diff --git a/README.md b/README.md
index 080ab96..9edc299 100644
--- a/README.md
+++ b/README.md
@@ -67,7 +67,9 @@ The check validates four things for every non-break-glass Agent PR:
 
 2. **Title form** — for a `role/bug` branch the title must start with
    `[bug-<id>] `. For a `chore` branch the title must have no `[bug-id]`
-   prefix. If both carry a bug-id they must match.
+   prefix. If both carry a bug-id they must match. The description is a
+   plain-language imperative; Conventional Commit forms such as `fix(scope):`
+   are rejected.
 
 3. **Tracking and attribution** — on Bug-backed work, `## Tracking` contains both the literal
    `Fixes bug-<id>` automation token and the matching navigable
diff --git a/check.sh b/check.sh
index ed81cea..6d3abb6 100755
--- a/check.sh
+++ b/check.sh
@@ -121,6 +121,12 @@ if echo "${TITLE}" | grep -qE "^\[bug-[a-z0-9]+\] ."; then
   TITLE_BUG=$(echo "${TITLE}" | sed -E 's|^\[(bug-[a-z0-9]+)\].*|\1|')
 fi
 
+TITLE_DESCRIPTION=$(printf '%s\n' "${TITLE}" | sed -E 's/^\[bug-[a-z0-9]+\] //')
+if printf '%s\n' "${TITLE_DESCRIPTION}" | grep -qE '^[[:alnum:]-]+(\([^)]*\))?!?:[[:space:]]'; then
+  echo "FAIL[check-naming]: title must use a plain-language imperative without Conventional Commit syntax"
+  FAILED=1
+fi
+
 if [ "${BRANCH_KIND}" = "role-bug" ]; then
   if [ -z "${TITLE_BUG}" ]; then
     echo "FAIL[check-naming]: title must lead with [${BRANCH_BUG}]"
diff --git a/tests/run b/tests/run
index 1ca7d5a..ad9ec4a 100755
--- a/tests/run
+++ b/tests/run
@@ -123,8 +123,9 @@ check "bug-id mismatch"                 1 "dev/bug-x7k2m9/fix-resize"     "[bug-
 
 # fail: chore branch with [bug-id] title prefix
 check "chore with bug-id title"         1 "chore/bump-deps"                "[bug-abc123] Bump deps"      "dev"
-check "role/bug Conventional title"     0 "dev/bug-x7k2m9/fix-resize"     "[bug-x7k2m9] fix(hub): fix resize" "dev"
-check "chore Conventional title"        0 "chore/bump-deps"                "chore(deps): bump deps"      "dev"
+check "role/bug Conventional title"     1 "dev/bug-x7k2m9/fix-resize"     "[bug-x7k2m9] fix(hub): fix resize" "dev"
+check "chore Conventional title"        1 "chore/bump-deps"                "chore(deps): bump deps"      "dev"
+check "role/bug breaking title"         1 "dev/bug-x7k2m9/fix-resize"     "[bug-x7k2m9] fix!: break resize" "dev"
 
 # fail: invalid branch forms
 check "invalid — no role prefix"        1 "feature/foo-bar"                "Add feature"                 "dev"