Stable Memory

If you're building on Internet Computer, this is your guide to not losing user data when you upgrade a canister. It covers the persistent actor pattern in Motoko (where `let` and `var` just work automatically) and StableBTreeMap with MemoryManager in Rust (because thread_local RefCell gets wiped on every deploy). The mistakes section is genuinely useful: it walks through the pre_upgrade instruction trap that bricks canisters, the type change gotchas in Motoko, and why Bound::Unbounded beats Bound::Bounded for forward compatibility. Includes working code for both languages with CBOR serialization. Read this before your first canister upgrade, not after you've lost production data.

Install to Claude Code

npx -y skills add dfinity/icskills --skill stable-memory --agent claude-code