diff --git a/apps/web/src/components/chat/turnDetailAnnouncement.test.ts b/apps/web/src/components/chat/turnDetailAnnouncement.test.ts
index c5eaa080ff921..99fcfcd4fd864 100644
--- a/apps/web/src/components/chat/turnDetailAnnouncement.test.ts
+++ b/apps/web/src/components/chat/turnDetailAnnouncement.test.ts
@@ -133,6 +133,11 @@ describe("turnDetail", () => {
     expect(turnDetail(entries, undefined, null).activity).toBe(activity);
   });
 
+  it("cuts a long step without splitting an emoji", () => {
+    const edit = work("edit", { itemType: "file_change", changedFiles: [`${"a".repeat(111)}😀z`] });
+    expect(turnDetail([prompt, edit], undefined, null).activity).not.toMatch(/[\uD800-\uDFFF]/u);
+  });
+
   it.each<{
     name: string;
     entries: ReadonlyArray<TimelineEntry>;
@@ -297,6 +302,12 @@ describe("nextTurnDetailAnnouncement", () => {
     ).toEqual(["T3 Code: Tests pass in web. See the docs"]);
   });
 
+  it("cuts a long message without splitting an emoji", () => {
+    const long = { ...said("long", true, true), text: `${"a".repeat(1999)}😀z` };
+    const [spoken] = speak("messages", [frame(null), frame(null, [long])]);
+    expect(spoken).not.toMatch(/[\uD800-\uDFFF]/u);
+  });
+
   it("says a step again after waiting on the user", () => {
     expect(
       speak("everything", [
diff --git a/apps/web/src/components/chat/turnDetailAnnouncement.ts b/apps/web/src/components/chat/turnDetailAnnouncement.ts
index 0728674ad8744..acebdfb9f7003 100644
--- a/apps/web/src/components/chat/turnDetailAnnouncement.ts
+++ b/apps/web/src/components/chat/turnDetailAnnouncement.ts
@@ -34,6 +34,13 @@ const ACTIVITY_MAX_LENGTH = 120;
 // Parsing is synchronous, and nobody listens to a longer message through a live region.
 const MESSAGE_MAX_LENGTH = 2_000;
 
+/** The first `maxLength` code points of `text`, or null when it has no more than that. */
+function cutText(text: string, maxLength: number): string | null {
+  if (text.length <= maxLength) return null;
+  const characters = Array.from(text);
+  return characters.length > maxLength ? characters.slice(0, maxLength).join("") : null;
+}
+
 // On screen these labels are a path or a query beside an icon.
 function withVerb(work: WorkLogEntry, label: string) {
   if (work.itemType === "file_change") return `Editing ${label}`;
@@ -66,7 +73,8 @@ function stepLabel(work: WorkLogEntry, workspaceRoot: string | undefined): strin
   const label = liveWorkEntryLabel(work, workspaceRoot, true).replace(/\s+/g, " ").trim();
   if (label === "") return null;
   const spoken = withVerb(work, label);
-  return spoken.length > ACTIVITY_MAX_LENGTH ? `${spoken.slice(0, ACTIVITY_MAX_LENGTH)}…` : spoken;
+  const cut = cutText(spoken, ACTIVITY_MAX_LENGTH);
+  return cut === null ? spoken : `${cut}…`;
 }
 
 /**
@@ -189,11 +197,12 @@ export function nextTurnDetailAnnouncement(
           previous.messages.get(message.id) !== true &&
           (message.fresh || previous.messages.has(message.id)),
       )
-      .map((message) =>
-        message.text.length > MESSAGE_MAX_LENGTH
-          ? `${markdownPlainText(message.text.slice(0, MESSAGE_MAX_LENGTH))} More in the thread.`
-          : markdownPlainText(message.text),
-      )
+      .map((message) => {
+        const cut = cutText(message.text, MESSAGE_MAX_LENGTH);
+        return cut === null
+          ? markdownPlainText(message.text)
+          : `${markdownPlainText(cut)} More in the thread.`;
+      })
       .filter((text) => text !== "")
       .map((text) => `${MESSAGE_AUTHOR}: ${text}`),
     activity: