fix(channels): treat an empty agent reply as delivered

CHANGELOG.md

@@ -4,6 +4,9 @@ All notable changes to ShellClaw are documented here. Format follows [Keep a Cha
 
 ## [Unreleased]
 
+### Fixed
+- An empty agent reply is a completed delivery for Telegram, Discord, and WebChat. Those channels reject an empty post, and treating that rejection as a failed send skipped the cron ack, so the job stayed due and reran the agent and its tools on every poll.
+
 ## [1.0.1] - 2026-10-18
 
 ### Fixed

src/channels/discord.c

@@ -959,12 +959,16 @@ static int discord_send(const char *recipient, const char *text,
 	(void)attachments;
 	if (att_count > 0)
 		return -1;
-	if (!dc->token || !recipient || !text || text[0] == '\0')
+	if (!dc->token || !recipient || !text)
 		return -1;
 	/* A single REST message is capped at 2000 characters, so a longer
 	 * reply is delivered as several messages. */
 	if (discord_recipient_channel_id(recipient, ctx.channel_id, sizeof(ctx.channel_id)) != 0)
 		return -1;
+	/* Discord rejects an empty content body. A -1 here skips the cron ack
+	 * and the job reruns the agent on every poll. */
+	if (text[0] == '\0')
+		return 0;
 	if (snprintf(ctx.auth_hdr, sizeof(ctx.auth_hdr), "Authorization: Bot %s", dc->token) >=
 	    (int)sizeof(ctx.auth_hdr))
 		return -1;

src/channels/telegram.c

@@ -471,7 +471,7 @@ static int tg_send(const char *recipient, const char *text,
 
 	(void)attachments;
 	(void)att_count;
-	if (!g_tg.initialized || !g_tg.token || !recipient || !text || text[0] == '\0')
+	if (!g_tg.initialized || !g_tg.token || !recipient || !text)
 		return -1;
 	chat_id = strchr(recipient, ':');
 	if (chat_id)
@@ -480,6 +480,10 @@ static int tg_send(const char *recipient, const char *text,
 		chat_id = recipient;
 	if (chat_id[0] == '\0')
 		return -1;
+	/* Telegram rejects an empty sendMessage. Returning -1 made cron skip
+	 * its ack, so a null model reply stayed due and reran the agent. */
+	if (text[0] == '\0')
+		return 0;
 	ctx.chat_id = chat_id;
 	ctx.posted_before = 0;
 	if (channel_send_chunked(text, TG_TEXT_MAX, tg_post_piece, &ctx, &fail) != 0) {

src/channels/webchat.c

@@ -48,6 +48,10 @@ static int webchat_send(const char *recipient, const char *text,
 	(void)attachments;
 	(void)att_count;
 	if (!recipient || !text) return -1;
+	/* ws_send_to rejects a zero-length frame. Cron would treat that as a
+	 * failed delivery and rerun the agent. There is nothing to enqueue. */
+	if (text[0] == '\0')
+		return 0;
 	return ws_send_to(recipient, text);
 }
 

src/core/dispatch.c

@@ -36,7 +36,10 @@ static int send_then_maybe_ack_cron(const channel_t *ch, const channel_incoming_
 	if (!ch || !ch->send || !msg)
 		return -1;
 	send_err = ch->send(msg->session_id, text, NULL, 0);
-	if (send_err != 0)
+	/* An empty reply cannot be posted. A channel that still returns -1
+	 * must not skip the cron ack: the job would stay due and the agent,
+	 * tools included, would run again on every poll. */
+	if (send_err != 0 && !(text && text[0] == '\0'))
 		return send_err;
 	if (agent_err != 0)
 		return 0;

tests/test_dispatch.c

@@ -55,6 +55,9 @@ static int mock_send(const char *session_id, const char *text,
 	g_last_session[sizeof(g_last_session) - 1] = '\0';
 	strncpy(g_last_text, text ? text : "", sizeof(g_last_text) - 1);
 	g_last_text[sizeof(g_last_text) - 1] = '\0';
+	/* Telegram, Discord, and WebChat reject an empty post. */
+	if (!text || text[0] == '\0')
+		return -1;
 	return 0;
 }
 
@@ -126,6 +129,28 @@ static const provider_t fail_provider = {
 	.cleanup = spy_cleanup,
 };
 
+static int empty_chat(const provider_message_t *messages, size_t message_count,
+		      const provider_tool_def_t *tools, size_t tool_count,
+		      provider_response_t *response)
+{
+	(void)messages;
+	(void)message_count;
+	(void)tools;
+	(void)tool_count;
+	response->error = 0;
+	response->content = NULL;
+	response->tool_calls = NULL;
+	response->tool_calls_count = 0;
+	return 0;
+}
+
+static const provider_t empty_provider = {
+	.name = "empty",
+	.init = spy_init,
+	.chat = empty_chat,
+	.cleanup = spy_cleanup,
+};
+
 static int lockcheck_chat(const provider_message_t *messages, size_t message_count,
 			  const provider_tool_def_t *tools, size_t tool_count,
 			  provider_response_t *response)
@@ -439,6 +464,51 @@ static int test_cron_agent_failure_does_not_ack(void)
 	return 0;
 }
 
+/* A finished cron turn whose model content is null (no tool calls, or the
+ * tool cap hit on a tool-call turn) must ack. Otherwise next_run stays due
+ * and the next poll reruns the agent. */
+static int test_cron_empty_reply_acks_job(void)
+{
+	const char *db_path = "build/test_dispatch_cron_empty.db";
+	char tmpl[] = "/tmp/shellclaw_test_dispatch_cron_empty_XXXXXX";
+	channel_incoming_msg_t msg = {0};
+	config_t *cfg = NULL;
+	cron_job_row_t row;
+	long long due_at;
+	int fd;
+	reset_send_spy();
+	memory_cleanup();
+	remove(db_path);
+	ASSERT(memory_init(db_path) == 0);
+	due_at = (long long)time(NULL) - 1;
+	ASSERT(cron_job_create("cron_empty", "interval:60", "remind me", "telegram", "42",
+			       due_at, 1) == 0);
+	fd = mkstemp(tmpl);
+	ASSERT(fd >= 0);
+	close(fd);
+	ASSERT(write_minimal_toml(tmpl) == 0);
+	cfg = load_minimal_cfg(tmpl);
+	ASSERT(cfg != NULL);
+	bootstrap_set_cfg(cfg);
+	bootstrap_set_provider_for_test(&empty_provider);
+	bootstrap_reset_tools_for_test();
+	msg.session_id = "telegram:42";
+	msg.user_id = "cron_empty";
+	msg.text = "remind me";
+	ASSERT(handle_message(&cron_mock_channel, &msg) == 0);
+	ASSERT(g_send_calls == 1);
+	ASSERT(g_last_text[0] == '\0');
+	memset(&row, 0, sizeof(row));
+	ASSERT(cron_job_get_by_id("cron_empty", &row) == 1);
+	ASSERT(row.next_run > due_at);
+	cron_job_row_free(&row);
+	config_free(cfg);
+	unlink(tmpl);
+	memory_cleanup();
+	remove(db_path);
+	return 0;
+}
+
 static int test_handle_message_holds_agent_mutex(void)
 {
 	channel_incoming_msg_t msg = {0};
@@ -502,6 +572,7 @@ int main(void)
 	RUN(test_handle_message_holds_agent_mutex());
 	RUN(test_cron_slash_commands_ack_jobs());
 	RUN(test_cron_agent_failure_does_not_ack());
+	RUN(test_cron_empty_reply_acks_job());
 	puts("test_dispatch OK");
 	return 0;
 }

tests/test_telegram.c

@@ -285,6 +285,31 @@ static void test_vtable_fields_set(void)
 	MU_ASSERT(ch->cleanup != NULL, "cleanup not null");
 }
 
+/* An empty agent reply used to return -1 before any HTTP call. Cron treats
+ * that as a failed delivery and leaves next_run in the past, so the same job
+ * reruns the agent on every poll. Telegram would 400 an empty sendMessage,
+ * so the only successful outcome is to post nothing. */
+static void test_send_empty_text_succeeds(void)
+{
+	const channel_t *ch;
+	config_t *cfg = load_test_config("/tmp/test_tg_empty_send.toml", "42");
+	MU_ASSERT(cfg != NULL, "load config");
+	setenv("TG_TOK", "test-token", 1);
+	ch = channel_telegram_get();
+	MU_ASSERT(ch->init(cfg) == 0, "telegram init");
+	MU_ASSERT(ch->send("telegram:42", "", NULL, 0) == 0,
+		"empty reply to a chat id is not a delivery failure");
+	MU_ASSERT(ch->send("42", "", NULL, 0) == 0,
+		"empty reply to a raw chat id is not a delivery failure");
+	MU_ASSERT(ch->send("telegram:", "", NULL, 0) != 0,
+		"empty chat id still fails");
+	MU_ASSERT(ch->send(NULL, "", NULL, 0) != 0, "missing recipient still fails");
+	ch->cleanup();
+	unsetenv("TG_TOK");
+	config_free(cfg);
+	remove("/tmp/test_tg_empty_send.toml");
+}
+
 int main(void)
 {
 	MU_RUN(test_parse_valid_text_message);
@@ -298,6 +323,7 @@ MU_RUN(test_getupdates_url_requests_one_update);
 	MU_RUN(test_send_response_requires_ok);
 	MU_RUN(test_429_retry_after_parsed_and_capped);
 	MU_RUN(test_vtable_fields_set);
+	MU_RUN(test_send_empty_text_succeeds);
 	printf("%d tests run, %d failed\n", tests_run, tests_failed);
 	return tests_failed ? 1 : 0;
 }