Osaka Upgrade Is Live on MST Blockchain Mainnet
What It Involves and What Changed on the Chain ?
Direct Answer
Yes. The Osaka upgrade is live on MST Blockchain mainnet. It activated at 19:20 UTC on 25 October 2026 (00:50 IST on 26 October), starting at block 21,645,894. It adds three execution-layer changes: a 16,777,216 gas cap on any single transaction, a new CLZ opcode, and a 1,024-byte input limit on the MODEXP precompile. Block time stayed at 3 seconds.
What the Osaka upgrade involves, what it changed on the MST chain, and what developers should check.
Osaka was step 10 of 12 in the mainnet release on 25 October. It arrived on its scheduled second, and the chain kept producing a block every 3.000 seconds straight through it. We announced Osaka on testnet ahead of this release. This post covers what the upgrade is, what it now does on mainnet, and what to look at in your own applications.
#21,645,894
First block on Osaka rules
16,777,216
Gas cap per transaction
1,024 bytes
MODEXP input limit
800 / 800
Blocks exactly 3.000 s apart in the Osaka and Mendel window
What Is the Osaka Upgrade?
Osaka is the execution-layer half of Fusaka, an upgrade from the Ethereum ecosystem. Fusaka pairs two parts: Osaka, which covers the execution layer (how transactions and smart contracts run), and Fulu, which covers the consensus layer (how nodes agree on blocks).
MST Blockchain is an EVM-compatible Layer 1, so the execution-layer changes are the ones developers feel. They set the rules for what a transaction is allowed to do and what a contract is able to call. That is the part of Osaka that is now running on MST mainnet.
When It Went Live
Osaka was not a standalone release. It was one stop in a planned sequence of 13 upgrades on 25 October. Here is the part of the sequence around it:
Upgrade UTC IST First block Fermi18:5500:25#21,645,394 Osaka19:2000:50#21,645,894 Mendel19:4001:10#21,646,294 Pasteur20:0001:30#21,646,694
Osaka's first block carried the timestamp 19:20:00, exactly as scheduled. From that block to the start of Pasteur, all 800 blocks were measured at 3,000 milliseconds apart.
The Three Technical Changes
On MST mainnet, Osaka brings three changes. For each one we ran a test before activation and the same test after, so the change can be seen arriving at the right moment and not earlier.
1
Per-transaction gas cap
16,777,216 gas (2 to the power of 24)
Every block has limited room. Without a ceiling, a single transaction can ask for a very large share of it. Osaka sets that ceiling: no transaction may set a gas limit above 16,777,216. A transaction that does is rejected by the node and never enters the chain.
There is plenty of headroom for normal use. The largest transaction gas limit seen on MST mainnet in the 30 days before the upgrade was 6.28 million, under 40% of the cap.
Before Osaka
A transaction with a gas limit of 16,777,217 was accepted and mined in block #21,640,719.
After Osaka
The same request was rejected with: transaction gas limit too high (cap: 16777216, tx: 16777217).
2
CLZ opcode (count leading zeros)
A new low-level instruction for smart contracts
CLZ returns the number of zero bits at the start of a 256-bit value. The value 1 has a single 1 at the very end, so CLZ(1) is 255. Contracts that do bit-level work, such as finding the highest set bit of a number, can now do it with one instruction instead of extra code.
It also gives smart-contract languages and compilers one more primitive to build on.
Before Osaka
Calling CLZ returned an invalid opcode error.
After Osaka
CLZ(1) returned 255.
3
MODEXP input limit
Inputs capped at 1,024 bytes
MODEXP is a built-in precompile for modular exponentiation, the big-number maths behind several kinds of cryptographic checks. Osaka puts an upper bound on the size of its inputs, which in turn bounds how much work a single call can demand.
Calls within the limit behave as before. Only oversized inputs are affected.
Before Osaka
A 1,025-byte input was accepted.
After Osaka
The same input was rejected with: length exceeded 1024 bytes.
What Stayed the Same
Several of the upgrades in the 25 October release behave differently on BNB Smart Chain, where they shorten block time. MST kept its own configuration, and Osaka did not touch it:
3 s
Block time
200
Blocks per epoch
13
Validators per epoch header
0
Out-of-turn blocks
A Note on P-256 (secp256r1)
Descriptions of Fusaka usually list native P-256 support, the curve behind phone passkeys and WebAuthn. On MST mainnet that precompile did not wait for Osaka. It arrived earlier in the same release with the Haber upgrade at 16:35 UTC, and it was verified then at address 0x0000000000000000000000000000000000000100. So passkey-style signature verification is already live on mainnet, alongside Osaka.
What Developers Should Check
1
Transaction gas limits
Look for any script or tool that sets a gas limit above 16,777,216, including very large batch jobs or oversized deployments. Those requests are now rejected. If you have one, split the work across several transactions.
2
MODEXP callers
If a contract calls the MODEXP precompile, confirm its inputs stay within 1,024 bytes.
3
Using CLZ
Contracts that rely on CLZ now work on MST mainnet. They would fail on any chain that has not activated the opcode, so check the target network before deploying elsewhere.
4
Rest of the release
Osaka landed alongside Cancun, Prague and nine other upgrades. Mainnet now supports blob transactions and EIP-7702 smart accounts too. The node reports Pasteur as the current fork, with no further forks scheduled.
How It Was Verified
Two minutes after Osaka activated, read-only checks confirmed CLZ and the MODEXP limit. The gas cap was proven with a live transaction: accepted before activation (transaction 0xd9666f9a...3503, block #21,640,719) and rejected after. Fifteen minutes after Pasteur, the final check at 20:15 UTC showed 3.000-second blocks, a 200-block epoch and 13 validators. Anyone can look up the transaction on mstscan.com.
The full set of test transactions and contract addresses is in our hard fork verification reference.
What Comes Next
The upgrade work is not entirely finished. Fast finality is not yet enabled on mainnet. It will be switched on by validator operators one validator at a time, with 9 of 13 votes needed. The same approach ran on the Coral testnet without interrupting block production.
Test Against the Upgraded Chain
Osaka is live on mainnet. Check your transactions and contracts, and use the Coral testnet to try changes before they go live.
MST Mainnet ExplorerCoral Testnet
Frequently Asked Questions
Is the Osaka upgrade live on MST Blockchain mainnet?
Yes. The Osaka upgrade activated on MST Blockchain mainnet at 19:20 UTC on 25 October 2026 (00:50 IST on 26 October), starting at block 21,645,894. It was step 10 of 12 in the mainnet release and activated on its scheduled second.
What does the Osaka upgrade change on MST Blockchain?
Osaka adds three execution-layer changes on MST mainnet: a hard cap of 16,777,216 gas on any single transaction, a new CLZ (count leading zeros) opcode, and an input length limit of 1,024 bytes on the MODEXP precompile. Each was tested before and after activation.
What is the per-transaction gas cap on MST mainnet?
The cap is 16,777,216 gas per transaction, which is 2 to the power of 24. A transaction with a higher gas limit is rejected by the node and never enters the chain. The largest transaction gas limit used on MST mainnet in the 30 days before the upgrade was 6.28 million.
What does the CLZ opcode do?
CLZ stands for count leading zeros. It returns the number of zero bits at the start of a 256-bit value, so CLZ(1) returns 255. Before Osaka, MST mainnet rejected the opcode as invalid. After activation it returns the correct result.
Did the Osaka upgrade change MST's block time?
No. MST kept its 3-second block time and 200-block validator epoch. Every one of the 800 blocks produced across the Osaka and Mendel window was exactly 3.000 seconds apart.
Do I need to change my smart contracts after Osaka?
Most applications should not be affected. Check any transaction that sets a gas limit above 16,777,216 and any contract that calls the MODEXP precompile with inputs larger than 1,024 bytes. Contracts that want to use CLZ can now do so on mainnet.
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MST Blockchain
mstblockchain.com · October 2026