DEX in Telegram Mini App on TON: Building Swaps and Liquidity

Building a DEX in a Telegram Mini App on TON

The TON ecosystem has taken off: Mini Apps gained access to 900 million users, the blockchain entered the top 5 in DeFi activity, and total liquidity in pools exceeded 300 million TON. Many teams tried to port the familiar Uniswap interface but faced a surprise — a DEX on TON is fundamentally different from Ethereum counterparts. We specialize in such applications and know every pitfall: from asynchronous messages to webview limitations. A typical DEX on TON is not a Uniswap clone; the architecture is built on the actor model, where each contract is an independent process exchanging messages through queues. The Telegram Mini App adds its own constraints: a small screen, gestures, themes.

Let's dive into the key features of token swapping.

How Does a Swap Work on TON?

In Ethereum, swap() is an atomic operation: either everything executes or it rolls back. In TON, each contract is a separate actor, messages between them are asynchronous. A swap on StonFi works like this:

1. The user sends a jetton transfer with op-code 0xf8a7ea5 to the LP Pool.
2. The LP Pool processes the message and sends the output jetton back.
3. If something goes wrong, a bounced message returns the original tokens.

This flow takes 3–5 seconds and several blocks. The UI must reflect this: not a 5-second spinner, but a clear state "transaction sent, awaiting confirmation." We poll the transaction status via the TON API (/v2/transactions/{hash}) every 1–2 seconds. The average transaction cost is 0.05 TON — an order of magnitude lower than on Ethereum.

What Limitations Does the Telegram Mini App Impose?

The Mini App runs in a webview with limited space — typically 375px wide and up to 600px tall. Here are three patterns we implement in every project.

MainButton — Telegram's native button at the bottom of the screen. We use it for the primary action (Swap, Confirm), not rendering our own button on top.

WebApp.MainButton.setText('Confirm Swap');
WebApp.MainButton.onClick(() => executeSwap());
WebApp.MainButton.show();

HapticFeedback — on successful transaction: WebApp.HapticFeedback.notificationOccurred('success'). On error: 'error'. A small detail that noticeably improves the app's feel.

Theme: WebApp.themeParams returns the colors of the current Telegram theme. The app must adapt to the user's dark/light theme, not fix its own.

BackButton: when navigating deeper (transaction details, token selection) — show WebApp.BackButton, hide it on return.

How Does TON Connect Surpass the Built-in Wallet?

TON Connect is a wallet connection protocol, similar to WalletConnect for TON. In the context of Telegram Mini Apps, there's a nuance: Tonkeeper, MyTonWallet, and the built-in Telegram Wallet all implement TON Connect, but with different capabilities. The built-in Telegram Wallet (available via window.Telegram.WebApp.openInvoice) only works for TON transfers, not for jetton operations. For DEX swaps, an external wallet via @tonconnect/ui-react is required. TON Connect is 5 times more convenient for Jetton swaps: it supports any decentralized transfers, not just TON. This means a deep link to the wallet's mobile app — an extra UX step we explain to the user via a hint.

Mini App Architecture

Tech Stack

Jetton Addresses and the Friendly Address Format

In TON, there is no global token address — each user has their own jetton wallet address (derived from the master jetton contract + owner address). Before displaying a balance or performing a swap, you need to get the user's jetton wallet address:

const jettonMaster = Address.parse(USDT_MASTER_ADDRESS);
const jettonWalletAddress = await tonClient.runMethod(
  jettonMaster, 
  'get_wallet_address',
  [{ type: 'slice', cell: beginCell().storeAddress(userAddress).endCell() }]
);

This is an async call for each token, which we cache. Without caching, the UI lags when loading balances — a typical beginner mistake.

Price Charts

To display a price chart inside the Mini App, we use TradingView Lightweight Charts (minimal bundle ~50KB). Data: OHLCV from the StonFi subgraph or TON API historical prices. Update via WebSocket if realtime is needed, polling every 30 seconds if near-realtime is sufficient. Important: charts are not interactive on mobile webview — pinch-to-zoom conflicts with Telegram's native scroll. We implement only a static chart with tap-to-view a specific candle.

Liquidity Management

If the Mini App includes LP functionality (add/remove liquidity), we display the current pool share and impermanent loss. IL is calculated off-chain:

IL% = 2 * sqrt(price_ratio) / (1 + price_ratio) - 1

Where price_ratio = current_price / entry_price. If IL > 5%, we show a warning to the user.

Working Process

What's Included

• Integration of TON Connect and support for multiple wallets (Tonkeeper, MyTonWallet).
• Full swap interface with routing through StonFi and DeDust.
• Price chart display (TradingView Lightweight Charts).
• Caching mechanism for jetton wallet addresses for fast balance loading.
• Handling of asynchronous transactions with status polling and bounced messages.
• Adaptation to Telegram themes (dark/light) and native elements (MainButton, HapticFeedback).
• Technical documentation and team training.

We have been developing DeFi services for over 10 years and have completed 30+ projects on Ethereum, Solana, and TON. Every code undergoes auditing with Slither and Mythril. We guarantee stable smart contract operation and deadlines. Contact us to evaluate your project — we'll offer an optimal solution considering your business requirements. Request DEX Mini App development and get an engineer's consultation.

DeFi Protocol Development

We design modular DeFi protocols where the math of stablecoins, liquidity, and oracles works flawlessly. Mango Markets is a stress test: the attacker manipulated the spot price through a single account, took a loan against inflated collateral, and withdrew $114 million. The oracle took the price from a single source without TWAP. Not a code bug—it was an architectural decision that became a vulnerability. Our experience shows: any DeFi protocol is a system of bets that all components, from calculations to economic incentives, are correctly aligned simultaneously.

We don't write code under the 'if it works, don't touch it' mindset. We model stress scenarios: cascading liquidations, depegs, flash loans. Only then do we build events that won't break the protocol.

Why are oracles a critical component of DeFi?

Most major DeFi hacks started with oracle manipulation. Let's break down the three layers we use in every project.

Spot price as oracle—not an option. Uniswap v2 spot price can be shifted by a flash loan in one transaction. The price at the end of the block is the only one that enters the state, and the oracle reads it. Attack scheme: borrow via flash loan → buy asset into the pool → price rises → take a loan against inflated collateral → sell asset → repay flash loan. One transaction.

TWAP as protection. Uniswap v3 observe() averages the price over a period (30 minutes). Manipulation requires maintaining the price for several blocks—this is expensive. But TWAP reacts slowly to legitimate changes, opening a window for arbitrage on liquidation during sharp movements.

Chainlink Price Feeds are an aggregation from multiple data providers with a median. Standard for lending. Problem: heartbeat 1–24 hours and deviation threshold 0.5%. If the price doesn't move, the feed may not update for a day. In volatile markets—lag.

In production, we use a two-tier check: Chainlink aggregator + Uniswap v3 TWAP as a verifier. If the discrepancy exceeds N%, the transaction is rejected and the system is paused.

How to protect a DeFi protocol from flash loan attacks?

Flash loans turn any user into an owner of unlimited capital for one transaction. Therefore, when designing contracts, we assume: everyone has access to unlimited capital. This completely changes the threat model.

Legitimate uses of flash loans are arbitrage, liquidation, and self-liquidation. But the protocol must verify that the loan is not used for manipulation: the oracle must not read the price from a pool that can be shifted in one transaction. We add checks on block.timestamp and minimum liquidity depth.

Key Components of DeFi Architecture

AMM: From x*y=k to Concentrated Liquidity

Uniswap v2 uses x * y = k. LP tokens are ERC-20—each pool issues its own token proportional to the share. Problem: liquidity is spread across the entire curve, most of it unused.

Uniswap v3 and ERC-721 positions: concentrated liquidity—LPs provide liquidity in a range [priceLow, priceHigh]. Capital efficiency up to 4000x for stable pairs. But ERC-721 breaks vault strategies built for ERC-20. Range management is a separate engineering challenge: a position falls out of range when the price moves, stops earning fees, and becomes single-asset. Protocols like Arrakis Finance automatically rebalance. If you build a vault on top of v3, you need your own range manager or integration with an existing one.

Slippage in v3 is calculated via sqrtPriceX96—96-bit fixed-point math. Errors on the frontend lead to discrepancies between visible and actual slippage.

Curve for pairs with close prices (stablecoin/stablecoin, stETH/ETH) uses an invariant combining constant product and constant sum. Lower slippage within the peg range. Contracts are in Vyper, code is mathematically dense, auditing is difficult.

Lending Protocols: Collateral, Liquidation, Bad Debt

LTV defines the maximum loan against collateral. Liquidation threshold is the level for liquidation. The difference is the buffer for the liquidator. Typical example: LTV 75%, liquidation threshold 80%, bonus 5%. If the price drops 20%+, the position is open for liquidation.

Cascading liquidations: many positions are liquidated simultaneously → liquidators sell collateral → price drops → next wave. LUNA/UST 2022 is a classic cascade.

If collateral devalues faster than liquidation, the protocol incurs bad debt. Aave uses a Safety Module (staked AAVE), Compound uses reserves. Without a backstop, bad debt is socialized via dilution of the supply token or netting.

Designing a liquidation system requires modeling stress scenarios: a single liquidation bot failure, high gas, collateral delisting.

Yield Farming and Incentive Mechanics

Liquidity mining distributes governance tokens to LP providers. Problem: mercenary capital—farmers come, sell tokens, leave. TVL is illusory.

Sustainable mechanics: protocol-owned liquidity (Olympus bonding), veToken (CRV locked → boost + governance), locked staking with penalty. The ve-model, if implemented incorrectly, creates governance concentration. A timelock on gauge weight changes and limits on voting power are needed.

What Our DeFi Protocol Development Includes

• Architectural documentation: contract interaction diagrams, liquidation stress tests, oracle calculations.
• Implementation in Solidity 0.8.x with OpenZeppelin 5.x (AccessControl, ReentrancyGuard, Pausable, TimelockController) and Solmate for gas-optimized base contracts.
• Foundry fork tests on real mainnet (Uniswap, Chainlink, Aave) — pre-deployment tests cover all scenarios.
• Audit: at least two independent auditors for TVL over $1M. Code4rena or Sherlock for bug bounty.
• Deployment with Gnosis Safe 3/5 multisig + timelock 48–72 hours.
• Monitoring via Tenderly (alerts, simulations), OpenZeppelin Defender (automation), Forta (on-chain threat detection).
• Post-launch support: updates, patches, upgrades via proxy.

Our Expertise and Experience

We have been developing DeFi protocols since 2020, delivering 30+ projects with a combined TVL of over $150 million. Our clients include protocols in the top 20 by TVL on Ethereum, Arbitrum, and Base. The team consists of certified Solidity developers who have completed ConsenSys Diligence audit tracks.

DeFi basic principles that we apply in practice.

Timelines

• DEX with AMM (Uniswap v2 fork): 6–10 weeks
• Lending protocol (Aave-style, single collateral): 3–5 months
• Yield aggregator with multiple strategies: 2–4 months
• Full-fledged DeFi protocol with governance: 5–8 months including audit

Cost is calculated individually—contact us for a project estimate.

Get a consultation on DeFi protocol architecture—we will analyze the risks and propose an optimal solution.