@polygonlabs/zod-codecs

Zod v4 codecs for the wire formats JSON-on-the-wire services keep reinventing.

JSON has no native int64, no unbounded big integer, no precision-preserving decimal, and no native Date. Services serialise these as strings and hope every consumer decodes them the same way. This package ships the four decode/encode pairs the team has been writing inline, with the wire-format validation and runtime-type validation declared together.

Install

pnpm add @polygonlabs/zod-codecs zod

zod is a peer dependency. Requires Zod v4.

Codecs

| Codec | Wire | Runtime | Use for | | --- | --- | --- | --- | | Int64Codec | digit-string | bigint, int64-bounded | values that exceed Number.MAX_SAFE_INTEGER but fit in 64 bits — block heights, monotonic IDs, fixed-width counters | | BigIntegerCodec | digit-string | bigint, unbounded | values that can exceed int64 — wei amounts, raw uint256 values | | DecimalStringCodec | decimal-number string | string (validated) | financial / on-chain decimals where IEEE-754 precision is unacceptable | | IsoDateCodec | ISO-8601 string | Date | datetimes — bare z.date() doesn't make sense on the JSON wire |

Usage

import { z } from 'zod';
import {
  BigIntegerCodec,
  DecimalStringCodec,
  Int64Codec,
  IsoDateCodec
} from '@polygonlabs/zod-codecs';

const Trade = z.object({
  id: Int64Codec,                    // sequence number — fits in int64
  amountWei: BigIntegerCodec,        // uint256 wei value — needs unbounded bigint
  feeBps: DecimalStringCodec,        // basis points with fractional precision
  executedAt: IsoDateCodec
});

const parsed = await Trade.parseAsync({
  id: '12345',
  amountWei: '12345678901234567890123456789',
  feeBps: '0.0025',
  executedAt: '2025-04-28T13:45:00Z'
});
// parsed.id          → 12345n
// parsed.amountWei   → 12345678901234567890123456789n
// parsed.feeBps      → '0.0025'
// parsed.executedAt  → Date instance

z.encode(schema, value) runs the encode side and produces the wire shape:

import { z } from 'zod';

await z.encode(Trade, parsed);
// → {
//     id: '12345',
//     amountWei: '12345678901234567890123456789',
//     feeBps: '0.0025',
//     executedAt: '2025-04-28T13:45:00.000Z'
//   }

OpenAPI metadata

Codecs ship without .openapi() metadata baked in. Description, x-go-type hints, and example values are caller-specific — chain them at the registration site.

In zod v4, ZodCodec is a sibling class of ZodType rather than a subclass, so extendZodWithOpenApi from @asteasolutions/zod-to-openapi (which patches only ZodType.prototype.openapi) doesn't reach codecs — chaining .openapi(...) on a codec throws TypeError: not a function. This package's ./openapi entry-point fixes that:

import { z } from 'zod';
import { extendZodAndCodecsWithOpenApi } from '@polygonlabs/zod-codecs/openapi';
import { Int64Codec } from '@polygonlabs/zod-codecs';

extendZodAndCodecsWithOpenApi(z);

const BlockNumber = Int64Codec.openapi({
  description: 'Block height — fits in int64.',
  'x-go-type': 'int64'
});

extendZodAndCodecsWithOpenApi is a drop-in replacement for extendZodWithOpenApi — it calls through to the upstream patch and additionally extends the same patch to ZodCodec.prototype, so codec fields and regular fields behave identically (description, example, param: { in, name } for parameter declarations, refId merging across chained calls). Idempotent — safe to call multiple times.

@asteasolutions/zod-to-openapi is an optional peer dependency: the ./openapi entry-point is the only thing in this package that imports it. Codec consumers that don't generate OpenAPI never need it installed.

Pairs naturally with @polygonlabs/zod-to-openapi-heyapi

@polygonlabs/zod-to-openapi-heyapi is the team's @hey-api/openapi-ts plugin that sources Zod schemas (with codecs) from a zod-to-openapi OpenAPIRegistry, so generated clients call the codecs at runtime and hand callers the runtime shapes (bigint, Date) directly. This codec package is the recommended companion when using that plugin.

It is not a hard requirement — these codecs work standalone in any Zod-on-the-wire context: server validation, tRPC, MCP tooling, queue payloads, anywhere a JSON document crosses a trust boundary.