diff --git a/packages/mom/src/agent.ts b/packages/mom/src/agent.ts
index 22fcba76..d8f279ef 100644
--- a/packages/mom/src/agent.ts
+++ b/packages/mom/src/agent.ts
@@ -690,11 +690,11 @@ function createRunner(sandboxConfig: SandboxConfig, channelId: string, channelDi
 						.map((c) => c.text)
 						.join("\n") || "";
 
-				// Check for [SILENT] marker - delete message instead of posting
+				// Check for [SILENT] marker - delete message and thread instead of posting
 				if (finalText.trim() === "[SILENT]" || finalText.trim().startsWith("[SILENT]")) {
 					try {
 						await ctx.deleteMessage();
-						log.logInfo("Silent response - deleted status message");
+						log.logInfo("Silent response - deleted message and thread");
 					} catch (err) {
 						const errMsg = err instanceof Error ? err.message : String(err);
 						log.logWarning("Failed to delete message for silent response", errMsg);
diff --git a/packages/mom/src/main.ts b/packages/mom/src/main.ts
index 933a8464..c1c483e3 100644
--- a/packages/mom/src/main.ts
+++ b/packages/mom/src/main.ts
@@ -116,6 +116,7 @@ function getState(channelId: string): ChannelState {
 
 function createSlackContext(event: SlackEvent, slack: SlackBot, state: ChannelState, isEvent?: boolean) {
 	let messageTs: string | null = null;
+	const threadMessageTs: string[] = [];
 	let accumulatedText = "";
 	let isWorking = true;
 	const workingIndicator = " ...";
@@ -175,7 +176,8 @@ function createSlackContext(event: SlackEvent, slack: SlackBot, state: ChannelSt
 		respondInThread: async (text: string) => {
 			updatePromise = updatePromise.then(async () => {
 				if (messageTs) {
-					await slack.postInThread(event.channel, messageTs, text);
+					const ts = await slack.postInThread(event.channel, messageTs, text);
+					threadMessageTs.push(ts);
 				}
 			});
 			await updatePromise;
@@ -210,6 +212,16 @@ function createSlackContext(event: SlackEvent, slack: SlackBot, state: ChannelSt
 
 		deleteMessage: async () => {
 			updatePromise = updatePromise.then(async () => {
+				// Delete thread messages first (in reverse order)
+				for (let i = threadMessageTs.length - 1; i >= 0; i--) {
+					try {
+						await slack.deleteMessage(event.channel, threadMessageTs[i]);
+					} catch {
+						// Ignore errors deleting thread messages
+					}
+				}
+				threadMessageTs.length = 0;
+				// Then delete main message
 				if (messageTs) {
 					await slack.deleteMessage(event.channel, messageTs);
 					messageTs = null;
diff --git a/packages/mom/src/slack.ts b/packages/mom/src/slack.ts
index 6bfd93f4..2f9d72f0 100644
--- a/packages/mom/src/slack.ts
+++ b/packages/mom/src/slack.ts
@@ -197,8 +197,9 @@ export class SlackBot {
 		await this.webClient.chat.delete({ channel, ts });
 	}
 
-	async postInThread(channel: string, threadTs: string, text: string): Promise<void> {
-		await this.webClient.chat.postMessage({ channel, thread_ts: threadTs, text });
+	async postInThread(channel: string, threadTs: string, text: string): Promise<string> {
+		const result = await this.webClient.chat.postMessage({ channel, thread_ts: threadTs, text });
+		return result.ts as string;
 	}
 
 	async uploadFile(channel: string, filePath: string, title?: string): Promise<void> {