-check' } });
+  if (!res.ok) throw new Error(`HTTP ${res.status}`);
+  live = entryOf(await res.text());
+} catch (e) {
+  // Offline, or the site is down. Neither is a defect in this change, and a
+  // check that fails when the network does gets muted.
+  console.log(`  could not reach ${SITE} (${e.message}) — skipping`);
+  process.exit(0);
+}
+
+if (!live) {
+  console.error(`  ${SITE} serves no index-*.js bundle. Either it is not this app, or it is broken.`);
+  process.exit(1);
+}
+if (live === local) {
+  console.log(`  deployed: ${live} — the live site is this build`);
+  process.exit(0);
+}
+console.log(`\n  the live site is NOT this build:\n`);
+console.log(`    ${SITE.padEnd(28)} ${live}`);
+console.log(`    dist/index.html              ${local}\n`);
+console.log('  Merging does not deploy this site. The build output lives in a second');
+console.log('  repository and is copied there by hand — see anomaly-register A51.');