refactor(ai-chat): drop thinking-token text from typing indicator

The live typing placeholder now shows only the bouncing dots; the
"Thinking… · N tokens" line is removed. Clean up the dead plumbing:

- typing-indicator: remove thinkingTokens prop, thinkingLine and the
  <Text> line; keep the animated dots and the dimmed name label
- message-list: remove tailThinkingTokens helper, the thinkingTokens
  prop pass-through, and the now-unused liveTurnTokens import
- delete tail-thinking-tokens.test.ts (tested the removed helper)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

apps/client/src/features/ai-chat/components/message-list.tsx

@@ -6,7 +6,6 @@ import MessageItem from "@/features/ai-chat/components/message-item.tsx";
 import TypingIndicator from "@/features/ai-chat/components/typing-indicator.tsx";
 import { isToolPart, toolRunState, ToolUiPart } from "@/features/ai-chat/utils/tool-parts.tsx";
 import { assistantMessageHasVisibleContent } from "@/features/ai-chat/utils/message-content.ts";
-import { liveTurnTokens } from "@/features/ai-chat/utils/count-stream-tokens.ts";
 import classes from "@/features/ai-chat/components/ai-chat.module.css";
 
 interface MessageListProps {
@@ -95,19 +94,6 @@ export function typingIndicatorShowsName(messages: UIMessage[]): boolean {
   return !assistantMessageHasVisibleContent(last);
 }
 
-/**
- * The live thinking-token count to show on the standalone typing indicator. It
- * is the reasoning split of the tail assistant message (estimate while streaming,
- * authoritative once the server attaches usage at a step/turn boundary). Returns
- * 0 when the turn has produced no reasoning yet — the indicator then shows the
- * plain "Thinking…" line.
- */
-export function tailThinkingTokens(messages: UIMessage[]): number {
-  const last = messages[messages.length - 1];
-  if (!last || last.role !== "assistant") return 0;
-  return liveTurnTokens(last).reasoning;
-}
-
 /**
  * Scrollable transcript. Auto-scrolls to the newest message as it streams in,
  * but only while the user is pinned to the bottom — if they scrolled up to read
@@ -208,7 +194,6 @@ export default function MessageList({
           <TypingIndicator
             assistantName={assistantName}
             showName={typingIndicatorShowsName(messages)}
-            thinkingTokens={tailThinkingTokens(messages)}
           />
         )}
       </Stack>

apps/client/src/features/ai-chat/components/tail-thinking-tokens.test.ts

@@ -1,50 +0,0 @@
-import { describe, expect, it } from "vitest";
-import type { UIMessage } from "@ai-sdk/react";
-import { tailThinkingTokens } from "@/features/ai-chat/components/message-list.tsx";
-
-/**
- * Pure-helper tests for `tailThinkingTokens`: the live thinking-token count the
- * standalone typing indicator shows. It is the reasoning split of the tail
- * assistant message (estimate while streaming, authoritative once usage arrives).
- */
-const msg = (
-  role: "user" | "assistant",
-  parts: unknown[],
-  metadata?: unknown,
-): UIMessage =>
-  ({ id: Math.random().toString(), role, parts, metadata }) as UIMessage;
-
-describe("tailThinkingTokens", () => {
-  it("is 0 when there are no messages", () => {
-    expect(tailThinkingTokens([])).toBe(0);
-  });
-
-  it("is 0 when the tail message is the user's", () => {
-    expect(tailThinkingTokens([msg("user", [{ type: "text", text: "q" }])])).toBe(0);
-  });
-
-  it("is 0 when the assistant has produced no reasoning yet", () => {
-    expect(
-      tailThinkingTokens([msg("assistant", [{ type: "text", text: "answer" }])]),
-    ).toBe(0);
-  });
-
-  it("estimates reasoning tokens from streamed reasoning text", () => {
-    // 8 chars -> 2 tokens.
-    expect(
-      tailThinkingTokens([
-        msg("assistant", [{ type: "reasoning", text: "12345678" }]),
-      ]),
-    ).toBe(2);
-  });
-
-  it("uses authoritative usage.reasoningTokens once the server attaches it", () => {
-    expect(
-      tailThinkingTokens([
-        msg("assistant", [{ type: "reasoning", text: "x" }], {
-          usage: { outputTokens: 100, reasoningTokens: 42 },
-        }),
-      ]),
-    ).toBe(42);
-  });
-});

apps/client/src/features/ai-chat/components/typing-indicator.tsx

@@ -16,12 +16,6 @@ interface TypingIndicatorProps {
    * assistant row above already shows the same name, to avoid a duplicate label.
    */
   showName?: boolean;
-  /**
-   * Live thinking/reasoning token count for the in-flight turn. When > 0 the
-   * typing line becomes `Thinking… · {count} tokens` (like Claude Code). Omitted
-   * / 0 keeps the plain `Thinking…` line.
-   */
-  thinkingTokens?: number;
 }
 
 /**
@@ -32,18 +26,12 @@ interface TypingIndicatorProps {
  *
  * Mirrors the assistant row layout in MessageItem (the dimmed label), so it reads
  * as the assistant's bubble taking shape. The dimmed label uses the configured
- * identity name when provided (otherwise the generic "AI agent"), while the
- * typing line is always the generic "Thinking…" (it never includes the
- * role/identity name).
+ * identity name when provided (otherwise the generic "AI agent"); below it the
+ * animated dots stand in for the nascent bubble until content arrives.
  */
-export default function TypingIndicator({ assistantName, showName = true, thinkingTokens }: TypingIndicatorProps) {
+export default function TypingIndicator({ assistantName, showName = true }: TypingIndicatorProps) {
   const { t } = useTranslation();
   const name = resolveAssistantName(assistantName);
-  // Show the running thinking-token count only once there is something to count.
-  const thinkingLine =
-    thinkingTokens && thinkingTokens > 0
-      ? t("Thinking… · {{count}} tokens", { count: thinkingTokens })
-      : t("Thinking…");
 
   return (
     <Box className={classes.messageRow}>
@@ -58,9 +46,6 @@ export default function TypingIndicator({ assistantName, showName = true, thinki
           <span />
           <span />
         </span>
-        <Text size="sm" c="dimmed">
-          {thinkingLine}
-        </Text>
       </Group>
     </Box>
   );