feat: PoC redeem frontrun protection

AGENTS.md

@@ -6,6 +6,7 @@ This is a Cloudflare Workers project that implements various services for [Go Na
 It uses [Bun](https://bun.com/) for JavaScript and Typescript runtime and package management (instead of Nodejs + npm).
 
 The content is organized into a Bun workspace. See @README.md for:
+
 - High-level architecture and component interactions
 - Detailed setup instructions
 - Functional flow documentation
@@ -15,13 +16,13 @@ The content is organized into a Bun workspace. See @README.md for:
 
 All packages are in the `./packages` directory:
 
-| Package | Type | Purpose |
-|---------|------|---------|
-| `btcindexer` | Service (Worker) | Bitcoin-to-Sui bridging and minting |
-| `sui-indexer` | Service (Worker) | Sui blockchain monitoring and redemption |
-| `block-ingestor` | Service (Worker) | Receives Bitcoin blocks via REST API |
-| `compliance` | Service (Worker) | Sanctions and geo-blocking data |
-| `lib` | Shared Library | Common utilities and types |
+| Package          | Type             | Purpose                                  |
+| ---------------- | ---------------- | ---------------------------------------- |
+| `btcindexer`     | Service (Worker) | Bitcoin-to-Sui bridging and minting      |
+| `sui-indexer`    | Service (Worker) | Sui blockchain monitoring and redemption |
+| `block-ingestor` | Service (Worker) | Receives Bitcoin blocks via REST API     |
+| `compliance`     | Service (Worker) | Sanctions and geo-blocking data          |
+| `lib`            | Shared Library   | Common utilities and types               |
 
 ### Core Technologies
 
@@ -96,7 +97,7 @@ See @README.md for Cloudflare RPC documentation and examples.
 
 **Location**: `./packages/btcindexer`
 
-### Architecture
+### BTCIndexer Architecture
 
 - `src/index.ts` - Main entry with HTTP handlers and scheduled cron
 - `src/btcindexer.ts` - Bitcoin indexing and deposit detection logic
@@ -105,14 +106,14 @@ See @README.md for Cloudflare RPC documentation and examples.
 - `src/cf-storage.ts` - Cloudflare D1/KV storage layer
 - `src/bitcoin-merkle-tree.ts` - Merkle proof generation
 
-### Key Features
+### BTCIndexer Key Features
 
 1. **Bitcoin Block Processing**: Cron job runs every minute to scan blocks, identify nBTC deposits via OP_RETURN outputs
 2. **Cross-Chain Minting**: Tracks deposits and mints corresponding nBTC on Sui with Merkle proof validation
 3. **Data Storage**: Uses D1 for transaction data, KV for block storage
 4. **Queue Consumption**: Consumes blocks from `block-queue` populated by block-ingestor
 
-### Configuration
+### BTCIndexer Configuration
 
 - **Cron**: Every minute (`* * * * *`)
 - **D1 Database**: `btcindexer-dev`
@@ -121,7 +122,7 @@ See @README.md for Cloudflare RPC documentation and examples.
 - **Service Bindings**: `SuiIndexer`, `Compliance`
 - **Secrets**: `NBTC_MINTING_SIGNER_MNEMONIC` (via Secrets Store)
 
-### Database Schema
+### BTCIndexer Database Schema
 
 See migration files in `packages/btcindexer/db/migrations/`:
 
@@ -138,7 +139,7 @@ See migration files in `packages/btcindexer/db/migrations/`:
 
 **Location**: `./packages/sui-indexer`
 
-### Architecture
+### Sui Indexer Architecture
 
 - `src/index.ts` - Entry point with scheduled task
 - `src/processor.ts` - Sui event indexing
@@ -156,13 +157,13 @@ The Sui Indexer integrates with IKA (MPC service) for threshold signature operat
 - Manages presign objects for Bitcoin transaction signing
 - Implements coin selection logic for redemption transactions
 
-### Key Features
+### Sui Indexer Key Features
 
 1. **Event Monitoring**: Indexes Sui events for nBTC redemption requests
 2. **Redemption Processing**: Handles burn-and-redeem flow with IKA MPC
 3. **UTXO Management**: Manages UTXO lifecycle (available → locked → spent)
 
-### Configuration
+### Sui Indexer Configuration
 
 - **Cron**: Every minute (`* * * * *`)
 - **D1 Database**: Shared `btcindexer-dev`
@@ -176,18 +177,18 @@ The Sui Indexer integrates with IKA (MPC service) for threshold signature operat
 
 See @packages/block-ingestor/README.md for detailed architecture.
 
-### Architecture
+### Block Ingestor Architecture
 
 - `src/index.ts` - HTTP router and handlers
 - `src/ingest.ts` - Block ingestion logic
 - `src/api/put-blocks.ts` - msgpack encoding/decoding
 - `src/api/client.ts` - Client for sending blocks
 
-### Key Features
+### Block Ingestor Key Features
 
 Receives Bitcoin blocks via REST API, validates them, and enqueues to `block-queue` for processing by BTCIndexer.
 
-### Configuration
+### Block Ingestor Configuration
 
 - **KV Namespace**: `BtcBlocks` (shared with btcindexer)
 - **Queue Producer**: `block-queue`
@@ -197,33 +198,33 @@ Receives Bitcoin blocks via REST API, validates them, and enqueues to `block-que
 
 **Location**: `./packages/compliance`
 
-### Architecture
+### Compliance Architecture
 
 - `src/index.ts` - Scheduled worker entry point
 - `src/sanction.ts` - Sanctions list updating logic
 - `src/storage.ts` - D1 storage for sanctions
 - `src/rpc.ts` - RPC interface for other services to query compliance data
 
-### Key Features
+### Compliance Key Features
 
 1. **Sanctions List Updates**: Daily cron job fetches and updates sanctions data
 2. **Compliance API**: Exposes RPC methods for other services to check addresses
 3. **Geo-blocking**: Supports geo-blocking rules
 
-### Configuration
+### Compliance Configuration
 
 - **Cron**: Daily at 1am (`0 1 * * *`)
 - **D1 Database**: `compliance`
 
-### Database Schema
+### Compliance Database Schema
 
 See migration files in `packages/compliance/db/migrations/`.
 
 ## Lib
 
 **Location**: `./packages/lib`
 
-### Architecture
+### Lib Architecture
 
 Shared library package containing utilities used across all services:
 
@@ -237,7 +238,7 @@ Shared library package containing utilities used across all services:
 - `src/rpc-types.ts` - Shared RPC type definitions
 - `src/test-helpers/` - Test utilities including D1 initialization
 
-### Key Features
+### Lib Key Features
 
 1. **Shared Types**: Network enums, block records, transaction status types
 2. **Testing Support**: Mock RPC implementations and D1 test helpers
@@ -255,7 +256,7 @@ Shared library package containing utilities used across all services:
 
 - **Framework**: Bun's built-in test framework with Miniflare for mocking Workers
 - **Mock RPC**: Each service provides `RPCMock` implementation for isolated testing
-- **Test Data**: Real Bitcoin regtest blocks from https://learnmeabitcoin.com/explorer/
+- **Test Data**: Real Bitcoin regtest blocks from [learnmeabitcoin.com](https://learnmeabitcoin.com/explorer/)
 - **Test Helpers**: Located in `packages/lib/src/test-helpers/`
 
 ### Configuration Pattern

packages/sui-indexer/src/redeem-service.ts

@@ -326,9 +326,6 @@ export class RedeemService {
 		const availableUtxos = await this.storage.getAvailableUtxos(req.setup_id);
 		const selectedUtxos = selectUtxos(availableUtxos, req.amount);
 
-		// TODO: we should continue only if our solution is better than the existing one - in case
-		//   someone frontrun us.
-
 		if (!selectedUtxos) {
 			logger.warn({
 				msg: "Insufficient UTXOs for request",
@@ -338,26 +335,41 @@ export class RedeemService {
 			return;
 		}
 
+		const client = this.getSuiClient(req.sui_network);
+		const proposalArgs = {
+			redeemId: req.redeem_id,
+			utxoIds: selectedUtxos.map((u) => u.nbtc_utxo_id),
+			nbtcPkg: req.nbtc_pkg,
+			nbtcContract: req.nbtc_contract,
+		};
+
 		try {
-			const client = this.getSuiClient(req.sui_network);
-			const txDigest = await client.proposeRedeemUtxos({
-				redeemId: req.redeem_id,
-				utxoIds: selectedUtxos.map((u) => u.nbtc_utxo_id),
-				nbtcPkg: req.nbtc_pkg,
-				nbtcContract: req.nbtc_contract,
-			});
+			const result = await client.proposeRedeemUtxos(proposalArgs);
 
-			logger.info({
-				msg: "Proposed UTXOs for redeem request",
-				redeemId: req.redeem_id,
-				txDigest: txDigest,
-			});
-			await this.storage.markRedeemProposed(
-				req.redeem_id,
-				selectedUtxos.map((u) => u.nbtc_utxo_id),
-				this.utxoLockTimeMs,
-			);
+			if (result.success) {
+				logger.info({
+					msg: "Proposed UTXOs for redeem request",
+					redeemId: req.redeem_id,
+					txDigest: result.digest,
+				});
+				await this.storage.markRedeemProposed(
+					req.redeem_id,
+					selectedUtxos.map((u) => u.nbtc_utxo_id),
+					this.utxoLockTimeMs,
+				);
+			} else {
+				// Contract abort: someone already proposed a better solution.
+				// Mark as proposed without locking UTXOs so the redeem continue.
+				logger.info({
+					msg: "Proposal rejected on-chain, another worker proposed a better solution",
+					redeemId: req.redeem_id,
+					txDigest: result.digest,
+					error: result.error,
+				});
+				await this.storage.markRedeemProposed(req.redeem_id, [], 0);
+			}
 		} catch (e: unknown) {
+			// Network error: leave as pending so next cron retry.
 			logError(
 				{
 					msg: "Failed to propose UTXOs for redeem request",

packages/sui-indexer/src/redeem-sui-client.ts

@@ -20,7 +20,9 @@ export interface SuiClientCfg {
 
 export interface SuiClient {
 	ikaClient(): IkaClient;
-	proposeRedeemUtxos(args: ProposeRedeemCall): Promise<string>;
+	proposeRedeemUtxos(
+		args: ProposeRedeemCall,
+	): Promise<{ success: boolean; digest: string | null; error: string | null }>;
 	solveRedeemRequest(args: SolveRedeemCall): Promise<string>;
 	finalizeRedeem(args: FinalizeRedeemCall): Promise<string>;
 	requestIkaPresigns(count: number): Promise<string[]>;
@@ -111,7 +113,9 @@ class SuiClientImp implements SuiClient {
 		return Buffer.from(decoded).toString("hex");
 	}
 
-	async proposeRedeemUtxos(args: ProposeRedeemCall): Promise<string> {
+	async proposeRedeemUtxos(
+		args: ProposeRedeemCall,
+	): Promise<{ success: boolean; digest: string | null; error: string | null }> {
 		const tx = new Transaction();
 
 		tx.add(
@@ -135,11 +139,11 @@ class SuiClientImp implements SuiClient {
 			},
 		});
 
-		if (result.effects?.status.status !== "success") {
-			throw new Error(`Transaction failed: ${result.effects?.status.error}`);
-		}
-
-		return result.digest;
+		return {
+			success: result.effects?.status.status === "success",
+			digest: result.digest ?? null,
+			error: result.effects?.status.error ?? null,
+		};
 	}
 
 	async solveRedeemRequest(args: SolveRedeemCall): Promise<string> {