❓ The Problem

Blockchains are immutable 🪨 …but real-world apps need to evolve:

• Bug fixes 🐞
• UX improvements 🎨
• Economic tweaks ⚖️

If you just redeploy a module or mutate live objects without a plan, you risk: 💥 breaking invariants 💥 trapping user assets 💥 mismatching client logic

👉 The solution: safe upgrade & migration strategies.

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🚀 Upgrade Approaches — High Level

1. Non-breaking changes ✅

   • Add new modules/types.
   • Append non-critical fields.
   • Clients that don’t care can ignore them.

2. Breaking changes (with migration) 🔄

   • Publish new modules.
   • Write explicit migration functions that convert old state into new types.

3. Indirection & upgradeable references 🪞

   • Use pointers (like ImplPointer) that reference current logic.
   • Upgrade by swapping the pointer to a new implementation.

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🏗️ Safe Upgrade Design Patterns

A. Indirection (proxy/pointer) pattern

• Create a small immutable ImplPointer object 🔑.
• Consumers read logic/data via this pointer.
• Upgrading = swapping pointer under admin capability (low contention).

B. Versioned objects + migration helpers

• Publish ModuleV2.
• Add migrate(old_obj) function that consumes V1 objects and returns V2.
• Users or admins can trigger migration.

C. Config & parameter objects

• Store parameters in isolated config objects ⚙️.
• Update them with admin capability.
• Emit events so off-chain indexers stay synced 📡.

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🧭 Step-by-Step Migration Recipe

1. Audit invariants 📋 — write down the rules that must always hold (balances, ownership).
2. Design new schema ✏️ — decide what fields to keep, rename, or drop.
3. Write migration function 🛠️ — consume old object → validate → create new one.
4. Test on devnet 🧪 — with realistic data volumes.
5. Provide opt-in path 🚪 — let users self-migrate when possible.
6. Controlled bulk migration ⏳ — batch in steps, monitor, include rollback.
7. Emit audit events 🔍 — every migration logs source/destination IDs + checksums.

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🎨 Example: Changing Token Representation

• Old: TokenV1 { owner: address, meta_hash: string }
• New: TokenV2 { owner: address, meta_pointer: object::ID, issued_at: u64 }

Migration function:

• Consumes TokenV1.
• Creates new metadata object.
• Returns TokenV2.
• Emits TokenMigrated event 📢.

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🛡️ Operational Best Practices

✅ Limit admin power in hot paths (keep admin objects separate). ✅ Canary migration 🐤 — test on a small subset first. ✅ Backups & snapshots 💾 — off-chain state snapshots = safety net. ✅ Versioning metadata 🔢 — add version fields to objects for easier debugging.

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⚠️ Pitfalls to Avoid

❌ Silent incompatible changes — never repurpose fields secretly. ❌ Single-point admin swap — use multisig for critical upgrades. ❌ Breaking client assumptions — always publish changelogs + SDK shims.

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✅ Outcome

With careful planning — indirection, versioned migrations, and solid testing — you can:

• Keep user assets safe 🔒
• Evolve your app without breaking trust 🤝
• Maintain a clear audit trail of changes 📜

Safe migration isn’t just a dev practice — it’s how you keep your Sui app alive and thriving 🌱.