From 9545f91757ad056537f7b9fbb372ac450e0ab7af Mon Sep 17 00:00:00 2001
From: Hubert Bugaj <lesny.rumcajs+github@gmail.com>
Date: Mon, 16 Feb 2026 09:26:40 +0100
Subject: [PATCH 1/2] fix: don't mark tipsets with temporal errors as
 permanently bad

---
 src/chain_sync/chain_follower.rs | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/src/chain_sync/chain_follower.rs b/src/chain_sync/chain_follower.rs
index ef7cebc16ec4..4764046293e1 100644
--- a/src/chain_sync/chain_follower.rs
+++ b/src/chain_sync/chain_follower.rs
@@ -22,7 +22,9 @@ use crate::{
     chain::ChainStore,
     chain_sync::{
         ForkSyncInfo, ForkSyncStage, SyncStatus, SyncStatusReport, TipsetValidator,
-        bad_block_cache::BadBlockCache, metrics, tipset_syncer::validate_tipset,
+        bad_block_cache::BadBlockCache,
+        metrics,
+        tipset_syncer::{TipsetSyncerError, validate_tipset},
     },
     libp2p::{NetworkEvent, PubsubMessage, hello::HelloRequest},
     message_pool::{MessagePool, MpoolRpcProvider},
@@ -846,6 +848,14 @@ impl SyncTask {
                     tipset,
                     is_proposed_head,
                 }),
+                // If temporal drift error, don't mark as bad, just skip validation and try again
+                // later. This mirrors internal logic where temporal drift doesn't mark a block as
+                // bad permanently, since it could be valid later on. If not done, a single
+                // time-traveling block could cause the node to be stuck without making progress.
+                Err(e) if matches!(e, TipsetSyncerError::TimeTravellingBlock { .. }) => {
+                    warn!("Time travelling block detected, skipping tipset for now: {e}");
+                    None
+                }
                 Err(e) => {
                     warn!("Error validating tipset: {e}");
                     Some(SyncEvent::BadTipset(tipset))

From b7a27e3022978c096a6c91042bcece7f197e9fe7 Mon Sep 17 00:00:00 2001
From: Hubert Bugaj <lesny.rumcajs+github@gmail.com>
Date: Mon, 16 Feb 2026 11:00:17 +0100
Subject: [PATCH 2/2] changelog

---
 CHANGELOG.md | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 3663f7721bfa..9f1a826cfbd3 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -35,6 +35,8 @@
 
 ### Fixed
 
+- [#6613](https://github.com/ChainSafe/forest/pull/6613): Fixed chain sync getting stuck when encountering time-travelling blocks by not marking the corresponding tipsets as permanently bad.
+
 ## Forest v0.32.1 "Malfoy"
 
 This is a non-mandatory release for all node operators. It sets F3 initial power table on calibnet for late F3 participation and F3 data verification scenarios. It also includes new V2 RPC methods, a few bug fixes and `lotus-gateway` compatibility fixes.