feat(backend): WebSocket endpoint for real-time indexing progress (#149)

[DevanshuNEU]

Summary

Adds WebSocket support for real-time indexing progress in the playground. Instead of polling every 2 seconds, the frontend can now subscribe to a WebSocket and receive instant updates as each file is processed.

Changes

New Files

• backend/routes/ws_playground.py - WebSocket endpoint handler
• backend/tests/test_ws_playground.py - Test suite (7 tests)

Modified Files

• backend/main.py - Register new WS route
• backend/services/anonymous_indexer.py - Add Redis Pub/Sub publishing

Endpoint

WS /api/v1/ws/playground/{job_id}

Event Types

{"type": "connected", "job_id": "...", "message": "Listening for indexing events"}
{"type": "cloning", "repo_name": "flask", "message": "Cloning repository..."}
{"type": "progress", "files_processed": 25, "files_total": 100, "current_file": "src/app.py", "functions_found": 150, "percent": 25}
{"type": "completed", "repo_id": "anon_xxx", "stats": {...}, "message": "Indexing complete!"}
{"type": "error", "error": "clone_failed", "message": "...", "recoverable": false}

Architecture

Background Job → Redis Pub/Sub → WebSocket → Browser
                job:{id}:events

Tests

All 7 tests passing:

• WebSocket rejects invalid job IDs
• WebSocket handles missing Redis gracefully
• Pub/Sub events published on status changes
• Progress events include current file info
• Completed events include stats
• No duplicate PROCESSING events
• Event types are strings (not enum objects)

Why WebSocket over Polling?

The killer feature is the streaming file list - showing each file as it's processed in real-time. Polling every 2 seconds can't deliver that smooth experience. For the HN launch demo, this creates the "watching the AI work" moment.

Closes #149

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1 Skipped Deployment

Project	Deployment	Review	Updated (UTC)
opencodeintel	Ignored	Preview	Jan 5, 2026 8:53pm