diff --git a/src/Terminal.ts b/src/Terminal.ts
index 54ae3322..f519ae58 100644
--- a/src/Terminal.ts
+++ b/src/Terminal.ts
@@ -23,7 +23,7 @@
 
 import { IInputHandlingTerminal, IViewport, ICompositionHelper, ITerminalOptions, ITerminal, IBrowser, ILinkifier, ILinkMatcherOptions, CustomKeyEventHandler, LinkMatcherHandler, IMouseZoneManager } from './Types';
 import { IRenderer, CharacterJoinerHandler } from 'browser/renderer/Types';
-import { CompositionHelper } from './CompositionHelper';
+import { CompositionHelper } from 'browser/input/CompositionHelper';
 import { Viewport } from './Viewport';
 import { rightClickHandler, moveTextAreaUnderMouseCursor, pasteHandler, copyHandler } from './Clipboard';
 import { C0 } from 'common/data/EscapeSequences';
@@ -581,7 +581,7 @@ export class Terminal extends Disposable implements ITerminal, IDisposable, IInp
 
     this._compositionView = document.createElement('div');
     this._compositionView.classList.add('composition-view');
-    this._compositionHelper = new CompositionHelper(this.textarea, this._compositionView, this, this._charSizeService, this._coreService);
+    this._compositionHelper = new CompositionHelper(this.textarea, this._compositionView, this._bufferService, this.optionsService, this._charSizeService, this._coreService);
     this._helperContainer.appendChild(this._compositionView);
 
     // Performance: Add viewport and helper elements from the fragment
diff --git a/src/CompositionHelper.test.ts b/src/browser/input/CompositionHelper.test.ts
similarity index 94%
rename from src/CompositionHelper.test.ts
rename to src/browser/input/CompositionHelper.test.ts
index 64207fa0..b9a4f668 100644
--- a/src/CompositionHelper.test.ts
+++ b/src/browser/input/CompositionHelper.test.ts
@@ -4,13 +4,11 @@
  */
 
 import { assert } from 'chai';
-import { CompositionHelper } from './CompositionHelper';
-import { ITerminal } from './Types';
+import { CompositionHelper } from 'browser/input/CompositionHelper';
 import { MockCharSizeService } from 'browser/TestUtils.test';
-import { MockCoreService } from '../out/common/TestUtils.test';
+import { MockCoreService, MockBufferService, MockOptionsService } from 'common/TestUtils.test';
 
 describe('CompositionHelper', () => {
-  let terminal: ITerminal;
   let compositionHelper: CompositionHelper;
   let compositionView: HTMLElement;
   let textarea: HTMLTextAreaElement;
@@ -38,25 +36,13 @@ describe('CompositionHelper', () => {
         top: 0
       }
     } as any;
-    terminal = {
-      element: {
-        querySelector: () => {
-          return { offsetLeft: 0, offsetTop: 0 };
-        }
-      },
-      buffer: {
-        isCursorInViewport: true
-      },
-      options: {
-        lineHeight: 1
-      }
-    } as any;
     const coreService = new MockCoreService();
     coreService.triggerDataEvent = (text: string) => {
       handledText += text;
     };
     handledText = '';
-    compositionHelper = new CompositionHelper(textarea, compositionView, terminal, new MockCharSizeService(10, 10), coreService);
+    const bufferService = new MockBufferService(10, 5);
+    compositionHelper = new CompositionHelper(textarea, compositionView, bufferService, new MockOptionsService(), new MockCharSizeService(10, 10), coreService);
   });
 
   describe('Input', () => {
diff --git a/src/CompositionHelper.ts b/src/browser/input/CompositionHelper.ts
similarity index 90%
rename from src/CompositionHelper.ts
rename to src/browser/input/CompositionHelper.ts
index 010585f8..a8c8bb14 100644
--- a/src/CompositionHelper.ts
+++ b/src/browser/input/CompositionHelper.ts
@@ -3,9 +3,8 @@
  * @license MIT
  */
 
-import { ITerminal } from './Types';
 import { ICharSizeService } from 'browser/services/Services';
-import { ICoreService } from 'common/services/Services';
+import { IBufferService, ICoreService, IOptionsService } from 'common/services/Services';
 
 interface IPosition {
   start: number;
@@ -35,22 +34,17 @@ export class CompositionHelper {
    */
   private _isSendingComposition: boolean;
 
-  /**
-   * Creates a new CompositionHelper.
-   * @param _textarea The textarea that xterm uses for input.
-   * @param _compositionView The element to display the in-progress composition in.
-   * @param _terminal The Terminal to forward the finished composition to.
-   */
   constructor(
     private readonly _textarea: HTMLTextAreaElement,
     private readonly _compositionView: HTMLElement,
-    private readonly _terminal: ITerminal,
+    private readonly _bufferService: IBufferService,
+    private readonly _optionsService: IOptionsService,
     private readonly _charSizeService: ICharSizeService,
     private readonly _coreService: ICoreService
   ) {
     this._isComposing = false;
     this._isSendingComposition = false;
-    this._compositionPosition = { start: null, end: null };
+    this._compositionPosition = { start: 0, end: 0 };
   }
 
   /**
@@ -198,17 +192,17 @@ export class CompositionHelper {
       return;
     }
 
-    if (this._terminal.buffer.isCursorInViewport) {
-      const cellHeight = Math.ceil(this._charSizeService.height * this._terminal.options.lineHeight);
-      const cursorTop = this._terminal.buffer.y * cellHeight;
-      const cursorLeft = this._terminal.buffer.x * this._charSizeService.width;
+    if (this._bufferService.buffer.isCursorInViewport) {
+      const cellHeight = Math.ceil(this._charSizeService.height * this._optionsService.options.lineHeight);
+      const cursorTop = this._bufferService.buffer.y * cellHeight;
+      const cursorLeft = this._bufferService.buffer.x * this._charSizeService.width;
 
       this._compositionView.style.left = cursorLeft + 'px';
       this._compositionView.style.top = cursorTop + 'px';
       this._compositionView.style.height = cellHeight + 'px';
       this._compositionView.style.lineHeight = cellHeight + 'px';
-      this._compositionView.style.fontFamily = this._terminal.options.fontFamily;
-      this._compositionView.style.fontSize = this._terminal.options.fontSize + 'px';
+      this._compositionView.style.fontFamily = this._optionsService.options.fontFamily;
+      this._compositionView.style.fontSize = this._optionsService.options.fontSize + 'px';
       // Sync the textarea to the exact position of the composition view so the IME knows where the
       // text is.
       const compositionViewBounds = this._compositionView.getBoundingClientRect();
diff --git a/src/browser/services/SelectionService.test.ts b/src/browser/services/SelectionService.test.ts
index fc9cafdd..b00fa29f 100644
--- a/src/browser/services/SelectionService.test.ts
+++ b/src/browser/services/SelectionService.test.ts
@@ -13,7 +13,7 @@ import { IBufferService, IOptionsService } from 'common/services/Services';
 import { MockCharSizeService, MockMouseService } from 'browser/TestUtils.test';
 import { CellData } from 'common/buffer/CellData';
 import { IBuffer } from 'common/buffer/Types';
-import { isWindows } from '../../../out/common/Platform';
+import { isWindows } from 'common/Platform';
 
 class TestSelectionService extends SelectionService {
   constructor(