Fix sticky zone width calculations for ANSI content

.claude/CLAUDE.md

@@ -73,7 +73,7 @@ Only update the `Status` field — do not modify any other frontmatter or prompt
 <!-- BEGIN:REPO:current-state -->
 ## Current State
 Branch: `main`
-In-progress: PR #131 (fix #107, empty piped stdin hang) open, auto-merge enabled.
+In-progress: Nothing. PR #136 (fix #133, sticky zone ANSI width math) open, auto-merge enabled.
 <!-- END:REPO:current-state -->
 
 <!-- BEGIN:REPO:architecture -->

.claude/sessions/2026-03-27.md

@@ -43,3 +43,11 @@
 - Decisions: None.
 - Next: PR #131 pending CI and auto-merge.
 - Violations: None
+
+### 18:25 - release/1.0.0-alpha.71
+
+- Did: Added `verify-commit-signatures` workflow (copied from mcp-exec repo), consolidated duplicate `### Fixed` sections in CHANGELOG, added missing #122 fix entry, bumped version to 1.0.0-alpha.71, created PR #132 (auto-merge), published release after merge, confirmed 1.0.0-alpha.71 live on npm.
+- Files: `.github/workflows/verify-commit-signatures.yml`, `CHANGELOG.md`, `package.json`
+- Decisions: Used `feature/version-1.0.0-alpha.71` branch per shellicar-oss convention. Prompt status update to "in-progress" timed out (fleet repo outside working dir) but was resolved by the system. Release is a pre-release (contains hyphen) so `--prerelease` flag was used.
+- Next: Nothing. Release complete.
+- Violations: None

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

@@ -0,0 +1,9 @@
+# Session Log: 2026-03-28
+
+### 20:23 - fix/sticky-zone-width-math (#133) Stage 2
+
+- Did: Staged and committed code changes from Stage 1 (src/ansi.ts, src/renderer.ts, src/terminal.ts plus leftover session-end files from March 27 release session), pushed branch, created PR #136 with Closes #133, auto-merge enabled.
+- Files: `src/ansi.ts`, `src/renderer.ts`, `src/terminal.ts`, `.claude/CLAUDE.md`, `.claude/sessions/2026-03-27.md`
+- 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

src/ansi.ts

@@ -0,0 +1,11 @@
+// biome-ignore lint/suspicious/noControlCharactersInRegex: matching terminal escape sequences requires \x1b
+const ANSI_PATTERN = /\x1b\[[0-9;]*m/g;
+
+/**
+ * Strips ANSI SGR escape codes and returns the visible character length.
+ * Handles colour, bold, inverse, and reset sequences only.
+ * Does not account for multi-width characters (emoji, CJK).
+ */
+export function stripAnsiLength(str: string): number {
+  return str.replace(ANSI_PATTERN, '').length;
+}

src/renderer.ts

@@ -3,6 +3,7 @@
  * Computes what to display without writing to stdout.
  */
 
+import { stripAnsiLength } from './ansi.js';
 import type { EditorState } from './editor.js';
 
 const CONTINUATION = '  ';
@@ -23,12 +24,13 @@ export function prepareEditor(editor: EditorState, prompt: string): EditorRender
   }
 
   const cursorPrefix = editor.cursor.row === 0 ? prompt : CONTINUATION;
-  const cursorCol = cursorPrefix.length + editor.cursor.col;
+  const cursorCol = stripAnsiLength(cursorPrefix) + editor.cursor.col;
 
   let cursorRow = 0;
   for (let i = 0; i < editor.cursor.row; i++) {
-    cursorRow += Math.max(1, Math.ceil(lines[i].length / columns));
+    cursorRow += Math.max(1, Math.ceil(stripAnsiLength(lines[i]) / columns));
   }
+  cursorRow += Math.floor(cursorCol / columns);
 
   return { lines, cursorRow, cursorCol };
 }

src/terminal.ts

@@ -2,6 +2,7 @@ import { inspect } from 'node:util';
 import { DateTimeFormatter, LocalTime } from '@js-joda/core';
 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';
@@ -312,7 +313,7 @@ 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(this.editorContent.lines[i].length / columns));
+      editorScreenLines += Math.max(1, Math.ceil(stripAnsiLength(this.editorContent.lines[i]) / columns));
     }
 
     // Clear any leftover lines from previous render
@@ -321,7 +322,7 @@ 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(this.editorContent.lines[i].length / columns));
+      this.cursorLinesFromBottom += Math.max(1, Math.ceil(stripAnsiLength(this.editorContent.lines[i]) / columns));
     }
     if (this.cursorLinesFromBottom > 0) {
       output += cursorUp(this.cursorLinesFromBottom);