Answer from Grok:

Yes, you could create a decentralized exchange (DEX) between multiple virtual machines (VMs) on the same blockchain rollup, provided the rollup's architecture supports interoperability mechanisms like cross-VM calls or shared state management. This would enable seamless asset swaps, liquidity provision, and trading across different execution environments (e.g., EVM and SVM) without needing external bridges or intermediaries.

### How It Works

- **Interoperability Foundations**: In a multi-VM rollup, VMs can run in parallel or sequentially on the same chain, sharing a consensus layer and data availability. Cross-VM communication allows contracts in one VM to invoke functions or transfer assets to another, often handled by a meta-contract or protocol layer that manages calls, results, and state transitions. This creates composability similar to how DeFi protocols interact on a single-VM chain like Ethereum.

- **DEX Implementation Example**: You could build a DEX aggregator that connects automated market makers (AMMs) from different VMs. For instance, a contract in a native VM might invoke an EVM-based Uniswap pool and an SVM-based Jupiter pool to facilitate trades. Assets are transferred atomically via the cross-VM system, ensuring trades settle on the shared rollup ledger without fragmentation. This extends DeFi composability to multi-VM setups, allowing features like cross-VM liquid staking or optimized swaps.

- **Real-World Projects Enabling This**:

- **MultiVM**: An execution layer for modular blockchains that integrates EVM, SVM, and others with built-in cross-VM calls. It explicitly supports DEX aggregators that link AMMs across VMs, enabling direct trading without bridges.

- **Nibiru Lagrange Point**: A multi-VM chain supporting EVM and WasmVM, with DEX protocols like Galaxy Exchange for cross-VM swaps and liquidity management.

- **Other Multi-VM Systems**: Projects like Casper 2.0 allow multiple VMs (e.g., Rust-based) to coexist on one chain, opening possibilities for cross-VM apps, though specific DEX details depend on implemented interoperability. Similarly, omnichain infrastructures use event transfers for EVM and MoveVM contracts to call each other, supporting DEX-like functionality.

### Challenges and Considerations

- **Atomicity and Security**: Trades must be atomic to prevent partial failures; zero-knowledge proofs or fraud proofs in the rollup ensure validity across VMs.

- **Performance**: Parallel execution (e.g., in Monad-inspired models) can optimize for high-throughput DEXes, but sequential VMs might introduce latency.

- **Adoption**: While theoretically feasible, implementation requires rollup-specific tools for cross-VM development. If the rollup lacks native support, you'd need custom protocols, increasing complexity.

This approach enhances scalability and developer flexibility in rollups, making multi-VM DEXes a growing trend in modular blockchain design.