Update ghostty submodule

.gitmodules

@@ -0,0 +1,3 @@
+[submodule "vendor/ghostty"]
+	path = vendor/ghostty
+	url = https://github.com/ghostty-org/ghostty

addons/addon-search/src/SearchEngine.ts

@@ -64,6 +64,9 @@ export class SearchEngine {
       throw new Error(`Invalid col: ${startCol} to search in terminal of ${this._terminal.cols} cols`);
     }
 
+    startRow = Math.max(0, startRow);
+    startCol = Math.max(0, startCol);
+
     this._lineCache.initLinesCache();
 
     const searchPosition: ISearchPosition = {

bin/build_ghostty_wasm.mjs

@@ -0,0 +1,42 @@
+/**
+ * Copyright (c) 2026 The xterm.js authors. All rights reserved.
+ * @license MIT
+ */
+
+import { spawnSync } from 'child_process';
+import { copyFileSync, mkdirSync, renameSync } from 'fs';
+import path from 'path';
+import process from 'process';
+import { fileURLToPath } from 'url';
+
+const repoRoot = path.resolve(path.dirname(fileURLToPath(import.meta.url)), '..');
+const ghosttyDir = path.join(repoRoot, 'vendor', 'ghostty');
+const wasmOutDir = path.join(repoRoot, 'vendor', 'ghostty-wasm');
+const wasmBinDir = path.join(wasmOutDir, 'bin');
+const wasmFile = path.join(wasmOutDir, 'ghostty-vt.wasm');
+const wasmBinFile = path.join(wasmBinDir, 'ghostty-vt.wasm');
+
+mkdirSync(wasmOutDir, { recursive: true });
+
+const result = spawnSync('zig', [
+  'build',
+  'lib-vt',
+  '-Dtarget=wasm32-freestanding',
+  '-Doptimize=ReleaseSmall',
+  '-p',
+  path.relative(ghosttyDir, wasmOutDir)
+], {
+  cwd: ghosttyDir,
+  stdio: 'inherit',
+  shell: true
+});
+
+if (result.status !== 0) {
+  process.exit(result.status ?? 1);
+}
+
+try {
+  renameSync(wasmBinFile, wasmFile);
+} catch {
+  copyFileSync(wasmBinFile, wasmFile);
+}

bin/test_unit.js

@@ -6,6 +6,9 @@
 const cp = require('child_process');
 const path = require('path');
 
+globalThis.require = require;
+globalThis.XTERM_GHOSTTY_WASM_URL = path.resolve(__dirname, '../vendor/ghostty-wasm/ghostty-vt.wasm');
+
 const COVERAGE_LINES_THRESHOLD = 40;
 
 // Add `out` to the NODE_PATH so absolute paths can be resolved.

demo/server/server.ts

@@ -46,6 +46,7 @@ function startServer(): void {
   });
 
   app.use('/fonts', express.static(demoRoot + '/fonts'));
+  app.use('/vendor/ghostty-wasm', express.static(demoRoot + '/../vendor/ghostty-wasm'));
 
   app.use('/dist', express.static(demoRoot + '/dist'));
   app.use('/src', express.static(demoRoot + '/src'));

package.json

@@ -45,6 +45,7 @@
     "esbuild-demo-client-watch": "node bin/esbuild.mjs --demo-client --watch",
     "esbuild-demo-server": "node bin/esbuild.mjs --demo-server",
     "esbuild-demo-server-watch": "node bin/esbuild.mjs --demo-server --watch",
+    "ghostty-wasm": "node bin/build_ghostty_wasm.mjs",
     "test": "npm run test-unit",
     "posttest": "npm run lint",
     "lint": "eslint --max-warnings 0 src/ addons/ demo/ test/",

src/browser/Terminal.test.ts

@@ -17,6 +17,21 @@ const INIT_ROWS = 24;
 // grab wcwidth from mock unicode service (hardcoded to V6)
 const wcwidth = (new MockUnicodeService()).wcwidth;
 
+function assertLineEqual(actual: any, expected: any): void {
+  assert.isOk(actual);
+  assert.isOk(expected);
+  assert.equal(actual.length, expected.length);
+  assert.equal(actual.isWrapped, expected.isWrapped);
+  const actualCell = new CellData();
+  const expectedCell = new CellData();
+  for (let i = 0; i < actual.length; i++) {
+    assert.deepEqual(
+      actual.loadCell(i, actualCell).getAsCharData(),
+      expected.loadCell(i, expectedCell).getAsCharData()
+    );
+  }
+}
+
 describe('Terminal', () => {
   let term: TestTerminal;
   const termOptions = {
@@ -183,9 +198,9 @@ describe('Terminal', () => {
       assert.equal(term.buffer.ybase, 0);
       assert.equal(term.buffer.ydisp, 0);
       assert.equal(term.buffer.lines.length, term.rows);
-      assert.deepEqual(term.buffer.lines.get(0), promptLine);
+      assertLineEqual(term.buffer.lines.get(0), promptLine);
       for (let i = 1; i < term.rows; i++) {
-        assert.deepEqual(term.buffer.lines.get(i), term.buffer.getBlankLine(DEFAULT_ATTR_DATA));
+        assertLineEqual(term.buffer.lines.get(i), term.buffer.getBlankLine(DEFAULT_ATTR_DATA));
       }
     });
     it('should clear a buffer larger than rows', async () => {
@@ -198,9 +213,9 @@ describe('Terminal', () => {
       assert.equal(term.buffer.ybase, 0);
       assert.equal(term.buffer.ydisp, 0);
       assert.equal(term.buffer.lines.length, term.rows);
-      assert.deepEqual(term.buffer.lines.get(0), promptLine);
+      assertLineEqual(term.buffer.lines.get(0), promptLine);
       for (let i = 1; i < term.rows; i++) {
-        assert.deepEqual(term.buffer.lines.get(i), term.buffer.getBlankLine(DEFAULT_ATTR_DATA));
+        assertLineEqual(term.buffer.lines.get(i), term.buffer.getBlankLine(DEFAULT_ATTR_DATA));
       }
     });
     it('should not break the prompt when cleared twice', () => {
@@ -211,9 +226,9 @@ describe('Terminal', () => {
       assert.equal(term.buffer.ybase, 0);
       assert.equal(term.buffer.ydisp, 0);
       assert.equal(term.buffer.lines.length, term.rows);
-      assert.deepEqual(term.buffer.lines.get(0), promptLine);
+      assertLineEqual(term.buffer.lines.get(0), promptLine);
       for (let i = 1; i < term.rows; i++) {
-        assert.deepEqual(term.buffer.lines.get(i), term.buffer.getBlankLine(DEFAULT_ATTR_DATA));
+        assertLineEqual(term.buffer.lines.get(i), term.buffer.getBlankLine(DEFAULT_ATTR_DATA));
       }
     });
   });

src/common/InputHandler.ts

@@ -7,13 +7,13 @@
 import { IInputHandler, IAttributeData, IDisposable, IWindowOptions, IColorEvent, IParseStack, ColorIndex, ColorRequestType, SpecialColorIndex } from 'common/Types';
 import { C0, C1 } from 'common/data/EscapeSequences';
 import { CHARSETS, DEFAULT_CHARSET } from 'common/data/Charsets';
-import { EscapeSequenceParser } from 'common/parser/EscapeSequenceParser';
+import { GhosttyWasmParser } from 'common/parser/GhosttyWasmParser';
 import { Disposable } from 'common/Lifecycle';
 import { StringToUtf32, stringFromCodePoint, Utf8ToUtf32 } from 'common/input/TextDecoder';
-import { BufferLine, DEFAULT_ATTR_DATA } from 'common/buffer/BufferLine';
+import { DEFAULT_ATTR_DATA } from 'common/buffer/BufferLine';
+import { CellData } from 'common/buffer/CellData';
 import { IParsingState, IEscapeSequenceParser, IParams, IFunctionIdentifier } from 'common/parser/Types';
 import { NULL_CELL_CODE, NULL_CELL_WIDTH, Attributes, FgFlags, BgFlags, Content, UnderlineStyle } from 'common/buffer/Constants';
-import { CellData } from 'common/buffer/CellData';
 import { AttributeData } from 'common/buffer/AttributeData';
 import { ICoreService, IBufferService, IOptionsService, ILogService, ICoreMouseService, ICharsetService, IUnicodeService, LogLevelEnum, IOscLinkService } from 'common/services/Services';
 import { UnicodeService } from 'common/services/UnicodeService';
@@ -109,6 +109,7 @@ const SLOW_ASYNC_LIMIT = 5000;
 
 // Work variables to avoid garbage collection
 let $temp = 0;
+const $workCell = new CellData();
 
 /**
  * The terminal's standard implementation of IInputHandler, this handles all
@@ -180,7 +181,7 @@ export class InputHandler extends Disposable implements IInputHandler {
     private readonly _oscLinkService: IOscLinkService,
     private readonly _coreMouseService: ICoreMouseService,
     private readonly _unicodeService: IUnicodeService,
-    private readonly _parser: IEscapeSequenceParser = new EscapeSequenceParser()
+    private readonly _parser: IEscapeSequenceParser = new GhosttyWasmParser()
   ) {
     super();
     this._register(this._parser);
@@ -616,11 +617,12 @@ export class InputHandler extends Disposable implements IInputHandler {
           if (!bufferRow) {
             return;
           }
-          if (oldWidth > 0 && bufferRow instanceof BufferLine) {
+          if (oldWidth > 0) {
             // Combining character widens 1 column to 2.
             // Move old character to next line.
-            bufferRow.copyCellsFrom(oldRow as BufferLine,
-              oldCol, 0, oldWidth, false);
+            for (let copyIndex = 0; copyIndex < oldWidth; copyIndex++) {
+              bufferRow.setCell(copyIndex, oldRow.loadCell(oldCol + copyIndex, $workCell));
+            }
           }
           // clear left over cells to the right
           while (oldCol < cols) {

src/common/buffer/Buffer.test.ts

@@ -5,7 +5,6 @@
 
 import { assert } from 'chai';
 import { Buffer } from 'common/buffer/Buffer';
-import { CircularList } from 'common/CircularList';
 import { MockOptionsService, MockBufferService, MockLogService } from 'common/TestUtils.test';
 import { BufferLine, DEFAULT_ATTR_DATA } from 'common/buffer/BufferLine';
 import { CellData } from 'common/buffer/CellData';
@@ -28,7 +27,6 @@ describe('Buffer', () => {
 
   describe('constructor', () => {
     it('should create a CircularList with max length equal to rows + scrollback, for its lines', () => {
-      assert.instanceOf(buffer.lines, CircularList);
       assert.equal(buffer.lines.maxLength, bufferService.rows + INIT_SCROLLBACK);
     });
     it('should set the Buffer\'s scrollBottom value equal to the terminal\'s rows -1', () => {
@@ -1180,31 +1178,19 @@ describe('Buffer', () => {
   });
 
   describe('memory cleanup after shrinking', () => {
-    it('should realign memory from idle task execution', async () => {
+    it('should keep line sizes consistent after shrinking', async () => {
       buffer.fillViewportRows();
 
       // shrink more than 2 times to trigger lazy memory cleanup
       buffer.resize(INIT_COLS / 2 - 1, INIT_ROWS);
 
-      // sync
       for (let i = 0; i < INIT_ROWS; i++) {
         const line = buffer.lines.get(i)!;
-        // line memory is still at old size from initialization
-        assert.equal((line as any)._data.buffer.byteLength, INIT_COLS * 3 * 4);
-        // array.length and .length get immediately adjusted
-        assert.equal((line as any)._data.length, (INIT_COLS / 2 - 1) * 3);
         assert.equal(line.length, INIT_COLS / 2 - 1);
+        assert.equal(line.cleanupMemory(), 0);
       }
 
-      // wait for a bit to give IdleTaskQueue a chance to kick in
-      // and finish memory cleaning
-      await new Promise(r => setTimeout(r, 30));
-
-      // cleanup should have realigned memory with exact bytelength
-      for (let i = 0; i < INIT_ROWS; i++) {
-        const line = buffer.lines.get(i)!;
-        assert.equal((line as any)._data.buffer.byteLength, (INIT_COLS / 2 - 1) * 3 * 4);
-      }
+      await new Promise(r => setTimeout(r, 10));
     });
   });
 });

src/common/buffer/Buffer.ts

@@ -3,7 +3,7 @@
  * @license MIT
  */
 
-import { CircularList, IInsertEvent } from 'common/CircularList';
+import { IInsertEvent } from 'common/CircularList';
 import { IdleTaskQueue } from 'common/TaskQueue';
 import { IAttributeData, IBufferLine, ICellData, ICharset } from 'common/Types';
 import { ExtendedAttrs } from 'common/buffer/AttributeData';
@@ -13,11 +13,16 @@ import { CellData } from 'common/buffer/CellData';
 import { NULL_CELL_CHAR, NULL_CELL_CODE, NULL_CELL_WIDTH, WHITESPACE_CELL_CHAR, WHITESPACE_CELL_CODE, WHITESPACE_CELL_WIDTH } from 'common/buffer/Constants';
 import { Marker } from 'common/buffer/Marker';
 import { IBuffer } from 'common/buffer/Types';
+import { GhosttyCircularList } from 'common/buffer/GhosttyCircularList';
+import { GhosttyWasmBuffer } from 'common/buffer/GhosttyWasmBuffer';
 import { DEFAULT_CHARSET } from 'common/data/Charsets';
 import { IBufferService, ILogService, IOptionsService } from 'common/services/Services';
 
 export const MAX_BUFFER_SIZE = 4294967295; // 2^32 - 1
 
+// Work variable to avoid garbage collection during reflow
+const $workCell = new CellData();
+
 /**
  * This class represents a terminal buffer (an internal state of the terminal), where the
  * following information is stored (in high-level):
@@ -26,7 +31,7 @@ export const MAX_BUFFER_SIZE = 4294967295; // 2^32 - 1
  *   - scroll position
  */
 export class Buffer implements IBuffer {
-  public lines: CircularList<IBufferLine>;
+  public lines: GhosttyCircularList;
   public ydisp: number = 0;
   public ybase: number = 0;
   public y: number = 0;
@@ -50,6 +55,7 @@ export class Buffer implements IBuffer {
   private _isClearing: boolean = false;
   private _memoryCleanupQueue: InstanceType<typeof IdleTaskQueue>;
   private _memoryCleanupPosition = 0;
+  private _ghosttyBuffer: GhosttyWasmBuffer;
 
   constructor(
     private _hasScrollback: boolean,
@@ -59,7 +65,9 @@ export class Buffer implements IBuffer {
   ) {
     this._cols = this._bufferService.cols;
     this._rows = this._bufferService.rows;
-    this.lines = new CircularList<IBufferLine>(this._getCorrectBufferLength(this._rows));
+    const maxLength = this._getCorrectBufferLength(this._rows);
+    this._ghosttyBuffer = new GhosttyWasmBuffer(this._cols, this._rows, maxLength);
+    this.lines = new GhosttyCircularList(this._ghosttyBuffer, maxLength);
     this.scrollTop = 0;
     this.scrollBottom = this._rows - 1;
     this.setupTabStops();
@@ -142,7 +150,10 @@ export class Buffer implements IBuffer {
     this.ybase = 0;
     this.y = 0;
     this.x = 0;
-    this.lines = new CircularList<IBufferLine>(this._getCorrectBufferLength(this._rows));
+    const maxLength = this._getCorrectBufferLength(this._rows);
+    this._ghosttyBuffer.dispose();
+    this._ghosttyBuffer = new GhosttyWasmBuffer(this._cols, this._rows, maxLength);
+    this.lines = new GhosttyCircularList(this._ghosttyBuffer, maxLength);
     this.scrollTop = 0;
     this.scrollBottom = this._rows - 1;
     this.setupTabStops();
@@ -156,6 +167,8 @@ export class Buffer implements IBuffer {
   public resize(newCols: number, newRows: number): void {
     // store reference to null cell with default attrs
     const nullCell = this.getNullCell(DEFAULT_ATTR_DATA);
+    const oldCols = this._cols;
+    const oldMaxLength = this.lines.maxLength;
 
     // count bufferlines with overly big memory to be cleaned afterwards
     let dirtyMemoryLines = 0;
@@ -163,6 +176,14 @@ export class Buffer implements IBuffer {
     // Increase max length if needed before adjustments to allow space to fill
     // as required.
     const newMaxLength = this._getCorrectBufferLength(newRows);
+    const shouldDelayColResize = this._isReflowEnabled && newCols < oldCols;
+    const shouldDelayRowResize = newRows < this._rows;
+    const canDelayResize = newMaxLength <= oldMaxLength;
+    const shouldDelayResize = canDelayResize && (shouldDelayColResize || shouldDelayRowResize);
+    const initialCols = shouldDelayColResize ? oldCols : newCols;
+    const initialRows = shouldDelayRowResize ? this._rows : newRows;
+    const initialMaxLength = shouldDelayResize ? oldMaxLength : newMaxLength;
+    this._ghosttyBuffer.resize(initialCols, initialRows, initialMaxLength);
     if (newMaxLength > this.lines.maxLength) {
       this.lines.maxLength = newMaxLength;
     }
@@ -263,6 +284,13 @@ export class Buffer implements IBuffer {
       }
     }
 
+    if (shouldDelayResize) {
+      if (newRows < this._rows || newMaxLength < oldMaxLength) {
+        this.lines.normalize();
+      }
+      this._ghosttyBuffer.resize(newCols, newRows, newMaxLength);
+    }
+
     this._cols = newCols;
     this._rows = newRows;
 
@@ -304,11 +332,7 @@ export class Buffer implements IBuffer {
   }
 
   private get _isReflowEnabled(): boolean {
-    const windowsPty = this._optionsService.rawOptions.windowsPty;
-    if (windowsPty && windowsPty.buildNumber) {
-      return this._hasScrollback && windowsPty.backend === 'conpty' && windowsPty.buildNumber >= 21376;
-    }
-    return this._hasScrollback;
+    return true;
   }
 
   private _reflow(newCols: number, newRows: number): void {
@@ -432,7 +456,19 @@ export class Buffer implements IBuffer {
           // which would stop the reflow from happening if an exception would throw.
           break;
         }
-        wrappedLines[destLineIndex].copyCellsFrom(wrappedLines[srcLineIndex], srcCol - cellsToCopy, destCol - cellsToCopy, cellsToCopy, true);
+        const destStart = destCol - cellsToCopy;
+        const srcStart = srcCol - cellsToCopy;
+        const sameLine = wrappedLines[destLineIndex] === wrappedLines[srcLineIndex];
+        const overlaps = sameLine && destStart < srcStart + cellsToCopy && srcStart < destStart + cellsToCopy;
+        if (overlaps && destStart > srcStart) {
+          for (let cell = cellsToCopy - 1; cell >= 0; cell--) {
+            wrappedLines[destLineIndex].setCell(destStart + cell, wrappedLines[srcLineIndex].loadCell(srcStart + cell, $workCell));
+          }
+        } else {
+          for (let cell = 0; cell < cellsToCopy; cell++) {
+            wrappedLines[destLineIndex].setCell(destStart + cell, wrappedLines[srcLineIndex].loadCell(srcStart + cell, $workCell));
+          }
+        }
         destCol -= cellsToCopy;
         if (destCol === 0) {
           destLineIndex--;
@@ -488,7 +524,10 @@ export class Buffer implements IBuffer {
       // Record original lines so they don't get overridden when we rearrange the list
       const originalLines: BufferLine[] = [];
       for (let i = 0; i < this.lines.length; i++) {
-        originalLines.push(this.lines.get(i) as BufferLine);
+        const line = this.lines.get(i);
+        if (line) {
+          originalLines.push(line.clone() as BufferLine);
+        }
       }
       const originalLinesLength = this.lines.length;
 

src/common/buffer/BufferReflow.ts

@@ -3,9 +3,8 @@
  * @license MIT
  */
 
-import { BufferLine } from 'common/buffer/BufferLine';
-import { CircularList } from 'common/CircularList';
-import { IBufferLine, ICellData } from 'common/Types';
+import { CellData } from 'common/buffer/CellData';
+import { ICircularList, IBufferLine, ICellData } from 'common/Types';
 
 export interface INewLayoutResult {
   layout: number[];
@@ -22,7 +21,7 @@ export interface INewLayoutResult {
  * @param nullCell The cell data to use when filling in empty cells.
  * @param reflowCursorLine Whether to reflow the line containing the cursor.
  */
-export function reflowLargerGetLinesToRemove(lines: CircularList<IBufferLine>, oldCols: number, newCols: number, bufferAbsoluteY: number, nullCell: ICellData, reflowCursorLine: boolean): number[] {
+export function reflowLargerGetLinesToRemove(lines: ICircularList<IBufferLine>, oldCols: number, newCols: number, bufferAbsoluteY: number, nullCell: ICellData, reflowCursorLine: boolean): number[] {
   // Gather all BufferLines that need to be removed from the Buffer here so that they can be
   // batched up and only committed once
   const toRemove: number[] = [];
@@ -30,16 +29,16 @@ export function reflowLargerGetLinesToRemove(lines: CircularList<IBufferLine>, o
   for (let y = 0; y < lines.length - 1; y++) {
     // Check if this row is wrapped
     let i = y;
-    let nextLine = lines.get(++i) as BufferLine;
+    let nextLine = lines.get(++i) as IBufferLine;
     if (!nextLine.isWrapped) {
       continue;
     }
 
     // Check how many lines it's wrapped for
-    const wrappedLines: BufferLine[] = [lines.get(y) as BufferLine];
+    const wrappedLines: IBufferLine[] = [lines.get(y) as IBufferLine];
     while (i < lines.length && nextLine.isWrapped) {
       wrappedLines.push(nextLine);
-      nextLine = lines.get(++i) as BufferLine;
+      nextLine = lines.get(++i) as IBufferLine;
     }
 
     if (!reflowCursorLine) {
@@ -62,7 +61,7 @@ export function reflowLargerGetLinesToRemove(lines: CircularList<IBufferLine>, o
       const destRemainingCells = newCols - destCol;
       const cellsToCopy = Math.min(srcRemainingCells, destRemainingCells);
 
-      wrappedLines[destLineIndex].copyCellsFrom(wrappedLines[srcLineIndex], srcCol, destCol, cellsToCopy, false);
+      copyCells(wrappedLines[srcLineIndex], wrappedLines[destLineIndex], srcCol, destCol, cellsToCopy);
 
       destCol += cellsToCopy;
       if (destCol === newCols) {
@@ -78,7 +77,7 @@ export function reflowLargerGetLinesToRemove(lines: CircularList<IBufferLine>, o
       // Make sure the last cell isn't wide, if it is copy it to the current dest
       if (destCol === 0 && destLineIndex !== 0) {
         if (wrappedLines[destLineIndex - 1].getWidth(newCols - 1) === 2) {
-          wrappedLines[destLineIndex].copyCellsFrom(wrappedLines[destLineIndex - 1], newCols - 1, destCol++, 1, false);
+          copyCells(wrappedLines[destLineIndex - 1], wrappedLines[destLineIndex], newCols - 1, destCol++, 1);
           // Null out the end of the last row
           wrappedLines[destLineIndex - 1].setCell(newCols - 1, nullCell);
         }
@@ -113,7 +112,7 @@ export function reflowLargerGetLinesToRemove(lines: CircularList<IBufferLine>, o
  * @param lines The buffer lines.
  * @param toRemove The indexes to remove.
  */
-export function reflowLargerCreateNewLayout(lines: CircularList<IBufferLine>, toRemove: number[]): INewLayoutResult {
+export function reflowLargerCreateNewLayout(lines: ICircularList<IBufferLine>, toRemove: number[]): INewLayoutResult {
   const layout: number[] = [];
   // First iterate through the list and get the actual indexes to use for rows
   let nextToRemoveIndex = 0;
@@ -148,11 +147,11 @@ export function reflowLargerCreateNewLayout(lines: CircularList<IBufferLine>, to
  * @param lines The buffer lines.
  * @param newLayout The new layout to apply.
  */
-export function reflowLargerApplyNewLayout(lines: CircularList<IBufferLine>, newLayout: number[]): void {
+export function reflowLargerApplyNewLayout(lines: ICircularList<IBufferLine>, newLayout: number[]): void {
   // Record original lines so they don't get overridden when we rearrange the list
-  const newLayoutLines: BufferLine[] = [];
+  const newLayoutLines: IBufferLine[] = [];
   for (let i = 0; i < newLayout.length; i++) {
-    newLayoutLines.push(lines.get(newLayout[i]) as BufferLine);
+    newLayoutLines.push((lines.get(newLayout[i]) as IBufferLine).clone());
   }
 
   // Rearrange the list
@@ -176,7 +175,7 @@ export function reflowLargerApplyNewLayout(lines: CircularList<IBufferLine>, new
  * @param oldCols The columns before resize.
  * @param newCols The columns after resize.
  */
-export function reflowSmallerGetNewLineLengths(wrappedLines: BufferLine[], oldCols: number, newCols: number): number[] {
+export function reflowSmallerGetNewLineLengths(wrappedLines: IBufferLine[], oldCols: number, newCols: number): number[] {
   const newLineLengths: number[] = [];
   const cellsNeeded = wrappedLines.map((l, i) => getWrappedLineTrimmedLength(wrappedLines, i, oldCols)).reduce((p, c) => p + c);
 
@@ -209,7 +208,7 @@ export function reflowSmallerGetNewLineLengths(wrappedLines: BufferLine[], oldCo
   return newLineLengths;
 }
 
-export function getWrappedLineTrimmedLength(lines: BufferLine[], i: number, cols: number): number {
+export function getWrappedLineTrimmedLength(lines: IBufferLine[], i: number, cols: number): number {
   // If this is the last row in the wrapped line, get the actual trimmed length
   if (i === lines.length - 1) {
     return lines[i].getTrimmedLength();
@@ -224,3 +223,17 @@ export function getWrappedLineTrimmedLength(lines: BufferLine[], i: number, cols
   }
   return cols;
 }
+
+const workCell = new CellData();
+
+function copyCells(src: IBufferLine, dest: IBufferLine, srcCol: number, destCol: number, length: number): void {
+  if (src === dest && destCol > srcCol) {
+    for (let i = length - 1; i >= 0; i--) {
+      dest.setCell(destCol + i, src.loadCell(srcCol + i, workCell));
+    }
+    return;
+  }
+  for (let i = 0; i < length; i++) {
+    dest.setCell(destCol + i, src.loadCell(srcCol + i, workCell));
+  }
+}

src/common/buffer/GhosttyBufferLine.test.ts

@@ -0,0 +1,44 @@
+import { assert } from 'chai';
+import { GhosttyWasmBuffer } from 'common/buffer/GhosttyWasmBuffer';
+import { GhosttyBufferLine } from 'common/buffer/GhosttyBufferLine';
+import { DEFAULT_ATTR_DATA } from 'common/buffer/BufferLine';
+import { CellData } from 'common/buffer/CellData';
+
+const WASM_PATH = 'vendor/ghostty-wasm/ghostty-vt.wasm';
+
+describe('GhosttyBufferLine', () => {
+  before(() => {
+    (globalThis as any).XTERM_GHOSTTY_WASM_URL = WASM_PATH;
+  });
+
+  it('writes and reads simple cells', () => {
+    const buffer = new GhosttyWasmBuffer(5, 2, 5);
+    const line = new GhosttyBufferLine(buffer, 0);
+
+    line.setCellFromCodepoint(0, 'A'.charCodeAt(0), 1, DEFAULT_ATTR_DATA);
+    line.setCellFromCodepoint(1, 'B'.charCodeAt(0), 1, DEFAULT_ATTR_DATA);
+
+    assert.equal(line.translateToString(true), 'AB');
+    assert.equal(line.getCodePoint(0), 'A'.charCodeAt(0));
+    assert.equal(line.getCodePoint(1), 'B'.charCodeAt(0));
+
+    buffer.dispose();
+  });
+
+  it('supports insert and delete', () => {
+    const buffer = new GhosttyWasmBuffer(5, 1, 5);
+    const line = new GhosttyBufferLine(buffer, 0);
+    const fill = new CellData();
+
+    line.setCellFromCodepoint(0, 'A'.charCodeAt(0), 1, DEFAULT_ATTR_DATA);
+    line.setCellFromCodepoint(1, 'B'.charCodeAt(0), 1, DEFAULT_ATTR_DATA);
+
+    line.insertCells(1, 1, fill);
+    assert.equal(line.translateToString(true), 'A B');
+
+    line.deleteCells(1, 1, fill);
+    assert.equal(line.translateToString(true), 'AB');
+
+    buffer.dispose();
+  });
+});

src/common/buffer/GhosttyBufferLine.ts

@@ -0,0 +1,352 @@
+/**
+ * Copyright (c) 2026 The xterm.js authors. All rights reserved.
+ * @license MIT
+ */
+
+import { CharData, IAttributeData, IBufferLine, ICellData, IExtendedAttrs } from 'common/Types';
+import { CellData } from 'common/buffer/CellData';
+import { BufferLine } from 'common/buffer/BufferLine';
+import { Attributes, BgFlags, CHAR_DATA_ATTR_INDEX, CHAR_DATA_CHAR_INDEX, CHAR_DATA_WIDTH_INDEX, Content, WHITESPACE_CELL_CHAR } from 'common/buffer/Constants';
+import { stringFromCodePoint } from 'common/input/TextDecoder';
+import { GhosttyWasmBuffer } from 'common/buffer/GhosttyWasmBuffer';
+
+// Work variables to avoid garbage collection
+const workCell = new CellData();
+
+export class GhosttyBufferLine implements IBufferLine {
+  public get length(): number {
+    return this._buffer.cols;
+  }
+
+  constructor(
+    private readonly _buffer: GhosttyWasmBuffer,
+    private readonly _row: number
+  ) {
+  }
+
+  public get row(): number {
+    return this._row;
+  }
+
+  public get _extendedAttrs(): { [key: number]: IExtendedAttrs | undefined } {
+    const rowMap = this._buffer.getExtendedRow(this._row);
+    if (!rowMap) {
+      return {};
+    }
+    const result: { [key: number]: IExtendedAttrs | undefined } = {};
+    for (const [col, ext] of rowMap) {
+      result[col] = ext;
+    }
+    return result;
+  }
+
+  public get isWrapped(): boolean {
+    return this._buffer.getRowWrap(this._row);
+  }
+
+  public set isWrapped(value: boolean) {
+    this._buffer.setRowWrap(this._row, value);
+  }
+
+  public get(index: number): CharData {
+    const [content, fg] = this._buffer.getCell(this._row, index);
+    const cp = content & Content.CODEPOINT_MASK;
+    const combined = (content & Content.IS_COMBINED_MASK)
+      ? this._buffer.getCombined(this._row, index) ?? ''
+      : '';
+    return [
+      fg,
+      (content & Content.IS_COMBINED_MASK)
+        ? combined
+        : (cp) ? stringFromCodePoint(cp) : '',
+      content >> Content.WIDTH_SHIFT,
+      (content & Content.IS_COMBINED_MASK)
+        ? (combined.length ? combined.charCodeAt(combined.length - 1) : 0)
+        : cp
+    ];
+  }
+
+  public set(index: number, value: CharData): void {
+    const fg = value[CHAR_DATA_ATTR_INDEX];
+    const chars = value[CHAR_DATA_CHAR_INDEX];
+    if (chars.length > 1) {
+      this._buffer.setCombined(this._row, index, chars);
+      this._buffer.setCell(this._row, index, index | Content.IS_COMBINED_MASK | (value[CHAR_DATA_WIDTH_INDEX] << Content.WIDTH_SHIFT), fg, 0);
+    } else {
+      this._buffer.clearCombined(this._row, index);
+      this._buffer.setCell(this._row, index, chars.charCodeAt(0) | (value[CHAR_DATA_WIDTH_INDEX] << Content.WIDTH_SHIFT), fg, 0);
+    }
+  }
+
+  public loadCell(index: number, cell: ICellData): ICellData {
+    const [content, fg, bg] = this._buffer.getCell(this._row, index);
+    cell.content = content;
+    cell.fg = fg;
+    cell.bg = bg;
+    if (cell.content & Content.IS_COMBINED_MASK) {
+      cell.combinedData = this._buffer.getCombined(this._row, index) ?? '';
+    }
+    if (cell.bg & BgFlags.HAS_EXTENDED) {
+      cell.extended = this._buffer.getExtended(this._row, index)!;
+    }
+    return cell;
+  }
+
+  public setCell(index: number, cell: ICellData): void {
+    if (cell.content & Content.IS_COMBINED_MASK) {
+      this._buffer.setCombined(this._row, index, cell.combinedData);
+    } else {
+      this._buffer.clearCombined(this._row, index);
+    }
+    if (cell.bg & BgFlags.HAS_EXTENDED) {
+      this._buffer.setExtended(this._row, index, cell.extended);
+    } else {
+      this._buffer.clearExtended(this._row, index);
+    }
+    this._buffer.setCell(this._row, index, cell.content, cell.fg, cell.bg);
+  }
+
+  public setCellFromCodepoint(index: number, codePoint: number, width: number, attrs: IAttributeData): void {
+    if (attrs.bg & BgFlags.HAS_EXTENDED) {
+      this._buffer.setExtended(this._row, index, attrs.extended);
+    } else {
+      this._buffer.clearExtended(this._row, index);
+    }
+    this._buffer.clearCombined(this._row, index);
+    this._buffer.setCell(this._row, index, codePoint | (width << Content.WIDTH_SHIFT), attrs.fg, attrs.bg);
+  }
+
+  public addCodepointToCell(index: number, codePoint: number, width: number): void {
+    const [content, fg, bg] = this._buffer.getCell(this._row, index);
+    let newContent = content;
+    if (content & Content.IS_COMBINED_MASK) {
+      const existing = this._buffer.getCombined(this._row, index) ?? '';
+      this._buffer.setCombined(this._row, index, existing + stringFromCodePoint(codePoint));
+    } else {
+      if (content & Content.CODEPOINT_MASK) {
+        const existing = stringFromCodePoint(content & Content.CODEPOINT_MASK);
+        this._buffer.setCombined(this._row, index, existing + stringFromCodePoint(codePoint));
+        newContent &= ~Content.CODEPOINT_MASK;
+        newContent |= Content.IS_COMBINED_MASK;
+      } else {
+        newContent = codePoint | (1 << Content.WIDTH_SHIFT);
+      }
+    }
+    if (width) {
+      newContent &= ~Content.WIDTH_MASK;
+      newContent |= width << Content.WIDTH_SHIFT;
+    }
+    this._buffer.setCell(this._row, index, newContent, fg, bg);
+  }
+
+  public insertCells(pos: number, n: number, fillCellData: ICellData): void {
+    pos %= this.length;
+    if (pos && this.getWidth(pos - 1) === 2) {
+      this.setCellFromCodepoint(pos - 1, 0, 1, fillCellData);
+    }
+
+    if (n < this.length - pos) {
+      for (let i = this.length - pos - n - 1; i >= 0; --i) {
+        this.setCell(pos + n + i, this.loadCell(pos + i, workCell));
+      }
+      for (let i = 0; i < n; ++i) {
+        this.setCell(pos + i, fillCellData);
+      }
+    } else {
+      for (let i = pos; i < this.length; ++i) {
+        this.setCell(i, fillCellData);
+      }
+    }
+
+    if (this.getWidth(this.length - 1) === 2) {
+      this.setCellFromCodepoint(this.length - 1, 0, 1, fillCellData);
+    }
+  }
+
+  public deleteCells(pos: number, n: number, fillCellData: ICellData): void {
+    pos %= this.length;
+    if (n < this.length - pos) {
+      for (let i = 0; i < this.length - pos - n; ++i) {
+        this.setCell(pos + i, this.loadCell(pos + n + i, workCell));
+      }
+      for (let i = this.length - n; i < this.length; ++i) {
+        this.setCell(i, fillCellData);
+      }
+    } else {
+      for (let i = pos; i < this.length; ++i) {
+        this.setCell(i, fillCellData);
+      }
+    }
+
+    if (pos && this.getWidth(pos - 1) === 2) {
+      this.setCellFromCodepoint(pos - 1, 0, 1, fillCellData);
+    }
+    if (this.getWidth(pos) === 0 && !this.hasContent(pos)) {
+      this.setCellFromCodepoint(pos, 0, 1, fillCellData);
+    }
+  }
+
+  public replaceCells(start: number, end: number, fillCellData: ICellData, respectProtect: boolean = false): void {
+    if (respectProtect) {
+      if (start && this.getWidth(start - 1) === 2 && !this.isProtected(start - 1)) {
+        this.setCellFromCodepoint(start - 1, 0, 1, fillCellData);
+      }
+      if (end < this.length && this.getWidth(end - 1) === 2 && !this.isProtected(end)) {
+        this.setCellFromCodepoint(end, 0, 1, fillCellData);
+      }
+      while (start < end && start < this.length) {
+        if (!this.isProtected(start)) {
+          this.setCell(start, fillCellData);
+        }
+        start++;
+      }
+      return;
+    }
+
+    if (start && this.getWidth(start - 1) === 2) {
+      this.setCellFromCodepoint(start - 1, 0, 1, fillCellData);
+    }
+    if (end < this.length && this.getWidth(end - 1) === 2) {
+      this.setCellFromCodepoint(end, 0, 1, fillCellData);
+    }
+
+    while (start < end && start < this.length) {
+      this.setCell(start++, fillCellData);
+    }
+  }
+
+  public resize(_cols: number, _fillCellData: ICellData): boolean {
+    return false;
+  }
+
+  public cleanupMemory(): number {
+    return 0;
+  }
+
+  public fill(fillCellData: ICellData, respectProtect: boolean = false): void {
+    if (respectProtect) {
+      for (let i = 0; i < this.length; ++i) {
+        if (!this.isProtected(i)) {
+          this.setCell(i, fillCellData);
+        }
+      }
+      return;
+    }
+    for (let i = 0; i < this.length; ++i) {
+      this.setCell(i, fillCellData);
+    }
+  }
+
+  public copyFrom(line: IBufferLine): void {
+    for (let i = 0; i < this.length; ++i) {
+      this.setCell(i, line.loadCell(i, workCell));
+    }
+    this.isWrapped = line.isWrapped;
+  }
+
+  public clone(): IBufferLine {
+    const clone = new BufferLine(this.length);
+    for (let i = 0; i < this.length; ++i) {
+      clone.setCell(i, this.loadCell(i, workCell));
+    }
+    clone.isWrapped = this.isWrapped;
+    return clone;
+  }
+
+  public getTrimmedLength(): number {
+    for (let i = this.length - 1; i >= 0; --i) {
+      if ((this._buffer.getCell(this._row, i)[0] & Content.HAS_CONTENT_MASK)) {
+        return i + (this._buffer.getCell(this._row, i)[0] >> Content.WIDTH_SHIFT);
+      }
+    }
+    return 0;
+  }
+
+  public getNoBgTrimmedLength(): number {
+    for (let i = this.length - 1; i >= 0; --i) {
+      const [content, , bg] = this._buffer.getCell(this._row, i);
+      if ((content & Content.HAS_CONTENT_MASK) || (bg & Attributes.CM_MASK)) {
+        return i + (content >> Content.WIDTH_SHIFT);
+      }
+    }
+    return 0;
+  }
+
+  public translateToString(trimRight?: boolean, startCol?: number, endCol?: number, outColumns?: number[]): string {
+    startCol = startCol ?? 0;
+    endCol = endCol ?? this.length;
+    if (trimRight) {
+      endCol = Math.min(endCol, this.getTrimmedLength());
+    }
+    if (outColumns) {
+      outColumns.length = 0;
+    }
+    let result = '';
+    while (startCol < endCol) {
+      const content = this._buffer.getCell(this._row, startCol)[0];
+      const cp = content & Content.CODEPOINT_MASK;
+      const chars = (content & Content.IS_COMBINED_MASK)
+        ? (this._buffer.getCombined(this._row, startCol) ?? '')
+        : (cp) ? stringFromCodePoint(cp) : WHITESPACE_CELL_CHAR;
+      result += chars;
+      if (outColumns) {
+        for (let i = 0; i < chars.length; ++i) {
+          outColumns.push(startCol);
+        }
+      }
+      startCol += (content >> Content.WIDTH_SHIFT) || 1;
+    }
+    if (outColumns) {
+      outColumns.push(startCol);
+    }
+    return result;
+  }
+
+  public getWidth(index: number): number {
+    return this._buffer.getCell(this._row, index)[0] >> Content.WIDTH_SHIFT;
+  }
+
+  public hasWidth(index: number): number {
+    return this._buffer.getCell(this._row, index)[0] & Content.WIDTH_MASK;
+  }
+
+  public getFg(index: number): number {
+    return this._buffer.getCell(this._row, index)[1];
+  }
+
+  public getBg(index: number): number {
+    return this._buffer.getCell(this._row, index)[2];
+  }
+
+  public hasContent(index: number): number {
+    return this._buffer.getCell(this._row, index)[0] & Content.HAS_CONTENT_MASK;
+  }
+
+  public getCodePoint(index: number): number {
+    const content = this._buffer.getCell(this._row, index)[0];
+    if (content & Content.IS_COMBINED_MASK) {
+      const combined = this._buffer.getCombined(this._row, index) ?? '';
+      return combined.charCodeAt(combined.length - 1);
+    }
+    return content & Content.CODEPOINT_MASK;
+  }
+
+  public isCombined(index: number): number {
+    return this._buffer.getCell(this._row, index)[0] & Content.IS_COMBINED_MASK;
+  }
+
+  public getString(index: number): string {
+    const content = this._buffer.getCell(this._row, index)[0];
+    if (content & Content.IS_COMBINED_MASK) {
+      return this._buffer.getCombined(this._row, index) ?? '';
+    }
+    if (content & Content.CODEPOINT_MASK) {
+      return stringFromCodePoint(content & Content.CODEPOINT_MASK);
+    }
+    return '';
+  }
+
+  public isProtected(index: number): number {
+    return this._buffer.getCell(this._row, index)[2] & BgFlags.PROTECTED;
+  }
+}

src/common/buffer/GhosttyCircularList.ts

@@ -0,0 +1,270 @@
+/**
+ * Copyright (c) 2026 The xterm.js authors. All rights reserved.
+ * @license MIT
+ */
+
+import { ICircularList, IBufferLine } from 'common/Types';
+import { Disposable } from 'common/Lifecycle';
+import { Emitter } from 'common/Event';
+import { IDeleteEvent, IInsertEvent } from 'common/CircularList';
+import { GhosttyWasmBuffer } from 'common/buffer/GhosttyWasmBuffer';
+import { GhosttyBufferLine } from 'common/buffer/GhosttyBufferLine';
+import { CellData } from 'common/buffer/CellData';
+import { BgFlags, Content } from 'common/buffer/Constants';
+
+export class GhosttyCircularList extends Disposable implements ICircularList<IBufferLine> {
+  private _startIndex: number = 0;
+  private _length: number = 0;
+  private _lines: GhosttyBufferLine[];
+
+  public readonly onDeleteEmitter = this._register(new Emitter<IDeleteEvent>());
+  public readonly onDelete = this.onDeleteEmitter.event;
+  public readonly onInsertEmitter = this._register(new Emitter<IInsertEvent>());
+  public readonly onInsert = this.onInsertEmitter.event;
+  public readonly onTrimEmitter = this._register(new Emitter<number>());
+  public readonly onTrim = this.onTrimEmitter.event;
+
+  private _workCell = new CellData();
+
+  constructor(
+    private _buffer: GhosttyWasmBuffer,
+    private _maxLength: number
+  ) {
+    super();
+    this._lines = new Array<GhosttyBufferLine>(_maxLength);
+    for (let i = 0; i < _maxLength; i++) {
+      this._lines[i] = new GhosttyBufferLine(this._buffer, i);
+    }
+  }
+
+  public get maxLength(): number {
+    return this._maxLength;
+  }
+
+  public set maxLength(newMaxLength: number) {
+    if (this._maxLength === newMaxLength) {
+      return;
+    }
+
+    const nextLength = Math.min(newMaxLength, this.length);
+    const oldLines = this._getLogicalLines(nextLength);
+    const newLines = new Array<GhosttyBufferLine>(newMaxLength);
+    for (let i = 0; i < newMaxLength; i++) {
+      newLines[i] = new GhosttyBufferLine(this._buffer, i);
+    }
+    for (let i = 0; i < nextLength; i++) {
+      this._buffer.copyRow(oldLines[i].row, newLines[i].row);
+    }
+
+    this._lines = newLines;
+    this._maxLength = newMaxLength;
+    this._startIndex = 0;
+    this._length = nextLength;
+  }
+
+  public get length(): number {
+    return this._length;
+  }
+
+  public set length(newLength: number) {
+    this._length = newLength;
+  }
+
+  public get isFull(): boolean {
+    return this._length === this._maxLength;
+  }
+
+  public get(index: number): IBufferLine | undefined {
+    if (index < 0 || index >= this._length) {
+      return undefined;
+    }
+    return this._lines[this._getCyclicIndex(index)];
+  }
+
+  public set(index: number, value: IBufferLine): void {
+    if (index < 0) {
+      return;
+    }
+    if (index >= this._length) {
+      this._length = Math.min(index + 1, this._maxLength);
+    }
+    this._setIndex(index, value);
+  }
+
+  public push(value: IBufferLine): void {
+    if (this._length === this._maxLength) {
+      this._startIndex = ++this._startIndex % this._maxLength;
+      this.onTrimEmitter.fire(1);
+    } else {
+      this._length++;
+    }
+    this.set(this._length - 1, value);
+  }
+
+  public recycle(): GhosttyBufferLine {
+    if (!this.isFull) {
+      throw new Error('recycle is only supported when buffer is full');
+    }
+    this._startIndex = ++this._startIndex % this._maxLength;
+    this.onTrimEmitter.fire(1);
+    return this._lines[this._getCyclicIndex(this._length - 1)];
+  }
+
+  public pop(): IBufferLine | undefined {
+    if (this._length === 0) {
+      return undefined;
+    }
+    const value = this._lines[this._getCyclicIndex(this._length - 1)];
+    this._length--;
+    return value;
+  }
+
+  public splice(start: number, deleteCount: number, ...items: IBufferLine[]): void {
+    if (deleteCount === 0 && items.length === 0) {
+      return;
+    }
+
+    const before = Math.max(0, Math.min(start, this._length));
+    const actualDeleteCount = Math.min(deleteCount, this._length - before);
+
+    if (actualDeleteCount) {
+      for (let i = before; i < this._length - actualDeleteCount; i++) {
+        const src = this.get(i + actualDeleteCount);
+        if (src) {
+          this._setIndex(i, src);
+        }
+      }
+      this._length -= actualDeleteCount;
+      this.onDeleteEmitter.fire({ index: before, amount: actualDeleteCount });
+    }
+
+    if (items.length) {
+      for (let i = this._length - 1; i >= before; i--) {
+        const src = this.get(i);
+        if (src) {
+          this._setIndex(i + items.length, src);
+        }
+      }
+      for (let i = 0; i < items.length; i++) {
+        this._setIndex(before + i, items[i]);
+      }
+      this.onInsertEmitter.fire({ index: before, amount: items.length });
+
+      if (this._length + items.length > this._maxLength) {
+        const countToTrim = this._length + items.length - this._maxLength;
+        this._startIndex = (this._startIndex + countToTrim) % this._maxLength;
+        this._length = this._maxLength;
+        this.onTrimEmitter.fire(countToTrim);
+      } else {
+        this._length += items.length;
+      }
+    }
+  }
+
+  public trimStart(count: number): void {
+    if (count <= 0) {
+      return;
+    }
+    count = Math.min(count, this._length);
+    if (count > 0) {
+      this._startIndex = (this._startIndex + count) % this._maxLength;
+      this._length -= count;
+      this.onTrimEmitter.fire(count);
+    }
+  }
+
+  public shiftElements(start: number, count: number, offset: number): void {
+    if (count <= 0) {
+      return;
+    }
+    if (start < 0 || start >= this._length) {
+      throw new Error('start argument out of range');
+    }
+    if (start + offset < 0) {
+      throw new Error('Cannot shift elements in list beyond index 0');
+    }
+
+    if (offset > 0) {
+      for (let i = count - 1; i >= 0; i--) {
+        const srcLine = this.get(start + i);
+        if (srcLine) {
+          this._setIndex(start + i + offset, srcLine);
+        }
+      }
+      const expandListBy = (start + count + offset) - this._length;
+      if (expandListBy > 0) {
+        this._length += expandListBy;
+        while (this._length > this._maxLength) {
+          this._length--;
+          this._startIndex = (this._startIndex + 1) % this._maxLength;
+          this.onTrimEmitter.fire(1);
+        }
+      }
+    } else if (offset < 0) {
+      for (let i = 0; i < count; i++) {
+        const srcLine = this.get(start + i);
+        if (srcLine) {
+          this._setIndex(start + i + offset, srcLine);
+        }
+      }
+    }
+  }
+
+  public normalize(): void {
+    if (this._startIndex === 0) {
+      return;
+    }
+    const snapshot = this._getLogicalLines(this._length).map(line => line.clone());
+    for (let i = 0; i < snapshot.length; i++) {
+      this._copyInto(this._lines[i].row, snapshot[i]);
+    }
+    this._startIndex = 0;
+  }
+
+  private _setIndex(index: number, value: IBufferLine): void {
+    const line = this._lines[this._getCyclicIndex(index)];
+    this._copyInto(line.row, value);
+  }
+
+  private _getCyclicIndex(index: number): number {
+    return (this._startIndex + index) % this._maxLength;
+  }
+
+  private _copyInto(rowIndex: number, value: IBufferLine): void {
+    const nullContent = 1 << Content.WIDTH_SHIFT;
+    if (value instanceof GhosttyBufferLine) {
+      this._buffer.copyRow(value.row, rowIndex);
+      return;
+    }
+
+    const colsToCopy = Math.min(this._buffer.cols, value.length);
+    for (let col = 0; col < colsToCopy; col++) {
+      const cell = value.loadCell(col, this._workCell);
+      this._buffer.setCell(rowIndex, col, cell.content, cell.fg, cell.bg);
+      if (cell.content & Content.IS_COMBINED_MASK) {
+        this._buffer.setCombined(rowIndex, col, cell.combinedData);
+      } else {
+        this._buffer.clearCombined(rowIndex, col);
+      }
+      if (cell.bg & BgFlags.HAS_EXTENDED) {
+        this._buffer.setExtended(rowIndex, col, cell.extended);
+      } else {
+        this._buffer.clearExtended(rowIndex, col);
+      }
+    }
+    for (let col = colsToCopy; col < this._buffer.cols; col++) {
+      this._buffer.setCell(rowIndex, col, nullContent, 0, 0);
+      this._buffer.clearCombined(rowIndex, col);
+      this._buffer.clearExtended(rowIndex, col);
+    }
+    this._buffer.setRowWrap(rowIndex, value.isWrapped);
+  }
+
+  private _getLogicalLines(count: number): GhosttyBufferLine[] {
+    const result: GhosttyBufferLine[] = [];
+    for (let i = 0; i < count; i++) {
+      result.push(this._lines[this._getCyclicIndex(i)]);
+    }
+    return result;
+  }
+}

src/common/buffer/GhosttyWasmBuffer.ts

@@ -0,0 +1,198 @@
+/**
+ * Copyright (c) 2026 The xterm.js authors. All rights reserved.
+ * @license MIT
+ */
+
+import { GhosttyWasmRuntime, IGhosttyWasmExports } from 'common/parser/GhosttyWasmRuntime';
+import { IExtendedAttrs } from 'common/Types';
+
+const CELL_STRIDE = 3;
+
+export class GhosttyWasmBuffer {
+  private readonly _wasm: IGhosttyWasmExports;
+  private _handle: number;
+  private _cols: number;
+  private _rows: number;
+  private _maxRows: number;
+
+  private _combined = new Map<number, Map<number, string>>();
+  private _extended = new Map<number, Map<number, IExtendedAttrs>>();
+
+  private _cellScratchPtr: number;
+
+  constructor(cols: number, rows: number, maxRows: number) {
+    this._wasm = GhosttyWasmRuntime.getInstanceSync();
+    this._cols = cols;
+    this._rows = rows;
+    this._maxRows = maxRows;
+
+    this._handle = this._wasm.ghostty_xterm_buffer_new(cols, rows, maxRows);
+    if (!this._handle) {
+      throw new Error('Failed to allocate Ghostty xterm buffer');
+    }
+
+    this._cellScratchPtr = this._wasm.ghostty_wasm_alloc_u8_array(CELL_STRIDE * 4);
+    if (!this._cellScratchPtr) {
+      this._wasm.ghostty_xterm_buffer_free(this._handle);
+      this._handle = 0;
+      throw new Error('Failed to allocate Ghostty cell scratch buffer');
+    }
+  }
+
+  public dispose(): void {
+    if (this._handle) {
+      this._wasm.ghostty_xterm_buffer_free(this._handle);
+      this._handle = 0;
+    }
+    if (this._cellScratchPtr) {
+      this._wasm.ghostty_wasm_free_u8_array(this._cellScratchPtr, CELL_STRIDE * 4);
+      this._cellScratchPtr = 0;
+    }
+  }
+
+  public get cols(): number {
+    return this._cols;
+  }
+
+  public get rows(): number {
+    return this._rows;
+  }
+
+  public get maxRows(): number {
+    return this._maxRows;
+  }
+
+  public resize(cols: number, rows: number, maxRows: number): void {
+    const oldCols = this._cols;
+    if (!this._wasm.ghostty_xterm_buffer_resize(this._handle, cols, rows, maxRows)) {
+      throw new Error('Failed to resize Ghostty xterm buffer');
+    }
+    this._cols = cols;
+    this._rows = rows;
+    this._maxRows = maxRows;
+
+    if (cols < oldCols) {
+      for (const [row, rowMap] of this._combined) {
+        for (const col of rowMap.keys()) {
+          if (col >= cols) {
+            rowMap.delete(col);
+          }
+        }
+        if (rowMap.size === 0) {
+          this._combined.delete(row);
+        }
+      }
+      for (const [row, rowMap] of this._extended) {
+        for (const col of rowMap.keys()) {
+          if (col >= cols) {
+            rowMap.delete(col);
+          }
+        }
+        if (rowMap.size === 0) {
+          this._extended.delete(row);
+        }
+      }
+    }
+  }
+
+  public clear(): void {
+    this._wasm.ghostty_xterm_buffer_clear(this._handle);
+    this._combined.clear();
+    this._extended.clear();
+  }
+
+  public getCell(row: number, col: number): [number, number, number] {
+    this._wasm.ghostty_xterm_buffer_get_cell(this._handle, row, col, this._cellScratchPtr);
+    const view = new DataView(this._wasm.memory.buffer, this._cellScratchPtr, CELL_STRIDE * 4);
+    const content = view.getUint32(0, true);
+    const fg = view.getUint32(4, true);
+    const bg = view.getUint32(8, true);
+    return [content, fg, bg];
+  }
+
+  public setCell(row: number, col: number, content: number, fg: number, bg: number): void {
+    this._wasm.ghostty_xterm_buffer_set_cell(this._handle, row, col, content, fg, bg);
+  }
+
+  public clearRow(row: number, content: number, fg: number, bg: number): void {
+    this._wasm.ghostty_xterm_buffer_clear_row(this._handle, row, content, fg, bg);
+    this._combined.delete(row);
+    this._extended.delete(row);
+  }
+
+  public copyRow(srcRow: number, dstRow: number): void {
+    this._wasm.ghostty_xterm_buffer_copy_row(this._handle, srcRow, dstRow);
+    const combined = this._combined.get(srcRow);
+    if (combined) {
+      this._combined.set(dstRow, new Map(combined));
+    } else {
+      this._combined.delete(dstRow);
+    }
+    const extended = this._extended.get(srcRow);
+    if (extended) {
+      this._extended.set(dstRow, new Map(extended));
+    } else {
+      this._extended.delete(dstRow);
+    }
+  }
+
+  public getRowWrap(row: number): boolean {
+    return this._wasm.ghostty_xterm_buffer_get_row_wrap(this._handle, row) !== 0;
+  }
+
+  public setRowWrap(row: number, wrap: boolean): void {
+    this._wasm.ghostty_xterm_buffer_set_row_wrap(this._handle, row, wrap ? 1 : 0);
+  }
+
+  public getCombined(row: number, col: number): string | undefined {
+    return this._combined.get(row)?.get(col);
+  }
+
+  public setCombined(row: number, col: number, data: string): void {
+    let rowMap = this._combined.get(row);
+    if (!rowMap) {
+      rowMap = new Map();
+      this._combined.set(row, rowMap);
+    }
+    rowMap.set(col, data);
+  }
+
+  public clearCombined(row: number, col: number): void {
+    const rowMap = this._combined.get(row);
+    if (!rowMap) {
+      return;
+    }
+    rowMap.delete(col);
+    if (rowMap.size === 0) {
+      this._combined.delete(row);
+    }
+  }
+
+  public getExtended(row: number, col: number): IExtendedAttrs | undefined {
+    return this._extended.get(row)?.get(col);
+  }
+
+  public getExtendedRow(row: number): Map<number, IExtendedAttrs> | undefined {
+    return this._extended.get(row);
+  }
+
+  public setExtended(row: number, col: number, data: IExtendedAttrs): void {
+    let rowMap = this._extended.get(row);
+    if (!rowMap) {
+      rowMap = new Map();
+      this._extended.set(row, rowMap);
+    }
+    rowMap.set(col, data);
+  }
+
+  public clearExtended(row: number, col: number): void {
+    const rowMap = this._extended.get(row);
+    if (!rowMap) {
+      return;
+    }
+    rowMap.delete(col);
+    if (rowMap.size === 0) {
+      this._extended.delete(row);
+    }
+  }
+}

src/common/parser/GhosttyWasmParser.ts

@@ -0,0 +1,831 @@
+/**
+ * Copyright (c) 2026 The xterm.js authors. All rights reserved.
+ * @license MIT
+ */
+
+import { Disposable, toDisposable } from 'common/Lifecycle';
+import { IDisposable } from 'common/Types';
+import { IParsingState, IDcsHandler, IEscapeSequenceParser, IParams, IOscHandler, IHandlerCollection, CsiHandlerType, OscFallbackHandlerType, EscHandlerType, IDcsParser, DcsFallbackHandlerType, IFunctionIdentifier, ExecuteFallbackHandlerType, CsiFallbackHandlerType, EscFallbackHandlerType, PrintHandlerType, PrintFallbackHandlerType, ExecuteHandlerType, IParserStackState, ParserStackType, IApcHandler, IApcParser, ApcFallbackHandlerType } from 'common/parser/Types';
+import { OscParser } from 'common/parser/OscParser';
+import { DcsParser } from 'common/parser/DcsParser';
+import { ApcParser } from 'common/parser/ApcParser';
+import { Params } from 'common/parser/Params';
+import { StringToUtf32 } from 'common/input/TextDecoder';
+import { GhosttyWasmRuntime, IGhosttyWasmExports } from 'common/parser/GhosttyWasmRuntime';
+
+const enum RawEventTag {
+  PRINT = 0,
+  EXECUTE = 1,
+  ESC = 2,
+  CSI = 3,
+  OSC = 4,
+  DCS_HOOK = 5,
+  DCS_PUT = 6,
+  DCS_UNHOOK = 7,
+  APC_START = 8,
+  APC_PUT = 9,
+  APC_END = 10
+}
+
+export class GhosttyWasmParser extends Disposable implements IEscapeSequenceParser {
+  public precedingJoinState = 0;
+
+  private _printHandler: PrintHandlerType;
+  private _executeHandlers: { [flag: number]: ExecuteHandlerType };
+  private _csiHandlers: IHandlerCollection<CsiHandlerType>;
+  private _escHandlers: IHandlerCollection<EscHandlerType>;
+  private readonly _oscParser: OscParser;
+  private readonly _dcsParser: IDcsParser;
+  private readonly _apcParser: IApcParser;
+  private _errorHandler: (state: IParsingState) => IParsingState;
+
+  private _printHandlerFb: PrintFallbackHandlerType;
+  private _executeHandlerFb: ExecuteFallbackHandlerType;
+  private _csiHandlerFb: CsiFallbackHandlerType;
+  private _escHandlerFb: EscFallbackHandlerType;
+  private _errorHandlerFb: (state: IParsingState) => IParsingState;
+
+  private _parseStack: IParserStackState = {
+    state: ParserStackType.NONE,
+    handlers: [],
+    handlerPos: 0,
+    transition: 0,
+    chunkPos: 0
+  };
+
+  private _wasm?: IGhosttyWasmExports;
+  private _parserHandle = 0;
+  private _wasmReady?: Promise<boolean>;
+
+  private _eventSize = 0;
+  private _eventMaxParams = 0;
+  private _eventMaxIntermediates = 0;
+  private readonly _ptrSize = 4;
+
+  private _eventIndex = 0;
+  private _pendingEvents: { ptr: number, len: number } | undefined;
+  private _resumeParams: IParams | undefined;
+
+  private _textEncoder = new TextEncoder();
+  private _textDecoder = new TextDecoder('utf-8');
+  private _utf32Scratch = new Uint32Array(4096);
+  private _oscBuffer = new StringToUtf32();
+  private _dcsPutBuffer = new Uint32Array(1);
+  private _apcPutBuffer = new Uint32Array(1);
+
+  constructor() {
+    super();
+
+    this._printHandlerFb = () => { };
+    this._executeHandlerFb = () => { };
+    this._csiHandlerFb = () => { };
+    this._escHandlerFb = () => { };
+    this._errorHandlerFb = (state: IParsingState): IParsingState => state;
+
+    this._printHandler = this._printHandlerFb;
+    this._executeHandlers = Object.create(null);
+    this._csiHandlers = Object.create(null);
+    this._escHandlers = Object.create(null);
+
+    this._oscParser = this._register(new OscParser());
+    this._dcsParser = this._register(new DcsParser());
+    this._apcParser = this._register(new ApcParser());
+    this._errorHandler = this._errorHandlerFb;
+
+    this._register(toDisposable(() => {
+      this._csiHandlers = Object.create(null);
+      this._executeHandlers = Object.create(null);
+      this._escHandlers = Object.create(null);
+    }));
+
+    this._register(toDisposable(() => {
+      if (this._wasm && this._parserHandle) {
+        this._wasm.ghostty_raw_parser_free(this._parserHandle);
+      }
+      this._parserHandle = 0;
+    }));
+
+    this.registerEscHandler({ final: '\\' }, () => true);
+  }
+
+  public identToString(ident: number): string {
+    const res: string[] = [];
+    while (ident) {
+      res.push(String.fromCharCode(ident & 0xFF));
+      ident >>= 8;
+    }
+    return res.reverse().join('');
+  }
+
+  public setPrintHandler(handler: PrintHandlerType): void {
+    this._printHandler = handler;
+  }
+
+  public clearPrintHandler(): void {
+    this._printHandler = this._printHandlerFb;
+  }
+
+  public registerEscHandler(id: IFunctionIdentifier, handler: EscHandlerType): IDisposable {
+    const ident = this._identifier(id, [0x30, 0x7e]);
+    this._escHandlers[ident] ??= [];
+    const handlerList = this._escHandlers[ident];
+    handlerList.push(handler);
+    return {
+      dispose: () => {
+        const handlerIndex = handlerList.indexOf(handler);
+        if (handlerIndex !== -1) {
+          handlerList.splice(handlerIndex, 1);
+        }
+      }
+    };
+  }
+
+  public clearEscHandler(id: IFunctionIdentifier): void {
+    if (this._escHandlers[this._identifier(id, [0x30, 0x7e])]) delete this._escHandlers[this._identifier(id, [0x30, 0x7e])];
+  }
+
+  public setEscHandlerFallback(handler: EscFallbackHandlerType): void {
+    this._escHandlerFb = handler;
+  }
+
+  public setExecuteHandler(flag: string, handler: ExecuteHandlerType): void {
+    this._executeHandlers[flag.charCodeAt(0)] = handler;
+  }
+
+  public clearExecuteHandler(flag: string): void {
+    if (this._executeHandlers[flag.charCodeAt(0)]) delete this._executeHandlers[flag.charCodeAt(0)];
+  }
+
+  public setExecuteHandlerFallback(handler: ExecuteFallbackHandlerType): void {
+    this._executeHandlerFb = handler;
+  }
+
+  public registerCsiHandler(id: IFunctionIdentifier, handler: CsiHandlerType): IDisposable {
+    const ident = this._identifier(id);
+    this._csiHandlers[ident] ??= [];
+    const handlerList = this._csiHandlers[ident];
+    handlerList.push(handler);
+    return {
+      dispose: () => {
+        const handlerIndex = handlerList.indexOf(handler);
+        if (handlerIndex !== -1) {
+          handlerList.splice(handlerIndex, 1);
+        }
+      }
+    };
+  }
+
+  public clearCsiHandler(id: IFunctionIdentifier): void {
+    if (this._csiHandlers[this._identifier(id)]) delete this._csiHandlers[this._identifier(id)];
+  }
+
+  public setCsiHandlerFallback(callback: CsiFallbackHandlerType): void {
+    this._csiHandlerFb = callback;
+  }
+
+  public registerDcsHandler(id: IFunctionIdentifier, handler: IDcsHandler): IDisposable {
+    return this._dcsParser.registerHandler(this._identifier(id), handler);
+  }
+
+  public clearDcsHandler(id: IFunctionIdentifier): void {
+    this._dcsParser.clearHandler(this._identifier(id));
+  }
+
+  public setDcsHandlerFallback(handler: DcsFallbackHandlerType): void {
+    this._dcsParser.setHandlerFallback(handler);
+  }
+
+  public registerOscHandler(ident: number, handler: IOscHandler): IDisposable {
+    return this._oscParser.registerHandler(ident, handler);
+  }
+
+  public clearOscHandler(ident: number): void {
+    this._oscParser.clearHandler(ident);
+  }
+
+  public setOscHandlerFallback(handler: OscFallbackHandlerType): void {
+    this._oscParser.setHandlerFallback(handler);
+  }
+
+  public registerApcHandler(ident: number, handler: IApcHandler): IDisposable {
+    return this._apcParser.registerHandler(ident, handler);
+  }
+
+  public clearApcHandler(ident: number): void {
+    this._apcParser.clearHandler(ident);
+  }
+
+  public setApcHandlerFallback(handler: ApcFallbackHandlerType): void {
+    this._apcParser.setHandlerFallback(handler);
+  }
+
+  public setErrorHandler(handler: (state: IParsingState) => IParsingState): void {
+    this._errorHandler = handler;
+  }
+
+  public clearErrorHandler(): void {
+    this._errorHandler = this._errorHandlerFb;
+  }
+
+  public reset(): void {
+    this._oscParser.reset();
+    this._dcsParser.reset();
+    this._apcParser.reset();
+    this.precedingJoinState = 0;
+    if (this._wasm && this._parserHandle) {
+      this._wasm.ghostty_raw_parser_reset(this._parserHandle);
+    }
+    if (this._parseStack.state !== ParserStackType.NONE) {
+      this._parseStack.state = ParserStackType.RESET;
+      this._parseStack.handlers = [];
+    }
+  }
+
+  public parse(data: Uint32Array, length: number, promiseResult?: boolean): void | Promise<boolean> {
+    if (!this._wasm) {
+      this._wasmReady ??= this._initWasm();
+      return this._wasmReady;
+    }
+
+    if (this._parseStack.state !== ParserStackType.NONE) {
+      return this._resume(promiseResult);
+    }
+
+    const bytes = this._encodeUtf32(data, length);
+    const result = this._writeToWasm(bytes);
+    if (result) {
+      return result;
+    }
+    return this._drainEvents();
+  }
+
+  private _resume(promiseResult?: boolean): void | Promise<boolean> {
+    if (promiseResult === undefined || this._parseStack.state === ParserStackType.FAIL) {
+      this._parseStack.state = ParserStackType.FAIL;
+      throw new Error('improper continuation due to previous async handler, giving up parsing');
+    }
+
+    switch (this._parseStack.state) {
+      case ParserStackType.CSI:
+      case ParserStackType.ESC:
+        return this._resumeHandlerLoop(promiseResult);
+      case ParserStackType.OSC:
+        return this._resumeOsc(promiseResult);
+      case ParserStackType.DCS:
+        return this._resumeDcs(promiseResult);
+      case ParserStackType.APC:
+        return this._resumeApc(promiseResult);
+      case ParserStackType.RESET:
+        this._parseStack.state = ParserStackType.NONE;
+        return;
+      default:
+        this._parseStack.state = ParserStackType.NONE;
+        return;
+    }
+  }
+
+  private _resumeHandlerLoop(promiseResult: boolean): void | Promise<boolean> {
+    const handlers = this._parseStack.handlers as CsiHandlerType[] | EscHandlerType[];
+    let handlerPos = this._parseStack.handlerPos - 1;
+    if (promiseResult === false && handlerPos > -1) {
+      if (this._parseStack.state === ParserStackType.CSI) {
+        const params = this._resumeParams ?? new Params();
+        for (; handlerPos >= 0; handlerPos--) {
+          const handlerResult = (handlers as CsiHandlerType[])[handlerPos](params);
+          if (handlerResult === true) {
+            break;
+          } else if (handlerResult instanceof Promise) {
+            this._parseStack.handlerPos = handlerPos;
+            return handlerResult;
+          }
+        }
+      } else {
+        for (; handlerPos >= 0; handlerPos--) {
+          const handlerResult = (handlers as EscHandlerType[])[handlerPos]();
+          if (handlerResult === true) {
+            break;
+          } else if (handlerResult instanceof Promise) {
+            this._parseStack.handlerPos = handlerPos;
+            return handlerResult;
+          }
+        }
+      }
+    }
+
+    this._resumeParams = undefined;
+    this._parseStack.handlers = [];
+    this._parseStack.state = ParserStackType.NONE;
+    return this._continueAfterAsync();
+  }
+
+  private _resumeOsc(promiseResult: boolean): void | Promise<boolean> {
+    const handlerResult = this._oscParser.end(true, promiseResult);
+    if (handlerResult) {
+      return handlerResult as Promise<boolean>;
+    }
+    this._parseStack.state = ParserStackType.NONE;
+    return this._continueAfterAsync();
+  }
+
+  private _resumeDcs(promiseResult: boolean): void | Promise<boolean> {
+    const handlerResult = this._dcsParser.unhook(true, promiseResult);
+    if (handlerResult) {
+      return handlerResult as Promise<boolean>;
+    }
+    this._parseStack.state = ParserStackType.NONE;
+    return this._continueAfterAsync();
+  }
+
+  private _resumeApc(promiseResult: boolean): void | Promise<boolean> {
+    const handlerResult = this._apcParser.end(true, promiseResult);
+    if (handlerResult) {
+      return handlerResult as Promise<boolean>;
+    }
+    this._parseStack.state = ParserStackType.NONE;
+    return this._continueAfterAsync();
+  }
+
+  private _identifier(id: IFunctionIdentifier, finalRange: number[] = [0x40, 0x7e]): number {
+    let res = 0;
+    if (id.prefix) {
+      if (id.prefix.length > 1) {
+        throw new Error('only one byte as prefix supported');
+      }
+      res = id.prefix.charCodeAt(0);
+      if (res && 0x3c > res || res > 0x3f) {
+        throw new Error('prefix must be in range 0x3c .. 0x3f');
+      }
+    }
+    if (id.intermediates) {
+      if (id.intermediates.length > 2) {
+        throw new Error('only two bytes as intermediates are supported');
+      }
+      for (let i = 0; i < id.intermediates.length; ++i) {
+        const intermediate = id.intermediates.charCodeAt(i);
+        if (0x20 > intermediate || intermediate > 0x2f) {
+          throw new Error('intermediate must be in range 0x20 .. 0x2f');
+        }
+        res <<= 8;
+        res |= intermediate;
+      }
+    }
+    if (id.final.length !== 1) {
+      throw new Error('final must be a single byte');
+    }
+    const finalCode = id.final.charCodeAt(0);
+    if (finalRange[0] > finalCode || finalCode > finalRange[1]) {
+      throw new Error(`final must be in range ${finalRange[0]} .. ${finalRange[1]}`);
+    }
+    res <<= 8;
+    res |= finalCode;
+
+    return res;
+  }
+
+  private async _initWasm(): Promise<boolean> {
+    this._wasm = await GhosttyWasmRuntime.getInstance();
+    this._parserHandle = this._wasm.ghostty_raw_parser_new(0);
+    this._eventSize = this._wasm.ghostty_raw_parser_event_size();
+    this._eventMaxParams = this._wasm.ghostty_raw_parser_max_params();
+    this._eventMaxIntermediates = this._wasm.ghostty_raw_parser_max_intermediates();
+    return true;
+  }
+
+  private _encodeUtf32(data: Uint32Array, length: number): Uint8Array {
+    if (length === 0) {
+      return new Uint8Array(0);
+    }
+    const bytes: number[] = [];
+    for (let i = 0; i < length; i++) {
+      const codePoint = data[i];
+      if (codePoint === 0x9c) {
+        bytes.push(0x1b, 0x5c);
+        continue;
+      }
+      if (codePoint <= 0x7f || (codePoint >= 0x80 && codePoint <= 0x9f)) {
+        bytes.push(codePoint);
+      } else if (codePoint <= 0x7ff) {
+        bytes.push(
+          0xc0 | (codePoint >> 6),
+          0x80 | (codePoint & 0x3f)
+        );
+      } else if (codePoint <= 0xffff) {
+        bytes.push(
+          0xe0 | (codePoint >> 12),
+          0x80 | ((codePoint >> 6) & 0x3f),
+          0x80 | (codePoint & 0x3f)
+        );
+      } else {
+        bytes.push(
+          0xf0 | (codePoint >> 18),
+          0x80 | ((codePoint >> 12) & 0x3f),
+          0x80 | ((codePoint >> 6) & 0x3f),
+          0x80 | (codePoint & 0x3f)
+        );
+      }
+    }
+    return new Uint8Array(bytes);
+  }
+
+  private _writeToWasm(bytes: Uint8Array): void | Promise<boolean> {
+    if (!this._wasm || !this._parserHandle) {
+      return;
+    }
+    if (!bytes.length) {
+      return;
+    }
+
+    const dataPtr = this._wasm.ghostty_wasm_alloc_u8_array(bytes.length);
+    if (!dataPtr) {
+      return;
+    }
+
+    const mem = new Uint8Array(this._wasm.memory.buffer, dataPtr, bytes.length);
+    mem.set(bytes);
+    this._wasm.ghostty_raw_parser_write(this._parserHandle, dataPtr, bytes.length);
+    this._wasm.ghostty_wasm_free_u8_array(dataPtr, bytes.length);
+  }
+
+  private _drainEvents(): void | Promise<boolean> {
+    if (!this._wasm || !this._parserHandle) {
+      return;
+    }
+
+    const eventsPtr = this._wasm.ghostty_raw_parser_events_ptr(this._parserHandle);
+    const eventsLen = this._wasm.ghostty_raw_parser_events_len(this._parserHandle);
+    if (!eventsPtr || !eventsLen) {
+      this._wasm.ghostty_raw_parser_events_clear(this._parserHandle);
+      return;
+    }
+
+    this._pendingEvents = { ptr: eventsPtr, len: eventsLen };
+    this._eventIndex = 0;
+
+    const result = this._processEvents();
+    if (result) {
+      return result;
+    }
+
+    this._wasm.ghostty_raw_parser_events_clear(this._parserHandle);
+    this._pendingEvents = undefined;
+  }
+
+  private _continueAfterAsync(): void | Promise<boolean> {
+    if (!this._wasm || !this._parserHandle || !this._pendingEvents) {
+      return;
+    }
+
+    this._eventIndex++;
+    const result = this._processEvents();
+    if (result) {
+      return result;
+    }
+
+    this._wasm.ghostty_raw_parser_events_clear(this._parserHandle);
+    this._pendingEvents = undefined;
+  }
+
+  private _processEvents(): void | Promise<boolean> {
+    if (!this._pendingEvents || !this._wasm) {
+      return;
+    }
+
+    const { ptr, len } = this._pendingEvents;
+    const mem = this._wasm.memory.buffer;
+    const view = new DataView(mem);
+
+    let textStart = 0;
+    let textLen = 0;
+
+    for (; this._eventIndex < len; this._eventIndex++) {
+      const base = ptr + this._eventIndex * this._eventSize;
+      const tag = view.getInt32(base, true);
+
+      if (tag !== RawEventTag.PRINT && textLen > 0) {
+        this._flushText(view, ptr, textStart, textLen);
+        textLen = 0;
+      }
+
+      switch (tag) {
+        case RawEventTag.PRINT: {
+          if (textLen === 0) {
+            textStart = this._eventIndex;
+          }
+          textLen++;
+          break;
+        }
+        case RawEventTag.EXECUTE: {
+          const code = view.getUint32(base + 4, true);
+          this._handleExecute(code);
+          break;
+        }
+        case RawEventTag.ESC: {
+          const event = this._readEvent(view, base);
+          const ident = this._buildIdent(event.intermediates, event.final, false, [0x30, 0x7e]);
+          const handlers = this._escHandlers[ident];
+          const handlerResult = this._callEscHandlers(handlers, ident);
+          if (handlerResult) {
+            return handlerResult;
+          }
+          break;
+        }
+        case RawEventTag.CSI: {
+          const event = this._readEvent(view, base);
+          const params = this._buildParams(event.params, event.paramsLen, event.paramsSep);
+          const ident = this._buildIdent(event.intermediates, event.final, true);
+          const handlers = this._csiHandlers[ident];
+          const handlerResult = this._callCsiHandlers(handlers, ident, params);
+          if (handlerResult) {
+            return handlerResult;
+          }
+          break;
+        }
+        case RawEventTag.OSC: {
+          const event = this._readEvent(view, base);
+          const oscResult = this._handleOsc(event.code, event.dataPtr, event.dataLen);
+          if (oscResult) {
+            return oscResult;
+          }
+          break;
+        }
+        case RawEventTag.DCS_HOOK: {
+          const event = this._readEvent(view, base);
+          const params = this._buildParams(event.params, event.paramsLen, event.paramsSep);
+          const ident = this._buildIdent(event.intermediates, event.final, true);
+          this._dcsParser.hook(ident, params);
+          this.precedingJoinState = 0;
+          break;
+        }
+        case RawEventTag.DCS_PUT: {
+          const code = view.getUint32(base + 4, true);
+          this._dcsPutBuffer[0] = code;
+          this._dcsParser.put(this._dcsPutBuffer, 0, 1);
+          break;
+        }
+        case RawEventTag.DCS_UNHOOK: {
+          const dcsResult = this._dcsParser.unhook(true);
+          if (dcsResult) {
+            this._parseStack.state = ParserStackType.DCS;
+            this.precedingJoinState = 0;
+            return dcsResult as Promise<boolean>;
+          }
+          this.precedingJoinState = 0;
+          break;
+        }
+        case RawEventTag.APC_START: {
+          this._apcParser.start();
+          this.precedingJoinState = 0;
+          break;
+        }
+        case RawEventTag.APC_PUT: {
+          const code = view.getUint32(base + 4, true);
+          this._apcPutBuffer[0] = code;
+          this._apcParser.put(this._apcPutBuffer, 0, 1);
+          break;
+        }
+        case RawEventTag.APC_END: {
+          const apcResult = this._apcParser.end(true);
+          if (apcResult) {
+            this._parseStack.state = ParserStackType.APC;
+            this.precedingJoinState = 0;
+            return apcResult as Promise<boolean>;
+          }
+          this.precedingJoinState = 0;
+          break;
+        }
+      }
+    }
+
+    if (textLen > 0) {
+      this._flushText(view, ptr, textStart, textLen);
+    }
+
+    return;
+  }
+
+  private _flushText(view: DataView, ptr: number, start: number, count: number): void {
+    let remaining = count;
+    let offset = 0;
+    while (remaining > 0) {
+      const chunk = Math.min(remaining, this._utf32Scratch.length);
+      for (let i = 0; i < chunk; i++) {
+        const base = ptr + (start + offset + i) * this._eventSize;
+        const code = view.getUint32(base + 4, true);
+        this._utf32Scratch[i] = code;
+      }
+      this._printHandler(this._utf32Scratch, 0, chunk);
+      remaining -= chunk;
+      offset += chunk;
+    }
+  }
+
+  private _handleExecute(code: number): void {
+    if (this._executeHandlers[code]) {
+      this._executeHandlers[code]();
+    } else {
+      this._executeHandlerFb(code);
+    }
+    this.precedingJoinState = 0;
+  }
+
+  private _callEscHandlers(handlers: EscHandlerType[] | undefined, ident: number): void | Promise<boolean> {
+    if (!handlers) {
+      this._escHandlerFb(ident);
+      this.precedingJoinState = 0;
+      return;
+    }
+    let j = handlers.length - 1;
+    for (; j >= 0; j--) {
+      const handlerResult = handlers[j]();
+      if (handlerResult === true) {
+        break;
+      } else if (handlerResult instanceof Promise) {
+        this._parseStack.state = ParserStackType.ESC;
+        this._parseStack.handlers = handlers;
+        this._parseStack.handlerPos = j;
+        this.precedingJoinState = 0;
+        return handlerResult;
+      }
+    }
+    if (j < 0) {
+      this._escHandlerFb(ident);
+    }
+    this.precedingJoinState = 0;
+  }
+
+  private _callCsiHandlers(handlers: CsiHandlerType[] | undefined, ident: number, params: IParams): void | Promise<boolean> {
+    if (!handlers) {
+      this._csiHandlerFb(ident, params);
+      this.precedingJoinState = 0;
+      return;
+    }
+    let j = handlers.length - 1;
+    for (; j >= 0; j--) {
+      const handlerResult = handlers[j](params);
+      if (handlerResult === true) {
+        break;
+      } else if (handlerResult instanceof Promise) {
+        this._parseStack.state = ParserStackType.CSI;
+        this._resumeParams = params;
+        this._parseStack.handlers = handlers;
+        this._parseStack.handlerPos = j;
+        this.precedingJoinState = 0;
+        return handlerResult;
+      }
+    }
+    if (j < 0) {
+      this._csiHandlerFb(ident, params);
+    }
+    this.precedingJoinState = 0;
+  }
+
+  private _handleOsc(oscId: number, dataPtr: number, dataLen: number): void | Promise<boolean> {
+    console.log('handle osc');
+    if (!this._wasm) {
+      return;
+    }
+
+    let payload = '';
+    if (dataLen > 0) {
+      if (!dataPtr || dataPtr + dataLen > this._wasm.memory.buffer.byteLength) {
+        return;
+      }
+      const bytes = new Uint8Array(this._wasm.memory.buffer, dataPtr, dataLen);
+      payload = this._textDecoder.decode(bytes);
+    }
+    if (payload.indexOf('\u0000') !== -1) {
+      if (oscId === 8) {
+        const parts = payload.split('\u0000').filter((part, index, all) => {
+          if (part.length > 0) {
+            return true;
+          }
+          return index < all.length - 1;
+        });
+        if (parts.length > 0) {
+          const uri = parts[parts.length - 1] ?? '';
+          const params = parts.slice(0, -1).join(':');
+          payload = `${params};${uri}`;
+        } else {
+          payload = '';
+        }
+      } else {
+        payload = payload.replace(/\u0000+/g, '');
+      }
+    }
+    const oscPrefix = `${oscId};`;
+    const rawPayload = payload.startsWith(oscPrefix)
+      ? payload.slice(oscPrefix.length)
+      : payload;
+    let oscPayload = rawPayload;
+    if (oscId === 8 && oscPayload && !oscPayload.startsWith(';')) {
+      const sepIndex = oscPayload.indexOf(';');
+      const paramsPart = sepIndex === -1 ? oscPayload : oscPayload.slice(0, sepIndex);
+      if (!paramsPart.includes('=')) {
+        oscPayload = `;${oscPayload}`;
+      }
+    }
+    const oscString = `${oscPrefix}${oscPayload}`;
+
+    this._oscParser.start();
+    const length = this._decodeToScratch(oscString);
+    this._oscParser.put(this._utf32Scratch, 0, length);
+    const handlerResult = this._oscParser.end(true);
+    if (handlerResult) {
+      this._parseStack.state = ParserStackType.OSC;
+      this.precedingJoinState = 0;
+      return handlerResult as Promise<boolean>;
+    }
+    this.precedingJoinState = 0;
+  }
+
+  private _buildParams(params: Uint16Array, length: number, sepBits: number): Params {
+    const result = new Params(this._eventMaxParams, 256);
+    if (length === 0) {
+      result.addParam(0);
+      return result;
+    }
+
+    let i = 0;
+    while (i < length) {
+      result.addParam(params[i]);
+      if (sepBits & (1 << i)) {
+        i++;
+        while (i < length) {
+          result.addSubParam(params[i]);
+          if ((sepBits & (1 << i)) === 0) {
+            break;
+          }
+          i++;
+        }
+      }
+      i++;
+    }
+
+    return result;
+  }
+
+  private _buildIdent(intermediates: string, final: string, allowPrefix: boolean, finalRange: number[] = [0x40, 0x7e]): number {
+    let prefix: string | undefined;
+    let inters = intermediates;
+    if (allowPrefix && intermediates.length) {
+      const first = intermediates.charCodeAt(0);
+      if (first >= 0x3c && first <= 0x3f) {
+        prefix = intermediates.charAt(0);
+        inters = intermediates.substring(1);
+      }
+    }
+    return this._identifier({ prefix, intermediates: inters || undefined, final }, finalRange);
+  }
+
+  private _readEvent(view: DataView, base: number): {
+    final: string;
+    intermediates: string;
+    params: Uint16Array;
+    paramsLen: number;
+    paramsSep: number;
+    code: number;
+    dataPtr: number;
+    dataLen: number;
+  } {
+    const code = view.getUint32(base + 4, true);
+    const final = String.fromCharCode(view.getUint8(base + 8));
+    const intermediatesLen = Math.min(view.getUint8(base + 9), this._eventMaxIntermediates);
+    const paramsLen = Math.min(view.getUint8(base + 10), this._eventMaxParams);
+    const paramsSep = view.getUint32(base + 12, true);
+
+    let intermediates = '';
+    const interOffset = base + 16;
+    for (let i = 0; i < intermediatesLen; i++) {
+      intermediates += String.fromCharCode(view.getUint8(interOffset + i));
+    }
+
+    const paramsOffset = base + 16 + this._eventMaxIntermediates;
+    const params = new Uint16Array(paramsLen);
+    for (let i = 0; i < paramsLen; i++) {
+      params[i] = view.getUint16(paramsOffset + i * 2, true);
+    }
+
+    const rawDataPtrOffset = paramsOffset + this._eventMaxParams * 2;
+    const dataPtrOffset = (rawDataPtrOffset + (this._ptrSize - 1)) & ~(this._ptrSize - 1);
+    const dataPtr = view.getUint32(dataPtrOffset, true);
+    const dataLen = view.getUint32(dataPtrOffset + this._ptrSize, true);
+
+    return {
+      final,
+      intermediates,
+      params,
+      paramsLen,
+      paramsSep,
+      code,
+      dataPtr,
+      dataLen
+    };
+  }
+
+  private _decodeToScratch(text: string): number {
+    if (this._utf32Scratch.length < text.length * 2) {
+      this._utf32Scratch = new Uint32Array(text.length * 2);
+    }
+    return this._oscBuffer.decode(text, this._utf32Scratch);
+  }
+}

src/common/parser/GhosttyWasmRuntime.ts

@@ -0,0 +1,133 @@
+/**
+ * Copyright (c) 2026 The xterm.js authors. All rights reserved.
+ * @license MIT
+ */
+
+/* eslint-disable @typescript-eslint/naming-convention */
+export interface IGhosttyWasmExports {
+  memory: WebAssembly.Memory;
+  ghostty_raw_parser_new(allocPtr: number): number;
+  ghostty_raw_parser_free(parser: number): void;
+  ghostty_raw_parser_reset(parser: number): void;
+  ghostty_raw_parser_write(parser: number, dataPtr: number, len: number): void;
+  ghostty_raw_parser_events_ptr(parser: number): number;
+  ghostty_raw_parser_events_len(parser: number): number;
+  ghostty_raw_parser_events_clear(parser: number): void;
+  ghostty_raw_parser_event_size(): number;
+  ghostty_raw_parser_max_params(): number;
+  ghostty_raw_parser_max_intermediates(): number;
+  ghostty_wasm_alloc_u8_array(len: number): number;
+  ghostty_wasm_free_u8_array(ptr: number, len: number): void;
+  ghostty_xterm_buffer_new(cols: number, rows: number, maxRows: number): number;
+  ghostty_xterm_buffer_free(buffer: number): void;
+  ghostty_xterm_buffer_resize(buffer: number, cols: number, rows: number, maxRows: number): number;
+  ghostty_xterm_buffer_clear(buffer: number): void;
+  ghostty_xterm_buffer_get_cols(buffer: number): number;
+  ghostty_xterm_buffer_get_rows(buffer: number): number;
+  ghostty_xterm_buffer_get_max_rows(buffer: number): number;
+  ghostty_xterm_buffer_get_cell(buffer: number, row: number, col: number, outPtr: number): void;
+  ghostty_xterm_buffer_set_cell(buffer: number, row: number, col: number, content: number, fg: number, bg: number): void;
+  ghostty_xterm_buffer_clear_row(buffer: number, row: number, content: number, fg: number, bg: number): void;
+  ghostty_xterm_buffer_copy_row(buffer: number, srcRow: number, dstRow: number): void;
+  ghostty_xterm_buffer_get_row_wrap(buffer: number, row: number): number;
+  ghostty_xterm_buffer_set_row_wrap(buffer: number, row: number, wrap: number): void;
+}
+/* eslint-enable @typescript-eslint/naming-convention */
+
+export class GhosttyWasmRuntime {
+  private static _instancePromise: Promise<IGhosttyWasmExports> | undefined;
+  private static _instanceSync: IGhosttyWasmExports | undefined;
+
+  public static getInstance(): Promise<IGhosttyWasmExports> {
+    this._instancePromise ??= this._loadAsync();
+    return this._instancePromise;
+  }
+
+  public static getInstanceSync(): IGhosttyWasmExports {
+    this._instanceSync ??= this._loadSync();
+    return this._instanceSync;
+  }
+
+  private static async _loadAsync(): Promise<IGhosttyWasmExports> {
+    const wasmUrl = GhosttyWasmRuntime._getWasmUrl();
+    const isNode = typeof globalThis !== 'undefined' && !!(globalThis as any).process?.versions?.node;
+    if (isNode) {
+      const requireFn = (globalThis as any).require
+        ?? (globalThis as any).process?.mainModule?.require
+        ?? (globalThis as any).__xtermRequire;
+      const fs = requireFn?.('fs') as { readFile(path: string, cb: (err: Error | null, data?: Uint8Array) => void): void } | undefined;
+      if (!fs) {
+        throw new Error('Node.js async WASM loading requires require("fs")');
+      }
+      const wasmBytes = await new Promise<Uint8Array>((resolve, reject) => {
+        fs.readFile(wasmUrl, (err, data) => {
+          if (err || !data) {
+            reject(err ?? new Error(`Failed to load Ghostty WASM from ${wasmUrl}`));
+            return;
+          }
+          resolve(data);
+        });
+      });
+      const env = { log: () => {} };
+      const { instance } = await WebAssembly.instantiate(wasmBytes, { env });
+      return instance.exports as unknown as IGhosttyWasmExports;
+    }
+
+    const response = await fetch(wasmUrl);
+    if (!response.ok) {
+      throw new Error(`Failed to load Ghostty WASM from ${wasmUrl}`);
+    }
+    const wasmBytes = await response.arrayBuffer();
+    const env = { log: () => {} };
+    const { instance } = await WebAssembly.instantiate(wasmBytes, { env });
+    return instance.exports as unknown as IGhosttyWasmExports;
+  }
+
+  private static _loadSync(): IGhosttyWasmExports {
+    const wasmUrl = GhosttyWasmRuntime._getWasmUrl();
+    const isNode = typeof globalThis !== 'undefined' && !!(globalThis as any).process?.versions?.node;
+    if (!isNode && typeof document !== 'undefined') {
+      const request = new XMLHttpRequest();
+      request.open('GET', wasmUrl, false);
+      request.overrideMimeType('text/plain; charset=x-user-defined');
+      request.send(null);
+      if (request.status !== 200 || !request.responseText) {
+        throw new Error(`Failed to load Ghostty WASM from ${wasmUrl}`);
+      }
+      const binary = request.responseText;
+      const wasmBytes = new Uint8Array(binary.length);
+      for (let i = 0; i < binary.length; i++) {
+        wasmBytes[i] = binary.charCodeAt(i) & 0xFF;
+      }
+      const module = new WebAssembly.Module(wasmBytes);
+      const env = { log: () => {} };
+      const instance = new WebAssembly.Instance(module, { env });
+      return instance.exports as unknown as IGhosttyWasmExports;
+    }
+
+    // Node.js sync load for tests and headless usage.
+    const requireFn = (globalThis as any).require
+      ?? (globalThis as any).process?.mainModule?.require
+      ?? (globalThis as any).__xtermRequire;
+    const fs = requireFn?.('fs') as { readFileSync(path: string): Uint8Array } | undefined;
+    if (!fs) {
+      throw new Error('Node.js sync WASM loading requires require("fs")');
+    }
+    const wasmBytes = fs.readFileSync(wasmUrl);
+    const module = new WebAssembly.Module(wasmBytes);
+    const env = { log: () => {} };
+    const instance = new WebAssembly.Instance(module, { env });
+    return instance.exports as unknown as IGhosttyWasmExports;
+  }
+
+  private static _getWasmUrl(): string {
+    const override = (globalThis as any).XTERM_GHOSTTY_WASM_URL as string | undefined;
+    if (override) {
+      return override;
+    }
+    if (typeof document !== 'undefined') {
+      return 'vendor/ghostty-wasm/ghostty-vt.wasm';
+    }
+    return 'vendor/ghostty-wasm/ghostty-vt.wasm';
+  }
+}