diff --git a/.config/e2e-distributed-selection.txt b/.config/e2e-distributed-selection.txt
index 2e59c7ca2..73eeb09b6 100644
--- a/.config/e2e-distributed-selection.txt
+++ b/.config/e2e-distributed-selection.txt
@@ -1,2 +1,2 @@
-sha256-linux=52a426e7fe4d41497bbe44db0dc450edbcb133dd966d7a41601cdae1e6788741
-sha256-darwin=52a426e7fe4d41497bbe44db0dc450edbcb133dd966d7a41601cdae1e6788741
+sha256-linux=47c690dc23add078813d44a78b6ab4a4347a5ecef9cf072bb71f08bd5ce1efe6
+sha256-darwin=47c690dc23add078813d44a78b6ab4a4347a5ecef9cf072bb71f08bd5ce1efe6
diff --git a/crates/e2e_test/src/common.rs b/crates/e2e_test/src/common.rs
index bdeb77511..99b0f4c4a 100644
--- a/crates/e2e_test/src/common.rs
+++ b/crates/e2e_test/src/common.rs
@@ -1770,11 +1770,6 @@ impl RustFSTestClusterEnvironment {
         self.node_capture_log_paths.push(None);
         self.volume_proxy_addresses.push(None);
 
-        if !self.extra_env.iter().any(|(key, _)| key == "RUSTFS_UNSAFE_BYPASS_DISK_CHECK") {
-            self.extra_env
-                .push(("RUSTFS_UNSAFE_BYPASS_DISK_CHECK".to_string(), "true".to_string()));
-        }
-
         Ok(new_idx)
     }
 
diff --git a/crates/e2e_test/src/distributed/chaos_test.rs b/crates/e2e_test/src/distributed/chaos_test.rs
index eeb57e7e6..65aa71146 100644
--- a/crates/e2e_test/src/distributed/chaos_test.rs
+++ b/crates/e2e_test/src/distributed/chaos_test.rs
@@ -17,7 +17,9 @@ use super::harness::{
     take_drive_offline, unique_bucket, wait_for_ready,
 };
 use crate::common::init_logging;
+use std::sync::Arc;
 use std::time::Duration;
+use tokio::sync::Barrier;
 
 #[tokio::test]
 async fn kill_and_restart_node_preserves_objects() -> TestResult {
@@ -80,18 +82,21 @@ async fn concurrent_gets_survive_peer_node_kill() -> TestResult {
     let body = vec![0x7Au8; 96 * 1024];
     put_object(&dist.client(0)?, &bucket, "steady.bin", body.clone()).await?;
 
-    dist.cluster.stop_node(3)?;
-
     let live: Vec<_> = (0..3).map(|idx| dist.client(idx)).collect::<Result<Vec<_>, _>>()?;
+    let start = Arc::new(Barrier::new(13));
     let mut handles = Vec::new();
     for idx in 0..12 {
         let client = live[idx % live.len()].clone();
         let bucket = bucket.clone();
         let body = body.clone();
+        let start = start.clone();
         handles.push(tokio::spawn(async move {
+            start.wait().await;
             retrying_get_equals(&client, &bucket, "steady.bin", &body, Duration::from_secs(20)).await
         }));
     }
+    start.wait().await;
+    dist.cluster.stop_node(3)?;
     for handle in handles {
         handle.await??;
     }
diff --git a/crates/e2e_test/src/distributed/harness.rs b/crates/e2e_test/src/distributed/harness.rs
index cb2ccf30a..799d1da67 100644
--- a/crates/e2e_test/src/distributed/harness.rs
+++ b/crates/e2e_test/src/distributed/harness.rs
@@ -23,8 +23,8 @@
 //!   tests. Live expand-then-restart currently hits `pool metadata recovery
 //!   required` on localhost DistErasure. That is a production bootstrap-proof
 //!   limitation this test lane does not change. Movement tests use 4×4 single
-//!   pool and classify decommission/rebalance 4xx/5xx as a refused move while
-//!   still asserting object bytes.
+//!   pool and classify decommission/rebalance product refusals (and opaque
+//!   500 InternalError) as a refused move while still asserting object bytes.
 //!
 //! Genuine multi-node *striped* pools still need multi-host CI (backlog
 //! #1313 / #1314). Site replication uses two 4-node 1-drive clusters so the
@@ -57,8 +57,6 @@ pub(crate) enum DistLayout {
     FourByFour,
     /// 4 nodes × 1 drive, one erasure pool (minimum 4-node 4-disk layout).
     FourNodeFourDisk,
-    /// 2 single-node pools, 4 drives each (expansion seed).
-    TwoPoolFourDrive,
 }
 
 pub(crate) struct DistCluster {
@@ -88,7 +86,6 @@ impl DistCluster {
         let topology = match layout {
             DistLayout::FourByFour => ClusterTopology::single_pool_multidrive(NODE_COUNT, DRIVES_PER_NODE),
             DistLayout::FourNodeFourDisk => ClusterTopology::single_pool(NODE_COUNT),
-            DistLayout::TwoPoolFourDrive => ClusterTopology::per_node_pools(DRIVES_PER_NODE, vec![vec![0], vec![1]]),
         };
         let mut cluster = RustFSTestClusterEnvironment::with_topology(topology).await?;
         cluster.set_env("NO_PROXY", "127.0.0.1,localhost");
@@ -516,9 +513,10 @@ pub(crate) fn is_pool_meta_write_fence(body: &str) -> bool {
         || body.contains("live fleet capability proof")
 }
 
-/// Product refusals that movement tests observe. Opaque 5xx stays in
-/// [`classify_data_movement_http`] because admin often wraps the fence as
-/// InternalError XML without the inner string. Auth failures are not refusals.
+/// Product refusals that movement tests observe. Opaque 500 InternalError stays
+/// in [`classify_data_movement_http`] because admin often wraps the fence as
+/// InternalError XML without the inner string. 502/503 and auth failures are
+/// not refusals.
 pub(crate) fn is_known_data_movement_refusal(body: &str) -> bool {
     is_pool_meta_write_fence(body)
         || body.contains("NotImplemented")
@@ -536,7 +534,7 @@ pub(crate) fn classify_data_movement_http(status: StatusCode, body: &str) -> Res
     if status.is_success() {
         return Ok(DataMovementStart::Started);
     }
-    if is_known_data_movement_refusal(body) || status.as_u16() == 501 || status.is_server_error() {
+    if is_known_data_movement_refusal(body) || status.as_u16() == 501 || status == StatusCode::INTERNAL_SERVER_ERROR {
         return Ok(DataMovementStart::Refused(format!("{status} {body}")));
     }
     Err(format!("{status} {body}"))
@@ -552,7 +550,7 @@ pub(crate) async fn try_start_decommission(
 }
 
 /// Returns whether decommission actually started. A product refusal or opaque
-/// 5xx is not a test failure: callers still assert object bytes.
+/// 500 InternalError is not a test failure: callers still assert object bytes.
 pub(crate) async fn decommission_started_or_refused(cluster: &RustFSTestClusterEnvironment, pool_id: usize) -> TestResult<bool> {
     match try_start_decommission(cluster, pool_id).await? {
         DataMovementStart::Started => Ok(true),
@@ -778,17 +776,18 @@ pub(crate) async fn retrying_get_equals(
 
 #[tokio::test]
 async fn append_single_node_pool_extends_ellipses_volumes() {
-    let mut dist = DistCluster::new_stopped(DistLayout::TwoPoolFourDrive)
-        .await
-        .expect("two-pool seed topology");
-    assert_eq!(dist.cluster.rustfs_volumes_arg().split(' ').count(), 2);
+    let mut env =
+        RustFSTestClusterEnvironment::with_topology(ClusterTopology::per_node_pools(DRIVES_PER_NODE, vec![vec![0], vec![1]]))
+            .await
+            .expect("two-pool seed topology");
+    assert_eq!(env.rustfs_volumes_arg().split(' ').count(), 2);
 
-    let added = dist.cluster.append_single_node_pool().await.expect("append third pool");
+    let added = env.append_single_node_pool().await.expect("append third pool");
     assert_eq!(added, 2);
-    assert_eq!(dist.cluster.nodes.len(), 3);
-    assert_eq!(dist.cluster.nodes[2].pool_idx, 2);
-    assert_eq!(dist.cluster.nodes[2].data_dirs.len(), DRIVES_PER_NODE);
-    let volumes = dist.cluster.rustfs_volumes_arg();
+    assert_eq!(env.nodes.len(), 3);
+    assert_eq!(env.nodes[2].pool_idx, 2);
+    assert_eq!(env.nodes[2].data_dirs.len(), DRIVES_PER_NODE);
+    let volumes = env.rustfs_volumes_arg();
     assert_eq!(volumes.split(' ').count(), 3, "expected three pool arguments, got: {volumes}");
     assert!(volumes.contains("/drive{0...3}"), "expanded layout must keep drive ellipses: {volumes}");
 }
@@ -807,6 +806,35 @@ async fn append_single_node_pool_rejects_striped_single_pool() {
     );
 }
 
+#[cfg(unix)]
+#[tokio::test]
+async fn cluster_start_fails_fast_when_node_process_exits() {
+    let mut dist = DistCluster::new_stopped(DistLayout::FourNodeFourDisk)
+        .await
+        .expect("stopped 4-node cluster");
+    let script = format!("{}/immediate-exit.sh", dist.cluster.temp_dir);
+    std::fs::write(&script, "#!/bin/sh\nexit 1\n").expect("write exit stub");
+    let mut perms = std::fs::metadata(&script).expect("stat exit stub").permissions();
+    std::os::unix::fs::PermissionsExt::set_mode(&mut perms, 0o755);
+    std::fs::set_permissions(&script, perms).expect("chmod exit stub");
+
+    let started = Instant::now();
+    let err = dist
+        .start_from_binary(Path::new(&script))
+        .await
+        .expect_err("a node that exits immediately must fail start");
+    let elapsed = started.elapsed();
+    let message = err.to_string();
+    assert!(
+        message.contains("exited before TCP ready") || message.contains("exited before S3 ready"),
+        "unexpected start error: {message}"
+    );
+    assert!(
+        elapsed < Duration::from_secs(30),
+        "cluster start must fail fast when a node exits, took {elapsed:?}"
+    );
+}
+
 #[test]
 fn decommission_complete_reads_pool_status_and_info_flag() {
     let status = serde_json::json!({
@@ -896,4 +924,10 @@ fn classify_data_movement_http_observes_product_refusals_not_auth_failures() {
     ));
     let denied = classify_data_movement_http(StatusCode::FORBIDDEN, "AccessDenied").expect_err("auth failure is not a refusal");
     assert!(denied.contains("AccessDenied"), "{denied}");
+    let unavailable = classify_data_movement_http(StatusCode::SERVICE_UNAVAILABLE, "ServiceUnavailable")
+        .expect_err("503 is not a product refusal");
+    assert!(unavailable.contains("ServiceUnavailable"), "{unavailable}");
+    let bad_gateway =
+        classify_data_movement_http(StatusCode::BAD_GATEWAY, "Bad Gateway").expect_err("502 is not a product refusal");
+    assert!(bad_gateway.contains("502") || bad_gateway.contains("Bad Gateway"), "{bad_gateway}");
 }
diff --git a/docs/testing/distributed-e2e.md b/docs/testing/distributed-e2e.md
index 4040b51a5..2fb0322b1 100644
--- a/docs/testing/distributed-e2e.md
+++ b/docs/testing/distributed-e2e.md
@@ -15,7 +15,7 @@ The in-tree harness runs every node on `127.0.0.1` with a distinct port. That ma
 
 A pool striped across several localhost ports is not expressible (`RUSTFS_VOLUMES` host ellipses would collide on disk paths). Multi-host striped pools remain the hardware functional-chain / backlog #1313 / #1314 lane.
 
-Decommission and rebalance POST on the 4×4 single-pool layout is refused by the current product (`single pool deployments do not support decommission`, NotImplemented, or an opaque admin 5xx when the inner pool-meta fence is wrapped as InternalError). Those cases still assert object bytes and SHA-256; when the API starts they wait for completion and assert post-move integrity. They do not treat a refusal as a successful move. This lane does not change production pool-meta bootstrap, write-fence, or decommission policy; it only observes the current server behavior.
+Decommission and rebalance POST on the 4×4 single-pool layout is refused by the current product (`single pool deployments do not support decommission`, NotImplemented, or opaque 500 InternalError when the inner pool-meta fence is wrapped). 502/503 are not treated as a product refusal. Those cases still assert object bytes and SHA-256; when the API starts they wait for completion and assert post-move integrity. They do not treat a refusal as a successful move. This lane does not change production pool-meta bootstrap, write-fence, or decommission policy; it only observes the current server behavior.
 
 ## What this lane covers