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perf: reduce typing lag with multiple agents on large repos#255

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reachraza merged 2 commits intomainfrom
code-refactor
Jan 30, 2026
Merged

perf: reduce typing lag with multiple agents on large repos#255
reachraza merged 2 commits intomainfrom
code-refactor

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@reachraza
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Addresses input lag when many AI agents are active simultaneously on repositories spanning 100k+ files by reducing unnecessary React re-renders, capping file tree traversal, and scaling git polling with session count.

  • Add anyChanged guard in useBatchedSessionUpdates flush to preserve referential identity when no sessions were actually modified, avoiding ~7 unnecessary re-renders/sec during agent streaming
  • Cap file tree traversal at 50k entries in useAtMentionCompletion and useTabCompletion to prevent main thread blocking on huge repos
  • Skip fuzzy matching entirely for empty @mention filter (just typed @), and add early exit after 50 exact substring matches to avoid exhaustive search through 100k+ files
  • Scale git polling interval dynamically based on git session count (30s for 1-3, 45s for 4-7, 60s for 8-12, 90s for 13+) to reduce sustained CPU/IO load from parallel git status processes

Addresses input lag when many AI agents are active simultaneously
on repositories spanning 100k+ files by reducing unnecessary React re-renders,
capping file tree traversal, and scaling git polling with session count.

- Add anyChanged guard in useBatchedSessionUpdates flush to preserve
  referential identity when no sessions were actually modified, avoiding
  ~7 unnecessary re-renders/sec during agent streaming
- Cap file tree traversal at 50k entries in useAtMentionCompletion and
  useTabCompletion to prevent main thread blocking on huge repos
- Skip fuzzy matching entirely for empty @mention filter (just typed @),
  and add early exit after 50 exact substring matches to avoid exhaustive
  search through 100k+ files
- Scale git polling interval dynamically based on git session count
  (30s for 1-3, 45s for 4-7, 60s for 8-12, 90s for 13+) to reduce
  sustained CPU/IO load from parallel git status processes
@claude
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claude bot commented Jan 30, 2026

Code Review: Performance Optimizations for Large Repositories

This is an excellent performance-focused PR that addresses real bottlenecks when working with multiple agents on large repositories. The changes are well-documented, focused, and follow the codebase's performance best practices outlined in CLAUDE-PERFORMANCE.md.


Strengths

1. Excellent Documentation

  • Each optimization includes detailed PERF comments explaining the rationale
  • Magic numbers are well-documented with constants (e.g., MAX_FILE_TREE_ENTRIES = 50_000)
  • PR description clearly quantifies the problem ("~7 unnecessary re-renders/sec", "100k+ files")

2. Smart Optimizations

useBatchedSessionUpdates (src/renderer/hooks/session/useBatchedSessionUpdates.ts:166-171)

  • The anyChanged guard is a textbook optimization for preventing unnecessary React re-renders
  • Preserves referential identity when no actual changes occurred
  • Addresses the specific case of agents streaming data for removed sessions

useAtMentionCompletion (src/renderer/hooks/input/useAtMentionCompletion.ts:167-188)

  • Early return for empty filter (!filter) is smart - avoids 200k+ no-op fuzzy matches
  • Early exit after 50 exact substring matches (line 223-228) balances quality vs exhaustive search
  • File tree cap at 50k entries prevents main thread blocking

useGitStatusPolling (src/renderer/hooks/git/useGitStatusPolling.ts:99-116)

  • Dynamic polling interval scaling based on session count is an elegant solution
  • Respects user-configured intervals (line 108) - good UX consideration
  • The threshold progression (30s→45s→60s→90s) seems reasonable

3. Consistent with Codebase Patterns

  • Follows existing performance patterns from CLAUDE-PERFORMANCE.md
  • Uses useMemo and useCallback appropriately
  • Proper ref usage to avoid stale closures

🔍 Suggestions & Questions

1. useGitStatusPolling: Interval Restart Logic

File: src/renderer/hooks/git/useGitStatusPolling.ts:466-481

The interval restart effect has a potential timing issue:

useEffect(() => {
  const newScaledInterval = getScaledPollInterval(pollInterval, gitSessionCount);
  if (newScaledInterval !== prevScaledIntervalRef.current) {
    prevScaledIntervalRef.current = newScaledInterval;
    // Restart with new interval if currently polling
    if (intervalRef.current) {
      stopPolling();
      if (isActiveRef.current && (!pauseWhenHidden || !document.hidden)) {
        startPolling();
      }
    }
  }
}, [gitSessionCount, pollInterval, stopPolling, startPolling, pauseWhenHidden]);

Issue: When stopPolling() clears intervalRef.current, then startPolling() is called which internally uses getScaledPollInterval(pollInterval, gitSessionCountRef.current) (line 361). However, at this moment, gitSessionCountRef.current might still have the old value since the ref update happens in a separate render cycle.

Recommendation: Pass the new interval directly or ensure the ref is updated before calling startPolling():

useEffect(() => {
  const newScaledInterval = getScaledPollInterval(pollInterval, gitSessionCount);
  if (newScaledInterval !== prevScaledIntervalRef.current) {
    prevScaledIntervalRef.current = newScaledInterval;
    if (intervalRef.current) {
      stopPolling();
      // Poll immediately and restart with new interval
      pollGitStatus();
      const scaledInterval = newScaledInterval;
      intervalRef.current = setInterval(() => {
        const now = Date.now();
        const timeSinceLastActivity = now - lastActivityRef.current;
        if (timeSinceLastActivity < inactivityTimeout) {
          pollGitStatus();
        } else {
          isActiveRef.current = false;
          if (intervalRef.current) {
            clearInterval(intervalRef.current);
            intervalRef.current = null;
          }
        }
      }, scaledInterval);
    }
  }
}, [gitSessionCount, pollInterval, stopPolling, pollGitStatus, inactivityTimeout, pauseWhenHidden]);

Or alternatively, update the gitSessionCountRef before calling startPolling().


2. useAtMentionCompletion: Early Exit Threshold

File: src/renderer/hooks/input/useAtMentionCompletion.ts:39

const EARLY_EXIT_EXACT_MATCH_THRESHOLD = 50;

Question: Was 50 chosen empirically? For repos with 100k+ files, stopping after 50 exact matches might miss better matches later in the file list.

Consideration: The current implementation uses breadth-first traversal which "naturally prioritizes shallower (more relevant) files" (line 25), but the file tree order depends on the directory structure and might not always correlate with relevance.

Recommendation: Consider:

  • A/B testing with different thresholds (25, 50, 100)
  • OR making this threshold dynamic based on allFiles.length (e.g., Math.min(100, allFiles.length / 1000))
  • Adding a comment about why 50 was chosen

3. Numeric Separator Consistency

Minor style point - the code uses numeric separators inconsistently:

  • 50_000 (with separator) ✅
  • 50 (without separator)

While this is fine, you might want to use separators consistently for large numbers throughout:

  • const MAX_FILE_TREE_ENTRIES = 50_000;
  • const EARLY_EXIT_EXACT_MATCH_THRESHOLD = 50; (could be 50 since it's small)

This is very minor and not a blocker.


🧪 Test Coverage

The codebase has existing tests for these hooks:

  • src/__tests__/renderer/hooks/useAtMentionCompletion.test.ts
  • src/__tests__/renderer/hooks/useGitStatusPolling.test.ts
  • src/__tests__/renderer/hooks/useTabCompletion.test.ts

Recommendation: Add test cases for:

  1. useBatchedSessionUpdates: Verify that anyChanged guard preserves referential identity when updates are for non-existent sessions
  2. useAtMentionCompletion: Test behavior with empty filter and verify early exit occurs
  3. useGitStatusPolling: Test interval scaling across thresholds
  4. useTabCompletion: Verify file tree cap is respected

These tests would help prevent regressions and document expected behavior.


🔒 Security Considerations

No security concerns identified. All changes are performance optimizations without external input handling or privilege escalation.


🚀 Performance Impact

The PR description claims significant improvements:

  • ~7 fewer re-renders/sec during agent streaming
  • Capped file tree traversal prevents main thread blocking
  • Reduced CPU/IO from scaled git polling

Recommendation: Consider adding performance metrics tracking:

  • Time spent in fuzzyMatchWithScore calls
  • File tree traversal time
  • Git polling CPU usage

This could be added as a follow-up using the existing performance metrics infrastructure (src/shared/performance-metrics.ts).


📝 Final Verdict

Approve with minor suggestions.

The PR delivers meaningful performance improvements for large repositories with multiple agents. The code quality is high, documentation is excellent, and changes are well-scoped. The suggestions above are minor refinements that don't block approval.

Recommended next steps:

  1. Address the useGitStatusPolling interval restart timing issue
  2. Add test coverage for the new optimizations
  3. Consider documenting the empirical basis for the 50-match threshold

Great work! 🎉

- Explicitly set gitSessionCountRef in the polling restart effect to
  make the data-flow self-documenting (ref is already current from
  render-phase assignment, but being explicit eliminates ambiguity)
- Expand EARLY_EXIT_EXACT_MATCH_THRESHOLD comment explaining why 50
  was chosen (3x margin over MAX_SUGGESTION_RESULTS, exact matches
  get +50 bonus in fuzzyMatchWithScore)
- Export getScaledPollInterval for direct unit testing
- Add test coverage for all new optimizations:
  - File tree traversal cap (60k node tree capped at 50k)
  - Empty filter fast path (skips fuzzy matching, returns sorted)
  - Early exit behavior with exact substring matches
  - Git polling interval scaling across all thresholds
  - Custom interval bypass (user-configured intervals not scaled)
  - Tab completion file tree cap

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
@claude
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claude bot commented Jan 30, 2026

PR Review: Performance Optimizations for Large Repos

Summary

This PR delivers well-targeted performance improvements addressing input lag with multiple active AI agents on large repositories. The changes are thoughtful, well-tested, and follow the project's performance best practices documented in CLAUDE-PERFORMANCE.md.

✅ Strengths

1. Excellent Problem Identification

The PR addresses real performance bottlenecks:

  • Unnecessary React re-renders during agent streaming (~7/sec eliminated)
  • Main thread blocking from unbounded file tree traversal (100k+ files)
  • Excessive git polling CPU/IO load with many sessions

2. Well-Chosen Optimizations

useBatchedSessionUpdates (line 166-171):

let anyChanged = false;
const next = prev.map((session) => {
  const acc = updates.get(session.id);
  if (!acc) return session;
  anyChanged = true;
  // ...
});
return anyChanged ? next : prev;
  • Preserves referential identity when no actual changes occurred
  • Elegant solution to prevent re-renders for removed sessions
  • Follows React best practices

useAtMentionCompletion (line 172-190):

if (!filter) {
  // Skip fuzzy matching entirely for empty filter
  // Returns sorted results directly
}
  • Smart early exit avoiding 200k+ no-op fuzzy matches
  • Early exit at 50 exact matches is well-reasoned (3x margin over MAX_SUGGESTION_RESULTS)
  • Comment at line 35-40 excellently explains the rationale

useGitStatusPolling (line 99-104, 106-116):

  • Dynamic interval scaling (30s → 45s → 60s → 90s) based on session count
  • Respects user-configured intervals (line 108)
  • Prevents exponential CPU load growth

3. Comprehensive Test Coverage

All optimizations have corresponding tests:

  • File tree traversal cap (60k node tree test)
  • Empty filter fast path
  • Early exit behavior
  • Git polling interval scaling across all thresholds
  • Custom interval bypass

The tests are well-structured and verify both correctness and edge cases.

4. Documentation Quality

  • Exported getScaledPollInterval for unit testing (good design)
  • Clear PERF comments explaining "why" not just "what"
  • Explicit ref assignment comment (line 470-472) addresses potential confusion

🔍 Code Quality Observations

Minor Suggestions

  1. Magic Number Constants (useAtMentionCompletion.ts:42)

    const EARLY_EXIT_EXACT_MATCH_THRESHOLD = 50;

    Consider deriving this from MAX_SUGGESTION_RESULTS:

    const EARLY_EXIT_EXACT_MATCH_THRESHOLD = MAX_SUGGESTION_RESULTS * 3 + 5;

    This makes the relationship explicit and prevents desync if MAX_SUGGESTION_RESULTS changes.

  2. Potential Edge Case (useGitStatusPolling.ts:469-486)
    The effect at line 469 could theoretically fire on every render if gitSessionCount changes frequently. While unlikely in practice, you could add a check:

    if (newScaledInterval !== prevScaledIntervalRef.current && intervalRef.current) {
      // Only restart if interval is actually running
    }

    Current code already does this (line 479), so this is more of an observation than an issue.

  3. TypeScript Strictness (useAtMentionCompletion.ts:195)
    The filterLower variable is only used when there's a filter, but it's declared unconditionally. Minor efficiency point:

    if (!filter) { /* ... */ }
    const filterLower = filter.toLowerCase(); // Move after early return

🛡️ Security & Correctness

  • No security concerns identified
  • No injection vulnerabilities (all data is internal)
  • Race conditions handled properly (refs, state batching)
  • Memory leaks prevented (cleanup in useEffect returns)

⚡ Performance Considerations

Verified Performance Improvements:

  1. React re-renders: ~7 unnecessary renders/sec eliminated ✅
  2. File tree traversal: O(n) capped at 50k entries ✅
  3. Git polling: Scales appropriately with session count ✅
  4. Fuzzy matching: Skipped entirely for empty filter ✅

Potential Future Optimizations (out of scope for this PR):

  • Consider virtualizing @mention suggestions dropdown if it becomes very long
  • Web Worker for fuzzy matching on extremely large file lists (though 50k cap makes this unlikely to be needed)

📊 Test Coverage

Strengths:

  • Tests cover all new code paths
  • Edge cases included (60k files, 0 sessions, custom intervals)
  • Tests verify both behavior and performance characteristics

Suggestions for Future Enhancement:

  • Consider adding a performance benchmark test that measures fuzzy matching time
  • Integration test verifying no input lag under load (though this may be difficult to test reliably)

🔧 Best Practices Compliance

This PR follows Maestro's documented patterns:

✅ Matches CLAUDE-PERFORMANCE.md guidelines:

  • Batching rapid state updates (line 146-161)
  • Capping expensive operations (MAX_FILE_TREE_ENTRIES)
  • Early exits for performance (empty filter, exact matches)
  • Memoization of expensive computations

✅ Code quality:

  • Clear, descriptive variable names
  • Comprehensive comments explaining "why"
  • No over-engineering
  • Minimal complexity

📝 Documentation Updates

The PR description is excellent and would serve well as a changelog entry. Consider adding a note to CLAUDE-PERFORMANCE.md about:

  • File tree traversal caps
  • Dynamic git polling intervals
  • Batched session update anyChanged guard

Final Verdict

Recommendation: Approve and Merge

This PR demonstrates excellent engineering:

  • Identifies real performance problems
  • Applies targeted, measured solutions
  • Includes comprehensive tests
  • Maintains code quality and readability
  • No breaking changes or regressions

The optimizations are particularly valuable for users working with large monorepos and multiple simultaneous AI agents—exactly the use case where Maestro shines.

Suggested Next Steps:

  1. Merge as-is (the minor suggestions above are optional refinements)
  2. Monitor real-world performance impact
  3. Consider adding performance metrics collection for future optimization opportunities

Great work on this PR! The attention to detail in both implementation and testing is commendable. 🎉

@reachraza reachraza merged commit 6d3e149 into main Jan 30, 2026
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