fix(channels): add reply_to field to ChannelMessage for correct reply routing

ChannelMessage.sender was used both for display (username) and as the
reply target in Channel::send(). For Telegram, sender is the username
(e.g. "unknown") while send() requires the numeric chat_id, causing
"Bad Request: chat not found" errors.

Add a dedicated reply_to field to ChannelMessage that stores the
channel-specific reply address (Telegram chat_id, Discord channel_id,
Slack channel, etc.). Update all channel implementations and dispatch
code to use reply_to for send/start_typing/stop_typing calls.

This also fixes the same latent bug in Discord and Slack channels where
sender (user ID) was incorrectly passed as the reply target.

examples/custom_channel.rs

@@ -12,6 +12,8 @@ use tokio::sync::mpsc;
 pub struct ChannelMessage {
     pub id: String,
     pub sender: String,
+    /// Channel-specific reply address (e.g. Telegram chat_id, Discord channel_id).
+    pub reply_to: String,
     pub content: String,
     pub channel: String,
     pub timestamp: u64,
@@ -90,9 +92,12 @@ impl Channel for TelegramChannel {
                             continue;
                         }
 
+                        let chat_id = msg["chat"]["id"].to_string();
+
                         let channel_msg = ChannelMessage {
                             id: msg["message_id"].to_string(),
                             sender,
+                            reply_to: chat_id,
                             content: msg["text"].as_str().unwrap_or("").to_string(),
                             channel: "telegram".into(),
                             timestamp: msg["date"].as_u64().unwrap_or(0),

src/channels/cli.rs

@@ -40,6 +40,7 @@ impl Channel for CliChannel {
             let msg = ChannelMessage {
                 id: Uuid::new_v4().to_string(),
                 sender: "user".to_string(),
+                reply_to: "user".to_string(),
                 content: line,
                 channel: "cli".to_string(),
                 timestamp: std::time::SystemTime::now()
@@ -90,6 +91,7 @@ mod tests {
         let msg = ChannelMessage {
             id: "test-id".into(),
             sender: "user".into(),
+            reply_to: "user".into(),
             content: "hello".into(),
             channel: "cli".into(),
             timestamp: 1_234_567_890,
@@ -106,6 +108,7 @@ mod tests {
         let msg = ChannelMessage {
             id: "id".into(),
             sender: "s".into(),
+            reply_to: "s".into(),
             content: "c".into(),
             channel: "ch".into(),
             timestamp: 0,

src/channels/dingtalk.rs

@@ -229,6 +229,7 @@ impl Channel for DingTalkChannel {
                     let channel_msg = ChannelMessage {
                         id: Uuid::new_v4().to_string(),
                         sender: sender_id.to_string(),
+                        reply_to: sender_id.to_string(),
                         content: content.to_string(),
                         channel: "dingtalk".to_string(),
                         timestamp: std::time::SystemTime::now()

src/channels/discord.rs

@@ -353,6 +353,7 @@ impl Channel for DiscordChannel {
                             format!("discord_{message_id}")
                         },
                         sender: author_id.to_string(),
+                        reply_to: channel_id.clone(),
                         content: content.to_string(),
                         channel: "discord".to_string(),
                         timestamp: std::time::SystemTime::now()

src/channels/email_channel.rs

@@ -428,7 +428,8 @@ impl Channel for EmailChannel {
                         } // MutexGuard dropped before await
                         let msg = ChannelMessage {
                             id,
-                            sender,
+                            sender: sender.clone(),
+                            reply_to: sender,
                             content,
                             channel: "email".to_string(),
                             timestamp: ts,

src/channels/imessage.rs

@@ -172,6 +172,7 @@ end tell"#
                         let msg = ChannelMessage {
                             id: rowid.to_string(),
                             sender: sender.clone(),
+                            reply_to: sender.clone(),
                             content: text,
                             channel: "imessage".to_string(),
                             timestamp: std::time::SystemTime::now()

src/channels/irc.rs

@@ -565,7 +565,8 @@ impl Channel for IrcChannel {
                     let seq = MSG_SEQ.fetch_add(1, Ordering::Relaxed);
                     let channel_msg = ChannelMessage {
                         id: format!("irc_{}_{seq}", chrono::Utc::now().timestamp_millis()),
-                        sender: reply_to,
+                        sender: reply_to.clone(),
+                        reply_to,
                         content,
                         channel: "irc".to_string(),
                         timestamp: std::time::SystemTime::now()

src/channels/lark.rs

@@ -613,6 +613,7 @@ impl LarkChannel {
         messages.push(ChannelMessage {
             id: Uuid::new_v4().to_string(),
             sender: chat_id.to_string(),
+            reply_to: chat_id.to_string(),
             content: text,
             channel: "lark".to_string(),
             timestamp,

src/channels/matrix.rs

@@ -230,6 +230,7 @@ impl Channel for MatrixChannel {
                     let msg = ChannelMessage {
                         id: format!("mx_{}", chrono::Utc::now().timestamp_millis()),
                         sender: event.sender.clone(),
+                        reply_to: event.sender.clone(),
                         content: body.clone(),
                         channel: "matrix".to_string(),
                         timestamp: std::time::SystemTime::now()

src/channels/mod.rs

@@ -171,7 +171,7 @@ async fn process_channel_message(ctx: Arc<ChannelRuntimeContext>, msg: traits::C
     let target_channel = ctx.channels_by_name.get(&msg.channel).cloned();
 
     if let Some(channel) = target_channel.as_ref() {
-        if let Err(e) = channel.start_typing(&msg.sender).await {
+        if let Err(e) = channel.start_typing(&msg.reply_to).await {
             tracing::debug!("Failed to start typing on {}: {e}", channel.name());
         }
     }
@@ -200,7 +200,7 @@ async fn process_channel_message(ctx: Arc<ChannelRuntimeContext>, msg: traits::C
     .await;
 
     if let Some(channel) = target_channel.as_ref() {
-        if let Err(e) = channel.stop_typing(&msg.sender).await {
+        if let Err(e) = channel.stop_typing(&msg.reply_to).await {
             tracing::debug!("Failed to stop typing on {}: {e}", channel.name());
         }
     }
@@ -213,7 +213,7 @@ async fn process_channel_message(ctx: Arc<ChannelRuntimeContext>, msg: traits::C
                 truncate_with_ellipsis(&response, 80)
             );
             if let Some(channel) = target_channel.as_ref() {
-                if let Err(e) = channel.send(&response, &msg.sender).await {
+                if let Err(e) = channel.send(&response, &msg.reply_to).await {
                     eprintln!("  ❌ Failed to reply on {}: {e}", channel.name());
                 }
             }
@@ -224,7 +224,7 @@ async fn process_channel_message(ctx: Arc<ChannelRuntimeContext>, msg: traits::C
                 started_at.elapsed().as_millis()
             );
             if let Some(channel) = target_channel.as_ref() {
-                let _ = channel.send(&format!("⚠️ Error: {e}"), &msg.sender).await;
+                let _ = channel.send(&format!("⚠️ Error: {e}"), &msg.reply_to).await;
             }
         }
         Err(_) => {
@@ -241,7 +241,7 @@ async fn process_channel_message(ctx: Arc<ChannelRuntimeContext>, msg: traits::C
                 let _ = channel
                     .send(
                         "⚠️ Request timed out while waiting for the model. Please try again.",
-                        &msg.sender,
+                        &msg.reply_to,
                     )
                     .await;
             }
@@ -1232,6 +1232,7 @@ mod tests {
             traits::ChannelMessage {
                 id: "msg-1".to_string(),
                 sender: "alice".to_string(),
+                reply_to: "alice".to_string(),
                 content: "What is the BTC price now?".to_string(),
                 channel: "test-channel".to_string(),
                 timestamp: 1,
@@ -1321,6 +1322,7 @@ mod tests {
         tx.send(traits::ChannelMessage {
             id: "1".to_string(),
             sender: "alice".to_string(),
+            reply_to: "alice".to_string(),
             content: "hello".to_string(),
             channel: "test-channel".to_string(),
             timestamp: 1,
@@ -1330,6 +1332,7 @@ mod tests {
         tx.send(traits::ChannelMessage {
             id: "2".to_string(),
             sender: "bob".to_string(),
+            reply_to: "bob".to_string(),
             content: "world".to_string(),
             channel: "test-channel".to_string(),
             timestamp: 2,
@@ -1573,6 +1576,7 @@ mod tests {
         let msg = traits::ChannelMessage {
             id: "msg_abc123".into(),
             sender: "U123".into(),
+            reply_to: "U123".into(),
             content: "hello".into(),
             channel: "slack".into(),
             timestamp: 1,
@@ -1586,6 +1590,7 @@ mod tests {
         let msg1 = traits::ChannelMessage {
             id: "msg_1".into(),
             sender: "U123".into(),
+            reply_to: "U123".into(),
             content: "first".into(),
             channel: "slack".into(),
             timestamp: 1,
@@ -1593,6 +1598,7 @@ mod tests {
         let msg2 = traits::ChannelMessage {
             id: "msg_2".into(),
             sender: "U123".into(),
+            reply_to: "U123".into(),
             content: "second".into(),
             channel: "slack".into(),
             timestamp: 2,
@@ -1612,6 +1618,7 @@ mod tests {
         let msg1 = traits::ChannelMessage {
             id: "msg_1".into(),
             sender: "U123".into(),
+            reply_to: "U123".into(),
             content: "I'm Paul".into(),
             channel: "slack".into(),
             timestamp: 1,
@@ -1619,6 +1626,7 @@ mod tests {
         let msg2 = traits::ChannelMessage {
             id: "msg_2".into(),
             sender: "U123".into(),
+            reply_to: "U123".into(),
             content: "I'm 45".into(),
             channel: "slack".into(),
             timestamp: 2,

src/channels/slack.rs

@@ -161,6 +161,7 @@ impl Channel for SlackChannel {
                     let channel_msg = ChannelMessage {
                         id: format!("slack_{channel_id}_{ts}"),
                         sender: user.to_string(),
+                        reply_to: channel_id.to_string(),
                         content: text.to_string(),
                         channel: "slack".to_string(),
                         timestamp: std::time::SystemTime::now()

src/channels/telegram.rs

@@ -598,6 +598,7 @@ Allowlist Telegram @username or numeric user ID, then run `zeroclaw onboard --ch
                     let msg = ChannelMessage {
                         id: format!("telegram_{chat_id}_{message_id}"),
                         sender: username.to_string(),
+                        reply_to: chat_id.clone(),
                         content: text.to_string(),
                         channel: "telegram".to_string(),
                         timestamp: std::time::SystemTime::now()

src/channels/traits.rs

@@ -5,6 +5,9 @@ use async_trait::async_trait;
 pub struct ChannelMessage {
     pub id: String,
     pub sender: String,
+    /// Channel-specific reply address (e.g. Telegram chat_id, Discord channel_id, Slack channel).
+    /// Used by `Channel::send()` to route the reply to the correct destination.
+    pub reply_to: String,
     pub content: String,
     pub channel: String,
     pub timestamp: u64,
@@ -62,6 +65,7 @@ mod tests {
             tx.send(ChannelMessage {
                 id: "1".into(),
                 sender: "tester".into(),
+                reply_to: "tester".into(),
                 content: "hello".into(),
                 channel: "dummy".into(),
                 timestamp: 123,
@@ -76,6 +80,7 @@ mod tests {
         let message = ChannelMessage {
             id: "42".into(),
             sender: "alice".into(),
+            reply_to: "alice".into(),
             content: "ping".into(),
             channel: "dummy".into(),
             timestamp: 999,

src/channels/whatsapp.rs

@@ -119,7 +119,8 @@ impl WhatsAppChannel {
 
                     messages.push(ChannelMessage {
                         id: Uuid::new_v4().to_string(),
-                        sender: normalized_from,
+                        sender: normalized_from.clone(),
+                        reply_to: normalized_from,
                         content,
                         channel: "whatsapp".to_string(),
                         timestamp,

src/gateway/mod.rs

@@ -709,7 +709,7 @@ async fn handle_whatsapp_message(
         {
             Ok(response) => {
                 // Send reply via WhatsApp
-                if let Err(e) = wa.send(&response, &msg.sender).await {
+                if let Err(e) = wa.send(&response, &msg.reply_to).await {
                     tracing::error!("Failed to send WhatsApp reply: {e}");
                 }
             }
@@ -718,7 +718,7 @@ async fn handle_whatsapp_message(
                 let _ = wa
                     .send(
                         "Sorry, I couldn't process your message right now.",
-                        &msg.sender,
+                        &msg.reply_to,
                     )
                     .await;
             }
@@ -860,6 +860,7 @@ mod tests {
         let msg = ChannelMessage {
             id: "wamid-123".into(),
             sender: "+1234567890".into(),
+            reply_to: "+1234567890".into(),
             content: "hello".into(),
             channel: "whatsapp".into(),
             timestamp: 1,