apply storage changes

Change image storage to use new ExtendedAttrs payload field

.github/workflows/ci.yml

@@ -6,14 +6,19 @@ on:
   pull_request:
     branches: [ "master" ]
 
+permissions:
+  contents: read 
+
 jobs:
   build:
     runs-on: ubuntu-latest
     timeout-minutes: 10
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@93cb6efe18208431cddfb8368fd83d5badbf9bfd # v5
+      with:
+        persist-credentials: false
     - name: Use Node.js 22.x
-      uses: actions/setup-node@v3
+      uses: actions/setup-node@a0853c24544627f65ddf259abe73b1d18a591444 # v5
       with:
         node-version: 22.x
         cache: 'npm'
@@ -69,7 +74,7 @@ jobs:
           ./addons/addon-webgl/out/* \
           ./addons/addon-webgl/out-*st/*
     - name: Upload artifacts
-      uses: actions/upload-artifact@v4
+      uses: actions/upload-artifact@b7c566a772e6b6bfb58ed0dc250532a479d7789f # v6
       with:
         name: build-artifacts
         path: compressed-build.zip
@@ -79,9 +84,11 @@ jobs:
     runs-on: ubuntu-latest
     timeout-minutes: 10
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@93cb6efe18208431cddfb8368fd83d5badbf9bfd # v5
+      with:
+        persist-credentials: false
     - name: Use Node.js 22.x
-      uses: actions/setup-node@v3
+      uses: actions/setup-node@a0853c24544627f65ddf259abe73b1d18a591444 # v5
       with:
         node-version: 22.x
         cache: 'npm'
@@ -100,16 +107,18 @@ jobs:
     runs-on: ubuntu-latest
     timeout-minutes: 10
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@93cb6efe18208431cddfb8368fd83d5badbf9bfd # v5
+      with:
+        persist-credentials: false
     - name: Use Node.js 22.x
-      uses: actions/setup-node@v3
+      uses: actions/setup-node@a0853c24544627f65ddf259abe73b1d18a591444 # v5
       with:
         node-version: 22.x
         cache: 'npm'
     - name: Install dependencies
       run: |
         npm ci
-    - uses: actions/download-artifact@v4
+    - uses: actions/download-artifact@37930b1c2abaa49bbe596cd826c3c89aef350131 # v7
       with:
         name: build-artifacts
     - name: Unzip artifacts
@@ -129,6 +138,7 @@ jobs:
         exit $EXIT_CODE
 
   test-unit:
+    needs: build
     timeout-minutes: 20
     strategy:
       matrix:
@@ -136,21 +146,18 @@ jobs:
         runs-on: [ubuntu, macos, windows]
     runs-on: ${{ matrix.runs-on }}-latest
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@93cb6efe18208431cddfb8368fd83d5badbf9bfd # v5
+      with:
+        persist-credentials: false
     - name: Use Node.js ${{ matrix.node-version }}.x
-      uses: actions/setup-node@v3
+      uses: actions/setup-node@a0853c24544627f65ddf259abe73b1d18a591444 # v5
       with:
         node-version: ${{ matrix.node-version }}.x
         cache: 'npm'
     - name: Install dependencies
       run: |
         npm ci
-    - name: Wait for build job
-      uses: NathanFirmo/wait-for-other-job@v1.1.1
-      with:
-        token: ${{ secrets.GITHUB_TOKEN }}
-        job: build
-    - uses: actions/download-artifact@v4
+    - uses: actions/download-artifact@37930b1c2abaa49bbe596cd826c3c89aef350131 # v7
       with:
         name: build-artifacts
     - name: Unzip artifacts
@@ -166,6 +173,7 @@ jobs:
       run: npm run test-unit --forbid-only
 
   test-integration:
+    needs: build
     timeout-minutes: 20
     strategy:
       matrix:
@@ -174,9 +182,11 @@ jobs:
         browser: [chromium, firefox, webkit]
     runs-on: ${{ matrix.runs-on }}
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@93cb6efe18208431cddfb8368fd83d5badbf9bfd # v5
+      with:
+        persist-credentials: false
     - name: Use Node.js ${{ matrix.node-version }}.x
-      uses: actions/setup-node@v3
+      uses: actions/setup-node@a0853c24544627f65ddf259abe73b1d18a591444 # v5
       with:
         node-version: ${{ matrix.node-version }}.x
         cache: 'npm'
@@ -185,12 +195,7 @@ jobs:
         npm ci
     - name: Install playwright
       run: npx playwright install --with-deps ${{ matrix.browser }}
-    - name: Wait for build job
-      uses: NathanFirmo/wait-for-other-job@v1.1.1
-      with:
-        token: ${{ secrets.GITHUB_TOKEN }}
-        job: build
-    - uses: actions/download-artifact@v4
+    - uses: actions/download-artifact@37930b1c2abaa49bbe596cd826c3c89aef350131 # v7
       with:
         name: build-artifacts
     - name: Unzip artifacts
@@ -240,9 +245,11 @@ jobs:
       matrix:
         node-version: [22]
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@93cb6efe18208431cddfb8368fd83d5badbf9bfd # v5
+      with:
+        persist-credentials: false
     - name: Use Node.js ${{ matrix.node-version }}.x
-      uses: actions/setup-node@v3
+      uses: actions/setup-node@a0853c24544627f65ddf259abe73b1d18a591444 # v5
       with:
         node-version: ${{ matrix.node-version }}.x
         cache: 'npm'
@@ -251,7 +258,7 @@ jobs:
         npm ci
     - name: Install playwright
       run: npx playwright install
-    - uses: actions/download-artifact@v4
+    - uses: actions/download-artifact@37930b1c2abaa49bbe596cd826c3c89aef350131 # v7
       with:
         name: build-artifacts
     - name: Unzip artifacts

.github/workflows/codeql-analysis.yml

@@ -8,6 +8,11 @@ on:
   schedule:
     - cron: '41 17 * * 0'
 
+permissions:
+  actions: read          
+  contents: read          
+  security-events: write 
+
 jobs:
   analyze:
     name: Analyze
@@ -24,12 +29,14 @@ jobs:
 
     steps:
     - name: Checkout repository
-      uses: actions/checkout@v3
+      uses: actions/checkout@93cb6efe18208431cddfb8368fd83d5badbf9bfd # v5
+      with:
+        persist-credentials: false
     - name: Initialize CodeQL
-      uses: github/codeql-action/init@v2
+      uses: github/codeql-action/init@8aad20d150bbac5944a9f9d289da16a4b0d87c1e # v4
       with:
         languages: ${{ matrix.language }}
     - name: Autobuild
-      uses: github/codeql-action/autobuild@v2
+      uses: github/codeql-action/autobuild@8aad20d150bbac5944a9f9d289da16a4b0d87c1e # v4
     - name: Perform CodeQL Analysis
-      uses: github/codeql-action/analyze@v2
+      uses: github/codeql-action/analyze@8aad20d150bbac5944a9f9d289da16a4b0d87c1e # v4

.github/workflows/copilot-setup-steps.yml

@@ -9,6 +9,9 @@ on:
     paths:
       - .github/workflows/copilot-setup-steps.yml
 
+permissions:
+  contents: read
+
 jobs:
   copilot-setup-steps:
     runs-on: ubuntu-latest
@@ -18,9 +21,11 @@ jobs:
 
     steps:
       - name: Checkout code
-        uses: actions/checkout@v4
+        uses: actions/checkout@93cb6efe18208431cddfb8368fd83d5badbf9bfd # v5
+        with:
+          persist-credentials: false
       - name: Use Node.js 22.x
-        uses: actions/setup-node@v3
+        uses: actions/setup-node@a0853c24544627f65ddf259abe73b1d18a591444 # v5
         with:
           node-version: 22.x
           cache: 'npm'

.github/workflows/release.yml

@@ -6,13 +6,18 @@ on:
     # without running tests to save time to publish
     branches: [ "master" ]
 
+permissions:
+  contents: read
+
 jobs:
   release:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@93cb6efe18208431cddfb8368fd83d5badbf9bfd # v5
+      with:
+        persist-credentials: false
     - name: Use Node.js 22.x
-      uses: actions/setup-node@v3
+      uses: actions/setup-node@a0853c24544627f65ddf259abe73b1d18a591444 # v5
       with:
         node-version: 22.x
         cache: 'npm'

README.md

@@ -254,6 +254,13 @@ Xterm.js is used in many world-class applications to provide great terminal expe
 - [**WooTTY**](https://github.com/icoretech/wootty): Flawless browser terminal for real operators.
 - [**Orca**](https://github.com/stablyai/orca): Agentic development environment for 100x builders.
 - [**4bit**](https://ciembor.github.io/4bit): Terminal Color Scheme Designer.
+- [**Cate**](https://github.com/0-AI-UG/cate): Open source desktop IDE on an infinite zoomable canvas. Editor, browser, and terminal panels float in spatial space; the terminals are xterm.js with the WebGL addon, backed by node-pty.
+- [**OmnyShell PWA**](https://github.com/OmnyGrid/omnyshell_web): Web client for [**OmnyShell**](https://github.com/OmnyGrid/omnyshell), featuring remote terminals, a built-in IDE, AI-assisted workflows, and detachable/resumable sessions for seamless browser-based access to nodes.
+- [**kmux**](https://github.com/kkd927/kmux): A keyboard-centric terminal workspace for running parallel AI coding agents side by side on macOS and Linux.
+- [**LynxHub**](https://github.com/KindaBrazy/LynxHub): Cross-platform, extensible terminal and browser for AI management.
+- [**Codeman**](https://github.com/Ark0N/Codeman): Self-hosted mission control for AI coding agents, streaming live tmux sessions to browser and phone.
+- [**JSVIsion**](https://github.com/blendsdk/jsvision): A Turbo Vision-Style TUI SDK for TypeScript. We use xterm.js in our docs to show live JSVision examples running in a web terminal.
+- [**BitFun**](https://github.com/GCWing/BitFun): Open-source desktop AI agent whose integrated terminals and read-only terminal output views use xterm.js with the Fit, Web Links, and WebGL addons.
 - [And much more...](https://github.com/xtermjs/xterm.js/network/dependents?package_id=UGFja2FnZS0xNjYzMjc4OQ%3D%3D)
 
 Do you use xterm.js in your application as well? Please [open a Pull Request](https://github.com/sourcelair/xterm.js/pulls) to include it here. We would love to have it on our list. Please add any new contributions to the end of the list.

addons/addon-clipboard/src/ClipboardAddon.ts

@@ -78,13 +78,43 @@ export class BrowserClipboardProvider implements IClipboardProvider {
   }
 }
 
+/**
+ * TODO: Once the base64 handling on Uint8Arrays is more common,
+ * remove the btoa/atob fallbacks below.
+ */
+interface IUint8ArrayB64 extends Uint8Array {
+  toBase64(): string;
+}
+interface IUint8ArrayB64Ctor extends Uint8ArrayConstructor {
+  fromBase64(s: string): IUint8ArrayB64;
+}
+
 export class Base64 implements IBase64 {
   public encodeText(data: string): string {
-    return btoa(data);
+    const bytes = new TextEncoder().encode(data) as IUint8ArrayB64;
+    if (bytes.toBase64 !== undefined) {
+      return bytes.toBase64();
+    }
+    let bin = '';
+    for (let i = 0; i < bytes.length; i++) {
+      bin += String.fromCharCode(bytes[i]);
+    }
+    return btoa(bin);
   }
   public decodeText(data: string): string {
+    if ((Uint8Array as IUint8ArrayB64Ctor).fromBase64 !== undefined) {
+      try {
+        return new TextDecoder().decode((Uint8Array as IUint8ArrayB64Ctor).fromBase64(data));
+      } catch {}
+      return '';
+    }
     try {
-      return atob(data);
+      const bin = atob(data);
+      const bytes = new Uint8Array(bin.length);
+      for (let i = 0; i < bin.length; ++i) {
+        bytes[i] = bin.charCodeAt(i);
+      }
+      return new TextDecoder().decode(bytes);
     } catch {}
     return '';
   }

addons/addon-clipboard/test/ClipboardAddon.test.ts

@@ -29,7 +29,7 @@ test.describe('ClipboardAddon', () => {
       await ctx.page.context().grantPermissions(['clipboard-read', 'clipboard-write']);
     }
     await ctx.page.evaluate(`
-      window.term.reset()
+      window.term.reset();
       window.clipboard?.dispose();
       window.clipboard = new ClipboardAddon();
       window.term.loadAddon(window.clipboard);
@@ -92,4 +92,22 @@ test.describe('ClipboardAddon', () => {
       deepEqual(await ctx.page.evaluate(() => window.navigator.clipboard.readText()), '');
     });
   });
+
+  test.describe('non-ASCII', () => {
+    const testDataEncoded = '4oKsbWzDpMO8dMOf';
+    const testDataDecoded = '€mläütß';
+    test('write simple string', async () => {
+      await ctx.proxy.write(`\x1b]52;c;${testDataEncoded}\x07`);
+      deepEqual(await ctx.page.evaluate(() => window.navigator.clipboard.readText()), testDataDecoded);
+    });
+    test('read simple string', async () => {
+      await ctx.page.evaluate(`
+        window.data2 = [];
+        window.term.onData(e => data2.push(e));
+      `);
+      await ctx.page.evaluate((d) => window.navigator.clipboard.writeText(d), testDataDecoded);
+      await ctx.proxy.write(`\x1b]52;c;?\x07`);
+      deepEqual(await ctx.page.evaluate('window.data2'), [`\x1b]52;c;${testDataEncoded}\x07`]);
+    });
+  });
 });

addons/addon-image/README.md

@@ -98,7 +98,7 @@ terminal.loadAddon(imageAddon);
   Set by default, change it with `{iipSupport: true}`.
 
   The IIP implementation has the following features / restrictions (sequence will silently fail for unmet conditions):
-  - Supported formats: PNG, JPEG, GIF and QOI
+  - Supported formats: PNG, JPEG, GIF, QOI, WEBP and AVIF
   - No animation support.
   - Image type hinting is not supported (always deducted from data header).
   - File download is not supported.
@@ -112,6 +112,13 @@ terminal.loadAddon(imageAddon);
   - ReportCellSize sequence is supported.
   - Hi-res display support is currently limited (image gets blurred).
 
+- **Note on IIP image format support**  
+  For all image formats except QOI the addon only does the dimension extraction and leaves
+  the image decoding to the underlying browser engine. Note that some formats are implemented
+  and enabled with different constraints by browser vendors, especially newer formats
+  (e.g. under Firefox you might need to change the setting _image.avif.compliance_strictness_ to 0
+  to get broader AVIF support).
+
 - **Kitty Graphics Support (TGP)**  
   Set by default, change it with `{kittySupport: true}`.
 

addons/addon-image/src/AnimationManager.ts

@@ -0,0 +1,630 @@
+/**
+ * Copyright (c) 2026 The xterm.js authors. All rights reserved.
+ * @license MIT
+ */
+
+import type { IDisposable } from '@xterm/xterm';
+import type { ImageRenderer } from './ImageRenderer';
+import { ImageTileInfo, type ImageStorage } from './ImageStorage';
+import type { IImageSpec, ITerminalExt, IResetHandler } from './Types';
+import type { IMetrics } from 'IIPMetrics';
+
+
+/**
+ * Note on Firefox Bug (https://bugzilla.mozilla.org/show_bug.cgi?id=2066911)
+ *
+ * ImageDecoder.decode() returns a corrupted VideoFrame,
+ * if the frame was closed from a previous decode.
+ *
+ * Therefore the AnimationManager class implements certain
+ * firefox shims gated by the isFirefox boolean:
+ * - IAnimation.highest tracks highest frameID ever decoded
+ * - whenever frameID is lesser or equal zu highest create new decoder
+ * - raw image bytes need to be held for new decoder
+ *
+ * To be removed once the bug got fixed.
+ */
+
+
+interface IAnimation {
+  /** image id in storage */
+  id: number;
+  /** image bytes */
+  data: Blob;
+  /** metrics of the image */
+  metrics: IMetrics;
+  /** width */
+  w: number;
+  /** height */
+  h: number;
+  /** number of frames */
+  numFrames: number;
+  frames: number[];
+  /** ImageDecoder instance */
+  decoder: ImageDecoder | undefined;
+  decoderPromise: Promise<ImageDecoder> | undefined;
+  cache: BitmapBuffer;
+  /** start timestamp */
+  startTime: number | undefined;
+  /** whether a decode task ist scheduled */
+  scheduled: boolean;
+  /** whether the image is in viewport */
+  inViewport: boolean;
+  /** firefox bug helper */
+  highest: number;
+  /** playtime of animation */
+  playtime: number;
+  /** frame timestamps */
+  timestamps: number[];
+  /** frame ID targeted by animation */
+  current: number;
+  /** frame ID currently visible (owned by spec.actual) */
+  actual: number;
+  /** idx of current on frames */
+  frameIdx: number;
+}
+
+
+interface IImageDraw {
+  imageId: number;
+  imgSpec: IImageSpec;
+  tileId: number;
+  col: number;
+  row: number;
+  count: number;
+}
+
+
+interface IBufferSlot {
+  id: number;
+  bm: ImageBitmap | null;
+}
+
+
+const enum Constants {
+  BUFFERSIZE = 4,
+  BUFFERMOD = BUFFERSIZE - 1,
+  MAX_FRAMES = 65535
+}
+
+
+class BitmapBuffer implements IDisposable {
+  private readonly _d: IBufferSlot[];
+  private _disposed = false;
+
+  constructor() {
+    this._d = Array(Constants.BUFFERSIZE).fill(0).map(() => ({ id: -1, bm: null }));
+  }
+
+  public dispose(): void {
+    this.clear();
+    this._disposed = true;
+  }
+
+  public peek(id: number): ImageBitmap | null {
+    const slot = this._d[id & Constants.BUFFERMOD];
+    return id === slot.id ? slot.bm : null;
+  }
+
+  public pop(id: number): ImageBitmap | null {
+    const slot = this._d[id & Constants.BUFFERMOD];
+    const res = id === slot.id
+      ? slot.bm
+      : (slot.bm?.close(), null);
+    slot.bm = null;
+    slot.id = -1;
+    return res;
+  }
+
+  public push(id: number, bm: ImageBitmap): void {
+    /**
+     * A late decode task might still push bitmaps.
+     * Since push gives the buffer ownership of
+     * the bitmap, we use the isDisposed flag to
+     * free it right away.
+     */
+    if (this._disposed) {
+      bm.close();
+      return;
+    }
+    const slot = this._d[id & Constants.BUFFERMOD];
+    slot.bm?.close();
+    slot.bm = bm;
+    slot.id = id;
+  }
+
+  public clear(): void {
+    for (let i = 0; i < Constants.BUFFERSIZE; ++i) {
+      const slot = this._d[i];
+      slot.bm?.close();
+      slot.bm = null;
+      slot.id = -1;
+    }
+  }
+}
+
+
+// eslint-disable-next-line
+declare const InstallTrigger: any;
+
+
+// FIXME: move to AnimationManager ctor to control it from xterm side
+const isChromium = (window as any).chrome !== undefined;
+const isFirefox: boolean = typeof InstallTrigger !== 'undefined' || 'MozAppearance' in document.documentElement.style;
+
+
+/**
+ * Helper to create a read to use ImageDecoder instance from a blob.
+ */
+async function BlobDecoder(blob: Blob, type: string): Promise<ImageDecoder> {
+  /**
+   * Dealing with browser bugs - in theory this should be possible:
+   *
+   *    const decoder = new ImageDecoder({ data: blob.stream(), type, preferAnimation: true });
+   *    await decoder.tracks.ready;
+   *    return decoder;
+   *
+   * But this straightforward handling with blob.stream() uncovers several bugs:
+   * 1. Chromium: Fails to stream chunked blobs reliably.
+   * 2. Firefox: Native lifecycle race condition. Closing an old decoder breaks the
+   *    shared underlying native stream of the same blob for new decoders, throwing
+   *    an uncatchable "Closed decoder" DOMException during `tracks.ready`.
+   *
+   * So we use a safer approach by pulling full raw bytes over first and transferring ownership.
+   */
+  const data = await blob.arrayBuffer();
+  const decoder = new ImageDecoder({ data, type, preferAnimation: true, transfer: [data] });
+  await decoder.tracks.ready;
+  if (isChromium && type === 'image/avif') {
+    // chromium bug: random frame access in AVIF is
+    // only possible after reading frame 0
+    const res = await decoder.decode({ frameIndex: 0 });
+    res.image.close();
+  }
+  return decoder;
+}
+
+
+/**
+ * AnimationManager - orchestrates rendering of animated images.
+ *
+ * Current Workflow
+ * When IIPMetrics.imageType reports an animated image the IIP handler
+ * stores the image in the storage and registers an animation of it.
+ *
+ * The animation manager works mostly self-contained:
+ * - RAF loop
+ * - 3 frame ahead decoding
+ * - own bitmap ownership handling
+ *
+ * There are a few intersections with the ImageStorage and the ImageRenderer,
+ * which still need to be consolidated (TODOs):
+ * - ImageStorage: API for announcing memory state, better eviction strategy
+ * - ImageRenderer: API for better drawing primitives
+ *
+ * In particular the ownership model of ImageSpec bitmaps (actual and orig)
+ * needs a better story. We prolly need here an API to flip bitmaps.
+ */
+export class AnimationManager implements IDisposable, IResetHandler {
+  private _animations = new Map<number, IAnimation>();
+  private _animationFrame: number | undefined = undefined;
+  private _draws: IImageDraw[] = [];
+
+
+  constructor(
+    private _storage: ImageStorage,
+    private _renderer: ImageRenderer,
+    private _terminal: ITerminalExt
+  ) {}
+
+
+  private _requestAF(cb: FrameRequestCallback): number | undefined {
+    return this._terminal._core._coreBrowserService?.window.requestAnimationFrame(cb);
+  }
+
+
+  private _cancelAF(id: number): void | undefined {
+    return this._terminal._core._coreBrowserService?.window.cancelAnimationFrame(id);
+  }
+
+
+  public dispose(): void {
+    this.reset();
+  }
+
+
+  /**
+   * Reset handler.
+   * Stops all animations and frees all ressources.
+   */
+  public reset(): void {
+    for (const anim of this._animations.values()) {
+      anim.inViewport = false;
+      this._closeDecoder(anim);
+      anim.cache.dispose();
+    }
+    this._animations.clear();
+    this._draws = [];
+    if (this._animationFrame) this._cancelAF(this._animationFrame);
+    this._animationFrame = undefined;
+  }
+
+
+  /**
+   * Main hook to register an animated image for animation.
+   *
+   * @param id Image ID of the image storage the image was registered under.
+   * @param data Raw data bytes of the image.
+   * @param metrics Metrics of the image as returned by IIPMetrics.imageType.
+   * @param w Output width in pixel.
+   * @param h Output height in pixel.
+   */
+  public async registerAnimation(id: number, data: Blob, metrics: IMetrics, w: number, h: number): Promise<void> {
+    let decoder = await BlobDecoder(data, metrics.mime);
+    const track = decoder.tracks.selectedTrack;
+    if (!track || track.frameCount < 2) {
+      decoder.close();
+      return;
+    }
+
+    const frameCount = Math.min(track.frameCount, Constants.MAX_FRAMES);
+    const frames: number[] = [];
+    const timestamps: number[] = [];
+    const durations: number[] = [];
+    let elapsed = 0;
+
+    for (let i = 0; i < frameCount; i++) {
+      try {
+        const result = await decoder.decode({ frameIndex: i });
+        const frame = result.image;
+        const width = frame.displayWidth;
+        const height = frame.displayHeight;
+        const duration = (frame.duration ?? 0) / 1000;
+        frame.close();
+        // skip wrong dimensions and zero duration
+        if (width !== metrics.width || height !== metrics.height || !duration) {
+          if (durations.length) {
+            durations[durations.length - 1] += duration;
+            elapsed += duration;
+          }
+          continue;
+        }
+        frames.push(i);
+        timestamps.push(elapsed);
+        durations.push(duration);
+        elapsed += duration;
+      } catch {
+        break;
+      }
+    }
+
+    /**
+     * FIXME: still needs a consolidation of short frame durations:
+     * We don't track v-sync, but just decode the next 3 follow-up frames.
+     * This creates nonsense decoder pressure decoding frames,
+     * that effectively never make it to the screen.
+     * Currently our shortest time resolution is 1ms,
+     * thus with 60 fps we would decode 15 1ms frames for no reason.
+     * We prolly should introduce a lower bound of 8ms:
+     * - in sync with 120 fps
+     * - only every second frame is nonsense with 60 fps
+     */
+
+    if (frames.length < 2 || elapsed <= 0) {
+      decoder.close();
+      return;
+    }
+
+    if (isFirefox) {
+      decoder.close();
+      decoder = await BlobDecoder(data, metrics.mime);
+    }
+
+    const anim: IAnimation = {
+      id, data, w, h, decoder,
+      metrics,
+      numFrames: frames.length,
+      decoderPromise: undefined,
+      cache: new BitmapBuffer(),
+      frames,
+      startTime: undefined,
+      current: 0,
+      actual: 0,
+      scheduled: false,  // set by _schedule
+      inViewport: true,  // start with active prefetching
+      highest: -1,
+      playtime: elapsed,
+      timestamps,
+      frameIdx: 0
+    };
+    this._animations.set(id, anim);
+    this.viewportUpdated();
+    // early schedule to give decoder time to fill the cache before RAF
+    this._schedule(anim);
+    this._animationFrame ??= this._requestAF(this._loop);
+  }
+
+
+  /**
+   * Remove the animation for the given image id.
+   */
+  public unregisterAnimation(id: number): void {
+    const a = this._animations.get(id);
+    if (a) {
+      a.inViewport = false;
+      this._closeDecoder(a);
+      a.cache.dispose();
+      this._animations.delete(id);
+    }
+  }
+
+
+  /**
+   * onRender handler.
+   * Scratches the viewport buffer to collect draws for animation RAF
+   * and to pause/resume invisible/visible animations.
+   */
+  public viewportUpdated(_range?: { start: number, end: number }): void {
+    const rows = this._terminal.rows;
+    const cols = this._terminal.cols;
+    const buffer = this._terminal._core.buffer;
+    const actives: Set<number> = new Set();
+    this._draws = [];
+    for (let row = 0; row < rows; ++row) {
+      const line = buffer.lines.get(row + buffer.ydisp);
+      if (!line) break;
+      for (let col = 0; col < cols; ++col) {
+        const e = line.getExtended(col)?.payload;
+        if (e instanceof ImageTileInfo) {
+          const imageId = e.imageId;
+          if (imageId === undefined || imageId === -1) {
+            continue;
+          }
+          const imgSpec = this._storage.getImage(imageId);
+          if (e.tileId !== -1) {
+            const startTile = e.tileId;
+            const startCol = col;
+            let count = 1;
+            /**
+             * merge tiles to the right into a single draw call, if:
+             * - not at end of line
+             * - cell has same image id
+             * - cell has consecutive tile id
+             */
+            while (++col < cols) {
+              const nextE = line.getExtended(col)?.payload;
+              if (!(nextE instanceof ImageTileInfo) || nextE.imageId !== imageId || nextE.tileId !== startTile + count) {
+                break;
+              }
+              count++;
+            }
+            col--;
+            if (imgSpec && this._animations.has(imageId)) {
+              this._draws.push({ imageId, imgSpec, tileId: startTile, col: startCol, row, count });
+              actives.add(imageId);
+            }
+          }
+        }
+      }
+    }
+    this._updateAnimations(actives);
+  }
+
+
+  /**
+   * Get the frameIdx for elapsed time.
+   * Note: The returned value is not the frame ID,
+   * but the index for IAnimation.frames.
+   */
+  private _timedFrameIdx(a: IAnimation, elapsed: number): number {
+    elapsed %= a.playtime;
+    let low = 0;
+    let high = a.timestamps.length - 1;
+    while (low <= high) {
+      const mid = (low + high) >> 1;
+      const startTime = a.timestamps[mid];
+      if (elapsed < startTime) {
+        high = mid - 1;
+      } else {
+        if (mid === a.timestamps.length - 1 || elapsed < a.timestamps[mid + 1]) {
+          return mid;
+        }
+        low = mid + 1;
+      }
+    }
+    return 0;
+  }
+
+  /**
+   * Pause/resume decoding from viewport changes.
+   */
+  private _updateAnimations(visibles: Set<number>): void {
+    for (const [id, anim] of this._animations) {
+      const isVisible = visibles.has(id);
+      if (isVisible && !anim.inViewport) {
+        /**
+        * There are two strategies possible here:
+        *
+        * 1. Resume decoding and pumping frames as soon as possible.
+        * 2. Delay resuming further by a debounce to prevent flooding
+        *    new decoder instances on heavy scrolling.
+        *
+        * Currently the code below does 1. as the impact is rather
+        * small from tests and gives the better user experience.
+        */
+        anim.inViewport = true;
+        const frameIdx = this._timedFrameIdx(anim, performance.now() - anim.startTime!);
+        anim.frameIdx = frameIdx;
+        anim.current = anim.frames[frameIdx];
+        if (!anim.decoder && !anim.decoderPromise) {
+          anim.decoderPromise = BlobDecoder(anim.data, anim.metrics.mime);
+        }
+        this._schedule(anim);
+      } else if (!isVisible && anim.inViewport) {
+        anim.inViewport = false;
+        anim.cache.clear();
+        this._closeDecoder(anim);
+      }
+    }
+    if (visibles.size && this._animationFrame === undefined) {
+      this._animationFrame = this._requestAF(this._loop);
+    }
+  }
+
+
+  /**
+   * RAF for animations in viewport.
+   */
+  private _loop = (ts: number): void => {
+    if (!this._animations.size) {
+      this._animationFrame = undefined;
+      return;
+    }
+
+    let mustRender = false;
+    let anyVisible = false;
+
+    for (const anim of this._animations.values()) {
+      if (!anim.inViewport) continue;
+
+      const spec = this._storage.getImage(anim.id);
+      if (!spec) {
+        this.unregisterAnimation(anim.id);
+        continue;
+      }
+      anyVisible = true;
+      anim.startTime ??= ts;
+      const frameIdx = this._timedFrameIdx(anim, ts - anim.startTime);
+      anim.frameIdx = frameIdx;
+      const current = anim.frames[frameIdx];
+
+      if (current !== anim.current) {
+        anim.current = current;
+        const bm = anim.cache.pop(current);
+        if (bm) {
+          // FIXME: setting spec.actual delegates draws from onRender back to ImageStorage.render
+          // --> should be avoided to prevent double draws within same AF
+          // idea: create a mutex on image spec to tell storage.render to skip
+
+          // by swapping spec.actual we take ownership, thus have to close it here
+          // but only if we have more than 4 frames (ringbuffer size is 4)
+          // for <= 4 frames we move the bitmap back into cache
+          // FIXME: create a bitmap swapping API in storage
+          if (spec.actual instanceof ImageBitmap) {
+            if (anim.numFrames > Constants.BUFFERSIZE) {
+              spec.actual.close();
+            } else {
+              anim.cache.push(anim.actual, spec.actual);
+            }
+          }
+          spec.actual = bm;
+          anim.actual = current;
+          mustRender = true;
+        }
+        this._schedule(anim);
+      }
+    }
+
+    // FIXME: merge clears and draws into col x row rects
+    if (mustRender) {
+      for (let i = 0; i < this._draws.length; ++i) {
+        const d = this._draws[i];
+        this._renderer.clearLines(d.row, d.row);
+        this._renderer.draw(d.imgSpec, d.tileId, d.col, d.row, d.count);
+      }
+    }
+    this._animationFrame = anyVisible ? this._requestAF(this._loop) : undefined;
+  };
+
+
+  /**
+   * Try to schedule frame decoding.
+   */
+  private _schedule(a: IAnimation): void {
+    if (!a.scheduled) {
+      let needsSchedule = false;
+      // FIXME: do we need a == 4 test too?
+      if (a.numFrames > 3) {
+        needsSchedule =
+          !a.cache.peek(a.frames[(a.frameIdx + 1) % a.numFrames]) ||
+          !a.cache.peek(a.frames[(a.frameIdx + 2) % a.numFrames]) ||
+          !a.cache.peek(a.frames[(a.frameIdx + 3) % a.numFrames]);
+      } else if (a.numFrames === 3) {
+        needsSchedule =
+          !a.cache.peek(a.frames[(a.frameIdx + 1) % a.numFrames]) ||
+          !a.cache.peek(a.frames[(a.frameIdx + 2) % a.numFrames]);
+      } else {
+        needsSchedule =
+          !a.cache.peek(a.frames[(a.frameIdx + 1) % a.numFrames]);
+      }
+      if (needsSchedule) {
+        a.scheduled = true;
+        setTimeout(() => this._decode(a), 0);
+      }
+    }
+  }
+
+
+  /**
+   * Decode up to next 3 frames.
+   */
+  private async _decode(a: IAnimation): Promise<void> {
+    if (!a.inViewport) {
+      a.scheduled = false;
+      return;
+    }
+    if (!a.decoder) {
+      const decP = a.decoderPromise;
+      a.decoderPromise = undefined;
+      a.decoder = await (decP ?? BlobDecoder(a.data, a.metrics.mime));
+    }
+    const n1 = a.frames[(a.frameIdx + 1) % a.numFrames];
+    const n2 = a.frames[(a.frameIdx + 2) % a.numFrames];
+    const n3 = a.frames[(a.frameIdx + 3) % a.numFrames];
+    for (const n of [n1, n2, n3]) {
+      if (!a.cache.peek(n)) {
+        if (isFirefox) {
+          if (n <= a.highest) {
+            a.highest = -1;
+            a.decoder?.close();
+            a.decoder = await BlobDecoder(a.data, a.metrics.mime);
+          }
+          a.highest = Math.max(n, a.highest);
+        }
+        let res: ImageDecodeResult;
+        try {
+          res = await a.decoder.decode({ frameIndex: n });
+        } catch { continue; }
+        let bm: ImageBitmap;
+        try {
+          // FIXME: we should not resize here yet
+          // BETTER: rescale during draw:
+          // - eases the GPU druing decoding
+          // - rescales only what needs to be drawn
+          // --> funneling down
+          // FIXME: needs changes in image spec and rendering functions
+          bm = await createImageBitmap(res.image, { resizeWidth: a.w, resizeHeight: a.h });
+        } catch { continue; } finally { res?.image?.close(); }
+        if (!a.inViewport) {
+          bm.close();
+          break;
+        }
+        a.cache.push(n, bm);
+      }
+    }
+    a.scheduled = false;
+  }
+
+
+  /**
+   * Close the decoder defensively.
+   */
+  private _closeDecoder(a: IAnimation): void {
+    const decoder = a.decoder;
+    a.decoder = undefined;
+    try { decoder?.close(); } catch {}
+    const decP = a.decoderPromise;
+    a.decoderPromise = undefined;
+    decP?.then(dec => dec && dec !== decoder ? dec.close() : null).catch(() => {});
+  }
+}

addons/addon-image/src/IIPHandler.ts

@@ -2,14 +2,15 @@
  * Copyright (c) 2023 The xterm.js authors. All rights reserved.
  * @license MIT
  */
-import { IImageAddonOptions, IOscHandler, IResetHandler, ITerminalExt } from './Types';
+import type { IImageAddonOptions, IOscHandler, IResetHandler, ITerminalExt } from './Types';
 import { ImageRenderer } from './ImageRenderer';
-import { IIPImageStorage } from './IIPImageStorage';
+import type { IIPImageStorage } from './IIPImageStorage';
 import { CELL_SIZE_DEFAULT } from './ImageStorage';
 import Base64Decoder from 'xterm-wasm-parts/lib/base64/Base64Decoder.wasm';
 import QoiDecoder from 'xterm-wasm-parts/lib/qoi/QoiDecoder.wasm';
 import { HeaderParser, IHeaderFields, HeaderState, SequenceType } from './IIPHeaderParser';
 import { imageType, UNSUPPORTED_TYPE } from './IIPMetrics';
+import type { AnimationManager } from 'AnimationManager';
 
 // Local const enum mirror - esbuild can't inline const enums from external packages
 const enum DecoderConst {
@@ -39,7 +40,6 @@ export class IIPHandler implements IOscHandler, IResetHandler {
   private _header: IHeaderFields = DEFAULT_HEADER;
   private _dec: Base64Decoder;
   private _qoiDec: QoiDecoder;
-  private _metrics = UNSUPPORTED_TYPE;
   private _isMultipart = false;
   private _abortMulti = false;
 
@@ -47,7 +47,8 @@ export class IIPHandler implements IOscHandler, IResetHandler {
     private readonly _opts: IImageAddonOptions,
     private readonly _renderer: ImageRenderer,
     private readonly _storage: IIPImageStorage,
-    private readonly _coreTerminal: ITerminalExt
+    private readonly _coreTerminal: ITerminalExt,
+    private readonly _aniManager: AnimationManager | undefined
   ) {
     const maxEncodedBytes = Math.ceil(this._opts.iipSizeLimit * 4 / 3);
     const initialBytes = Math.min(DecoderConst.INITIAL_DATA, maxEncodedBytes);
@@ -63,7 +64,6 @@ export class IIPHandler implements IOscHandler, IResetHandler {
 
   public start(): void {
     this._aborted = false;
-    this._metrics  = UNSUPPORTED_TYPE;
     this._hp.reset();
   }
 
@@ -120,14 +120,14 @@ export class IIPHandler implements IOscHandler, IResetHandler {
 
     if (seqType === SequenceType.REPORTCELLSIZE) {
       // OSC 1337 ; ReportCellSize=[height];[width];[scale] ST
-      let width = CELL_SIZE_DEFAULT.width;
-      let height = CELL_SIZE_DEFAULT.height;
+      let w = CELL_SIZE_DEFAULT.width;
+      let h = CELL_SIZE_DEFAULT.height;
       if (this._renderer.dimensions) {
-        width = this._renderer.dimensions.css.canvas.width / this._coreTerminal.cols;
-        height = this._renderer.dimensions.css.canvas.height / this._coreTerminal.rows;
+        w = this._renderer.dimensions.css.canvas.width / this._coreTerminal.cols;
+        h = this._renderer.dimensions.css.canvas.height / this._coreTerminal.rows;
       }
       const scale = this._coreTerminal._core._coreBrowserService?.dpr ?? 1;
-      const report = `\x1b]1337;ReportCellSize=${height.toFixed(3)};${width.toFixed(3)};${scale.toFixed(3)}\x1b\\`;
+      const report = `\x1b]1337;ReportCellSize=${h.toFixed(3)};${w.toFixed(3)};${scale.toFixed(3)}\x1b\\`;
       this._coreTerminal.input(report, false);
       return true;
     }
@@ -154,17 +154,24 @@ export class IIPHandler implements IOscHandler, IResetHandler {
 
     // early exit condition chain
     let cond: number | boolean;
+    let metrics = UNSUPPORTED_TYPE;
     if (cond = success) {
       if (cond = !this._dec.end()) {
-        this._metrics = imageType(this._dec.data8);
-        if (cond = this._metrics.mime !== 'unsupported') {
-          w = this._metrics.width;
-          h = this._metrics.height;
+        metrics = imageType(this._dec.data8);
+        if (cond = metrics.mime !== 'unsupported') {
+          w = metrics.width;
+          h = metrics.height;
           if (cond = w && h && w * h < this._opts.pixelLimit) {
             [w, h] = this._resize(w, h).map(Math.floor);
             cond = w && h && w * h < this._opts.pixelLimit;
+          } else {
+            console.warn(`IIP: image dimension issue ${metrics.width}x${metrics.height}`);
           }
+        } else {
+          console.warn('IIP: unsupported image type');
         }
+      } else {
+        console.warn('IIP: error during BASE64 decoding');
       }
     }
     if (!cond) {
@@ -173,7 +180,7 @@ export class IIPHandler implements IOscHandler, IResetHandler {
     }
 
     let blob: Blob | ImageData;
-    if (this._metrics.mime === 'image/qoi') {
+    if (metrics.mime === 'image/qoi') {
       const data = this._qoiDec.decode(this._dec.data8);
       blob = new ImageData(
         new Uint8ClampedArray(data.buffer, data.byteOffset, data.byteLength),
@@ -190,12 +197,20 @@ export class IIPHandler implements IOscHandler, IResetHandler {
         return true;
       }
     } else {
-      blob = new Blob([this._dec.data8], { type: this._metrics.mime });
+      blob = new Blob([this._dec.data8], { type: metrics.mime });
     }
     this._dec.release();
     return createImageBitmap(blob, { resizeWidth: w, resizeHeight: h })
       .then(bm => {
-        this._storage.addImage(bm);
+        const id = this._storage.addImage(bm);
+        if (this._aniManager && metrics.animated) {
+          this._aniManager.registerAnimation(id, blob as Blob, metrics, w, h).catch(() => {});
+        }
+        return true;
+      })
+      .catch(e => {
+        console.warn(`IIP: decoding error ${metrics.mime} ${metrics.width}x${metrics.height}`, e);
+        // FIXME: try ImageDecoder here instead (e.g. some AVIF work in Firefox)
         return true;
       });
   }

addons/addon-image/src/IIPImageStorage.ts

@@ -22,7 +22,7 @@ export class IIPImageStorage {
    * Add an IIP image to storage.
    * Always uses scrolling mode — cursor advances past the image.
    */
-  public addImage(img: HTMLCanvasElement | ImageBitmap): void {
-    this._storage.addImage(img, this._addImageOpts);
+  public addImage(img: HTMLCanvasElement | ImageBitmap): number {
+    return this._storage.addImage(img, this._addImageOpts);
   }
 }

addons/addon-image/src/IIPMetrics.test.ts

@@ -12,26 +12,48 @@ const fs = require('fs');
 
 
 const TEST_IMAGES: [string, IMetrics][] = [
-  ['w3c_home_256.gif', { mime: 'image/gif', width: 72, height: 48 }],
-  ['w3c_home_256.jpg', { mime: 'image/jpeg', width: 72, height: 48 }],
-  ['w3c_home_256.png', { mime: 'image/png', width: 72, height: 48 }],
-  ['w3c_home_2.gif', { mime: 'image/gif', width: 72, height: 48 }],
-  ['w3c_home_2.jpg', { mime: 'image/jpeg', width: 72, height: 48 }],
-  ['w3c_home_2.png', { mime: 'image/png', width: 72, height: 48 }],
-  ['w3c_home_animation.gif', { mime: 'image/gif', width: 72, height: 48 }],
-  ['w3c_home.gif', { mime: 'image/gif', width: 72, height: 48 }],
-  ['w3c_home_gray.gif', { mime: 'image/gif', width: 72, height: 48 }],
-  ['w3c_home_gray.jpg', { mime: 'image/jpeg', width: 72, height: 48 }],
-  ['w3c_home_gray.png', { mime: 'image/png', width: 72, height: 48 }],
-  ['w3c_home.jpg', { mime: 'image/jpeg', width: 72, height: 48 }],
-  ['w3c_home.png', { mime: 'image/png', width: 72, height: 48 }],
-  ['w3c_home_noexif.jpg', { mime: 'image/jpeg', width: 72, height: 48 }],
-  ['spinfox.png', { mime: 'image/png', width: 148, height: 148 }],
-  ['iphone_hdr_YES.jpg', { mime: 'image/jpeg', width: 3264, height: 2448 }],
-  ['nikon-e950.jpg', { mime: 'image/jpeg', width: 800, height: 600 }],
-  ['agfa-makernotes.jpg', { mime: 'image/jpeg', width: 8, height: 8 }],
-  ['sony-alpha-6000.jpg', { mime: 'image/jpeg', width: 6000, height: 4000 }],
-  ['dice.qoi', { mime: 'image/qoi', width: 800, height: 600 }],
+  ['w3c_home_256.gif', { mime: 'image/gif', width: 72, height: 48, animated: false }],
+  ['w3c_home_256.jpg', { mime: 'image/jpeg', width: 72, height: 48, animated: false }],
+  ['w3c_home_256.png', { mime: 'image/png', width: 72, height: 48, animated: false }],
+  ['w3c_home_2.gif', { mime: 'image/gif', width: 72, height: 48, animated: false }],
+  ['w3c_home_2.jpg', { mime: 'image/jpeg', width: 72, height: 48, animated: false }],
+  ['w3c_home_2.png', { mime: 'image/png', width: 72, height: 48, animated: false }],
+  ['w3c_home_animation.gif', { mime: 'image/gif', width: 72, height: 48, animated: true }],
+  ['w3c_home.gif', { mime: 'image/gif', width: 72, height: 48, animated: false }],
+  ['w3c_home_gray.gif', { mime: 'image/gif', width: 72, height: 48, animated: false }],
+  ['w3c_home_gray.jpg', { mime: 'image/jpeg', width: 72, height: 48, animated: false }],
+  ['w3c_home_gray.png', { mime: 'image/png', width: 72, height: 48, animated: false }],
+  ['w3c_home.jpg', { mime: 'image/jpeg', width: 72, height: 48, animated: false }],
+  ['w3c_home.png', { mime: 'image/png', width: 72, height: 48, animated: false }],
+  ['w3c_home_noexif.jpg', { mime: 'image/jpeg', width: 72, height: 48, animated: false }],
+  ['spinfox.png', { mime: 'image/png', width: 148, height: 148, animated: true }],
+  ['iphone_hdr_YES.jpg', { mime: 'image/jpeg', width: 3264, height: 2448, animated: false }],
+  ['nikon-e950.jpg', { mime: 'image/jpeg', width: 800, height: 600, animated: false }],
+  ['agfa-makernotes.jpg', { mime: 'image/jpeg', width: 8, height: 8, animated: false }],
+  ['sony-alpha-6000.jpg', { mime: 'image/jpeg', width: 6000, height: 4000, animated: false }],
+  ['dice.qoi', { mime: 'image/qoi', width: 800, height: 600, animated: false }],
+  // VP8
+  ['1.webp', { mime: 'image/webp', width: 550, height: 368, animated: false }],
+  ['2.webp', { mime: 'image/webp', width: 550, height: 404, animated: false }],
+  ['3.webp', { mime: 'image/webp', width: 1280, height: 720, animated: false }],
+  ['4.webp', { mime: 'image/webp', width: 1024, height: 772, animated: false }],
+  ['5.webp', { mime: 'image/webp', width: 1024, height: 752, animated: false }],
+  // VP8X
+  ['1_webp_a.webp', { mime: 'image/webp', width: 400, height: 301, animated: false }],
+  ['2_webp_a.webp', { mime: 'image/webp', width: 386, height: 395, animated: false }],
+  ['3_webp_a.webp', { mime: 'image/webp', width: 800, height: 600, animated: false }],
+  ['4_webp_a.webp', { mime: 'image/webp', width: 421, height: 163, animated: false }],
+  ['5_webp_a.webp', { mime: 'image/webp', width: 300, height: 300, animated: false }],
+  // VP8L
+  ['1_webp_ll.webp', { mime: 'image/webp', width: 400, height: 301, animated: false }],
+  ['2_webp_ll.webp', { mime: 'image/webp', width: 386, height: 395, animated: false }],
+  ['3_webp_ll.webp', { mime: 'image/webp', width: 800, height: 600, animated: false }],
+  ['4_webp_ll.webp', { mime: 'image/webp', width: 421, height: 163, animated: false }],
+  ['5_webp_ll.webp', { mime: 'image/webp', width: 300, height: 300, animated: false }],
+  // some AVIF test images
+  ['fox.profile2.12bpc.yuv444.odd-width.odd-height.avif', { mime: 'image/avif', width: 1203, height: 799, animated: false }],
+  ['hato.profile0.8bpc.yuv420.avif', { mime: 'image/avif', width: 3082, height: 2048, animated: false }],
+  ['kimono.crop.avif', { mime: 'image/avif', width: 722, height: 1024, animated: false }],
 ];
 
 

addons/addon-image/src/IIPMetrics.ts

@@ -4,62 +4,140 @@
  */
 
 
-export type ImageType = 'image/png' | 'image/jpeg' | 'image/gif' | 'image/qoi' | 'unsupported' | '';
+export type ImageType = 'image/png' | 'image/jpeg' | 'image/gif' | 'image/qoi' | 'image/webp' | 'image/avif' | 'unsupported' | '';
 
 export interface IMetrics {
   mime: ImageType;
   width: number;
   height: number;
+  animated: boolean;
 }
 
 export const UNSUPPORTED_TYPE: IMetrics = {
   mime: 'unsupported',
   width: 0,
-  height: 0
+  height: 0,
+  animated: false
 };
 
 export function imageType(d: Uint8Array): IMetrics {
-  if (d.length < 24) {
+  if (d.length < 32) {
     return UNSUPPORTED_TYPE;
   }
-  const d32 = new Uint32Array(d.buffer, d.byteOffset, 6);
+  const d32 = new Uint32Array(d.buffer, d.byteOffset, 8);
   // PNG: 89 50 4E 47 0D 0A 1A 0A (8 first bytes == magic number for PNG)
   // + first chunk must be IHDR
   if (d32[0] === 0x474E5089 && d32[1] === 0x0A1A0A0D && d32[3] === 0x52444849) {
     return {
       mime: 'image/png',
-      width: d[16] << 24 | d[17] << 16 | d[18] << 8 | d[19],
-      height: d[20] << 24 | d[21] << 16 | d[22] << 8 | d[23]
+      width:  d[16] << 24 | d[17] << 16 | d[18] << 8 | d[19],
+      height: d[20] << 24 | d[21] << 16 | d[22] << 8 | d[23],
+      animated: isAPNG(d)
     };
   }
   // JPEG: FF D8 FF
   if (d[0] === 0xFF && d[1] === 0xD8 && d[2] === 0xFF) {
     const [width, height] = jpgSize(d);
-    return { mime: 'image/jpeg', width, height };
+    return { mime: 'image/jpeg', width, height, animated: false };
   }
   // GIF: GIF87a or GIF89a
   if (d32[0] === 0x38464947 && (d[4] === 0x37 || d[4] === 0x39) && d[5] === 0x61) {
     return {
       mime: 'image/gif',
-      width: d[7] << 8 | d[6],
-      height: d[9] << 8 | d[8]
+      width:  d[6] | d[7] << 8,
+      height: d[8] | d[9] << 8,
+      animated: isAGIF(d)
     };
   }
   // QOI: qoif
   if (d32[0] === 0x66696F71) {
     return {
       mime: 'image/qoi',
-      width: d[4] << 24 | d[5] << 16 | d[6] << 8 | d[7],
-      height: d[8] << 24 | d[9] << 16 | d[10] << 8 | d[11]
+      width:  d[4] << 24 | d[5] << 16 | d[ 6] << 8 | d[ 7],
+      height: d[8] << 24 | d[9] << 16 | d[10] << 8 | d[11],
+      animated: false
     };
   }
+  // WEBP: RIFF | xxxx | WEBP | VP8x
+  if (d32[0] === 0x46464952 && d32[2] === 0x50424557 && (d32[3] & 0xFFFFFF) === 0x385056) {
+    switch (d[15]) {
+      case 0x58:  // Extended WebP VP8X --> "X"
+        return {
+          mime: 'image/webp',
+          width:  (d[24] | d[25] << 8 | d[26] << 16) + 1,
+          height: (d[27] | d[28] << 8 | d[29] << 16) + 1,
+          animated: (d[20] & 0x02) !== 0
+        };
+      case 0x4C:  // Lossless WebP VP8L --> "L"
+        if (d[20] !== 0x2f) return UNSUPPORTED_TYPE;
+        const dim = d[21] | d[22] << 8 | d[23] << 16 | d[24] << 24;
+        return {
+          mime: 'image/webp',
+          width:  (dim        & 0x3FFF) + 1,
+          height: (dim >>> 14 & 0x3FFF) + 1,
+          animated: false
+        };
+      case 0x20:  // Lossy WebP VP8  --> " "
+        if (d[23] !== 0x9d || d[24] !== 0x01 || d[25] !== 0x2a) return UNSUPPORTED_TYPE;
+        return {
+          mime: 'image/webp',
+          width:  (d[26] | d[27] << 8) & 0x3FFF,
+          height: (d[28] | d[29] << 8) & 0x3FFF,
+          animated: false
+        };
+    }
+    return UNSUPPORTED_TYPE;
+  }
+  // AVIF: Box size | ftyp | avif/avis
+  if (d32[1] === 0x70797466 && (d32[2] === 0x66697661 || d32[2] === 0x73697661)) {
+    let pos = -1;
+    let anim = d32[2] === 0x73697661; // avis is meant to be animated
+    // search for boxes within first 1024 bytes
+    const limit = Math.min(d.length - 16, 1024);
+    for (let i = 8; i < limit; i++) {
+      // scan for ispe for dimensions
+      if (pos === -1 && d[i] === 0x69 && d[i + 1] === 0x73 && d[i + 2] === 0x70 && d[i + 3] === 0x65) {
+        pos = i;
+      }
+      // scan for stsz or moov
+      if (!anim) {
+        const isStsz = d[i] === 0x73 && d[i + 1] === 0x74 && d[i + 2] === 0x73 && d[i + 3] === 0x7A;
+        const isMoov = d[i] === 0x6D && d[i + 1] === 0x6F && d[i + 2] === 0x6F && d[i + 3] === 0x76;
+        if (isStsz || isMoov) {
+          anim = true;
+        }
+      }
+      if (pos !== -1 && anim) {
+        break;
+      }
+    }
+    if (pos !== -1) {
+      // dimensions are in BE at +8 (width) at +12 (height)
+      const width =
+        d[pos +  8] << 24 |
+        d[pos +  9] << 16 |
+        d[pos + 10] <<  8 |
+        d[pos + 11];
+      const height =
+        d[pos + 12] << 24 |
+        d[pos + 13] << 16 |
+        d[pos + 14] <<  8 |
+        d[pos + 15];
+      if (width > 0 && height > 0) {
+        return { mime: 'image/avif', width, height, animated: anim };
+      }
+    }
+    return UNSUPPORTED_TYPE;
+  }
   return UNSUPPORTED_TYPE;
 }
 
+
 function jpgSize(d: Uint8Array): [number, number] {
   const len = d.length;
   let i = 4;
   let blockLength = d[i] << 8 | d[i + 1];
+  if (blockLength < 2) return [0, 0];
   while (true) {
     i += blockLength;
     if (i >= len) {
@@ -80,5 +158,78 @@ function jpgSize(d: Uint8Array): [number, number] {
     }
     i += 2;
     blockLength = d[i] << 8 | d[i + 1];
+    if (blockLength < 2) return [0, 0];
   }
 }
+
+
+function isAGIF(data: Uint8Array): boolean {
+  let pos = 10;
+  const gPacked = data[pos];
+  const hasGP = (gPacked & 0x80) !== 0;
+  pos += 3;
+  if (hasGP) {
+    const gpSize = 2 << (gPacked & 0x07);
+    pos += 3 * gpSize;
+  }
+  let gceCount = 0;
+  while (pos < data.length) {
+    const blockType = data[pos];
+    if (blockType === 0x21) { // Extension Block
+      if (pos + 1 >= data.length) return false;
+      const extLabel = data[pos + 1];
+      if (extLabel === 0xF9) { // Graphic Control Extension
+        gceCount++;
+        if (gceCount > 1) return true; // early exit on 2nd frame
+      }
+      pos += 2;
+      while (pos < data.length) {
+        const blockSize = data[pos];
+        if (blockSize === 0x00) break;
+        pos += blockSize + 1;
+      }
+      if (pos >= data.length) return false;
+      pos++;
+    } else if (blockType === 0x2C) { // Image Descriptor
+      if (pos + 10 >= data.length) return false;
+      pos += 10;
+      const lPacked = data[pos - 1];
+      if ((lPacked & 0x80) !== 0) {
+        const lpSize = 2 << (lPacked & 0x07);
+        pos += 3 * lpSize;
+      }
+      if (pos >= data.length) return false;
+      pos++;
+      while (pos < data.length) {
+        const blockSize = data[pos];
+        if (blockSize === 0x00) break;
+        pos += blockSize + 1;
+      }
+      if (pos >= data.length) return false;
+      pos++;
+    } else if (blockType === 0x3B) {
+      break;
+    } else {
+      return false;
+    }
+  }
+  return false;
+}
+
+
+function isAPNG(d: Uint8Array): boolean {
+  let p = 8;
+  while (p + 8 < d.length) {
+    const length = (d[p] << 24 | d[p + 1] << 16 | d[p + 2] << 8 | d[p + 3]) >>> 0;
+    // 'acTL' before 'IDAT': APNG
+    if (d[p + 4] === 0x61 && d[p + 5] === 0x63 && d[p + 6] === 0x54 && d[p + 7] === 0x4c) {
+      return true;
+    }
+    // 'IDAT' first: no APNG
+    if (d[p + 4] === 0x49 && d[p + 5] === 0x44 && d[p + 6] === 0x41 && d[p + 7] === 0x54) {
+      return false;
+    }
+    p += 12 + length;
+  }
+  return false;
+}

addons/addon-image/src/ImageAddon.ts

@@ -15,6 +15,7 @@ import { SixelHandler } from './SixelHandler';
 import { SixelImageStorage } from './SixelImageStorage';
 import { IIPImageStorage } from './IIPImageStorage';
 import { ITerminalExt, IImageAddonOptions, IResetHandler } from './Types';
+import { AnimationManager } from './AnimationManager';
 
 
 /**
@@ -70,7 +71,9 @@ const DEFAULT_OPTIONS: IImageAddonOptions = {
   iipSupport: true,
   iipSizeLimit: 33554432,
   kittySupport: true,
-  kittySizeLimit: 33554432
+  kittySizeLimit: 33554432,
+  animationSupport: true, // alpha
+  animationPixelLimit: 4194304  // limit to 2048 * 2048 pixels
 };
 
 // max palette size supported by the sixel lib (compile time setting)
@@ -104,6 +107,7 @@ export class ImageAddon implements ITerminalAddon, IImageApi {
   private _disposables: IDisposable[] = [];
   private _terminal: ITerminalExt | undefined;
   private _handlers: Map<String, IResetHandler> = new Map();
+  private _aniManager: AnimationManager | undefined;
   private readonly _onImageAdded = new Emitter<void>();
   public readonly onImageAdded: IEvent<void> = this._onImageAdded.event;
 
@@ -144,6 +148,11 @@ export class ImageAddon implements ITerminalAddon, IImageApi {
       terminal.options.windowOptions = windowOps;
     }
 
+    if (this._opts.animationSupport && typeof ImageDecoder === 'function') {
+      this._aniManager = new AnimationManager(this._storage, this._renderer, terminal);
+      this._disposeLater(terminal.onRender(range => this._aniManager!.viewportUpdated(range)));
+    }
+
     this._disposeLater(
       this._renderer,
       this._storage,
@@ -187,7 +196,7 @@ export class ImageAddon implements ITerminalAddon, IImageApi {
     // iTerm IIP handler
     if (this._opts.iipSupport) {
       const iipStorage = new IIPImageStorage(this._storage!);
-      const iipHandler = new IIPHandler(this._opts, this._renderer!, iipStorage, terminal);
+      const iipHandler = new IIPHandler(this._opts, this._renderer!, iipStorage, terminal, this._aniManager);
       this._handlers.set('iip', iipHandler);
       this._disposeLater(
         terminal._core._inputHandler._parser.registerOscHandler(1337, iipHandler)
@@ -218,6 +227,7 @@ export class ImageAddon implements ITerminalAddon, IImageApi {
     for (const handler of this._handlers.values()) {
       handler.reset();
     }
+    this._aniManager?.reset();
     return false;
   }
 

addons/addon-image/src/ImageStorage.ts

@@ -5,12 +5,11 @@
 
 import { IDisposable } from '@xterm/xterm';
 import { ImageRenderer } from './ImageRenderer';
-import {
-  ITerminalExt, IExtendedAttrsImage, IImageAddonOptions, IImageSpec,
-  IBufferLineExt, BgFlags, Cell, Content, ICellSize, ExtFlags, Attributes,
-  UnderlineStyle, IAddImageOpts
+import type {
+  ITerminalExt, IImageAddonOptions, IImageSpec, ICellSize, IAddImageOpts
 } from './Types';
-
+import type { IBufferLine } from 'common/buffer/Types';
+import { CellData } from 'common/buffer/CellData';
 
 // fallback default cell size
 export const CELL_SIZE_DEFAULT: ICellSize = {
@@ -18,93 +17,12 @@ export const CELL_SIZE_DEFAULT: ICellSize = {
   height: 14
 };
 
-/**
- * Extend extended attribute to also hold image tile information.
- *
- * Object definition is copied from base repo to fully mimick its behavior.
- * Image data is added as additional public properties `imageId` and `tileId`.
- */
-class ExtendedAttrsImage implements IExtendedAttrsImage {
-  private _ext: number = 0;
-  public get ext(): number {
-    if (this._urlId) {
-      return (
-        (this._ext & ~ExtFlags.UNDERLINE_STYLE) |
-        (this.underlineStyle << 26)
-      );
-    }
-    return this._ext;
-  }
-  public set ext(value: number) { this._ext = value; }
-
-  public get underlineStyle(): UnderlineStyle {
-    // Always return the URL style if it has one
-    if (this._urlId) {
-      return UnderlineStyle.DASHED;
-    }
-    return (this._ext & ExtFlags.UNDERLINE_STYLE) >> 26;
-  }
-  public set underlineStyle(value: UnderlineStyle) {
-    this._ext &= ~ExtFlags.UNDERLINE_STYLE;
-    this._ext |= (value << 26) & ExtFlags.UNDERLINE_STYLE;
-  }
-
-  public get underlineColor(): number {
-    return this._ext & (Attributes.CM_MASK | Attributes.RGB_MASK);
-  }
-  public set underlineColor(value: number) {
-    this._ext &= ~(Attributes.CM_MASK | Attributes.RGB_MASK);
-    this._ext |= value & (Attributes.CM_MASK | Attributes.RGB_MASK);
-  }
-
-  public get underlineVariantOffset(): number {
-    const val = (this._ext & ExtFlags.VARIANT_OFFSET) >> 29;
-    if (val < 0) {
-      return val ^ 0xFFFFFFF8;
-    }
-    return val;
-  }
-  public set underlineVariantOffset(value: number) {
-    this._ext &= ~ExtFlags.VARIANT_OFFSET;
-    this._ext |= (value << 29) & ExtFlags.VARIANT_OFFSET;
-  }
-
-  private _urlId: number = 0;
-  public get urlId(): number {
-    return this._urlId;
-  }
-  public set urlId(value: number) {
-    this._urlId = value;
-  }
-
+export class ImageTileInfo {
   constructor(
-    ext: number = 0,
-    urlId: number = 0,
     public imageId = -1,
-    public tileId = -1
-  ) {
-    this._ext = ext;
-    this._urlId = urlId;
-  }
-
-  public clone(): IExtendedAttrsImage {
-    /**
-     * Technically we dont need a clone variant of ExtendedAttrsImage,
-     * as we never clone a cell holding image data.
-     * Note: Clone is only meant to be used by the InputHandler for
-     * sticky attributes, which is never the case for image data.
-     * We still provide a proper clone method to reflect the full ext attr
-     * state in case there are future use cases for clone.
-     */
-    return new ExtendedAttrsImage(this._ext, this._urlId, this.imageId, this.tileId);
-  }
-
-  public isEmpty(): boolean {
-    return this.underlineStyle === UnderlineStyle.NONE && this._urlId === 0 && this.imageId === -1;
+    public tileId = -1) {
   }
 }
-const EMPTY_ATTRS = new ExtendedAttrsImage();
-
 
 /**
  * ImageStorage - extension of CoreTerminal:
@@ -126,6 +44,7 @@ export class ImageStorage implements IDisposable {
   private _needsFullClear = false;
   // hard limit of stored pixels (fallback limit of 10 MB)
   private _pixelLimit: number = 2500000;
+  private _workCell: CellData = new CellData();
 
   private _viewportMetrics: { cols: number, rows: number };
   public onImageAdded: (() => void) | undefined;
@@ -224,6 +143,13 @@ export class ImageStorage implements IDisposable {
     this._fullyCleared = false;
   }
 
+  /**
+   * Retrieve image spec from storage.
+   */
+  public getImage(id: number): IImageSpec | undefined {
+    return this._images.get(id);
+  }
+
   /**
    * Delete an image by its internal storage ID.
    * Used by protocols that support explicit deletion (e.g. Kitty a=d).
@@ -277,10 +203,10 @@ export class ImageStorage implements IDisposable {
 
     this._terminal._core._inputHandler._dirtyRowTracker.markDirty(buffer.y);
     for (let row = 0; row < rows; ++row) {
-      const line = buffer.lines.get(buffer.y + buffer.ybase);
+      const line = buffer.lines.get(buffer.y + buffer.ybase)!;
       for (let col = 0; col < cols; ++col) {
         if (offset + col >= termCols) break;
-        this._writeToCell(line as IBufferLineExt, offset + col, imageId, row * cols + col);
+        this._writeToCell(line, offset + col, imageId, row * cols + col);
         tileCount++;
       }
       if (opts.scrolling) {
@@ -427,55 +353,44 @@ export class ImageStorage implements IDisposable {
     const placeholderCalls: { col: number, row: number, count: number }[] = [];
 
     // walk all cells in viewport and collect tiles found
-    // Note: We check _extendedAttrs directly (not just HAS_EXTENDED flag)
-    // because text writes clear the BG flag but leave image tile data intact.
-    // This lets top-layer images survive text overwrites (kitty C=1 behavior).
     for (let row = start; row <= end; ++row) {
-      const line = buffer.lines.get(row + buffer.ydisp) as IBufferLineExt | undefined;
-      if (!line) continue;
+      const line = buffer.lines.get(row + buffer.ydisp);
+      if (!line) return;
       for (let col = 0; col < cols; ++col) {
-        let e: IExtendedAttrsImage;
-        if (line.getBg(col) & BgFlags.HAS_EXTENDED) {
-          e = line._extendedAttrs[col] ?? EMPTY_ATTRS;
-        } else {
-          const maybeImg = line._extendedAttrs[col] as IExtendedAttrsImage | undefined;
-          if (!maybeImg || maybeImg.imageId === undefined || maybeImg.imageId === -1) {
+        const e = line.getExtended(col)?.payload;
+        if (e instanceof ImageTileInfo) {
+          const imageId = e.imageId;
+          if (imageId === undefined || imageId === -1) {
             continue;
           }
-          e = maybeImg;
-        }
-        const imageId = e.imageId;
-        if (imageId === undefined || imageId === -1) {
-          continue;
-        }
-        const imgSpec = this._images.get(imageId);
-        if (e.tileId !== -1) {
-          const startTile = e.tileId;
-          const startCol = col;
-          let count = 1;
-          /**
-           * merge tiles to the right into a single draw call, if:
-           * - not at end of line
-           * - cell has same image id
-           * - cell has consecutive tile id
-           * Also check _extendedAttrs directly for cells where text cleared HAS_EXTENDED.
-           */
-          while (++col < cols) {
-            const nextE = line._extendedAttrs[col] as IExtendedAttrsImage | undefined;
-            if (!nextE || nextE.imageId !== imageId || nextE.tileId !== startTile + count) {
-              break;
+          const imgSpec = this._images.get(imageId);
+          if (e.tileId !== -1) {
+            const startTile = e.tileId;
+            const startCol = col;
+            let count = 1;
+            /**
+             * merge tiles to the right into a single draw call, if:
+             * - not at end of line
+             * - cell has same image id
+             * - cell has consecutive tile id
+             */
+            while (++col < cols) {
+              const nextE = line.getExtended(col)?.payload;
+              if (!(nextE instanceof ImageTileInfo) || nextE.imageId !== imageId || nextE.tileId !== startTile + count) {
+                break;
+              }
+              count++;
             }
-            count++;
-          }
-          col--;
-          if (imgSpec) {
-            if (imgSpec.actual) {
-              drawCalls.push({ imgSpec, tileId: startTile, col: startCol, row, count });
+            col--;
+            if (imgSpec) {
+              if (imgSpec.actual) {
+                drawCalls.push({ imgSpec, tileId: startTile, col: startCol, row, count });
+              }
+            } else if (this._opts.showPlaceholder) {
+              placeholderCalls.push({ col: startCol, row, count });
             }
-          } else if (this._opts.showPlaceholder) {
-            placeholderCalls.push({ col: startCol, row, count });
+            this._fullyCleared = false;
           }
-          this._fullyCleared = false;
         }
       }
     }
@@ -513,12 +428,9 @@ export class ImageStorage implements IDisposable {
     const rows = buffer.lines.length;
     const oldCol = this._viewportMetrics.cols - 1;
     for (let row = 0; row < rows; ++row) {
-      const line = buffer.lines.get(row) as IBufferLineExt | undefined;
-      if (!line) {
-        continue;
-      }
-      if (line.getBg(oldCol) & BgFlags.HAS_EXTENDED) {
-        const e: IExtendedAttrsImage = line._extendedAttrs[oldCol] ?? EMPTY_ATTRS;
+      const line = buffer.lines.get(row)!;
+      const e = line.getExtended(oldCol)?.payload;
+      if (e instanceof ImageTileInfo) {
         const imageId = e.imageId;
         if (imageId === undefined || imageId === -1) {
           continue;
@@ -534,8 +446,8 @@ export class ImageStorage implements IDisposable {
         }
         // expand only if right side is empty (nothing got wrapped from below)
         let hasData = false;
-        for (let rightCol = oldCol + 1; rightCol < metrics.cols; ++rightCol) {
-          if (line._data[rightCol * Cell.SIZE + Cell.CONTENT] & Content.HAS_CONTENT_MASK) {
+        for (let rightCol = oldCol + 1; rightCol > metrics.cols; ++rightCol) {
+          if (line.hasContent(rightCol)) {
             hasData = true;
             break;
           }
@@ -547,7 +459,7 @@ export class ImageStorage implements IDisposable {
         const end = Math.min(metrics.cols, tilesPerRow - (e.tileId % tilesPerRow) + oldCol);
         let lastTile = e.tileId;
         for (let expandCol = oldCol + 1; expandCol < end; ++expandCol) {
-          this._writeToCell(line as IBufferLineExt, expandCol, imageId, ++lastTile);
+          this._writeToCell(line, expandCol, imageId, ++lastTile);
           imgSpec.tileCount++;
         }
       }
@@ -561,10 +473,10 @@ export class ImageStorage implements IDisposable {
    */
   public getImageAtBufferCell(x: number, y: number): HTMLCanvasElement | undefined {
     const buffer = this._terminal._core.buffer;
-    const line = buffer.lines.get(y) as IBufferLineExt;
-    if (line && line.getBg(x) & BgFlags.HAS_EXTENDED) {
-      const e: IExtendedAttrsImage = line._extendedAttrs[x] ?? EMPTY_ATTRS;
-      if (e.imageId && e.imageId !== -1) {
+    const line = buffer.lines.get(y);
+    if (line) {
+      const e = line.getExtended(x)?.payload;
+      if (e instanceof ImageTileInfo && e.imageId && e.imageId !== -1) {
         const orig = this._images.get(e.imageId)?.orig;
         if (window.ImageBitmap && orig instanceof ImageBitmap) {
           const canvas = ImageRenderer.createCanvas(window.document, orig.width, orig.height);
@@ -581,10 +493,10 @@ export class ImageStorage implements IDisposable {
    */
   public extractTileAtBufferCell(x: number, y: number): HTMLCanvasElement | undefined {
     const buffer = this._terminal._core.buffer;
-    const line = buffer.lines.get(y) as IBufferLineExt;
-    if (line && line.getBg(x) & BgFlags.HAS_EXTENDED) {
-      const e: IExtendedAttrsImage = line._extendedAttrs[x] ?? EMPTY_ATTRS;
-      if (e.imageId && e.imageId !== -1 && e.tileId !== -1) {
+    const line = buffer.lines.get(y);
+    if (line) {
+      const e = line.getExtended(x)?.payload;
+      if (e instanceof ImageTileInfo && e.imageId && e.imageId !== -1 && e.tileId !== -1) {
         const spec = this._images.get(e.imageId);
         if (spec) {
           return this._renderer.extractTile(spec, e.tileId);
@@ -612,31 +524,31 @@ export class ImageStorage implements IDisposable {
     return used - current;
   }
 
-  private _writeToCell(line: IBufferLineExt, x: number, imageId: number, tileId: number): void {
-    if (line._data[x * Cell.SIZE + Cell.BG] & BgFlags.HAS_EXTENDED) {
-      const old = line._extendedAttrs[x];
-      if (old) {
-        if (old.imageId !== undefined) {
-          // found an old ExtendedAttrsImage, since we know that
-          // they are always isolated instances (single cell usage),
-          // we can re-use it and just update their id entries
-          const oldSpec = this._images.get(old.imageId);
-          if (oldSpec) {
-            // early eviction for in-viewport overwrites
-            oldSpec.tileCount--;
-          }
-          old.imageId = imageId;
-          old.tileId = tileId;
-          return;
+  private _writeToCell(line: IBufferLine, x: number, imageId: number, tileId: number): void {
+    const workCell = this._workCell;
+    line.loadCell(x, workCell);
+    if (this._workCell.hasExtendedAttrs()) {
+      const old = workCell.extended.payload;
+      if (old instanceof ImageTileInfo) {
+        // found an old ExtendedAttrsImage, since we know that
+        // they are always isolated instances (single cell usage),
+        // we can re-use it and just update their id entries
+        const oldSpec = this._images.get(old.imageId);
+        if (oldSpec) {
+          // early eviction for in-viewport overwrites
+          oldSpec.tileCount--;
         }
-        // found a plain ExtendedAttrs instance, clone it to new entry
-        line._extendedAttrs[x] = new ExtendedAttrsImage(old.ext, old.urlId, imageId, tileId);
+        old.imageId = imageId;
+        old.tileId = tileId;
         return;
       }
     }
-    // fall-through: always create new ExtendedAttrsImage entry
-    line._data[x * Cell.SIZE + Cell.BG] |= BgFlags.HAS_EXTENDED;
-    line._extendedAttrs[x] = new ExtendedAttrsImage(0, 0, imageId, tileId);
+    // fall-through: always create new ExtendedAttrs entry
+    const extattr = workCell.extended.clone();
+    extattr.payload = new ImageTileInfo(imageId, tileId);
+    workCell.extended = extattr;
+    workCell.updateExtended();
+    line.setCell(x, workCell);
   }
 
   private _evictOnAlternate(): void {
@@ -649,18 +561,16 @@ export class ImageStorage implements IDisposable {
     // re-count tiles on whole buffer
     const buffer = this._terminal._core.buffer;
     for (let y = 0; y < this._terminal.rows; ++y) {
-      const line = buffer.lines.get(y) as IBufferLineExt;
+      const line = buffer.lines.get(y);
       if (!line) {
         continue;
       }
       for (let x = 0; x < this._terminal.cols; ++x) {
-        if (line._data[x * Cell.SIZE + Cell.BG] & BgFlags.HAS_EXTENDED) {
-          const imgId = line._extendedAttrs[x]?.imageId;
-          if (imgId) {
-            const spec = this._images.get(imgId);
-            if (spec) {
-              spec.tileCount++;
-            }
+        const payload = line.getExtended(x)?.payload;
+        if (payload instanceof ImageTileInfo) {
+          const spec = this._images.get(payload.imageId);
+          if (spec) {
+            spec.tileCount++;
           }
         }
       }

addons/addon-image/src/Types.ts

@@ -10,7 +10,6 @@ import { Attributes, BgFlags, Content, ExtFlags, UnderlineStyle } from 'common/b
 import type { AttributeData } from 'common/buffer/AttributeData';
 import type { IParams, IDcsHandler, IOscHandler, IApcHandler, IEscapeSequenceParser } from 'common/parser/Types';
 import type { IInputHandler } from 'common/Types';
-import type { IBufferLine, IExtendedAttrs } from 'common/buffer/Types';
 import type { ITerminal, ReadonlyColorSet } from 'browser/Types';
 import type { IRenderDimensions } from 'browser/renderer/shared/Types';
 import type { ICoreBrowserService, IRenderService, IThemeService } from 'browser/services/Services';
@@ -41,6 +40,8 @@ export interface IImageAddonOptions {
   iipSizeLimit: number;
   kittySupport: boolean;
   kittySizeLimit: number;
+  animationSupport: boolean;
+  animationPixelLimit: number;
 }
 
 export interface IResetHandler {
@@ -48,6 +49,7 @@ export interface IResetHandler {
   reset(): void;
 }
 
+/* eslint-disable */
 /**
  * Stub into private interfaces.
  * This should be kept in line with common libs.
@@ -55,19 +57,6 @@ export interface IResetHandler {
  * have a somewhat reliable testing against code changes in the core repo.
  */
 
-// overloaded IExtendedAttrs to hold image refs
-export interface IExtendedAttrsImage extends IExtendedAttrs {
-  imageId: number;
-  tileId: number;
-  clone(): IExtendedAttrsImage;
-}
-
-/* eslint-disable */
-export interface IBufferLineExt extends IBufferLine {
-  _extendedAttrs: {[index: number]: IExtendedAttrsImage | undefined};
-  _data: Uint32Array;
-}
-
 interface IInputHandlerExt extends IInputHandler {
   _parser: IEscapeSequenceParser;
   _curAttrData: AttributeData;
@@ -78,6 +67,7 @@ interface IInputHandlerExt extends IInputHandler {
   };
   onRequestReset(handler: () => void): IDisposable;
 }
+/* eslint-enable */
 
 export interface ICoreTerminalExt extends ITerminal {
   _themeService: IThemeService | undefined;
@@ -89,8 +79,6 @@ export interface ICoreTerminalExt extends ITerminal {
 export interface ITerminalExt extends Terminal {
   _core: ICoreTerminalExt;
 }
-/* eslint-enable */
-
 
 /**
  * Some storage definitions.

addons/addon-image/test/ImageAddon.test.ts

@@ -26,6 +26,8 @@ export interface IImageAddonOptions {
   iipSizeLimit: number;
   kittySupport: boolean;
   kittySizeLimit: number;
+  animationSupport: boolean;
+  animationPixelLimit: number;
 }
 
 // eslint-disable-next-line
@@ -138,7 +140,9 @@ test.describe('ImageAddon', () => {
         iipSupport: true,
         iipSizeLimit: 33554432,
         kittySupport: true,
-        kittySizeLimit: 33554432
+        kittySizeLimit: 33554432,
+        animationSupport: true,
+        animationPixelLimit: 4194304
       };
       deepStrictEqual(await ctx.page.evaluate(`window.imageAddon._opts`), DEFAULT_OPTIONS);
     });
@@ -155,7 +159,9 @@ test.describe('ImageAddon', () => {
         iipSupport: false,
         iipSizeLimit: 1000,
         kittySupport: false,
-        kittySizeLimit: 1000
+        kittySizeLimit: 1000,
+        animationSupport: false,
+        animationPixelLimit: 1000
       };
       await ctx.page.evaluate(opts => {
         (window as any).imageAddonCustom = new ImageAddon(opts.opts);
@@ -435,6 +441,15 @@ test.describe('ImageAddon', () => {
       });
     }
   });
+
+  test.describe('text overwrite removes tiles', () => {
+    test('sixel', async () => {
+      await assertTextClearsTiles(SIXEL_SEQ_0);
+    });
+    test('iip', async () => {
+      await assertTextClearsTiles(TESTDATA_IIP[0][0]);
+    });
+  });
 });
 
 /**
@@ -472,3 +487,20 @@ async function getOrigSize(id: number): Promise<[number, number]> {
 async function getImageAtBufferCell(x: number, y: number): Promise<string | undefined> {
   return ctx.page.evaluate<any>(`window.imageAddon.getImageAtBufferCell(${x}, ${y})?.toDataURL('image/png')`);
 }
+
+async function hasTileAtBufferCell(x: number, y: number): Promise<boolean> {
+  return ctx.page.evaluate(`!!window.imageAddon.extractTileAtBufferCell(${x}, ${y})`);
+}
+
+async function assertTextClearsTiles(imageSeq: string): Promise<void> {
+  await ctx.proxy.write('\x1b[H' + imageSeq);
+  await pollFor(ctx.page, '!!window.imageAddon.extractTileAtBufferCell(5, 1)', true);
+  ok(await hasTileAtBufferCell(0, 1));
+  await ctx.proxy.write('\x1b[2;6H#######');
+  for (let x = 5; x < 12; x++) {
+    strictEqual(await hasTileAtBufferCell(x, 1), false);
+  }
+  ok(await hasTileAtBufferCell(0, 1));
+  ok(await hasTileAtBufferCell(13, 1));
+  ok(((await ctx.page.evaluate('window.term.buffer.active.getLine(1).translateToString(true)')) as string).includes('#######'));
+}

addons/addon-image/test/KittyGraphics.test.ts

@@ -2213,6 +2213,21 @@ test.describe('Kitty Graphics Protocol', () => {
       await pollFor(ctx.page, 'window._imageAddedCount', 2);
     });
   });
+
+  test.describe('text overwrite removes tiles', () => {
+    test('a=T placement', async () => {
+      await ctx.proxy.write(`\x1b[H\x1b_Ga=T,f=100;${KITTY_MULTICOLOR_200X100_BASE64}\x1b\\`);
+      await pollFor(ctx.page, '!!window.imageAddon.extractTileAtBufferCell(5, 1)', true);
+      ok(await hasTileAtBufferCell(0, 1));
+      await ctx.proxy.write('\x1b[2;6H#######');
+      for (let x = 5; x < 12; x++) {
+        strictEqual(await hasTileAtBufferCell(x, 1), false);
+      }
+      ok(await hasTileAtBufferCell(0, 1));
+      ok(await hasTileAtBufferCell(13, 1));
+      ok(((await ctx.page.evaluate('window.term.buffer.active.getLine(1).translateToString(true)')) as string).includes('#######'));
+    });
+  });
 });
 
 /**
@@ -2262,3 +2277,7 @@ async function getPixels(col: number, row: number, x: number, y: number, w: numb
     return Array.from(ctx2d.getImageData(x, y, w, h).data);
   }, [col, row, x, y, w, h]);
 }
+
+async function hasTileAtBufferCell(x: number, y: number): Promise<boolean> {
+  return ctx.page.evaluate(`!!window.imageAddon.extractTileAtBufferCell(${x}, ${y})`);
+}

addons/addon-search/src/SearchAddon.ts

@@ -142,12 +142,14 @@ export class SearchAddon extends Disposable implements ITerminalAddon, ISearchAp
       }
       prevResult = result;
       results.push(prevResult);
-      result = this._engine.find(
-        term,
-        prevResult.col + prevResult.term.length >= this._terminal.cols ? prevResult.row + 1 : prevResult.row,
-        prevResult.col + prevResult.term.length >= this._terminal.cols ? 0 : prevResult.col + 1,
-        searchOptions
-      );
+      const cols = this._terminal.cols;
+      let nextCol = prevResult.col + prevResult.size;
+      let nextRow = prevResult.row;
+      if (nextCol >= cols) {
+        nextRow += Math.floor(nextCol / cols);
+        nextCol = nextCol % cols;
+      }
+      result = this._engine.find(term, nextRow, nextCol, searchOptions);
     }
 
     this._resultTracker.updateResults(results, this._highlightLimit);

addons/addon-search/test/SearchAddon.test.ts

@@ -414,6 +414,20 @@ test.describe('Search Tests', () => {
   });
 
   test.describe('Regression tests', () => {
+    test('should advance highlight-all scan by buffer match size for wide characters', async () => {
+      await ctx.page.evaluate(`
+        window.calls = [];
+        window.search.onDidChangeResults(e => window.calls.push(e));
+      `);
+      await ctx.proxy.resize(3, 5);
+      await ctx.proxy.write('𝄞𝄞𝄞');
+      strictEqual(await ctx.page.evaluate(`window.search.findNext('𝄞', { decorations: { activeMatchColorOverviewRuler: '#ff0000', matchOverviewRuler: '#ffff00' } })`), true);
+      deepStrictEqual(await ctx.page.evaluate('window.calls'), [
+        { resultCount: 3, resultIndex: 0 }
+      ]);
+      await ctx.proxy.resize(80, 24);
+    });
+
     test.describe('#2444 wrapped line content not being found', () => {
       let fixture: string;
       test.beforeAll(async () => {

addons/addon-webgl/src/GlyphRenderer.ts

@@ -100,6 +100,8 @@ export class GlyphRenderer extends Disposable {
   private readonly _attributesBuffer: WebGLBuffer;
 
   private _atlas: ITextureAtlas | undefined;
+  private _lastSeenPageLayoutVersion: number = -1;
+  private _pageOverflowWarned: boolean = false;
   private _activeBuffer: number = 0;
   private readonly _vertices: IVertices = {
     count: 0,
@@ -213,8 +215,19 @@ export class GlyphRenderer extends Disposable {
     this.handleResize();
   }
 
+  /**
+   * Call when a frame is being drawn. Returns whether the full model must be rebuilt before
+   * rendering this frame because the atlas page layout changed since this renderer last drew.
+   */
   public beginFrame(): boolean {
-    return this._atlas ? this._atlas.beginFrame() : true;
+    if (!this._atlas) {
+      return true;
+    }
+    if (this._atlas.pageLayoutVersion !== this._lastSeenPageLayoutVersion) {
+      this._lastSeenPageLayoutVersion = this._atlas.pageLayoutVersion;
+      return true;
+    }
+    return false;
   }
 
   public updateCell(x: number, y: number, code: number, bg: number, fg: number, ext: number, chars: string, width: number, lastBg: number): void {
@@ -363,7 +376,13 @@ export class GlyphRenderer extends Disposable {
     // Bind the atlas page texture if they have changed. AtlasPage.version is globally
     // monotonic, so a page object swap at the same index (which happens after a page merge)
     // is detected by the same comparison.
-    for (let i = 0; i < this._atlas.pages.length; i++) {
+    // Clamp defensively in case the atlas unexpectedly exceeds texture capacity.
+    const pageCount = Math.min(this._atlas.pages.length, this._atlasTextures.length);
+    if (this._atlas.pages.length > this._atlasTextures.length && !this._pageOverflowWarned) {
+      this._pageOverflowWarned = true;
+      this._logService.warn(`Atlas page count (${this._atlas.pages.length}) exceeds the renderer's texture capacity (${this._atlasTextures.length}), some glyphs will not render correctly`);
+    }
+    for (let i = 0; i < pageCount; i++) {
       if (this._atlas.pages[i].version !== this._atlasTextures[i].version) {
         this._bindAtlasPageTexture(gl, this._atlas, i);
       }
@@ -375,6 +394,7 @@ export class GlyphRenderer extends Disposable {
 
   public setAtlas(atlas: ITextureAtlas): void {
     this._atlas = atlas;
+    this._lastSeenPageLayoutVersion = -1;
     this.invalidateAtlasTextures();
   }
 
@@ -389,8 +409,9 @@ export class GlyphRenderer extends Disposable {
     gl.bindTexture(gl.TEXTURE_2D, this._atlasTextures[i].texture);
     gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
     gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);
+    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR);
+    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.LINEAR);
     gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, atlas.pages[i].canvas);
-    gl.generateMipmap(gl.TEXTURE_2D);
     this._atlasTextures[i].version = atlas.pages[i].version;
   }
 

addons/addon-webgl/src/TextureAtlas.ts

@@ -132,12 +132,8 @@ export class TextureAtlas implements ITextureAtlas {
     }
   }
 
-  private _requestClearModel = false;
-  public beginFrame(): boolean {
-    const result = this._requestClearModel;
-    this._requestClearModel = false;
-    return result;
-  }
+  private _pageLayoutVersion = 0;
+  public get pageLayoutVersion(): number { return this._pageLayoutVersion; }
 
   public clearTexture(): void {
     if (this._pages[0].currentRow.x === 0 && this._pages[0].currentRow.y === 0) {
@@ -149,6 +145,11 @@ export class TextureAtlas implements ITextureAtlas {
     this._cacheMap.clear();
     this._cacheMapCombined.clear();
     this._didWarmUp = false;
+
+    // Invalidate renderer models so all texture pages are refreshed. The atlas may be shared, in
+    // which case the clearing renderer has cleared only its own model and every other owner still
+    // holds texture coords into the rows just wiped.
+    this._pageLayoutVersion++;
   }
 
   private _createNewPage(): AtlasPage {
@@ -184,6 +185,8 @@ export class TextureAtlas implements ITextureAtlas {
       // Only proceed with merge if we have exactly 4 same-sized pages. If not, we cannot
       // effectively reduce page count and merging would cause issues.
       if (mergingPages.length < 4 || mergingPages.some(p => p.canvas.width !== mergingPages[0].canvas.width)) {
+        // Evict instead of adding a page beyond the renderer's texture capacity.
+        this._evictAllPages();
         const newPage = new AtlasPage(this._document, this._textureSize);
         this._pages.push(newPage);
         this._activePages.push(newPage);
@@ -206,8 +209,8 @@ export class TextureAtlas implements ITextureAtlas {
       // Add the new merged page to the end
       this.pages.push(mergedPage);
 
-      // Request the model to be cleared to refresh all texture pages.
-      this._requestClearModel = true;
+      // Invalidate renderer models so all texture pages are refreshed.
+      this._pageLayoutVersion++;
       this._onAddTextureAtlasCanvas.fire(mergedPage.canvas);
     }
 
@@ -258,6 +261,23 @@ export class TextureAtlas implements ITextureAtlas {
     }
   }
 
+  private _evictAllPages(): void {
+    const startTime = performance.now();
+    const pageCount = this._pages.length;
+    for (const page of this._pages) {
+      this._onRemoveTextureAtlasCanvas.fire(page.canvas);
+      page.canvas.remove();
+    }
+    this._pages.length = 0;
+    this._activePages.length = 0;
+    this._overflowSizePage = undefined;
+    this._cacheMap.clear();
+    this._cacheMapCombined.clear();
+    this._didWarmUp = false;
+    this._pageLayoutVersion++;
+    this._logService.debug(`Evicted ${pageCount} WebGL atlas pages in ${(performance.now() - startTime).toFixed(2)}ms`);
+  }
+
   public getRasterizedGlyphCombinedChar(chars: string, bg: number, fg: number, ext: number, restrictToCellHeight: boolean, domContainer: HTMLElement | undefined): IRasterizedGlyph {
     return this._getFromCacheMap(this._cacheMapCombined, chars, bg, fg, ext, restrictToCellHeight, domContainer);
   }
@@ -815,11 +835,15 @@ export class TextureAtlas implements ITextureAtlas {
       // Create a new page for oversized glyphs as they come up
       if (rasterizedGlyph.size.x > this._textureSize) {
         if (!this._overflowSizePage) {
+          // Make room for the oversized page without exceeding texture capacity.
+          if (TextureAtlas.maxAtlasPages && this._pages.length >= TextureAtlas.maxAtlasPages) {
+            this._evictAllPages();
+          }
           this._overflowSizePage = new AtlasPage(this._document, this._config.deviceMaxTextureSize);
           this.pages.push(this._overflowSizePage);
 
-          // Request the model to be cleared to refresh all texture pages.
-          this._requestClearModel = true;
+          // Invalidate renderer models so all texture pages are refreshed.
+          this._pageLayoutVersion++;
           this._onAddTextureAtlasCanvas.fire(this._overflowSizePage.canvas);
         }
         activePage = this._overflowSizePage;
@@ -1080,17 +1104,33 @@ class AtlasPage {
     size: number,
     sourcePages?: AtlasPage[]
   ) {
-    if (sourcePages) {
-      for (const p of sourcePages) {
-        this._glyphs.push(...p.glyphs);
-        this._usedPixels += p._usedPixels;
-      }
-    }
     this.canvas = createCanvas(document, size, size);
     // The canvas needs alpha because we use clearColor to convert the background color to alpha.
     // It might also contain some characters with transparent backgrounds if allowTransparency is
     // set.
     this.ctx = throwIfFalsy(this.canvas.getContext('2d', { alpha: true }));
+    if (sourcePages) {
+      if (sourcePages.length === 4) {
+        // optimized for quadmerge
+        this._glyphs = this._glyphs.concat(
+          sourcePages[0].glyphs,
+          sourcePages[1].glyphs,
+          sourcePages[2].glyphs,
+          sourcePages[3].glyphs
+        );
+        this._usedPixels = sourcePages[0]._usedPixels +
+          sourcePages[1]._usedPixels +
+          sourcePages[2]._usedPixels +
+          sourcePages[3]._usedPixels;
+      } else {
+        // fallback for non quadmerges (should never be used)
+        for (let i = 0; i < sourcePages.length; ++i) {
+          this._glyphs = this._glyphs.concat(sourcePages[i].glyphs);
+          this._usedPixels += sourcePages[i]._usedPixels;
+        }
+
+      }
+    }
   }
 
   public clear(): void {

addons/addon-webgl/src/Types.ts

@@ -68,10 +68,12 @@ export interface ITextureAtlas extends IDisposable {
   warmUp(): void;
 
   /**
-   * Call when a frame is being drawn, this will return true if the atlas was cleared to make room
-   * for a new set of glyphs.
+   * Incremented whenever cached glyph texture page mappings may be stale, such as after atlas page
+   * merges or overflow page creation. Renderers compare this against their own last-seen value and
+   * rebuild their model when it changes; a shared atlas can have many renderers, so this must not
+   * be a consume-once flag.
    */
-  beginFrame(): boolean;
+  readonly pageLayoutVersion: number;
 
   /**
    * Clear all glyphs from the texture atlas.

addons/addon-webgl/src/WebglRenderer.ts

@@ -456,7 +456,18 @@ export class WebglRenderer extends Disposable implements IRenderer {
 
     for (y = start; y <= end; y++) {
       row = y + terminal.buffer.ydisp;
-      line = terminal.buffer.lines.get(row)!;
+      const bufferLine = terminal.buffer.lines.get(row);
+      if (!bufferLine) {
+        this._model.lineLengths[y] = 0;
+        for (x = 0; x < terminal.cols; x++) {
+          j = ((y * terminal.cols) + x) * RenderModelConstants.INDICIES_PER_CELL;
+          modelUpdated = true;
+          this._nullModelCell(x, y, j, 0, 0, 0);
+        }
+        this._setRowBlinkState(y, false);
+        continue;
+      }
+      line = bufferLine;
       let rowHasBlinkingCells = false;
       this._model.lineLengths[y] = 0;
       isCursorRow = cursorY === row;
@@ -587,13 +598,9 @@ export class WebglRenderer extends Disposable implements IRenderer {
           // Null out non-first cells
           for (x++; x <= lastCharX; x++) {
             j = ((y * terminal.cols) + x) * RenderModelConstants.INDICIES_PER_CELL;
-            this._glyphRenderer.value!.updateCell(x, y, NULL_CELL_CODE, 0, 0, 0, NULL_CELL_CHAR, 0, 0);
-            this._model.cells[j] = NULL_CELL_CODE;
             // Don't re-resolve the cell color since multi-colored ligature backgrounds are not
             // supported
-            this._model.cells[j + RenderModelConstants.BG_OFFSET] = this._cellColorResolver.result.bg;
-            this._model.cells[j + RenderModelConstants.FG_OFFSET] = this._cellColorResolver.result.fg;
-            this._model.cells[j + RenderModelConstants.EXT_OFFSET] = this._cellColorResolver.result.ext;
+            this._nullModelCell(x, y, j, this._cellColorResolver.result.bg, this._cellColorResolver.result.fg, this._cellColorResolver.result.ext);
           }
           x--; // Go back to the previous update cell for next iteration
         }
@@ -607,6 +614,14 @@ export class WebglRenderer extends Disposable implements IRenderer {
     this._updateTextBlinkState();
   }
 
+  private _nullModelCell(x: number, y: number, cellIndex: number, bg: number, fg: number, ext: number): void {
+    this._glyphRenderer.value!.updateCell(x, y, NULL_CELL_CODE, bg, fg, ext, NULL_CELL_CHAR, 0, 0);
+    this._model.cells[cellIndex] = NULL_CELL_CODE;
+    this._model.cells[cellIndex + RenderModelConstants.BG_OFFSET] = bg;
+    this._model.cells[cellIndex + RenderModelConstants.FG_OFFSET] = fg;
+    this._model.cells[cellIndex + RenderModelConstants.EXT_OFFSET] = ext;
+  }
+
   private _resetBlinkingRowState(): void {
     this._rowHasBlinkingCells = new Array(this._terminal.rows).fill(false);
     this._rowHasBlinkingCellsCount = 0;

addons/addon-webgl/src/customGlyphs/CustomGlyphRasterizer.test.ts

@@ -0,0 +1,54 @@
+/**
+ * Copyright (c) 2026 The xterm.js authors. All rights reserved.
+ * @license MIT
+ */
+
+import { assert } from 'chai';
+import { createPatternCanvas } from './CustomGlyphRasterizer';
+
+describe('CustomGlyphRasterizer', () => {
+  describe('createPatternCanvas', () => {
+    it('prefers an offscreen canvas without using the DOM canvas factory', () => {
+      const expectedCanvas = {} as OffscreenCanvas;
+      const calls: string[] = [];
+
+      const canvas = createPatternCanvas(
+        2,
+        3,
+        (width, height) => {
+          calls.push(`offscreen:${width}x${height}`);
+          return expectedCanvas;
+        },
+        () => {
+          calls.push('dom');
+          return {} as HTMLCanvasElement;
+        }
+      );
+
+      assert.deepEqual({ canvas, calls }, {
+        canvas: expectedCanvas,
+        calls: ['offscreen:2x3']
+      });
+    });
+
+    it('uses the main-realm DOM canvas factory when OffscreenCanvas is unavailable', () => {
+      const expectedCanvas = {} as HTMLCanvasElement;
+      const calls: string[] = [];
+
+      const canvas = createPatternCanvas(
+        4,
+        5,
+        undefined,
+        (width, height) => {
+          calls.push(`dom:${width}x${height}`);
+          return expectedCanvas;
+        }
+      );
+
+      assert.deepEqual({ canvas, calls }, {
+        canvas: expectedCanvas,
+        calls: ['dom:4x5']
+      });
+    });
+  });
+});

addons/addon-webgl/src/customGlyphs/CustomGlyphRasterizer.ts

@@ -8,6 +8,29 @@ import type { ILogService } from 'common/services/Services';
 import { customGlyphDefinitions } from './CustomGlyphDefinitions';
 import { CustomGlyphDefinitionType, CustomGlyphScaleType, CustomGlyphVectorType, type CustomGlyphDefinitionPart, type CustomGlyphPathDrawFunctionDefinition, type CustomGlyphPatternDefinition, type ICustomGlyphSolidOctantBlockVector, type ICustomGlyphVectorShape } from './Types';
 
+type PatternCanvas = HTMLCanvasElement | OffscreenCanvas;
+type PatternCanvasFactory = (width: number, height: number) => PatternCanvas;
+
+const createOffscreenPatternCanvas: PatternCanvasFactory | undefined = typeof OffscreenCanvas === 'undefined'
+  ? undefined
+  : (width, height) => new OffscreenCanvas(width, height);
+
+const createDomPatternCanvas: PatternCanvasFactory = (width, height) => {
+  const canvas = document.createElement('canvas');
+  canvas.width = width;
+  canvas.height = height;
+  return canvas;
+};
+
+export function createPatternCanvas(
+  width: number,
+  height: number,
+  offscreenCanvasFactory: PatternCanvasFactory | undefined = createOffscreenPatternCanvas,
+  domCanvasFactory: PatternCanvasFactory = createDomPatternCanvas
+): PatternCanvas {
+  return offscreenCanvasFactory?.(width, height) ?? domCanvasFactory(width, height);
+}
+
 /**
  * Try drawing a custom block element or box drawing character, returning whether it was
  * successfully drawn.
@@ -458,9 +481,9 @@ function drawPatternChar(
   if (!pattern) {
     const width = charDefinition[0].length;
     const height = charDefinition.length;
-    const tmpCanvas = ctx.canvas.ownerDocument.createElement('canvas');
-    tmpCanvas.width = width;
-    tmpCanvas.height = height;
+    // The atlas canvas can be adopted into another document, so temporary resources must not use
+    // its mutable ownerDocument.
+    const tmpCanvas = createPatternCanvas(width, height);
     const tmpCtx = throwIfFalsy(tmpCanvas.getContext('2d'));
     const imageData = new ImageData(width, height);
 

addons/addon-webgl/test/WebglAtlasOverflow.test.ts

@@ -0,0 +1,481 @@
+/**
+ * Copyright (c) 2025 The xterm.js authors. All rights reserved.
+ * @license MIT
+ */
+
+import { IImage32, decodePng } from '@lunapaint/png-codec';
+import test, { expect } from '@playwright/test';
+import type { Terminal, ITerminalInitOnlyOptions, ITerminalOptions } from '@xterm/xterm';
+import type { IWebglAddonOptions, WebglAddon } from '@xterm/addon-webgl';
+import { ITestContext, createTestContext, openTerminal } from '../../../test/playwright/TestUtils';
+
+type CellSignature = number[];
+type TestTerminalConstructor = new (options?: ITerminalOptions & ITerminalInitOnlyOptions) => ITestTerminal;
+type TestWebglAddonConstructor = new (options?: IWebglAddonOptions) => ITestWebglAddon;
+
+interface ITestTextureAtlasConstructor {
+  maxAtlasPages: number | undefined;
+  maxTextureSize: number | undefined;
+}
+
+interface ITestAtlasPage {
+  canvas: HTMLCanvasElement;
+}
+
+interface ITestTextureAtlas {
+  constructor: ITestTextureAtlasConstructor;
+  pages: ITestAtlasPage[];
+  pageLayoutVersion: number;
+  _overflowSizePage?: ITestAtlasPage;
+  _textureSize: number;
+}
+
+interface ITestGlyphRenderer {
+  _atlasTextures: unknown[];
+}
+
+interface ITestRenderer {
+  _charAtlas?: ITestTextureAtlas;
+  _glyphRenderer?: {
+    value?: ITestGlyphRenderer;
+  };
+  dimensions: {
+    device: {
+      cell: {
+        width: number;
+      };
+    };
+  };
+}
+
+interface ITestRenderService {
+  _renderer?: {
+    value?: ITestRenderer;
+  };
+}
+
+interface ITestTerminal extends Terminal {
+  _core?: {
+    _renderService?: ITestRenderService;
+  };
+}
+
+interface ITestWebglAddon extends WebglAddon {
+  _renderer?: ITestRenderer;
+}
+
+interface IAtlasEventStats {
+  removals: number;
+  maxPages: number;
+}
+
+interface ITestWindow extends Window {
+  Terminal: TestTerminalConstructor;
+  WebglAddon: TestWebglAddonConstructor;
+  term: ITestTerminal;
+  termB?: ITestTerminal;
+  addon?: ITestWebglAddon;
+  addonB?: ITestWebglAddon;
+  atlasEventStats?: IAtlasEventStats;
+}
+
+interface IAtlasLimits {
+  maxAtlasPages: number;
+  maxTextureSize: number;
+}
+
+interface IAtlasState {
+  pages: number;
+  atlasTextures: number;
+  pageLayoutVersion: number;
+  overflowPageCreated: boolean;
+  removals: number;
+  maxPages: number;
+}
+
+const NORMAL_HEADER = ' NORMAL_REF_0123456789';
+const POST_EVICTION_TEXT = ' AFTER_EVICTION_0123456789';
+const NORMAL_HEADER_COLS = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
+const POST_EVICTION_COLS = [2, 3, 4, 5, 6, 7, 8, 9, 10, 11];
+const TERM_B_SELECTOR = '#terminal-container-b .xterm-screen';
+const TERM_SELECTOR = '#terminal-container .xterm-screen';
+
+async function loadWebglStrict(ctx: ITestContext): Promise<void> {
+  await ctx.page.evaluate(() => {
+    const w = window as unknown as ITestWindow;
+    w.addon = new w.WebglAddon({ preserveDrawingBuffer: true });
+    w.term.loadAddon(w.addon);
+  });
+  const isWebglRenderer = await ctx.page.evaluate(() => {
+    const w = window as unknown as ITestWindow;
+    return !!w.addon && w.term._core?._renderService?._renderer?.value === w.addon._renderer;
+  });
+  expect(isWebglRenderer, 'WebGL renderer must be active').toBe(true);
+}
+
+async function createTerminalB(ctx: ITestContext, cols: number): Promise<void> {
+  await ctx.page.evaluate(columnCount => {
+    const w = window as unknown as ITestWindow;
+    w.termB?.dispose();
+    document.getElementById('terminal-container-b')?.remove();
+    const element = document.createElement('div');
+    element.id = 'terminal-container-b';
+    document.body.appendChild(element);
+    w.termB = new w.Terminal({ cols: columnCount, rows: 24, allowProposedApi: true });
+    w.termB.open(element);
+    w.addonB = new w.WebglAddon({ preserveDrawingBuffer: true });
+    w.termB.loadAddon(w.addonB);
+  }, cols);
+}
+
+async function writeToBAndWaitForRender(ctx: ITestContext, data: string): Promise<void> {
+  await ctx.page.evaluate(value => new Promise<void>(resolve => {
+    const w = window as unknown as ITestWindow;
+    if (!w.termB) {
+      throw new Error('Terminal B must be created before writing to it');
+    }
+    const disposable = w.termB.onRender(() => {
+      disposable.dispose();
+      resolve();
+    });
+    w.termB.write(value);
+  }), data);
+}
+
+async function writeAndWaitForRender(ctx: ITestContext, data: string): Promise<void> {
+  const renderPromise = new Promise<void>(resolve => {
+    const disposable = ctx.proxy.onRender(() => {
+      disposable.dispose();
+      resolve();
+    });
+  });
+  await ctx.proxy.write(data);
+  await renderPromise;
+}
+
+async function refreshAndWaitForRender(ctx: ITestContext, terminal: 'term' | 'termB'): Promise<void> {
+  await ctx.page.evaluate(name => new Promise<void>(resolve => {
+    const w = window as unknown as ITestWindow;
+    const term = w[name];
+    if (!term) {
+      throw new Error(`${name} must exist before refreshing it`);
+    }
+    const disposable = term.onRender(() => {
+      disposable.dispose();
+      resolve();
+    });
+    term.refresh(0, term.rows - 1);
+  }), terminal);
+}
+
+async function configureAtlasLimits(ctx: ITestContext): Promise<IAtlasLimits> {
+  const limits = await ctx.page.evaluate(() => {
+    const w = window as unknown as ITestWindow;
+    const atlas = w.term._core?._renderService?._renderer?.value?._charAtlas;
+    if (!atlas || atlas.constructor.maxAtlasPages === undefined || atlas.constructor.maxTextureSize === undefined) {
+      return undefined;
+    }
+    const result = {
+      maxAtlasPages: atlas.constructor.maxAtlasPages,
+      maxTextureSize: atlas.constructor.maxTextureSize
+    };
+    atlas.constructor.maxAtlasPages = 4;
+    atlas.constructor.maxTextureSize = 512;
+    return result;
+  });
+  expect(limits, 'TextureAtlas limits must be initialized').toBeDefined();
+  return limits!;
+}
+
+async function restoreAtlasLimits(ctx: ITestContext, limits: IAtlasLimits | undefined): Promise<void> {
+  if (!limits) {
+    return;
+  }
+  await ctx.page.evaluate(original => {
+    const w = window as unknown as ITestWindow;
+    const atlas = w.term._core?._renderService?._renderer?.value?._charAtlas;
+    if (atlas) {
+      atlas.constructor.maxAtlasPages = original.maxAtlasPages;
+      atlas.constructor.maxTextureSize = original.maxTextureSize;
+    }
+  }, limits);
+}
+
+async function installAtlasEventStats(ctx: ITestContext): Promise<void> {
+  const installed = await ctx.page.evaluate(() => {
+    const w = window as unknown as ITestWindow;
+    const atlas = w.term._core?._renderService?._renderer?.value?._charAtlas;
+    if (!atlas || !w.addon) {
+      return false;
+    }
+    const stats: IAtlasEventStats = {
+      removals: 0,
+      maxPages: atlas.pages.length
+    };
+    w.atlasEventStats = stats;
+    w.addon.onAddTextureAtlasCanvas(() => {
+      stats.maxPages = Math.max(stats.maxPages, atlas.pages.length);
+    });
+    w.addon.onRemoveTextureAtlasCanvas(() => stats.removals++);
+    return true;
+  });
+  expect(installed, 'atlas event tracking must be installed').toBe(true);
+}
+
+async function getAtlasState(ctx: ITestContext): Promise<IAtlasState> {
+  const state = await ctx.page.evaluate(() => {
+    const w = window as unknown as ITestWindow;
+    const renderer = w.term._core?._renderService?._renderer?.value;
+    const atlas = renderer?._charAtlas;
+    const glyphRenderer = renderer?._glyphRenderer?.value;
+    const stats = w.atlasEventStats;
+    if (!atlas || !glyphRenderer || !stats) {
+      return undefined;
+    }
+    return {
+      pages: atlas.pages.length,
+      atlasTextures: glyphRenderer._atlasTextures.length,
+      pageLayoutVersion: atlas.pageLayoutVersion,
+      overflowPageCreated: !!atlas._overflowSizePage,
+      removals: stats.removals,
+      maxPages: stats.maxPages
+    };
+  });
+  expect(state, 'atlas state must be available').toBeDefined();
+  return state!;
+}
+
+function generateUniqueGlyphFlood(count: number, cols: number, offset: number): string {
+  const base = 0x4E00;
+  const range = 0x9FFF - base;
+  const perRow = Math.max(1, Math.floor(cols / 2));
+  let result = '';
+  for (let i = 0; i < count; i++) {
+    result += String.fromCodePoint(base + ((offset + i) % range));
+    if ((i + 1) % perRow === 0 && i + 1 < count) {
+      result += '\r\n';
+    }
+  }
+  return result;
+}
+
+async function captureRowSignatures(ctx: ITestContext, selector: string, cols: number, row: number, sampleCols: number[], debugName: string): Promise<CellSignature[]> {
+  const screenshotOptions = process.env.DEBUG ? { path: `out-esbuild-test/playwright/${debugName}.png` } : undefined;
+  const buffer = await ctx.page.locator(selector).screenshot(screenshotOptions);
+  const frame = {
+    cols,
+    rows: 24,
+    decoded: (await decodePng(new Uint8Array(buffer), { force32: true })).image
+  };
+  return sampleCols.map(col => cellSignature(frame, col, row));
+}
+
+function cellSignature(frame: { cols: number, rows: number, decoded: IImage32 }, col: number, row: number): CellSignature {
+  const grid = 4;
+  const data = frame.decoded.data;
+  const imageWidth = frame.decoded.width;
+  const cellWidth = frame.decoded.width / frame.cols;
+  const cellHeight = frame.decoded.height / frame.rows;
+  const x0 = (col - 1) * cellWidth;
+  const y0 = (row - 1) * cellHeight;
+  const sums = new Array<number>(grid * grid * 4).fill(0);
+  const counts = new Array<number>(grid * grid).fill(0);
+  const startX = Math.max(0, Math.floor(x0));
+  const startY = Math.max(0, Math.floor(y0));
+  const endX = Math.min(frame.decoded.width, Math.ceil(x0 + cellWidth));
+  const endY = Math.min(frame.decoded.height, Math.ceil(y0 + cellHeight));
+
+  for (let y = startY; y < endY; y++) {
+    const gy = Math.min(grid - 1, Math.max(0, Math.floor(((y - y0) / cellHeight) * grid)));
+    for (let x = startX; x < endX; x++) {
+      const gx = Math.min(grid - 1, Math.max(0, Math.floor(((x - x0) / cellWidth) * grid)));
+      const sub = gy * grid + gx;
+      const i = (y * imageWidth + x) * 4;
+      sums[sub * 4] += data[i];
+      sums[sub * 4 + 1] += data[i + 1];
+      sums[sub * 4 + 2] += data[i + 2];
+      sums[sub * 4 + 3] += data[i + 3];
+      counts[sub]++;
+    }
+  }
+
+  const signature = new Array<number>(grid * grid * 4).fill(0);
+  for (let sub = 0; sub < counts.length; sub++) {
+    if (counts[sub] > 0) {
+      signature[sub * 4] = sums[sub * 4] / counts[sub];
+      signature[sub * 4 + 1] = sums[sub * 4 + 1] / counts[sub];
+      signature[sub * 4 + 2] = sums[sub * 4 + 2] / counts[sub];
+      signature[sub * 4 + 3] = sums[sub * 4 + 3] / counts[sub];
+    }
+  }
+  return signature;
+}
+
+function signatureDiff(actual: CellSignature, reference: CellSignature): number {
+  let diff = 0;
+  for (let i = 0; i < actual.length; i++) {
+    diff = Math.max(diff, Math.abs(actual[i] - reference[i]));
+  }
+  return diff;
+}
+
+function expectSignatureMatches(actual: CellSignature, reference: CellSignature, message: string): void {
+  const diff = signatureDiff(actual, reference);
+  expect(diff, `${message}; max channel diff ${diff}`).toBeLessThanOrEqual(14);
+}
+
+test.describe('atlas page overflow (#6038)', () => {
+  test.skip(({ browserName }) => browserName !== 'chromium');
+  test.describe.configure({ timeout: 90000 });
+
+  test('evicts normal pages when the page cap cannot be reduced by merging', async ({ browser }) => {
+    const ctx = await createTestContext(browser);
+    const errors: string[] = [];
+    const onError = (error: Error): void => { errors.push(error.message); };
+    let limits: IAtlasLimits | undefined;
+    ctx.page.on('pageerror', onError);
+    try {
+      await openTerminal(ctx, { cols: 80, rows: 24 });
+      await loadWebglStrict(ctx);
+      limits = await configureAtlasLimits(ctx);
+
+      await openTerminal(ctx, { cols: 80, rows: 24 });
+      await loadWebglStrict(ctx);
+      await createTerminalB(ctx, 80);
+      await installAtlasEventStats(ctx);
+
+      const atlasShared = await ctx.page.evaluate(() => {
+        const w = window as unknown as ITestWindow;
+        return w.term._core?._renderService?._renderer?.value?._charAtlas === w.termB?._core?._renderService?._renderer?.value?._charAtlas;
+      });
+      expect(atlasShared, 'terminals with equal configs should share one texture atlas').toBe(true);
+
+      await writeToBAndWaitForRender(ctx, `\x1b[H${NORMAL_HEADER}\x1b[2;1H${POST_EVICTION_TEXT}`);
+      const headerReference = await captureRowSignatures(ctx, TERM_B_SELECTOR, 80, 1, NORMAL_HEADER_COLS, 'atlas-overflow-header-reference');
+      const postReference = await captureRowSignatures(ctx, TERM_B_SELECTOR, 80, 2, POST_EVICTION_COLS, 'atlas-overflow-post-reference');
+      await writeToBAndWaitForRender(ctx, '\x1b[2;1H\x1b[2K');
+
+      const initialState = await getAtlasState(ctx);
+      const glyphsPerChunk = 23 * 40 - 1;
+      for (let chunk = 0; chunk < 24; chunk++) {
+        await ctx.proxy.write('\x1b[H\x1b[2J' + generateUniqueGlyphFlood(glyphsPerChunk, 80, chunk * glyphsPerChunk));
+        await ctx.page.waitForTimeout(50);
+        const state = await getAtlasState(ctx);
+        if (state.removals > 0 || state.pages > state.atlasTextures || errors.length > 0) {
+          break;
+        }
+      }
+
+      const evictionState = await getAtlasState(ctx);
+      expect(evictionState.removals, 'normal atlas pages must be evicted at the page cap').toBeGreaterThan(0);
+      expect(evictionState.pageLayoutVersion, 'eviction must invalidate renderer models').toBeGreaterThan(initialState.pageLayoutVersion);
+      expect(evictionState.maxPages, 'atlas pages must stay within renderer texture capacity').toBeLessThanOrEqual(evictionState.atlasTextures);
+      expect(errors, `renderer must not throw during atlas eviction: ${errors[0] ?? ''}`).toEqual([]);
+
+      await writeToBAndWaitForRender(ctx, `\x1b[2;1H${POST_EVICTION_TEXT}`);
+      const termBHeader = await ctx.page.evaluate(() => {
+        const w = window as unknown as ITestWindow;
+        return w.termB?.buffer.active.getLine(0)?.translateToString(true);
+      });
+      expect(termBHeader, 'terminal B buffer must still contain the header').toBe(NORMAL_HEADER);
+
+      const headerAfter = await captureRowSignatures(ctx, TERM_B_SELECTOR, 80, 1, NORMAL_HEADER_COLS, 'atlas-overflow-header-after');
+      const postAfter = await captureRowSignatures(ctx, TERM_B_SELECTOR, 80, 2, POST_EVICTION_COLS, 'atlas-overflow-post-after');
+      for (let i = 0; i < NORMAL_HEADER_COLS.length; i++) {
+        expectSignatureMatches(headerAfter[i], headerReference[i], `existing header col ${NORMAL_HEADER_COLS[i]} changed after eviction`);
+      }
+      for (let i = 0; i < POST_EVICTION_COLS.length; i++) {
+        expectSignatureMatches(postAfter[i], postReference[i], `new text col ${POST_EVICTION_COLS[i]} changed after eviction`);
+      }
+
+      const stableState = await getAtlasState(ctx);
+      await refreshAndWaitForRender(ctx, 'termB');
+      const refreshedState = await getAtlasState(ctx);
+      expect(refreshedState.pageLayoutVersion, 'an unchanged full refresh must not evict again').toBe(stableState.pageLayoutVersion);
+      expect(refreshedState.removals, 'an unchanged full refresh must not remove more pages').toBe(stableState.removals);
+    } finally {
+      ctx.page.off('pageerror', onError);
+      await restoreAtlasLimits(ctx, limits).catch(() => {});
+      await ctx.page.close();
+    }
+  });
+
+  test('evicts before adding an oversized glyph page at the page cap', async ({ browser }) => {
+    const ctx = await createTestContext(browser);
+    const errors: string[] = [];
+    const onError = (error: Error): void => { errors.push(error.message); };
+    let limits: IAtlasLimits | undefined;
+    ctx.page.on('pageerror', onError);
+    try {
+      await openTerminal(ctx, { cols: 160, rows: 24 });
+      await loadWebglStrict(ctx);
+      limits = await configureAtlasLimits(ctx);
+
+      await openTerminal(ctx, { cols: 160, rows: 24 });
+      await loadWebglStrict(ctx);
+      await installAtlasEventStats(ctx);
+
+      let state = await getAtlasState(ctx);
+      let offset = 0;
+      for (let chunk = 0; chunk < 120 && state.pages < state.atlasTextures; chunk++) {
+        const glyphCount = state.pages < state.atlasTextures - 1 ? 200 : 25;
+        await ctx.proxy.write('\x1b[H\x1b[2J' + generateUniqueGlyphFlood(glyphCount, 160, offset));
+        await ctx.page.waitForTimeout(50);
+        offset += glyphCount;
+        state = await getAtlasState(ctx);
+      }
+      expect(state.pages, 'normal atlas pages must reach the texture capacity before the oversized glyph').toBe(state.atlasTextures);
+      expect(state.overflowPageCreated, 'normal glyph filling must not create the oversized page').toBe(false);
+      expect(errors, `renderer must not fail while filling normal pages: ${errors[0] ?? ''}`).toEqual([]);
+
+      await writeAndWaitForRender(ctx, '\x1b[H\x1b[2K\x1b[24;1H');
+      const sampleCols = [1, 8, 16, 24, 32];
+      const blankSignatures = await captureRowSignatures(ctx, TERM_SELECTOR, 160, 1, sampleCols, 'atlas-overflow-wide-blank');
+      const joinedLength = await ctx.page.evaluate(() => {
+        const w = window as unknown as ITestWindow;
+        const renderer = w.term._core?._renderService?._renderer?.value;
+        const atlas = renderer?._charAtlas;
+        if (!renderer || !atlas) {
+          throw new Error('renderer and atlas must exist');
+        }
+        const cellWidth = renderer.dimensions.device.cell.width;
+        const length = Math.min(w.term.cols - 1, Math.ceil(atlas._textureSize / cellWidth) + 32);
+        if (length * cellWidth <= atlas._textureSize) {
+          throw new Error('joined glyph must be wider than a normal atlas page');
+        }
+        const marker = 'W'.repeat(length);
+        w.term.registerCharacterJoiner(text => text.startsWith(marker) ? [[0, length]] : []);
+        return length;
+      });
+
+      const beforeOversized = await getAtlasState(ctx);
+      await ctx.proxy.write(`\x1b[H${'W'.repeat(joinedLength)}`);
+      await ctx.page.waitForTimeout(50);
+      const oversizedState = await getAtlasState(ctx);
+      expect(oversizedState.overflowPageCreated, 'the joined glyph must use the oversized atlas page').toBe(true);
+      expect(oversizedState.removals, 'normal pages must be evicted before adding the oversized page').toBeGreaterThan(beforeOversized.removals);
+      expect(oversizedState.maxPages, 'oversized page creation must stay within renderer texture capacity').toBeLessThanOrEqual(oversizedState.atlasTextures);
+      expect(oversizedState.pageLayoutVersion, 'oversized eviction must invalidate renderer models').toBeGreaterThan(beforeOversized.pageLayoutVersion);
+      expect(errors, `renderer must not throw while adding the oversized page: ${errors[0] ?? ''}`).toEqual([]);
+
+      const wideSignatures = await captureRowSignatures(ctx, TERM_SELECTOR, 160, 1, sampleCols, 'atlas-overflow-wide-after');
+      for (let i = 0; i < sampleCols.length; i++) {
+        expect(signatureDiff(wideSignatures[i], blankSignatures[i]), `wide glyph col ${sampleCols[i]} must render visible pixels`).toBeGreaterThan(14);
+      }
+
+      const stableState = await getAtlasState(ctx);
+      await refreshAndWaitForRender(ctx, 'term');
+      const refreshedState = await getAtlasState(ctx);
+      expect(refreshedState.pageLayoutVersion, 'oversized glyph refresh must settle without another eviction').toBe(stableState.pageLayoutVersion);
+      expect(refreshedState.removals, 'oversized glyph refresh must not remove more pages').toBe(stableState.removals);
+      const wideAfterRefresh = await captureRowSignatures(ctx, TERM_SELECTOR, 160, 1, sampleCols, 'atlas-overflow-wide-refreshed');
+      for (let i = 0; i < sampleCols.length; i++) {
+        expectSignatureMatches(wideAfterRefresh[i], wideSignatures[i], `wide glyph col ${sampleCols[i]} changed after refresh`);
+      }
+    } finally {
+      ctx.page.off('pageerror', onError);
+      await restoreAtlasLimits(ctx, limits).catch(() => {});
+      await ctx.page.close();
+    }
+  });
+});

addons/addon-webgl/test/WebglAtlasStress.test.ts

@@ -0,0 +1,288 @@
+/**
+ * Copyright (c) 2025 The xterm.js authors. All rights reserved.
+ * @license MIT
+ */
+
+import { decodePng, type IImage32 } from '@lunapaint/png-codec';
+import test, { expect } from '@playwright/test';
+import type { Terminal, ITerminalInitOnlyOptions, ITerminalOptions } from '@xterm/xterm';
+import type { IWebglAddonOptions, WebglAddon } from '@xterm/addon-webgl';
+import { ITestContext, createTestContext, openTerminal } from '../../../test/playwright/TestUtils';
+
+type CellSignature = number[];
+type TestTerminalConstructor = new (options?: ITerminalOptions & ITerminalInitOnlyOptions) => ITestTerminal;
+type TestWebglAddonConstructor = new (options?: IWebglAddonOptions) => ITestWebglAddon;
+
+interface ITestTextureAtlas {
+  readonly pages: ReadonlyArray<{ readonly canvas: HTMLCanvasElement }>;
+}
+
+interface ITestGlyphRenderer {
+  readonly _atlasTextures: ReadonlyArray<unknown>;
+}
+
+interface ITestRenderer {
+  _charAtlas?: ITestTextureAtlas;
+  _glyphRenderer?: {
+    value?: ITestGlyphRenderer;
+  };
+}
+
+interface ITestRenderService {
+  _renderer?: {
+    value?: ITestRenderer;
+  };
+}
+
+interface ITestTerminal extends Terminal {
+  _core?: {
+    _renderService?: ITestRenderService;
+  };
+}
+
+interface ITestWebglAddon extends WebglAddon {
+  _renderer?: ITestRenderer;
+}
+
+interface IAtlasEventStats {
+  additions: number;
+  maxPages: number;
+}
+
+interface ITestWindow {
+  WebglAddon: TestWebglAddonConstructor;
+  term: ITestTerminal;
+  addon?: ITestWebglAddon;
+  atlasEventStats?: IAtlasEventStats;
+}
+
+interface IAtlasState {
+  additions: number;
+  atlasTextures: number;
+  maxPages: number;
+}
+
+const REFERENCE_LINE = 'Ref0123456789ABCDEF';
+const REFERENCE_COLS = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19];
+const TERM_SELECTOR = '#terminal-container .xterm-screen';
+
+async function loadWebglStrict(ctx: ITestContext): Promise<void> {
+  await ctx.page.evaluate(() => {
+    const w = window as unknown as ITestWindow;
+    w.addon = new w.WebglAddon({ preserveDrawingBuffer: true });
+    w.term.loadAddon(w.addon);
+  });
+  const isWebglRenderer = await ctx.page.evaluate(() => {
+    const w = window as unknown as ITestWindow;
+    return !!w.addon && w.term._core?._renderService?._renderer?.value === w.addon._renderer;
+  });
+  expect(isWebglRenderer, 'WebGL renderer must be active').toBe(true);
+}
+
+async function installAtlasEventStats(ctx: ITestContext): Promise<void> {
+  const installed = await ctx.page.evaluate(() => {
+    const w = window as unknown as ITestWindow;
+    const atlas = w.term._core?._renderService?._renderer?.value?._charAtlas;
+    if (!atlas || !w.addon) {
+      return false;
+    }
+    const stats: IAtlasEventStats = {
+      additions: 0,
+      maxPages: atlas.pages.length
+    };
+    w.atlasEventStats = stats;
+    w.addon.onAddTextureAtlasCanvas(() => {
+      stats.additions++;
+      stats.maxPages = Math.max(stats.maxPages, atlas.pages.length);
+    });
+    return true;
+  });
+  expect(installed, 'atlas event tracking must be installed').toBe(true);
+}
+
+async function getAtlasState(ctx: ITestContext): Promise<IAtlasState> {
+  const state = await ctx.page.evaluate(() => {
+    const w = window as unknown as ITestWindow;
+    const renderer = w.term._core?._renderService?._renderer?.value;
+    const glyphRenderer = renderer?._glyphRenderer?.value;
+    const stats = w.atlasEventStats;
+    if (!glyphRenderer || !stats) {
+      return undefined;
+    }
+    return {
+      additions: stats.additions,
+      atlasTextures: glyphRenderer._atlasTextures.length,
+      maxPages: stats.maxPages
+    };
+  });
+  expect(state, 'atlas state must be available').toBeDefined();
+  return state!;
+}
+
+async function writeAndWaitForRender(ctx: ITestContext, data: string): Promise<void> {
+  const renderPromise = new Promise<void>(resolve => {
+    const disposable = ctx.proxy.onRender(() => {
+      disposable.dispose();
+      resolve();
+    });
+  });
+  await ctx.proxy.write(data);
+  await renderPromise;
+}
+
+async function refreshAndWaitForRender(ctx: ITestContext): Promise<void> {
+  const renderPromise = new Promise<void>(resolve => {
+    const disposable = ctx.proxy.onRender(() => {
+      disposable.dispose();
+      resolve();
+    });
+  });
+  await ctx.proxy.refresh(0, (await ctx.proxy.rows) - 1);
+  await renderPromise;
+}
+
+function generateSyntheticTuiFrames(frameCount: number, cols: number, rows: number): string[] {
+  const spinner = ['|', '/', '-', '\\'];
+  const words = ['reading', 'rendering', 'atlas', 'terminal', 'buffer', 'tokens', 'diff', 'patch'];
+  const frames: string[] = [];
+  for (let frameIndex = 0; frameIndex < frameCount; frameIndex++) {
+    const lines = [
+      `+${'-'.repeat(cols - 2)}+`,
+      `|${(` ${spinner[frameIndex % spinner.length]} Copilot is working`).padEnd(cols - 2).slice(0, cols - 2)}|`,
+      `+${'-'.repeat(cols - 2)}+`
+    ];
+    for (let row = 3; row < rows - 1; row++) {
+      const foreground = 31 + ((frameIndex + row) % 6);
+      const text = `${words[(frameIndex + row) % words.length]} ${frameIndex}:${row}`;
+      lines.push(`\x1b[${foreground}m${text}\x1b[0m`);
+    }
+    lines.push(`\x1b[2mtokens ${1000 + frameIndex * 37}\x1b[0m`);
+    frames.push(`\x1b[2J\x1b[H${lines.join('\r\n')}`);
+  }
+  return frames;
+}
+
+function generateUniqueGlyphFlood(count: number, cols: number, offset: number): string {
+  const base = 0x4E00;
+  const range = 0x9FFF - base;
+  const perRow = Math.max(1, Math.floor(cols / 2));
+  let result = '';
+  for (let i = 0; i < count; i++) {
+    result += String.fromCodePoint(base + ((offset + i) % range));
+    if ((i + 1) % perRow === 0 && i + 1 < count) {
+      result += '\r\n';
+    }
+  }
+  return result;
+}
+
+async function captureRowSignatures(ctx: ITestContext, row: number, cols: number[], debugName: string): Promise<CellSignature[]> {
+  const screenshotOptions = process.env.DEBUG ? { path: `out-esbuild-test/playwright/${debugName}.png` } : undefined;
+  const buffer = await ctx.page.locator(TERM_SELECTOR).screenshot(screenshotOptions);
+  const frame = {
+    cols: await ctx.proxy.cols,
+    rows: await ctx.proxy.rows,
+    decoded: (await decodePng(new Uint8Array(buffer), { force32: true })).image
+  };
+  return cols.map(col => cellSignature(frame, col, row));
+}
+
+function cellSignature(frame: { cols: number, rows: number, decoded: IImage32 }, col: number, row: number): CellSignature {
+  const grid = 4;
+  const data = frame.decoded.data;
+  const imageWidth = frame.decoded.width;
+  const cellWidth = frame.decoded.width / frame.cols;
+  const cellHeight = frame.decoded.height / frame.rows;
+  const x0 = (col - 1) * cellWidth;
+  const y0 = (row - 1) * cellHeight;
+  const sums = new Array<number>(grid * grid * 4).fill(0);
+  const counts = new Array<number>(grid * grid).fill(0);
+  const startX = Math.max(0, Math.floor(x0));
+  const startY = Math.max(0, Math.floor(y0));
+  const endX = Math.min(frame.decoded.width, Math.ceil(x0 + cellWidth));
+  const endY = Math.min(frame.decoded.height, Math.ceil(y0 + cellHeight));
+
+  for (let y = startY; y < endY; y++) {
+    const gy = Math.min(grid - 1, Math.max(0, Math.floor(((y - y0) / cellHeight) * grid)));
+    for (let x = startX; x < endX; x++) {
+      const gx = Math.min(grid - 1, Math.max(0, Math.floor(((x - x0) / cellWidth) * grid)));
+      const sub = gy * grid + gx;
+      const i = (y * imageWidth + x) * 4;
+      sums[sub * 4] += data[i];
+      sums[sub * 4 + 1] += data[i + 1];
+      sums[sub * 4 + 2] += data[i + 2];
+      sums[sub * 4 + 3] += data[i + 3];
+      counts[sub]++;
+    }
+  }
+
+  const signature = new Array<number>(grid * grid * 4).fill(0);
+  for (let sub = 0; sub < counts.length; sub++) {
+    if (counts[sub] > 0) {
+      signature[sub * 4] = sums[sub * 4] / counts[sub];
+      signature[sub * 4 + 1] = sums[sub * 4 + 1] / counts[sub];
+      signature[sub * 4 + 2] = sums[sub * 4 + 2] / counts[sub];
+      signature[sub * 4 + 3] = sums[sub * 4 + 3] / counts[sub];
+    }
+  }
+  return signature;
+}
+
+function expectSignatureMatches(actual: CellSignature, reference: CellSignature, message: string): void {
+  let diff = 0;
+  for (let i = 0; i < actual.length; i++) {
+    diff = Math.max(diff, Math.abs(actual[i] - reference[i]));
+  }
+  expect(diff, `${message}; max channel diff ${diff}`).toBeLessThanOrEqual(14);
+}
+
+test.describe('WebGL atlas TUI stress (#6038)', () => {
+  test.skip(({ browserName }) => browserName !== 'chromium', 'WebGL atlas tests run on Chromium/SwiftShader only');
+  test.describe.configure({ timeout: 90000 });
+
+  test('primary-buffer glyphs survive alternate-buffer redraws and atlas page churn', async ({ browser }) => {
+    const ctx = await createTestContext(browser);
+    const errors: string[] = [];
+    const onError = (error: Error): void => { errors.push(error.message); };
+    ctx.page.on('pageerror', onError);
+    try {
+      await openTerminal(ctx, { cols: 80, rows: 24, scrollback: 5000 });
+      await loadWebglStrict(ctx);
+      await installAtlasEventStats(ctx);
+
+      await writeAndWaitForRender(ctx, REFERENCE_LINE);
+      const reference = await captureRowSignatures(ctx, 1, REFERENCE_COLS, 'atlas-stress-reference');
+
+      await writeAndWaitForRender(ctx, '\x1b[?1049h');
+      for (const frame of generateSyntheticTuiFrames(30, 80, 24)) {
+        await writeAndWaitForRender(ctx, frame);
+      }
+      const glyphsPerViewport = 23 * 40 - 1;
+      for (let chunk = 0; chunk < 4; chunk++) {
+        await writeAndWaitForRender(ctx, `\x1b[2J\x1b[H${generateUniqueGlyphFlood(glyphsPerViewport, 80, chunk * glyphsPerViewport)}`);
+      }
+      await writeAndWaitForRender(ctx, '\x1b[?1049l');
+      await refreshAndWaitForRender(ctx);
+
+      const state = await getAtlasState(ctx);
+      expect(state.additions, 'stress workload must add atlas pages').toBeGreaterThan(0);
+      expect(state.maxPages, 'stress workload must exercise multiple atlas pages').toBeGreaterThan(1);
+      expect(state.maxPages, 'atlas pages must remain within renderer texture capacity').toBeLessThanOrEqual(state.atlasTextures);
+      expect(errors, `renderer must not throw during TUI stress: ${errors[0] ?? ''}`).toEqual([]);
+
+      const primaryText = await ctx.page.evaluate(() => {
+        const w = window as unknown as ITestWindow;
+        return w.term.buffer.active.getLine(0)?.translateToString(true);
+      });
+      expect(primaryText, 'primary buffer must still contain the reference line').toBe(REFERENCE_LINE);
+
+      const after = await captureRowSignatures(ctx, 1, REFERENCE_COLS, 'atlas-stress-after');
+      for (let i = 0; i < REFERENCE_COLS.length; i++) {
+        expectSignatureMatches(after[i], reference[i], `primary-buffer glyph at col ${REFERENCE_COLS[i]} changed after TUI stress`);
+      }
+    } finally {
+      ctx.page.off('pageerror', onError);
+      await ctx.page.close();
+    }
+  });
+});

addons/addon-webgl/test/WebglCustomGlyphs.test.ts

@@ -0,0 +1,77 @@
+/**
+ * Copyright (c) 2026 The xterm.js authors. All rights reserved.
+ * @license MIT
+ */
+
+import test, { expect } from '@playwright/test';
+import { platform } from 'os';
+import { ITestContext, createTestContext, openTerminal } from '../../../test/playwright/TestUtils';
+
+interface ITestRendererWithAtlasCanvas {
+  readonly _charAtlas?: {
+    readonly _tmpCanvas?: HTMLCanvasElement;
+  };
+}
+
+async function writeAndWaitForRender(ctx: ITestContext, data: string): Promise<void> {
+  const renderPromise = new Promise<void>(resolve => {
+    const disposable = ctx.proxy.onRender(() => {
+      disposable.dispose();
+      resolve();
+    });
+  });
+  await ctx.proxy.write(data);
+  await renderPromise;
+}
+
+test.describe('WebGL custom glyphs', () => {
+  if (platform() === 'linux') {
+    test.skip(({ browserName }) => browserName === 'firefox' || browserName === 'webkit');
+  }
+
+  test('pattern glyphs render after the terminal is adopted into another document', async ({ browser }) => {
+    const ctx = await createTestContext(browser);
+    const errors: string[] = [];
+    const onError = (error: Error): void => { errors.push(error.message); };
+    ctx.page.on('pageerror', onError);
+    try {
+      await openTerminal(ctx);
+      await ctx.page.evaluate(`
+        window.addon = new window.WebglAddon({ customGlyphs: true });
+        window.term.loadAddon(window.addon);
+      `);
+      await ctx.page.evaluate(() => {
+        const frame = document.createElement('iframe');
+        document.body.appendChild(frame);
+        const auxiliaryDocument = frame.contentDocument;
+        if (!auxiliaryDocument?.body || !window.term.element) {
+          throw new Error('Auxiliary document and terminal element must be available');
+        }
+        const renderer = window.term._core?._renderService?._renderer?.value as ITestRendererWithAtlasCanvas | undefined;
+        const atlasCanvas = renderer?._charAtlas?._tmpCanvas;
+        if (!atlasCanvas) {
+          throw new Error('Texture atlas canvas must be available');
+        }
+        // Model the atlas state after an uncached glyph has attached the measurement canvas.
+        window.term.element.appendChild(atlasCanvas);
+        auxiliaryDocument.body.appendChild(window.term.element);
+        if (atlasCanvas.ownerDocument !== auxiliaryDocument) {
+          throw new Error('Texture atlas canvas must be adopted into the auxiliary document');
+        }
+        auxiliaryDocument.createElement = () => {
+          throw new Error('Not allowed to create elements in the auxiliary document');
+        };
+      });
+
+      await writeAndWaitForRender(ctx, '\u2591');
+      await writeAndWaitForRender(ctx, 'X');
+
+      const line = await ctx.page.evaluate(() => window.term.buffer.active.getLine(0)?.translateToString(true));
+      expect(errors, `renderer must not create pattern canvases in the auxiliary document: ${errors[0] ?? ''}`).toEqual([]);
+      expect(line).toBe('\u2591X');
+    } finally {
+      ctx.page.off('pageerror', onError);
+      await ctx.page.close();
+    }
+  });
+});

addons/addon-webgl/test/WebglSharedAtlasGarble.test.ts

@@ -0,0 +1,282 @@
+/**
+ * Copyright (c) 2025 The xterm.js authors. All rights reserved.
+ * @license MIT
+ */
+
+import { IImage32, decodePng } from '@lunapaint/png-codec';
+import test, { expect } from '@playwright/test';
+import type { Terminal, ITerminalInitOnlyOptions, ITerminalOptions } from '@xterm/xterm';
+import type { IWebglAddonOptions, WebglAddon } from '@xterm/addon-webgl';
+import { ITestContext, createTestContext, openTerminal } from '../../../test/playwright/TestUtils';
+
+type CellSignature = number[];
+type TestTerminalConstructor = new (options?: ITerminalOptions & ITerminalInitOnlyOptions) => ITestTerminal;
+type TestWebglAddonConstructor = new (options?: IWebglAddonOptions) => ITestWebglAddon;
+
+interface ITestTextureAtlasConstructor {
+  maxAtlasPages: number | undefined;
+}
+
+interface ITestTextureAtlas {
+  constructor: ITestTextureAtlasConstructor;
+}
+
+interface ITestRenderer {
+  _charAtlas?: ITestTextureAtlas;
+}
+
+interface ITestRenderService {
+  _renderer?: {
+    value?: ITestRenderer;
+  };
+}
+
+interface ITestTerminal extends Terminal {
+  _core?: {
+    _renderService?: ITestRenderService;
+  };
+}
+
+interface ITestWebglAddon extends WebglAddon {
+  _renderer?: ITestRenderer;
+}
+
+declare global {
+  interface Window { // eslint-disable-line @typescript-eslint/naming-convention
+    Terminal: TestTerminalConstructor;
+    WebglAddon: TestWebglAddonConstructor;
+    term: ITestTerminal;
+    termB?: ITestTerminal;
+    addon?: ITestWebglAddon;
+    addonB?: ITestWebglAddon;
+  }
+}
+
+const HEADER = ' HEADER_REF_0123456789';
+const HEADER_COLS = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
+const TERM_B_SELECTOR = '#terminal-container-b .xterm-screen';
+
+async function loadWebglStrict(ctx: ITestContext): Promise<void> {
+  await ctx.page.evaluate(() => {
+    window.addon = new window.WebglAddon({ preserveDrawingBuffer: true });
+    window.term.loadAddon(window.addon);
+  });
+  const isWebglRenderer = await ctx.page.evaluate(() => {
+    return !!window.addon && window.term?._core?._renderService?._renderer?.value === window.addon._renderer;
+  });
+  expect(isWebglRenderer, 'WebGL renderer must be active').toBe(true);
+}
+
+async function createTerminalB(ctx: ITestContext): Promise<void> {
+  await ctx.page.evaluate(() => {
+    window.termB?.dispose();
+    document.getElementById('terminal-container-b')?.remove();
+    const el = document.createElement('div');
+    el.id = 'terminal-container-b';
+    document.body.appendChild(el);
+    window.termB = new window.Terminal({ cols: 80, rows: 24, allowProposedApi: true });
+    window.termB.open(el);
+    window.addonB = new window.WebglAddon({ preserveDrawingBuffer: true });
+    window.termB.loadAddon(window.addonB);
+  });
+}
+
+async function writeToBAndWaitForRender(ctx: ITestContext, data: string): Promise<void> {
+  await ctx.page.evaluate(d => new Promise<void>(resolve => {
+    const termB = window.termB;
+    if (!termB) {
+      throw new Error('Terminal B must be created before writing to it');
+    }
+    const disposable = termB.onRender(() => {
+      disposable.dispose();
+      resolve();
+    });
+    termB.write(d);
+  }), data);
+}
+
+async function writeAndWaitForRender(ctx: ITestContext, data: string): Promise<void> {
+  const renderPromise = new Promise<void>(resolve => {
+    const disposable = ctx.proxy.onRender(() => {
+      disposable.dispose();
+      resolve();
+    });
+  });
+  await ctx.proxy.write(data);
+  await renderPromise;
+}
+
+async function setMaxAtlasPages(ctx: ITestContext, maxAtlasPages: number): Promise<void> {
+  const applied = await ctx.page.evaluate(max => {
+    const atlas = window.term?._core?._renderService?._renderer?.value?._charAtlas;
+    if (!atlas) {
+      return false;
+    }
+    atlas.constructor.maxAtlasPages = max;
+    return true;
+  }, maxAtlasPages);
+  expect(applied, 'should be able to set TextureAtlas.maxAtlasPages').toBe(true);
+}
+
+async function resetMaxAtlasPages(ctx: ITestContext): Promise<void> {
+  await ctx.page.evaluate(() => {
+    const atlas = window.term?._core?._renderService?._renderer?.value?._charAtlas;
+    if (atlas) {
+      atlas.constructor.maxAtlasPages = undefined;
+    }
+  });
+}
+
+function generateColoredAsciiFlood(cells: number, offset: number = 0): string {
+  const letters = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
+  let out = '';
+  for (let i = 0; i < cells; i++) {
+    const ch = letters[(offset + i) % letters.length];
+    const fg = (offset + i) % 256;
+    const bg = (offset + i * 7) % 256;
+    out += `\x1b[38;5;${fg}m\x1b[48;5;${bg}m${ch}`;
+    if ((i + 1) % 78 === 0 && i + 1 < cells) {
+      out += '\x1b[0m\r\n';
+    }
+  }
+  return out + '\x1b[0m';
+}
+
+async function captureRowSignatures(ctx: ITestContext, row: number, cols: number[]): Promise<CellSignature[]> {
+  const screenshotOptions = process.env.DEBUG ? { path: 'out-esbuild-test/playwright/shared-atlas-term-b.png' } : undefined;
+  const buffer = await ctx.page.locator(TERM_B_SELECTOR).screenshot(screenshotOptions);
+  const frame = {
+    cols: 80,
+    rows: 24,
+    decoded: (await decodePng(new Uint8Array(buffer), { force32: true })).image
+  };
+  return cols.map(col => cellSignature(frame, col, row));
+}
+
+function cellSignature(frame: { cols: number, rows: number, decoded: IImage32 }, col: number, row: number): CellSignature {
+  const grid = 4;
+  const data = frame.decoded.data;
+  const imageWidth = frame.decoded.width;
+  const cellWidth = frame.decoded.width / frame.cols;
+  const cellHeight = frame.decoded.height / frame.rows;
+  const x0 = (col - 1) * cellWidth;
+  const y0 = (row - 1) * cellHeight;
+  const sums = new Array<number>(grid * grid * 4).fill(0);
+  const counts = new Array<number>(grid * grid).fill(0);
+  const startX = Math.max(0, Math.floor(x0));
+  const startY = Math.max(0, Math.floor(y0));
+  const endX = Math.min(frame.decoded.width, Math.ceil(x0 + cellWidth));
+  const endY = Math.min(frame.decoded.height, Math.ceil(y0 + cellHeight));
+
+  for (let y = startY; y < endY; y++) {
+    const gy = Math.min(grid - 1, Math.max(0, Math.floor(((y - y0) / cellHeight) * grid)));
+    for (let x = startX; x < endX; x++) {
+      const gx = Math.min(grid - 1, Math.max(0, Math.floor(((x - x0) / cellWidth) * grid)));
+      const sub = gy * grid + gx;
+      const i = (y * imageWidth + x) * 4;
+      sums[sub * 4] += data[i];
+      sums[sub * 4 + 1] += data[i + 1];
+      sums[sub * 4 + 2] += data[i + 2];
+      sums[sub * 4 + 3] += data[i + 3];
+      counts[sub]++;
+    }
+  }
+
+  const signature = new Array<number>(grid * grid * 4).fill(0);
+  for (let sub = 0; sub < counts.length; sub++) {
+    if (counts[sub] > 0) {
+      signature[sub * 4] = sums[sub * 4] / counts[sub];
+      signature[sub * 4 + 1] = sums[sub * 4 + 1] / counts[sub];
+      signature[sub * 4 + 2] = sums[sub * 4 + 2] / counts[sub];
+      signature[sub * 4 + 3] = sums[sub * 4 + 3] / counts[sub];
+    }
+  }
+  return signature;
+}
+
+function expectSignatureMatches(actual: CellSignature, reference: CellSignature, message: string): void {
+  let diff = 0;
+  for (let i = 0; i < actual.length; i++) {
+    diff = Math.max(diff, Math.abs(actual[i] - reference[i]));
+  }
+  expect(diff, `${message}; max channel diff ${diff}`).toBeLessThanOrEqual(14);
+}
+
+test.describe('shared-atlas garble across terminals (#6038)', () => {
+  test.skip(({ browserName }) => browserName !== 'chromium');
+  test.describe.configure({ timeout: 60000 });
+
+  test('keeps a second terminal rendering correctly after shared atlas page merges', async ({ browser }) => {
+    const ctx = await createTestContext(browser);
+    try {
+      await openTerminal(ctx, { cols: 80, rows: 24 });
+      await loadWebglStrict(ctx);
+      await createTerminalB(ctx);
+
+      const atlasShared = await ctx.page.evaluate(() => {
+        return window.term._core?._renderService?._renderer?.value?._charAtlas === window.termB?._core?._renderService?._renderer?.value?._charAtlas;
+      });
+      expect(atlasShared, 'terminals with equal configs should share one texture atlas').toBe(true);
+
+      await setMaxAtlasPages(ctx, 4);
+
+      await writeToBAndWaitForRender(ctx, HEADER);
+      const reference = await captureRowSignatures(ctx, 1, HEADER_COLS);
+
+      for (let c = 0; c < 10; c++) {
+        await writeAndWaitForRender(ctx, '\x1b[2;1H' + generateColoredAsciiFlood(23 * 78, c * 23 * 78));
+      }
+
+      await writeToBAndWaitForRender(ctx, '\x1b[24;1Hx');
+      const termBHeader = await ctx.page.evaluate(() => window.termB?.buffer.active.getLine(0)?.translateToString(true));
+      expect(termBHeader, 'terminal B buffer must still contain the header').toBe(HEADER);
+
+      const after = await captureRowSignatures(ctx, 1, HEADER_COLS);
+      for (let i = 0; i < HEADER_COLS.length; i++) {
+        expectSignatureMatches(after[i], reference[i], `terminal B header col ${HEADER_COLS[i]} garbled by terminal A's atlas merges`);
+      }
+    } finally {
+      await resetMaxAtlasPages(ctx).catch(() => {});
+      await ctx.page.close();
+    }
+  });
+
+  test('keeps a second terminal rendering correctly after terminal A clears the shared atlas', async ({ browser }) => {
+    const ctx = await createTestContext(browser);
+    try {
+      await openTerminal(ctx, { cols: 80, rows: 24 });
+      await loadWebglStrict(ctx);
+      await createTerminalB(ctx);
+
+      const atlasShared = await ctx.page.evaluate(() => {
+        return window.term._core?._renderService?._renderer?.value?._charAtlas === window.termB?._core?._renderService?._renderer?.value?._charAtlas;
+      });
+      expect(atlasShared, 'terminals with equal configs should share one texture atlas').toBe(true);
+
+      await writeToBAndWaitForRender(ctx, HEADER);
+      const reference = await captureRowSignatures(ctx, 1, HEADER_COLS);
+
+      // Terminal A alone clears the shared atlas, as embedders do to force a redraw (VS Code calls
+      // this for every terminal on OS resume). This wipes the pages that terminal B's model still
+      // holds texture coords into.
+      await ctx.proxy.clearTextureAtlas();
+
+      // Terminal A repopulates the cleared pages with a different glyph set, so B's stale coords now
+      // resolve to whatever A rasterized into those slots.
+      await writeAndWaitForRender(ctx, '\x1b[2;1H' + generateColoredAsciiFlood(23 * 78));
+
+      // Nudge B into a render that does not touch row 1, mirroring a terminal that is idle but
+      // visible. Row 1 must still be drawn from a model B rebuilt against the current atlas.
+      await writeToBAndWaitForRender(ctx, '\x1b[24;1Hx');
+      const termBHeader = await ctx.page.evaluate(() => window.termB?.buffer.active.getLine(0)?.translateToString(true));
+      expect(termBHeader, 'terminal B buffer must still contain the header').toBe(HEADER);
+
+      const after = await captureRowSignatures(ctx, 1, HEADER_COLS);
+      for (let i = 0; i < HEADER_COLS.length; i++) {
+        expectSignatureMatches(after[i], reference[i], `terminal B header col ${HEADER_COLS[i]} garbled by terminal A's atlas clear`);
+      }
+    } finally {
+      await ctx.page.close();
+    }
+  });
+});

demo/client/components/window/addonImageWindow.ts

@@ -67,6 +67,8 @@ export class AddonImageWindow extends BaseWindow implements IControlWindow {
     dlIip.appendChild(dtIip);
     this._addDdWithButton(dlIip, 'image-demo3', 'palette (png File)');
     this._addDdWithButton(dlIip, 'image-demo4', 'dice (qoi MultipartFile)');
+    this._addDdWithButton(dlIip, 'image-demo5', 'rose (webp File)');
+    this._addDdWithButton(dlIip, 'image-demo6', 'kimono (avif MultipartFile)');
     container.appendChild(dlIip);
 
     // Kitty demos
@@ -173,11 +175,15 @@ export class AddonImageWindow extends BaseWindow implements IControlWindow {
     document.getElementById('image-demo2')!.addEventListener('click',
       sixelDemo('https://raw.githubusercontent.com/jerch/node-sixel/master/testfiles/test2.sixel'));
     document.getElementById('image-demo3')!.addEventListener('click',
-      iipDemo('https://raw.githubusercontent.com/jerch/node-sixel/master/palette.png'));
+      iipDemo('https://raw.githubusercontent.com/xtermjs/xterm.js/master/addons/addon-image/fixture/palette.png'));
     document.getElementById('image-demo4')!.addEventListener('click',
-      iipDemoMulti('https://raw.githubusercontent.com/jerch/xterm-wasm-parts/master/fixtures/qoi/dice.qoi'));
+      iipDemoMulti('https://raw.githubusercontent.com/xtermjs/xterm.js/master/addons/addon-image/fixture/testimages/dice.qoi'));
+    document.getElementById('image-demo5')!.addEventListener('click',
+      iipDemo('https://raw.githubusercontent.com/xtermjs/xterm.js/master/addons/addon-image/fixture/testimages/1_webp_a.webp'));
+    document.getElementById('image-demo6')!.addEventListener('click',
+      iipDemoMulti('https://raw.githubusercontent.com/xtermjs/xterm.js/master/addons/addon-image/fixture/testimages/kimono.crop.avif'));
     document.getElementById('image-demo-kitty1')!.addEventListener('click',
-      kittyDemo('https://raw.githubusercontent.com/jerch/node-sixel/master/palette.png'));
+      kittyDemo('https://raw.githubusercontent.com/xtermjs/xterm.js/master/addons/addon-image/fixture/palette.png'));
 
     // demo for image retrieval API
     this._terminal.element!.addEventListener('click', (ev: MouseEvent) => {

demo/client/components/window/webglWindow.ts

@@ -11,8 +11,35 @@ export class WebglWindow extends BaseWindow implements IControlWindow {
   public readonly label = 'webgl';
 
   private _textureAtlasContainer!: HTMLElement;
+  private _stressRunning = false;
+  private _scrollOutput: HTMLInputElement | undefined;
 
   public build(container: HTMLElement): void {
+    const stressButtons = document.createElement('div');
+    const stressStart = document.createElement('button');
+    stressStart.id = 'stress-start';
+    stressStart.textContent = 'atlas stress start';
+    stressStart.addEventListener('click', () => this._stress());
+    stressButtons.appendChild(stressStart);
+
+    const stressStop = document.createElement('button');
+    stressStop.id = 'stress-stop';
+    stressStop.textContent = 'atlas stress stop';
+    stressStop.addEventListener('click', () => this._stressRunning = false);
+    stressButtons.appendChild(stressStop);
+    container.appendChild(stressButtons);
+
+    const stressOptions = document.createElement('div');
+    this._scrollOutput = document.createElement('input');
+    this._scrollOutput.type = 'checkbox';
+    this._scrollOutput.id = 'scroll-output';
+    stressOptions.appendChild(this._scrollOutput);
+    const scrollOutputLabel = document.createElement('label');
+    scrollOutputLabel.htmlFor = 'scroll-output';
+    scrollOutputLabel.textContent = 'Scroll output';
+    stressOptions.appendChild(scrollOutputLabel);
+    container.appendChild(stressOptions);
+
     const zoomCheckbox = document.createElement('input');
     zoomCheckbox.type = 'checkbox';
     zoomCheckbox.id = 'texture-atlas-zoom';
@@ -48,4 +75,33 @@ export class WebglWindow extends BaseWindow implements IControlWindow {
     canvas.style.width = `${canvas.width / dpr}px`;
     canvas.style.height = `${canvas.height / dpr}px`;
   }
+
+  private async _stress(): Promise<void> {
+    const TEXT = '!"#$%&\'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~';
+    if (this._stressRunning) {
+      return;
+    }
+    this._stressRunning = true;
+    const scrollOutput = !!(this._scrollOutput?.checked);
+    for (let r = 0; r < 256; r += 2) {
+      for (let g = 0; g < 256; g += 2) {
+        let s: string[] = [];
+        for (let b = 0; b < 256; b += 2) {
+          if (!this._stressRunning) {
+            return;
+          }
+          const rbg = `RGB: ${[r, g, b]}`;
+          s.push(`\r\x1b[38;2;${r};${g};${b}m${rbg.padEnd(18, ' ')}${TEXT}`);
+          if (s.length >= 16) {
+            if (scrollOutput) {
+              await new Promise<void>(r => this._terminal.write(s.join('\r\n') + '\r\n', r));
+            } else {
+              await new Promise<void>(r => this._terminal.write('\x1b[H' + s.join('\r\n'), r));
+            }
+            s = [];
+          }
+        }
+      }
+    }
+  }
 }

package-lock.json

@@ -663,9 +663,9 @@
       }
     },
     "node_modules/@esbuild/aix-ppc64": {
-      "version": "0.28.0",
-      "resolved": "https://registry.npmjs.org/@esbuild/aix-ppc64/-/aix-ppc64-0.28.0.tgz",
-      "integrity": "sha512-lhRUCeuOyJQURhTxl4WkpFTjIsbDayJHih5kZC1giwE+MhIzAb7mEsQMqMf18rHLsrb5qI1tafG20mLxEWcWlA==",
+      "version": "0.28.1",
+      "resolved": "https://registry.npmjs.org/@esbuild/aix-ppc64/-/aix-ppc64-0.28.1.tgz",
+      "integrity": "sha512-Svl7tq8k/08+p6CXPpRjQ1fKX+1odH/BQbb48fV6fj3CWHhsoIOoY87w1oHXm0qEpkIK3ZfVgp0hed3XBXzXMQ==",
       "cpu": [
         "ppc64"
       ],
@@ -680,9 +680,9 @@
       }
     },
     "node_modules/@esbuild/android-arm": {
-      "version": "0.28.0",
-      "resolved": "https://registry.npmjs.org/@esbuild/android-arm/-/android-arm-0.28.0.tgz",
-      "integrity": "sha512-wqh0ByljabXLKHeWXYLqoJ5jKC4XBaw6Hk08OfMrCRd2nP2ZQ5eleDZC41XHyCNgktBGYMbqnrJKq/K/lzPMSQ==",
+      "version": "0.28.1",
+      "resolved": "https://registry.npmjs.org/@esbuild/android-arm/-/android-arm-0.28.1.tgz",
+      "integrity": "sha512-0k2F129Xdio1TdJfzJ8sy1Q47vUD2NnwdhiAf7drUN1EBTfPf4hsFCtmMgu/6m8JSzsBrlmVjudMBQqOfG8usQ==",
       "cpu": [
         "arm"
       ],
@@ -697,9 +697,9 @@
       }
     },
     "node_modules/@esbuild/android-arm64": {
-      "version": "0.28.0",
-      "resolved": "https://registry.npmjs.org/@esbuild/android-arm64/-/android-arm64-0.28.0.tgz",
-      "integrity": "sha512-+WzIXQOSaGs33tLEgYPYe/yQHf0WTU0X42Jca3y8NWMbUVhp7rUnw+vAsRC/QiDrdD31IszMrZy+qwPOPjd+rw==",
+      "version": "0.28.1",
+      "resolved": "https://registry.npmjs.org/@esbuild/android-arm64/-/android-arm64-0.28.1.tgz",
+      "integrity": "sha512-34EGEbCIAgosYz6goLcopX6Mo7NyGv9tfwEM2/7Ce2VcVRk568iSvniGWcUXIy7wEDR1wzolcxcriFVrWYcwBg==",
       "cpu": [
         "arm64"
       ],
@@ -714,9 +714,9 @@
       }
     },
     "node_modules/@esbuild/android-x64": {
-      "version": "0.28.0",
-      "resolved": "https://registry.npmjs.org/@esbuild/android-x64/-/android-x64-0.28.0.tgz",
-      "integrity": "sha512-+VJggoaKhk2VNNqVL7f6S189UzShHC/mR9EE8rDdSkdpN0KflSwWY/gWjDrNxxisg8Fp1ZCD9jLMo4m0OUfeUA==",
+      "version": "0.28.1",
+      "resolved": "https://registry.npmjs.org/@esbuild/android-x64/-/android-x64-0.28.1.tgz",
+      "integrity": "sha512-dbwY7ltSMDWsRatcRpCnES4F+im88OCUgGZjy52shC7GqHRE/cYlxNbB4Z4UpJswpcc4Qxd2oE/ufM0p61IKng==",
       "cpu": [
         "x64"
       ],
@@ -731,9 +731,9 @@
       }
     },
     "node_modules/@esbuild/darwin-arm64": {
-      "version": "0.28.0",
-      "resolved": "https://registry.npmjs.org/@esbuild/darwin-arm64/-/darwin-arm64-0.28.0.tgz",
-      "integrity": "sha512-0T+A9WZm+bZ84nZBtk1ckYsOvyA3x7e2Acj1KdVfV4/2tdG4fzUp91YHx+GArWLtwqp77pBXVCPn2We7Letr0Q==",
+      "version": "0.28.1",
+      "resolved": "https://registry.npmjs.org/@esbuild/darwin-arm64/-/darwin-arm64-0.28.1.tgz",
+      "integrity": "sha512-TZbWkQY7kvTAXbXUT7uVACR5cMHsDiSz9z7ZKAX/RTq/WJEk3QyRr0wZpNhBDX+/0CtdqUIJlOiodQcta6tY3Q==",
       "cpu": [
         "arm64"
       ],
@@ -748,9 +748,9 @@
       }
     },
     "node_modules/@esbuild/darwin-x64": {
-      "version": "0.28.0",
-      "resolved": "https://registry.npmjs.org/@esbuild/darwin-x64/-/darwin-x64-0.28.0.tgz",
-      "integrity": "sha512-fyzLm/DLDl/84OCfp2f/XQ4flmORsjU7VKt8HLjvIXChJoFFOIL6pLJPH4Yhd1n1gGFF9mPwtlN5Wf82DZs+LQ==",
+      "version": "0.28.1",
+      "resolved": "https://registry.npmjs.org/@esbuild/darwin-x64/-/darwin-x64-0.28.1.tgz",
+      "integrity": "sha512-zfdzgK9ACBNZLI/CyHTOx81SyNbM6YXn7rxSgX97VjyiPl9W1i4Ka4fgKECEoFCKGpvBj5qArWIGgQjOwkgskQ==",
       "cpu": [
         "x64"
       ],
@@ -765,9 +765,9 @@
       }
     },
     "node_modules/@esbuild/freebsd-arm64": {
-      "version": "0.28.0",
-      "resolved": "https://registry.npmjs.org/@esbuild/freebsd-arm64/-/freebsd-arm64-0.28.0.tgz",
-      "integrity": "sha512-l9GeW5UZBT9k9brBYI+0WDffcRxgHQD8ShN2Ur4xWq/NFzUKm3k5lsH4PdaRgb2w7mI9u61nr2gI2mLI27Nh3Q==",
+      "version": "0.28.1",
+      "resolved": "https://registry.npmjs.org/@esbuild/freebsd-arm64/-/freebsd-arm64-0.28.1.tgz",
+      "integrity": "sha512-wG2EA8ENdEI0qhkSZMjfqrdY+ziCYCPMmtZjjIwOmXFjmyzEHn+UUxk5of+SYsjtfs3VpnlC7QLzSI5hY/rOAw==",
       "cpu": [
         "arm64"
       ],
@@ -782,9 +782,9 @@
       }
     },
     "node_modules/@esbuild/freebsd-x64": {
-      "version": "0.28.0",
-      "resolved": "https://registry.npmjs.org/@esbuild/freebsd-x64/-/freebsd-x64-0.28.0.tgz",
-      "integrity": "sha512-BXoQai/A0wPO6Es3yFJ7APCiKGc1tdAEOgeTNy3SsB491S3aHn4S4r3e976eUnPdU+NbdtmBuLncYir2tMU9Nw==",
+      "version": "0.28.1",
+      "resolved": "https://registry.npmjs.org/@esbuild/freebsd-x64/-/freebsd-x64-0.28.1.tgz",
+      "integrity": "sha512-i7dZ9vQgnvSCzi/rYCXNgtF/U+eKZNJBzu3eTQbRgHnM7tNSizLOkRFAl3qzVc/Op/u5YkHHa4pf/3DOYHthLQ==",
       "cpu": [
         "x64"
       ],
@@ -799,9 +799,9 @@
       }
     },
     "node_modules/@esbuild/linux-arm": {
-      "version": "0.28.0",
-      "resolved": "https://registry.npmjs.org/@esbuild/linux-arm/-/linux-arm-0.28.0.tgz",
-      "integrity": "sha512-CjaaREJagqJp7iTaNQjjidaNbCKYcd4IDkzbwwxtSvjI7NZm79qiHc8HqciMddQ6CKvJT6aBd8lO9kN/ZudLlw==",
+      "version": "0.28.1",
+      "resolved": "https://registry.npmjs.org/@esbuild/linux-arm/-/linux-arm-0.28.1.tgz",
+      "integrity": "sha512-qVXBOHQS+d5Y722GwJzJUtOLlX7km3CraOaGormF1pDtPd2C/l1SHRPgjLunLGe51Sh5YYWKMFDyV4SxgMQYTQ==",
       "cpu": [
         "arm"
       ],
@@ -816,9 +816,9 @@
       }
     },
     "node_modules/@esbuild/linux-arm64": {
-      "version": "0.28.0",
-      "resolved": "https://registry.npmjs.org/@esbuild/linux-arm64/-/linux-arm64-0.28.0.tgz",
-      "integrity": "sha512-RVyzfb3FWsGA55n6WY0MEIEPURL1FcbhFE6BffZEMEekfCzCIMtB5yyDcFnVbTnwk+CLAgTujmV/Lgvih56W+A==",
+      "version": "0.28.1",
+      "resolved": "https://registry.npmjs.org/@esbuild/linux-arm64/-/linux-arm64-0.28.1.tgz",
+      "integrity": "sha512-yHs+0uc8+nvEAfAfxrWQKK5peSNzBc4PegcMO0EJ2hT71uA7vB8Ihg2e77R2P7SG5uYjPbHlLLmve4LLLRCf0g==",
       "cpu": [
         "arm64"
       ],
@@ -833,9 +833,9 @@
       }
     },
     "node_modules/@esbuild/linux-ia32": {
-      "version": "0.28.0",
-      "resolved": "https://registry.npmjs.org/@esbuild/linux-ia32/-/linux-ia32-0.28.0.tgz",
-      "integrity": "sha512-KBnSTt1kxl9x70q+ydterVdl+Cn0H18ngRMRCEQfrbqdUuntQQ0LoMZv47uB97NljZFzY6HcfqEZ2SAyIUTQBQ==",
+      "version": "0.28.1",
+      "resolved": "https://registry.npmjs.org/@esbuild/linux-ia32/-/linux-ia32-0.28.1.tgz",
+      "integrity": "sha512-d1z4ZuP0ajrfz/FhGT4vv278rX8KnPPJx8i5+AtK7TYbx9Le9F1hyzurZpkEyjkGa9dUGhQow4C1NmeGvqxN2w==",
       "cpu": [
         "ia32"
       ],
@@ -850,9 +850,9 @@
       }
     },
     "node_modules/@esbuild/linux-loong64": {
-      "version": "0.28.0",
-      "resolved": "https://registry.npmjs.org/@esbuild/linux-loong64/-/linux-loong64-0.28.0.tgz",
-      "integrity": "sha512-zpSlUce1mnxzgBADvxKXX5sl8aYQHo2ezvMNI8I0lbblJtp8V4odlm3Yzlj7gPyt3T8ReksE6bK+pT3WD+aJRg==",
+      "version": "0.28.1",
+      "resolved": "https://registry.npmjs.org/@esbuild/linux-loong64/-/linux-loong64-0.28.1.tgz",
+      "integrity": "sha512-M5sRjUVZrkm1OAPR3dlOYzNmN+loZKGVi1VUQGrwuqLcbR6qeAz+famMhjASeH3YVKvZz+zT1jlh/keC3Rj/lg==",
       "cpu": [
         "loong64"
       ],
@@ -867,9 +867,9 @@
       }
     },
     "node_modules/@esbuild/linux-mips64el": {
-      "version": "0.28.0",
-      "resolved": "https://registry.npmjs.org/@esbuild/linux-mips64el/-/linux-mips64el-0.28.0.tgz",
-      "integrity": "sha512-2jIfP6mmjkdmeTlsX/9vmdmhBmKADrWqN7zcdtHIeNSCH1SqIoNI63cYsjQR8J+wGa4Y5izRcSHSm8K3QWmk3w==",
+      "version": "0.28.1",
+      "resolved": "https://registry.npmjs.org/@esbuild/linux-mips64el/-/linux-mips64el-0.28.1.tgz",
+      "integrity": "sha512-mRObBZeHh2OxcBFPWE/FjylkRgZdYuiTR3vaTozquCGOH14iP9oN4x4Ge81CoIDYQrXmIxpFumJBu5MtZpnQJQ==",
       "cpu": [
         "mips64el"
       ],
@@ -884,9 +884,9 @@
       }
     },
     "node_modules/@esbuild/linux-ppc64": {
-      "version": "0.28.0",
-      "resolved": "https://registry.npmjs.org/@esbuild/linux-ppc64/-/linux-ppc64-0.28.0.tgz",
-      "integrity": "sha512-bc0FE9wWeC0WBm49IQMPSPILRocGTQt3j5KPCA8os6VprfuJ7KD+5PzESSrJ6GmPIPJK965ZJHTUlSA6GNYEhg==",
+      "version": "0.28.1",
+      "resolved": "https://registry.npmjs.org/@esbuild/linux-ppc64/-/linux-ppc64-0.28.1.tgz",
+      "integrity": "sha512-slScBsMAb3GFDcdrCgLwZtPYRoH2H/youv10QiZyRjmsP48fznoveWytSgCI/R0ZcUgpc0ZhIUEx6LHts8yrfQ==",
       "cpu": [
         "ppc64"
       ],
@@ -901,9 +901,9 @@
       }
     },
     "node_modules/@esbuild/linux-riscv64": {
-      "version": "0.28.0",
-      "resolved": "https://registry.npmjs.org/@esbuild/linux-riscv64/-/linux-riscv64-0.28.0.tgz",
-      "integrity": "sha512-SQPZOwoTTT/HXFXQJG/vBX8sOFagGqvZyXcgLA3NhIqcBv1BJU1d46c0rGcrij2B56Z2rNiSLaZOYW5cUk7yLQ==",
+      "version": "0.28.1",
+      "resolved": "https://registry.npmjs.org/@esbuild/linux-riscv64/-/linux-riscv64-0.28.1.tgz",
+      "integrity": "sha512-kw0owk1o0GFETUJyW0jc0G4Yzs0BHZn0JDZ8JRT088vjJYX777BAs1fDGxAC+q831qOs2DTC96mNsG2opdfyyQ==",
       "cpu": [
         "riscv64"
       ],
@@ -918,9 +918,9 @@
       }
     },
     "node_modules/@esbuild/linux-s390x": {
-      "version": "0.28.0",
-      "resolved": "https://registry.npmjs.org/@esbuild/linux-s390x/-/linux-s390x-0.28.0.tgz",
-      "integrity": "sha512-SCfR0HN8CEEjnYnySJTd2cw0k9OHB/YFzt5zgJEwa+wL/T/raGWYMBqwDNAC6dqFKmJYZoQBRfHjgwLHGSrn3Q==",
+      "version": "0.28.1",
+      "resolved": "https://registry.npmjs.org/@esbuild/linux-s390x/-/linux-s390x-0.28.1.tgz",
+      "integrity": "sha512-/lAIjX8aYFRByhh6L5rYtPEDRqa9de/4V/juOXcta5frjvzXO4/sqEtyytse0g3zZFuWu5cDN0MkLz2qRDD2Ag==",
       "cpu": [
         "s390x"
       ],
@@ -935,9 +935,9 @@
       }
     },
     "node_modules/@esbuild/linux-x64": {
-      "version": "0.28.0",
-      "resolved": "https://registry.npmjs.org/@esbuild/linux-x64/-/linux-x64-0.28.0.tgz",
-      "integrity": "sha512-us0dSb9iFxIi8srnpl931Nvs65it/Jd2a2K3qs7fz2WfGPHqzfzZTfec7oxZJRNPXPnNYZtanmRc4AL/JwVzHQ==",
+      "version": "0.28.1",
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@@ -986,9 +986,9 @@
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@@ -1003,9 +1003,9 @@
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@@ -1020,9 +1020,9 @@
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@@ -1037,9 +1037,9 @@
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+      "resolved": "https://registry.npmjs.org/@esbuild/sunos-x64/-/sunos-x64-0.28.1.tgz",
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@@ -1054,9 +1054,9 @@
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-      "resolved": "https://registry.npmjs.org/@esbuild/win32-arm64/-/win32-arm64-0.28.0.tgz",
-      "integrity": "sha512-Q9StnDmQ/enxnpxCCLSg0oo4+34B9TdXpuyPeTedN/6+iXBJ4J+zwfQI28u/Jl40nOYAxGoNi7mFP40RUtkmUA==",
+      "version": "0.28.1",
+      "resolved": "https://registry.npmjs.org/@esbuild/win32-arm64/-/win32-arm64-0.28.1.tgz",
+      "integrity": "sha512-lCv9eK/H6ZJWbE7bh2nw54CZ9M2nupBxJcTsdk/QQnWkdSjKGuxmmH8/GWrlT1eMmZfn4dGcCjRte397WqfQXA==",
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@@ -1071,9 +1071,9 @@
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-      "resolved": "https://registry.npmjs.org/@esbuild/win32-ia32/-/win32-ia32-0.28.0.tgz",
-      "integrity": "sha512-zF3ag/gfiCe6U2iczcRzSYJKH1DCI+ByzSENHlM2FcDbEeo5Zd2C86Aq0tKUYAJJ1obRP84ymxIAksZUcdztHA==",
+      "version": "0.28.1",
+      "resolved": "https://registry.npmjs.org/@esbuild/win32-ia32/-/win32-ia32-0.28.1.tgz",
+      "integrity": "sha512-zvb/mB2bSCoJOpoCBgYKKpX6YM6mJBlBUVUtVj41DlZJVEB6/0CKlRYxP5wWl1C1ILiCoAU5wZZ4q1P3qeS6Eg==",
       "cpu": [
         "ia32"
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@@ -1088,9 +1088,9 @@
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     "node_modules/@esbuild/win32-x64": {
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-      "resolved": "https://registry.npmjs.org/@esbuild/win32-x64/-/win32-x64-0.28.0.tgz",
-      "integrity": "sha512-pEl1bO9mfAmIC+tW5btTmrKaujg3zGtUmWNdCw/xs70FBjwAL3o9OEKNHvNmnyylD6ubxUERiEhdsL0xBQ9efw==",
+      "version": "0.28.1",
+      "resolved": "https://registry.npmjs.org/@esbuild/win32-x64/-/win32-x64-0.28.1.tgz",
+      "integrity": "sha512-bm4Mowrv+GXMlpWX++EcXw/iLyd1o3+bJkC2DkWXYVvgZCqD/bSj9ctZeAMC3cIxgjRVR2Dufaiu4YPxr5gW1A==",
       "cpu": [
         "x64"
       ],
@@ -3061,16 +3061,16 @@
       }
     },
     "node_modules/brace-expansion": {
-      "version": "5.0.6",
-      "resolved": "https://registry.npmjs.org/brace-expansion/-/brace-expansion-5.0.6.tgz",
-      "integrity": "sha512-kLpxurY4Z4r9sgMsyG0Z9uzsBlgiU/EFKhj/h91/8yHu0edo7XuixOIH3VcJ8kkxs6/jPzoI6U9Vj3WqbMQ94g==",
+      "version": "5.0.9",
+      "resolved": "https://registry.npmjs.org/brace-expansion/-/brace-expansion-5.0.9.tgz",
+      "integrity": "sha512-ScQ4IuvIEF1TMlP7Zt+vjJ//9zlPb2SDcxWxM3bk8s6t6GGdJ7KO1dCcTidOPJKePW30LE/2cT7wCyPho9/Wxg==",
       "dev": true,
       "license": "MIT",
       "dependencies": {
         "balanced-match": "^4.0.2"
       },
       "engines": {
-        "node": "18 || 20 || >=22"
+        "node": "20 || >=22"
       }
     },
     "node_modules/braces": {
@@ -3519,15 +3519,15 @@
       }
     },
     "node_modules/concurrently": {
-      "version": "9.2.1",
-      "resolved": "https://registry.npmjs.org/concurrently/-/concurrently-9.2.1.tgz",
-      "integrity": "sha512-fsfrO0MxV64Znoy8/l1vVIjjHa29SZyyqPgQBwhiDcaW8wJc2W3XWVOGx4M3oJBnv/zdUZIIp1gDeS98GzP8Ng==",
+      "version": "9.2.4",
+      "resolved": "https://registry.npmjs.org/concurrently/-/concurrently-9.2.4.tgz",
+      "integrity": "sha512-TZ0CEhyzvFjgtAvHTusDMgj7wNdihCh7LLLrzdUOXIhdlnL2JBBGA9eJxR24rtqgmdjh3OA3hrN1rCHj6HM8qA==",
       "dev": true,
       "license": "MIT",
       "dependencies": {
         "chalk": "4.1.2",
         "rxjs": "7.8.2",
-        "shell-quote": "1.8.3",
+        "shell-quote": "1.9.0",
         "supports-color": "8.1.1",
         "tree-kill": "1.2.2",
         "yargs": "17.7.2"
@@ -3869,9 +3869,9 @@
       "license": "MIT"
     },
     "node_modules/esbuild": {
-      "version": "0.28.0",
-      "resolved": "https://registry.npmjs.org/esbuild/-/esbuild-0.28.0.tgz",
-      "integrity": "sha512-sNR9MHpXSUV/XB4zmsFKN+QgVG82Cc7+/aaxJ8Adi8hyOac+EXptIp45QBPaVyX3N70664wRbTcLTOemCAnyqw==",
+      "version": "0.28.1",
+      "resolved": "https://registry.npmjs.org/esbuild/-/esbuild-0.28.1.tgz",
+      "integrity": "sha512-HrJrvZv5ayxBzPfwphOoNzkzOIIlifzk0KJrGK2c8R4+LKpMtpYLQeUdjnwjWv/LZlkH2laZk+4w78pi99D4Vw==",
       "dev": true,
       "hasInstallScript": true,
       "license": "MIT",
@@ -3882,32 +3882,32 @@
         "node": ">=18"
       },
       "optionalDependencies": {
-        "@esbuild/aix-ppc64": "0.28.0",
-        "@esbuild/android-arm": "0.28.0",
-        "@esbuild/android-arm64": "0.28.0",
-        "@esbuild/android-x64": "0.28.0",
-        "@esbuild/darwin-arm64": "0.28.0",
-        "@esbuild/darwin-x64": "0.28.0",
-        "@esbuild/freebsd-arm64": "0.28.0",
-        "@esbuild/freebsd-x64": "0.28.0",
-        "@esbuild/linux-arm": "0.28.0",
-        "@esbuild/linux-arm64": "0.28.0",
-        "@esbuild/linux-ia32": "0.28.0",
-        "@esbuild/linux-loong64": "0.28.0",
-        "@esbuild/linux-mips64el": "0.28.0",
-        "@esbuild/linux-ppc64": "0.28.0",
-        "@esbuild/linux-riscv64": "0.28.0",
-        "@esbuild/linux-s390x": "0.28.0",
-        "@esbuild/linux-x64": "0.28.0",
-        "@esbuild/netbsd-arm64": "0.28.0",
-        "@esbuild/netbsd-x64": "0.28.0",
-        "@esbuild/openbsd-arm64": "0.28.0",
-        "@esbuild/openbsd-x64": "0.28.0",
-        "@esbuild/openharmony-arm64": "0.28.0",
-        "@esbuild/sunos-x64": "0.28.0",
-        "@esbuild/win32-arm64": "0.28.0",
-        "@esbuild/win32-ia32": "0.28.0",
-        "@esbuild/win32-x64": "0.28.0"
+        "@esbuild/aix-ppc64": "0.28.1",
+        "@esbuild/android-arm": "0.28.1",
+        "@esbuild/android-arm64": "0.28.1",
+        "@esbuild/android-x64": "0.28.1",
+        "@esbuild/darwin-arm64": "0.28.1",
+        "@esbuild/darwin-x64": "0.28.1",
+        "@esbuild/freebsd-arm64": "0.28.1",
+        "@esbuild/freebsd-x64": "0.28.1",
+        "@esbuild/linux-arm": "0.28.1",
+        "@esbuild/linux-arm64": "0.28.1",
+        "@esbuild/linux-ia32": "0.28.1",
+        "@esbuild/linux-loong64": "0.28.1",
+        "@esbuild/linux-mips64el": "0.28.1",
+        "@esbuild/linux-ppc64": "0.28.1",
+        "@esbuild/linux-riscv64": "0.28.1",
+        "@esbuild/linux-s390x": "0.28.1",
+        "@esbuild/linux-x64": "0.28.1",
+        "@esbuild/netbsd-arm64": "0.28.1",
+        "@esbuild/netbsd-x64": "0.28.1",
+        "@esbuild/openbsd-arm64": "0.28.1",
+        "@esbuild/openbsd-x64": "0.28.1",
+        "@esbuild/openharmony-arm64": "0.28.1",
+        "@esbuild/sunos-x64": "0.28.1",
+        "@esbuild/win32-arm64": "0.28.1",
+        "@esbuild/win32-ia32": "0.28.1",
+        "@esbuild/win32-x64": "0.28.1"
       }
     },
     "node_modules/escalade": {
@@ -4308,9 +4308,9 @@
       }
     },
     "node_modules/express-ws/node_modules/ws": {
-      "version": "7.5.10",
-      "resolved": "https://registry.npmjs.org/ws/-/ws-7.5.10.tgz",
-      "integrity": "sha512-+dbF1tHwZpXcbOJdVOkzLDxZP1ailvSxM6ZweXTegylPny803bFhA+vqBYw4s31NSAk4S2Qz+AKXK9a4wkdjcQ==",
+      "version": "7.5.13",
+      "resolved": "https://registry.npmjs.org/ws/-/ws-7.5.13.tgz",
+      "integrity": "sha512-rsKI6xDBFVf4r/x8XyChGK04QR/XHroxs/jUcoWvtEZM8TPU/X/uIY9B1CsSzYws9ZJb/6bbBu7dPhFW00CAoA==",
       "dev": true,
       "license": "MIT",
       "engines": {
@@ -4351,9 +4351,9 @@
       "license": "MIT"
     },
     "node_modules/fast-uri": {
-      "version": "3.1.2",
-      "resolved": "https://registry.npmjs.org/fast-uri/-/fast-uri-3.1.2.tgz",
-      "integrity": "sha512-rVjf7ArG3LTk+FS6Yw81V1DLuZl1bRbNrev6Tmd/9RaroeeRRJhAt7jg/6YFxbvAQXUCavSoZhPPj6oOx+5KjQ==",
+      "version": "3.1.5",
+      "resolved": "https://registry.npmjs.org/fast-uri/-/fast-uri-3.1.5.tgz",
+      "integrity": "sha512-gHwA1O9LDIcKunMKhObS/HimwtehO1nPUECKAu5TpKgaO19fcWEl4bliWe1jWxVFvIXztJjjQ4L8XQ1EU9f7Jw==",
       "dev": true,
       "funding": [
         {
@@ -4749,9 +4749,9 @@
       "license": "MIT"
     },
     "node_modules/glob/node_modules/brace-expansion": {
-      "version": "2.1.0",
-      "resolved": "https://registry.npmjs.org/brace-expansion/-/brace-expansion-2.1.0.tgz",
-      "integrity": "sha512-TN1kCZAgdgweJhWWpgKYrQaMNHcDULHkWwQIspdtjV4Y5aurRdZpjAqn6yX3FPqTA9ngHCc4hJxMAMgGfve85w==",
+      "version": "2.1.4",
+      "resolved": "https://registry.npmjs.org/brace-expansion/-/brace-expansion-2.1.4.tgz",
+      "integrity": "sha512-hGfVzPxthbf3+2yjg/RBs60cB0FhqBS/zvdV/4wn4/BmN0bNMMHPc4V/BbFieqf1TKAGGAHnY4eSjajCl0f2Xg==",
       "dev": true,
       "license": "MIT",
       "dependencies": {
@@ -5795,9 +5795,9 @@
       "license": "MIT"
     },
     "node_modules/mocha/node_modules/brace-expansion": {
-      "version": "2.1.0",
-      "resolved": "https://registry.npmjs.org/brace-expansion/-/brace-expansion-2.1.0.tgz",
-      "integrity": "sha512-TN1kCZAgdgweJhWWpgKYrQaMNHcDULHkWwQIspdtjV4Y5aurRdZpjAqn6yX3FPqTA9ngHCc4hJxMAMgGfve85w==",
+      "version": "2.1.4",
+      "resolved": "https://registry.npmjs.org/brace-expansion/-/brace-expansion-2.1.4.tgz",
+      "integrity": "sha512-hGfVzPxthbf3+2yjg/RBs60cB0FhqBS/zvdV/4wn4/BmN0bNMMHPc4V/BbFieqf1TKAGGAHnY4eSjajCl0f2Xg==",
       "dev": true,
       "license": "MIT",
       "dependencies": {
@@ -7127,9 +7127,9 @@
       }
     },
     "node_modules/shell-quote": {
-      "version": "1.8.3",
-      "resolved": "https://registry.npmjs.org/shell-quote/-/shell-quote-1.8.3.tgz",
-      "integrity": "sha512-ObmnIF4hXNg1BqhnHmgbDETF8dLPCggZWBjkQfhZpbszZnYur5DUljTcCHii5LC3J5E0yeO/1LIMyH+UvHQgyw==",
+      "version": "1.9.0",
+      "resolved": "https://registry.npmjs.org/shell-quote/-/shell-quote-1.9.0.tgz",
+      "integrity": "sha512-Iov+JwFv/2HcTpcwNMKd8+IWNb8tboQJNQTkAY/LLVK7gGH9jy+LGkVqPxfekHl+yMmiqXszdGWXgkfml7hjqA==",
       "dev": true,
       "license": "MIT",
       "engines": {
@@ -7975,9 +7975,9 @@
       }
     },
     "node_modules/undici": {
-      "version": "7.25.0",
-      "resolved": "https://registry.npmjs.org/undici/-/undici-7.25.0.tgz",
-      "integrity": "sha512-xXnp4kTyor2Zq+J1FfPI6Eq3ew5h6Vl0F/8d9XU5zZQf1tX9s2Su1/3PiMmUANFULpmksxkClamIZcaUqryHsQ==",
+      "version": "7.29.0",
+      "resolved": "https://registry.npmjs.org/undici/-/undici-7.29.0.tgz",
+      "integrity": "sha512-IDxfleLmmbSskfWSUATiN1nfn2rDuvnMOqb5CWR92iIfojA0Ud+ulOAAEQ57LPr9rWmsreUyf5lwyao+7GNNVw==",
       "dev": true,
       "license": "MIT",
       "engines": {
@@ -8452,9 +8452,9 @@
       "license": "ISC"
     },
     "node_modules/ws": {
-      "version": "8.20.1",
-      "resolved": "https://registry.npmjs.org/ws/-/ws-8.20.1.tgz",
-      "integrity": "sha512-It4dO0K5v//JtTXuPkfEOaI3uUN87iYPnqo/ZzqCoG3g8uhA66QUMs/SrM0YK7/NAu+r4LMh/9dq2A7k+rHs+w==",
+      "version": "8.21.3",
+      "resolved": "https://registry.npmjs.org/ws/-/ws-8.21.3.tgz",
+      "integrity": "sha512-201TZ/kPWxoPr/OKWjquZR1SWKXcvxdH+e1xrx89b3YbmzLMFCLfnaG1HFIgWzJOEWZ7MvpK++odZufgYR50Rw==",
       "dev": true,
       "license": "MIT",
       "engines": {

src/browser/CoreBrowserTerminal.ts

@@ -492,6 +492,7 @@ export class CoreBrowserTerminal extends CoreTerminal implements ITerminal {
       // https://issuetracker.google.com/issues/260170397
       this.textarea.setAttribute('aria-multiline', 'false');
     }
+    this.textarea.setAttribute('autocomplete', 'off');
     this.textarea.setAttribute('autocorrect', 'off');
     this.textarea.setAttribute('autocapitalize', 'off');
     this.textarea.setAttribute('spellcheck', 'false');
@@ -1072,10 +1073,6 @@ export class CoreBrowserTerminal extends CoreTerminal implements ITerminal {
    * Clear the entire buffer, making the prompt line the new first line.
    */
   public clear(): void {
-    if (this.buffer.ybase === 0 && this.buffer.y === 0) {
-      // Don't clear if it's already clear
-      return;
-    }
     this.buffer.clearAllMarkers();
     this.buffer.lines.set(0, this.buffer.lines.get(this.buffer.ybase + this.buffer.y)!);
     this.buffer.lines.length = 1;

src/browser/renderer/dom/DomRenderer.ts

@@ -536,9 +536,14 @@ export class DomRenderer extends Disposable implements IRenderer {
     for (let y = start; y <= end; y++) {
       const row = y + buffer.ydisp;
       const rowElement = this._rowElements[y];
+      if (!rowElement) {
+        continue;
+      }
       const lineData = buffer.lines.get(row);
-      if (!rowElement || !lineData) {
-        break;
+      if (!lineData) {
+        rowElement.replaceChildren();
+        this._setRowBlinkState(y, false);
+        continue;
       }
       rowElement.replaceChildren(
         ...this._rowFactory.createRow(
@@ -610,9 +615,14 @@ export class DomRenderer extends Disposable implements IRenderer {
     for (let i = y; i <= y2; ++i) {
       const row = i + buffer.ydisp;
       const rowElement = this._rowElements[i];
+      if (!rowElement) {
+        continue;
+      }
       const bufferline = buffer.lines.get(row);
-      if (!rowElement || !bufferline) {
-        break;
+      if (!bufferline) {
+        rowElement.replaceChildren();
+        this._setRowBlinkState(i, false);
+        continue;
       }
       rowElement.replaceChildren(
         ...this._rowFactory.createRow(

src/browser/renderer/dom/DomRendererRowFactory.test.ts

@@ -6,16 +6,14 @@
 import jsdom = require('jsdom');
 import { assert } from 'chai';
 import { DomRendererRowFactory } from './DomRendererRowFactory';
-import { NULL_CELL_CODE, NULL_CELL_WIDTH, NULL_CELL_CHAR, DEFAULT_ATTR, FgFlags, BgFlags, Attributes, UnderlineStyle } from '../../../common/buffer/Constants';
+import { DEFAULT_ATTR, FgFlags, BgFlags, Attributes, UnderlineStyle } from '../../../common/buffer/Constants';
 import { BufferLine, DEFAULT_ATTR_DATA } from '../../../common/buffer/BufferLine';
-import { BufferLineStringCache } from '../../../common/buffer/BufferLineStringCache';
 import { IBufferLine } from '../../../common/buffer/Types';
 import { CellData } from '../../../common/buffer/CellData';
 import { MockCoreService, MockDecorationService, MockOptionsService, createCellData, NULL_CELL_DATA } from '../../../common/TestUtils.test';
 import { MockCharacterJoinerService, MockCoreBrowserService, MockThemeService } from '../../TestUtils.test';
 import { TestWidthCache } from './WidthCache.test';
 
-const TEST_STRING_CACHE = new BufferLineStringCache();
 
 describe('DomRendererRowFactory', () => {
   let dom: jsdom.JSDOM;
@@ -517,7 +515,7 @@ describe('DomRendererRowFactory', () => {
   }
 
   function createEmptyLineData(cols: number): IBufferLine {
-    const lineData = new BufferLine(TEST_STRING_CACHE, cols);
+    const lineData = new BufferLine(cols);
     for (let i = 0; i < cols; i++) {
       lineData.setCell(i, NULL_CELL_DATA);
     }

src/browser/selection/SelectionModel.test.ts

@@ -64,6 +64,13 @@ describe('SelectionModel', () => {
       assert.deepEqual(model.finalSelectionStart, undefined);
       assert.deepEqual(model.finalSelectionEnd, undefined);
     });
+    it('should reset selection start to origin when start row is trimmed', () => {
+      model.selectionStart = [50, 0];
+      model.selectionEnd = [10, 2];
+      assert.equal(model.handleTrim(1), true);
+      assert.deepEqual(model.finalSelectionStart, [0, 0]);
+      assert.deepEqual(model.finalSelectionEnd, [10, 1]);
+    });
   });
 
   describe('finalSelectionStart', () => {

src/browser/selection/SelectionModel.ts

@@ -135,9 +135,10 @@ export class SelectionModel {
       return true;
     }
 
-    // If the selection start is trimmed, ensure the start column is 0.
+    // If the selection start row is trimmed away, reset to the buffer origin.
     if (this.selectionStart && this.selectionStart[1] < 0) {
-      this.selectionStart[1] = 0;
+      this.selectionStart = [0, 0];
+      return true;
     }
     return false;
   }

src/browser/services/CharacterJoinerService.test.ts

@@ -7,12 +7,10 @@ import { assert } from 'chai';
 import { ICharacterJoinerService } from './Services';
 import { CharacterJoinerService } from './CharacterJoinerService';
 import { BufferLine } from '../../common/buffer/BufferLine';
-import { BufferLineStringCache } from '../../common/buffer/BufferLineStringCache';
 import { IBufferLine } from '../../common/buffer/Types';
 import { CellData } from '../../common/buffer/CellData';
 import { MockBufferService, createCellData } from '../../common/TestUtils.test';
 
-const TEST_STRING_CACHE = new BufferLineStringCache();
 
 describe('CharacterJoinerService', () => {
   let service: ICharacterJoinerService;
@@ -25,7 +23,7 @@ describe('CharacterJoinerService', () => {
     lines.set(2, lineData([['a -> b -', 0xFFFFFFFF], ['> c -> d', 0]]));
 
     lines.set(3, lineData([['no joined ranges']]));
-    lines.set(4, new BufferLine(TEST_STRING_CACHE, 0));
+    lines.set(4, new BufferLine(0));
     lines.set(5, lineData([['a', 0x11111111], [' -> b -> c -> '], ['d', 0x22222222]]));
     const line6 = lineData([['wi']]);
     line6.resize(line6.length + 1, createCellData(0, '￥', 2));
@@ -270,7 +268,7 @@ describe('CharacterJoinerService', () => {
 type IPartialLineData = ([string] | [string, number]);
 
 function lineData(data: IPartialLineData[]): IBufferLine {
-  const tline = new BufferLine(TEST_STRING_CACHE, 0);
+  const tline = new BufferLine(0);
   for (let i = 0; i < data.length; ++i) {
     const line = data[i][0];
     const attr = (data[i][1] || 0) as number;

src/browser/services/CharacterJoinerService.ts

@@ -100,6 +100,7 @@ export class CharacterJoinerService implements ICharacterJoinerService {
 
     const ranges: [number, number][] = [];
     const lineStr = line.translateToString(true);
+    const trimmedLength = line.getTrimmedLength();
 
     // Because some cells can be represented by multiple javascript characters,
     // we track the cell and the string indexes separately. This allows us to
@@ -111,7 +112,7 @@ export class CharacterJoinerService implements ICharacterJoinerService {
     let rangeAttrFG = line.getFg(0);
     let rangeAttrBG = line.getBg(0);
 
-    for (let x = 0; x < line.getTrimmedLength(); x++) {
+    for (let x = 0; x < trimmedLength; x++) {
       line.loadCell(x, this._workCell);
 
       if (this._workCell.getWidth() === 0) {
@@ -147,7 +148,7 @@ export class CharacterJoinerService implements ICharacterJoinerService {
     }
 
     // Process any trailing ranges.
-    if (this._bufferService.cols - rangeStartColumn > 1) {
+    if (trimmedLength - rangeStartColumn > 1) {
       const joinedRanges = this._getJoinedRanges(
         lineStr,
         rangeStartStringIndex,
@@ -216,7 +217,8 @@ export class CharacterJoinerService implements ICharacterJoinerService {
       return;
     }
 
-    for (let x = startCol; x < this._bufferService.cols; x++) {
+    const trimmedLength = line.getTrimmedLength();
+    for (let x = startCol; x < trimmedLength; x++) {
       const width = line.getWidth(x);
       const length = line.getString(x).length || WHITESPACE_CELL_CHAR.length;
 
@@ -264,7 +266,7 @@ export class CharacterJoinerService implements ICharacterJoinerService {
     // If there is still a range left at the end, it must extend all the way to
     // the end of the line.
     if (currentRange) {
-      currentRange[1] = this._bufferService.cols;
+      currentRange[1] = trimmedLength;
     }
   }
 

src/browser/services/MouseService.test.ts

@@ -351,3 +351,96 @@ describe('MouseService mouseEventsRequireAlt', () => {
     assert.isFalse(element.classList.contains(MouseEventCssClasses.ENABLE_MOUSE_EVENTS));
   });
 });
+
+describe('MouseService multi-window', () => {
+  interface IRecordingDocument {
+    doc: Document;
+    added: string[];
+    removed: string[];
+    listeners: { [type: string]: EventListener[] };
+  }
+
+  function createRecordingDocument(): IRecordingDocument {
+    const added: string[] = [];
+    const removed: string[] = [];
+    const listeners: { [type: string]: EventListener[] } = {};
+    const doc = {
+      addEventListener: (type: string, listener: EventListener) => {
+        added.push(type);
+        (listeners[type] ??= []).push(listener);
+      },
+      removeEventListener: (type: string) => removed.push(type)
+    } as any;
+    return { doc, added, removed, listeners };
+  }
+
+  it('should manage protocol mouseup/mousemove listeners on the element\'s current document, not the document the terminal was opened with', () => {
+    const mouseStateService = new MouseStateService();
+    const optionsService = new OptionsService({});
+    const mouseService = new MouseService(
+      new MockRenderService(),
+      {
+        getMouseReportCoords: () => ({ col: 0, row: 0, x: 0, y: 0 })
+      } as any,
+      mouseStateService,
+      {
+        triggerDataEvent: () => {},
+        triggerBinaryEvent: () => {},
+        decPrivateModes: { applicationCursorKeys: false }
+      } as any,
+      bufferService,
+      optionsService,
+      new TestSelectionService(),
+      logService,
+      new MockCoreBrowserService()
+    );
+
+    // Simulate a terminal that was opened with one document but whose element now lives in
+    // another document (eg. it was moved to a child window)
+    const openDocument = createRecordingDocument();
+    const childDocument = createRecordingDocument();
+    const elementListeners: { [type: string]: EventListener[] } = {};
+    const element = {
+      classList: {
+        add: () => {},
+        remove: () => {},
+        contains: () => false
+      },
+      addEventListener: (type: string, listener: EventListener) => {
+        (elementListeners[type] ??= []).push(listener);
+      },
+      removeEventListener: () => {},
+      ownerDocument: childDocument.doc
+    } as any;
+
+    mouseService.bindMouse({
+      element,
+      screenElement: createTestMouseTargetElement(),
+      document: openDocument.doc
+    }, disposable => disposable, () => {});
+    mouseStateService.activeProtocol = 'ANY';
+
+    elementListeners['mousedown'][0]({
+      type: 'mousedown',
+      button: 0,
+      buttons: 1,
+      altKey: false,
+      ctrlKey: false,
+      shiftKey: false,
+      preventDefault: () => {}
+    } as any);
+    assert.deepEqual(childDocument.added, ['mouseup', 'mousemove']);
+    assert.deepEqual(openDocument.added, []);
+
+    childDocument.listeners['mouseup'][0]({
+      type: 'mouseup',
+      button: 0,
+      buttons: 0,
+      altKey: false,
+      ctrlKey: false,
+      shiftKey: false
+    } as any);
+    assert.deepEqual(childDocument.removed, ['mouseup', 'mousemove']);
+    assert.deepEqual(openDocument.removed, []);
+  });
+});

src/browser/services/MouseService.ts

@@ -7,7 +7,7 @@ import { addDisposableListener } from '../Dom';
 import { IBufferService, IMouseStateService, ICoreService, ILogService, IOptionsService } from '../../common/services/Services';
 import { CoreMouseAction, CoreMouseButton, CoreMouseEventType, ICoreMouseEvent, IDisposable } from '../../common/Types';
 import { C0 } from '../../common/data/EscapeSequences';
-import { DisposableStore, MutableDisposable, toDisposable } from '../../common/Lifecycle';
+import { DisposableStore, MutableDisposable } from '../../common/Lifecycle';
 import { ICoreBrowserService, IMouseCoordsService, IMouseService, IMouseServiceTarget, IRenderService, ISelectionService } from './Services';
 import { Gesture, EventType as GestureEventType, IGestureEvent } from '../scrollable/touch';
 
@@ -21,6 +21,8 @@ interface IMouseBindContext {
   readonly target: IMouseServiceTarget;
   readonly focus: () => void;
   readonly requestedEvents: RequestedMouseEvents;
+  readonly mouseupListener: MutableDisposable<IDisposable>;
+  readonly mousedragListener: MutableDisposable<IDisposable>;
 }
 
 export class MouseService implements IMouseService {
@@ -61,7 +63,11 @@ export class MouseService implements IMouseService {
       mousedrag: null,
       mousemove: null
     };
-    const ctx: IMouseBindContext = { target, focus, requestedEvents };
+    const mouseupListener = new MutableDisposable<IDisposable>();
+    const mousedragListener = new MutableDisposable<IDisposable>();
+    register(mouseupListener);
+    register(mousedragListener);
+    const ctx: IMouseBindContext = { target, focus, requestedEvents, mouseupListener, mousedragListener };
     const eventListeners: Record<'mouseup' | 'wheel' | 'mousedrag' | 'mousemove', EventListener> = {
       mouseup: (ev: Event) => this._handleMouseUp(ctx, ev as MouseEvent),
       wheel: (ev: Event) => this._handleWheel(ctx, ev as WheelEvent),
@@ -85,16 +91,6 @@ export class MouseService implements IMouseService {
     // force initial onProtocolChange so we dont miss early mouse requests
     this._mouseStateService.activeProtocol = this._mouseStateService.activeProtocol;
 
-    // Ensure document-level listeners are removed on dispose
-    register(toDisposable(() => {
-      if (requestedEvents.mouseup) {
-        document.removeEventListener('mouseup', requestedEvents.mouseup);
-      }
-      if (requestedEvents.mousedrag) {
-        document.removeEventListener('mousemove', requestedEvents.mousedrag);
-      }
-    }));
-
     /**
      * "Always on" event listeners.
      */
@@ -199,12 +195,8 @@ export class MouseService implements IMouseService {
     this._sendEvent(ctx, ev);
     if (!ev.buttons) {
       // if no other button is held remove global handlers
-      if (ctx.requestedEvents.mouseup) {
-        ctx.target.document.removeEventListener('mouseup', ctx.requestedEvents.mouseup);
-      }
-      if (ctx.requestedEvents.mousedrag) {
-        ctx.target.document.removeEventListener('mousemove', ctx.requestedEvents.mousedrag);
-      }
+      ctx.mouseupListener.clear();
+      ctx.mousedragListener.clear();
     }
   }
 
@@ -246,11 +238,14 @@ export class MouseService implements IMouseService {
     // of the terminal element.
     // Note: Other emulators also do this for 'mousedown' while a button
     // is held, we currently limit 'mousedown' to the terminal only.
+    // Use the element's current document in case it moved to another window after open.
+    const { element, document: targetDocument } = ctx.target;
+    const listenerDocument = element.ownerDocument ?? targetDocument;
     if (ctx.requestedEvents.mouseup) {
-      ctx.target.document.addEventListener('mouseup', ctx.requestedEvents.mouseup);
+      ctx.mouseupListener.value = addDisposableListener(listenerDocument, 'mouseup', ctx.requestedEvents.mouseup);
     }
     if (ctx.requestedEvents.mousedrag) {
-      ctx.target.document.addEventListener('mousemove', ctx.requestedEvents.mousedrag);
+      ctx.mousedragListener.value = addDisposableListener(listenerDocument, 'mousemove', ctx.requestedEvents.mousedrag);
     }
   }
 
@@ -398,7 +393,7 @@ export class MouseService implements IMouseService {
   }
 
   private _handleProtocolChange(ctx: IMouseBindContext, eventListeners: Record<'mouseup' | 'wheel' | 'mousedrag' | 'mousemove', EventListener>, events: CoreMouseEventType): void {
-    const { element, document } = ctx.target;
+    const { element } = ctx.target;
     const { requestedEvents } = ctx;
     // apply global changes on events
     if (events) {
@@ -433,18 +428,14 @@ export class MouseService implements IMouseService {
     }
 
     if (!(events & CoreMouseEventType.UP)) {
-      if (requestedEvents.mouseup) {
-        document.removeEventListener('mouseup', requestedEvents.mouseup);
-      }
+      ctx.mouseupListener.clear();
       requestedEvents.mouseup = null;
     } else {
       requestedEvents.mouseup ??= eventListeners.mouseup;
     }
 
     if (!(events & CoreMouseEventType.DRAG)) {
-      if (requestedEvents.mousedrag) {
-        document.removeEventListener('mousemove', requestedEvents.mousedrag);
-      }
+      ctx.mousedragListener.clear();
       requestedEvents.mousedrag = null;
     } else {
       requestedEvents.mousedrag ??= eventListeners.mousedrag;

src/browser/services/SelectionService.test.ts

@@ -9,13 +9,11 @@ import { SelectionModel } from '../selection/SelectionModel';
 import { IBuffer, IBufferLine } from '../../common/buffer/Types';
 import { MockBufferService, MockOptionsService, MockCoreService, MockMouseStateService, createCellData } from '../../common/TestUtils.test';
 import { BufferLine } from '../../common/buffer/BufferLine';
-import { BufferLineStringCache } from '../../common/buffer/BufferLineStringCache';
 import { IBufferService, IOptionsService } from '../../common/services/Services';
 import { MockCoreBrowserService, MockMouseService, MockRenderService } from '../TestUtils.test';
 import { CellData } from '../../common/buffer/CellData';
 import { IRenderService } from './Services';
 
-const TEST_STRING_CACHE = new BufferLineStringCache();
 
 class TestSelectionService extends SelectionService {
   constructor(
@@ -60,7 +58,7 @@ describe('SelectionService', () => {
   });
 
   function stringToRow(text: string): IBufferLine {
-    const result = new BufferLine(TEST_STRING_CACHE, text.length);
+    const result = new BufferLine(text.length);
     for (let i = 0; i < text.length; i++) {
       result.setCell(i, createCellData(0, text.charAt(i), 1));
     }
@@ -68,7 +66,7 @@ describe('SelectionService', () => {
   }
 
   function stringArrayToRow(chars: string[]): IBufferLine {
-    const line = new BufferLine(TEST_STRING_CACHE, chars.length);
+    const line = new BufferLine(chars.length);
     chars.map((c, idx) => line.setCell(idx, createCellData(0, c, 1)));
     return line;
   }
@@ -123,7 +121,7 @@ describe('SelectionService', () => {
         [0, 'o', 1, 'o'.charCodeAt(0)],
         [0, 'o', 1, 'o'.charCodeAt(0)]
       ];
-      const line = new BufferLine(TEST_STRING_CACHE, data.length);
+      const line = new BufferLine(data.length);
       for (let i = 0; i < data.length; ++i) line.setCell(i, CellData.fromCharData(data[i]));
       buffer.lines.set(0, line);
       // Ensure wide characters take up 2 columns

src/browser/services/SelectionService.ts

@@ -704,7 +704,7 @@ export class SelectionService extends Disposable implements ISelectionService {
         if (this._activeSelectionMode !== SelectionMode.COLUMN) {
           this._model.selectionEnd[0] = this._bufferService.cols;
         }
-        this._model.selectionEnd[1] = Math.min(buffer.ydisp + this._bufferService.rows, buffer.lines.length - 1);
+        this._model.selectionEnd[1] = Math.min(buffer.ydisp + this._bufferService.rows - 1, buffer.lines.length - 1);
       } else {
         if (this._activeSelectionMode !== SelectionMode.COLUMN) {
           this._model.selectionEnd[0] = 0;

src/common/Event.ts

@@ -27,11 +27,13 @@ export class Emitter<T> {
       }
 
       const entry = { fn: listener, thisArgs };
+      this._listeners = this._listeners.slice();
       this._listeners.push(entry);
 
       const result = toDisposable(() => {
         const idx = this._listeners.indexOf(entry);
         if (idx !== -1) {
+          this._listeners = this._listeners.slice();
           this._listeners.splice(idx, 1);
         }
       });
@@ -50,23 +52,16 @@ export class Emitter<T> {
   }
 
   public fire(event: T): void {
-    if (this._disposed) {
+    if (this._disposed || !this._listeners.length) {
       return;
     }
-    switch (this._listeners.length) {
-      case 0: return;
-      case 1: {
-        const { fn, thisArgs } = this._listeners[0];
-        fn.call(thisArgs, event);
-        return;
-      }
-      default: {
-        // Snapshot listeners to allow modifications during iteration (2+ listeners)
-        const listeners = this._listeners.slice();
-        for (const { fn, thisArgs } of listeners) {
-          fn.call(thisArgs, event);
-        }
-      }
+    if (this._listeners.length === 1) {
+      this._listeners[0].fn.call(this._listeners[0].thisArgs, event);
+      return;
+    }
+    const listeners = this._listeners;
+    for (let i = 0, len = listeners.length; i < len; ++i) {
+      listeners[i].fn.call(listeners[i].thisArgs, event);
     }
   }
 

src/common/InputHandler.test.ts

@@ -2394,6 +2394,54 @@ describe('InputHandler', () => {
     });
   });
 
+  describe('ED3 - erase saved lines', () => {
+    beforeEach(() => {
+      bufferService.resize(10, 5);
+    });
+    it('should stop locking the viewport when the scrollback the user scrolled into is erased', async () => {
+      for (let i = 0; i < 20; ++i) {
+        await inputHandler.parseP(`old ${i}\r\n`);
+      }
+      bufferService.scrollLines(-5);
+      assert.strictEqual(bufferService.isUserScrolling, true);
+
+      await inputHandler.parseP('\x1b[3J');
+
+      assert.strictEqual(bufferService.isUserScrolling, false);
+      assert.strictEqual(bufferService.buffer.ybase, 0);
+      assert.strictEqual(bufferService.buffer.ydisp, 0);
+
+      for (let i = 0; i < 20; ++i) {
+        await inputHandler.parseP(`new ${i}\r\n`);
+      }
+
+      assert.strictEqual(bufferService.buffer.ydisp, bufferService.buffer.ybase);
+    });
+    it('should not reset the scroll position when erasing scrollback on a resized alt buffer', async () => {
+      bufferService.resize(10, 50);
+      bufferService.resize(10, 5);
+      for (let i = 0; i < 20; ++i) {
+        await inputHandler.parseP(`old ${i}\r\n`);
+      }
+      bufferService.scrollLines(-5);
+      const ydisp = bufferService.buffer.ydisp;
+
+      await inputHandler.parseP('\x1b[?1049h');
+      for (let i = 0; i < 20; ++i) {
+        await inputHandler.parseP(`new ${i}\r\n`);
+      }
+      await inputHandler.parseP('\x1b[3J\x1b[?1049l');
+
+      assert.strictEqual(bufferService.isUserScrolling, true);
+      assert.strictEqual(bufferService.buffer.ydisp, ydisp);
+
+      await inputHandler.parseP('more\r\n');
+
+      assert.strictEqual(bufferService.isUserScrolling, true);
+      assert.strictEqual(bufferService.buffer.ydisp, ydisp);
+    });
+  });
+
   describe('DECSCA and DECSED/DECSEL', () => {
     it('default is unprotected', async () => {
       await inputHandler.parseP('some text');

src/common/InputHandler.ts

@@ -1286,6 +1286,11 @@ export class InputHandler extends Disposable implements IInputHandler {
           this._activeBuffer.lines.trimStart(scrollBackSize);
           this._activeBuffer.ybase = Math.max(this._activeBuffer.ybase - scrollBackSize, 0);
           this._activeBuffer.ydisp = Math.max(this._activeBuffer.ydisp - scrollBackSize, 0);
+          // isUserScrolling tracks the normal buffer's viewport, so ED3 on the alt
+          // screen must not touch it
+          if (this._activeBuffer === this._bufferService.buffers.normal) {
+            this._bufferService.isUserScrolling = false;
+          }
           // Force a scroll event to refresh viewport
           this._onScroll.fire(0);
         }

src/common/buffer/AttributeData.ts

@@ -139,6 +139,7 @@ export class AttributeData implements IAttributeData {
  */
 export class ExtendedAttrs implements IExtendedAttrs {
   private _ext: number = 0;
+  public payload: Object | undefined;
   public get ext(): number {
     if (this._urlId) {
       return (
@@ -207,6 +208,6 @@ export class ExtendedAttrs implements IExtendedAttrs {
    * that needs to be persistant in the buffer.
    */
   public isEmpty(): boolean {
-    return this.underlineStyle === UnderlineStyle.NONE && this._urlId === 0;
+    return this.underlineStyle === UnderlineStyle.NONE && this._urlId === 0 && this.payload === undefined;
   }
 }

src/common/buffer/Buffer.test.ts

@@ -8,24 +8,14 @@ import { Buffer } from './Buffer';
 import { CircularList } from '../CircularList';
 import { MockOptionsService, MockBufferService, MockLogService, createCellData } from '../TestUtils.test';
 import { BufferLine, DEFAULT_ATTR_DATA } from './BufferLine';
-import { BufferLineStringCache } from './BufferLineStringCache';
 import { CellData } from './CellData';
-import { ExtendedAttrs } from './AttributeData';
+
 
 const INIT_COLS = 80;
 const INIT_ROWS = 24;
 const INIT_SCROLLBACK = 1000;
-const TEST_STRING_CACHE = new BufferLineStringCache();
 
-class TestBuffer extends Buffer {
-  public getStringCache(): BufferLineStringCache {
-    return (this as unknown as { _stringCache: BufferLineStringCache })._stringCache;
-  }
-
-  public getStringCacheClearTimeout(): unknown {
-    return (this.getStringCache() as unknown as { _clearTimeout: { value: unknown } })._clearTimeout.value;
-  }
-}
+class TestBuffer extends Buffer {}
 
 describe('Buffer', () => {
   let optionsService: MockOptionsService;
@@ -1202,7 +1192,7 @@ describe('Buffer', () => {
 
   describe ('translateBufferLineToString', () => {
     it('should handle selecting a section of ascii text', () => {
-      const line = new BufferLine(TEST_STRING_CACHE, 4);
+      const line = new BufferLine(4);
       line.setCell(0, createCellData(0, 'a', 1));
       line.setCell(1, createCellData(0, 'b', 1));
       line.setCell(2, createCellData(0, 'c', 1));
@@ -1214,7 +1204,7 @@ describe('Buffer', () => {
     });
 
     it('should handle a cut-off double width character by including it', () => {
-      const line = new BufferLine(TEST_STRING_CACHE, 3);
+      const line = new BufferLine(3);
       line.setCell(0, createCellData(0, '語', 2));
       line.setCell(1, createCellData(0, '', 0));
       line.setCell(2, createCellData(0, 'a', 1));
@@ -1225,7 +1215,7 @@ describe('Buffer', () => {
     });
 
     it('should handle a zero width character in the middle of the string by not including it', () => {
-      const line = new BufferLine(TEST_STRING_CACHE, 3);
+      const line = new BufferLine(3);
       line.setCell(0, createCellData(0, '語', 2));
       line.setCell(1, createCellData(0, '', 0));
       line.setCell(2, createCellData(0, 'a', 1));
@@ -1242,7 +1232,7 @@ describe('Buffer', () => {
     });
 
     it('should handle single width emojis', () => {
-      const line = new BufferLine(TEST_STRING_CACHE, 2);
+      const line = new BufferLine(2);
       line.setCell(0, createCellData(0, '😁', 1));
       line.setCell(1, createCellData(0, 'a', 1));
       buffer.lines.set(0, line);
@@ -1255,7 +1245,7 @@ describe('Buffer', () => {
     });
 
     it('should handle double width emojis', () => {
-      const line = new BufferLine(TEST_STRING_CACHE, 2);
+      const line = new BufferLine(2);
       line.setCell(0, createCellData(0, '😁', 2));
       line.setCell(1, createCellData(0, '', 0));
       buffer.lines.set(0, line);
@@ -1266,7 +1256,7 @@ describe('Buffer', () => {
       const str2 = buffer.translateBufferLineToString(0, true, 0, 2);
       assert.equal(str2, '😁');
 
-      const line2 = new BufferLine(TEST_STRING_CACHE, 3);
+      const line2 = new BufferLine(3);
       line2.setCell(0, createCellData(0, '😁', 2));
       line2.setCell(1, createCellData(0, '', 0));
       line2.setCell(2, createCellData(0, 'a', 1));
@@ -1277,99 +1267,6 @@ describe('Buffer', () => {
     });
   });
 
-  describe('line string cache cleanup', () => {
-    it('should clear shared cache entries with a single timer', () => {
-      const originalSetTimeout = globalThis.setTimeout;
-      const originalClearTimeout = globalThis.clearTimeout;
-      const originalDateNow = Date.now;
-      let timeoutId = 0;
-      let now = 0;
-      const clearedTimeouts: number[] = [];
-      const scheduledTimeouts = new Map<number, { delay: number, fire: () => void }>();
-      (globalThis as any).setTimeout = ((handler: (...args: any[]) => void, timeout?: number) => {
-        const id = ++timeoutId;
-        scheduledTimeouts.set(id, {
-          delay: timeout ?? 0,
-          fire: () => {
-            scheduledTimeouts.delete(id);
-            handler();
-          }
-        });
-        return id as ReturnType<typeof setTimeout>;
-      }) as typeof setTimeout;
-      (globalThis as any).clearTimeout = ((id: ReturnType<typeof setTimeout>) => {
-        const numericId = id as unknown as number;
-        clearedTimeouts.push(numericId);
-        scheduledTimeouts.delete(numericId);
-      }) as typeof clearTimeout;
-      Date.now = () => now;
-      try {
-        buffer.fillViewportRows();
-        buffer.lines.get(0)!.setCell(0, createCellData(0, 'a', 1));
-        buffer.lines.get(1)!.setCell(0, createCellData(0, 'b', 1));
-
-        assert.equal(buffer.translateBufferLineToString(0, false), `a${' '.repeat(INIT_COLS - 1)}`);
-        assert.equal(buffer.translateBufferLineToString(1, false), `b${' '.repeat(INIT_COLS - 1)}`);
-
-        const cache = buffer.getStringCache();
-        assert.equal(cache.entries.size, 2);
-        assert.ok(buffer.getStringCacheClearTimeout() !== undefined);
-        assert.equal(scheduledTimeouts.size, 1);
-        assert.equal([...scheduledTimeouts.values()][0].delay, 15000);
-        const initialTimerCreationCount = timeoutId;
-
-        now = 5000;
-        assert.equal(buffer.translateBufferLineToString(0, false), `a${' '.repeat(INIT_COLS - 1)}`);
-        assert.equal(timeoutId, initialTimerCreationCount);
-        assert.equal(scheduledTimeouts.size, 1);
-        assert.deepEqual(clearedTimeouts, []);
-
-        now = 15000;
-        [...scheduledTimeouts.values()][0].fire();
-        assert.equal(timeoutId, initialTimerCreationCount + 1);
-        assert.ok(buffer.getStringCacheClearTimeout() !== undefined);
-        assert.equal(scheduledTimeouts.size, 1);
-        assert.equal([...scheduledTimeouts.values()][0].delay, 5000);
-
-        now = 20000;
-        [...scheduledTimeouts.values()][0].fire();
-
-        assert.equal(cache.entries.size, 0);
-        assert.equal(buffer.getStringCacheClearTimeout(), undefined);
-
-        assert.equal(buffer.translateBufferLineToString(0, false), `a${' '.repeat(INIT_COLS - 1)}`);
-        assert.equal(cache.entries.size, 1);
-      } finally {
-        Date.now = originalDateNow;
-        globalThis.setTimeout = originalSetTimeout;
-        globalThis.clearTimeout = originalClearTimeout;
-      }
-    });
-
-    it('should reset line string cache state on clear and resize', () => {
-      buffer.fillViewportRows();
-      buffer.lines.get(0)!.setCell(0, createCellData(0, 'a', 1));
-      buffer.translateBufferLineToString(0, false);
-
-      const cache = buffer.getStringCache();
-      assert.equal(cache.entries.size, 1);
-      assert.ok(buffer.getStringCacheClearTimeout() !== undefined);
-
-      buffer.clear();
-      assert.equal(cache.entries.size, 0);
-      assert.equal(buffer.getStringCacheClearTimeout(), undefined);
-
-      buffer.fillViewportRows();
-      buffer.lines.get(0)!.setCell(0, createCellData(0, 'b', 1));
-      buffer.translateBufferLineToString(0, false);
-      assert.equal(cache.entries.size, 1);
-
-      buffer.resize(INIT_COLS - 1, INIT_ROWS);
-      assert.equal(cache.entries.size, 0);
-      assert.equal(buffer.getStringCacheClearTimeout(), undefined);
-    });
-  });
-
   describe('memory cleanup after shrinking', () => {
     it('should realign memory from idle task execution', async () => {
       buffer.fillViewportRows();

src/common/buffer/Buffer.ts

@@ -10,7 +10,6 @@ import { ICharset } from '../Types';
 import { IAttributeData, IBuffer, IBufferLine, ICellData } from './Types';
 import { ExtendedAttrs } from './AttributeData';
 import { BufferLine, DEFAULT_ATTR_DATA } from './BufferLine';
-import { BufferLineStringCache } from './BufferLineStringCache';
 import { getWrappedLineTrimmedLength, reflowLargerApplyNewLayout, reflowLargerCreateNewLayout, reflowLargerGetLinesToRemove, reflowSmallerGetNewLineLengths } from './BufferReflow';
 import { CellData } from './CellData';
 import { NULL_CELL_CHAR, NULL_CELL_CODE, NULL_CELL_WIDTH, WHITESPACE_CELL_CHAR, WHITESPACE_CELL_CODE, WHITESPACE_CELL_WIDTH } from './Constants';
@@ -52,7 +51,6 @@ export class Buffer extends Disposable implements IBuffer {
   private _isClearing: boolean = false;
   private _memoryCleanupQueue: InstanceType<typeof IdleTaskQueue>;
   private _memoryCleanupPosition = 0;
-  private readonly _stringCache: BufferLineStringCache;
 
   constructor(
     private _hasScrollback: boolean,
@@ -70,7 +68,6 @@ export class Buffer extends Disposable implements IBuffer {
     this._memoryCleanupQueue = new IdleTaskQueue(this._logService);
     this._register(toDisposable(() => this._memoryCleanupQueue.clear()));
     this._register(toDisposable(() => this.clearAllMarkers()));
-    this._stringCache = this._register(new BufferLineStringCache());
   }
 
   public getNullCell(attr?: IAttributeData): ICellData {
@@ -100,7 +97,7 @@ export class Buffer extends Disposable implements IBuffer {
   }
 
   public getBlankLine(attr: IAttributeData, isWrapped?: boolean): IBufferLine {
-    return new BufferLine(this._stringCache, this._bufferService.cols, this.getNullCell(attr), isWrapped);
+    return new BufferLine(this._bufferService.cols, this.getNullCell(attr), isWrapped);
   }
 
   public get hasScrollback(): boolean {
@@ -145,7 +142,6 @@ export class Buffer extends Disposable implements IBuffer {
    * Clears the buffer to its initial state, discarding all previous data.
    */
   public clear(): void {
-    this._stringCache.clear();
     this.ydisp = 0;
     this.ybase = 0;
     this.y = 0;
@@ -164,7 +160,6 @@ export class Buffer extends Disposable implements IBuffer {
   public resize(newCols: number, newRows: number): void {
     // store reference to null cell with default attrs
     const nullCell = this.getNullCell(DEFAULT_ATTR_DATA);
-    this._stringCache.clear();
 
     // count bufferlines with overly big memory to be cleaned afterwards
     let dirtyMemoryLines = 0;
@@ -199,7 +194,7 @@ export class Buffer extends Disposable implements IBuffer {
             if (this._optionsService.rawOptions.windowsPty.backend !== undefined || this._optionsService.rawOptions.windowsPty.buildNumber !== undefined) {
               // Just add the new missing rows on Windows as conpty reprints the screen with its
               // view of the world. Once a line enters scrollback for conpty it remains there
-              this.lines.push(new BufferLine(this._stringCache, newCols, nullCell, false));
+              this.lines.push(new BufferLine(newCols, nullCell, false));
             } else {
               if (this.ybase > 0 && this.lines.length <= this.ybase + this.y + addToY + 1) {
                 // There is room above the buffer and there are no empty elements below the line,
@@ -213,7 +208,7 @@ export class Buffer extends Disposable implements IBuffer {
               } else {
                 // Add a blank line if there is no buffer left at the top to scroll to, or if there
                 // are blank lines after the cursor
-                this.lines.push(new BufferLine(this._stringCache, newCols, nullCell, false));
+                this.lines.push(new BufferLine(newCols, nullCell, false));
               }
             }
           }
@@ -354,7 +349,7 @@ export class Buffer extends Disposable implements IBuffer {
         }
         if (this.lines.length < newRows) {
           // Add an extra row at the bottom of the viewport
-          this.lines.push(new BufferLine(this._stringCache, newCols, nullCell, false));
+          this.lines.push(new BufferLine(newCols, nullCell, false));
         }
       } else {
         if (this.ydisp === this.ybase) {

src/common/buffer/BufferLine.test.ts

@@ -4,19 +4,16 @@
  */
 import { NULL_CELL_CHAR, NULL_CELL_WIDTH, NULL_CELL_CODE, DEFAULT_ATTR, Content, UnderlineStyle, BgFlags, Attributes, FgFlags } from './Constants';
 import { BufferLine } from './BufferLine';
-import { BufferLineStringCache } from './BufferLineStringCache';
 import { CellData } from './CellData';
 import { CharData, IBufferLine, ICellData } from './Types';
 import { assert } from 'chai';
 import { AttributeData } from './AttributeData';
 import { createCellData, NULL_CELL_DATA, extendedAttributes } from '../TestUtils.test';
 
-const TEST_STRING_CACHE = new BufferLineStringCache();
-
 
 class TestBufferLine extends BufferLine {
   constructor(cols: number, fillCellData?: ICellData, isWrapped: boolean = false) {
-    super(TEST_STRING_CACHE, cols, fillCellData, isWrapped);
+    super(cols, fillCellData, isWrapped);
   }
 
   public get combined(): {[index: number]: string} {
@@ -24,19 +21,19 @@ class TestBufferLine extends BufferLine {
   }
 
   public get cachedString(): string | undefined {
-    return this._getStringCacheEntry(false)?.value;
+    return this._cacheValid ? this._cache : undefined;
   }
 
   public set cachedString(value: string | undefined) {
-    this._getStringCacheEntry(true)!.value = value;
+    this._cache = value ?? '';
   }
 
   public get isCachedStringTrimmed(): boolean {
-    return this._getStringCacheEntry(false)?.isTrimmed ?? false;
+    return this._cacheTrimmed;
   }
 
   public set isCachedStringTrimmed(value: boolean) {
-    this._getStringCacheEntry(true)!.isTrimmed = value;
+    this._cacheTrimmed = value;
   }
 
   public toArray(): CharData[] {

src/common/buffer/BufferLine.ts

@@ -8,7 +8,6 @@ import { AttributeData } from './AttributeData';
 import { CellData } from './CellData';
 import { Attributes, BgFlags, CHAR_DATA_ATTR_INDEX, CHAR_DATA_CHAR_INDEX, CHAR_DATA_WIDTH_INDEX, Content, NULL_CELL_CHAR, NULL_CELL_CODE, NULL_CELL_WIDTH, WHITESPACE_CELL_CHAR } from './Constants';
 import { stringFromCodePoint } from '../input/TextDecoder';
-import { StringBuilder } from '../StringBuilder';
 
 // Buffer memory layout:
 //
@@ -37,24 +36,20 @@ const enum Cell {
   BG = 2  // currently unused
 }
 
+
+interface IExtendedAttrsExt extends IExtendedAttrs {
+  _ext: number;
+  _urlId: number;
+}
+
+
 export const DEFAULT_ATTR_DATA = Object.freeze(new AttributeData());
 
 // Work variables to avoid garbage collection
 let $startIndex = 0;
 const $workCell = new CellData();
-const $translateToStringBuilder = new StringBuilder();
+const $extended = DEFAULT_ATTR_DATA.extended.clone() as IExtendedAttrsExt;
 
-export interface IBufferLineStringCacheEntry {
-  value: string | undefined;
-  isTrimmed: boolean;
-  generation: number;
-}
-
-export interface IBufferLineStringCache {
-  generation: number;
-  allocateEntry(): IBufferLineStringCacheEntry;
-  touch?(): void;
-}
 
 /**
  * Typed array based bufferline implementation.
@@ -77,11 +72,14 @@ export class BufferLine implements IBufferLine {
   protected _combined: {[index: number]: string} = {};
   /** Sparse cache; only read when `HAS_EXTENDED` is set in `_data`. */
   protected _extendedAttrs: {[index: number]: IExtendedAttrs | undefined} = {};
-  protected _stringCacheEntryRef: WeakRef<IBufferLineStringCacheEntry> | undefined;
   public length: number;
 
+  /** line text cache */
+  protected _cacheValid = false;
+  protected _cache: string = '';
+  protected _cacheTrimmed = false;
+
   constructor(
-    protected readonly _stringCache: IBufferLineStringCache,
     cols: number,
     fillCellData?: ICellData,
     public isWrapped: boolean = false
@@ -118,7 +116,7 @@ export class BufferLine implements IBufferLine {
    * @deprecated
    */
   public set(index: number, value: CharData): void {
-    this._invalidateStringCache();
+    this._cacheValid = false;
     this._data[index * Constants.CELL_INDICIES + Cell.FG] = value[CHAR_DATA_ATTR_INDEX];
     if (value[CHAR_DATA_CHAR_INDEX].length > 1) {
       this._combined[index] = value[1];
@@ -210,21 +208,30 @@ export class BufferLine implements IBufferLine {
     } else {
       cell.combinedData = '';
     }
-    if (cell.bg & BgFlags.HAS_EXTENDED) {
-      cell.extended = this._extendedAttrs[index]!;
-    } else {
-      // Do not mutate cell.extended in place: it may still reference this line's map entry from a
-      // prior loadCell into a reused CellData (e.g. $workCell during insert/delete).
-      cell.extended = DEFAULT_ATTR_DATA.extended.clone();
-    }
+    cell.extended = this.getExtended(index);
     return cell;
   }
 
+  public getExtended(index: number): IExtendedAttrs {
+    $startIndex = index * Constants.CELL_INDICIES;
+    if (this._data[$startIndex + Cell.BG] & BgFlags.HAS_EXTENDED) {
+      return this._extendedAttrs[index]!;
+    }
+    // Do not mutate cell.extended in place: it may still reference this line's map entry from a
+    // prior loadCell into a reused CellData (e.g. $workCell during insert/delete).
+    // We use $extended as blueprint and reset the internals
+    // mimicking the ctor to avoid a new allocation.
+    $extended._ext = 0;
+    $extended._urlId = 0;
+    $extended.payload = undefined;
+    return $extended;
+  }
+
   /**
    * Set data at `index` to `cell`.
    */
   public setCell(index: number, cell: ICellData): void {
-    this._invalidateStringCache();
+    this._cacheValid = false;
     if (cell.content & Content.IS_COMBINED_MASK) {
       this._combined[index] = cell.combinedData;
     }
@@ -242,13 +249,14 @@ export class BufferLine implements IBufferLine {
    * it gets an optimized access method.
    */
   public setCellFromCodepoint(index: number, codePoint: number, width: number, attrs: IAttributeData): void {
-    this._invalidateStringCache();
+    this._cacheValid = false;
     if (attrs.bg & BgFlags.HAS_EXTENDED) {
       this._extendedAttrs[index] = attrs.extended;
     }
-    this._data[index * Constants.CELL_INDICIES + Cell.CONTENT] = codePoint | (width << Content.WIDTH_SHIFT);
-    this._data[index * Constants.CELL_INDICIES + Cell.FG] = attrs.fg;
-    this._data[index * Constants.CELL_INDICIES + Cell.BG] = attrs.bg;
+    const $idx = index * Constants.CELL_INDICIES;
+    this._data[$idx + Cell.CONTENT] = codePoint | (width << Content.WIDTH_SHIFT);
+    this._data[$idx + Cell.FG] = attrs.fg;
+    this._data[$idx + Cell.BG] = attrs.bg;
   }
 
   /**
@@ -258,7 +266,7 @@ export class BufferLine implements IBufferLine {
    * by the previous `setDataFromCodePoint` call, we can omit it here.
    */
   public addCodepointToCell(index: number, codePoint: number, width: number): void {
-    this._invalidateStringCache();
+    this._cacheValid = false;
     let content = this._data[index * Constants.CELL_INDICIES + Cell.CONTENT];
     if (content & Content.IS_COMBINED_MASK) {
       // we already have a combined string, simply add
@@ -285,7 +293,7 @@ export class BufferLine implements IBufferLine {
   }
 
   public insertCells(pos: number, n: number, fillCellData: ICellData): void {
-    this._invalidateStringCache();
+    this._cacheValid = false;
     pos %= this.length;
 
     // handle fullwidth at pos: reset cell one to the left if pos is second cell of a wide char
@@ -313,7 +321,7 @@ export class BufferLine implements IBufferLine {
   }
 
   public deleteCells(pos: number, n: number, fillCellData: ICellData): void {
-    this._invalidateStringCache();
+    this._cacheValid = false;
     pos %= this.length;
     if (n < this.length - pos) {
       for (let i = 0; i < this.length - pos - n; ++i) {
@@ -340,7 +348,7 @@ export class BufferLine implements IBufferLine {
   }
 
   public replaceCells(start: number, end: number, fillCellData: ICellData, respectProtect: boolean = false): void {
-    this._invalidateStringCache();
+    this._cacheValid = false;
     // full branching on respectProtect==true, hopefully getting fast JIT for standard case
     if (respectProtect) {
       if (start && this.getWidth(start - 1) === 2 && !this.isProtected(start - 1)) {
@@ -380,7 +388,7 @@ export class BufferLine implements IBufferLine {
    * excess memory (true after shrinking > Constants.CLEANUP_THRESHOLD).
    */
   public resize(cols: number, fillCellData: ICellData): boolean {
-    this._invalidateStringCache();
+    this._cacheValid = false;
     if (cols === this.length) {
       return this._data.length * 4 * Constants.CLEANUP_THRESHOLD < this._data.buffer.byteLength;
     }
@@ -440,7 +448,7 @@ export class BufferLine implements IBufferLine {
 
   /** fill a line with fillCharData */
   public fill(fillCellData: ICellData, respectProtect: boolean = false): void {
-    this._invalidateStringCache();
+    this._cacheValid = false;
     // full branching on respectProtect==true, hopefully getting fast JIT for standard case
     if (respectProtect) {
       for (let i = 0; i < this.length; ++i) {
@@ -458,8 +466,7 @@ export class BufferLine implements IBufferLine {
   }
 
   /** alter to a full copy of line  */
-  public copyFrom(line: BufferLine): void {
-    this._invalidateStringCache();
+  public copyFrom(line: BufferLine, blank?: boolean): void {
     if (this.length !== line.length) {
       this._data = new Uint32Array(line._data);
     } else {
@@ -467,16 +474,29 @@ export class BufferLine implements IBufferLine {
       this._data.set(line._data);
     }
     this.length = line.length;
-    this._copySparseMapsFrom(line);
+    if (blank) {
+      // a blank line may never hold combined or extended attrs,
+      // thus we can skip handling them
+      this._combined = {};
+      this._extendedAttrs = {};
+    } else {
+      this._copySparseMapsFrom(line);
+    }
+    this._cache = '';
+    this._cacheValid = false;
     this.isWrapped = line.isWrapped;
   }
 
   /** create a new clone */
-  public clone(): IBufferLine {
-    const newLine = new BufferLine(this._stringCache, 0, undefined, false);
+  public clone(blank?: boolean): IBufferLine {
+    const newLine = new BufferLine(0, undefined, false);
     newLine._data = new Uint32Array(this._data);
     newLine.length = this.length;
-    newLine._copySparseMapsFrom(this);
+    if (!blank) {
+      // a blank line may never hold combined or extended attrs,
+      // thus we can skip handling them
+      newLine._copySparseMapsFrom(this);
+    }
     newLine.isWrapped = this.isWrapped;
     return newLine;
   }
@@ -500,7 +520,7 @@ export class BufferLine implements IBufferLine {
   }
 
   public copyCellsFrom(src: BufferLine, srcCol: number, destCol: number, length: number, applyInReverse: boolean): void {
-    this._invalidateStringCache();
+    this._cacheValid = false;
     const srcData = src._data;
     if (applyInReverse) {
       for (let cell = length - 1; cell >= 0; cell--) {
@@ -534,17 +554,13 @@ export class BufferLine implements IBufferLine {
    * returned string, the corresponding entries in `outColumns` will have the same column number.
    */
   public translateToString(trimRight?: boolean, startCol?: number, endCol?: number, outColumns?: number[]): string {
-    const isCanonicalRequest = (startCol === undefined || startCol === 0) && endCol === undefined && outColumns === undefined;
-    if (isCanonicalRequest) {
-      this._stringCache.touch?.();
-    }
-    const stringCacheEntry = isCanonicalRequest ? this._getStringCacheEntry(false) : undefined;
-    if (isCanonicalRequest && stringCacheEntry?.value !== undefined) {
+    const isCanonical = (startCol === undefined || startCol === 0) && endCol === undefined && outColumns === undefined;
+    if (isCanonical && this._cacheValid) {
       if (trimRight) {
-        return stringCacheEntry.isTrimmed ? stringCacheEntry.value : stringCacheEntry.value.trimEnd();
+        return this._cacheTrimmed ? this._cache : this._cache.trimEnd();
       }
-      if (!stringCacheEntry.isTrimmed) {
-        return stringCacheEntry.value;
+      if (!this._cacheTrimmed) {
+        return this._cache;
       }
     }
     startCol = startCol ?? 0;
@@ -555,12 +571,12 @@ export class BufferLine implements IBufferLine {
     if (outColumns) {
       outColumns.length = 0;
     }
-    $translateToStringBuilder.reset();
+    const cellContents: string[] = [];
     while (startCol < endCol) {
       const content = this._data[startCol * Constants.CELL_INDICIES + Cell.CONTENT];
       const cp = content & Content.CODEPOINT_MASK;
       const chars = (content & Content.IS_COMBINED_MASK) ? this._combined[startCol] : (cp) ? stringFromCodePoint(cp) : WHITESPACE_CELL_CHAR;
-      $translateToStringBuilder.append(chars);
+      cellContents.push(chars);
       if (outColumns) {
         for (let i = 0; i < chars.length; ++i) {
           outColumns.push(startCol);
@@ -571,39 +587,15 @@ export class BufferLine implements IBufferLine {
     if (outColumns) {
       outColumns.push(startCol);
     }
-    const result = $translateToStringBuilder.toString();
-    $translateToStringBuilder.reset();
-    if (isCanonicalRequest) {
-      const cacheEntry = this._getStringCacheEntry(true)!;
-      cacheEntry.value = result;
-      cacheEntry.isTrimmed = !!trimRight;
+    const result = cellContents.join('');
+    if (isCanonical) {
+      this._cache = result;
+      this._cacheValid = true;
+      this._cacheTrimmed = !!trimRight;
     }
     return result;
   }
 
-  protected _getStringCacheEntry(createIfNeeded: boolean): IBufferLineStringCacheEntry | undefined {
-    const cachedEntry = this._stringCacheEntryRef?.deref();
-    if (cachedEntry) {
-      if (cachedEntry.generation === this._stringCache.generation) {
-        return cachedEntry;
-      }
-    }
-    if (!createIfNeeded) {
-      return undefined;
-    }
-    const cacheEntry = this._stringCache.allocateEntry();
-    this._stringCacheEntryRef = new WeakRef(cacheEntry);
-    return cacheEntry;
-  }
-
-  private _invalidateStringCache(): void {
-    const cacheEntry = this._getStringCacheEntry(false);
-    if (cacheEntry) {
-      cacheEntry.value = undefined;
-      cacheEntry.isTrimmed = false;
-    }
-  }
-
   /** Copy sparse map entries for a single cell when `_data` flags require them. */
   private _copyCellMapsFrom(src: BufferLine, srcCol: number, destCol: number): void {
     const srcStart = srcCol * Constants.CELL_INDICIES;

src/common/buffer/BufferLineStringCache.ts

@@ -1,69 +0,0 @@
-/**
- * Copyright (c) 2026 The xterm.js authors. All rights reserved.
- * @license MIT
- */
-
-import type { IBufferLineStringCache, IBufferLineStringCacheEntry } from './BufferLine';
-import { disposableTimeout } from '../Async';
-import { Disposable, MutableDisposable, toDisposable, type IDisposable } from '../Lifecycle';
-
-const enum Constants {
-  CACHE_TTL_MS = 15000
-}
-
-export class BufferLineStringCache extends Disposable implements IBufferLineStringCache {
-  public generation: number = 0;
-  public readonly entries: Set<IBufferLineStringCacheEntry> = new Set();
-  private readonly _clearTimeout = this._register(new MutableDisposable<IDisposable>());
-  private _lastAccessTimestamp: number = 0;
-
-  constructor() {
-    super();
-    this._register(toDisposable(() => this.entries.clear()));
-  }
-
-  public touch(): void {
-    this._scheduleClear();
-  }
-
-  public allocateEntry(): IBufferLineStringCacheEntry {
-    const entry: IBufferLineStringCacheEntry = {
-      value: undefined,
-      isTrimmed: false,
-      generation: this.generation
-    };
-    this.entries.add(entry);
-    this._scheduleClear();
-    return entry;
-  }
-
-  public clear(): void {
-    this._clearTimeout.clear();
-    this._lastAccessTimestamp = 0;
-    this.generation++;
-    for (const entry of this.entries) {
-      entry.value = undefined;
-      entry.isTrimmed = false;
-    }
-    this.entries.clear();
-  }
-
-  private _scheduleClear(): void {
-    this._lastAccessTimestamp = Date.now();
-    if (this._clearTimeout.value) {
-      return;
-    }
-    this._scheduleClearTimeout(Constants.CACHE_TTL_MS);
-  }
-
-  private _scheduleClearTimeout(timeoutMs: number): void {
-    this._clearTimeout.value = disposableTimeout(() => {
-      const elapsed = Date.now() - this._lastAccessTimestamp;
-      if (elapsed >= Constants.CACHE_TTL_MS) {
-        this.clear();
-        return;
-      }
-      this._scheduleClearTimeout(Constants.CACHE_TTL_MS - elapsed);
-    }, timeoutMs);
-  }
-}

src/common/buffer/BufferReflow.test.ts

@@ -5,18 +5,16 @@
 import { assert } from 'chai';
 import { CircularList } from '../CircularList';
 import { BufferLine } from './BufferLine';
-import { BufferLineStringCache } from './BufferLineStringCache';
 import { CellData } from './CellData';
 import { NULL_CELL_CHAR, NULL_CELL_WIDTH, NULL_CELL_CODE } from './Constants';
 import { reflowLargerGetLinesToRemove, reflowSmallerGetNewLineLengths } from './BufferReflow';
 import { IBufferLine } from './Types';
 
-const TEST_STRING_CACHE = new BufferLineStringCache();
 
 describe('BufferReflow', () => {
   describe('reflowSmallerGetNewLineLengths', () => {
     it('should return correct line lengths for a small line with wide characters', () => {
-      const line = new BufferLine(TEST_STRING_CACHE, 4);
+      const line = new BufferLine(4);
       line.set(0, [0, '汉', 2, '汉'.charCodeAt(0)]);
       line.set(1, [0, '', 0, 0]);
       line.set(2, [0, '语', 2, '语'.charCodeAt(0)]);
@@ -26,7 +24,7 @@ describe('BufferReflow', () => {
       assert.deepEqual(reflowSmallerGetNewLineLengths([line], 4, 2), [2, 2], 'line: 汉, 语');
     });
     it('should return correct line lengths for a large line with wide characters', () => {
-      const line = new BufferLine(TEST_STRING_CACHE, 12);
+      const line = new BufferLine(12);
       for (let i = 0; i < 12; i += 4) {
         line.set(i, [0, '汉', 2, '汉'.charCodeAt(0)]);
         line.set(i + 2, [0, '语', 2, '语'.charCodeAt(0)]);
@@ -48,7 +46,7 @@ describe('BufferReflow', () => {
       assert.deepEqual(reflowSmallerGetNewLineLengths([line], 12, 2), [2, 2, 2, 2, 2, 2], 'line: 汉, 语, 汉, 语, 汉, 语');
     });
     it('should return correct line lengths for a string with wide and single characters', () => {
-      const line = new BufferLine(TEST_STRING_CACHE, 6);
+      const line = new BufferLine(6);
       line.set(0, [0, 'a', 1, 'a'.charCodeAt(0)]);
       line.set(1, [0, '汉', 2, '汉'.charCodeAt(0)]);
       line.set(2, [0, '', 0, 0]);
@@ -62,14 +60,14 @@ describe('BufferReflow', () => {
       assert.deepEqual(reflowSmallerGetNewLineLengths([line], 6, 2), [1, 2, 2, 1], 'line: a, 汉, 语, b');
     });
     it('should return correct line lengths for a wrapped line with wide and single characters', () => {
-      const line1 = new BufferLine(TEST_STRING_CACHE, 6);
+      const line1 = new BufferLine(6);
       line1.set(0, [0, 'a', 1, 'a'.charCodeAt(0)]);
       line1.set(1, [0, '汉', 2, '汉'.charCodeAt(0)]);
       line1.set(2, [0, '', 0, 0]);
       line1.set(3, [0, '语', 2, '语'.charCodeAt(0)]);
       line1.set(4, [0, '', 0, 0]);
       line1.set(5, [0, 'b', 1, 'b'.charCodeAt(0)]);
-      const line2 = new BufferLine(TEST_STRING_CACHE, 6, undefined, true);
+      const line2 = new BufferLine(6, undefined, true);
       line2.set(0, [0, 'a', 1, 'a'.charCodeAt(0)]);
       line2.set(1, [0, '汉', 2, '汉'.charCodeAt(0)]);
       line2.set(2, [0, '', 0, 0]);
@@ -84,7 +82,7 @@ describe('BufferReflow', () => {
       assert.deepEqual(reflowSmallerGetNewLineLengths([line1, line2], 6, 2), [1, 2, 2, 2, 2, 2, 1], 'lines: a, 汉, 语, ba, 汉, 语, b');
     });
     it('should work on lines ending in null space', () => {
-      const line = new BufferLine(TEST_STRING_CACHE, 5);
+      const line = new BufferLine(5);
       line.set(0, [0, '汉', 2, '汉'.charCodeAt(0)]);
       line.set(1, [0, '', 0, 0]);
       line.set(2, [0, '语', 2, '语'.charCodeAt(0)]);
@@ -102,7 +100,7 @@ describe('BufferReflow', () => {
     function createWrappedLines(chars: string): CircularList<IBufferLine> {
       const lines = new CircularList<IBufferLine>(chars.length);
       for (let i = 0; i < chars.length; i++) {
-        const line = new BufferLine(TEST_STRING_CACHE, 1);
+        const line = new BufferLine(1);
         line.set(0, [0, chars[i], 1, chars.charCodeAt(i)]);
         line.isWrapped = i > 0;
         lines.push(line);

src/common/buffer/BufferSet.test.ts

@@ -82,45 +82,4 @@ describe('BufferSet', () => {
       assert.equal(bufferSet.alt.markers.length, 0);
     });
   });
-
-  describe('lifecycle', () => {
-    it('should dispose previous buffers on reset', () => {
-      const oldNormal = bufferSet.normal as any;
-      oldNormal.lines.get(0)!.setCell(0, createCellData(0, 'a', 1));
-      oldNormal.translateBufferLineToString(0, false);
-
-      const oldCache = oldNormal._stringCache;
-      assert.equal(oldCache.entries.size, 1);
-      assert.notEqual(oldCache._clearTimeout.value, undefined);
-
-      bufferSet.reset();
-
-      assert.notEqual(bufferSet.normal, oldNormal);
-      assert.equal(oldCache.entries.size, 0);
-      assert.equal(oldCache._clearTimeout.value, undefined);
-    });
-
-    it('should dispose both buffers when disposed', () => {
-      const normal = bufferSet.normal as any;
-      normal.lines.get(0)!.setCell(0, createCellData(0, 'a', 1));
-      normal.translateBufferLineToString(0, false);
-
-      bufferSet.activateAltBuffer();
-      const alt = bufferSet.alt as any;
-      alt.lines.get(0)!.setCell(0, createCellData(0, 'b', 1));
-      alt.translateBufferLineToString(0, false);
-
-      const normalCache = normal._stringCache;
-      const altCache = alt._stringCache;
-      assert.notEqual(normalCache._clearTimeout.value, undefined);
-      assert.notEqual(altCache._clearTimeout.value, undefined);
-
-      bufferSet.dispose();
-
-      assert.equal(normalCache.entries.size, 0);
-      assert.equal(altCache.entries.size, 0);
-      assert.equal(normalCache._clearTimeout.value, undefined);
-      assert.equal(altCache._clearTimeout.value, undefined);
-    });
-  });
 });

src/common/buffer/Types.ts

@@ -20,6 +20,7 @@ export interface IExtendedAttrs {
   underlineColor: number;
   underlineVariantOffset: number;
   urlId: number;
+  payload: Object | undefined;
   clone(): IExtendedAttrs;
   isEmpty(): boolean;
 }
@@ -131,8 +132,8 @@ export interface IBufferLine {
   resize(cols: number, fill: ICellData): boolean;
   cleanupMemory(): number;
   fill(fillCellData: ICellData, respectProtect?: boolean): void;
-  copyFrom(line: IBufferLine): void;
-  clone(): IBufferLine;
+  copyFrom(line: IBufferLine, blank?: boolean): void;
+  clone(blank?: boolean): IBufferLine;
   getTrimmedLength(): number;
   getNoBgTrimmedLength(): number;
   translateToString(trimRight?: boolean, startCol?: number, endCol?: number, outColumns?: number[]): string;
@@ -146,6 +147,7 @@ export interface IBufferLine {
   getCodePoint(index: number): number;
   isCombined(index: number): number;
   getString(index: number): string;
+  getExtended(index: number): IExtendedAttrs;
 }
 
 export interface IMarker extends IDisposable {

src/common/input/TextDecoder.test.ts

@@ -79,7 +79,7 @@ function assertDecodedRange(
   }
   const target = new Uint32Array(count);
   const length = decode(input, target);
-  assert.equal(length, count);
+  assert.strictEqual(length, count);
   let mismatchIndex = -1;
   let index = 0;
   for (let i = min; i < max; ++i) {
@@ -92,8 +92,8 @@ function assertDecodedRange(
     }
     index++;
   }
-  assert.equal(mismatchIndex, -1);
-  assert.equal(outputToString(target, length), input);
+  assert.strictEqual(mismatchIndex, -1);
+  assert.strictEqual(outputToString(target, length), input);
 }
 
 const BATCH_SIZE = 8192;
@@ -116,9 +116,9 @@ describe('text encodings', () => {
     const data = new Uint32Array(s.length);
     for (let i = 0; i < s.length; ++i) {
       data[i] = s.charCodeAt(i);
-      assert.equal(stringFromCodePoint(data[i]), s[i]);
+      assert.strictEqual(stringFromCodePoint(data[i]), s[i]);
     }
-    assert.equal(utf32ToString(data), s);
+    assert.strictEqual(utf32ToString(data), s);
   });
 
   describe('StringToUtf32 decoder', () => {
@@ -159,7 +159,7 @@ describe('text encodings', () => {
         const decoder = new StringToUtf32();
         const target = new Uint32Array(5);
         const length = decoder.decode(String.fromCharCode(0xFEFF), target);
-        assert.equal(length, 0);
+        assert.strictEqual(length, 0);
         decoder.clear();
       });
     });
@@ -169,7 +169,7 @@ describe('text encodings', () => {
       const target = new Uint32Array(500);
       for (let i = 0; i < TEST_STRINGS.length; ++i) {
         const length = decoder.decode(TEST_STRINGS[i], target);
-        assert.equal(toString(target, length), TEST_STRINGS[i]);
+        assert.strictEqual(toString(target, length), TEST_STRINGS[i]);
         decoder.clear();
       }
     });
@@ -184,7 +184,7 @@ describe('text encodings', () => {
           const written = decoder.decode(input[i], target);
           decoded += toString(target, written);
         }
-        assert(decoded, 'Ä€𝄞Ö𝄞€Ü𝄞€');
+        assert.strictEqual(decoded, 'Ä€𝄞Ö𝄞€Ü𝄞€');
       });
     });
   });
@@ -226,7 +226,7 @@ describe('text encodings', () => {
         const target = new Uint32Array(5);
         const utf8Data = stringToUtf8Bytes(String.fromCharCode(0xFEFF));
         const length = decoder.decode(utf8Data, target);
-        assert.equal(length, 0);
+        assert.strictEqual(length, 0);
         decoder.clear();
       });
     });
@@ -237,7 +237,7 @@ describe('text encodings', () => {
       for (let i = 0; i < TEST_STRINGS.length; ++i) {
         const utf8Data = stringToUtf8Bytes(TEST_STRINGS[i]);
         const length = decoder.decode(utf8Data, target);
-        assert.equal(toString(target, length), TEST_STRINGS[i]);
+        assert.strictEqual(toString(target, length), TEST_STRINGS[i]);
         decoder.clear();
       }
     });
@@ -252,7 +252,7 @@ describe('text encodings', () => {
           const written = decoder.decode(utf8Data.slice(i, i + 1), target);
           decoded += toString(target, written);
         }
-        assert(decoded, 'ÄÖÜßöäü');
+        assert.strictEqual(decoded, 'ÄÖÜßöäü');
       });
 
       it('2/3 byte sequences - advance by 1', () => {
@@ -264,7 +264,7 @@ describe('text encodings', () => {
           const written = decoder.decode(utf8Data.slice(i, i + 1), target);
           decoded += toString(target, written);
         }
-        assert(decoded, 'Āր܀߀ö€ä€ü');
+        assert.strictEqual(decoded, 'Āր܀߀ö€ä€ü');
       });
 
       it('2/3/4 byte sequences - advance by 1', () => {
@@ -276,7 +276,7 @@ describe('text encodings', () => {
           const written = decoder.decode(utf8Data.slice(i, i + 1), target);
           decoded += toString(target, written);
         }
-        assert(decoded, 'Ä€𝄞Ö𝄞€Ü𝄞€');
+        assert.strictEqual(decoded, 'Ä€𝄞Ö𝄞€Ü𝄞€');
       });
 
       it('2/3/4 byte sequences - advance by 2', () => {
@@ -288,7 +288,7 @@ describe('text encodings', () => {
           const written = decoder.decode(utf8Data.slice(i, i + 2), target);
           decoded += toString(target, written);
         }
-        assert(decoded, 'Ä€𝄞Ö𝄞€Ü𝄞€');
+        assert.strictEqual(decoded, 'Ä€𝄞Ö𝄞€Ü𝄞€');
       });
 
       it('2/3/4 byte sequences - advance by 3', () => {
@@ -300,7 +300,7 @@ describe('text encodings', () => {
           const written = decoder.decode(utf8Data.slice(i, i + 3), target);
           decoded += toString(target, written);
         }
-        assert(decoded, 'Ä€𝄞Ö𝄞€Ü𝄞€');
+        assert.strictEqual(decoded, 'Ä€𝄞Ö𝄞€Ü𝄞€');
       });
 
       it('BOMs (3 byte sequences) - advance by 2', () => {
@@ -312,7 +312,7 @@ describe('text encodings', () => {
           const written = decoder.decode(utf8Data.slice(i, i + 2), target);
           decoded += toString(target, written);
         }
-        assert.equal(decoded, '');
+        assert.strictEqual(decoded, '');
       });
 
       it('test break after 3 bytes - issue #2495', () => {
@@ -320,11 +320,37 @@ describe('text encodings', () => {
         const target = new Uint32Array(5);
         const utf8Data = fromByteString('\xf0\xa0\x9c\x8e');
         let written = decoder.decode(utf8Data.slice(0, 3), target);
-        assert.equal(written, 0);
+        assert.strictEqual(written, 0);
         written = decoder.decode(utf8Data.slice(3), target);
-        assert.equal(written, 1);
-        assert(toString(target, written), '𠜎');
+        assert.strictEqual(written, 1);
+        assert.strictEqual(toString(target, written), '𠜎');
       });
+
+      describe('0x80 not swallowed in continuation', () => {
+        it('A—B', () => {
+          const decoder = new Utf8ToUtf32();
+          const target = new Uint32Array(5);
+          const utf8Data = new TextEncoder().encode('A—BA—BA—BA—BA—B');
+          let decoded = '';
+          for (let i = 0; i < utf8Data.length; i += 2) {
+            const written = decoder.decode(utf8Data.slice(i, i + 2), target);
+            decoded += toString(target, written);
+          }
+          assert.strictEqual(decoded, 'A—BA—BA—BA—BA—B');
+        });
+        it('A𐀀B', () => {
+          const decoder = new Utf8ToUtf32();
+          const target = new Uint32Array(5);
+          const utf8Data = new TextEncoder().encode('A𐀀BA𐀀BA𐀀BA𐀀BA𐀀B');
+          let decoded = '';
+          for (let i = 0; i < utf8Data.length; i += 2) {
+            const written = decoder.decode(utf8Data.slice(i, i + 2), target);
+            decoded += toString(target, written);
+          }
+          assert.strictEqual(decoded, 'A𐀀BA𐀀BA𐀀BA𐀀BA𐀀B');
+        });
+      });
+
     });
   });
 });

src/common/input/TextDecoder.ts

@@ -158,9 +158,9 @@ export class Utf8ToUtf32 {
       cp &= ((((cp & 0xE0) === 0xC0)) ? 0x1F : (((cp & 0xF0) === 0xE0)) ? 0x0F : 0x07);
       let pos = 0;
       let tmp: number;
-      while ((tmp = this.interim[++pos] & 0x3F) && pos < 4) {
+      while ((tmp = this.interim[++pos]) && pos < 4) {
         cp <<= 6;
-        cp |= tmp;
+        cp |= tmp & 0x3F;
       }
       // missing bytes - read ahead from input
       const type = (((this.interim[0] & 0xE0) === 0xC0)) ? 2 : (((this.interim[0] & 0xF0) === 0xE0)) ? 3 : 4;

src/common/services/BufferService.ts

@@ -86,12 +86,12 @@ export class BufferService extends Disposable implements IBufferService {
       // Insert the line using the fastest method
       if (bottomRow === buffer.lines.length - 1) {
         if (willBufferBeTrimmed) {
-          buffer.lines.recycle().copyFrom(newLine);
+          buffer.lines.recycle().copyFrom(newLine, true);
         } else {
-          buffer.lines.push(newLine.clone());
+          buffer.lines.push(newLine.clone(true));
         }
       } else {
-        buffer.lines.splice(bottomRow + 1, 0, newLine.clone());
+        buffer.lines.splice(bottomRow + 1, 0, newLine.clone(true));
       }
 
       // Only adjust ybase and ydisp when the buffer is not trimmed
@@ -113,7 +113,7 @@ export class BufferService extends Disposable implements IBufferService {
       // scrollback, instead we can just shift them in-place.
       const scrollRegionHeight = bottomRow - topRow + 1 /* as it's zero-based */;
       buffer.lines.shiftElements(topRow + 1, scrollRegionHeight - 1, -1);
-      buffer.lines.set(bottomRow, newLine.clone());
+      buffer.lines.set(bottomRow, newLine.clone(true));
     }
 
     // Move the viewport to the bottom of the buffer unless the user is

src/common/services/DecorationService.ts

@@ -214,7 +214,7 @@ export class DecorationLineCache extends Disposable {
   }
 
   private _handleBufferLinesTrim(amount: number): void {
-    if (amount <= 0) {
+    if (amount <= 0 || !this._decorationsByLine.size) {
       return;
     }
     const newMap = new Map<number, IInternalDecoration[]>();

src/headless/Terminal.ts

@@ -99,10 +99,6 @@ export class Terminal extends CoreTerminal {
    * Clear the entire buffer, making the prompt line the new first line.
    */
   public clear(): void {
-    if (this.buffer.ybase === 0 && this.buffer.y === 0) {
-      // Don't clear if it's already clear
-      return;
-    }
     this.buffer.clearAllMarkers();
     this.buffer.lines.set(0, this.buffer.lines.get(this.buffer.ybase + this.buffer.y)!);
     this.buffer.lines.length = 1;