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.readonly() freezes the input on a failed parse, and safeParse throws for typed arrays #6745
Description
$ZodReadonly calls Object.freeze(payload.value) even when the inner schema failed, so safeParse freezes the caller's rejected object, and throws instead of returning an error when the rejected value is a non-empty typed array or Buffer.
import { z } from "zod";
const input = { x: 1 };
const res = z.string().readonly().safeParse(input);
console.log(res.success, Object.isFrozen(input));
z.array(z.number()).readonly().safeParse(new Uint8Array(1));node t.mjs
Actual:
false true
file:///.../node_modules/zod/v4/core/schemas.js:2404
payload.value = Object.freeze(payload.value);
^
TypeError: Cannot freeze array buffer views with elements
Expected: false false, and the second call returns { success: false, error: ... } without throwing.
Tested with zod 4.6.7 and main 19c40d2 (bundled from source), Node.js v26.13.0.
handleReadonlyResult in packages/zod/src/v4/core/schemas.ts freezes whenever !payload.memo; it could skip the freeze when payload.issues.length > 0.
Credit: https://ucsbplse.github.io/
Activity
hamarshehmhmd commentedon Nov 7, 2026
Confirmed on main (19c40d2). Skipping the freeze on failure, like you suggested, fixes both cases:
function handleReadonlyResult(payload: ParsePayload): ParsePayload { // A repeat visit hands back a node that is still being built; freezing it here would make the rest of its keys fail to assign. - if (!payload.memo) payload.value = Object.freeze(payload.value); + // A failed parse hands back the caller's input, which must not be frozen (and typed arrays cannot be). + if (!payload.memo && payload.issues.length === 0) payload.value = Object.freeze(payload.value); return payload; }Before → after:
The async path (
.refine(async ...)+safeParseAsync) also leaves the input unfrozen, since it goes through the same helper.Regression test added to
packages/zod/src/v4/classic/tests/readonly.test.ts. It covers sync object, async object andUint8Array, and fails on main in both thezodandcompile-modeprojects.nub run test packages/zod/src/v4: 411 files, 6799 tests passed, no type errorsHappy to open a PR.