diff --git a/.github/workflows/no-secrets.yml b/.github/workflows/no-secrets.yml
new file mode 100644
index 0000000..cc6e028
--- /dev/null
+++ b/.github/workflows/no-secrets.yml
@@ -0,0 +1,27 @@
+name: Tracked Secret Hygiene
+
+on:
+  pull_request:
+  push:
+    branches:
+      - main
+  workflow_dispatch:
+
+permissions:
+  contents: read
+
+concurrency:
+  group: secret-hygiene-${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  secret-scan:
+    name: Scan tracked text files
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check out source
+        uses: actions/checkout@v4
+
+      - name: Scan for secret-like values
+        shell: bash
+        run: php scripts/no-secrets-check.php
diff --git a/docs/ENGINE_IMPLEMENTATION_AUDIT.md b/docs/ENGINE_IMPLEMENTATION_AUDIT.md
index 50b5fcd..83983e9 100644
--- a/docs/ENGINE_IMPLEMENTATION_AUDIT.md
+++ b/docs/ENGINE_IMPLEMENTATION_AUDIT.md
@@ -51,6 +51,12 @@ The 31-case policy result currently linked from the README is historical evidenc
 
 Legal provenance is also unresolved on current `main`: the root `LICENSE` path is absent, and GitHub reports no repository license. The README's proprietary-license statement remains the only checked-in guidance. This audit does not invent an MIT or other license; PR #6 proposes a license change and should be resolved by its owner before any legal claim is published. Preserve existing attribution and history until that choice is merged.
 
+## Tracked configuration and secret scan
+
+The repository currently has no tracked `.env` or `.env.*` files; `.gitignore` excludes runtime environment files while allowing future redacted `.env.example` templates. The new `scripts/no-secrets-check.php` scans Git-tracked text files and reports only path, line, and rule identifiers—never matched values. It rejects private-key markers, common provider/GitHub/AWS token formats, and credential-like assignments.
+
+The sole allowlisted match is the deterministic evaluator fixture `interaction-policy-eval-secret-2026` in `scripts/authority-policy-eval.php`; it is not a runtime credential and is matched by exact path and literal. The [tracked secret hygiene workflow](../.github/workflows/no-secrets.yml) runs the check on pull requests and pushes to `main`. Branch-protection required status is not asserted here and must be verified separately before relying on it as a merge gate.
+
 ## Recommended next work
 
 Implement each no-op method only with its owning contract's intended semantics and a focused test. Until then, keep the methods visible as compatibility scaffolds and keep portfolio language at the deterministic baseline level recorded in [AI_ENGINEERING.md](AI_ENGINEERING.md).
diff --git a/scripts/no-secrets-check.php b/scripts/no-secrets-check.php
new file mode 100644
index 0000000..4f56734
--- /dev/null
+++ b/scripts/no-secrets-check.php
@@ -0,0 +1,76 @@
+<?php
+
+declare(strict_types=1);
+
+$root = dirname(__DIR__);
+$trackedOutput = shell_exec('git -C ' . escapeshellarg($root) . ' ls-files -z');
+if (!is_string($trackedOutput)) {
+    fwrite(STDERR, "Unable to enumerate tracked files.\n");
+    exit(2);
+}
+
+$trackedFiles = array_values(array_filter(explode("\0", $trackedOutput), static fn(string $path): bool => $path !== ''));
+$rules = [
+    'private-key' => '/-----BEGIN [^-]+ PRIVATE KEY-----/',
+    'known-token' => '/(?<![A-Za-z0-9])(?:sk|pk|rk)-[A-Za-z0-9]{16,}(?![A-Za-z0-9])/',
+    'github-token' => '/(?<![A-Za-z0-9])(?:ghp|github_pat)_[A-Za-z0-9_]{20,}(?![A-Za-z0-9])/',
+    'aws-access-key' => '/\bAKIA[0-9A-Z]{16}\b/',
+    'credential-assignment' => "/\b(?:api[_-]?key|secret|password|token)\b\s*[:=]\s*[\"']?([A-Za-z0-9_\/.=+\-]{12,})/i",
+];
+$allowlistedFixtures = [
+    'scripts/authority-policy-eval.php' => 'interaction-policy-eval-secret-2026',
+];
+
+$findings = [];
+$allowlistedMatches = 0;
+$textFileCount = 0;
+
+foreach ($trackedFiles as $relativePath) {
+    $absolutePath = $root . DIRECTORY_SEPARATOR . str_replace('/', DIRECTORY_SEPARATOR, $relativePath);
+    if (!is_file($absolutePath)) {
+        continue;
+    }
+
+    $contents = file_get_contents($absolutePath);
+    if (!is_string($contents) || str_contains($contents, "\0")) {
+        continue;
+    }
+    $textFileCount++;
+
+    foreach ($rules as $rule => $pattern) {
+        $matches = [];
+        if (preg_match_all($pattern, $contents, $matches, PREG_OFFSET_CAPTURE) === false || $matches[0] === []) {
+            continue;
+        }
+
+        foreach ($matches[0] as $match) {
+            $value = (string) $match[0];
+            $offset = (int) $match[1];
+            $line = 1 + substr_count(substr($contents, 0, $offset), "\n");
+            $prefix = substr($contents, 0, $offset + strlen($value));
+            $lines = explode("\n", $prefix);
+            $lineText = (string) ($lines[array_key_last($lines)] ?? '');
+            $isAllowlistedFixture = $rule === 'credential-assignment'
+                && isset($allowlistedFixtures[$relativePath])
+                && str_contains($lineText, $allowlistedFixtures[$relativePath]);
+
+            if ($isAllowlistedFixture) {
+                $allowlistedMatches++;
+                continue;
+            }
+
+            $findings[$relativePath . ':' . $line . ':' . $rule] = true;
+        }
+    }
+}
+
+if ($findings !== []) {
+    ksort($findings);
+    fwrite(STDERR, "Secret-like values detected (values redacted):\n");
+    foreach (array_keys($findings) as $finding) {
+        fwrite(STDERR, " - {$finding}\n");
+    }
+    exit(1);
+}
+
+echo "No secret-like values found in {$textFileCount} tracked text files; allowlisted deterministic fixture matches: {$allowlistedMatches}.\n";