fix(discord): post the rendered screen, not the raw stream, as the alert tail

A full-screen UI repaints in place, so the raw output stream read as garbage. Read capture-pane instead and drop rules, blanks and escape codes.

src/discord-bridge.ts

@@ -184,6 +184,24 @@ export function getDiscordStartupHint(): string | undefined {
   return activeStartupHint;
 }
 
+/**
+ * The last lines of a rendered screen for a post: colour and charset codes removed, blank lines and
+ * pure rule lines (box drawing, dashes) dropped, the last 14 lines, at most 900 characters, cut on a line.
+ */
+export function screenTail(screen: string, maxLines = 14, maxChars = 900): string {
+  const lines = screen
+    // eslint-disable-next-line no-control-regex
+    .replace(/\u001b\[[0-9;?]*[ -/]*[@-~]|\u001b[()][A-Za-z0-9]|\u001b[@-Z\\-_]/g, '')
+    // eslint-disable-next-line no-control-regex
+    .replace(/[\u0000-\u0008\u000b-\u001f\u007f-\u009f]/g, '')
+    .split(/\r?\n/)
+    .map((l) => l.trimEnd())
+    .filter((l) => l.trim() !== '' && !/^[\s\-_=\u2500-\u257f]+$/.test(l));
+  let out = lines.slice(-maxLines);
+  while (out.length > 1 && out.join('\n').length > maxChars) out = out.slice(1);
+  return out.join('\n').slice(-maxChars);
+}
+
 /** Final path segment only, `[A-Za-z0-9._-]`, no leading dot, at most 80 characters. */
 export function safeAttachmentName(name: string): string {
   const base = (name.split(/[\\/]/).pop() ?? '').replace(/[^A-Za-z0-9._-]+/g, '_').replace(/^[._]+/, '');

src/web/server.ts

@@ -45,8 +45,7 @@ import { looksLikeHostReboot, newestPersistedActivity, planRebootRestore } from
 import { rebootRestoreRegistry } from './reboot-restore-registry.js';
 import { dataPath, getDataDir, CODEMAN_INSTANCE } from '../config/instance.js';
 import { WebhookNotifier, readWebhookConfig } from '../webhook-notify.js';
-import { DiscordBridge } from '../discord-bridge.js';
-import { stripAnsi } from '../utils/regex-patterns.js';
+import { DiscordBridge, screenTail } from '../discord-bridge.js';
 import { stopHostSensors } from '../host-sensors.js';
 import type { WebhookUrgency } from '../types/push.js';
 import { webviewFetch } from './webview-egress.js';
@@ -3010,7 +3009,7 @@ export class WebServer extends EventEmitter {
         urgency: template.urgency as WebhookUrgency,
         sessionId: sessionId || undefined,
         sessionName: sessionName || undefined,
-        tail: dcSession ? WebServer.outputTail(dcSession) : undefined,
+        tail: dcSession ? this.discordTail(dcSession) : undefined,
         host: this.windowTitle,
       })
       .catch(() => undefined);
@@ -3096,14 +3095,14 @@ export class WebServer extends EventEmitter {
     }
   }
 
-  /** The last few lines the CLI printed, with colour codes removed, for a Discord alert. */
-  private static outputTail(session: { textOutput: string; terminalBuffer: string }): string {
-    const raw = session.textOutput || session.terminalBuffer.slice(-4000);
-    const lines = stripAnsi(raw)
-      .split(/\r?\n/)
-      .map((l) => l.trimEnd())
-      .filter((l) => l.trim() !== '');
-    return lines.slice(-12).join('\n').slice(-900);
+  /**
+   * What the person would see on the tab right now, for a Discord alert: the rendered tmux screen
+   * (`capture-pane -p`), never the raw output stream, which a full-screen UI repaints in place and
+   * reads as garbage. A session with no pane falls back to its plain text output, else nothing.
+   */
+  private discordTail(session: { muxName?: string | null; textOutput: string }): string {
+    const pane = session.muxName ? (this.mux.capturePaneText?.(session.muxName) ?? null) : null;
+    return screenTail(pane ?? session.textOutput ?? '');
   }
 
   /** The notification body for an event (shared by Web Push and the webhook channel). */

test/discord-bridge.test.ts

@@ -12,6 +12,7 @@ import {
   DISCORD_STARTUP_HINT,
   isDiscordCdnUrl,
   safeAttachmentName,
+  screenTail,
   DEFAULT_DISCORD_CONFIG,
   DiscordApi,
   DiscordBridge,
@@ -643,3 +644,43 @@ describe('DiscordBridge files and startup hint', () => {
     off.stop();
   });
 });
+
+describe('screenTail', () => {
+  it('keeps the last lines of a rendered screen and drops rules, blanks and escape codes', () => {
+    const screen = [
+      'old line',
+      '',
+      '\u001b[1mWhich option?\u001b[0m',
+      '─────────────────────────',
+      '  1. Cap GPUs',
+      '  2. Cap CPU',
+      '\u001b(B',
+      '  4. Type something.',
+      '━━━━━━━━━━━━━━━━━━━━━━━━━',
+      'Enter to select · Esc to cancel\u001b(B',
+    ].join('\n');
+    expect(screenTail(screen)).toBe(
+      [
+        'old line',
+        'Which option?',
+        '  1. Cap GPUs',
+        '  2. Cap CPU',
+        '  4. Type something.',
+        'Enter to select · Esc to cancel',
+      ].join('\n')
+    );
+  });
+
+  it('caps lines and characters, cutting on a line', () => {
+    const many = Array.from({ length: 40 }, (_v, i) => `line ${i}`).join('\n');
+    expect(screenTail(many).split('\n')).toHaveLength(14);
+    expect(screenTail(many).endsWith('line 39')).toBe(true);
+    const wide = Array.from({ length: 5 }, () => 'x'.repeat(400)).join('\n');
+    expect(screenTail(wide).length).toBeLessThanOrEqual(900);
+  });
+
+  it('is empty for nothing', () => {
+    expect(screenTail('')).toBe('');
+    expect(screenTail('\n\n ───── \n')).toBe('');
+  });
+});