Align browser registerMarker alt-buffer guard with headless

Block registerMarker on the alternate buffer in CoreBrowserTerminal,
matching headless addMarker behavior. Update public typings to
IMarker | undefined and add regression tests.

Fixes #5937

Co-authored-by: Daniel Imms <Tyriar@users.noreply.github.com>

.gitignore

@@ -22,6 +22,9 @@ build/
 yarn.lock
 test-results/
 
+# Tracing/debug files
+.cursor/nal-trace/
+
 # Keep bundled code out of Git
 dist/
 demo/dist/

README.md

@@ -253,6 +253,7 @@ Xterm.js is used in many world-class applications to provide great terminal expe
 - [**SSH Connection Manager**](https://github.com/Amtrend/ssh-manager): Modern web-based SSH terminal and SFTP manager with AES-256 encryption, PWA support, and session management.
 - [**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.
 - [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-image/src/SixelHandler.ts

@@ -91,7 +91,7 @@ export class SixelHandler implements IDcsHandler, IResetHandler {
     const height = this._dec.height;
 
     // partial fix for https://github.com/jerch/xterm-addon-image/issues/37
-    if (!width || ! height) {
+    if (!width || !height) {
       if (height) {
         this._storage.advanceCursor(height);
       }

addons/addon-image/src/kitty/KittyGraphicsHandler.ts

@@ -533,8 +533,8 @@ export class KittyGraphicsHandler implements IApcHandler, IResetHandler, IDispos
 
   private _sendResponse(id: number, message: string, quiet: number, placementId?: number): void {
     const isOk = message === 'OK';
-    if (isOk && quiet === 1) return;
-    if (!isOk && quiet === 2) return;
+    if (isOk && quiet >= 1) return;
+    if (!isOk && quiet >= 2) return;
 
     const pPart = placementId ? `,p=${placementId}` : '';
     const response = `\x1b_Gi=${id}${pPart};${message}\x1b\\`;

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

@@ -617,6 +617,18 @@ test.describe('Kitty Graphics Protocol', () => {
       strictEqual(await ctx.page.evaluate('window.kittyGotResponse'), false);
     });
 
+    test('suppresses OK response when q=2', async () => {
+      await ctx.page.evaluate(() => {
+        (window as any).kittyGotResponse = false;
+        (window as any).term.onData(() => { (window as any).kittyGotResponse = true; });
+      });
+
+      await ctx.proxy.write(`\x1b_Gi=81,a=q,q=2,f=100;${KITTY_BLACK_1X1_BASE64}\x1b\\`);
+      await timeout(100);
+
+      strictEqual(await ctx.page.evaluate('window.kittyGotResponse'), false);
+    });
+
     test('suppresses error response when q=2', async () => {
       await ctx.page.evaluate(() => {
         (window as any).kittyGotResponse = false;
@@ -797,6 +809,30 @@ test.describe('Kitty Graphics Protocol', () => {
 
       strictEqual(await ctx.page.evaluate('window.kittyGotResponse'), false);
     });
+
+    test('a=t OK suppressed by q=2', async () => {
+      await ctx.page.evaluate(() => {
+        (window as any).kittyGotResponse = false;
+        (window as any).term.onData(() => { (window as any).kittyGotResponse = true; });
+      });
+
+      await ctx.proxy.write(`\x1b_Gi=181,a=t,q=2,f=100;${KITTY_BLACK_1X1_BASE64}\x1b\\`);
+      await timeout(100);
+
+      strictEqual(await ctx.page.evaluate('window.kittyGotResponse'), false);
+    });
+
+    test('a=T OK suppressed by q=2', async () => {
+      await ctx.page.evaluate(() => {
+        (window as any).kittyGotResponse = false;
+        (window as any).term.onData(() => { (window as any).kittyGotResponse = true; });
+      });
+
+      await ctx.proxy.write(`\x1b_Gi=191,a=T,q=2,f=100;${KITTY_BLACK_1X1_BASE64}\x1b\\`);
+      await timeout(100);
+
+      strictEqual(await ctx.page.evaluate('window.kittyGotResponse'), false);
+    });
   });
 
   test.describe('Transmission medium rejection', () => {
@@ -1146,6 +1182,22 @@ test.describe('Kitty Graphics Protocol', () => {
       strictEqual(await getImageStorageLength(), 1);
     });
 
+    test('OK response suppressed by q=2', async () => {
+      await ctx.proxy.write(`\x1b_Ga=t,f=100,i=221;${KITTY_BLACK_1X1_BASE64}\x1b\\`);
+      await timeout(100);
+
+      await ctx.page.evaluate(() => {
+        (window as any).kittyGotResponse = false;
+        (window as any).term.onData(() => { (window as any).kittyGotResponse = true; });
+      });
+
+      await ctx.proxy.write(`\x1b_Ga=p,i=221,q=2\x1b\\`);
+      await timeout(100);
+
+      strictEqual(await ctx.page.evaluate('window.kittyGotResponse'), false);
+      strictEqual(await getImageStorageLength(), 1);
+    });
+
     test('ENOENT error suppressed by q=2', async () => {
       await ctx.page.evaluate(() => {
         (window as any).kittyGotResponse = false;

addons/addon-ligatures/package.json

@@ -20,7 +20,7 @@
     "package": "webpack",
     "pretest": "npm run build",
     "test": "nyc mocha out/**/*.test.js",
-    "prepublish": "npm run package"
+    "prepublishOnly": "npm run package"
   },
   "keywords": [
     "font",
@@ -37,7 +37,7 @@
   "devDependencies": {
     "@types/lru-cache": "^5.1.0",
     "@types/opentype.js": "^0.7.0",
-    "axios": "^1.15.0",
+    "axios": "^1.15.2",
     "font-finder": "^1.1.0",
     "mkdirp": "0.5.5",
     "yauzl": "^3.2.1"

addons/addon-search/src/DecorationManager.ts

@@ -131,6 +131,9 @@ export class DecorationManager extends Disposable {
     const decorations: IDecoration[] = [];
     for (const range of decorationRanges) {
       const marker = this._terminal.registerMarker(range[0]);
+      if (!marker) {
+        continue;
+      }
       const decoration = this._terminal.registerDecoration({
         marker,
         x: range[1],

addons/addon-webgl/src/CharAtlasUtils.test.ts

@@ -0,0 +1,87 @@
+/**
+ * Copyright (c) 2026 The xterm.js authors. All rights reserved.
+ * @license MIT
+ */
+
+import { assert } from 'chai';
+import { configEquals } from './CharAtlasUtils';
+import { ICharAtlasConfig } from './Types';
+import { NULL_COLOR } from 'common/Color';
+import { IColor } from 'common/Types';
+
+function createTestConfig(overrides: Partial<ICharAtlasConfig> = {}): ICharAtlasConfig {
+  const color: IColor = { css: '#ffffff', rgba: 0xffffffff };
+  const contrastCache = {
+    clear: () => {},
+    setCss: () => {},
+    getCss: () => undefined,
+    setColor: () => {},
+    getColor: () => undefined
+  };
+  const colors = {
+    foreground: color,
+    background: color,
+    cursor: NULL_COLOR,
+    cursorAccent: NULL_COLOR,
+    selectionForeground: undefined,
+    selectionBackgroundTransparent: NULL_COLOR,
+    selectionBackgroundOpaque: NULL_COLOR,
+    selectionInactiveBackgroundTransparent: NULL_COLOR,
+    selectionInactiveBackgroundOpaque: NULL_COLOR,
+    overviewRulerBorder: NULL_COLOR,
+    scrollbarSliderBackground: NULL_COLOR,
+    scrollbarSliderHoverBackground: NULL_COLOR,
+    scrollbarSliderActiveBackground: NULL_COLOR,
+    ansi: new Array(256).fill(color),
+    contrastCache,
+    halfContrastCache: contrastCache
+  };
+  return {
+    customGlyphs: true,
+    devicePixelRatio: 1,
+    deviceMaxTextureSize: 4096,
+    letterSpacing: 0,
+    lineHeight: 1,
+    fontSize: 15,
+    fontFamily: 'monospace',
+    fontWeight: 'normal',
+    fontWeightBold: 'bold',
+    deviceCellWidth: 10,
+    deviceCellHeight: 20,
+    deviceCharWidth: 8,
+    deviceCharHeight: 16,
+    allowTransparency: false,
+    drawBoldTextInBrightColors: true,
+    minimumContrastRatio: 1,
+    colors,
+    ...overrides
+  };
+}
+
+describe('CharAtlasUtils', () => {
+  describe('configEquals', () => {
+    it('should return true for identical configs', () => {
+      const a = createTestConfig();
+      const b = createTestConfig();
+      assert.ok(configEquals(a, b));
+    });
+
+    it('should return false when deviceMaxTextureSize differs', () => {
+      const a = createTestConfig();
+      const b = createTestConfig({ deviceMaxTextureSize: 8192 });
+      assert.ok(!configEquals(a, b));
+    });
+
+    it('should return false when deviceCellWidth differs', () => {
+      const a = createTestConfig();
+      const b = createTestConfig({ deviceCellWidth: 11 });
+      assert.ok(!configEquals(a, b));
+    });
+
+    it('should return false when deviceCellHeight differs', () => {
+      const a = createTestConfig();
+      const b = createTestConfig({ deviceCellHeight: 21 });
+      assert.ok(!configEquals(a, b));
+    });
+  });
+});

addons/addon-webgl/src/CharAtlasUtils.ts

@@ -59,6 +59,7 @@ export function configEquals(a: ICharAtlasConfig, b: ICharAtlasConfig): boolean
     }
   }
   return a.devicePixelRatio === b.devicePixelRatio &&
+      a.deviceMaxTextureSize === b.deviceMaxTextureSize &&
       a.customGlyphs === b.customGlyphs &&
       a.lineHeight === b.lineHeight &&
       a.letterSpacing === b.letterSpacing &&
@@ -67,6 +68,8 @@ export function configEquals(a: ICharAtlasConfig, b: ICharAtlasConfig): boolean
       a.fontWeight === b.fontWeight &&
       a.fontWeightBold === b.fontWeightBold &&
       a.allowTransparency === b.allowTransparency &&
+      a.deviceCellWidth === b.deviceCellWidth &&
+      a.deviceCellHeight === b.deviceCellHeight &&
       a.deviceCharWidth === b.deviceCharWidth &&
       a.deviceCharHeight === b.deviceCharHeight &&
       a.drawBoldTextInBrightColors === b.drawBoldTextInBrightColors &&

addons/addon-webgl/src/GlyphRenderer.ts

@@ -9,7 +9,7 @@ import { Disposable, toDisposable } from 'common/Lifecycle';
 import { Terminal } from '@xterm/xterm';
 import { IRenderModel, IWebGL2RenderingContext, IWebGLVertexArrayObject, type IRasterizedGlyph, type ITextureAtlas } from './Types';
 import { createProgram, GLTexture, PROJECTION_MATRIX } from './WebglUtils';
-import type { IOptionsService } from 'common/services/Services';
+import type { ILogService, IOptionsService } from 'common/services/Services';
 import { allowRescaling, throwIfFalsy } from 'browser/renderer/shared/RendererUtils';
 
 interface IVertices {
@@ -114,7 +114,8 @@ export class GlyphRenderer extends Disposable {
     private readonly _terminal: Terminal,
     private readonly _gl: IWebGL2RenderingContext,
     private _dimensions: IRenderDimensions,
-    private readonly _optionsService: IOptionsService
+    private readonly _optionsService: IOptionsService,
+    private readonly _logService: ILogService
   ) {
     super();
 
@@ -127,7 +128,7 @@ export class GlyphRenderer extends Disposable {
       TextureAtlas.maxTextureSize = throwIfFalsy(gl.getParameter(gl.MAX_TEXTURE_SIZE) as number | null);
     }
 
-    this._program = throwIfFalsy(createProgram(gl, vertexShaderSource, createFragmentShaderSource(TextureAtlas.maxAtlasPages)));
+    this._program = throwIfFalsy(createProgram(gl, vertexShaderSource, createFragmentShaderSource(TextureAtlas.maxAtlasPages), this._logService));
     this._register(toDisposable(() => gl.deleteProgram(this._program)));
 
     // Uniform locations
@@ -136,8 +137,9 @@ export class GlyphRenderer extends Disposable {
     this._textureLocation = throwIfFalsy(gl.getUniformLocation(this._program, 'u_texture'));
 
     // Create and set the vertex array object
-    this._vertexArrayObject = gl.createVertexArray();
-    gl.bindVertexArray(this._vertexArrayObject);
+    const vertexArrayObject = this._vertexArrayObject = gl.createVertexArray();
+    this._register(toDisposable(() => gl.deleteVertexArray(vertexArrayObject)));
+    gl.bindVertexArray(vertexArrayObject);
 
     // Setup a_unitquad, this defines the 4 vertices of a rectangle
     const unitQuadVertices = new Float32Array([0, 0, 1, 0, 0, 1, 1, 1]);
@@ -358,7 +360,9 @@ export class GlyphRenderer extends Disposable {
     gl.bindBuffer(gl.ARRAY_BUFFER, this._attributesBuffer);
     gl.bufferData(gl.ARRAY_BUFFER, activeBuffer.subarray(0, bufferLength), gl.STREAM_DRAW);
 
-    // Bind the atlas page texture if they have changed
+    // 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++) {
       if (this._atlas.pages[i].version !== this._atlasTextures[i].version) {
         this._bindAtlasPageTexture(gl, this._atlas, i);
@@ -371,6 +375,10 @@ export class GlyphRenderer extends Disposable {
 
   public setAtlas(atlas: ITextureAtlas): void {
     this._atlas = atlas;
+    this.invalidateAtlasTextures();
+  }
+
+  public invalidateAtlasTextures(): void {
     for (const glTexture of this._atlasTextures) {
       glTexture.version = -1;
     }

addons/addon-webgl/src/RectangleRenderer.ts

@@ -14,6 +14,7 @@ import { RenderModelConstants } from './RenderModel';
 import { IRenderModel, IWebGL2RenderingContext, IWebGLVertexArrayObject } from './Types';
 import { createProgram, expandFloat32Array, PROJECTION_MATRIX } from './WebglUtils';
 import { throwIfFalsy } from 'browser/renderer/shared/RendererUtils';
+import type { ILogService } from 'common/services/Services';
 
 const enum VertexAttribLocations {
   POSITION = 0,
@@ -89,21 +90,23 @@ export class RectangleRenderer extends Disposable {
     private _terminal: Terminal,
     private _gl: IWebGL2RenderingContext,
     private _dimensions: IRenderDimensions,
-    private readonly _themeService: IThemeService
+    private readonly _themeService: IThemeService,
+    private readonly _logService: ILogService
   ) {
     super();
 
     const gl = this._gl;
 
-    this._program = throwIfFalsy(createProgram(gl, vertexShaderSource, fragmentShaderSource));
+    this._program = throwIfFalsy(createProgram(gl, vertexShaderSource, fragmentShaderSource, this._logService));
     this._register(toDisposable(() => gl.deleteProgram(this._program)));
 
     // Uniform locations
     this._projectionLocation = throwIfFalsy(gl.getUniformLocation(this._program, 'u_projection'));
 
     // Create and set the vertex array object
-    this._vertexArrayObject = gl.createVertexArray();
-    gl.bindVertexArray(this._vertexArrayObject);
+    const vertexArrayObject = this._vertexArrayObject = gl.createVertexArray();
+    this._register(toDisposable(() => gl.deleteVertexArray(vertexArrayObject)));
+    gl.bindVertexArray(vertexArrayObject);
 
     // Setup a_unitquad, this defines the 4 vertices of a rectangle
     const unitQuadVertices = new Float32Array([0, 0, 1, 0, 0, 1, 1, 1]);
@@ -336,8 +339,9 @@ export class RectangleRenderer extends Disposable {
       }
     }
 
-    if (vertices.attributes.length < offset + 4) {
-      vertices.attributes = expandFloat32Array(vertices.attributes, this._terminal.rows * this._terminal.cols * INDICES_PER_RECTANGLE);
+    if (vertices.attributes.length < offset + INDICES_PER_RECTANGLE) {
+      // +1 for the viewport-clear rectangle at offset 0.
+      vertices.attributes = expandFloat32Array(vertices.attributes, (this._terminal.rows * this._terminal.cols + 1) * INDICES_PER_RECTANGLE);
     }
     $x1 = startX * this._dimensions.device.cell.width;
     $y1 = y * this._dimensions.device.cell.height;

addons/addon-webgl/src/TextureAtlas.ts

@@ -109,6 +109,7 @@ export class TextureAtlas implements ITextureAtlas {
       page.canvas.remove();
     }
     this._onAddTextureAtlasCanvas.dispose();
+    this._onRemoveTextureAtlasCanvas.dispose();
   }
 
   public warmUp(): void {
@@ -133,7 +134,9 @@ export class TextureAtlas implements ITextureAtlas {
 
   private _requestClearModel = false;
   public beginFrame(): boolean {
-    return this._requestClearModel;
+    const result = this._requestClearModel;
+    this._requestClearModel = false;
+    return result;
   }
 
   public clearTexture(): void {
@@ -193,7 +196,7 @@ export class TextureAtlas implements ITextureAtlas {
 
       // Merge into the new page
       const mergedPage = this._mergePages(mergingPages, mergedPageIndex);
-      mergedPage.version++;
+      mergedPage.version = ++AtlasPage.nextVersion;
 
       // Delete the pages, shifting glyph texture pages as needed
       for (let i = sortedMergingPagesIndexes.length - 1; i >= 0; i--) {
@@ -251,7 +254,7 @@ export class TextureAtlas implements ITextureAtlas {
       for (const g of adjustingPage.glyphs) {
         g.texturePage--;
       }
-      adjustingPage.version++;
+      adjustingPage.version = ++AtlasPage.nextVersion;
     }
   }
 
@@ -527,7 +530,7 @@ export class TextureAtlas implements ITextureAtlas {
     let customGlyph = false;
     if (this._config.customGlyphs !== false) {
       const variantOffset = this._workAttributeData.getUnderlineVariantOffset();
-      customGlyph = tryDrawCustomGlyph(this._tmpCtx, chars, padding, padding, this._config.deviceCellWidth, this._config.deviceCellHeight, this._config.deviceCharWidth, this._config.deviceCharHeight, this._config.fontSize, this._config.devicePixelRatio, backgroundColor.css, variantOffset);
+      customGlyph = tryDrawCustomGlyph(this._tmpCtx, chars, padding, padding, this._config.deviceCellWidth, this._config.deviceCellHeight, this._config.deviceCharWidth, this._config.deviceCharHeight, this._config.fontSize, this._config.devicePixelRatio, this._logService, backgroundColor.css, variantOffset);
     }
 
     // Whether to clear pixels based on a threshold difference between the glyph color and the
@@ -937,7 +940,7 @@ export class TextureAtlas implements ITextureAtlas {
       rasterizedGlyph.size.y
     );
     activePage.addGlyph(rasterizedGlyph);
-    activePage.version++;
+    activePage.version = ++AtlasPage.nextVersion;
 
     return rasterizedGlyph;
   }
@@ -1047,9 +1050,13 @@ class AtlasPage {
   }
 
   /**
-   * Used to check whether the canvas of the atlas page has changed.
+   * Monotonically increasing across all atlas pages globally. Used to detect when the texture
+   * unit at a given index needs to be re-uploaded — both for content changes within the same
+   * page and for a page object swap at the same index (which happens after a page merge,
+   * where a per-page counter could coincide with the previously-bound page's value).
    */
-  public version = 0;
+  public static nextVersion: number = 0;
+  public version = ++AtlasPage.nextVersion;
 
   // Texture atlas current positioning data. The texture packing strategy used is to fill from
   // left-to-right and top-to-bottom. When the glyph being written is less than half of the current
@@ -1092,7 +1099,7 @@ class AtlasPage {
     this.currentRow.y = 0;
     this.currentRow.height = 0;
     this.fixedRows.length = 0;
-    this.version++;
+    this.version = ++AtlasPage.nextVersion;
   }
 }
 

addons/addon-webgl/src/Types.ts

@@ -28,6 +28,7 @@ export interface ICursorRenderModel {
 export interface IWebGL2RenderingContext extends WebGLRenderingContext {
   vertexAttribDivisor(index: number, divisor: number): void;
   createVertexArray(): IWebGLVertexArrayObject;
+  deleteVertexArray(vao: IWebGLVertexArrayObject): void;
   bindVertexArray(vao: IWebGLVertexArrayObject): void;
   drawElementsInstanced(mode: number, count: number, type: number, offset: number, instanceCount: number): void;
 }

addons/addon-webgl/src/WebglAddon.ts

@@ -9,7 +9,7 @@ import { ICharacterJoinerService, ICharSizeService, ICoreBrowserService, IRender
 import { ITerminal } from 'browser/Types';
 import { Disposable, toDisposable } from 'common/Lifecycle';
 import { getSafariVersion, isSafari } from 'common/Platform';
-import { ICoreService, IDecorationService, IOptionsService } from 'common/services/Services';
+import { ICoreService, IDecorationService, ILogService, IOptionsService } from 'common/services/Services';
 import { IWebGL2RenderingContext } from './Types';
 import { WebglRenderer } from './WebglRenderer';
 import { Emitter, EventUtils } from 'common/Event';
@@ -65,6 +65,7 @@ export class WebglAddon extends Disposable implements ITerminalAddon, IWebglApi
     const charSizeService: ICharSizeService = unsafeCore._charSizeService;
     const coreBrowserService: ICoreBrowserService = unsafeCore._coreBrowserService;
     const decorationService: IDecorationService = unsafeCore._decorationService;
+    const logService: ILogService = unsafeCore._logService;
     const themeService: IThemeService = unsafeCore._themeService;
 
     this._renderer = this._register(new WebglRenderer(
@@ -74,6 +75,7 @@ export class WebglAddon extends Disposable implements ITerminalAddon, IWebglApi
       coreBrowserService,
       coreService,
       decorationService,
+      logService,
       optionsService,
       themeService,
       this._customGlyphs,

addons/addon-webgl/src/WebglRenderer.ts

@@ -15,7 +15,7 @@ import { AttributeData } from 'common/buffer/AttributeData';
 import { CellData } from 'common/buffer/CellData';
 import { Attributes, Content, FgFlags, NULL_CELL_CHAR, NULL_CELL_CODE } from 'common/buffer/Constants';
 import { TextBlinkStateManager } from 'browser/renderer/shared/TextBlinkStateManager';
-import { ICoreService, IDecorationService, IOptionsService } from 'common/services/Services';
+import { ICoreService, IDecorationService, ILogService, IOptionsService } from 'common/services/Services';
 import { Terminal } from '@xterm/xterm';
 import { GlyphRenderer } from './GlyphRenderer';
 import { RectangleRenderer } from './RectangleRenderer';
@@ -28,6 +28,10 @@ import { addDisposableListener } from 'browser/Dom';
 import { combinedDisposable, Disposable, MutableDisposable, toDisposable } from 'common/Lifecycle';
 import { createRenderDimensions } from 'browser/renderer/shared/RendererUtils';
 
+const enum Constants {
+  MERGE_RETRY_LIMIT = 32
+}
+
 export class WebglRenderer extends Disposable implements IRenderer {
   private _renderLayers: IRenderLayer[];
   private _cursorBlinkStateManager: MutableDisposable<CursorBlinkStateManager> = this._register(new MutableDisposable());
@@ -73,6 +77,7 @@ export class WebglRenderer extends Disposable implements IRenderer {
     private readonly _coreBrowserService: ICoreBrowserService,
     private readonly _coreService: ICoreService,
     private readonly _decorationService: IDecorationService,
+    private readonly _logService: ILogService,
     private readonly _optionsService: IOptionsService,
     private readonly _themeService: IThemeService,
     private readonly _customGlyphs: boolean = true,
@@ -118,19 +123,19 @@ export class WebglRenderer extends Disposable implements IRenderer {
     this._deviceMaxTextureSize = this._gl.getParameter(this._gl.MAX_TEXTURE_SIZE);
 
     this._register(addDisposableListener(this._canvas, 'webglcontextlost', (e) => {
-      console.log('webglcontextlost event received');
+      this._logService.debug('webglcontextlost event received');
       // Prevent the default behavior in order to enable WebGL context restoration.
       e.preventDefault();
       // Wait a few seconds to see if the 'webglcontextrestored' event is fired.
       // If not, dispatch the onContextLoss notification to observers.
       this._contextRestorationTimeout = setTimeout(() => {
         this._contextRestorationTimeout = undefined;
-        console.warn('webgl context not restored; firing onContextLoss');
+        this._logService.warn('webgl context not restored; firing onContextLoss');
         this._onContextLoss.fire(e);
       }, 3000 /* ms */);
     }));
     this._register(addDisposableListener(this._canvas, 'webglcontextrestored', (e) => {
-      console.warn('webglcontextrestored event received');
+      this._logService.warn('webglcontextrestored event received');
       clearTimeout(this._contextRestorationTimeout);
       this._contextRestorationTimeout = undefined;
       // The texture atlas and glyph renderer must be fully reinitialized
@@ -154,6 +159,8 @@ export class WebglRenderer extends Disposable implements IRenderer {
     this._isAttached = this._core.screenElement!.isConnected;
 
     this._register(toDisposable(() => {
+      clearTimeout(this._contextRestorationTimeout);
+      this._contextRestorationTimeout = undefined;
       for (const l of this._renderLayers) {
         l.dispose();
       }
@@ -270,8 +277,8 @@ export class WebglRenderer extends Disposable implements IRenderer {
    * Initializes members dependent on WebGL context state.
    */
   private _initializeWebGLState(): [RectangleRenderer, GlyphRenderer] {
-    this._rectangleRenderer.value = new RectangleRenderer(this._terminal, this._gl, this.dimensions, this._themeService);
-    this._glyphRenderer.value = new GlyphRenderer(this._terminal, this._gl, this.dimensions, this._optionsService);
+    this._rectangleRenderer.value = new RectangleRenderer(this._terminal, this._gl, this.dimensions, this._themeService, this._logService);
+    this._glyphRenderer.value = new GlyphRenderer(this._terminal, this._gl, this.dimensions, this._optionsService, this._logService);
 
     // Update dimensions and acquire char atlas
     this.handleCharSizeChanged();
@@ -375,6 +382,19 @@ export class WebglRenderer extends Disposable implements IRenderer {
       this._updateModel(start, end);
     }
 
+    // A mid-update atlas page merge invalidates vertex data and may not bump the host
+    // page's version, so re-run the update and force a full texture rebind.
+    let merged = false;
+    let mergeRetries = 0;
+    while (this._charAtlas && this._glyphRenderer.value.beginFrame() && mergeRetries++ < Constants.MERGE_RETRY_LIMIT) {
+      merged = true;
+      this._clearModel(true);
+      this._updateModel(0, this._terminal.rows - 1);
+    }
+    if (merged) {
+      this._glyphRenderer.value.invalidateAtlasTextures();
+    }
+
     // Render
     this._rectangleRenderer.value.renderBackgrounds();
     this._glyphRenderer.value.render(this._model);

addons/addon-webgl/src/WebglUtils.ts

@@ -4,6 +4,7 @@
  */
 
 import { throwIfFalsy } from 'browser/renderer/shared/RendererUtils';
+import type { ILogService } from 'common/services/Services';
 
 /**
  * A matrix that when multiplies will translate 0-1 coordinates (left to right,
@@ -16,21 +17,21 @@ export const PROJECTION_MATRIX = new Float32Array([
   -1, 1, 0, 1
 ]);
 
-export function createProgram(gl: WebGLRenderingContext, vertexSource: string, fragmentSource: string): WebGLProgram | undefined {
+export function createProgram(gl: WebGLRenderingContext, vertexSource: string, fragmentSource: string, logService: ILogService): WebGLProgram | undefined {
   const program = throwIfFalsy(gl.createProgram());
-  gl.attachShader(program, throwIfFalsy(createShader(gl, gl.VERTEX_SHADER, vertexSource)));
-  gl.attachShader(program, throwIfFalsy(createShader(gl, gl.FRAGMENT_SHADER, fragmentSource)));
+  gl.attachShader(program, throwIfFalsy(createShader(gl, gl.VERTEX_SHADER, vertexSource, logService)));
+  gl.attachShader(program, throwIfFalsy(createShader(gl, gl.FRAGMENT_SHADER, fragmentSource, logService)));
   gl.linkProgram(program);
   const success = gl.getProgramParameter(program, gl.LINK_STATUS);
   if (success) {
     return program;
   }
 
-  console.error(gl.getProgramInfoLog(program));
+  logService.error(gl.getProgramInfoLog(program));
   gl.deleteProgram(program);
 }
 
-export function createShader(gl: WebGLRenderingContext, type: number, source: string): WebGLShader | undefined {
+export function createShader(gl: WebGLRenderingContext, type: number, source: string, logService: ILogService): WebGLShader | undefined {
   const shader = throwIfFalsy(gl.createShader(type));
   gl.shaderSource(shader, source);
   gl.compileShader(shader);
@@ -39,7 +40,7 @@ export function createShader(gl: WebGLRenderingContext, type: number, source: st
     return shader;
   }
 
-  console.error(gl.getShaderInfoLog(shader));
+  logService.error(gl.getShaderInfoLog(shader));
   gl.deleteShader(shader);
 }
 

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

@@ -4,6 +4,7 @@
  */
 
 import { throwIfFalsy } from 'browser/renderer/shared/RendererUtils';
+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';
 
@@ -22,6 +23,7 @@ export function tryDrawCustomGlyph(
   deviceCharHeight: number,
   fontSize: number,
   devicePixelRatio: number,
+  logService: ILogService,
   backgroundColor?: string,
   variantOffset: number = 0
 ): boolean {
@@ -30,7 +32,7 @@ export function tryDrawCustomGlyph(
     // Normalize to array for uniform handling
     const parts = Array.isArray(unifiedCharDefinition) ? unifiedCharDefinition : [unifiedCharDefinition];
     for (const part of parts) {
-      drawDefinitionPart(ctx, part, xOffset, yOffset, deviceCellWidth, deviceCellHeight, deviceCharWidth, deviceCharHeight, fontSize, devicePixelRatio, backgroundColor, variantOffset);
+      drawDefinitionPart(ctx, part, xOffset, yOffset, deviceCellWidth, deviceCellHeight, deviceCharWidth, deviceCharHeight, fontSize, devicePixelRatio, logService, backgroundColor, variantOffset);
     }
     return true;
   }
@@ -49,6 +51,7 @@ function drawDefinitionPart(
   deviceCharHeight: number,
   fontSize: number,
   devicePixelRatio: number,
+  logService: ILogService,
   backgroundColor?: string,
   variantOffset: number = 0
 ): void {
@@ -79,7 +82,7 @@ function drawDefinitionPart(
       drawPatternChar(ctx, part.data, drawXOffset, drawYOffset, drawWidth, drawHeight, variantOffset);
       break;
     case CustomGlyphDefinitionType.PATH_FUNCTION:
-      drawPathFunctionCharacter(ctx, part.data, drawXOffset, drawYOffset, drawWidth, drawHeight, devicePixelRatio, part.strokeWidth);
+      drawPathFunctionCharacter(ctx, part.data, drawXOffset, drawYOffset, drawWidth, drawHeight, devicePixelRatio, logService, part.strokeWidth);
       break;
     case CustomGlyphDefinitionType.PATH:
       drawPathDefinitionCharacter(ctx, part.data, drawXOffset, drawYOffset, drawWidth, drawHeight, devicePixelRatio, part.strokeWidth);
@@ -88,7 +91,7 @@ function drawDefinitionPart(
       drawPathNegativeDefinitionCharacter(ctx, part.data, drawXOffset, drawYOffset, drawWidth, drawHeight, devicePixelRatio, backgroundColor);
       break;
     case CustomGlyphDefinitionType.VECTOR_SHAPE:
-      drawVectorShape(ctx, part.data, drawXOffset, drawYOffset, drawWidth, drawHeight, fontSize, devicePixelRatio);
+      drawVectorShape(ctx, part.data, drawXOffset, drawYOffset, drawWidth, drawHeight, fontSize, devicePixelRatio, logService);
       break;
     case CustomGlyphDefinitionType.BRAILLE:
       drawBrailleCharacter(ctx, part.data, drawXOffset, drawYOffset, drawWidth, drawHeight);
@@ -510,6 +513,7 @@ function drawPathFunctionCharacter(
   deviceCellWidth: number,
   deviceCellHeight: number,
   devicePixelRatio: number,
+  logService: ILogService,
   strokeWidth?: number
 ): void {
   ctx.save();
@@ -536,7 +540,7 @@ function drawPathFunctionCharacter(
     }
     const f = svgToCanvasInstructionMap[type];
     if (!f) {
-      console.error(`Could not find drawing instructions for "${type}"`);
+      logService.error(`Could not find drawing instructions for "${type}"`);
       continue;
     }
     const args: string[] = instruction.substring(1).split(',');
@@ -598,7 +602,8 @@ function drawVectorShape(
   deviceCellWidth: number,
   deviceCellHeight: number,
   fontSize: number,
-  devicePixelRatio: number
+  devicePixelRatio: number,
+  logService: ILogService
 ): void {
   // Clip the cell to make sure drawing doesn't occur beyond bounds
   const clipRegion = new Path2D();
@@ -619,7 +624,7 @@ function drawVectorShape(
     }
     const f = svgToCanvasInstructionMap[type];
     if (!f) {
-      console.error(`Could not find drawing instructions for "${type}"`);
+      logService.error(`Could not find drawing instructions for "${type}"`);
       continue;
     }
     const args: string[] = instruction.substring(1).split(',');

bin/kitty_keytester.py

@@ -1,196 +0,0 @@
-from termios import tcgetattr, tcsetattr, TCSADRAIN, TIOCGWINSZ, TCSAFLUSH
-from tty import setcbreak, setraw
-import os
-import sys
-from contextlib import contextmanager
-from select import select
-from time import sleep
-from json import dumps, loads
-from typing import Optional, Tuple, Union
-
-
-class TerminalContext:
-    def __init__(self, fd: int, close_fd=False) -> None:
-        if not os.isatty(fd):
-            raise TypeError('fd is not a terminal')
-        self.close_fd = close_fd
-        self.fd = fd
-        self.is_cbreak = False
-        self.is_raw = False
-        self._initial_attr = self.termios_attributes
-
-    @classmethod
-    def from_cterm(cls):
-        fd = os.open(os.ctermid(), os.O_RDWR)
-        return TerminalContext(fd, True)
-
-    def close(self) -> None:
-        tcsetattr(self.fd, TCSADRAIN, self._initial_attr)
-        if self.close_fd:
-            os.close(self.fd)
-
-    @property
-    def termios_attributes(self) -> list:
-        return tcgetattr(self.fd)
-    
-    @property
-    def ttyname(self) -> str:
-        return os.ttyname(self.fd)
-    
-    @contextmanager
-    def cbreak_mode(self):
-        """
-        Enter cbreak mode context.
-        """
-        if self.is_cbreak:
-            yield
-            return
-        tattr = self.termios_attributes
-        try:
-            setcbreak(self.fd, TCSADRAIN)
-            self.is_cbreak = True
-            yield
-        finally:
-            tcsetattr(self.fd, TCSADRAIN, tattr)
-            self.is_cbreak = False
-
-    @contextmanager
-    def raw_mode(self):
-        """
-        Enter cbreak mode context.
-        """
-        if self.is_raw:
-            yield
-            return
-        tattr = self.termios_attributes
-        try:
-            setraw(self.fd, TCSADRAIN)
-            self.is_raw = True
-            yield
-        finally:
-            tcsetattr(self.fd, TCSADRAIN, tattr)
-            self.is_raw = False
-
-    @contextmanager
-    def custom_state(self, undo=None):
-        """
-        Enter custom terminal state, that needs to to be undone by ``undo``.
-        Useful, if you want to apply a custom terminal state and
-        have to make sure, that it gets properly reset to previous state.
-        """
-        try:
-            yield
-        finally:
-            if undo:
-                undo()
-
-    def write(self, data: Union[str, bytes]) -> None:
-        """
-        Write string or bytes directly to the terminal.
-        """
-        if isinstance(data, str):
-            data = data.encode('utf-8')
-        sent = os.write(self.fd, data)
-        while sent:
-            data = data[sent:]
-            sent = os.write(self.fd, data)
-
-    def read(self, amount: int = 1024, timeout: Optional[float] = None) -> bytes:
-        """
-        Blocking read from the terminal.
-        If nothing was sent from the terminal within ``timeout``,
-        empty bytes are returned.
-        """
-        can_read, _, _ = select([self.fd], [], [], timeout)
-        if can_read:
-            return os.read(self.fd, amount)
-        return b''
-
-
-@contextmanager
-def cterminal_context():
-    t = TerminalContext.from_cterm()
-    try:
-        yield t
-    finally:
-        t.close()
-
-
-def extract_events(data: list[str]):
-    if len(data) < 5:
-        raise Exception('not enough reports')
-    types = set(data)
-    if len(types) == 1:
-        return {'PRESS': data[0], 'REPEAT': data[0], 'RELEASE': None}
-    if len(types) == 2:
-        last = data.pop()
-        if last != data[0] and len(set(data)) == 1:
-            return {'PRESS': data[0], 'REPEAT': data[0], 'RELEASE': last}
-        raise Exception('weird reports, 2 types')
-    if len(types) == 3:
-        first = data.pop(0)
-        last = data.pop()
-        if first != last and first != data[0] and last != data[0]:
-            return {'PRESS': first, 'REPEAT': data[0], 'RELEASE': last}
-        raise Exception('weird reports, 3 types')
-    raise Exception('more than 3 types')
-
-
-def query(term: TerminalContext, mode: int):
-    with term.custom_state(undo=lambda:term.write('\x1b[<u')):
-        term.write(f'\x1b[>{mode}u')
-        term.read(timeout=.1)
-        print('PRESS (within 5s) and HOLD (for 5s)\r')
-        data: list[bytes] = []
-        cur = term.read(timeout=5)
-        while cur:
-            data.append(cur)
-            cur = term.read(timeout=.5)
-            if len(data) > 5:
-                print('RELEASE\r', end='')
-        try:
-            return extract_events([b.decode('utf-8') for b in data])
-        except Exception as e:
-            print('Error:', e, '\r')
-            print(data, '\r')
-    term.read(timeout=.1)
-
-
-def save(filedata: dict[str, dict[str, str]], filename, entry, mode, events):
-    try:
-        filedata[entry][mode] = events
-    except KeyError:
-        filedata[entry] = {mode: events}
-    with open(filename, 'w') as f:
-        f.write(dumps(filedata, indent=2))
-
-
-def main():
-    mode = 1
-    filedata = {}
-    print(sys.argv)
-    if len(sys.argv) != 3:
-        print('ERROR: not enough arguments')
-        print('Usage: python kitty_keytester.py <mode> <json-file>')
-        return
-    mode = int(sys.argv[1])
-    filename = sys.argv[2]
-    if os.path.exists(filename):
-        with open(filename) as f:
-            filedata = loads(f.read())
-    with cterminal_context() as term:
-        while True:
-            with term.raw_mode():
-                events = query(term, mode)
-            if events:
-                print(events)
-                entry = input('Entry: ')
-                if entry:
-                    save(filedata, filename, entry, str(mode), events)
-            cont = input('Continue? (y)')
-            if cont not in ['y', '']:
-                break
-
-
-if __name__ == '__main__':
-    main()

demo/client/components/window/optionsWindow.ts

@@ -252,6 +252,11 @@ export class OptionsWindow extends BaseWindow implements IControlWindow {
             input.value = 'auto';
             this._handlers.updateTerminalSize();
           }
+          const screenElement = document.querySelector('.xterm-screen');
+          if (screenElement instanceof HTMLElement) {
+            screenElement.style.outline = this._autoResize ? ''
+              : 'solid thin red';
+          }
         } else if (o === 'theme') {
           value = this._getTheme();
         }

demo/client/components/window/testWindow.ts

@@ -753,7 +753,7 @@ async function loadTestLongLines(term: Terminal, addons: AddonCollection): Promi
 
 function addDecoration(term: Terminal, dim: number = 1): void {
   term.options.scrollbar = { ...(term.options.scrollbar ?? {}), width: 14, overviewRuler: term.options.scrollbar?.overviewRuler ?? {} };
-  const marker = term.registerMarker(1);
+  const marker = term.registerMarker(1)!;
   const decoration = term.registerDecoration({
     marker,
     height: dim,
@@ -770,14 +770,14 @@ function addDecoration(term: Terminal, dim: number = 1): void {
 
 function addOverviewRuler(term: Terminal): void {
   term.options.scrollbar = { ...(term.options.scrollbar ?? {}), width: 14, overviewRuler: term.options.scrollbar?.overviewRuler ?? {} };
-  term.registerDecoration({ marker: term.registerMarker(1), overviewRulerOptions: { color: '#ef2929' } });
-  term.registerDecoration({ marker: term.registerMarker(3), overviewRulerOptions: { color: '#8ae234' } });
-  term.registerDecoration({ marker: term.registerMarker(5), overviewRulerOptions: { color: '#729fcf' } });
-  term.registerDecoration({ marker: term.registerMarker(7), overviewRulerOptions: { color: '#ef2929', position: 'left' } });
-  term.registerDecoration({ marker: term.registerMarker(7), overviewRulerOptions: { color: '#8ae234', position: 'center' } });
-  term.registerDecoration({ marker: term.registerMarker(7), overviewRulerOptions: { color: '#729fcf', position: 'right' } });
-  term.registerDecoration({ marker: term.registerMarker(10), overviewRulerOptions: { color: '#8ae234', position: 'center' } });
-  term.registerDecoration({ marker: term.registerMarker(10), overviewRulerOptions: { color: '#ffffff80', position: 'full' } });
+  term.registerDecoration({ marker: term.registerMarker(1)!, overviewRulerOptions: { color: '#ef2929' } });
+  term.registerDecoration({ marker: term.registerMarker(3)!, overviewRulerOptions: { color: '#8ae234' } });
+  term.registerDecoration({ marker: term.registerMarker(5)!, overviewRulerOptions: { color: '#729fcf' } });
+  term.registerDecoration({ marker: term.registerMarker(7)!, overviewRulerOptions: { color: '#ef2929', position: 'left' } });
+  term.registerDecoration({ marker: term.registerMarker(7)!, overviewRulerOptions: { color: '#8ae234', position: 'center' } });
+  term.registerDecoration({ marker: term.registerMarker(7)!, overviewRulerOptions: { color: '#729fcf', position: 'right' } });
+  term.registerDecoration({ marker: term.registerMarker(10)!, overviewRulerOptions: { color: '#8ae234', position: 'center' } });
+  term.registerDecoration({ marker: term.registerMarker(10)!, overviewRulerOptions: { color: '#ffffff80', position: 'full' } });
 }
 
 let decorationStressTestDecorations: IDisposable[] | undefined;
@@ -795,7 +795,7 @@ function decorationStressTest(term: Terminal): void {
       for (let y = 0; y < term.buffer.active.length; y++) {
         const cursorOffsetY = y - cursorY;
         const decoration = term.registerDecoration({
-          marker: term.registerMarker(cursorOffsetY),
+          marker: term.registerMarker(cursorOffsetY)!,
           x,
           width: 4,
           backgroundColor: '#FF0000',

eslint.config.mjs

@@ -43,6 +43,7 @@ export default tseslint.config(
         singleline: { delimiter: 'comma', requireLast: false }
       }],
       '@stylistic/type-annotation-spacing': 'warn',
+      '@stylistic/space-unary-ops': 'warn',
 
       '@typescript-eslint/array-type': ['warn', { default: 'array', readonly: 'generic' }],
       '@typescript-eslint/consistent-type-assertions': 'warn',
@@ -85,6 +86,7 @@ export default tseslint.config(
       'eqeqeq': ['warn', 'always'],
       'jsdoc/check-alignment': 'warn',
       'jsdoc/check-param-names': 'warn',
+      'jsdoc/multiline-blocks': 'warn',
       'jsdoc/no-multi-asterisks': 'warn',
       'keyword-spacing': 'warn',
       'max-len': ['warn', {

fixtures/kitty_keyboard/german_qwertz_capslock_numlock.json

@@ -1,373 +0,0 @@
-{
-  "Escape +CapsLock": {
-    "1": {
-      "PRESS": "\u001b[27;65u",
-      "REPEAT": "\u001b[27;65u",
-      "RELEASE": null
-    }
-  },
-  "F1 +CapsLock": {
-    "1": {
-      "PRESS": "\u001b[1;65P",
-      "REPEAT": "\u001b[1;65P",
-      "RELEASE": null
-    }
-  },
-  "Insert +CapsLock": {
-    "1": {
-      "PRESS": "\u001b[2;65~",
-      "REPEAT": "\u001b[2;65~",
-      "RELEASE": null
-    }
-  },
-  "Delete +CapsLock": {
-    "1": {
-      "PRESS": "\u001b[3;65~",
-      "REPEAT": "\u001b[3;65~",
-      "RELEASE": null
-    }
-  },
-  "PageUp +CapsLock": {
-    "1": {
-      "PRESS": "\u001b[5;65~",
-      "REPEAT": "\u001b[5;65~",
-      "RELEASE": null
-    }
-  },
-  "Dead (Backquote) +CapsLock": {
-    "1": {
-      "PRESS": "^",
-      "REPEAT": "^",
-      "RELEASE": null
-    }
-  },
-  "1 (Digit1) +CapsLock": {
-    "1": {
-      "PRESS": "1",
-      "REPEAT": "1",
-      "RELEASE": null
-    }
-  },
-  "\u00df (Minus) +CapsLock": {
-    "1": {
-      "PRESS": "\u1e9e",
-      "REPEAT": "\u1e9e",
-      "RELEASE": null
-    }
-  },
-  "Dead (Equal) +CapsLock": {
-    "1": {
-      "PRESS": "\u00b4",
-      "REPEAT": "\u00b4",
-      "RELEASE": null
-    }
-  },
-  "Backspace +CapsLock": {
-    "1": {
-      "PRESS": "\u007f",
-      "REPEAT": "\u007f",
-      "RELEASE": null
-    }
-  },
-  "Tab +CapsLock": {
-    "1": {
-      "PRESS": "\t",
-      "REPEAT": "\t",
-      "RELEASE": null
-    }
-  },
-  "Q (KeyQ) +CapsLock": {
-    "1": {
-      "PRESS": "Q",
-      "REPEAT": "Q",
-      "RELEASE": null
-    }
-  },
-  "\u00dc (BracketLeft) +CapsLock": {
-    "1": {
-      "PRESS": "\u00dc",
-      "REPEAT": "\u00dc",
-      "RELEASE": null
-    }
-  },
-  "+ (BracketRight) +CapsLock": {
-    "1": {
-      "PRESS": "+",
-      "REPEAT": "+",
-      "RELEASE": null
-    }
-  },
-  "Enter +CapsLock": {
-    "1": {
-      "PRESS": "\r",
-      "REPEAT": "\r",
-      "RELEASE": null
-    }
-  },
-  "\u00d6 (Semicolon) +CapsLock": {
-    "1": {
-      "PRESS": "\u00d6",
-      "REPEAT": "\u00d6",
-      "RELEASE": null
-    }
-  },
-  "\u00c4 (Quote) +CapsLock": {
-    "1": {
-      "PRESS": "\u00c4",
-      "REPEAT": "\u00c4",
-      "RELEASE": null
-    }
-  },
-  "# (Bashslash) +CapsLock": {
-    "1": {
-      "PRESS": "#",
-      "REPEAT": "#",
-      "RELEASE": null
-    }
-  },
-  "< (IntlBackslash) +CapsLock": {
-    "1": {
-      "PRESS": "<",
-      "REPEAT": "<",
-      "RELEASE": null
-    }
-  },
-  ", (Comma) +CapsLock": {
-    "1": {
-      "PRESS": ",",
-      "REPEAT": ",",
-      "RELEASE": null
-    }
-  },
-  ". (Period) +CapsLock": {
-    "1": {
-      "PRESS": ".",
-      "REPEAT": ".",
-      "RELEASE": null
-    }
-  },
-  "- (Slash) +CapsLock": {
-    "1": {
-      "PRESS": "-",
-      "REPEAT": "-",
-      "RELEASE": null
-    }
-  },
-  "ArrowUp +CapsLock": {
-    "1": {
-      "PRESS": "\u001b[1;65A",
-      "REPEAT": "\u001b[1;65A",
-      "RELEASE": null
-    }
-  },
-  "PageDown +CapsLock": {
-    "1": {
-      "PRESS": "\u001b[6;65~",
-      "REPEAT": "\u001b[6;65~",
-      "RELEASE": null
-    }
-  },
-  "Home +CapsLock": {
-    "1": {
-      "PRESS": "\u001b[1;65H",
-      "REPEAT": "\u001b[1;65H",
-      "RELEASE": null
-    }
-  },
-  "End +CapsLock": {
-    "1": {
-      "PRESS": "\u001b[1;65F",
-      "REPEAT": "\u001b[1;65F",
-      "RELEASE": null
-    }
-  },
-  "+ (NumpadAdd) +CapsLock": {
-    "1": {
-      "PRESS": "+",
-      "REPEAT": "+",
-      "RELEASE": null
-    }
-  },
-  "Enter (NumpadEnter) +CapsLock": {
-    "1": {
-      "PRESS": "\u001b[57414;65u",
-      "REPEAT": "\u001b[57414;65u",
-      "RELEASE": null
-    }
-  },
-  "Insert (Numpad0) +CapsLock": {
-    "1": {
-      "PRESS": "\u001b[57425;65u",
-      "REPEAT": "\u001b[57425;65u",
-      "RELEASE": null
-    }
-  },
-  "\u0000 (NumpadDecimal) +CapsLock": {
-    "1": {
-      "PRESS": "\u001b[57426;65u",
-      "REPEAT": "\u001b[57426;65u",
-      "RELEASE": null
-    }
-  },
-  "Numlock +CapsLock": {
-    "1": {
-      "PRESS": null,
-      "REPEAT": null,
-      "RELEASE": null
-    }
-  },
-  "CapsLock +CapsLock": {
-    "1": {
-      "PRESS": null,
-      "REPEAT": null,
-      "RELEASE": null
-    }
-  },
-  "Shift (ShiftLeft) +CapsLock": {
-    "1": {
-      "PRESS": null,
-      "REPEAT": null,
-      "RELEASE": null
-    }
-  },
-  "Shift (ShiftRight) +CapsLock": {
-    "1": {
-      "PRESS": null,
-      "REPEAT": null,
-      "RELEASE": null
-    }
-  },
-  "Control (ControlLeft) +CapsLock": {
-    "1": {
-      "PRESS": null,
-      "REPEAT": null,
-      "RELEASE": null
-    }
-  },
-  "Meta (MetaLeft) +CapsLock": {
-    "1": {
-      "PRESS": null,
-      "REPEAT": null,
-      "RELEASE": null
-    }
-  },
-  "Alt (AltLeft) +CapsLock": {
-    "1": {
-      "PRESS": null,
-      "REPEAT": null,
-      "RELEASE": null
-    }
-  },
-  "AltGraph (AltRight) +CapsLock": {
-    "1": {
-      "PRESS": null,
-      "REPEAT": null,
-      "RELEASE": null
-    }
-  },
-  "Control (ControlRight) +CapsLock": {
-    "1": {
-      "PRESS": null,
-      "REPEAT": null,
-      "RELEASE": null
-    }
-  },
-  "/ (NumpadDivide) +NumLock": {
-    "1": {
-      "PRESS": "/",
-      "REPEAT": "/",
-      "RELEASE": null
-    }
-  },
-  "* (NumpadMultiply) +NumLock": {
-    "1": {
-      "PRESS": "*",
-      "REPEAT": "*",
-      "RELEASE": null
-    }
-  },
-  "- (NumpadSubtract) +NumLock": {
-    "1": {
-      "PRESS": "-",
-      "REPEAT": "-",
-      "RELEASE": null
-    }
-  },
-  "0 (Numpad0) +NumLock": {
-    "1": {
-      "PRESS": "0",
-      "REPEAT": "0",
-      "RELEASE": null
-    }
-  },
-  "1 (Numpad1) +NumLock": {
-    "1": {
-      "PRESS": "1",
-      "REPEAT": "1",
-      "RELEASE": null
-    }
-  },
-  "2 (Numpad2) +NumLock": {
-    "1": {
-      "PRESS": "2",
-      "REPEAT": "2",
-      "RELEASE": null
-    }
-  },
-  "3 (Numpad3) +NumLock": {
-    "1": {
-      "PRESS": "3",
-      "REPEAT": "3",
-      "RELEASE": null
-    }
-  },
-  "4 (Numpad4) +NumLock": {
-    "1": {
-      "PRESS": "4",
-      "REPEAT": "4",
-      "RELEASE": null
-    }
-  },
-  "5 (Numpad5) +NumLock": {
-    "1": {
-      "PRESS": "5",
-      "REPEAT": "5",
-      "RELEASE": null
-    }
-  },
-  "6 (Numpad6) +NumLock": {
-    "1": {
-      "PRESS": "6",
-      "REPEAT": "6",
-      "RELEASE": null
-    }
-  },
-  "7 (Numpad7) +NumLock": {
-    "1": {
-      "PRESS": "7",
-      "REPEAT": "7",
-      "RELEASE": null
-    }
-  },
-  "8 (Numpad8) +NumLock": {
-    "1": {
-      "PRESS": "8",
-      "REPEAT": "8",
-      "RELEASE": null
-    }
-  },
-  "9 (Numpad9) +NumLock": {
-    "1": {
-      "PRESS": "9",
-      "REPEAT": "9",
-      "RELEASE": null
-    }
-  },
-  ", (NumpadDecimal) +NumLock": {
-    "1": {
-      "PRESS": ",",
-      "REPEAT": ",",
-      "RELEASE": null
-    }
-  }
-}

fixtures/kitty_keyboard/german_qwertz_no_modifier.json

@@ -1,702 +0,0 @@
-{
-  "Escape": {
-    "1": {
-      "PRESS": "\u001b[27u",
-      "REPEAT": "\u001b[27u",
-      "RELEASE": null
-    }
-  },
-  "F1": {
-    "1": {
-      "PRESS": "\u001b[P",
-      "REPEAT": "\u001b[P",
-      "RELEASE": null
-    }
-  },
-  "F2": {
-    "1": {
-      "PRESS": "\u001b[Q",
-      "REPEAT": "\u001b[Q",
-      "RELEASE": null
-    }
-  },
-  "F3": {
-    "1": {
-      "PRESS": "\u001b[13~",
-      "REPEAT": "\u001b[13~",
-      "RELEASE": null
-    }
-  },
-  "F4": {
-    "1": {
-      "PRESS": "\u001b[S",
-      "REPEAT": "\u001b[S",
-      "RELEASE": null
-    }
-  },
-  "F5": {
-    "1": {
-      "PRESS": "\u001b[15~",
-      "REPEAT": "\u001b[15~",
-      "RELEASE": null
-    }
-  },
-  "F6": {
-    "1": {
-      "PRESS": "\u001b[17~",
-      "REPEAT": "\u001b[17~",
-      "RELEASE": null
-    }
-  },
-  "F7": {
-    "1": {
-      "PRESS": "\u001b[18~",
-      "REPEAT": "\u001b[18~",
-      "RELEASE": null
-    }
-  },
-  "F8": {
-    "1": {
-      "PRESS": "\u001b[19~",
-      "REPEAT": "\u001b[19~",
-      "RELEASE": null
-    }
-  },
-  "F9": {
-    "1": {
-      "PRESS": "\u001b[20~",
-      "REPEAT": "\u001b[20~",
-      "RELEASE": null
-    }
-  },
-  "F10": {
-    "1": {
-      "PRESS": "\u001b[21~",
-      "REPEAT": "\u001b[21~",
-      "RELEASE": null
-    }
-  },
-  "F11": {
-    "1": {
-      "PRESS": "\u001b[23~",
-      "REPEAT": "\u001b[23~",
-      "RELEASE": null
-    }
-  },
-  "F12": {
-    "1": {
-      "PRESS": "\u001b[24~",
-      "REPEAT": "\u001b[24~",
-      "RELEASE": null
-    }
-  },
-  "Insert": {
-    "1": {
-      "PRESS": "\u001b[2~",
-      "REPEAT": "\u001b[2~",
-      "RELEASE": null
-    }
-  },
-  "Delete": {
-    "1": {
-      "PRESS": "\u001b[3~",
-      "REPEAT": "\u001b[3~",
-      "RELEASE": null
-    }
-  },
-  "PageUp": {
-    "1": {
-      "PRESS": "\u001b[5~",
-      "REPEAT": "\u001b[5~",
-      "RELEASE": null
-    }
-  },
-  "PageDown": {
-    "1": {
-      "PRESS": "\u001b[6~",
-      "REPEAT": "\u001b[6~",
-      "RELEASE": null
-    }
-  },
-  "Home": {
-    "1": {
-      "PRESS": "\u001b[H",
-      "REPEAT": "\u001b[H",
-      "RELEASE": null
-    }
-  },
-  "End": {
-    "1": {
-      "PRESS": "\u001b[F",
-      "REPEAT": "\u001b[F",
-      "RELEASE": null
-    }
-  },
-  "Dead (Backquote)": {
-    "1": {
-      "PRESS": "^",
-      "REPEAT": "^",
-      "RELEASE": null
-    }
-  },
-  "1 (Digit1)": {
-    "1": {
-      "PRESS": "1",
-      "REPEAT": "1",
-      "RELEASE": null
-    }
-  },
-  "2 (Digit2)": {
-    "1": {
-      "PRESS": "2",
-      "REPEAT": "2",
-      "RELEASE": null
-    }
-  },
-  "3 (Digit3)": {
-    "1": {
-      "PRESS": "3",
-      "REPEAT": "3",
-      "RELEASE": null
-    }
-  },
-  "4 (Digit4)": {
-    "1": {
-      "PRESS": "4",
-      "REPEAT": "4",
-      "RELEASE": null
-    }
-  },
-  "5 (Digit5)": {
-    "1": {
-      "PRESS": "5",
-      "REPEAT": "5",
-      "RELEASE": null
-    }
-  },
-  "6 (Digit6)": {
-    "1": {
-      "PRESS": "6",
-      "REPEAT": "6",
-      "RELEASE": null
-    }
-  },
-  "7 (Digit7)": {
-    "1": {
-      "PRESS": "7",
-      "REPEAT": "7",
-      "RELEASE": null
-    }
-  },
-  "8 (Digit8)": {
-    "1": {
-      "PRESS": "8",
-      "REPEAT": "8",
-      "RELEASE": null
-    }
-  },
-  "9 (Digit9)": {
-    "1": {
-      "PRESS": "9",
-      "REPEAT": "9",
-      "RELEASE": null
-    }
-  },
-  "0 (Digit0)": {
-    "1": {
-      "PRESS": "0",
-      "REPEAT": "0",
-      "RELEASE": null
-    }
-  },
-  "\u00df (Minus)": {
-    "1": {
-      "PRESS": "\u00df",
-      "REPEAT": "\u00df",
-      "RELEASE": null
-    }
-  },
-  "Dead (Equal)": {
-    "1": {
-      "PRESS": "\u00b4",
-      "REPEAT": "\u00b4",
-      "RELEASE": null
-    }
-  },
-  "Backspace": {
-    "1": {
-      "PRESS": "\u007f",
-      "REPEAT": "\u007f",
-      "RELEASE": null
-    }
-  },
-  "Tab": {
-    "1": {
-      "PRESS": "\t",
-      "REPEAT": "\t",
-      "RELEASE": null
-    }
-  },
-  "q (KeyQ)": {
-    "1": {
-      "PRESS": "q",
-      "REPEAT": "q",
-      "RELEASE": null
-    }
-  },
-  "w (KeyW)": {
-    "1": {
-      "PRESS": "w",
-      "REPEAT": "w",
-      "RELEASE": null
-    }
-  },
-  "e (KeyE)": {
-    "1": {
-      "PRESS": "e",
-      "REPEAT": "e",
-      "RELEASE": null
-    }
-  },
-  "r (KeyR)": {
-    "1": {
-      "PRESS": "r",
-      "REPEAT": "r",
-      "RELEASE": null
-    }
-  },
-  "t (KeyT)": {
-    "1": {
-      "PRESS": "t",
-      "REPEAT": "t",
-      "RELEASE": null
-    }
-  },
-  "z (KeyY)": {
-    "1": {
-      "PRESS": "z",
-      "REPEAT": "z",
-      "RELEASE": null
-    }
-  },
-  "u (KeyU)": {
-    "1": {
-      "PRESS": "u",
-      "REPEAT": "u",
-      "RELEASE": null
-    }
-  },
-  "i (KeyI)": {
-    "1": {
-      "PRESS": "i",
-      "REPEAT": "i",
-      "RELEASE": null
-    }
-  },
-  "o (KeyO)": {
-    "1": {
-      "PRESS": "o",
-      "REPEAT": "o",
-      "RELEASE": null
-    }
-  },
-  "p (KeyP)": {
-    "1": {
-      "PRESS": "p",
-      "REPEAT": "p",
-      "RELEASE": null
-    }
-  },
-  "\u00fc (BracketLeft)": {
-    "1": {
-      "PRESS": "\u00fc",
-      "REPEAT": "\u00fc",
-      "RELEASE": null
-    }
-  },
-  "+ (BracketRight)": {
-    "1": {
-      "PRESS": "+",
-      "REPEAT": "+",
-      "RELEASE": null
-    }
-  },
-  "Enter": {
-    "1": {
-      "PRESS": "\r",
-      "REPEAT": "\r",
-      "RELEASE": null
-    }
-  },
-  "a (KeyA)": {
-    "1": {
-      "PRESS": "a",
-      "REPEAT": "a",
-      "RELEASE": null
-    }
-  },
-  "s (KeyS)": {
-    "1": {
-      "PRESS": "s",
-      "REPEAT": "s",
-      "RELEASE": null
-    }
-  },
-  "d (KeyD)": {
-    "1": {
-      "PRESS": "d",
-      "REPEAT": "d",
-      "RELEASE": null
-    }
-  },
-  "f (KeyF)": {
-    "1": {
-      "PRESS": "f",
-      "REPEAT": "f",
-      "RELEASE": null
-    }
-  },
-  "g (KeyG)": {
-    "1": {
-      "PRESS": "g",
-      "REPEAT": "g",
-      "RELEASE": null
-    }
-  },
-  "h (KeyH)": {
-    "1": {
-      "PRESS": "h",
-      "REPEAT": "h",
-      "RELEASE": null
-    }
-  },
-  "j (KeyJ)": {
-    "1": {
-      "PRESS": "j",
-      "REPEAT": "j",
-      "RELEASE": null
-    }
-  },
-  "k (KeyK)": {
-    "1": {
-      "PRESS": "k",
-      "REPEAT": "k",
-      "RELEASE": null
-    }
-  },
-  "l (KeyL)": {
-    "1": {
-      "PRESS": "l",
-      "REPEAT": "l",
-      "RELEASE": null
-    }
-  },
-  "\u00f6 (Semicolon)": {
-    "1": {
-      "PRESS": "\u00f6",
-      "REPEAT": "\u00f6",
-      "RELEASE": null
-    }
-  },
-  "\u00e4 (Quote)": {
-    "1": {
-      "PRESS": "\u00e4",
-      "REPEAT": "\u00e4",
-      "RELEASE": null
-    }
-  },
-  "# (Backslash)": {
-    "1": {
-      "PRESS": "#",
-      "REPEAT": "#",
-      "RELEASE": null
-    }
-  },
-  "< (IntlBackslash)": {
-    "1": {
-      "PRESS": "<",
-      "REPEAT": "<",
-      "RELEASE": null
-    }
-  },
-  "y (KeyZ)": {
-    "1": {
-      "PRESS": "y",
-      "REPEAT": "y",
-      "RELEASE": null
-    }
-  },
-  "x (KeyX)": {
-    "1": {
-      "PRESS": "x",
-      "REPEAT": "x",
-      "RELEASE": null
-    }
-  },
-  "c (KeyC)": {
-    "1": {
-      "PRESS": "c",
-      "REPEAT": "c",
-      "RELEASE": null
-    }
-  },
-  "v (KeyV)": {
-    "1": {
-      "PRESS": "v",
-      "REPEAT": "v",
-      "RELEASE": null
-    }
-  },
-  "b (KeyB)": {
-    "1": {
-      "PRESS": "b",
-      "REPEAT": "b",
-      "RELEASE": null
-    }
-  },
-  "n (KeyN)": {
-    "1": {
-      "PRESS": "n",
-      "REPEAT": "n",
-      "RELEASE": null
-    }
-  },
-  "m (KeyM)": {
-    "1": {
-      "PRESS": "m",
-      "REPEAT": "m",
-      "RELEASE": null
-    }
-  },
-  ", (Comma)": {
-    "1": {
-      "PRESS": ",",
-      "REPEAT": ",",
-      "RELEASE": null
-    }
-  },
-  ". (Period)": {
-    "1": {
-      "PRESS": ".",
-      "REPEAT": ".",
-      "RELEASE": null
-    }
-  },
-  "- (Slash)": {
-    "1": {
-      "PRESS": "-",
-      "REPEAT": "-",
-      "RELEASE": null
-    }
-  },
-  "ArrowLeft": {
-    "1": {
-      "PRESS": "\u001b[D",
-      "REPEAT": "\u001b[D",
-      "RELEASE": null
-    }
-  },
-  "ArrowUp": {
-    "1": {
-      "PRESS": "\u001b[A",
-      "REPEAT": "\u001b[A",
-      "RELEASE": null
-    }
-  },
-  "ArrowRight": {
-    "1": {
-      "PRESS": "\u001b[C",
-      "REPEAT": "\u001b[C",
-      "RELEASE": null
-    }
-  },
-  "ArrowDown": {
-    "1": {
-      "PRESS": "\u001b[B",
-      "REPEAT": "\u001b[B",
-      "RELEASE": null
-    }
-  },
-  "/ (NumpadDivide)": {
-    "1": {
-      "PRESS": "/",
-      "REPEAT": "/",
-      "RELEASE": null
-    }
-  },
-  "* (NumpadMultiply)": {
-    "1": {
-      "PRESS": "*",
-      "REPEAT": "*",
-      "RELEASE": null
-    }
-  },
-  "- (NumpadSubtract)": {
-    "1": {
-      "PRESS": "-",
-      "REPEAT": "-",
-      "RELEASE": null
-    }
-  },
-  "Home (Numpad7)": {
-    "1": {
-      "PRESS": "\u001b[57423u",
-      "REPEAT": "\u001b[57423u",
-      "RELEASE": null
-    }
-  },
-  "ArrowUp (Numpad8)": {
-    "1": {
-      "PRESS": "\u001b[57419u",
-      "REPEAT": "\u001b[57419u",
-      "RELEASE": null
-    }
-  },
-  "PageUp (Numpad9)": {
-    "1": {
-      "PRESS": "\u001b[57421u",
-      "REPEAT": "\u001b[57421u",
-      "RELEASE": null
-    }
-  },
-  "+ (NumpadAdd)": {
-    "1": {
-      "PRESS": "+",
-      "REPEAT": "+",
-      "RELEASE": null
-    }
-  },
-  "ArrowLeft (Numpad4)": {
-    "1": {
-      "PRESS": "\u001b[57417u",
-      "REPEAT": "\u001b[57417u",
-      "RELEASE": null
-    }
-  },
-  "Clear (Numpad5)": {
-    "1": {
-      "PRESS": "\u001b[E",
-      "REPEAT": "\u001b[E",
-      "RELEASE": null
-    }
-  },
-  "ArrowRight (Numpad6)": {
-    "1": {
-      "PRESS": "\u001b[57418u",
-      "REPEAT": "\u001b[57418u",
-      "RELEASE": null
-    }
-  },
-  "End (Numpad1)": {
-    "1": {
-      "PRESS": "\u001b[57424u",
-      "REPEAT": "\u001b[57424u",
-      "RELEASE": null
-    }
-  },
-  "ArrowDown (Numpad2)": {
-    "1": {
-      "PRESS": "\u001b[57420u",
-      "REPEAT": "\u001b[57420u",
-      "RELEASE": null
-    }
-  },
-  "PageDown (Numpad3)": {
-    "1": {
-      "PRESS": "\u001b[57422u",
-      "REPEAT": "\u001b[57422u",
-      "RELEASE": null
-    }
-  },
-  "Enter (NumpadEnter)": {
-    "1": {
-      "PRESS": "\u001b[57414u",
-      "REPEAT": "\u001b[57414u",
-      "RELEASE": null
-    }
-  },
-  "Insert (Numpad0)": {
-    "1": {
-      "PRESS": "\u001b[57425u",
-      "REPEAT": "\u001b[57425u",
-      "RELEASE": null
-    }
-  },
-  "\u0000 (NumpadDecimal)": {
-    "1": {
-      "PRESS": "\u001b[57426u",
-      "REPEAT": "\u001b[57426u",
-      "RELEASE": null
-    }
-  },
-  "Numlock": {
-    "1": {
-      "PRESS": null,
-      "REPEAT": null,
-      "RELEASE": null
-    }
-  },
-  "CapsLock": {
-    "1": {
-      "PRESS": null,
-      "REPEAT": null,
-      "RELEASE": null
-    }
-  },
-  "Shift (ShiftLeft)": {
-    "1": {
-      "PRESS": null,
-      "REPEAT": null,
-      "RELEASE": null
-    }
-  },
-  "Shift (ShiftRight)": {
-    "1": {
-      "PRESS": null,
-      "REPEAT": null,
-      "RELEASE": null
-    }
-  },
-  "Control (ControlLeft)": {
-    "1": {
-      "PRESS": null,
-      "REPEAT": null,
-      "RELEASE": null
-    }
-  },
-  "Meta (MetaLeft)": {
-    "1": {
-      "PRESS": null,
-      "REPEAT": null,
-      "RELEASE": null
-    }
-  },
-  "Alt (AltLeft)": {
-    "1": {
-      "PRESS": null,
-      "REPEAT": null,
-      "RELEASE": null
-    }
-  },
-  "  (Space)": {
-    "1": {
-      "PRESS": " ",
-      "REPEAT": " ",
-      "RELEASE": null
-    }
-  },
-  "AltGraph (AltRight)": {
-    "1": {
-      "PRESS": null,
-      "REPEAT": null,
-      "RELEASE": null
-    }
-  },
-  "Control (ControlRight)": {
-    "1": {
-      "PRESS": null,
-      "REPEAT": null,
-      "RELEASE": null
-    }
-  }
-}

fixtures/kitty_keyboard/german_qwertz_shift.json

@@ -1,331 +0,0 @@
-{
-  "Escape +Shift": {
-    "1": {
-      "PRESS": "\u001b[27;2u",
-      "REPEAT": "\u001b[27;2u",
-      "RELEASE": null
-    }
-  },
-  "F1 +Shift": {
-    "1": {
-      "PRESS": "\u001b[1;2P",
-      "REPEAT": "\u001b[1;2P",
-      "RELEASE": null
-    }
-  },
-  "Delete +Shift": {
-    "1": {
-      "PRESS": "\u001b[3;2~",
-      "REPEAT": "\u001b[3;2~",
-      "RELEASE": null
-    }
-  },
-  "PageUp +Shift": {
-    "1": {
-      "PRESS": "\u001b[5;2~",
-      "REPEAT": "\u001b[5;2~",
-      "RELEASE": null
-    }
-  },
-  "Dead (Backquote) +Shift": {
-    "1": {
-      "PRESS": "\u00b0",
-      "REPEAT": "\u00b0",
-      "RELEASE": null
-    }
-  },
-  "! (Digit1) +Shift": {
-    "1": {
-      "PRESS": "!",
-      "REPEAT": "!",
-      "RELEASE": null
-    }
-  },
-  "\" (Digit2) +Shift": {
-    "1": {
-      "PRESS": "\"",
-      "REPEAT": "\"",
-      "RELEASE": null
-    }
-  },
-  "\u00a7 (Digit3) +Shift": {
-    "1": {
-      "PRESS": "\u00a7",
-      "REPEAT": "\u00a7",
-      "RELEASE": null
-    }
-  },
-  "$ (Digit4) +Shifft": {
-    "1": {
-      "PRESS": "$",
-      "REPEAT": "$",
-      "RELEASE": null
-    }
-  },
-  "% (Digit5) +Shift": {
-    "1": {
-      "PRESS": "%",
-      "REPEAT": "%",
-      "RELEASE": null
-    }
-  },
-  "& (Digit6) +Shift": {
-    "1": {
-      "PRESS": "&",
-      "REPEAT": "&",
-      "RELEASE": null
-    }
-  },
-  "/ (Digit7) +Shift": {
-    "1": {
-      "PRESS": "/",
-      "REPEAT": "/",
-      "RELEASE": null
-    }
-  },
-  "( (Digit8) +Shift": {
-    "1": {
-      "PRESS": "(",
-      "REPEAT": "(",
-      "RELEASE": null
-    }
-  },
-  ") (Digit9) +Shift": {
-    "1": {
-      "PRESS": ")",
-      "REPEAT": ")",
-      "RELEASE": null
-    }
-  },
-  "= (Digit0) +Shift": {
-    "1": {
-      "PRESS": "=",
-      "REPEAT": "=",
-      "RELEASE": null
-    }
-  },
-  "? (Minus) +Shift": {
-    "1": {
-      "PRESS": "?",
-      "REPEAT": "?",
-      "RELEASE": null
-    }
-  },
-  "Backspace +Shift": {
-    "1": {
-      "PRESS": "\u001b[127;2u",
-      "REPEAT": "\u001b[127;2u",
-      "RELEASE": null
-    }
-  },
-  "Tab +Shift": {
-    "1": {
-      "PRESS": "\u001b[9;2u",
-      "REPEAT": "\u001b[9;2u",
-      "RELEASE": null
-    }
-  },
-  "Q (KeyQ) +Shift": {
-    "1": {
-      "PRESS": "Q",
-      "REPEAT": "Q",
-      "RELEASE": null
-    }
-  },
-  "\u00dc (BracketLeft) +Shift": {
-    "1": {
-      "PRESS": "\u00dc",
-      "REPEAT": "\u00dc",
-      "RELEASE": null
-    }
-  },
-  "* (BracketRight) +Shift": {
-    "1": {
-      "PRESS": "*",
-      "REPEAT": "*",
-      "RELEASE": null
-    }
-  },
-  "Enter +Shift": {
-    "1": {
-      "PRESS": "\u001b[13;2u",
-      "REPEAT": "\u001b[13;2u",
-      "RELEASE": null
-    }
-  },
-  "\u00d6 (Semicolon) +Shift": {
-    "1": {
-      "PRESS": "\u00d6",
-      "REPEAT": "\u00d6",
-      "RELEASE": null
-    }
-  },
-  "\u00c4 (Quote) +Shift": {
-    "1": {
-      "PRESS": "\u00c4",
-      "REPEAT": "\u00c4",
-      "RELEASE": null
-    }
-  },
-  "' (Backslash) +Shift": {
-    "1": {
-      "PRESS": "'",
-      "REPEAT": "'",
-      "RELEASE": null
-    }
-  },
-  "> (IntlBackslash) +Shift": {
-    "1": {
-      "PRESS": ">",
-      "REPEAT": ">",
-      "RELEASE": null
-    }
-  },
-  "; (Comma) +Shift": {
-    "1": {
-      "PRESS": ";",
-      "REPEAT": ";",
-      "RELEASE": null
-    }
-  },
-  ": (Period) +Shift": {
-    "1": {
-      "PRESS": ":",
-      "REPEAT": ":",
-      "RELEASE": null
-    }
-  },
-  "_ (Slash) +Shift": {
-    "1": {
-      "PRESS": "_",
-      "REPEAT": "_",
-      "RELEASE": null
-    }
-  },
-  "ArrowUp +Shift": {
-    "1": {
-      "PRESS": "\u001b[1;2A",
-      "REPEAT": "\u001b[1;2A",
-      "RELEASE": null
-    }
-  },
-  "PageDown +Shift": {
-    "1": {
-      "PRESS": "\u001b[6;2~",
-      "REPEAT": "\u001b[6;2~",
-      "RELEASE": null
-    }
-  },
-  "Home +Shift": {
-    "1": {
-      "PRESS": "\u001b[1;2H",
-      "REPEAT": "\u001b[1;2H",
-      "RELEASE": null
-    }
-  },
-  "Home (Numpad7) +Shift": {
-    "1": {
-      "PRESS": "\u001b[57423;2u",
-      "REPEAT": "\u001b[57423;2u",
-      "RELEASE": null
-    }
-  },
-  "ArrowUp (Numapd8) +Shift": {
-    "1": {
-      "PRESS": "\u001b[57419;2u",
-      "REPEAT": "\u001b[57419;2u",
-      "RELEASE": null
-    }
-  },
-  "Clear (Numpad5) +Shift": {
-    "1": {
-      "PRESS": "\u001b[1;2E",
-      "REPEAT": "\u001b[1;2E",
-      "RELEASE": null
-    }
-  },
-  "Enter (NumpadEnter) +Shift": {
-    "1": {
-      "PRESS": "\u001b[57414;2u",
-      "REPEAT": "\u001b[57414;2u",
-      "RELEASE": null
-    }
-  },
-  "Insert (Numpad0) +Shift": {
-    "1": {
-      "PRESS": "\u001b[57425;2u",
-      "REPEAT": "\u001b[57425;2u",
-      "RELEASE": null
-    }
-  },
-  "\u0000 (NumpadDecimal) +Shift": {
-    "1": {
-      "PRESS": "\u001b[57426;2u",
-      "REPEAT": "\u001b[57426;2u",
-      "RELEASE": null
-    }
-  },
-  "Numlock +Shift": {
-    "1": {
-      "PRESS": null,
-      "REPEAT": null,
-      "RELEASE": null
-    }
-  },
-  "CapsLock +Shift": {
-    "1": {
-      "PRESS": null,
-      "REPEAT": null,
-      "RELEASE": null
-    }
-  },
-  "Shift (ShiftRight) +Shift": {
-    "1": {
-      "PRESS": null,
-      "REPEAT": null,
-      "RELEASE": null
-    }
-  },
-  "Control (ControlLeft) +Shift": {
-    "1": {
-      "PRESS": null,
-      "REPEAT": null,
-      "RELEASE": null
-    }
-  },
-  "Meta (MetaLeft) +Shift": {
-    "1": {
-      "PRESS": null,
-      "REPEAT": null,
-      "RELEASE": null
-    }
-  },
-  "Alt (AltLeft) +Shift": {
-    "1": {
-      "PRESS": null,
-      "REPEAT": null,
-      "RELEASE": null
-    }
-  },
-  "  (Space) +Shift": {
-    "1": {
-      "PRESS": " ",
-      "REPEAT": " ",
-      "RELEASE": null
-    }
-  },
-  "AltGraph (AltRight) +Shift": {
-    "1": {
-      "PRESS": null,
-      "REPEAT": null,
-      "RELEASE": null
-    }
-  },
-  "Control (ControlRight) +Shift": {
-    "1": {
-      "PRESS": null,
-      "REPEAT": null,
-      "RELEASE": null
-    }
-  }
-}

package.json

@@ -56,7 +56,6 @@
     "test-unit": "node ./bin/test_unit.js",
     "test-unit-slow-tests": "npm run test-unit | grep \"ms)\"",
     "test-unit-coverage": "node ./bin/test_unit.js --coverage",
-    "test-unit-dev": "cross-env NODE_PATH='./out' mocha",
     "test-integration": "node ./bin/test_integration.js --workers=75%",
     "test-integration-chromium": "node ./bin/test_integration.js --workers=75% \"--project=Chromium\"",
     "test-integration-firefox": "node ./bin/test_integration.js --workers=75% \"--project=FirefoxStable\"",
@@ -80,15 +79,11 @@
     "@playwright/test": "^1.57.0",
     "@stylistic/eslint-plugin": "^4.4.1",
     "@types/chai": "^4.2.22",
-    "@types/debug": "^4.1.7",
-    "@types/deep-equal": "^1.0.1",
     "@types/express": "4",
     "@types/express-ws": "^3.0.1",
     "@types/jsdom": "^27.0.0",
     "@types/mocha": "^9.0.0",
     "@types/node": "^22.19.3",
-    "@types/trusted-types": "^1.0.6",
-    "@types/utf8": "^3.0.0",
     "@types/webpack": "^5.28.0",
     "@types/ws": "^8.2.0",
     "@typescript-eslint/eslint-plugin": "^8.50.1",
@@ -96,8 +91,6 @@
     "@typescript/native-preview": "^7.0.0-dev.20260213.1",
     "chai": "^4.3.4",
     "concurrently": "^9.1.2",
-    "cross-env": "^7.0.3",
-    "deep-equal": "^2.0.5",
     "esbuild": "~0.25.2",
     "eslint": "^9.39.2",
     "eslint-plugin-jsdoc": "^50.8.0",
@@ -113,7 +106,6 @@
     "ts-loader": "^9.3.1",
     "typescript": "^5.9.3",
     "typescript-eslint": "^8.50.1",
-    "utf8": "^3.0.0",
     "webpack": "^5.61.0",
     "webpack-cli": "^4.9.1",
     "ws": "^8.2.3",

src/browser/CoreBrowserTerminal.ts

@@ -563,8 +563,9 @@ export class CoreBrowserTerminal extends CoreTerminal implements ITerminal {
 
     try {
       this._onWillOpen.fire(this.element);
+    } catch (e) {
+      this._logService.error('onWillOpen handler threw an exception', e);
     }
-    catch { /* fails to load addon for some reason */ }
     if (!this._renderService.hasRenderer()) {
       this._renderService.setRenderer(this._createRenderer());
     }
@@ -767,7 +768,12 @@ export class CoreBrowserTerminal extends CoreTerminal implements ITerminal {
     return this.buffer.markers;
   }
 
-  public registerMarker(cursorYOffset: number): IMarker {
+  public registerMarker(cursorYOffset: number): IMarker | undefined {
+    // Disallow markers on the alt buffer
+    if (this.buffer !== this.buffers.normal) {
+      return;
+    }
+
     return this.buffer.addMarker(this.buffer.ybase + this.buffer.y + cursorYOffset);
   }
 

src/browser/Linkifier.test.ts

@@ -43,6 +43,20 @@ describe('Linkifier2', () => {
     },
     activate: () => { }
   };
+  const multiLineLink: ILink = {
+    text: 'foo',
+    range: {
+      start: {
+        x: 2,
+        y: 1
+      },
+      end: {
+        x: 4,
+        y: 2
+      }
+    },
+    activate: () => { }
+  };
 
   beforeEach(() => {
     const dom = new jsdom.JSDOM();
@@ -86,4 +100,30 @@ describe('Linkifier2', () => {
     linkifier.linkLeave({ classList: { add: () => { } } } as any, link, {} as any);
   });
 
+  it('onShowLinkUnderline event range is correct for wrapped links', done => {
+    linkifier.onShowLinkUnderline(e => {
+      assert.equal(multiLineLink.range.start.x - 1, e.x1);
+      assert.equal(multiLineLink.range.start.y - 1, e.y1);
+      assert.equal(multiLineLink.range.end.x, e.x2);
+      assert.equal(multiLineLink.range.end.y - 1, e.y2);
+
+      done();
+    });
+
+    linkifier.linkHover({ classList: { add: () => { } } } as any, multiLineLink, {} as any);
+  });
+
+  it('onHideLinkUnderline event range is correct for wrapped links', done => {
+    linkifier.onHideLinkUnderline(e => {
+      assert.equal(multiLineLink.range.start.x - 1, e.x1);
+      assert.equal(multiLineLink.range.start.y - 1, e.y1);
+      assert.equal(multiLineLink.range.end.x, e.x2);
+      assert.equal(multiLineLink.range.end.y - 1, e.y2);
+
+      done();
+    });
+
+    linkifier.linkLeave({ classList: { add: () => { } } } as any, multiLineLink, {} as any);
+  });
+
 });

src/browser/OscLinkProvider.test.ts

@@ -0,0 +1,105 @@
+/**
+ * Copyright (c) 2026 The xterm.js authors. All rights reserved.
+ * @license MIT
+ */
+
+import { assert } from 'chai';
+import { OscLinkProvider } from 'browser/OscLinkProvider';
+import { ILink } from 'browser/Types';
+import { createCellData, MockBufferService, MockOptionsService } from 'common/TestUtils.test';
+import { IBufferService, IOscLinkService } from 'common/services/Services';
+import { IBufferLine, IOscLinkData } from 'common/Types';
+
+class TestOscLinkService implements IOscLinkService {
+  public serviceBrand: any;
+  public registerLink(_linkData: IOscLinkData): number { return 0; }
+  public addLineToLink(_linkId: number, _y: number): void { }
+  public getLinkData(linkId: number): IOscLinkData | undefined {
+    return { uri: `https://example.com/${linkId}` };
+  }
+}
+
+function setText(line: IBufferLine | undefined, x: number, text: string): void {
+  if (!line) {
+    throw new Error('Missing buffer line');
+  }
+  for (let i = 0; i < text.length; i++) {
+    line.setCell(x + i, createCellData(0, text[i], 1));
+  }
+}
+
+function setUrl(line: IBufferLine | undefined, x: number, text: string, linkId: number): void {
+  if (!line) {
+    throw new Error('Missing buffer line');
+  }
+  for (let i = 0; i < text.length; i++) {
+    const cell = createCellData(0, text[i], 1);
+    cell.extended.urlId = linkId;
+    cell.updateExtended();
+    line.setCell(x + i, cell);
+  }
+}
+
+function getLinks(provider: OscLinkProvider, y: number): Promise<ILink[]> {
+  return new Promise(resolve => provider.provideLinks(y, links => resolve(links ?? [])));
+}
+
+describe('OscLinkProvider', () => {
+  let bufferService: IBufferService;
+  let provider: OscLinkProvider;
+
+  beforeEach(() => {
+    const optionsService = new MockOptionsService();
+    bufferService = new MockBufferService(5, 5, optionsService);
+    provider = new OscLinkProvider(bufferService, optionsService, new TestOscLinkService());
+  });
+
+  it('expands a wrapped link range backward to the previous line', async () => {
+    const line1 = bufferService.buffer.lines.get(0);
+    const line2 = bufferService.buffer.lines.get(1);
+    setText(line1, 0, 'aa');
+    setUrl(line1, 2, 'bbb', 1);
+    setUrl(line2, 0, 'cccc', 1);
+    setText(line2, 4, 'x');
+    line2!.isWrapped = true;
+
+    const links = await getLinks(provider, 2);
+    assert.lengthOf(links, 1);
+    assert.deepEqual(links[0].range, {
+      start: { x: 3, y: 1 },
+      end: { x: 4, y: 2 }
+    });
+  });
+
+  it('expands a wrapped link range forward when a link ends at line boundary', async () => {
+    const line1 = bufferService.buffer.lines.get(0);
+    const line2 = bufferService.buffer.lines.get(1);
+    setUrl(line1, 0, 'aaaaa', 1);
+    setUrl(line2, 0, 'bb', 1);
+    setText(line2, 2, 'ccc');
+    line2!.isWrapped = true;
+
+    const links = await getLinks(provider, 1);
+    assert.lengthOf(links, 1);
+    assert.deepEqual(links[0].range, {
+      start: { x: 1, y: 1 },
+      end: { x: 2, y: 2 }
+    });
+  });
+
+  it('does not merge wrapped links with different url ids', async () => {
+    const line1 = bufferService.buffer.lines.get(0);
+    const line2 = bufferService.buffer.lines.get(1);
+    setUrl(line1, 0, 'aaaaa', 1);
+    setUrl(line2, 0, 'bbb', 2);
+    setText(line2, 3, 'cc');
+    line2!.isWrapped = true;
+
+    const links = await getLinks(provider, 1);
+    assert.lengthOf(links, 1);
+    assert.deepEqual(links[0].range, {
+      start: { x: 1, y: 1 },
+      end: { x: 5, y: 1 }
+    });
+  });
+});

src/browser/OscLinkProvider.ts

@@ -6,6 +6,7 @@
 import { IBufferRange, ILink } from 'browser/Types';
 import { ILinkProvider } from 'browser/services/Services';
 import { CellData } from 'common/buffer/CellData';
+import { IBufferLine } from 'common/Types';
 import { IBufferService, IOptionsService, IOscLinkService } from 'common/services/Services';
 
 export class OscLinkProvider implements ILinkProvider {
@@ -57,19 +58,8 @@ export class OscLinkProvider implements ILinkProvider {
       if (finishLink || (currentStart !== -1 && x === lineLength - 1)) {
         const text = this._oscLinkService.getLinkData(currentLinkId)?.uri;
         if (text) {
-          // These ranges are 1-based
-          const range: IBufferRange = {
-            start: {
-              x: currentStart + 1,
-              y
-            },
-            end: {
-              // Offset end x if it's a link that ends on the last cell in the line
-              x: x + (!finishLink && x === lineLength - 1 ? 1 : 0),
-              y
-            }
-          };
-
+          const endX = x + (!finishLink && x === lineLength - 1 ? 1 : 0);
+          const range = this._getRangeWithLineWrap(y, currentStart, endX, currentLinkId);
           let ignoreLink = false;
           if (!linkHandler?.allowNonHttpProtocols) {
             try {
@@ -111,6 +101,82 @@ export class OscLinkProvider implements ILinkProvider {
     //       id
     callback(result);
   }
+
+  /**
+   * Expand a single-line OSC 8 range to a contiguous wrapped range for the same link id.
+   */
+  private _getRangeWithLineWrap(y: number, startX: number, endX: number, linkId: number): IBufferRange {
+    let startY = y;
+    let finalStartX = startX;
+    let endY = y;
+    let finalEndX = endX;
+
+    // Expand upward only when this segment starts at column 0 and the current line is wrapped.
+    while (finalStartX === 0) {
+      const currentLine = this._bufferService.buffer.lines.get(startY - 1);
+      if (!currentLine?.isWrapped) {
+        break;
+      }
+      const previousLine = this._bufferService.buffer.lines.get(startY - 2);
+      if (!previousLine) {
+        break;
+      }
+      const previousLineLength = previousLine.getTrimmedLength();
+      if (previousLineLength === 0 || !this._hasUrlId(previousLine, previousLineLength - 1, linkId)) {
+        break;
+      }
+      let previousStartX = previousLineLength - 1;
+      while (previousStartX > 0 && this._hasUrlId(previousLine, previousStartX - 1, linkId)) {
+        previousStartX--;
+      }
+      startY--;
+      finalStartX = previousStartX;
+    }
+
+    // Expand downward only when this segment reaches trimmed EOL and the next line is wrapped.
+    while (true) {
+      const currentLine = this._bufferService.buffer.lines.get(endY - 1);
+      if (!currentLine) {
+        break;
+      }
+      const currentLineLength = currentLine.getTrimmedLength();
+      if (finalEndX !== currentLineLength) {
+        break;
+      }
+      const nextLine = this._bufferService.buffer.lines.get(endY);
+      if (!nextLine?.isWrapped) {
+        break;
+      }
+      const nextLineLength = nextLine.getTrimmedLength();
+      if (nextLineLength === 0 || !this._hasUrlId(nextLine, 0, linkId)) {
+        break;
+      }
+      let nextEndX = 1;
+      while (nextEndX < nextLineLength && this._hasUrlId(nextLine, nextEndX, linkId)) {
+        nextEndX++;
+      }
+      endY++;
+      finalEndX = nextEndX;
+    }
+
+    // IBufferRange uses 1-based coordinates.
+    return {
+      start: {
+        x: finalStartX + 1,
+        y: startY
+      },
+      end: {
+        x: finalEndX,
+        y: endY
+      }
+    };
+  }
+
+  private _hasUrlId(line: IBufferLine, x: number, linkId: number): boolean {
+    const cell = this._workCell;
+    line.loadCell(x, cell);
+    return !!cell.hasExtendedAttrs() && cell.extended.urlId === linkId;
+  }
 }
 
 function defaultActivate(e: MouseEvent, uri: string): void {

src/browser/Terminal.test.ts

@@ -1146,6 +1146,16 @@ describe('Terminal', () => {
     assert.equal(termConverting.buffer.lines.get(1)!.translateToString(true), 'World');
   });
 
+  describe('registerMarker', () => {
+    it('should return undefined on the alt buffer', async () => {
+      assert.isDefined(term.registerMarker(0));
+      await term.writeP('\x1b[?47h');
+      assert.isUndefined(term.registerMarker(0));
+      await term.writeP('\x1b[?47l');
+      assert.isDefined(term.registerMarker(0));
+    });
+  });
+
   // FIXME: move to common/CoreTerminal.test once the trimming is moved over
   describe('marker lifecycle', () => {
     // create a 10x5 terminal with markers on every line

src/browser/public/Terminal.ts

@@ -166,7 +166,7 @@ export class Terminal extends Disposable implements ITerminalApi {
   public deregisterCharacterJoiner(joinerId: number): void {
     this._core.deregisterCharacterJoiner(joinerId);
   }
-  public registerMarker(cursorYOffset: number = 0): IMarker {
+  public registerMarker(cursorYOffset: number = 0): IMarker | undefined {
     this._verifyIntegers(cursorYOffset);
     return this._core.registerMarker(cursorYOffset);
   }

src/browser/services/MouseCoordsService.ts

@@ -18,7 +18,7 @@ export class MouseCoordsService implements IMouseCoordsService {
 
   public getCoords(event: {clientX: number, clientY: number}, element: HTMLElement, colCount: number, rowCount: number, isSelection?: boolean): [number, number] | undefined {
     return getCoords(
-      window,
+      getWindow(element),
       event,
       element,
       colCount,

src/browser/services/RenderService.ts

@@ -29,6 +29,7 @@ export class RenderService extends Disposable implements IRenderService {
   private _renderDebouncer: IRenderDebouncerWithCallback;
   private _pausedResizeTask: DebouncedIdleTask;
   private _observerDisposable = this._register(new MutableDisposable());
+  private _intersectionObserver: IntersectionObserver | undefined;
 
   private _isPaused: boolean = false;
   private _needsFullRefresh: boolean = false;
@@ -127,8 +128,12 @@ export class RenderService extends Disposable implements IRenderService {
     // and resume based on terminal visibility if so
     if ('IntersectionObserver' in w) {
       const observer = new w.IntersectionObserver(e => this._handleIntersectionChange(e[e.length - 1]), { threshold: 0 });
+      this._observerDisposable.value = toDisposable(() => {
+        this._intersectionObserver?.disconnect();
+        this._intersectionObserver = undefined;
+      });
+      this._intersectionObserver = observer;
       observer.observe(screenElement);
-      this._observerDisposable.value = toDisposable(() => observer.disconnect());
     }
   }
 

src/browser/services/SelectionService.ts

@@ -9,7 +9,7 @@ import { moveToCellSequence } from 'browser/input/MoveToCell';
 import { SelectionModel } from 'browser/selection/SelectionModel';
 import { ISelectionRedrawRequestEvent, ISelectionRequestScrollLinesEvent } from 'browser/selection/Types';
 import { ICoreBrowserService, IMouseCoordsService, IRenderService, ISelectionService } from 'browser/services/Services';
-import { Disposable, toDisposable } from 'common/Lifecycle';
+import { Disposable, MutableDisposable, toDisposable } from 'common/Lifecycle';
 import * as Browser from 'common/Platform';
 import { IBufferLine, ICellData, IDisposable } from 'common/Types';
 import { getRangeLength } from 'common/buffer/BufferRange';
@@ -102,7 +102,7 @@ export class SelectionService extends Disposable implements ISelectionService {
 
   private _mouseMoveListener: EventListener;
   private _mouseUpListener: EventListener;
-  private _trimListener: IDisposable;
+  private readonly _trimListener = this._register(new MutableDisposable<IDisposable>());
   private _workCell: CellData = new CellData();
 
   private _mouseDownTimeStamp: number = 0;
@@ -140,7 +140,7 @@ export class SelectionService extends Disposable implements ISelectionService {
         this.clearSelection();
       }
     });
-    this._trimListener = this._bufferService.buffer.lines.onTrim(amount => this._handleTrim(amount));
+    this._trimListener.value = this._bufferService.buffer.lines.onTrim(amount => this._handleTrim(amount));
     this._register(this._bufferService.buffers.onBufferActivate(e => this._handleBufferActivate(e)));
 
     this.enable();
@@ -769,8 +769,7 @@ export class SelectionService extends Disposable implements ISelectionService {
     // reverseIndex) and delete in a splice is only ever used when the same
     // number of elements was just added. Given this is could actually be
     // beneficial to leave the selection as is for these cases.
-    this._trimListener.dispose();
-    this._trimListener = e.activeBuffer.lines.onTrim(amount => this._handleTrim(amount));
+    this._trimListener.value = e.activeBuffer.lines.onTrim(amount => this._handleTrim(amount));
   }
 
   /**

src/common/Async.ts

@@ -73,6 +73,42 @@ export class TimeoutTimer implements IDisposable {
   }
 }
 
+/**
+ * Schedules a single runner on the microtask queue. Unlike {@link TimeoutTimer}, a scheduled
+ * microtask cannot be unqueued; {@link cancel} prevents the runner from executing if it has not
+ * run yet.
+ */
+export class MicrotaskTimer implements IDisposable {
+  private _isScheduled = false;
+  private _isDisposed = false;
+
+  public dispose(): void {
+    this.cancel();
+    this._isDisposed = true;
+  }
+
+  public cancel(): void {
+    this._isScheduled = false;
+  }
+
+  public set(runner: () => void): void {
+    if (this._isDisposed) {
+      throw new Error('Calling set on a disposed MicrotaskTimer');
+    }
+    if (this._isScheduled) {
+      return;
+    }
+    this._isScheduled = true;
+    queueMicrotask(() => {
+      if (!this._isScheduled) {
+        return;
+      }
+      this._isScheduled = false;
+      runner();
+    });
+  }
+}
+
 export class IntervalTimer implements IDisposable {
   private _disposable: IDisposable | undefined;
   private _isDisposed = false;

src/common/Clone.test.ts

@@ -1,129 +0,0 @@
-/**
- * Copyright (c) 2016 The xterm.js authors. All rights reserved.
- * @license MIT
- */
-
-import { assert } from 'chai';
-import { clone } from 'common/Clone';
-
-describe('clone', () => {
-  it('should clone simple objects', () => {
-    const test = {
-      a: 1,
-      b: 2
-    };
-
-    assert.deepEqual(clone(test), { a: 1, b: 2 });
-  });
-
-  it('should clone nested objects', () => {
-    const test = {
-      bar: {
-        a: 1,
-        b: 2,
-        c: {
-          foo: 'bar'
-        }
-      }
-    };
-
-    assert.deepEqual(clone(test), {
-      bar: {
-        a: 1,
-        b: 2,
-        c: {
-          foo: 'bar'
-        }
-      }
-    });
-  });
-
-  it('should clone array values', () => {
-    const test = {
-      a: [1, 2, 3],
-      b: [1, null, 'test', { foo: 'bar' }]
-    };
-
-    assert.deepEqual(clone(test), {
-      a: [1, 2, 3],
-      b: [1, null, 'test', { foo: 'bar' }]
-    });
-  });
-
-  it('should stop mutation from occuring on the original object', () => {
-    const test = {
-      a: 1,
-      b: 2,
-      c: {
-        foo: 'bar'
-      }
-    };
-
-    const cloned = clone(test);
-
-    test.a = 5;
-    test.c.foo = 'barbaz';
-
-    assert.deepEqual(cloned, {
-      a: 1,
-      b: 2,
-      c: {
-        foo: 'bar'
-      }
-    });
-  });
-
-  it('should clone to a maximum depth of 5 by default', () => {
-    const test = {
-      a: {
-        b: {
-          c: {
-            d: {
-              e: {
-                f: 'foo'
-              }
-            }
-          }
-        }
-      }
-    };
-
-    const cloned = clone(test);
-
-    test.a.b.c.d.e.f = 'bar';
-
-    // The values at a greater depth then 5 should not be cloned
-    assert.equal((cloned as any).a.b.c.d.e.f, 'bar');
-  });
-
-  it('should allow an optional maximum depth to be set', () => {
-    const test = {
-      a: {
-        b: {
-          c: 'foo'
-        }
-      }
-    };
-
-    const cloned = clone(test, 2);
-
-    test.a.b.c = 'bar';
-
-    // The values at a greater depth then 2 should not be cloned
-    assert.equal((cloned as any).a.b.c, 'bar');
-  });
-
-  it('should not throw when cloning a recursive reference', () => {
-    const test = {
-      a: {
-        b: {
-          c: {}
-        }
-      }
-    };
-
-    test.a.b.c = test;
-
-    assert.doesNotThrow(() => clone(test));
-  });
-});

src/common/Clone.ts

@@ -1,23 +0,0 @@
-/**
- * Copyright (c) 2016 The xterm.js authors. All rights reserved.
- * @license MIT
- */
-
-/*
- * A simple utility for cloning values
- */
-export function clone<T>(val: T, depth: number = 5): T {
-  if (typeof val !== 'object') {
-    return val;
-  }
-
-  // If we're cloning an array, use an array as the base, otherwise use an object
-  const clonedObject: any = Array.isArray(val) ? [] : {};
-
-  for (const key in val) {
-    // Recursively clone eack item unless we're at the maximum depth
-    clonedObject[key] = depth <= 1 ? val[key] : (val[key] && clone(val[key], depth - 1));
-  }
-
-  return clonedObject as T;
-}

src/common/InputHandler.test.ts

@@ -14,7 +14,6 @@ import { Params } from 'common/parser/Params';
 import { MockCoreService, MockBufferService, MockOptionsService, MockLogService, MockMouseStateService, MockCharsetService, MockUnicodeService, MockOscLinkService, extendedAttributes } from 'common/TestUtils.test';
 import { IBufferService, ICoreService, type IOscLinkService } from 'common/services/Services';
 import { DEFAULT_OPTIONS } from 'common/services/OptionsService';
-import { clone } from 'common/Clone';
 import { BufferService } from 'common/services/BufferService';
 import { CoreService } from 'common/services/CoreService';
 import { OscLinkService } from 'common/services/OscLinkService';
@@ -227,32 +226,32 @@ describe('InputHandler', () => {
       assert.equal(coreService.decPrivateModes.cursorStyle, undefined);
       assert.equal(coreService.decPrivateModes.cursorBlink, undefined);
 
-      optionsService.options = clone(DEFAULT_OPTIONS);
+      optionsService.options = structuredClone(DEFAULT_OPTIONS);
       inputHandler.setCursorStyle(Params.fromArray([1]));
       assert.equal(coreService.decPrivateModes.cursorStyle, 'block');
       assert.equal(coreService.decPrivateModes.cursorBlink, true);
 
-      optionsService.options = clone(DEFAULT_OPTIONS);
+      optionsService.options = structuredClone(DEFAULT_OPTIONS);
       inputHandler.setCursorStyle(Params.fromArray([2]));
       assert.equal(coreService.decPrivateModes.cursorStyle, 'block');
       assert.equal(coreService.decPrivateModes.cursorBlink, false);
 
-      optionsService.options = clone(DEFAULT_OPTIONS);
+      optionsService.options = structuredClone(DEFAULT_OPTIONS);
       inputHandler.setCursorStyle(Params.fromArray([3]));
       assert.equal(coreService.decPrivateModes.cursorStyle, 'underline');
       assert.equal(coreService.decPrivateModes.cursorBlink, true);
 
-      optionsService.options = clone(DEFAULT_OPTIONS);
+      optionsService.options = structuredClone(DEFAULT_OPTIONS);
       inputHandler.setCursorStyle(Params.fromArray([4]));
       assert.equal(coreService.decPrivateModes.cursorStyle, 'underline');
       assert.equal(coreService.decPrivateModes.cursorBlink, false);
 
-      optionsService.options = clone(DEFAULT_OPTIONS);
+      optionsService.options = structuredClone(DEFAULT_OPTIONS);
       inputHandler.setCursorStyle(Params.fromArray([5]));
       assert.equal(coreService.decPrivateModes.cursorStyle, 'bar');
       assert.equal(coreService.decPrivateModes.cursorBlink, true);
 
-      optionsService.options = clone(DEFAULT_OPTIONS);
+      optionsService.options = structuredClone(DEFAULT_OPTIONS);
       inputHandler.setCursorStyle(Params.fromArray([6]));
       assert.equal(coreService.decPrivateModes.cursorStyle, 'bar');
       assert.equal(coreService.decPrivateModes.cursorBlink, false);

src/common/InputHandler.ts

@@ -2590,10 +2590,6 @@ export class InputHandler extends Disposable implements IInputHandler {
    * | 3      | CMY color.                                                    | #N      |
    * | 4      | CMYK color.                                                   | #N      |
    * | 5      | Indexed (256 colors) as `Ps ; 5 ; INDEX` or `Ps : 5 : INDEX`. | #Y      |
-   *
-   *
-   * FIXME: blinking is implemented in attrs, but not working in renderers?
-   * FIXME: remove dead branch for p=100
    */
   public charAttributes(params: IParams): boolean {
     // Optimize a single SGR0.

src/common/StringBuilder.test.ts

@@ -0,0 +1,143 @@
+/**
+ * Copyright (c) 2026 The xterm.js authors. All rights reserved.
+ * @license MIT
+ */
+
+import { assert } from 'chai';
+import { LimitedStringBuilder, StringBuilder } from 'common/StringBuilder';
+
+describe('StringBuilder', () => {
+  it('should start empty', () => {
+    const builder = new StringBuilder();
+    assert.strictEqual(builder.length, 0);
+    assert.strictEqual(builder.toString(), '');
+  });
+
+  it('should append a single chunk', () => {
+    const builder = new StringBuilder();
+    builder.append('hello');
+    assert.strictEqual(builder.length, 5);
+    assert.strictEqual(builder.toString(), 'hello');
+  });
+
+  it('should join multiple chunks in order', () => {
+    const builder = new StringBuilder();
+    builder.append('foo');
+    builder.append('bar');
+    builder.append('baz');
+    assert.strictEqual(builder.length, 9);
+    assert.strictEqual(builder.toString(), 'foobarbaz');
+  });
+
+  it('should handle empty chunks', () => {
+    const builder = new StringBuilder();
+    builder.append('');
+    builder.append('a');
+    builder.append('');
+    assert.strictEqual(builder.length, 1);
+    assert.strictEqual(builder.toString(), 'a');
+  });
+
+  it('should reset accumulated data', () => {
+    const builder = new StringBuilder();
+    builder.append('hello');
+    builder.reset();
+    assert.strictEqual(builder.length, 0);
+    assert.strictEqual(builder.toString(), '');
+  });
+
+  it('should allow appending after reset', () => {
+    const builder = new StringBuilder();
+    builder.append('old');
+    builder.reset();
+    builder.append('new');
+    assert.strictEqual(builder.toString(), 'new');
+  });
+
+  it('should accumulate many small chunks without quadratic concatenation', () => {
+    const builder = new StringBuilder();
+    const chunk = 'x';
+    const count = 10000;
+    for (let i = 0; i < count; i++) {
+      builder.append(chunk);
+    }
+    assert.strictEqual(builder.length, count);
+    assert.strictEqual(builder.toString(), 'x'.repeat(count));
+  });
+});
+
+describe('LimitedStringBuilder', () => {
+  it('should expose the configured limit', () => {
+    const builder = new LimitedStringBuilder(42);
+    assert.strictEqual(builder.limit, 42);
+  });
+
+  it('should start empty', () => {
+    const builder = new LimitedStringBuilder(10);
+    assert.strictEqual(builder.length, 0);
+    assert.strictEqual(builder.toString(), '');
+  });
+
+  it('should accept data up to the limit', () => {
+    const builder = new LimitedStringBuilder(10);
+    assert.strictEqual(builder.append('12345'), false);
+    assert.strictEqual(builder.append('67890'), false);
+    assert.strictEqual(builder.length, 10);
+    assert.strictEqual(builder.toString(), '1234567890');
+  });
+
+  it('should accept a single chunk exactly at the limit', () => {
+    const builder = new LimitedStringBuilder(5);
+    assert.strictEqual(builder.append('abcde'), false);
+    assert.strictEqual(builder.length, 5);
+    assert.strictEqual(builder.toString(), 'abcde');
+  });
+
+  it('should reject data exceeding the limit and clear the buffer', () => {
+    const builder = new LimitedStringBuilder(5);
+    builder.append('abc');
+    assert.strictEqual(builder.append('def'), true);
+    assert.strictEqual(builder.length, 0);
+    assert.strictEqual(builder.toString(), '');
+  });
+
+  it('should reject a single chunk larger than the limit', () => {
+    const builder = new LimitedStringBuilder(3);
+    assert.strictEqual(builder.append('toolong'), true);
+    assert.strictEqual(builder.length, 0);
+    assert.strictEqual(builder.toString(), '');
+  });
+
+  it('should allow appending again after reset following a limit breach', () => {
+    const builder = new LimitedStringBuilder(3);
+    assert.strictEqual(builder.append('abcd'), true);
+    builder.reset();
+    assert.strictEqual(builder.append('ab'), false);
+    assert.strictEqual(builder.toString(), 'ab');
+  });
+
+  it('should accumulate many chunks before hitting the limit', () => {
+    const limit = 100;
+    const builder = new LimitedStringBuilder(limit);
+    const chunk = 'A';
+    for (let i = 0; i < limit; i++) {
+      assert.strictEqual(builder.append(chunk), false);
+    }
+    assert.strictEqual(builder.toString(), 'A'.repeat(limit));
+    assert.strictEqual(builder.append('B'), true);
+    assert.strictEqual(builder.toString(), '');
+  });
+
+  it('should reject when limit is zero and any data is appended', () => {
+    const builder = new LimitedStringBuilder(0);
+    assert.strictEqual(builder.append('a'), true);
+    assert.strictEqual(builder.length, 0);
+  });
+
+  it('should allow zero-length appends at the limit', () => {
+    const builder = new LimitedStringBuilder(0);
+    assert.strictEqual(builder.append(''), false);
+    assert.strictEqual(builder.length, 0);
+    assert.strictEqual(builder.toString(), '');
+  });
+});

src/common/StringBuilder.ts

@@ -0,0 +1,67 @@
+/**
+ * Copyright (c) 2026 The xterm.js authors. All rights reserved.
+ * @license MIT
+ */
+
+/**
+ * Accumulates string data from multiple chunks without O(n²) string concatenation.
+ */
+export class StringBuilder {
+  private _chunks: string[] = [];
+  private _length = 0;
+
+  public get length(): number {
+    return this._length;
+  }
+
+  public reset(): void {
+    this._chunks.length = 0;
+    this._length = 0;
+  }
+
+  public append(chunk: string): void {
+    this._chunks.push(chunk);
+    this._length += chunk.length;
+  }
+
+  public toString(): string {
+    return this._chunks.join('');
+  }
+}
+
+/**
+ * String builder that rejects payloads larger than a fixed limit.
+ */
+export class LimitedStringBuilder {
+  private readonly _builder = new StringBuilder();
+
+  constructor(private readonly _limit: number) { }
+
+  public get length(): number {
+    return this._builder.length;
+  }
+
+  public get limit(): number {
+    return this._limit;
+  }
+
+  public reset(): void {
+    this._builder.reset();
+  }
+
+  /**
+   * @returns true if the limit was exceeded (buffer is cleared in that case)
+   */
+  public append(chunk: string): boolean {
+    this._builder.append(chunk);
+    if (this._builder.length > this._limit) {
+      this._builder.reset();
+      return true;
+    }
+    return false;
+  }
+
+  public toString(): string {
+    return this._builder.toString();
+  }
+}

src/common/TestUtils.test.ts

@@ -5,7 +5,6 @@
 
 import { IBufferService, ICoreService, ILogService, IOptionsService, ITerminalOptions, IMouseStateService, ICharsetService, UnicodeCharProperties, UnicodeCharWidth, IUnicodeService, IUnicodeVersionProvider, LogLevelEnum, IDecorationService, IInternalDecoration, IOscLinkService, type IBufferResizeEvent } from 'common/services/Services';
 import { UnicodeService } from 'common/services/UnicodeService';
-import { clone } from 'common/Clone';
 import { DEFAULT_OPTIONS } from 'common/services/OptionsService';
 import { IBufferSet, IBuffer } from 'common/buffer/Types';
 import { BufferSet } from 'common/buffer/BufferSet';
@@ -157,7 +156,7 @@ export class MockLogService implements ILogService {
 
 export class MockOptionsService implements IOptionsService {
   public serviceBrand: any;
-  public readonly rawOptions: Required<ITerminalOptions> = clone(DEFAULT_OPTIONS);
+  public readonly rawOptions: Required<ITerminalOptions> = structuredClone(DEFAULT_OPTIONS);
   public options: Required<ITerminalOptions> = this.rawOptions;
   public onOptionChange: IEvent<keyof ITerminalOptions> = new Emitter<keyof ITerminalOptions>().event;
   constructor(testOptions?: Partial<ITerminalOptions>) {

src/common/Types.ts

@@ -528,8 +528,8 @@ export interface IInputHandler {
   /** CSI ' } */ insertColumns(params: IParams): boolean;
   /** CSI ' ~ */ deleteColumns(params: IParams): boolean;
 
-  /** OSC 0
-      OSC 2 */ setTitle(data: string): boolean;
+  /** OSC 0 */
+  /** OSC 2 */ setTitle(data: string): boolean;
   /** OSC 4 */ setOrReportIndexedColor(data: string): boolean;
   /** OSC 10 */ setOrReportFgColor(data: string): boolean;
   /** OSC 11 */ setOrReportBgColor(data: string): boolean;
@@ -542,24 +542,24 @@ export interface IInputHandler {
   /** ESC E */ nextLine(): boolean;
   /** ESC = */ keypadApplicationMode(): boolean;
   /** ESC > */ keypadNumericMode(): boolean;
-  /** ESC % G
-      ESC % @ */ selectDefaultCharset(): boolean;
-  /** ESC ( C
-      ESC ) C
-      ESC * C
-      ESC + C
-      ESC - C
-      ESC . C
-      ESC / C */ selectCharset(collectAndFlag: string): boolean;
+  /** ESC % G */
+  /** ESC % @ */ selectDefaultCharset(): boolean;
+  /** ESC ( C */
+  /** ESC ) C */
+  /** ESC * C */
+  /** ESC + C */
+  /** ESC - C */
+  /** ESC . C */
+  /** ESC / C */ selectCharset(collectAndFlag: string): boolean;
   /** ESC D */ index(): boolean;
   /** ESC H */ tabSet(): boolean;
   /** ESC M */ reverseIndex(): boolean;
   /** ESC c */ fullReset(): boolean;
-  /** ESC n
-      ESC o
-      ESC |
-      ESC }
-      ESC ~ */ setgLevel(level: number): boolean;
+  /** ESC n */
+  /** ESC o */
+  /** ESC | */
+  /** ESC } */
+  /** ESC ~ */ setgLevel(level: number): boolean;
   /** ESC # 8 */ screenAlignmentPattern(): boolean;
 }
 

src/common/input/TextDecoder.test.ts

@@ -5,7 +5,6 @@
 
 import { assert } from 'chai';
 import { StringToUtf32, stringFromCodePoint, Utf8ToUtf32, utf32ToString } from 'common/input/TextDecoder';
-import { encode } from 'utf8';
 
 
 // convert UTF32 codepoints to string
@@ -29,6 +28,35 @@ function fromByteString(s: string): Uint8Array {
   return result;
 }
 
+function stringToUtf8Bytes(s: string): Uint8Array {
+  const bytes: number[] = [];
+  for (let i = 0; i < s.length; i++) {
+    let cp = s.charCodeAt(i);
+    if (cp >= 0xD800 && cp <= 0xDBFF && i + 1 < s.length) {
+      const next = s.charCodeAt(i + 1);
+      if (next >= 0xDC00 && next <= 0xDFFF) {
+        cp = 0x10000 + ((cp - 0xD800) << 10) + (next - 0xDC00);
+        i++;
+      }
+    }
+    if (cp < 0x80) {
+      bytes.push(cp);
+    } else if (cp < 0x800) {
+      bytes.push(0xC0 | (cp >> 6), 0x80 | (cp & 0x3F));
+    } else if (cp < 0x10000) {
+      bytes.push(0xE0 | (cp >> 12), 0x80 | ((cp >> 6) & 0x3F), 0x80 | (cp & 0x3F));
+    } else {
+      bytes.push(
+        0xF0 | (cp >> 18),
+        0x80 | ((cp >> 12) & 0x3F),
+        0x80 | ((cp >> 6) & 0x3F),
+        0x80 | (cp & 0x3F)
+      );
+    }
+  }
+  return new Uint8Array(bytes);
+}
+
 function assertDecodedRange(
   min: number,
   max: number,
@@ -172,7 +200,7 @@ describe('text encodings', () => {
             max,
             (i) => (i >= 0xD800 && i <= 0xDFFF) || i === 0xFEFF,
             (i) => String.fromCharCode(i),
-            (input, target) => decoder.decode(fromByteString(encode(input)), target),
+            (input, target) => decoder.decode(stringToUtf8Bytes(input), target),
             (data, length) => toString(data, length)
           );
         });
@@ -187,7 +215,7 @@ describe('text encodings', () => {
             max,
             () => false,
             (i) => stringFromCodePoint(i),
-            (input, target) => decoder.decode(fromByteString(encode(input)), target),
+            (input, target) => decoder.decode(stringToUtf8Bytes(input), target),
             (data, length) => toString(data, length)
           );
         });
@@ -196,7 +224,7 @@ describe('text encodings', () => {
       it('0xFEFF(BOM)', () => {
         const decoder = new Utf8ToUtf32();
         const target = new Uint32Array(5);
-        const utf8Data = fromByteString(encode(String.fromCharCode(0xFEFF)));
+        const utf8Data = stringToUtf8Bytes(String.fromCharCode(0xFEFF));
         const length = decoder.decode(utf8Data, target);
         assert.equal(length, 0);
         decoder.clear();
@@ -207,7 +235,7 @@ describe('text encodings', () => {
       const decoder = new Utf8ToUtf32();
       const target = new Uint32Array(500);
       for (let i = 0; i < TEST_STRINGS.length; ++i) {
-        const utf8Data = fromByteString(encode(TEST_STRINGS[i]));
+        const utf8Data = stringToUtf8Bytes(TEST_STRINGS[i]);
         const length = decoder.decode(utf8Data, target);
         assert.equal(toString(target, length), TEST_STRINGS[i]);
         decoder.clear();

src/common/input/WriteBuffer.test.ts

@@ -125,5 +125,20 @@ describe('WriteBuffer', () => {
       assert.deepEqual(stack, []);
       assert.deepEqual(cbStack, []);
     });
+    it('flushSync fires onWriteParsed', () => {
+      let parsed = 0;
+      wb.onWriteParsed(() => parsed++);
+      wb.write('a');
+      wb.write('b');
+      assert.equal(parsed, 0);
+      wb.flushSync();
+      assert.equal(parsed, 1);
+    });
+    it('flushSync with no pending writes does not fire onWriteParsed', () => {
+      let parsed = 0;
+      wb.onWriteParsed(() => parsed++);
+      wb.flushSync();
+      assert.equal(parsed, 0);
+    });
   });
 });

src/common/input/WriteBuffer.ts

@@ -71,7 +71,9 @@ export class WriteBuffer extends Disposable {
 
     // Process all pending chunks synchronously
     let chunk: string | Uint8Array | undefined;
+    let didProcess = false;
     while (chunk = this._writeBuffer.shift()) {
+      didProcess = true;
       this._action(chunk);
       const cb = this._callbacks.shift();
       if (cb) cb();
@@ -84,6 +86,9 @@ export class WriteBuffer extends Disposable {
     this._callbacks.length = 0;
 
     this._isSyncWriting = false;
+    if (didProcess) {
+      this._onWriteParsed.fire();
+    }
   }
 
   /**

src/common/parser/ApcParser.ts

@@ -7,6 +7,7 @@ import { IApcHandler, IHandlerCollection, ApcFallbackHandlerType, IApcParser, IS
 import { ParserConstants } from 'common/parser/Constants';
 import { utf32ToString } from 'common/input/TextDecoder';
 import { IDisposable } from 'common/Types';
+import { LimitedStringBuilder } from 'common/StringBuilder';
 
 const EMPTY_HANDLERS: IApcHandler[] = [];
 
@@ -153,13 +154,13 @@ export class ApcParser implements IApcParser {
 export class ApcHandler implements IApcHandler {
   private static _payloadLimit = ParserConstants.PAYLOAD_LIMIT;
 
-  private _data = '';
+  private _data = new LimitedStringBuilder(ApcHandler._payloadLimit);
   private _hitLimit: boolean = false;
 
   constructor(private _handler: (data: string) => boolean | Promise<boolean>) { }
 
   public start(): void {
-    this._data = '';
+    this._data.reset();
     this._hitLimit = false;
   }
 
@@ -167,9 +168,7 @@ export class ApcHandler implements IApcHandler {
     if (this._hitLimit) {
       return;
     }
-    this._data += utf32ToString(data, start, end);
-    if (this._data.length > ApcHandler._payloadLimit) {
-      this._data = '';
+    if (this._data.append(utf32ToString(data, start, end))) {
       this._hitLimit = true;
     }
   }
@@ -179,18 +178,18 @@ export class ApcHandler implements IApcHandler {
     if (this._hitLimit) {
       ret = false;
     } else if (success) {
-      ret = this._handler(this._data);
+      ret = this._handler(this._data.toString());
       if (ret instanceof Promise) {
         // need to hold data until `ret` got resolved
         // dont care for errors, data will be freed anyway on next start
         return ret.then(res => {
-          this._data = '';
+          this._data.reset();
           this._hitLimit = false;
           return res;
         });
       }
     }
-    this._data = '';
+    this._data.reset();
     this._hitLimit = false;
     return ret;
   }

src/common/parser/DcsParser.ts

@@ -8,6 +8,7 @@ import { IDcsHandler, IParams, IHandlerCollection, IDcsParser, DcsFallbackHandle
 import { utf32ToString } from 'common/input/TextDecoder';
 import { Params } from 'common/parser/Params';
 import { ParserConstants } from 'common/parser/Constants';
+import { LimitedStringBuilder } from 'common/StringBuilder';
 
 const EMPTY_HANDLERS: IDcsHandler[] = [];
 
@@ -140,7 +141,7 @@ EMPTY_PARAMS.addParam(0);
 export class DcsHandler implements IDcsHandler {
   private static _payloadLimit = ParserConstants.PAYLOAD_LIMIT;
 
-  private _data = '';
+  private _data = new LimitedStringBuilder(DcsHandler._payloadLimit);
   private _params: IParams = EMPTY_PARAMS;
   private _hitLimit: boolean = false;
 
@@ -152,7 +153,7 @@ export class DcsHandler implements IDcsHandler {
     // perf optimization:
     // clone only, if we have non empty params, otherwise stick with default
     this._params = (params.length > 1 || params.params[0]) ? params.clone() : EMPTY_PARAMS;
-    this._data = '';
+    this._data.reset();
     this._hitLimit = false;
   }
 
@@ -160,9 +161,7 @@ export class DcsHandler implements IDcsHandler {
     if (this._hitLimit) {
       return;
     }
-    this._data += utf32ToString(data, start, end);
-    if (this._data.length > DcsHandler._payloadLimit) {
-      this._data = '';
+    if (this._data.append(utf32ToString(data, start, end))) {
       this._hitLimit = true;
     }
   }
@@ -172,20 +171,20 @@ export class DcsHandler implements IDcsHandler {
     if (this._hitLimit) {
       ret = false;
     } else if (success) {
-      ret = this._handler(this._data, this._params);
+      ret = this._handler(this._data.toString(), this._params);
       if (ret instanceof Promise) {
         // need to hold data and params until `ret` got resolved
         // dont care for errors, data will be freed anyway on next start
         return ret.then(res => {
           this._params = EMPTY_PARAMS;
-          this._data = '';
+          this._data.reset();
           this._hitLimit = false;
           return res;
         });
       }
     }
     this._params = EMPTY_PARAMS;
-    this._data = '';
+    this._data.reset();
     this._hitLimit = false;
     return ret;
   }

src/common/parser/OscParser.ts

@@ -7,6 +7,7 @@ import { IOscHandler, IHandlerCollection, OscFallbackHandlerType, IOscParser, IS
 import { OscState, ParserConstants } from 'common/parser/Constants';
 import { utf32ToString } from 'common/input/TextDecoder';
 import { IDisposable } from 'common/Types';
+import { LimitedStringBuilder } from 'common/StringBuilder';
 
 const EMPTY_HANDLERS: IOscHandler[] = [];
 
@@ -194,13 +195,13 @@ export class OscParser implements IOscParser {
 export class OscHandler implements IOscHandler {
   private static _payloadLimit = ParserConstants.PAYLOAD_LIMIT;
 
-  private _data = '';
+  private _data = new LimitedStringBuilder(OscHandler._payloadLimit);
   private _hitLimit: boolean = false;
 
   constructor(private _handler: (data: string) => boolean | Promise<boolean>) { }
 
   public start(): void {
-    this._data = '';
+    this._data.reset();
     this._hitLimit = false;
   }
 
@@ -208,9 +209,7 @@ export class OscHandler implements IOscHandler {
     if (this._hitLimit) {
       return;
     }
-    this._data += utf32ToString(data, start, end);
-    if (this._data.length > OscHandler._payloadLimit) {
-      this._data = '';
+    if (this._data.append(utf32ToString(data, start, end))) {
       this._hitLimit = true;
     }
   }
@@ -220,18 +219,18 @@ export class OscHandler implements IOscHandler {
     if (this._hitLimit) {
       ret = false;
     } else if (success) {
-      ret = this._handler(this._data);
+      ret = this._handler(this._data.toString());
       if (ret instanceof Promise) {
         // need to hold data until `ret` got resolved
         // dont care for errors, data will be freed anyway on next start
         return ret.then(res => {
-          this._data = '';
+          this._data.reset();
           this._hitLimit = false;
           return res;
         });
       }
     }
-    this._data = '';
+    this._data.reset();
     this._hitLimit = false;
     return ret;
   }

src/common/public/BufferNamespaceApi.ts

@@ -20,7 +20,7 @@ export class BufferNamespaceApi extends Disposable implements IBufferNamespaceAp
     super();
     this._normal = new BufferApiView(this._core.buffers.normal, 'normal');
     this._alternate = new BufferApiView(this._core.buffers.alt, 'alternate');
-    this._core.buffers.onBufferActivate(() => this._onBufferChange.fire(this.active));
+    this._register(this._core.buffers.onBufferActivate(() => this._onBufferChange.fire(this.active)));
   }
   public get active(): IBufferApi {
     if (this._core.buffers.active === this._core.buffers.normal) { return this.normal; }

src/common/services/CoreService.ts

@@ -3,7 +3,6 @@
  * @license MIT
  */
 
-import { clone } from 'common/Clone';
 import { Disposable } from 'common/Lifecycle';
 import { IDecPrivateModes, IKittyKeyboardState, IModes } from 'common/Types';
 import { IBufferService, ICoreService, ILogService, IOptionsService } from 'common/services/Services';
@@ -61,14 +60,14 @@ export class CoreService extends Disposable implements ICoreService {
   ) {
     super();
     this.isCursorInitialized = _optionsService.rawOptions.showCursorImmediately ?? false;
-    this.modes = clone(DEFAULT_MODES);
-    this.decPrivateModes = clone(DEFAULT_DEC_PRIVATE_MODES);
+    this.modes = structuredClone(DEFAULT_MODES);
+    this.decPrivateModes = structuredClone(DEFAULT_DEC_PRIVATE_MODES);
     this.kittyKeyboard = DEFAULT_KITTY_KEYBOARD_STATE();
   }
 
   public reset(): void {
-    this.modes = clone(DEFAULT_MODES);
-    this.decPrivateModes = clone(DEFAULT_DEC_PRIVATE_MODES);
+    this.modes = structuredClone(DEFAULT_MODES);
+    this.decPrivateModes = structuredClone(DEFAULT_DEC_PRIVATE_MODES);
     this.kittyKeyboard = DEFAULT_KITTY_KEYBOARD_STATE();
   }
 

src/common/services/DecorationService.test.ts

@@ -4,11 +4,13 @@
  */
 
 import { assert } from 'chai';
-import { DecorationService } from './DecorationService';
+import { DecorationLineCache, DecorationService } from './DecorationService';
 import { IMarker } from 'common/Types';
 import { Disposable } from 'common/Lifecycle';
 import { Emitter } from 'common/Event';
-import { MockLogService } from 'common/TestUtils.test';
+import { MockLogService, MockBufferService, MockOptionsService } from 'common/TestUtils.test';
+import { Buffer } from 'common/buffer/Buffer';
+import { DEFAULT_ATTR_DATA } from 'common/buffer/BufferLine';
 
 function createFakeMarker(line: number): IMarker {
   return Object.freeze(new class extends Disposable {
@@ -19,11 +21,16 @@ function createFakeMarker(line: number): IMarker {
   }());
 }
 
+function createDecorationService(): DecorationService {
+  const bufferService = new MockBufferService(80, 24, new MockOptionsService());
+  return new DecorationService(new MockLogService(), bufferService);
+}
+
 const fakeMarker: IMarker = createFakeMarker(1);
 
 describe('DecorationService', () => {
   it('should set isDisposed to true after dispose', () => {
-    const service = new DecorationService(new MockLogService());
+    const service = createDecorationService();
     const decoration = service.registerDecoration({
       marker: fakeMarker
     });
@@ -35,7 +42,7 @@ describe('DecorationService', () => {
 
   describe('forEachDecorationAtCell', () => {
     it('should find decoration at its marker line', () => {
-      const service = new DecorationService(new MockLogService());
+      const service = createDecorationService();
       const decoration = service.registerDecoration({
         marker: createFakeMarker(5),
         width: 10
@@ -48,7 +55,7 @@ describe('DecorationService', () => {
     });
 
     it('should find decoration with height > 1 on subsequent lines', () => {
-      const service = new DecorationService(new MockLogService());
+      const service = createDecorationService();
       const decoration = service.registerDecoration({
         marker: createFakeMarker(5),
         width: 10,
@@ -74,7 +81,7 @@ describe('DecorationService', () => {
     });
 
     it('should not find decoration outside its x range', () => {
-      const service = new DecorationService(new MockLogService());
+      const service = createDecorationService();
       const decoration = service.registerDecoration({
         marker: createFakeMarker(5),
         x: 5,
@@ -99,11 +106,35 @@ describe('DecorationService', () => {
       service.forEachDecorationAtCell(8, 5, undefined, d => foundAtX8.push(d));
       assert.strictEqual(foundAtX8.length, 0);
     });
+
+    it('should find multi-line decoration when single-line decorations exist on other lines', () => {
+      const bufferService = new MockBufferService(80, 24, new MockOptionsService());
+      const serviceWithBuffer = new DecorationService(new MockLogService(), bufferService);
+      const buffer = bufferService.buffer;
+      (buffer as Buffer).fillViewportRows();
+
+      for (let i = 0; i < 100; i++) {
+        serviceWithBuffer.registerDecoration({
+          marker: buffer.addMarker(i),
+          width: 5
+        });
+      }
+      const multiLine = serviceWithBuffer.registerDecoration({
+        marker: buffer.addMarker(10),
+        width: 10,
+        height: 3
+      });
+      assert.ok(multiLine);
+
+      const found: typeof multiLine[] = [];
+      serviceWithBuffer.forEachDecorationAtCell(0, 11, undefined, d => found.push(d));
+      assert.include(found, multiLine);
+    });
   });
 
   describe('getDecorationsAtCell', () => {
     it('should find decoration with height > 1 on subsequent lines', () => {
-      const service = new DecorationService(new MockLogService());
+      const service = createDecorationService();
       const decoration = service.registerDecoration({
         marker: createFakeMarker(5),
         width: 10,
@@ -117,4 +148,73 @@ describe('DecorationService', () => {
       assert.strictEqual([...service.getDecorationsAtCell(0, 8)].length, 0);
     });
   });
+
+  describe('DecorationLineCache', () => {
+    it('should return undefined for lines with no indexed decorations', () => {
+      const cache = new DecorationLineCache();
+      assert.isUndefined(cache.getDecorationsOnLine(0));
+    });
+  });
+
+  describe('line index maintenance', () => {
+    it('should keep lookups correct after buffer trim', () => {
+      const bufferService = new MockBufferService(80, 5, new MockOptionsService({ scrollback: 0 }));
+      const service = new DecorationService(new MockLogService(), bufferService);
+      const buffer = bufferService.buffer;
+      (buffer as Buffer).fillViewportRows();
+
+      const marker = buffer.addMarker(buffer.lines.length - 1);
+      const decoration = service.registerDecoration({ marker, width: 10 });
+      assert.ok(decoration);
+
+      buffer.lines.onTrimEmitter.fire(1);
+
+      const found: typeof decoration[] = [];
+      service.forEachDecorationAtCell(0, marker.line, undefined, d => found.push(d));
+      assert.strictEqual(found.length, 1);
+    });
+
+    it('should remove decoration from line index when marker is trimmed off buffer', () => {
+      const bufferService = new MockBufferService(80, 5, new MockOptionsService({ scrollback: 0 }));
+      const service = new DecorationService(new MockLogService(), bufferService);
+      const buffer = bufferService.buffer;
+      (buffer as Buffer).fillViewportRows();
+
+      const marker = buffer.addMarker(0);
+      const decoration = service.registerDecoration({ marker, width: 10 });
+      assert.ok(decoration);
+
+      buffer.lines.onTrimEmitter.fire(1);
+      assert.isTrue(marker.isDisposed);
+      assert.isTrue(decoration!.isDisposed);
+
+      const found: typeof decoration[] = [];
+      service.forEachDecorationAtCell(0, 0, undefined, d => found.push(d));
+      assert.strictEqual(found.length, 0);
+    });
+
+    it('should keep multi-line decoration indexed after line insert', async () => {
+      const bufferService = new MockBufferService(80, 10, new MockOptionsService({ scrollback: 100 }));
+      const service = new DecorationService(new MockLogService(), bufferService);
+      const buffer = bufferService.buffer;
+      (buffer as Buffer).fillViewportRows();
+
+      const marker = buffer.addMarker(3);
+      const decoration = service.registerDecoration({ marker, width: 10, height: 3 });
+      assert.ok(decoration);
+
+      buffer.lines.splice(5, 0, buffer.getBlankLine(DEFAULT_ATTR_DATA));
+      await new Promise<void>(resolve => queueMicrotask(resolve));
+
+      const foundOnSpan: typeof decoration[] = [];
+      for (let line = marker.line; line < marker.line + 3; line++) {
+        service.forEachDecorationAtCell(0, line, undefined, d => foundOnSpan.push(d));
+      }
+      assert.include(foundOnSpan, decoration);
+
+      const foundOutsideSpan: typeof decoration[] = [];
+      service.forEachDecorationAtCell(0, marker.line + 3, undefined, d => foundOutsideSpan.push(d));
+      assert.strictEqual(foundOutsideSpan.length, 0);
+    });
+  });
 });

src/common/services/DecorationService.ts

@@ -3,19 +3,19 @@
  * @license MIT
  */
 
+import type { IDeleteEvent, IInsertEvent } from 'common/CircularList';
+import { MicrotaskTimer } from 'common/Async';
 import { css } from 'common/Color';
-import { Disposable, DisposableStore, toDisposable } from 'common/Lifecycle';
-import { IDecorationService, IInternalDecoration, ILogService } from 'common/services/Services';
+import { Disposable, DisposableStore, MutableDisposable, toDisposable } from 'common/Lifecycle';
+import { IBufferService, IDecorationService, IInternalDecoration, ILogService } from 'common/services/Services';
 import { SortedList } from 'common/SortedList';
-import { IColor } from 'common/Types';
+import { IColor, ICircularList } from 'common/Types';
 import { IDecoration, IDecorationOptions, IMarker } from '@xterm/xterm';
 import { Emitter } from 'common/Event';
 
 // Work variables to avoid garbage collection
 let $xmin = 0;
 let $xmax = 0;
-let $ymin = 0;
-let $ymax = 0;
 
 export class DecorationService extends Disposable implements IDecorationService {
   public serviceBrand: any;
@@ -27,6 +27,8 @@ export class DecorationService extends Disposable implements IDecorationService
    */
   private readonly _decorations: SortedList<IInternalDecoration>;
 
+  private readonly _lineCache = this._register(new DecorationLineCache());
+
   private readonly _onDecorationRegistered = this._register(new Emitter<IInternalDecoration>());
   public readonly onDecorationRegistered = this._onDecorationRegistered.event;
   private readonly _onDecorationRemoved = this._register(new Emitter<IInternalDecoration>());
@@ -34,12 +36,19 @@ export class DecorationService extends Disposable implements IDecorationService
 
   public get decorations(): IterableIterator<IInternalDecoration> { return this._decorations.values(); }
 
-  constructor(@ILogService private readonly _logService: ILogService) {
+  constructor(
+    @ILogService private readonly _logService: ILogService,
+    @IBufferService private readonly _bufferService: IBufferService
+  ) {
     super();
 
     this._decorations = new SortedList(e => e?.marker.line, this._logService);
 
     this._register(toDisposable(() => this.reset()));
+    this._register(this._bufferService.buffers.onBufferActivate(() => {
+      this._lineCache.attachToBufferLines(this._bufferService.buffer.lines);
+    }));
+    this._lineCache.attachToBufferLines(this._bufferService.buffer.lines);
   }
 
   public registerDecoration(options: IDecorationOptions): IDecoration | undefined {
@@ -53,12 +62,14 @@ export class DecorationService extends Disposable implements IDecorationService
         listener.dispose();
         if (decoration) {
           if (this._decorations.delete(decoration)) {
+            this._lineCache.remove(decoration);
             this._onDecorationRemoved.fire(decoration);
           }
           markerDispose.dispose();
         }
       });
       this._decorations.insert(decoration);
+      this._lineCache.add(decoration);
       this._onDecorationRegistered.fire(decoration);
     }
     return decoration;
@@ -69,19 +80,17 @@ export class DecorationService extends Disposable implements IDecorationService
       d.dispose();
     }
     this._decorations.clear();
+    this._lineCache.clear();
   }
 
   public *getDecorationsAtCell(x: number, line: number, layer?: 'bottom' | 'top'): IterableIterator<IInternalDecoration> {
+    const bucket = this._lineCache.getDecorationsOnLine(line);
+    if (!bucket) {
+      return;
+    }
     let xmin = 0;
     let xmax = 0;
-    let ymin = 0;
-    let ymax = 0;
-    for (const d of this._decorations.values()) {
-      ymin = d.marker.line;
-      ymax = ymin + (d.options.height ?? 1);
-      if (line < ymin || line >= ymax) {
-        continue;
-      }
+    for (const d of bucket) {
       xmin = d.options.x ?? 0;
       xmax = xmin + (d.options.width ?? 1);
       if (x >= xmin && x < xmax && (!layer || (d.options.layer ?? 'bottom') === layer)) {
@@ -91,12 +100,11 @@ export class DecorationService extends Disposable implements IDecorationService
   }
 
   public forEachDecorationAtCell(x: number, line: number, layer: 'bottom' | 'top' | undefined, callback: (decoration: IInternalDecoration) => void): void {
-    for (const d of this._decorations.values()) {
-      $ymin = d.marker.line;
-      $ymax = $ymin + (d.options.height ?? 1);
-      if (line < $ymin || line >= $ymax) {
-        continue;
-      }
+    const bucket = this._lineCache.getDecorationsOnLine(line);
+    if (!bucket) {
+      return;
+    }
+    for (const d of bucket) {
       $xmin = d.options.x ?? 0;
       $xmax = $xmin + (d.options.width ?? 1);
       if (x >= $xmin && x < $xmax && (!layer || (d.options.layer ?? 'bottom') === layer)) {
@@ -106,10 +114,235 @@ export class DecorationService extends Disposable implements IDecorationService
   }
 }
 
+/**
+ * Per-logical-line index of decorations for fast cell lookup.
+ *
+ * Keys are marker.line coordinates (logical buffer lines), not CircularList ring slots.
+ * Multi-line decorations appear in every line bucket they span. The index is kept aligned
+ * with marker.line updates via buffer line trim/insert/delete events.
+ */
+export class DecorationLineCache extends Disposable {
+  private readonly _decorationsByLine: Map<number, IInternalDecoration[]> = new Map();
+  private readonly _decorations = new Set<IInternalDecoration>();
+  private readonly _bufferLineListeners = this._register(new MutableDisposable<DisposableStore>());
+  private readonly _lineIndexSyncTimer = this._register(new MicrotaskTimer());
+  private _lineIndexSyncCallbacks: (() => void)[] = [];
+
+  public clear(): void {
+    this._lineIndexSyncCallbacks.length = 0;
+    this._lineIndexSyncTimer.cancel();
+    this._decorationsByLine.clear();
+    this._decorations.clear();
+  }
+
+  public add(decoration: IInternalDecoration): void {
+    this._decorations.add(decoration);
+    this._addToLineBuckets(decoration);
+  }
+
+  public remove(decoration: IInternalDecoration): void {
+    this._decorations.delete(decoration);
+    this._removeFromLineBuckets(decoration);
+  }
+
+  public getDecorationsOnLine(line: number): ReadonlyArray<IInternalDecoration> | undefined {
+    return this._decorationsByLine.get(line);
+  }
+
+  public attachToBufferLines(lines: ICircularList<unknown>): void {
+    const store = new DisposableStore();
+    this._bufferLineListeners.value = store;
+    store.add(lines.onTrim(amount => this._handleBufferLinesTrim(amount)));
+    store.add(lines.onInsert(event => this._handleBufferLinesInsert(event)));
+    store.add(lines.onDelete(event => this._handleBufferLinesDelete(event)));
+  }
+
+  private _getDecorationHeight(decoration: IInternalDecoration): number {
+    return decoration.options.height ?? 1;
+  }
+
+  private _addToLineBuckets(decoration: IInternalDecoration): void {
+    const start = decoration.marker.line;
+    if (start < 0) {
+      return;
+    }
+    decoration._indexedStartLine = start;
+    const height = this._getDecorationHeight(decoration);
+    for (let line = start; line < start + height; line++) {
+      let bucket = this._decorationsByLine.get(line);
+      if (!bucket) {
+        bucket = [];
+        this._decorationsByLine.set(line, bucket);
+      }
+      bucket.push(decoration);
+    }
+  }
+
+  private _removeFromLineBuckets(decoration: IInternalDecoration): void {
+    const start = decoration._indexedStartLine;
+    const height = this._getDecorationHeight(decoration);
+    for (let line = start; line < start + height; line++) {
+      const bucket = this._decorationsByLine.get(line);
+      if (!bucket) {
+        continue;
+      }
+      const index = bucket.indexOf(decoration);
+      if (index !== -1) {
+        bucket.splice(index, 1);
+      }
+      if (bucket.length === 0) {
+        this._decorationsByLine.delete(line);
+      }
+    }
+  }
+
+  private _reindexDecoration(decoration: IInternalDecoration): void {
+    this._removeFromLineBuckets(decoration);
+    if (!decoration.marker.isDisposed && decoration.marker.line >= 0) {
+      this._addToLineBuckets(decoration);
+    }
+  }
+
+  /** Re-index after marker line updates (buffer listeners may run before markers). */
+  private _scheduleLineIndexSync(callback: () => void): void {
+    this._lineIndexSyncCallbacks.push(callback);
+    this._lineIndexSyncTimer.set(() => {
+      const callbacks = this._lineIndexSyncCallbacks;
+      this._lineIndexSyncCallbacks = [];
+      for (const cb of callbacks) {
+        cb();
+      }
+    });
+  }
+
+  private _handleBufferLinesTrim(amount: number): void {
+    if (amount <= 0) {
+      return;
+    }
+    const newMap = new Map<number, IInternalDecoration[]>();
+    for (const [line, bucket] of this._decorationsByLine) {
+      const newLine = line - amount;
+      if (newLine < 0) {
+        continue;
+      }
+      const existing = newMap.get(newLine);
+      if (existing) {
+        existing.push(...bucket);
+      } else {
+        newMap.set(newLine, bucket.slice());
+      }
+    }
+    this._decorationsByLine.clear();
+    for (const [line, bucket] of newMap) {
+      this._decorationsByLine.set(line, bucket);
+    }
+    for (const d of this._decorations) {
+      if (!d.marker.isDisposed) {
+        d._indexedStartLine -= amount;
+      }
+    }
+  }
+
+  private _handleBufferLinesInsert(event: IInsertEvent): void {
+    this._scheduleLineIndexSync(() => this._applyBufferLinesInsert(event));
+  }
+
+  private _handleBufferLinesDelete(event: IDeleteEvent): void {
+    this._scheduleLineIndexSync(() => this._applyBufferLinesDelete(event));
+  }
+
+  private _mergeLineBucket(newMap: Map<number, IInternalDecoration[]>, line: number, bucket: IInternalDecoration[]): void {
+    const existing = newMap.get(line);
+    if (existing) {
+      existing.push(...bucket);
+    } else {
+      newMap.set(line, bucket.slice());
+    }
+  }
+
+  /**
+   * Shift indexed line keys and sync start lines. O(unique indexed lines), not O(decoration count).
+   * Decorations that span the insert point are re-indexed individually (rare vs single-line hits).
+   */
+  private _applyBufferLinesInsert(event: IInsertEvent): void {
+    const { index, amount } = event;
+    const spanCrossers: IInternalDecoration[] = [];
+    for (const d of this._decorations) {
+      if (d.marker.isDisposed) {
+        continue;
+      }
+      const start = d._indexedStartLine;
+      if (start < index && start + this._getDecorationHeight(d) > index) {
+        spanCrossers.push(d);
+        this._removeFromLineBuckets(d);
+      }
+    }
+    const newMap = new Map<number, IInternalDecoration[]>();
+    for (const [line, bucket] of this._decorationsByLine) {
+      const newLine = line >= index ? line + amount : line;
+      this._mergeLineBucket(newMap, newLine, bucket);
+    }
+    this._decorationsByLine.clear();
+    for (const [line, bucket] of newMap) {
+      this._decorationsByLine.set(line, bucket);
+    }
+    for (const d of this._decorations) {
+      if (d.marker.isDisposed) {
+        continue;
+      }
+      if (d._indexedStartLine >= index) {
+        d._indexedStartLine = d.marker.line;
+      }
+    }
+    for (const d of spanCrossers) {
+      this._addToLineBuckets(d);
+    }
+  }
+
+  /**
+   * Drop deleted line keys, shift keys below, sync start lines. Full re-index only when a
+   * multi-line decoration spans across the deleted range but survives.
+   */
+  private _applyBufferLinesDelete(event: IDeleteEvent): void {
+    const deleteEnd = event.index + event.amount;
+    const newMap = new Map<number, IInternalDecoration[]>();
+    for (const [line, bucket] of this._decorationsByLine) {
+      if (line >= event.index && line < deleteEnd) {
+        continue;
+      }
+      const newLine = line >= deleteEnd ? line - event.amount : line;
+      this._mergeLineBucket(newMap, newLine, bucket);
+    }
+    this._decorationsByLine.clear();
+    for (const [line, bucket] of newMap) {
+      this._decorationsByLine.set(line, bucket);
+    }
+    const toReindex: IInternalDecoration[] = [];
+    for (const d of this._decorations) {
+      if (d.marker.isDisposed) {
+        continue;
+      }
+      const start = d._indexedStartLine;
+      const height = this._getDecorationHeight(d);
+      if (start >= deleteEnd) {
+        d._indexedStartLine = d.marker.line;
+      } else if (start < event.index && start + height > deleteEnd) {
+        toReindex.push(d);
+      }
+    }
+    for (const d of toReindex) {
+      this._reindexDecoration(d);
+    }
+  }
+}
+
 class Decoration extends DisposableStore implements IInternalDecoration {
   public readonly marker: IMarker;
   public element: HTMLElement | undefined;
 
+  /** Start line used for line-index removal when marker.line is cleared on dispose. */
+  public _indexedStartLine: number;
+
   public readonly onRenderEmitter = this.add(new Emitter<HTMLElement>());
   public readonly onRender = this.onRenderEmitter.event;
   private readonly _onDispose = this.add(new Emitter<void>());
@@ -144,6 +377,7 @@ class Decoration extends DisposableStore implements IInternalDecoration {
   ) {
     super();
     this.marker = options.marker;
+    this._indexedStartLine = options.marker.line;
     if (this.options.overviewRulerOptions && !this.options.overviewRulerOptions.position) {
       this.options.overviewRulerOptions.position = 'full';
     }

src/common/services/Services.ts

@@ -396,4 +396,6 @@ export interface IInternalDecoration extends IDecoration {
   readonly backgroundColorRGB: IColor | undefined;
   readonly foregroundColorRGB: IColor | undefined;
   readonly onRenderEmitter: Emitter<HTMLElement>;
+  /** @internal Start line for line-index removal; kept in sync on buffer line shifts. */
+  _indexedStartLine: number;
 }

src/headless/Terminal.ts

@@ -108,6 +108,7 @@ export class Terminal extends CoreTerminal {
       // 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;
     this.buffer.ydisp = 0;

src/headless/public/Terminal.test.ts

@@ -114,6 +114,29 @@ describe('Headless API Tests', function (): void {
     }
   });
 
+  it('clear disposes markers', async () => {
+    term = new Terminal({ rows: 5, allowProposedApi: true });
+    for (let i = 0; i < 10; i++) {
+      await writeSync('\n\rtest' + i);
+    }
+    const markers = [
+      term.registerMarker(1)!,
+      term.registerMarker(2)!,
+      term.registerMarker(3)!,
+      term.registerMarker(4)!
+    ];
+    let disposeCount = 0;
+    for (const marker of markers) {
+      marker.onDispose(() => disposeCount++);
+    }
+    term.clear();
+    strictEqual(disposeCount, markers.length);
+    for (const marker of markers) {
+      strictEqual(marker.isDisposed, true);
+    }
+    strictEqual(term.markers.length, 0);
+  });
+
   describe('options', () => {
     const termOptions = {
       cols: 80,
@@ -396,6 +419,18 @@ describe('Headless API Tests', function (): void {
       strictEqual(term.buffer.normal.getLine(0)!.translateToString(), 'norm ');
       strictEqual(term.buffer.alternate.getLine(0), undefined);
     });
+
+    it('registerMarker returns undefined on the alt buffer', async () => {
+      term = new Terminal({ cols: 5, allowProposedApi: true });
+      strictEqual(term.buffer.active.type, 'normal');
+      strictEqual(term.registerMarker(0)!.line, 0);
+      await writeSync('\x1b[?47h');
+      strictEqual(term.buffer.active.type, 'alternate');
+      strictEqual(term.registerMarker(0), undefined);
+      await writeSync('\x1b[?47l');
+      strictEqual(term.buffer.active.type, 'normal');
+      strictEqual(term.registerMarker(0)!.line, 0);
+    });
   });
 
   describe('modes', () => {

test/benchmark/DecorationService.benchmark.ts

@@ -0,0 +1,109 @@
+/**
+ * Copyright (c) 2026 The xterm.js authors. All rights reserved.
+ * @license MIT
+ */
+
+import { perfContext, before, RuntimeCase } from 'xterm-benchmark';
+import { DecorationService } from 'common/services/DecorationService';
+import { MockLogService, MockBufferService, MockOptionsService } from 'common/TestUtils.test';
+const enum Constants {
+  COLS = 80,
+  ROWS = 30,
+  SINGLE_LINE_DECORATION_COUNT = 20_000,
+  MULTI_LINE_DECORATION_COUNT = 19_999,
+  MULTI_LINE_HEIGHT = 2,
+  VIEWPORT_SCAN_ITERATIONS = 20
+}
+
+function registerSingleLineDecorations(service: DecorationService, bufferService: MockBufferService, count: number): void {
+  const buffer = bufferService.buffer;
+  for (let i = 0; i < count; i++) {
+    const line = i % 5000;
+    const marker = buffer.addMarker(line);
+    service.registerDecoration({ marker, width: Constants.COLS });
+  }
+}
+
+function registerMixedDecorations(service: DecorationService, bufferService: MockBufferService): void {
+  const buffer = bufferService.buffer;
+  for (let i = 0; i < Constants.MULTI_LINE_DECORATION_COUNT; i++) {
+    const line = i % 5000;
+    const marker = buffer.addMarker(line);
+    service.registerDecoration({ marker, width: Constants.COLS });
+  }
+  const multiLineMarker = buffer.addMarker(10);
+  service.registerDecoration({
+    marker: multiLineMarker,
+    width: Constants.COLS,
+    height: Constants.MULTI_LINE_HEIGHT
+  });
+}
+
+function scanVisibleGrid(service: DecorationService, rows: number, cols: number): number {
+  let hitCount = 0;
+  for (let row = 0; row < rows; row++) {
+    for (let col = 0; col < cols; col++) {
+      service.forEachDecorationAtCell(col, row, undefined, () => {
+        hitCount++;
+      });
+    }
+  }
+  return hitCount;
+}
+
+perfContext('DecorationService.forEachDecorationAtCell', () => {
+  perfContext('single-line dense / sparse line hit', () => {
+    let service: DecorationService;
+    let bufferService: MockBufferService;
+    before(() => {
+      bufferService = new MockBufferService(Constants.COLS, Constants.ROWS, new MockOptionsService());
+      service = new DecorationService(new MockLogService(), bufferService);
+      registerSingleLineDecorations(service, bufferService, Constants.SINGLE_LINE_DECORATION_COUNT);
+    });
+    new RuntimeCase('', () => {
+      let hitCount = 0;
+      for (let i = 0; i < Constants.VIEWPORT_SCAN_ITERATIONS; i++) {
+        service.forEachDecorationAtCell(0, 0, undefined, () => {
+          hitCount++;
+        });
+      }
+      return { payloadSize: Constants.VIEWPORT_SCAN_ITERATIONS, hitCount };
+    }, { fork: false }).showAverageRuntime();
+  });
+
+  perfContext('mixed single-line + multi-line / sparse line hit', () => {
+    let service: DecorationService;
+    let bufferService: MockBufferService;
+    before(() => {
+      bufferService = new MockBufferService(Constants.COLS, Constants.ROWS, new MockOptionsService());
+      service = new DecorationService(new MockLogService(), bufferService);
+      registerMixedDecorations(service, bufferService);
+    });
+    new RuntimeCase('', () => {
+      let hitCount = 0;
+      for (let i = 0; i < Constants.VIEWPORT_SCAN_ITERATIONS; i++) {
+        service.forEachDecorationAtCell(0, 10, undefined, () => {
+          hitCount++;
+        });
+      }
+      return { payloadSize: Constants.VIEWPORT_SCAN_ITERATIONS, hitCount };
+    }, { fork: false }).showAverageRuntime();
+  });
+
+  perfContext('viewport grid scan', () => {
+    let service: DecorationService;
+    let bufferService: MockBufferService;
+    before(() => {
+      bufferService = new MockBufferService(Constants.COLS, Constants.ROWS, new MockOptionsService());
+      service = new DecorationService(new MockLogService(), bufferService);
+      registerSingleLineDecorations(service, bufferService, Constants.SINGLE_LINE_DECORATION_COUNT);
+    });
+    new RuntimeCase('', () => {
+      let totalHits = 0;
+      for (let i = 0; i < Constants.VIEWPORT_SCAN_ITERATIONS; i++) {
+        totalHits += scanVisibleGrid(service, Constants.ROWS, Constants.COLS);
+      }
+      return { payloadSize: Constants.VIEWPORT_SCAN_ITERATIONS * Constants.ROWS * Constants.COLS, totalHits };
+    }, { fork: false }).showAverageRuntime();
+  });
+});

test/playwright/TestUtils.ts

@@ -284,7 +284,7 @@ export class TerminalProxy implements ITerminalProxyCustomMethods, PlaywrightApi
   }
   public async input(data: string, wasUserInput: boolean = true): Promise<void> { return this.evaluate(([term]) => term.input(data, wasUserInput)); }
   public async resize(cols: number, rows: number): Promise<void> { return this._page.evaluate(([term, cols, rows]) => term.resize(cols, rows), [await this.getHandle(), cols, rows] as const); }
-  public async registerMarker(y?: number | undefined): Promise<IMarker> { return this._page.evaluate(([term, y]) => term.registerMarker(y), [await this.getHandle(), y] as const); }
+  public async registerMarker(y?: number | undefined): Promise<IMarker | undefined> { return this._page.evaluate(([term, y]) => term.registerMarker(y), [await this.getHandle(), y] as const); }
   public async registerDecoration(decorationOptions: IDecorationOptions): Promise<IDecoration | undefined> { return this._page.evaluate(([term, decorationOptions]) => term.registerDecoration(decorationOptions), [await this.getHandle(), decorationOptions] as const); }
   public async clearTextureAtlas(): Promise<void> { return this.evaluate(([term]) => term.clearTextureAtlas()); }
   // #endregion

typings/xterm.d.ts

@@ -1257,11 +1257,12 @@ declare module '@xterm/xterm' {
     deregisterCharacterJoiner(joinerId: number): void;
 
     /**
-     * Adds a marker to the normal buffer and returns it.
+     * Adds a marker to the normal buffer and returns it. If the alt buffer is
+     * active, undefined is returned.
      * @param cursorYOffset The y position offset of the marker from the cursor.
      * @returns The new marker or undefined.
      */
-    registerMarker(cursorYOffset?: number): IMarker;
+    registerMarker(cursorYOffset?: number): IMarker | undefined;
 
     /**
      * Registers a decoration to the terminal.