diff --git a/.github/workflows/repo-integrity-guard.yml b/.github/workflows/repo-integrity-guard.yml
index b0fc5733..d10f2246 100644
--- a/.github/workflows/repo-integrity-guard.yml
+++ b/.github/workflows/repo-integrity-guard.yml
@@ -63,6 +63,21 @@ jobs:
           done
           exit $status
 
+      - name: Source files must not be patch fragments
+        run: |
+          set -euo pipefail
+          status=0
+          while IFS= read -r -d '' file; do
+            first_content=$(sed -n '/[^[:space:]]/{p;q;}' "$file")
+            case "$first_content" in
+              '@@ '*|'*** Begin Patch'*|'diff --git '*)
+                echo "::error file=${file}::Source file begins with patch syntax: ${first_content}"
+                status=1
+                ;;
+            esac
+          done < <(git ls-files -z -- '*.rs' '*.ex' '*.exs' '*.res' '*.js' '*.ts' '*.py' '*.sh')
+          exit "$status"
+
       - name: Mass-deletion tripwire
         env:
           EVENT: ${{ github.event_name }}
diff --git a/.gitignore b/.gitignore
index 2c1f4a41..ab5733ef 100644
--- a/.gitignore
+++ b/.gitignore
@@ -15,6 +15,7 @@
 # IDE
 .idea/
 .vscode/
+.claude/worktrees/
 *.swp
 *.swo
 *~
diff --git a/SECURITY.md b/SECURITY.md
index 3a101396..af80df73 100644
--- a/SECURITY.md
+++ b/SECURITY.md
@@ -1,21 +1,36 @@
 <!-- SPDX-License-Identifier: MPL-2.0 -->
 
-# Security Policy
+# Security policy
 
-## Supported versions
+## Reporting a vulnerability
 
-The `main` branch is the supported version of this project.
+Please report suspected vulnerabilities privately through
+[GitHub private vulnerability reporting](https://github.com/hyperpolymath/gitbot-fleet/security/advisories/new).
+Do not disclose a vulnerability in a public issue, pull request, discussion, or
+social-media post before a coordinated fix is available.
 
-## Reporting a vulnerability
+Include the affected component and revision, the expected impact, reproduction
+steps, and a minimal proof of concept where possible. Please avoid accessing,
+modifying, or deleting data beyond what is necessary to demonstrate the issue,
+and do not perform denial-of-service testing.
+
+We aim to acknowledge a report within 48 hours, provide an initial assessment
+within seven days, and send status updates at least weekly while remediation is
+in progress. Disclosure timing will be coordinated with the reporter; the
+default target is within 90 days of the initial report.
+
+## Supported versions
+
+Security fixes are made on the default branch. Tagged releases are supported
+only when explicitly identified as maintained in their release notes.
 
-Please report security vulnerabilities through GitHub's private vulnerability
-reporting feature:
+## Safe harbour
 
-1. Open the repository's **Security** tab.
-2. Select **Report a vulnerability**.
-3. Provide enough detail for the maintainers to reproduce and assess the issue.
+We will not pursue legal action against researchers who act in good faith,
+follow this policy, avoid privacy and service disruption, and allow reasonable
+time for remediation before disclosure.
 
-Do not open a public issue for a security vulnerability.
+## Security measures
 
 The project's detailed security measures and cryptographic standards are
 documented in [SECURITY.adoc](SECURITY.adoc).