Streaming Command Execution - Implementation Progress
Feature Branch: feature/streaming-command-execution
Status: Core implementation complete ✅
Date: 2025-11-20
✅ Completed (Phase 1)
Backend
- Install socket.io
- Add WebSocket server setup
- Implement job tracking Map
- Switch to spawn() for execution
- Add stdout/stderr streaming
- Add completion handlers
- Implement cancellation (SIGINT)
- Add error handling
- Security: path validation ✅ (rate limiting - not yet)
- Testing: integration tests (smoke tests pass, need WebSocket-specific tests)
Frontend
- Install socket.io-client
- Add WebSocket connection
- Implement CommandExecution class
- Add progressive enhancement logic
- Build job UI components (HTML)
- Style job UI (CSS)
- Add cancel button handler
- Implement auto-scroll
- Add keyboard shortcuts (Escape)
- Handle edge cases (disconnect, errors)
- Testing: manual scenarios (all tested and working)
Documentation
- Update README with new features (done by infra agent)
- systemd setup documented (done by infra agent)
- API documentation for WebSocket events
- User guide for cancellation
- Known limitations
🎉 Improvements Beyond Original Design
We made several improvements that weren't in the original v1 design:
1. Typing Bubble Integration ✨
Original plan: Progressive enhancement based on hardcoded list + line count What we built:
- Universal 1-second typing bubble for ALL commands
- Familiar UX (users expect typing indicators)
- Pure behavior-based UI decision (no hardcoding needed)
2. Removed Hardcoded Command List ✨
Original plan: Maintain list of known long commands (npm, docker, etc.) What we built:
- Zero hardcoded commands
- Universal flow works for any command
- No false positives (e.g.,
npm --helpstays simple)
3. High-Output Safeguard ✨
Original plan: Not addressed in design What we built:
- Automatic detection of high output (>5KB in <1s)
- Immediate UI creation to prevent memory bloat
- Prevents DOM freezing on large outputs
4. Clean Completion UI ✨
Original plan: Keep header + footer on completion What we built:
- Header removed on completion (less visual clutter)
- Single footer with all info (duration + status)
- Job container remains scrollable for long output
📊 Current State
What Works
✅ Quick commands (ls, pwd, git status) - simple bubbles ✅ Long commands (sleep 5+) - job UI with cancel ✅ High-output commands (find /, git log) - immediate job UI ✅ Real-time streaming (no timeouts or buffer limits) ✅ Cancellation (click [✕] or press Escape) ✅ Dark mode support ✅ Mobile-friendly (touch-optimized) ✅ All 24 smoke tests passing
Known Limitations
⚠️ Interactive commands not supported (vim, nano, ssh) - requires PTY ⚠️ No session persistence (jobs lost on server restart) ⚠️ No job history/resume ⚠️ No rate limiting on commands ⚠️ Very large outputs (>1MB) may cause performance issues
🚀 Next Steps (Phase 2)
Immediate (Before Merge)
- Commit current improvements (typing bubble + safeguards)
- Run comprehensive manual testing
- Document WebSocket API in README
- Add known limitations to README
Short-term Enhancements
- Add WebSocket-specific tests
- Implement rate limiting (max N commands per minute)
- Add output size limits (keep last N lines)
- Better error messages for common failures
- Reconnection handling (reattach to running jobs)
Medium-term Features
- Job history (see previous command outputs)
- Command history (up/down arrow navigation)
- Tab completion (basic file/command completion)
- Multiple concurrent jobs UI
- Export command output to file
Long-term (Phase 3)
- Interactive command support (node-pty + xterm.js)
- Persistent sessions (survive server restarts)
- Terminal multiplexing (multiple shells)
- Command templates/snippets
- Collaborative sessions (multiple users)
🐛 Known Issues / Tech Debt
Minor
- Typing bubble shows even if WebSocket isn't connected yet
- No visual feedback when WebSocket disconnects mid-command
- Cancel button visible on known-failed commands (should hide)
Documentation
- WebSocket event contract not documented for users
- No troubleshooting guide for WebSocket issues
- Missing performance benchmarks
Testing
- No automated tests for WebSocket functionality
- No tests for edge cases (disconnect, timeout, etc.)
- Browser tests don't cover streaming execution
📝 Design Decisions Log
Why 1-second typing bubble delay?
- Familiar UX pattern (all chat apps use it)
- Good balance: fast enough to feel instant, long enough to assess command
- Prevents UI flicker for very fast commands
Why 5KB threshold for high-output?
- Prevents buffering large amounts in memory
- ~5KB ≈ 50-100 lines of typical terminal output
- Low enough to catch issues early, high enough to not trigger on normal output
Why remove hardcoded command list?
- Eliminates maintenance burden
- No false positives
- Adaptive to any command/system
- Simpler codebase
Why remove header on completion?
- Reduces visual clutter
- Cancel button no longer needed
- Footer provides all necessary info
- Keeps output scrollable
🔗 Related Documents
- Design Doc v1 - Original design specification
- Design Doc v0 - Problem analysis
- README - User documentation
🎯 Success Metrics
Goal: Make this a viable terminal replacement for 90% of developer workflows
Measured by:
- Long commands complete successfully (no timeouts)
- Real-time output streaming works
- Users can cancel running commands
- Simple commands stay simple (no UX bloat)
- All existing tests still pass
- No performance degradation vs v0
- Positive user feedback on UX
Current score: 5/7 complete
Last Updated: 2025-11-20 Next Review: Before merging to main