diff --git a/CHANGELOG.md b/CHANGELOG.md
index 1d660aa04..d50c4158f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,10 @@
 
 All notable changes to the Movement TypeScript SDK will be captured in this file. This changelog is written by hand for now. It adheres to the format set out by [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
+# Unreleased
+
+- Raise `DEFAULT_TXN_EXP_SEC_FROM_NOW` from 20 to 120 seconds. A hardware wallet needs a device chooser plus an on-device confirmation, routinely 15 to 60 seconds, and a browser extension adds an approval prompt on top. At 20 seconds the node accepted such a transaction into its mempool and then dropped it once expiry passed, leaving the caller with a hash for a transaction that never confirmed. Callers that want the old window can still pass `options.expireTimestamp`, or set `transactionGenerationConfig.defaultTxnExpirySecFromNow` on `MovementConfig`.
+
 # 5.1.7 (2026-03-25)
 
 - Add mainnet Movement Name Service (MNS) router contract address to `NetworkToMnsContract`, enabling `movement.mns` on `Network.MAINNET`.
diff --git a/src/utils/const.ts b/src/utils/const.ts
index a36ff28f1..8fd757b04 100644
--- a/src/utils/const.ts
+++ b/src/utils/const.ts
@@ -31,12 +31,18 @@ export const DEFAULT_MAX_GAS_AMOUNT = 200000;
  *
  * This time is how long until the blockchain nodes will reject the transaction.
  *
+ * Two minutes covers the flows where signing is not instant. A hardware wallet needs a device
+ * chooser plus an on-device confirmation, which routinely takes 15 to 60 seconds; a browser
+ * extension adds a user approval prompt on top of that. With a shorter window the node accepts
+ * the transaction into its mempool and then drops it once expiry passes, so the caller holds a
+ * hash for a transaction that never confirms.
+ *
  * Note that the transaction expiration time varies based on network connection and network load.  It may need to be
  * increased for the transaction to be processed.
  * @group Implementation
  * @category Utils
  */
-export const DEFAULT_TXN_EXP_SEC_FROM_NOW = 20;
+export const DEFAULT_TXN_EXP_SEC_FROM_NOW = 120;
 
 /**
  * The default number of seconds to wait for a transaction to be processed.