diff --git a/actions/setup/js/install_frontmatter_skills.cjs b/actions/setup/js/install_frontmatter_skills.cjs
index dfc0c5a02ce..4d6664529de 100644
--- a/actions/setup/js/install_frontmatter_skills.cjs
+++ b/actions/setup/js/install_frontmatter_skills.cjs
@@ -132,17 +132,18 @@ function appendSkillInstallFailure(skillSpec, errorMessage) {
  * @returns {Promise<void>}
  */
 async function writeSkillSummary(skillDir, skills, installedSkillCount, failures) {
-  core.summary
-    .addRaw("### Frontmatter skills installed\n\n")
-    .addRaw(`- Engine skill directory: \`${skillDir}\`\n`)
-    .addRaw(`- Requested references: \`${JSON.stringify(skills)}\`\n`)
-    .addRaw(`- Installed SKILL.md files: ${installedSkillCount}\n`);
+  let body = "";
+  body += `- Engine skill directory: \`${skillDir}\`\n`;
+  body += `- Requested references: \`${JSON.stringify(skills)}\`\n`;
+  body += `- Installed SKILL.md files: ${installedSkillCount}\n`;
   if (failures.length > 0) {
-    core.summary.addRaw("\n#### ⚠️ Skill install failures\n\n");
+    body += "\n#### Skill install failures\n\n";
     for (const f of failures) {
-      core.summary.addRaw(`- \`${f.skill}\`: ${f.error}\n`);
+      body += `- \`${f.skill}\`: ${f.error}\n`;
     }
   }
+  const openAttr = failures.length > 0 ? " open" : "";
+  core.summary.addRaw(`### Frontmatter skills installed\n\n<details${openAttr}>\n<summary>Skill install details</summary>\n\n${body}\n</details>\n\n`);
   await core.summary.write();
 }
 
diff --git a/actions/setup/js/install_frontmatter_skills.test.cjs b/actions/setup/js/install_frontmatter_skills.test.cjs
index 48c38921fcf..061b09c599a 100644
--- a/actions/setup/js/install_frontmatter_skills.test.cjs
+++ b/actions/setup/js/install_frontmatter_skills.test.cjs
@@ -123,6 +123,7 @@ describe("install_frontmatter_skills", () => {
     expect(global.exec.exec).toHaveBeenNthCalledWith(2, "gh", ["skill", "install", "githubnext/skills", "review/security", "--pin", "def456", "--agent", "claude-code", "--dir", "/tmp/gh-aw/.claude/skills", "--force"]);
     expect(global.exec.exec).toHaveBeenNthCalledWith(3, "gh", ["skill", "install", "${{ inputs.skill_ref }}", "--agent", "claude-code", "--dir", "/tmp/gh-aw/.claude/skills", "--force"]);
     expect(global.core.summary.addRaw).toHaveBeenCalledWith(expect.stringContaining("### Frontmatter skills installed"));
+    expect(global.core.summary.addRaw).toHaveBeenCalledWith(expect.stringContaining("<details>"));
     expect(global.core.summary.addRaw).toHaveBeenCalledWith(expect.stringContaining('["githubnext/skills@abc123","githubnext/skills/review/security@def456","${{ inputs.skill_ref }}"]'));
   });
 
@@ -145,5 +146,6 @@ describe("install_frontmatter_skills", () => {
     const failures = JSON.parse(fs.readFileSync("/tmp/gh-aw/skill_install_failures.json", "utf8"));
     expect(failures).toEqual([{ skill: "bad/repo@abc123", error: "exit code 1 HTTP 404" }]);
     expect(global.core.warning).toHaveBeenCalledWith(expect.stringContaining("Failed to install skill 'bad/repo@abc123'"));
+    expect(global.core.summary.addRaw).toHaveBeenCalledWith(expect.stringContaining("<details open>"));
   });
 });