@@ -61,6 +61,12 @@ def real_git(*command):
         if scenario.get("graphql_errors"):
             response["errors"] = [{"message": "fixture GraphQL failure"}]
         print(json.dumps(response))
+    elif args == ["api", "repos/cortexkit/magic-context/pulls/123"]:
+        prior = sum(item["name"] == "gh" and item["args"] == args for item in previous)
+        body = scenario.get("body", "A plain description.")
+        if prior and "body" in scenario.get("recheck", {}):
+            body = scenario["recheck"]["body"]
+        print(json.dumps({"number": 123, "body": body}))
     elif args[:1] == ["api"] and any("/check-runs?per_page=100" in arg for arg in args):
         if "--paginate" not in args or "--slurp" not in args or not any(scenario["head"] in arg for arg in args):
             sys.exit("Check-runs query must paginate the exact head")
 
@@ -127,12 +127,38 @@ check_runs() {
 $pending"
 }
 
+# GitHub closes an issue when a closing keyword ("Fixes #N") appears in a PR
+# description at merge or in a commit message pushed to master. This script also
+# puts the PR title in its merge commit message. Issues must stay open until the
+# fix is released, so a keyword in the title, the description or any merged
+# commit message is refused.
+CLOSING_KEYWORD='(^|[^[:alnum:]_])(fix(es|ed)?|close[sd]?|resolve[sd]?):?[[:space:]]+([[:alnum:]_.-]+/[[:alnum:]_.-]+)?#[0-9]+'
+
 check_title() {
-  local closing
-  closing=$(run jq -nr --arg title "$title" '$title | test("(^|[^[:alnum:]_])(fix(es|ed)?|close[sd]?|resolve[sd]?)[[:space:]]+#[0-9]+"; "i")')
+  local closing pull body
+  closing=$(run jq -nr --arg title "$title" --arg re "$CLOSING_KEYWORD" '$title | test($re; "i")')
   if [ "$closing" = true ]; then
     die 'PR title contains a GitHub closing keyword with a number. Edit the title/message before merging; no automatic issue closing is allowed.'
   fi
+  pull=$(run gh api "repos/$REPOSITORY/pulls/$number")
+  body=$(run jq -r '.body // ""' <<< "$pull")
+  closing=$(run jq -nr --arg body "$body" --arg re "$CLOSING_KEYWORD" '$body | test($re; "i")')
+  if [ "$closing" = true ]; then
+    die 'PR description contains a GitHub closing keyword with a number. Remove it from the description before merging; no automatic issue closing is allowed.'
+  fi
+}
+
+# Run after the PR head is fetched: the merge keeps the contributor's commits,
+# so their messages reach master unchanged.
+check_commit_messages() {
+  local messages closing
+  messages=$(run git log --format='%h %s%n%b' "master..$head")
+  closing=$(printf '%s\n' "$messages" | grep -iE "$CLOSING_KEYWORD" || true)
+  if [ -n "$closing" ]; then
+    die "A commit message in PR #$number contains a GitHub closing keyword, which would close the issue as soon as master is pushed:
+$closing
+Ask the contributor to reword the commit, or squash the PR into one commit with a clean message, before merging."
+  fi
 }
 
 head=''
@@ -157,6 +183,7 @@ master_sha=$(run git rev-parse master)
 run git fetch origin "pull/$number/head"
 fetched_head=$(run git rev-parse FETCH_HEAD)
 [ "$fetched_head" = "$head" ] || die 'PR head changed between the GitHub query and fetch; retry with the new head.'
+check_commit_messages
 
 worktree="${TMPDIR:-/tmp}/magic-context/merge-pr-$number"
 [ ! -e "$worktree" ] && [ ! -L "$worktree" ] || die "Temporary worktree already exists: $worktree (not removed)."
 
@@ -82,14 +82,14 @@ def git(self, *args):
         self.assertEqual(result.returncode, 0, result.stderr)
         return result.stdout
 
-    def prepare_pr(self, paths):
+    def prepare_pr(self, paths, message="Fixture PR"):
         self.git("checkout", "-B", "fixture-pr", self.master)
         for name in paths:
             path = self.repo / name
             path.parent.mkdir(parents=True, exist_ok=True)
             path.write_text("export const changed = true;\n")
         self.git("add", ".")
-        self.git("commit", "-m", "Fixture PR")
+        self.git("commit", "-m", message)
         self.scenario["head"] = self.git("rev-parse", "HEAD").strip()
         self.git("checkout", "master")
 
@@ -214,6 +214,27 @@ def test_closing_keyword_in_title_refuses(self):
                 self.scenario["title"] = title
                 self.assert_refused(self.run_script(), "closing keyword")
 
+    def test_closing_keyword_in_description_refuses(self):
+        for body in ("Summary.\n\nFixes #777", "fixes: #7", "Closes cortexkit/magic-context#9"):
+            with self.subTest(body=body):
+                self.scenario["body"] = body
+                self.assert_refused(self.run_script(), "PR description contains a GitHub closing keyword")
+
+    def test_closing_keyword_in_commit_message_refuses(self):
+        self.prepare_pr(["packages/plugin/demo.ts"], message="fix(agents): keep named allows\n\nFixes #777")
+        run = self.run_script()
+        self.assert_refused(run, "commit message in PR #123 contains a GitHub closing keyword")
+        self.assertIn("Fixes #777", run.stderr)
+
+    def test_issue_mentions_without_closing_keyword_proceed(self):
+        self.scenario["body"] = "Implements the direction agreed in issue #777 (see #777)."
+        self.prepare_pr(["packages/plugin/demo.ts"], message="fix(agents): keep named allows (#777)")
+        self.assertEqual(self.run_script().returncode, 0)
+
+    def test_rechecks_description_after_gates(self):
+        self.scenario["recheck"] = {"body": "Fixes #123"}
+        self.assert_refused(self.run_script(), "PR description contains a GitHub closing keyword")
+
     def test_head_changed_between_query_and_fetch_refuses(self):
         self.scenario["fetched_head"] = self.master
         self.assert_refused(self.run_script(), "head changed between")