streaming: tool as first-class streaming role in chat log

session/session.go

@@ -127,7 +127,8 @@ func (sess *Session) EnsureTrailingNewline() {
 // startEventLog subscribes to the agent's "event" bus topic and writes
 // all events to the session chat log.
 func (sess *Session) startEventLog() {
-	streamingRole := "" // tracks current streaming role ("assistant" or "reasoning")
+	streamingRole := "" // tracks current streaming role ("assistant", "reasoning", or "tool")
+
 	sess.Core.Bus().Subscribe("event", func(ev agent.Event) {
 		switch ev.Role {
 		case "assistant", "reasoning":
@@ -144,6 +145,40 @@ func (sess *Session) startEventLog() {
 				streamingRole = ev.Role
 			}
 			sess.AppendLog(FormatEvent(ev))
+
+		case "tool":
+			// Tool events can stream (multiple chunks with same name) or
+			// arrive as a single final result. Write header on first chunk,
+			// then append content. Duplicate final result is suppressed.
+			if streamingRole == "tool" {
+				// Continuation of streaming tool output.
+				if ev.Content != "" {
+					sess.AppendLog([]byte(ev.Content))
+				} else {
+					// Empty content = final result marker; streaming is done.
+					sess.AppendLog([]byte("\n"))
+					streamingRole = ""
+				}
+				return
+			}
+			if streamingRole != "" {
+				sess.AppendLog([]byte("\n"))
+				streamingRole = ""
+			}
+			// First tool event — write header and start streaming.
+			sess.AppendLog([]byte("[tool:" + ev.Name + "]\n"))
+			if ev.Content != "" {
+				sess.AppendLog([]byte(ev.Content))
+			}
+			streamingRole = "tool"
+
+		case "call":
+			if streamingRole != "" {
+				sess.AppendLog([]byte("\n"))
+				streamingRole = ""
+			}
+			sess.AppendLog(FormatEvent(ev))
+
 		default:
 			if streamingRole != "" {
 				sess.AppendLog([]byte("\n"))
@@ -1190,8 +1225,6 @@ func FormatEvent(ev agent.Event) []byte {
 		return []byte("[stalled]\n")
 	case "maxsteps":
 		return []byte("[maxsteps]\n" + ev.Content + "\n")
-	case "exec":
-		return []byte("[exec]\n" + ev.Content + "\n")
 	default:
 		return nil
 	}