diff --git a/.github/dependabot.yml b/.github/dependabot.yml
index dbd4f71..d2746ef 100644
--- a/.github/dependabot.yml
+++ b/.github/dependabot.yml
@@ -1,9 +1,24 @@
 version: 2
 updates:
+  - package-ecosystem: "cargo"
+    directory: "/rust"
+    pull-request-branch-name:
+      separator: "-"
+    schedule:
+      interval: "weekly"
+    cooldown:
+      default-days: 7
+    groups:
+      rust-dependencies:
+        patterns:
+          - "*"
+
   - package-ecosystem: "github-actions"
     directory: "/"
     schedule:
       interval: "weekly"
+    cooldown:
+      default-days: 7
     groups:
       actions-dependencies:
         patterns:
diff --git a/.github/pinact.yaml b/.github/pinact.yaml
new file mode 100644
index 0000000..75ff053
--- /dev/null
+++ b/.github/pinact.yaml
@@ -0,0 +1,9 @@
+version: 3
+rules:
+  # Branch refs that must keep tracking their branch: there is no stable tag
+  # to pin to. lean-update's `dev` carries the fork's features, and the shared
+  # ci-workflows actions are consumed from `main`.
+  - ignore: true
+    conditions:
+      - expr: ActionName == "argumentcomputer/lean-update"
+      - expr: ActionName matches "^argumentcomputer/ci-workflows/"
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 0b33c99..60d08dd 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -7,6 +7,9 @@ on:
       - main
   workflow_dispatch:
 
+permissions:
+  contents: read
+
 concurrency:
   group: ${{ github.workflow }}-${{ github.head_ref || github.run_id }}
   cancel-in-progress: true
@@ -16,9 +19,11 @@ jobs:
     name: Lean Tests
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v7
-      - uses: actions-rust-lang/setup-rust-toolchain@v2
-      - uses: leanprover/lean-action@v1
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          persist-credentials: false
+      - uses: actions-rust-lang/setup-rust-toolchain@ecabd13d1c56bd1345c230e542e9144811ad706f # v2.0.0
+      - uses: leanprover/lean-action@50fcf42d2e460296f1a34b402e990d1b24f8b596 # v1.6.0
         with:
           build-args: "--wfail"
           test: true
@@ -27,15 +32,20 @@ jobs:
     needs: lean-test
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v7
-      - uses: actions-rust-lang/setup-rust-toolchain@v2
-      # Only restore the cache, since the `test` job will save the test binary to the cache first
-      - uses: actions/cache/restore@v6
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
         with:
-          path: ./test/.lake
-          key: lake-${{ runner.os }}-${{ runner.arch }}-${{ hashFiles('lean-toolchain') }}-${{ hashFiles('test/lake-manifest.json') }}-${{ github.sha }}
-          restore-keys: lake-${{ runner.os }}-${{ runner.arch }}-${{ hashFiles('lean-toolchain') }}-${{ hashFiles('test/lake-manifest.json') }}
-      - uses: leanprover/lean-action@v1
+          persist-credentials: false
+      - uses: actions-rust-lang/setup-rust-toolchain@ecabd13d1c56bd1345c230e542e9144811ad706f # v2.0.0
+      # Restore the `.lake` that lean-action saved in the lean-test job for
+      # this commit, so the test binary is not rebuilt from scratch. Restore
+      # only: lean-action below runs with its cache off to avoid a second save
+      # under the same key.
+      - uses: actions/cache/restore@55cc8345863c7cc4c66a329aec7e433d2d1c52a9 # v6.1.0
+        with:
+          path: ./.lake
+          key: lake-${{ runner.os }}-${{ runner.arch }}-${{ hashFiles('lean-toolchain') }}-${{ hashFiles('lake-manifest.json') }}-${{ github.sha }}
+          restore-keys: lake-${{ runner.os }}-${{ runner.arch }}-${{ hashFiles('lean-toolchain') }}-${{ hashFiles('lake-manifest.json') }}
+      - uses: leanprover/lean-action@50fcf42d2e460296f1a34b402e990d1b24f8b596 # v1.6.0
         with:
           auto-config: false
           build: true
@@ -57,12 +67,14 @@ jobs:
     name: Nix Tests
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v7
-      - uses: cachix/install-nix-action@v31
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          persist-credentials: false
+      - uses: cachix/install-nix-action@13d8dd58da0234aa297dedd986986ccb8e7f3e24 # v31.11.1
         with:
           nix_path: nixpkgs=channel:nixos-unstable
-          github_access_token: ${{ secrets.GITHUB_TOKEN }}
-      - uses: cachix/cachix-action@v17
+          github_access_token: ${{ github.token }}
+      - uses: cachix/cachix-action@38b082610b782e7e93e209c35fd730d399dee866 # v17
         with:
           name: argumentcomputer
           authToken: ${{ secrets.CACHIX_AUTH_TOKEN }}
@@ -74,3 +86,14 @@ jobs:
       # Catch-all: near-free after the steps above; fails if a check is added
       # to the flake without a step here.
       - run: nix flake check --accept-flake-config
+
+  lints:
+    name: Lint workflows
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          persist-credentials: false
+      # actionlint, shellcheck over composite action scripts, pinact (actions
+      # must be SHA-pinned with a matching version comment) and zizmor
+      - uses: argumentcomputer/ci-workflows/.github/actions/lint-workflows@main
diff --git a/.github/workflows/update.yml b/.github/workflows/update.yml
index b84c49f..94a8b9d 100644
--- a/.github/workflows/update.yml
+++ b/.github/workflows/update.yml
@@ -14,11 +14,13 @@ jobs:
   update:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v7
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          persist-credentials: false
 
-      - uses: cachix/install-nix-action@v31
+      - uses: cachix/install-nix-action@13d8dd58da0234aa297dedd986986ccb8e7f3e24 # v31.11.1
         with:
-          github_access_token: ${{ secrets.GITHUB_TOKEN }}
+          github_access_token: ${{ github.token }}
 
       # `dev` carries pinned-tag updates and lean4-nix gating; `main` only
       # mirrors upstream and ignores these inputs.
diff --git a/.github/zizmor.yml b/.github/zizmor.yml
new file mode 100644
index 0000000..576392f
--- /dev/null
+++ b/.github/zizmor.yml
@@ -0,0 +1,8 @@
+rules:
+  unpinned-uses:
+    config:
+      policies:
+        # Branch-tracking refs allowed by .github/pinact.yaml
+        "argumentcomputer/lean-update": ref-pin
+        "argumentcomputer/ci-workflows/*": ref-pin
+        "*": hash-pin