diff --git a/.github/workflows/push.yaml b/.github/workflows/push.yaml
index 8605abf3c..65549fc51 100644
--- a/.github/workflows/push.yaml
+++ b/.github/workflows/push.yaml
@@ -73,15 +73,38 @@ jobs:
       - name: Run tests
         run: make test
       - uses: codecov/codecov-action@v6
+  Docs:
+    runs-on: ubuntu-latest
+    # Deploy only a release that reached PyPI. As its own job, a failed
+    # deploy cannot fail Test or Publish.
+    needs: [Test, Publish]
+    if: |
+      (github.repository == 'PolicyEngine/policyengine-core')
+      && (github.event.head_commit.message == 'Update PolicyEngine Core')
+    permissions:
+      contents: write
+    # One deploy at a time; a newly queued deploy replaces one still waiting.
+    concurrency:
+      group: gh-pages-deploy
+      cancel-in-progress: false
+    steps:
+      - name: Checkout repo
+        uses: actions/checkout@v6
+      - name: Set up Python
+        uses: actions/setup-python@v6
+        with:
+          python-version: "3.14"
+      - name: Install uv
+        uses: astral-sh/setup-uv@v8.1.0
+      - name: Install package
+        run: make install
       - name: Generate documentation
         run: make documentation
       - name: Deploy documentation
-        if: matrix.os == 'ubuntu-latest'
         uses: JamesIves/github-pages-deploy-action@v4
         with:
-          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
-          BRANCH: gh-pages # The branch the action should deploy to.
-          FOLDER: docs/_build/html # The folder the action should deploy.
+          branch: gh-pages
+          folder: docs/_build/html
   Publish:
     runs-on: ubuntu-latest
     if: |
diff --git a/changelog.d/fix-docs-deploy.changed.md b/changelog.d/fix-docs-deploy.changed.md
new file mode 100644
index 000000000..25cff6928
--- /dev/null
+++ b/changelog.d/fix-docs-deploy.changed.md
@@ -0,0 +1 @@
+The release workflow deploys the documentation site again, from a Docs job that runs once the tests pass and the release reaches PyPI; the deploy step had been skipped on every release since September 2024 because it checked a matrix the Test job no longer has.
diff --git a/docs/_config.yml b/docs/_config.yml
index 4bec1e9dd..e7f504b0e 100644
--- a/docs/_config.yml
+++ b/docs/_config.yml
@@ -20,6 +20,7 @@ sphinx:
     html_css_files:
       - style.css
   extra_extensions:
+    - "sphinx.ext.githubpages"
     - "sphinx.ext.autodoc"
     - "sphinxarg.ext"
     - "sphinx.ext.viewcode"
diff --git a/tests/core/test_docs_deployment.py b/tests/core/test_docs_deployment.py
new file mode 100644
index 000000000..20f4a3706
--- /dev/null
+++ b/tests/core/test_docs_deployment.py
@@ -0,0 +1,143 @@
+import re
+from pathlib import Path
+
+import pytest
+import yaml
+
+
+ROOT = Path(__file__).resolve().parents[2]
+WORKFLOWS = ROOT / ".github" / "workflows"
+PUSH_WORKFLOW = WORKFLOWS / "push.yaml"
+DOCS_CONFIG = ROOT / "docs" / "_config.yml"
+MAKEFILE = ROOT / "Makefile"
+DEPLOY_ACTION = "JamesIves/github-pages-deploy-action@"
+PYPI_ACTION = "pypa/gh-action-pypi-publish@"
+
+
+def load_jobs(workflow: Path) -> dict:
+    return yaml.safe_load(workflow.read_text())["jobs"]
+
+
+def as_list(value) -> list:
+    if value is None:
+        return []
+    return [value] if isinstance(value, str) else list(value)
+
+
+def strings_in(node):
+    if isinstance(node, str):
+        yield node
+    elif isinstance(node, dict):
+        for value in node.values():
+            yield from strings_in(value)
+    elif isinstance(node, list):
+        for item in node:
+            yield from strings_in(item)
+
+
+def matrix_keys(job: dict) -> set | None:
+    """Keys a job's matrix defines, or None when an expression builds it."""
+    matrix = (job.get("strategy") or {}).get("matrix") or {}
+    if not isinstance(matrix, dict):
+        return None
+    keys = set(matrix) - {"include", "exclude"}
+    include = matrix.get("include", [])
+    if not isinstance(include, list):
+        return None
+    for entry in include:
+        if not isinstance(entry, dict):
+            return None
+        keys |= set(entry)
+    return keys
+
+
+def jobs_using(jobs: dict, action: str) -> list:
+    return [
+        name
+        for name, job in jobs.items()
+        if any(step.get("uses", "").startswith(action) for step in job.get("steps", []))
+    ]
+
+
+def upstream_jobs(jobs: dict, name: str) -> set:
+    seen = set()
+    pending = as_list(jobs[name].get("needs"))
+    while pending:
+        needed = pending.pop()
+        if needed not in seen:
+            seen.add(needed)
+            pending.extend(as_list(jobs[needed].get("needs")))
+    return seen
+
+
+@pytest.mark.parametrize(
+    "workflow", sorted(WORKFLOWS.glob("*.y*ml")), ids=lambda path: path.name
+)
+def test_workflow_matrix_references_have_a_matrix(workflow: Path):
+    # The Test job lost its matrix in September 2024 but kept a step guarded
+    # by ``matrix.os == 'ubuntu-latest'``, so that condition never held and
+    # the documentation deploy was skipped on every release afterwards.
+    for name, job in load_jobs(workflow).items():
+        defined = matrix_keys(job)
+        if defined is None:
+            continue
+        referenced = {
+            key
+            for text in strings_in(job)
+            for key in re.findall(r"\bmatrix\.([A-Za-z_][\w-]*)", text)
+        }
+        missing = referenced - defined
+        assert not missing, (
+            f"{workflow.name} job {name} references matrix keys "
+            f"{sorted(missing)} that its strategy does not define"
+        )
+
+
+def test_release_deploys_documentation_after_publishing():
+    jobs = load_jobs(PUSH_WORKFLOW)
+    assert jobs_using(jobs, DEPLOY_ACTION) == ["Docs"]
+    docs = jobs["Docs"]
+    steps = docs["steps"]
+    deploy = next(
+        step for step in steps if step.get("uses", "").startswith(DEPLOY_ACTION)
+    )
+    build = next(step for step in steps if step.get("run") == "make documentation")
+
+    assert docs["if"] == jobs["Test"]["if"]
+    assert {"Test", "Publish"} <= set(as_list(docs.get("needs")))
+    # A condition on the deploy step is how it went unnoticed for two years.
+    assert "if" not in deploy
+    assert steps.index(build) < steps.index(deploy)
+    # GitHub Pages serves the gh-pages branch root. The action's ``token``
+    # input defaults to the job token, which needs write access to push.
+    assert deploy["with"]["branch"] == "gh-pages"
+    assert deploy["with"]["folder"] == "docs/_build/html"
+    assert docs["permissions"].get("contents") == "write"
+    # A constant group serializes deploys across release runs.
+    concurrency = docs["concurrency"]
+    if isinstance(concurrency, str):
+        concurrency = {"group": concurrency}
+    assert "${{" not in concurrency["group"]
+    assert concurrency.get("cancel-in-progress", False) is False
+
+
+def test_documentation_build_matches_deploy_folder():
+    recipe = re.search(
+        r"^documentation:.*\n((?:\t.*\n?)+)", MAKEFILE.read_text(), re.MULTILINE
+    )
+    extensions = yaml.safe_load(DOCS_CONFIG.read_text())["sphinx"]["extra_extensions"]
+
+    # ``jb build docs`` writes HTML to docs/_build/html, the deployed folder.
+    assert recipe is not None
+    assert "jb build docs" in [line.strip() for line in recipe.group(1).splitlines()]
+    # Pages builds a branch source with Jekyll unless its root has .nojekyll,
+    # which this extension writes into the HTML output.
+    assert "sphinx.ext.githubpages" in extensions
+
+
+def test_documentation_deploy_cannot_block_pypi_publishing():
+    jobs = load_jobs(PUSH_WORKFLOW)
+
+    for name in jobs_using(jobs, PYPI_ACTION):
+        assert name != "Docs"
+        assert "Docs" not in upstream_jobs(jobs, name)