From e82ba71911ad971d0be9219e9f8d064c61a57746 Mon Sep 17 00:00:00 2001
From: Vincent Koc <vincentkoc@ieee.org>
Date: Fri, 13 Mar 2026 18:39:28 -0400
Subject: [PATCH] fix(browser): follow up batch failure and limit handling
 (#45506)

* fix(browser): propagate nested batch failures

* fix(browser): validate top-level batch limits

* test(browser): cover nested batch failures

* test(browser): cover top-level batch limits
---
 .../pw-tools-core.interactions.batch.test.ts  | 19 +++++++++++++++++++
 src/browser/pw-tools-core.interactions.ts     |  6 +++++-
 src/browser/routes/agent.act.ts               |  3 +++
 ...-contract-form-layout-act-commands.test.ts | 16 ++++++++++++++++
 4 files changed, 43 insertions(+), 1 deletion(-)

diff --git a/src/browser/pw-tools-core.interactions.batch.test.ts b/src/browser/pw-tools-core.interactions.batch.test.ts
index 2801ebe8190..fbd2de4cbc6 100644
--- a/src/browser/pw-tools-core.interactions.batch.test.ts
+++ b/src/browser/pw-tools-core.interactions.batch.test.ts
@@ -82,4 +82,23 @@ describe("batchViaPlaywright", () => {
       targetId: "tab-1",
     });
   });
+
+  it("propagates nested batch failures to the parent batch result", async () => {
+    const result = await batchViaPlaywright({
+      cdpUrl: "http://127.0.0.1:9222",
+      targetId: "tab-1",
+      actions: [
+        {
+          kind: "batch",
+          actions: [{ kind: "evaluate", fn: "() => 1" }],
+        },
+      ],
+    });
+
+    expect(result).toEqual({
+      results: [
+        { ok: false, error: "act:evaluate is disabled by config (browser.evaluateEnabled=false)" },
+      ],
+    });
+  });
 });
diff --git a/src/browser/pw-tools-core.interactions.ts b/src/browser/pw-tools-core.interactions.ts
index dee8a03316c..da0efa0c145 100644
--- a/src/browser/pw-tools-core.interactions.ts
+++ b/src/browser/pw-tools-core.interactions.ts
@@ -845,7 +845,7 @@ async function executeSingleAction(
       break;
     case "batch":
       // Nested batches: delegate recursively
-      await batchViaPlaywright({
+      const nestedResult = await batchViaPlaywright({
         cdpUrl,
         targetId: effectiveTargetId,
         actions: action.actions,
@@ -853,6 +853,10 @@ async function executeSingleAction(
         evaluateEnabled,
         depth: depth + 1,
       });
+      const nestedFailure = nestedResult.results.find((result) => !result.ok);
+      if (nestedFailure) {
+        throw new Error(nestedFailure.error ?? "Nested batch action failed");
+      }
       break;
     default:
       throw new Error(`Unsupported batch action kind: ${(action as { kind: string }).kind}`);
diff --git a/src/browser/routes/agent.act.ts b/src/browser/routes/agent.act.ts
index 0c4c9e71967..05557fe1129 100644
--- a/src/browser/routes/agent.act.ts
+++ b/src/browser/routes/agent.act.ts
@@ -1043,6 +1043,9 @@ export function registerBrowserAgentActRoutes(
             if (!actions.length) {
               return jsonError(res, 400, "actions are required");
             }
+            if (countBatchActions(actions) > MAX_BATCH_ACTIONS) {
+              return jsonError(res, 400, `batch exceeds maximum of ${MAX_BATCH_ACTIONS} actions`);
+            }
             const targetIdError = validateBatchTargetIds(actions, tab.targetId);
             if (targetIdError) {
               return jsonError(res, 403, targetIdError);
diff --git a/src/browser/server.agent-contract-form-layout-act-commands.test.ts b/src/browser/server.agent-contract-form-layout-act-commands.test.ts
index 912d024916c..16ade600bec 100644
--- a/src/browser/server.agent-contract-form-layout-act-commands.test.ts
+++ b/src/browser/server.agent-contract-form-layout-act-commands.test.ts
@@ -287,6 +287,22 @@ describe("browser control server", () => {
     slowTimeoutMs,
   );
 
+  it(
+    "rejects oversized top-level batches before dispatch",
+    async () => {
+      const base = await startServerAndBase();
+
+      const batchRes = await postJson<{ error?: string }>(`${base}/act`, {
+        kind: "batch",
+        actions: Array.from({ length: 101 }, () => ({ kind: "press", key: "Enter" })),
+      });
+
+      expect(batchRes.error).toContain("batch exceeds maximum of 100 actions");
+      expect(pwMocks.batchViaPlaywright).not.toHaveBeenCalled();
+    },
+    slowTimeoutMs,
+  );
+
   it("agent contract: hooks + response + downloads + screenshot", async () => {
     const base = await startServerAndBase();