From 7177137cde1cebd19b45cd6bea37d5412488dfe1 Mon Sep 17 00:00:00 2001
From: spoukyii <61633921+spoukyii@users.noreply.github.com>
Date: Tue, 3 Nov 2026 12:37:14 -0800
Subject: [PATCH 1/2] test(client-runtime): cover an untitled subagent prompt
 that ends on an emoji at the cut

---
 packages/client-runtime/src/state/subagentRuntime.test.ts | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/packages/client-runtime/src/state/subagentRuntime.test.ts b/packages/client-runtime/src/state/subagentRuntime.test.ts
index c40c9fe42d81e..0d65e1d36a2fd 100644
--- a/packages/client-runtime/src/state/subagentRuntime.test.ts
+++ b/packages/client-runtime/src/state/subagentRuntime.test.ts
@@ -119,6 +119,13 @@ describe("projectedSubagentsToRuntime workflow expansion", () => {
       expect(members?.[0]?.speed).toBeUndefined();
     },
   );
+
+  it("titles an untitled subagent from its prompt without splitting an emoji", () => {
+    const [untitled] = projectedSubagentsToRuntime([
+      subagent({ title: null, prompt: `${"a".repeat(76)}😀 and more work.` }),
+    ]);
+    expect(untitled?.title).toBe(`${"a".repeat(76)}...`);
+  });
 });
 
 describe("deriveWorkflowGroups over a dynamic workflow", () => {

From ebf626ee89b7b220bfe1195fb3363d1d23819b0a Mon Sep 17 00:00:00 2001
From: spoukyii <61633921+spoukyii@users.noreply.github.com>
Date: Tue, 3 Nov 2026 12:37:45 -0800
Subject: [PATCH 2/2] fix(client-runtime): untitled subagent titles no longer
 end in a broken character

A subagent with no title of its own is titled from its prompt. A prompt
longer than 80 UTF-16 code units is cut at 77 units and gets "...". When
an emoji straddled the cut, the title kept only its high surrogate and
showed a replacement character before the "...". The full title shows
in the mobile Agents sheet header of a Claude workflow that has no title
and no name yet, and in that header's screen-reader labels on web and
mobile.

The cut now steps back one unit when it would land between a high and a
low surrogate, the same check #29563 and #29163 added to thread titles.

Bug: an untitled subagent's title ends in a broken character when an emoji sits at the 77-unit cut
---
 .../client-runtime/src/state/subagentRuntime.ts   | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/packages/client-runtime/src/state/subagentRuntime.ts b/packages/client-runtime/src/state/subagentRuntime.ts
index e3807362fbdf6..df6e4ce6e8870 100644
--- a/packages/client-runtime/src/state/subagentRuntime.ts
+++ b/packages/client-runtime/src/state/subagentRuntime.ts
@@ -175,6 +175,17 @@ function workflowMembersToRuntime(
   });
 }
 
+function promptTitle(prompt: string): string {
+  if (prompt.length <= 80) return prompt;
+  let end = 77;
+  const previous = prompt.charCodeAt(end - 1);
+  const next = prompt.charCodeAt(end);
+  if (previous >= 0xd800 && previous <= 0xdbff && next >= 0xdc00 && next <= 0xdfff) {
+    end -= 1;
+  }
+  return `${prompt.slice(0, end)}...`;
+}
+
 export function projectedSubagentsToRuntime(
   subagents: ReadonlyArray<{
     readonly id: string;
@@ -200,9 +211,7 @@ export function projectedSubagentsToRuntime(
     const coordinator = {
       id: subagent.id,
       kind: workflow === undefined ? "subagent" : "workflow",
-      title:
-        subagent.title ??
-        (subagent.prompt.length > 80 ? `${subagent.prompt.slice(0, 77)}...` : subagent.prompt),
+      title: subagent.title ?? promptTitle(subagent.prompt),
       role: null,
       model: subagent.model,
       effort: null,