How to Architect an Intent-Driven DeFi Aggregator

An intent-driven aggregator shifts the paradigm from transaction execution to outcome specification. Instead of requiring users to manually construct a complex swap with specific routes and protocols, they simply declare a goal, such as "Swap 1 ETH for the best possible amount of USDC on Ethereum within 30 seconds." The aggregator's architecture is responsible for solving for this intent, finding the optimal path, and submitting the transaction on the user's behalf. This requires a backend system that interprets, solves, and fulfills these declarative statements.

The core architecture consists of three primary layers. The Intent Expression Layer defines a standard for users to submit their goals, often using a domain-specific language (DSL) or structured JSON schema. The Solver Network Layer is a competitive marketplace of off-chain solvers that take the expressed intent, compute the optimal execution path across DEXs and bridges, and submit a bundled solution. Finally, the Execution and Settlement Layer verifies the solver's proposed transaction, ensures it satisfies the intent constraints, and submits it to the blockchain, often using a private mempool or a specific intent-centric infrastructure like Anoma or SUAVE.

A critical component is the solver design. Solvers are specialized programs that listen for posted intents. For a swap intent, a solver will query liquidity across aggregated DEXs like Uniswap, Curve, and Balancer, factor in gas costs, and propose a transaction bundle that maximizes the user's output. They compete on the quality of their solution, and the winning solver's transaction is executed. Architecturally, this means running or connecting to a network of these solvers, which can be permissionless or permissioned, and implementing a mechanism to select the best solution.

For developers, implementing this starts with defining the intent schema. A basic swap intent in JSON might include fields for inToken, inAmount, outToken, and constraints like deadline or minOutAmount. The backend must then expose an endpoint to accept these intents and broadcast them to solvers. A reference flow is: User signs intent -> Aggregator API receives it -> Intent is published to solver network -> Solvers submit signed solution bundles -> Aggregator verifies and submits winning bundle.

Key technical challenges include intent privacy (solutions like threshold decryption), solver incentivization (paying solvers via fees or MEV capture), and security verification (ensuring the executed transaction cannot deviate from the intent). Projects like CowSwap (via CoW Protocol) and UniswapX have pioneered these patterns, using batch auctions and filler networks, respectively. Your architecture must decide on a trust model—whether to use a centralized coordinator, a decentralized intent pool, or a shared sequencer network.

To begin prototyping, use existing SDKs and infrastructure. The Flashbots SUAVE chain provides a test environment for preference-driven block building. For solver logic, you can fork and modify open-source searcher bots from repositories like flashbots/searcher-sponsored-tx. The end goal is an aggregator that abstracts away blockchain complexity, offering users a simpler, often more efficient, and potentially MEV-resistant experience by architecting a system where users state what they want, not how to do it.

An intent-driven architecture shifts the paradigm from explicit transaction execution to declarative user goals. Instead of specifying "swap 1 ETH for USDC on Uniswap V3," a user expresses an intent like "get the best price for 1 ETH into USDC within 30 seconds." The aggregator's solver network is then responsible for discovering and executing the optimal path. This requires a robust backend to interpret intents, a solver competition mechanism, and secure settlement layers. Foundational protocols for this model include ERC-4337 for account abstraction and intents standards like Anoma's Taiga or CowSwap's CoW Protocol.

Your core development stack must handle off-chain computation and on-chain settlement. A typical setup includes a Node.js or Python backend for the solver engine, integrated with TypeScript for type-safe interaction with Ethereum libraries. You will need the Ethers.js v6 or Viem library for blockchain communication and GraphQL clients like Apollo or Urql to query indexed data from The Graph for real-time liquidity and price information. For managing private keys and signing transactions for solver bundles, a secure signer service using Hardhat or Foundry for local testing is essential.

Understanding the solver economics is critical. Solvers compete to fulfill user intents profitably, earning fees from the spread or explicit rewards. Your architecture must include a bidding system where solvers submit solution bundles and associated fees. This often involves an auction mechanism run by a centralized coordinator or a decentralized MEV-boost-like relay. You'll need to integrate with Flashbots Protect RPC or similar services to access the private mempool, ensuring solver transactions are not front-run. The settlement layer typically uses a smart contract wallet (like a Safe) or an ERC-4337 bundler to atomically execute the winning solution.

In traditional DeFi, users must manually specify every transaction detail: which protocols to use, the exact swap path, and the gas fees to pay. An intent-based system inverts this model. Here, a user submits a declarative goal, such as "Swap 1 ETH for the maximum possible amount of USDC on Polygon within 30 seconds." This intent is a signed message containing constraints (e.g., deadline, minimum output) but not the execution path. The architecture's core challenge is to fulfill this intent optimally and trustlessly.

The fulfillment process is managed by specialized actors called solvers. Solvers are off-chain agents—which can be individuals, DAOs, or sophisticated algorithms—that compete to find the best execution path for a user's intent. They scan liquidity across DEXs, bridges, and lending protocols to construct a transaction bundle that meets the user's constraints. The winning solver submits a proof of their solution, often in the form of a calldata bundle, to a public settlement layer on-chain, which verifies the solution satisfies the intent before execution.

Architecting this system requires clear separation of concerns. The User Interface captures the intent and signs it. The Solver Network is a permissionless or permissioned set of competing solvers. The Settlement Contract on-chain is the critical trust anchor; it holds the user's funds in escrow, validates the solver's proposed transaction against the intent's constraints, and executes it atomically. This design, used by protocols like CowSwap and UniswapX, removes execution burden from users and can achieve better prices through competition.

Key technical considerations include intent representation and solver incentives. Intents are typically expressed as structured data signed with EIP-712, allowing for complex conditional logic. Solvers are incentivized by a fee, often taken from the surplus they generate for the user (e.g., giving the user a better price than their minimum). The settlement contract must be meticulously audited, as its logic defines the security model, ensuring solvers cannot steal funds or execute unauthorized actions.

To build a basic aggregator, start with a smart contract for intent settlement. It should have functions to lockFundsWithIntent and settleIntent. The off-chain solver service listens for posted intents, runs an optimization algorithm (checking prices via APIs from 1inch, 0x, etc.), and submits the best bundle. A simple implementation might use a sealed-bid auction where solvers submit encrypted solutions, which are revealed and verified on-chain to prevent front-running and ensure fair competition.

An intent is a declarative statement of a user's desired outcome, such as "swap 1 ETH for the maximum possible amount of USDC within the next 5 minutes," without specifying the exact path or protocol to achieve it. This is a fundamental shift from the traditional transaction-based model, where users must manually specify every step. To enable this, you must define a structured data schema that captures the core components of an intent: the signer, the assets involved (input and desired output), any constraints (e.g., slippage, deadline), and the solver who can fulfill it. The EIP-4337 Account Abstraction standard provides a foundational framework for user operation bundles, which can be extended to encode intents.

The user interface (UI) is the critical bridge that translates human goals into this structured intent data. A well-designed intent-centric UI moves away from complex transaction builders. Instead, it presents high-level objectives. For example, a user might select "Maximize Yield" and provide parameters like principal amount, risk tolerance, and desired chain. The UI's job is to construct a corresponding intent object. This often involves using a domain-specific language (DSL) or a JSON schema that solvers can parse. A simple intent object in JSON might look like:

jsonCopy
{
  "standard": "chainscore-intent-v1",
  "signer": "0x1234...",
  "actions": [{
    "type": "swap",
    "in": {"token": "ETH", "amount": "1000000000000000000"},
    "out": {"token": "USDC"},
    "constraints": {"deadline": 1700000000, "minOut": "1800"}
  }]
}

Defining this standard requires careful consideration of composability and extensibility. Your intent schema should allow for multiple actions (e.g., swap then deposit into a vault) and support new types of constraints or assets over time. It must also include a signature scheme so the intent can be cryptographically signed by the user's wallet, delegating authority to a solver without handing over private keys. This setup creates a clear separation of concerns: the user declares what they want, the interface encodes it, and downstream solvers compete to figure out how to execute it most efficiently across the fragmented DeFi landscape.

A solver network is a decentralized set of independent actors or bots that compete to fulfill user intents. When a user submits an intent (e.g., "Swap 1 ETH for the best possible amount of USDC"), it is broadcast to this network. Each solver uses its own algorithms and private liquidity sources to propose a fulfillment plan, known as a filled intent bundle. This bundle includes the exact transaction sequence, associated fees, and a proof that the solution meets the user's constraints. The design incentivizes competition, as solvers are rewarded for submitting the most optimal (e.g., highest output, lowest cost) valid solution.

The routing engine is the on-chain or off-chain component that manages this competition. Its primary functions are to receive intent declarations, collect and validate solver bids, and select the winning solution. A common implementation uses a sealed-bid auction mechanism. Solvers submit their signed bundles to the engine within a specified time window. After the window closes, the engine reveals all bids, verifies their correctness (e.g., checking on-chain liquidity, simulating the transaction), and selects the bundle that provides the best outcome for the user. This winning bundle is then submitted for on-chain execution.

Architecting the solver network requires defining clear interfaces. The core is the Intent data structure, which standardizes how user goals are expressed. A basic swap intent in Solidity might include fields for inputToken, inputAmount, outputToken, and a minOutputAmount constraint. Solvers implement a standard interface to generate IntentSolution structs. Off-chain, a solver might use a pathfinding algorithm that searches across multiple DEXs (Uniswap V3, Curve, Balancer) and bridges, often representing liquidity as a graph where nodes are tokens and edges are pools with exchange rates.

Key technical challenges include solution simulation and MEV resistance. Before proposing a solution, a solver must simulate it against the latest blockchain state to guarantee its validity and the quoted output. This requires access to a high-performance node or a service like Tenderly or Foundry's cast. To mitigate MEV, the routing engine should use a commit-reveal scheme to prevent solvers from front-running each other's solutions, and may incorporate fair ordering protocols like FCFS (First-Come-First-Served) or PGA (Proposer-Builder Separation) principles from Ethereum's design.

For development, you can start by deploying a simple auction contract. The contract would define an submitIntent function for users and a submitSolution function for solvers that commits a hash of their bundle. A revealAndExecute function would later allow solvers to reveal their full bundle, enabling the contract to verify and execute the best one. Off-chain, a solver bot can be built using the Ethers.js or Viem libraries to listen for new intents, run a pathfinding algorithm like Dijkstra on a DEX liquidity graph, and submit the resulting transaction calldata as a bid.

After an intent is resolved into a concrete transaction path, the execution layer must handle settlement. A naive approach of broadcasting the raw transaction to a public mempool exposes users to front-running and sandwich attacks, where searchers can profit by inserting their own transactions before and after the user's. To mitigate this, your architecture must incorporate MEV-aware execution strategies. The primary defense is using private transaction relays like Flashbots Protect RPC, BloxRoute, or Eden Network. These services submit transactions directly to block builders, bypassing the public mempool and reducing the surface area for predatory MEV.

For more sophisticated protection, consider implementing transaction simulation and bundle building. Before final submission, simulate the transaction's execution to check for unexpected slippage or state changes that could indicate a pending attack. Aggregators like 1inch and CowSwap use batch auctions and Coincidence of Wants (CoW) to settle orders peer-to-peer when possible, eliminating on-chain liquidity costs and MEV entirely for matched orders. For unmatched orders, they use MEV-aware solvers who compete in a sealed-bid auction to provide the best settlement, aligning economic incentives with user outcomes.

The settlement logic should also account for gas optimization and revert protection. Use gas estimation services that consider base fee predictions and priority fee markets to avoid underpriced transactions that get stuck. Implement conditional execution logic, such as setting slippage tolerances based on real-time volatility data or using TWAP (Time-Weighted Average Price) oracles as reference prices instead of the instantaneous spot price. This prevents maximal extractable value (MEV) bots from manipulating the price right before your transaction executes.

Here is a simplified conceptual flow for an MEV-aware executor in pseudocode:

codeCopy
function executeIntent(intentSolution) {
  // 1. Simulate transaction
  const simulationResult = simulateTx(intentSolution.tx);
  if (simulationResult.expectedSlippage > maxTolerance) revert();

  // 2. Build & submit via private relay
  const privateTx = {
    tx: intentSolution.tx,
    preferences: { hint: 'mev-protect' }
  };
  const txHash = submitViaPrivateRelay(FlashbotsRPC, privateTx);

  // 3. Monitor & handle reverts
  monitorTransaction(txHash, {
    onRevert: (reason) => handleRevert(intentSolution)
  });
}

This structure prioritizes user protection by validating the execution path before committing real funds.

Finally, design for settlement finality and user feedback. Provide users with clear status updates and a transaction receipt that explains key metrics: effective exchange rate achieved, total fees paid (including gas), and an estimate of MEV saved by using your protected path. Transparency builds trust. By architecting your execution and settlement layer with these MEV-aware principles, you transform your aggregator from a simple router into a defensive execution system that actively guards user value.

Settlement smart contracts are the on-chain executors that transform a user's signed intent into a final on-chain transaction. Their primary responsibility is to validate the intent's conditions—such as minimum output amounts, deadline, and permitted executors—and then atomically execute the required swaps, transfers, or other actions. Unlike a standard DEX router that executes a pre-defined path, a settlement contract must be generic enough to handle a variety of decomposed intent solutions provided by a solver network. This requires a modular architecture where the core settlement logic is separate from the specific action executors.

A robust settlement contract typically implements a conditional execution pattern. It first verifies the intent signature and checks that the current blockchain state (e.g., token prices from an oracle) satisfies the user's constraints. Only then does it proceed to execute the solution's steps. For a swap intent, this involves transferring the user's input tokens to the contract, routing them through the specified pools or protocols, and finally sending the output tokens back to the user. All of this must happen in a single transaction to prevent front-running and sandwich attacks, ensuring the user receives at least the minimum amount they specified.

Key security considerations for settlement contracts include reentrancy guards, comprehensive input validation, and strict access controls limiting who can trigger settlement (typically to a permissioned set of solvers or a decentralized solver network). Contracts should also implement a deadline check to invalidate stale intents and handle failed transactions gracefully, reverting all state changes if any step fails. Using established libraries like OpenZeppelin and following standards such as ERC-1271 for signature validation is crucial. The contract should emit clear events for off-chain indexers to track intent fulfillment and solver performance.

Here is a simplified conceptual structure for a settlement contract's core function:

solidityCopy
function settleIntent(
    Intent calldata intent,
    bytes calldata solverSignature,
    Action[] calldata actions
) external onlyAllowedSolver {
    // 1. Validate intent signature & deadline
    require(_validateIntentSignature(intent), "Invalid intent");
    require(block.timestamp <= intent.deadline, "Intent expired");
    
    // 2. Transfer input tokens from user to this contract
    IERC20(intent.inputToken).safeTransferFrom(intent.user, address(this), intent.inputAmount);
    
    // 3. Execute the sequence of actions (swaps, transfers)
    for (uint i = 0; i < actions.length; i++) {
        (bool success, ) = address(actions[i].target).call(actions[i].data);
        require(success, "Action failed");
    }
    
    // 4. Verify output constraint & send to user
    uint256 outputBalance = IERC20(intent.outputToken).balanceOf(address(this));
    require(outputBalance >= intent.minOutputAmount, "Slippage exceeded");
    IERC20(intent.outputToken).safeTransfer(intent.user, outputBalance);
    
    emit IntentSettled(intent.hash, msg.sender, outputBalance);
}

In production systems, settlement is often separated into a dispatcher contract and executor modules. The dispatcher handles intent validation and routing, while specialized executor contracts (e.g., a UniswapV3Executor, a CurveExecutor) contain the protocol-specific logic. This separation improves upgradability and security. Furthermore, many aggregators like 1inch and CowSwap use a settlement contract that interacts with a permit2-like token approval standard, allowing users to sign a one-time approval for the intent, which eliminates the need for a separate ERC-20 approve transaction and significantly improves the user experience.

Finally, thorough testing is non-negotiable. Settlement contracts should be tested against mainnet forks using frameworks like Foundry or Hardhat to simulate real trading conditions. Tests must cover edge cases: partial fill scenarios, oracle price deviations, solver misconduct, and gas optimization for complex multi-hop routes. The contract's economic security should be audited by multiple firms, as it will routinely custody significant user funds. A well-architected settlement layer is the critical component that ensures user intents are fulfilled securely, efficiently, and exactly as specified.

You now have a functional blueprint for an intent-centric architecture. The core flow—user submits a signed intent, the solver network competes to fulfill it, and a settlement layer executes the winning solution—decouples user experience from execution complexity. Key components like the intent standard (ERC-4337, SUAVE), a robust solver incentive mechanism, and secure cross-chain settlement are essential. The primary advantage is shifting risk and gas optimization from the end-user to specialized solvers.

To move from concept to production, focus on these implementation steps. First, choose and extend a foundational standard; using ERC-4337 UserOperations for EVM chains or Cosmos SDK modules for app-chains provides a starting point. Second, implement a solver selection and bidding system, potentially using a MEV-boost-like auction. Third, rigorously test the settlement layer's failure modes, ensuring it can handle solver censorship or failed transactions without compromising user funds. Tools like Foundry and Hardhat are indispensable for this phase.

Advanced architectural patterns can enhance your aggregator. Consider implementing intent composability, where a single user intent can trigger a sequence of actions across multiple protocols (e.g., "swap ETH for USDC, then deposit into Aave"). Explore privacy-preserving intents using zero-knowledge proofs (ZKPs) via Aztec Network or zkBob to hide transaction amounts or destinations. Another frontier is cross-domain intent propagation, allowing solvers on one chain (e.g., Ethereum) to fulfill intents that require actions on another (e.g., Arbitrum), using protocols like Chainlink CCIP or LayerZero for message passing.

The ecosystem for intent-driven applications is rapidly evolving. Engage with existing projects and infrastructure: study UniswapX and Cow Swap for solver market design, Anoma for its intent-centric architecture, and Flashbots SUAVE for encrypted mempool concepts. Contributing to or auditing open-source intent standards helps establish best practices. As account abstraction adoption grows on networks like Polygon, Optimism, and Arbitrum, your aggregator's addressable market expands significantly.

Finally, prioritize security and user trust. Conduct formal verification of critical settlement contracts, implement timelocks for protocol upgrades, and establish a bug bounty program. Educate users on the security model: their funds remain in their smart contract wallet until settlement, and solvers only compete for the right to execute, not to custody assets. By building on this architectural foundation and engaging with the nascent intent ecosystem, you can create a powerful platform that abstracts away DeFi's complexity.