diff --git a/.github/dependabot.yml b/.github/dependabot.yml
new file mode 100644
index 00000000..ae43c534
--- /dev/null
+++ b/.github/dependabot.yml
@@ -0,0 +1,24 @@
+# Dependabot configuration.
+#
+# All workflows pin third-party actions by commit SHA per CodeQL findings
+# 21 + 22 on PR #32 and the chore/pin-action-shas plan in
+# openarmature-coord/docs/future-work.md. SHA-pinning is a security
+# posture choice — tag refs are mutable, SHAs are not — and Dependabot is
+# the maintenance pair: it surfaces version bumps as PRs (with updated
+# SHA + version comment), so the security benefit doesn't trade off
+# against keeping actions current.
+#
+# Monthly cadence keeps the PR volume bounded. Action releases cluster
+# around new GitHub Actions runner features and GH platform updates; a
+# month is long enough for batched updates but short enough to catch
+# real security advisories in time.
+version: 2
+updates:
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "monthly"
+    open-pull-requests-limit: 10
+    commit-message:
+      prefix: "chore"
+      include: "scope"
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 05981a61..ec888591 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -21,13 +21,13 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@v6
+        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd  # v6.0.2
         with:
           # Conformance fixtures live in the openarmature-spec submodule.
           submodules: recursive
 
       - name: Install uv
-        uses: astral-sh/setup-uv@v8.1.0
+        uses: astral-sh/setup-uv@08807647e7069bb48b6ef5acd8ec9567f424441b  # v8.1.0
         with:
           enable-cache: true
 
diff --git a/.github/workflows/codeql.yml b/.github/workflows/codeql.yml
index fba94227..916cde9b 100644
--- a/.github/workflows/codeql.yml
+++ b/.github/workflows/codeql.yml
@@ -40,10 +40,10 @@ jobs:
         language: [actions, python]
     steps:
       - name: Checkout
-        uses: actions/checkout@v6
+        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd  # v6.0.2
 
       - name: Initialize CodeQL
-        uses: github/codeql-action/init@v3
+        uses: github/codeql-action/init@7fd177fa680c9881b53cdab4d346d32574c9f7f4  # v3.35.4
         with:
           languages: ${{ matrix.language }}
           # Reference the in-tree config so the rule-suppressions land.
@@ -56,6 +56,6 @@ jobs:
           queries: security-and-quality
 
       - name: Perform CodeQL Analysis
-        uses: github/codeql-action/analyze@v3
+        uses: github/codeql-action/analyze@7fd177fa680c9881b53cdab4d346d32574c9f7f4  # v3.35.4
         with:
           category: "/language:${{ matrix.language }}"
diff --git a/.github/workflows/docs.yml b/.github/workflows/docs.yml
index 8490357e..c2e0cfd0 100644
--- a/.github/workflows/docs.yml
+++ b/.github/workflows/docs.yml
@@ -33,7 +33,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@v6
+        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd  # v6.0.2
         with:
           # mkdocstrings imports the package source; the spec submodule
           # is not referenced by docs but keep the conventional recursive
@@ -41,7 +41,7 @@ jobs:
           submodules: recursive
 
       - name: Install uv
-        uses: astral-sh/setup-uv@v8.1.0
+        uses: astral-sh/setup-uv@08807647e7069bb48b6ef5acd8ec9567f424441b  # v8.1.0
         with:
           enable-cache: true
 
@@ -62,7 +62,7 @@ jobs:
         # Only deploy on pushes to main. PR builds prove the site
         # builds but do not deploy.
         if: github.event_name == 'push' && github.ref == 'refs/heads/main'
-        uses: cloudflare/wrangler-action@v3
+        uses: cloudflare/wrangler-action@ebbaa1584979971c8614a24965b4405ff95890e0  # v4.0.0
         with:
           apiToken: ${{ secrets.CF_API_TOKEN }}
           accountId: ${{ secrets.CF_ACCOUNT_ID }}
diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index f8194896..c8447fac 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -23,13 +23,13 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@v6
+        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd  # v6.0.2
         with:
           # Conformance fixtures live in the openarmature-spec submodule.
           submodules: recursive
 
       - name: Install uv
-        uses: astral-sh/setup-uv@v8.1.0
+        uses: astral-sh/setup-uv@08807647e7069bb48b6ef5acd8ec9567f424441b  # v8.1.0
         with:
           enable-cache: true
 
@@ -86,12 +86,12 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@v6
+        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd  # v6.0.2
         with:
           submodules: recursive
 
       - name: Install uv
-        uses: astral-sh/setup-uv@v8.1.0
+        uses: astral-sh/setup-uv@08807647e7069bb48b6ef5acd8ec9567f424441b  # v8.1.0
         with:
           enable-cache: true
 
@@ -102,7 +102,7 @@ jobs:
         run: uv build
 
       - name: Upload dist artifact
-        uses: actions/upload-artifact@v7
+        uses: actions/upload-artifact@043fb46d1a93c77aae656e7c1c64a875d1fc6a0a  # v7.0.1
         with:
           name: dist
           path: dist/
@@ -119,13 +119,13 @@ jobs:
       id-token: write
     steps:
       - name: Download dist artifact
-        uses: actions/download-artifact@v8
+        uses: actions/download-artifact@3e5f45b2cfb9172054b4087a40e8e0b5a5461e7c  # v8.0.1
         with:
           name: dist
           path: dist/
 
       - name: Publish to TestPyPI
-        uses: pypa/gh-action-pypi-publish@release/v1
+        uses: pypa/gh-action-pypi-publish@cef221092ed1bacb1cc03d23a2d87d1d172e277b  # release/v1 branch tip
         with:
           repository-url: https://test.pypi.org/legacy/
 
@@ -145,13 +145,13 @@ jobs:
       id-token: write
     steps:
       - name: Download dist artifact
-        uses: actions/download-artifact@v8
+        uses: actions/download-artifact@3e5f45b2cfb9172054b4087a40e8e0b5a5461e7c  # v8.0.1
         with:
           name: dist
           path: dist/
 
       - name: Publish to PyPI
-        uses: pypa/gh-action-pypi-publish@release/v1
+        uses: pypa/gh-action-pypi-publish@cef221092ed1bacb1cc03d23a2d87d1d172e277b  # release/v1 branch tip
 
   # GitHub Release with auto-generated notes from commits since the last
   # tag. Only fires on real releases (no suffix); pre-release tags leave
@@ -164,16 +164,16 @@ jobs:
       contents: write
     steps:
       - name: Checkout
-        uses: actions/checkout@v6
+        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd  # v6.0.2
 
       - name: Download dist artifact
-        uses: actions/download-artifact@v8
+        uses: actions/download-artifact@3e5f45b2cfb9172054b4087a40e8e0b5a5461e7c  # v8.0.1
         with:
           name: dist
           path: dist/
 
       - name: Create GitHub Release
-        uses: softprops/action-gh-release@v2
+        uses: softprops/action-gh-release@3bb12739c298aeb8a4eeaf626c5b8d85266b0e65  # v2.6.2
         with:
           files: dist/*
           generate_release_notes: true