diff --git a/.github/workflows/advisory-inventory.yml b/.github/workflows/advisory-inventory.yml
new file mode 100644
index 00000000..f881eac3
--- /dev/null
+++ b/.github/workflows/advisory-inventory.yml
@@ -0,0 +1,31 @@
+name: Advisory inventory
+
+# Every open dependency advisory at moderate or above has a triage row in
+# SECURITY-EXPOSURE.md (scripts/security/check-exposure-coverage.mjs). It
+# runs on every push to main (ci.yml's security-exposure job) and here, once
+# a day, because an advisory can be published with nothing merged. A
+# failure is one alert about main, answered by one triage row or one bump;
+# pull requests are gated only on what they themselves add.
+
+on:
+  schedule:
+    - cron: '41 6 * * *'
+  workflow_dispatch:
+
+permissions:
+  contents: read
+
+jobs:
+  inventory:
+    runs-on: ubuntu-latest
+    timeout-minutes: 15
+    steps:
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1  # v7.0.1
+      - uses: actions/setup-node@820762786026740c76f36085b0efc47a31fe5020  # v7.0.0
+        with:
+          node-version: 22
+          cache: npm
+          cache-dependency-path: package-lock.json
+      - run: npm ci
+      - name: Every open advisory has a triage row
+        run: node scripts/security/check-exposure-coverage.mjs
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index f5a37405..c4b0d005 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -757,6 +757,13 @@ jobs:
   # SECURITY-EXPOSURE.md. Forces every new alert to be triaged with a
   # documented decision (override / dismiss / track / patch) instead of
   # accumulating silently. See also SECURITY-EXPOSURE.md operational notes.
+  # Dependency advisories, in the place each can be acted on. On a pull
+  # request: fail only on a vulnerable dependency the pull request's own
+  # changes bring in (GitHub's dependency review), unless SECURITY-EXPOSURE.md
+  # already triages it. On main: every open advisory has a triage row (the
+  # inventory, also run daily by advisory-inventory.yml). Until 0.21.0 the
+  # inventory ran on every pull request, so each newly published advisory
+  # turned every open PR red at once, about changes none of them made.
   security-exposure:
     runs-on: ubuntu-latest
     timeout-minutes: 20
@@ -764,13 +771,28 @@ jobs:
       contents: read
     steps:
       - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1  # v7.0.1
+      - name: Advisories already triaged in SECURITY-EXPOSURE.md
+        if: github.event_name == 'pull_request'
+        id: triaged
+        run: echo "ids=$(grep -oE 'GHSA(-[0-9a-z]{4}){3}' SECURITY-EXPOSURE.md | sort -u | paste -sd, -)" >> "$GITHUB_OUTPUT"
+      - name: No vulnerable dependency added by this pull request
+        if: github.event_name == 'pull_request'
+        uses: actions/dependency-review-action@a1d282b36b6f3519aa1f3fc636f609c47dddb294  # v5.0.0
+        with:
+          fail-on-severity: moderate
+          allow-ghsas: ${{ steps.triaged.outputs.ids }}
+          license-check: false
+          comment-summary-in-pr: never
       - uses: actions/setup-node@820762786026740c76f36085b0efc47a31fe5020  # v7.0.0
+        if: github.event_name != 'pull_request'
         with:
           node-version: 22
           cache: npm
           cache-dependency-path: package-lock.json
-      - run: npm ci
-      - name: Check exposure coverage
+      - if: github.event_name != 'pull_request'
+        run: npm ci
+      - name: Every open advisory has a triage row
+        if: github.event_name != 'pull_request'
         run: node scripts/security/check-exposure-coverage.mjs
 
   # Smoke-build the Dockerfile on every PR. The host build (`build` job)
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index f7bc7817..cc2192b7 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -89,7 +89,7 @@ Match the formatting of the file you are editing. CI does not run Prettier, and
   | `Real clients (ubuntu-latest)` | Claude Code and Gemini CLI connect to this commit through the config `iris-eval install` writes |
   | `Real clients (macos-latest)` | The same, on macOS |
   | `Real clients (windows-latest)` | The same, on Windows |
-  | `security-exposure` | Every open dependency advisory has an assessed row in `SECURITY-EXPOSURE.md` |
+  | `security-exposure` | On a pull request: no dependency it adds carries an advisory of moderate or above, unless `SECURITY-EXPOSURE.md` already triages it. On main: every open advisory has an assessed row there |
   | `website-lint-and-typecheck` | Lint, typecheck and production build of `website/` |
   | `Hardcoded-claim scanner` | No number/claim restated outside the truthbase |
   | `Truthbase regen vs committed` | `.claims.json` and the rendered files regenerate identical to what you committed |
diff --git a/scripts/security/check-exposure-coverage.mjs b/scripts/security/check-exposure-coverage.mjs
index 472bd8e0..9d18891b 100644
--- a/scripts/security/check-exposure-coverage.mjs
+++ b/scripts/security/check-exposure-coverage.mjs
@@ -34,6 +34,14 @@
 // not have permission to read Dependabot alerts, so an API-based gate
 // would require a PAT secret per repo.
 //
+// Where it runs (0.21.0): on every push to main (ci.yml's security-exposure
+// job) and daily (advisory-inventory.yml), not on pull requests. There it
+// turned every open PR red whenever an advisory was published, about
+// changes none of them made; a pull request is now gated by GitHub's
+// dependency review on the dependencies it adds, with the GHSA ids triaged
+// in SECURITY-EXPOSURE.md allowed. Both remain satisfiable inside the
+// change they block.
+//
 // Run locally:  node scripts/security/check-exposure-coverage.mjs
 // Run in CI:    same — no secrets needed
 //