Streaming Command Execution - Implementation Progress

Feature Branch: feature/streaming-command-execution Status: Core implementation complete ✅ Date: 2025-11-20

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✅ 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

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🎉 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 --help stays 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

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📊 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

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🚀 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)

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🐛 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

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📝 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

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🔗 Related Documents

• Design Doc v1 - Original design specification
• Design Doc v0 - Problem analysis
• README - User documentation

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🎯 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

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Last Updated: 2025-11-20 Next Review: Before merging to main