diff --git a/swarm-controller/src/main.rs b/swarm-controller/src/main.rs
index d6230d84..581116c9 100644
--- a/swarm-controller/src/main.rs
+++ b/swarm-controller/src/main.rs
@@ -12,6 +12,7 @@
 //! Distinct from `hive-c0re`, which is per-hive: c0re owns the agents on
 //! one host, this owns what is true across hives.
 
+use std::os::unix::fs::PermissionsExt as _;
 use std::path::PathBuf;
 
 use anyhow::{Context, Result};
@@ -67,6 +68,18 @@ async fn main() -> Result<()> {
 
     let listener = tokio::net::UnixListener::bind(&path)
         .with_context(|| format!("binding {}", path.display()))?;
+
+    // `bind` leaves the socket 0755, and connecting needs write — the
+    // gateway's nginx is a different user, so it would be locked out.
+    // 0666 matches how hive-c0re publishes the per-agent sockets
+    // (`socket_server::start`), and rests on the same argument: **the
+    // containing directory is the access control, not the socket mode.**
+    // This directory holds one socket and is bind-mounted into exactly
+    // one container. That is also why it must not be shared with
+    // hive-c0re's `/run/hyperhive` — with a 0666 socket, a directory
+    // that carries more than it should is the whole vulnerability.
+    std::fs::set_permissions(&path, std::fs::Permissions::from_mode(0o666))
+        .with_context(|| format!("chmod {}", path.display()))?;
     tracing::info!(socket = %path.display(), "swarm-controller listening");
 
     let app = Router::new().route("/health", get(health));