diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index bc7321fa..43bf3d99 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -221,7 +221,10 @@ jobs:
       - uses: actions/setup-python@v7
         with:
           python-version: "3.12"
-      - run: pip install black flake8
+          cache: pip
+          cache-dependency-path: requirements-dev.txt
+      # The exact black and flake8 pins from requirements-dev.txt, so a new release cannot turn CI red.
+      - run: pip install $(grep -E '^(black|flake8)==' requirements-dev.txt)
       - run: black --check .
       - run: flake8 .
 
@@ -235,6 +238,8 @@ jobs:
       - uses: actions/setup-node@v7
         with:
           node-version: "24"
+          cache: npm
+          cache-dependency-path: tools/vendor/package-lock.json
 
       - name: Check shipped extension and page modules parse
         run: |
diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index ca3295df..9106e4fc 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -13,9 +13,11 @@ repos:
         language: system
         types: [python]
 
+      # Fails at the severity CI enforces (code-quality.yml: -lll, high only), never stricter.
+      # pre-commit appends the staged files, so no shell wrapper can drop the first one.
       - id: bandit
         name: bandit
-        entry: bash -c 'bandit "$@" -ll -q 2>&1; true'
+        entry: bandit -lll -q
         language: system
         types: [python]
         exclude: ^(tests/|reference/)
diff --git a/requirements-dev.txt b/requirements-dev.txt
index 43e2130a..6db215e2 100644
--- a/requirements-dev.txt
+++ b/requirements-dev.txt
@@ -8,8 +8,8 @@ coverage>=7.16.2
 numpy>=2.2.6  # WD14 engine tests
 
 # Code quality
-black>=26.10.1
-flake8>=7.4.1
+black==26.10.1
+flake8==7.4.1
 
 # Security scanning
 bandit[toml]>=1.9.4
diff --git a/tests/vendor/ci-workflow.test.mjs b/tests/vendor/ci-workflow.test.mjs
index f489fd64..cfafcaae 100644
--- a/tests/vendor/ci-workflow.test.mjs
+++ b/tests/vendor/ci-workflow.test.mjs
@@ -247,3 +247,32 @@ test('the Python matrix and coverage run the suite through the watchdog runner',
         assert.doesNotMatch(found.get(id), /unittest discover/, `${id} no longer runs the bare unittest discover`);
     }
 });
+
+// CI hygiene (#352): lint tools are pinned, the bandit hook can fail, the JS job caches npm.
+const readRepoFile = path => readFileSync(new URL(`../../${path}`, import.meta.url), 'utf8');
+
+test('black and flake8 are pinned exactly and the lint job installs those pins', () => {
+    const requirements = readRepoFile('requirements-dev.txt');
+    assert.match(requirements, /^black==\d+\.\d+\.\d+$/m, 'black is pinned exactly');
+    assert.match(requirements, /^flake8==\d+\.\d+\.\d+$/m, 'flake8 is pinned exactly');
+    const lint = jobs(readWorkflow('test.yml')).get('lint');
+    assert.match(lint, /pip install \$\(grep -E '\^\(black\|flake8\)==' requirements-dev\.txt\)/);
+    assert.doesNotMatch(lint, /pip install black flake8/, 'lint no longer installs the latest releases');
+});
+
+test('the frontend modules job caches npm keyed on the vendor lockfile', () => {
+    const setupNode = steps(jobs(readWorkflow('test.yml')).get('js-test'))
+        .find(step => /uses: actions\/setup-node@v\d+/.test(step));
+    assert.match(setupNode, /^ {10}cache: npm$/m);
+    assert.match(setupNode, /^ {10}cache-dependency-path: tools\/vendor\/package-lock\.json$/m);
+});
+
+test('the bandit pre-commit hook fails at the severity CI enforces and passes every file', () => {
+    const quality = readWorkflow('code-quality.yml');
+    assert.match(quality, /^ {8}run: bandit -r \. -lll -q --exclude /m, 'CI fails on high severity');
+    const hook = /- id: bandit\n([\s\S]*?)(?=\n {6}(?:- id:|#)|\n*$)/.exec(readRepoFile('.pre-commit-config.yaml'))?.[1];
+    assert.ok(hook, 'the bandit hook exists');
+    assert.match(hook, /^ {8}entry: bandit -lll -q$/m, 'the hook enforces the same -lll level as CI');
+    assert.doesNotMatch(hook, /true|exit-zero|bash -c/, 'nothing masks the exit code or drops a file');
+    assert.doesNotMatch(hook, /pass_filenames: false/, 'the hook scans the staged files');
+});