diff --git a/.github/dependabot.yml b/.github/dependabot.yml
new file mode 100644
index 0000000..7d3d03c
--- /dev/null
+++ b/.github/dependabot.yml
@@ -0,0 +1,32 @@
+# Every action in .github/workflows is pinned by commit, so a moved tag cannot
+# change what runs. The cost is that pins go stale; this keeps them current,
+# one reviewable pull request a week per ecosystem.
+version: 2
+updates:
+  - package-ecosystem: github-actions
+    directory: /
+    schedule:
+      interval: weekly
+    # A release this new has had no time to be found out if it is bad.
+    cooldown:
+      default-days: 7
+    groups:
+      actions:
+        patterns: ["*"]
+    commit-message:
+      prefix: ci
+
+  # uv.lock, which CI installs with --locked. The floors in pyproject are
+  # tested by the lowest-direct job and are raised by hand, not here.
+  - package-ecosystem: uv
+    directory: /
+    schedule:
+      interval: weekly
+    cooldown:
+      default-days: 7
+    versioning-strategy: lockfile-only
+    groups:
+      dependencies:
+        patterns: ["*"]
+    commit-message:
+      prefix: deps
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 048ddaa..f7b6736 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -35,14 +35,16 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        os: [ubuntu-latest, windows-latest]
-        python: ["3.12", "3.13"]
+        # Every platform and every Python that requires-python admits and
+        # that has a release, so ">=3.12" states what is tested.
+        os: [ubuntu-latest, windows-latest, macos-latest]
+        python: ["3.12", "3.13", "3.14"]
 
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@fbc6f3992d24b796d5a048ff273f7fcc4a7b6c09 # v5.1.0
 
       - name: Install uv
-        uses: astral-sh/setup-uv@v7
+        uses: astral-sh/setup-uv@37802adc94f370d6bfd71619e3f0bf239e1f3b78 # v7.6.0
         with:
           python-version: ${{ matrix.python }}
           enable-cache: true
@@ -74,10 +76,10 @@ jobs:
     name: the oldest dependencies pyproject allows
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@fbc6f3992d24b796d5a048ff273f7fcc4a7b6c09 # v5.1.0
 
       - name: Install uv
-        uses: astral-sh/setup-uv@v7
+        uses: astral-sh/setup-uv@37802adc94f370d6bfd71619e3f0bf239e1f3b78 # v7.6.0
         with:
           python-version: "3.12"
 
@@ -102,10 +104,10 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@fbc6f3992d24b796d5a048ff273f7fcc4a7b6c09 # v5.1.0
 
       - name: Install uv
-        uses: astral-sh/setup-uv@v7
+        uses: astral-sh/setup-uv@37802adc94f370d6bfd71619e3f0bf239e1f3b78 # v7.6.0
         with:
           python-version: "3.13"
           enable-cache: true
@@ -165,7 +167,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@fbc6f3992d24b796d5a048ff273f7fcc4a7b6c09 # v5.1.0
 
       - name: Tracked prose, source, site, and templates contain no em dash
         run: |
@@ -197,10 +199,10 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@fbc6f3992d24b796d5a048ff273f7fcc4a7b6c09 # v5.1.0
 
       - name: Install uv
-        uses: astral-sh/setup-uv@v7
+        uses: astral-sh/setup-uv@37802adc94f370d6bfd71619e3f0bf239e1f3b78 # v7.6.0
         with:
           python-version: "3.13"
           enable-cache: true
diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index d9ab2ae..f0918b6 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -14,29 +14,61 @@ on:
         required: true
         type: string
 
-permissions:
-  contents: write # attaching assets to the release
+# No job gets a token it does not need, so each names its own. The build runs
+# the project's code and every dependency's, so it can only read; the job that
+# can write runs none of it.
+permissions: {}
 
+# Keyed on the tag itself, not the ref, so a tag push and a manual re-run of
+# the same tag queue behind each other instead of racing to replace the same
+# assets.
 concurrency:
-  group: release-${{ github.ref }}
+  group: release-${{ inputs.tag || github.ref_name }}
   cancel-in-progress: false
 
 jobs:
-  release:
-    name: build and attach the distributions
+  resolve:
+    name: the tag is a release tag
     runs-on: ubuntu-latest
+    outputs:
+      tag: ${{ steps.tag.outputs.tag }}
+    steps:
+      # The tag arrives through the environment and is checked before any
+      # other job sees it. A dispatch input is free text, and one expanded
+      # straight into a script is a script of the caller's choosing.
+      - id: tag
+        env:
+          TAG: ${{ inputs.tag || github.ref_name }}
+        run: |
+          if ! [[ "$TAG" =~ ^v[0-9]+\.[0-9]+\.[0-9]+$ ]]; then
+            echo "::error::the tag is not a release tag of the form v1.2.3"
+            exit 1
+          fi
+          echo "tag=$TAG" >> "$GITHUB_OUTPUT"
+
+  build:
+    name: build and check the distributions
+    needs: resolve
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+    env:
+      TAG: ${{ needs.resolve.outputs.tag }}
 
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@fbc6f3992d24b796d5a048ff273f7fcc4a7b6c09 # v5.1.0
         with:
-          ref: ${{ inputs.tag || github.ref }}
+          ref: refs/tags/${{ needs.resolve.outputs.tag }}
           fetch-depth: 0
+          persist-credentials: false
 
       - name: Install uv
-        uses: astral-sh/setup-uv@v7
+        uses: astral-sh/setup-uv@37802adc94f370d6bfd71619e3f0bf239e1f3b78 # v7.6.0
         with:
           python-version: "3.13"
-          enable-cache: true
+          # A release builds from a clean download, never from a cache that
+          # another workflow could have written.
+          enable-cache: false
 
       - name: Sync dependencies
         run: uv sync --locked
@@ -46,12 +78,11 @@ jobs:
       # because the test asserting the version used a substring match.
       - name: The tag and the package version must agree
         run: |
-          tag="${{ inputs.tag || github.ref_name }}"
-          expected="${tag#v}"
+          expected="${TAG#v}"
           actual="$(uv run python -c 'import plumbline; print(plumbline.__version__)')"
-          echo "tag $tag implies version $expected; package says $actual"
+          echo "tag $TAG implies version $expected; package says $actual"
           if [ "$expected" != "$actual" ]; then
-            echo "::error::tag $tag does not match __version__ $actual. Bump the version or move the tag; do not release a mismatch."
+            echo "::error::tag $TAG does not match __version__ $actual. Bump the version or move the tag; do not release a mismatch."
             exit 1
           fi
 
@@ -67,8 +98,7 @@ jobs:
 
       - name: The artifact names carry the released version
         run: |
-          tag="${{ inputs.tag || github.ref_name }}"
-          version="${tag#v}"
+          version="${TAG#v}"
           ls -l dist/
           test -f "dist/plumbline-${version}-py3-none-any.whl" \
             || { echo "::error::expected dist/plumbline-${version}-py3-none-any.whl"; exit 1; }
@@ -88,18 +118,52 @@ jobs:
           print("installed", plumbline.__version__, "clean")
           PY
 
+      - name: Hand the distributions to the publishing job
+        uses: actions/upload-artifact@043fb46d1a93c77aae656e7c1c64a875d1fc6a0a # v7.0.1
+        with:
+          name: dist
+          path: dist/
+          if-no-files-found: error
+          retention-days: 7
+
+  publish:
+    name: attest and attach the distributions
+    needs: [resolve, build]
+    runs-on: ubuntu-latest
+    # This job holds the only write token, so it checks out nothing and runs
+    # no project code: it signs what the build made and attaches it.
+    permissions:
+      contents: write # attaching assets to the release
+      id-token: write # signing the provenance
+      attestations: write # storing the provenance
+    env:
+      TAG: ${{ needs.resolve.outputs.tag }}
+      GH_TOKEN: ${{ github.token }}
+      GH_REPO: ${{ github.repository }}
+
+    steps:
+      - name: Collect the distributions
+        uses: actions/download-artifact@3e5f45b2cfb9172054b4087a40e8e0b5a5461e7c # v8.0.1
+        with:
+          name: dist
+          path: dist
+
+      # Anyone can then check that a wheel came from this workflow at this
+      # tag: gh attestation verify plumbline-*.whl -R TMHSDigital/plumbline
+      - name: Record where the distributions came from
+        uses: actions/attest-build-provenance@4d101475d8b20a2381f78447822ac1eab6504dd8 # v4.2.2
+        with:
+          subject-path: dist/*
+
       - name: Attach the distributions to the release
-        env:
-          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
         run: |
-          tag="${{ inputs.tag || github.ref_name }}"
           # The release notes are written by hand, so this only ever adds
           # assets to a release that already exists. It does not create one and
           # it does not generate notes from commit messages.
-          if ! gh release view "$tag" > /dev/null 2>&1; then
-            echo "::error::no release exists for $tag. Create it with written notes first, then re-run this workflow."
+          if ! gh release view "$TAG" > /dev/null 2>&1; then
+            echo "::error::no release exists for $TAG. Create it with written notes first, then re-run this workflow."
             exit 1
           fi
-          gh release upload "$tag" dist/* --clobber
+          gh release upload "$TAG" dist/* --clobber
           echo "attached:"
-          gh release view "$tag" --json assets --jq '.assets[].name'
+          gh release view "$TAG" --json assets --jq '.assets[].name'
diff --git a/.github/workflows/site.yml b/.github/workflows/site.yml
index ef40a24..39ff25a 100644
--- a/.github/workflows/site.yml
+++ b/.github/workflows/site.yml
@@ -31,10 +31,10 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@fbc6f3992d24b796d5a048ff273f7fcc4a7b6c09 # v5.1.0
 
       - name: Install uv
-        uses: astral-sh/setup-uv@v7
+        uses: astral-sh/setup-uv@37802adc94f370d6bfd71619e3f0bf239e1f3b78 # v7.6.0
         with:
           python-version: "3.13"
           enable-cache: true
@@ -72,7 +72,7 @@ jobs:
       # The exact bytes the deploy job publishes. On a pull request this is
       # also a downloadable preview of the site.
       - name: Keep the assembled site
-        uses: actions/upload-pages-artifact@v5
+        uses: actions/upload-pages-artifact@fc324d3547104276b827a68afc52ff2a11cc49c9 # v5.0.0
         with:
           path: _site
 
@@ -82,7 +82,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@fbc6f3992d24b796d5a048ff273f7fcc4a7b6c09 # v5.1.0
 
       # The renderer's refusals (raw HTML off the allowlist, broken links and
       # anchors, remote images, a modified vendored file) each have a case.
@@ -90,7 +90,7 @@ jobs:
         run: node scripts/render_docs.mjs --self-test
 
       - name: Fetch the assembled site
-        uses: actions/download-artifact@v8
+        uses: actions/download-artifact@3e5f45b2cfb9172054b4087a40e8e0b5a5461e7c # v8.0.1
         with:
           name: github-pages
           path: artifact
@@ -129,7 +129,7 @@ jobs:
     steps:
       - name: Publish the checked site
         id: deployment
-        uses: actions/deploy-pages@v5
+        uses: actions/deploy-pages@368f82528645a54fb793d4d04e342629a3f51346 # v5.0.1
 
   live:
     name: the live site resolves as the checked one did
@@ -137,7 +137,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@fbc6f3992d24b796d5a048ff273f7fcc4a7b6c09 # v5.1.0
 
       # What Pages actually serves, including a real 404 for a missing path,
       # which only a request to the live site can show. The CDN can take a
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 64cfd3d..8e527cc 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -83,6 +83,19 @@ different event from one that moved because it was wrong.
 
 ### Fixed
 
+- The release workflow gave its whole run a write token while it executed the
+  project's code and every dependency's, expanded the tag, which a manual run
+  takes as free text, straight into shell, and let a tag push and a manual run
+  of the same tag race to replace the same assets (#51). The tag is now checked
+  against `vX.Y.Z` in a job of its own and passed through the environment; the
+  build job can only read; a separate job with no checkout and no project code
+  signs build provenance for the wheel and sdist
+  (`gh attestation verify`) and attaches them; and runs queue per tag.
+- Every action was referenced by a movable major tag (#52). Each is now pinned
+  to a commit, with its version beside it, and Dependabot keeps the pins and
+  uv.lock current, waiting a week after any release. CI now also runs on macOS
+  and Python 3.14, so `requires-python = ">=3.12"` says what is tested.
+
 - The dependency floors in pyproject were never tested, and three were wrong:
   scipy 1.14.0 has no wheel for Python 3.13, anthropic before 0.77 lacks the
   structured output types the generative adapter uses, and typer before 0.16
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index d4eace9..650bd8e 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -59,7 +59,8 @@ uv run ruff format --check .
 uv run mypy --strict
 ```
 
-CI runs these on Python 3.12 and 3.13, on Ubuntu and Windows.
+CI runs these on Python 3.12, 3.13 and 3.14, on Ubuntu, Windows and macOS, and
+runs the tests once more on the oldest dependencies pyproject allows.
 
 **Tests never need a network connection or an API key.** Every test must pass
 without either. If a change needs a live call to be tested, the live call is
@@ -80,9 +81,10 @@ The flow:
 4. **Open a pull request.** No approval is required, because there is currently
    one maintainer and a rule demanding one would only demand it of them. CI is
    the gate that actually matters.
-5. **CI must be green** before merge. The required checks are the four test
-   jobs (ruff, ruff format, mypy --strict and pytest, on Python 3.12 and 3.13,
-   on Ubuntu and Windows), the quickstart as the README documents it, the prose
+5. **CI must be green** before merge. The required checks are the nine test
+   jobs (ruff, ruff format, mypy --strict and pytest, on Python 3.12, 3.13 and
+   3.14, on Ubuntu, Windows and macOS), the tests on the oldest dependencies
+   pyproject allows, the quickstart as the README documents it, the prose
    check (no em dashes, no `--` used as a dash), the built wheel, and the site's
    two checks (the floor agrees with the Python; every link, anchor, meta tag
    and policy resolves, and the pages work in a real browser).
diff --git a/README.md b/README.md
index ef5d182..611dd95 100644
--- a/README.md
+++ b/README.md
@@ -341,7 +341,8 @@ Specific, and none of them are going to surprise you later.
 - **Probabilities from a hosted API may arrive quantized.** That bounds the
   resolution of any threshold or bin computed from them. METHODOLOGY says what
   the bound is and where it bites.
-- **Verified on Windows and Ubuntu, Python 3.12 and 3.13.** macOS is untested.
+- **Verified on Ubuntu, Windows, and macOS, Python 3.12 through 3.14**, and on
+  the oldest release of each dependency that pyproject allows.
 - **Two of the three transports have never run outside the test suite.** See
   the adapters table above and
   [issue #3](https://github.com/TMHSDigital/plumbline/issues/3).
diff --git a/pyproject.toml b/pyproject.toml
index bb52ca6..b881f8f 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -12,6 +12,7 @@ classifiers = [
     "License :: OSI Approved :: Apache Software License",
     "Programming Language :: Python :: 3.12",
     "Programming Language :: Python :: 3.13",
+    "Programming Language :: Python :: 3.14",
 ]
 # Each floor is the oldest release the whole test suite passes on, checked by
 # the lowest-direct job in CI. The SDKs are capped below their next breaking