bantam/main.go

// Bantam agent: tiny, powerful, DIY
// Created by Luxferre in 2026, released into the public domain

package main

import (
  "bufio"
  "bytes"
  "context"
  "encoding/json"
  "errors"
  "fmt"
  "io"
  "net"
  "net/http"
  "os"
  "os/exec"
  "path/filepath"
  "sort"
  "strconv"
  "strings"
  "time"
  "unicode/utf8"
)

const MAX_DEPTH = 5 // subagent recursion depth limit

var (
  COL   bool          // ANSI color enabled
  hist  []string      // line history (mirrors ~/.bantam_history)
  histF string        // history file path
  stdin *bufio.Reader // stdin reader for the REPL
)

type Cfg struct {
  Endpoint        string
  Model           string
  APIKey          string
  Temperature     float64
  Timeout         int
  ShellTimeout    int
  MaxALIterations int
  Stream          bool
  Color           string
}

var defCfg = Cfg{"https://opencode.ai/zen/v1", "big-pickle", "-", 0.7, 300, 120, 1000, true, "auto"}

func atoiD(s string, d int) int {
  if v, e := strconv.Atoi(strings.TrimSpace(s)); e == nil {
    return v
  }
  return d
}

func getCfg(path string) Cfg {
  cfg := defCfg
  if d, err := os.ReadFile(path); err == nil {
    for _, ln := range strings.Split(string(d), "\n") {
      ln = strings.TrimSpace(ln)
      if ln == "" || ln[0] == '#' || !strings.Contains(ln, "=") { continue }
      k, v, _ := strings.Cut(ln, "=")
      k, v = strings.TrimSpace(k), strings.TrimSpace(v)
      switch k {
      case "endpoint": cfg.Endpoint = v
      case "model": cfg.Model = v
      case "api_key": cfg.APIKey = v
      case "temperature": if f, e := strconv.ParseFloat(v, 64); e == nil { cfg.Temperature = f }
      case "timeout": cfg.Timeout = atoiD(v, cfg.Timeout)
      case "shell_timeout": cfg.ShellTimeout = atoiD(v, cfg.ShellTimeout)
      case "max_al_iterations": cfg.MaxALIterations = atoiD(v, cfg.MaxALIterations)
      case "stream": cfg.Stream = v == "true" || v == "1" || v == "yes"
      case "color": cfg.Color = v
      }
    }
  }
  if (cfg.APIKey == "" || cfg.APIKey == "-") && os.Getenv("OPENAI_API_KEY") != "" { cfg.APIKey = os.Getenv("OPENAI_API_KEY") }
  return cfg
}

const defaultSystemPrompt = `You are Bantam, a tiny, powerful AI agent. Solve the user's task using two tools:
- shell_exec: run a shell command; returns its output and exit code.
- run_subagent: delegate a sub-task to a child agent; returns its reply.

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. Delegate large or independent sub-tasks to run_subagent. Stop as soon as the goal is met and report concisely: results, not process.

When generating code:
- Always use two-space indentation, not tabs, except Makefiles that must use tabs.
- No whitespace between keywords and opening braces in C-like languages.
- Write optimally and with as few third-party dependencies as possible.
- Always test.
- No emojis in code or documentation.
- Respect AGENTS.md, GEMINI.md, CLAUDE.md contents in the project.`

func prompt(path string) string {
  if d, err := os.ReadFile(path); err == nil {
    return strings.TrimSpace(string(d))
  }
  return defaultSystemPrompt
}

func c(t string, cs ...int) string {
  if !COL || len(cs) == 0 { return t }
  s := make([]string, len(cs))
  for i, x := range cs { s[i] = strconv.Itoa(x) }
  return "\033[" + strings.Join(s, ";") + "m" + t + "\033[0m"
}

func col(cfg Cfg) bool {
  if os.Getenv("NO_COLOR") != "" || os.Getenv("BANTAM_NO_COLOR") != "" { return false }
  switch strings.ToLower(cfg.Color) {
  case "always": return true
  case "never": return false
  }
  return isTerminal(int(os.Stdout.Fd()))
}

type Message struct {
  Role             string     `json:"role"`
  Content          *string    `json:"content"`
  ReasoningContent string     `json:"reasoning_content,omitempty"`
  ToolCalls        []ToolCall `json:"tool_calls,omitempty"`
  ToolCallID       string     `json:"tool_call_id,omitempty"`
}

type ToolCall struct {
  ID       string `json:"id"`
  Type     string `json:"type"`
  Function struct {
    Name      string `json:"name"`
    Arguments string `json:"arguments"`
  } `json:"function"`
}

var TOOLS = []map[string]any{
  {"type": "function", "function": map[string]any{"name": "shell_exec", "description": "Run a shell command, return output and exit code.", "parameters": map[string]any{"type": "object", "properties": map[string]any{"command": map[string]any{"type": "string"}}, "required": []string{"command"}}}},
  {"type": "function", "function": map[string]any{"name": "run_subagent", "description": "Run a child agent with a prompt.", "parameters": map[string]any{"type": "object", "properties": map[string]any{"prompt": map[string]any{"type": "string"}}, "required": []string{"prompt"}}}},
}

func strp(s string) *string { return &s }

type streamDelta struct {
  Choices []struct {
    Delta struct {
      ReasoningContent string `json:"reasoning_content"`
      Reasoning        string `json:"reasoning"`
      Content          string `json:"content"`
      ToolCalls        []struct {
        Index    int    `json:"index"`
        ID       string `json:"id"`
        Function struct {
          Name      string `json:"name"`
          Arguments string `json:"arguments"`
        } `json:"function"`
      } `json:"tool_calls"`
    } `json:"delta"`
  } `json:"choices"`
}

func sanitizeMessages(msgs []Message) {
  for i := range msgs {
    if msgs[i].Role == "assistant" && len(msgs[i].ToolCalls) > 0 {
      for j := range msgs[i].ToolCalls {
        tc := &msgs[i].ToolCalls[j]
        astr := tc.Function.Arguments
        var a map[string]any
        if err := json.Unmarshal([]byte(astr), &a); err != nil || a == nil {
          fixed, _ := json.Marshal(map[string]string{"invalid_raw": astr})
          tc.Function.Arguments = string(fixed)
        }
      }
    }
  }
}

func isInvalidAssistantErr(err error) bool {
  s := err.Error()
  return strings.Contains(s, "Invalid assistant message") || strings.Contains(s, "content or tool_calls must be set")
}

func llm(cfg *Cfg, msgs []Message, tools []map[string]any) (Message, error) {
  sanitizeMessages(msgs)
  p := map[string]any{"model": cfg.Model, "temperature": cfg.Temperature, "messages": msgs, "stream": cfg.Stream}
  if tools != nil { p["tools"] = tools }
  body, _ := json.Marshal(p)
  client := &http.Client{Transport: &http.Transport{
    DialContext:           (&net.Dialer{Timeout: time.Duration(cfg.Timeout) * time.Second}).DialContext,
    ResponseHeaderTimeout: time.Duration(cfg.Timeout) * time.Second,
  }}
  fib := []int{1, 1, 2, 3, 5, 8, 13, 21, 34}
  pend := c("...requesting...", 1, 2)
  var resp *http.Response
  var err error
  for i := 0; i <= len(fib); i++ {
    if COL { fmt.Print("\r" + pend) } else { fmt.Println(pend) }
    req, _ := http.NewRequest("POST", strings.TrimRight(cfg.Endpoint, "/")+"/chat/completions", bytes.NewReader(body))
    req.Header.Set("Content-Type", "application/json")
    req.Header.Set("User-Agent", "Mozilla/5.0 (compatible; Bantam/1.0)")
    if cfg.APIKey != "" && cfg.APIKey != "-" { req.Header.Set("Authorization", "Bearer "+cfg.APIKey) }
    resp, err = client.Do(req)
    var is4xxClientErr bool
    if err == nil && resp.StatusCode >= 400 {
      b, _ := io.ReadAll(io.LimitReader(resp.Body, 4096))
      resp.Body.Close()
      err = fmt.Errorf("HTTP %d: %s", resp.StatusCode, strings.TrimSpace(string(b)))
      if resp.StatusCode < 500 && resp.StatusCode != 408 && resp.StatusCode != 429 {
        is4xxClientErr = true
      }
      resp = nil
    }
    if err == nil { break }
    if COL { fmt.Print("\r\033[K") }
    if is4xxClientErr {
      return Message{}, err
    }
    if i < len(fib) {
      fmt.Println(c(fmt.Sprintf("[network error: %v, retrying in %ds...]", err, fib[i]), 31))
      time.Sleep(time.Duration(fib[i]) * time.Second)
    }
  }
  if err != nil {
    if COL { fmt.Print("\r\033[K") }
    return Message{}, err
  }
  defer resp.Body.Close()
  if COL { fmt.Print("\r\033[K") }
  if !cfg.Stream {
    var cr struct {
      Choices []struct {
        Message struct {
          Message
          Reasoning string `json:"reasoning"`
        } `json:"message"`
      } `json:"choices"`
    }
    if err := json.NewDecoder(resp.Body).Decode(&cr); err != nil { return Message{}, err }
    if len(cr.Choices) == 0 { return Message{}, errors.New("empty choices in LLM response") }
    m := cr.Choices[0].Message.Message
    if m.ReasoningContent == "" { m.ReasoningContent = cr.Choices[0].Message.Reasoning }
    return m, nil
  }
  return parseStream(resp.Body)
}

func parseStream(r io.Reader) (Message, error) {
  var content, reas string
  var rh, ch bool
  tcs := map[int]*ToolCall{}
  var order []int
  sc := bufio.NewScanner(r)
  sc.Buffer(make([]byte, 0, 64*1024), 4*1024*1024)
  for sc.Scan() {
    ln := strings.TrimSpace(sc.Text())
    if !strings.HasPrefix(ln, "data:") { continue }
    data := strings.TrimSpace(ln[5:])
    if data == "[DONE]" { break }
    var d streamDelta
    if json.Unmarshal([]byte(data), &d) != nil || len(d.Choices) == 0 { continue }
    dl := d.Choices[0].Delta
    rc := dl.ReasoningContent
    if rc == "" { rc = dl.Reasoning }
    if rc != "" {
      if !rh { fmt.Println(c("--- reasoning start ---", 36)); rh = true }
      fmt.Print(c(rc, 2))
      reas += rc
    }
    if dl.Content != "" {
      if rh && !ch { fmt.Print("\n" + c("--- reasoning end ---", 36) + "\n\n") }
      ch = true
      fmt.Print(dl.Content)
      content += dl.Content
    }
    for _, tc := range dl.ToolCalls {
      t, ok := tcs[tc.Index]
      if !ok {
        t = &ToolCall{Type: "function"}
        tcs[tc.Index] = t
        order = append(order, tc.Index)
      }
      if tc.ID != "" { t.ID = tc.ID }
      if tc.Function.Name != "" { t.Function.Name += tc.Function.Name }
      if tc.Function.Arguments != "" { t.Function.Arguments += tc.Function.Arguments }
    }
  }
  if rh && !ch {
    fmt.Print("\n" + c("--- reasoning end ---", 36) + "\n")
  } else if ch {
    fmt.Print("\n")
  }
  m := Message{Role: "assistant"}
  if content != "" { m.Content = strp(content) }
  if reas != "" { m.ReasoningContent = reas }
  if len(tcs) > 0 {
    m.ToolCalls = make([]ToolCall, 0, len(order))
    for _, idx := range order { m.ToolCalls = append(m.ToolCalls, *tcs[idx]) }
  }
  return m, sc.Err()
}

func shell(cmd string, timeout int) string {
  ctx, cancel := context.WithTimeout(context.Background(), time.Duration(timeout)*time.Second)
  defer cancel()
  out, err := exec.CommandContext(ctx, "sh", "-c", cmd).CombinedOutput()
  res := strings.TrimSpace(string(out))
  if ctx.Err() == context.DeadlineExceeded {
    return fmt.Sprintf("%s\n\n[shell timeout after %ds]\nexit: -1", res, timeout)
  }
  code := 0
  if err != nil {
    if ee, ok := err.(*exec.ExitError); ok {
      code = ee.ExitCode()
    } else {
      code = -1
    }
  }
  return fmt.Sprintf("%s\n\nexit: %d", res, code)
}

func last(msgs []Message) string {
  for i := len(msgs) - 1; i >= 0; i-- {
    if msgs[i].Role == "assistant" && msgs[i].Content != nil && *msgs[i].Content != "" {
      return *msgs[i].Content
    }
  }
  return ""
}

func AL(cfg *Cfg, msgs []Message, sp string, depth int) ([]Message, error) {
  done := false
  for i := 0; i < cfg.MaxALIterations && !done; i++ {
    m, err := llm(cfg, msgs, TOOLS)
    if err != nil {
      if isInvalidAssistantErr(err) {
        stripped := false
        for j := len(msgs) - 1; j >= 0; j-- {
          if msgs[j].Role == "assistant" {
            fmt.Println(c("[stripped malformed assistant message]", 33))
            msgs = append(msgs[:j], msgs[j+1:]...)
            stripped = true
            break
          }
        }
        if stripped { continue }
      }
      return msgs, err
    }
    for j := range m.ToolCalls {
      tc := &m.ToolCalls[j]
      astr := tc.Function.Arguments
      var a map[string]any
      if err := json.Unmarshal([]byte(astr), &a); err != nil || a == nil {
        fixed, _ := json.Marshal(map[string]string{"invalid_raw": astr})
        tc.Function.Arguments = string(fixed)
      }
    }
    msgs = append(msgs, m)
    if !cfg.Stream {
      if m.ReasoningContent != "" {
        fmt.Println(c("--- reasoning start ---", 36) + "\n" + c(m.ReasoningContent, 2) + "\n" + c("--- reasoning end ---", 36))
      }
      if m.Content != nil { fmt.Println(*m.Content) }
    }
    if len(m.ToolCalls) == 0 { done = true; break }
    for _, tc := range m.ToolCalls {
      fn, astr := tc.Function.Name, tc.Function.Arguments
      fmt.Println(c(fmt.Sprintf("[tool call: %s(%s)]", fn, astr), 33))
      res, sty := "", 2
      var a map[string]any
      if err := json.Unmarshal([]byte(astr), &a); err != nil || a == nil {
        res, sty = fmt.Sprintf("[tool error: invalid JSON args for %s: %v. Raw: %q]", fn, err, astr), 31
      } else {
        switch fn {
        case "shell_exec":
          cmd, _ := a["command"].(string)
          res = shell(cmd, cfg.ShellTimeout)
        case "run_subagent":
          pr, _ := a["prompt"].(string)
          if depth >= MAX_DEPTH {
            res, sty = fmt.Sprintf("[subagent depth limit (%d) reached, child not spawned]", MAX_DEPTH), 31
          } else if subr, err := AL(cfg, []Message{{Role: "system", Content: strp(sp + "\n\nImportant: this is a child agent")}, {Role: "user", Content: strp(pr)}}, sp, depth+1); err != nil {
            res, sty = "[subagent error: "+err.Error()+"]", 31
          } else {
            res, sty = last(subr), 2
          }
        default:
          res, sty = "Unknown tool: "+fn, 31
        }
      }
      fmt.Println(c("[tool result: "+fn+"]", 32) + "\n" + c(res, sty) + "\n")
      msgs = append(msgs, Message{Role: "tool", ToolCallID: tc.ID, Content: strp(res)})
    }
  }
  if !done {
    msgs = append(msgs, Message{Role: "assistant", Content: strp(fmt.Sprintf("[max AL iterations (%d) reached]", cfg.MaxALIterations))})
  }
  return msgs, nil
}

func homeDir() string {
  if h, err := os.UserHomeDir(); err == nil && h != "" {
    return h
  }
  return "."
}

func sdir() string {
  d := filepath.Join(homeDir(), ".bantam", "sessions")
  os.MkdirAll(d, 0755)
  return d
}

type Session struct {
  ID       string    `json:"id"`
  Created  string    `json:"created"`
  Summary  string    `json:"summary"`
  Messages []Message `json:"messages"`
}

func summary(msgs []Message) string {
  for _, m := range msgs {
    if m.Role == "user" && m.Content != nil && strings.TrimSpace(*m.Content) != "" {
      t := strings.Join(strings.Fields(*m.Content), " ")
      if len(t) > 80 { t = t[:80] + "..." }
      return t
    }
  }
  return "(empty session)"
}

func fileExists(p string) bool {
  _, err := os.Stat(p)
  return err == nil
}

func saveSession(msgs []Message) (string, string) {
  d := sdir()
  base := time.Now().Format("20060102-150405")
  sid, path := base, filepath.Join(d, base+".json")
  for i := 1; fileExists(path); i++ {
    sid = fmt.Sprintf("%s-%d", base, i)
    path = filepath.Join(d, sid+".json")
  }
  s := Session{sid, time.Now().Format("2006-01-02 15:04:05"), summary(msgs), msgs}
  b, _ := json.MarshalIndent(s, "", "  ")
  os.WriteFile(path, b, 0644)
  return sid, s.Summary
}

func sessions() []Session {
  out := []Session{}
  d := filepath.Join(homeDir(), ".bantam", "sessions")
  entries, err := os.ReadDir(d)
  if err != nil {
    return out
  }
  for _, e := range entries {
    if e.IsDir() || !strings.HasSuffix(e.Name(), ".json") { continue }
    b, err := os.ReadFile(filepath.Join(d, e.Name()))
    if err != nil { continue }
    var s Session
    if json.Unmarshal(b, &s) != nil { continue }
    if s.ID == "" { s.ID = strings.TrimSuffix(e.Name(), ".json") }
    out = append(out, s)
  }
  sort.Slice(out, func(i, j int) bool { return out[i].ID > out[j].ID })
  return out
}

func loadSession(sid string) ([]Message, error) {
  ss := sessions()
  for i := range ss {
    if ss[i].ID == sid { return ss[i].Messages, nil }
  }
  var pref []*Session
  for i := range ss {
    if strings.HasPrefix(ss[i].ID, sid) { pref = append(pref, &ss[i]) }
  }
  if len(pref) == 1 { return pref[0].Messages, nil }
  if len(pref) > 1 {
    names := make([]string, len(pref))
    for i, s := range pref { names[i] = s.ID }
    return nil, fmt.Errorf("ambiguous prefix: %s", strings.Join(names, ", "))
  }
  return nil, fmt.Errorf("session not found: %s", sid)
}

func autosave(msgs []Message) {
  s := Session{"autosave", time.Now().Format("2006-01-02 15:04:05"), summary(msgs), msgs}
  b, _ := json.MarshalIndent(s, "", "  ")
  os.WriteFile(filepath.Join(sdir(), "autosave.json"), b, 0644)
}

func summarize(cfg *Cfg, msgs []Message) (string, error) {
  var sb strings.Builder
  for _, m := range msgs {
    if m.Role == "system" { continue }
    ct := ""
    if m.Content != nil { ct = *m.Content }
    if ct == "" && len(m.ToolCalls) > 0 {
      jc := make([]map[string]any, 0, len(m.ToolCalls))
      for _, tc := range m.ToolCalls {
        jc = append(jc, map[string]any{"function": map[string]any{"name": tc.Function.Name, "arguments": tc.Function.Arguments}})
      }
      b, _ := json.Marshal(jc)
      ct = string(b)
    }
    if ct == "" { continue }
    if len(ct) > 4000 { ct = ct[:4000] + "...[truncated]" }
    sb.WriteString(m.Role + ": " + ct + "\n\n")
  }
  if sb.Len() == 0 { return "", errors.New("no conversation to summarize") }
  joined := sb.String()
  if len(joined) > 100000 { joined = joined[len(joined)-100000:] + "\n...[earlier parts truncated]" }
  sys := "You are a conversation summarizer for an AI agent's context window. Summarize concisely but completely, preserving all important facts, decisions, code, errors, and the current task state, so the agent can continue the work without the original messages. Output only the summary."
  cc := *cfg
  cc.Stream = false
  m, err := llm(&cc, []Message{{Role: "system", Content: strp(sys)}, {Role: "user", Content: strp("Summarize this conversation:\n\n" + joined)}}, nil)
  if err != nil { return "", err }
  s := ""
  if m.Content != nil { s = *m.Content }
  if s == "" { s = m.ReasoningContent }
  if strings.TrimSpace(s) == "" { return "", errors.New("LLM returned an empty summary") }
  return strings.TrimSpace(s), nil
}

func compact(cfg *Cfg, msgs []Message) ([]Message, string, error) {
  if len(msgs) == 0 || msgs[0].Role != "system" {
    return msgs, "", errors.New("session has no system message")
  }
  s, err := summarize(cfg, msgs)
  if err != nil { return msgs, "", err }
  return []Message{{Role: "system", Content: msgs[0].Content}, {Role: "user", Content: strp("Summary of the previous conversation:\n" + s + "\n\nPlease continue from here.")}}, s, nil
}

func loadHistory() {
  histF = filepath.Join(homeDir(), ".bantam_history")
  b, err := os.ReadFile(histF)
  if err != nil { return }
  for _, ln := range strings.Split(string(b), "\n") {
    if ln = strings.TrimRight(ln, "\r"); ln != "" { hist = append(hist, ln) }
  }
}

func addHistory(s string) {
  if s == "" || (len(hist) > 0 && hist[len(hist)-1] == s) { return }
  hist = append(hist, s)
}

func saveHistory() {
  os.WriteFile(histF, []byte(strings.Join(hist, "\n")+"\n"), 0644)
}

func visibleLen(s string) int {
  n := 0
  for i := 0; i < len(s); {
    switch s[i] {
    case 0x1b:
      j := i + 1
      if j < len(s) && s[j] == '[' {
        j++
        for j < len(s) && !(s[j] >= 0x40 && s[j] <= 0x7e) { j++ }
        if j < len(s) { j++ }
        i = j
      } else {
        i++
      }
    case 0x01, 0x02:
      i++
    default:
      _, size := utf8.DecodeRuneInString(s[i:])
      n++
      i += size
    }
  }
  return n
}

type editor struct {
  prompt string
  buf    []rune
  pos    int
  hist   []string
  hpos   int
  draft  string
  crow   int
}

func textPos(promptLen, W int, s string, pos int) (row, col int) {
  row, col = 0, promptLen
  pend := false
  for i, r := range []rune(s) {
    if i == pos { return row, col }
    if r == '\n' {
      row++
      col = 0
      pend = false
      continue
    }
    if pend {
      row++
      col = 0
      pend = false
    }
    if col == W-1 {
      pend = true
    } else {
      col++
    }
  }
  return row, col
}

func (e *editor) draw() {
  W := termWidth()
  s := string(e.buf)
  P := visibleLen(e.prompt)
  er, _ := textPos(P, W, s, len([]rune(s)))
  pr, pc := textPos(P, W, s, e.pos)
  if e.crow > 0 { fmt.Printf("\033[%dA", e.crow) }
  fmt.Print("\r\033[J" + e.prompt + s)
  if up := er - pr; up > 0 { fmt.Printf("\033[%dA", up) }
  fmt.Print("\r")
  if pc > 0 { fmt.Printf("\033[%dC", pc) }
  e.crow = pr
}

func (e *editor) histNav(up bool) {
  if up {
    if len(e.hist) == 0 { return }
    if e.hpos < 0 {
      e.draft = string(e.buf)
      e.hpos = len(e.hist) - 1
    } else if e.hpos > 0 {
      e.hpos--
    }
    e.buf = []rune(e.hist[e.hpos])
  } else {
    if e.hpos < 0 { return }
    e.hpos++
    if e.hpos >= len(e.hist) {
      e.hpos = -1
      e.buf = []rune(e.draft)
    } else {
      e.buf = []rune(e.hist[e.hpos])
    }
  }
  e.pos = len(e.buf)
}

func readPlain(prompt string) (string, bool) {
  fmt.Print(prompt)
  line, err := stdin.ReadString('\n')
  if err != nil && line == "" { return "", false }
  return strings.TrimRight(line, "\r\n"), true
}

func readLine(prompt string) (string, bool) {
  if !isTerminal(int(os.Stdin.Fd())) { return readPlain(prompt) }
  restore, err := makeRaw(int(os.Stdin.Fd()))
  if err != nil { return readPlain(prompt) }
  defer restore()
  e := &editor{prompt: prompt, hpos: -1, hist: hist}
  for {
    e.draw()
    rn, _, err := stdin.ReadRune()
    if err != nil {
      fmt.Print("\r\n")
      return "", false
    }
    switch rn {
    case '\r':
      fmt.Print("\r\n")
      return string(e.buf), true
    case '\n':
      e.buf = append(e.buf, 0)
      copy(e.buf[e.pos+1:], e.buf[e.pos:])
      e.buf[e.pos] = '\n'
      e.pos++
    case 0x03:
      fmt.Print("\r\n")
      return "", false
    case 0x04:
      if len(e.buf) == 0 {
        fmt.Print("\r\n")
        return "", false
      }
    case 0x7f, 0x08:
      if e.pos > 0 {
        e.buf = append(e.buf[:e.pos-1], e.buf[e.pos:]...)
        e.pos--
      }
    case 0x1b:
      b1, err1 := stdin.ReadByte()
      b2, err2 := stdin.ReadByte()
      if err1 != nil || err2 != nil { continue }
      if b1 == '[' {
        switch b2 {
        case 'A':
          e.histNav(true)
        case 'B':
          e.histNav(false)
        case 'C':
          if e.pos < len(e.buf) { e.pos++ }
        case 'D':
          if e.pos > 0 { e.pos-- }
        }
      }
    default:
      if rn >= 32 {
        e.buf = append(e.buf, 0)
        copy(e.buf[e.pos+1:], e.buf[e.pos:])
        e.buf[e.pos] = rn
        e.pos++
      }
    }
  }
}

func main() {
  sp := prompt("system.txt")
  cfg := getCfg("model.cfg")
  COL = col(cfg)
  stdin = bufio.NewReader(os.Stdin)
  msgs := []Message{{Role: "system", Content: strp(sp)}}
  if len(os.Args) > 1 && os.Args[1] != "" {
    p := os.Args[1]
    data, err := os.ReadFile(p)
    if err != nil {
      fmt.Println(c("Error: file '"+p+"' not found.", 31))
      os.Exit(1)
    }
    msgs = append(msgs, Message{Role: "user", Content: strp(strings.TrimSpace(string(data)))})
    if msgs, err = AL(&cfg, msgs, sp, 0); err != nil {
      fmt.Println(c("[error: "+err.Error()+"]", 31))
      os.Exit(1)
    }
    autosave(msgs)
    return
  }
  loadHistory()
  fmt.Println(c("Bantam Agent ready", 1, 32) + c("  (Ctrl+J = new line)", 2))
  fmt.Println(c(fmt.Sprintf("endpoint: %s  model: %s  temp: %v", cfg.Endpoint, cfg.Model, cfg.Temperature), 2))
  for {
    u, ok := readLine(c("> ", 1, 36))
    if !ok {
      fmt.Println()
      break
    }
    u = strings.TrimSpace(u)
    if u == "" { continue }
    addHistory(u)
    switch {
    case u == "/quit":
      goto done
    case u == "/clear":
      msgs = []Message{{Role: "system", Content: strp(sp)}}
      autosave(msgs)
      continue
    case u == "/save":
      sid, sm := saveSession(msgs)
      fmt.Println(c("[session saved: "+sid+"]", 32) + "  " + c(sm, 2))
      continue
    case u == "/list":
      ss := sessions()
      if len(ss) == 0 {
        fmt.Println(c("No sessions saved yet.", 33))
        continue
      }
      for _, s := range ss {
        mk := c("  (autosave)", 33)
        if s.ID != "autosave" { mk = "" }
        fmt.Println(c(s.ID, 32) + mk + c(fmt.Sprintf("  %s  [%d msgs]", s.Created, len(s.Messages)), 2))
        fmt.Println("  " + c(s.Summary, 2))
      }
      continue
    case strings.HasPrefix(u, "/load"):
      parts := strings.Fields(u)
      if len(parts) < 2 {
        fmt.Println(c("Usage: /load <session-id>", 31))
        continue
      }
      lm, err := loadSession(parts[1])
      if err != nil {
        fmt.Println(c("Session not found: "+err.Error(), 31))
        continue
      }
      msgs = lm
      autosave(msgs)
      fmt.Println(c("[session loaded: "+parts[1]+"]", 32) + "  " + c(summary(msgs), 2))
      continue
    case u == "/compact":
      if len(msgs) <= 1 {
        fmt.Println(c("Nothing to compact yet.", 33))
        continue
      }
      fmt.Println(c("[compacting conversation...]", 33))
      nm, sm, err := compact(&cfg, msgs)
      if err != nil {
        fmt.Println(c("[compact failed: "+err.Error()+"]", 31))
        continue
      }
      msgs = nm
      autosave(msgs)
      fmt.Println(c(fmt.Sprintf("[compacted to %d messages]", len(msgs)), 32))
      fmt.Println(c("--- summary ---", 33) + "\n" + c(sm, 2))
      continue
    case u == "/help":
      fmt.Println(c("Bantam commands:", 1, 36))
      for _, kv := range [][2]string{{"/quit", "exit"}, {"/clear", "reset to system prompt"}, {"/save", "save session"}, {"/list", "list sessions"}, {"/load <id>", "load session"}, {"/compact", "compact context"}, {"/help", "show help"}} {
        fmt.Println(c(fmt.Sprintf("  %-12s", kv[0]), 1, 32) + kv[1])
      }
      continue
    }
    msgs = append(msgs, Message{Role: "user", Content: strp(u)})
    var err error
    if msgs, err = AL(&cfg, msgs, sp, 0); err != nil {
      fmt.Println(c("[error: "+err.Error()+"]", 31))
    }
    autosave(msgs)
  }
done:
  autosave(msgs)
  saveHistory()
}