diff --git a/CMakeLists.txt b/CMakeLists.txt
index f139cf4..a7c22cc 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -29,7 +29,6 @@ set(UIRC_SOURCE
 set(UIRC_HEADERS
 	src/uirc.h
 	src/ctcp.h
-	src/errors.h
 	src/modes.h
 	src/replies.h
 	src/types.h
diff --git a/src/assemblers/assemblers.h b/src/assemblers/assemblers.h
index 4356068..fea5d11 100644
--- a/src/assemblers/assemblers.h
+++ b/src/assemblers/assemblers.h
@@ -20,16 +20,18 @@
 
 #include "../types.h" // IRC_User IRC_Message
 
-#include <stdbool.h> // bool
-#include <stddef.h>  // size_t
+#include <corelibs/llist.h> // llist_t
+#include <stdbool.h>        // bool
+#include <sys/types.h>      // ssize_t ssize_t
 
 #ifndef UIRC_GUARD_PUBLIC_ASSEMBLERS
 #define UIRC_GUARD_PUBLIC_ASSEMBLERS
 
-signed long uirc_assembler_user(char* buf, IRC_User* u, size_t len);
+ssize_t uirc_assembler_user(char* buf, const IRC_User* u, size_t len);
 
 #ifdef UIRC_FEATURE_IRCV3
-signed long uirc_assembler_tag(char* buf, const IRC_Tag* t, size_t len);
+ssize_t uirc_assembler_tag(char* buf, const IRC_Tag* t, size_t len);
+ssize_t uirc_assembler_tag_list(char* buf, const llist_t* t, size_t len);
 #endif /* UIRC_FEATURE_IRCV3*/
 
 /*!
@@ -42,6 +44,6 @@ signed long uirc_assembler_tag(char* buf, const IRC_Tag* t, size_t len);
  * \param[out] buf String representation of message (if successful)
  * \warning in and buf SHOULD NOT be NULL, this will trigger a ASSERT so it's required to check it where needed
  */
-signed long uirc_assembler_message(char* buf, IRC_Message* m, size_t len);
+ssize_t uirc_assembler_message(char* buf, const IRC_Message* m, size_t len);
 #endif /* UIRC_GUARD_PUBLIC_ASSEMBLERS */
 
diff --git a/src/assemblers/message.c b/src/assemblers/message.c
index 6d3bb0c..2629fcc 100644
--- a/src/assemblers/message.c
+++ b/src/assemblers/message.c
@@ -16,65 +16,40 @@
  *  along with uIRC.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-#include "../errors.h"  // ERR_UIRC_*
-#include "../types.h"   // IRC_Message
-#include "assemblers.h" // Assm_mesg() Assm_tags() Assm_user()
+#include "../types.h"   // IRC_Message IRC_Tag IRC_User
+#include "assemblers.h" // uirc_assembler_*
 
 #include <assert.h>    // assert()
-#include <stdbool.h>   // false
 #include <stdio.h>     // NULL, snprintf()
-#include <string.h>    // strlen()
 #include <sys/types.h> // size_t
 
-signed long
-uirc_assembler_message(char* buf, IRC_Message* m, size_t len)
+ssize_t
+uirc_assembler_message(char* buf, const IRC_Message* m, size_t len)
 {
 	assert(buf != NULL);
 	assert(m != NULL);
 
-	char* const sv = buf;
-	signed long ret;
+	const char* const sv = buf;
 
 #ifdef UIRC_FEATURE_IRCV3
-	if (m->tag_list != NULL && m->tag_list->content != NULL) {
-		for (llist_t* l = m->tag_list; l != NULL && l->content != NULL && ((IRC_Tag*) l->content)->key != NULL;) {
-			if (m->tag_list == l) {
-				if (len > 1) {
-					*(buf++) = '@';
-					len--;
-				} else
-					return UIRC_ERR_BUFFER_FULL;
-			} else {
-				if (len > 1) {
-					*(buf++) = ';';
-					len--;
-				} else
-					return UIRC_ERR_BUFFER_FULL;
-			}
-
-			if ((ret = uirc_assembler_tag(buf, l->content, len)) >= 0) {
-				buf += (size_t) ret;
-				len -= (size_t) ret;
-			} else
-				return ret;
-
-			if ((l = l->next) == NULL) {
-				if (len > 1) {
-					*(buf++) = ' ';
-					len--;
-				} else
-					return UIRC_ERR_BUFFER_FULL;
-			}
-		}
+	if (m->tag_list != NULL) {
+		ssize_t ret;
+		if ((ret = uirc_assembler_tag_list(buf, m->tag_list, len)) >= 0) {
+			buf += (size_t) ret;
+			len -= (size_t) ret;
+		} else
+			return ret;
 	}
+	assert(sv <= buf);
 #endif /* UIRC_FEATURE_IRCV3 */
 	if (m->source != NULL && (m->source->nick != NULL || m->source->host != NULL)) {
 		if (len > 1) {
 			*(buf++) = ':';
 			len--;
 		} else
-			return UIRC_ERR_BUFFER_FULL;
+			return -1;
 
+		ssize_t ret;
 		if ((ret = uirc_assembler_user(buf, m->source, len)) >= 0) {
 			buf += (size_t) ret;
 			len -= (size_t) ret;
@@ -85,28 +60,34 @@ uirc_assembler_message(char* buf, IRC_Message* m, size_t len)
 			*(buf++) = ' ';
 			len--;
 		} else
-			return UIRC_ERR_BUFFER_FULL;
+			return -1;
 	}
+	assert(sv <= buf);
 
 	if (m->command != NULL) {
-		if (len < 2) return UIRC_ERR_BUFFER_FULL;
+		if (len < 2) return -1;
+		int ret;
 		if ((ret = snprintf(buf, len, "%s ", m->command)) >= 0) {
 			buf += (size_t) ret;
 			len -= (size_t) ret;
 		} else
-			return UIRC_ERR_BUFFER_ERR;
+			return -1;
 	} else
-		return UIRC_ERR_INVALID_FORMAT;
+		return -1;
+	assert(sv <= buf);
 
 	for (unsigned int i = 0; i < IRC_MAXARGS && m->args[i] != NULL; i++) {
-		if (len < 2) return UIRC_ERR_BUFFER_FULL;
+		if (len < 2) return -1;
+		int ret;
 		if ((ret = snprintf(buf, len, (i + 1 == IRC_MAXARGS || (m->args[i + 1] == NULL && m->trailing)) ? ":%s" : "%s ", m->args[i])) >= 0) {
 			buf += (size_t) ret;
 			len -= (size_t) ret;
 		} else
-			return UIRC_ERR_BUFFER_ERR;
+			return -1;
 	}
+	assert(sv <= buf);
+	printf("%li\n", buf - sv);
 
-	return (buf += ret) - sv;
+	return (ssize_t)(buf - sv);
 }
 
diff --git a/src/assemblers/tag.c b/src/assemblers/tag.c
index 5b42455..2daba4e 100644
--- a/src/assemblers/tag.c
+++ b/src/assemblers/tag.c
@@ -16,49 +16,88 @@
  *  along with uIRC.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-#include "../errors.h"  // ERR_UIRC_*
 #include "../types.h"   // IRC_Tag
-#include "assemblers.h" // Assm_user()
+#include "assemblers.h" // uirc_assembler_tag_*
 
-#include <assert.h>  // assert()
-#include <stdbool.h> // bool
-#include <stddef.h>  // size_t
-#include <stdio.h>   // NULL
+#include <assert.h>         // assert()
+#include <corelibs/llist.h> // llist_t
+#include <stdio.h>          // NULL
+#include <sys/types.h>      // size_t ssize_t
 
-signed long
+ssize_t
 uirc_assembler_tag(char* buf, const IRC_Tag* t, size_t len)
 {
-	assert(buf != NULL);
 	assert(t != NULL);
+	assert(buf != NULL);
 	assert(t->key != NULL);
 
-	char* const sv = buf;
-	int         res;
+	const char* const sv = buf;
+	int               res;
 
 	if (t->clientbound) {
 		if (len > 1) {
 			*(buf++) = '+';
 			len--;
 		} else
-			return UIRC_ERR_BUFFER_FULL;
+			return -1;
 	}
 
-	if (len < 1) return UIRC_ERR_BUFFER_FULL;
+	if (len < 1) return -1;
 	if ((res = snprintf(buf, len, "%s", t->key)) >= 0) {
 		buf += (size_t) res;
 		len -= (size_t) res;
 	} else
-		return UIRC_ERR_BUFFER_ERR;
+		return -1;
 
 	if (t->value != NULL) {
-		if (len < 1) return UIRC_ERR_BUFFER_FULL;
+		if (len < 1) return -1;
 		if ((res = snprintf(buf, len, "=%s", t->value)) >= 0) {
 			buf += (size_t) res;
 			len -= (size_t) res;
 		} else
-			return UIRC_ERR_BUFFER_ERR;
+			return -1;
 	}
 
 	return buf - sv;
 }
 
+ssize_t
+uirc_assembler_tag_list(char* buf, const llist_t* tl, size_t len)
+{
+	assert(tl != NULL);
+	assert(buf != NULL);
+
+	const char* const sv = buf;
+	for (; tl->content != NULL && ((IRC_Tag*) tl->content)->key != NULL;) {
+		if (buf == sv) {
+			if (len > 1) {
+				*(buf++) = '@';
+				len--;
+			} else
+				return -1;
+		} else {
+			if (len > 1) {
+				*(buf++) = ';';
+				len--;
+			} else
+				return -1;
+		}
+
+		ssize_t ret;
+		if ((ret = uirc_assembler_tag(buf, tl->content, len)) >= 0) {
+			buf += (size_t) ret;
+			len -= (size_t) ret;
+		} else
+			return -1;
+
+		if ((tl = tl->next) == NULL) {
+			if (len > 1) {
+				*(buf++) = ' ';
+				len--;
+			} else
+				return -1;
+			break;
+		}
+	}
+	return buf - sv;
+}
diff --git a/src/assemblers/user.c b/src/assemblers/user.c
index 2c6f188..fc4e256 100644
--- a/src/assemblers/user.c
+++ b/src/assemblers/user.c
@@ -16,48 +16,50 @@
  *  along with uIRC.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-#include "../errors.h"  // ERR_UIRC_*
 #include "../types.h"   // IRC_User
 #include "assemblers.h" // Assm_user()
 
 #include <assert.h>    // assert()
 #include <stdbool.h>   // bool
-#include <stdio.h>     // NULL
+#include <stdio.h>     // NULL snprintf()
 #include <sys/types.h> // size_t
 
-signed long
-uirc_assembler_user(char* buf, IRC_User* u, size_t len)
+ssize_t
+uirc_assembler_user(char* buf, const IRC_User* u, size_t len)
 {
 	assert(buf != NULL);
 	assert(u != NULL);
 
-	ssize_t     res;
 	char* const sv = buf;
 
 	if (u->nick != NULL) {
-		if (len < 1) return UIRC_ERR_BUFFER_FULL;
+		if (len < 1) return -1;
+		int res;
 		if ((res = snprintf(buf, len, "%s", u->nick)) >= 0) {
 			buf += (size_t) res;
 			len -= (size_t) res;
 		} else
-			return UIRC_ERR_BUFFER_ERR;
+			return -1;
 	}
 	if (u->user != NULL) {
-		if (len < 1) return UIRC_ERR_BUFFER_FULL;
+		if (len < 1) return -1;
+		int res;
 		if ((res = snprintf(buf, len, "!%s", u->user)) >= 0) {
 			buf += (size_t) res;
 			len -= (size_t) res;
 		} else
-			return UIRC_ERR_BUFFER_ERR;
+			return -1;
 	}
 	if (u->host != NULL) {
-		if (len < 1) return UIRC_ERR_BUFFER_FULL;
+		if (len < 1) return -1;
+		int res;
 		if ((res = snprintf(buf, len, (u->nick != NULL || u->user != NULL) ? "@%s" : "%s", u->host)) >= 0) {
 			buf += (size_t) res;
 			len -= (size_t) res;
 		} else
-			return UIRC_ERR_BUFFER_ERR;
+			return -1;
 	}
+
 	return buf - sv;
 }