diff --git a/actions/setup/js/runtime_import.cjs b/actions/setup/js/runtime_import.cjs
index 29adeea26f1..948c0535649 100644
--- a/actions/setup/js/runtime_import.cjs
+++ b/actions/setup/js/runtime_import.cjs
@@ -746,6 +746,17 @@ async function processRuntimeImport(filepathOrUrl, optional, workspaceDir, start
   let filepath = filepathOrUrl;
   let isAgentsPath = false;
 
+  // Strip leading "/" or "//" (and any number of slashes) for repo-root-absolute paths
+  // (e.g. /.agents/skills/..., //.github/agents/...).
+  // After stripping, the existing .agents/ and .github/ prefix checks handle resolution correctly.
+  // Only strip when the result begins with .agents/ or .github/ to preserve security restrictions.
+  if (filepath.startsWith("/")) {
+    const stripped = filepath.replace(/^\/+/, "");
+    if (stripped.startsWith(".agents/") || stripped.startsWith(".agents\\") || stripped.startsWith(".github/") || stripped.startsWith(".github\\")) {
+      filepath = stripped;
+    }
+  }
+
   // Check if this is a .agents/ path (top-level folder for skills)
   if (filepath.startsWith(".agents/")) {
     isAgentsPath = true;
diff --git a/actions/setup/js/runtime_import.test.cjs b/actions/setup/js/runtime_import.test.cjs
index a83110f92ae..2c6c83f7feb 100644
--- a/actions/setup/js/runtime_import.test.cjs
+++ b/actions/setup/js/runtime_import.test.cjs
@@ -466,6 +466,54 @@ describe("runtime_import", () => {
           const result = await processRuntimeImport(".agents/test-skill.md", !1, tempDir);
           expect(result).toBe(content);
         }),
+        it("should support /.agents/ prefix (leading slash, repo-root-absolute)", async () => {
+          // Regression test: /.agents/skills/my-skill/instructions.md should resolve to
+          // <workspace>/.agents/skills/my-skill/instructions.md (not .github/workflows/.agents/...)
+          const skillsDir = path.join(tempDir, ".agents", "skills", "my-skill");
+          fs.mkdirSync(skillsDir, { recursive: true });
+          const content = "# My Skill\n\nThis is the skill content.";
+          fs.writeFileSync(path.join(skillsDir, "instructions.md"), content);
+          const result = await processRuntimeImport("/.agents/skills/my-skill/instructions.md", !1, tempDir);
+          expect(result).toBe(content);
+        }),
+        it("should support //.agents/ prefix (double leading slash, repo-root-absolute)", async () => {
+          // Regression test: //.agents/skills/my-skill/instructions.md (double slash) should also
+          // resolve to <workspace>/.agents/skills/my-skill/instructions.md
+          const skillsDir = path.join(tempDir, ".agents", "skills", "my-skill");
+          fs.mkdirSync(skillsDir, { recursive: true });
+          const content = "# My Skill (double slash)\n\nThis is the skill content.";
+          fs.writeFileSync(path.join(skillsDir, "instructions.md"), content);
+          const result = await processRuntimeImport("//.agents/skills/my-skill/instructions.md", !1, tempDir);
+          expect(result).toBe(content);
+        }),
+        it("should support /.github/ prefix (leading slash, repo-root-absolute)", async () => {
+          // Regression test: /.github/agents/planner.md should resolve to
+          // <workspace>/.github/agents/planner.md (not .github/workflows/.github/agents/...)
+          const agentsDir = path.join(tempDir, ".github", "agents");
+          fs.mkdirSync(agentsDir, { recursive: true });
+          const content = "# Planner Agent\n\nThis is the planner content.";
+          fs.writeFileSync(path.join(agentsDir, "planner.md"), content);
+          const result = await processRuntimeImport("/.github/agents/planner.md", !1, tempDir);
+          expect(result).toBe(content);
+        }),
+        it("should support //.github/ prefix (double leading slash, repo-root-absolute)", async () => {
+          // Regression test: //.github/agents/planner.md (double slash) should also resolve to
+          // <workspace>/.github/agents/planner.md
+          const agentsDir = path.join(tempDir, ".github", "agents");
+          fs.mkdirSync(agentsDir, { recursive: true });
+          const content = "# Planner Agent (double slash)\n\nThis is the planner content.";
+          fs.writeFileSync(path.join(agentsDir, "planner.md"), content);
+          const result = await processRuntimeImport("//.github/agents/planner.md", !1, tempDir);
+          expect(result).toBe(content);
+        }),
+        it("should reject /-prefixed paths not under .agents/ or .github/", async () => {
+          // A leading "/" that does not map to .agents/ or .github/ should NOT be stripped.
+          // It falls through to the default branch, and path joining preserves the absolute path
+          // (/etc/passwd on POSIX), which is then rejected by the .github base-folder security check.
+          // Assert the security rejection rather than a file-not-found error so the test remains
+          // stable across platforms.
+          await expect(processRuntimeImport("/etc/passwd", !1, tempDir)).rejects.toThrow("Security: Path");
+        }),
         it("should support nested .github/workflows/shared/ path (issue: runtime-import fails for .github/workflows/* paths)", async () => {
           // Regression test: .github/workflows/shared/reporting.md should resolve to
           // <workspace>/.github/workflows/shared/reporting.md (not <workspace>/workflows/shared/reporting.md)