Improve built-in terminal reliability and remote replay performance

apps/app/package.json

@@ -75,6 +75,7 @@
     "@tiptap/starter-kit": "^3.26.0",
     "@tiptap/suggestion": "^3.26.0",
     "@xterm/addon-fit": "^0.11.0",
+    "@xterm/addon-unicode11": "^0.9.0",
     "@xterm/addon-web-links": "^0.12.0",
     "@xterm/xterm": "^6.0.0",
     "ansi-to-html": "^0.7.2",
@@ -127,10 +128,10 @@
     "@types/node": "^22.0.0",
     "@types/react": "^19.0.0",
     "@types/react-dom": "^19.0.0",
-    "bb-plugin-automations": "workspace:*",
     "@typescript-eslint/parser": "^8.63.0",
     "@vitejs/plugin-react": "^6.0.1",
     "babel-plugin-react-compiler": "^1.0.0",
+    "bb-plugin-automations": "workspace:*",
     "eslint": "^9.39.3",
     "eslint-plugin-react-hooks": "^7.0.1",
     "mdast-util-to-hast": "^13.2.1",

apps/app/src/components/thread/terminal/ThreadTerminalContent.tsx

@@ -123,6 +123,7 @@ export function ThreadTerminalContent({
       isPanelOpen={controller.isPanelOpen}
       onOpenLink={onOpenLink}
       onSelectionAddToChat={onSelectionAddToChat}
+      onSessionChange={controller.handleActiveTerminalSessionChange}
       onTitleChange={controller.handleActiveTerminalTitleChange}
       onUserInput={controller.handleActiveTerminalUserInput}
       session={controller.activeSession}

apps/app/src/components/thread/terminal/ThreadTerminalPanel.stories.tsx

@@ -76,6 +76,8 @@ function noopAction(): void {}
 
 function noopTerminalIdAction(_terminalId: string): void {}
 
+function noopSessionChange(_session: TerminalSession): void {}
+
 function noopTitleChange(_title: string): void {}
 
 function makeController({
@@ -98,6 +100,7 @@ function makeController({
     canCreateTerminal,
     closingTerminalId,
     emptyTerminalMessage,
+    handleActiveTerminalSessionChange: noopSessionChange,
     handleActiveTerminalTitleChange: noopTitleChange,
     handleActiveTerminalUserInput: noopAction,
     handleClosePanel: noopAction,
@@ -237,10 +240,7 @@ function RunningTerminalPreview() {
 export function Overview() {
   return (
     <StoryCard labelWidth="190px">
-      <StoryRow
-        label="disconnected"
-        hint="Replacement available."
-      >
+      <StoryRow label="disconnected" hint="Replacement available.">
         <TerminalContentStage controller={disconnectedController} />
       </StoryRow>
       <StoryRow
@@ -252,7 +252,10 @@ export function Overview() {
       <StoryRow label="starting" hint="Session exists but is not running yet.">
         <TerminalContentStage controller={startingController} />
       </StoryRow>
-      <StoryRow label="exited" hint="Terminal has ended and cannot accept input.">
+      <StoryRow
+        label="exited"
+        hint="Terminal has ended and cannot accept input."
+      >
         <TerminalContentStage controller={exitedController} />
       </StoryRow>
       <StoryRow label="empty" hint="Right panel tab with no visible sessions.">

apps/app/src/components/thread/terminal/ThreadTerminalView.test.ts

@@ -1,5 +1,57 @@
 import { describe, expect, it, vi } from "vitest";
-import { buildTerminalThemeFromCssColors } from "./ThreadTerminalView";
+import { TERMINAL_DATA_MAX_BYTES } from "@bb/domain";
+import {
+  buildTerminalThemeFromCssColors,
+  decodeTerminalOutputBytes,
+  encodeTerminalInputChunks,
+  TERMINAL_ALLOW_PROPOSED_API,
+  TERMINAL_FONT_FAMILY,
+  TERMINAL_UNICODE_VERSION,
+} from "./ThreadTerminalView";
+
+describe("terminal output encoding", () => {
+  it("splits large paste input at the wire limit without losing UTF-8 bytes", () => {
+    const input = `${"a".repeat(TERMINAL_DATA_MAX_BYTES - 1)}🙂tail`;
+    const chunks = encodeTerminalInputChunks(input);
+    const decoded = Buffer.concat(
+      chunks.map((chunk) => Buffer.from(chunk, "base64")),
+    );
+
+    expect(chunks).toHaveLength(2);
+    expect(
+      chunks.every(
+        (chunk) =>
+          Buffer.from(chunk, "base64").byteLength <= TERMINAL_DATA_MAX_BYTES,
+      ),
+    ).toBe(true);
+    expect(decoded.toString("utf8")).toBe(input);
+  });
+
+  it("keeps UTF-8 bytes intact when a glyph spans output chunks", () => {
+    const encoded = new TextEncoder().encode("🙂");
+    const first = decodeTerminalOutputBytes(
+      Buffer.from(encoded.subarray(0, 2)).toString("base64"),
+    );
+    const second = decodeTerminalOutputBytes(
+      Buffer.from(encoded.subarray(2)).toString("base64"),
+    );
+    const decoder = new TextDecoder();
+
+    expect(
+      decoder.decode(first, { stream: true }) + decoder.decode(second),
+    ).toBe("🙂");
+  });
+
+  it("enables the proposed xterm API required by the Unicode addon", () => {
+    expect(TERMINAL_ALLOW_PROPOSED_API).toBe(true);
+    expect(TERMINAL_UNICODE_VERSION).toBe("11");
+  });
+
+  it("prefers installed Nerd Font families before system monospace fallbacks", () => {
+    expect(TERMINAL_FONT_FAMILY).toContain("Nerd Font");
+    expect(TERMINAL_FONT_FAMILY).toContain("ui-monospace");
+  });
+});
 
 describe("buildTerminalThemeFromCssColors", () => {
   it("paints the terminal canvas and cursor cutout with the sidebar surface", () => {