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-831-oss-replacer Type: L3 Worker Category: 8XX Optimization Parent: ln-830-code-modernization-coordinator Executes OSS replacement plans from ln-645-open-source-replacer auditor. For each custom module with an OSS alternative: install package, rewrite imports, run tests, keep or discard atomically. Overview Aspect Details Input Migration plan from docs/project/codebase_audit.md (ln-645 section) OR target module Output Replaced modules, migration report Companion ln-645-open-source-replacer (finds candidates) → ln-831 (executes replacement) Workflow Phases: Pre-flight → Load Plan → Prioritize → Replace Loop → Report Phase 0: Pre-flight Checks Check Required Action if Missing Migration plan OR target module Yes Block replacement Test infrastructure Yes Block (need tests for verification) Package manager available Yes Block (need to install OSS packages) Git clean state Yes Block (need clean baseline for revert) MANDATORY READ: Load shared/references/ci_tool_detection.md — use Test Frameworks section for test detection. Worktree & Branch Isolation MANDATORY READ: Load shared/references/git_worktree_fallback.md — use ln-831 row. Phase 1: Load Migration Plan From Audit Report Read docs/project/codebase_audit.md , extract ln-645 findings: Field Description custom_module Path to custom implementation loc Lines of code in custom module oss_package Recommended OSS replacement confidence How well OSS covers functionality (HIGH/MEDIUM/LOW) api_mapping Custom function → OSS equivalent From Target Module If no audit report: analyze target module, search Context7/Ref for OSS alternatives. MANDATORY READ: Load shared/references/research_tool_fallback.md for MCP tool chain. Phase 2: Prioritize Replacements Priority Criteria 1 (highest) HIGH confidence + >200 LOC (max code reduction) 2 HIGH confidence + 100-200 LOC 3 MEDIUM confidence + >200 LOC 4 MEDIUM confidence + 100-200 LOC Skip LOW confidence (too risky for automated replacement) Phase 3: Replace Loop (Keep/Discard) Per-Module Cycle FOR each replacement candidate (R1..RN): 1. INSTALL: Add OSS package npm install {package} / dotnet add package / pip install 2. REWRITE: Update imports + call sites using api_mapping 3. VERIFY: Run tests IF tests FAIL → DISCARD (revert ALL: uninstall package, restore files) → next 4. TESTS PASS → KEEP 5. DELETE: Remove old custom module (only after keep) 6. LOG: Record replacement for report Atomic Revert on Discard Step Revert Action Package installed Uninstall: npm uninstall / dotnet remove package / pip uninstall Files modified git checkout -- {modified_files} Lock file changed git checkout -- {lock_file} Safety Rules Rule Description One module at a time Never replace multiple modules simultaneously No API signature changes Public API of replaced module must stay compatible Tests required Skip module if no tests cover it (too risky) Confidence gate Skip LOW confidence replacements Phase 4: Report Results Report Schema Field Description source Audit report path or target module candidates_total Total replacement candidates replacements_applied Successfully replaced modules replacements_discarded Failed replacements with reasons replacements_skipped LOW confidence / no test coverage loc_removed Total lines of custom code removed packages_added New OSS packages installed details[] Per-replacement: module, package, LOC removed Configuration Options :

Source

audit_report : "docs/project/codebase_audit.md" target_module : ""

Confidence

min_confidence : "MEDIUM"

MEDIUM | HIGH

Verification

run_tests : true

Safety

require_test_coverage : true

Skip modules with no tests

delete_old_module : true

Delete custom module after successful replacement

Error Handling Error Cause Solution Package not found OSS package name changed Search Context7/Ref for current name API mismatch OSS API differs from mapping Query docs for correct API, attempt fix Circular dependency New package conflicts Skip replacement, log as manual No test coverage Custom module untested Skip (too risky for automated replacement) References ../ln-645-open-source-replacer/SKILL.md (companion: finds candidates) shared/references/ci_tool_detection.md (test detection) shared/references/research_tool_fallback.md (MCP tool chain) Definition of Done Migration plan loaded from audit report or target module analyzed Candidates prioritized by confidence + LOC Each replacement applied atomically: install → rewrite → test → keep/discard Discarded replacements fully reverted (package + files + lock) Kept replacements: old custom module deleted Report returned with candidates total, applied, discarded, LOC removed Version: 1.0.0 Last Updated: 2026-03-08