add pollHealthChecker interface for optional RPC health checks

multinode/config/config.go

@@ -34,6 +34,9 @@ type MultiNode struct {
 	FinalityDepth                *uint32
 	FinalityTagEnabled           *bool
 	FinalizedBlockOffset         *uint32
+
+	// Finalized State Availability Check
+	FinalizedStateCheckFailureThreshold *uint32
 }
 
 func (c *MultiNodeConfig) Enabled() bool {
@@ -94,6 +97,10 @@ func (c *MultiNodeConfig) FinalityTagEnabled() bool { return *c.MultiNode.Finali
 
 func (c *MultiNodeConfig) FinalizedBlockOffset() uint32 { return *c.MultiNode.FinalizedBlockOffset }
 
+func (c *MultiNodeConfig) FinalizedStateCheckFailureThreshold() uint32 {
+	return *c.MultiNode.FinalizedStateCheckFailureThreshold
+}
+
 func (c *MultiNodeConfig) SetFrom(f *MultiNodeConfig) {
 	if f.MultiNode.Enabled != nil {
 		c.MultiNode.Enabled = f.MultiNode.Enabled
@@ -150,4 +157,9 @@ func (c *MultiNodeConfig) SetFrom(f *MultiNodeConfig) {
 	if f.MultiNode.FinalizedBlockOffset != nil {
 		c.MultiNode.FinalizedBlockOffset = f.MultiNode.FinalizedBlockOffset
 	}
+
+	// Finalized State Availability Check
+	if f.MultiNode.FinalizedStateCheckFailureThreshold != nil {
+		c.MultiNode.FinalizedStateCheckFailureThreshold = f.MultiNode.FinalizedStateCheckFailureThreshold
+	}
 }

multinode/go.mod

@@ -7,7 +7,7 @@ require (
 	github.com/pkg/errors v0.9.1
 	github.com/prometheus/client_model v0.6.2
 	github.com/smartcontractkit/chainlink-common v0.10.1-0.20260305114348-b8bbac30bfc7
-	github.com/smartcontractkit/chainlink-framework/metrics v0.0.0-20250717121125-2350c82883e2
+	github.com/smartcontractkit/chainlink-framework/metrics v0.0.0-20260310180305-3ee91a6d9ae9
 	github.com/stretchr/testify v1.11.1
 	go.uber.org/zap v1.27.1
 )

multinode/go.sum

@@ -80,8 +80,8 @@ github.com/smartcontractkit/chainlink-common v0.10.1-0.20260305114348-b8bbac30bf
 github.com/smartcontractkit/chainlink-common v0.10.1-0.20260305114348-b8bbac30bfc7/go.mod h1:0ghbAr7tRO0tT5ZqBXhOyzgUO37tNNe33Yn0hskauVM=
 github.com/smartcontractkit/chainlink-common/pkg/chipingress v0.0.10 h1:FJAFgXS9oqASnkS03RE1HQwYQQxrO4l46O5JSzxqLgg=
 github.com/smartcontractkit/chainlink-common/pkg/chipingress v0.0.10/go.mod h1:oiDa54M0FwxevWwyAX773lwdWvFYYlYHHQV1LQ5HpWY=
-github.com/smartcontractkit/chainlink-framework/metrics v0.0.0-20250717121125-2350c82883e2 h1:ysZjKH+BpWlQhF93kr/Lc668UlCvT9NjfcsGdZT19I8=
-github.com/smartcontractkit/chainlink-framework/metrics v0.0.0-20250717121125-2350c82883e2/go.mod h1:jo+cUqNcHwN8IF7SInQNXDZ8qzBsyMpnLdYbDswviFc=
+github.com/smartcontractkit/chainlink-framework/metrics v0.0.0-20260310180305-3ee91a6d9ae9 h1:GK+2aFpW/Z5ZnMGCa9NU6o7LKHQ/9xJVZx2yMAMudnc=
+github.com/smartcontractkit/chainlink-framework/metrics v0.0.0-20260310180305-3ee91a6d9ae9/go.mod h1:HG/aei0MgBOpsyRLexdKGtOUO8yjSJO3iUu0Uu8KBm4=
 github.com/smartcontractkit/freeport v0.1.3-0.20250716200817-cb5dfd0e369e h1:Hv9Mww35LrufCdM9wtS9yVi/rEWGI1UnjHbcKKU0nVY=
 github.com/smartcontractkit/freeport v0.1.3-0.20250716200817-cb5dfd0e369e/go.mod h1:T4zH9R8R8lVWKfU7tUvYz2o2jMv1OpGCdpY2j2QZXzU=
 github.com/smartcontractkit/libocr v0.0.0-20250912173940-f3ab0246e23d h1:LokA9PoCNb8mm8mDT52c3RECPMRsGz1eCQORq+J3n74=

multinode/node.go

@@ -27,6 +27,7 @@ type NodeConfig interface {
 	DeathDeclarationDelay() time.Duration
 	NewHeadsPollInterval() time.Duration
 	VerifyChainID() bool
+	FinalizedStateCheckFailureThreshold() uint32
 }
 
 type ChainConfig interface {
@@ -48,13 +49,15 @@ type nodeMetrics interface {
 	IncrementNodeTransitionsToInvalidChainID(ctx context.Context, nodeName string)
 	IncrementNodeTransitionsToUnusable(ctx context.Context, nodeName string)
 	IncrementNodeTransitionsToSyncing(ctx context.Context, nodeName string)
+	IncrementNodeTransitionsToFinalizedStateNotAvailable(ctx context.Context, nodeName string)
 	RecordNodeClientVersion(ctx context.Context, nodeName string, version string)
 	SetHighestSeenBlock(ctx context.Context, nodeName string, blockNumber int64)
 	SetHighestFinalizedBlock(ctx context.Context, nodeName string, blockNumber int64)
 	IncrementSeenBlocks(ctx context.Context, nodeName string)
 	IncrementPolls(ctx context.Context, nodeName string)
 	IncrementPollsFailed(ctx context.Context, nodeName string)
 	IncrementPollsSuccess(ctx context.Context, nodeName string)
+	IncrementFinalizedStateFailed(ctx context.Context, nodeName string)
 }
 
 type Node[
@@ -273,7 +276,7 @@ func (n *node[CHAIN_ID, HEAD, RPC]) verifyChainID(callerCtx context.Context, lgg
 		// The node is already closed, and any subsequent transition is invalid.
 		// To make spotting such transitions a bit easier, return the invalid node state.
 		return nodeStateLen
-	case nodeStateDialed, nodeStateOutOfSync, nodeStateInvalidChainID, nodeStateSyncing:
+	case nodeStateDialed, nodeStateOutOfSync, nodeStateInvalidChainID, nodeStateSyncing, nodeStateFinalizedStateNotAvailable:
 	default:
 		panic(fmt.Sprintf("cannot verify node in state %v", st))
 	}

multinode/node_fsm.go

@@ -35,6 +35,8 @@ func (n nodeState) String() string {
 		return "Syncing"
 	case nodeStateFinalizedBlockOutOfSync:
 		return "FinalizedBlockOutOfSync"
+	case nodeStateFinalizedStateNotAvailable:
+		return "FinalizedStateNotAvailable"
 	default:
 		return fmt.Sprintf("nodeState(%d)", n)
 	}
@@ -72,6 +74,8 @@ const (
 	nodeStateSyncing
 	// nodeStateFinalizedBlockOutOfSync - node is lagging behind on latest finalized block
 	nodeStateFinalizedBlockOutOfSync
+	// nodeStateFinalizedStateNotAvailable - node cannot serve historical state at finalized block
+	nodeStateFinalizedStateNotAvailable
 	// nodeStateLen tracks the number of states
 	nodeStateLen
 )
@@ -182,7 +186,7 @@ func (n *node[CHAIN_ID, HEAD, RPC]) transitionToAlive(fn func()) {
 		return
 	}
 	switch n.state {
-	case nodeStateDialed, nodeStateInvalidChainID, nodeStateSyncing:
+	case nodeStateDialed, nodeStateInvalidChainID, nodeStateSyncing, nodeStateFinalizedStateNotAvailable:
 		n.state = nodeStateAlive
 	default:
 		panic(transitionFail(n.state, nodeStateAlive))
@@ -288,6 +292,8 @@ func (n *node[CHAIN_ID, HEAD, RPC]) declareState(state nodeState) {
 		n.declareSyncing()
 	case nodeStateAlive:
 		n.declareAlive()
+	case nodeStateFinalizedStateNotAvailable:
+		n.declareFinalizedStateNotAvailable()
 	default:
 		panic(fmt.Sprintf("%#v state declaration is not implemented", state))
 	}
@@ -351,6 +357,33 @@ func (n *node[CHAIN_ID, HEAD, RPC]) transitionToSyncing(fn func()) {
 	fn()
 }
 
+func (n *node[CHAIN_ID, HEAD, RPC]) declareFinalizedStateNotAvailable() {
+	n.transitionToFinalizedStateNotAvailable(func() {
+		n.lfcLog.Errorw("RPC Node cannot serve finalized state", "nodeState", n.state)
+		n.wg.Add(1)
+		go n.finalizedStateNotAvailableLoop()
+	})
+}
+
+func (n *node[CHAIN_ID, HEAD, RPC]) transitionToFinalizedStateNotAvailable(fn func()) {
+	ctx, cancel := n.stopCh.NewCtx()
+	defer cancel()
+	n.metrics.IncrementNodeTransitionsToFinalizedStateNotAvailable(ctx, n.name)
+	n.stateMu.Lock()
+	defer n.stateMu.Unlock()
+	if n.state == nodeStateClosed {
+		return
+	}
+	switch n.state {
+	case nodeStateAlive:
+		n.rpc.Close()
+		n.state = nodeStateFinalizedStateNotAvailable
+	default:
+		panic(transitionFail(n.state, nodeStateFinalizedStateNotAvailable))
+	}
+	fn()
+}
+
 func transitionFail(from nodeState, to nodeState) string {
 	return fmt.Sprintf("cannot transition from %#v to %#v", from, to)
 }

multinode/node_fsm_test.go

@@ -36,7 +36,7 @@ func TestUnit_Node_StateTransitions(t *testing.T) {
 
 	t.Run("transitionToAlive", func(t *testing.T) {
 		const destinationState = nodeStateAlive
-		allowedStates := []nodeState{nodeStateDialed, nodeStateInvalidChainID, nodeStateSyncing}
+		allowedStates := []nodeState{nodeStateDialed, nodeStateInvalidChainID, nodeStateSyncing, nodeStateFinalizedStateNotAvailable}
 		rpc := newMockRPCClient[ID, Head](t)
 		testTransition(t, rpc, testNode.transitionToAlive, destinationState, allowedStates...)
 	})