diff --git a/src/handle_swap_sign_transaction.c b/src/handle_swap_sign_transaction.c
index 16c8b7f..604b8a2 100644
--- a/src/handle_swap_sign_transaction.c
+++ b/src/handle_swap_sign_transaction.c
@@ -5,9 +5,12 @@
 #include "shared_context.h"
 #include "utils.h"
 #ifdef HAVE_NBGL
-#include "utils.h"
+#include "nbgl_use_case.h"
 #endif  // HAVE_NBGL
 
+// Save the BSS address where we will write the return value when finished
+static uint8_t* G_swap_sign_return_value_address;
+
 bool copy_transaction_parameters(create_transaction_parameters_t* sign_transaction_params,
                                  chain_config_t* config) {
     // first copy parameters to stack, and then to global data.
@@ -49,11 +52,21 @@ bool copy_transaction_parameters(create_transaction_parameters_t* sign_transacti
                    stack_data.maxFee,
                    sizeof(stack_data.maxFee));
 
+    // Full reset the global variables
     os_explicit_zero_BSS_segment();
+    // Keep the address at which we'll reply the signing status
+    G_swap_sign_return_value_address = &sign_transaction_params->result;
+    // Commit the values read from exchange to the clean global space
+
     memcpy(&strings.common, &stack_data, sizeof(stack_data));
     return true;
 }
 
+void __attribute__((noreturn)) finalize_exchange_sign_transaction(bool is_success) {
+    *G_swap_sign_return_value_address = is_success;
+    os_lib_end();
+}
+
 void handle_swap_sign_transaction(chain_config_t* config) {
     UX_INIT();
 #ifdef HAVE_NBGL
diff --git a/src/handle_swap_sign_transaction.h b/src/handle_swap_sign_transaction.h
index 21b52c3..d34a6d8 100644
--- a/src/handle_swap_sign_transaction.h
+++ b/src/handle_swap_sign_transaction.h
@@ -1,5 +1,4 @@
-#ifndef _HANDLE_SWAP_SIGN_TRANSACTION_H_
-#define _HANDLE_SWAP_SIGN_TRANSACTION_H_
+#pragma once
 
 #include "swap_lib_calls.h"
 #include "chainConfig.h"
@@ -9,4 +8,4 @@ bool copy_transaction_parameters(create_transaction_parameters_t* sign_transacti
 
 void handle_swap_sign_transaction(chain_config_t* config);
 
-#endif  // _HANDLE_SWAP_SIGN_TRANSACTION_H_
\ No newline at end of file
+void __attribute__((noreturn)) finalize_exchange_sign_transaction(bool is_success);
diff --git a/src/swap_lib_calls.h b/src/swap_lib_calls.h
index 4fd0284..2870347 100644
--- a/src/swap_lib_calls.h
+++ b/src/swap_lib_calls.h
@@ -1,9 +1,15 @@
-#ifndef _SWAP_LIB_CALLS_H_
-#define _SWAP_LIB_CALLS_H_
+#pragma once
+
+/* This file is the shared API between Exchange and the apps started in Library mode for Exchange
+ *
+ * DO NOT MODIFY THIS FILE IN APPLICATIONS OTHER THAN EXCHANGE
+ * On modification in Exchange, forward the changes to all applications supporting Exchange
+ */
 
 #include "stdbool.h"
 #include "chainConfig.h"
 #include "shared_context.h"
+#include "stdint.h"
 
 #define RUN_APPLICATION 1
 
@@ -13,19 +19,27 @@
 
 #define GET_PRINTABLE_AMOUNT 4
 
+/*
+ * Amounts are stored as bytes, with a max size of 16 (see protobuf
+ * specifications). Max 16B integer is 340282366920938463463374607431768211455
+ * in decimal, which is a 32-long char string.
+ * The printable amount also contains spaces, the ticker symbol (with variable
+ * size, up to 12 in Ethereum for instance) and a terminating null byte, so 50
+ * bytes total should be a fair maximum.
+ */
 #define MAX_PRINTABLE_AMOUNT_SIZE 50
 
 // structure that should be send to specific coin application to get address
 typedef struct check_address_parameters_s {
     // IN
-    const unsigned char* const coin_configuration;
-    const unsigned char coin_configuration_length;
+    uint8_t *coin_configuration;
+    uint8_t coin_configuration_length;
     // serialized path, segwit, version prefix, hash used, dictionary etc.
-    // fields and serialization format depends on spesific coin app
-    const unsigned char* const address_parameters;
-    const unsigned char address_parameters_length;
-    const char* const address_to_check;
-    const char* const extra_id_to_check;
+    // fields and serialization format depends on specific coin app
+    uint8_t *address_parameters;
+    uint8_t address_parameters_length;
+    char *address_to_check;
+    char *extra_id_to_check;
     // OUT
     int result;
 } check_address_parameters_t;
@@ -33,37 +47,37 @@ typedef struct check_address_parameters_s {
 // structure that should be send to specific coin application to get printable amount
 typedef struct get_printable_amount_parameters_s {
     // IN
-    const unsigned char* const coin_configuration;
-    const unsigned char coin_configuration_length;
-    const unsigned char* const amount;
-    const unsigned char amount_length;
-    const bool is_fee;
+    uint8_t *coin_configuration;
+    uint8_t coin_configuration_length;
+    uint8_t *amount;
+    uint8_t amount_length;
+    bool is_fee;
     // OUT
     char printable_amount[MAX_PRINTABLE_AMOUNT_SIZE];
-    // int result;
 } get_printable_amount_parameters_t;
 
 typedef struct create_transaction_parameters_s {
-    const unsigned char* const coin_configuration;
-    const unsigned char coin_configuration_length;
-    const unsigned char* const amount;
-    const unsigned char amount_length;
-    const unsigned char* const fee_amount;
-    const unsigned char fee_amount_length;
-    const char* const destination_address;
-    const char* const destination_address_extra_id;
+    // IN
+    uint8_t *coin_configuration;
+    uint8_t coin_configuration_length;
+    uint8_t *amount;
+    uint8_t amount_length;
+    uint8_t *fee_amount;
+    uint8_t fee_amount_length;
+    char *destination_address;
+    char *destination_address_extra_id;
+    // OUT
+    uint8_t result;
 } create_transaction_parameters_t;
 
 typedef struct libargs_s {
     unsigned int id;
     unsigned int command;
-    chain_config_t* chain_config;
+    chain_config_t *chain_config;
     union {
-        check_address_parameters_t* check_address;
-        create_transaction_parameters_t* create_transaction;
-        get_printable_amount_parameters_t* get_printable_amount;
-        caller_app_t* caller_app;
+        check_address_parameters_t *check_address;
+        create_transaction_parameters_t *create_transaction;
+        get_printable_amount_parameters_t *get_printable_amount;
+        caller_app_t *caller_app;
     };
 } libargs_t;
-
-#endif  // _SWAP_LIB_CALLS_H_
diff --git a/src_features/signTx/ui_common_signTx.c b/src_features/signTx/ui_common_signTx.c
index fec6ca8..e57bb21 100644
--- a/src_features/signTx/ui_common_signTx.c
+++ b/src_features/signTx/ui_common_signTx.c
@@ -2,12 +2,14 @@
 #include "shared_context.h"
 #include "utils.h"
 #include "common_ui.h"
+#include "handle_swap_sign_transaction.h"
 
 unsigned int io_seproxyhal_touch_tx_ok(__attribute__((unused)) const bagl_element_t *e) {
     uint8_t privateKeyData[INT256_LENGTH];
     uint8_t signature[100];
     cx_ecfp_private_key_t privateKey;
     uint32_t tx = 0;
+    int err;
     io_seproxyhal_io_heartbeat();
     os_perso_derive_node_bip32(CX_CURVE_256K1,
                                tmpCtx.transactionContext.bip32.path,
@@ -59,10 +61,19 @@ unsigned int io_seproxyhal_touch_tx_ok(__attribute__((unused)) const bagl_elemen
     tx = 65;
     G_io_apdu_buffer[tx++] = 0x90;
     G_io_apdu_buffer[tx++] = 0x00;
+
     // Send back the response, do not restart the event loop
-    io_exchange(CHANNEL_APDU | IO_RETURN_AFTER_TX, tx);
+    err = io_exchange(CHANNEL_APDU | IO_RETURN_AFTER_TX, tx);
     if (G_called_from_swap) {
-        os_sched_exit(0);
+        PRINTF("G_called_from_swap\n");
+
+        // If we are in swap mode and have validated a TX, we send it and immediately quit
+        if (err == 0) {
+            finalize_exchange_sign_transaction(true);
+        } else {
+            PRINTF("Unrecoverable\n");
+            os_sched_exit(-1);
+        }
     }
     reset_app_context();
     // Display back the original UX