AztecProtocol · AztecBot · May 20, 2026 · May 20, 2026
diff --git a/yarn-project/archiver/package.json b/yarn-project/archiver/package.json
@@ -81,7 +81,7 @@
     "lodash.omit": "^4.5.0",
     "tslib": "^2.5.0",
     "viem": "npm:@aztec/viem@2.38.2",
-    "zod": "^3.23.8"
+    "zod": "^4"
   },
   "devDependencies": {
     "@jest/globals": "^30.0.0",

diff --git a/yarn-project/aztec.js/package.json b/yarn-project/aztec.js/package.json
@@ -104,7 +104,7 @@
     "axios": "^1.15.1",
     "tslib": "^2.4.0",
     "viem": "npm:@aztec/viem@2.38.2",
-    "zod": "^3.23.8"
+    "zod": "^4"
   },
   "devDependencies": {
     "@aztec/builder": "workspace:^",

diff --git a/yarn-project/aztec.js/src/wallet/wallet.ts b/yarn-project/aztec.js/src/wallet/wallet.ts
@@ -14,7 +14,15 @@ import type { AztecAddress } from '@aztec/stdlib/aztec-address';
 import { type ContractInstanceWithAddress, ContractInstanceWithAddressSchema } from '@aztec/stdlib/contract';
 import { Gas, ManaUsageEstimate } from '@aztec/stdlib/gas';
 import { LogId } from '@aztec/stdlib/logs';
-import { AbiDecodedSchema, type ApiSchemaFor, optional, schemas, zodFor } from '@aztec/stdlib/schemas';
+import {
+  AbiDecodedSchema,
+  type ApiSchemaFor,
+  getSchemaParameters,
+  getSchemaReturnType,
+  optional,
+  schemas,
+  zodFor,
+} from '@aztec/stdlib/schemas';
 import type { ExecutionPayload, InTx } from '@aztec/stdlib/tx';
 import {
   Capsule,
@@ -545,56 +553,60 @@ const OffchainOutputSchema = z.object({
  * This is the single source of truth for method schemas - batch schemas are derived from this.
  */
 const WalletMethodSchemas = {
-  getChainInfo: z
-    .function()
-    .args()
-    .returns(z.object({ chainId: schemas.Fr, version: schemas.Fr })),
-  getContractMetadata: z.function().args(schemas.AztecAddress).returns(ContractMetadataSchema),
-  getContractClassMetadata: z.function().args(schemas.Fr).returns(ContractClassMetadataSchema),
-  getPrivateEvents: z
-    .function()
-    .args(EventMetadataDefinitionSchema, PrivateEventFilterSchema)
-    .returns(z.array(PrivateEventSchema)),
-  registerSender: z.function().args(schemas.AztecAddress, optional(z.string())).returns(schemas.AztecAddress),
-  getAddressBook: z
-    .function()
-    .args()
-    .returns(z.array(z.object({ alias: z.string(), item: schemas.AztecAddress }))),
-  getAccounts: z
-    .function()
-    .args()
-    .returns(z.array(z.object({ alias: z.string(), item: schemas.AztecAddress }))),
-  registerContract: z
-    .function()
-    .args(ContractInstanceWithAddressSchema, optional(ContractArtifactSchema), optional(schemas.Fr))
-    .returns(ContractInstanceWithAddressSchema),
-  registerContractClass: z.function().args(ContractArtifactSchema).returns(z.void()),
-  simulateTx: z
-    .function()
-    .args(ExecutionPayloadSchema, SimulateOptionsSchema)
-    .returns(TxSimulationResultWithAppOffset.schema),
-  executeUtility: z
-    .function()
-    .args(
+  getChainInfo: z.function({ input: z.tuple([]), output: z.object({ chainId: schemas.Fr, version: schemas.Fr }) }),
+  getContractMetadata: z.function({ input: z.tuple([schemas.AztecAddress]), output: ContractMetadataSchema }),
+  getContractClassMetadata: z.function({ input: z.tuple([schemas.Fr]), output: ContractClassMetadataSchema }),
+  getPrivateEvents: z.function({
+    input: z.tuple([EventMetadataDefinitionSchema, PrivateEventFilterSchema]),
+    output: z.array(PrivateEventSchema),
+  }),
+  registerSender: z.function({
+    input: z.tuple([schemas.AztecAddress, optional(z.string())]),
+    output: schemas.AztecAddress,
+  }),
+  getAddressBook: z.function({
+    input: z.tuple([]),
+    output: z.array(z.object({ alias: z.string(), item: schemas.AztecAddress })),
+  }),
+  getAccounts: z.function({
+    input: z.tuple([]),
+    output: z.array(z.object({ alias: z.string(), item: schemas.AztecAddress })),
+  }),
+  registerContract: z.function({
+    input: z.tuple([ContractInstanceWithAddressSchema, optional(ContractArtifactSchema), optional(schemas.Fr)]),
+    output: ContractInstanceWithAddressSchema,
+  }),
+  registerContractClass: z.function({ input: z.tuple([ContractArtifactSchema]), output: z.void() }),
+  simulateTx: z.function({
+    input: z.tuple([ExecutionPayloadSchema, SimulateOptionsSchema]),
+    output: TxSimulationResultWithAppOffset.schema,
+  }),
+  executeUtility: z.function({
+    input: z.tuple([
       FunctionCall.schema,
       z.object({
         scopes: z.array(schemas.AztecAddress),
         authWitnesses: optional(z.array(AuthWitness.schema)),
       }),
-    )
-    .returns(UtilityExecutionResult.schema),
-  profileTx: z.function().args(ExecutionPayloadSchema, ProfileOptionsSchema).returns(TxProfileResult.schema),
-  sendTx: z
-    .function()
-    .args(ExecutionPayloadSchema, SendOptionsSchema)
-    .returns(
-      z.union([
-        z.object({ txHash: TxHash.schema }).merge(OffchainOutputSchema),
-        z.object({ receipt: TxReceipt.schema }).merge(OffchainOutputSchema),
-      ]),
-    ),
-  createAuthWit: z.function().args(schemas.AztecAddress, MessageHashOrIntentSchema).returns(AuthWitness.schema),
-  requestCapabilities: z.function().args(AppCapabilitiesSchema).returns(WalletCapabilitiesSchema),
+    ]),
+    output: UtilityExecutionResult.schema,
+  }),
+  profileTx: z.function({
+    input: z.tuple([ExecutionPayloadSchema, ProfileOptionsSchema]),
+    output: TxProfileResult.schema,
+  }),
+  sendTx: z.function({
+    input: z.tuple([ExecutionPayloadSchema, SendOptionsSchema]),
+    output: z.union([
+      z.object({ txHash: TxHash.schema }).merge(OffchainOutputSchema),
+      z.object({ receipt: TxReceipt.schema }).merge(OffchainOutputSchema),
+    ]),
+  }),
+  createAuthWit: z.function({
+    input: z.tuple([schemas.AztecAddress, MessageHashOrIntentSchema]),
+    output: AuthWitness.schema,
+  }),
+  requestCapabilities: z.function({ input: z.tuple([AppCapabilitiesSchema]), output: WalletCapabilitiesSchema }),
 };
 
 /**
@@ -605,19 +617,19 @@ const WalletMethodSchemas = {
 function createBatchSchemas<T extends Record<string, z.ZodFunction<z.ZodTuple<any, any>, z.ZodTypeAny>>>(
   methodSchemas: T,
 ) {
-  const names = Object.keys(methodSchemas) as (keyof T)[];
+  const names = Object.keys(methodSchemas) as Extract<keyof T, string>[];
 
   const namesAndArgs = names.map(name =>
     z.object({
       name: z.literal(name),
-      args: methodSchemas[name].parameters(),
+      args: getSchemaParameters(methodSchemas[name]),
     }),
   );
 
   const namesAndReturns = names.map(name =>
     z.object({
       name: z.literal(name),
-      result: methodSchemas[name].returnType(),
+      result: getSchemaReturnType(methodSchemas[name]),
     }),
   );
 
@@ -636,5 +648,5 @@ export { BatchedMethodSchema, BatchedResultSchema };
 export const WalletSchema: ApiSchemaFor<Wallet> = {
   ...WalletMethodSchemas,
   // @ts-expect-error - ApiSchemaFor cannot properly type generic methods with readonly arrays
-  batch: z.function().args(z.array(BatchedMethodSchema)).returns(z.array(BatchedResultSchema)),
+  batch: z.function({ input: z.tuple([z.array(BatchedMethodSchema)]), output: z.array(BatchedResultSchema) }),
 };
diff --git a/yarn-project/blob-client/package.json b/yarn-project/blob-client/package.json
@@ -67,7 +67,7 @@
     "source-map-support": "^0.5.21",
     "tslib": "^2.4.0",
     "viem": "npm:@aztec/viem@2.38.2",
-    "zod": "^3.23.8"
+    "zod": "^4"
   },
   "devDependencies": {
     "@jest/globals": "^30.0.0",

diff --git a/yarn-project/bot/package.json b/yarn-project/bot/package.json
@@ -71,7 +71,7 @@
     "source-map-support": "^0.5.21",
     "tslib": "^2.4.0",
     "viem": "npm:@aztec/viem@2.38.2",
-    "zod": "^3.23.8"
+    "zod": "^4"
   },
   "devDependencies": {
     "@jest/globals": "^30.0.0",

diff --git a/yarn-project/bot/src/interface.ts b/yarn-project/bot/src/interface.ts
@@ -22,11 +22,11 @@ export interface BotRunnerApi {
 }
 
 export const BotRunnerApiSchema: ApiSchemaFor<BotRunnerApi> = {
-  start: z.function().args().returns(z.void()),
-  stop: z.function().args().returns(z.void()),
-  run: z.function().args().returns(z.void()),
-  setup: z.function().args().returns(z.void()),
-  getInfo: z.function().args().returns(BotInfoSchema),
-  getConfig: z.function().args().returns(BotConfigSchema),
-  update: z.function().args(BotConfigSchema).returns(z.void()),
+  start: z.function({ input: z.tuple([]), output: z.void() }),
+  stop: z.function({ input: z.tuple([]), output: z.void() }),
+  run: z.function({ input: z.tuple([]), output: z.void() }),
+  setup: z.function({ input: z.tuple([]), output: z.void() }),
+  getInfo: z.function({ input: z.tuple([]), output: BotInfoSchema }),
+  getConfig: z.function({ input: z.tuple([]), output: BotConfigSchema }),
+  update: z.function({ input: z.tuple([BotConfigSchema]), output: z.void() }),
 };
diff --git a/yarn-project/end-to-end/package.json b/yarn-project/end-to-end/package.json
@@ -104,7 +104,7 @@
     "typescript": "^5.3.3",
     "util": "^0.12.5",
     "viem": "npm:@aztec/viem@2.38.2",
-    "zod": "^3.23.8"
+    "zod": "^4"
   },
   "devDependencies": {
     "0x": "^5.7.0",

diff --git a/yarn-project/end-to-end/src/test-wallet/wallet_worker_script.ts b/yarn-project/end-to-end/src/test-wallet/wallet_worker_script.ts
@@ -3,7 +3,7 @@ import type { SendOptions } from '@aztec/aztec.js/wallet';
 import { jsonStringify } from '@aztec/foundation/json-rpc';
 import { createLogger } from '@aztec/foundation/log';
 import type { ApiSchema, Fr } from '@aztec/foundation/schemas';
-import { parseWithOptionals, schemaHasMethod } from '@aztec/foundation/schemas';
+import { getSchemaParameters, parseWithOptionals, schemaHasMethod } from '@aztec/foundation/schemas';
 import { NodeListener, TransportServer } from '@aztec/foundation/transport';
 import { ExecutionPayload, Tx } from '@aztec/stdlib/tx';
 
@@ -46,7 +46,7 @@ try {
       throw new Error(`Unknown method: ${msg.fn}`);
     }
     const jsonParams = JSON.parse(msg.args) as unknown[];
-    const args: any[] = await parseWithOptionals(jsonParams, schema[msg.fn].parameters());
+    const args: any[] = await parseWithOptionals(jsonParams, getSchemaParameters(schema[msg.fn]));
     // we have to erase the fn type in order to be able to spread ...args
     const handler: ((...args: any[]) => Promise<any>) | undefined =
       msg.fn in customMethods ? customMethods[msg.fn as keyof typeof customMethods] : undefined;

diff --git a/yarn-project/end-to-end/src/test-wallet/worker_wallet.ts b/yarn-project/end-to-end/src/test-wallet/worker_wallet.ts
@@ -22,7 +22,7 @@ import type { Fr } from '@aztec/foundation/curves/bn254';
 import { jsonStringify } from '@aztec/foundation/json-rpc';
 import { createLogger } from '@aztec/foundation/log';
 import { promiseWithResolvers } from '@aztec/foundation/promise';
-import type { ApiSchema } from '@aztec/foundation/schemas';
+import { type ApiSchema, getSchemaReturnType } from '@aztec/foundation/schemas';
 import { sleep } from '@aztec/foundation/sleep';
 import { NodeConnector, TransportClient } from '@aztec/foundation/transport';
 import type { PXEConfig } from '@aztec/pxe/config';
@@ -124,7 +124,7 @@ export class WorkerWallet implements Wallet {
   private async call(fn: string, ...args: any[]): Promise<any> {
     const resultJson = await this.callRaw(fn, ...args);
     const methodSchema = (WorkerWalletSchema as ApiSchema)[fn];
-    return methodSchema.returnType().parseAsync(JSON.parse(resultJson));
+    return getSchemaReturnType(methodSchema).parseAsync(JSON.parse(resultJson));
   }
 
   getChainInfo(): Promise<ChainInfo> {

diff --git a/yarn-project/end-to-end/src/test-wallet/worker_wallet_schema.ts b/yarn-project/end-to-end/src/test-wallet/worker_wallet_schema.ts
@@ -8,6 +8,6 @@ import { z } from 'zod';
 /** Schema for the WorkerWallet API — extends WalletSchema with proveTx and registerAccount. */
 export const WorkerWalletSchema = {
   ...WalletSchema,
-  proveTx: z.function().args(ExecutionPayloadSchema, SendOptionsSchema).returns(Tx.schema),
-  registerAccount: z.function().args(schemas.Fr, schemas.Fr).returns(AztecAddress.schema),
+  proveTx: z.function({ input: z.tuple([ExecutionPayloadSchema, SendOptionsSchema]), output: Tx.schema }),
+  registerAccount: z.function({ input: z.tuple([schemas.Fr, schemas.Fr]), output: AztecAddress.schema }),
 };
diff --git a/yarn-project/entrypoints/package.json b/yarn-project/entrypoints/package.json
@@ -72,7 +72,7 @@
     "@aztec/protocol-contracts": "workspace:^",
     "@aztec/stdlib": "workspace:^",
     "tslib": "^2.4.0",
-    "zod": "^3.23.8"
+    "zod": "^4"
   },
   "devDependencies": {
     "@jest/globals": "^30.0.0",

diff --git a/yarn-project/epoch-cache/package.json b/yarn-project/epoch-cache/package.json
@@ -35,7 +35,7 @@
     "jest-mock-extended": "^4.0.0",
     "tslib": "^2.4.0",
     "viem": "npm:@aztec/viem@2.38.2",
-    "zod": "^3.23.8"
+    "zod": "^4"
   },
   "devDependencies": {
     "@jest/globals": "^30.0.0",

diff --git a/yarn-project/ethereum/package.json b/yarn-project/ethereum/package.json
@@ -59,7 +59,7 @@
     "lodash.pickby": "^4.5.0",
     "tslib": "^2.4.0",
     "viem": "npm:@aztec/viem@2.38.2",
-    "zod": "^3.23.8"
+    "zod": "^4"
   },
   "devDependencies": {
     "@jest/globals": "^30.0.0",

diff --git a/yarn-project/foundation/package.json b/yarn-project/foundation/package.json
@@ -166,7 +166,7 @@
     "pino-pretty": "^13.0.0",
     "sha3": "^2.1.4",
     "undici": "^5.28.5",
-    "zod": "^3.23.8"
+    "zod": "^4"
   },
   "devDependencies": {
     "@jest/globals": "^30.0.0",

diff --git a/yarn-project/foundation/src/branded-types/checkpoint_number.ts b/yarn-project/foundation/src/branded-types/checkpoint_number.ts
@@ -103,7 +103,7 @@ CheckpointNumber.INITIAL = CheckpointNumber(1);
 function makeCheckpointNumberSchema(minValue: number) {
   return z
     .union([z.number(), z.bigint(), z.string()])
-    .pipe(z.coerce.number().int().min(minValue))
+    .pipe(z.coerce.number<string | number | bigint>().int().min(minValue))
     .transform(value => CheckpointNumber(value));
 }
 

diff --git a/yarn-project/foundation/src/branded-types/epoch.ts b/yarn-project/foundation/src/branded-types/epoch.ts
@@ -84,5 +84,5 @@ EpochNumber.ZERO = EpochNumber(0);
  */
 export const EpochNumberSchema = z
   .union([z.number(), z.bigint(), z.string()])
-  .pipe(z.coerce.number().int().min(0))
+  .pipe(z.coerce.number<string | number | bigint>().int().min(0))
   .transform(value => EpochNumber(value));
diff --git a/yarn-project/foundation/src/branded-types/index_within_checkpoint.ts b/yarn-project/foundation/src/branded-types/index_within_checkpoint.ts
@@ -84,5 +84,5 @@ IndexWithinCheckpoint.ZERO = IndexWithinCheckpoint(0);
  */
 export const IndexWithinCheckpointSchema = z
   .union([z.number(), z.bigint(), z.string()])
-  .pipe(z.coerce.number().int().min(0))
+  .pipe(z.coerce.number<string | number | bigint>().int().min(0))
   .transform(value => IndexWithinCheckpoint(value));
diff --git a/yarn-project/foundation/src/branded-types/slot.ts b/yarn-project/foundation/src/branded-types/slot.ts
@@ -89,5 +89,5 @@ SlotNumber.ZERO = SlotNumber(0);
  */
 export const SlotNumberSchema = z
   .union([z.number(), z.bigint(), z.string()])
-  .pipe(z.coerce.number().int().min(0))
+  .pipe(z.coerce.number<string | number | bigint>().int().min(0))
   .transform(value => SlotNumber(value));
diff --git a/yarn-project/foundation/src/config/secret_value.ts b/yarn-project/foundation/src/config/secret_value.ts
@@ -43,7 +43,7 @@ export class SecretValue<T> {
   /**
    * Returns a Zod schema
    */
-  static schema<O>(valueSchema: ZodType<O, any, any>): ZodType<SecretValue<O>, any, any> {
+  static schema<O>(valueSchema: ZodType<O, any>): ZodType<SecretValue<O>, any> {
     return valueSchema.transform(value => new SecretValue<O>(value));
   }
 }
diff --git a/yarn-project/foundation/src/json-rpc/client/safe_json_rpc_client.test.ts b/yarn-project/foundation/src/json-rpc/client/safe_json_rpc_client.test.ts
@@ -16,9 +16,9 @@ interface TestService {
 }
 
 const schema: ApiSchemaFor<TestService> = {
-  setValue: z.function().args(z.string()).returns(z.string()),
-  getValue: z.function().args().returns(z.string().optional()),
-  badReturn: z.function().args().returns(z.number()),
+  setValue: z.function({ input: z.tuple([z.string()]), output: z.string() }),
+  getValue: z.function({ input: z.tuple([]), output: z.string().optional() }),
+  badReturn: z.function({ input: z.tuple([]), output: z.number() }),
 };
 
 describe('SafeJsonRpcClient', () => {

diff --git a/yarn-project/foundation/src/json-rpc/client/safe_json_rpc_client.ts b/yarn-project/foundation/src/json-rpc/client/safe_json_rpc_client.ts
@@ -2,7 +2,7 @@ import { format } from 'util';
 
 import { type Logger, createLogger } from '../../log/pino-logger.js';
 import { type PromiseWithResolvers, promiseWithResolvers } from '../../promise/utils.js';
-import { type ApiSchema, type ApiSchemaFor, schemaHasMethod } from '../../schemas/api.js';
+import { type ApiSchema, type ApiSchemaFor, getSchemaReturnType, schemaHasMethod } from '../../schemas/api.js';
 import { jsonStringify } from '../convert.js';
 import { type JsonRpcFetch, defaultFetch } from './fetch.js';
 
@@ -236,7 +236,7 @@ export function createSafeJsonRpcClient<T extends object>(
     if ([null, undefined, 'null', 'undefined'].includes(response.result)) {
       return;
     }
-    return (schema as ApiSchema)[methodName].returnType().parseAsync(response.result);
+    return getSchemaReturnType((schema as ApiSchema)[methodName]).parseAsync(response.result);
   };
 
   const clientId = nextClientId++;

diff --git a/yarn-project/foundation/src/json-rpc/fixtures/test_state.ts b/yarn-project/foundation/src/json-rpc/fixtures/test_state.ts
@@ -130,14 +130,14 @@ export class TestState implements TestStateApi {
 }
 
 export const TestStateSchema: ApiSchemaFor<TestStateApi> = {
-  getNote: z.function().args(z.number()).returns(TestNote.schema.optional()),
-  getNotes: z.function().args(optional(schemas.Integer)).returns(z.array(TestNote.schema)),
-  getNotes2: z.function().args(optional(schemas.BigInt)).returns(z.array(TestNote.schema)),
-  getNotes3: z.function().args(optional(schemas.Integer)).returns(z.array(TestNote.schema)),
-  clear: z.function().returns(z.void()),
-  addNotes: z.function().args(z.array(TestNote.schema)).returns(z.array(TestNote.schema)),
-  fail: z.function().returns(z.void()),
-  count: z.function().returns(z.number()),
-  getStatus: z.function().returns(z.object({ status: z.string(), count: schemas.BigInt })),
-  getTuple: z.function().returns(z.tuple([z.string(), optional(z.string()), z.number()])),
+  getNote: z.function({ input: z.tuple([z.number()]), output: TestNote.schema.optional() }),
+  getNotes: z.function({ input: z.tuple([optional(schemas.Integer)]), output: z.array(TestNote.schema) }),
+  getNotes2: z.function({ input: z.tuple([optional(schemas.BigInt)]), output: z.array(TestNote.schema) }),
+  getNotes3: z.function({ input: z.tuple([optional(schemas.Integer)]), output: z.array(TestNote.schema) }),
+  clear: z.function({ input: z.tuple([]), output: z.void() }),
+  addNotes: z.function({ input: z.tuple([z.array(TestNote.schema)]), output: z.array(TestNote.schema) }),
+  fail: z.function({ input: z.tuple([]), output: z.void() }),
+  count: z.function({ input: z.tuple([]), output: z.number() }),
+  getStatus: z.function({ input: z.tuple([]), output: z.object({ status: z.string(), count: schemas.BigInt }) }),
+  getTuple: z.function({ input: z.tuple([]), output: z.tuple([z.string(), optional(z.string()), z.number()]) }),
 };