tool call vis improvement

main.go

@@ -1136,24 +1136,49 @@ func parseStream(ctx context.Context, r io.Reader) (Message, Usage, error) {
   var order []int
   var toolCallsShown bool
 
-  // Live, in-place display of tool calls as they stream in, so the user sees
+  // Progressive, per-token display of tool calls as they stream in, so the
-  // the invocation text being shaped instead of a blank pause. Only used when
+  // user watches the invocation being shaped token by token (like reasoning
-  // stdout is a terminal; piped/redirected output is left untouched.
+  // text) instead of a blank pause. Only used when stdout is a terminal;
+  // piped/redirected output is left untouched. Each fragment is appended
+  // directly to the terminal; the closing ")" is emitted only when the call is
+  // finalized, so the visible text is always a true prefix of the final form.
   tty := isTerminal(int(os.Stdout.Fd()))
   liveIdx := -1
-  liveActive := false
+  livePrinted := ""
-  showLive := func() {
+  liveTarget := func(t *ToolCall, closed bool) string {
+    s := "[tool call: " + t.Function.Name
+    if closed || t.Function.Arguments != "" {
+      s += "(" + filterText(t.Function.Arguments)
+      if closed { s += ")]" }
+    }
+    return s
+  }
+  finishLive := func(closed bool) {
+    if liveIdx < 0 { return }
+    target := liveTarget(tcs[liveIdx], closed)
+    if len(target) > len(livePrinted) {
+      fmt.Print(c(target[len(livePrinted):], 33))
+    }
+    if closed { fmt.Print("\n") }
+    livePrinted = ""
+    liveIdx = -1
+  }
+  stepLive := func() {
     if !tty || len(order) == 0 { return }
     cur := order[len(order)-1]
-    txt := fmt.Sprintf("[tool call: %s(%s)]", tcs[cur].Function.Name, filterText(tcs[cur].Function.Arguments))
+    if liveIdx != -1 && liveIdx != cur {
-    if liveActive && liveIdx != cur {
+      // A different tool call is now being shaped: finalize the previous one.
-      // A new tool call started; finalize the previous live line.
+      finishLive(true)
-      fmt.Print("\n")
-      liveActive = false
     }
-    fmt.Print("\r\033[K" + c(txt, 33))
+    if liveIdx == -1 {
-    liveActive = true
       liveIdx = cur
+      livePrinted = ""
+    }
+    target := liveTarget(tcs[cur], false)
+    if len(target) > len(livePrinted) {
+      fmt.Print(c(target[len(livePrinted):], 33))
+      livePrinted = target
+    }
     toolCallsShown = true
   }
 
@@ -1247,7 +1272,7 @@ func parseStream(ctx context.Context, r io.Reader) (Message, Usage, error) {
         if tc.Function.Name != "" { t.Function.Name += tc.Function.Name }
         if tc.Function.Arguments != "" { t.Function.Arguments += tc.Function.Arguments }
       }
-      showLive()
+      stepLive()
     }
   }
   if err := ctx.Err(); err != nil { return Message{}, lastUsage, err }
@@ -1260,10 +1285,9 @@ func parseStream(ctx context.Context, r io.Reader) (Message, Usage, error) {
       fmt.Println(renderMDLine(lineBuf, &mdSt))
     }
   }
-  if liveActive {
+  if liveIdx >= 0 {
     // Finalize the in-progress tool-call line so following output starts fresh.
-    fmt.Print("\n")
+    finishLive(true)
-    liveActive = false
   }
   if inReasoning {
     fmt.Print("\n" + c("--- reasoning end ---", 36) + "\n")