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 agentmods add skills/arjunprabhulal/devops-skills/data-migrationnpx skills add arjunprabhulal/devops-skills --skill data-migrationgit clone --depth 1 https://github.com/arjunprabhulal/devops-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/arjunprabhulal/devops-skills/data-migration)<a href="https://agentmods.dev/skills/arjunprabhulal/devops-skills/data-migration"><img src="https://agentmods.dev/badge/skills/arjunprabhulal/devops-skills/data-migration.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 | $0.00116 | $0.01594 |
| Opus 5 | $0.00058 | $0.00797 |
| Sonnet 5 | $0.00023 | $0.00319 |
| Haiku 4.5 | $0.00012 | $0.00159 |
Grade A, and why
data-migration 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 3d 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 — 130 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Data Migration
The instinct when a schema needs to change is to write one migration that gets the database from old shape to new shape and run it. That instinct is exactly what causes downtime: a single atomic cutover means the old code and the new code cannot both be correct at the same moment, so somewhere in the deploy there is a window where reads or writes are wrong.
The fix is to stop treating "old schema" and "new schema" as two states connected by one migration, and instead treat the migration as a sequence of states where old and new coexist, each individually safe, each individually undoable.
A migration that cannot be paused halfway through, with both old and new still working, is not actually a migration — it is a scheduled outage with a script attached.
For a worked SQL walkthrough of the expand, backfill, and contract phases, read
references/expand-contract.md.
1. Split every migration into expand, migrate, contract
Expand-then-contract is the pattern underneath every zero-downtime schema change: add the new thing without touching the old thing, move the data, then remove the old thing only once nothing depends on it anymore.
- Expand: add the new column, table, or field alongside the existing one. Nothing reads or depends on it yet, so this step alone cannot break anything running in production.
- Migrate: backfill historical data and start writing to both old and new. This is the phase with real risk, and it is where the rest of this skill's sections apply.
- Contract: once every reader has moved to the new shape and it has run correctly for a observation period, remove the old column, table, or field.
Each phase ships as its own deploy, sequenced with normal rollout controls — see
deployment-strategies for how to stage and gate a rollout, since migration phases are just
deploys with an extra constraint: the previous phase must already be stable in production.
Done when: the migration is written as three separate, independently deployable changes, not one script that jumps from old shape to new shape.
What ships with it
1 file 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.
- 3d ago First seen · 130 lines · 116 tokens per session scan A b49574be87b7
data-migration is a skill published in the GitHub repository arjunprabhulal/devops-skills (2 stars, last pushed 9d ago), licensed MIT. It adds 116 tokens to every session and 1,594 once invoked, about $0.0006 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 2026-08-31.
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