diff --git a/errors/errno.fugu b/errors/errno.fugu
index 005c0ad..db22626 100755
--- a/errors/errno.fugu
+++ b/errors/errno.fugu
@@ -1437,4 +1437,6 @@ errors sdhc SDHCD_ERR_ {
 errors shelly SHELLY_ERR_ {
     failure BUFFER_OVERFLOW      "Buffer limits reached",
     failure WRITE                "String write failed",
+    failure SPAWN_RPC                 "Spawn RPC failed",
+    failure PS_RPC                    "ps RPC failed",
 };
\ No newline at end of file
diff --git a/lib/aos/ump_chan.c b/lib/aos/ump_chan.c
index c9fd08f..c28ccd2 100644
--- a/lib/aos/ump_chan.c
+++ b/lib/aos/ump_chan.c
@@ -287,6 +287,7 @@ static void ump_worker_schedule(struct ump_worker_context *worker_context) {
     // this is supposed to be called single threaded and only upon event trigger
     // hence this cannot be a reregister and thus not fail
     assert(err_is_ok(err));
+    thread_yield();
 }
 
 /**
diff --git a/usr/shelly/shelly.c b/usr/shelly/shelly.c
index 3ad4d53..487fb3d 100644
--- a/usr/shelly/shelly.c
+++ b/usr/shelly/shelly.c
@@ -81,20 +81,20 @@ static void handle_lpuart_interrupt(void * arg) {
             global_state->buf[global_state->buffer_i] = '\0';
             global_state->buffer_i += 1;
 
-            err = shelly_write_str("\n\xd");
+            err = shelly_write_str("\n\r");
             if (err_is_fail(err)) USER_PANIC_ERR(err, "while trying to write string");
 
             err = handle_shelly_cmd(global_state->buf, global_state->buffer_i);
-            if (err_is_fail(err)) USER_PANIC_ERR(err, "while running command");
+            if (err_is_fail(err)) DEBUG_ERR(err, "while running command");
 
             shelly_reset_buffer();
 
-            err = shelly_write_str("\n\xd>");
+            err = shelly_write_str("\n\r>");
             if (err_is_fail(err)) USER_PANIC_ERR(err, "while trying to write string");
         } else {
             err = shelly_buffer_append(input_char);
             if (err_is_fail(err)) {
-                err = shelly_write_str("shelly buffer full! resetting...\n");
+                err = shelly_write_str("shelly buffer full! resetting...\n\r");
                 if (err_is_fail(err)) USER_PANIC_ERR(err, "while trying to write string");
             }
         }
@@ -147,6 +147,8 @@ static void handle_client_request(void *arg, size_t header_size, void *header_bu
     assert(local_state);
     assert(global_state);
 
+    // SHELLY_DEBUG("[handle_client_request] client_id=%d\n", local_state->client_id);
+
     struct shelly_header * header = (struct shelly_header *) header_buf;
 
     if (header->type == SHELLY_MSG_GETCHAR) {
@@ -272,7 +274,7 @@ int main(int argc, char *argv[])
 
     SHELLY_DEBUG("registered as shelly server\n");
 
-    err = shelly_write_str("welcome to Shelly(TM)(TM)!\n");
+    err = shelly_write_str("Welcome to Shelly(TM)(TM)!\n\r");
     if (err_is_fail(err)) USER_PANIC_ERR(err, "while trying to write welcome message");
 
     while (true) {
diff --git a/usr/shelly/shelly_cmd.c b/usr/shelly/shelly_cmd.c
index eb8e8e7..99d2f02 100644
--- a/usr/shelly/shelly_cmd.c
+++ b/usr/shelly/shelly_cmd.c
@@ -28,25 +28,32 @@ static errval_t shelly_cmd_run(char * line) {
     domainid_t pid;
     struct aos_rpc * rpc = aos_rpc_get_process_channel();
     err = aos_rpc_process_spawn(rpc, line, 0, &pid);
-    if (err_is_fail(err)) USER_PANIC_ERR(err, "Failed to spawn process");
-    SHELLY_DEBUG("[shelly_cmd_run] spawned process\n");
+    if (err == SPAWN_ERR_FIND_MODULE) {
+        err = shelly_write_str("[run]:couldn't find module:\n\r");
+        if (err_is_fail(err)) return err;
+        err = shelly_write_str(line);
+        if (err_is_fail(err)) return err;
+        err = shelly_write_str("\n\r");
+        if (err_is_fail(err)) return err;
+    } else if (err_is_fail(err)) return err_push(err, SHELLY_ERR_SPAWN_RPC);
 
-    // // get process name
-    // char *name;
-    // err = aos_rpc_process_get_name(rpc, pid, &name);
-    // if (err_is_fail(err)) USER_PANIC_ERR(err, "Failed to get process name");
-    // printf("Process Name: %s\n", name);
+    return SYS_ERR_OK;
+}
 
-    // // get all PIDs
-    // domainid_t *pids;
-    // size_t pid_count;
-    // err = aos_rpc_process_get_all_pids(rpc, &pids, &pid_count);
-    // if (err_is_fail(err)) USER_PANIC_ERR(err, "Failed to get all PIDs");
-    // printf("PIDs:\n");
-    // for(size_t i = 0; i < pid_count; ++i) {
-    //     printf(" %lu\n", pids[i]);
-    // }
+static errval_t shelly_cmd_ps(char * line) {
+    errval_t err;
 
+    domainid_t *pids;
+    size_t pid_count;
+    struct aos_rpc * rpc = aos_rpc_get_process_channel();
+    err = aos_rpc_process_get_all_pids(rpc, &pids, &pid_count);
+    if (err_is_fail(err)) return err_push(err, SHELLY_ERR_PS_RPC);
+    shelly_write_str("PIDs:\n\r");
+    char buf[256];
+    for(size_t i = 0; i < pid_count; ++i) {
+        snprintf(buf, 256, " %lu\n\r", pids[i]);
+        shelly_write_str(buf);
+    }
     return SYS_ERR_OK;
 }
 
@@ -66,9 +73,11 @@ static errval_t handle_shelly_cmd(char* line, size_t len) {
         return shelly_cmd_echo(remaining_line);
     } else if (strcmp(cmd, "run") == 0) {
         return shelly_cmd_run(remaining_line);
+    } else if (strcmp(cmd, "ps") == 0) {
+        return shelly_cmd_ps(remaining_line);
     } else {
         char buf[256];
-        snprintf(buf, 256, "unknown command %s\n", cmd);
+        snprintf(buf, 256, "unknown command \"%s\"\n\r", cmd);
         shelly_write_str(buf);
     }