diff --git a/scripts/build/deps/webkit.ts b/scripts/build/deps/webkit.ts
index f84dd77e0e19..e72d7f057570 100644
--- a/scripts/build/deps/webkit.ts
+++ b/scripts/build/deps/webkit.ts
@@ -3,7 +3,7 @@
  * for local mode. Override via `--webkit-version=<hash>` to test a branch.
  * From https://github.com/oven-sh/WebKit releases.
  */
-export const WEBKIT_VERSION = "549170099226f816a4b204ea1d8fa102fb79eefa";
+export const WEBKIT_VERSION = "autobuild-preview-pr-348-c106f67d";
 
 /**
  * WebKit (JavaScriptCore) — the JS engine.
diff --git a/test/js/bun/jsc/typedarray-uint32max-index.test.ts b/test/js/bun/jsc/typedarray-uint32max-index.test.ts
new file mode 100644
index 000000000000..671d144c0869
--- /dev/null
+++ b/test/js/bun/jsc/typedarray-uint32max-index.test.ts
@@ -0,0 +1,146 @@
+import { expect, test } from "bun:test";
+import { bunEnv, bunExe } from "harness";
+
+// A Uint8Array can have length up to MAX_ARRAY_BUFFER_SIZE (2**32 on 64-bit),
+// so 4294967295 (UINT32_MAX) is a valid index. Regular JS arrays top out at
+// MAX_ARRAY_INDEX (2**32 - 2), and the TypedArray [[Get]]/[[Set]] paths were
+// reusing that cap, which left the last element unreachable via bracket access
+// while [[HasProperty]] and DataView could still see it.
+// https://tc39.es/ecma262/#sec-isvalidintegerindex
+
+const fixture = /* js */ `
+"use strict";
+const LEN = 2 ** 32;
+const IDX = LEN - 1; // 4294967295
+const KEY = String(IDX); // "4294967295"
+
+let u;
+try {
+  u = new Uint8Array(LEN);
+} catch {
+  console.log(JSON.stringify({ skipped: true }));
+  process.exit(0);
+}
+if (u.length !== LEN) throw new Error("unexpected length " + u.length);
+
+// Seed the last byte via a path that was never broken.
+new DataView(u.buffer).setUint8(IDX, 11);
+
+const out = {
+  initialGetNum: u[IDX],
+  initialGetStr: u[KEY],
+  at: u.at(IDX),
+  inNum: IDX in u,
+  inStr: KEY in u,
+  hasOwn: Object.hasOwn(u, KEY),
+  gopd: Object.getOwnPropertyDescriptor(u, KEY),
+};
+
+u[IDX] = 22;
+out.afterIndexedSet = u[IDX];
+out.afterIndexedSetDV = new DataView(u.buffer).getUint8(IDX);
+
+Reflect.set(u, KEY, 33);
+out.afterReflectSet = u[IDX];
+out.afterReflectSetDV = new DataView(u.buffer).getUint8(IDX);
+
+try {
+  Object.defineProperty(u, KEY, { value: 44, writable: true, enumerable: true, configurable: true });
+  out.afterDefine = new DataView(u.buffer).getUint8(IDX);
+} catch (e) {
+  out.afterDefine = "threw: " + e.constructor.name;
+}
+
+out.deleteInBounds = Reflect.deleteProperty(u, KEY);
+
+// Keep matching spec for adjacent cases:
+out.oneBeyond = u["4294967296"];
+out.minusZero = u["-0"];
+
+// On a short view, the same index is out of bounds.
+const small = new Uint8Array(8);
+out.smallGet = small[IDX];
+out.smallIn = KEY in small;
+out.smallDelete = Reflect.deleteProperty(small, KEY);
+let smallDefineThrew = false;
+try {
+  Object.defineProperty(small, KEY, { value: 1, writable: true, enumerable: true, configurable: true });
+} catch {
+  smallDefineThrew = true;
+}
+out.smallDefineThrew = smallDefineThrew;
+
+// Other 1-byte element types at max length.
+const i8 = new Int8Array(u.buffer);
+i8[IDX] = -7;
+out.i8 = i8[IDX];
+const uc = new Uint8ClampedArray(u.buffer);
+uc[IDX] = 300;
+out.uc = uc[IDX];
+
+// Structure-keyed caches (HasOwnPropertyCache, GetBy/InBy IC miss entries)
+// must not be keyed on the shared TypedArray structure for this index, since
+// the answer is length-dependent. Allocate both views first so GC between the
+// two probes doesn't hide a stale entry by clearing the cache.
+const icSmall = new Uint8Array(u.buffer, 0, 8);
+new DataView(u.buffer).setUint8(IDX, 55);
+out.hasOwnSmallFirst = Object.hasOwn(icSmall, KEY);
+out.hasOwnBigAfter = Object.hasOwn(u, KEY);
+function probeGet(x) { return x["4294967295"]; }
+function probeIn(x) { return "4294967295" in x; }
+for (let i = 0; i < 200; i++) { probeGet(icSmall); probeIn(icSmall); }
+out.icGetBig = probeGet(u);
+out.icInBig = probeIn(u);
+
+console.log(JSON.stringify(out));
+`;
+
+test("TypedArray indexed access at 4294967295 on a 2**32-length view", async () => {
+  await using proc = Bun.spawn({
+    cmd: [bunExe(), "-e", fixture],
+    env: {
+      ...bunEnv,
+      ASAN_OPTIONS: [bunEnv.ASAN_OPTIONS, "allocator_may_return_null=1"].filter(Boolean).join(":"),
+    },
+    stdout: "pipe",
+    stderr: "pipe",
+  });
+  const [stdout, stderr, exitCode] = await Promise.all([proc.stdout.text(), proc.stderr.text(), proc.exited]);
+
+  expect(stderr).toBe("");
+  const out = JSON.parse(stdout.trim());
+  if (out.skipped) {
+    console.log("skipping: could not allocate a 2**32-byte Uint8Array");
+    expect(exitCode).toBe(0);
+    return;
+  }
+
+  expect(out).toEqual({
+    initialGetNum: 11,
+    initialGetStr: 11,
+    at: 11,
+    inNum: true,
+    inStr: true,
+    hasOwn: true,
+    gopd: { value: 11, writable: true, enumerable: true, configurable: true },
+    afterIndexedSet: 22,
+    afterIndexedSetDV: 22,
+    afterReflectSet: 33,
+    afterReflectSetDV: 33,
+    afterDefine: 44,
+    deleteInBounds: false,
+    oneBeyond: undefined,
+    minusZero: undefined,
+    smallGet: undefined,
+    smallIn: false,
+    smallDelete: true,
+    smallDefineThrew: true,
+    i8: -7,
+    uc: 255,
+    hasOwnSmallFirst: false,
+    hasOwnBigAfter: true,
+    icGetBig: 55,
+    icInBig: true,
+  });
+  expect(exitCode).toBe(0);
+});