diff --git a/packages.conf b/packages.conf
index 87f2d54..a670754 100644
--- a/packages.conf
+++ b/packages.conf
@@ -70,6 +70,7 @@ DEV_TOOLS=(
   asdf-vm
   base-devel
   bat
+  bun
   # Hermes' Matrix support builds python-olm, which needs clang++ and cmake
   clang
   cmake
diff --git a/sandbox/agent b/sandbox/agent
index cb80451..6917026 100755
--- a/sandbox/agent
+++ b/sandbox/agent
@@ -129,6 +129,10 @@ while IFS= read -r path; do
   case "$path" in "$HOME"/*) mkdir -p "$path" ;; esac
 done < <(jq -rs "$MERGE | .filesystem.allowWrite[]? | strings" "${ours[@]}")
 
+# srt sets TMPDIR to /tmp/claude, which nothing creates, unless told otherwise;
+# temp files then fail, and GTK aborts. /tmp is writable in every profile.
+export CLAUDE_CODE_TMPDIR=/tmp
+
 # Hermes' terminal reaches its gateway, in another sandbox, through a relay
 case "$profile" in
   hermes) exec "$srt" --settings "$settings" -- bash "$SANDBOX/hermes-bridge" "$real" "$@" ;;