diff --git a/.github/workflows/ci-security.yml b/.github/workflows/ci-security.yml
new file mode 100644
index 0000000..4d248bf
--- /dev/null
+++ b/.github/workflows/ci-security.yml
@@ -0,0 +1,33 @@
+name: Security scanners
+
+# Scan integration changes and refresh vulnerability intelligence weekly.
+on:
+  pull_request:
+    branches: [main, develop, maintenance]
+    types: [opened, synchronize, reopened, edited]
+  push:
+    branches: [main, develop, maintenance]
+  schedule:
+    - cron: '12 22 * * 5'
+  workflow_dispatch:
+
+permissions:
+  contents: read
+
+# Local reuse lets this public helper validate its own review candidate.
+jobs:
+  security:
+    if: github.event_name != 'pull_request' || github.event.action != 'edited' || github.event.changes.base != null
+    uses: ./.github/workflows/reusable-public-security.yml
+  summary-tests:
+    runs-on: ubuntu-24.04
+    timeout-minutes: 5
+    steps:
+      - name: Check out current public source
+        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+        with:
+          persist-credentials: false
+      - name: Exercise privacy and policy boundaries
+        run: |
+          python3 -B scripts/security/test_summarize.py
+          python3 -B scripts/security/test_policy.py
diff --git a/.github/workflows/reusable-public-security.yml b/.github/workflows/reusable-public-security.yml
new file mode 100644
index 0000000..67e1541
--- /dev/null
+++ b/.github/workflows/reusable-public-security.yml
@@ -0,0 +1,125 @@
+name: Public security scanners
+
+on:
+  workflow_call:
+
+# Public callers need only source read access, including for untrusted forks.
+permissions:
+  contents: read
+
+# Both scanners always use fresh GitHub-hosted runners, with no inherited secrets.
+jobs:
+  gitleaks:
+    runs-on: ubuntu-24.04
+    timeout-minutes: 15
+    steps:
+      - name: Require a public caller
+        env:
+          CALLER_PRIVATE: ${{ github.event.repository.private }}
+        run: test "$CALLER_PRIVATE" = 'false'
+      - name: Check out caller source without persisted credentials
+        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+        with:
+          fetch-depth: 0
+          persist-credentials: false
+          path: source
+      - name: Check out immutable public scanner utilities
+        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+        with:
+          repository: PrestonCoreSystems/.github
+          ref: 291e6ec865eb08e522e7fc04b51124aa58714524
+          persist-credentials: false
+          path: scanner-tools
+      - name: Reject PR scanner policy edits
+        if: github.event_name == 'pull_request'
+        working-directory: source
+        env:
+          BASE_SHA: ${{ github.event.pull_request.base.sha }}
+        run: bash "$GITHUB_WORKSPACE/scanner-tools/scripts/security/check-policy.sh" "$BASE_SHA"
+      - name: Install checksum-verified gitleaks 8.30.1
+        env:
+          TOOL_SHA256: '551f6fc83ea457d62a0d98237cbad105af8d557003051f41f3e7ca7b3f2470eb'
+        run: |
+          set -euo pipefail
+          directory=$(mktemp -d "$RUNNER_TEMP/public-gitleaks.XXXXXX")
+          curl --fail --location --proto '=https' --tlsv1.2 --max-time 180 \
+            --output "$directory/tool.tar.gz" 'https://github.com/gitleaks/gitleaks/releases/download/v8.30.1/gitleaks_8.30.1_linux_x64.tar.gz'
+          printf '%s  %s\n' "$TOOL_SHA256" "$directory/tool.tar.gz" | sha256sum --check --status
+          tar --extract --gzip --file "$directory/tool.tar.gz" --directory "$directory" gitleaks
+          chmod 0755 "$directory/gitleaks"
+          printf '%s\n' "$directory" >> "$GITHUB_PATH"
+      - name: Scan current source into a private temporary report
+        id: scan
+        working-directory: source
+        env:
+          REPORT: ${{ runner.temp }}/public-gitleaks-report.json
+        run: |
+          umask 077
+          gitleaks dir --redact --ignore-gitleaks-allow --no-banner --no-color --timeout 120 --exit-code 0 --report-format json --report-path "$REPORT" .
+      - name: Publish counts and enforce findings
+        if: always() && steps.scan.outcome == 'success'
+        env:
+          REPORT: ${{ runner.temp }}/public-gitleaks-report.json
+        run: python3 "$GITHUB_WORKSPACE/scanner-tools/scripts/security/summarize.py" 'gitleaks' "$REPORT"
+      - name: Remove temporary report
+        if: always()
+        env:
+          REPORT: ${{ runner.temp }}/public-gitleaks-report.json
+        run: rm -f -- "$REPORT"
+  trivy:
+    runs-on: ubuntu-24.04
+    timeout-minutes: 15
+    steps:
+      - name: Require a public caller
+        env:
+          CALLER_PRIVATE: ${{ github.event.repository.private }}
+        run: test "$CALLER_PRIVATE" = 'false'
+      - name: Check out caller source without persisted credentials
+        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+        with:
+          fetch-depth: 0
+          persist-credentials: false
+          path: source
+      - name: Check out immutable public scanner utilities
+        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+        with:
+          repository: PrestonCoreSystems/.github
+          ref: 291e6ec865eb08e522e7fc04b51124aa58714524
+          persist-credentials: false
+          path: scanner-tools
+      - name: Reject PR scanner policy edits
+        if: github.event_name == 'pull_request'
+        working-directory: source
+        env:
+          BASE_SHA: ${{ github.event.pull_request.base.sha }}
+        run: bash "$GITHUB_WORKSPACE/scanner-tools/scripts/security/check-policy.sh" "$BASE_SHA"
+      - name: Install checksum-verified trivy 0.74.0
+        env:
+          TOOL_SHA256: '2ae6fe3ee734b7fdf11335663e18c75ea12dccc76062f09f164a3b0f8be4371a'
+        run: |
+          set -euo pipefail
+          directory=$(mktemp -d "$RUNNER_TEMP/public-trivy.XXXXXX")
+          curl --fail --location --proto '=https' --tlsv1.2 --max-time 180 \
+            --output "$directory/tool.tar.gz" 'https://github.com/aquasecurity/trivy/releases/download/v0.74.0/trivy_0.74.0_Linux-64bit.tar.gz'
+          printf '%s  %s\n' "$TOOL_SHA256" "$directory/tool.tar.gz" | sha256sum --check --status
+          tar --extract --gzip --file "$directory/tool.tar.gz" --directory "$directory" trivy
+          chmod 0755 "$directory/trivy"
+          printf '%s\n' "$directory" >> "$GITHUB_PATH"
+      - name: Scan current source into a private temporary report
+        id: scan
+        working-directory: source
+        env:
+          REPORT: ${{ runner.temp }}/public-trivy-report.json
+        run: |
+          umask 077
+          trivy fs --quiet --scanners vuln,secret,misconfig --severity HIGH,CRITICAL --ignore-unfixed --exit-code 0 --format json --output "$REPORT" .
+      - name: Publish counts and enforce findings
+        if: always() && steps.scan.outcome == 'success'
+        env:
+          REPORT: ${{ runner.temp }}/public-trivy-report.json
+        run: python3 "$GITHUB_WORKSPACE/scanner-tools/scripts/security/summarize.py" 'trivy' "$REPORT"
+      - name: Remove temporary report
+        if: always()
+        env:
+          REPORT: ${{ runner.temp }}/public-trivy-report.json
+        run: rm -f -- "$REPORT"
diff --git a/SCANNER-HELPERS.md b/SCANNER-HELPERS.md
new file mode 100644
index 0000000..731aea9
--- /dev/null
+++ b/SCANNER-HELPERS.md
@@ -0,0 +1,25 @@
+# Public scanner helpers
+
+Public repositories use this hosted-only workflow because private reusable sources
+cannot be shared with public callers. This code is authored from public upstream
+interfaces and contains no private Core source. Consumers must pin the accepted
+public workflow commit. No App or repository visibility change is needed.
+
+GitLeaks 8.30.1 scans current content with redaction. Trivy 0.74.0 scans HIGH and
+CRITICAL vulnerabilities, secrets and misconfiguration, excluding unfixed
+vulnerabilities. Each release archive has a fixed SHA-256 checksum. Only finding
+counts reach job logs. Temporary reports are deleted, and no raw reports or source
+snippets are uploaded. Invalid or unavailable scans fail instead of claiming clean.
+
+Both jobs always use GitHub-hosted Ubuntu runners and read-only source permissions.
+No secrets or configurable shell inputs are accepted. Forks use the same hosted
+route. PR scanner policy edits are refused and require a separate reviewed policy
+transition. GitLeaks ignores inline allow comments, and newly added inline Trivy
+exclusions are refused. Application deployment, paid scanning and required statuses are outside
+this workflow.
+
+The organization repository validates its candidate through local reusable-workflow
+syntax. Its scanner utility dependency is immutable and separately committed.
+The seven focused tests cover private-value omission, unknown reports, finding exits,
+immutable-base policy admission and added inline Trivy exclusions. Actual engines
+still require source-bound CI after a source change.
diff --git a/scripts/security/check-policy.sh b/scripts/security/check-policy.sh
new file mode 100644
index 0000000..b8a2db4
--- /dev/null
+++ b/scripts/security/check-policy.sh
@@ -0,0 +1,22 @@
+#!/usr/bin/env bash
+# Compare against an actual immutable base; never let a PR weaken its own scanner policy.
+set -euo pipefail
+base=${1:?An immutable PR base is required}
+if ! [[ "$base" =~ ^[0-9a-f]{40}$ ]]; then
+  printf '%s\n' 'An immutable PR base is required.' >&2
+  exit 2
+fi
+git cat-file -e "$base^{commit}"
+changed=$(git diff --name-only "$base" HEAD -- .gitleaks.toml .gitleaksignore .trivyignore .trivyignore.yaml trivy.yaml trivy-secret.yaml)
+if [[ -n "$changed" ]]; then
+  printf '%s\n' 'Scanner policy changed in this PR; a separate reviewed policy transition is required.' >&2
+  exit 1
+fi
+
+# Inspect added lines without logging source; inline exclusions also change scanner policy.
+directive="trivy:""ignore"
+diff=$(git diff --no-ext-diff --unified=0 "$base" HEAD --)
+if printf '%s\n' "$diff" | awk -v directive="$directive" '/^\+[^+]/ && index($0, directive) { found=1 } END { exit !found }'; then
+  printf '%s\n' 'New inline Trivy exclusions require a separate reviewed policy transition.' >&2
+  exit 1
+fi
diff --git a/scripts/security/summarize.py b/scripts/security/summarize.py
new file mode 100644
index 0000000..4e2df2d
--- /dev/null
+++ b/scripts/security/summarize.py
@@ -0,0 +1,49 @@
+#!/usr/bin/env python3
+"""Publish counts only; secret matches, source snippets and paths stay out of logs."""
+import json
+from pathlib import Path
+import sys
+
+
+def summarize(tool, report):
+    """Reject malformed reports rather than reporting an unknown result as clean."""
+    if tool == 'gitleaks':
+        if not isinstance(report, list) or not all(isinstance(x, dict) and isinstance(x.get('RuleID'), str) for x in report):
+            raise ValueError('invalid report')
+        return {'scanner': tool, 'findings': len(report)}
+    if tool != 'trivy' or not isinstance(report, dict) or report.get('SchemaVersion') != 2:
+        raise ValueError('invalid report')
+    results = report.get('Results', [])
+    if not isinstance(results, list):
+        raise ValueError('invalid results')
+    counts = {'vulnerability': 0, 'secret': 0, 'misconfiguration': 0}
+    for result in results:
+        if not isinstance(result, dict):
+            raise ValueError('invalid result')
+        for field, kind in [('Vulnerabilities', 'vulnerability'), ('Secrets', 'secret'), ('Misconfigurations', 'misconfiguration')]:
+            entries = result.get(field, [])
+            if not isinstance(entries, list):
+                raise ValueError('invalid entries')
+            for entry in entries:
+                if not isinstance(entry, dict) or entry.get('Severity') not in {'UNKNOWN', 'LOW', 'MEDIUM', 'HIGH', 'CRITICAL'}:
+                    raise ValueError('invalid finding')
+                if entry['Severity'] in {'HIGH', 'CRITICAL'}:
+                    counts[kind] += 1
+    return {'scanner': tool, 'findings': sum(counts.values()), 'counts': counts}
+
+
+def main():
+    """Only fixed diagnostic text is emitted when reading or parsing fails."""
+    try:
+        if len(sys.argv) != 3:
+            raise ValueError('arguments')
+        result = summarize(sys.argv[1], json.loads(Path(sys.argv[2]).read_text()))
+        print(json.dumps(result, sort_keys=True))
+        return 1 if result['findings'] else 0
+    except (OSError, ValueError, TypeError, KeyError):
+        print('Scanner report unavailable or invalid; result is unknown.', file=sys.stderr)
+        return 2
+
+
+if __name__ == '__main__':
+    sys.exit(main())
diff --git a/scripts/security/test_policy.py b/scripts/security/test_policy.py
new file mode 100644
index 0000000..173a913
--- /dev/null
+++ b/scripts/security/test_policy.py
@@ -0,0 +1,49 @@
+"""Exercise actual shell admission with isolated Git fixtures and no credentials."""
+from pathlib import Path
+import subprocess
+import tempfile
+import unittest
+
+SCRIPT = Path(__file__).with_name('check-policy.sh').resolve()
+
+
+class PolicyTests(unittest.TestCase):
+    def test_immutable_base_and_policy_change(self):
+        with tempfile.TemporaryDirectory() as directory:
+            root = Path(directory)
+
+            def git(*args):
+                return subprocess.check_output(['git', *args], cwd=root, stderr=subprocess.DEVNULL, text=True).strip()
+
+            def commit():
+                git('add', '.')
+                git('-c', 'user.name=Scanner Fixture', '-c', 'user.email=fixture@example.invalid', 'commit', '-m', 'fixture')
+
+            git('init')
+            (root / 'README.md').write_text('Synthetic fixture only.\n')
+            commit()
+            base = git('rev-parse', 'HEAD')
+            for candidate, expected in [(base, 0), ('HEAD', 2), ('a' * 40, 128)]:
+                result = subprocess.run(['bash', str(SCRIPT), candidate], cwd=root, capture_output=True)
+                self.assertEqual(result.returncode, expected)
+            (root / '.gitleaks.toml').write_text('[extend]\nuseDefault = true\n')
+            commit()
+            result = subprocess.run(['bash', str(SCRIPT), base], cwd=root, capture_output=True)
+            self.assertEqual(result.returncode, 1)
+
+    def test_added_inline_trivy_exclusion_is_rejected(self):
+        with tempfile.TemporaryDirectory() as directory:
+            root = Path(directory)
+            commands = [['git', 'init'], ['git', '-c', 'user.name=Scanner Fixture', '-c', 'user.email=fixture@example.invalid', 'commit', '--allow-empty', '-m', 'fixture']]
+            for command in commands:
+                subprocess.run(command, cwd=root, check=True, capture_output=True)
+            base = subprocess.check_output(['git', 'rev-parse', 'HEAD'], cwd=root, text=True).strip()
+            (root / 'Dockerfile').write_text('#' + 'trivy:' + 'ignore:EXAMPLE\nFROM scratch\n')
+            subprocess.run(['git', 'add', '.'], cwd=root, check=True)
+            subprocess.run(['git', '-c', 'user.name=Scanner Fixture', '-c', 'user.email=fixture@example.invalid', 'commit', '-m', 'fixture'], cwd=root, check=True, capture_output=True)
+            result = subprocess.run(['bash', str(SCRIPT), base], cwd=root, capture_output=True)
+            self.assertEqual(result.returncode, 1)
+
+
+if __name__ == '__main__':
+    unittest.main()
diff --git a/scripts/security/test_summarize.py b/scripts/security/test_summarize.py
new file mode 100644
index 0000000..f187181
--- /dev/null
+++ b/scripts/security/test_summarize.py
@@ -0,0 +1,49 @@
+"""Exercise privacy and fail-closed behavior using synthetic findings only."""
+import importlib.util
+import json
+from pathlib import Path
+import subprocess
+import sys
+import tempfile
+import unittest
+
+SCRIPT = Path(__file__).with_name('summarize.py')
+SPEC = importlib.util.spec_from_file_location('summary', SCRIPT)
+MODULE = importlib.util.module_from_spec(SPEC)
+SPEC.loader.exec_module(MODULE)
+
+
+class SummaryTests(unittest.TestCase):
+    def test_gitleaks_counts_without_values(self):
+        result = MODULE.summarize('gitleaks', [{'RuleID': 'example', 'Secret': 'PRIVATE_CANARY', 'Match': 'PRIVATE_CANARY'}])
+        self.assertEqual(result, {'scanner': 'gitleaks', 'findings': 1})
+        self.assertNotIn('PRIVATE_CANARY', json.dumps(result))
+
+    def test_trivy_counts_each_scanner_without_values(self):
+        row = {'Target': 'PRIVATE_PATH', **{key: [{'Severity': 'HIGH', 'Match': 'PRIVATE_CANARY'}, {'Severity': 'LOW'}] for key in ['Vulnerabilities', 'Secrets', 'Misconfigurations']}}
+        result = MODULE.summarize('trivy', {'SchemaVersion': 2, 'Results': [row]})
+        self.assertEqual(result['findings'], 3)
+        self.assertEqual(set(result['counts'].values()), {1})
+        self.assertNotIn('PRIVATE', json.dumps(result))
+
+    def test_empty_valid_reports(self):
+        self.assertEqual(MODULE.summarize('gitleaks', [])['findings'], 0)
+        self.assertEqual(MODULE.summarize('trivy', {'SchemaVersion': 2})['findings'], 0)
+
+    def test_malformed_reports_are_unknown(self):
+        for tool, value in [('other', []), ('gitleaks', {}), ('gitleaks', [None]), ('trivy', {}), ('trivy', {'SchemaVersion': 2, 'Results': None}), ('trivy', {'SchemaVersion': 2, 'Results': [{'Secrets': [{'Severity': 'invented'}]}]})]:
+            with self.subTest(tool=tool, value=value), self.assertRaises(ValueError):
+                MODULE.summarize(tool, value)
+
+    def test_cli_unknown_and_finding_exits_are_distinct(self):
+        with tempfile.TemporaryDirectory() as directory:
+            path = Path(directory) / 'report.json'
+            for payload, expected in [('[{"RuleID":"example","Secret":"PRIVATE_CANARY"}]', 1), ('[]', 0), ('PRIVATE_CANARY', 2)]:
+                path.write_text(payload)
+                result = subprocess.run([sys.executable, str(SCRIPT), 'gitleaks', str(path)], capture_output=True, text=True)
+                self.assertEqual(result.returncode, expected)
+                self.assertNotIn('PRIVATE_CANARY', result.stdout + result.stderr)
+
+
+if __name__ == '__main__':
+    unittest.main()