diff --git a/cmd/crates/soroban-spec-typescript/src/project_template/src/assembled-tx.ts b/cmd/crates/soroban-spec-typescript/src/project_template/src/assembled-tx.ts
index 79ba90f5f..dd2e91b44 100644
--- a/cmd/crates/soroban-spec-typescript/src/project_template/src/assembled-tx.ts
+++ b/cmd/crates/soroban-spec-typescript/src/project_template/src/assembled-tx.ts
@@ -23,6 +23,8 @@ export class NotImplementedError extends Error { }
 export class ExpiredStateError extends Error { }
 export class NeedsMoreSignaturesError extends Error { }
 export class WalletDisconnectedError extends Error { }
+export class SendResultOnlyError extends Error { }
+export class SendFailedError extends Error { }
 
 type SendTx = SorobanRpc.SendTransactionResponse;
 type GetTx = SorobanRpc.GetTransactionResponse;
@@ -51,8 +53,7 @@ export class AssembledTransaction<T> {
 
   static async fromSimulation<T>(options: AssembledTransactionClassOptions<T>): Promise<AssembledTransaction<T>> {
     const tx = new AssembledTransaction(options)
-    await tx.simulate()
-    return tx
+    return await tx.simulate()
   }
 
   constructor(public options: AssembledTransactionClassOptions<T>) {
@@ -61,7 +62,7 @@ export class AssembledTransaction<T> {
     });
   }
 
-  simulate = async () => {
+  simulate = async (): Promise<this> => {
     const contract = new Contract(this.options.contractId);
 
     this.txUnsigned = new TransactionBuilder(await this.getAccount(), {
@@ -79,6 +80,8 @@ export class AssembledTransaction<T> {
       this.options.networkPassphrase,
       this.simulation
     ).build()
+
+    return this
   }
 
   getWallet = async (): Promise<Wallet> => {
@@ -126,8 +129,8 @@ export class AssembledTransaction<T> {
 
   /**
    * Sign a transaction with the injected `wallet` (default to Freighter) and
-   * add the fully-reconstructed to this object as `txSigned`. It can then be
-   * sent with {@link send}.
+   * add the fully-reconstructed transaction to this object as `txSigned`. It
+   * can then be sent with {@link send}.
    */
   sign = async (): Promise<this> => {
     if (!this.txUnsigned) {
@@ -143,6 +146,9 @@ export class AssembledTransaction<T> {
       throw new WalletDisconnectedError('Wallet is not connected')
     }
 
+    // throw errors if transaction needs restore first or if it's otherwise not an expected simulation type
+    this.ensureSuccessfulHostFunctionSimulation()
+
     const wallet = await this.getWallet()
     const signed = await wallet.signTransaction(this.txUnsigned.toXDR(), {
       networkPassphrase: this.options.networkPassphrase,
@@ -256,8 +262,18 @@ export class AssembledTransaction<T> {
 
     // 2. otherwise, maybe it was merely sent with `sendTransaction`
     if (this.sendTransactionResponse) {
-      // if it didn't await, it returned the result of `sendTransaction`
-      return this.options.parseResultXdr(this.sendTransactionResponse.errorResultXdr!)
+      const errorResultXdr = this.sendTransactionResponse.errorResultXdr &&
+        xdr.TransactionResult.fromXDR(
+          this.sendTransactionResponse.errorResultXdr, "base64"
+        ).result().results().toString()
+      if (errorResultXdr) {
+        throw new SendFailedError(
+          `Transaction simulation looked correct, but attempting to send the transaction failed. Check \`simulation\` and \`sendTransactionResponseAll\` to troubleshoot. Decoded \`sendTransactionResponse.errorResultXdr\`: ${errorResultXdr}`
+        )
+      }
+      throw new SendResultOnlyError(
+        `Transaction was sent to the network, but not yet awaited. No result to show. Await transaction completion with \`getTransaction(sendTransactionResponse.hash)\``
+      )
     }
 
     // 3. finally, if neither of those are present, then parse the simulation result