diff --git a/package-lock.json b/package-lock.json
index ce261ea94d..916df12cc5 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -37625,8 +37625,8 @@
         "@xterm/addon-search": "^0.17.0-beta.213",
         "@xterm/addon-unicode11": "^0.10.0-beta.213",
         "@xterm/addon-web-links": "^0.13.0-beta.213",
-        "@xterm/addon-webgl": "^0.20.0-beta.212",
-        "@xterm/xterm": "^6.1.0-beta.213",
+        "@xterm/addon-webgl": "0.20.0-beta.291",
+        "@xterm/xterm": "6.1.0-beta.292",
         "buffer": "^6.0.3",
         "expo": "~57.0.30",
         "expo-asset": "~57.0.20",
@@ -38535,12 +38535,12 @@
       }
     },
     "packages/app/node_modules/@xterm/addon-webgl": {
-      "version": "0.20.0-beta.212",
-      "resolved": "https://registry.npmjs.org/@xterm/addon-webgl/-/addon-webgl-0.20.0-beta.212.tgz",
-      "integrity": "sha512-RzaTYeukTXTJth+Sl7FzCmb8AqiyDrNWNnqG+/300qJbfHYfCMmBlBVZ0yCTSZIWMdgFbgkhmnmBN7Yzs6xoBA==",
+      "version": "0.20.0-beta.291",
+      "resolved": "https://registry.npmjs.org/@xterm/addon-webgl/-/addon-webgl-0.20.0-beta.291.tgz",
+      "integrity": "sha512-gH7r5g8f2NWMhBtaeApuwLQTJmX4uq7zT0okjeNWkFAD0nxzbUPB+kt6sogZZ5K90XYPt2OLu/bhuvF6DmKqOQ==",
       "license": "MIT",
       "peerDependencies": {
-        "@xterm/xterm": "^6.1.0-beta.213"
+        "@xterm/xterm": "^6.1.0-beta.292"
       }
     },
     "packages/app/node_modules/@xterm/headless": {
@@ -38554,9 +38554,9 @@
       ]
     },
     "packages/app/node_modules/@xterm/xterm": {
-      "version": "6.1.0-beta.213",
-      "resolved": "https://registry.npmjs.org/@xterm/xterm/-/xterm-6.1.0-beta.213.tgz",
-      "integrity": "sha512-bq5nJkgoZDSg6Ma4zgiQ7jlooGNo7U+HDa6vnhx43yXsVEK2laIF7R08bMYAuU0B+C9xX0gwSrcsW18GxjUoJQ==",
+      "version": "6.1.0-beta.292",
+      "resolved": "https://registry.npmjs.org/@xterm/xterm/-/xterm-6.1.0-beta.292.tgz",
+      "integrity": "sha512-17zqK5tM/l6qeD7McF42OrEJ6w3XqJ2vFVKdWqu0cYLzdFqMWAHp2oFNc8Fj5DmqDSl1E1FZEg6IFflDllTvLA==",
       "license": "MIT",
       "workspaces": [
         "addons/*"
diff --git a/packages/app/package.json b/packages/app/package.json
index 3eddd9b53f..6dd914a94f 100644
--- a/packages/app/package.json
+++ b/packages/app/package.json
@@ -76,8 +76,8 @@
     "@xterm/addon-search": "^0.17.0-beta.213",
     "@xterm/addon-unicode11": "^0.10.0-beta.213",
     "@xterm/addon-web-links": "^0.13.0-beta.213",
-    "@xterm/addon-webgl": "^0.20.0-beta.212",
-    "@xterm/xterm": "^6.1.0-beta.213",
+    "@xterm/addon-webgl": "0.20.0-beta.291",
+    "@xterm/xterm": "6.1.0-beta.292",
     "buffer": "^6.0.3",
     "expo": "~57.0.30",
     "expo-asset": "~57.0.20",
diff --git a/packages/app/src/terminal/runtime/terminal-glyph-rendering.browser.test.ts b/packages/app/src/terminal/runtime/terminal-glyph-rendering.browser.test.ts
new file mode 100644
index 0000000000..35629f01f8
--- /dev/null
+++ b/packages/app/src/terminal/runtime/terminal-glyph-rendering.browser.test.ts
@@ -0,0 +1,203 @@
+import "@xterm/xterm/css/xterm.css";
+import { page } from "vitest/browser";
+import { afterEach, expect, it } from "vitest";
+import type { Terminal } from "@xterm/xterm";
+import { encodeTerminalOutput, TerminalEmulatorRuntime } from "./terminal-emulator-runtime";
+
+interface TerminalView {
+  root: HTMLDivElement;
+  host: HTMLDivElement;
+  runtime: TerminalEmulatorRuntime;
+  terminal: Terminal;
+}
+
+interface RowImage {
+  width: number;
+  height: number;
+  pixels: Uint8ClampedArray;
+}
+
+const views: TerminalView[] = [];
+const header = "HEADER_0123456789 한글 日本語";
+
+function mountTerminal(left: number): TerminalView {
+  const root = document.createElement("div");
+  Object.assign(root.style, {
+    position: "fixed",
+    left: `${left}px`,
+    top: "0",
+    width: "440px",
+    height: "360px",
+    overflow: "hidden",
+  });
+  const host = document.createElement("div");
+  Object.assign(host.style, { width: "100%", height: "100%" });
+  root.appendChild(host);
+  document.body.appendChild(root);
+  const runtime = new TerminalEmulatorRuntime();
+  runtime.mount({
+    root,
+    host,
+    initialSnapshot: null,
+    scrollback: 1000,
+    fontFamily: "monospace",
+    fontSize: 16,
+    theme: { background: "#101010", foreground: "#eeeeee", cursor: "#eeeeee" },
+  });
+  const terminal = window.__paseoTerminal;
+  if (!terminal) throw new Error("Terminal did not mount");
+  const view = { root, host, runtime, terminal };
+  views.push(view);
+  return view;
+}
+
+function write(view: TerminalView, text: string): Promise<void> {
+  return new Promise((resolve) => {
+    view.runtime.write({ data: encodeTerminalOutput(text), onCommitted: resolve });
+  });
+}
+
+function webglCanvas(view: TerminalView): HTMLCanvasElement {
+  for (const canvas of view.host.querySelectorAll(".xterm-screen canvas")) {
+    if (canvas instanceof HTMLCanvasElement && canvas.getContext("webgl2")) return canvas;
+  }
+  throw new Error("Real WebGL is required; DOM fallback cannot test glyph corruption");
+}
+
+async function mountPair() {
+  await page.viewport(1000, 600);
+  const active = mountTerminal(0);
+  const sibling = mountTerminal(460);
+  await document.fonts.ready;
+  await expect
+    .poll(() => active.host.querySelectorAll(".xterm-screen canvas").length)
+    .toBeGreaterThan(0);
+  await expect
+    .poll(() => sibling.host.querySelectorAll(".xterm-screen canvas").length)
+    .toBeGreaterThan(0);
+  webglCanvas(active);
+  webglCanvas(sibling);
+  await write(active, "\x1b[?25l");
+  await write(sibling, "\x1b[?25l");
+  return { active, sibling };
+}
+
+function captureHeader(input: { view: TerminalView; output?: string }): Promise<RowImage> {
+  const { view, output } = input;
+  return new Promise((resolve, reject) => {
+    const timeout = setTimeout(() => {
+      rendered.dispose();
+      reject(new Error("Terminal did not render within 2 seconds"));
+    }, 2000);
+    const rendered = view.terminal.onRender(() => {
+      rendered.dispose();
+      clearTimeout(timeout);
+      try {
+        // Copy during onRender, before WebGL discards its default drawing buffer.
+        const source = webglCanvas(view);
+        const canvas = document.createElement("canvas");
+        canvas.width = source.width;
+        canvas.height = Math.round(source.height / view.terminal.rows);
+        const context = canvas.getContext("2d");
+        if (!context) throw new Error("Canvas 2D pixel capture is unavailable");
+        context.drawImage(source, 0, 0);
+        const pixels = context.getImageData(0, 0, canvas.width, canvas.height).data;
+        resolve({ width: canvas.width, height: canvas.height, pixels });
+      } catch (error) {
+        reject(error);
+      }
+    });
+    if (output === undefined) view.terminal.refresh(0, view.terminal.rows - 1);
+    else view.runtime.write({ data: encodeTerminalOutput(output) });
+  });
+}
+
+function expectSamePixels(input: { expected: RowImage; actual: RowImage; label: string }): void {
+  const { expected, actual, label } = input;
+  expect(actual.width, label).toBe(expected.width);
+  expect(actual.height, label).toBe(expected.height);
+  let changed = 0;
+  for (let index = 0; index < expected.pixels.length; index += 1) {
+    if (expected.pixels[index] !== actual.pixels[index]) changed += 1;
+  }
+  expect(changed, label).toBe(0);
+}
+
+function coloredOutput(input: { cells: number; offset: number }): string {
+  const alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
+  let output = "";
+  for (let index = 0; index < input.cells; index += 1) {
+    const value = index + input.offset;
+    const foreground = `${value % 256};${(value >> 8) % 256};${(value * 13) % 256}`;
+    const background = (value * 7) % 256;
+    output += `\x1b[38;2;${foreground}m\x1b[48;5;${background}m${alphabet[value % alphabet.length]}`;
+  }
+  return `${output}\x1b[0m`;
+}
+
+afterEach(() => {
+  for (const view of views.splice(0)) {
+    view.runtime.unmount();
+    view.root.remove();
+  }
+});
+
+it("preserves another terminal's glyph pixels when a shared atlas is cleared", async () => {
+  const { active, sibling } = await mountPair();
+  await write(sibling, header);
+  const before = await captureHeader({ view: sibling });
+  const visibleChannels = before.pixels.filter(
+    (channel, index) => index % 4 !== 3 && channel > 100,
+  );
+  expect(visibleChannels.length).toBeGreaterThan(100);
+
+  active.terminal.clearTextureAtlas();
+  await captureHeader({ view: active, output: coloredOutput({ cells: 2000, offset: 0 }) });
+  const after = await captureHeader({
+    view: sibling,
+    output: `\x1b[${sibling.terminal.rows};1Hx`,
+  });
+  expect(sibling.terminal.buffer.active.getLine(0)?.translateToString(true)).toBe(header);
+  expectSamePixels({ expected: before, actual: after, label: "sibling after atlas clear" });
+});
+
+it("preserves both headers while ordinary output grows the shared glyph atlas", async () => {
+  const { active, sibling } = await mountPair();
+  const cells = active.terminal.cols * (active.terminal.rows - 2);
+  // Startup glyphs can stay on an unmerged page and hide this bug. Allocate the
+  // reference after some output, as a real long-running TUI does.
+  for (let batch = 0; batch < 16; batch += 1) {
+    await captureHeader({
+      view: active,
+      output: `\x1b[H${coloredOutput({ cells, offset: batch * cells })}`,
+    });
+  }
+  const lateHeader = `\x1b[H\x1b[0m\x1b[2K\x1b[38;2;253;251;247m${header}\x1b[0m`;
+  await write(active, lateHeader);
+  await write(sibling, lateHeader);
+  const activeBefore = await captureHeader({ view: active });
+  const siblingBefore = await captureHeader({ view: sibling });
+
+  for (let batch = 0; batch < 256; batch += 1) {
+    const activeFrame = await captureHeader({
+      view: active,
+      output: `\x1b[2;1H${coloredOutput({ cells, offset: (batch + 16) * cells })}`,
+    });
+    const siblingFrame = await captureHeader({
+      view: sibling,
+      output: `\x1b[${sibling.terminal.rows};1H${batch % 10}`,
+    });
+    expect(active.terminal.buffer.active.getLine(0)?.translateToString(true)).toBe(header);
+    expect(sibling.terminal.buffer.active.getLine(0)?.translateToString(true)).toBe(header);
+    expectSamePixels({
+      expected: activeBefore,
+      actual: activeFrame,
+      label: `active frame ${batch}`,
+    });
+    expectSamePixels({
+      expected: siblingBefore,
+      actual: siblingFrame,
+      label: `sibling frame ${batch}`,
+    });
+  }
+}, 30000);
diff --git a/packages/app/vitest.config.ts b/packages/app/vitest.config.ts
index 3254fc5e0c..ae7f935823 100644
--- a/packages/app/vitest.config.ts
+++ b/packages/app/vitest.config.ts
@@ -96,7 +96,10 @@ export default defineConfig({
           include: ["src/**/*.browser.{test,spec}.{ts,tsx}"],
           browser: {
             enabled: true,
-            provider: playwright(),
+            provider: playwright({
+              // Exercise real WebGL glyph rendering on GPU-less CI runners.
+              launchOptions: { args: ["--enable-unsafe-swiftshader"] },
+            }),
             headless: true,
             connectTimeout: 180_000,
             instances: [{ browser: "chromium" }],