diff --git a/core/types/src/index.test.ts b/core/types/src/index.test.ts
index 3c210d688..1cbc7a90c 100644
--- a/core/types/src/index.test.ts
+++ b/core/types/src/index.test.ts
@@ -2,7 +2,14 @@
 // SPDX-License-Identifier: Apache-2.0
 
 import { describe, expect, it } from 'vitest'
-import { WalletEvent, isSpliceMessage, isSpliceMessageEvent } from './index'
+import {
+    WalletEvent,
+    isSpliceMessage,
+    isSpliceMessageEvent,
+    SynchronizerId,
+} from './index'
+
+const SYNCHRONIZER_ID_EXAMPLE = 'sync::122012312312312312123'
 
 describe('isSpliceMessage', () => {
     it('accepts each splice message variant', () => {
@@ -54,6 +61,24 @@ describe('isSpliceMessage', () => {
     })
 })
 
+describe('SynchronizerId', () => {
+    it('accepts a well-formed synchronizer id', () => {
+        expect(SynchronizerId.safeParse(SYNCHRONIZER_ID_EXAMPLE).success).toBe(
+            true
+        )
+    })
+
+    it('rejects values missing the "::" separator', () => {
+        expect(SynchronizerId.safeParse('not-a-synchronizer-id').success).toBe(
+            false
+        )
+    })
+
+    it('rejects values shorter than 10 characters', () => {
+        expect(SynchronizerId.safeParse('a::b').success).toBe(false)
+    })
+})
+
 describe('isSpliceMessageEvent', () => {
     it('accepts objects with valid splice message data', () => {
         const message = {
diff --git a/core/types/src/index.ts b/core/types/src/index.ts
index 98b306e0b..4262e4278 100644
--- a/core/types/src/index.ts
+++ b/core/types/src/index.ts
@@ -26,6 +26,10 @@ export const PartyId = z
 
 export type PartyId = z.infer<typeof PartyId>
 
+export const SynchronizerId = z.string().includes('::').min(10)
+
+export type SynchronizerId = z.infer<typeof SynchronizerId>
+
 export const HttpUrl = z
     .url({
         message: 'Must be a valid HTTP or HTTPS URL',
diff --git a/sdk/wallet-sdk/src/wallet/init/types/context.ts b/sdk/wallet-sdk/src/wallet/init/types/context.ts
index 44f64fad8..1d174fe88 100644
--- a/sdk/wallet-sdk/src/wallet/init/types/context.ts
+++ b/sdk/wallet-sdk/src/wallet/init/types/context.ts
@@ -2,6 +2,7 @@
 // SPDX-License-Identifier: Apache-2.0
 
 import { AbstractLedgerProvider } from '@canton-network/core-provider-ledger'
+import { SynchronizerId } from '@canton-network/core-types'
 import { SDKLogger } from '../../logger/logger.js'
 import { SDKErrorHandler } from '../../error/handler.js'
 
@@ -10,7 +11,7 @@ export type SDKContext = {
     userId: string
     logger: SDKLogger
     error: SDKErrorHandler
-    defaultSynchronizerId: string
+    defaultSynchronizerId: SynchronizerId
 }
 
 export type OfflineSDKContext = {
diff --git a/sdk/wallet-sdk/src/wallet/namespace/party/external/signed.ts b/sdk/wallet-sdk/src/wallet/namespace/party/external/signed.ts
index ab98168bc..98005c611 100644
--- a/sdk/wallet-sdk/src/wallet/namespace/party/external/signed.ts
+++ b/sdk/wallet-sdk/src/wallet/namespace/party/external/signed.ts
@@ -10,7 +10,7 @@ import {
     OnboardingTransactions,
 } from './types.js'
 
-import { PartyId } from '@canton-network/core-types'
+import { PartyId, SynchronizerId } from '@canton-network/core-types'
 import {
     AbstractLedgerProvider,
     LedgerProvider,
@@ -315,7 +315,7 @@ export class SignedPartyCreationService {
 
     private async allocate(
         ledgerProvider: AbstractLedgerProvider,
-        synchronizerId: string,
+        synchronizerId: SynchronizerId,
         onboardingTransactions: OnboardingTransactions,
         multiHashSignatures: MultiHashSignatures
     ): Promise<Ops.PostV2PartiesExternalAllocate['ledgerApi']['result']> {
diff --git a/sdk/wallet-sdk/src/wallet/namespace/party/external/types.ts b/sdk/wallet-sdk/src/wallet/namespace/party/external/types.ts
index 54f11b172..282da4af5 100644
--- a/sdk/wallet-sdk/src/wallet/namespace/party/external/types.ts
+++ b/sdk/wallet-sdk/src/wallet/namespace/party/external/types.ts
@@ -2,13 +2,14 @@
 // SPDX-License-Identifier: Apache-2.0
 
 import { Ops } from '@canton-network/core-provider-ledger'
+import { SynchronizerId } from '@canton-network/core-types'
 import { TokenProviderConfig } from '@canton-network/core-wallet-auth'
 
 export type CreatePartyOptions = Partial<{
     isAdmin: boolean
     partyHint: string
     confirmingThreshold: number
-    synchronizerId: string
+    synchronizerId: SynchronizerId
     confirmingParticipantEndpoints: ParticipantEndpointConfig[]
     observingParticipantEndpoints: ParticipantEndpointConfig[]
     localParticipantObservationOnly: boolean
diff --git a/sdk/wallet-sdk/src/wallet/namespace/token/utxos/mergeDelegation.ts b/sdk/wallet-sdk/src/wallet/namespace/token/utxos/mergeDelegation.ts
index c926fcf3e..c10988504 100644
--- a/sdk/wallet-sdk/src/wallet/namespace/token/utxos/mergeDelegation.ts
+++ b/sdk/wallet-sdk/src/wallet/namespace/token/utxos/mergeDelegation.ts
@@ -8,7 +8,7 @@ import {
     ExerciseCommand,
 } from '@canton-network/core-token-standard-service'
 import { Holding, PrettyContract } from '@canton-network/core-tx-parser'
-import { PartyId } from '@canton-network/core-types'
+import { PartyId, SynchronizerId } from '@canton-network/core-types'
 import { LedgerNamespace } from '../../ledger/index.js'
 import { UtxoNamespace } from './index.js'
 import { resolveProviderParty } from '../utils.js'
@@ -23,7 +23,7 @@ export class MergeDelegationNamespace {
         this.ledger = new LedgerNamespace(ctx.commonCtx)
     }
 
-    async setup(synchronizerId: string = '', validatorParty?: PartyId) {
+    async setup(synchronizerId: SynchronizerId = '', validatorParty?: PartyId) {
         const providerParty = resolveProviderParty(
             this.ctx,
             'setup',