From 71457fa10074b3b7cd9e87a96a82bf0b786f442c Mon Sep 17 00:00:00 2001
From: Ganghyun Kim <58307870+kyleok@users.noreply.github.com>
Date: Sun, 25 Jan 2026 04:52:34 +0900
Subject: [PATCH] fix(tui): strip <final> tags in TUI display (#1613)

Add <final> tag handling to stripThinkingTags() to prevent reasoning-tag
provider responses from leaking incomplete tags during streaming.

When using providers like google-antigravity/*, ollama, or minimax, the
model wraps responses in <think>...</think> and <final>...</final> tags.
The TUI was only stripping <think> tags, causing <final> to leak through
and display as the response ~50% of the time.

This is a defense-in-depth fix for the TUI layer.

Fixes: #1561

Co-authored-by: Claude Code <noreply@anthropic.com>
---
 ui/src/ui/format.test.ts | 17 +++++++++++++++++
 ui/src/ui/format.ts      |  6 +++---
 2 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/ui/src/ui/format.test.ts b/ui/src/ui/format.test.ts
index dc785481c..d7acecebb 100644
--- a/ui/src/ui/format.test.ts
+++ b/ui/src/ui/format.test.ts
@@ -21,5 +21,22 @@ describe("stripThinkingTags", () => {
   it("returns original text when no tags exist", () => {
     expect(stripThinkingTags("Hello")).toBe("Hello");
   });
+
+  it("strips <final>…</final> segments", () => {
+    const input = "<final>\n\nHello there\n\n</final>";
+    expect(stripThinkingTags(input)).toBe("Hello there\n\n");
+  });
+
+  it("strips mixed <think> and <final> tags", () => {
+    const input = "<think>reasoning</think>\n\n<final>Hello</final>";
+    expect(stripThinkingTags(input)).toBe("Hello");
+  });
+
+  it("handles incomplete <final tag gracefully", () => {
+    // When streaming splits mid-tag, we may see "<final" without closing ">"
+    // This should not crash and should handle gracefully
+    expect(stripThinkingTags("<final\nHello")).toBe("<final\nHello");
+    expect(stripThinkingTags("Hello</final>")).toBe("Hello");
+  });
 });
 
diff --git a/ui/src/ui/format.ts b/ui/src/ui/format.ts
index 8e52af89a..e8f4e4991 100644
--- a/ui/src/ui/format.ts
+++ b/ui/src/ui/format.ts
@@ -67,9 +67,9 @@ export function parseList(input: string): string[] {
     .filter((v) => v.length > 0);
 }
 
-const THINKING_TAG_RE = /<\s*\/?\s*think(?:ing)?\s*>/gi;
-const THINKING_OPEN_RE = /<\s*think(?:ing)?\s*>/i;
-const THINKING_CLOSE_RE = /<\s*\/\s*think(?:ing)?\s*>/i;
+const THINKING_TAG_RE = /<\s*\/?\s*(?:think(?:ing)?|final)\s*>/gi;
+const THINKING_OPEN_RE = /<\s*(?:think(?:ing)?|final)\s*>/i;
+const THINKING_CLOSE_RE = /<\s*\/\s*(?:think(?:ing)?|final)\s*>/i;
 
 export function stripThinkingTags(value: string): string {
   if (!value) return value;