diff --git a/scripts/e2e/lib/release-scenarios/assertions.mjs b/scripts/e2e/lib/release-scenarios/assertions.mjs
index 4289d837ca9..9c1c8595f70 100644
--- a/scripts/e2e/lib/release-scenarios/assertions.mjs
+++ b/scripts/e2e/lib/release-scenarios/assertions.mjs
@@ -16,6 +16,7 @@ const command = process.argv[2];
 const SCAN_CHUNK_BYTES = 64 * 1024;
 const SCAN_CARRY_CHARS = 256;
 const ERROR_DETAIL_TAIL_BYTES = 16 * 1024;
+const JSON_ARTIFACT_MAX_BYTES = 2 * 1024 * 1024;
 
 function assert(condition, message) {
   if (!condition) {
@@ -23,8 +24,30 @@ function assert(condition, message) {
   }
 }
 
-function readJson(file) {
-  return JSON.parse(fs.readFileSync(file, "utf8"));
+function readJson(file, maxBytes = JSON_ARTIFACT_MAX_BYTES) {
+  const stat = fs.statSync(file);
+  if (!stat.isFile()) {
+    throw new Error(`${file} is not a file`);
+  }
+  if (stat.size > maxBytes) {
+    throw new Error(
+      `JSON artifact exceeded ${maxBytes} bytes: ${file} (${stat.size} bytes). Tail: ${readTextFileTail(
+        file,
+        ERROR_DETAIL_TAIL_BYTES,
+      )}`,
+    );
+  }
+  const text = fs.readFileSync(file, "utf8");
+  const bytes = Buffer.byteLength(text, "utf8");
+  if (bytes > maxBytes) {
+    throw new Error(
+      `JSON artifact exceeded ${maxBytes} bytes: ${file} (${bytes} bytes). Tail: ${readTextFileTail(
+        file,
+        ERROR_DETAIL_TAIL_BYTES,
+      )}`,
+    );
+  }
+  return JSON.parse(text);
 }
 
 function fileContainsText(file, needle) {
diff --git a/test/scripts/release-scenarios-assertions.test.ts b/test/scripts/release-scenarios-assertions.test.ts
index 77a9c9425b9..fe18294b71c 100644
--- a/test/scripts/release-scenarios-assertions.test.ts
+++ b/test/scripts/release-scenarios-assertions.test.ts
@@ -129,6 +129,31 @@ describe("release scenario assertions", () => {
     }
   });
 
+  it("rejects oversized JSON artifacts before parsing release scenario outputs", () => {
+    const root = mkdtempSync(path.join(tmpdir(), "openclaw-release-scenarios-"));
+    const outputPath = path.join(root, "describe.json");
+    const requestLogPath = path.join(root, "requests.jsonl");
+
+    try {
+      writeFileSync(
+        outputPath,
+        `DO_NOT_DUMP_OLD_JSON${"x".repeat(2 * 1024 * 1024)}\nrecent json tail`,
+        "utf8",
+      );
+      writeFileSync(requestLogPath, "/v1/responses\n", "utf8");
+
+      const result = runAssertion(["assert-image-describe", outputPath, requestLogPath]);
+
+      expect(result.status).not.toBe(0);
+      expect(result.stderr).toContain("JSON artifact exceeded");
+      expect(result.stderr).toContain("recent json tail");
+      expect(result.stderr).not.toContain("DO_NOT_DUMP_OLD_JSON");
+      expect(result.stderr.length).toBeLessThan(80 * 1024);
+    } finally {
+      rmSync(root, { force: true, recursive: true });
+    }
+  });
+
   it("scans large request logs for image generation requests", () => {
     const root = mkdtempSync(path.join(tmpdir(), "openclaw-release-scenarios-"));
     const outputPath = path.join(root, "generate.json");