feat: add GetNoteError endpoint in ntx builder

CHANGELOG.md

@@ -5,6 +5,8 @@
 ### Enhancements
 
 - Expose per-tree RocksDB tuning options ([#1782](https://github.com/0xMiden/node/pull/1782)).
+- Added a gRPC server to the NTX builder, configurable via `--ntx-builder.url` / `MIDEN_NODE_NTX_BUILDER_URL` (https://github.com/0xMiden/node/issues/1758).
+- Added `GetNoteError` gRPC endpoint to query the latest execution error for network notes (https://github.com/0xMiden/node/issues/1758).
 - Added verbose `info!`-level logging to the network transaction builder for transaction execution, note filtering failures, and transaction outcomes ([#1770](https://github.com/0xMiden/node/pull/1770)).
 - [BREAKING] Move block proving from Blocker Producer to the Store ([#1579](https://github.com/0xMiden/node/pull/1579)).
 - [BREAKING] Updated miden-base dependencies to use `next` branch; renamed `NoteInputs` to `NoteStorage`, `.inputs()` to `.storage()`, and database `inputs` column to `storage` ([#1595](https://github.com/0xMiden/node/pull/1595)).

bin/node/src/commands/bundled.rs

@@ -246,10 +246,44 @@ impl BundledCommand {
                 .id()
         };
 
+        // Prepare network transaction builder (bind listener + config before starting RPC,
+        // so that the ntx-builder URL is available for the RPC proxy).
+        let mut ntx_builder_url_for_rpc = None;
+        let ntx_builder_prepared = if should_start_ntx_builder {
+            let store_ntx_builder_url = Url::parse(&format!("http://{store_ntx_builder_address}"))
+                .context("Failed to parse URL")?;
+            let block_producer_url = block_producer_url.clone();
+            let validator_url = validator_url.clone();
+
+            let builder_config = ntx_builder.into_builder_config(
+                store_ntx_builder_url,
+                block_producer_url,
+                validator_url,
+                &data_directory,
+            );
+
+            // Bind a listener for the ntx-builder gRPC server.
+            let ntx_builder_listener = TcpListener::bind("127.0.0.1:0")
+                .await
+                .context("Failed to bind to ntx-builder gRPC endpoint")?;
+            let ntx_builder_address = ntx_builder_listener
+                .local_addr()
+                .context("Failed to retrieve the ntx-builder's gRPC address")?;
+            ntx_builder_url_for_rpc = Some(
+                Url::parse(&format!("http://{ntx_builder_address}"))
+                    .context("Failed to parse ntx-builder URL")?,
+            );
+
+            Some((builder_config, ntx_builder_listener))
+        } else {
+            None
+        };
+
         // Start RPC component.
         let rpc_id = {
             let block_producer_url = block_producer_url.clone();
             let validator_url = validator_url.clone();
+            let ntx_builder_url = ntx_builder_url_for_rpc;
             join_set
                 .spawn(async move {
                     let store_url = Url::parse(&format!("http://{store_rpc_address}"))
@@ -259,6 +293,7 @@ impl BundledCommand {
                         store_url,
                         block_producer_url: Some(block_producer_url),
                         validator_url,
+                        ntx_builder_url,
                         grpc_options,
                     }
                     .serve()
@@ -275,27 +310,15 @@ impl BundledCommand {
             (rpc_id, "rpc"),
         ]);
 
-        // Start network transaction builder. The endpoint is available after loading completes.
-        if should_start_ntx_builder {
-            let store_ntx_builder_url = Url::parse(&format!("http://{store_ntx_builder_address}"))
-                .context("Failed to parse URL")?;
-            let block_producer_url = block_producer_url.clone();
-            let validator_url = validator_url.clone();
-
-            let builder_config = ntx_builder.into_builder_config(
-                store_ntx_builder_url,
-                block_producer_url,
-                validator_url,
-                &data_directory,
-            );
-
+        // Start network transaction builder.
+        if let Some((builder_config, ntx_builder_listener)) = ntx_builder_prepared {
             let id = join_set
                 .spawn(async move {
                     builder_config
                         .build()
                         .await
                         .context("failed to initialize ntx builder")?
-                        .run()
+                        .run(Some(ntx_builder_listener))
                         .await
                         .context("failed while serving ntx builder component")
                 })

bin/node/src/commands/mod.rs

@@ -47,6 +47,7 @@ const ENV_NTX_SCRIPT_CACHE_SIZE: &str = "MIDEN_NTX_DATA_STORE_SCRIPT_CACHE_SIZE"
 const ENV_VALIDATOR_KEY: &str = "MIDEN_NODE_VALIDATOR_KEY";
 const ENV_VALIDATOR_KMS_KEY_ID: &str = "MIDEN_NODE_VALIDATOR_KMS_KEY_ID";
 const ENV_NTX_DATA_DIRECTORY: &str = "MIDEN_NODE_NTX_DATA_DIRECTORY";
+const ENV_NTX_BUILDER_URL: &str = "MIDEN_NODE_NTX_BUILDER_URL";
 
 const DEFAULT_NTX_TICKER_INTERVAL: Duration = Duration::from_millis(200);
 const DEFAULT_NTX_IDLE_TIMEOUT: Duration = Duration::from_secs(5 * 60);

bin/node/src/commands/rpc.rs

@@ -4,7 +4,13 @@ use miden_node_utils::clap::GrpcOptionsExternal;
 use miden_node_utils::grpc::UrlExt;
 use url::Url;
 
-use super::{ENV_BLOCK_PRODUCER_URL, ENV_RPC_URL, ENV_STORE_RPC_URL, ENV_VALIDATOR_URL};
+use super::{
+    ENV_BLOCK_PRODUCER_URL,
+    ENV_NTX_BUILDER_URL,
+    ENV_RPC_URL,
+    ENV_STORE_RPC_URL,
+    ENV_VALIDATOR_URL,
+};
 use crate::commands::ENV_ENABLE_OTEL;
 
 #[derive(clap::Subcommand)]
@@ -28,6 +34,11 @@ pub enum RpcCommand {
         #[arg(long = "validator.url", env = ENV_VALIDATOR_URL, value_name = "URL")]
         validator_url: Url,
 
+        /// The network transaction builder's gRPC url. If unset, the `GetNoteError` endpoint
+        /// will be unavailable.
+        #[arg(long = "ntx-builder.url", env = ENV_NTX_BUILDER_URL, value_name = "URL")]
+        ntx_builder_url: Option<Url>,
+
         /// Enables the exporting of traces for OpenTelemetry.
         ///
         /// This can be further configured using environment variables as defined in the official
@@ -47,6 +58,7 @@ impl RpcCommand {
             store_url,
             block_producer_url,
             validator_url,
+            ntx_builder_url,
             enable_otel: _,
             grpc_options,
         } = self;
@@ -61,6 +73,7 @@ impl RpcCommand {
             store_url,
             block_producer_url,
             validator_url,
+            ntx_builder_url,
             grpc_options,
         }
         .serve()

crates/ntx-builder/Cargo.toml

@@ -21,16 +21,19 @@ futures                    = { workspace = true }
 libsqlite3-sys             = { workspace = true }
 miden-node-db              = { workspace = true }
 miden-node-proto           = { workspace = true }
+miden-node-proto-build     = { features = ["internal"], workspace = true }
 miden-node-utils           = { workspace = true }
 miden-protocol             = { default-features = true, workspace = true }
 miden-remote-prover-client = { features = ["tx-prover"], workspace = true }
 miden-standards            = { workspace = true }
 miden-tx                   = { default-features = true, workspace = true }
 thiserror                  = { workspace = true }
 tokio                      = { features = ["rt-multi-thread"], workspace = true }
-tokio-stream               = { workspace = true }
+tokio-stream               = { features = ["net"], workspace = true }
 tokio-util                 = { workspace = true }
 tonic                      = { workspace = true }
+tonic-reflection           = { workspace = true }
+tower-http                 = { workspace = true }
 tracing                    = { workspace = true }
 url                        = { workspace = true }
 

crates/ntx-builder/src/actor/mod.rs

@@ -24,7 +24,6 @@ use url::Url;
 use crate::chain_state::ChainState;
 use crate::clients::{BlockProducerClient, StoreClient};
 use crate::db::Db;
-use crate::inflight_note::InflightNetworkNote;
 
 // ACTOR REQUESTS
 // ================================================================================================
@@ -36,7 +35,7 @@ pub enum ActorRequest {
     /// the oneshot channel, preventing race conditions where the actor could re-select the same
     /// notes before the failure is persisted.
     NotesFailed {
-        nullifiers: Vec<Nullifier>,
+        failed_notes: Vec<(Nullifier, String)>,
         block_num: BlockNumber,
         ack_tx: tokio::sync::oneshot::Sender<()>,
     },
@@ -411,23 +410,66 @@ impl AccountActor {
                 );
                 self.cache_note_scripts(scripts_to_cache).await;
                 if !failed.is_empty() {
-                    let nullifiers: Vec<_> =
-                        failed.into_iter().map(|note| note.note.nullifier()).collect();
-                    self.mark_notes_failed(&nullifiers, block_num).await;
+                    let failed_notes: Vec<_> = failed
+                        .into_iter()
+                        .map(|f| {
+                            let error_msg = f.error.as_report();
+                            tracing::info!(
+                                note.id = %f.note.id(),
+                                nullifier = %f.note.nullifier(),
+                                err = %error_msg,
+                                "note failed: consumability check",
+                            );
+                            (f.note.nullifier(), error_msg)
+                        })
+                        .collect();
+                    self.mark_notes_failed(&failed_notes, block_num).await;
                 }
                 self.mode = ActorMode::TransactionInflight(tx_id);
             },
             // Transaction execution failed.
             Err(err) => {
+                let error_msg = err.as_report();
                 tracing::error!(
                     %account_id,
                     ?note_ids,
-                    err = err.as_report(),
+                    err = %error_msg,
                     "network transaction failed",
                 );
                 self.mode = ActorMode::NoViableNotes;
-                let nullifiers: Vec<_> = notes.iter().map(InflightNetworkNote::nullifier).collect();
-                self.mark_notes_failed(&nullifiers, block_num).await;
+
+                // For `AllNotesFailed`, use the per-note errors which contain the
+                // specific reason each note failed (e.g. consumability check details).
+                let failed_notes: Vec<_> =
+                    if let execute::NtxError::AllNotesFailed(per_note) = err {
+                        per_note
+                            .into_iter()
+                            .map(|f| {
+                                let note_error = f.error.as_report();
+                                tracing::info!(
+                                    note.id = %f.note.id(),
+                                    nullifier = %f.note.nullifier(),
+                                    err = %note_error,
+                                    "note failed: consumability check",
+                                );
+                                (f.note.nullifier(), note_error)
+                            })
+                            .collect()
+                    } else {
+                        notes
+                            .iter()
+                            .map(|note| {
+                                tracing::info!(
+                                    note.id = %note.to_inner().as_note().id(),
+                                    nullifier = %note.nullifier(),
+                                    err = %error_msg,
+                                    "note failed: transaction execution error",
+                                );
+                                (note.nullifier(), error_msg.clone())
+                            })
+                            .collect()
+                    };
+                self.mark_notes_failed(&failed_notes, block_num).await;
             },
         }
     }
@@ -449,12 +491,16 @@ impl AccountActor {
     /// Sends a request to the coordinator to mark notes as failed and waits for the DB write to
     /// complete. This prevents a race condition where the actor could re-select the same notes
     /// before the failure counts are updated in the database.
-    async fn mark_notes_failed(&self, nullifiers: &[Nullifier], block_num: BlockNumber) {
+    async fn mark_notes_failed(
+        &self,
+        failed_notes: &[(Nullifier, String)],
+        block_num: BlockNumber,
+    ) {
         let (ack_tx, ack_rx) = tokio::sync::oneshot::channel();
         if self
             .request_tx
             .send(ActorRequest::NotesFailed {
-                nullifiers: nullifiers.to_vec(),
+                failed_notes: failed_notes.to_vec(),
                 block_num,
                 ack_tx,
             })

crates/ntx-builder/src/builder.rs

@@ -7,7 +7,9 @@ use miden_node_proto::domain::account::NetworkAccountId;
 use miden_node_proto::domain::mempool::MempoolEvent;
 use miden_protocol::account::delta::AccountUpdateDetails;
 use miden_protocol::block::BlockHeader;
+use tokio::net::TcpListener;
 use tokio::sync::{RwLock, mpsc};
+use tokio::task::JoinSet;
 use tokio_stream::StreamExt;
 use tonic::Status;
 
@@ -17,6 +19,7 @@ use crate::chain_state::ChainState;
 use crate::clients::StoreClient;
 use crate::coordinator::Coordinator;
 use crate::db::Db;
+use crate::server::NtxBuilderRpcServer;
 
 // NETWORK TRANSACTION BUILDER
 // ================================================================================================
@@ -86,17 +89,45 @@ impl NetworkTransactionBuilder {
 
     /// Runs the network transaction builder event loop until a fatal error occurs.
     ///
+    /// If a `TcpListener` is provided, a gRPC server is also spawned to expose the
+    /// `GetNoteError` endpoint.
+    ///
     /// This method:
-    /// 1. Spawns a background task to load existing network accounts from the store
-    /// 2. Runs the main event loop, processing mempool events and managing actors
+    /// 1. Optionally starts a gRPC server for note error queries
+    /// 2. Spawns a background task to load existing network accounts from the store
+    /// 3. Runs the main event loop, processing mempool events and managing actors
     ///
     /// # Errors
     ///
     /// Returns an error if:
     /// - The mempool event stream ends unexpectedly
     /// - An actor encounters a fatal error
     /// - The account loader task fails
-    pub async fn run(mut self) -> anyhow::Result<()> {
+    /// - The gRPC server fails
+    pub async fn run(self, listener: Option<TcpListener>) -> anyhow::Result<()> {
+        let mut join_set = JoinSet::new();
+
+        // Start the gRPC server if a listener is provided.
+        if let Some(listener) = listener {
+            let server = NtxBuilderRpcServer::new(self.db.clone());
+            join_set.spawn(async move {
+                server.serve(listener).await.context("ntx-builder gRPC server failed")
+            });
+        }
+
+        join_set.spawn(self.run_event_loop());
+
+        // Wait for either the event loop or the gRPC server to complete.
+        // Any completion is treated as fatal.
+        if let Some(result) = join_set.join_next().await {
+            result.context("ntx-builder task panicked")??;
+        }
+
+        Ok(())
+    }
+
+    /// Runs the main event loop.
+    async fn run_event_loop(mut self) -> anyhow::Result<()> {
         // Spawn a background task to load network accounts from the store.
         // Accounts are sent through a channel and processed in the main event loop.
         let (account_tx, mut account_rx) =
@@ -245,9 +276,9 @@ impl NetworkTransactionBuilder {
     /// Processes a request from an account actor.
     async fn handle_actor_request(&mut self, request: ActorRequest) -> Result<(), anyhow::Error> {
         match request {
-            ActorRequest::NotesFailed { nullifiers, block_num, ack_tx } => {
+            ActorRequest::NotesFailed { failed_notes, block_num, ack_tx } => {
                 self.db
-                    .notes_failed(nullifiers, block_num)
+                    .notes_failed(failed_notes, block_num)
                     .await
                     .context("failed to mark notes as failed")?;
                 let _ = ack_tx.send(());

crates/ntx-builder/src/db/migrations/2026020900000_setup/up.sql

@@ -44,10 +44,14 @@ CREATE TABLE notes (
     account_id      BLOB    NOT NULL,
     -- Serialized SingleTargetNetworkNote.
     note_data       BLOB    NOT NULL,
+    -- Note ID bytes.
+    note_id         BLOB,
     -- Backoff tracking: number of failed execution attempts.
     attempt_count   INTEGER NOT NULL DEFAULT 0,
     -- Backoff tracking: block number of the last failed attempt. NULL if never attempted.
     last_attempt    INTEGER,
+    -- Latest execution error message. NULL if no error recorded.
+    last_error      TEXT,
     -- NULL if the note came from a committed block; transaction ID if created by inflight tx.
     created_by      BLOB,
     -- NULL if unconsumed; transaction ID of the consuming inflight tx.
@@ -60,6 +64,7 @@ CREATE TABLE notes (
 CREATE INDEX idx_notes_account ON notes(account_id);
 CREATE INDEX idx_notes_created_by ON notes(created_by) WHERE created_by IS NOT NULL;
 CREATE INDEX idx_notes_consumed_by ON notes(consumed_by) WHERE consumed_by IS NOT NULL;
+CREATE INDEX idx_notes_note_id ON notes(note_id) WHERE note_id IS NOT NULL;
 
 -- Persistent cache of note scripts, keyed by script root hash.
 -- Survives restarts so scripts don't need to be re-fetched from the store.