diff --git a/.github/dependabot.yml b/.github/dependabot.yml
new file mode 100644
index 00000000..203c9c5e
--- /dev/null
+++ b/.github/dependabot.yml
@@ -0,0 +1,22 @@
+version: 2
+updates:
+  - package-ecosystem: 'npm'
+    # Yarn workspace root: one yarn.lock covers every packages/* workspace.
+    directory: '/'
+    schedule:
+      interval: 'daily'
+    cooldown:
+      default-days: 7
+    ignore:
+      # vitest 5 drops vite as a dependency, which Yarn 1 then never installs (see #52).
+      - dependency-name: 'vitest'
+        update-types: ['version-update:semver-major']
+  - package-ecosystem: 'github-actions'
+    # '/' covers .github/workflows only; the composite actions pin their own actions.
+    directories:
+      - '/'
+      - '/.github/actions/*'
+    schedule:
+      interval: 'weekly'
+    cooldown:
+      default-days: 7
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 88cd5f2d..43811193 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -4,6 +4,9 @@ on:
   push:
     branches: [main]
   pull_request:
+  # Weekly, so an advisory published against an unchanged lockfile still surfaces.
+  schedule:
+    - cron: '0 13 * * 1'
 
 # The `setup` job installs deps and builds @launchdarkly/ai-server (the core client),
 # then shares the compiled output with downstream jobs via the `client-dist`
@@ -89,6 +92,30 @@ jobs:
       - name: Package consistency (sherif)
         run: yarn lint:pkg
 
+  # ─── Dependency audit ───────────────────────────────────────────────────────
+  audit:
+    name: Dependency audit
+    runs-on: ubuntu-latest
+    # A newly published advisory must not turn every open PR red; push and the weekly run still fail.
+    continue-on-error: ${{ github.event_name == 'pull_request' }}
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Enable Corepack
+        run: corepack enable
+
+      - name: Set up Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: 24
+          cache: yarn
+
+      - name: Install dependencies
+        run: yarn install --frozen-lockfile
+
+      - name: Audit runtime dependencies
+        run: make audit
+
   # ─── Type check ─────────────────────────────────────────────────────────────
   typecheck:
     name: Type check
diff --git a/Makefile b/Makefile
index 9796d8c7..f7d03973 100644
--- a/Makefile
+++ b/Makefile
@@ -1,4 +1,11 @@
-.PHONY: start build clean test typecheck lint lint-fix lint-packages lint-packages-fix format format-fix code-check code-fix review size size-install
+.PHONY: start build clean test typecheck lint lint-fix lint-packages lint-packages-fix format format-fix code-check code-fix review size size-install audit
+
+# Fail on known high or critical vulnerabilities in runtime (non-dev) dependencies
+# Yarn 1 exits with a bitmask of severities found (info 1, low 2, moderate 4, high 8, critical 16) and
+# --level only filters the printed list, so test bits 8|16. Exactly 1 is also yarn's error exit: fail closed.
+audit:
+	yarn audit --groups dependencies --level high; s=$$?; \
+	if [ $$s -eq 1 ] || [ $$((s & 24)) -ne 0 ]; then echo "make audit: failed (yarn audit exit $$s)"; exit 1; fi
 
 # Run main.ts (yarn start)
 start: