diff --git a/blockchain/v2/routine.go b/blockchain/v2/routine.go
index e4ca52add..dad0e737f 100644
--- a/blockchain/v2/routine.go
+++ b/blockchain/v2/routine.go
@@ -58,7 +58,7 @@ func (rt *Routine) setMetrics(metrics *Metrics) {
 }
 
 func (rt *Routine) start() {
-	rt.logger.Info(fmt.Sprintf("%s: run", rt.name))
+	rt.logger.Info("routine start", "msg", log.NewLazySprintf("%s: run", rt.name))
 	running := atomic.CompareAndSwapUint32(rt.running, uint32(0), uint32(1))
 	if !running {
 		panic(fmt.Sprintf("%s is already running", rt.name))
@@ -98,7 +98,7 @@ func (rt *Routine) start() {
 			return
 		}
 		rt.metrics.EventsOut.With("routine", rt.name).Add(1)
-		rt.logger.Debug(fmt.Sprintf("%s: produced %T %+v", rt.name, oEvent, oEvent))
+		rt.logger.Debug("routine start", "msg", log.NewLazySprintf("%s: produced %T %+v", rt.name, oEvent, oEvent))
 
 		// Skip rTrySchedule and rProcessBlock events as they clutter the history
 		// due to their frequency.
@@ -118,7 +118,7 @@ func (rt *Routine) start() {
 
 // XXX: look into returning OpError in the net package
 func (rt *Routine) send(event Event) bool {
-	rt.logger.Debug(fmt.Sprintf("%s: received %T %+v", rt.name, event, event))
+	rt.logger.Debug("routine send", "msg", log.NewLazySprintf("%s: received %T %+v", rt.name, event, event))
 	if !rt.isRunning() {
 		return false
 	}
@@ -150,7 +150,7 @@ func (rt *Routine) stop() {
 		return
 	}
 
-	rt.logger.Info(fmt.Sprintf("%s: stop", rt.name))
+	rt.logger.Info("routine stop", "msg", log.NewLazySprintf("%s: stop", rt.name))
 	rt.queue.Dispose() // this should block until all queue items are free?
 }
 
diff --git a/consensus/reactor.go b/consensus/reactor.go
index 73f190394..d6b22786b 100644
--- a/consensus/reactor.go
+++ b/consensus/reactor.go
@@ -1265,12 +1265,12 @@ func (ps *PeerState) SetHasVote(vote *types.Vote) {
 }
 
 func (ps *PeerState) setHasVote(height int64, round int32, voteType tmproto.SignedMsgType, index int32) {
-	logger := ps.logger.With(
+	ps.logger.Debug("setHasVote",
 		"peerH/R",
-		fmt.Sprintf("%d/%d", ps.PRS.Height, ps.PRS.Round),
+		log.NewLazySprintf("%d/%d", ps.PRS.Height, ps.PRS.Round),
 		"H/R",
-		fmt.Sprintf("%d/%d", height, round))
-	logger.Debug("setHasVote", "type", voteType, "index", index)
+		log.NewLazySprintf("%d/%d", height, round),
+		"type", voteType, "index", index)
 
 	// NOTE: some may be nil BitArrays -> no side effects.
 	psVotes := ps.getVoteBitArray(height, round, voteType)
diff --git a/consensus/state.go b/consensus/state.go
index 0e74583f8..9e6d980a3 100644
--- a/consensus/state.go
+++ b/consensus/state.go
@@ -981,7 +981,7 @@ func (cs *State) enterNewRound(height int64, round int32) {
 	if cs.Height != height || round < cs.Round || (cs.Round == round && cs.Step != cstypes.RoundStepNewHeight) {
 		logger.Debug(
 			"entering new round with invalid args",
-			"current", fmt.Sprintf("%v/%v/%v", cs.Height, cs.Round, cs.Step),
+			"current", log.NewLazySprintf("%v/%v/%v", cs.Height, cs.Round, cs.Step),
 		)
 		return
 	}
@@ -990,7 +990,7 @@ func (cs *State) enterNewRound(height int64, round int32) {
 		logger.Debug("need to set a buffer and log message here for sanity", "start_time", cs.StartTime, "now", now)
 	}
 
-	logger.Debug("entering new round", "current", fmt.Sprintf("%v/%v/%v", cs.Height, cs.Round, cs.Step))
+	logger.Debug("entering new round", "current", log.NewLazySprintf("%v/%v/%v", cs.Height, cs.Round, cs.Step))
 
 	// increment validators if necessary
 	validators := cs.Validators
@@ -1063,12 +1063,12 @@ func (cs *State) enterPropose(height int64, round int32) {
 	if cs.Height != height || round < cs.Round || (cs.Round == round && cstypes.RoundStepPropose <= cs.Step) {
 		logger.Debug(
 			"entering propose step with invalid args",
-			"current", fmt.Sprintf("%v/%v/%v", cs.Height, cs.Round, cs.Step),
+			"current", log.NewLazySprintf("%v/%v/%v", cs.Height, cs.Round, cs.Step),
 		)
 		return
 	}
 
-	logger.Debug("entering propose step", "current", fmt.Sprintf("%v/%v/%v", cs.Height, cs.Round, cs.Step))
+	logger.Debug("entering propose step", "current", log.NewLazySprintf("%v/%v/%v", cs.Height, cs.Round, cs.Step))
 
 	defer func() {
 		// Done enterPropose:
@@ -1230,7 +1230,7 @@ func (cs *State) enterPrevote(height int64, round int32) {
 	if cs.Height != height || round < cs.Round || (cs.Round == round && cstypes.RoundStepPrevote <= cs.Step) {
 		logger.Debug(
 			"entering prevote step with invalid args",
-			"current", fmt.Sprintf("%v/%v/%v", cs.Height, cs.Round, cs.Step),
+			"current", log.NewLazySprintf("%v/%v/%v", cs.Height, cs.Round, cs.Step),
 		)
 		return
 	}
@@ -1241,7 +1241,7 @@ func (cs *State) enterPrevote(height int64, round int32) {
 		cs.newStep()
 	}()
 
-	logger.Debug("entering prevote step", "current", fmt.Sprintf("%v/%v/%v", cs.Height, cs.Round, cs.Step))
+	logger.Debug("entering prevote step", "current", log.NewLazySprintf("%v/%v/%v", cs.Height, cs.Round, cs.Step))
 
 	// Sign and broadcast vote as necessary
 	cs.doPrevote(height, round)
@@ -1290,7 +1290,7 @@ func (cs *State) enterPrevoteWait(height int64, round int32) {
 	if cs.Height != height || round < cs.Round || (cs.Round == round && cstypes.RoundStepPrevoteWait <= cs.Step) {
 		logger.Debug(
 			"entering prevote wait step with invalid args",
-			"current", fmt.Sprintf("%v/%v/%v", cs.Height, cs.Round, cs.Step),
+			"current", log.NewLazySprintf("%v/%v/%v", cs.Height, cs.Round, cs.Step),
 		)
 		return
 	}
@@ -1302,7 +1302,7 @@ func (cs *State) enterPrevoteWait(height int64, round int32) {
 		))
 	}
 
-	logger.Debug("entering prevote wait step", "current", fmt.Sprintf("%v/%v/%v", cs.Height, cs.Round, cs.Step))
+	logger.Debug("entering prevote wait step", "current", log.NewLazySprintf("%v/%v/%v", cs.Height, cs.Round, cs.Step))
 
 	defer func() {
 		// Done enterPrevoteWait:
@@ -1326,12 +1326,12 @@ func (cs *State) enterPrecommit(height int64, round int32) {
 	if cs.Height != height || round < cs.Round || (cs.Round == round && cstypes.RoundStepPrecommit <= cs.Step) {
 		logger.Debug(
 			"entering precommit step with invalid args",
-			"current", fmt.Sprintf("%v/%v/%v", cs.Height, cs.Round, cs.Step),
+			"current", log.NewLazySprintf("%v/%v/%v", cs.Height, cs.Round, cs.Step),
 		)
 		return
 	}
 
-	logger.Debug("entering precommit step", "current", fmt.Sprintf("%v/%v/%v", cs.Height, cs.Round, cs.Step))
+	logger.Debug("entering precommit step", "current", log.NewLazySprintf("%v/%v/%v", cs.Height, cs.Round, cs.Step))
 
 	defer func() {
 		// Done enterPrecommit:
@@ -1449,7 +1449,7 @@ func (cs *State) enterPrecommitWait(height int64, round int32) {
 		logger.Debug(
 			"entering precommit wait step with invalid args",
 			"triggered_timeout", cs.TriggeredTimeoutPrecommit,
-			"current", fmt.Sprintf("%v/%v", cs.Height, cs.Round),
+			"current", log.NewLazySprintf("%v/%v", cs.Height, cs.Round),
 		)
 		return
 	}
@@ -1461,7 +1461,7 @@ func (cs *State) enterPrecommitWait(height int64, round int32) {
 		))
 	}
 
-	logger.Debug("entering precommit wait step", "current", fmt.Sprintf("%v/%v/%v", cs.Height, cs.Round, cs.Step))
+	logger.Debug("entering precommit wait step", "current", log.NewLazySprintf("%v/%v/%v", cs.Height, cs.Round, cs.Step))
 
 	defer func() {
 		// Done enterPrecommitWait:
@@ -1480,12 +1480,12 @@ func (cs *State) enterCommit(height int64, commitRound int32) {
 	if cs.Height != height || cstypes.RoundStepCommit <= cs.Step {
 		logger.Debug(
 			"entering commit step with invalid args",
-			"current", fmt.Sprintf("%v/%v/%v", cs.Height, cs.Round, cs.Step),
+			"current", log.NewLazySprintf("%v/%v/%v", cs.Height, cs.Round, cs.Step),
 		)
 		return
 	}
 
-	logger.Debug("entering commit step", "current", fmt.Sprintf("%v/%v/%v", cs.Height, cs.Round, cs.Step))
+	logger.Debug("entering commit step", "current", log.NewLazySprintf("%v/%v/%v", cs.Height, cs.Round, cs.Step))
 
 	defer func() {
 		// Done enterCommit:
@@ -1518,7 +1518,7 @@ func (cs *State) enterCommit(height int64, commitRound int32) {
 		if !cs.ProposalBlockParts.HasHeader(blockID.PartSetHeader) {
 			logger.Info(
 				"commit is for a block we do not know about; set ProposalBlock=nil",
-				"proposal", cs.ProposalBlock.Hash(),
+				"proposal", log.NewLazyBlockHash(cs.ProposalBlock),
 				"commit", blockID.Hash,
 			)
 
@@ -1555,7 +1555,7 @@ func (cs *State) tryFinalizeCommit(height int64) {
 		// TODO: ^^ wait, why does it matter that we're a validator?
 		logger.Debug(
 			"failed attempt to finalize commit; we do not have the commit block",
-			"proposal_block", cs.ProposalBlock.Hash(),
+			"proposal_block", log.NewLazyBlockHash(cs.ProposalBlock),
 			"commit_block", blockID.Hash,
 		)
 		return
@@ -1571,7 +1571,7 @@ func (cs *State) finalizeCommit(height int64) {
 	if cs.Height != height || cs.Step != cstypes.RoundStepCommit {
 		logger.Debug(
 			"entering finalize commit step",
-			"current", fmt.Sprintf("%v/%v/%v", cs.Height, cs.Round, cs.Step),
+			"current", log.NewLazySprintf("%v/%v/%v", cs.Height, cs.Round, cs.Step),
 		)
 		return
 	}
@@ -1597,11 +1597,11 @@ func (cs *State) finalizeCommit(height int64) {
 
 	logger.Info(
 		"finalizing commit of block",
-		"hash", block.Hash(),
+		"hash", log.NewLazyBlockHash(block),
 		"root", block.AppHash,
 		"num_txs", len(block.Txs),
 	)
-	logger.Debug(fmt.Sprintf("%v", block))
+	logger.Debug("committed block", "block", log.NewLazySprintf("%v", block))
 
 	fail.Fail() // XXX
 
@@ -1918,7 +1918,7 @@ func (cs *State) handleCompleteProposal(blockHeight int64) {
 			cs.Logger.Debug(
 				"updating valid block to new proposal block",
 				"valid_round", cs.Round,
-				"valid_block_hash", cs.ProposalBlock.Hash(),
+				"valid_block_hash", log.NewLazyBlockHash(cs.ProposalBlock),
 			)
 
 			cs.ValidRound = cs.Round
@@ -2092,7 +2092,7 @@ func (cs *State) addVote(vote *types.Vote, peerID p2p.ID) (added bool, err error
 				} else {
 					cs.Logger.Debug(
 						"valid block we do not know about; set ProposalBlock=nil",
-						"proposal", cs.ProposalBlock.Hash(),
+						"proposal", log.NewLazyBlockHash(cs.ProposalBlock),
 						"block_id", blockID.Hash,
 					)
 
diff --git a/libs/log/lazy.go b/libs/log/lazy.go
new file mode 100644
index 000000000..521fa1952
--- /dev/null
+++ b/libs/log/lazy.go
@@ -0,0 +1,42 @@
+package log
+
+import (
+	"fmt"
+
+	tmbytes "github.com/tendermint/tendermint/libs/bytes"
+)
+
+type LazySprintf struct {
+	format string
+	args   []interface{}
+}
+
+// NewLazySprintf defers fmt.Sprintf until the Stringer interface is invoked.
+// This is particularly useful for avoiding calling Sprintf when debugging is not
+// active.
+func NewLazySprintf(format string, args ...interface{}) *LazySprintf {
+	return &LazySprintf{format, args}
+}
+
+func (l *LazySprintf) String() string {
+	return fmt.Sprintf(l.format, l.args...)
+}
+
+type LazyBlockHash struct {
+	block hashable
+}
+
+type hashable interface {
+	Hash() tmbytes.HexBytes
+}
+
+// NewLazyBlockHash defers block Hash until the Stringer interface is invoked.
+// This is particularly useful for avoiding calling Sprintf when debugging is not
+// active.
+func NewLazyBlockHash(block hashable) *LazyBlockHash {
+	return &LazyBlockHash{block}
+}
+
+func (l *LazyBlockHash) String() string {
+	return l.block.Hash().String()
+}
diff --git a/libs/log/tmfmt_logger.go b/libs/log/tmfmt_logger.go
index 01cf72192..391ae478a 100644
--- a/libs/log/tmfmt_logger.go
+++ b/libs/log/tmfmt_logger.go
@@ -87,6 +87,12 @@ func (l tmfmtLogger) Log(keyvals ...interface{}) error {
 		if b, ok := keyvals[i+1].([]byte); ok {
 			keyvals[i+1] = strings.ToUpper(hex.EncodeToString(b))
 		}
+
+		// Realize stringers
+		if s, ok := keyvals[i+1].(fmt.Stringer); ok {
+			keyvals[i+1] = s.String()
+		}
+
 	}
 
 	// Form a custom Tendermint line
diff --git a/libs/os/os.go b/libs/os/os.go
index 79e340d19..a24e1ba7f 100644
--- a/libs/os/os.go
+++ b/libs/os/os.go
@@ -8,6 +8,8 @@ import (
 	"os"
 	"os/signal"
 	"syscall"
+
+	"github.com/tendermint/tendermint/libs/log"
 )
 
 type logger interface {
@@ -21,7 +23,7 @@ func TrapSignal(logger logger, cb func()) {
 	signal.Notify(c, os.Interrupt, syscall.SIGTERM)
 	go func() {
 		for sig := range c {
-			logger.Info(fmt.Sprintf("captured %v, exiting...", sig))
+			logger.Info("signal trapped", "msg", log.NewLazySprintf("captured %v, exiting...", sig))
 			if cb != nil {
 				cb()
 			}
diff --git a/libs/service/service.go b/libs/service/service.go
index 5efd0f04d..a3f1b4cb6 100644
--- a/libs/service/service.go
+++ b/libs/service/service.go
@@ -136,7 +136,11 @@ func (bs *BaseService) Start() error {
 			atomic.StoreUint32(&bs.started, 0)
 			return ErrAlreadyStopped
 		}
-		bs.Logger.Info(fmt.Sprintf("Starting %v service", bs.name), "impl", bs.impl.String())
+		bs.Logger.Info("service start",
+			"msg",
+			log.NewLazySprintf("Starting %v service", bs.name),
+			"impl",
+			bs.impl.String())
 		err := bs.impl.OnStart()
 		if err != nil {
 			// revert flag
@@ -145,7 +149,11 @@ func (bs *BaseService) Start() error {
 		}
 		return nil
 	}
-	bs.Logger.Debug(fmt.Sprintf("Not starting %v service -- already started", bs.name), "impl", bs.impl)
+	bs.Logger.Debug("service start",
+		"msg",
+		log.NewLazySprintf("Not starting %v service -- already started", bs.name),
+		"impl",
+		bs.impl)
 	return ErrAlreadyStarted
 }
 
@@ -165,12 +173,20 @@ func (bs *BaseService) Stop() error {
 			atomic.StoreUint32(&bs.stopped, 0)
 			return ErrNotStarted
 		}
-		bs.Logger.Info(fmt.Sprintf("Stopping %v service", bs.name), "impl", bs.impl)
+		bs.Logger.Info("service stop",
+			"msg",
+			log.NewLazySprintf("Stopping %v service", bs.name),
+			"impl",
+			bs.impl)
 		bs.impl.OnStop()
 		close(bs.quit)
 		return nil
 	}
-	bs.Logger.Debug(fmt.Sprintf("Stopping %v service (already stopped)", bs.name), "impl", bs.impl)
+	bs.Logger.Debug("service stop",
+		"msg",
+		log.NewLazySprintf("Stopping %v service (already stopped)", bs.name),
+		"impl",
+		bs.impl)
 	return ErrAlreadyStopped
 }
 
@@ -183,7 +199,11 @@ func (bs *BaseService) OnStop() {}
 // will be returned if the service is running.
 func (bs *BaseService) Reset() error {
 	if !atomic.CompareAndSwapUint32(&bs.stopped, 1, 0) {
-		bs.Logger.Debug(fmt.Sprintf("Can't reset %v service. Not stopped", bs.name), "impl", bs.impl)
+		bs.Logger.Debug("service reset",
+			"msg",
+			log.NewLazySprintf("Can't reset %v service. Not stopped", bs.name),
+			"impl",
+			bs.impl)
 		return fmt.Errorf("can't reset running %s", bs.name)
 	}
 
diff --git a/p2p/conn/connection.go b/p2p/conn/connection.go
index dfbd76f0a..44ff83893 100644
--- a/p2p/conn/connection.go
+++ b/p2p/conn/connection.go
@@ -352,7 +352,7 @@ func (c *MConnection) Send(chID byte, msgBytes []byte) bool {
 		return false
 	}
 
-	c.Logger.Debug("Send", "channel", chID, "conn", c, "msgBytes", fmt.Sprintf("%X", msgBytes))
+	c.Logger.Debug("Send", "channel", chID, "conn", c, "msgBytes", log.NewLazySprintf("%X", msgBytes))
 
 	// Send message to channel.
 	channel, ok := c.channelsIdx[chID]
@@ -369,7 +369,7 @@ func (c *MConnection) Send(chID byte, msgBytes []byte) bool {
 		default:
 		}
 	} else {
-		c.Logger.Debug("Send failed", "channel", chID, "conn", c, "msgBytes", fmt.Sprintf("%X", msgBytes))
+		c.Logger.Debug("Send failed", "channel", chID, "conn", c, "msgBytes", log.NewLazySprintf("%X", msgBytes))
 	}
 	return success
 }
@@ -381,7 +381,7 @@ func (c *MConnection) TrySend(chID byte, msgBytes []byte) bool {
 		return false
 	}
 
-	c.Logger.Debug("TrySend", "channel", chID, "conn", c, "msgBytes", fmt.Sprintf("%X", msgBytes))
+	c.Logger.Debug("TrySend", "channel", chID, "conn", c, "msgBytes", log.NewLazySprintf("%X", msgBytes))
 
 	// Send message to channel.
 	channel, ok := c.channelsIdx[chID]
diff --git a/p2p/pex/addrbook.go b/p2p/pex/addrbook.go
index 76b21e8dc..95936a43c 100644
--- a/p2p/pex/addrbook.go
+++ b/p2p/pex/addrbook.go
@@ -17,6 +17,7 @@ import (
 	"github.com/minio/highwayhash"
 
 	"github.com/tendermint/tendermint/crypto"
+	"github.com/tendermint/tendermint/libs/log"
 	tmmath "github.com/tendermint/tendermint/libs/math"
 	tmrand "github.com/tendermint/tendermint/libs/rand"
 	"github.com/tendermint/tendermint/libs/service"
@@ -739,7 +740,7 @@ func (a *addrBook) expireNew(bucketIdx int) {
 	for addrStr, ka := range a.bucketsNew[bucketIdx] {
 		// If an entry is bad, throw it away
 		if ka.isBad() {
-			a.Logger.Info(fmt.Sprintf("expiring bad address %v", addrStr))
+			a.Logger.Info("expire new", "msg", log.NewLazySprintf("expiring bad address %v", addrStr))
 			a.removeFromBucket(ka, bucketTypeNew, bucketIdx)
 			return
 		}
diff --git a/p2p/switch.go b/p2p/switch.go
index f4f335b32..fa87cbccd 100644
--- a/p2p/switch.go
+++ b/p2p/switch.go
@@ -8,6 +8,7 @@ import (
 
 	"github.com/tendermint/tendermint/config"
 	"github.com/tendermint/tendermint/libs/cmap"
+	"github.com/tendermint/tendermint/libs/log"
 	"github.com/tendermint/tendermint/libs/rand"
 	"github.com/tendermint/tendermint/libs/service"
 	"github.com/tendermint/tendermint/p2p/conn"
@@ -261,7 +262,7 @@ func (sw *Switch) OnStop() {
 //
 // NOTE: Broadcast uses goroutines, so order of broadcast may not be preserved.
 func (sw *Switch) Broadcast(chID byte, msgBytes []byte) chan bool {
-	sw.Logger.Debug("Broadcast", "channel", chID, "msgBytes", fmt.Sprintf("%X", msgBytes))
+	sw.Logger.Debug("Broadcast", "channel", chID, "msgBytes", log.NewLazySprintf("%X", msgBytes))
 
 	peers := sw.peers.List()
 	var wg sync.WaitGroup
diff --git a/p2p/upnp/probe.go b/p2p/upnp/probe.go
index ae641abbb..00047dac2 100644
--- a/p2p/upnp/probe.go
+++ b/p2p/upnp/probe.go
@@ -18,19 +18,19 @@ func makeUPNPListener(intPort int, extPort int, logger log.Logger) (NAT, net.Lis
 	if err != nil {
 		return nil, nil, nil, fmt.Errorf("nat upnp could not be discovered: %v", err)
 	}
-	logger.Info(fmt.Sprintf("ourIP: %v", nat.(*upnpNAT).ourIP))
+	logger.Info("make upnp listener", "msg", log.NewLazySprintf("ourIP: %v", nat.(*upnpNAT).ourIP))
 
 	ext, err := nat.GetExternalAddress()
 	if err != nil {
 		return nat, nil, nil, fmt.Errorf("external address error: %v", err)
 	}
-	logger.Info(fmt.Sprintf("External address: %v", ext))
+	logger.Info("make upnp listener", "msg", log.NewLazySprintf("External address: %v", ext))
 
 	port, err := nat.AddPortMapping("tcp", extPort, intPort, "Tendermint UPnP Probe", 0)
 	if err != nil {
 		return nat, nil, ext, fmt.Errorf("port mapping error: %v", err)
 	}
-	logger.Info(fmt.Sprintf("Port mapping mapped: %v", port))
+	logger.Info("make upnp listener", "msg", log.NewLazySprintf("Port mapping mapped: %v", port))
 
 	// also run the listener, open for all remote addresses.
 	listener, err := net.Listen("tcp", fmt.Sprintf(":%v", intPort))
@@ -45,17 +45,23 @@ func testHairpin(listener net.Listener, extAddr string, logger log.Logger) (supp
 	go func() {
 		inConn, err := listener.Accept()
 		if err != nil {
-			logger.Info(fmt.Sprintf("Listener.Accept() error: %v", err))
+			logger.Info("test hair pin", "msg", log.NewLazySprintf("Listener.Accept() error: %v", err))
 			return
 		}
-		logger.Info(fmt.Sprintf("Accepted incoming connection: %v -> %v", inConn.LocalAddr(), inConn.RemoteAddr()))
+		logger.Info("test hair pin",
+			"msg",
+			log.NewLazySprintf("Accepted incoming connection: %v -> %v", inConn.LocalAddr(), inConn.RemoteAddr()))
 		buf := make([]byte, 1024)
 		n, err := inConn.Read(buf)
 		if err != nil {
-			logger.Info(fmt.Sprintf("Incoming connection read error: %v", err))
+			logger.Info("test hair pin",
+				"msg",
+				log.NewLazySprintf("Incoming connection read error: %v", err))
 			return
 		}
-		logger.Info(fmt.Sprintf("Incoming connection read %v bytes: %X", n, buf))
+		logger.Info("test hair pin",
+			"msg",
+			log.NewLazySprintf("Incoming connection read %v bytes: %X", n, buf))
 		if string(buf) == "test data" {
 			supportsHairpin = true
 			return
@@ -65,16 +71,16 @@ func testHairpin(listener net.Listener, extAddr string, logger log.Logger) (supp
 	// Establish outgoing
 	outConn, err := net.Dial("tcp", extAddr)
 	if err != nil {
-		logger.Info(fmt.Sprintf("Outgoing connection dial error: %v", err))
+		logger.Info("test hair pin", "msg", log.NewLazySprintf("Outgoing connection dial error: %v", err))
 		return
 	}
 
 	n, err := outConn.Write([]byte("test data"))
 	if err != nil {
-		logger.Info(fmt.Sprintf("Outgoing connection write error: %v", err))
+		logger.Info("test hair pin", "msg", log.NewLazySprintf("Outgoing connection write error: %v", err))
 		return
 	}
-	logger.Info(fmt.Sprintf("Outgoing connection wrote %v bytes", n))
+	logger.Info("test hair pin", "msg", log.NewLazySprintf("Outgoing connection wrote %v bytes", n))
 
 	// Wait for data receipt
 	time.Sleep(1 * time.Second)
diff --git a/rpc/jsonrpc/client/ws_client.go b/rpc/jsonrpc/client/ws_client.go
index 1c7ade657..44bf5f098 100644
--- a/rpc/jsonrpc/client/ws_client.go
+++ b/rpc/jsonrpc/client/ws_client.go
@@ -12,6 +12,7 @@ import (
 	"github.com/gorilla/websocket"
 	metrics "github.com/rcrowley/go-metrics"
 
+	"github.com/tendermint/tendermint/libs/log"
 	tmrand "github.com/tendermint/tendermint/libs/rand"
 	"github.com/tendermint/tendermint/libs/service"
 	tmsync "github.com/tendermint/tendermint/libs/sync"
@@ -511,7 +512,7 @@ func (c *WSClient) readRoutine() {
 		// c.wg.Wait() in c.Stop(). Note we rely on Quit being closed so that it sends unlimited Quit signals to stop
 		// both readRoutine and writeRoutine
 
-		c.Logger.Info("got response", "id", response.ID, "result", fmt.Sprintf("%X", response.Result))
+		c.Logger.Info("got response", "id", response.ID, "result", log.NewLazySprintf("%X", response.Result))
 
 		select {
 		case <-c.Quit():
diff --git a/rpc/jsonrpc/server/http_server.go b/rpc/jsonrpc/server/http_server.go
index bc9785dea..f653e6cc6 100644
--- a/rpc/jsonrpc/server/http_server.go
+++ b/rpc/jsonrpc/server/http_server.go
@@ -51,7 +51,7 @@ func DefaultConfig() *Config {
 //
 // NOTE: This function blocks - you may want to call it in a go-routine.
 func Serve(listener net.Listener, handler http.Handler, logger log.Logger, config *Config) error {
-	logger.Info(fmt.Sprintf("Starting RPC HTTP server on %s", listener.Addr()))
+	logger.Info("serve", "msg", log.NewLazySprintf("Starting RPC HTTP server on %s", listener.Addr()))
 	s := &http.Server{
 		Handler:        RecoverAndLogHandler(maxBytesHandler{h: handler, n: config.MaxBodyBytes}, logger),
 		ReadTimeout:    config.ReadTimeout,
@@ -75,7 +75,7 @@ func ServeTLS(
 	logger log.Logger,
 	config *Config,
 ) error {
-	logger.Info(fmt.Sprintf("Starting RPC HTTPS server on %s (cert: %q, key: %q)",
+	logger.Info("serve tls", "msg", log.NewLazySprintf("Starting RPC HTTPS server on %s (cert: %q, key: %q)",
 		listener.Addr(), certFile, keyFile))
 	s := &http.Server{
 		Handler:        RecoverAndLogHandler(maxBytesHandler{h: handler, n: config.MaxBodyBytes}, logger),
diff --git a/statesync/syncer.go b/statesync/syncer.go
index 115b98749..e4c02988b 100644
--- a/statesync/syncer.go
+++ b/statesync/syncer.go
@@ -144,7 +144,7 @@ func (s *syncer) SyncAny(discoveryTime time.Duration, retryHook func()) (sm.Stat
 	}
 
 	if discoveryTime > 0 {
-		s.logger.Info(fmt.Sprintf("Discovering snapshots for %v", discoveryTime))
+		s.logger.Info("sync any", "msg", log.NewLazySprintf("Discovering snapshots for %v", discoveryTime))
 		time.Sleep(discoveryTime)
 	}
 
@@ -166,7 +166,7 @@ func (s *syncer) SyncAny(discoveryTime time.Duration, retryHook func()) (sm.Stat
 				return sm.State{}, nil, errNoSnapshots
 			}
 			retryHook()
-			s.logger.Info(fmt.Sprintf("Discovering snapshots for %v", discoveryTime))
+			s.logger.Info("sync any", "msg", log.NewLazySprintf("Discovering snapshots for %v", discoveryTime))
 			time.Sleep(discoveryTime)
 			continue
 		}
diff --git a/test/e2e/node/main.go b/test/e2e/node/main.go
index b7dbd96e9..b109d5397 100644
--- a/test/e2e/node/main.go
+++ b/test/e2e/node/main.go
@@ -111,7 +111,7 @@ func startApp(cfg *Config) error {
 	if err != nil {
 		return err
 	}
-	logger.Info(fmt.Sprintf("Server listening on %v (%v protocol)", cfg.Listen, cfg.Protocol))
+	logger.Info("start app", "msg", log.NewLazySprintf("Server listening on %v (%v protocol)", cfg.Listen, cfg.Protocol))
 	return nil
 }
 
@@ -261,7 +261,7 @@ func startSigner(cfg *Config) error {
 	if err != nil {
 		return err
 	}
-	logger.Info(fmt.Sprintf("Remote signer connecting to %v", cfg.PrivValServer))
+	logger.Info("start signer", "msg", log.NewLazySprintf("Remote signer connecting to %v", cfg.PrivValServer))
 	return nil
 }
 
diff --git a/test/e2e/runner/cleanup.go b/test/e2e/runner/cleanup.go
index d99ca54cf..fbe7aa0b4 100644
--- a/test/e2e/runner/cleanup.go
+++ b/test/e2e/runner/cleanup.go
@@ -6,6 +6,7 @@ import (
 	"os"
 	"path/filepath"
 
+	"github.com/tendermint/tendermint/libs/log"
 	e2e "github.com/tendermint/tendermint/test/e2e/pkg"
 )
 
@@ -59,7 +60,7 @@ func cleanupDir(dir string) error {
 		return err
 	}
 
-	logger.Info(fmt.Sprintf("Removing testnet directory %q", dir))
+	logger.Info("cleanup dir", "msg", log.NewLazySprintf("Removing testnet directory %q", dir))
 
 	// On Linux, some local files in the volume will be owned by root since Tendermint
 	// runs as root inside the container, so we need to clean them up from within a
diff --git a/test/e2e/runner/load.go b/test/e2e/runner/load.go
index 4e1a6ebba..5f6d1e1ba 100644
--- a/test/e2e/runner/load.go
+++ b/test/e2e/runner/load.go
@@ -8,6 +8,7 @@ import (
 	"math"
 	"time"
 
+	"github.com/tendermint/tendermint/libs/log"
 	rpchttp "github.com/tendermint/tendermint/rpc/client/http"
 	e2e "github.com/tendermint/tendermint/test/e2e/pkg"
 	"github.com/tendermint/tendermint/types"
@@ -35,7 +36,7 @@ func Load(ctx context.Context, testnet *e2e.Testnet, multiplier int) error {
 	defer cancel()
 
 	// Spawn job generator and processors.
-	logger.Info(fmt.Sprintf("Starting transaction load (%v workers)...", concurrency))
+	logger.Info("load", "msg", log.NewLazySprintf("Starting transaction load (%v workers)...", concurrency))
 	started := time.Now()
 
 	go loadGenerate(ctx, chTx, multiplier)
@@ -58,7 +59,7 @@ func Load(ctx context.Context, testnet *e2e.Testnet, multiplier int) error {
 			if success == 0 {
 				return errors.New("failed to submit any transactions")
 			}
-			logger.Info(fmt.Sprintf("Ending transaction load after %v txs (%.1f tx/s)...",
+			logger.Info("load", "msg", log.NewLazySprintf("Ending transaction load after %v txs (%.1f tx/s)...",
 				success, float64(success)/time.Since(started).Seconds()))
 			return nil
 		}
diff --git a/test/e2e/runner/perturb.go b/test/e2e/runner/perturb.go
index 46019ef23..f47aa72bf 100644
--- a/test/e2e/runner/perturb.go
+++ b/test/e2e/runner/perturb.go
@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"time"
 
+	"github.com/tendermint/tendermint/libs/log"
 	rpctypes "github.com/tendermint/tendermint/rpc/core/types"
 	e2e "github.com/tendermint/tendermint/test/e2e/pkg"
 )
@@ -28,7 +29,7 @@ func PerturbNode(node *e2e.Node, perturbation e2e.Perturbation) (*rpctypes.Resul
 	testnet := node.Testnet
 	switch perturbation {
 	case e2e.PerturbationDisconnect:
-		logger.Info(fmt.Sprintf("Disconnecting node %v...", node.Name))
+		logger.Info("perturb node", "msg", log.NewLazySprintf("Disconnecting node %v...", node.Name))
 		if err := execDocker("network", "disconnect", testnet.Name+"_"+testnet.Name, node.Name); err != nil {
 			return nil, err
 		}
@@ -38,7 +39,7 @@ func PerturbNode(node *e2e.Node, perturbation e2e.Perturbation) (*rpctypes.Resul
 		}
 
 	case e2e.PerturbationKill:
-		logger.Info(fmt.Sprintf("Killing node %v...", node.Name))
+		logger.Info("perturb node", "msg", log.NewLazySprintf("Killing node %v...", node.Name))
 		if err := execCompose(testnet.Dir, "kill", "-s", "SIGKILL", node.Name); err != nil {
 			return nil, err
 		}
@@ -47,7 +48,7 @@ func PerturbNode(node *e2e.Node, perturbation e2e.Perturbation) (*rpctypes.Resul
 		}
 
 	case e2e.PerturbationPause:
-		logger.Info(fmt.Sprintf("Pausing node %v...", node.Name))
+		logger.Info("perturb node", "msg", log.NewLazySprintf("Pausing node %v...", node.Name))
 		if err := execCompose(testnet.Dir, "pause", node.Name); err != nil {
 			return nil, err
 		}
@@ -57,7 +58,7 @@ func PerturbNode(node *e2e.Node, perturbation e2e.Perturbation) (*rpctypes.Resul
 		}
 
 	case e2e.PerturbationRestart:
-		logger.Info(fmt.Sprintf("Restarting node %v...", node.Name))
+		logger.Info("perturb node", "msg", log.NewLazySprintf("Restarting node %v...", node.Name))
 		if err := execCompose(testnet.Dir, "restart", node.Name); err != nil {
 			return nil, err
 		}
@@ -70,6 +71,8 @@ func PerturbNode(node *e2e.Node, perturbation e2e.Perturbation) (*rpctypes.Resul
 	if err != nil {
 		return nil, err
 	}
-	logger.Info(fmt.Sprintf("Node %v recovered at height %v", node.Name, status.SyncInfo.LatestBlockHeight))
+	logger.Info("perturb node",
+		"msg",
+		log.NewLazySprintf("Node %v recovered at height %v", node.Name, status.SyncInfo.LatestBlockHeight))
 	return status, nil
 }
diff --git a/test/e2e/runner/setup.go b/test/e2e/runner/setup.go
index e1c82d589..34155f225 100644
--- a/test/e2e/runner/setup.go
+++ b/test/e2e/runner/setup.go
@@ -21,6 +21,7 @@ import (
 
 	"github.com/tendermint/tendermint/config"
 	"github.com/tendermint/tendermint/crypto/ed25519"
+	"github.com/tendermint/tendermint/libs/log"
 	"github.com/tendermint/tendermint/p2p"
 	"github.com/tendermint/tendermint/privval"
 	e2e "github.com/tendermint/tendermint/test/e2e/pkg"
@@ -41,7 +42,7 @@ const (
 
 // Setup sets up the testnet configuration.
 func Setup(testnet *e2e.Testnet) error {
-	logger.Info(fmt.Sprintf("Generating testnet files in %q", testnet.Dir))
+	logger.Info("setup", "msg", log.NewLazySprintf("Generating testnet files in %q", testnet.Dir))
 
 	err := os.MkdirAll(testnet.Dir, os.ModePerm)
 	if err != nil {
diff --git a/test/e2e/runner/start.go b/test/e2e/runner/start.go
index 9a612d147..0dab98f22 100644
--- a/test/e2e/runner/start.go
+++ b/test/e2e/runner/start.go
@@ -5,6 +5,7 @@ import (
 	"sort"
 	"time"
 
+	"github.com/tendermint/tendermint/libs/log"
 	e2e "github.com/tendermint/tendermint/test/e2e/pkg"
 )
 
@@ -48,7 +49,7 @@ func Start(testnet *e2e.Testnet) error {
 		if _, err := waitForNode(node, 0, 15*time.Second); err != nil {
 			return err
 		}
-		logger.Info(fmt.Sprintf("Node %v up on http://127.0.0.1:%v", node.Name, node.ProxyPort))
+		logger.Info("start", "msg", log.NewLazySprintf("Node %v up on http://127.0.0.1:%v", node.Name, node.ProxyPort))
 	}
 
 	networkHeight := testnet.InitialHeight
@@ -103,7 +104,7 @@ func Start(testnet *e2e.Testnet) error {
 		if err != nil {
 			return err
 		}
-		logger.Info(fmt.Sprintf("Node %v up on http://127.0.0.1:%v at height %v",
+		logger.Info("start", "msg", log.NewLazySprintf("Node %v up on http://127.0.0.1:%v at height %v",
 			node.Name, node.ProxyPort, status.SyncInfo.LatestBlockHeight))
 	}
 
diff --git a/test/e2e/runner/wait.go b/test/e2e/runner/wait.go
index 232d230d9..d89a8baac 100644
--- a/test/e2e/runner/wait.go
+++ b/test/e2e/runner/wait.go
@@ -1,9 +1,9 @@
 package main
 
 import (
-	"fmt"
 	"time"
 
+	"github.com/tendermint/tendermint/libs/log"
 	e2e "github.com/tendermint/tendermint/test/e2e/pkg"
 )
 
@@ -19,7 +19,7 @@ func Wait(testnet *e2e.Testnet, blocks int64) error {
 
 // WaitUntil waits until a given height has been reached.
 func WaitUntil(testnet *e2e.Testnet, height int64) error {
-	logger.Info(fmt.Sprintf("Waiting for all nodes to reach height %v...", height))
+	logger.Info("wait until", "msg", log.NewLazySprintf("Waiting for all nodes to reach height %v...", height))
 	_, err := waitForAllNodes(testnet, height, waitingTime(len(testnet.Nodes)))
 	if err != nil {
 		return err
diff --git a/test/maverick/consensus/misbehavior.go b/test/maverick/consensus/misbehavior.go
index db4f072ea..e8fe42f1d 100644
--- a/test/maverick/consensus/misbehavior.go
+++ b/test/maverick/consensus/misbehavior.go
@@ -5,6 +5,7 @@ import (
 
 	tmcon "github.com/tendermint/tendermint/consensus"
 	cstypes "github.com/tendermint/tendermint/consensus/types"
+	"github.com/tendermint/tendermint/libs/log"
 	tmproto "github.com/tendermint/tendermint/proto/tendermint/types"
 	"github.com/tendermint/tendermint/types"
 )
@@ -300,7 +301,7 @@ func defaultReceivePrevote(cs *State, vote *types.Vote) {
 			} else {
 				cs.Logger.Info(
 					"valid block we do not know about; set ProposalBlock=nil",
-					"proposal", cs.ProposalBlock.Hash(),
+					"proposal", log.NewLazyBlockHash(cs.ProposalBlock),
 					"blockID", blockID.Hash,
 				)
 
diff --git a/test/maverick/consensus/state.go b/test/maverick/consensus/state.go
index e4ff82793..e67868214 100644
--- a/test/maverick/consensus/state.go
+++ b/test/maverick/consensus/state.go
@@ -242,7 +242,7 @@ func (cs *State) enterPropose(height int64, round int32) {
 	logger := cs.Logger.With("height", height, "round", round)
 
 	if cs.Height != height || round < cs.Round || (cs.Round == round && cstypes.RoundStepPropose <= cs.Step) {
-		logger.Debug(fmt.Sprintf(
+		logger.Debug("enter propose", "msg", log.NewLazySprintf(
 			"enterPropose(%v/%v): Invalid args. Current step: %v/%v/%v",
 			height,
 			round,
@@ -251,7 +251,9 @@ func (cs *State) enterPropose(height int64, round int32) {
 			cs.Step))
 		return
 	}
-	logger.Info(fmt.Sprintf("enterPropose(%v/%v). Current: %v/%v/%v", height, round, cs.Height, cs.Round, cs.Step))
+	logger.Info("enter propose",
+		"msg",
+		log.NewLazySprintf("enterPropose(%v/%v). Current: %v/%v/%v", height, round, cs.Height, cs.Round, cs.Step))
 
 	defer func() {
 		// Done enterPropose:
@@ -279,7 +281,7 @@ func (cs *State) enterPropose(height int64, round int32) {
 // Otherwise vote nil.
 func (cs *State) enterPrevote(height int64, round int32) {
 	if cs.Height != height || round < cs.Round || (cs.Round == round && cstypes.RoundStepPrevote <= cs.Step) {
-		cs.Logger.Debug(fmt.Sprintf(
+		cs.Logger.Debug("enter prevote", "msg", log.NewLazySprintf(
 			"enterPrevote(%v/%v): Invalid args. Current step: %v/%v/%v",
 			height,
 			round,
@@ -295,7 +297,9 @@ func (cs *State) enterPrevote(height int64, round int32) {
 		cs.newStep()
 	}()
 
-	cs.Logger.Debug(fmt.Sprintf("enterPrevote(%v/%v); current: %v/%v/%v", height, round, cs.Height, cs.Round, cs.Step))
+	cs.Logger.Debug("enter prevote",
+		"msg",
+		log.NewLazySprintf("enterPrevote(%v/%v); current: %v/%v/%v", height, round, cs.Height, cs.Round, cs.Step))
 
 	// Sign and broadcast vote as necessary
 	if b, ok := cs.misbehaviors[cs.Height]; ok {
@@ -318,17 +322,20 @@ func (cs *State) enterPrecommit(height int64, round int32) {
 	logger := cs.Logger.With("height", height, "round", round)
 
 	if cs.Height != height || round < cs.Round || (cs.Round == round && cstypes.RoundStepPrecommit <= cs.Step) {
-		logger.Debug(fmt.Sprintf(
-			"enterPrecommit(%v/%v): Invalid args. Current step: %v/%v/%v",
-			height,
-			round,
-			cs.Height,
-			cs.Round,
-			cs.Step))
+		logger.Debug("enter precommit",
+			"msg",
+			log.NewLazySprintf("enterPrecommit(%v/%v): Invalid args. Current step: %v/%v/%v",
+				height,
+				round,
+				cs.Height,
+				cs.Round,
+				cs.Step))
 		return
 	}
 
-	logger.Info(fmt.Sprintf("enterPrecommit(%v/%v). Current: %v/%v/%v", height, round, cs.Height, cs.Round, cs.Step))
+	logger.Info("enter precommit",
+		"msg",
+		log.NewLazySprintf("enterPrecommit(%v/%v). Current: %v/%v/%v", height, round, cs.Height, cs.Round, cs.Step))
 
 	defer func() {
 		// Done enterPrecommit:
@@ -372,7 +379,9 @@ func (cs *State) addVote(
 			return
 		}
 
-		cs.Logger.Info(fmt.Sprintf("Added to lastPrecommits: %v", cs.LastCommit.StringShort()))
+		cs.Logger.Info("add vote",
+			"msg",
+			log.NewLazySprintf("Added to lastPrecommits: %v", cs.LastCommit.StringShort()))
 		_ = cs.eventBus.PublishEventVote(types.EventDataVote{Vote: vote})
 		cs.evsw.FireEvent(types.EventVote, vote)
 
@@ -1103,7 +1112,7 @@ func (cs *State) enterNewRound(height int64, round int32) {
 	logger := cs.Logger.With("height", height, "round", round)
 
 	if cs.Height != height || round < cs.Round || (cs.Round == round && cs.Step != cstypes.RoundStepNewHeight) {
-		logger.Debug(fmt.Sprintf(
+		logger.Debug("enter new round", "msg", log.NewLazySprintf(
 			"enterNewRound(%v/%v): Invalid args. Current step: %v/%v/%v",
 			height,
 			round,
@@ -1117,7 +1126,9 @@ func (cs *State) enterNewRound(height int64, round int32) {
 		logger.Debug("need to set a buffer and log message here for sanity", "startTime", cs.StartTime, "now", now)
 	}
 
-	logger.Info(fmt.Sprintf("enterNewRound(%v/%v). Current: %v/%v/%v", height, round, cs.Height, cs.Round, cs.Step))
+	logger.Info("enter new round",
+		"msg",
+		log.NewLazySprintf("enterNewRound(%v/%v). Current: %v/%v/%v", height, round, cs.Height, cs.Round, cs.Step))
 
 	// Increment validators if necessary
 	validators := cs.Validators
@@ -1217,7 +1228,9 @@ func (cs *State) defaultDecideProposal(height int64, round int32) {
 			cs.sendInternalMessage(msgInfo{&tmcon.BlockPartMessage{Height: cs.Height, Round: cs.Round, Part: part}, ""})
 		}
 		cs.Logger.Info("Signed proposal", "height", height, "round", round, "proposal", proposal)
-		cs.Logger.Debug(fmt.Sprintf("Signed proposal block: %v", block))
+		cs.Logger.Debug("default decide proposal",
+			"msg",
+			log.NewLazySprintf("Signed proposal block: %v", block))
 	} else if !cs.replayMode {
 		cs.Logger.Error("enterPropose: Error signing proposal", "height", height, "round", round, "err", err)
 	}
@@ -1281,20 +1294,24 @@ func (cs *State) enterPrevoteWait(height int64, round int32) {
 	logger := cs.Logger.With("height", height, "round", round)
 
 	if cs.Height != height || round < cs.Round || (cs.Round == round && cstypes.RoundStepPrevoteWait <= cs.Step) {
-		logger.Debug(fmt.Sprintf(
-			"enterPrevoteWait(%v/%v): Invalid args. Current step: %v/%v/%v",
-			height,
-			round,
-			cs.Height,
-			cs.Round,
-			cs.Step))
+		logger.Debug("enter prevote wait",
+			"msg",
+			log.NewLazySprintf(
+				"enterPrevoteWait(%v/%v): Invalid args. Current step: %v/%v/%v",
+				height,
+				round,
+				cs.Height,
+				cs.Round,
+				cs.Step))
 		return
 	}
 	if !cs.Votes.Prevotes(round).HasTwoThirdsAny() {
 		panic(fmt.Sprintf("enterPrevoteWait(%v/%v), but Prevotes does not have any +2/3 votes", height, round))
 	}
 
-	logger.Debug(fmt.Sprintf("enterPrevoteWait(%v/%v); current: %v/%v/%v", height, round, cs.Height, cs.Round, cs.Step))
+	logger.Debug("enter prevote wait",
+		"msg",
+		log.NewLazySprintf("enterPrevoteWait(%v/%v); current: %v/%v/%v", height, round, cs.Height, cs.Round, cs.Step))
 
 	defer func() {
 		// Done enterPrevoteWait:
@@ -1311,8 +1328,9 @@ func (cs *State) enterPrecommitWait(height int64, round int32) {
 	logger := cs.Logger.With("height", height, "round", round)
 
 	if cs.Height != height || round < cs.Round || (cs.Round == round && cs.TriggeredTimeoutPrecommit) {
-		logger.Debug(
-			fmt.Sprintf(
+		logger.Debug("state enter precommit wait",
+			"msg",
+			log.NewLazySprintf(
 				"enterPrecommitWait(%v/%v): Invalid args. "+
 					"Current state is Height/Round: %v/%v/, TriggeredTimeoutPrecommit:%v",
 				height, round, cs.Height, cs.Round, cs.TriggeredTimeoutPrecommit))
@@ -1321,7 +1339,9 @@ func (cs *State) enterPrecommitWait(height int64, round int32) {
 	if !cs.Votes.Precommits(round).HasTwoThirdsAny() {
 		panic(fmt.Sprintf("enterPrecommitWait(%v/%v), but Precommits does not have any +2/3 votes", height, round))
 	}
-	logger.Info(fmt.Sprintf("enterPrecommitWait(%v/%v). Current: %v/%v/%v", height, round, cs.Height, cs.Round, cs.Step))
+	logger.Info("enter precommit wait",
+		"msg",
+		log.NewLazySprintf("enterPrecommitWait(%v/%v). Current: %v/%v/%v", height, round, cs.Height, cs.Round, cs.Step))
 
 	defer func() {
 		// Done enterPrecommitWait:
@@ -1338,16 +1358,19 @@ func (cs *State) enterCommit(height int64, commitRound int32) {
 	logger := cs.Logger.With("height", height, "commitRound", commitRound)
 
 	if cs.Height != height || cstypes.RoundStepCommit <= cs.Step {
-		logger.Debug(fmt.Sprintf(
-			"enterCommit(%v/%v): Invalid args. Current step: %v/%v/%v",
-			height,
-			commitRound,
-			cs.Height,
-			cs.Round,
-			cs.Step))
+		logger.Debug("enter commit",
+			"msg",
+			log.NewLazySprintf("enterCommit(%v/%v): Invalid args. Current step: %v/%v/%v",
+				height,
+				commitRound,
+				cs.Height,
+				cs.Round,
+				cs.Step))
 		return
 	}
-	logger.Info(fmt.Sprintf("enterCommit(%v/%v). Current: %v/%v/%v", height, commitRound, cs.Height, cs.Round, cs.Step))
+	logger.Info("enter commit",
+		"msg",
+		log.NewLazySprintf("enterCommit(%v/%v). Current: %v/%v/%v", height, commitRound, cs.Height, cs.Round, cs.Step))
 
 	defer func() {
 		// Done enterCommit:
@@ -1380,7 +1403,7 @@ func (cs *State) enterCommit(height int64, commitRound int32) {
 		if !cs.ProposalBlockParts.HasHeader(blockID.PartSetHeader) {
 			logger.Info(
 				"commit is for a block we do not know about; set ProposalBlock=nil",
-				"proposal", cs.ProposalBlock.Hash(),
+				"proposal", log.NewLazyBlockHash(cs.ProposalBlock),
 				"commit", blockID.Hash,
 			)
 
@@ -1417,7 +1440,7 @@ func (cs *State) tryFinalizeCommit(height int64) {
 		// TODO: ^^ wait, why does it matter that we're a validator?
 		logger.Debug(
 			"attempt to finalize failed; we do not have the commit block",
-			"proposal-block", cs.ProposalBlock.Hash(),
+			"proposal-block", log.NewLazyBlockHash(cs.ProposalBlock),
 			"commit-block", blockID.Hash,
 		)
 		return
@@ -1430,12 +1453,13 @@ func (cs *State) tryFinalizeCommit(height int64) {
 // Increment height and goto cstypes.RoundStepNewHeight
 func (cs *State) finalizeCommit(height int64) {
 	if cs.Height != height || cs.Step != cstypes.RoundStepCommit {
-		cs.Logger.Debug(fmt.Sprintf(
-			"finalizeCommit(%v): Invalid args. Current step: %v/%v/%v",
-			height,
-			cs.Height,
-			cs.Round,
-			cs.Step))
+		cs.Logger.Debug("finalize commit",
+			"msg",
+			log.NewLazySprintf("finalizeCommit(%v): Invalid args. Current step: %v/%v/%v",
+				height,
+				cs.Height,
+				cs.Round,
+				cs.Step))
 		return
 	}
 
@@ -1461,7 +1485,7 @@ func (cs *State) finalizeCommit(height int64) {
 		"root", block.AppHash,
 		"N", len(block.Txs),
 	)
-	cs.Logger.Debug(fmt.Sprintf("%v", block))
+	cs.Logger.Debug("finalize commit", "msg", log.NewLazySprintf("%v", block))
 
 	fail.Fail() // XXX