diff --git a/addons/addon-search/src/SearchEngine.ts b/addons/addon-search/src/SearchEngine.ts
index 7e89c03a17..1760bc2bd1 100644
--- a/addons/addon-search/src/SearchEngine.ts
+++ b/addons/addon-search/src/SearchEngine.ts
@@ -60,7 +60,7 @@ export class SearchEngine {
       this._terminal.clearSelection();
       return undefined;
     }
-    if (startCol > this._terminal.cols) {
+    if (startCol >= this._terminal.cols) {
       throw new Error(`Invalid col: ${startCol} to search in terminal of ${this._terminal.cols} cols`);
     }
 
diff --git a/addons/addon-web-links/src/WebLinkProvider.ts b/addons/addon-web-links/src/WebLinkProvider.ts
index 0a826eb3a0..5df5d268a2 100644
--- a/addons/addon-web-links/src/WebLinkProvider.ts
+++ b/addons/addon-web-links/src/WebLinkProvider.ts
@@ -57,7 +57,8 @@ function isUrl(urlString: string): boolean {
 
 export class LinkComputer {
   public static computeLink(y: number, regex: RegExp, terminal: Terminal, activate: (event: MouseEvent, uri: string) => void): ILink[] {
-    const rex = new RegExp(regex.source, (regex.flags || '') + 'g');
+    const flags = regex.flags.includes('g') ? regex.flags : `${regex.flags}g`;
+    const rex = new RegExp(regex.source, flags);
 
     const [lines, startLineIndex] = LinkComputer._getWindowedLineStrings(y - 1, terminal);
     const line = lines.join('');
diff --git a/addons/addon-webgl/src/TextureAtlas.ts b/addons/addon-webgl/src/TextureAtlas.ts
index 53d2d056f4..9d42ca9e1b 100644
--- a/addons/addon-webgl/src/TextureAtlas.ts
+++ b/addons/addon-webgl/src/TextureAtlas.ts
@@ -191,7 +191,7 @@ export class TextureAtlas implements ITextureAtlas {
         return newPage;
       }
 
-      const sortedMergingPagesIndexes = mergingPages.map(e => e.glyphs[0].texturePage).sort((a, b) => a > b ? 1 : -1);
+      const sortedMergingPagesIndexes = mergingPages.map(e => e.glyphs[0].texturePage).sort((a, b) => a - b);
       const mergedPageIndex = this.pages.length - mergingPages.length;
 
       // Merge into the new page
diff --git a/bin/esbuild_all.mjs b/bin/esbuild_all.mjs
index 1a3aadea56..789cb5df00 100644
--- a/bin/esbuild_all.mjs
+++ b/bin/esbuild_all.mjs
@@ -19,14 +19,17 @@ for (const addon of addons) {
 // Demo job - This requires the others to be built so it's not included when building all
 // jobs.push(createJob('demo-client', [`--demo-client`]));
 
-await Promise.all(jobs.map((job, i) => {
+const codes = await Promise.all(jobs.map(job => {
   return new Promise(r => {
     job.cp.on('exit', code => {
       log(`Finished \x1b[32m${job.name}\x1b[0m${code ? ' \x1b[31mwith errors\x1b[0m' : ''}`);
-      r(code);
+      r(code ?? 1);
     });
   });
 }));
+if (codes.some(code => code !== 0)) {
+  process.exit(1);
+}
 
 /**
  * @param {string} message
diff --git a/bin/setup-full.mjs b/bin/setup-full.mjs
index 2db85d87a6..35a62cbd7a 100644
--- a/bin/setup-full.mjs
+++ b/bin/setup-full.mjs
@@ -5,7 +5,7 @@ import { spawnSync } from 'node:child_process';
 import { basename, dirname, resolve, sep } from 'node:path';
 import { fileURLToPath } from 'node:url';
 
-const repoRoot = resolve(dirname(fileURLToPath(import.meta.url)), '../..');
+const repoRoot = resolve(dirname(fileURLToPath(import.meta.url)), '..');
 const nodeModulesPath = resolve(repoRoot, 'node_modules');
 const npmExecutable = process.platform === 'win32' ? 'npm.cmd' : 'npm';
 
@@ -13,7 +13,7 @@ const npmExecutable = process.platform === 'win32' ? 'npm.cmd' : 'npm';
 
 /** @param {string} message */
 function log(message) {
-  console.info(`[setup-fast] ${message}`);
+  console.info(`[setup-full] ${message}`);
 }
 
 /** @param {string[]} args */
diff --git a/bin/test_integration.js b/bin/test_integration.js
index 37e6aca7c5..0a2531e23b 100644
--- a/bin/test_integration.js
+++ b/bin/test_integration.js
@@ -12,7 +12,7 @@ let argv = process.argv.slice(2);
 let suiteFilter = undefined;
 while (argv.some(e => e.startsWith('--suite='))) {
   const i = argv.findIndex(e => e.startsWith('--suite='));
-  const match = argv[i].match(/--suite=(?<suitename>.+)/)
+  const match = argv[i].match(/--suite=(?<suitename>.+)/);
   suiteFilter = match?.groups?.suitename ?? undefined;
   argv.splice(i, 1);
 }
@@ -42,12 +42,18 @@ if (suiteFilter) {
   configs = configs.filter(e => e.name === suiteFilter);
 }
 
+if (suiteFilter && configs.length === 0) {
+  console.error(`Unknown suite: ${suiteFilter}`);
+  process.exit(1);
+}
+
 function npmBinScript(script) {
   return path.resolve(__dirname, `../node_modules/.bin/` + (process.platform === 'win32' ?
     `${script}.cmd` : script));
 }
 
 async function run() {
+  let exitCode = 0;
   for (const config of configs) {
     const command = npmBinScript('playwright');
     const args = ['test', '-c', config.path, ...argv];
@@ -62,10 +68,13 @@ async function run() {
 
     if (run.error) {
       console.error(run.error);
-      process.exit(run.status ?? -1);
+      process.exit(run.status ?? 1);
     }
 
-    process.exit(run.status);
+    if (run.status) {
+      exitCode = run.status;
+    }
   }
+  process.exit(exitCode);
 }
 run();
diff --git a/bin/test_mousemodes.js b/bin/test_mousemodes.js
index 0f12d208b9..8954c1d777 100644
--- a/bin/test_mousemodes.js
+++ b/bin/test_mousemodes.js
@@ -177,7 +177,7 @@ const ENC = {
 }
 
 function printMenu() {
-  console.log('\x1b[2J\x1b\[HTest mouse reports [Ctrl-C to exit]');
+  console.log('\x1b[2J\x1b[HTest mouse reports [Ctrl-C to exit]');
   console.log();
   console.log('  Selected protocol [Ctrl-A to switch]');
   const protocols = Object.keys(PROTOCOLS);
diff --git a/bin/test_unit.js b/bin/test_unit.js
index 58fdd9a321..2ff7f62507 100644
--- a/bin/test_unit.js
+++ b/bin/test_unit.js
@@ -21,7 +21,7 @@ if (process.argv.length > 2) {
   flagArgs = args.filter(e => e.startsWith('--'));
   // ability to inject particular test files via
   // npm run test [testFileA testFileB ...]
-  files = args.filter(e => !e.startsWith('--'));
+  const files = args.filter(e => !e.startsWith('--'));
   if (files.length) {
     testFiles = files;
   }
@@ -39,8 +39,6 @@ if (checkCoverage) {
     ...testFiles,
     ...flagArgs
   ];
-  console.info('executable', executable);
-  console.info('args', args);
   const run = cp.spawnSync(
     executable,
     args,
@@ -51,7 +49,7 @@ if (checkCoverage) {
       stdio: 'inherit'
     }
   );
-  process.exit(run.status);
+  process.exit(run.status ?? -1);
 }
 
 const run = cp.spawnSync(
diff --git a/package.json b/package.json
index 43e569d028..d3da864b6a 100644
--- a/package.json
+++ b/package.json
@@ -61,9 +61,9 @@
     "test-integration-firefox": "node ./bin/test_integration.js --workers=75% \"--project=FirefoxStable\"",
     "test-integration-webkit": "node ./bin/test_integration.js --workers=75% \"--project=WebKit\"",
     "test-integration-debug": "node ./bin/test_integration.js  --workers=1 --headed --timeout=30000",
-    "benchmark": "xterm-benchmark -r 5 -c test/benchmark/benchmark.json",
-    "benchmark-baseline": "xterm-benchmark -r 5 -c test/benchmark/benchmark.json --baseline out-test/benchmark/*benchmark.js",
-    "benchmark-eval": "xterm-benchmark -r 5 -c test/benchmark/benchmark.json --eval out-test/benchmark/*benchmark.js",
+    "benchmark": "NODE_PATH=./out xterm-benchmark -r 5 -c test/benchmark/benchmark.json",
+    "benchmark-baseline": "NODE_PATH=./out xterm-benchmark -r 5 -c test/benchmark/benchmark.json --baseline out-test/benchmark/*benchmark.js",
+    "benchmark-eval": "NODE_PATH=./out xterm-benchmark -r 5 -c test/benchmark/benchmark.json --eval out-test/benchmark/*benchmark.js",
     "clean": "rm -rf lib out addons/*/lib addons/*/out",
     "vtfeatures": "node bin/extract_vtfeatures.js src/*/*.ts src/*/*/*.ts src/*.ts addons/**/src/*.ts",
     "prepackage": "npm run build",
diff --git a/src/common/buffer/BufferLine.ts b/src/common/buffer/BufferLine.ts
index 4b6f6e8bbf..30b4ed3bb6 100644
--- a/src/common/buffer/BufferLine.ts
+++ b/src/common/buffer/BufferLine.ts
@@ -73,7 +73,9 @@ export interface IBufferLineStringCache {
  */
 export class BufferLine implements IBufferLine {
   protected _data: Uint32Array;
+  /** Sparse cache; only read when `IS_COMBINED_MASK` is set in `_data`. */
   protected _combined: {[index: number]: string} = {};
+  /** Sparse cache; only read when `HAS_EXTENDED` is set in `_data`. */
   protected _extendedAttrs: {[index: number]: IExtendedAttrs | undefined} = {};
   protected _stringCacheEntryRef: WeakRef<IBufferLineStringCacheEntry> | undefined;
   public length: number;
@@ -205,9 +207,15 @@ export class BufferLine implements IBufferLine {
     cell.bg = this._data[$startIndex + Cell.BG];
     if (cell.content & Content.IS_COMBINED_MASK) {
       cell.combinedData = this._combined[index];
+    } else {
+      cell.combinedData = '';
     }
     if (cell.bg & BgFlags.HAS_EXTENDED) {
       cell.extended = this._extendedAttrs[index]!;
+    } else {
+      // Do not mutate cell.extended in place: it may still reference this line's map entry from a
+      // prior loadCell into a reused CellData (e.g. $workCell during insert/delete).
+      cell.extended = DEFAULT_ATTR_DATA.extended.clone();
     }
     return cell;
   }
@@ -459,14 +467,7 @@ export class BufferLine implements IBufferLine {
       this._data.set(line._data);
     }
     this.length = line.length;
-    this._combined = {};
-    for (const el in line._combined) {
-      this._combined[el] = line._combined[el];
-    }
-    this._extendedAttrs = {};
-    for (const el in line._extendedAttrs) {
-      this._extendedAttrs[el] = line._extendedAttrs[el];
-    }
+    this._copySparseMapsFrom(line);
     this.isWrapped = line.isWrapped;
   }
 
@@ -475,12 +476,7 @@ export class BufferLine implements IBufferLine {
     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) {
-      newLine._combined[el] = this._combined[el];
-    }
-    for (const el in this._extendedAttrs) {
-      newLine._extendedAttrs[el] = this._extendedAttrs[el];
-    }
+    newLine._copySparseMapsFrom(this);
     newLine.isWrapped = this.isWrapped;
     return newLine;
   }
@@ -511,27 +507,14 @@ export class BufferLine implements IBufferLine {
         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) * Constants.CELL_INDICIES + Cell.BG] & BgFlags.HAS_EXTENDED) {
-          this._extendedAttrs[destCol + cell] = src._extendedAttrs[srcCol + cell];
-        }
+        this._copyCellMapsFrom(src, srcCol + cell, destCol + cell);
       }
     } else {
       for (let cell = 0; cell < length; cell++) {
         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) * Constants.CELL_INDICIES + Cell.BG] & BgFlags.HAS_EXTENDED) {
-          this._extendedAttrs[destCol + cell] = src._extendedAttrs[srcCol + cell];
-        }
-      }
-    }
-
-    // Move any combined data over as needed, FIXME: repeat for extended attrs
-    const srcCombinedKeys = Object.keys(src._combined);
-    for (let i = 0; i < srcCombinedKeys.length; i++) {
-      const key = parseInt(srcCombinedKeys[i], 10);
-      if (key >= srcCol) {
-        this._combined[key - srcCol + destCol] = src._combined[key];
+        this._copyCellMapsFrom(src, srcCol + cell, destCol + cell);
       }
     }
   }
@@ -620,4 +603,24 @@ export class BufferLine implements IBufferLine {
       cacheEntry.isTrimmed = false;
     }
   }
+
+  /** Copy sparse map entries for a single cell when `_data` flags require them. */
+  private _copyCellMapsFrom(src: BufferLine, srcCol: number, destCol: number): void {
+    const srcStart = srcCol * Constants.CELL_INDICIES;
+    if (src._data[srcStart + Cell.CONTENT] & Content.IS_COMBINED_MASK) {
+      this._combined[destCol] = src._combined[srcCol];
+    }
+    if (src._data[srcStart + Cell.BG] & BgFlags.HAS_EXTENDED) {
+      this._extendedAttrs[destCol] = src._extendedAttrs[srcCol];
+    }
+  }
+
+  /** Rebuild sparse maps from another line, keyed only by `_data` flags. */
+  private _copySparseMapsFrom(line: BufferLine): void {
+    this._combined = {};
+    this._extendedAttrs = {};
+    for (let i = 0; i < line.length; i++) {
+      this._copyCellMapsFrom(line, i, i);
+    }
+  }
 }
diff --git a/test/benchmark/DecorationService.benchmark.ts b/test/benchmark/DecorationService.benchmark.ts
index 534a1fa30e..1a2033de1b 100644
--- a/test/benchmark/DecorationService.benchmark.ts
+++ b/test/benchmark/DecorationService.benchmark.ts
@@ -4,8 +4,8 @@
  */
 
 import { perfContext, before, RuntimeCase } from 'xterm-benchmark';
-import { DecorationService } from '../../src/common/services/DecorationService';
-import { MockLogService, MockBufferService, MockOptionsService } from '../../src/common/TestUtils.test';
+import { DecorationService } from 'common/services/DecorationService';
+import { MockLogService, MockBufferService, MockOptionsService } from 'common/TestUtils.test';
 const enum Constants {
   COLS = 80,
   ROWS = 30,
diff --git a/test/benchmark/EscapeSequenceParser.benchmark.ts b/test/benchmark/EscapeSequenceParser.benchmark.ts
index c2cecfdbbb..5c9f372fb5 100644
--- a/test/benchmark/EscapeSequenceParser.benchmark.ts
+++ b/test/benchmark/EscapeSequenceParser.benchmark.ts
@@ -4,12 +4,12 @@
  */
 import { perfContext, before, beforeEach, ThroughputRuntimeCase } from 'xterm-benchmark';
 
-import { EscapeSequenceParser } from '../../src/common/parser/EscapeSequenceParser';
-import { C0, C1 } from '../../src/common/data/EscapeSequences';
-import { IDcsHandler, IOscHandler, IApcHandler, IParams } from '../../src/common/parser/Types';
-import { OscHandler } from '../../src/common/parser/OscParser';
-import { DcsHandler } from '../../src/common/parser/DcsParser';
-import { ApcHandler } from '../../src/common/parser/ApcParser';
+import { EscapeSequenceParser } from 'common/parser/EscapeSequenceParser';
+import { C0, C1 } from 'common/data/EscapeSequences';
+import { IDcsHandler, IOscHandler, IApcHandler, IParams } from 'common/parser/Types';
+import { OscHandler } from 'common/parser/OscParser';
+import { DcsHandler } from 'common/parser/DcsParser';
+import { ApcHandler } from 'common/parser/ApcParser';
 
 const SIZE = 5000000;
 
diff --git a/test/benchmark/Event.benchmark.ts b/test/benchmark/Event.benchmark.ts
index ba3f8de9ce..9cd8216dc1 100644
--- a/test/benchmark/Event.benchmark.ts
+++ b/test/benchmark/Event.benchmark.ts
@@ -4,7 +4,7 @@
  */
 
 import { perfContext, before, RuntimeCase } from 'xterm-benchmark';
-import { Emitter } from '../../src/common/Event';
+import { Emitter } from 'common/Event';
 
 const ITERATIONS = 1_000_000;
 
diff --git a/test/benchmark/Terminal.benchmark.ts b/test/benchmark/Terminal.benchmark.ts
index 97579cb30a..fb06b429e3 100644
--- a/test/benchmark/Terminal.benchmark.ts
+++ b/test/benchmark/Terminal.benchmark.ts
@@ -6,8 +6,8 @@
 import { perfContext, before, ThroughputRuntimeCase } from 'xterm-benchmark';
 
 import { spawn } from 'node-pty';
-import { Utf8ToUtf32, stringFromCodePoint } from '../../src/common/input/TextDecoder';
-import { CoreBrowserTerminal } from '../../src/browser/CoreBrowserTerminal';
+import { Utf8ToUtf32, stringFromCodePoint } from 'common/input/TextDecoder';
+import { CoreBrowserTerminal } from 'browser/CoreBrowserTerminal';
 
 perfContext('Terminal: ls -lR /usr/lib', () => {
   let content = '';
diff --git a/test/benchmark/tsconfig.json b/test/benchmark/tsconfig.json
index fe2af282c2..c8e17ee617 100644
--- a/test/benchmark/tsconfig.json
+++ b/test/benchmark/tsconfig.json
@@ -11,7 +11,11 @@
     "moduleResolution": "nodenext",
     "strict": false,
     "target": "es2021",
-    "module": "nodenext"
+    "module": "nodenext",
+    "paths": {
+      "common/*": ["../../src/common/*"],
+      "browser/*": ["../../src/browser/*"]
+    }
   },
   "include": [
     "./**/*",