fix: call matrix::sync_agent on rebuild, mirrors startup sweep

hive-c0re/src/auto_update.rs

@@ -119,6 +119,12 @@ pub async fn rebuild_agent(
             // (e.g. first-spawn seeding failed transiently) without
             // requiring a full hive-c0re restart.
             crate::forge::sync_agent(name, crate::forge::core_token().as_deref()).await;
+            // Mirror the matrix side of the startup sweep: if hive-matrix
+            // is present, ensure this agent has a registered user + token.
+            // Idempotent (skips if token file already exists). Keeps the
+            // rebuild path equivalent to the startup sweep for newly-spawned
+            // agents that missed ensure_all().
+            crate::matrix::sync_agent_standalone(name).await;
             // Wake the agent on its next turn so claude sees a
             // "you were rebuilt — check /state/ for notes, --continue
             // session intact" hint. Covers dashboard rebuild, admin

hive-c0re/src/matrix.rs

@@ -280,6 +280,35 @@ pub async fn sync_agent(client: &reqwest::Client, name: &str, register_token: &s
     }
 }
 
+/// Standalone per-agent sync that handles its own setup: checks if
+/// hive-matrix is present, reads the registration token, and builds
+/// an HTTP client before delegating to [`sync_agent`]. Mirrors the
+/// setup in [`ensure_all`] so the rebuild path and the startup sweep
+/// stay equivalent. No-op when the matrix container is absent.
+pub async fn sync_agent_standalone(name: &str) {
+    if !is_present().await {
+        return;
+    }
+    let register_token = match ensure_register_token() {
+        Ok(t) => t,
+        Err(e) => {
+            tracing::warn!(%name, error = ?e, "matrix: ensure_register_token failed");
+            return;
+        }
+    };
+    let client = match reqwest::Client::builder()
+        .timeout(std::time::Duration::from_secs(HTTP_TIMEOUT_SECS))
+        .build()
+    {
+        Ok(c) => c,
+        Err(e) => {
+            tracing::warn!(%name, error = ?e, "matrix: build HTTP client failed");
+            return;
+        }
+    };
+    sync_agent(&client, name, &register_token).await;
+}
+
 /// Sweep every existing container (manager + sub-agents) and ensure
 /// each has a matrix user + token on the local homeserver. Called once
 /// at hive-c0re startup, alongside `forge::ensure_all`. No-op when the