Paths: File paths (shared/, references/, ../ln-*) are relative to skills repo root. If not found at CWD, locate this SKILL.md directory and go up one level for repo root.

ln-813-runtime-optimizer

Type: L3 Worker Category: 8XX Optimization Parent: ln-810-performance-optimization-coordinator

Fixes runtime performance issues found by ln-653-runtime-performance-auditor. Each fix verified via tests + lint with keep/discard pattern.

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Overview

| Aspect | Details | |--------|---------| | Input | Audit findings from docs/project/persistence_audit.md (ln-653 section) OR target file | | Output | Optimized code, verification report | | Companion | ln-653-runtime-performance-auditor (finds issues) → ln-813 (fixes them) |

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Workflow

Phases: Pre-flight → Load Findings → Prioritize → Fix Loop → Report

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Phase 0: Pre-flight Checks

| Check | Required | Action if Missing | |-------|----------|-------------------| | Audit findings OR target file | Yes | Block optimization | | Test infrastructure | Yes | Block (need tests for verification) | | Linter available | No | Skip lint step in verification | | Git clean state | Yes | Block (need clean baseline for revert) |

MANDATORY READ: Load shared/references/ci_tool_detection.md — use Test Frameworks + Linters sections.

Worktree & Branch Isolation

MANDATORY READ: Load shared/references/git_worktree_fallback.md — use ln-813 row.

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Phase 1: Load Findings

From Audit Report

Read docs/project/persistence_audit.md, extract ln-653 findings:

| Finding Type | Optimization | |--------------|-------------| | Blocking IO in async | asyncio.to_thread(), aiofiles, async HTTP client | | String concat in loop | StringBuilder (.NET), "".join() (Python), template literals (JS) | | Unnecessary allocations | Pre-allocate collections, object pooling, Span<T> | | Sync sleep in async | asyncio.sleep(), Task.Delay(), setTimeout | | Redundant serialization | Cache serialized form, avoid round-trip JSON in memory |

From Target File

If no audit report: scan target file for runtime patterns matching the table above.

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Phase 2: Prioritize Fixes

| Priority | Criteria | |----------|----------| | 1 (highest) | Blocking IO in async context (blocks event loop) | | 2 | Sync sleep in async (starves thread pool) | | 3 | Allocations in hot loop (GC pressure) | | 4 | String concatenation patterns | | 5 | Other micro-optimizations |

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Phase 3: Fix Loop (Keep/Discard)

Per-Fix Cycle

FOR each finding (F1..FN):
  1. APPLY: Edit code (surgical change)
  2. VERIFY: Run tests
     IF tests FAIL → DISCARD (revert) → next finding
  3. VERIFY: Run lint (if available)
     IF lint FAIL → DISCARD (revert) → next finding
  4. BOTH PASS → KEEP
  5. LOG: Record fix for report

Keep/Discard Decision

| Condition | Decision | |-----------|----------| | No tests cover affected file/function | SKIP finding — log as "uncovered, skipped" | | Tests + lint pass | KEEP | | Tests fail | DISCARD + log reason | | Lint fail (new warnings) | DISCARD + log reason | | Lint unavailable | KEEP (tests sufficient) |

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Phase 4: Report Results

Report Schema

| Field | Description | |-------|-------------| | source | Audit report path or target file | | findings_total | Total findings from audit | | fixes_applied | Successfully kept fixes | | fixes_discarded | Failed fixes with reasons | | fix_details[] | Per-fix: finding type, file, before/after description |

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Configuration

Options:
  # Source
  audit_report: "docs/project/persistence_audit.md"
  target_file: ""

  # Verification
  run_tests: true
  run_lint: true

  # Scope
  fix_types:
    - blocking_io
    - sync_sleep
    - unnecessary_alloc
    - string_concat
    - redundant_serialization

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Error Handling

| Error | Cause | Solution | |-------|-------|----------| | No audit findings | ln-653 not run or no issues | Report "no findings to optimize" | | Async rewrite complex | Deep call chain affected | Log as manual step, skip | | Framework-specific pattern | Unknown async framework | Query Context7/Ref for docs |

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References

• ../ln-653-runtime-performance-auditor/SKILL.md (companion: finds issues)
• shared/references/ci_tool_detection.md (test + lint detection)

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Definition of Done

• Findings loaded from audit report or target file scan
• Fixes prioritized (blocking IO first, then sync sleep, allocations, string concat)
• Each fix applied with keep/discard: tests + lint pass → keep, either fails → discard
• Report returned with findings total, fixes applied, fixes discarded

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Version: 1.0.0 Last Updated: 2026-03-08