feat: add screenshot list and file serving endpoints for debug viewer

Co-authored-by: Cursor <cursoragent@cursor.com>

src/server/httpServer.ts

@@ -1,5 +1,7 @@
 import express, { Express, Request, Response } from 'express';
 import { Server } from 'http';
+import path from 'path';
+import fs from 'fs';
 import { logger } from '../utils/logger';
 import { config } from '../config';
 import { runAuthTests, runSingleVariant, getVariantIds } from '../bot/authTestProcedure';
@@ -184,5 +186,61 @@ export class HttpServer {
         res.status(500).json({ error: (error as Error).message });
       }
     });
+
+    // List screenshots for a session
+    // Filename format: {sessionId}-{step}-{timestamp}.png
+    this._app.get('/api/bot/screenshots/:sessionId', (req: Request, res: Response) => {
+      try {
+        const { sessionId } = req.params;
+        const screenshotDir = config.screenshotDir;
+
+        if (!fs.existsSync(screenshotDir)) {
+          res.json({ screenshots: [] });
+          return;
+        }
+
+        const files = fs.readdirSync(screenshotDir)
+          .filter(f => f.startsWith(`${sessionId}-`) && f.endsWith('.png'))
+          .sort();
+
+        const screenshots = files.map(name => {
+          const stats = fs.statSync(path.join(screenshotDir, name));
+          const withoutExt = name.replace('.png', '');
+          const parts = withoutExt.split('-');
+          // sessionId is a UUID (5 parts joined by -), step follows, timestamp is last
+          const timestamp = parseInt(parts[parts.length - 1], 10) || 0;
+          const step = parts.slice(5, -1).join('-');
+          return { name, step, timestamp, sizeBytes: stats.size };
+        });
+
+        res.json({ screenshots });
+      } catch (error) {
+        logger.error('Error listing screenshots:', error);
+        res.status(500).json({ error: (error as Error).message });
+      }
+    });
+
+    // Serve a single screenshot file
+    this._app.get('/api/bot/screenshots/file/:filename', (req: Request, res: Response) => {
+      try {
+        const { filename } = req.params;
+
+        if (!filename.endsWith('.png') || filename.includes('..') || filename.includes('/') || filename.includes('\\')) {
+          res.status(400).json({ error: 'Invalid filename' });
+          return;
+        }
+
+        const filepath = path.join(config.screenshotDir, filename);
+        if (!fs.existsSync(filepath)) {
+          res.status(404).json({ error: 'Screenshot not found' });
+          return;
+        }
+
+        res.type('image/png').sendFile(path.resolve(filepath));
+      } catch (error) {
+        logger.error('Error serving screenshot:', error);
+        res.status(500).json({ error: (error as Error).message });
+      }
+    });
   }
 }