Extend Smart Contracts

Extend the smart contracts

move/packages/sui_stack_messaging/ is canonical and already published. Do not fork it. To add custom behavior, write your own Move package that depends on it, then wire that package to the canonical TypeScript SDK (via the SealPolicy interface or a $extend() extension). The repo ships two worked Move examples in move/packages/example_app/.

This SKILL.md is a router: it covers what's specific to extending sui_stack_messaging and points to the verbose walk-throughs in reference/. For general Move-language quality checks, the community-maintained move-code-quality-skill is one option.

For canonical mainnet/testnet package IDs (sui_stack_messaging and sui_groups), see the "Canonical package addresses" section in the repo-root CLAUDE.md / AGENTS.md.

What extending looks like

The shape is always the same:

1. Scaffold a separate Move package that adds a [dependencies] entry on sui_stack_messaging (and usually sui_groups). You never modify, re-publish, or fork the canonical package.
2. Write custom entry / public functions or a witness type against the canonical types — PermissionedGroup<Messaging>, EncryptionHistory, and the Messaging* permissions.
3. Publish your package with sui client publish (not the maintainer-only publish/ helper).
4. Wire it to the SDK — either through the SealPolicy interface or as a $extend() extension layered on top of suiStackMessaging.

Start from reference/package-layout.md for the layout and a fresh-package skeleton.

Which pattern do I need?

Decision notes:

• Custom permission — first ask whether you need one. The four canonical permissions (MessagingSender, MessagingReader, MessagingEditor, MessagingDeleter) compose freely. A "moderator who can delete but not edit" is just MessagingDeleter granted without MessagingEditor — no new Move at all. Only declare a new witness type when none of the canonical permissions express your role.
• A Seal policy is client-side wiring, not a $extend() extension — it plugs in via encryption.sealPolicy. The actor-object and permission patterns are pure Move plus the @mysten/sui-groups SDK.
• Granting a custom permission enforces nothing by itself — it only stores on-chain. You enforce it off-chain (fork the relayer) or on-chain (your own Move check). reference/custom-permission.md covers both.

Reference files

• reference/package-layout.md — the move/packages/ layout you build against, plus the skeleton for a fresh extension package (Move.toml deps, why no [addresses] block, pin your revs).
• reference/seal-policy.md — Extension pattern 1: custom Seal policy (subscription / token-gated reader); Move shape plus client-side SealPolicy wiring.
• reference/gated-membership.md — Extension pattern 2: paid / gated self-serve join via the actor-object pattern.
• reference/custom-permission.md — Extension pattern 3: declare, grant, and enforce a custom permission type across Move / SDK / relayer.
• reference/build-and-publish.md — build & test commands and the publish safety checklist (irreversible, costs real SUI; testnet-first; pin deps).
• reference/wire-to-sdk.md — after publishing, expose your package as a $extend() SDK extension on top of suiStackMessaging.

What NOT to do

• Do not fork sui_stack_messaging to add a new policy. Build a new package that depends on it. Forking puts you on a separate upgrade path from canonical.
• Do not redefine messaging permission types (MessagingSender, etc.) in your package. Add new types alongside.
• Do not edit Published.toml for the canonical package. It is committed and load-bearing for upgrade paths.
• Do not add an [addresses] block to your Move.toml — it flips your package to old-style and breaks the build against the new-style canonical package (details in reference/package-layout.md).
• Do not use the maintainer-only publish/ helper for your extension — use sui client publish directly (details in reference/build-and-publish.md).

Cross-links

• Extending guide (TS side, with Move snippets): docs/sui-stack-messaging/Extending.md.
• Move package architecture: move/design_docs/REQUIREMENTS.md.
• Per-module design docs: move/design_docs/sui_stack_messaging/{messaging,seal_policies,encryption_history,group_leaver,group_manager,metadata,version}.md.
• Worked examples: move/design_docs/example_app/{custom_seal_policy,paid_join_rule}.md.
• General Move quality check (community-maintained, optional): https://github.com/1NickPappas/move-code-quality-skill.