fix(acp): show mention_filter in startup config summary (#4228)

crates/buzz-acp/README.md

@@ -248,9 +248,11 @@ Forum event kinds:
 
 > **Note:** Without `--no-mention-filter` (or `require_mention = false`), the default `subscribe=mentions` mode filters events that don't @mention the agent — forum posts will be invisible.
 
+After startup, confirm the flag in the journal: `mention_filter=off` means the `#p` gate is disabled; `mention_filter=on` under `subscribe=Mentions` means only @mentions wake the agent (#4228).
+
 ## How It Works
 
-1. **Startup** — Spawns N agent subprocesses (default 1), sends ACP `initialize` to each, connects to the relay with NIP-42 auth.
+1. **Startup** — Spawns N agent subprocesses (default 1), sends ACP `initialize` to each, connects to the relay with NIP-42 auth. Logs a one-line config summary (relay, pubkey, subscribe mode, **`mention_filter=on|off`**, dedup, respond_to, …) so operators can confirm `--no-mention-filter` took effect from the journal alone.
 2. **Channel discovery** — Queries the relay REST API for accessible channels, subscribes to each.
 3. **Event loop** — Listens for @mention events (kind 9 with the agent's pubkey in a `#p` tag). Events queue per channel.
 4. **Prompting** — When events are pending and no prompt is in flight for that channel, drains all queued events for the oldest channel into a single batched prompt via ACP `session/prompt`.

crates/buzz-acp/src/config.rs

@@ -335,7 +335,11 @@ pub struct CliArgs {
     #[arg(long, env = "BUZZ_ACP_CHANNELS", value_delimiter = ',')]
     pub channels: Option<Vec<String>>,
 
-    #[arg(long, env = "BUZZ_ACP_NO_MENTION_FILTER")]
+    #[arg(
+        long,
+        env = "BUZZ_ACP_NO_MENTION_FILTER",
+        help = "Disable the #p mention gate (logged as mention_filter=off in the startup summary)"
+    )]
     pub no_mention_filter: bool,
 
     #[arg(long, env = "BUZZ_ACP_CONFIG", default_value = "./buzz-acp.toml")]
@@ -1108,6 +1112,9 @@ impl Config {
     }
 
     /// Human-readable summary (no secrets).
+    ///
+    /// Includes `mention_filter=on|off` so `--no-mention-filter` deployments are
+    /// distinguishable from gated `subscribe=mentions` in journal logs (#4228).
     pub fn summary(&self) -> String {
         let respond_to_detail = match &self.respond_to {
             RespondTo::Allowlist => {
@@ -1123,7 +1130,7 @@ impl Config {
             format!(" allowed_respond_to=[{}]", modes.join(","))
         };
         format!(
-            "relay={} pubkey={} agent_cmd={} {} mcp_cmd={} idle_timeout={}s max_turn={}s agents={} heartbeat={}s subscribe={:?} dedup={:?} meh={:?} ignore_self={} context_limit={} max_turns_per_session={} presence={} typing={} memory={} model={} permission_mode={} {}{}",
+            "relay={} pubkey={} agent_cmd={} {} mcp_cmd={} idle_timeout={}s max_turn={}s agents={} heartbeat={}s subscribe={:?} mention_filter={} dedup={:?} meh={:?} ignore_self={} context_limit={} max_turns_per_session={} presence={} typing={} memory={} model={} permission_mode={} {}{}",
             self.relay_url,
             self.keys.public_key().to_hex(),
             self.agent_command,
@@ -1134,6 +1141,7 @@ impl Config {
             self.agents,
             self.heartbeat_interval_secs,
             self.subscribe_mode,
+            if self.no_mention_filter { "off" } else { "on" },
             self.dedup_mode,
             self.multiple_event_handling,
             self.ignore_self,
@@ -2454,6 +2462,39 @@ channels = "ALL"
         );
     }
 
+    #[test]
+    fn test_summary_mention_filter_on_by_default() {
+        let config = test_config(SubscribeMode::Mentions);
+        let s = config.summary();
+        assert!(
+            s.contains("mention_filter=on"),
+            "default config should show mention_filter=on, got: {s}"
+        );
+    }
+
+    #[test]
+    fn test_summary_mention_filter_off_when_no_mention_filter() {
+        let mut config = test_config(SubscribeMode::Mentions);
+        config.no_mention_filter = true;
+        let s = config.summary();
+        assert!(
+            s.contains("mention_filter=off"),
+            "--no-mention-filter should show mention_filter=off, got: {s}"
+        );
+    }
+
+    #[test]
+    fn test_summary_mention_filter_distinguishes_no_mention_filter() {
+        let mut gated = test_config(SubscribeMode::Mentions);
+        let mut ungated = test_config(SubscribeMode::Mentions);
+        ungated.no_mention_filter = true;
+        assert_ne!(
+            gated.summary(),
+            ungated.summary(),
+            "gated and ungated mentions mode must produce distinct summary lines"
+        );
+    }
+
     #[test]
     fn test_validate_allowlist_valid_entries() {
         let entries = vec!["ab".repeat(32), "cd".repeat(32)];