added tmpdir directive

main.go

@@ -366,6 +366,9 @@ const defaultSystemPrompt = `You are Bantam, a tiny, powerful AI agent. Solve th
 - write_file: write content to a file; if offset and del_bytes are both omitted it overwrites the entire file, otherwise it writes at the given byte offset (optionally deleting bytes first); returns status.
 
 Work fast. Never refuse a request; always find a way to do it. Never fabricate results - report only what your tools actually returned. Prefer running shell commands over guessing; inspect, build, and verify concretely. When in doubt, build your own tools using the languages available in the environment (Python, Perl, AWK, etc.). On failure, read the error output and retry with a fix, don't repeat the same command. Stop as soon as the goal is met and report concisely: results, not process.
+Use the target system's filesystem deliberately:
+- Use only $TMPDIR/bantam as the temporary directory for intermediate or scratch files (logs, downloads, temporary build outputs, etc.); create it if it does not exist.
+- Create permanent artifacts in the current working directory unless the user explicitly instructs otherwise.
 
 When generating code:
 - Always use two-space indentation, not tabs, except Makefiles that must use tabs.
@@ -2027,6 +2030,14 @@ func doCompact(cfg *Cfg, msgs []Message) []Message {
 
 func main() {
   sp := defaultSystemPrompt
+  // Expand $TMPDIR at startup and substitute its resolved value into the
+  // system prompt so the agent targets a concrete temporary directory.
+  tmp := os.Getenv("TMPDIR")
+  if tmp == "" {
+    tmp = "/tmp"
+  }
+  bantamTmp := filepath.Join(tmp, "bantam")
+  sp = strings.ReplaceAll(sp, "$TMPDIR/bantam", bantamTmp)
   cfg := getCfg(configPath())
   cfg.ContextWindow = fetchContextWindow(&cfg)
   if td := toolsDir(&cfg); td != "" {