deprecation-and-migration

80 / 100 · Low risk

Fine to try.

By addyosmani/agent-skills (GitHub) · coding · 117,315 stars · scanned at commit 39b723c

Manages deprecation and migration. Use when removing old systems, APIs, or features. Use when migrating users from one implementation to another. Use when migrating a database schema in production, such as renaming or dropping a column without downtime (expand/contract). Use when deciding whether to maintain or sunset existing code.

Works with any agent that supports SKILL.md skills.

What this skill can do

Downloads and installs other software

The author does not mention this. It runs automatically when the plugin is installed.

Found in 2 places.

skills/deprecation-and-migration/SKILL.md, line 913. Run the migration verification script: `npx migrate-check`
hooks/session-start.sh, line 19echo '{"hookSpecificOutput": {"hookEventName": "SessionStart", "additionalContext": "agent-skills: jq is required for the session-start hook but was not found o

Connects to the internet

The author does not mention this. It runs automatically when the plugin is installed.

Found in 16 places.

hooks/SDD-CACHE.md, line 3Cross-session citation cache for [`source-driven-development`](../skills/source-driven-development/SKILL.md). Skips redundant `WebFetch` calls without weakening
hooks/SDD-CACHE.md, line 20"matcher": "WebFetch",
hooks/SDD-CACHE.md, line 32"matcher": "WebFetch",

Show 13 more

hooks/SDD-CACHE.md, line 57The stored body is not raw HTML — `WebFetch` post-processes each response through a model using the caller's prompt, so what we cache is one agent's reading of
hooks/SDD-CACHE.md, line 65| `PreToolUse WebFetch` | If an entry exists, sends a `HEAD` request with `If-None-Match` / `If-Modified-Since`. On `304`, blocks the fetch and returns the cach
hooks/SDD-CACHE.md, line 66| `PostToolUse WebFetch` | Captures the response, issues a `HEAD` request to record the current `ETag` / `Last-Modified`, and stores `{url, prompt, etag, last_m
hooks/SDD-CACHE.md, line 76- Cache hit: `WebFetch` is blocked via exit code 2. Claude Code delivers the hook's stderr payload back to the agent as a tool error — this is the intended sign
hooks/SDD-CACHE.md, line 77- Cache miss or stale: `WebFetch` runs normally; the result is stored for next time.
hooks/SDD-CACHE.md, line 1216. Verify the second `WebFetch` is blocked and the cached content is returned (visible in the session transcript as a tool error with `[sdd-cache]` prefix).
hooks/SDD-CACHE.md, line 157- **Every cache write costs an extra HEAD.** Claude Code doesn't expose the response headers that `WebFetch` already received, so the post hook re-queries the o
hooks/sdd-cache-post.sh, line 82HEAD_OUT=$(curl -sI -L --max-time 5 "$URL" 2>/dev/null | tr -d '\r' || true)
hooks/sdd-cache-pre.sh, line 71STATUS=$(curl -sI -o /dev/null -w "%{http_code}" \
hooks/sdd-cache-pre.sh, line 78dbg "not 304, letting WebFetch proceed"
hooks/sdd-cache-pre.sh, line 85dbg "cache HIT, blocking WebFetch with ${#CONTENT} bytes of cached content"
hooks/sdd-cache-pre.sh, line 97printf 'content below as if WebFetch had just returned it.\n\n'
hooks/sdd-cache-pre.sh, line 99printf 'Original WebFetch prompt: "%s". If your angle differs, judge\n' "$ORIGINAL_PROMPT"

Install

Paste this into your terminal. It downloads exactly the version we scanned, not whatever is newest.

if [ -e ~/.agents/skills/'deprecation-and-migration' ] || [ -L ~/.agents/skills/'deprecation-and-migration' ]; then echo 'A skill folder named deprecation-and-migration already exists — not replacing it' >&2; false; else d=$(mktemp -d) && git clone --quiet --filter=blob:none --no-checkout 'https://github.com/addyosmani/agent-skills' "$d" && git -C "$d" checkout --quiet '39b723ceebf81474d0557c1fecd01eddab585563' -- 'skills/deprecation-and-migration' && mkdir -p ~/.agents/skills && cp -R "$d"/'skills/deprecation-and-migration' ~/.agents/skills/'deprecation-and-migration' && rm -rf "$d"; fi

Codex reads ~/.agents/skills directly. For Claude Code, Cursor, Copilot, Gemini CLI, Antigravity or OpenCode, also link it. For Claude Code: ln -s ~/.agents/skills/'deprecation-and-migration' ~/.claude/skills/'deprecation-and-migration' (other agents: ~/.cursor/skills, ~/.copilot/skills, ~/.gemini/skills, ~/.gemini/config/skills, ~/.config/opencode/skills). Or install through the finder skill, which does both.

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Score history

Date	Version	Score
2026-11-14	`39b723c`	80
2026-11-08	`301b02b`	80
2026-11-06	`301b02b`	80