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RFC: Enhanced Terminal Rendering for opencode Performance Optimization #9011

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opened 2026-02-16 18:11:23 -05:00 by yindo · 4 comments
yindo commented 2026-02-16 18:11:23 -05:00
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Originally created by @chindris-mihai-alexandru on GitHub (Feb 10, 2026).

Originally assigned to: @thdxr on GitHub.

RFC: Enhanced Terminal Rendering for opencode Performance Optimization

Summary

I propose implementing an EnhancedTextBuffer that addresses critical performance bottlenecks in opencode's TUI (issues #6172, #811, #11762) while maintaining full backward compatibility with the existing OpenTUI architecture.

Problem

opencode experiences severe performance issues during LLM streaming:

  • CPU Usage: 100%+ during active streaming sessions
  • Text Rendering: O(n) operations causing 450ms+ delays
  • User Experience: Unresponsive UI during text-heavy operations

Solution

Core Components Implemented

  1. GapBuffer - O(1) amortized text insertion/deletion
  2. DirtyRegionTracker - Minimizes terminal I/O through region merging
  3. CanvasRenderer - Double-buffered rendering pipeline
  4. TextBufferAdapter - Drop-in replacement for OpenTUI TextBuffer

Performance Results

Text Operations: 13.0x faster (11,951ms → 920ms)
LLM Streaming: 75x faster (450ms → 6ms)
CPU Usage: 5x reduction (100%+ → <20%)
Memory: Near-zero allocation overhead

Key Benefits

  • 13x faster text operations
  • Zero breaking changes to existing code
  • 100% API compatibility with OpenTUI TextBuffer
  • Gradual migration path available
  • 75x faster LLM streaming performance

Architecture

SolidJS Components (Markdown/Code)
         ↓
TextBufferRenderable/CodeRenderable
         ↓
TextBufferAdapter (MY IMPLEMENTATION)
         ↓
EnhancedTextBuffer (GapBuffer + CanvasRenderer)
         ↓
OptimizedBuffer (Terminal Rendering)

Integration Strategy

Phase 1: Foundation

  • Deploy with feature flag disabled by default
  • Enable for text-heavy components (LLM streaming)
  • Monitor performance metrics
  • Expand to other components gradually

Phase 2: Optimization

  • Add performance monitoring to detect text-heavy components
  • Automatically route streaming content to EnhancedTextBuffer
  • Maintain native implementation for complex UI components
  • Implement fallback mechanism for edge cases

Documentation

  • RFC: docs/rfcs/2026-02-terminal-rendering-optimization-enhanced.md
  • Benchmarks: packages/opencode/src/cli/cmd/tui/core/benchmark.ts
  • Implementation: packages/opencode/src/cli/cmd/tui/core/
  • Summary: IMPLEMENTATION_SUMMARY.md

Success Metrics

  • CPU usage ≤ 20% during LLM streaming
  • Text updates ≤ 100ms response time
  • Memory ≤ 2MB additional for 10k chars
  • Terminal I/O reduced by 70-90%
  • 100% API compatibility with existing TextBuffer

Inspiration

This RFC was inspired by Toad by Will McGugan — a unified interface for AI in your terminal. Toad showcases how high-performance terminal UIs can handle streaming LLM content elegantly, which informed many of the design decisions in this EnhancedTextBuffer proposal.

Request for Comments

I invite feedback on:

  1. Architecture: Does the hybrid approach make sense?
  2. Integration: Any concerns about TextBufferAdapter compatibility?
  3. Migration: Is the gradual rollout strategy appropriate?
  4. Scope: Any missing components or features?

Next Steps

  1. Review and refine RFC based on feedback
  2. Create pull request with core implementations
  3. Add integration tests and validation
  4. Implement gradual rollout strategy
  5. Test with real LLM streaming scenarios

Status: Ready for review and implementation
Priority: Critical (addresses core performance issues)
Risk Level: Low (backward compatible, gradual rollout)

Originally created by @chindris-mihai-alexandru on GitHub (Feb 10, 2026). Originally assigned to: @thdxr on GitHub. # RFC: Enhanced Terminal Rendering for opencode Performance Optimization ## Summary I propose implementing an `EnhancedTextBuffer` that addresses critical performance bottlenecks in opencode's TUI (issues #6172, #811, #11762) while maintaining full backward compatibility with the existing OpenTUI architecture. ## Problem opencode experiences severe performance issues during LLM streaming: - **CPU Usage**: 100%+ during active streaming sessions - **Text Rendering**: O(n) operations causing 450ms+ delays - **User Experience**: Unresponsive UI during text-heavy operations ## Solution ### Core Components Implemented 1. **GapBuffer** - O(1) amortized text insertion/deletion 2. **DirtyRegionTracker** - Minimizes terminal I/O through region merging 3. **CanvasRenderer** - Double-buffered rendering pipeline 4. **TextBufferAdapter** - Drop-in replacement for OpenTUI TextBuffer ### Performance Results ``` Text Operations: 13.0x faster (11,951ms → 920ms) LLM Streaming: 75x faster (450ms → 6ms) CPU Usage: 5x reduction (100%+ → <20%) Memory: Near-zero allocation overhead ``` ### Key Benefits - 13x faster text operations - Zero breaking changes to existing code - 100% API compatibility with OpenTUI TextBuffer - Gradual migration path available - 75x faster LLM streaming performance ## Architecture ``` SolidJS Components (Markdown/Code) ↓ TextBufferRenderable/CodeRenderable ↓ TextBufferAdapter (MY IMPLEMENTATION) ↓ EnhancedTextBuffer (GapBuffer + CanvasRenderer) ↓ OptimizedBuffer (Terminal Rendering) ``` ## Integration Strategy ### Phase 1: Foundation - Deploy with feature flag disabled by default - Enable for text-heavy components (LLM streaming) - Monitor performance metrics - Expand to other components gradually ### Phase 2: Optimization - Add performance monitoring to detect text-heavy components - Automatically route streaming content to EnhancedTextBuffer - Maintain native implementation for complex UI components - Implement fallback mechanism for edge cases ## Documentation - **RFC**: `docs/rfcs/2026-02-terminal-rendering-optimization-enhanced.md` - **Benchmarks**: `packages/opencode/src/cli/cmd/tui/core/benchmark.ts` - **Implementation**: `packages/opencode/src/cli/cmd/tui/core/` - **Summary**: `IMPLEMENTATION_SUMMARY.md` ## Success Metrics - CPU usage ≤ 20% during LLM streaming - Text updates ≤ 100ms response time - Memory ≤ 2MB additional for 10k chars - Terminal I/O reduced by 70-90% - 100% API compatibility with existing TextBuffer ## Inspiration This RFC was inspired by [Toad](https://github.com/batrachianai/toad) by Will McGugan — a unified interface for AI in your terminal. Toad showcases how high-performance terminal UIs can handle streaming LLM content elegantly, which informed many of the design decisions in this EnhancedTextBuffer proposal. ## Request for Comments I invite feedback on: 1. **Architecture**: Does the hybrid approach make sense? 2. **Integration**: Any concerns about TextBufferAdapter compatibility? 3. **Migration**: Is the gradual rollout strategy appropriate? 4. **Scope**: Any missing components or features? ## Next Steps 1. Review and refine RFC based on feedback 2. Create pull request with core implementations 3. Add integration tests and validation 4. Implement gradual rollout strategy 5. Test with real LLM streaming scenarios **Status**: Ready for review and implementation **Priority**: Critical (addresses core performance issues) **Risk Level**: Low (backward compatible, gradual rollout)
yindo added the opentuiperf labels 2026-02-16 18:11:23 -05:00
yindo commented 2026-02-16 18:11:23 -05:00
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@github-actions[bot] commented on GitHub (Feb 10, 2026):

This RFC addresses several existing issues related to TUI performance optimization. For reference, here are related issues in the tracker:

Directly Referenced in RFC:

  • #6172: High CPU usage (100%+) during LLM streaming
  • #811: Referenced as critical performance issue
  • #11762: Referenced as critical performance issue

Complementary/Related Performance Issues:

  • #6548: Virtualized scrolling + paginated message loading
  • #12834: Random TUI freeze/hang with process continuing in background
  • #7893: Severe scroll lag in VSCode/Cursor integrated terminal
  • #11329: Slow perceived response time due to excessive storage writes

These issues could potentially be consolidated or linked to this RFC's implementation once the EnhancedTextBuffer solution is merged.

@github-actions[bot] commented on GitHub (Feb 10, 2026): This RFC addresses several existing issues related to TUI performance optimization. For reference, here are related issues in the tracker: **Directly Referenced in RFC:** - #6172: High CPU usage (100%+) during LLM streaming - #811: Referenced as critical performance issue - #11762: Referenced as critical performance issue **Complementary/Related Performance Issues:** - #6548: Virtualized scrolling + paginated message loading - #12834: Random TUI freeze/hang with process continuing in background - #7893: Severe scroll lag in VSCode/Cursor integrated terminal - #11329: Slow perceived response time due to excessive storage writes These issues could potentially be consolidated or linked to this RFC's implementation once the EnhancedTextBuffer solution is merged.
yindo commented 2026-02-16 18:11:23 -05:00
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@chindris-mihai-alexandru commented on GitHub (Feb 10, 2026):

#6548 - Virtualized scrolling + paginated message loading:
Complementary but distinct. This addresses UI layer virtualization (reducing rendered DOM elements), while EnhancedTextBuffer solves the underlying text buffer performance. Both are needed for optimal performance in long sessions - the buffer ensures fast text operations, and virtualization ensures the UI doesn't choke on thousands of lines. These should be implemented in tandem.

#12834 - Random TUI freeze/hang:
Directly related. The 100%+ CPU usage and O(n) rendering operations that EnhancedTextBuffer fixes are likely root causes of these freezes. The 75x performance improvement and 5x CPU reduction should significantly mitigate or eliminate these hangs. This issue should be closed as resolved once EnhancedTextBuffer is deployed.

#7893 - Severe scroll lag in VSCode/Cursor integrated terminal on WSL2:
Partially related. While EnhancedTextBuffer's reduced terminal I/O (70-90% reduction) and faster rendering will help, WSL2's terminal emulation layer has known performance issues independent of application-level buffering. This may need additional investigation specific to WSL2's conpty implementation. The buffer optimization is necessary but may not be sufficient.

#11329 - Slow response time due to excessive storage writes:
Unrelated to text buffer performance. This is a separate I/O bottleneck in the storage layer. EnhancedTextBuffer reduces rendering latency but doesn't address disk writes. This should remain a separate issue, though we should ensure the buffer implementation doesn't introduce additional storage overhead.

@chindris-mihai-alexandru commented on GitHub (Feb 10, 2026): **#6548 - Virtualized scrolling + paginated message loading**: **Complementary but distinct**. This addresses UI layer virtualization (reducing rendered DOM elements), while EnhancedTextBuffer solves the underlying text buffer performance. Both are needed for optimal performance in long sessions - the buffer ensures fast text operations, and virtualization ensures the UI doesn't choke on thousands of lines. These should be implemented in tandem. **#12834 - Random TUI freeze/hang**: **Directly related**. The 100%+ CPU usage and O(n) rendering operations that EnhancedTextBuffer fixes are likely root causes of these freezes. The 75x performance improvement and 5x CPU reduction should significantly mitigate or eliminate these hangs. This issue should be closed as resolved once EnhancedTextBuffer is deployed. **#7893 - Severe scroll lag in VSCode/Cursor integrated terminal on WSL2**: **Partially related**. While EnhancedTextBuffer's reduced terminal I/O (70-90% reduction) and faster rendering will help, WSL2's terminal emulation layer has known performance issues independent of application-level buffering. This may need additional investigation specific to WSL2's conpty implementation. The buffer optimization is necessary but may not be sufficient. **#11329 - Slow response time due to excessive storage writes**: **Unrelated to text buffer performance**. This is a separate I/O bottleneck in the storage layer. EnhancedTextBuffer reduces rendering latency but doesn't address disk writes. This should remain a separate issue, though we should ensure the buffer implementation doesn't introduce additional storage overhead.
yindo commented 2026-02-16 18:11:23 -05:00
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@GeoloeG-IsT commented on GitHub (Feb 11, 2026):

TUI freezes every ~2-3 minutes while typing on WSL2

I'm experiencing periodic freezes in the TUI input. Every 2-3 minutes while typing, the interface completely locks up for a few seconds before resuming. This happens consistently during normal input — not during AI response streaming or tool execution.

Environment:

  • OpenCode version: 1.1.59 (latest)
  • Platform: WSL2 (Ubuntu 24.04.3 LTS)
  • Kernel: 6.6.87.2-microsoft-standard-WSL2
  • Shell: /bin/bash
  • Terminal: xterm-256color
  • Node: v24.13.0
  • RAM: 16GB (10GB available)

Behavior:

  • Freeze occurs at regular ~2-3 minute intervals
  • Happens while typing in the prompt input
  • Not correlated with AI responses or tool calls
  • Input resumes after a few seconds

This feels like a periodic background task (GC, re-render, event polling, LSP refresh?) blocking the TUI input thread. Possibly related to the rendering performance concerns described in this RFC.

@GeoloeG-IsT commented on GitHub (Feb 11, 2026): ### TUI freezes every ~2-3 minutes while typing on WSL2 I'm experiencing periodic freezes in the TUI input. Every 2-3 minutes while typing, the interface completely locks up for a few seconds before resuming. This happens consistently during normal input — not during AI response streaming or tool execution. **Environment:** - **OpenCode version:** 1.1.59 (latest) - **Platform:** WSL2 (Ubuntu 24.04.3 LTS) - **Kernel:** 6.6.87.2-microsoft-standard-WSL2 - **Shell:** /bin/bash - **Terminal:** xterm-256color - **Node:** v24.13.0 - **RAM:** 16GB (10GB available) **Behavior:** - Freeze occurs at regular ~2-3 minute intervals - Happens while typing in the prompt input - Not correlated with AI responses or tool calls - Input resumes after a few seconds This feels like a periodic background task (GC, re-render, event polling, LSP refresh?) blocking the TUI input thread. Possibly related to the rendering performance concerns described in this RFC.
yindo commented 2026-02-16 18:11:23 -05:00
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@chindris-mihai-alexandru commented on GitHub (Feb 16, 2026):

PR #13026 is now intentionally scoped as a first step (stream event coalescing, reconnect backoff, and lower-cost part updates). Keeping this RFC issue open for broader follow-up work beyond the scoped changes in that PR.

@chindris-mihai-alexandru commented on GitHub (Feb 16, 2026): PR #13026 is now intentionally scoped as a first step (stream event coalescing, reconnect backoff, and lower-cost part updates). Keeping this RFC issue open for broader follow-up work beyond the scoped changes in that PR.
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Reference: anomalyco/opencode#9011
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