diff --git a/.github/workflows/skill-docs.yml b/.github/workflows/skill-docs.yml
index 700a8222ae..ba4c6d0ab9 100644
--- a/.github/workflows/skill-docs.yml
+++ b/.github/workflows/skill-docs.yml
@@ -31,3 +31,5 @@ jobs:
             echo "Generated Factory SKILL.md files are stale. Run: bun run gen:skill-docs --host factory"
             exit 1
           }
+      - name: Validate generated skill frontmatter
+        run: bun run skill:frontmatter
diff --git a/SKILL.md b/SKILL.md
index a35e923c65..278e6317f7 100644
--- a/SKILL.md
+++ b/SKILL.md
@@ -2,7 +2,7 @@
 name: gstack
 preamble-tier: 1
 version: 1.1.0
-description: Fast headless browser for QA testing and site dogfooding. (gstack)
+description: "Fast headless browser for QA testing and site dogfooding. (gstack)"
 allowed-tools:
   - Bash
   - Read
diff --git a/autoplan/SKILL.md b/autoplan/SKILL.md
index f8c20cd592..375d4f7813 100644
--- a/autoplan/SKILL.md
+++ b/autoplan/SKILL.md
@@ -2,7 +2,7 @@
 name: autoplan
 preamble-tier: 3
 version: 1.0.0
-description: Auto-review pipeline — reads the full CEO, design, eng, and DX review skills from disk and runs them sequentially with auto-decisions using 6 decision principles. (gstack)
+description: "Auto-review pipeline — reads the full CEO, design, eng, and DX review skills from disk and runs them sequentially with auto-decisions using 6 decision principles. (gstack)"
 benefits-from: [office-hours]
 triggers:
   - run all reviews
diff --git a/benchmark-models/SKILL.md b/benchmark-models/SKILL.md
index 38baa88519..58f5cc9dce 100644
--- a/benchmark-models/SKILL.md
+++ b/benchmark-models/SKILL.md
@@ -2,7 +2,7 @@
 name: benchmark-models
 preamble-tier: 1
 version: 1.0.0
-description: Cross-model benchmark for gstack skills. (gstack)
+description: "Cross-model benchmark for gstack skills. (gstack)"
 triggers:
   - cross model benchmark
   - compare claude gpt gemini
diff --git a/benchmark/SKILL.md b/benchmark/SKILL.md
index d2b54a2c4e..8315b51032 100644
--- a/benchmark/SKILL.md
+++ b/benchmark/SKILL.md
@@ -2,7 +2,7 @@
 name: benchmark
 preamble-tier: 1
 version: 1.0.0
-description: Performance regression detection using the browse daemon. (gstack)
+description: "Performance regression detection using the browse daemon. (gstack)"
 triggers:
   - performance benchmark
   - check page speed
diff --git a/browse/SKILL.md b/browse/SKILL.md
index 9f73f00053..0e8e721947 100644
--- a/browse/SKILL.md
+++ b/browse/SKILL.md
@@ -2,7 +2,7 @@
 name: browse
 preamble-tier: 1
 version: 1.1.0
-description: Fast headless browser for QA testing and site dogfooding. (gstack)
+description: "Fast headless browser for QA testing and site dogfooding. (gstack)"
 triggers:
   - browse a page
   - headless browser
diff --git a/canary/SKILL.md b/canary/SKILL.md
index e7a1715f8f..af83d34864 100644
--- a/canary/SKILL.md
+++ b/canary/SKILL.md
@@ -2,7 +2,7 @@
 name: canary
 preamble-tier: 2
 version: 1.0.0
-description: Post-deploy canary monitoring. (gstack)
+description: "Post-deploy canary monitoring. (gstack)"
 allowed-tools:
   - Bash
   - Read
diff --git a/careful/SKILL.md b/careful/SKILL.md
index 678d66c16b..61fb0d50e0 100644
--- a/careful/SKILL.md
+++ b/careful/SKILL.md
@@ -1,7 +1,7 @@
 ---
 name: careful
 version: 0.1.0
-description: Safety guardrails for destructive commands. (gstack)
+description: "Safety guardrails for destructive commands. (gstack)"
 triggers:
   - be careful
   - warn before destructive
diff --git a/codex/SKILL.md b/codex/SKILL.md
index af351d7f10..011c60a448 100644
--- a/codex/SKILL.md
+++ b/codex/SKILL.md
@@ -2,7 +2,7 @@
 name: codex
 preamble-tier: 3
 version: 1.0.0
-description: OpenAI Codex CLI wrapper — three modes. (gstack)
+description: "OpenAI Codex CLI wrapper — three modes. (gstack)"
 triggers:
   - codex review
   - second opinion
diff --git a/context-restore/SKILL.md b/context-restore/SKILL.md
index 7a272722e7..a3f9fb26f4 100644
--- a/context-restore/SKILL.md
+++ b/context-restore/SKILL.md
@@ -2,7 +2,7 @@
 name: context-restore
 preamble-tier: 2
 version: 1.0.0
-description: Restore working context saved earlier by /context-save. (gstack)
+description: "Restore working context saved earlier by /context-save. (gstack)"
 allowed-tools:
   - Bash
   - Read
diff --git a/context-save/SKILL.md b/context-save/SKILL.md
index 014407fbe4..e560ee44ce 100644
--- a/context-save/SKILL.md
+++ b/context-save/SKILL.md
@@ -2,7 +2,7 @@
 name: context-save
 preamble-tier: 2
 version: 1.0.0
-description: Save working context. (gstack)
+description: "Save working context. (gstack)"
 allowed-tools:
   - Bash
   - Read
diff --git a/cso/SKILL.md b/cso/SKILL.md
index ebacf1ac09..339dd54ad9 100644
--- a/cso/SKILL.md
+++ b/cso/SKILL.md
@@ -2,7 +2,7 @@
 name: cso
 preamble-tier: 2
 version: 2.0.0
-description: Chief Security Officer mode. (gstack)
+description: "Chief Security Officer mode. (gstack)"
 allowed-tools:
   - Bash
   - Read
diff --git a/devex-review/SKILL.md b/devex-review/SKILL.md
index 14ed560d23..80fca1cfcd 100644
--- a/devex-review/SKILL.md
+++ b/devex-review/SKILL.md
@@ -2,7 +2,7 @@
 name: devex-review
 preamble-tier: 3
 version: 1.0.0
-description: Live developer experience audit. (gstack)
+description: "Live developer experience audit. (gstack)"
 triggers:
   - live dx audit
   - test developer experience
diff --git a/document-generate/SKILL.md b/document-generate/SKILL.md
index 2c7e6f0727..43e3f9d3d6 100644
--- a/document-generate/SKILL.md
+++ b/document-generate/SKILL.md
@@ -2,7 +2,7 @@
 name: document-generate
 preamble-tier: 2
 version: 1.0.0
-description: Generate missing documentation from scratch for a feature, module, or entire project. (gstack)
+description: "Generate missing documentation from scratch for a feature, module, or entire project. (gstack)"
 allowed-tools:
   - Bash
   - Read
diff --git a/document-release/SKILL.md b/document-release/SKILL.md
index 43ba9adb12..2934c2c563 100644
--- a/document-release/SKILL.md
+++ b/document-release/SKILL.md
@@ -2,7 +2,7 @@
 name: document-release
 preamble-tier: 2
 version: 1.0.0
-description: Post-ship documentation update. (gstack)
+description: "Post-ship documentation update. (gstack)"
 allowed-tools:
   - Bash
   - Read
diff --git a/freeze/SKILL.md b/freeze/SKILL.md
index fc82b1bea8..3b31ce40bf 100644
--- a/freeze/SKILL.md
+++ b/freeze/SKILL.md
@@ -1,7 +1,7 @@
 ---
 name: freeze
 version: 0.1.0
-description: Restrict file edits to a specific directory for the session. (gstack)
+description: "Restrict file edits to a specific directory for the session. (gstack)"
 triggers:
   - freeze edits to directory
   - lock editing scope
diff --git a/gstack-upgrade/SKILL.md b/gstack-upgrade/SKILL.md
index 9f0f2f7ea6..cc0bf19c02 100644
--- a/gstack-upgrade/SKILL.md
+++ b/gstack-upgrade/SKILL.md
@@ -1,7 +1,7 @@
 ---
 name: gstack-upgrade
 version: 1.1.0
-description: Upgrade gstack to the latest version.
+description: "Upgrade gstack to the latest version."
 triggers:
   - upgrade gstack
   - update gstack version
diff --git a/health/SKILL.md b/health/SKILL.md
index 921a7b5b4b..3e8af16615 100644
--- a/health/SKILL.md
+++ b/health/SKILL.md
@@ -2,7 +2,7 @@
 name: health
 preamble-tier: 2
 version: 1.0.0
-description: Code quality dashboard. (gstack)
+description: "Code quality dashboard. (gstack)"
 triggers:
   - code health check
   - quality dashboard
diff --git a/investigate/SKILL.md b/investigate/SKILL.md
index daf6be6d81..68407f6b96 100644
--- a/investigate/SKILL.md
+++ b/investigate/SKILL.md
@@ -2,7 +2,7 @@
 name: investigate
 preamble-tier: 2
 version: 1.0.0
-description: Systematic debugging with root cause investigation. (gstack)
+description: "Systematic debugging with root cause investigation. (gstack)"
 allowed-tools:
   - Bash
   - Read
diff --git a/ios-design-review/SKILL.md b/ios-design-review/SKILL.md
index 7bfbdd851a..4b8f894f7e 100644
--- a/ios-design-review/SKILL.md
+++ b/ios-design-review/SKILL.md
@@ -2,7 +2,7 @@
 name: ios-design-review
 preamble-tier: 3
 version: 1.0.0
-description: Visual design audit for iOS apps on real hardware. (gstack)
+description: "Visual design audit for iOS apps on real hardware. (gstack)"
 allowed-tools:
   - Bash
   - Read
diff --git a/ios-fix/SKILL.md b/ios-fix/SKILL.md
index 2d1c3d4b10..6e5ec0487c 100644
--- a/ios-fix/SKILL.md
+++ b/ios-fix/SKILL.md
@@ -2,7 +2,7 @@
 name: ios-fix
 preamble-tier: 3
 version: 1.0.0
-description: Autonomous iOS bug fixer. (gstack)
+description: "Autonomous iOS bug fixer. (gstack)"
 allowed-tools:
   - Bash
   - Read
diff --git a/ios-qa/SKILL.md b/ios-qa/SKILL.md
index 0d40c16e55..eb47f69264 100644
--- a/ios-qa/SKILL.md
+++ b/ios-qa/SKILL.md
@@ -2,7 +2,7 @@
 name: ios-qa
 preamble-tier: 3
 version: 1.0.0
-description: Live-device iOS QA for SwiftUI apps. (gstack)
+description: "Live-device iOS QA for SwiftUI apps. (gstack)"
 allowed-tools:
   - Bash
   - Read
diff --git a/ios-sync/SKILL.md b/ios-sync/SKILL.md
index e7a8039247..f53eb197d3 100644
--- a/ios-sync/SKILL.md
+++ b/ios-sync/SKILL.md
@@ -2,7 +2,7 @@
 name: ios-sync
 preamble-tier: 3
 version: 1.0.0
-description: Regenerate the iOS debug bridge against the latest upstream gstack templates. (gstack)
+description: "Regenerate the iOS debug bridge against the latest upstream gstack templates. (gstack)"
 allowed-tools:
   - Bash
   - Read
diff --git a/land-and-deploy/SKILL.md b/land-and-deploy/SKILL.md
index 2eb9faa6c0..b34ab67499 100644
--- a/land-and-deploy/SKILL.md
+++ b/land-and-deploy/SKILL.md
@@ -2,7 +2,7 @@
 name: land-and-deploy
 preamble-tier: 4
 version: 1.0.0
-description: Land and deploy workflow. (gstack)
+description: "Land and deploy workflow. (gstack)"
 allowed-tools:
   - Bash
   - Read
diff --git a/landing-report/SKILL.md b/landing-report/SKILL.md
index aec9978baf..367d4385b5 100644
--- a/landing-report/SKILL.md
+++ b/landing-report/SKILL.md
@@ -1,7 +1,7 @@
 ---
 name: landing-report
 version: 0.1.0
-description: Read-only queue dashboard for workspace-aware ship. (gstack)
+description: "Read-only queue dashboard for workspace-aware ship. (gstack)"
 triggers:
   - landing report
   - version queue
diff --git a/learn/SKILL.md b/learn/SKILL.md
index 08a78b23ca..b0a8742adf 100644
--- a/learn/SKILL.md
+++ b/learn/SKILL.md
@@ -2,7 +2,7 @@
 name: learn
 preamble-tier: 2
 version: 1.0.0
-description: Manage project learnings.
+description: "Manage project learnings."
 triggers:
   - show learnings
   - what have we learned
diff --git a/make-pdf/SKILL.md b/make-pdf/SKILL.md
index 141c60a314..fd55adda77 100644
--- a/make-pdf/SKILL.md
+++ b/make-pdf/SKILL.md
@@ -2,7 +2,7 @@
 name: make-pdf
 preamble-tier: 1
 version: 1.0.0
-description: Turn any markdown file into a publication-quality PDF. (gstack)
+description: "Turn any markdown file into a publication-quality PDF. (gstack)"
 triggers:
   - markdown to pdf
   - generate pdf
diff --git a/office-hours/SKILL.md b/office-hours/SKILL.md
index efa58f7def..a733b945a0 100644
--- a/office-hours/SKILL.md
+++ b/office-hours/SKILL.md
@@ -2,7 +2,7 @@
 name: office-hours
 preamble-tier: 3
 version: 2.0.0
-description: YC Office Hours — two modes. (gstack)
+description: "YC Office Hours — two modes. (gstack)"
 allowed-tools:
   - Bash
   - Read
diff --git a/open-gstack-browser/SKILL.md b/open-gstack-browser/SKILL.md
index 64a93770e7..0f51dfd0de 100644
--- a/open-gstack-browser/SKILL.md
+++ b/open-gstack-browser/SKILL.md
@@ -1,7 +1,7 @@
 ---
 name: open-gstack-browser
 version: 0.2.0
-description: Launch GStack Browser — AI-controlled Chromium with the sidebar extension baked in.
+description: "Launch GStack Browser — AI-controlled Chromium with the sidebar extension baked in."
 triggers:
   - open gstack browser
   - launch chromium
diff --git a/package.json b/package.json
index 280299e0c3..b750a5559e 100644
--- a/package.json
+++ b/package.json
@@ -31,6 +31,7 @@
     "test:gemini": "EVALS=1 bun test test/gemini-e2e.test.ts",
     "test:gemini:all": "EVALS=1 EVALS_ALL=1 bun test test/gemini-e2e.test.ts",
     "skill:check": "bun run scripts/skill-check.ts",
+    "skill:frontmatter": "bun run scripts/skill-frontmatter-check.ts",
     "dev:skill": "bun run scripts/dev-skill.ts",
     "start": "bun run browse/src/server.ts",
     "eval:list": "bun run scripts/eval-list.ts",
diff --git a/pair-agent/SKILL.md b/pair-agent/SKILL.md
index 533a29dc73..3ff48a628c 100644
--- a/pair-agent/SKILL.md
+++ b/pair-agent/SKILL.md
@@ -1,7 +1,7 @@
 ---
 name: pair-agent
 version: 0.1.0
-description: Pair a remote AI agent with your browser. (gstack)
+description: "Pair a remote AI agent with your browser. (gstack)"
 triggers:
   - pair with agent
   - connect remote agent
diff --git a/plan-ceo-review/SKILL.md b/plan-ceo-review/SKILL.md
index 57cbf54640..3033d0a1b6 100644
--- a/plan-ceo-review/SKILL.md
+++ b/plan-ceo-review/SKILL.md
@@ -3,7 +3,7 @@ name: plan-ceo-review
 preamble-tier: 3
 interactive: true
 version: 1.0.0
-description: CEO/founder-mode plan review. (gstack)
+description: "CEO/founder-mode plan review. (gstack)"
 benefits-from: [office-hours]
 allowed-tools:
   - Read
diff --git a/plan-design-review/SKILL.md b/plan-design-review/SKILL.md
index b1b110ae15..4b931b3207 100644
--- a/plan-design-review/SKILL.md
+++ b/plan-design-review/SKILL.md
@@ -3,7 +3,7 @@ name: plan-design-review
 preamble-tier: 3
 interactive: true
 version: 2.0.0
-description: Designer's eye plan review — interactive, like CEO and Eng review. (gstack)
+description: "Designer's eye plan review — interactive, like CEO and Eng review. (gstack)"
 allowed-tools:
   - Read
   - Edit
diff --git a/plan-devex-review/SKILL.md b/plan-devex-review/SKILL.md
index 7336b70a55..e6bda0a1af 100644
--- a/plan-devex-review/SKILL.md
+++ b/plan-devex-review/SKILL.md
@@ -3,7 +3,7 @@ name: plan-devex-review
 preamble-tier: 3
 interactive: true
 version: 2.0.0
-description: Interactive developer experience plan review. (gstack)
+description: "Interactive developer experience plan review. (gstack)"
 benefits-from: [office-hours]
 allowed-tools:
   - Read
diff --git a/plan-eng-review/SKILL.md b/plan-eng-review/SKILL.md
index c4ec10bb60..c6304645ef 100644
--- a/plan-eng-review/SKILL.md
+++ b/plan-eng-review/SKILL.md
@@ -3,7 +3,7 @@ name: plan-eng-review
 preamble-tier: 3
 interactive: true
 version: 1.0.0
-description: Eng manager-mode plan review. (gstack)
+description: "Eng manager-mode plan review. (gstack)"
 benefits-from: [office-hours]
 allowed-tools:
   - Read
diff --git a/qa-only/SKILL.md b/qa-only/SKILL.md
index db1c3dd081..978bf0926e 100644
--- a/qa-only/SKILL.md
+++ b/qa-only/SKILL.md
@@ -2,7 +2,7 @@
 name: qa-only
 preamble-tier: 4
 version: 1.0.0
-description: Report-only QA testing. (gstack)
+description: "Report-only QA testing. (gstack)"
 allowed-tools:
   - Bash
   - Read
diff --git a/qa/SKILL.md b/qa/SKILL.md
index c5fdf9b565..0250eeed69 100644
--- a/qa/SKILL.md
+++ b/qa/SKILL.md
@@ -2,7 +2,7 @@
 name: qa
 preamble-tier: 4
 version: 2.0.0
-description: Systematically QA test a web application and fix bugs found. (gstack)
+description: "Systematically QA test a web application and fix bugs found. (gstack)"
 allowed-tools:
   - Bash
   - Read
diff --git a/retro/SKILL.md b/retro/SKILL.md
index 287f24e35d..5e16e4dfbf 100644
--- a/retro/SKILL.md
+++ b/retro/SKILL.md
@@ -2,7 +2,7 @@
 name: retro
 preamble-tier: 2
 version: 2.0.0
-description: Weekly engineering retrospective. (gstack)
+description: "Weekly engineering retrospective. (gstack)"
 allowed-tools:
   - Bash
   - Read
diff --git a/review/SKILL.md b/review/SKILL.md
index 4d8049d540..54bde2c729 100644
--- a/review/SKILL.md
+++ b/review/SKILL.md
@@ -2,7 +2,7 @@
 name: review
 preamble-tier: 4
 version: 1.0.0
-description: Pre-landing PR review. (gstack)
+description: "Pre-landing PR review. (gstack)"
 allowed-tools:
   - Bash
   - Read
diff --git a/scrape/SKILL.md b/scrape/SKILL.md
index 0af5db5068..5f45dbfa73 100644
--- a/scrape/SKILL.md
+++ b/scrape/SKILL.md
@@ -1,7 +1,7 @@
 ---
 name: scrape
 version: 1.0.0
-description: Pull data from a web page. (gstack)
+description: "Pull data from a web page. (gstack)"
 allowed-tools:
   - Bash
   - Read
diff --git a/scripts/skill-check.ts b/scripts/skill-check.ts
index 9182737ee1..8788695310 100644
--- a/scripts/skill-check.ts
+++ b/scripts/skill-check.ts
@@ -8,7 +8,7 @@
  *   - Freshness check (generated files match committed files)
  */
 
-import { validateSkill } from '../test/helpers/skill-parser';
+import { validateSkill, validateSkillFrontmatter } from '../test/helpers/skill-parser';
 import { discoverTemplates, discoverSkillFiles } from './discover-skills';
 import * as fs from 'fs';
 import * as path from 'path';
@@ -35,6 +35,16 @@ let hasErrors = false;
 console.log('  Skills:');
 for (const file of SKILL_FILES) {
   const fullPath = path.join(ROOT, file);
+  const frontmatterErrors = validateSkillFrontmatter(fullPath);
+  if (frontmatterErrors.length > 0) {
+    hasErrors = true;
+    console.log(`  ❌ ${file.padEnd(30)} — invalid frontmatter`);
+    for (const err of frontmatterErrors) {
+      console.log(`      line ${err.line}: ${err.message}`);
+    }
+    continue;
+  }
+
   const result = validateSkill(fullPath);
 
   if (result.warnings.length > 0) {
diff --git a/scripts/skill-frontmatter-check.ts b/scripts/skill-frontmatter-check.ts
new file mode 100644
index 0000000000..b82065cd59
--- /dev/null
+++ b/scripts/skill-frontmatter-check.ts
@@ -0,0 +1,54 @@
+#!/usr/bin/env bun
+/**
+ * Validate YAML frontmatter for generated SKILL.md files.
+ *
+ * This is intentionally narrower than skill:check so CI can run it after
+ * regenerating only the host outputs relevant to a workflow.
+ */
+
+import { discoverSkillFiles } from './discover-skills';
+import { validateSkillFrontmatter } from '../test/helpers/skill-parser';
+import * as fs from 'fs';
+import * as path from 'path';
+
+const ROOT = path.resolve(import.meta.dir, '..');
+
+function walkSkillFiles(dir: string, acc: string[]): void {
+  for (const entry of fs.readdirSync(dir, { withFileTypes: true })) {
+    if (entry.name === '.git' || entry.name === 'node_modules') continue;
+    const fullPath = path.join(dir, entry.name);
+    if (entry.isDirectory()) {
+      walkSkillFiles(fullPath, acc);
+      continue;
+    }
+    if (entry.name === 'SKILL.md') {
+      acc.push(path.relative(ROOT, fullPath));
+    }
+  }
+}
+
+const files = new Set(discoverSkillFiles(ROOT));
+for (const hostDir of ['.agents', '.factory']) {
+  const fullPath = path.join(ROOT, hostDir);
+  if (fs.existsSync(fullPath)) {
+    const hostFiles: string[] = [];
+    walkSkillFiles(fullPath, hostFiles);
+    for (const file of hostFiles) files.add(file);
+  }
+}
+
+const errors: string[] = [];
+for (const file of [...files].sort()) {
+  const fullPath = path.join(ROOT, file);
+  for (const error of validateSkillFrontmatter(fullPath)) {
+    errors.push(`${file}:${error.line}: ${error.message}`);
+  }
+}
+
+if (errors.length > 0) {
+  console.error('Invalid SKILL.md frontmatter:');
+  for (const error of errors) console.error(`  ${error}`);
+  process.exit(1);
+}
+
+console.log(`Validated frontmatter for ${files.size} SKILL.md files.`);
diff --git a/setup-browser-cookies/SKILL.md b/setup-browser-cookies/SKILL.md
index 2f91f4d687..69580b84e5 100644
--- a/setup-browser-cookies/SKILL.md
+++ b/setup-browser-cookies/SKILL.md
@@ -2,7 +2,7 @@
 name: setup-browser-cookies
 preamble-tier: 1
 version: 1.0.0
-description: Import cookies from your real Chromium browser into the headless browse session. (gstack)
+description: "Import cookies from your real Chromium browser into the headless browse session. (gstack)"
 triggers:
   - import browser cookies
   - login to test site
diff --git a/setup-deploy/SKILL.md b/setup-deploy/SKILL.md
index a35ab97640..d652c1d6ed 100644
--- a/setup-deploy/SKILL.md
+++ b/setup-deploy/SKILL.md
@@ -2,7 +2,7 @@
 name: setup-deploy
 preamble-tier: 2
 version: 1.0.0
-description: Configure deployment settings for /land-and-deploy.
+description: "Configure deployment settings for /land-and-deploy."
 triggers:
   - configure deploy
   - setup deployment
diff --git a/skillify/SKILL.md b/skillify/SKILL.md
index e7911473eb..cda09062ab 100644
--- a/skillify/SKILL.md
+++ b/skillify/SKILL.md
@@ -1,7 +1,7 @@
 ---
 name: skillify
 version: 1.0.0
-description: Codify the most recent successful /scrape flow into a permanent browser-skill on disk. (gstack)
+description: "Codify the most recent successful /scrape flow into a permanent browser-skill on disk. (gstack)"
 allowed-tools:
   - Bash
   - Read
diff --git a/spec/SKILL.md b/spec/SKILL.md
index 7279b9c377..dd047f79a8 100644
--- a/spec/SKILL.md
+++ b/spec/SKILL.md
@@ -1,7 +1,7 @@
 ---
 name: spec
 version: 0.1.0
-description: Turn vague intent into a precise, executable spec in five phases. (gstack)
+description: "Turn vague intent into a precise, executable spec in five phases. (gstack)"
 allowed-tools:
   - Bash
   - Read
diff --git a/sync-gbrain/SKILL.md b/sync-gbrain/SKILL.md
index 4a3a5bc1d7..307efe8fb4 100644
--- a/sync-gbrain/SKILL.md
+++ b/sync-gbrain/SKILL.md
@@ -2,7 +2,7 @@
 name: sync-gbrain
 preamble-tier: 2
 version: 1.0.0
-description: Keep gbrain current with this repo's code and refresh agent search guidance in CLAUDE.md. Wraps the gstack-gbrain-sync orchestrator with state (gstack)
+description: "Keep gbrain current with this repo's code and refresh agent search guidance in CLAUDE.md. Wraps the gstack-gbrain-sync orchestrator with state (gstack)"
 triggers:
   - sync gbrain
   - refresh gbrain
diff --git a/test/helpers/skill-parser.ts b/test/helpers/skill-parser.ts
index 0e3271ba1b..d4152a6b6e 100644
--- a/test/helpers/skill-parser.ts
+++ b/test/helpers/skill-parser.ts
@@ -34,6 +34,11 @@ export interface ValidationResult {
   warnings: string[];
 }
 
+export interface FrontmatterError {
+  line: number;
+  message: string;
+}
+
 /**
  * Extract all $B invocations from bash code blocks in a SKILL.md file.
  */
@@ -138,6 +143,50 @@ export function validateSkill(skillPath: string): ValidationResult {
   return result;
 }
 
+/**
+ * Lightweight frontmatter validation for the YAML subset used by SKILL.md.
+ *
+ * This intentionally does not try to be a complete YAML parser. It catches the
+ * class of errors that make agents skip skills: missing delimiters and plain
+ * scalar values that contain ": " without being quoted or written as a block.
+ */
+export function validateSkillFrontmatter(skillPath: string): FrontmatterError[] {
+  const content = fs.readFileSync(skillPath, 'utf-8');
+  const errors: FrontmatterError[] = [];
+
+  if (!content.startsWith('---\n')) {
+    return [{ line: 1, message: 'missing opening frontmatter delimiter' }];
+  }
+
+  const fmEnd = content.indexOf('\n---', 4);
+  if (fmEnd === -1) {
+    return [{ line: 1, message: 'missing closing frontmatter delimiter' }];
+  }
+
+  const frontmatter = content.slice(4, fmEnd);
+  const lines = frontmatter.split('\n');
+  for (let i = 0; i < lines.length; i++) {
+    const line = lines[i];
+    const match = line.match(/^\s*[A-Za-z0-9_-]+:\s+(.+?)\s*$/);
+    if (!match) continue;
+
+    const value = match[1].trim();
+    const isQuoted = value.startsWith('"') || value.startsWith("'");
+    const isBlockScalar = value === '|' || value === '>' || value.startsWith('|') || value.startsWith('>');
+    const isFlowValue = value.startsWith('[') || value.startsWith('{');
+    if (isQuoted || isBlockScalar || isFlowValue) continue;
+
+    if (/:\s/.test(value)) {
+      errors.push({
+        line: i + 2,
+        message: 'plain YAML scalar contains ": "; quote it or use a block scalar',
+      });
+    }
+  }
+
+  return errors;
+}
+
 /**
  * Extract all REMOTE_SLUG=$(...) assignment patterns from .md files in given subdirectories.
  * Returns a Map from filename → array of full assignment lines found.
diff --git a/test/skill-validation.test.ts b/test/skill-validation.test.ts
index df5cb79947..82b8385ce6 100644
--- a/test/skill-validation.test.ts
+++ b/test/skill-validation.test.ts
@@ -1,5 +1,5 @@
 import { describe, test, expect } from 'bun:test';
-import { validateSkill, extractRemoteSlugPatterns, extractWeightsFromTable } from './helpers/skill-parser';
+import { validateSkill, validateSkillFrontmatter, extractRemoteSlugPatterns, extractWeightsFromTable } from './helpers/skill-parser';
 import { ALL_COMMANDS, COMMAND_DESCRIPTIONS, READ_COMMANDS, WRITE_COMMANDS, META_COMMANDS } from '../browse/src/commands';
 import { SNAPSHOT_FLAGS } from '../browse/src/snapshot';
 import * as fs from 'fs';
@@ -24,6 +24,30 @@ function readShipUnion(): string {
 }
 
 describe('SKILL.md command validation', () => {
+  test('all SKILL.md files have loadable YAML frontmatter', () => {
+    const skillFiles: string[] = [];
+    const walk = (dir: string) => {
+      for (const entry of fs.readdirSync(dir, { withFileTypes: true })) {
+        if (entry.name === 'node_modules' || entry.name === '.git') continue;
+        const fullPath = path.join(dir, entry.name);
+        if (entry.isDirectory()) {
+          walk(fullPath);
+        } else if (entry.name === 'SKILL.md') {
+          skillFiles.push(fullPath);
+        }
+      }
+    };
+    walk(ROOT);
+
+    const errors = skillFiles.flatMap((skillPath) =>
+      validateSkillFrontmatter(skillPath).map((error) =>
+        `${path.relative(ROOT, skillPath)}:${error.line}: ${error.message}`
+      )
+    );
+
+    expect(errors).toEqual([]);
+  });
+
   test('all $B commands in SKILL.md are valid browse commands', () => {
     const result = validateSkill(path.join(ROOT, 'SKILL.md'));
     expect(result.invalid).toHaveLength(0);
diff --git a/unfreeze/SKILL.md b/unfreeze/SKILL.md
index a07f1cf5f7..61b5e0aa6f 100644
--- a/unfreeze/SKILL.md
+++ b/unfreeze/SKILL.md
@@ -1,7 +1,7 @@
 ---
 name: unfreeze
 version: 0.1.0
-description: Clear the freeze boundary set by /freeze, allowing edits to all directories again. (gstack)
+description: "Clear the freeze boundary set by /freeze, allowing edits to all directories again. (gstack)"
 triggers:
   - unfreeze edits
   - unlock all directories