From 6bb2dab202ea7ae467a5f181065dc99543cf96f3 Mon Sep 17 00:00:00 2001
From: julio4 <30329843+julio4@users.noreply.github.com>
Date: Wed, 8 Jul 2026 23:42:33 +0900
Subject: [PATCH] fix: supervise flashblock scheduler task

---
 crates/op-rbuilder/src/builder/payload.rs | 25 +++++++++++++++++++----
 crates/op-rbuilder/src/metrics.rs         |  3 +++
 2 files changed, 24 insertions(+), 4 deletions(-)

diff --git a/crates/op-rbuilder/src/builder/payload.rs b/crates/op-rbuilder/src/builder/payload.rs
index 48e6b51f..35a40d2b 100644
--- a/crates/op-rbuilder/src/builder/payload.rs
+++ b/crates/op-rbuilder/src/builder/payload.rs
@@ -20,6 +20,7 @@ use crate::{
 };
 use alloy_primitives::B256;
 use eyre::WrapErr as _;
+use futures::FutureExt;
 use op_alloy_rpc_types_engine::OpFlashblockPayload;
 use reth_chainspec::EthChainSpec;
 use reth_node_api::PayloadBuilderError;
@@ -796,16 +797,32 @@ where
             .map_err(|e| PayloadBuilderError::Other(e.into()))?;
 
         let (tx, rx) = mpsc::channel((expected_flashblocks + 1) as usize);
-        tokio::spawn(
+        let scheduler_payload_id = fb_payload.payload_id;
+        let scheduler_task =
             self.task_metrics
                 .flashblock_timer
                 .instrument(flashblock_scheduler.run(
                     tx,
                     payload_cancel.clone(),
                     fb_cancel,
-                    fb_payload.payload_id,
-                )),
-        );
+                    scheduler_payload_id,
+                ));
+        let scheduler_metrics = self.builder_ctx.metrics.clone();
+
+        self.executor.spawn_task(async move {
+            if std::panic::AssertUnwindSafe(scheduler_task)
+                .catch_unwind()
+                .await
+                .is_err()
+            {
+                scheduler_metrics.flashblock_scheduler_death.increment(1);
+                error!(
+                    target: "payload_builder",
+                    id = %scheduler_payload_id,
+                    "Flashblock scheduler task panicked, no further flashblocks will be triggered for this payload",
+                );
+            }
+        });
 
         // State data was extracted in Phase 1 block scope above.
         // We carry (CacheState, Option<TransitionState>) between iterations
diff --git a/crates/op-rbuilder/src/metrics.rs b/crates/op-rbuilder/src/metrics.rs
index 1aa9f251..1c2835d6 100644
--- a/crates/op-rbuilder/src/metrics.rs
+++ b/crates/op-rbuilder/src/metrics.rs
@@ -200,6 +200,9 @@ pub struct OpRBuilderMetrics {
     pub continuous_fee_improvement: Histogram,
     /// Builds completed but not published due to resolved gate
     pub flashblock_publish_suppressed_total: Counter,
+    /// Flashblock scheduler task ended abnormally (panicked) instead of
+    /// completing or being cancelled normally
+    pub flashblock_scheduler_death: Counter,
     /// TODO: Use labels for these
     /// Payload job ended because getPayload resolved
     pub payload_job_cancellation_resolved: Counter,