diff --git a/.github/workflows/secret-scan.yml b/.github/workflows/secret-scan.yml
new file mode 100644
index 0000000..bc42eec
--- /dev/null
+++ b/.github/workflows/secret-scan.yml
@@ -0,0 +1,37 @@
+# Issue #224: scan every pull request for committed secrets and fail the
+# check when gitleaks finds one. Runs the gitleaks CLI directly (pinned
+# version, checksum-verified) instead of gitleaks/gitleaks-action, which
+# needs a paid license key for repos owned by an organization.
+# Only the PR's own commits are scanned (base..head), so old history does
+# not block new PRs. Config and allowlist: .gitleaks.toml.
+name: Secret Scan
+on:
+  pull_request:
+    branches: [main]
+permissions:
+  contents: read
+jobs:
+  gitleaks:
+    runs-on: ubuntu-latest
+    env:
+      GITLEAKS_VERSION: 8.28.0
+      GITLEAKS_SHA256: a65b5253807a68ac0cafa4414031fd740aeb55f54fb7e55f386acb52e6a840eb
+    steps:
+      - uses: actions/checkout@v7
+        with:
+          fetch-depth: 0
+      - name: Install gitleaks
+        run: |
+          curl -sSfL -o gitleaks.tar.gz \
+            "https://github.com/gitleaks/gitleaks/releases/download/v${GITLEAKS_VERSION}/gitleaks_${GITLEAKS_VERSION}_linux_x64.tar.gz"
+          echo "${GITLEAKS_SHA256}  gitleaks.tar.gz" | sha256sum -c -
+          tar -xzf gitleaks.tar.gz -C "$RUNNER_TEMP" gitleaks
+          rm gitleaks.tar.gz
+      - name: Scan PR commits
+        env:
+          BASE_SHA: ${{ github.event.pull_request.base.sha }}
+          HEAD_SHA: ${{ github.event.pull_request.head.sha }}
+        run: |
+          "$RUNNER_TEMP/gitleaks" git --no-banner --redact --verbose \
+            --config .gitleaks.toml \
+            --log-opts="${BASE_SHA}..${HEAD_SHA}" .
diff --git a/.gitleaks.toml b/.gitleaks.toml
new file mode 100644
index 0000000..8c77448
--- /dev/null
+++ b/.gitleaks.toml
@@ -0,0 +1,46 @@
+# gitleaks config for the Secret Scan workflow (issue #224).
+# Starts from gitleaks' built-in rules and adds a Stellar secret-seed rule,
+# since that is the key type this project actually handles.
+# Every allowlist entry below is narrow on purpose; add to it only for
+# values that are provably not secrets (public data, published test vectors).
+
+[extend]
+useDefault = true
+
+[[rules]]
+id = "stellar-secret-seed"
+description = "Stellar secret seed (S... strkey)"
+regex = '''\bS[A-Z2-7]{55}\b'''
+keywords = ["s"]
+
+  # Placeholder seeds such as SXXXX...XXXX used in docs.
+  [[rules.allowlists]]
+  description = "All-X placeholder seed"
+  regexTarget = "match"
+  regexes = ['''^SX{55}$''']
+
+  # Published testnet test vectors used by example tests. Allowed only
+  # inside examples/, and only these exact values; any other seed in
+  # examples/ still fails the scan.
+  [[rules.allowlists]]
+  description = "Known testnet test vectors in examples/"
+  condition = "AND"
+  paths = ['''^examples/''']
+  regexes = ['''SCKB3ECHCPVM4HJPNCQWTQWJJ5XRL6UNKLTTCIH4B7TB22NKJ5GUFMIV''']
+
+[[allowlists]]
+# Applies to all rules (gitleaks 8.28 ignores targetRules for extended
+# default rules). Safe: a G... strkey is always public.
+# Stellar public keys (G... strkeys) are public account IDs, not secrets,
+# but the built-in generic-api-key rule flags `"key": "G..."` in fixtures.
+description = "Stellar public account IDs"
+regexTarget = "secret"
+regexes = ['''^G[A-Z2-7]{55}$''']
+
+[[allowlists]]
+# Minified identifier in the ncc bundle, not a credential.
+description = "False positive in actions/verify-audit-cid/dist bundle"
+condition = "AND"
+paths = ['''^actions/verify-audit-cid/dist/index\.js$''']
+regexTarget = "secret"
+regexes = ['''^hasV2Preconditions$''']
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index c149519..ec82407 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -104,6 +104,8 @@ Email: **niriumprotocol@gmail.com**
 
 Include: description, reproduction steps, potential impact, and any suggested remediation.
 
+If the **Secret Scan** check fails on your PR, treat the key as leaked: revoke or rotate it, remove it from your branch (amend/rebase so no commit contains it), and push again. If it is a false positive or a public test vector, add a narrow, commented entry to `.gitleaks.toml` instead of disabling the check.
+
 ---
 
 ## License