Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add sethdford/claude-skills --skill schema-evolutiongit clone --depth 1 https://github.com/sethdford/claude-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/sethdford/claude-skills/schema-evolution)<a href="https://agentmods.dev/skills/sethdford/claude-skills/schema-evolution"><img src="https://agentmods.dev/badge/skills/sethdford/claude-skills/schema-evolution.svg" alt="Measured on agentmods" 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 | $0.00035 | $0.00613 |
| Opus 5 | $0.00017 | $0.00307 |
| Sonnet 5 | $0.00007 | $0.00123 |
| Haiku 4.5 | $0.00003 | $0.00061 |
Grade A, and why
schema-evolution 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 7d 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.
How it starts
The opening of the file, as written. The whole thing — 48 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Schema Evolution
Evolve database schemas safely while maintaining backwards compatibility and minimizing downtime.
Context
You are planning schema changes in production systems. Design migrations that don't break deployed clients or services. Read current schemas, deployment frequency, and rollback requirements.
Domain Context
Based on production database migration best practices:
- Backwards Compatibility: Old code continues working with new schema; new code works with both
- Forwards Compatibility: New code can read old data; gracefully handles missing fields
- Zero-Downtime Deployment: Database changes don't require application downtime
- Additive Changes: Adding columns/tables is safe; dropping/renaming requires care
- Dual-Write Pattern: Write to both old and new schema during migration; switch reads
Instructions
-
Plan Phase 1 (Additive): Add new columns/tables. Code ignores new columns for now. Deploy database changes. All existing code still works.
-
Plan Phase 2 (Dual Write): Update application code to write to both old and new schema. Reads can use either. Let data double-write for period (hours to days).
-
Plan Phase 3 (Migrate Data): Background job migrates existing data to new schema. Backfill new fields from old data via transformation.
-
Plan Phase 4 (Code Switch): Update code to read from new schema, write to both. Gradually shift reads: 10% new, 90% old → 50/50 → 100% new.
-
Plan Phase 5 (Cleanup): Once all code reads new schema, remove old schema if safe. Keep removal as separate deployment after week of monitoring.
Anti-Patterns
- Big-Bang Migration: Deploy schema and code changes simultaneously. Result: downtime, hard rollback. Guard: Separate database and application deployments; deploy database first.
- Dropping Columns Without Wrapping Code: Assume all code updated. Result: errors in production. Guard: Wait 1+ releases before drop; deploy code removal first, schema cleanup second.
- No Rollback Plan: Assume migrations succeed. Result: stuck in bad state. Guard: Practice rollbacks; keep old schema for period; verify data integrity.
- Ignoring Hot Data: Migrate huge table in single pass. Result: locks, downtime. Guard: Use online migration tools (pt-online-schema-change, pg-repack); batch smaller tables.
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.
- 7d ago First seen · 48 lines · 35 tokens per session scan A 6b4351ff2243
schema-evolution is a skill published in the GitHub repository sethdford/claude-skills (38 stars, last pushed 5mo ago), licensed MIT. It adds 35 tokens to every session and 613 once invoked, about $0.0002 per session on Opus 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 2026-08-30.
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