feat: add update-branch support to safe-outputs update-pull-request (#27244)

Author: Copilot

.github/workflows/changeset.lock.yml

@@ -445,7 +445,7 @@ function executeCustomValidation(item, customValidation, lineNum, itemType) {
   // Parse custom validation rule
   if (customValidation.startsWith("requiresOneOf:")) {
     const fields = customValidation.slice("requiresOneOf:".length).split(",");
-    const hasValidField = fields.some(field => item[field] !== undefined);
+    const hasValidField = fields.some(field => item[field] !== undefined && item[field] !== false);
     if (!hasValidField) {
       return {
         isValid: false,

.github/workflows/smoke-claude.lock.yml

@@ -46,6 +46,16 @@ const SAMPLE_VALIDATION_CONFIG = {
       issue_number: { issueOrPRNumber: true },
     },
   },
+  update_pull_request: {
+    defaultMax: 1,
+    customValidation: "requiresOneOf:title,body,update_branch",
+    fields: {
+      title: { type: "string", sanitize: true, maxLength: 256 },
+      body: { type: "string", sanitize: true, maxLength: 65000 },
+      update_branch: { type: "boolean" },
+      pull_request_number: { issueOrPRNumber: true },
+    },
+  },
   assign_to_agent: {
     defaultMax: 1,
     customValidation: "requiresOneOf:issue_number,pull_number",
@@ -399,6 +409,23 @@ describe("safe_output_type_validator", () => {
       expect(result.error).toContain("issue_number");
       expect(result.error).toContain("pull_number");
     });
+
+    it("should fail for update_pull_request when update_branch is false and no title/body is provided", async () => {
+      const { validateItem } = await import("./safe_output_type_validator.cjs");
+
+      const result = validateItem({ type: "update_pull_request", update_branch: false }, "update_pull_request", 1);
+
+      expect(result.isValid).toBe(false);
+      expect(result.error).toContain("requires at least one of");
+    });
+
+    it("should pass for update_pull_request when update_branch is true", async () => {
+      const { validateItem } = await import("./safe_output_type_validator.cjs");
+
+      const result = validateItem({ type: "update_pull_request", update_branch: true }, "update_pull_request", 1);
+
+      expect(result.isValid).toBe(true);
+    });
   });
 
   describe("custom validation: startLineLessOrEqualLine", () => {

actions/setup/js/safe_output_type_validator.cjs

@@ -783,6 +783,10 @@
           "enum": ["replace", "append", "prepend"],
           "description": "How to update the PR body: 'replace' (default - completely overwrite), 'append' (add to end with separator), or 'prepend' (add to start with separator). Title is always replaced."
         },
+        "update_branch": {
+          "type": "boolean",
+          "description": "When true, update the pull request branch with the latest base branch changes before applying other updates. Defaults to false."
+        },
         "pull_request_number": {
           "type": ["number", "string"],
           "description": "Pull request number to update. This is the numeric ID from the GitHub URL (e.g., 234 in github.com/owner/repo/pull/234). Required when the workflow target is '*' (any PR)."

actions/setup/js/safe_output_type_validator.test.cjs

@@ -235,6 +235,8 @@ interface UpdatePullRequestItem extends BaseSafeOutputItem {
   body?: string;
   /** Update operation for body: 'replace' (default), 'append', or 'prepend' */
   operation?: "replace" | "append" | "prepend";
+  /** When true, updates the pull request branch with the latest base branch changes before other updates */
+  update_branch?: boolean;
   /** Optional pull request number for target "*" */
   pull_request_number?: number | string;
   /** Whether the PR should be a draft (true) or ready for review (false) */