Adopt string-width for terminal width calculations

.claude/CLAUDE.md

@@ -72,8 +72,8 @@ Only update the `Status` field — do not modify any other frontmatter or prompt
 
 <!-- BEGIN:REPO:current-state -->
 ## Current State
-Branch: `main`
-In-progress: Nothing. PR #136 (fix #133, sticky zone ANSI width math) open, auto-merge enabled.
+Branch: `refactor/adopt-string-width`
+In-progress: Nothing. PR #139 (refactor #137, adopt string-width) open, auto-merge enabled.
 <!-- END:REPO:current-state -->
 
 <!-- BEGIN:REPO:architecture -->

.claude/sessions/2026-03-28.md

@@ -7,3 +7,11 @@
 - Decisions: Bundled leftover staged session-end files from the March 27 release session into the code commit since they had not been committed. CI and CodeQL checks in progress; auto-merge will complete when checks pass.
 - Next: Await PR #136 auto-merge.
 - Violations: None
+
+### 21:30 - refactor/adopt-string-width (#137) Stage 2
+
+- Did: Staged and committed string-width adoption changes, pushed branch, created PR #139 with Closes #137, auto-merge enabled.
+- Files: `package.json`, `pnpm-lock.yaml`, `src/StatusLineBuilder.ts`, `src/ansi.ts` (deleted), `src/renderer.ts`, `src/terminal.ts`
+- Decisions: Label `enhancement` chosen as adoption of a library is an improvement, not a pure bug fix.
+- Next: Await PR #139 auto-merge.
+- Violations: None

package.json

@@ -44,6 +44,7 @@
     "@js-joda/core": "^5.7.0",
     "@shellicar/mcp-exec": "1.0.0-preview.6",
     "sharp": "^0.34.5",
+    "string-width": "^8.2.0",
     "zod": "^4.3.6"
   },
   "packageManager": "pnpm@10.33.0+sha512.10568bb4a6afb58c9eb3630da90cc9516417abebd3fabbe6739f0ae795728da1491e9db5a544c76ad8eb7570f5c4bb3d6c637b2cb41bfdcdb47fa823c8649319",

src/StatusLineBuilder.ts

@@ -1,18 +1,17 @@
+import stringWidth from 'string-width';
+
 export class StatusLineBuilder {
   public output = '';
-  public visibleLength = 0;
 
-  /** Append text that is visible on screen (counts toward line width). */
+  /** Append text that is visible on screen. */
   public text(s: string): this {
     this.output += s;
-    this.visibleLength += s.length;
     return this;
   }
 
-  /** Append an emoji (2 terminal columns wide). */
+  /** Append an emoji. */
   public emoji(s: string): this {
     this.output += s;
-    this.visibleLength += 2;
     return this;
   }
 
@@ -23,6 +22,6 @@ export class StatusLineBuilder {
   }
 
   public screenLines(columns: number): number {
-    return Math.max(1, Math.ceil(this.visibleLength / columns));
+    return Math.max(1, Math.ceil(stringWidth(this.output) / columns));
   }
 }

src/renderer.ts

@@ -3,7 +3,7 @@
  * Computes what to display without writing to stdout.
  */
 
-import { stripAnsiLength } from './ansi.js';
+import stringWidth from 'string-width';
 import type { EditorState } from './editor.js';
 
 const CONTINUATION = '  ';
@@ -24,11 +24,11 @@ export function prepareEditor(editor: EditorState, prompt: string): EditorRender
   }
 
   const cursorPrefix = editor.cursor.row === 0 ? prompt : CONTINUATION;
-  const cursorCol = stripAnsiLength(cursorPrefix) + editor.cursor.col;
+  const cursorCol = stringWidth(cursorPrefix) + editor.cursor.col;
 
   let cursorRow = 0;
   for (let i = 0; i < editor.cursor.row; i++) {
-    cursorRow += Math.max(1, Math.ceil(stripAnsiLength(lines[i]) / columns));
+    cursorRow += Math.max(1, Math.ceil(stringWidth(lines[i]) / columns));
   }
   cursorRow += Math.floor(cursorCol / columns);
 

src/terminal.ts

@@ -1,8 +1,8 @@
 import { inspect } from 'node:util';
 import { DateTimeFormatter, LocalTime } from '@js-joda/core';
+import stringWidth from 'string-width';
 import type { AppState } from './AppState.js';
 import type { AttachmentStore } from './AttachmentStore.js';
-import { stripAnsiLength } from './ansi.js';
 import type { CommandMode } from './CommandMode.js';
 import type { EditorState } from './editor.js';
 import { type EditorRender, prepareEditor } from './renderer.js';
@@ -270,9 +270,7 @@ export class Terminal {
         output += '\n';
       }
       output += clearLine + line;
-      // biome-ignore lint/suspicious/noControlCharactersInRegex: matching terminal escape sequences requires \x1b
-      const visibleLength = line.replace(/\x1b\[[0-9;]*m/g, '').length;
-      questionScreenLines += Math.max(1, Math.ceil(visibleLength / columns));
+      questionScreenLines += Math.max(1, Math.ceil(stringWidth(line) / columns));
       hasOutput = true;
     }
 
@@ -313,7 +311,7 @@ export class Terminal {
     for (let i = 0; i < this.editorContent.lines.length; i++) {
       output += '\n';
       output += clearLine + this.editorContent.lines[i];
-      editorScreenLines += Math.max(1, Math.ceil(stripAnsiLength(this.editorContent.lines[i]) / columns));
+      editorScreenLines += Math.max(1, Math.ceil(stringWidth(this.editorContent.lines[i]) / columns));
     }
 
     // Clear any leftover lines from previous render
@@ -322,7 +320,7 @@ export class Terminal {
     // Position cursor within editor
     this.cursorLinesFromBottom = 0;
     for (let i = this.editorContent.lines.length - 1; i > this.editorContent.cursorRow; i--) {
-      this.cursorLinesFromBottom += Math.max(1, Math.ceil(stripAnsiLength(this.editorContent.lines[i]) / columns));
+      this.cursorLinesFromBottom += Math.max(1, Math.ceil(stringWidth(this.editorContent.lines[i]) / columns));
     }
     if (this.cursorLinesFromBottom > 0) {
       output += cursorUp(this.cursorLinesFromBottom);