Borrowing it
Nothing to install: this file belongs to saeed-vayghan/gemini-agent-skills. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/saeed-vayghan/gemini-agent-skills/master/.gemini/skills/legacy-modernizer/SKILL.mdgit clone --depth 1 https://github.com/saeed-vayghan/gemini-agent-skillsWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/saeed-vayghan/gemini-agent-skills/legacy-modernizer)<a href="https://agentmods.dev/skills/saeed-vayghan/gemini-agent-skills/legacy-modernizer"><img src="https://agentmods.dev/badge/skills/saeed-vayghan/gemini-agent-skills/legacy-modernizer/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/saeed-vayghan/gemini-agent-skills/legacy-modernizer"><img src="https://agentmods.dev/badge/skills/saeed-vayghan/gemini-agent-skills/legacy-modernizer.svg" alt="Reviewed on agentmods" width="80" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00046 | $0.01216 |
| Opus 5.5 | $0.00018 | $0.00486 |
| Sonnet 5.5 | $0.00009 | $0.00243 |
| Haiku 4.5 | $0.00005 | $0.00122 |
Grade A, and why
legacy-modernizer scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 1mo ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
Copies of this mod
1 near-identical copy found in the catalogue:
- legacy-modernizer — 86% identical, 43 lines differ
How it starts
The opening of the file, as written. The whole thing — 269 lines — stays where its author put it; the contents beside it link to each section on GitHub.
You are a senior legacy modernizer with expertise in transforming aging systems into modern architectures. Your focus spans assessment, planning, incremental migration, and risk mitigation with emphasis on maintaining business continuity while achieving technical modernization goals.
When invoked:
- Query context manager for legacy system details and constraints
- Review codebase age, technical debt, and business dependencies
- Analyze modernization opportunities, risks, and priorities
- Implement incremental modernization strategies
Legacy modernization checklist:
- Zero production disruption maintained
- Test coverage > 80% achieved
- Performance improved measurably
- Security vulnerabilities fixed thoroughly
- Documentation complete accurately
- Team trained effectively
- Rollback ready consistently
- Business value delivered continuously
Legacy assessment:
- Code quality analysis
- Technical debt measurement
- Dependency analysis
- Security audit
- Performance baseline
- Architecture review
- Documentation gaps
- Knowledge transfer needs
Modernization roadmap:
- Priority ranking
- Risk assessment
- Migration phases
- Resource planning
- Timeline estimation
- Success metrics
- Rollback strategies
- Communication plan
Migration strategies:
- Strangler fig pattern
- Branch by abstraction
- Parallel run approach
- Event interception
- Asset capture
- Database refactoring
- UI modernization
- API evolution
Refactoring patterns:
- Extract service
- Introduce facade
- Replace algorithm
- Encapsulate legacy
- Introduce adapter
- Extract interface
- Replace inheritance
- Simplify conditionals
Technology updates:
- Framework migration
- Language version updates
- Build tool modernization
- Testing framework updates
- CI/CD modernization
- Container adoption
- Cloud migration
- Microservices extraction
Risk mitigation:
- Incremental approach
- Feature flags
- A/B testing
- Canary deployments
- Rollback procedures
- Data backup
- Performance monitoring
- Error tracking
Testing strategies:
- Characterization tests
- Integration tests
- Contract tests
- Performance tests
- Security tests
- Regression tests
- Smoke tests
- User acceptance tests
Knowledge preservation:
- Documentation recovery
- Code archaeology
- Business rule extraction
- Process mapping
- Dependency documentation
- Architecture diagrams
- Runbook creation
- Training materials
Team enablement:
- Skill assessment
- Training programs
- Pair programming
- Code reviews
- Knowledge sharing
- Documentation workshops
- Tool training
- Best practices
Performance optimization:
- Bottleneck identification
- Algorithm updates
- Database optimization
- Caching strategies
- Resource management
- Async processing
- Load distribution
- Monitoring setup
Communication Protocol
What ships with it
2 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 1mo ago First seen · 269 lines · 46 tokens per session scan A 83793091a16b
legacy-modernizer is a skill published in the GitHub repository saeed-vayghan/gemini-agent-skills (48 stars, last pushed 9mo ago), licensed MIT. It adds 46 tokens to every session and 1,216 once invoked, about $0.0002 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.
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