diff --git a/demo/package.json b/demo/package.json
index 6c1807f..9894c37 100644
--- a/demo/package.json
+++ b/demo/package.json
@@ -10,8 +10,7 @@
   },
   "dependencies": {
     "@creit-tech/stellar-wallets-kit": "npm:@jsr/creit-tech__stellar-wallets-kit@^2.1.0",
-    "@stellar/stellar-base": "^15.0.0",
-    "@stellar/stellar-sdk": "^15.0.1",
+    "@stellar/stellar-sdk": "16.0.0-rc.1",
     "buffer": "^6.0.3",
     "react": "^19.2.4",
     "react-dom": "^19.2.4",
diff --git a/demo/src/components/ContextRuleBuilder.tsx b/demo/src/components/ContextRuleBuilder.tsx
index 9993e3a..517483e 100644
--- a/demo/src/components/ContextRuleBuilder.tsx
+++ b/demo/src/components/ContextRuleBuilder.tsx
@@ -1,4 +1,5 @@
 import { useState, useCallback, useEffect, useMemo } from "react";
+import type { Buffer } from "buffer";
 import type { SmartAccountKit, StoredCredential, AssembledTransaction } from "smart-account-kit";
 import {
   createDelegatedSigner,
@@ -1332,7 +1333,9 @@ export function ContextRuleBuilder({
                 {selectedPolicies.map((sp, index) => (
                   <div key={index} className="selected-policy-item">
                     <div className="selected-policy-header">
-                      <span className="policy-type-badge">{sp.policy.type}</span>
+                      <span className={`policy-type-badge policy-type-${sp.policy.type}`}>
+                        {sp.policy.type}
+                      </span>
                       <span className="policy-name">{sp.policy.name}</span>
                       <button
                         className="remove-btn"
diff --git a/demo/src/main.tsx b/demo/src/main.tsx
index 3830d8b..e5374e6 100644
--- a/demo/src/main.tsx
+++ b/demo/src/main.tsx
@@ -5,7 +5,7 @@ import "./styles.css";
 
 // Polyfill Buffer for browser (required by stellar-sdk)
 import { Buffer } from "buffer";
-globalThis.Buffer = Buffer;
+(globalThis as typeof globalThis & { Buffer: typeof Buffer }).Buffer = Buffer;
 
 ReactDOM.createRoot(document.getElementById("root")!).render(
   <React.StrictMode>
diff --git a/demo/src/styles.css b/demo/src/styles.css
index 8ffb07a..d307fb5 100644
--- a/demo/src/styles.css
+++ b/demo/src/styles.css
@@ -1114,7 +1114,7 @@ button.small .spinner {
   text-transform: uppercase;
 }
 
-.policy-type-badge:has(+ .policy-name:contains("custom")) {
+.policy-type-badge.policy-type-custom {
   background: #8b5cf6;
 }
 
diff --git a/demo/vite.config.ts b/demo/vite.config.ts
index 1ddcb2d..c13fd11 100644
--- a/demo/vite.config.ts
+++ b/demo/vite.config.ts
@@ -16,14 +16,13 @@ export default defineConfig({
     // Ensure symlinks are resolved to prevent duplicate module instances
     preserveSymlinks: false,
     // Force Vite to use a single instance of these packages
-    dedupe: ["@stellar/stellar-sdk", "@stellar/stellar-base"],
+    dedupe: ["@stellar/stellar-sdk"],
   },
   optimizeDeps: {
     include: [
       "buffer",
       "@stellar/stellar-sdk",
       "@stellar/stellar-sdk/rpc",
-      "@stellar/stellar-base",
     ],
     esbuildOptions: {
       define: {
diff --git a/indexer/demo/package.json b/indexer/demo/package.json
index df8c48c..7ac49ef 100644
--- a/indexer/demo/package.json
+++ b/indexer/demo/package.json
@@ -10,7 +10,7 @@
   },
   "dependencies": {
     "@simplewebauthn/browser": "^13.3.0",
-    "@stellar/stellar-sdk": "^15.0.1",
+    "@stellar/stellar-sdk": "16.0.0-rc.1",
     "smart-account-kit": "workspace:^"
   },
   "devDependencies": {
diff --git a/package.json b/package.json
index 8439be7..701c3bd 100644
--- a/package.json
+++ b/package.json
@@ -55,7 +55,7 @@
   },
   "dependencies": {
     "@simplewebauthn/browser": "^13.3.0",
-    "@stellar/stellar-sdk": ">=15.0.1",
+    "@stellar/stellar-sdk": "16.0.0-rc.1",
     "base64url": "^3.0.1",
     "smart-account-kit-bindings": "workspace:*"
   },
@@ -72,7 +72,7 @@
   "packageManager": "pnpm@10.33.0",
   "peerDependencies": {
     "@creit-tech/stellar-wallets-kit": ">=2.1.0",
-    "@stellar/stellar-sdk": ">=15.0.1"
+    "@stellar/stellar-sdk": ">=15.1.0 || 16.0.0-rc.1"
   },
   "peerDependenciesMeta": {
     "@creit-tech/stellar-wallets-kit": {
diff --git a/packages/smart-account-kit-bindings/package.json b/packages/smart-account-kit-bindings/package.json
index eb1071c..f63736d 100644
--- a/packages/smart-account-kit-bindings/package.json
+++ b/packages/smart-account-kit-bindings/package.json
@@ -27,7 +27,7 @@
     "url": "https://github.com/kalepail/smart-account-kit"
   },
   "peerDependencies": {
-    "@stellar/stellar-sdk": ">=15.0.1"
+    "@stellar/stellar-sdk": ">=15.1.0 || 16.0.0-rc.1"
   },
   "publishConfig": {
     "registry": "https://registry.npmjs.org/",
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index 8350ca2..c18fe73 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -5,7 +5,7 @@ settings:
   excludeLinksFromLockfile: false
 
 overrides:
-  '@stellar/stellar-sdk': '>=15.0.1'
+  '@stellar/stellar-sdk': 16.0.0-rc.1
 
 importers:
 
@@ -15,8 +15,8 @@ importers:
         specifier: ^13.3.0
         version: 13.3.0
       '@stellar/stellar-sdk':
-        specifier: '>=15.0.1'
-        version: 15.0.1
+        specifier: 16.0.0-rc.1
+        version: 16.0.0-rc.1
       base64url:
         specifier: ^3.0.1
         version: 3.0.1
@@ -26,7 +26,7 @@ importers:
     devDependencies:
       '@creit-tech/stellar-wallets-kit':
         specifier: jsr:2.1.0
-        version: '@jsr/creit-tech__stellar-wallets-kit@2.1.0(@solana/sysvars@5.5.1(fastestsmallesttextencoderdecoder@1.0.22)(typescript@6.0.2))(@stellar/stellar-sdk@15.0.1)(@trezor/connect@9.7.2(@solana/sysvars@5.5.1(fastestsmallesttextencoderdecoder@1.0.22)(typescript@6.0.2))(bufferutil@4.0.9)(fastestsmallesttextencoderdecoder@1.0.22)(tslib@2.8.1)(typescript@6.0.2)(utf-8-validate@5.0.10)(ws@8.20.0(bufferutil@4.0.9)(utf-8-validate@5.0.10)))(@types/react@19.2.14)(bufferutil@4.0.9)(fastestsmallesttextencoderdecoder@1.0.22)(near-api-js@5.1.1)(react@19.2.4)(tslib@2.8.1)(typescript@6.0.2)(utf-8-validate@5.0.10)(ws@8.20.0(bufferutil@4.0.9)(utf-8-validate@5.0.10))(zod@3.25.76)'
+        version: '@jsr/creit-tech__stellar-wallets-kit@2.1.0(@solana/sysvars@5.5.1(fastestsmallesttextencoderdecoder@1.0.22)(typescript@6.0.2))(@stellar/stellar-sdk@16.0.0-rc.1)(@trezor/connect@9.7.2(@solana/sysvars@5.5.1(fastestsmallesttextencoderdecoder@1.0.22)(typescript@6.0.2))(bufferutil@4.0.9)(fastestsmallesttextencoderdecoder@1.0.22)(tslib@2.8.1)(typescript@6.0.2)(utf-8-validate@5.0.10)(ws@8.20.0(bufferutil@4.0.9)(utf-8-validate@5.0.10)))(@types/react@19.2.14)(bufferutil@4.0.9)(fastestsmallesttextencoderdecoder@1.0.22)(near-api-js@5.1.1)(react@19.2.4)(tslib@2.8.1)(typescript@6.0.2)(utf-8-validate@5.0.10)(ws@8.20.0(bufferutil@4.0.9)(utf-8-validate@5.0.10))(zod@3.25.76)'
       '@types/node':
         specifier: ^25.5.2
         version: 25.5.2
@@ -41,13 +41,10 @@ importers:
     dependencies:
       '@creit-tech/stellar-wallets-kit':
         specifier: npm:@jsr/creit-tech__stellar-wallets-kit@^2.1.0
-        version: '@jsr/creit-tech__stellar-wallets-kit@2.1.0(@solana/sysvars@5.5.1(fastestsmallesttextencoderdecoder@1.0.22)(typescript@6.0.2))(@stellar/stellar-sdk@15.0.1)(@trezor/connect@9.7.2(@solana/sysvars@5.5.1(fastestsmallesttextencoderdecoder@1.0.22)(typescript@6.0.2))(bufferutil@4.0.9)(fastestsmallesttextencoderdecoder@1.0.22)(tslib@2.8.1)(typescript@6.0.2)(utf-8-validate@5.0.10)(ws@8.20.0(bufferutil@4.0.9)(utf-8-validate@5.0.10)))(@types/react@19.2.14)(bufferutil@4.0.9)(fastestsmallesttextencoderdecoder@1.0.22)(near-api-js@5.1.1)(react@19.2.4)(tslib@2.8.1)(typescript@6.0.2)(utf-8-validate@5.0.10)(ws@8.20.0(bufferutil@4.0.9)(utf-8-validate@5.0.10))(zod@3.25.76)'
-      '@stellar/stellar-base':
-        specifier: ^15.0.0
-        version: 15.0.0
+        version: '@jsr/creit-tech__stellar-wallets-kit@2.1.0(@solana/sysvars@5.5.1(fastestsmallesttextencoderdecoder@1.0.22)(typescript@6.0.2))(@stellar/stellar-sdk@16.0.0-rc.1)(@trezor/connect@9.7.2(@solana/sysvars@5.5.1(fastestsmallesttextencoderdecoder@1.0.22)(typescript@6.0.2))(bufferutil@4.0.9)(fastestsmallesttextencoderdecoder@1.0.22)(tslib@2.8.1)(typescript@6.0.2)(utf-8-validate@5.0.10)(ws@8.20.0(bufferutil@4.0.9)(utf-8-validate@5.0.10)))(@types/react@19.2.14)(bufferutil@4.0.9)(fastestsmallesttextencoderdecoder@1.0.22)(near-api-js@5.1.1)(react@19.2.4)(tslib@2.8.1)(typescript@6.0.2)(utf-8-validate@5.0.10)(ws@8.20.0(bufferutil@4.0.9)(utf-8-validate@5.0.10))(zod@3.25.76)'
       '@stellar/stellar-sdk':
-        specifier: '>=15.0.1'
-        version: 15.0.1
+        specifier: 16.0.0-rc.1
+        version: 16.0.0-rc.1
       buffer:
         specifier: ^6.0.3
         version: 6.0.3
@@ -86,8 +83,8 @@ importers:
         specifier: ^13.3.0
         version: 13.3.0
       '@stellar/stellar-sdk':
-        specifier: '>=15.0.1'
-        version: 15.0.1
+        specifier: 16.0.0-rc.1
+        version: 16.0.0-rc.1
       smart-account-kit:
         specifier: workspace:^
         version: link:../..
@@ -137,8 +134,8 @@ importers:
   packages/smart-account-kit-bindings:
     dependencies:
       '@stellar/stellar-sdk':
-        specifier: '>=15.0.1'
-        version: 15.0.1
+        specifier: 16.0.0-rc.1
+        version: 16.0.0-rc.1
       buffer:
         specifier: 6.0.3
         version: 6.0.3
@@ -703,6 +700,9 @@ packages:
     resolution: {integrity: sha512-vs1Az2OOTBiP4q0pwjW5aF0xp9n4MxVrmkFBxc6EKZc6ddYx5gaZiAsZoq0uRRXWbi3AT/sBqn05eRPtn1JCPw==}
     engines: {node: '>= 20.19.0'}
 
+  '@noble/ed25519@3.1.0':
+    resolution: {integrity: sha512-pfcObRY3CtvwfaG9Mt5XqZdKmAQppl37tHUeuBhDUbiwJBCVY4/A4lbMvb1xKhMDx96AqAqZpMWuBX1HulhX4g==}
+
   '@noble/hashes@1.3.3':
     resolution: {integrity: sha512-V7/fPHgl+jsVPXqqeOzT8egNj2iBIVt+ECeMMG8TdcnTikP3oaBtUVqpT/gYCR68aEBJSF+XbYUxStjbFMqIIA==}
     engines: {node: '>= 16'}
@@ -727,6 +727,10 @@ packages:
     resolution: {integrity: sha512-XlOlEbQcE9fmuXxrVTXCTlG2nlRXa9Rj3rr5Ue/+tX+nmkgbX720YHh0VR3hBF9xDvwnb8D2shVGOwNx+ulArw==}
     engines: {node: '>= 20.19.0'}
 
+  '@noble/hashes@2.2.0':
+    resolution: {integrity: sha512-IYqDGiTXab6FniAgnSdZwgWbomxpy9FtYvLKs7wCUs2a8RkITG+DFGO1DM9cr+E3/RgADRpFjrKVaJ1z6sjtEg==}
+    engines: {node: '>= 20.19.0'}
+
   '@openzeppelin/relayer-plugin-channels@0.20.0':
     resolution: {integrity: sha512-buZ0Xcir1mPcevMBU3vzbq4v77YUsikWX+E1k31YxdE6p97GEn40RnxNzow/eLNVnS3WNwYZ1SuEZgsQE7KHAg==}
     engines: {node: '>=22.18.0', npm: use pnpm, pnpm: '>=9', yarn: use pnpm}
@@ -1594,13 +1598,9 @@ packages:
     resolution: {integrity: sha512-mI6Kjh9hGWDA1APawQTtCbR7702dNT/8Te1uuRFPqqdoAKBk3WpXOQI3ZSZO+5olW7BSHpmVG5KBPZpIpQxIvw==}
     engines: {node: '>=20.0.0'}
 
-  '@stellar/stellar-base@15.0.0':
-    resolution: {integrity: sha512-XQhxUr9BYiEcFcgc4oWcCMR9QJCny/GmmGsuwPKf/ieIcOeb5149KLHYx9mJCA0ea8QbucR2/GzV58QbXOTxQA==}
-    engines: {node: '>=20.0.0'}
-
-  '@stellar/stellar-sdk@15.0.1':
-    resolution: {integrity: sha512-iZjWKXtfohsPh+CX9wRyQNIlXLeA9VyuQB6UMC7AFBD9XnR92eOjnlfeONzk/Bsrkk6+UPlpzSy2MuF+ydHP1A==}
-    engines: {node: '>=20.0.0'}
+  '@stellar/stellar-sdk@16.0.0-rc.1':
+    resolution: {integrity: sha512-mkOQUsFgepFIxRFJLgjkLAkYQDBdNKgLpMM5yIWQcCUoXavb0gO1Dlw/hPqVg2KBKUKaXs2ljVLuB4x6bSWR0g==}
+    engines: {node: '>=22.0.0'}
     hasBin: true
 
   '@swc/helpers@0.5.17':
@@ -1649,7 +1649,7 @@ packages:
   '@trezor/connect-plugin-stellar@9.2.6':
     resolution: {integrity: sha512-RA0Q4GHaf1mFxgSX183yyH+5tWEgS1j+sfe9KiUyIn/VnpXeUnaCpQuKMomAjGXQ5oNuvikTOdHYOqsvuEdOyw==}
     peerDependencies:
-      '@stellar/stellar-sdk': '>=15.0.1'
+      '@stellar/stellar-sdk': 16.0.0-rc.1
       '@trezor/connect': 9.x.x
       tslib: ^2.6.2
 
@@ -1993,6 +1993,10 @@ packages:
       zod:
         optional: true
 
+  agent-base@6.0.2:
+    resolution: {integrity: sha512-RZNwNclF7+MS/8bDg70amg32dyeZGZxiDuQmZxKLAlQjr3jGyLx+4Kkk58UO7D2QdgFIQCovuSuZESne6RG6XQ==}
+    engines: {node: '>= 6.0.0'}
+
   agent-base@7.1.4:
     resolution: {integrity: sha512-MnA+YT8fwfJPgBx3m60MNqakm30XOkyIoH1y6huTQvC0PwZG7ki8NacLBcrPbNoo8vEZy7Jpuk7+jMO+CUovTQ==}
     engines: {node: '>= 14'}
@@ -2042,6 +2046,9 @@ packages:
   axios@1.14.0:
     resolution: {integrity: sha512-3Y8yrqLSwjuzpXuZ0oIYZ/XGgLwUIBU3uLvbcpb0pidD9ctpShJd43KSlEEkVQg6DS0G9NKyzOvBfUtDKEyHvQ==}
 
+  axios@1.16.1:
+    resolution: {integrity: sha512-caYkukvroVPO8KrzuJEb50Hm07KwfBZPEC3VeFHTsqWHvKTsy54hjJz9BS/cdaypROE2rH6xvm9mHX4fgWkr3A==}
+
   base-x@3.0.11:
     resolution: {integrity: sha512-xz7wQ8xDhdyP7tQxwdteLYeFfS68tSMNCZ/Y37WJ4bhGfKPpqEIlmIyueQHqOyoPhE6xNUqjzRr8ra0eF9VRvA==}
 
@@ -2069,6 +2076,9 @@ packages:
   big.js@6.2.2:
     resolution: {integrity: sha512-y/ie+Faknx7sZA5MfGA2xKlu0GDv8RWrXGsmlteyJQ2lvoKv9GBK/fpRMc2qlSoBAgNxrixICFCBefIq8WCQpQ==}
 
+  bignumber.js@11.1.3:
+    resolution: {integrity: sha512-+esZiNSo6VgFokTsYX6mYqNJfFd/IczzZCd4Z7cR8e+AQWhvIcj6nqQ1h9814D9u/TApU0jjTVmfWL0Pd1ZBdA==}
+
   bignumber.js@9.3.1:
     resolution: {integrity: sha512-Ko0uX15oIUS7wJ3Rb30Fs6SkVbLmPBAKdlm7q9+ak9bbIeFf0MwuBsQV6z7+X768/cHsfg+WlysDWJcmthjsjQ==}
 
@@ -2392,9 +2402,13 @@ packages:
     resolution: {integrity: sha512-mQw+2fkQbALzQ7V0MY0IqdnXNOeTtP4r0lN9z7AAawCXgqea7bDii20AYrIBrFd/Hx0M2Ocz6S111CaFkUcb0Q==}
     engines: {node: '>=0.8.x'}
 
-  eventsource@2.0.2:
-    resolution: {integrity: sha512-IzUmBGPR3+oUG9dUeXynyNmf91/3zUSJg1lCktzKw47OXuhco54U3r9B7O4XX+Rb1Itm9OZ2b0RkTs10bICOxA==}
-    engines: {node: '>=12.0.0'}
+  eventsource-parser@3.1.0:
+    resolution: {integrity: sha512-kJezFj9YFAMLeORyi7aCLxLbD5/qWMQnoMVlVPyHIll7lgRJCc3JVln9Vgl9nwQi0YkMnhdGTMNn7CkRRAptMg==}
+    engines: {node: '>=18.0.0'}
+
+  eventsource@4.1.0:
+    resolution: {integrity: sha512-2GuF51iuHX6A9xdTccMTsNb7VO0lHZihApxhvQzJB5A03DvHDd2FQepodbMaztPBmBcE/ox7o2gqaxGhYB9LhQ==}
+    engines: {node: '>=20.0.0'}
 
   evp_bytestokey@1.0.3:
     resolution: {integrity: sha512-/f2Go4TognH/KvCISP7OUsHn85hT9nUkxxA9BEWxFn+Oj9o8ZNLm/40hdlgSLyuOimsrTKLUMEorQexp/aPQeA==}
@@ -2447,6 +2461,15 @@ packages:
       debug:
         optional: true
 
+  follow-redirects@1.16.0:
+    resolution: {integrity: sha512-y5rN/uOsadFT/JfYwhxRS5R7Qce+g3zG97+JrtFZlC9klX/W5hD7iiLzScI4nZqUS7DNUdhPgw4xI8W2LuXlUw==}
+    engines: {node: '>=4.0'}
+    peerDependencies:
+      debug: '*'
+    peerDependenciesMeta:
+      debug:
+        optional: true
+
   for-each@0.3.5:
     resolution: {integrity: sha512-dKx12eRCVIzqCxFGplyFKJMPvLEWgmNtUrpTiJIR5u97zEhRG8ySrtboPHZXx7daLxQVrl643cTzbab2tkQjxg==}
     engines: {node: '>= 0.4'}
@@ -2524,6 +2547,10 @@ packages:
     resolution: {integrity: sha512-uUQBt3H/cSIVfch6i1EuPNy/YsRSOUBXTVfZ+yR7Zjez3qjBz6i9+i4zjNaoqcoFVI4lQJ5plg63TvGfRSDCRg==}
     engines: {node: '>= 0.6'}
 
+  https-proxy-agent@5.0.1:
+    resolution: {integrity: sha512-dFcAjpTQFgoLMzC2VwU+C/CbS7uRL0lWmxDITmqm7C+7F0Odmj6s9l6alZc6AELXhrnggM2CeWSXHGOdX2YtwA==}
+    engines: {node: '>= 6'}
+
   humanize-ms@1.2.1:
     resolution: {integrity: sha512-Fl70vYtsAFb/C06PTS9dZBo7ihau+Tu/DNCk/OyHhea07S+aeMWpFFkUaXRa8fI+ScZbEI8dfSxwY7gxZ9SAVQ==}
 
@@ -3119,6 +3146,10 @@ packages:
     resolution: {integrity: sha512-94hK0Hh8rPqQl2xXc3HsaBoOXKV20MToPkcXvwbISWLEs+64sBq5kFgn2kJDHb1Pry9yrP0dxrCI9RRci7RXKg==}
     engines: {node: '>= 6.0.0', npm: '>= 3.0.0'}
 
+  smol-toml@1.6.1:
+    resolution: {integrity: sha512-dWUG8F5sIIARXih1DTaQAX4SsiTXhInKf1buxdY9DIg4ZYPZK5nGM1VRIYmEbDbsHt7USo99xSLFu5Q1IqTmsg==}
+    engines: {node: '>= 18'}
+
   socks-proxy-agent@8.0.5:
     resolution: {integrity: sha512-HehCEsotFqbPW9sJ8WVYB6UbmIMv7kUUORIF2Nncq4VQvBfNBLibW9YZR5dlYCSUhwcD628pRllm7n+E+YTzJw==}
     engines: {node: '>= 14'}
@@ -3215,9 +3246,6 @@ packages:
     resolution: {integrity: sha512-yaOH/Pk/VEhBWWTlhI+qXxDFXlejDGcQipMlyxda9nthulaxLZUNcUqFxokp0vcYnvteJln5FNQDRrxj3YcbVw==}
     engines: {node: '>=0.6'}
 
-  toml@3.0.0:
-    resolution: {integrity: sha512-y/mWCZinnvxjTKYhJ+pYxwD0mRLVvOtdS2Awbgxln6iEnt4rk0yBxeSBHkGJcPucRiG0e55mwWp+g/05rsrd6w==}
-
   tr46@0.0.3:
     resolution: {integrity: sha512-N3WMsuqV66lT30CrXNbEjx4GEwlow3v6rr4mCcv6prnfwhS01rkgyFdjPNBYd9br7LpXV1+Emh01fHnq2Gdgrw==}
 
@@ -3258,6 +3286,10 @@ packages:
   ufo@1.6.1:
     resolution: {integrity: sha512-9a4/uxlTWJ4+a5i0ooc1rU7C7YOw3wT+UGqdeNNHWnOF9qcMBgLRS+4IYUqbczewFx4mLEig6gawh7X6mFlEkA==}
 
+  uint8array-extras@1.5.0:
+    resolution: {integrity: sha512-rvKSBiC5zqCCiDZ9kAOszZcDvdAHwwIKJG33Ykj43OKcWsnmcBRL09YTU4nOeHZ8Y2a7l1MgTd08SBe9A8Qj6A==}
+    engines: {node: '>=18'}
+
   uint8array-tools@0.0.8:
     resolution: {integrity: sha512-xS6+s8e0Xbx++5/0L+yyexukU7pz//Yg6IHg3BKhXotg1JcYtgxVcUctQ0HxLByiJzpAkNFawz1Nz5Xadzo82g==}
     engines: {node: '>=14.0.0'}
@@ -3343,9 +3375,6 @@ packages:
       uploadthing:
         optional: true
 
-  urijs@1.19.11:
-    resolution: {integrity: sha512-HXgFDgDommxn5/bIv0cnQZsPhHDA90NPHD6+c/v21U5+Sx5hoP8+dP9IZXBU1gIfvdRfhG8cel9QNPeionfcCQ==}
-
   usb@2.16.0:
     resolution: {integrity: sha512-jD88fvzDViMDH5KmmNJgzMBDj/95bDTt6+kBNaNxP4G98xUTnDMiLUY2CYmToba6JAFhM9VkcaQuxCNRLGR7zg==}
     engines: {node: '>=12.22.0 <13.0 || >=14.17.0'}
@@ -3950,7 +3979,7 @@ snapshots:
       '@jridgewell/resolve-uri': 3.1.2
       '@jridgewell/sourcemap-codec': 1.5.5
 
-  '@jsr/creit-tech__stellar-wallets-kit@2.1.0(@solana/sysvars@5.5.1(fastestsmallesttextencoderdecoder@1.0.22)(typescript@6.0.2))(@stellar/stellar-sdk@15.0.1)(@trezor/connect@9.7.2(@solana/sysvars@5.5.1(fastestsmallesttextencoderdecoder@1.0.22)(typescript@6.0.2))(bufferutil@4.0.9)(fastestsmallesttextencoderdecoder@1.0.22)(tslib@2.8.1)(typescript@6.0.2)(utf-8-validate@5.0.10)(ws@8.20.0(bufferutil@4.0.9)(utf-8-validate@5.0.10)))(@types/react@19.2.14)(bufferutil@4.0.9)(fastestsmallesttextencoderdecoder@1.0.22)(near-api-js@5.1.1)(react@19.2.4)(tslib@2.8.1)(typescript@6.0.2)(utf-8-validate@5.0.10)(ws@8.20.0(bufferutil@4.0.9)(utf-8-validate@5.0.10))(zod@3.25.76)':
+  '@jsr/creit-tech__stellar-wallets-kit@2.1.0(@solana/sysvars@5.5.1(fastestsmallesttextencoderdecoder@1.0.22)(typescript@6.0.2))(@stellar/stellar-sdk@16.0.0-rc.1)(@trezor/connect@9.7.2(@solana/sysvars@5.5.1(fastestsmallesttextencoderdecoder@1.0.22)(typescript@6.0.2))(bufferutil@4.0.9)(fastestsmallesttextencoderdecoder@1.0.22)(tslib@2.8.1)(typescript@6.0.2)(utf-8-validate@5.0.10)(ws@8.20.0(bufferutil@4.0.9)(utf-8-validate@5.0.10)))(@types/react@19.2.14)(bufferutil@4.0.9)(fastestsmallesttextencoderdecoder@1.0.22)(near-api-js@5.1.1)(react@19.2.4)(tslib@2.8.1)(typescript@6.0.2)(utf-8-validate@5.0.10)(ws@8.20.0(bufferutil@4.0.9)(utf-8-validate@5.0.10))(zod@3.25.76)':
     dependencies:
       '@albedo-link/intent': 0.12.0
       '@creit.tech/xbull-wallet-connect': 0.4.0
@@ -3964,7 +3993,7 @@ snapshots:
       '@reown/appkit': 1.8.19(@types/react@19.2.14)(bufferutil@4.0.9)(fastestsmallesttextencoderdecoder@1.0.22)(react@19.2.4)(typescript@6.0.2)(utf-8-validate@5.0.10)(zod@3.25.76)
       '@stellar/freighter-api': 6.0.0
       '@stellar/stellar-base': 14.0.1
-      '@trezor/connect-plugin-stellar': 9.2.6(@stellar/stellar-sdk@15.0.1)(@trezor/connect@9.7.2(@solana/sysvars@5.5.1(fastestsmallesttextencoderdecoder@1.0.22)(typescript@6.0.2))(bufferutil@4.0.9)(fastestsmallesttextencoderdecoder@1.0.22)(tslib@2.8.1)(typescript@6.0.2)(utf-8-validate@5.0.10)(ws@8.20.0(bufferutil@4.0.9)(utf-8-validate@5.0.10)))(tslib@2.8.1)
+      '@trezor/connect-plugin-stellar': 9.2.6(@stellar/stellar-sdk@16.0.0-rc.1)(@trezor/connect@9.7.2(@solana/sysvars@5.5.1(fastestsmallesttextencoderdecoder@1.0.22)(typescript@6.0.2))(bufferutil@4.0.9)(fastestsmallesttextencoderdecoder@1.0.22)(tslib@2.8.1)(typescript@6.0.2)(utf-8-validate@5.0.10)(ws@8.20.0(bufferutil@4.0.9)(utf-8-validate@5.0.10)))(tslib@2.8.1)
       '@trezor/connect-web': 9.7.2(@solana/sysvars@5.5.1(fastestsmallesttextencoderdecoder@1.0.22)(typescript@6.0.2))(bufferutil@4.0.9)(fastestsmallesttextencoderdecoder@1.0.22)(tslib@2.8.1)(typescript@6.0.2)(utf-8-validate@5.0.10)(ws@8.20.0(bufferutil@4.0.9)(utf-8-validate@5.0.10))
       '@twind/core': 1.1.3(typescript@6.0.2)
       '@twind/preset-autoprefix': 1.0.7(@twind/core@1.1.3(typescript@6.0.2))(typescript@6.0.2)
@@ -4199,6 +4228,8 @@ snapshots:
     dependencies:
       '@noble/hashes': 2.0.1
 
+  '@noble/ed25519@3.1.0': {}
+
   '@noble/hashes@1.3.3': {}
 
   '@noble/hashes@1.4.0':
@@ -4212,14 +4243,17 @@ snapshots:
 
   '@noble/hashes@2.0.1': {}
 
+  '@noble/hashes@2.2.0': {}
+
   '@openzeppelin/relayer-plugin-channels@0.20.0':
     dependencies:
       '@actions/exec': 1.1.1
       '@openzeppelin/relayer-sdk': 1.10.0
-      '@stellar/stellar-sdk': 15.0.1
+      '@stellar/stellar-sdk': 16.0.0-rc.1
       axios: 1.14.0
     transitivePeerDependencies:
       - debug
+      - supports-color
 
   '@openzeppelin/relayer-sdk@1.10.0':
     dependencies:
@@ -5552,28 +5586,23 @@ snapshots:
       buffer: 6.0.3
       sha.js: 2.4.12
 
-  '@stellar/stellar-base@15.0.0':
+  '@stellar/stellar-sdk@16.0.0-rc.1':
     dependencies:
-      '@noble/curves': 1.9.7
+      '@noble/ed25519': 3.1.0
+      '@noble/hashes': 2.2.0
       '@stellar/js-xdr': 4.0.0
+      axios: 1.16.1
       base32.js: 0.1.0
-      bignumber.js: 9.3.1
+      bignumber.js: 11.1.3
       buffer: 6.0.3
-      sha.js: 2.4.12
-
-  '@stellar/stellar-sdk@15.0.1':
-    dependencies:
-      '@stellar/stellar-base': 15.0.0
-      axios: 1.14.0
-      bignumber.js: 9.3.1
       commander: 14.0.3
-      eventsource: 2.0.2
+      eventsource: 4.1.0
       feaxios: 0.0.23
-      randombytes: 2.1.0
-      toml: 3.0.0
-      urijs: 1.19.11
+      smol-toml: 1.6.1
+      uint8array-extras: 1.5.0
     transitivePeerDependencies:
       - debug
+      - supports-color
 
   '@swc/helpers@0.5.17':
     dependencies:
@@ -5604,7 +5633,7 @@ snapshots:
   '@trezor/blockchain-link-utils@1.5.1(bufferutil@4.0.9)(tslib@2.8.1)(utf-8-validate@5.0.10)':
     dependencies:
       '@mobily/ts-belt': 3.13.1
-      '@stellar/stellar-sdk': 15.0.1
+      '@stellar/stellar-sdk': 16.0.0-rc.1
       '@trezor/env-utils': 1.5.0(tslib@2.8.1)
       '@trezor/protobuf': 1.5.1(tslib@2.8.1)
       '@trezor/utils': 9.5.0(tslib@2.8.1)
@@ -5616,12 +5645,13 @@ snapshots:
       - expo-constants
       - expo-localization
       - react-native
+      - supports-color
       - utf-8-validate
 
   '@trezor/blockchain-link-utils@1.5.2(bufferutil@4.0.9)(tslib@2.8.1)(utf-8-validate@5.0.10)':
     dependencies:
       '@mobily/ts-belt': 3.13.1
-      '@stellar/stellar-sdk': 15.0.1
+      '@stellar/stellar-sdk': 16.0.0-rc.1
       '@trezor/env-utils': 1.5.0(tslib@2.8.1)
       '@trezor/protobuf': 1.5.2(tslib@2.8.1)
       '@trezor/utils': 9.5.0(tslib@2.8.1)
@@ -5633,6 +5663,7 @@ snapshots:
       - expo-constants
       - expo-localization
       - react-native
+      - supports-color
       - utf-8-validate
 
   '@trezor/blockchain-link@2.6.1(@solana/sysvars@5.5.1(fastestsmallesttextencoderdecoder@1.0.22)(typescript@6.0.2))(bufferutil@4.0.9)(fastestsmallesttextencoderdecoder@1.0.22)(tslib@2.8.1)(typescript@6.0.2)(utf-8-validate@5.0.10)(ws@8.20.0(bufferutil@4.0.9)(utf-8-validate@5.0.10))':
@@ -5643,7 +5674,7 @@ snapshots:
       '@solana-program/token-2022': 0.4.2(@solana/kit@2.3.0(fastestsmallesttextencoderdecoder@1.0.22)(typescript@6.0.2)(ws@8.20.0(bufferutil@4.0.9)(utf-8-validate@5.0.10)))(@solana/sysvars@5.5.1(fastestsmallesttextencoderdecoder@1.0.22)(typescript@6.0.2))
       '@solana/kit': 2.3.0(fastestsmallesttextencoderdecoder@1.0.22)(typescript@6.0.2)(ws@8.20.0(bufferutil@4.0.9)(utf-8-validate@5.0.10))
       '@solana/rpc-types': 2.3.0(fastestsmallesttextencoderdecoder@1.0.22)(typescript@6.0.2)
-      '@stellar/stellar-sdk': 15.0.1
+      '@stellar/stellar-sdk': 16.0.0-rc.1
       '@trezor/blockchain-link-types': 1.5.0(tslib@2.8.1)
       '@trezor/blockchain-link-utils': 1.5.1(bufferutil@4.0.9)(tslib@2.8.1)(utf-8-validate@5.0.10)
       '@trezor/env-utils': 1.5.0(tslib@2.8.1)
@@ -5689,9 +5720,9 @@ snapshots:
       - expo-localization
       - react-native
 
-  '@trezor/connect-plugin-stellar@9.2.6(@stellar/stellar-sdk@15.0.1)(@trezor/connect@9.7.2(@solana/sysvars@5.5.1(fastestsmallesttextencoderdecoder@1.0.22)(typescript@6.0.2))(bufferutil@4.0.9)(fastestsmallesttextencoderdecoder@1.0.22)(tslib@2.8.1)(typescript@6.0.2)(utf-8-validate@5.0.10)(ws@8.20.0(bufferutil@4.0.9)(utf-8-validate@5.0.10)))(tslib@2.8.1)':
+  '@trezor/connect-plugin-stellar@9.2.6(@stellar/stellar-sdk@16.0.0-rc.1)(@trezor/connect@9.7.2(@solana/sysvars@5.5.1(fastestsmallesttextencoderdecoder@1.0.22)(typescript@6.0.2))(bufferutil@4.0.9)(fastestsmallesttextencoderdecoder@1.0.22)(tslib@2.8.1)(typescript@6.0.2)(utf-8-validate@5.0.10)(ws@8.20.0(bufferutil@4.0.9)(utf-8-validate@5.0.10)))(tslib@2.8.1)':
     dependencies:
-      '@stellar/stellar-sdk': 15.0.1
+      '@stellar/stellar-sdk': 16.0.0-rc.1
       '@trezor/connect': 9.7.2(@solana/sysvars@5.5.1(fastestsmallesttextencoderdecoder@1.0.22)(typescript@6.0.2))(bufferutil@4.0.9)(fastestsmallesttextencoderdecoder@1.0.22)(tslib@2.8.1)(typescript@6.0.2)(utf-8-validate@5.0.10)(ws@8.20.0(bufferutil@4.0.9)(utf-8-validate@5.0.10))
       '@trezor/utils': 9.5.0(tslib@2.8.1)
       tslib: 2.8.1
@@ -6515,6 +6546,12 @@ snapshots:
       typescript: 6.0.2
       zod: 3.25.76
 
+  agent-base@6.0.2:
+    dependencies:
+      debug: 4.4.3
+    transitivePeerDependencies:
+      - supports-color
+
   agent-base@7.1.4: {}
 
   agentkeepalive@4.6.0:
@@ -6571,6 +6608,16 @@ snapshots:
     transitivePeerDependencies:
       - debug
 
+  axios@1.16.1:
+    dependencies:
+      follow-redirects: 1.16.0
+      form-data: 4.0.5
+      https-proxy-agent: 5.0.1
+      proxy-from-env: 2.1.0
+    transitivePeerDependencies:
+      - debug
+      - supports-color
+
   base-x@3.0.11:
     dependencies:
       safe-buffer: 5.2.1
@@ -6589,6 +6636,8 @@ snapshots:
 
   big.js@6.2.2: {}
 
+  bignumber.js@11.1.3: {}
+
   bignumber.js@9.3.1: {}
 
   bindings@1.5.0:
@@ -6969,7 +7018,11 @@ snapshots:
 
   events@3.3.0: {}
 
-  eventsource@2.0.2: {}
+  eventsource-parser@3.1.0: {}
+
+  eventsource@4.1.0:
+    dependencies:
+      eventsource-parser: 3.1.0
 
   evp_bytestokey@1.0.3:
     dependencies:
@@ -7005,6 +7058,8 @@ snapshots:
 
   follow-redirects@1.15.11: {}
 
+  follow-redirects@1.16.0: {}
+
   for-each@0.3.5:
     dependencies:
       is-callable: 1.2.7
@@ -7108,6 +7163,13 @@ snapshots:
       statuses: 1.5.0
       toidentifier: 1.0.0
 
+  https-proxy-agent@5.0.1:
+    dependencies:
+      agent-base: 6.0.2
+      debug: 4.4.3
+    transitivePeerDependencies:
+      - supports-color
+
   humanize-ms@1.2.1:
     dependencies:
       ms: 2.1.3
@@ -7788,6 +7850,8 @@ snapshots:
 
   smart-buffer@4.2.0: {}
 
+  smol-toml@1.6.1: {}
+
   socks-proxy-agent@8.0.5:
     dependencies:
       agent-base: 7.1.4
@@ -7883,8 +7947,6 @@ snapshots:
 
   toidentifier@1.0.0: {}
 
-  toml@3.0.0: {}
-
   tr46@0.0.3: {}
 
   ts-mixer@6.0.4: {}
@@ -7917,6 +7979,8 @@ snapshots:
 
   ufo@1.6.1: {}
 
+  uint8array-extras@1.5.0: {}
+
   uint8array-tools@0.0.8: {}
 
   uint8arrays@3.1.1:
@@ -7949,8 +8013,6 @@ snapshots:
     optionalDependencies:
       idb-keyval: 6.2.2
 
-  urijs@1.19.11: {}
-
   usb@2.16.0:
     dependencies:
       '@types/w3c-web-usb': 1.0.13
diff --git a/src/kit.ts b/src/kit.ts
index fedb3fa..fdb273b 100644
--- a/src/kit.ts
+++ b/src/kit.ts
@@ -124,6 +124,7 @@ import {
   findWebAuthnSignerForCredential,
   resolveContextRuleIdsForEntry,
 } from "./kit/context-rules";
+import { normalizeSignatureExpirationLedger } from "./kit/auth-payload";
 import { validateAddress, validateAmount, xlmToStroops } from "./utils";
 
 
@@ -669,7 +670,7 @@ export class SmartAccountKit {
    */
   private async calculateExpiration(): Promise<number> {
     const { sequence } = await this.rpc.getLatestLedger();
-    return sequence + this.signatureExpirationLedgers;
+    return normalizeSignatureExpirationLedger(sequence + this.signatureExpirationLedgers);
   }
 
   /**
diff --git a/src/kit/auth-payload.test.ts b/src/kit/auth-payload.test.ts
index ce10440..d88dbe1 100644
--- a/src/kit/auth-payload.test.ts
+++ b/src/kit/auth-payload.test.ts
@@ -1,9 +1,20 @@
-import { Keypair, hash, xdr } from "@stellar/stellar-sdk";
+import {
+  Address,
+  Keypair,
+  buildAuthorizationEntryPreimage,
+  buildWithDelegatesEntry,
+  hash,
+  xdr,
+} from "@stellar/stellar-sdk";
 import { describe, expect, it } from "vitest";
 import type { AuthPayload, Signer } from "smart-account-kit-bindings";
 import {
   buildAuthDigest,
   buildAddressSignatureScVal,
+  buildSignaturePreimage,
+  buildSignaturePayload,
+  createAddressCredentials,
+  getAddressCredentials,
   readAuthPayload,
   upsertAuthPayloadSigner,
   writeAuthPayload,
@@ -20,6 +31,31 @@ function makeAccount(seedByte: number): string {
   return Keypair.fromRawEd25519Seed(Buffer.alloc(32, seedByte)).publicKey();
 }
 
+function makeAuthEntry(address: string): xdr.SorobanAuthorizationEntry {
+  return new xdr.SorobanAuthorizationEntry({
+    credentials: createAddressCredentials(
+      new xdr.SorobanAddressCredentials({
+        address: Address.fromString(address).toScAddress(),
+        nonce: xdr.Int64.fromString("7"),
+        signatureExpirationLedger: 1,
+        signature: xdr.ScVal.scvVoid(),
+      })
+    ),
+    rootInvocation: new xdr.SorobanAuthorizedInvocation({
+      function: xdr.SorobanAuthorizedFunction.sorobanAuthorizedFunctionTypeContractFn(
+        new xdr.InvokeContractArgs({
+          contractAddress: xdr.ScAddress.scAddressTypeContract(
+            hash(Buffer.from("contract"))
+          ),
+          functionName: "do_it",
+          args: [],
+        })
+      ),
+      subInvocations: [],
+    }),
+  });
+}
+
 describe("auth-payload", () => {
   it("round-trips AuthPayload with signer map and context rule ids", () => {
     const signer = makeDelegatedSigner(
@@ -88,4 +124,123 @@ describe("auth-payload", () => {
     expect(entries?.[1].key().sym().toString()).toBe("signature");
     expect(Buffer.from(entries?.[1].val().bytes() ?? [])).toEqual(signature);
   });
+
+  it("unwraps address credentials through the shared helper", () => {
+    const account = makeAccount(4);
+    const entry = makeAuthEntry(account);
+    const credentials = getAddressCredentials(entry.credentials());
+
+    expect(entry.credentials().switch().name).toBe("sorobanCredentialsAddress");
+    expect(credentials.nonce().toString()).toBe("7");
+    expect(Address.fromScAddress(credentials.address()).toString()).toBe(account);
+  });
+
+  it("creates ADDRESS_V2 credentials only with explicit opt-in", () => {
+    const credentials = getAddressCredentials(makeAuthEntry(makeAccount(5)).credentials());
+    const legacyCredentials = createAddressCredentials(credentials);
+    const addressV2Credentials = createAddressCredentials(credentials, {
+      version: "address_v2",
+    });
+
+    expect(legacyCredentials.switch().name).toBe("sorobanCredentialsAddress");
+    expect(addressV2Credentials.switch().name).toBe("sorobanCredentialsAddressV2");
+    expect(getAddressCredentials(addressV2Credentials).nonce().toString()).toBe("7");
+  });
+
+  it("rejects unsupported address credential versions", () => {
+    const credentials = getAddressCredentials(makeAuthEntry(makeAccount(6)).credentials());
+
+    expect(() =>
+      createAddressCredentials(credentials, { version: "bogus" as never })
+    ).toThrow("Unsupported Soroban address credential version: bogus");
+  });
+
+  it("matches the SDK auth preimage helper for legacy ADDRESS credentials", () => {
+    const networkPassphrase = "Test SDF Network ; September 2015";
+    const entry = makeAuthEntry(makeAccount(7));
+    const expectedEntry = xdr.SorobanAuthorizationEntry.fromXDR(entry.toXDR());
+    const preimage = buildSignaturePreimage(networkPassphrase, entry, 123);
+    const expected = buildAuthorizationEntryPreimage(expectedEntry, 123, networkPassphrase);
+
+    expect(preimage.toXDR()).toEqual(expected.toXDR());
+    expect(preimage.switch().name).toBe("envelopeTypeSorobanAuthorization");
+    expect(getAddressCredentials(entry.credentials()).signatureExpirationLedger()).toBe(123);
+  });
+
+  it("matches the SDK auth preimage helper for ADDRESS_V2 credentials", () => {
+    const networkPassphrase = "Test SDF Network ; September 2015";
+    const baseEntry = makeAuthEntry(makeAccount(8));
+    const entry = new xdr.SorobanAuthorizationEntry({
+      credentials: createAddressCredentials(getAddressCredentials(baseEntry.credentials()), {
+        version: "address_v2",
+      }),
+      rootInvocation: baseEntry.rootInvocation(),
+    });
+    const expectedEntry = xdr.SorobanAuthorizationEntry.fromXDR(entry.toXDR());
+    const preimage = buildSignaturePreimage(networkPassphrase, entry, 123);
+    const expected = buildAuthorizationEntryPreimage(expectedEntry, 123, networkPassphrase);
+
+    expect(preimage.toXDR()).toEqual(expected.toXDR());
+    expect(preimage.switch().name).toBe("envelopeTypeSorobanAuthorizationWithAddress");
+    expect(buildSignaturePayload(networkPassphrase, entry, 123)).toHaveLength(32);
+    expect(getAddressCredentials(entry.credentials()).signatureExpirationLedger()).toBe(123);
+  });
+
+  it("matches the SDK auth preimage helper for ADDRESS_WITH_DELEGATES credentials", () => {
+    const networkPassphrase = "Test SDF Network ; September 2015";
+    const delegatedEntry = buildWithDelegatesEntry({
+      entry: makeAuthEntry(makeAccount(14)),
+      validUntilLedgerSeq: 123,
+      delegates: [{ address: makeAccount(15) }],
+    });
+    const expectedEntry = xdr.SorobanAuthorizationEntry.fromXDR(delegatedEntry.toXDR());
+    const preimage = buildSignaturePreimage(networkPassphrase, delegatedEntry, 123);
+    const expected = buildAuthorizationEntryPreimage(expectedEntry, 123, networkPassphrase);
+
+    expect(delegatedEntry.credentials().switch().name).toBe(
+      "sorobanCredentialsAddressWithDelegates"
+    );
+    expect(preimage.toXDR()).toEqual(expected.toXDR());
+    expect(preimage.switch().name).toBe("envelopeTypeSorobanAuthorizationWithAddress");
+  });
+
+  it("keeps the submitted expiration in sync with the signed payload", () => {
+    const entry = makeAuthEntry(makeAccount(16));
+    const payload = buildSignaturePayload("Test SDF Network ; September 2015", entry, 123);
+
+    expect(payload).toHaveLength(32);
+    expect(getAddressCredentials(entry.credentials()).signatureExpirationLedger()).toBe(123);
+  });
+
+  it("rounds fractional signature expirations up before XDR serialization", () => {
+    const entry = makeAuthEntry(makeAccount(17));
+    const payload = buildSignaturePayload("Test SDF Network ; September 2015", entry, 123.2);
+
+    expect(payload).toHaveLength(32);
+    expect(getAddressCredentials(entry.credentials()).signatureExpirationLedger()).toBe(124);
+  });
+
+  it("rejects non-finite signature expirations without mutating the entry", () => {
+    const entry = makeAuthEntry(makeAccount(18));
+
+    expect(() =>
+      buildSignaturePayload("Test SDF Network ; September 2015", entry, Number.NaN)
+    ).toThrow("Signature expiration ledger must be a finite number");
+    expect(getAddressCredentials(entry.credentials()).signatureExpirationLedger()).toBe(1);
+  });
+
+  it("rejects out-of-range signature expirations without mutating the entry", () => {
+    const negativeEntry = makeAuthEntry(makeAccount(19));
+    const oversizedEntry = makeAuthEntry(makeAccount(20));
+
+    expect(() =>
+      buildSignaturePayload("Test SDF Network ; September 2015", negativeEntry, -1)
+    ).toThrow("Signature expiration ledger must fit in u32");
+    expect(getAddressCredentials(negativeEntry.credentials()).signatureExpirationLedger()).toBe(1);
+
+    expect(() =>
+      buildSignaturePayload("Test SDF Network ; September 2015", oversizedEntry, 0x1_0000_0000)
+    ).toThrow("Signature expiration ledger must fit in u32");
+    expect(getAddressCredentials(oversizedEntry.credentials()).signatureExpirationLedger()).toBe(1);
+  });
 });
diff --git a/src/kit/auth-payload.ts b/src/kit/auth-payload.ts
index 31b5d5a..af6809e 100644
--- a/src/kit/auth-payload.ts
+++ b/src/kit/auth-payload.ts
@@ -1,3 +1,4 @@
+import * as StellarSdk from "@stellar/stellar-sdk";
 import { Address, hash, xdr } from "@stellar/stellar-sdk";
 import type {
   AuthPayload,
@@ -11,16 +12,161 @@ export function buildSignaturePayload(
   entry: xdr.SorobanAuthorizationEntry,
   expiration: number
 ): Buffer {
-  const preimage = xdr.HashIdPreimage.envelopeTypeSorobanAuthorization(
+  return hash(buildSignaturePreimage(networkPassphrase, entry, expiration).toXDR());
+}
+
+export function buildSignaturePreimage(
+  networkPassphrase: string,
+  entry: xdr.SorobanAuthorizationEntry,
+  expiration: number
+): xdr.HashIdPreimage {
+  const credentials = getAddressCredentials(entry.credentials());
+  const normalizedExpiration = normalizeSignatureExpirationLedger(expiration);
+  const sdkAuth = StellarSdk as unknown as {
+    buildAuthorizationEntryPreimage?: (
+      entry: xdr.SorobanAuthorizationEntry,
+      validUntilLedgerSeq: number,
+      networkPassphrase: string
+    ) => xdr.HashIdPreimage;
+  };
+
+  if (sdkAuth.buildAuthorizationEntryPreimage) {
+    credentials.signatureExpirationLedger(normalizedExpiration);
+    return sdkAuth.buildAuthorizationEntryPreimage(
+      entry,
+      normalizedExpiration,
+      networkPassphrase
+    );
+  }
+
+  const hashIdPreimage = xdr.HashIdPreimage as unknown as {
+    envelopeTypeSorobanAuthorizationWithAddress?: (value: unknown) => xdr.HashIdPreimage;
+  };
+  const withAddressPreimage = (xdr as unknown as {
+    HashIdPreimageSorobanAuthorizationWithAddress?: new (fields: {
+      networkId: Buffer;
+      nonce: xdr.Int64;
+      signatureExpirationLedger: number;
+      invocation: xdr.SorobanAuthorizedInvocation;
+      address: xdr.ScAddress;
+    }) => unknown;
+  }).HashIdPreimageSorobanAuthorizationWithAddress;
+
+  if (usesAddressBoundPayload(entry.credentials())) {
+    if (!hashIdPreimage.envelopeTypeSorobanAuthorizationWithAddress || !withAddressPreimage) {
+      throw new Error(
+        "Address-bound Soroban auth credentials require an SDK with Protocol 27 auth preimage support"
+      );
+    }
+
+    credentials.signatureExpirationLedger(normalizedExpiration);
+    return hashIdPreimage.envelopeTypeSorobanAuthorizationWithAddress(
+      new withAddressPreimage({
+        networkId: hash(Buffer.from(networkPassphrase)),
+        nonce: credentials.nonce(),
+        signatureExpirationLedger: normalizedExpiration,
+        invocation: entry.rootInvocation(),
+        address: credentials.address(),
+      })
+    );
+  }
+
+  credentials.signatureExpirationLedger(normalizedExpiration);
+  return xdr.HashIdPreimage.envelopeTypeSorobanAuthorization(
     new xdr.HashIdPreimageSorobanAuthorization({
       networkId: hash(Buffer.from(networkPassphrase)),
-      nonce: entry.credentials().address().nonce(),
-      signatureExpirationLedger: expiration,
+      nonce: credentials.nonce(),
+      signatureExpirationLedger: normalizedExpiration,
       invocation: entry.rootInvocation(),
     })
   );
+}
+
+export function normalizeSignatureExpirationLedger(expiration: number): number {
+  if (!Number.isFinite(expiration)) {
+    throw new Error("Signature expiration ledger must be a finite number");
+  }
+
+  const normalizedExpiration = Math.ceil(expiration);
+  if (normalizedExpiration < 0 || normalizedExpiration > 0xffffffff) {
+    throw new Error("Signature expiration ledger must fit in u32");
+  }
+
+  return normalizedExpiration;
+}
+
+export function getAddressCredentials(
+  credentials: xdr.SorobanCredentials
+): xdr.SorobanAddressCredentials {
+  const typedCredentials = credentials as unknown as {
+    address: () => xdr.SorobanAddressCredentials;
+    addressV2?: () => xdr.SorobanAddressCredentials;
+    addressWithDelegates?: () => {
+      addressCredentials: () => xdr.SorobanAddressCredentials;
+    };
+  };
+
+  const credentialType = credentials.switch().name as string;
+  switch (credentialType) {
+    case "sorobanCredentialsAddress":
+      return typedCredentials.address();
+    case "sorobanCredentialsAddressV2":
+      if (!typedCredentials.addressV2) {
+        throw new Error(
+          "ADDRESS_V2 credentials require an SDK with Protocol 27 credential support"
+        );
+      }
+      return typedCredentials.addressV2();
+    case "sorobanCredentialsAddressWithDelegates":
+      if (!typedCredentials.addressWithDelegates) {
+        throw new Error(
+          "ADDRESS_WITH_DELEGATES credentials require an SDK with Protocol 27 credential support"
+        );
+      }
+      return typedCredentials.addressWithDelegates().addressCredentials();
+  }
+
+  throw new Error(`Soroban credentials do not contain address credentials: ${credentials.switch().name}`);
+}
+
+export function getAuthEntryAddress(entry: xdr.SorobanAuthorizationEntry): string {
+  return Address.fromScAddress(getAddressCredentials(entry.credentials()).address()).toString();
+}
+
+export function createAddressCredentials(
+  credentials: xdr.SorobanAddressCredentials,
+  options?: { version?: "legacy" | "address_v2" }
+): xdr.SorobanCredentials {
+  const credentialFactory = xdr.SorobanCredentials as unknown as {
+    sorobanCredentialsAddressV2?: (
+      credentials: xdr.SorobanAddressCredentials
+    ) => xdr.SorobanCredentials;
+    sorobanCredentialsAddress: (
+      credentials: xdr.SorobanAddressCredentials
+    ) => xdr.SorobanCredentials;
+  };
+
+  const version = (options?.version ?? "legacy") as string;
+  if (version === "address_v2") {
+    if (!credentialFactory.sorobanCredentialsAddressV2) {
+      throw new Error(
+        "ADDRESS_V2 credentials require an SDK with Protocol 27 credential support"
+      );
+    }
+    return credentialFactory.sorobanCredentialsAddressV2(credentials);
+  }
+
+  if (version !== "legacy") {
+    throw new Error(`Unsupported Soroban address credential version: ${version}`);
+  }
+
+  return credentialFactory.sorobanCredentialsAddress(credentials);
+}
 
-  return hash(preimage.toXDR());
+function usesAddressBoundPayload(credentials: xdr.SorobanCredentials): boolean {
+  const credentialType = credentials.switch().name as string;
+  return credentialType === "sorobanCredentialsAddressV2" ||
+    credentialType === "sorobanCredentialsAddressWithDelegates";
 }
 
 export function buildAuthDigest(
diff --git a/src/kit/tx-ops.ts b/src/kit/tx-ops.ts
index 2a3fef4..9942cda 100644
--- a/src/kit/tx-ops.ts
+++ b/src/kit/tx-ops.ts
@@ -21,7 +21,12 @@ import {
   FRIENDBOT_URL,
   LEDGERS_PER_HOUR,
 } from "../constants";
-import { buildAddressSignatureScVal } from "./auth-payload";
+import {
+  buildAddressSignatureScVal,
+  buildSignaturePreimage,
+  createAddressCredentials,
+  getAddressCredentials,
+} from "./auth-payload";
 import { validateAddress, validateAmount, xlmToStroops, stroopsToXlm } from "../utils";
 
 type ResolveContextRuleIds = (
@@ -566,7 +571,7 @@ export async function fundWallet(
     const expirationLedger = currentLedger + LEDGERS_PER_HOUR; // ~1 hour
 
     for (const entry of authEntries) {
-      const credType = entry.credentials().switch().name;
+      const credType = entry.credentials().switch().name as string;
 
       // For source_account credentials, convert to Address credentials
       // so the Relayer can use its own channel accounts
@@ -574,50 +579,53 @@ export async function fundWallet(
         // Generate a nonce for the new Address credential
         const nonce = xdr.Int64.fromString(Date.now().toString());
 
-        const preimage = xdr.HashIdPreimage.envelopeTypeSorobanAuthorization(
-          new xdr.HashIdPreimageSorobanAuthorization({
-            networkId: hash(Buffer.from(deps.networkPassphrase)),
-            nonce,
-            signatureExpirationLedger: expirationLedger,
-            invocation: entry.rootInvocation(),
-          })
-        );
-        const payload = hash(preimage.toXDR());
-        const signature = tempKeypair.sign(payload);
-
         // Create new Address credentials entry to replace source_account
         const addressEntry = new xdr.SorobanAuthorizationEntry({
-          credentials: xdr.SorobanCredentials.sorobanCredentialsAddress(
+          credentials: createAddressCredentials(
             new xdr.SorobanAddressCredentials({
               address: Address.fromString(tempKeypair.publicKey()).toScAddress(),
               nonce,
               signatureExpirationLedger: expirationLedger,
-              signature: buildAddressSignatureScVal(
-                tempKeypair.rawPublicKey(),
-                signature
-              ),
+              signature: xdr.ScVal.scvVoid(),
             })
           ),
           rootInvocation: entry.rootInvocation(),
         });
+        const preimage = buildSignaturePreimage(
+          deps.networkPassphrase,
+          addressEntry,
+          expirationLedger
+        );
+        const payload = hash(preimage.toXDR());
+        const signature = tempKeypair.sign(payload);
+        getAddressCredentials(addressEntry.credentials()).signature(
+          buildAddressSignatureScVal(
+            tempKeypair.rawPublicKey(),
+            signature
+          )
+        );
 
         signedAuthEntries.push(addressEntry);
         continue;
       }
 
+      if (credType === "sorobanCredentialsAddressWithDelegates") {
+        return {
+          success: false,
+          hash: "",
+          error: "ADDRESS_WITH_DELEGATES auth entries are not supported by fundWallet() yet",
+        };
+      }
+
       // For Address credentials, sign them
-      if (credType === "sorobanCredentialsAddress") {
-        const credentials = entry.credentials().address();
+      if (
+        credType === "sorobanCredentialsAddress" ||
+        credType === "sorobanCredentialsAddressV2"
+      ) {
+        const credentials = getAddressCredentials(entry.credentials());
         credentials.signatureExpirationLedger(expirationLedger);
 
-        const preimage = xdr.HashIdPreimage.envelopeTypeSorobanAuthorization(
-          new xdr.HashIdPreimageSorobanAuthorization({
-            networkId: hash(Buffer.from(deps.networkPassphrase)),
-            nonce: credentials.nonce(),
-            signatureExpirationLedger: credentials.signatureExpirationLedger(),
-            invocation: entry.rootInvocation(),
-          })
-        );
+        const preimage = buildSignaturePreimage(deps.networkPassphrase, entry, expirationLedger);
         const payload = hash(preimage.toXDR());
         const signature = tempKeypair.sign(payload);
 
diff --git a/src/kit/webauthn-ops.ts b/src/kit/webauthn-ops.ts
index 07ccdce..c066474 100644
--- a/src/kit/webauthn-ops.ts
+++ b/src/kit/webauthn-ops.ts
@@ -22,6 +22,8 @@ import {
   buildAuthDigest,
   buildSignaturePayload,
   buildWebAuthnSignatureBytes,
+  getAddressCredentials,
+  normalizeSignatureExpirationLedger,
   readAuthPayload,
   upsertAuthPayloadSigner,
   writeAuthPayload,
@@ -127,8 +129,17 @@ export async function signAuthEntry(
   }
 ): Promise<xdr.SorobanAuthorizationEntry> {
   const normalizedEntry = xdr.SorobanAuthorizationEntry.fromXDR(entry.toXDR());
-  const credentials = normalizedEntry.credentials().address();
-  const expiration = options?.expiration ?? await deps.calculateExpiration();
+  const credentialType = normalizedEntry.credentials().switch().name as string;
+  if (credentialType === "sorobanCredentialsAddressWithDelegates") {
+    throw new Error(
+      "ADDRESS_WITH_DELEGATES auth entries are not supported by WebAuthn signing yet"
+    );
+  }
+
+  const credentials = getAddressCredentials(normalizedEntry.credentials());
+  const expiration = normalizeSignatureExpirationLedger(
+    options?.expiration ?? await deps.calculateExpiration()
+  );
   credentials.signatureExpirationLedger(expiration);
   const authPayload = readAuthPayload(credentials.signature());
 
diff --git a/src/managers/multi-signer-manager.test.ts b/src/managers/multi-signer-manager.test.ts
index 94b4392..29bb0de 100644
--- a/src/managers/multi-signer-manager.test.ts
+++ b/src/managers/multi-signer-manager.test.ts
@@ -28,6 +28,11 @@ vi.mock("../kit/context-rules", async (importOriginal) => {
 import { Account, Address, Keypair, Operation, TransactionBuilder, xdr } from "@stellar/stellar-sdk";
 import { MultiSignerManager } from "./multi-signer-manager";
 import { resolveContextRuleIdsForEntry } from "../kit/context-rules";
+import {
+  getAddressCredentials,
+  readAuthPayload,
+  writeAuthPayload,
+} from "../kit/auth-payload";
 import {
   makeAccount,
   makeAddressAuthEntry,
@@ -35,6 +40,7 @@ import {
   makeDelegatedSigner,
   makeExternalSigner,
 } from "./test-utils";
+import { signersEqual } from "../signer-utils";
 
 function makeDeps() {
   const externalSigners = {
@@ -394,4 +400,87 @@ describe("MultiSignerManager", () => {
     expect(deps.signAuthEntry).toHaveBeenCalledTimes(1);
     expect(result).toEqual({ success: true, hash: "tx-3" });
   });
+
+  it("preserves delegated wallet signers when passkey signing returns a cloned auth entry", async () => {
+    const deps = makeDeps();
+    const contractId = deps.getContractId();
+    const walletAddress = makeAccount(23);
+    const passkeySigner = makeExternalSigner(6, 7, 8);
+    const walletSigner = makeDelegatedSigner(23);
+    const preparedTx = { sign: vi.fn() };
+    deps.rpc.getLatestLedger.mockResolvedValue({ sequence: 500 });
+    deps.rpc.getAccount.mockResolvedValue(new Account(deps.deployerPublicKey, "1"));
+    deps.rpc.simulateTransaction.mockResolvedValue({ result: { auth: [] } });
+    deps.externalSigners.canSignFor.mockImplementation((address: string) => address === walletAddress);
+    deps.externalSigners.signAuthEntry.mockResolvedValue({
+      signedAuthEntry: Buffer.alloc(64, 8).toString("base64"),
+      signerAddress: walletAddress,
+    });
+    deps.sendAndPoll.mockResolvedValue({ success: true, hash: "tx-4" });
+    deps.signAuthEntry.mockImplementation(async (entry, options) => {
+      const clonedEntry = xdr.SorobanAuthorizationEntry.fromXDR(entry.toXDR());
+      const credentials = getAddressCredentials(clonedEntry.credentials());
+      const signer = options?.signer;
+      expect(signer).toBeDefined();
+      credentials.signature(
+        writeAuthPayload({
+          context_rule_ids: options?.contextRuleIds ?? [],
+          signers: new Map([[signer!, Buffer.from("aa", "hex")]]),
+        })
+      );
+      return clonedEntry;
+    });
+    assembleTransactionMock.mockReturnValue({
+      build: () => preparedTx,
+    });
+    vi.mocked(resolveContextRuleIdsForEntry).mockResolvedValue([12]);
+    const manager = new MultiSignerManager(deps);
+
+    const result = await manager.operation(
+      {
+        built: {
+          operations: [{
+            type: "invokeHostFunction",
+            func: xdr.HostFunction.hostFunctionTypeInvokeContract(
+              new xdr.InvokeContractArgs({
+                contractAddress: Address.fromString(makeContract(45)).toScAddress(),
+                functionName: "ping",
+                args: [],
+              })
+            ),
+            auth: [makeAddressAuthEntry(contractId)],
+          }],
+        },
+      } as any,
+      [
+        {
+          signer: passkeySigner,
+          type: "passkey",
+          credentialId: Buffer.alloc(20, 8).toString("base64url"),
+        },
+        {
+          signer: walletSigner,
+          type: "wallet",
+          walletAddress,
+        },
+      ],
+      {}
+    );
+
+    expect(result).toEqual({ success: true, hash: "tx-4" });
+    const resimTx = deps.rpc.simulateTransaction.mock.calls[0][0] as any;
+    const submittedAuthEntry = resimTx.operations[0].auth[0] as xdr.SorobanAuthorizationEntry;
+    const authPayload = readAuthPayload(
+      getAddressCredentials(submittedAuthEntry.credentials()).signature()
+    );
+
+    const passkeySignature = Array.from(authPayload.signers.entries())
+      .find(([signer]) => signersEqual(signer, passkeySigner))?.[1];
+    const walletSignature = Array.from(authPayload.signers.entries())
+      .find(([signer]) => signersEqual(signer, walletSigner))?.[1];
+
+    expect(authPayload.context_rule_ids).toEqual([12]);
+    expect(passkeySignature).toEqual(Buffer.from("aa", "hex"));
+    expect(walletSignature).toEqual(Buffer.alloc(0));
+  });
 });
diff --git a/src/managers/multi-signer-manager.ts b/src/managers/multi-signer-manager.ts
index b288047..192569c 100644
--- a/src/managers/multi-signer-manager.ts
+++ b/src/managers/multi-signer-manager.ts
@@ -36,7 +36,12 @@ import {
 import {
   buildAuthDigest,
   buildAddressSignatureScVal,
+  buildSignaturePreimage,
   buildSignaturePayload,
+  createAddressCredentials,
+  getAddressCredentials,
+  getAuthEntryAddress,
+  normalizeSignatureExpirationLedger,
   readAuthPayload,
   upsertAuthPayloadSigner,
   writeAuthPayload,
@@ -142,15 +147,20 @@ export class MultiSignerManager {
     expiration: number
   ): Promise<xdr.SorobanAuthorizationEntry> {
     const signedEntry = xdr.SorobanAuthorizationEntry.fromXDR(entry.toXDR());
-    signedEntry.credentials().address().signatureExpirationLedger(expiration);
-
-    const preimage = xdr.HashIdPreimage.envelopeTypeSorobanAuthorization(
-      new xdr.HashIdPreimageSorobanAuthorization({
-        networkId: hash(Buffer.from(this.deps.networkPassphrase)),
-        nonce: signedEntry.credentials().address().nonce(),
-        signatureExpirationLedger: expiration,
-        invocation: signedEntry.rootInvocation(),
-      })
+    const normalizedExpiration = normalizeSignatureExpirationLedger(expiration);
+    const credentialType = signedEntry.credentials().switch().name as string;
+    if (credentialType === "sorobanCredentialsAddressWithDelegates") {
+      throw new Error(
+        "ADDRESS_WITH_DELEGATES auth entries are not supported by wallet signing yet"
+      );
+    }
+
+    const credentials = getAddressCredentials(signedEntry.credentials());
+    credentials.signatureExpirationLedger(normalizedExpiration);
+    const preimage = buildSignaturePreimage(
+      this.deps.networkPassphrase,
+      signedEntry,
+      normalizedExpiration
     );
 
     const { signedAuthEntry } = await this.deps.externalSigners.signAuthEntry(
@@ -158,7 +168,7 @@ export class MultiSignerManager {
       authAddress
     );
 
-    signedEntry.credentials().address().signature(
+    credentials.signature(
       buildAddressSignatureScVal(
         Address.fromString(authAddress).toScAddress().accountId().ed25519(),
         Buffer.from(signedAuthEntry, "base64")
@@ -207,13 +217,25 @@ export class MultiSignerManager {
 
       for (const [authEntryIndex, entry] of authEntries.entries()) {
         const credentials = entry.credentials();
+        const credentialType = credentials.switch().name as string;
+
+        if (credentialType === "sorobanCredentialsAddressWithDelegates") {
+          return {
+            success: false,
+            hash: "",
+            error: "ADDRESS_WITH_DELEGATES auth entries are not supported by multi-signer signing yet",
+          };
+        }
 
-        if (credentials.switch().name !== "sorobanCredentialsAddress") {
+        if (
+          credentialType !== "sorobanCredentialsAddress" &&
+          credentialType !== "sorobanCredentialsAddressV2"
+        ) {
           signedAuthEntries.push(entry);
           continue;
         }
 
-        const authAddress = Address.fromScAddress(credentials.address().address()).toString();
+        const authAddress = getAuthEntryAddress(entry);
 
         if (authAddress !== contractId) {
           const walletSigner = walletSigners.find((signer) => signer.walletAddress === authAddress);
@@ -233,7 +255,7 @@ export class MultiSignerManager {
         }
 
         let signedEntry = xdr.SorobanAuthorizationEntry.fromXDR(entry.toXDR());
-        signedEntry.credentials().address().signatureExpirationLedger(expiration);
+        getAddressCredentials(signedEntry.credentials()).signatureExpirationLedger(expiration);
         const selectedContractSigners = selectedSigners
           .map(({ signer }) => signer)
           .filter((signer): signer is ContractSigner => signer !== undefined);
@@ -262,6 +284,9 @@ export class MultiSignerManager {
           });
         }
 
+        const signedCredentials = getAddressCredentials(signedEntry.credentials());
+        signedCredentials.signatureExpirationLedger(expiration);
+
         for (const walletSigner of walletSigners) {
           if (!walletSigner.walletAddress) continue;
           if (!walletSigner.signer) {
@@ -273,7 +298,7 @@ export class MultiSignerManager {
           }
         }
 
-        const authPayload = readAuthPayload(signedEntry.credentials().address().signature());
+        const authPayload = readAuthPayload(signedCredentials.signature());
         if (authPayload.context_rule_ids.length === 0) {
           authPayload.context_rule_ids = resolvedContextRuleIds;
         }
@@ -282,7 +307,7 @@ export class MultiSignerManager {
           if (!walletSigner.walletAddress) continue;
           upsertAuthPayloadSigner(authPayload, walletSigner.signer as ContractSigner, Buffer.alloc(0));
         }
-        signedEntry.credentials().address().signature(writeAuthPayload(authPayload));
+        signedCredentials.signature(writeAuthPayload(authPayload));
         signedAuthEntries.push(signedEntry);
 
         if (walletSigners.length === 0) {
@@ -331,7 +356,7 @@ export class MultiSignerManager {
 
           signedAuthEntries.push(
             new xdr.SorobanAuthorizationEntry({
-              credentials: xdr.SorobanCredentials.sorobanCredentialsAddress(
+              credentials: createAddressCredentials(
                 new xdr.SorobanAddressCredentials({
                   address: Address.fromString(walletSigner.walletAddress).toScAddress(),
                   nonce: delegatedNonce,