[Upgrade] SPB testnet to v1.6.0-spb-hotfix

[AkKoks]

SPB Testnet Hotfix Upgrade to v1.6.0-spb-hotfix

Proposal

Network: tacchain_2391-1
Current version: v1.6.0
Target upgrade name: v1.6.0-spb-hotfix
Target build tag: v1.6.0-beta.3
Target commit: 2f1263a5

Overview

This proposal applies a hotfix upgrade for the SPB testnet.

After the previous v1.6.0 upgrade, we found that one historical governance proposal still contains x/vm params encoded with the old upstream protobuf schema. The module state migration was applied, but the old encoded governance proposal payload was not rewritten. Because of that, attempts to query this proposal, or the full proposal list, may fail with a protobuf decode error.

The v1.6.0-spb-hotfix upgrade handler repairs the affected historical governance proposal state so the gov proposal queries can decode correctly again.

For mainnet, this fix will be included directly in the regular v1.6.0 migration path. The v1.6.0-spb-hotfix upgrade is only for the already-upgraded SPB testnet.

Release Artifacts

Artifact	Value
Git tag / build tag	v1.6.0-beta.3
Commit	2f1263a5e32e7dd7d41d2a8b6a028fa4dd9265b1
GitHub release	https://github.com/TacBuild/tacchain/releases/tag/v1.6.0-beta.3

The upgrade proposal plan.info uses .tar.gz binary archives for Cosmovisor compatibility:

Platform	Archive	SHA256
linux/amd64	tacchaind-linux-amd64.tar.gz	eb7f4f2d794490cd0356f9c4225d80b7e0d702dc5bac7f430e8aaa45f4cf3e97
linux/arm64	tacchaind-linux-arm64.tar.gz	4c4620f7a1640e88768a8cc0bcfa1abfed53f4ea5ce98719fb89e8bbd0d9b26d

If your Cosmovisor setup is configured to automatically download and switch binaries from the upgrade plan.info, it should be able to use these archive URLs automatically.

Upgrade Timeline

The target block height will be finalized before proposal submission.

Event	Date (UTC)	Block
Governance proposal submitted	June 5, 2026, 10:00	-
Voting period ends	June 5, 2026, 13:00	-
Upgrade activation time	June 5, 2026, 14:00	20117300
Node update deadline	after upgrade height	-

Validator Actions

Validators should vote during the voting period and prepare the v1.6.0-beta.3 binary before the upgrade height.

At the upgrade height, the chain will halt with the upgrade name v1.6.0-spb-hotfix. After the halt:

1. Stop tacchaind.
2. Back up the node home directory.
3. Replace the binary with the v1.6.0-beta.3 build.
4. Start tacchaind.

The upgrade handler runs automatically on the first block after restart. No manual state migration is required.