diff --git a/.changeset/pink-moons-admire.md b/.changeset/pink-moons-admire.md
new file mode 100644
index 00000000..7f0a41a1
--- /dev/null
+++ b/.changeset/pink-moons-admire.md
@@ -0,0 +1,5 @@
+---
+"@rhinestone/sdk": patch
+---
+
+Support custom bundler / paymaster / provider transport using `factory` prop
diff --git a/bun.lock b/bun.lock
index 57d760cf..b2018826 100644
--- a/bun.lock
+++ b/bun.lock
@@ -1,5 +1,6 @@
 {
   "lockfileVersion": 1,
+  "configVersion": 0,
   "workspaces": {
     "": {
       "dependencies": {
diff --git a/src/accounts/json-rpc/index.test.ts b/src/accounts/json-rpc/index.test.ts
index a3c1a2cd..6aa32cfd 100644
--- a/src/accounts/json-rpc/index.test.ts
+++ b/src/accounts/json-rpc/index.test.ts
@@ -1,6 +1,6 @@
+import { http } from 'viem'
 import { base, mainnet } from 'viem/chains'
 import { describe, expect, test } from 'vitest'
-
 import { createTransport } from './index'
 
 describe('JSON-RPC', () => {
@@ -23,6 +23,16 @@ describe('JSON-RPC', () => {
       expect(transport).toBeDefined()
     })
 
+    test('Factory', () => {
+      const viemTransport = http('https://my-rpc.example.com')
+      const transport = createTransport(mainnet, {
+        type: 'factory',
+        getTransport: (_chainId: number) => viemTransport,
+      })
+      expect(transport).toBeDefined()
+      expect(transport).toBe(viemTransport)
+    })
+
     test('Custom throws error when URL not configured for chain', () => {
       expect(() =>
         createTransport(mainnet, {
diff --git a/src/accounts/json-rpc/index.ts b/src/accounts/json-rpc/index.ts
index e8e9173c..e9868e95 100644
--- a/src/accounts/json-rpc/index.ts
+++ b/src/accounts/json-rpc/index.ts
@@ -20,6 +20,9 @@ function createTransport(chain: Chain, provider?: ProviderConfig): Transport {
       const customUrl = getCustomUrl(chain.id, provider.urls)
       return http(customUrl)
     }
+    case 'factory': {
+      return provider.getTransport(chain.id)
+    }
   }
 }
 
diff --git a/src/accounts/utils.ts b/src/accounts/utils.ts
index 98057076..d412b9e0 100644
--- a/src/accounts/utils.ts
+++ b/src/accounts/utils.ts
@@ -1,4 +1,4 @@
-import type { Address, Client, Hex } from 'viem'
+import type { Address, Client, Hex, Transport } from 'viem'
 import {
   concatHex,
   encodeAbiParameters,
@@ -227,21 +227,33 @@ async function getAccountNonce(
 }
 
 function getBundlerClient(config: RhinestoneConfig, client: Client) {
-  function getBundlerEndpoint(config: BundlerConfig, chainId: number) {
+  function getBundlerTransport(config: BundlerConfig, chainId: number) {
     switch (config.type) {
       case 'pimlico':
-        return `https://api.pimlico.io/v2/${chainId}/rpc?apikey=${config.apiKey}`
+        return http(
+          `https://api.pimlico.io/v2/${chainId}/rpc?apikey=${config.apiKey}`,
+        )
       case 'biconomy':
-        return `https://bundler.biconomy.io/api/v3/${chainId}/${config.apiKey}`
+        return http(
+          `https://bundler.biconomy.io/api/v3/${chainId}/${config.apiKey}`,
+        )
+      case 'factory':
+        return config.getTransport(chainId)
     }
   }
 
-  function getPaymasterEndpoint(config: PaymasterConfig, chainId: number) {
+  function getPaymasterTransport(config: PaymasterConfig, chainId: number) {
     switch (config.type) {
       case 'pimlico':
-        return `https://api.pimlico.io/v2/${chainId}/rpc?apikey=${config.apiKey}`
+        return http(
+          `https://api.pimlico.io/v2/${chainId}/rpc?apikey=${config.apiKey}`,
+        )
       case 'biconomy':
-        return `https://paymaster.biconomy.io/api/v2/${chainId}/${config.apiKey}`
+        return http(
+          `https://paymaster.biconomy.io/api/v2/${chainId}/${config.apiKey}`,
+        )
+      case 'factory':
+        return config.getTransport(chainId)
     }
   }
 
@@ -251,42 +263,31 @@ function getBundlerClient(config: RhinestoneConfig, client: Client) {
     throw new Error('Chain id is required')
   }
 
-  const endpoint = bundler
-    ? getBundlerEndpoint(bundler, chainId)
-    : `https://public.pimlico.io/v2/${chainId}/rpc`
-  const paymasterEndpoint = paymaster
-    ? getPaymasterEndpoint(paymaster, chainId)
+  const transport = bundler
+    ? getBundlerTransport(bundler, chainId)
+    : http(`https://public.pimlico.io/v2/${chainId}/rpc`)
+  const paymasterTransport = paymaster
+    ? getPaymasterTransport(paymaster, chainId)
     : undefined
   return createBundlerClient({
     client,
-    transport: http(endpoint),
-    paymaster: paymasterEndpoint
+    transport: transport,
+    paymaster: paymasterTransport
       ? createPaymasterClient({
-          transport: http(paymasterEndpoint),
+          transport: paymasterTransport,
         })
       : undefined,
     userOperation: {
-      estimateFeesPerGas: () => getGasPriceEstimate(endpoint),
+      estimateFeesPerGas: () => getGasPriceEstimate(transport),
     },
   })
 }
 
-async function getGasPriceEstimate(bundlerUrl: string) {
-  const response = await fetch(bundlerUrl, {
-    method: 'POST',
-    headers: {
-      'Content-Type': 'application/json',
-    },
-    body: JSON.stringify({
-      jsonrpc: '2.0',
-      id: Date.now(),
-      // TODO do not rely on vendor-specific methods
-      method: 'pimlico_getUserOperationGasPrice',
-      params: [],
-    }),
-  })
-
-  const json = (await response.json()) as UserOperationGasPriceResponse
+async function getGasPriceEstimate(bundlerTransport: Transport) {
+  const json = (await bundlerTransport({}).request({
+    method: 'pimlico_getUserOperationGasPrice',
+    params: [],
+  })) as UserOperationGasPriceResponse
 
   return {
     maxFeePerGas: BigInt(json.result.fast.maxFeePerGas),
diff --git a/src/types.ts b/src/types.ts
index 824124c6..b01659e4 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -1,4 +1,4 @@
-import type { Account, Address, Chain, Hex } from 'viem'
+import type { Account, Address, Chain, Hex, Transport } from 'viem'
 import type { WebAuthnAccount } from 'viem/account-abstraction'
 import type { ModuleType } from './modules/common'
 import type { EnableSessionData } from './modules/validators/smart-sessions'
@@ -88,16 +88,30 @@ type ProviderConfig =
       type: 'custom'
       urls: Record<number, string>
     }
+  | {
+      type: 'factory'
+      getTransport: (chainId: number) => Transport
+    }
 
-interface BundlerConfig {
-  type: 'pimlico' | 'biconomy'
-  apiKey: string
-}
+type BundlerConfig =
+  | {
+      type: 'pimlico' | 'biconomy'
+      apiKey: string
+    }
+  | {
+      type: 'factory'
+      getTransport: (chainId: number) => Transport
+    }
 
-interface PaymasterConfig {
-  type: 'pimlico' | 'biconomy'
-  apiKey: string
-}
+type PaymasterConfig =
+  | {
+      type: 'pimlico' | 'biconomy'
+      apiKey: string
+    }
+  | {
+      type: 'factory'
+      getTransport: (chainId: number) => Transport
+    }
 
 type OwnerSet =
   | OwnableValidatorConfig