Extension Object Storage

Adds off-chain file storage with on-chain references for handling images, videos, and documents beyond IC limits. You use Storage.ExternalBlob types in your backend to track files while the actual content lives elsewhere with browser-cached HTTP access. Setup requires both the mops package and npm package together or uploads silently fail with 403s. The frontend ExternalBlob class handles uploads with progress tracking and gives you getDirectURL() for display or getBytes() for downloads. Main gotcha is never using Text for file fields and making sure the mixin goes in main.mo. Good fit if you need a gallery or file manager without hitting canister storage constraints.

skills.sh installs: 30.8K
GitHub stars: 2
last updated: Aug 21, 2026

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Install

$ npx -y skills add caffeinelabs/skills --skill extension-object-storage --agent claude-code

Installs into .claude/skills of the current project.

Files

Object Storage

Object storage extension for Caffeine AI.

Overview

This skill adds off-chain file/object storage with on-chain references. The MixinObjectStorage mixin provides infrastructure for file operations; you track uploaded files in your own data structures using Storage.ExternalBlob.

Required Setup Checklist

All four steps are mandatory. Skipping any one causes 403 Forbidden: Invalid payload at upload time.

mops dependency — add caffeineai-object-storage to mops.toml under [dependencies].
Mixin invocation — include MixinObjectStorage() in main.mo (imported from "mo:caffeineai-object-storage/Mixin").
Storage.ExternalBlob types — every data field that represents a file MUST use Storage.ExternalBlob, never Text.
Frontend npm package — @caffeineai/object-storage installed and ExternalBlob.fromBytes(bytes, file.type, file.name) used at the call site.