Show agent liveness, stuck/zombie detection and parse errors in admin

internal/claude/session.go

@@ -15,6 +15,7 @@ import (
 	"os"
 	"os/exec"
 	"sync"
+	"sync/atomic"
 	"time"
 
 	"g.fc.run/misc/byre/internal/mcp"
@@ -39,6 +40,21 @@ type Options struct {
 	Hooks       map[string][]HookMatcher
 	MCPServers  []*mcp.Server
 	Transcript  io.Writer
+	OnBadLine   func(line []byte, reason string)
+}
+
+var knownTypes = map[string]bool{
+	"assistant":              true,
+	"user":                   true,
+	"result":                 true,
+	"system":                 true,
+	"stream_event":           true,
+	"tool_progress":          true,
+	"rate_limit_event":       true,
+	"control_request":        true,
+	"control_response":       true,
+	"control_cancel_request": true,
+	"keep_alive":             true,
 }
 
 type Event struct {
@@ -175,6 +191,9 @@ type Session struct {
 
 	idMu sync.Mutex
 	id   string
+
+	onBadLine func(line []byte, reason string)
+	lastLine  atomic.Int64
 }
 
 type controlResult struct {
@@ -200,7 +219,9 @@ func Start(ctx context.Context, opts Options) (*Session, error) {
 		hooks:      map[string]HookFunc{},
 		servers:    map[string]*mcp.Server{},
 		id:         initialID(opts),
+		onBadLine:  opts.OnBadLine,
 	}
+	s.lastLine.Store(time.Now().UnixNano())
 
 	args, err := s.buildArgs(opts)
 	if err != nil {
@@ -355,6 +376,23 @@ func (s *Session) Done() <-chan struct{} {
 	return s.done
 }
 
+func (s *Session) Pid() int {
+	return s.cmd.Process.Pid
+}
+
+func (s *Session) LastLine() time.Time {
+	return time.Unix(0, s.lastLine.Load())
+}
+
+func (s *Session) Exited() bool {
+	select {
+	case <-s.done:
+		return true
+	default:
+		return false
+	}
+}
+
 func (s *Session) ID() string {
 	s.idMu.Lock()
 	defer s.idMu.Unlock()
@@ -493,8 +531,14 @@ func (s *Session) readLoop(stdout io.Reader) {
 	r := bufio.NewReader(stdout)
 	for {
 		line, err := r.ReadBytes('\n')
-		if len(line) > 1 && line[0] == '{' {
-			s.handleLine(line[:len(line)-1])
+		line = bytes.TrimRight(line, "\r\n")
+		if len(line) > 0 {
+			s.lastLine.Store(time.Now().UnixNano())
+		}
+		if len(line) > 0 && line[0] == '{' {
+			s.handleLine(line)
+		} else if len(line) > 0 {
+			s.badLine(line, "not a JSON object")
 		}
 		if err != nil {
 			if err != io.EOF {
@@ -510,10 +554,14 @@ func (s *Session) handleLine(line []byte) {
 	env := envelope{}
 	err := json.Unmarshal(line, &env)
 	if err != nil {
-		slog.Error("parse claude message", "err", err, "line", string(line))
+		s.badLine(line, err.Error())
 		return
 	}
 
+	if !knownTypes[env.Type] {
+		s.badLine(line, fmt.Sprintf("unrecognised type %q", env.Type))
+	}
+
 	s.writeMu.Lock()
 	if env.Type == "control_response" {
 		s.learnScrub(env.Response)
@@ -545,6 +593,13 @@ func (s *Session) handleLine(line []byte) {
 	s.events <- Event{Type: env.Type, Subtype: env.Subtype, Raw: append(json.RawMessage{}, line...), Read: read}
 }
 
+func (s *Session) badLine(line []byte, reason string) {
+	slog.Warn("bad claude line", "reason", reason, "line", string(line))
+	if s.onBadLine != nil {
+		s.onBadLine(line, reason)
+	}
+}
+
 func (s *Session) learnScrub(raw json.RawMessage) {
 	resp := struct {
 		Response struct {