Upcaster
Define a Protean event upcaster — a class that transforms old event payloads to match the current schema version, enabling event schema evolution without breaking stored events. Upcasters extend BaseUpcaster, implement an upcast(data) method, and are registered with @domain.upcaster(event_type=EventClass, from_version=1, to_version=2). The framework automatically chains individual upcasters and applies them lazily during deserialization. Use when the user asks to 'create an upcaster', 'handle event schema migration', 'evolve an event schema', 'add a field to an existing event', 'rename a field in an event', 'migrate old events', 'transform stored events', 'handle event versioning', or when they need to change an event's schema while keeping old stored events compatible.
Security AStatic scan found no risk patternsHow grading works ›
What this skill does
Upcaster is a community-contributed Claude Code skill in the orchestration-frameworks sub-category. It ships as a SKILL.md file that Claude Code auto-discovers under ~/.claude/skills/upcaster/ and loads when your prompt matches the skill's trigger.
When to invoke it: Use when the user asks to 'create an upcaster', 'handle event schema migration', 'evolve an event schema', 'add a field to an existing event', 'rename a field in an event', 'migrate old events', 'transform stored events', 'handle event versioning', or when they need to change an event's schema while keeping old stored events compatible.
Who uses this skill
The Upcaster Claude Code skill is built for Claude Code users and developers across all disciplines looking for general-purpose AI assistance. It's part of ClaudSkills (also referred to as Claude Skills or Claude Code Skills) — the open community-curated registry of 211,000+ SKILL.md files for Anthropic's Claude Code agent and the wider Claude ecosystem (Claude API, Claude Agent SDK).
How to install
Free
Manual install (2 steps)
mkdir -p ~/.claude/skills/upcaster
curl -L https://claudskills.com/skills/upcaster/SKILL.md \
-o ~/.claude/skills/upcaster/SKILL.md
Or just download SKILL.md directly and drop it into ~/.claude/skills/upcaster/. Claude Code auto-discovers it on next session.
Skills live at ~/.claude/skills/upcaster/SKILL.md on macOS/Linux, or %USERPROFILE%\.claude\skills\upcaster\SKILL.md on Windows. See the full install guide for step-by-step instructions.
Telegram
📱 Install from your phone or desktop Telegram
Open @claudskills_bot on Telegram, tap Open Desktop App, and the desktop app installs this skill for you. Or share the bot link with a colleague — they get the same one-tap install. Learn more →
Pro
One-click install via the desktop app
The ClaudSkills desktop app installs any skill directly into ~/.claude/skills/ with one click — no terminal required. Pro starts at $9/mo or $149 lifetime.
Pro
For the full experience including quality scoring and one-click install features for each skill — upgrade to Pro.
Frequently asked questions
How do I install the Upcaster Claude Code skill?
Install via the ClaudSkills desktop app (one click) or copy
SKILL.md from the source repository to
~/.claude/skills/upcaster/SKILL.md and restart Claude Code. Both flows are detailed at
claudskills.com/install/.
What does the Upcaster skill do?
Define a Protean event upcaster — a class that transforms old event payloads to match the current schema version, enabling event schema evolution without breaking stored events. Upcasters extend BaseUpcaster, implement an upcast(data) method, and are registered with @domain.upcaster(event_type=EventClass, from_version=1, to_version=2). The framework automatically chains individual upcasters and applies them lazily during deserialization. Use when the user asks to 'create an upcaster', 'handle event schema migration', 'evolve an event schema', 'add a field to an existing event', 'rename a field in an event', 'migrate old events', 'transform stored events', 'handle event versioning', or when they need to change an event's schema while keeping old stored events compatible.
Is this skill free to install?
Yes. ClaudSkills is an open registry — every skill keeps its source repository's license, and manual install via copy is free. ClaudSkills Pro ($9/mo, $79/yr, or $149 one-time) adds one-click install via the desktop app and a multi-signal Quality Score.
When should I use the Upcaster skill?
Use Upcaster when your Claude Code task falls under the General category — specifically in the orchestration frameworks area. Claude Code auto-discovers installed skills and invokes the right one based on the task description, so you can also ask Claude directly (e.g. "use Upcaster" or describe the task and let Claude pick). Browse related skills at
/category/general/.
What is a Claude Code skill and how does the Upcaster skill fit in?
A Claude Code skill is a
SKILL.md file that lives under
~/.claude/skills/<name>/ and tells the Claude Code CLI agent how to perform a specific task (instructions, prompts, allowed tools). Skills are auto-discovered at session start. Upcaster is one of 67,000+ skills indexed in the open ClaudSkills catalog, classified under the General category. Learn more at
/learn/what-is-a-claude-skill/.
Attribution & license
Cite this skill
If you reference this skill in a blog post, paper, or documentation, you can cite it as:
APA
proteanhq. (2026). Upcaster [Claude Code skill]. ClaudSkills. https://claudskills.com/skills/upcaster/
BibTeX
@misc{upcaster-2026,
author = {proteanhq},
title = {Upcaster [Claude Code skill]},
year = {2026},
publisher = {ClaudSkills},
url = {https://claudskills.com/skills/upcaster/}
}Embed this skill
Promote, attribute, or link this skill from your own README, blog post, or documentation. All three snippets are free to use — no sign-up, no API key. More distribution surfaces →
Badge
[](https://claudskills.com/skills/upcaster/?utm_source=badge&utm_medium=readme&utm_campaign=skill_badge)
<script>
<script src="https://claudskills.com/embed/upcaster.js" async></script>
<iframe>
<iframe src="https://claudskills.com/embed/upcaster.html" width="100%" height="160" frameborder="0" loading="lazy" title="ClaudSkills: Upcaster"></iframe>
Security scan
Grade A · scanned 2026-10-25 — free static scan against the OWASP Agentic Skills Top 10.
The scan flagged 1 of 10 categories (filesystem), including lower-severity patterns. Patterns shown inside code fences are weighted as examples rather than instructions — read the grading methodology for what this does and does not guarantee.
- ✓ Prompt injection
- ✓ Data exfiltration
- ✓ Supply chain
- ✓ Reverse shell
- ✓ Credentials
- ✓ Execution
- ⚠ Filesystem
- ✓ Persistence
- ✓ Obfuscation
- ✓ Network
Show this grade on your repo (click to copy):
[](https://claudskills.com/skills/upcaster/#security)
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