Sub-second finality: how to adapt your project

TON is rolling out Catchain 2.0, a consensus upgrade targeting sub-second block finality on mainnet in early April 2026.

What's changing:
– Block interval: ~2.5s → 200–400ms
– Finalization lag: ~10s → ~1s
– Throughput: up to ~5 blocks/sec

But a faster chain alone won't help users if apps still rely on old API.

We've published a step-by-step adoption guide covering:

🔹 Wallets & dApps: switch to TON Center Streaming API v2. Handle all four statuses: pending → confirmed → finalized → trace_invalidated.
🔹 Self-hosted nodes & liteservers: update to the latest release with Catchain 2.0 support before mainnet activation.
🔹 Indexers: prepare for up to 10x more blocks/sec. Connect to testnet and verify no lag accumulates over 30+ minutes.

Testnet already runs at sub-second speed. Test there now.

MyTonWallet and tonscan.org already use Streaming API and have nearly halved their reaction time, even before the mainnet upgrade.

📖 Full guide: How to adopt sub-second finality

Start adapting today. If your app isn't ready, users won't notice any improvement.

🫧 Tolk v1.3: moving toward a general-purpose language

After the previous post, this release may feel less surprising — but still a bit unusual.

The reason is simple: Tolk is no longer evolving only as a contract language. It is becoming a foundation for the toolchain I described earlier.

This release focuses on features beyond contracts — introducing general-purpose capabilities needed for libraries and frameworks.

✅ Notable changes in Tolk v1.3:

1. Type array<T> — dynamically sized arrays backed by TVM tuples.
2. Type unknown — a TVM primitive with unknown contents.
3. Type lisp_list<T> — nested two-element tuples (FunC-style).
4. Type string — text chunks backed by snaked cells, with StringBuilder for concatenation.
5. Compile-time string methods: "str".crc32(), "str".sha256(), etc.
6. Null coalescing operator — ?? like in TypeScript.
7. Import path mappings — import "@third_party/utils".
8. Compile-time reflection via @stdlib/reflection.
9. Custom serializers now support structures and generics.
10. The compiler now reports multiple errors at once.
11. Focused on stability — fixed dozens of minor issues found by LLM fuzzing.
12. Extensive internal refactoring towards being stateless and multi-threaded.

PR on GitHub with detailed info.

✔ Arrays: redesigned tuples

Working with TVM tuples has been fully redesigned. There is now array<T> — a dynamically sized container:

// array<int>
var numbers = [1, 2, 3];

// array<Point?>
var optPoints = [
    Point { x: 10, y: 20 },
    Point { x: 30, y: 40 },
    null,
];

- methods push, get(idx), etc.
- any T, including sub-arrays like array<array<int>>
- automatically serialized into snake cells
- max size: 255 (TVM limitation)

✔ The `unknown` type

Raw TVM tuple exists, but it's no longer built-in. It's just an array... of something unknown:

type tuple = array<unknown>

The unknown gives access to the untyped TVM stack, fully integrated into the type system.

✔ The `string` type

TVM has no strings — only binary slices. Strings were always just a convention over binary data.

Now Tolk has strings built-in.

// string
val str = "hello";

- strings are cells (not slices)
- long strings are snake cells under the hood
- methods calculateLength, equalTo, etc.
- on-chain/off-chain encoding for jettons and NFTs to comply with TEPs

StringBuilder encapsulates cell manipulation:

StringBuilder.create()  
    .append(content.commonContent)  
    .append(individualNftContent)  
    .build()

By the way, compile-time functions now look cleaner: "str".crc32() and so on.

✔ Import path mappings

The import statement now accepts @aliases:

import "@common/jettons"
import "@third_party/math-lib"

This is similar to widely used path mappings in TypeScript.

✔ Compile-time reflection

Many additions in v1.3 make sense not for contracts, but for frameworks. For example, take a look at one of reflect features:

fun log(msg: string, loc: SourceLocation = reflect.sourceLocation()) {
     debug.print(loc.lineNo);
}

fun demo() {
     log("a");    // prints K — current line no
     log("b");    // prints K+1
}

Why is this useful? It allows errors to point to the original call site — for example, expect(...) in tests — by carrying source location at compile time.

⚙️ A huge portion of internal refactoring

A lot of work has been done inside the compiler core, peephole optimizations, and memory management.

Final result: tolk compiler is now thread-safe and re-invokable within a single process. It will be embedded into an external toolchain written in Rust, communicating via FFI.

... And more

Dozens of independent improvements. Combined, they cover the requirements not only for contracts, but for abstract libraries and the upcoming toolchain.

Feel free to check the description on GitHub.

🌳 And one more thing! Wallet-v5, compiled with Tolk v1.3, reduces gas usage by 30% compared to FunC. As of Tolk v1.0, the savings were "only" 20%. Take a look at new benchmarks.

🚀 The AI Hackathon review period has been extended until April 3.

The results exceeded all expectations: over 160 submissions, 4x the previous contest.

The volume and variety of projects submitted have genuinely impressed us. A strong mix of thoughtful, creative, and technically impressive work from across the ecosystem.

We definitely didn’t expect that. So, we are extending the review period to April 3 to ensure we have enough time to review every submission thoroughly.

While you wait, two new features just dropped on the Identity platform:

🔹Makers. Add your teammates to submission. Everyone gets the participation badge.
🔹Comments. Talk about projects. Feedback, questions, discussion, all on submission pages.

Thank you for the energy, creativity, and effort you brought to this hackathon.

Keep building! ✨😎

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