Add frontmatter skills support with activation-time gh skill install and engine wiring (#42426)

* Add frontmatter skills support with activation install and aw_info wiring

Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>

* Polish skills install logging and aw_info parse warnings

Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>

* Allow skills frontmatter GitHub Actions expressions

Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>

* Tighten skills expression regex acceptance

Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>

* docs(adr): add draft ADR-42426 for frontmatter skills support

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* Fix skills frontmatter review follow-ups

Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>

* Document runtime skill detection alignment

Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>
Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>
Co-authored-by: Peli de Halleux <pelikhan@users.noreply.github.com>

Author: 4 people

.github/workflows/mattpocock-skills-reviewer.lock.yml

@@ -13,6 +13,14 @@ permissions:
   contents: read
   pull-requests: read
   copilot-requests: write
+skills:
+  - mattpocock/skills/diagnosing-bugs@801dca688564c529fa84f247f64472520d9ebe28
+  - mattpocock/skills/tdd@801dca688564c529fa84f247f64472520d9ebe28
+  - mattpocock/skills/improve-codebase-architecture@801dca688564c529fa84f247f64472520d9ebe28
+  - mattpocock/skills/grill-with-docs@801dca688564c529fa84f247f64472520d9ebe28
+  - mattpocock/skills/to-prd@801dca688564c529fa84f247f64472520d9ebe28
+  - mattpocock/skills/codebase-design@801dca688564c529fa84f247f64472520d9ebe28
+  - mattpocock/skills/domain-modeling@801dca688564c529fa84f247f64472520d9ebe28
 
 sandbox:
   agent:
@@ -28,35 +36,6 @@ imports:
       min-integrity: approved
   - shared/otlp.md
 pre-agent-steps:
-  - name: Upgrade gh CLI
-    run: |
-      bash "${RUNNER_TEMP}/gh-aw/actions/install_gh_cli.sh"
-      GH_VERSION=$(gh --version | head -1 | grep -oP '\d+\.\d+\.\d+')
-      echo "gh version: ${GH_VERSION}"
-      REQUIRED="2.90.0"
-      if ! printf '%s\n%s\n' "$REQUIRED" "$GH_VERSION" | sort -V -C; then
-        echo "::error::gh ${GH_VERSION} is older than required ${REQUIRED} (gh skill support requires v2.90+)"
-        exit 1
-      fi
-  - name: Install Matt Pocock skills
-    env:
-      GH_TOKEN: ${{ github.token }}
-    run: |
-      set -euo pipefail
-      SKILLS_DST="${RUNNER_TEMP}/gh-aw/mattpocock-skills"
-      mkdir -p "${SKILLS_DST}"
-      # Install only the skills referenced in this workflow's prompt, rather than
-      # all published skills, to reduce install time and network overhead.
-      for skill in diagnosing-bugs tdd improve-codebase-architecture grill-with-docs to-prd codebase-design domain-modeling; do
-        gh skill install mattpocock/skills "${skill}" --dir "${SKILLS_DST}" --force
-      done
-      SKILL_COUNT=$(find "${SKILLS_DST}" -name "SKILL.md" | wc -l)
-      echo "Installed ${SKILL_COUNT} skill(s):"
-      find "${SKILLS_DST}" -name "SKILL.md" | head -20
-      if [ "${SKILL_COUNT}" -eq 0 ]; then
-        echo "::error::No SKILL.md files found after installing mattpocock/skills"
-        exit 1
-      fi
   - name: Pre-fetch PR diff
     env:
       GH_TOKEN: ${{ github.token }}

.github/workflows/mattpocock-skills-reviewer.md

@@ -128,6 +128,12 @@ async function main(core, ctx) {
     awInfo.features = features;
   }
 
+  const skills = parseSkillsFromEnv(core);
+  if (skills) {
+    awInfo.skills = skills;
+    core.info(`Configured frontmatter skills (${skills.length}): ${skills.join(", ")}`);
+  }
+
   // Include aw_context when the workflow was triggered by a caller that relayed
   // orchestration context via workflow inputs or repository_dispatch client payload.
   // Validates JSON format and structure before populating the context key in aw_info.json.
@@ -218,6 +224,38 @@ async function main(core, ctx) {
     }
   }
 
+  /**
+   * Parse optional skills list from GH_AW_INFO_SKILLS.
+   * @param {typeof import('@actions/core')} core
+   * @returns {string[] | null}
+   */
+  function parseSkillsFromEnv(core) {
+    const skillsEnv = process.env.GH_AW_INFO_SKILLS;
+    if (!skillsEnv) {
+      return null;
+    }
+    try {
+      const parsed = JSON.parse(skillsEnv);
+      if (!Array.isArray(parsed)) {
+        core.warning("GH_AW_INFO_SKILLS must be a JSON array, ignoring");
+        return null;
+      }
+      const skills = [];
+      for (const [index, value] of parsed.entries()) {
+        if (typeof value === "string" && value.length > 0) {
+          skills.push(value);
+          continue;
+        }
+        core.warning(`Ignoring invalid GH_AW_INFO_SKILLS[${index}] value: ${JSON.stringify(value)}`);
+      }
+      return skills.length > 0 ? skills : null;
+    } catch (err) {
+      const message = err instanceof Error ? err.message : String(err);
+      core.warning(`Failed to parse GH_AW_INFO_SKILLS: ${skillsEnv} (${message})`);
+      return null;
+    }
+  }
+
   core.info("Generated aw_info.json at: " + tmpPath);
   core.info(JSON.stringify(awInfo, null, 2));