diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index dee5cb290..d6d64042c 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -134,10 +134,10 @@ jobs:
           fi
           agent-spec --version
 
-      - name: Tests (workspace: lib, bins, doctests, ux-harness)
+      - name: "Tests (workspace: lib, bins, doctests, ux-harness)"
         run: cargo test --workspace
 
-      - name: Static UX audit (gate policy: tools/ux-harness/gate.json)
+      - name: "Static UX audit (gate policy: tools/ux-harness/gate.json)"
         # Source-only audit: token contrast, token discipline, translation
         # coverage. Thresholds are a ratchet documented in gate.json.
         run: |
diff --git a/tests/ci_policy.rs b/tests/ci_policy.rs
index 6dccddbd0..2982d7c84 100644
--- a/tests/ci_policy.rs
+++ b/tests/ci_policy.rs
@@ -61,6 +61,43 @@ fn run_lines(job: &str) -> Vec<String> {
     out
 }
 
+/// GitHub silently refuses to run a workflow whose YAML does not parse — the
+/// run shows up as "workflow file issue" and, worse, the PR simply has no
+/// `spec gate` check at all, so a broken file looks green. Without a YAML
+/// dependency we enforce the one mistake that bit us: an unquoted scalar
+/// containing `: ` (e.g. `name: Tests (workspace: lib)`) is a nested mapping
+/// to YAML. Every single-line `name:` / `run:` value with `: ` must be quoted.
+#[test]
+fn ci_workflow_scalars_with_colon_space_are_quoted() {
+    for rel in [".github/workflows/main.yml", ".github/workflows/builds.yml"] {
+        let wf = read(rel);
+        for (i, line) in wf.lines().enumerate() {
+            let t = line.trim_start();
+            if t.starts_with('#') {
+                continue;
+            }
+            // Steps are list items: `- name: …` — drop the bullet before matching keys.
+            let t = t.strip_prefix("- ").map(str::trim_start).unwrap_or(t);
+            for key in ["name:", "run:", "if:", "key:"] {
+                let Some(rest) = t.strip_prefix(key) else { continue };
+                let v = rest.trim();
+                if v.is_empty() || v == "|" || v == ">" || v == "|-" {
+                    continue;
+                }
+                let quoted = (v.starts_with('"') && v.ends_with('"'))
+                    || (v.starts_with('\'') && v.ends_with('\''));
+                // `${{ ... }}` expressions are fine; a bare `: ` elsewhere is not.
+                let stripped = v.replace("${{", "").replace("}}", "");
+                assert!(
+                    quoted || !stripped.contains(": "),
+                    "{rel}:{}: unquoted YAML scalar contains `: ` — quote it: {line}",
+                    i + 1
+                );
+            }
+        }
+    }
+}
+
 #[test]
 fn ci_workflow_runs_all_cargo_test_targets() {
     let wf = read(".github/workflows/main.yml");