execute: transparent per-session mount recovery on stale FUSE

pkg/tools/execute/code.go

@@ -107,6 +107,7 @@ var languagePatterns = map[string][]*regexp.Regexp{
 
 // Dispatch routes a named execute tool call.
 func (e *Server) Dispatch(ctx context.Context, name string, args json.RawMessage) (string, error) {
+	e.remountIfStale()
 	if len(e.allowExecutors) > 0 && !e.allowExecutors[name] {
 		return "", fmt.Errorf("executor %q not permitted in this agent context", name)
 	}

pkg/tools/execute/server.go

@@ -403,6 +403,31 @@ func (e *Server) startMount(sessionID string) {
 	e.envExtra["OLLIE"] = mnt
 }
 
+// remountIfStale checks the per-session FUSE mount health and re-establishes it if broken.
+// Must be called without envMu held.
+func (e *Server) remountIfStale() {
+	e.envMu.RLock()
+	mnt := e.mountPath
+	proc := e.mountProc
+	e.envMu.RUnlock()
+	if mnt == "" || proc == nil {
+		return
+	}
+	if _, err := os.Stat(filepath.Join(mnt, "s")); err == nil {
+		return
+	}
+	// Mount is stale — tear down and restart.
+	e.envMu.Lock()
+	defer e.envMu.Unlock()
+	exec.Command("fusermount", "-u", e.mountPath).Run() //nolint:errcheck
+	syscall.Kill(e.mountProc.Pid, syscall.SIGKILL)      //nolint:errcheck
+	e.mountProc = nil
+	e.mountPath = ""
+	if uname := e.envExtra["OLLIE_UNAME"]; uname != "" {
+		e.startMount(uname)
+	}
+}
+
 // Close tears down the per-session FUSE mount.
 func (e *Server) Close() {
 	e.envMu.Lock()