feat: RPC node mode for query-only block following

README.md

@@ -60,7 +60,7 @@ dotnet build
 dotnet test
 ```
 
-2,781 tests across 16 test projects covering core types, cryptography, codec serialization, storage, networking, consensus, execution (including DEX), API, compliance, bridge, confidentiality, node configuration, SDK contracts, analyzers, wallet, and end-to-end integration.
+2,789 tests across 16 test projects covering core types, cryptography, codec serialization, storage, networking, consensus, execution (including DEX), API, compliance, bridge, confidentiality, node configuration, SDK contracts, analyzers, wallet, and end-to-end integration.
 
 ### Run a Local Node
 
@@ -76,16 +76,19 @@ The node starts in standalone mode on the devnet (chain ID 31337) with a REST AP
 docker compose up --build
 ```
 
-Spins up 4 validator nodes with pre-configured genesis accounts, RocksDB persistent storage, and automatic peer discovery via static peer lists.
+Spins up 4 validator nodes and 1 RPC node with pre-configured genesis accounts, RocksDB persistent storage, and automatic peer discovery via static peer lists.
 
-| Validator | REST API | P2P |
-|-----------|----------|-----|
-| validator-0 | `localhost:5100` | `30300` |
-| validator-1 | `localhost:5101` | `30301` |
-| validator-2 | `localhost:5102` | `30302` |
-| validator-3 | `localhost:5103` | `30303` |
+| Service | REST API | P2P | Role |
+|---------|----------|-----|------|
+| validator-0 | `localhost:5100` | `30300` | Consensus validator |
+| validator-1 | `localhost:5101` | `30301` | Consensus validator |
+| validator-2 | `localhost:5102` | `30302` | Consensus validator |
+| validator-3 | `localhost:5103` | `30303` | Consensus validator |
+| rpc-0 | `localhost:5200` | -- | Read-only RPC node |
 
-Each validator has a Docker volume (`validator-N-data`) for RocksDB persistence and connects to all other validators via environment-configured peer lists. Health checks poll `/v1/status` every 5 seconds.
+The RPC node (`rpc-0`) syncs blocks from `validator-0` via HTTP and serves the full API without participating in consensus. It has no P2P port and no validator keys. Submitted transactions are forwarded to the validator.
+
+Each service has a Docker volume for RocksDB persistence. Health checks poll `/v1/status` (validators) or `/v1/health` (RPC) every 5 seconds.
 
 ### CLI
 
@@ -210,6 +213,8 @@ Basalt.sln                              (42 C# projects)
 | `GET` | `/v1/solvers` | List registered solvers |
 | `POST` | `/v1/solvers/register` | Register an external solver |
 | `GET` | `/v1/dex/intents/pending` | Pending swap intent hashes (for solvers) |
+| `GET` | `/v1/sync/status` | Sync source status (latest block, hash, chain ID) |
+| `GET` | `/v1/sync/blocks?from=&count=` | Bulk block fetch for sync (max 100) |
 | `GET` | `/metrics` | Prometheus metrics |
 | `WS` | `/ws/blocks` | Real-time block notifications |
 
@@ -219,6 +224,8 @@ The node is configured via environment variables:
 
 | Variable | Default | Description |
 |----------|---------|-------------|
+| `BASALT_MODE` | `auto` | Node mode: `auto`, `validator`, `rpc`, or `standalone` |
+| `BASALT_SYNC_SOURCE` | -- | HTTP URL of sync source (required for `rpc` mode) |
 | `BASALT_CHAIN_ID` | `31337` | Chain identifier |
 | `BASALT_NETWORK` | `basalt-devnet` | Network name |
 | `BASALT_VALIDATOR_INDEX` | `-1` | Validator index in the set (enables consensus mode when >= 0 and peers are set) |

deploy/testnet/Caddyfile

@@ -30,22 +30,22 @@ http://caldera.basalt.foundation {
 :80 {
 	# REST API
 	handle /v1/* {
-		reverse_proxy validator-0:5000
+		reverse_proxy rpc-0:5000
 	}
 
 	# GraphQL
 	handle /graphql {
-		reverse_proxy validator-0:5000
+		reverse_proxy rpc-0:5000
 	}
 
 	# WebSocket
 	handle /ws/* {
-		reverse_proxy validator-0:5000
+		reverse_proxy rpc-0:5000
 	}
 
 	# Health check
 	handle /health {
-		reverse_proxy validator-0:5000 {
+		reverse_proxy rpc-0:5000 {
 			rewrite /v1/status
 		}
 	}

deploy/testnet/docker-compose.yml

@@ -45,7 +45,7 @@ services:
       - basalt-testnet
     restart: unless-stopped
     depends_on:
-      validator-0:
+      rpc-0:
         condition: service_healthy
       explorer:
         condition: service_started
@@ -158,11 +158,44 @@ services:
     cap_drop:
       - ALL
 
+  # ─── RPC Node 0 (public API, no consensus) ────────────────────────
+  rpc-0:
+    build:
+      context: ../..
+      dockerfile: Dockerfile
+    container_name: basalt-rpc-0
+    environment:
+      - BASALT_MODE=rpc
+      - BASALT_SYNC_SOURCE=http://validator-0:5000
+      - BASALT_NETWORK=basalt-testnet
+      - BASALT_CHAIN_ID=4242
+      - ASPNETCORE_URLS=http://+:5000
+      - BASALT_DATA_DIR=/data/basalt
+    volumes:
+      - rpc-0-data:/data/basalt
+    networks:
+      - basalt-testnet
+    restart: unless-stopped
+    security_opt:
+      - no-new-privileges:true
+    cap_drop:
+      - ALL
+    healthcheck:
+      test: ["CMD", "curl", "-sf", "http://localhost:5000/v1/health"]
+      interval: 10s
+      timeout: 5s
+      retries: 12
+      start_period: 30s
+    depends_on:
+      validator-0:
+        condition: service_healthy
+
 volumes:
   validator-0-data:
   validator-1-data:
   validator-2-data:
   validator-3-data:
+  rpc-0-data:
 
 networks:
   basalt-testnet:

docker-compose.yml

@@ -115,11 +115,45 @@ services:
     cap_drop:
       - ALL
 
+  rpc-0:
+    build:
+      context: .
+      dockerfile: Dockerfile
+    container_name: basalt-rpc-0
+    ports:
+      - "5200:5000"
+    environment:
+      - BASALT_MODE=rpc
+      - BASALT_SYNC_SOURCE=http://validator-0:5000
+      - BASALT_NETWORK=basalt-devnet
+      - BASALT_CHAIN_ID=31337
+      - ASPNETCORE_URLS=http://+:5000
+      - BASALT_DATA_DIR=/data/basalt
+    volumes:
+      - rpc-0-data:/data/basalt
+    networks:
+      - basalt-devnet
+    restart: unless-stopped
+    security_opt:
+      - no-new-privileges:true
+    cap_drop:
+      - ALL
+    healthcheck:
+      test: ["CMD", "curl", "-f", "http://localhost:5000/v1/health"]
+      interval: 5s
+      timeout: 3s
+      retries: 10
+      start_period: 15s
+    depends_on:
+      validator-0:
+        condition: service_healthy
+
 volumes:
   validator-0-data:
   validator-1-data:
   validator-2-data:
   validator-3-data:
+  rpc-0-data:
 
 networks:
   basalt-devnet:

src/api/Basalt.Api.Grpc/BasaltNodeService.cs

@@ -14,6 +14,7 @@ public sealed class BasaltNodeService : BasaltNode.BasaltNodeBase
     private readonly Mempool _mempool;
     private readonly TransactionValidator _validator;
     private readonly IStateDatabase _stateDb;
+    private readonly ITxForwarder? _txForwarder;
 
     /// <summary>H-3: Maximum concurrent SubscribeBlocks streams.</summary>
     private const int MaxSubscribeStreams = 100;
@@ -23,12 +24,14 @@ public BasaltNodeService(
         ChainManager chainManager,
         Mempool mempool,
         TransactionValidator validator,
-        IStateDatabase stateDb)
+        IStateDatabase stateDb,
+        ITxForwarder? txForwarder = null)
     {
         _chainManager = chainManager;
         _mempool = mempool;
         _validator = validator;
         _stateDb = stateDb;
+        _txForwarder = txForwarder;
     }
 
     public override Task<StatusReply> GetStatus(GetStatusRequest request, ServerCallContext context)
@@ -120,6 +123,9 @@ public override Task<TransactionReply> SubmitTransaction(SubmitTransactionReques
                 throw new RpcException(new Status(StatusCode.AlreadyExists,
                     "Transaction already in mempool or mempool is full"));
 
+            // Forward to validator (RPC mode — gRPC txs bypass REST tx endpoint)
+            _ = _txForwarder?.ForwardAsync(tx, context.CancellationToken);
+
             return Task.FromResult(new TransactionReply
             {
                 Hash = tx.Hash.ToHexString(),

src/api/Basalt.Api.Rest/FaucetEndpoint.cs

@@ -55,7 +55,8 @@ public static void MapFaucetEndpoint(
         ChainParameters chainParams,
         byte[] faucetPrivateKey,
         ILogger? logger = null,
-        ChainManager? chainManager = null)
+        ChainManager? chainManager = null,
+        ITxForwarder? txForwarder = null)
     {
         _faucetPrivateKey = faucetPrivateKey;
         _logger = logger;
@@ -207,6 +208,9 @@ public static void MapFaucetEndpoint(
             _logger?.LogInformation("Faucet tx {Hash} added to mempool (size={Size})",
                 signedTx.Hash.ToHexString()[..18] + "...", mempool.Count);
 
+            // Forward to validator (RPC mode — faucet txs bypass POST /v1/transactions)
+            _ = txForwarder?.ForwardAsync(signedTx, CancellationToken.None);
+
             // Record the request time
             _lastRequest[addrKey] = DateTimeOffset.UtcNow;
 

src/api/Basalt.Api.Rest/README.md

@@ -35,6 +35,8 @@ RESTful HTTP API for the Basalt blockchain node. Provides endpoints for submitti
 | `GET` | `/v1/solvers` | List registered solvers |
 | `POST` | `/v1/solvers/register` | Register an external solver |
 | `GET` | `/v1/dex/intents/pending` | Pending swap intent hashes (for solvers) |
+| `GET` | `/v1/sync/status` | Sync source status (latest block, hash, chain ID) |
+| `GET` | `/v1/sync/blocks?from=&count=` | Bulk block fetch for sync (max 100, hex-encoded raw blocks) |
 | `GET` | `/metrics` | Prometheus-format metrics |
 | `WS` | `/ws/blocks` | Real-time block notifications |
 
@@ -95,13 +97,13 @@ curl -X POST http://localhost:5000/v1/faucet \
   -d '{"address":"0x..."}'
 ```
 
-The faucet directly debits a configurable faucet address and credits the recipient in the state database. Configurable via static properties on `FaucetEndpoint`:
+The faucet creates and signs a real transfer transaction submitted through the mempool. In RPC mode, faucet transactions are forwarded to the sync source validator via `HttpTxForwarder`. Configurable via static properties on `FaucetEndpoint`:
 
 - `DripAmount` -- amount in base units (default: 100 BSLT).
 - `CooldownSeconds` -- per-address cooldown (default: 60 seconds).
-- `FaucetAddress` -- source address (default: `Address.Zero`).
+- `FaucetAddress` -- derived from the well-known faucet private key.
 
-Returns `{"success":true,"message":"Sent 100 BSLT to 0x...","txHash":"0x0000..."}` on success. The `txHash` field is a placeholder (`Hash256.Zero`) since the faucet modifies state directly rather than creating a transaction.
+Returns `{"success":true,"message":"Sent 100 BSLT to 0x...","txHash":"0x..."}` on success.
 
 ### Read-Only Contract Call