feat(channels): add MQTT pub/sub channel adapter

Cargo.toml

@@ -134,6 +134,9 @@ imap = "2"
 native-tls = "0.2"
 mailparse = "0.15"
 
+# MQTT
+rumqttc = "0.24"
+
 # Testing
 tokio-test = "0.4"
 tempfile = "3"

README.md

@@ -260,10 +260,40 @@ Connect your agents to every platform your users are on.
 **Social:** LINE, Viber, Facebook Messenger, Mastodon, Bluesky, Reddit, LinkedIn, Twitch
 **Community:** IRC, XMPP, Guilded, Revolt, Keybase, Discourse, Gitter
 **Privacy:** Threema, Nostr, Mumble, Nextcloud Talk, Rocket.Chat, Ntfy, Gotify
+**IoT/Edge:** MQTT
 **Workplace:** Pumble, Flock, Twist, DingTalk, Zalo, Webhooks
 
 Each adapter supports per-channel model overrides, DM/group policies, rate limiting, and output formatting.
 
+### MQTT Configuration
+
+MQTT is ideal for IoT devices, edge computing, and low-bandwidth environments. Configure it in `~/.openfang/config.toml`:
+
+```toml
+[channels.mqtt]
+broker_url = "tcp://broker.hivemq.com:1883"  # or "ssl://..." for TLS
+client_id = ""                                # empty = auto-generate
+subscribe_topic = "openfang/inbox"
+publish_topic_prefix = "openfang/reply"
+default_agent = "assistant"
+qos = 1                    # 0=at most once, 1=at least once, 2=exactly once
+use_tls = false
+keep_alive_secs = 60
+
+# Optional authentication
+username_env = "MQTT_USERNAME"
+password_env = "MQTT_PASSWORD"
+```
+
+Test with any MQTT client:
+```bash
+# Send a message
+mosquitto_pub -h broker.hivemq.com -t "openfang/inbox" -m "What's the weather?"
+
+# Subscribe to replies
+mosquitto_sub -h broker.hivemq.com -t "openfang/reply/#"
+```
+
 ---
 
 ## 27 LLM Providers — 123+ Models

crates/openfang-api/src/channel_bridge.rs

@@ -48,6 +48,7 @@ use openfang_channels::gitter::GitterAdapter;
 use openfang_channels::gotify::GotifyAdapter;
 use openfang_channels::linkedin::LinkedInAdapter;
 use openfang_channels::mumble::MumbleAdapter;
+use openfang_channels::mqtt::MqttAdapter;
 use openfang_channels::ntfy::NtfyAdapter;
 use openfang_channels::webhook::WebhookAdapter;
 use openfang_kernel::OpenFangKernel;
@@ -733,6 +734,7 @@ impl ChannelBridgeHandle for KernelBridgeAdapter {
             "gotify" => channels.gotify.as_ref().map(|c| c.overrides.clone()),
             "webhook" => channels.webhook.as_ref().map(|c| c.overrides.clone()),
             "linkedin" => channels.linkedin.as_ref().map(|c| c.overrides.clone()),
+            "mqtt" => channels.mqtt.as_ref().map(|c| c.overrides.clone()),
             _ => None,
         }
     }
@@ -1008,7 +1010,8 @@ pub async fn start_channel_bridge_with_config(
         || config.ntfy.is_some()
         || config.gotify.is_some()
         || config.webhook.is_some()
-        || config.linkedin.is_some();
+        || config.linkedin.is_some()
+        || config.mqtt.is_some();
 
     if !has_any {
         return (None, Vec::new());
@@ -1518,6 +1521,18 @@ pub async fn start_channel_bridge_with_config(
         }
     }
 
+    // MQTT
+    if let Some(ref mqtt_config) = config.mqtt {
+        if !mqtt_config.broker_url.is_empty() && !mqtt_config.subscribe_topic.is_empty() {
+            let adapter = Arc::new(MqttAdapter::from_config(mqtt_config.clone()));
+            adapters.push((adapter, mqtt_config.default_agent.clone()));
+            info!(
+                "MQTT adapter configured: {} -> {}",
+                mqtt_config.broker_url, mqtt_config.subscribe_topic
+            );
+        }
+    }
+
     if adapters.is_empty() {
         return (None, Vec::new());
     }

crates/openfang-channels/Cargo.toml

@@ -32,5 +32,8 @@ imap = { workspace = true }
 native-tls = { workspace = true }
 mailparse = { workspace = true }
 
+# MQTT support
+rumqttc = { workspace = true }
+
 [dev-dependencies]
 tokio-test = { workspace = true }

crates/openfang-channels/src/lib.rs

@@ -48,5 +48,6 @@ pub mod gitter;
 pub mod gotify;
 pub mod linkedin;
 pub mod mumble;
+pub mod mqtt;
 pub mod ntfy;
 pub mod webhook;