Try #5793:

config/mainnet.go

@@ -65,6 +65,10 @@ func MainnetConfig() Config {
 	hare3conf.Committee = 400
 	hare3conf.Enable = true
 	hare3conf.EnableLayer = 35117
+	hare3conf.CommitteeUpgrade = &hare3.CommitteeUpgrade{
+		Layer: 105_720, // July 15, 2024, 10:00:00 AM UTC
+		Size:  50,
+	}
 	return Config{
 		BaseConfig: BaseConfig{
 			DataDirParent:         defaultDataDir,

hare3/hare.go

@@ -31,21 +31,34 @@ import (
 	"github.com/spacemeshos/go-spacemesh/system"
 )
 
+type CommitteeUpgrade struct {
+	Layer types.LayerID
+	Size  uint16
+}
+
 type Config struct {
-	Enable          bool          `mapstructure:"enable"`
-	EnableLayer     types.LayerID `mapstructure:"enable-layer"`
-	DisableLayer    types.LayerID `mapstructure:"disable-layer"`
-	Committee       uint16        `mapstructure:"committee"`
-	Leaders         uint16        `mapstructure:"leaders"`
-	IterationsLimit uint8         `mapstructure:"iterations-limit"`
-	PreroundDelay   time.Duration `mapstructure:"preround-delay"`
-	RoundDuration   time.Duration `mapstructure:"round-duration"`
+	Enable           bool          `mapstructure:"enable"`
+	EnableLayer      types.LayerID `mapstructure:"enable-layer"`
+	DisableLayer     types.LayerID `mapstructure:"disable-layer"`
+	Committee        uint16        `mapstructure:"committee"`
+	CommitteeUpgrade *CommitteeUpgrade
+	Leaders          uint16        `mapstructure:"leaders"`
+	IterationsLimit  uint8         `mapstructure:"iterations-limit"`
+	PreroundDelay    time.Duration `mapstructure:"preround-delay"`
+	RoundDuration    time.Duration `mapstructure:"round-duration"`
 	// LogStats if true will log iteration statistics with INFO level at the start of the next iteration.
 	// This requires additional computation and should be used for debugging only.
 	LogStats     bool   `mapstructure:"log-stats"`
 	ProtocolName string `mapstructure:"protocolname"`
 }
 
+func (cfg *Config) CommitteeFor(layer types.LayerID) uint16 {
+	if cfg.CommitteeUpgrade != nil && layer >= cfg.CommitteeUpgrade.Layer {
+		return cfg.CommitteeUpgrade.Size
+	}
+	return cfg.Committee
+}
+
 func (cfg *Config) Validate(zdist time.Duration) error {
 	terminates := cfg.roundStart(IterRound{Iter: cfg.IterationsLimit, Round: hardlock})
 	if terminates > zdist {
@@ -63,6 +76,10 @@ func (cfg *Config) MarshalLogObject(encoder zapcore.ObjectEncoder) error {
 	encoder.AddUint32("enabled layer", cfg.EnableLayer.Uint32())
 	encoder.AddUint32("disabled layer", cfg.DisableLayer.Uint32())
 	encoder.AddUint16("committee", cfg.Committee)
+	if cfg.CommitteeUpgrade != nil {
+		encoder.AddUint32("committee upgrade layer", cfg.CommitteeUpgrade.Layer.Uint32())
+		encoder.AddUint16("committee upgrade size", cfg.CommitteeUpgrade.Size)
+	}
 	encoder.AddUint16("leaders", cfg.Leaders)
 	encoder.AddUint8("iterations limit", cfg.IterationsLimit)
 	encoder.AddDuration("preround delay", cfg.PreroundDelay)
@@ -352,7 +369,7 @@ func (h *Hare) onLayer(layer types.LayerID) {
 		beacon:  beacon,
 		signers: maps.Values(h.signers),
 		vrfs:    make([]*types.HareEligibility, len(h.signers)),
-		proto:   newProtocol(h.config.Committee/2 + 1),
+		proto:   newProtocol(h.config.CommitteeFor(layer)/2 + 1),
 	}
 	h.sessions[layer] = s.proto
 	h.mu.Unlock()

hare3/hare_test.go

@@ -952,3 +952,27 @@ func TestHare_AddProposal(t *testing.T) {
 	require.True(t, hare.IsKnown(p.Layer, p.ID()))
 	require.ErrorIs(t, hare.OnProposal(p), store.ErrProposalExists)
 }
+
+func TestHareConfig_CommitteeUpgrade(t *testing.T) {
+	t.Parallel()
+	t.Run("no upgrade", func(t *testing.T) {
+		cfg := Config{
+			Committee: 400,
+		}
+		require.Equal(t, cfg.Committee, cfg.CommitteeFor(0))
+		require.Equal(t, cfg.Committee, cfg.CommitteeFor(100))
+	})
+	t.Run("upgrade", func(t *testing.T) {
+		cfg := Config{
+			Committee: 400,
+			CommitteeUpgrade: &CommitteeUpgrade{
+				Layer: 16,
+				Size:  50,
+			},
+		}
+		require.EqualValues(t, cfg.Committee, cfg.CommitteeFor(0))
+		require.EqualValues(t, cfg.Committee, cfg.CommitteeFor(15))
+		require.EqualValues(t, 50, cfg.CommitteeFor(16))
+		require.EqualValues(t, 50, cfg.CommitteeFor(100))
+	})
+}

hare3/legacy_oracle.go

@@ -26,7 +26,7 @@ func (lg *legacyOracle) validate(msg *Message) grade {
 	if msg.Eligibility.Count == 0 {
 		return grade0
 	}
-	committee := int(lg.config.Committee)
+	committee := int(lg.config.CommitteeFor(msg.Layer))
 	if msg.Round == propose {
 		committee = int(lg.config.Leaders)
 	}
@@ -50,7 +50,7 @@ func (lg *legacyOracle) active(
 	ir IterRound,
 ) *types.HareEligibility {
 	vrf := eligibility.GenVRF(context.Background(), signer.VRFSigner(), beacon, layer, ir.Absolute())
-	committee := int(lg.config.Committee)
+	committee := int(lg.config.CommitteeFor(layer))
 	if ir.Round == propose {
 		committee = int(lg.config.Leaders)
 	}

systest/parameters/fastnet/smesher.json

@@ -27,6 +27,12 @@
             }
         }
     },
+    "hare3": {
+        "committeeupgrade": {
+            "layer": 16,
+            "size": 15
+        }
+    },
     "smeshing": {
         "smeshing-verifying-opts": {
             "smeshing-opts-verifying-min-workers": 1000000