diff --git a/bin/claude-rc b/bin/claude-rc
index 2c5b2eb..7adaf00 100755
--- a/bin/claude-rc
+++ b/bin/claude-rc
@@ -64,7 +64,11 @@ case "$cmd" in
         dir=$(reg_dir "$name")
         [ -n "$dir" ] || { echo "claude-rc: '$name' not in $REG" >&2; exit 1; }
         cd "$dir" || { echo "claude-rc: dir missing: $dir" >&2; exit 1; }
-        exec claude rc --name "$name"
+        # --spawn is mandatory for headless operation: without it `claude rc`
+        # prompts "Choose [1/2]" for spawn mode and blocks forever. Default to
+        # worktree (isolated session per spawn — safe for concurrent agents);
+        # override per-instance with CLAUDE_RC_SPAWN=same-dir|session.
+        exec claude rc --name "$name" --spawn "${CLAUDE_RC_SPAWN:-worktree}"
         ;;
     list|ls)
         printf '%-16s %-10s %s\n' NAME STATE DIR