We are releasing Compact 0.27.0 today. This version is compatible only with the current Preview environment, not with Testnet-02.
A future ledger update will arrive on Preview (timing pending). When that happens, Compact 0.27 will no longer work with Preview, and we will provide a newer version (0.28.x) aligned with the upgraded ledger.
Because of this, please follow the guidance below carefully.
Which Compact Version Should You Use?
If you are building on Testnet-02 (most developers)
You must continue using Compact 0.26.x.
Compact 0.27.0 will not work on Testnet-02.
If you accidentally upgrade, roll back using: compact update 0.26.0.
If you are building on the Preview environment
Once released, use Compact 0.27.0. This is the only version compatible with the current Preview ledger.
A new ledger upgrade is coming to Preview (no ETA yet), and at that point you will need to update again to Compact 0.28.x (or the matching alpha release). We will provide guidance before that migration happens.
Important Notes
1. compact update will install 0.27 by default
This means Testnet users who run: compact update will break their environment. Always specify the version explicitly if you are building on Testnet.
2. How to detect whether you are on the wrong version
If you compile or deploy a contract using the wrong version, you may see errors related to:
- runtime version mismatch
- missing ledger functionality
- unexpected failures during deploy
If you see deployment errors on Testnet after updating, immediately revert your toolchain: compact update 0.26.0.
We will publish known error patterns once we test them.
3. How to check your versions
Compact toolchain version:
compact compile --version
Devtools version (less relevant for compatibility):
compact --version
Network target is specified in your project config:
network = "testnet"
or
network = "preview"
Compatibility Table
| Network | Current Ledger Version | Compatible Compact Version Now | Compatible Compact Version Later |
|---|---|---|---|
| Testnet-02 | v4 | 0.26.x | TBD (future migration) |
| Preview | v6 (today) | 0.27.0 | 0.28.x after ledger upgrade |
Why this is happening
Preview and Testnet-02 sit on different versions of the ledger (v6 vs v4). These versions are not compatible, and the compiler must match the ledger.
Additionally:
- Preview is receiving a new audited ledger version
- 0.27 is aligned with the current Preview ledger
- 0.28 will be aligned with the upcoming Preview ledger
- Testnet-02 will remain on 0.26 until its next scheduled upgrade/reset
This is a normal part of hardening the platform ahead of Mainnet, but it does require careful coordination and communication.
What to Expect Next
We will publish:
- a follow-up notice when the Preview ledger update is scheduled
- updated guidance when Compact 0.28.x is ready
- known error patterns and troubleshooting steps for incorrect version usage
- an updated “Version Compatibility” section in the docs
Our goal is to make this transition as clear and safe as possible for all teams.
If you run into issues, please reach out in Discord or the forum and include:
- Your Compact version
- Your network (Preview or Testnet-02)
- The error message
- Whether you’re deploying or compiling
TL;DR:
- Compact 0.27.0 releases today.
- Preview → use 0.27
- Testnet-02 → stay on 0.26
- Future Preview ledger update will require 0.28. More info soon.