fix: do not crash when a fileChange start event omits changes

plugins/codex/scripts/lib/codex.mjs

@@ -248,7 +248,10 @@ function describeStartedItem(state, item) {
         phase: looksLikeVerificationCommand(item.command) ? "verifying" : "running"
       };
     case "fileChange":
-      return { message: `Applying ${item.changes.length} file change(s).`, phase: "editing" };
+      return {
+        message: `Applying ${Array.isArray(item.changes) ? item.changes.length : 0} file change(s).`,
+        phase: "editing"
+      };
     case "mcpToolCall":
       return { message: `Calling ${item.server}/${item.tool}.`, phase: "investigating" };
     case "dynamicToolCall":

tests/fake-codex-fixture.mjs

@@ -568,6 +568,13 @@ rl.on("line", (line) => {
         }
 
         const items = [
+          ...(BEHAVIOR === "file-change-started-without-changes"
+            ? [
+                {
+                  started: { type: "fileChange", id: "fc_" + turnId }
+                }
+              ]
+            : []),
           ...(BEHAVIOR === "with-reasoning"
             ? [
                 {

tests/runtime.test.mjs

@@ -175,6 +175,25 @@ test("task runs when the active provider does not require OpenAI login", () => {
   assert.match(result.stdout, /Handled the requested task/);
 });
 
+test("task survives fileChange started items that omit changes", () => {
+  const repo = makeTempDir();
+  const binDir = makeTempDir();
+  installFakeCodex(binDir, "file-change-started-without-changes");
+  initGitRepo(repo);
+  fs.writeFileSync(path.join(repo, "README.md"), "hello\n");
+  run("git", ["add", "README.md"], { cwd: repo });
+  run("git", ["commit", "-m", "init"], { cwd: repo });
+
+  const result = run("node", [SCRIPT, "task", "apply the patch"], {
+    cwd: repo,
+    env: buildEnv(binDir)
+  });
+
+  assert.equal(result.status, 0, result.stderr);
+  assert.match(result.stdout, /Handled the requested task/);
+  assert.doesNotMatch(result.stderr, /Cannot read properties of undefined/);
+});
+
 test("task runs without auth preflight so Codex can refresh an expired session", () => {
   const repo = makeTempDir();
   const binDir = makeTempDir();