diff --git a/.changeset/fix-double-check-frontmatter.md b/.changeset/fix-double-check-frontmatter.md
new file mode 100644
index 0000000..65cf3ac
--- /dev/null
+++ b/.changeset/fix-double-check-frontmatter.md
@@ -0,0 +1,12 @@
+---
+"@paulhammond/dotfiles": patch
+---
+
+Fix `double-check` skill being silently skipped by the skills.sh installer
+
+The skill's `description` frontmatter contained an inline `": "` (in
+`Provider-agnostic: it always picks...`). YAML reads colon-space inside an
+unquoted plain scalar as a nested mapping, so `npx skills add` failed to
+parse the frontmatter and silently dropped the skill — the installer found
+27 of 28 skills and `double-check` never landed in `~/.agents/skills/`.
+Replaced the colon with an em dash to match the description's existing style.
diff --git a/claude/.claude/skills/double-check/SKILL.md b/claude/.claude/skills/double-check/SKILL.md
index ce960f8..525ca25 100644
--- a/claude/.claude/skills/double-check/SKILL.md
+++ b/claude/.claude/skills/double-check/SKILL.md
@@ -1,6 +1,6 @@
 ---
 name: double-check
-description: Get an independent second opinion on finished work from a *different* AI provider's CLI agent — codex, claude, gemini, or cursor-agent — then run a constructive back-and-forth between the two agents until both genuinely agree. A model is biased toward its own reasoning, so self-review misses what cross-provider review catches. Use when the user says "double check this", "verify my work", "get a second opinion", "have another model check", "cross-check with codex/gemini", "is this actually right?", or before merging or shipping high-stakes, complex, or security-sensitive work. Provider-agnostic: it always picks a verifier *different* from whichever agent is hosting the session.
+description: Get an independent second opinion on finished work from a *different* AI provider's CLI agent — codex, claude, gemini, or cursor-agent — then run a constructive back-and-forth between the two agents until both genuinely agree. A model is biased toward its own reasoning, so self-review misses what cross-provider review catches. Use when the user says "double check this", "verify my work", "get a second opinion", "have another model check", "cross-check with codex/gemini", "is this actually right?", or before merging or shipping high-stakes, complex, or security-sensitive work. Provider-agnostic — it always picks a verifier *different* from whichever agent is hosting the session.
 ---
 
 # Double Check
diff --git a/test/run.sh b/test/run.sh
index af02563..c964698 100755
--- a/test/run.sh
+++ b/test/run.sh
@@ -4,4 +4,5 @@ set -e
 SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
 
 "$SCRIPT_DIR/opencode-compat.sh"
+"$SCRIPT_DIR/skills-frontmatter.sh"
 "$SCRIPT_DIR/install-claude-next-skills.sh"
diff --git a/test/skills-frontmatter.sh b/test/skills-frontmatter.sh
new file mode 100755
index 0000000..2451cab
--- /dev/null
+++ b/test/skills-frontmatter.sh
@@ -0,0 +1,113 @@
+#!/usr/bin/env bash
+#
+# Test that every skill's SKILL.md frontmatter parses the way the skills.sh
+# installer (`npx skills add`) parses it.
+#
+# The installer reads the YAML frontmatter with a strict parser and silently
+# drops any skill whose frontmatter fails to parse — the skill simply never
+# lands in ~/.agents/skills/. The classic trap is an inline ": " (colon +
+# space) inside an UNQUOTED `name:`/`description:` value: YAML reads that as a
+# nested mapping and throws, so the whole skill disappears with no error.
+# (This is exactly what hid the `double-check` skill.) A bare " #" in an
+# unquoted value is the same kind of trap — it starts a comment.
+#
+# This guard fails loudly in CI instead of letting a skill vanish at install
+# time.
+#
+# Usage:
+#   ./test/skills-frontmatter.sh
+#
+
+set -e
+
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
+REPO_ROOT="$(cd "$SCRIPT_DIR/.." && pwd)"
+SKILLS_DIR="$REPO_ROOT/claude/.claude/skills"
+FAILURES=0
+
+RED='\033[0;31m'
+GREEN='\033[0;32m'
+NC='\033[0m'
+
+fail() {
+  echo -e "${RED}FAIL${NC}: $1"
+  FAILURES=$((FAILURES + 1))
+}
+
+pass() {
+  echo -e "${GREEN}PASS${NC}: $1"
+}
+
+# Check a single `key: value` frontmatter line for YAML plain-scalar hazards.
+# Quoted values (starting with " or ') are left to the parser; only unquoted
+# plain scalars are at risk.
+check_scalar() {
+  local skill="$1" key="$2" value="$3"
+
+  # Trim leading whitespace from the value
+  value="${value#"${value%%[![:space:]]*}"}"
+
+  case "$value" in
+    '"'*|"'"*)
+      # Quoted scalar — the YAML parser handles escaping; nothing to flag.
+      return 0
+      ;;
+  esac
+
+  if printf '%s' "$value" | grep -q ': '; then
+    fail "$skill: unquoted '$key' contains \": \" (breaks YAML — quote it or use an em dash)"
+    return 1
+  fi
+
+  if printf '%s' "$value" | grep -q ' #'; then
+    fail "$skill: unquoted '$key' contains \" #\" (YAML reads it as a comment — quote it)"
+    return 1
+  fi
+
+  return 0
+}
+
+echo "Testing skill frontmatter parses for the skills.sh installer..."
+echo ""
+
+shopt -s nullglob
+for skill_md in "$SKILLS_DIR"/*/SKILL.md; do
+  skill="$(basename "$(dirname "$skill_md")")"
+
+  # Frontmatter must open on line 1 and have a closing ---
+  if ! head -1 "$skill_md" | grep -q '^---$'; then
+    fail "$skill: SKILL.md does not start with '---' frontmatter"
+    continue
+  fi
+
+  # Extract the frontmatter block (between the first two --- fences)
+  frontmatter="$(awk 'NR==1{next} /^---$/{exit} {print}' "$skill_md")"
+
+  name_line="$(printf '%s\n' "$frontmatter" | grep -m1 '^name:' || true)"
+  desc_line="$(printf '%s\n' "$frontmatter" | grep -m1 '^description:' || true)"
+
+  if [ -z "$name_line" ]; then
+    fail "$skill: frontmatter missing 'name:'"
+  fi
+  if [ -z "$desc_line" ]; then
+    fail "$skill: frontmatter missing 'description:'"
+  fi
+
+  ok=true
+  [ -n "$name_line" ] && { check_scalar "$skill" "name" "${name_line#name:}" || ok=false; }
+  [ -n "$desc_line" ] && { check_scalar "$skill" "description" "${desc_line#description:}" || ok=false; }
+
+  if [ "$ok" = true ] && [ -n "$name_line" ] && [ -n "$desc_line" ]; then
+    pass "$skill: frontmatter safe for skills.sh installer"
+  fi
+done
+
+echo ""
+
+if [ "$FAILURES" -gt 0 ]; then
+  echo -e "${RED}$FAILURES test(s) failed${NC}"
+  exit 1
+else
+  echo -e "${GREEN}All tests passed${NC}"
+  exit 0
+fi