diff --git a/AGENTS.md b/AGENTS.md
index c9954ed7e1..0d5d035884 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -57,6 +57,13 @@ export class MyAddon implements ITerminalAddon {
 - Proposed APIs require `allowProposedApi: true` option
 - Constructor-only options (cols, rows) cannot be changed after instantiation
 
+**Disposable Management**:
+- When a disposable object can be replaced over time, prefer a registered `MutableDisposable` over manual dispose/reassign logic.
+- Register it on the owning class (for example, `this._register(new MutableDisposable())`) and assign through `.value`; this automatically disposes the previous value and avoids accidentally leaking resources.
+
+**TypeScript Constants**:
+- Prefer `const enum` over top-level `const` declarations for primitive constants when appropriate, since values are inlined and avoid runtime property lookups.
+
 **Testing Utilities**: Use `TestUtils.ts` helpers:
 - `openTerminal(ctx, options)` for setup
 - `pollFor(page, fn, expectedValue)` for async assertions
diff --git a/addons/addon-fit/src/FitAddon.ts b/addons/addon-fit/src/FitAddon.ts
index 87b21e99e2..3db988acd5 100644
--- a/addons/addon-fit/src/FitAddon.ts
+++ b/addons/addon-fit/src/FitAddon.ts
@@ -19,8 +19,10 @@ interface ITerminalDimensions {
   cols: number;
 }
 
-const MINIMUM_COLS = 2;
-const MINIMUM_ROWS = 1;
+const enum Constants {
+  MINIMUM_COLS = 2,
+  MINIMUM_ROWS = 1
+}
 
 function getWindow(e: Node): Window {
   if (e?.ownerDocument?.defaultView) {
@@ -86,8 +88,8 @@ export class FitAddon implements ITerminalAddon, IFitApi {
     const availableHeight = parentElementHeight - elementPaddingVer;
     const availableWidth = parentElementWidth - elementPaddingHor - scrollbarWidth;
     const geometry = {
-      cols: Math.max(MINIMUM_COLS, Math.floor(availableWidth / dims.css.cell.width)),
-      rows: Math.max(MINIMUM_ROWS, Math.floor(availableHeight / dims.css.cell.height))
+      cols: Math.max(Constants.MINIMUM_COLS, Math.floor(availableWidth / dims.css.cell.width)),
+      rows: Math.max(Constants.MINIMUM_ROWS, Math.floor(availableHeight / dims.css.cell.height))
     };
     return geometry;
   }
diff --git a/addons/addon-image/src/ImageRenderer.ts b/addons/addon-image/src/ImageRenderer.ts
index 79b83a977e..b36cdd0041 100644
--- a/addons/addon-image/src/ImageRenderer.ts
+++ b/addons/addon-image/src/ImageRenderer.ts
@@ -8,8 +8,10 @@ import { IDisposable } from '@xterm/xterm';
 import { ICellSize, ImageLayer, ITerminalExt, IImageSpec, IRenderDimensions, IRenderService } from './Types';
 import { Disposable, MutableDisposable, toDisposable } from 'common/Lifecycle';
 
-const PLACEHOLDER_LENGTH = 4096;
-const PLACEHOLDER_HEIGHT = 24;
+const enum Constants {
+  PLACEHOLDER_LENGTH = 4096,
+  PLACEHOLDER_HEIGHT = 24
+}
 
 /**
  * ImageRenderer - terminal frontend extension:
@@ -110,7 +112,7 @@ export class ImageRenderer extends Disposable implements IDisposable {
   public showPlaceholder(value: boolean): void {
     if (value) {
       if (!this._placeholder && this.cellSize.height !== -1) {
-        this._createPlaceHolder(Math.max(this.cellSize.height + 1, PLACEHOLDER_HEIGHT));
+        this._createPlaceHolder(Math.max(this.cellSize.height + 1, Constants.PLACEHOLDER_HEIGHT));
       }
     } else {
       this._placeholderBitmap?.close();
@@ -249,7 +251,7 @@ export class ImageRenderer extends Disposable implements IDisposable {
       }
 
       if (!this._placeholder) {
-        this._createPlaceHolder(Math.max(height + 1, PLACEHOLDER_HEIGHT));
+        this._createPlaceHolder(Math.max(height + 1, Constants.PLACEHOLDER_HEIGHT));
       } else if (height >= this._placeholder!.height) {
         this._createPlaceHolder(height + 1);
       }
@@ -379,7 +381,7 @@ export class ImageRenderer extends Disposable implements IDisposable {
     return this._layers.has(layer);
   }
 
-  private _createPlaceHolder(height: number = PLACEHOLDER_HEIGHT): void {
+  private _createPlaceHolder(height: number = Constants.PLACEHOLDER_HEIGHT): void {
     this._placeholderBitmap?.close();
     this._placeholderBitmap = undefined;
 
@@ -403,7 +405,7 @@ export class ImageRenderer extends Disposable implements IDisposable {
     ctx.putImageData(imgData, 0, 0);
 
     // create placeholder line, width aligned to blueprint width
-    const width = (screen.width + bWidth - 1) & ~(bWidth - 1) || PLACEHOLDER_LENGTH;
+    const width = (screen.width + bWidth - 1) & ~(bWidth - 1) || Constants.PLACEHOLDER_LENGTH;
     this._placeholder = ImageRenderer.createCanvas(this.document, width, height);
     const ctx2 = this._placeholder.getContext('2d', { alpha: false });
     if (!ctx2) {
diff --git a/addons/addon-image/src/kitty/KittyGraphicsHandler.ts b/addons/addon-image/src/kitty/KittyGraphicsHandler.ts
index 17cd5ed9f9..f449f31863 100644
--- a/addons/addon-image/src/kitty/KittyGraphicsHandler.ts
+++ b/addons/addon-image/src/kitty/KittyGraphicsHandler.ts
@@ -16,24 +16,23 @@ import {
   IKittyCommand,
   IPendingTransmission,
   IKittyImageData,
-  BYTES_PER_PIXEL_RGB,
-  BYTES_PER_PIXEL_RGBA,
-  ALPHA_OPAQUE,
+  KittyPixelConstants,
   parseKittyCommand
 } from './KittyGraphicsTypes';
 
-// Memory limit for base64 decoder (4MB, same as IIPHandler)
-const DECODER_KEEP_DATA = 4194304;
-const DECODER_INITIAL_DATA = 4194304; // 4MB
-
-// Local mirror of const enum (esbuild can't inline const enums from external packages)
-const DECODER_OK: DecodeStatus.OK = 0;
-
-// Maximum control data size
-const MAX_CONTROL_DATA_SIZE = 512;
+const enum Constants {
+  // Memory limit for base64 decoder (4MB, same as IIPHandler)
+  DECODER_KEEP_DATA = 4194304,
+  DECODER_INITIAL_DATA = 4194304, // 4MB
+  // Local mirror of const enum (esbuild can't inline const enums from external packages)
+  DECODER_OK = 0,
+  // Maximum control data size
+  MAX_CONTROL_DATA_SIZE = 512,
+  // Semicolon codepoint
+  SEMICOLON = 0x3B
+}
 
-// Semicolon codepoint
-const SEMICOLON = 0x3B;
+const DECODER_OK = Constants.DECODER_OK as unknown as DecodeStatus.OK;
 
 // Kitty graphics protocol handler with streaming base64 decoding.
 export class KittyGraphicsHandler implements IApcHandler, IResetHandler, IDisposable {
@@ -50,7 +49,7 @@ export class KittyGraphicsHandler implements IApcHandler, IResetHandler, IDispos
   private _inControlData = true;
 
   // Buffer for control data.
-  private _controlData = new Uint32Array(MAX_CONTROL_DATA_SIZE);
+  private _controlData = new Uint32Array(Constants.MAX_CONTROL_DATA_SIZE);
   private _controlLength = 0;
 
   // Pre-calculated encoded size limit
@@ -77,7 +76,7 @@ export class KittyGraphicsHandler implements IApcHandler, IResetHandler, IDispos
     // Convert decoded size limit -> max encoded bytes.
     this._maxEncodedBytes = Math.ceil(this._opts.kittySizeLimit * 4 / 3);
     // ensure we preallocate more than configured limit while using 4mb initial size.
-    this._initialEncodedBytes = Math.min(DECODER_INITIAL_DATA, this._maxEncodedBytes);
+    this._initialEncodedBytes = Math.min(Constants.DECODER_INITIAL_DATA, this._maxEncodedBytes);
   }
 
   public reset(): void {
@@ -129,7 +128,7 @@ export class KittyGraphicsHandler implements IApcHandler, IResetHandler, IDispos
       // Scan for semicolon
       let controlEnd = end;
       for (let i = start; i < end; i++) {
-        if (data[i] === SEMICOLON) {
+        if (data[i] === Constants.SEMICOLON) {
           this._inControlData = false;
           controlEnd = i;
           break;
@@ -138,7 +137,7 @@ export class KittyGraphicsHandler implements IApcHandler, IResetHandler, IDispos
 
       // Copy control data
       const copyLength = controlEnd - start;
-      if (this._controlLength + copyLength > MAX_CONTROL_DATA_SIZE) {
+      if (this._controlLength + copyLength > Constants.MAX_CONTROL_DATA_SIZE) {
         this._aborted = true;
         return;
       }
@@ -201,7 +200,7 @@ export class KittyGraphicsHandler implements IApcHandler, IResetHandler, IDispos
       this._activeDecoder = pending.decoder;
     }
     if (!this._activeDecoder) {
-      this._activeDecoder = new Base64Decoder(DECODER_KEEP_DATA, this._maxEncodedBytes, this._initialEncodedBytes);
+      this._activeDecoder = new Base64Decoder(Constants.DECODER_KEEP_DATA, this._maxEncodedBytes, this._initialEncodedBytes);
       this._activeDecoder.init();
     }
 
@@ -484,7 +483,7 @@ export class KittyGraphicsHandler implements IApcHandler, IResetHandler, IDispos
         return true;
       }
 
-      const bytesPerPixel = format === KittyFormat.RGBA ? BYTES_PER_PIXEL_RGBA : BYTES_PER_PIXEL_RGB;
+      const bytesPerPixel = format === KittyFormat.RGBA ? KittyPixelConstants.BYTES_PER_PIXEL_RGBA : KittyPixelConstants.BYTES_PER_PIXEL_RGB;
       const expectedBytes = width * height * bytesPerPixel;
 
       if (bytes.length < expectedBytes) {
@@ -723,7 +722,7 @@ export class KittyGraphicsHandler implements IApcHandler, IResetHandler, IDispos
       throw new Error('Width and height required for raw pixel data');
     }
 
-    const bytesPerPixel = image.format === KittyFormat.RGBA ? BYTES_PER_PIXEL_RGBA : BYTES_PER_PIXEL_RGB;
+    const bytesPerPixel = image.format === KittyFormat.RGBA ? KittyPixelConstants.BYTES_PER_PIXEL_RGBA : KittyPixelConstants.BYTES_PER_PIXEL_RGB;
     const expectedBytes = width * height * bytesPerPixel;
 
     if (bytes.length < expectedBytes) {
@@ -734,13 +733,13 @@ export class KittyGraphicsHandler implements IApcHandler, IResetHandler, IDispos
 
     if (image.format === KittyFormat.RGBA) {
       // RGBA: use bytes directly — no copy needed
-      return createImageBitmap(new ImageData(new Uint8ClampedArray(bytes.buffer as ArrayBuffer, bytes.byteOffset, pixelCount * BYTES_PER_PIXEL_RGBA), width, height));
+      return createImageBitmap(new ImageData(new Uint8ClampedArray(bytes.buffer as ArrayBuffer, bytes.byteOffset, pixelCount * KittyPixelConstants.BYTES_PER_PIXEL_RGBA), width, height));
     }
 
     // RGB→RGBA: interleave alpha using uint32 block processing (4 pixels per iteration).
     // 3 uint32 reads + 4 uint32 writes per 4 pixels vs 28 byte reads/writes — ~6x faster.
     // Assumes little-endian (all modern browsers/Node.js).
-    const data = new Uint8ClampedArray(pixelCount * BYTES_PER_PIXEL_RGBA);
+    const data = new Uint8ClampedArray(pixelCount * KittyPixelConstants.BYTES_PER_PIXEL_RGBA);
     const src32 = new Uint32Array(bytes.buffer, bytes.byteOffset, Math.floor(bytes.byteLength / 4));
     const dst32 = new Uint32Array(data.buffer);
     const alignedPixels = pixelCount & ~3;  // round down to multiple of 4
@@ -759,15 +758,15 @@ export class KittyGraphicsHandler implements IApcHandler, IResetHandler, IDispos
     }
 
     // Handle remaining 1–3 pixels
-    let srcByte = alignedPixels * BYTES_PER_PIXEL_RGB;
-    let dstByte = alignedPixels * BYTES_PER_PIXEL_RGBA;
+    let srcByte = alignedPixels * KittyPixelConstants.BYTES_PER_PIXEL_RGB;
+    let dstByte = alignedPixels * KittyPixelConstants.BYTES_PER_PIXEL_RGBA;
     for (let i = alignedPixels; i < pixelCount; i++) {
       data[dstByte]     = bytes[srcByte];
       data[dstByte + 1] = bytes[srcByte + 1];
       data[dstByte + 2] = bytes[srcByte + 2];
-      data[dstByte + 3] = ALPHA_OPAQUE;
-      srcByte += BYTES_PER_PIXEL_RGB;
-      dstByte += BYTES_PER_PIXEL_RGBA;
+      data[dstByte + 3] = KittyPixelConstants.ALPHA_OPAQUE;
+      srcByte += KittyPixelConstants.BYTES_PER_PIXEL_RGB;
+      dstByte += KittyPixelConstants.BYTES_PER_PIXEL_RGBA;
     }
 
     return createImageBitmap(new ImageData(data, width, height));
diff --git a/addons/addon-image/src/kitty/KittyGraphicsTypes.ts b/addons/addon-image/src/kitty/KittyGraphicsTypes.ts
index 82b2b0a9a3..448ebcc051 100644
--- a/addons/addon-image/src/kitty/KittyGraphicsTypes.ts
+++ b/addons/addon-image/src/kitty/KittyGraphicsTypes.ts
@@ -82,9 +82,11 @@ export const enum KittyKey {
 }
 
 // Pixel format constants
-export const BYTES_PER_PIXEL_RGB = 3;
-export const BYTES_PER_PIXEL_RGBA = 4;
-export const ALPHA_OPAQUE = 255;
+export const enum KittyPixelConstants {
+  BYTES_PER_PIXEL_RGB = 3,
+  BYTES_PER_PIXEL_RGBA = 4,
+  ALPHA_OPAQUE = 255
+}
 
 // Parsed Kitty graphics command.
 export interface IKittyCommand {
diff --git a/addons/addon-serialize/test/SerializeAddon.test.ts b/addons/addon-serialize/test/SerializeAddon.test.ts
index ee5355fa65..fb42d807dc 100644
--- a/addons/addon-serialize/test/SerializeAddon.test.ts
+++ b/addons/addon-serialize/test/SerializeAddon.test.ts
@@ -49,7 +49,14 @@ test.describe('SerializeAddon', () => {
         for (let i = 0; i < buffer.length; i++) {
           // Do this intentionally to get content of underlining source
           const bufferLine = buffer.getLine(i)._line;
-          lines.push(JSON.stringify(bufferLine));
+          lines.push(JSON.stringify(bufferLine, (key, value) => {
+            // BufferLine caches are internal/transient and can legitimately differ
+            // across equivalent terminal states.
+            if (key === '_stringCache' || key === '_stringCacheEntryRef') {
+              return undefined;
+            }
+            return value;
+          }));
         }
         return {
           x: buffer.cursorX,
diff --git a/addons/addon-webgl/src/GlyphRenderer.ts b/addons/addon-webgl/src/GlyphRenderer.ts
index f5be446f68..568d3a4f96 100644
--- a/addons/addon-webgl/src/GlyphRenderer.ts
+++ b/addons/addon-webgl/src/GlyphRenderer.ts
@@ -78,9 +78,11 @@ void main() {
 }`);
 }
 
-const INDICES_PER_CELL = 11;
-const BYTES_PER_CELL = INDICES_PER_CELL * Float32Array.BYTES_PER_ELEMENT;
-const CELL_POSITION_INDICES = 2;
+const enum Constants {
+  INDICES_PER_CELL = 11,
+  BYTES_PER_CELL = INDICES_PER_CELL * 4/* Float32Array.BYTES_PER_ELEMENT */,
+  CELL_POSITION_INDICES = 2
+}
 
 // Work variables to avoid garbage collection
 let $i = 0;
@@ -160,22 +162,22 @@ export class GlyphRenderer extends Disposable {
     this._register(toDisposable(() => gl.deleteBuffer(this._attributesBuffer)));
     gl.bindBuffer(gl.ARRAY_BUFFER, this._attributesBuffer);
     gl.enableVertexAttribArray(VertexAttribLocations.OFFSET);
-    gl.vertexAttribPointer(VertexAttribLocations.OFFSET, 2, gl.FLOAT, false, BYTES_PER_CELL, 0);
+    gl.vertexAttribPointer(VertexAttribLocations.OFFSET, 2, gl.FLOAT, false, Constants.BYTES_PER_CELL, 0);
     gl.vertexAttribDivisor(VertexAttribLocations.OFFSET, 1);
     gl.enableVertexAttribArray(VertexAttribLocations.SIZE);
-    gl.vertexAttribPointer(VertexAttribLocations.SIZE, 2, gl.FLOAT, false, BYTES_PER_CELL, 2 * Float32Array.BYTES_PER_ELEMENT);
+    gl.vertexAttribPointer(VertexAttribLocations.SIZE, 2, gl.FLOAT, false, Constants.BYTES_PER_CELL, 2 * Float32Array.BYTES_PER_ELEMENT);
     gl.vertexAttribDivisor(VertexAttribLocations.SIZE, 1);
     gl.enableVertexAttribArray(VertexAttribLocations.TEXPAGE);
-    gl.vertexAttribPointer(VertexAttribLocations.TEXPAGE, 1, gl.FLOAT, false, BYTES_PER_CELL, 4 * Float32Array.BYTES_PER_ELEMENT);
+    gl.vertexAttribPointer(VertexAttribLocations.TEXPAGE, 1, gl.FLOAT, false, Constants.BYTES_PER_CELL, 4 * Float32Array.BYTES_PER_ELEMENT);
     gl.vertexAttribDivisor(VertexAttribLocations.TEXPAGE, 1);
     gl.enableVertexAttribArray(VertexAttribLocations.TEXCOORD);
-    gl.vertexAttribPointer(VertexAttribLocations.TEXCOORD, 2, gl.FLOAT, false, BYTES_PER_CELL, 5 * Float32Array.BYTES_PER_ELEMENT);
+    gl.vertexAttribPointer(VertexAttribLocations.TEXCOORD, 2, gl.FLOAT, false, Constants.BYTES_PER_CELL, 5 * Float32Array.BYTES_PER_ELEMENT);
     gl.vertexAttribDivisor(VertexAttribLocations.TEXCOORD, 1);
     gl.enableVertexAttribArray(VertexAttribLocations.TEXSIZE);
-    gl.vertexAttribPointer(VertexAttribLocations.TEXSIZE, 2, gl.FLOAT, false, BYTES_PER_CELL, 7 * Float32Array.BYTES_PER_ELEMENT);
+    gl.vertexAttribPointer(VertexAttribLocations.TEXSIZE, 2, gl.FLOAT, false, Constants.BYTES_PER_CELL, 7 * Float32Array.BYTES_PER_ELEMENT);
     gl.vertexAttribDivisor(VertexAttribLocations.TEXSIZE, 1);
     gl.enableVertexAttribArray(VertexAttribLocations.CELL_POSITION);
-    gl.vertexAttribPointer(VertexAttribLocations.CELL_POSITION, 2, gl.FLOAT, false, BYTES_PER_CELL, 9 * Float32Array.BYTES_PER_ELEMENT);
+    gl.vertexAttribPointer(VertexAttribLocations.CELL_POSITION, 2, gl.FLOAT, false, Constants.BYTES_PER_CELL, 9 * Float32Array.BYTES_PER_ELEMENT);
     gl.vertexAttribDivisor(VertexAttribLocations.CELL_POSITION, 1);
 
     // Setup static uniforms
@@ -222,12 +224,12 @@ export class GlyphRenderer extends Disposable {
   }
 
   private _updateCell(array: Float32Array, x: number, y: number, code: number | undefined, bg: number, fg: number, ext: number, chars: string, width: number, lastBg: number): void {
-    $i = (y * this._terminal.cols + x) * INDICES_PER_CELL;
+    $i = (y * this._terminal.cols + x) * Constants.INDICES_PER_CELL;
 
     // Exit early if this is a null character, allow space character to continue as it may have
     // underline/strikethrough styles
     if (code === NULL_CELL_CODE || code === undefined/* This is used for the right side of wide chars */) {
-      array.fill(0, $i, $i + INDICES_PER_CELL - 1 - CELL_POSITION_INDICES);
+      array.fill(0, $i, $i + Constants.INDICES_PER_CELL - 1 - Constants.CELL_POSITION_INDICES);
       return;
     }
 
@@ -288,7 +290,7 @@ export class GlyphRenderer extends Disposable {
 
   public clear(): void {
     const terminal = this._terminal;
-    const newCount = terminal.cols * terminal.rows * INDICES_PER_CELL;
+    const newCount = terminal.cols * terminal.rows * Constants.INDICES_PER_CELL;
 
     // Clear vertices
     if (this._vertices.count !== newCount) {
@@ -310,7 +312,7 @@ export class GlyphRenderer extends Disposable {
       for (let x = 0; x < terminal.cols; x++) {
         this._vertices.attributes[i + 9] = x / terminal.cols;
         this._vertices.attributes[i + 10] = y / terminal.rows;
-        i += INDICES_PER_CELL;
+        i += Constants.INDICES_PER_CELL;
       }
     }
   }
@@ -346,8 +348,8 @@ export class GlyphRenderer extends Disposable {
     // - So we don't send vertices for all the line-ending whitespace to the GPU
     let bufferLength = 0;
     for (let y = 0; y < renderModel.lineLengths.length; y++) {
-      const si = y * this._terminal.cols * INDICES_PER_CELL;
-      const sub = this._vertices.attributes.subarray(si, si + renderModel.lineLengths[y] * INDICES_PER_CELL);
+      const si = y * this._terminal.cols * Constants.INDICES_PER_CELL;
+      const sub = this._vertices.attributes.subarray(si, si + renderModel.lineLengths[y] * Constants.INDICES_PER_CELL);
       activeBuffer.set(sub, bufferLength);
       bufferLength += sub.length;
     }
@@ -364,7 +366,7 @@ export class GlyphRenderer extends Disposable {
     }
 
     // Draw the viewport
-    gl.drawElementsInstanced(gl.TRIANGLE_STRIP, 4, gl.UNSIGNED_BYTE, 0, bufferLength / INDICES_PER_CELL);
+    gl.drawElementsInstanced(gl.TRIANGLE_STRIP, 4, gl.UNSIGNED_BYTE, 0, bufferLength / Constants.INDICES_PER_CELL);
   }
 
   public setAtlas(atlas: ITextureAtlas): void {
diff --git a/addons/addon-webgl/src/RectangleRenderer.ts b/addons/addon-webgl/src/RectangleRenderer.ts
index d22068babe..4ad8d66ff0 100644
--- a/addons/addon-webgl/src/RectangleRenderer.ts
+++ b/addons/addon-webgl/src/RectangleRenderer.ts
@@ -10,7 +10,7 @@ import { Attributes, FgFlags } from 'common/buffer/Constants';
 import { Disposable, toDisposable } from 'common/Lifecycle';
 import { IColor } from 'common/Types';
 import { Terminal } from '@xterm/xterm';
-import { RENDER_MODEL_BG_OFFSET, RENDER_MODEL_FG_OFFSET, RENDER_MODEL_INDICIES_PER_CELL } from './RenderModel';
+import { RenderModelConstants } from './RenderModel';
 import { IRenderModel, IWebGL2RenderingContext, IWebGLVertexArrayObject } from './Types';
 import { createProgram, expandFloat32Array, PROJECTION_MATRIX } from './WebglUtils';
 import { throwIfFalsy } from 'browser/renderer/shared/RendererUtils';
@@ -217,9 +217,9 @@ export class RectangleRenderer extends Disposable {
       currentFg = 0;
       currentInverse = false;
       for (x = 0; x < terminal.cols; x++) {
-        modelIndex = ((y * terminal.cols) + x) * RENDER_MODEL_INDICIES_PER_CELL;
-        bg = model.cells[modelIndex + RENDER_MODEL_BG_OFFSET];
-        fg = model.cells[modelIndex + RENDER_MODEL_FG_OFFSET];
+        modelIndex = ((y * terminal.cols) + x) * RenderModelConstants.INDICIES_PER_CELL;
+        bg = model.cells[modelIndex + RenderModelConstants.BG_OFFSET];
+        fg = model.cells[modelIndex + RenderModelConstants.FG_OFFSET];
         inverse = !!(fg & FgFlags.INVERSE);
         if (bg !== currentBg || (fg !== currentFg && (currentInverse || inverse))) {
           // A rectangle needs to be drawn if going from non-default to another color
diff --git a/addons/addon-webgl/src/RenderModel.ts b/addons/addon-webgl/src/RenderModel.ts
index a94f317eea..6113a9bdcd 100644
--- a/addons/addon-webgl/src/RenderModel.ts
+++ b/addons/addon-webgl/src/RenderModel.ts
@@ -7,10 +7,12 @@ import { ICursorRenderModel, IRenderModel } from './Types';
 import { ISelectionRenderModel } from 'browser/renderer/shared/Types';
 import { createSelectionRenderModel } from 'browser/renderer/shared/SelectionRenderModel';
 
-export const RENDER_MODEL_INDICIES_PER_CELL = 4;
-export const RENDER_MODEL_BG_OFFSET = 1;
-export const RENDER_MODEL_FG_OFFSET = 2;
-export const RENDER_MODEL_EXT_OFFSET = 3;
+export const enum RenderModelConstants {
+  INDICIES_PER_CELL = 4,
+  BG_OFFSET = 1,
+  FG_OFFSET = 2,
+  EXT_OFFSET = 3
+}
 
 export const COMBINED_CHAR_BIT_MASK = 0x80000000;
 
@@ -27,7 +29,7 @@ export class RenderModel implements IRenderModel {
   }
 
   public resize(cols: number, rows: number): void {
-    const indexCount = cols * rows * RENDER_MODEL_INDICIES_PER_CELL;
+    const indexCount = cols * rows * RenderModelConstants.INDICIES_PER_CELL;
     if (indexCount !== this.cells.length) {
       this.cells = new Uint32Array(indexCount);
       this.lineLengths = new Uint32Array(rows);
diff --git a/addons/addon-webgl/src/WebglRenderer.ts b/addons/addon-webgl/src/WebglRenderer.ts
index 83f20c9e7b..91867ea261 100644
--- a/addons/addon-webgl/src/WebglRenderer.ts
+++ b/addons/addon-webgl/src/WebglRenderer.ts
@@ -19,7 +19,7 @@ import { ICoreService, IDecorationService, IOptionsService } from 'common/servic
 import { Terminal } from '@xterm/xterm';
 import { GlyphRenderer } from './GlyphRenderer';
 import { RectangleRenderer } from './RectangleRenderer';
-import { COMBINED_CHAR_BIT_MASK, RENDER_MODEL_BG_OFFSET, RENDER_MODEL_EXT_OFFSET, RENDER_MODEL_FG_OFFSET, RENDER_MODEL_INDICIES_PER_CELL, RenderModel } from './RenderModel';
+import { COMBINED_CHAR_BIT_MASK, RenderModel, RenderModelConstants } from './RenderModel';
 import { IWebGL2RenderingContext, type ITextureAtlas } from './Types';
 import { LinkRenderLayer } from './renderLayer/LinkRenderLayer';
 import { IRenderLayer } from './renderLayer/Types';
@@ -493,7 +493,7 @@ export class WebglRenderer extends Disposable implements IRenderer {
 
         chars = cell.getChars();
         code = cell.getCode();
-        i = ((y * terminal.cols) + x) * RENDER_MODEL_INDICIES_PER_CELL;
+        i = ((y * terminal.cols) + x) * RenderModelConstants.INDICIES_PER_CELL;
 
         if (!rowHasBlinkingCells && cell.isBlink()) {
           rowHasBlinkingCells = true;
@@ -538,9 +538,9 @@ export class WebglRenderer extends Disposable implements IRenderer {
 
         // Nothing has changed, no updates needed
         if (this._model.cells[i] === code &&
-            this._model.cells[i + RENDER_MODEL_BG_OFFSET] === this._cellColorResolver.result.bg &&
-            this._model.cells[i + RENDER_MODEL_FG_OFFSET] === this._cellColorResolver.result.fg &&
-            this._model.cells[i + RENDER_MODEL_EXT_OFFSET] === this._cellColorResolver.result.ext) {
+            this._model.cells[i + RenderModelConstants.BG_OFFSET] === this._cellColorResolver.result.bg &&
+            this._model.cells[i + RenderModelConstants.FG_OFFSET] === this._cellColorResolver.result.fg &&
+            this._model.cells[i + RenderModelConstants.EXT_OFFSET] === this._cellColorResolver.result.ext) {
           continue;
         }
 
@@ -553,9 +553,9 @@ export class WebglRenderer extends Disposable implements IRenderer {
 
         // Cache the results in the model
         this._model.cells[i] = code;
-        this._model.cells[i + RENDER_MODEL_BG_OFFSET] = this._cellColorResolver.result.bg;
-        this._model.cells[i + RENDER_MODEL_FG_OFFSET] = this._cellColorResolver.result.fg;
-        this._model.cells[i + RENDER_MODEL_EXT_OFFSET] = this._cellColorResolver.result.ext;
+        this._model.cells[i + RenderModelConstants.BG_OFFSET] = this._cellColorResolver.result.bg;
+        this._model.cells[i + RenderModelConstants.FG_OFFSET] = this._cellColorResolver.result.fg;
+        this._model.cells[i + RenderModelConstants.EXT_OFFSET] = this._cellColorResolver.result.ext;
 
         width = cell.getWidth();
         this._glyphRenderer.value!.updateCell(x, y, code, this._cellColorResolver.result.bg, this._cellColorResolver.result.fg, this._cellColorResolver.result.ext, chars, width, lastBg);
@@ -566,14 +566,14 @@ export class WebglRenderer extends Disposable implements IRenderer {
 
           // Null out non-first cells
           for (x++; x <= lastCharX; x++) {
-            j = ((y * terminal.cols) + x) * RENDER_MODEL_INDICIES_PER_CELL;
+            j = ((y * terminal.cols) + x) * RenderModelConstants.INDICIES_PER_CELL;
             this._glyphRenderer.value!.updateCell(x, y, NULL_CELL_CODE, 0, 0, 0, NULL_CELL_CHAR, 0, 0);
             this._model.cells[j] = NULL_CELL_CODE;
             // Don't re-resolve the cell color since multi-colored ligature backgrounds are not
             // supported
-            this._model.cells[j + RENDER_MODEL_BG_OFFSET] = this._cellColorResolver.result.bg;
-            this._model.cells[j + RENDER_MODEL_FG_OFFSET] = this._cellColorResolver.result.fg;
-            this._model.cells[j + RENDER_MODEL_EXT_OFFSET] = this._cellColorResolver.result.ext;
+            this._model.cells[j + RenderModelConstants.BG_OFFSET] = this._cellColorResolver.result.bg;
+            this._model.cells[j + RenderModelConstants.FG_OFFSET] = this._cellColorResolver.result.fg;
+            this._model.cells[j + RenderModelConstants.EXT_OFFSET] = this._cellColorResolver.result.ext;
           }
           x--; // Go back to the previous update cell for next iteration
         }
diff --git a/src/browser/AccessibilityManager.ts b/src/browser/AccessibilityManager.ts
index 1d3c44ae1d..6fc4213379 100644
--- a/src/browser/AccessibilityManager.ts
+++ b/src/browser/AccessibilityManager.ts
@@ -12,7 +12,9 @@ import { IBuffer } from 'common/buffer/Types';
 import { IInstantiationService } from 'common/services/Services';
 import { addDisposableListener } from 'browser/Dom';
 
-const MAX_ROWS_TO_READ = 20;
+const enum Constants {
+  MAX_ROWS_TO_READ = 20
+}
 
 const enum BoundaryPosition {
   TOP,
@@ -137,7 +139,7 @@ export class AccessibilityManager extends Disposable {
   }
 
   private _handleChar(char: string): void {
-    if (this._liveRegionLineCount < MAX_ROWS_TO_READ + 1) {
+    if (this._liveRegionLineCount < Constants.MAX_ROWS_TO_READ + 1) {
       if (this._charsToConsume.length > 0) {
         // Have the screen reader ignore the char if it was just input
         const shiftedChar = this._charsToConsume.shift();
@@ -150,7 +152,7 @@ export class AccessibilityManager extends Disposable {
 
       if (char === '\n') {
         this._liveRegionLineCount++;
-        if (this._liveRegionLineCount === MAX_ROWS_TO_READ + 1) {
+        if (this._liveRegionLineCount === Constants.MAX_ROWS_TO_READ + 1) {
           this._liveRegion.textContent = Strings.tooMuchOutput.get();
         }
       }
diff --git a/src/browser/renderer/dom/DomRenderer.ts b/src/browser/renderer/dom/DomRenderer.ts
index 08b5093dfb..6f873af7b5 100644
--- a/src/browser/renderer/dom/DomRenderer.ts
+++ b/src/browser/renderer/dom/DomRenderer.ts
@@ -19,13 +19,15 @@ import { Emitter } from 'common/Event';
 import { addDisposableListener } from 'browser/Dom';
 
 
-const TERMINAL_CLASS_PREFIX = 'xterm-dom-renderer-owner-';
-const ROW_CONTAINER_CLASS = 'xterm-rows';
-const FG_CLASS_PREFIX = 'xterm-fg-';
-const BG_CLASS_PREFIX = 'xterm-bg-';
-const FOCUS_CLASS = 'xterm-focus';
-const SELECTION_CLASS = 'xterm-selection';
-const CURSOR_BLINK_IDLE_CLASS = 'xterm-cursor-blink-idle';
+const enum Constants {
+  TERMINAL_CLASS_PREFIX = 'xterm-dom-renderer-owner-',
+  ROW_CONTAINER_CLASS = 'xterm-rows',
+  FG_CLASS_PREFIX = 'xterm-fg-',
+  BG_CLASS_PREFIX = 'xterm-bg-',
+  FOCUS_CLASS = 'xterm-focus',
+  SELECTION_CLASS = 'xterm-selection',
+  CURSOR_BLINK_IDLE_CLASS = 'xterm-cursor-blink-idle'
+}
 
 let nextTerminalId = 1;
 
@@ -76,12 +78,12 @@ export class DomRenderer extends Disposable implements IRenderer {
   ) {
     super();
     this._rowContainer = this._document.createElement('div');
-    this._rowContainer.classList.add(ROW_CONTAINER_CLASS);
+    this._rowContainer.classList.add(Constants.ROW_CONTAINER_CLASS);
     this._rowContainer.style.lineHeight = 'normal';
     this._rowContainer.setAttribute('aria-hidden', 'true');
     this._refreshRowElements(this._bufferService.cols, this._bufferService.rows);
     this._selectionContainer = this._document.createElement('div');
-    this._selectionContainer.classList.add(SELECTION_CLASS);
+    this._selectionContainer.classList.add(Constants.SELECTION_CLASS);
     this._selectionContainer.setAttribute('aria-hidden', 'true');
 
     this.dimensions = createRenderDimensions();
@@ -93,7 +95,7 @@ export class DomRenderer extends Disposable implements IRenderer {
 
     this._rowFactory = instantiationService.createInstance(DomRendererRowFactory, document);
 
-    this._element.classList.add(TERMINAL_CLASS_PREFIX + this._terminalClass);
+    this._element.classList.add(Constants.TERMINAL_CLASS_PREFIX + this._terminalClass);
     this._screenElement.appendChild(this._rowContainer);
     this._screenElement.appendChild(this._selectionContainer);
 
@@ -110,7 +112,7 @@ export class DomRenderer extends Disposable implements IRenderer {
     ));
 
     this._register(toDisposable(() => {
-      this._element.classList.remove(TERMINAL_CLASS_PREFIX + this._terminalClass);
+      this._element.classList.remove(Constants.TERMINAL_CLASS_PREFIX + this._terminalClass);
 
       // Outside influences such as React unmounts may manipulate the DOM before our disposal.
       // https://github.com/xtermjs/xterm.js/issues/2960
@@ -160,7 +162,7 @@ export class DomRenderer extends Disposable implements IRenderer {
     }
 
     const styles =
-      `${this._terminalSelector} .${ROW_CONTAINER_CLASS} span {` +
+      `${this._terminalSelector} .${Constants.ROW_CONTAINER_CLASS} span {` +
       ` display: inline-block;` +   // TODO: find workaround for inline-block (creates ~20% render penalty)
       ` height: 100%;` +
       ` vertical-align: top;` +
@@ -181,7 +183,7 @@ export class DomRenderer extends Disposable implements IRenderer {
 
     // Base CSS
     let styles =
-      `${this._terminalSelector} .${ROW_CONTAINER_CLASS} {` +
+      `${this._terminalSelector} .${Constants.ROW_CONTAINER_CLASS} {` +
       // Disabling pointer events circumvents a browser behavior that prevents `click` events from
       // being delivered if the target element is replaced during the click. This happened due to
       // refresh() being called during the mousedown handler to start a selection.
@@ -189,14 +191,14 @@ export class DomRenderer extends Disposable implements IRenderer {
       ` color: ${colors.foreground.css};` +
       `}`;
     styles +=
-      `${this._terminalSelector} .${ROW_CONTAINER_CLASS}, ${this._terminalSelector} .${ROW_CONTAINER_CLASS} span {` +
+      `${this._terminalSelector} .${Constants.ROW_CONTAINER_CLASS}, ${this._terminalSelector} .${Constants.ROW_CONTAINER_CLASS} span {` +
       ` font-family: ${this._optionsService.rawOptions.fontFamily};` +
       ` font-size: ${this._optionsService.rawOptions.fontSize}px;` +
       ` font-kerning: none;` +
       ` white-space: pre` +
       `}`;
     styles +=
-      `${this._terminalSelector} .${ROW_CONTAINER_CLASS} .xterm-dim {` +
+      `${this._terminalSelector} .${Constants.ROW_CONTAINER_CLASS} .xterm-dim {` +
       ` color: ${color.multiplyOpacity(colors.foreground, 0.5).css};` +
       `}`;
     // Text styles
@@ -242,70 +244,70 @@ export class DomRenderer extends Disposable implements IRenderer {
       `}`;
     // Cursor
     styles +=
-      `${this._terminalSelector} .${ROW_CONTAINER_CLASS}.${FOCUS_CLASS} .${RowCss.CURSOR_CLASS}.${RowCss.CURSOR_BLINK_CLASS}.${RowCss.CURSOR_STYLE_UNDERLINE_CLASS} {` +
+      `${this._terminalSelector} .${Constants.ROW_CONTAINER_CLASS}.${Constants.FOCUS_CLASS} .${RowCss.CURSOR_CLASS}.${RowCss.CURSOR_BLINK_CLASS}.${RowCss.CURSOR_STYLE_UNDERLINE_CLASS} {` +
       ` animation: ${blinkAnimationUnderlineId} 1s step-end infinite;` +
       `}` +
-      `${this._terminalSelector} .${ROW_CONTAINER_CLASS}.${FOCUS_CLASS} .${RowCss.CURSOR_CLASS}.${RowCss.CURSOR_BLINK_CLASS}.${RowCss.CURSOR_STYLE_BAR_CLASS} {` +
+      `${this._terminalSelector} .${Constants.ROW_CONTAINER_CLASS}.${Constants.FOCUS_CLASS} .${RowCss.CURSOR_CLASS}.${RowCss.CURSOR_BLINK_CLASS}.${RowCss.CURSOR_STYLE_BAR_CLASS} {` +
       ` animation: ${blinkAnimationBarId} 1s step-end infinite;` +
       `}` +
-      `${this._terminalSelector} .${ROW_CONTAINER_CLASS}.${FOCUS_CLASS} .${RowCss.CURSOR_CLASS}.${RowCss.CURSOR_BLINK_CLASS}.${RowCss.CURSOR_STYLE_BLOCK_CLASS} {` +
+      `${this._terminalSelector} .${Constants.ROW_CONTAINER_CLASS}.${Constants.FOCUS_CLASS} .${RowCss.CURSOR_CLASS}.${RowCss.CURSOR_BLINK_CLASS}.${RowCss.CURSOR_STYLE_BLOCK_CLASS} {` +
       ` animation: ${blinkAnimationBlockId} 1s step-end infinite;` +
       `}` +
       // Disable cursor blinking when idle
-      `${this._terminalSelector} .${ROW_CONTAINER_CLASS}.${CURSOR_BLINK_IDLE_CLASS} .${RowCss.CURSOR_CLASS}.${RowCss.CURSOR_BLINK_CLASS} {` +
+      `${this._terminalSelector} .${Constants.ROW_CONTAINER_CLASS}.${Constants.CURSOR_BLINK_IDLE_CLASS} .${RowCss.CURSOR_CLASS}.${RowCss.CURSOR_BLINK_CLASS} {` +
       ` animation: none !important;` +
       `}` +
       // !important helps fix an issue where the cursor will not render on top of the selection,
       // however it's very hard to fix this issue and retain the blink animation without the use of
       // !important. So this edge case fails when cursor blink is on.
-      `${this._terminalSelector} .${ROW_CONTAINER_CLASS} .${RowCss.CURSOR_CLASS}.${RowCss.CURSOR_STYLE_BLOCK_CLASS} {` +
+      `${this._terminalSelector} .${Constants.ROW_CONTAINER_CLASS} .${RowCss.CURSOR_CLASS}.${RowCss.CURSOR_STYLE_BLOCK_CLASS} {` +
       ` background-color: ${colors.cursor.css};` +
       ` color: ${colors.cursorAccent.css};` +
       `}` +
-      `${this._terminalSelector} .${ROW_CONTAINER_CLASS} .${RowCss.CURSOR_CLASS}.${RowCss.CURSOR_STYLE_BLOCK_CLASS}:not(.${RowCss.CURSOR_BLINK_CLASS}) {` +
+      `${this._terminalSelector} .${Constants.ROW_CONTAINER_CLASS} .${RowCss.CURSOR_CLASS}.${RowCss.CURSOR_STYLE_BLOCK_CLASS}:not(.${RowCss.CURSOR_BLINK_CLASS}) {` +
       ` background-color: ${colors.cursor.css} !important;` +
       ` color: ${colors.cursorAccent.css} !important;` +
       `}` +
-      `${this._terminalSelector} .${ROW_CONTAINER_CLASS} .${RowCss.CURSOR_CLASS}.${RowCss.CURSOR_STYLE_OUTLINE_CLASS} {` +
+      `${this._terminalSelector} .${Constants.ROW_CONTAINER_CLASS} .${RowCss.CURSOR_CLASS}.${RowCss.CURSOR_STYLE_OUTLINE_CLASS} {` +
       ` outline: 1px solid ${colors.cursor.css};` +
       ` outline-offset: -1px;` +
       `}` +
-      `${this._terminalSelector} .${ROW_CONTAINER_CLASS} .${RowCss.CURSOR_CLASS}.${RowCss.CURSOR_STYLE_BAR_CLASS} {` +
+      `${this._terminalSelector} .${Constants.ROW_CONTAINER_CLASS} .${RowCss.CURSOR_CLASS}.${RowCss.CURSOR_STYLE_BAR_CLASS} {` +
       ` box-shadow: ${this._optionsService.rawOptions.cursorWidth}px 0 0 ${colors.cursor.css} inset;` +
       `}` +
-      `${this._terminalSelector} .${ROW_CONTAINER_CLASS} .${RowCss.CURSOR_CLASS}.${RowCss.CURSOR_STYLE_UNDERLINE_CLASS} {` +
+      `${this._terminalSelector} .${Constants.ROW_CONTAINER_CLASS} .${RowCss.CURSOR_CLASS}.${RowCss.CURSOR_STYLE_UNDERLINE_CLASS} {` +
       ` border-bottom: 1px ${colors.cursor.css};` +
       ` border-bottom-style: solid;` +
       ` height: calc(100% - 1px);` +
       `}`;
     // Selection
     styles +=
-      `${this._terminalSelector} .${SELECTION_CLASS} {` +
+      `${this._terminalSelector} .${Constants.SELECTION_CLASS} {` +
       ` position: absolute;` +
       ` top: 0;` +
       ` left: 0;` +
       ` z-index: 1;` +
       ` pointer-events: none;` +
       `}` +
-      `${this._terminalSelector}.focus .${SELECTION_CLASS} div {` +
+      `${this._terminalSelector}.focus .${Constants.SELECTION_CLASS} div {` +
       ` position: absolute;` +
       ` background-color: ${colors.selectionBackgroundOpaque.css};` +
       `}` +
-      `${this._terminalSelector} .${SELECTION_CLASS} div {` +
+      `${this._terminalSelector} .${Constants.SELECTION_CLASS} div {` +
       ` position: absolute;` +
       ` background-color: ${colors.selectionInactiveBackgroundOpaque.css};` +
       `}`;
     // Colors
     for (const [i, c] of colors.ansi.entries()) {
       styles +=
-        `${this._terminalSelector} .${FG_CLASS_PREFIX}${i} { color: ${c.css}; }` +
-        `${this._terminalSelector} .${FG_CLASS_PREFIX}${i}.${RowCss.DIM_CLASS} { color: ${color.multiplyOpacity(c, 0.5).css}; }` +
-        `${this._terminalSelector} .${BG_CLASS_PREFIX}${i} { background-color: ${c.css}; }`;
+        `${this._terminalSelector} .${Constants.FG_CLASS_PREFIX}${i} { color: ${c.css}; }` +
+        `${this._terminalSelector} .${Constants.FG_CLASS_PREFIX}${i}.${RowCss.DIM_CLASS} { color: ${color.multiplyOpacity(c, 0.5).css}; }` +
+        `${this._terminalSelector} .${Constants.BG_CLASS_PREFIX}${i} { background-color: ${c.css}; }`;
     }
     styles +=
-      `${this._terminalSelector} .${FG_CLASS_PREFIX}${INVERTED_DEFAULT_COLOR} { color: ${color.opaque(colors.background).css}; }` +
-      `${this._terminalSelector} .${FG_CLASS_PREFIX}${INVERTED_DEFAULT_COLOR}.${RowCss.DIM_CLASS} { color: ${color.multiplyOpacity(color.opaque(colors.background), 0.5).css}; }` +
-      `${this._terminalSelector} .${BG_CLASS_PREFIX}${INVERTED_DEFAULT_COLOR} { background-color: ${colors.foreground.css}; }`;
+      `${this._terminalSelector} .${Constants.FG_CLASS_PREFIX}${INVERTED_DEFAULT_COLOR} { color: ${color.opaque(colors.background).css}; }` +
+      `${this._terminalSelector} .${Constants.FG_CLASS_PREFIX}${INVERTED_DEFAULT_COLOR}.${RowCss.DIM_CLASS} { color: ${color.multiplyOpacity(color.opaque(colors.background), 0.5).css}; }` +
+      `${this._terminalSelector} .${Constants.BG_CLASS_PREFIX}${INVERTED_DEFAULT_COLOR} { background-color: ${colors.foreground.css}; }`;
 
     this._themeStyleElement.textContent = styles;
   }
@@ -361,13 +363,13 @@ export class DomRenderer extends Disposable implements IRenderer {
   }
 
   public handleBlur(): void {
-    this._rowContainer.classList.remove(FOCUS_CLASS);
+    this._rowContainer.classList.remove(Constants.FOCUS_CLASS);
     this._cursorBlinkStateManager.pause();
     this.renderRows(0, this._bufferService.rows - 1);
   }
 
   public handleFocus(): void {
-    this._rowContainer.classList.add(FOCUS_CLASS);
+    this._rowContainer.classList.add(Constants.FOCUS_CLASS);
     this._cursorBlinkStateManager.resume();
     this.renderRows(this._bufferService.buffer.y, this._bufferService.buffer.y);
   }
@@ -561,7 +563,7 @@ export class DomRenderer extends Disposable implements IRenderer {
   }
 
   private get _terminalSelector(): string {
-    return `.${TERMINAL_CLASS_PREFIX}${this._terminalClass}`;
+    return `.${Constants.TERMINAL_CLASS_PREFIX}${this._terminalClass}`;
   }
 
   private _handleLinkHover(e: ILinkifierEvent): void {
@@ -667,7 +669,7 @@ class CursorBlinkStateManager {
 
   public restartBlinkAnimation(): void {
     if (this._isIdlePaused) {
-      this._rowContainer.classList.remove(CURSOR_BLINK_IDLE_CLASS);
+      this._rowContainer.classList.remove(Constants.CURSOR_BLINK_IDLE_CLASS);
     }
     this._resetIdleTimer();
   }
@@ -679,7 +681,7 @@ class CursorBlinkStateManager {
 
   public resume(): void {
     this._isIdlePaused = false;
-    this._rowContainer.classList.remove(CURSOR_BLINK_IDLE_CLASS);
+    this._rowContainer.classList.remove(Constants.CURSOR_BLINK_IDLE_CLASS);
     this._resetIdleTimer();
   }
 
@@ -699,7 +701,7 @@ class CursorBlinkStateManager {
   }
 
   private _stopBlinkingDueToIdle(): void {
-    this._rowContainer.classList.add(CURSOR_BLINK_IDLE_CLASS);
+    this._rowContainer.classList.add(Constants.CURSOR_BLINK_IDLE_CLASS);
     this._isIdlePaused = true;
     this._idleTimeout = undefined;
   }
diff --git a/src/browser/renderer/dom/DomRendererRowFactory.test.ts b/src/browser/renderer/dom/DomRendererRowFactory.test.ts
index 05fc8000c6..6ca84569a7 100644
--- a/src/browser/renderer/dom/DomRendererRowFactory.test.ts
+++ b/src/browser/renderer/dom/DomRendererRowFactory.test.ts
@@ -8,14 +8,14 @@ import { assert } from 'chai';
 import { DomRendererRowFactory } from 'browser/renderer/dom/DomRendererRowFactory';
 import { NULL_CELL_CODE, NULL_CELL_WIDTH, NULL_CELL_CHAR, DEFAULT_ATTR, FgFlags, BgFlags, Attributes, UnderlineStyle } from 'common/buffer/Constants';
 import { BufferLine, DEFAULT_ATTR_DATA } from 'common/buffer/BufferLine';
+import { BufferLineStringCache } from 'common/buffer/BufferLineStringCache';
 import { IBufferLine } from 'common/Types';
 import { CellData } from 'common/buffer/CellData';
 import { MockCoreService, MockDecorationService, MockOptionsService, createCellData, NULL_CELL_DATA } from 'common/TestUtils.test';
 import { MockCharacterJoinerService, MockCoreBrowserService, MockThemeService } from 'browser/TestUtils.test';
 import { TestWidthCache } from 'browser/renderer/dom/WidthCache.test';
 
-const dom = new jsdom.JSDOM('');
-
+const TEST_STRING_CACHE = new BufferLineStringCache();
 
 describe('DomRendererRowFactory', () => {
   let dom: jsdom.JSDOM;
@@ -517,7 +517,7 @@ describe('DomRendererRowFactory', () => {
   }
 
   function createEmptyLineData(cols: number): IBufferLine {
-    const lineData = new BufferLine(cols);
+    const lineData = new BufferLine(TEST_STRING_CACHE, cols);
     for (let i = 0; i < cols; i++) {
       lineData.setCell(i, NULL_CELL_DATA);
     }
diff --git a/src/browser/scrollable/scrollableElement.ts b/src/browser/scrollable/scrollableElement.ts
index e30b36fc36..4039d0c4ef 100644
--- a/src/browser/scrollable/scrollableElement.ts
+++ b/src/browser/scrollable/scrollableElement.ts
@@ -18,8 +18,10 @@ import * as platform from 'common/Platform';
 import { INewScrollDimensions, INewScrollPosition, IScrollDimensions, IScrollPosition, IScrollEvent, Scrollable, ScrollbarVisibility } from './scrollable';
 // import 'vs/css!./media/scrollbars';
 
-const HIDE_TIMEOUT = 500;
-const SCROLL_WHEEL_SENSITIVITY = 50;
+const enum Constants {
+  HIDE_TIMEOUT = 500,
+  SCROLL_WHEEL_SENSITIVITY = 50
+}
 
 class MouseWheelClassifierItem {
   public timestamp: number;
@@ -404,12 +406,12 @@ export class SmoothScrollableElement extends Widget {
 
       let desiredScrollPosition: INewScrollPosition = {};
       if (deltaY) {
-        const deltaScrollTop = SCROLL_WHEEL_SENSITIVITY * deltaY;
+        const deltaScrollTop = Constants.SCROLL_WHEEL_SENSITIVITY * deltaY;
         const desiredScrollTop = futureScrollPosition.scrollTop - (deltaScrollTop < 0 ? Math.floor(deltaScrollTop) : Math.ceil(deltaScrollTop));
         this._verticalScrollbar.writeScrollPosition(desiredScrollPosition, desiredScrollTop);
       }
       if (deltaX) {
-        const deltaScrollLeft = SCROLL_WHEEL_SENSITIVITY * deltaX;
+        const deltaScrollLeft = Constants.SCROLL_WHEEL_SENSITIVITY * deltaX;
         const desiredScrollLeft = futureScrollPosition.scrollLeft - (deltaScrollLeft < 0 ? Math.floor(deltaScrollLeft) : Math.ceil(deltaScrollLeft));
         this._horizontalScrollbar.writeScrollPosition(desiredScrollPosition, desiredScrollLeft);
       }
@@ -533,7 +535,7 @@ export class SmoothScrollableElement extends Widget {
 
   private _scheduleHide(): void {
     if (!this._mouseIsOver && !this._isDragging) {
-      this._hideTimeout.cancelAndSet(() => this._hide(), HIDE_TIMEOUT);
+      this._hideTimeout.cancelAndSet(() => this._hide(), Constants.HIDE_TIMEOUT);
     }
   }
 }
diff --git a/src/browser/services/CharacterJoinerService.test.ts b/src/browser/services/CharacterJoinerService.test.ts
index a0ccc67d6a..06730c7ac8 100644
--- a/src/browser/services/CharacterJoinerService.test.ts
+++ b/src/browser/services/CharacterJoinerService.test.ts
@@ -7,10 +7,13 @@ import { assert } from 'chai';
 import { ICharacterJoinerService } from 'browser/services/Services';
 import { CharacterJoinerService } from 'browser/services/CharacterJoinerService';
 import { BufferLine } from 'common/buffer/BufferLine';
+import { BufferLineStringCache } from 'common/buffer/BufferLineStringCache';
 import { IBufferLine } from 'common/Types';
 import { CellData } from 'common/buffer/CellData';
 import { MockBufferService, createCellData } from 'common/TestUtils.test';
 
+const TEST_STRING_CACHE = new BufferLineStringCache();
+
 describe('CharacterJoinerService', () => {
   let service: ICharacterJoinerService;
 
@@ -22,7 +25,7 @@ describe('CharacterJoinerService', () => {
     lines.set(2, lineData([['a -> b -', 0xFFFFFFFF], ['> c -> d', 0]]));
 
     lines.set(3, lineData([['no joined ranges']]));
-    lines.set(4, new BufferLine(0));
+    lines.set(4, new BufferLine(TEST_STRING_CACHE, 0));
     lines.set(5, lineData([['a', 0x11111111], [' -> b -> c -> '], ['d', 0x22222222]]));
     const line6 = lineData([['wi']]);
     line6.resize(line6.length + 1, createCellData(0, '￥', 2));
@@ -267,7 +270,7 @@ describe('CharacterJoinerService', () => {
 type IPartialLineData = ([string] | [string, number]);
 
 function lineData(data: IPartialLineData[]): IBufferLine {
-  const tline = new BufferLine(0);
+  const tline = new BufferLine(TEST_STRING_CACHE, 0);
   for (let i = 0; i < data.length; ++i) {
     const line = data[i][0];
     const attr = (data[i][1] || 0) as number;
diff --git a/src/browser/services/SelectionService.test.ts b/src/browser/services/SelectionService.test.ts
index 8deedb751c..be62ccc6b7 100644
--- a/src/browser/services/SelectionService.test.ts
+++ b/src/browser/services/SelectionService.test.ts
@@ -9,12 +9,15 @@ import { SelectionModel } from 'browser/selection/SelectionModel';
 import { IBufferLine } from 'common/Types';
 import { MockBufferService, MockOptionsService, MockCoreService, createCellData } from 'common/TestUtils.test';
 import { BufferLine } from 'common/buffer/BufferLine';
+import { BufferLineStringCache } from 'common/buffer/BufferLineStringCache';
 import { IBufferService, IOptionsService } from 'common/services/Services';
 import { MockCoreBrowserService, MockMouseService, MockRenderService } from 'browser/TestUtils.test';
 import { CellData } from 'common/buffer/CellData';
 import { IBuffer } from 'common/buffer/Types';
 import { IRenderService } from 'browser/services/Services';
 
+const TEST_STRING_CACHE = new BufferLineStringCache();
+
 class TestSelectionService extends SelectionService {
   constructor(
     bufferService: IBufferService,
@@ -55,7 +58,7 @@ describe('SelectionService', () => {
   });
 
   function stringToRow(text: string): IBufferLine {
-    const result = new BufferLine(text.length);
+    const result = new BufferLine(TEST_STRING_CACHE, text.length);
     for (let i = 0; i < text.length; i++) {
       result.setCell(i, createCellData(0, text.charAt(i), 1));
     }
@@ -63,7 +66,7 @@ describe('SelectionService', () => {
   }
 
   function stringArrayToRow(chars: string[]): IBufferLine {
-    const line = new BufferLine(chars.length);
+    const line = new BufferLine(TEST_STRING_CACHE, chars.length);
     chars.map((c, idx) => line.setCell(idx, createCellData(0, c, 1)));
     return line;
   }
@@ -118,7 +121,7 @@ describe('SelectionService', () => {
         [0, 'o', 1, 'o'.charCodeAt(0)],
         [0, 'o', 1, 'o'.charCodeAt(0)]
       ];
-      const line = new BufferLine(data.length);
+      const line = new BufferLine(TEST_STRING_CACHE, data.length);
       for (let i = 0; i < data.length; ++i) line.setCell(i, CellData.fromCharData(data[i]));
       buffer.lines.set(0, line);
       // Ensure wide characters take up 2 columns
diff --git a/src/browser/services/SelectionService.ts b/src/browser/services/SelectionService.ts
index e1b8510e96..39692a8719 100644
--- a/src/browser/services/SelectionService.ts
+++ b/src/browser/services/SelectionService.ts
@@ -18,27 +18,26 @@ import { IBuffer } from 'common/buffer/Types';
 import { IBufferService, ICoreService, IOptionsService } from 'common/services/Services';
 import { Emitter } from 'common/Event';
 
-/**
- * The number of pixels the mouse needs to be above or below the viewport in
- * order to scroll at the maximum speed.
- */
-const DRAG_SCROLL_MAX_THRESHOLD = 50;
-
-/**
- * The maximum scrolling speed
- */
-const DRAG_SCROLL_MAX_SPEED = 15;
-
-/**
- * The number of milliseconds between drag scroll updates.
- */
-const DRAG_SCROLL_INTERVAL = 50;
-
-/**
- * The maximum amount of time that can have elapsed for an alt click to move the
- * cursor.
- */
-const ALT_CLICK_MOVE_CURSOR_TIME = 500;
+const enum Constants {
+  /**
+   * The number of pixels the mouse needs to be above or below the viewport in
+   * order to scroll at the maximum speed.
+   */
+  DRAG_SCROLL_MAX_THRESHOLD = 50,
+  /**
+   * The maximum scrolling speed
+   */
+  DRAG_SCROLL_MAX_SPEED = 15,
+  /**
+   * The number of milliseconds between drag scroll updates.
+   */
+  DRAG_SCROLL_INTERVAL = 50,
+  /**
+   * The maximum amount of time that can have elapsed for an alt click to move the
+   * cursor.
+   */
+  ALT_CLICK_MOVE_CURSOR_TIME = 500
+}
 
 const NON_BREAKING_SPACE_CHAR = String.fromCharCode(160);
 const ALL_NON_BREAKING_SPACE_REGEX = new RegExp(NON_BREAKING_SPACE_CHAR, 'g');
@@ -424,9 +423,9 @@ export class SelectionService extends Disposable implements ISelectionService {
       offset -= terminalHeight;
     }
 
-    offset = Math.min(Math.max(offset, -DRAG_SCROLL_MAX_THRESHOLD), DRAG_SCROLL_MAX_THRESHOLD);
-    offset /= DRAG_SCROLL_MAX_THRESHOLD;
-    return (offset / Math.abs(offset)) + Math.round(offset * (DRAG_SCROLL_MAX_SPEED - 1));
+    offset = Math.min(Math.max(offset, -Constants.DRAG_SCROLL_MAX_THRESHOLD), Constants.DRAG_SCROLL_MAX_THRESHOLD);
+    offset /= Constants.DRAG_SCROLL_MAX_THRESHOLD;
+    return (offset / Math.abs(offset)) + Math.round(offset * (Constants.DRAG_SCROLL_MAX_SPEED - 1));
   }
 
   /**
@@ -500,7 +499,7 @@ export class SelectionService extends Disposable implements ISelectionService {
       this._screenElement.ownerDocument.addEventListener('mousemove', this._mouseMoveListener);
       this._screenElement.ownerDocument.addEventListener('mouseup', this._mouseUpListener);
     }
-    this._dragScrollIntervalTimer = this._coreBrowserService.window.setInterval(() => this._dragScroll(), DRAG_SCROLL_INTERVAL);
+    this._dragScrollIntervalTimer = this._coreBrowserService.window.setInterval(() => this._dragScroll(), Constants.DRAG_SCROLL_INTERVAL);
   }
 
   /**
@@ -675,7 +674,7 @@ export class SelectionService extends Disposable implements ISelectionService {
   }
 
   /**
-   * The callback that occurs every DRAG_SCROLL_INTERVAL ms that does the
+   * The callback that occurs every Constants.DRAG_SCROLL_INTERVAL ms that does the
    * scrolling of the viewport.
    */
   private _dragScroll(): void {
@@ -713,7 +712,7 @@ export class SelectionService extends Disposable implements ISelectionService {
 
     this._removeMouseDownListeners();
 
-    if (this.selectionText.length <= 1 && timeElapsed < ALT_CLICK_MOVE_CURSOR_TIME && event.altKey && this._optionsService.rawOptions.altClickMovesCursor) {
+    if (this.selectionText.length <= 1 && timeElapsed < Constants.ALT_CLICK_MOVE_CURSOR_TIME && event.altKey && this._optionsService.rawOptions.altClickMovesCursor) {
       if (this._bufferService.buffer.ybase === this._bufferService.buffer.ydisp) {
         const coordinates = this._mouseCoordsService.getCoords(
           event,
diff --git a/src/common/CoreTerminal.ts b/src/common/CoreTerminal.ts
index 0eff38f252..9bd7faaf50 100644
--- a/src/common/CoreTerminal.ts
+++ b/src/common/CoreTerminal.ts
@@ -24,7 +24,7 @@
 import { IInstantiationService, IOptionsService, IBufferService, ILogService, ICharsetService, ICoreService, IMouseStateService, IUnicodeService, LogLevelEnum, ITerminalOptions, IOscLinkService } from 'common/services/Services';
 import { InstantiationService } from 'common/services/InstantiationService';
 import { LogService } from 'common/services/LogService';
-import { BufferService, MINIMUM_COLS, MINIMUM_ROWS } from 'common/services/BufferService';
+import { BufferService, BufferServiceConstants } from 'common/services/BufferService';
 import { OptionsService } from 'common/services/OptionsService';
 import { IDisposable, IAttributeData, ICoreTerminal, IScrollEvent } from 'common/Types';
 import { CoreService } from 'common/services/CoreService';
@@ -173,8 +173,8 @@ export abstract class CoreTerminal extends Disposable implements ICoreTerminal {
       return;
     }
 
-    x = Math.max(x, MINIMUM_COLS);
-    y = Math.max(y, MINIMUM_ROWS);
+    x = Math.max(x, BufferServiceConstants.MINIMUM_COLS);
+    y = Math.max(y, BufferServiceConstants.MINIMUM_ROWS);
 
     // Flush pending writes before resize to avoid race conditions where async
     // writes are processed with incorrect dimensions
diff --git a/src/common/InputHandler.ts b/src/common/InputHandler.ts
index c4c2a8e2e1..2b7142dd02 100644
--- a/src/common/InputHandler.ts
+++ b/src/common/InputHandler.ts
@@ -41,12 +41,13 @@ const GLEVEL: { [key: string]: number } = { '(': 0, ')': 1, '*': 2, '+': 3, '-':
 /**
  * Max length of the UTF32 input buffer. Real memory consumption is 4 times higher.
  */
-const MAX_PARSEBUFFER_LENGTH = 131072;
-
-/**
- * Limit length of title and icon name stacks.
- */
-const STACK_LIMIT = 10;
+const enum Constants {
+  MAX_PARSEBUFFER_LENGTH = 131072,
+  /** Limit length of title and icon name stacks. */
+  STACK_LIMIT = 10,
+  // create a warning log if an async handler takes longer than the limit (in ms)
+  SLOW_ASYNC_LIMIT = 5000
+}
 
 // map params to window option
 function paramToWindowOption(n: number, opts: IWindowOptions): boolean {
@@ -85,9 +86,6 @@ export enum WindowsOptionsReportType {
   GET_CELL_SIZE_PIXELS = 1
 }
 
-// create a warning log if an async handler takes longer than the limit (in ms)
-const SLOW_ASYNC_LIMIT = 5000;
-
 // Work variables to avoid garbage collection
 let $temp = 0;
 
@@ -393,7 +391,7 @@ export class InputHandler extends Disposable implements IInputHandler {
     if (this._logService.logLevel <= LogLevelEnum.WARN) {
       let slowTimeout: ReturnType<typeof setTimeout> | undefined;
       const slowPromise = new Promise<never>((_res, rej) => {
-        slowTimeout = setTimeout(() => rej('#SLOW_TIMEOUT'), SLOW_ASYNC_LIMIT);
+        slowTimeout = setTimeout(() => rej('#SLOW_TIMEOUT'), Constants.SLOW_ASYNC_LIMIT);
       });
       Promise.race([p, slowPromise])
         .then(() => {
@@ -407,7 +405,7 @@ export class InputHandler extends Disposable implements IInputHandler {
           if (err !== '#SLOW_TIMEOUT') {
             throw err;
           }
-          console.warn(`async parser handler taking longer than ${SLOW_ASYNC_LIMIT} ms`);
+          console.warn(`async parser handler taking longer than ${Constants.SLOW_ASYNC_LIMIT} ms`);
         });
     }
   }
@@ -445,8 +443,8 @@ export class InputHandler extends Disposable implements IInputHandler {
       cursorStartX = this._parseStack.cursorStartX;
       cursorStartY = this._parseStack.cursorStartY;
       this._parseStack.paused = false;
-      if (data.length > MAX_PARSEBUFFER_LENGTH) {
-        start = this._parseStack.position + MAX_PARSEBUFFER_LENGTH;
+      if (data.length > Constants.MAX_PARSEBUFFER_LENGTH) {
+        start = this._parseStack.position + Constants.MAX_PARSEBUFFER_LENGTH;
       }
     }
 
@@ -463,8 +461,8 @@ export class InputHandler extends Disposable implements IInputHandler {
 
     // resize input buffer if needed
     if (this._parseBuffer.length < data.length) {
-      if (this._parseBuffer.length < MAX_PARSEBUFFER_LENGTH) {
-        this._parseBuffer = new Uint32Array(Math.min(data.length, MAX_PARSEBUFFER_LENGTH));
+      if (this._parseBuffer.length < Constants.MAX_PARSEBUFFER_LENGTH) {
+        this._parseBuffer = new Uint32Array(Math.min(data.length, Constants.MAX_PARSEBUFFER_LENGTH));
       }
     }
 
@@ -475,9 +473,9 @@ export class InputHandler extends Disposable implements IInputHandler {
     }
 
     // process big data in smaller chunks
-    if (data.length > MAX_PARSEBUFFER_LENGTH) {
-      for (let i = start; i < data.length; i += MAX_PARSEBUFFER_LENGTH) {
-        const end = i + MAX_PARSEBUFFER_LENGTH < data.length ? i + MAX_PARSEBUFFER_LENGTH : data.length;
+    if (data.length > Constants.MAX_PARSEBUFFER_LENGTH) {
+      for (let i = start; i < data.length; i += Constants.MAX_PARSEBUFFER_LENGTH) {
+        const end = i + Constants.MAX_PARSEBUFFER_LENGTH < data.length ? i + Constants.MAX_PARSEBUFFER_LENGTH : data.length;
         const len = (typeof data === 'string')
           ? this._stringDecoder.decode(data.substring(i, end), this._parseBuffer)
           : this._utf8Decoder.decode(data.subarray(i, end), this._parseBuffer);
@@ -2955,13 +2953,13 @@ export class InputHandler extends Disposable implements IInputHandler {
       case 22:  // PushTitle
         if (second === 0 || second === 2) {
           this._windowTitleStack.push(this._windowTitle);
-          if (this._windowTitleStack.length > STACK_LIMIT) {
+          if (this._windowTitleStack.length > Constants.STACK_LIMIT) {
             this._windowTitleStack.shift();
           }
         }
         if (second === 0 || second === 1) {
           this._iconNameStack.push(this._iconName);
-          if (this._iconNameStack.length > STACK_LIMIT) {
+          if (this._iconNameStack.length > Constants.STACK_LIMIT) {
             this._iconNameStack.shift();
           }
         }
diff --git a/src/common/buffer/Buffer.test.ts b/src/common/buffer/Buffer.test.ts
index 9c013c5def..abfea7b061 100644
--- a/src/common/buffer/Buffer.test.ts
+++ b/src/common/buffer/Buffer.test.ts
@@ -8,22 +8,34 @@ import { Buffer } from 'common/buffer/Buffer';
 import { CircularList } from 'common/CircularList';
 import { MockOptionsService, MockBufferService, MockLogService, createCellData } from 'common/TestUtils.test';
 import { BufferLine, DEFAULT_ATTR_DATA } from 'common/buffer/BufferLine';
+import { BufferLineStringCache } from 'common/buffer/BufferLineStringCache';
 import { CellData } from 'common/buffer/CellData';
 import { ExtendedAttrs } from 'common/buffer/AttributeData';
 
 const INIT_COLS = 80;
 const INIT_ROWS = 24;
 const INIT_SCROLLBACK = 1000;
+const TEST_STRING_CACHE = new BufferLineStringCache();
+
+class TestBuffer extends Buffer {
+  public getStringCache(): BufferLineStringCache {
+    return (this as unknown as { _stringCache: BufferLineStringCache })._stringCache;
+  }
+
+  public getStringCacheClearTimeout(): unknown {
+    return (this.getStringCache() as unknown as { _clearTimeout: { value: unknown } })._clearTimeout.value;
+  }
+}
 
 describe('Buffer', () => {
   let optionsService: MockOptionsService;
   let bufferService: MockBufferService;
-  let buffer: Buffer;
+  let buffer: TestBuffer;
 
   beforeEach(() => {
     optionsService = new MockOptionsService({ scrollback: INIT_SCROLLBACK });
     bufferService = new MockBufferService(INIT_COLS, INIT_ROWS);
-    buffer = new Buffer(true, optionsService, bufferService, new MockLogService());
+    buffer = new TestBuffer(true, optionsService, bufferService, new MockLogService());
   });
 
   describe('constructor', () => {
@@ -151,7 +163,7 @@ describe('Buffer', () => {
 
       describe('no scrollback', () => {
         it('should trim from the top of the buffer when the cursor reaches the bottom', () => {
-          buffer = new Buffer(true, new MockOptionsService({ scrollback: 0 }), bufferService, new MockLogService());
+          buffer = new TestBuffer(true, new MockOptionsService({ scrollback: 0 }), bufferService, new MockLogService());
           assert.equal(buffer.lines.maxLength, INIT_ROWS);
           buffer.y = INIT_ROWS - 1;
           buffer.fillViewportRows();
@@ -1054,7 +1066,7 @@ describe('Buffer', () => {
   describe('buffer marked to have no scrollback', () => {
     it('should always have a scrollback of 0', () => {
       // Test size on initialization
-      buffer = new Buffer(false, new MockOptionsService({ scrollback: 1000 }), bufferService, new MockLogService());
+      buffer = new TestBuffer(false, new MockOptionsService({ scrollback: 1000 }), bufferService, new MockLogService());
       buffer.fillViewportRows();
       assert.equal(buffer.lines.maxLength, INIT_ROWS);
       // Test size on buffer increase
@@ -1068,7 +1080,7 @@ describe('Buffer', () => {
 
   describe('addMarker', () => {
     it('should adjust a marker line when the buffer is trimmed', () => {
-      buffer = new Buffer(true, new MockOptionsService({ scrollback: 0 }), bufferService, new MockLogService());
+      buffer = new TestBuffer(true, new MockOptionsService({ scrollback: 0 }), bufferService, new MockLogService());
       buffer.fillViewportRows();
       const marker = buffer.addMarker(buffer.lines.length - 1);
       assert.equal(marker.line, buffer.lines.length - 1);
@@ -1076,7 +1088,7 @@ describe('Buffer', () => {
       assert.equal(marker.line, buffer.lines.length - 2);
     });
     it('should dispose of a marker if it is trimmed off the buffer', () => {
-      buffer = new Buffer(true, new MockOptionsService({ scrollback: 0 }), bufferService, new MockLogService());
+      buffer = new TestBuffer(true, new MockOptionsService({ scrollback: 0 }), bufferService, new MockLogService());
       buffer.fillViewportRows();
       assert.equal(buffer.markers.length, 0);
       const marker = buffer.addMarker(0);
@@ -1088,7 +1100,7 @@ describe('Buffer', () => {
     });
     it('should call onDispose', () => {
       const eventStack: string[] = [];
-      buffer = new Buffer(true, new MockOptionsService({ scrollback: 0 }), bufferService, new MockLogService());
+      buffer = new TestBuffer(true, new MockOptionsService({ scrollback: 0 }), bufferService, new MockLogService());
       buffer.fillViewportRows();
       assert.equal(buffer.markers.length, 0);
       const marker = buffer.addMarker(0);
@@ -1104,7 +1116,7 @@ describe('Buffer', () => {
 
   describe ('translateBufferLineToString', () => {
     it('should handle selecting a section of ascii text', () => {
-      const line = new BufferLine(4);
+      const line = new BufferLine(TEST_STRING_CACHE, 4);
       line.setCell(0, createCellData(0, 'a', 1));
       line.setCell(1, createCellData(0, 'b', 1));
       line.setCell(2, createCellData(0, 'c', 1));
@@ -1116,7 +1128,7 @@ describe('Buffer', () => {
     });
 
     it('should handle a cut-off double width character by including it', () => {
-      const line = new BufferLine(3);
+      const line = new BufferLine(TEST_STRING_CACHE, 3);
       line.setCell(0, createCellData(0, '語', 2));
       line.setCell(1, createCellData(0, '', 0));
       line.setCell(2, createCellData(0, 'a', 1));
@@ -1127,7 +1139,7 @@ describe('Buffer', () => {
     });
 
     it('should handle a zero width character in the middle of the string by not including it', () => {
-      const line = new BufferLine(3);
+      const line = new BufferLine(TEST_STRING_CACHE, 3);
       line.setCell(0, createCellData(0, '語', 2));
       line.setCell(1, createCellData(0, '', 0));
       line.setCell(2, createCellData(0, 'a', 1));
@@ -1144,7 +1156,7 @@ describe('Buffer', () => {
     });
 
     it('should handle single width emojis', () => {
-      const line = new BufferLine(2);
+      const line = new BufferLine(TEST_STRING_CACHE, 2);
       line.setCell(0, createCellData(0, '😁', 1));
       line.setCell(1, createCellData(0, 'a', 1));
       buffer.lines.set(0, line);
@@ -1157,7 +1169,7 @@ describe('Buffer', () => {
     });
 
     it('should handle double width emojis', () => {
-      const line = new BufferLine(2);
+      const line = new BufferLine(TEST_STRING_CACHE, 2);
       line.setCell(0, createCellData(0, '😁', 2));
       line.setCell(1, createCellData(0, '', 0));
       buffer.lines.set(0, line);
@@ -1168,7 +1180,7 @@ describe('Buffer', () => {
       const str2 = buffer.translateBufferLineToString(0, true, 0, 2);
       assert.equal(str2, '😁');
 
-      const line2 = new BufferLine(3);
+      const line2 = new BufferLine(TEST_STRING_CACHE, 3);
       line2.setCell(0, createCellData(0, '😁', 2));
       line2.setCell(1, createCellData(0, '', 0));
       line2.setCell(2, createCellData(0, 'a', 1));
@@ -1179,6 +1191,99 @@ describe('Buffer', () => {
     });
   });
 
+  describe('line string cache cleanup', () => {
+    it('should clear shared cache entries with a single timer', () => {
+      const originalSetTimeout = globalThis.setTimeout;
+      const originalClearTimeout = globalThis.clearTimeout;
+      const originalDateNow = Date.now;
+      let timeoutId = 0;
+      let now = 0;
+      const clearedTimeouts: number[] = [];
+      const scheduledTimeouts = new Map<number, { delay: number, fire: () => void }>();
+      (globalThis as any).setTimeout = ((handler: (...args: any[]) => void, timeout?: number) => {
+        const id = ++timeoutId;
+        scheduledTimeouts.set(id, {
+          delay: timeout ?? 0,
+          fire: () => {
+            scheduledTimeouts.delete(id);
+            handler();
+          }
+        });
+        return id as ReturnType<typeof setTimeout>;
+      }) as typeof setTimeout;
+      (globalThis as any).clearTimeout = ((id: ReturnType<typeof setTimeout>) => {
+        const numericId = id as unknown as number;
+        clearedTimeouts.push(numericId);
+        scheduledTimeouts.delete(numericId);
+      }) as typeof clearTimeout;
+      Date.now = () => now;
+      try {
+        buffer.fillViewportRows();
+        buffer.lines.get(0)!.setCell(0, createCellData(0, 'a', 1));
+        buffer.lines.get(1)!.setCell(0, createCellData(0, 'b', 1));
+
+        assert.equal(buffer.translateBufferLineToString(0, false), `a${' '.repeat(INIT_COLS - 1)}`);
+        assert.equal(buffer.translateBufferLineToString(1, false), `b${' '.repeat(INIT_COLS - 1)}`);
+
+        const cache = buffer.getStringCache();
+        assert.equal(cache.entries.size, 2);
+        assert.ok(buffer.getStringCacheClearTimeout() !== undefined);
+        assert.equal(scheduledTimeouts.size, 1);
+        assert.equal([...scheduledTimeouts.values()][0].delay, 15000);
+        const initialTimerCreationCount = timeoutId;
+
+        now = 5000;
+        assert.equal(buffer.translateBufferLineToString(0, false), `a${' '.repeat(INIT_COLS - 1)}`);
+        assert.equal(timeoutId, initialTimerCreationCount);
+        assert.equal(scheduledTimeouts.size, 1);
+        assert.deepEqual(clearedTimeouts, []);
+
+        now = 15000;
+        [...scheduledTimeouts.values()][0].fire();
+        assert.equal(timeoutId, initialTimerCreationCount + 1);
+        assert.ok(buffer.getStringCacheClearTimeout() !== undefined);
+        assert.equal(scheduledTimeouts.size, 1);
+        assert.equal([...scheduledTimeouts.values()][0].delay, 5000);
+
+        now = 20000;
+        [...scheduledTimeouts.values()][0].fire();
+
+        assert.equal(cache.entries.size, 0);
+        assert.equal(buffer.getStringCacheClearTimeout(), undefined);
+
+        assert.equal(buffer.translateBufferLineToString(0, false), `a${' '.repeat(INIT_COLS - 1)}`);
+        assert.equal(cache.entries.size, 1);
+      } finally {
+        Date.now = originalDateNow;
+        globalThis.setTimeout = originalSetTimeout;
+        globalThis.clearTimeout = originalClearTimeout;
+      }
+    });
+
+    it('should reset line string cache state on clear and resize', () => {
+      buffer.fillViewportRows();
+      buffer.lines.get(0)!.setCell(0, createCellData(0, 'a', 1));
+      buffer.translateBufferLineToString(0, false);
+
+      const cache = buffer.getStringCache();
+      assert.equal(cache.entries.size, 1);
+      assert.ok(buffer.getStringCacheClearTimeout() !== undefined);
+
+      buffer.clear();
+      assert.equal(cache.entries.size, 0);
+      assert.equal(buffer.getStringCacheClearTimeout(), undefined);
+
+      buffer.fillViewportRows();
+      buffer.lines.get(0)!.setCell(0, createCellData(0, 'b', 1));
+      buffer.translateBufferLineToString(0, false);
+      assert.equal(cache.entries.size, 1);
+
+      buffer.resize(INIT_COLS - 1, INIT_ROWS);
+      assert.equal(cache.entries.size, 0);
+      assert.equal(buffer.getStringCacheClearTimeout(), undefined);
+    });
+  });
+
   describe('memory cleanup after shrinking', () => {
     it('should realign memory from idle task execution', async () => {
       buffer.fillViewportRows();
diff --git a/src/common/buffer/Buffer.ts b/src/common/buffer/Buffer.ts
index 8efefd60a4..34ef02f6a7 100644
--- a/src/common/buffer/Buffer.ts
+++ b/src/common/buffer/Buffer.ts
@@ -4,10 +4,12 @@
  */
 
 import { CircularList, IInsertEvent } from 'common/CircularList';
+import { Disposable, toDisposable } from 'common/Lifecycle';
 import { IdleTaskQueue } from 'common/TaskQueue';
 import { IAttributeData, IBufferLine, ICellData, ICharset } from 'common/Types';
 import { ExtendedAttrs } from 'common/buffer/AttributeData';
 import { BufferLine, DEFAULT_ATTR_DATA } from 'common/buffer/BufferLine';
+import { BufferLineStringCache } from 'common/buffer/BufferLineStringCache';
 import { getWrappedLineTrimmedLength, reflowLargerApplyNewLayout, reflowLargerCreateNewLayout, reflowLargerGetLinesToRemove, reflowSmallerGetNewLineLengths } from 'common/buffer/BufferReflow';
 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';
@@ -25,7 +27,7 @@ export const MAX_BUFFER_SIZE = 4294967295; // 2^32 - 1
  *   - cursor position
  *   - scroll position
  */
-export class Buffer implements IBuffer {
+export class Buffer extends Disposable implements IBuffer {
   public lines: CircularList<IBufferLine>;
   public ydisp: number = 0;
   public ybase: number = 0;
@@ -50,6 +52,7 @@ export class Buffer implements IBuffer {
   private _isClearing: boolean = false;
   private _memoryCleanupQueue: InstanceType<typeof IdleTaskQueue>;
   private _memoryCleanupPosition = 0;
+  private readonly _stringCache: BufferLineStringCache;
 
   constructor(
     private _hasScrollback: boolean,
@@ -57,6 +60,7 @@ export class Buffer implements IBuffer {
     private _bufferService: IBufferService,
     private readonly _logService: ILogService
   ) {
+    super();
     this._cols = this._bufferService.cols;
     this._rows = this._bufferService.rows;
     this.lines = new CircularList<IBufferLine>(this._getCorrectBufferLength(this._rows));
@@ -64,6 +68,9 @@ export class Buffer implements IBuffer {
     this.scrollBottom = this._rows - 1;
     this.setupTabStops();
     this._memoryCleanupQueue = new IdleTaskQueue(this._logService);
+    this._register(toDisposable(() => this._memoryCleanupQueue.clear()));
+    this._register(toDisposable(() => this.clearAllMarkers()));
+    this._stringCache = this._register(new BufferLineStringCache());
   }
 
   public getNullCell(attr?: IAttributeData): ICellData {
@@ -93,7 +100,7 @@ export class Buffer implements IBuffer {
   }
 
   public getBlankLine(attr: IAttributeData, isWrapped?: boolean): IBufferLine {
-    return new BufferLine(this._bufferService.cols, this.getNullCell(attr), isWrapped);
+    return new BufferLine(this._stringCache, this._bufferService.cols, this.getNullCell(attr), isWrapped);
   }
 
   public get hasScrollback(): boolean {
@@ -138,6 +145,7 @@ export class Buffer implements IBuffer {
    * Clears the buffer to it's initial state, discarding all previous data.
    */
   public clear(): void {
+    this._stringCache.clear();
     this.ydisp = 0;
     this.ybase = 0;
     this.y = 0;
@@ -156,6 +164,7 @@ 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);
+    this._stringCache.clear();
 
     // count bufferlines with overly big memory to be cleaned afterwards
     let dirtyMemoryLines = 0;
@@ -190,7 +199,7 @@ export class Buffer implements IBuffer {
             if (this._optionsService.rawOptions.windowsPty.backend !== undefined || this._optionsService.rawOptions.windowsPty.buildNumber !== undefined) {
               // Just add the new missing rows on Windows as conpty reprints the screen with it's
               // view of the world. Once a line enters scrollback for conpty it remains there
-              this.lines.push(new BufferLine(newCols, nullCell));
+              this.lines.push(new BufferLine(this._stringCache, newCols, nullCell, false));
             } else {
               if (this.ybase > 0 && this.lines.length <= this.ybase + this.y + addToY + 1) {
                 // There is room above the buffer and there are no empty elements below the line,
@@ -204,7 +213,7 @@ export class Buffer implements IBuffer {
               } else {
                 // Add a blank line if there is no buffer left at the top to scroll to, or if there
                 // are blank lines after the cursor
-                this.lines.push(new BufferLine(newCols, nullCell));
+                this.lines.push(new BufferLine(this._stringCache, newCols, nullCell, false));
               }
             }
           }
@@ -345,7 +354,7 @@ export class Buffer implements IBuffer {
         }
         if (this.lines.length < newRows) {
           // Add an extra row at the bottom of the viewport
-          this.lines.push(new BufferLine(newCols, nullCell));
+          this.lines.push(new BufferLine(this._stringCache, newCols, nullCell, false));
         }
       } else {
         if (this.ydisp === this.ybase) {
diff --git a/src/common/buffer/BufferLine.test.ts b/src/common/buffer/BufferLine.test.ts
index dce68ebbfe..3aec288723 100644
--- a/src/common/buffer/BufferLine.test.ts
+++ b/src/common/buffer/BufferLine.test.ts
@@ -4,18 +4,41 @@
  */
 import { NULL_CELL_CHAR, NULL_CELL_WIDTH, NULL_CELL_CODE, DEFAULT_ATTR, Content, UnderlineStyle, BgFlags, Attributes, FgFlags } from 'common/buffer/Constants';
 import { BufferLine } from 'common/buffer//BufferLine';
+import { BufferLineStringCache } from 'common/buffer/BufferLineStringCache';
 import { CellData } from 'common/buffer/CellData';
-import { CharData, IBufferLine } from '../Types';
+import { CharData, IBufferLine, ICellData } from '../Types';
 import { assert } from 'chai';
 import { AttributeData } from 'common/buffer/AttributeData';
 import { createCellData, NULL_CELL_DATA, extendedAttributes } from 'common/TestUtils.test';
 
+const TEST_STRING_CACHE = new BufferLineStringCache();
+
 
 class TestBufferLine extends BufferLine {
+  constructor(cols: number, fillCellData?: ICellData, isWrapped: boolean = false) {
+    super(TEST_STRING_CACHE, cols, fillCellData, isWrapped);
+  }
+
   public get combined(): {[index: number]: string} {
     return this._combined;
   }
 
+  public get cachedString(): string | undefined {
+    return this._getStringCacheEntry(false)?.value;
+  }
+
+  public set cachedString(value: string | undefined) {
+    this._getStringCacheEntry(true)!.value = value;
+  }
+
+  public get isCachedStringTrimmed(): boolean {
+    return this._getStringCacheEntry(false)?.isTrimmed ?? false;
+  }
+
+  public set isCachedStringTrimmed(value: boolean) {
+    this._getStringCacheEntry(true)!.isTrimmed = value;
+  }
+
   public toArray(): CharData[] {
     const result = [];
     for (let i = 0; i < this.length; ++i) {
@@ -807,5 +830,81 @@ describe('BufferLine', function(): void {
       assert.equal(extendedAttributes(line, 3), extendedAttributes(initial, 3));
       assert.equal(extendedAttributes(line, 4), extendedAttributes(initial, 4));
     });
+
+    it('should cache canonical string translations', () => {
+      const line = new TestBufferLine(5);
+      line.setCell(0, createCellData(1, 'a', 1));
+      line.setCell(1, createCellData(1, 'b', 1));
+      line.setCell(2, createCellData(1, 'c', 1));
+
+      // Trimmed-only canonical request should cache the trimmed value.
+      const trimmed = line.translateToString(true, undefined, undefined, undefined);
+      assert.equal(trimmed, 'abc');
+      assert.equal(line.cachedString, 'abc');
+      assert.equal(line.isCachedStringTrimmed, true);
+
+      // Non-trimmed canonical request should refresh cache with the full value.
+      const translated = line.translateToString(false, undefined, undefined, undefined);
+      assert.equal(translated, 'abc  ');
+      assert.equal(line.cachedString, 'abc  ');
+      assert.equal(line.isCachedStringTrimmed, false);
+
+      // Once non-trimmed is cached, trimmed should be derived via trimEnd().
+      assert.equal(line.translateToString(true, undefined, undefined, undefined), 'abc');
+      assert.equal(line.cachedString, 'abc  ');
+      assert.equal(line.isCachedStringTrimmed, false);
+
+      line.cachedString = 'cached-non-trimmed  ';
+      line.isCachedStringTrimmed = false;
+      assert.equal(line.translateToString(false, undefined, undefined, undefined), 'cached-non-trimmed  ');
+      assert.equal(line.translateToString(true, undefined, undefined, undefined), 'cached-non-trimmed');
+
+      line.cachedString = 'cached-trimmed';
+      line.isCachedStringTrimmed = true;
+      assert.equal(line.translateToString(true, undefined, undefined, undefined), 'cached-trimmed');
+      assert.equal(line.translateToString(false, undefined, undefined, undefined), 'abc  ');
+      assert.equal(line.cachedString, 'abc  ');
+      assert.equal(line.isCachedStringTrimmed, false);
+
+      // Any optional translation argument should bypass cache.
+      assert.equal(line.translateToString(false, 0, 2, undefined), 'ab');
+      assert.equal(line.translateToString(true, 0, 2, undefined), 'ab');
+    });
+
+    it('should invalidate cached canonical strings on line mutations', () => {
+      const assertCacheInvalidated = (mutate: (line: TestBufferLine) => void): void => {
+        const line = new TestBufferLine(5);
+        line.fill(createCellData(1, 'a', 1));
+        line.translateToString(true, undefined, undefined, undefined);
+        assert.equal(line.cachedString, 'aaaaa');
+        assert.equal(line.isCachedStringTrimmed, true);
+        line.translateToString(false, undefined, undefined, undefined);
+        assert.equal(line.cachedString, 'aaaaa');
+        assert.equal(line.isCachedStringTrimmed, false);
+        mutate(line);
+        assert.equal(line.cachedString, undefined);
+        assert.equal(line.isCachedStringTrimmed, false);
+      };
+
+      assertCacheInvalidated(line => line.set(0, [0, 'b', 1, 'b'.charCodeAt(0)]));
+      assertCacheInvalidated(line => line.setCell(0, createCellData(1, 'b', 1)));
+      assertCacheInvalidated(line => line.setCellFromCodepoint(0, 'b'.charCodeAt(0), 1, createCellData(1, 'b', 1)));
+      assertCacheInvalidated(line => line.addCodepointToCell(0, 0x301, 0));
+      assertCacheInvalidated(line => line.insertCells(1, 1, createCellData(1, 'b', 1)));
+      assertCacheInvalidated(line => line.deleteCells(1, 1, createCellData(1, 'b', 1)));
+      assertCacheInvalidated(line => line.replaceCells(1, 3, createCellData(1, 'b', 1)));
+      assertCacheInvalidated(line => line.resize(6, createCellData(1, 'b', 1)));
+      assertCacheInvalidated(line => line.fill(createCellData(1, 'b', 1)));
+      assertCacheInvalidated(line => {
+        const src = new TestBufferLine(5);
+        src.fill(createCellData(1, 'x', 1));
+        line.copyFrom(src);
+      });
+      assertCacheInvalidated(line => {
+        const src = new TestBufferLine(5);
+        src.fill(createCellData(1, 'x', 1));
+        line.copyCellsFrom(src, 0, 0, 2, false);
+      });
+    });
   });
 });
diff --git a/src/common/buffer/BufferLine.ts b/src/common/buffer/BufferLine.ts
index e415851a0a..be200f1127 100644
--- a/src/common/buffer/BufferLine.ts
+++ b/src/common/buffer/BufferLine.ts
@@ -9,25 +9,26 @@ import { CellData } from 'common/buffer/CellData';
 import { Attributes, BgFlags, CHAR_DATA_ATTR_INDEX, CHAR_DATA_CHAR_INDEX, CHAR_DATA_WIDTH_INDEX, Content, NULL_CELL_CHAR, NULL_CELL_CODE, NULL_CELL_WIDTH, WHITESPACE_CELL_CHAR } from 'common/buffer/Constants';
 import { stringFromCodePoint } from 'common/input/TextDecoder';
 
-/**
- * buffer memory layout:
- *
- *   |             uint32_t             |        uint32_t         |        uint32_t         |
- *   |             `content`            |          `FG`           |          `BG`           |
- *   | wcwidth(2) comb(1) codepoint(21) | flags(8) R(8) G(8) B(8) | flags(8) R(8) G(8) B(8) |
- */
-
-
-/** typed array slots taken by one cell */
-const CELL_SIZE = 3;
+// Buffer memory layout:
+//
+// [0]: content `uint32_t` - wcwidth(2) comb(1) codepoint(21)
+// [1]: fg      `uint32_t` - flags(8) r(8) g(8) b(8)
+// [2]: bg      `uint32_t` - flags(8) r(8) g(8) b(8)
+
+const enum Constants {
+  /** The number of 32 bit array indices taken by one cell. */
+  CELL_INDICIES = 3,
+  /** Factor when to cleanup underlying array buffer after shrinking. */
+  CLEANUP_THRESHOLD = 2
+}
 
 /**
  * Cell member indices.
  *
  * Direct access:
- *    `content = data[column * CELL_SIZE + Cell.CONTENT];`
- *    `fg = data[column * CELL_SIZE + Cell.FG];`
- *    `bg = data[column * CELL_SIZE + Cell.BG];`
+ *    `content = data[column * Constants.CELL_INDICIES + Cell.CONTENT];`
+ *    `fg = data[column * Constants.CELL_INDICIES + Cell.FG];`
+ *    `bg = data[column * Constants.CELL_INDICIES + Cell.BG];`
  */
 const enum Cell {
   CONTENT = 0,
@@ -41,8 +42,17 @@ export const DEFAULT_ATTR_DATA = Object.freeze(new AttributeData());
 let $startIndex = 0;
 const $workCell = new CellData();
 
-/** Factor when to cleanup underlying array buffer after shrinking. */
-const CLEANUP_THRESHOLD = 2;
+export interface IBufferLineStringCacheEntry {
+  value: string | undefined;
+  isTrimmed: boolean;
+  generation: number;
+}
+
+export interface IBufferLineStringCache {
+  generation: number;
+  allocateEntry(): IBufferLineStringCacheEntry;
+  touch?(): void;
+}
 
 /**
  * Typed array based bufferline implementation.
@@ -63,10 +73,16 @@ export class BufferLine implements IBufferLine {
   protected _data: Uint32Array;
   protected _combined: {[index: number]: string} = {};
   protected _extendedAttrs: {[index: number]: IExtendedAttrs | undefined} = {};
+  protected _stringCacheEntryRef: WeakRef<IBufferLineStringCacheEntry> | undefined;
   public length: number;
 
-  constructor(cols: number, fillCellData?: ICellData, public isWrapped: boolean = false) {
-    this._data = new Uint32Array(cols * CELL_SIZE);
+  constructor(
+    protected readonly _stringCache: IBufferLineStringCache,
+    cols: number,
+    fillCellData?: ICellData,
+    public isWrapped: boolean = false
+  ) {
+    this._data = new Uint32Array(cols * Constants.CELL_INDICIES);
     const cell = fillCellData ?? CellData.fromCharData([0, NULL_CELL_CHAR, NULL_CELL_WIDTH, NULL_CELL_CODE]);
     for (let i = 0; i < cols; ++i) {
       this.setCell(i, cell);
@@ -79,10 +95,10 @@ export class BufferLine implements IBufferLine {
    * @deprecated
    */
   public get(index: number): CharData {
-    const content = this._data[index * CELL_SIZE + Cell.CONTENT];
+    const content = this._data[index * Constants.CELL_INDICIES + Cell.CONTENT];
     const cp = content & Content.CODEPOINT_MASK;
     return [
-      this._data[index * CELL_SIZE + Cell.FG],
+      this._data[index * Constants.CELL_INDICIES + Cell.FG],
       (content & Content.IS_COMBINED_MASK)
         ? this._combined[index]
         : (cp) ? stringFromCodePoint(cp) : '',
@@ -98,12 +114,13 @@ export class BufferLine implements IBufferLine {
    * @deprecated
    */
   public set(index: number, value: CharData): void {
-    this._data[index * CELL_SIZE + Cell.FG] = value[CHAR_DATA_ATTR_INDEX];
+    this._invalidateStringCache();
+    this._data[index * Constants.CELL_INDICIES + Cell.FG] = value[CHAR_DATA_ATTR_INDEX];
     if (value[CHAR_DATA_CHAR_INDEX].length > 1) {
       this._combined[index] = value[1];
-      this._data[index * CELL_SIZE + Cell.CONTENT] = index | Content.IS_COMBINED_MASK | (value[CHAR_DATA_WIDTH_INDEX] << Content.WIDTH_SHIFT);
+      this._data[index * Constants.CELL_INDICIES + Cell.CONTENT] = index | Content.IS_COMBINED_MASK | (value[CHAR_DATA_WIDTH_INDEX] << Content.WIDTH_SHIFT);
     } else {
-      this._data[index * CELL_SIZE + Cell.CONTENT] = value[CHAR_DATA_CHAR_INDEX].charCodeAt(0) | (value[CHAR_DATA_WIDTH_INDEX] << Content.WIDTH_SHIFT);
+      this._data[index * Constants.CELL_INDICIES + Cell.CONTENT] = value[CHAR_DATA_CHAR_INDEX].charCodeAt(0) | (value[CHAR_DATA_WIDTH_INDEX] << Content.WIDTH_SHIFT);
     }
   }
 
@@ -112,22 +129,22 @@ export class BufferLine implements IBufferLine {
    * use these when only one value is needed, otherwise use `loadCell`
    */
   public getWidth(index: number): number {
-    return this._data[index * CELL_SIZE + Cell.CONTENT] >> Content.WIDTH_SHIFT;
+    return this._data[index * Constants.CELL_INDICIES + Cell.CONTENT] >> Content.WIDTH_SHIFT;
   }
 
   /** Test whether content has width. */
   public hasWidth(index: number): number {
-    return this._data[index * CELL_SIZE + Cell.CONTENT] & Content.WIDTH_MASK;
+    return this._data[index * Constants.CELL_INDICIES + Cell.CONTENT] & Content.WIDTH_MASK;
   }
 
   /** Get FG cell component. */
   public getFg(index: number): number {
-    return this._data[index * CELL_SIZE + Cell.FG];
+    return this._data[index * Constants.CELL_INDICIES + Cell.FG];
   }
 
   /** Get BG cell component. */
   public getBg(index: number): number {
-    return this._data[index * CELL_SIZE + Cell.BG];
+    return this._data[index * Constants.CELL_INDICIES + Cell.BG];
   }
 
   /**
@@ -136,7 +153,7 @@ export class BufferLine implements IBufferLine {
    * from real empty cells.
    */
   public hasContent(index: number): number {
-    return this._data[index * CELL_SIZE + Cell.CONTENT] & Content.HAS_CONTENT_MASK;
+    return this._data[index * Constants.CELL_INDICIES + Cell.CONTENT] & Content.HAS_CONTENT_MASK;
   }
 
   /**
@@ -145,7 +162,7 @@ export class BufferLine implements IBufferLine {
    * a single UTF32 codepoint or the last codepoint of a combined string.
    */
   public getCodePoint(index: number): number {
-    const content = this._data[index * CELL_SIZE + Cell.CONTENT];
+    const content = this._data[index * Constants.CELL_INDICIES + Cell.CONTENT];
     if (content & Content.IS_COMBINED_MASK) {
       return this._combined[index].charCodeAt(this._combined[index].length - 1);
     }
@@ -154,12 +171,12 @@ export class BufferLine implements IBufferLine {
 
   /** Test whether the cell contains a combined string. */
   public isCombined(index: number): number {
-    return this._data[index * CELL_SIZE + Cell.CONTENT] & Content.IS_COMBINED_MASK;
+    return this._data[index * Constants.CELL_INDICIES + Cell.CONTENT] & Content.IS_COMBINED_MASK;
   }
 
   /** Returns the string content of the cell. */
   public getString(index: number): string {
-    const content = this._data[index * CELL_SIZE + Cell.CONTENT];
+    const content = this._data[index * Constants.CELL_INDICIES + Cell.CONTENT];
     if (content & Content.IS_COMBINED_MASK) {
       return this._combined[index];
     }
@@ -172,7 +189,7 @@ export class BufferLine implements IBufferLine {
 
   /** Get state of protected flag. */
   public isProtected(index: number): number {
-    return this._data[index * CELL_SIZE + Cell.BG] & BgFlags.PROTECTED;
+    return this._data[index * Constants.CELL_INDICIES + Cell.BG] & BgFlags.PROTECTED;
   }
 
   /**
@@ -180,7 +197,7 @@ export class BufferLine implements IBufferLine {
    * to GC as it significantly reduced the amount of new objects/references needed.
    */
   public loadCell(index: number, cell: ICellData): ICellData {
-    $startIndex = index * CELL_SIZE;
+    $startIndex = index * Constants.CELL_INDICIES;
     cell.content = this._data[$startIndex + Cell.CONTENT];
     cell.fg = this._data[$startIndex + Cell.FG];
     cell.bg = this._data[$startIndex + Cell.BG];
@@ -197,15 +214,16 @@ export class BufferLine implements IBufferLine {
    * Set data at `index` to `cell`.
    */
   public setCell(index: number, cell: ICellData): void {
+    this._invalidateStringCache();
     if (cell.content & Content.IS_COMBINED_MASK) {
       this._combined[index] = cell.combinedData;
     }
     if (cell.bg & BgFlags.HAS_EXTENDED) {
       this._extendedAttrs[index] = cell.extended;
     }
-    this._data[index * CELL_SIZE + Cell.CONTENT] = cell.content;
-    this._data[index * CELL_SIZE + Cell.FG] = cell.fg;
-    this._data[index * CELL_SIZE + Cell.BG] = cell.bg;
+    this._data[index * Constants.CELL_INDICIES + Cell.CONTENT] = cell.content;
+    this._data[index * Constants.CELL_INDICIES + Cell.FG] = cell.fg;
+    this._data[index * Constants.CELL_INDICIES + Cell.BG] = cell.bg;
   }
 
   /**
@@ -214,12 +232,13 @@ export class BufferLine implements IBufferLine {
    * it gets an optimized access method.
    */
   public setCellFromCodepoint(index: number, codePoint: number, width: number, attrs: IAttributeData): void {
+    this._invalidateStringCache();
     if (attrs.bg & BgFlags.HAS_EXTENDED) {
       this._extendedAttrs[index] = attrs.extended;
     }
-    this._data[index * CELL_SIZE + Cell.CONTENT] = codePoint | (width << Content.WIDTH_SHIFT);
-    this._data[index * CELL_SIZE + Cell.FG] = attrs.fg;
-    this._data[index * CELL_SIZE + Cell.BG] = attrs.bg;
+    this._data[index * Constants.CELL_INDICIES + Cell.CONTENT] = codePoint | (width << Content.WIDTH_SHIFT);
+    this._data[index * Constants.CELL_INDICIES + Cell.FG] = attrs.fg;
+    this._data[index * Constants.CELL_INDICIES + Cell.BG] = attrs.bg;
   }
 
   /**
@@ -229,7 +248,8 @@ export class BufferLine implements IBufferLine {
    * by the previous `setDataFromCodePoint` call, we can omit it here.
    */
   public addCodepointToCell(index: number, codePoint: number, width: number): void {
-    let content = this._data[index * CELL_SIZE + Cell.CONTENT];
+    this._invalidateStringCache();
+    let content = this._data[index * Constants.CELL_INDICIES + Cell.CONTENT];
     if (content & Content.IS_COMBINED_MASK) {
       // we already have a combined string, simply add
       this._combined[index] += stringFromCodePoint(codePoint);
@@ -251,10 +271,11 @@ export class BufferLine implements IBufferLine {
       content &= ~Content.WIDTH_MASK;
       content |= width << Content.WIDTH_SHIFT;
     }
-    this._data[index * CELL_SIZE + Cell.CONTENT] = content;
+    this._data[index * Constants.CELL_INDICIES + Cell.CONTENT] = content;
   }
 
   public insertCells(pos: number, n: number, fillCellData: ICellData): void {
+    this._invalidateStringCache();
     pos %= this.length;
 
     // handle fullwidth at pos: reset cell one to the left if pos is second cell of a wide char
@@ -282,6 +303,7 @@ export class BufferLine implements IBufferLine {
   }
 
   public deleteCells(pos: number, n: number, fillCellData: ICellData): void {
+    this._invalidateStringCache();
     pos %= this.length;
     if (n < this.length - pos) {
       for (let i = 0; i < this.length - pos - n; ++i) {
@@ -308,6 +330,7 @@ export class BufferLine implements IBufferLine {
   }
 
   public replaceCells(start: number, end: number, fillCellData: ICellData, respectProtect: boolean = false): void {
+    this._invalidateStringCache();
     // full branching on respectProtect==true, hopefully getting fast JIT for standard case
     if (respectProtect) {
       if (start && this.getWidth(start - 1) === 2 && !this.isProtected(start - 1)) {
@@ -344,13 +367,14 @@ export class BufferLine implements IBufferLine {
    * The underlying array buffer will not change if there is still enough space
    * to hold the new buffer line data.
    * Returns a boolean indicating, whether a `cleanupMemory` call would free
-   * excess memory (true after shrinking > CLEANUP_THRESHOLD).
+   * excess memory (true after shrinking > Constants.CLEANUP_THRESHOLD).
    */
   public resize(cols: number, fillCellData: ICellData): boolean {
+    this._invalidateStringCache();
     if (cols === this.length) {
-      return this._data.length * 4 * CLEANUP_THRESHOLD < this._data.buffer.byteLength;
+      return this._data.length * 4 * Constants.CLEANUP_THRESHOLD < this._data.buffer.byteLength;
     }
-    const uint32Cells = cols * CELL_SIZE;
+    const uint32Cells = cols * Constants.CELL_INDICIES;
     if (cols > this.length) {
       if (this._data.buffer.byteLength >= uint32Cells * 4) {
         // optimization: avoid alloc and data copy if buffer has enough room
@@ -385,17 +409,17 @@ export class BufferLine implements IBufferLine {
       }
     }
     this.length = cols;
-    return uint32Cells * 4 * CLEANUP_THRESHOLD < this._data.buffer.byteLength;
+    return uint32Cells * 4 * Constants.CLEANUP_THRESHOLD < this._data.buffer.byteLength;
   }
 
   /**
    * Cleanup underlying array buffer.
    * A cleanup will be triggered if the array buffer exceeds the actual used
-   * memory by a factor of CLEANUP_THRESHOLD.
+   * memory by a factor of Constants.CLEANUP_THRESHOLD.
    * Returns 0 or 1 indicating whether a cleanup happened.
    */
   public cleanupMemory(): number {
-    if (this._data.length * 4 * CLEANUP_THRESHOLD < this._data.buffer.byteLength) {
+    if (this._data.length * 4 * Constants.CLEANUP_THRESHOLD < this._data.buffer.byteLength) {
       const data = new Uint32Array(this._data.length);
       data.set(this._data);
       this._data = data;
@@ -406,6 +430,7 @@ export class BufferLine implements IBufferLine {
 
   /** fill a line with fillCharData */
   public fill(fillCellData: ICellData, respectProtect: boolean = false): void {
+    this._invalidateStringCache();
     // full branching on respectProtect==true, hopefully getting fast JIT for standard case
     if (respectProtect) {
       for (let i = 0; i < this.length; ++i) {
@@ -424,6 +449,7 @@ export class BufferLine implements IBufferLine {
 
   /** alter to a full copy of line  */
   public copyFrom(line: BufferLine): void {
+    this._invalidateStringCache();
     if (this.length !== line.length) {
       this._data = new Uint32Array(line._data);
     } else {
@@ -444,7 +470,7 @@ export class BufferLine implements IBufferLine {
 
   /** create a new clone */
   public clone(): IBufferLine {
-    const newLine = new BufferLine(0);
+    const newLine = new BufferLine(this._stringCache, 0, undefined, false);
     newLine._data = new Uint32Array(this._data);
     newLine.length = this.length;
     for (const el in this._combined) {
@@ -459,8 +485,8 @@ export class BufferLine implements IBufferLine {
 
   public getTrimmedLength(): number {
     for (let i = this.length - 1; i >= 0; --i) {
-      if ((this._data[i * CELL_SIZE + Cell.CONTENT] & Content.HAS_CONTENT_MASK)) {
-        return i + (this._data[i * CELL_SIZE + Cell.CONTENT] >> Content.WIDTH_SHIFT);
+      if ((this._data[i * Constants.CELL_INDICIES + Cell.CONTENT] & Content.HAS_CONTENT_MASK)) {
+        return i + (this._data[i * Constants.CELL_INDICIES + Cell.CONTENT] >> Content.WIDTH_SHIFT);
       }
     }
     return 0;
@@ -468,30 +494,31 @@ export class BufferLine implements IBufferLine {
 
   public getNoBgTrimmedLength(): number {
     for (let i = this.length - 1; i >= 0; --i) {
-      if ((this._data[i * CELL_SIZE + Cell.CONTENT] & Content.HAS_CONTENT_MASK) || (this._data[i * CELL_SIZE + Cell.BG] & Attributes.CM_MASK)) {
-        return i + (this._data[i * CELL_SIZE + Cell.CONTENT] >> Content.WIDTH_SHIFT);
+      if ((this._data[i * Constants.CELL_INDICIES + Cell.CONTENT] & Content.HAS_CONTENT_MASK) || (this._data[i * Constants.CELL_INDICIES + Cell.BG] & Attributes.CM_MASK)) {
+        return i + (this._data[i * Constants.CELL_INDICIES + Cell.CONTENT] >> Content.WIDTH_SHIFT);
       }
     }
     return 0;
   }
 
   public copyCellsFrom(src: BufferLine, srcCol: number, destCol: number, length: number, applyInReverse: boolean): void {
+    this._invalidateStringCache();
     const srcData = src._data;
     if (applyInReverse) {
       for (let cell = length - 1; cell >= 0; cell--) {
-        for (let i = 0; i < CELL_SIZE; i++) {
-          this._data[(destCol + cell) * CELL_SIZE + i] = srcData[(srcCol + cell) * CELL_SIZE + i];
+        for (let i = 0; i < Constants.CELL_INDICIES; i++) {
+          this._data[(destCol + cell) * Constants.CELL_INDICIES + i] = srcData[(srcCol + cell) * Constants.CELL_INDICIES + i];
         }
-        if (srcData[(srcCol + cell) * CELL_SIZE + Cell.BG] & BgFlags.HAS_EXTENDED) {
+        if (srcData[(srcCol + cell) * Constants.CELL_INDICIES + Cell.BG] & BgFlags.HAS_EXTENDED) {
           this._extendedAttrs[destCol + cell] = src._extendedAttrs[srcCol + cell];
         }
       }
     } else {
       for (let cell = 0; cell < length; cell++) {
-        for (let i = 0; i < CELL_SIZE; i++) {
-          this._data[(destCol + cell) * CELL_SIZE + i] = srcData[(srcCol + cell) * CELL_SIZE + i];
+        for (let i = 0; i < Constants.CELL_INDICIES; i++) {
+          this._data[(destCol + cell) * Constants.CELL_INDICIES + i] = srcData[(srcCol + cell) * Constants.CELL_INDICIES + i];
         }
-        if (srcData[(srcCol + cell) * CELL_SIZE + Cell.BG] & BgFlags.HAS_EXTENDED) {
+        if (srcData[(srcCol + cell) * Constants.CELL_INDICIES + Cell.BG] & BgFlags.HAS_EXTENDED) {
           this._extendedAttrs[destCol + cell] = src._extendedAttrs[srcCol + cell];
         }
       }
@@ -508,7 +535,8 @@ export class BufferLine implements IBufferLine {
   }
 
   /**
-   * Translates the buffer line to a string.
+   * Translates the buffer line to a string. Caching only applies to canonical full-line translation
+   * requests (regardless of `trimRight` value).
    *
    * @param trimRight Whether to trim any empty cells on the right.
    * @param startCol The column to start the string (0-based inclusive).
@@ -521,6 +549,19 @@ export class BufferLine implements IBufferLine {
    * returned string, the corresponding entries in `outColumns` will have the same column number.
    */
   public translateToString(trimRight?: boolean, startCol?: number, endCol?: number, outColumns?: number[]): string {
+    const isCanonicalRequest = (startCol === undefined || startCol === 0) && endCol === undefined && outColumns === undefined;
+    if (isCanonicalRequest) {
+      this._stringCache.touch?.();
+    }
+    const stringCacheEntry = isCanonicalRequest ? this._getStringCacheEntry(false) : undefined;
+    if (isCanonicalRequest && stringCacheEntry?.value !== undefined) {
+      if (trimRight) {
+        return stringCacheEntry.isTrimmed ? stringCacheEntry.value : stringCacheEntry.value.trimEnd();
+      }
+      if (!stringCacheEntry.isTrimmed) {
+        return stringCacheEntry.value;
+      }
+    }
     startCol = startCol ?? 0;
     endCol = endCol ?? this.length;
     if (trimRight) {
@@ -531,7 +572,7 @@ export class BufferLine implements IBufferLine {
     }
     let result = '';
     while (startCol < endCol) {
-      const content = this._data[startCol * CELL_SIZE + Cell.CONTENT];
+      const content = this._data[startCol * Constants.CELL_INDICIES + Cell.CONTENT];
       const cp = content & Content.CODEPOINT_MASK;
       const chars = (content & Content.IS_COMBINED_MASK) ? this._combined[startCol] : (cp) ? stringFromCodePoint(cp) : WHITESPACE_CELL_CHAR;
       result += chars;
@@ -545,6 +586,34 @@ export class BufferLine implements IBufferLine {
     if (outColumns) {
       outColumns.push(startCol);
     }
+    if (isCanonicalRequest) {
+      const cacheEntry = this._getStringCacheEntry(true)!;
+      cacheEntry.value = result;
+      cacheEntry.isTrimmed = !!trimRight;
+    }
     return result;
   }
+
+  protected _getStringCacheEntry(createIfNeeded: boolean): IBufferLineStringCacheEntry | undefined {
+    const cachedEntry = this._stringCacheEntryRef?.deref();
+    if (cachedEntry) {
+      if (cachedEntry.generation === this._stringCache.generation) {
+        return cachedEntry;
+      }
+    }
+    if (!createIfNeeded) {
+      return undefined;
+    }
+    const cacheEntry = this._stringCache.allocateEntry();
+    this._stringCacheEntryRef = new WeakRef(cacheEntry);
+    return cacheEntry;
+  }
+
+  private _invalidateStringCache(): void {
+    const cacheEntry = this._getStringCacheEntry(false);
+    if (cacheEntry) {
+      cacheEntry.value = undefined;
+      cacheEntry.isTrimmed = false;
+    }
+  }
 }
diff --git a/src/common/buffer/BufferLineStringCache.ts b/src/common/buffer/BufferLineStringCache.ts
new file mode 100644
index 0000000000..b365eef707
--- /dev/null
+++ b/src/common/buffer/BufferLineStringCache.ts
@@ -0,0 +1,69 @@
+/**
+ * Copyright (c) 2026 The xterm.js authors. All rights reserved.
+ * @license MIT
+ */
+
+import type { IBufferLineStringCache, IBufferLineStringCacheEntry } from 'common/buffer/BufferLine';
+import { disposableTimeout } from 'common/Async';
+import { Disposable, MutableDisposable, toDisposable, type IDisposable } from 'common/Lifecycle';
+
+const enum Constants {
+  CACHE_TTL_MS = 15000
+}
+
+export class BufferLineStringCache extends Disposable implements IBufferLineStringCache {
+  public generation: number = 0;
+  public readonly entries: Set<IBufferLineStringCacheEntry> = new Set();
+  private readonly _clearTimeout = this._register(new MutableDisposable<IDisposable>());
+  private _lastAccessTimestamp: number = 0;
+
+  constructor() {
+    super();
+    this._register(toDisposable(() => this.entries.clear()));
+  }
+
+  public touch(): void {
+    this._scheduleClear();
+  }
+
+  public allocateEntry(): IBufferLineStringCacheEntry {
+    const entry: IBufferLineStringCacheEntry = {
+      value: undefined,
+      isTrimmed: false,
+      generation: this.generation
+    };
+    this.entries.add(entry);
+    this._scheduleClear();
+    return entry;
+  }
+
+  public clear(): void {
+    this._clearTimeout.clear();
+    this._lastAccessTimestamp = 0;
+    this.generation++;
+    for (const entry of this.entries) {
+      entry.value = undefined;
+      entry.isTrimmed = false;
+    }
+    this.entries.clear();
+  }
+
+  private _scheduleClear(): void {
+    this._lastAccessTimestamp = Date.now();
+    if (this._clearTimeout.value) {
+      return;
+    }
+    this._scheduleClearTimeout(Constants.CACHE_TTL_MS);
+  }
+
+  private _scheduleClearTimeout(timeoutMs: number): void {
+    this._clearTimeout.value = disposableTimeout(() => {
+      const elapsed = Date.now() - this._lastAccessTimestamp;
+      if (elapsed >= Constants.CACHE_TTL_MS) {
+        this.clear();
+        return;
+      }
+      this._scheduleClearTimeout(Constants.CACHE_TTL_MS - elapsed);
+    }, timeoutMs);
+  }
+}
diff --git a/src/common/buffer/BufferReflow.test.ts b/src/common/buffer/BufferReflow.test.ts
index b351b89c42..d71186ddda 100644
--- a/src/common/buffer/BufferReflow.test.ts
+++ b/src/common/buffer/BufferReflow.test.ts
@@ -4,13 +4,16 @@
  */
 import { assert } from 'chai';
 import { BufferLine } from 'common/buffer/BufferLine';
+import { BufferLineStringCache } from 'common/buffer/BufferLineStringCache';
 import { NULL_CELL_CHAR, NULL_CELL_WIDTH, NULL_CELL_CODE } from 'common/buffer/Constants';
 import { reflowSmallerGetNewLineLengths } from 'common/buffer/BufferReflow';
 
+const TEST_STRING_CACHE = new BufferLineStringCache();
+
 describe('BufferReflow', () => {
   describe('reflowSmallerGetNewLineLengths', () => {
     it('should return correct line lengths for a small line with wide characters', () => {
-      const line = new BufferLine(4);
+      const line = new BufferLine(TEST_STRING_CACHE, 4);
       line.set(0, [0, '汉', 2, '汉'.charCodeAt(0)]);
       line.set(1, [0, '', 0, 0]);
       line.set(2, [0, '语', 2, '语'.charCodeAt(0)]);
@@ -20,7 +23,7 @@ describe('BufferReflow', () => {
       assert.deepEqual(reflowSmallerGetNewLineLengths([line], 4, 2), [2, 2], 'line: 汉, 语');
     });
     it('should return correct line lengths for a large line with wide characters', () => {
-      const line = new BufferLine(12);
+      const line = new BufferLine(TEST_STRING_CACHE, 12);
       for (let i = 0; i < 12; i += 4) {
         line.set(i, [0, '汉', 2, '汉'.charCodeAt(0)]);
         line.set(i + 2, [0, '语', 2, '语'.charCodeAt(0)]);
@@ -42,7 +45,7 @@ describe('BufferReflow', () => {
       assert.deepEqual(reflowSmallerGetNewLineLengths([line], 12, 2), [2, 2, 2, 2, 2, 2], 'line: 汉, 语, 汉, 语, 汉, 语');
     });
     it('should return correct line lengths for a string with wide and single characters', () => {
-      const line = new BufferLine(6);
+      const line = new BufferLine(TEST_STRING_CACHE, 6);
       line.set(0, [0, 'a', 1, 'a'.charCodeAt(0)]);
       line.set(1, [0, '汉', 2, '汉'.charCodeAt(0)]);
       line.set(2, [0, '', 0, 0]);
@@ -56,14 +59,14 @@ describe('BufferReflow', () => {
       assert.deepEqual(reflowSmallerGetNewLineLengths([line], 6, 2), [1, 2, 2, 1], 'line: a, 汉, 语, b');
     });
     it('should return correct line lengths for a wrapped line with wide and single characters', () => {
-      const line1 = new BufferLine(6);
+      const line1 = new BufferLine(TEST_STRING_CACHE, 6);
       line1.set(0, [0, 'a', 1, 'a'.charCodeAt(0)]);
       line1.set(1, [0, '汉', 2, '汉'.charCodeAt(0)]);
       line1.set(2, [0, '', 0, 0]);
       line1.set(3, [0, '语', 2, '语'.charCodeAt(0)]);
       line1.set(4, [0, '', 0, 0]);
       line1.set(5, [0, 'b', 1, 'b'.charCodeAt(0)]);
-      const line2 = new BufferLine(6, undefined, true);
+      const line2 = new BufferLine(TEST_STRING_CACHE, 6, undefined, true);
       line2.set(0, [0, 'a', 1, 'a'.charCodeAt(0)]);
       line2.set(1, [0, '汉', 2, '汉'.charCodeAt(0)]);
       line2.set(2, [0, '', 0, 0]);
@@ -78,7 +81,7 @@ describe('BufferReflow', () => {
       assert.deepEqual(reflowSmallerGetNewLineLengths([line1, line2], 6, 2), [1, 2, 2, 2, 2, 2, 1], 'lines: a, 汉, 语, ba, 汉, 语, b');
     });
     it('should work on lines ending in null space', () => {
-      const line = new BufferLine(5);
+      const line = new BufferLine(TEST_STRING_CACHE, 5);
       line.set(0, [0, '汉', 2, '汉'.charCodeAt(0)]);
       line.set(1, [0, '', 0, 0]);
       line.set(2, [0, '语', 2, '语'.charCodeAt(0)]);
diff --git a/src/common/buffer/BufferSet.test.ts b/src/common/buffer/BufferSet.test.ts
index 96737fee9f..8809a3cb66 100644
--- a/src/common/buffer/BufferSet.test.ts
+++ b/src/common/buffer/BufferSet.test.ts
@@ -6,7 +6,7 @@
 import { assert } from 'chai';
 import { BufferSet } from 'common/buffer/BufferSet';
 import { Buffer } from 'common/buffer/Buffer';
-import { MockOptionsService, MockBufferService, MockLogService } from 'common/TestUtils.test';
+import { MockOptionsService, MockBufferService, MockLogService, createCellData } from 'common/TestUtils.test';
 
 describe('BufferSet', () => {
   let bufferSet: BufferSet;
@@ -82,4 +82,45 @@ describe('BufferSet', () => {
       assert.equal(bufferSet.alt.markers.length, 0);
     });
   });
+
+  describe('lifecycle', () => {
+    it('should dispose previous buffers on reset', () => {
+      const oldNormal = bufferSet.normal as any;
+      oldNormal.lines.get(0)!.setCell(0, createCellData(0, 'a', 1));
+      oldNormal.translateBufferLineToString(0, false);
+
+      const oldCache = oldNormal._stringCache;
+      assert.equal(oldCache.entries.size, 1);
+      assert.notEqual(oldCache._clearTimeout.value, undefined);
+
+      bufferSet.reset();
+
+      assert.notEqual(bufferSet.normal, oldNormal);
+      assert.equal(oldCache.entries.size, 0);
+      assert.equal(oldCache._clearTimeout.value, undefined);
+    });
+
+    it('should dispose both buffers when disposed', () => {
+      const normal = bufferSet.normal as any;
+      normal.lines.get(0)!.setCell(0, createCellData(0, 'a', 1));
+      normal.translateBufferLineToString(0, false);
+
+      bufferSet.activateAltBuffer();
+      const alt = bufferSet.alt as any;
+      alt.lines.get(0)!.setCell(0, createCellData(0, 'b', 1));
+      alt.translateBufferLineToString(0, false);
+
+      const normalCache = normal._stringCache;
+      const altCache = alt._stringCache;
+      assert.notEqual(normalCache._clearTimeout.value, undefined);
+      assert.notEqual(altCache._clearTimeout.value, undefined);
+
+      bufferSet.dispose();
+
+      assert.equal(normalCache.entries.size, 0);
+      assert.equal(altCache.entries.size, 0);
+      assert.equal(normalCache._clearTimeout.value, undefined);
+      assert.equal(altCache._clearTimeout.value, undefined);
+    });
+  });
 });
diff --git a/src/common/buffer/BufferSet.ts b/src/common/buffer/BufferSet.ts
index 772a764424..32a4bf3b44 100644
--- a/src/common/buffer/BufferSet.ts
+++ b/src/common/buffer/BufferSet.ts
@@ -3,7 +3,7 @@
  * @license MIT
  */
 
-import { Disposable } from 'common/Lifecycle';
+import { Disposable, MutableDisposable } from 'common/Lifecycle';
 import { IAttributeData } from 'common/Types';
 import { Buffer } from 'common/buffer/Buffer';
 import { IBuffer, IBufferSet } from 'common/buffer/Types';
@@ -18,6 +18,8 @@ export class BufferSet extends Disposable implements IBufferSet {
   private _normal!: Buffer;
   private _alt!: Buffer;
   private _activeBuffer!: Buffer;
+  private readonly _normalBuffer = this._register(new MutableDisposable<Buffer>());
+  private readonly _altBuffer = this._register(new MutableDisposable<Buffer>());
 
   private readonly _onBufferActivate = this._register(new Emitter<{ activeBuffer: IBuffer, inactiveBuffer: IBuffer }>());
   public readonly onBufferActivate = this._onBufferActivate.event;
@@ -38,11 +40,13 @@ export class BufferSet extends Disposable implements IBufferSet {
 
   public reset(): void {
     this._normal = new Buffer(true, this._optionsService, this._bufferService, this._logService);
+    this._normalBuffer.value = this._normal;
     this._normal.fillViewportRows();
 
     // The alt buffer should never have scrollback.
     // See http://invisible-island.net/xterm/ctlseqs/ctlseqs.html#h2-The-Alternate-Screen-Buffer
     this._alt = new Buffer(false, this._optionsService, this._bufferService, this._logService);
+    this._altBuffer.value = this._alt;
     this._activeBuffer = this._normal;
     this._onBufferActivate.fire({
       activeBuffer: this._normal,
diff --git a/src/common/input/WriteBuffer.ts b/src/common/input/WriteBuffer.ts
index c9db076d65..b936c9dbf7 100644
--- a/src/common/input/WriteBuffer.ts
+++ b/src/common/input/WriteBuffer.ts
@@ -9,30 +9,30 @@ import { Emitter } from 'common/Event';
 
 declare const setTimeout: (handler: () => void, timeout?: number) => void;
 
-/**
- * Safety watermark to avoid memory exhaustion and browser engine crash on fast data input.
- * Enable flow control to avoid this limit and make sure that your backend correctly
- * propagates this to the underlying pty. (see docs for further instructions)
- * Since this limit is meant as a safety parachute to prevent browser crashs,
- * it is set to a very high number. Typically xterm.js gets unresponsive with
- * a 100 times lower number (>500 kB).
- */
-const DISCARD_WATERMARK = 50000000; // ~50 MB
-
-/**
- * The max number of ms to spend on writes before allowing the renderer to
- * catch up with a 0ms setTimeout. A value of < 33 to keep us close to
- * 30fps, and a value of < 16 to try to run at 60fps. Of course, the real FPS
- * depends on the time it takes for the renderer to draw the frame.
- */
-const WRITE_TIMEOUT_MS = 12;
-
-/**
- * Threshold of max held chunks in the write buffer, that were already processed.
- * This is a tradeoff between extensive write buffer shifts (bad runtime) and high
- * memory consumption by data thats not used anymore.
- */
-const WRITE_BUFFER_LENGTH_THRESHOLD = 50;
+const enum Constants {
+  /**
+   * Safety watermark to avoid memory exhaustion and browser engine crash on fast data input.
+   * Enable flow control to avoid this limit and make sure that your backend correctly
+   * propagates this to the underlying pty. (see docs for further instructions)
+   * Since this limit is meant as a safety parachute to prevent browser crashs,
+   * it is set to a very high number. Typically xterm.js gets unresponsive with
+   * a 100 times lower number (>500 kB).
+   */
+  DISCARD_WATERMARK = 50000000, // ~50 MB
+  /**
+   * The max number of ms to spend on writes before allowing the renderer to
+   * catch up with a 0ms setTimeout. A value of < 33 to keep us close to
+   * 30fps, and a value of < 16 to try to run at 60fps. Of course, the real FPS
+   * depends on the time it takes for the renderer to draw the frame.
+   */
+  WRITE_TIMEOUT_MS = 12,
+  /**
+   * Threshold of max held chunks in the write buffer, that were already processed.
+   * This is a tradeoff between extensive write buffer shifts (bad runtime) and high
+   * memory consumption by data thats not used anymore.
+   */
+  WRITE_BUFFER_LENGTH_THRESHOLD = 50
+}
 
 export class WriteBuffer extends Disposable {
   private _writeBuffer: (string | Uint8Array)[] = [];
@@ -133,7 +133,7 @@ export class WriteBuffer extends Disposable {
   }
 
   public write(data: string | Uint8Array, callback?: () => void): void {
-    if (this._pendingData > DISCARD_WATERMARK) {
+    if (this._pendingData > Constants.DISCARD_WATERMARK) {
       throw new Error('write data discarded, use flow control to avoid losing data');
     }
 
@@ -169,7 +169,7 @@ export class WriteBuffer extends Disposable {
    * effectively lowering the redrawing needs, schematically:
    *
    *   macroTask _innerWrite:
-   *     if (performance.now() - (lastTime | 0) < WRITE_TIMEOUT_MS):
+   *     if (performance.now() - (lastTime | 0) < Constants.WRITE_TIMEOUT_MS):
    *        schedule microTask _innerWrite(lastTime)
    *     else:
    *        schedule macroTask _innerWrite(0)
@@ -218,7 +218,7 @@ export class WriteBuffer extends Disposable {
          * responsibility to slice hard work), but we can at least schedule a screen update as we
          * gain control.
          */
-        const continuation: (r: boolean) => void = (r: boolean) => performance.now() - startTime >= WRITE_TIMEOUT_MS
+        const continuation: (r: boolean) => void = (r: boolean) => performance.now() - startTime >= Constants.WRITE_TIMEOUT_MS
           ? setTimeout(() => this._innerWrite(0, r))
           : this._innerWrite(startTime, r);
 
@@ -235,7 +235,7 @@ export class WriteBuffer extends Disposable {
          * current microtask queue (executed before setTimeout).
          */
         // const continuation: (r: boolean) => void = performance.now() - startTime >=
-        //     WRITE_TIMEOUT_MS
+        //     Constants.WRITE_TIMEOUT_MS
         //   ? r => setTimeout(() => this._innerWrite(0, r))
         //   : r => this._innerWrite(startTime, r);
 
@@ -255,14 +255,14 @@ export class WriteBuffer extends Disposable {
       this._bufferOffset++;
       this._pendingData -= data.length;
 
-      if (performance.now() - startTime >= WRITE_TIMEOUT_MS) {
+      if (performance.now() - startTime >= Constants.WRITE_TIMEOUT_MS) {
         break;
       }
     }
     if (this._writeBuffer.length > this._bufferOffset) {
       // Allow renderer to catch up before processing the next batch
       // trim already processed chunks if we are above threshold
-      if (this._bufferOffset > WRITE_BUFFER_LENGTH_THRESHOLD) {
+      if (this._bufferOffset > Constants.WRITE_BUFFER_LENGTH_THRESHOLD) {
         this._writeBuffer = this._writeBuffer.slice(this._bufferOffset);
         this._callbacks = this._callbacks.slice(this._bufferOffset);
         this._bufferOffset = 0;
diff --git a/src/common/parser/Params.ts b/src/common/parser/Params.ts
index 31872a0b24..8a77c78a4b 100644
--- a/src/common/parser/Params.ts
+++ b/src/common/parser/Params.ts
@@ -4,10 +4,16 @@
  */
 import { IParams, ParamsArray } from 'common/parser/Types';
 
-// max value supported for a single param/subparam (clamped to positive int32 range)
-const MAX_VALUE = 0x7FFFFFFF;
-// max allowed subparams for a single sequence (hardcoded limitation)
-const MAX_SUBPARAMS = 256;
+const enum Constants {
+  /**
+   * Max value supported for a single param/subparam (clamped to positive int32 range)
+   */
+  MAX_VALUE = 0x7FFFFFFF,
+  /**
+   * Max allowed subparams for a single sequence (hardcoded limitation)
+   */
+  MAX_SUBPARAMS = 256
+}
 
 /**
  * Params storage class.
@@ -70,7 +76,7 @@ export class Params implements IParams {
    * @param maxSubParamsLength max length of storable sub parameters
    */
   constructor(public maxLength: number = 32, public maxSubParamsLength: number = 32) {
-    if (maxSubParamsLength > MAX_SUBPARAMS) {
+    if (maxSubParamsLength > Constants.MAX_SUBPARAMS) {
       throw new Error('maxSubParamsLength must not be greater than 256');
     }
     this.params = new Int32Array(maxLength);
@@ -159,7 +165,7 @@ export class Params implements IParams {
       throw new Error('values lesser than -1 are not allowed');
     }
     this._subParamsIdx[this.length] = this._subParamsLength << 8 | this._subParamsLength;
-    this.params[this.length++] = value > MAX_VALUE ? MAX_VALUE : value;
+    this.params[this.length++] = value > Constants.MAX_VALUE ? Constants.MAX_VALUE : value;
   }
 
   /**
@@ -181,7 +187,7 @@ export class Params implements IParams {
     if (value < -1) {
       throw new Error('values lesser than -1 are not allowed');
     }
-    this._subParams[this._subParamsLength++] = value > MAX_VALUE ? MAX_VALUE : value;
+    this._subParams[this._subParamsLength++] = value > Constants.MAX_VALUE ? Constants.MAX_VALUE : value;
     this._subParamsIdx[this.length - 1]++;
   }
 
@@ -237,6 +243,6 @@ export class Params implements IParams {
 
     const store = this._digitIsSub ? this._subParams : this.params;
     const cur = store[length - 1];
-    store[length - 1] = ~cur ? Math.min(cur * 10 + value, MAX_VALUE) : value;
+    store[length - 1] = ~cur ? Math.min(cur * 10 + value, Constants.MAX_VALUE) : value;
   }
 }
diff --git a/src/common/services/BufferService.ts b/src/common/services/BufferService.ts
index 6a7ce2b343..06ac6b10a2 100644
--- a/src/common/services/BufferService.ts
+++ b/src/common/services/BufferService.ts
@@ -10,8 +10,10 @@ import { IBuffer, IBufferSet } from 'common/buffer/Types';
 import { IBufferService, ILogService, IOptionsService, type IBufferResizeEvent } from 'common/services/Services';
 import { Emitter } from 'common/Event';
 
-export const MINIMUM_COLS = 2; // Less than 2 can mess with wide chars
-export const MINIMUM_ROWS = 1;
+export const enum BufferServiceConstants {
+  MINIMUM_COLS = 2, // Less than 2 can mess with wide chars
+  MINIMUM_ROWS = 1
+}
 
 export class BufferService extends Disposable implements IBufferService {
   public serviceBrand: any;
@@ -37,8 +39,8 @@ export class BufferService extends Disposable implements IBufferService {
     @ILogService logService: ILogService
   ) {
     super();
-    this.cols = Math.max(optionsService.rawOptions.cols || 0, MINIMUM_COLS);
-    this.rows = Math.max(optionsService.rawOptions.rows || 0, MINIMUM_ROWS);
+    this.cols = Math.max(optionsService.rawOptions.cols || 0, BufferServiceConstants.MINIMUM_COLS);
+    this.rows = Math.max(optionsService.rawOptions.rows || 0, BufferServiceConstants.MINIMUM_ROWS);
     this.buffers = this._register(new BufferSet(optionsService, this, logService));
     this._register(this.buffers.onBufferActivate(e => {
       this._onScroll.fire(e.activeBuffer.ydisp);
diff --git a/src/common/services/ServiceRegistry.ts b/src/common/services/ServiceRegistry.ts
index 7d887bc612..af51d16412 100644
--- a/src/common/services/ServiceRegistry.ts
+++ b/src/common/services/ServiceRegistry.ts
@@ -11,13 +11,15 @@
 
 import { IServiceIdentifier } from 'common/services/Services';
 
-const DI_TARGET = 'di$target';
-const DI_DEPENDENCIES = 'di$dependencies';
+const enum Constants {
+  DI_TARGET = 'di$target',
+  DI_DEPENDENCIES = 'di$dependencies'
+}
 
 export const serviceRegistry: Map<string, IServiceIdentifier<any>> = new Map();
 
 export function getServiceDependencies(ctor: any): { id: IServiceIdentifier<any>, index: number, optional: boolean }[] {
-  return ctor[DI_DEPENDENCIES] || [];
+  return ctor[Constants.DI_DEPENDENCIES] || [];
 }
 
 export function createDecorator<T>(id: string): IServiceIdentifier<T> {
@@ -40,10 +42,10 @@ export function createDecorator<T>(id: string): IServiceIdentifier<T> {
 }
 
 function storeServiceDependency(id: Function, target: Function, index: number): void {
-  if ((target as any)[DI_TARGET] === target) {
-    (target as any)[DI_DEPENDENCIES].push({ id, index });
+  if ((target as any)[Constants.DI_TARGET] === target) {
+    (target as any)[Constants.DI_DEPENDENCIES].push({ id, index });
   } else {
-    (target as any)[DI_DEPENDENCIES] = [{ id, index }];
-    (target as any)[DI_TARGET] = target;
+    (target as any)[Constants.DI_DEPENDENCIES] = [{ id, index }];
+    (target as any)[Constants.DI_TARGET] = target;
   }
 }
diff --git a/src/common/tsconfig.json b/src/common/tsconfig.json
index 22501b9cfe..31a893756d 100644
--- a/src/common/tsconfig.json
+++ b/src/common/tsconfig.json
@@ -3,7 +3,9 @@
   "compilerOptions": {
     "lib": [
       "es2015",
-      "es2016.Array.Include"
+      "es2016.Array.Include",
+      "es2019.string",
+      "es2021.weakref"
     ],
     "outDir": "../../out",
     "types": [
diff --git a/src/headless/tsconfig.json b/src/headless/tsconfig.json
index 6ae7b1dc94..0c445bcfc8 100644
--- a/src/headless/tsconfig.json
+++ b/src/headless/tsconfig.json
@@ -3,7 +3,8 @@
   "compilerOptions": {
     "lib": [
       "es2015",
-      "es2016.Array.Include"
+      "es2016.Array.Include",
+      "es2021.weakref"
     ],
     "outDir": "../../out",
     "types": [