Overview of app.go

What is app.go?

The app.go file is the core of your Cosmos SDK application. It defines your blockchain application by composing together modules, keepers, and handlers that implement your chain’s functionality. This file is where you wire together all the components that make your blockchain work. The SimApp implementation serves as a reference example and testing application for the Cosmos SDK, demonstrating how to properly structure and initialize a blockchain application.

Core Components

SimApp Struct

The SimApp struct is the main application type that extends the ABCI application. It contains all the necessary components:

type SimApp struct {
    *baseapp.BaseApp           // Core ABCI application
    legacyAmino       *codec.LegacyAmino
    appCodec          codec.Codec
    txConfig          client.TxConfig
    interfaceRegistry types.InterfaceRegistry

    // Store keys for accessing state
    keys  map[string]*storetypes.KVStoreKey
    tkeys map[string]*storetypes.TransientStoreKey

    // Module keepers (business logic)
    AccountKeeper         authkeeper.AccountKeeper
    BankKeeper            bankkeeper.Keeper
    StakingKeeper         *stakingkeeper.Keeper
    // ... other keepers

    // Module manager
    ModuleManager      *module.Manager
    BasicModuleManager module.BasicManager
}

Key Initialization Steps

The NewSimApp constructor follows a specific initialization order:

1. Codec Setup

interfaceRegistry, _ := types.NewInterfaceRegistryWithOptions(...)
appCodec := codec.NewProtoCodec(interfaceRegistry)
legacyAmino := codec.NewLegacyAmino()
txConfig := tx.NewTxConfig(appCodec, tx.DefaultSignModes)

Codecs handle serialization and deserialization of messages and state. The interface registry enables protobuf Any type support.

2. BaseApp Creation

bApp := baseapp.NewBaseApp(appName, logger, db, txConfig.TxDecoder(), baseAppOptions...)

BaseApp provides the core ABCI interface implementation and transaction processing pipeline.

3. Store Keys Registration

keys := storetypes.NewKVStoreKeys(
    authtypes.StoreKey, banktypes.StoreKey, stakingtypes.StoreKey,
    // ... other module store keys
)

Each module gets its own isolated key-value store for persisting state.

4. Keeper Initialization

Keepers are initialized in dependency order. For example, the BankKeeper depends on AccountKeeper:

app.AccountKeeper = authkeeper.NewAccountKeeper(...)
app.BankKeeper = bankkeeper.NewBaseKeeper(
    appCodec,
    runtime.NewKVStoreService(keys[banktypes.StoreKey]),
    app.AccountKeeper,  // dependency
    BlockedAddresses(),
    authtypes.NewModuleAddress(govtypes.ModuleName).String(),
    logger,
)

5. Module Manager Setup

app.ModuleManager = module.NewManager(
    genutil.NewAppModule(...),
    auth.NewAppModule(...),
    bank.NewAppModule(...),
    // ... other modules
)

The Module Manager orchestrates module lifecycle operations.

Module Account Permissions

Module accounts are special accounts owned by modules rather than users:

maccPerms = map[string][]string{
    authtypes.FeeCollectorName:     nil,           // can receive fees
    minttypes.ModuleName:           {authtypes.Minter},  // can mint tokens
    stakingtypes.BondedPoolName:    {authtypes.Burner, authtypes.Staking},
    govtypes.ModuleName:            {authtypes.Burner},
}

Permissions control what operations each module account can perform (minting, burning, staking).

Execution Order

The Module Manager controls the order of operations during blockchain lifecycle events:

Begin Block Order

app.ModuleManager.SetOrderBeginBlockers(
    upgradetypes.ModuleName,  // Check for upgrades first
    minttypes.ModuleName,     // Mint new tokens
    distrtypes.ModuleName,    // Distribute rewards
    slashingtypes.ModuleName, // Process slashing
    // ...
)

This order ensures operations happen in the correct sequence (e.g., slashing happens after reward distribution).

End Block Order

app.ModuleManager.SetOrderEndBlockers(
    crisistypes.ModuleName,  // Check invariants
    govtypes.ModuleName,     // Process governance
    stakingtypes.ModuleName, // Update validator set
    // ...
)

Genesis Order

genesisModuleOrder := []string{
    authtypes.ModuleName,    // Accounts must exist first
    banktypes.ModuleName,    // Then balances
    stakingtypes.ModuleName, // Then staking
    // ...
}

Genesis initialization must happen in dependency order.

ABCI Lifecycle Methods

The application implements key ABCI methods that CometBFT calls:

InitChainer

func (app *SimApp) InitChainer(ctx sdk.Context, req *abci.RequestInitChain) (*abci.ResponseInitChain, error) {
    var genesisState GenesisState
    json.Unmarshal(req.AppStateBytes, &genesisState)
    return app.ModuleManager.InitGenesis(ctx, app.appCodec, genesisState)
}

Called once when the chain starts to initialize state from genesis.

BeginBlocker & EndBlocker

func (app *SimApp) BeginBlocker(ctx sdk.Context) (sdk.BeginBlock, error) {
    return app.ModuleManager.BeginBlock(ctx)
}

func (app *SimApp) EndBlocker(ctx sdk.Context) (sdk.EndBlock, error) {
    return app.ModuleManager.EndBlock(ctx)
}

Called at the beginning and end of each block to perform module-specific logic.

Ante and Post Handlers

AnteHandler

The AnteHandler processes transactions before message execution:

func (app *SimApp) setAnteHandler(txConfig client.TxConfig) {
    anteHandler, err := NewAnteHandler(
        HandlerOptions{
            ante.HandlerOptions{
                AccountKeeper:   app.AccountKeeper,
                BankKeeper:      app.BankKeeper,
                SignModeHandler: txConfig.SignModeHandler(),
                FeegrantKeeper:  app.FeeGrantKeeper,
                SigGasConsumer:  ante.DefaultSigVerificationGasConsumer,
            },
            &app.CircuitKeeper,
        },
    )
    app.SetAnteHandler(anteHandler)
}

AnteHandlers typically:

Verify signatures
Deduct fees
Check sequence numbers
Validate transaction format

PostHandler

PostHandlers run after message execution:

func (app *SimApp) setPostHandler() {
    postHandler, err := posthandler.NewPostHandler(
        posthandler.HandlerOptions{},
    )
    app.SetPostHandler(postHandler)
}

PostHandlers can implement features like transaction tips.

API and Service Registration

The application exposes gRPC and REST APIs:

func (app *SimApp) RegisterAPIRoutes(apiSvr *api.Server, apiConfig config.APIConfig) {
    // Register gRPC gateway routes
    authtx.RegisterGRPCGatewayRoutes(clientCtx, apiSvr.GRPCGatewayRouter)
    cmtservice.RegisterGRPCGatewayRoutes(clientCtx, apiSvr.GRPCGatewayRouter)

    // Register module routes
    app.BasicModuleManager.RegisterGRPCGatewayRoutes(clientCtx, apiSvr.GRPCGatewayRouter)
}

These routes allow clients to query state and submit transactions via HTTP.

Building Your Own Application

When creating your own blockchain application, follow the patterns demonstrated in SimApp:

Set up codecs and registries for serialization and type handling
Initialize BaseApp with your application name and configuration
Register store keys for each module that needs persistent storage
Initialize module keepers in dependency order (e.g., AccountKeeper before BankKeeper)
Configure the Module Manager with your selected modules
Set execution orders for BeginBlock, EndBlock, and Genesis operations
Configure module account permissions based on your requirements
Set up ante/post handlers for transaction processing
Register services and APIs for client interaction

The key is understanding how components interact and ensuring proper initialization order to avoid dependency issues.

Additional Resources

For hands-on tutorials on running a node, see the Cosmos SDK Node Tutorial.

Complete `app.go`

//go:build app_v1

package simapp

import (
    
	"encoding/json"
    "fmt"
    "io"
    "os"
    "path/filepath"
    "cosmossdk.io/log"
    "cosmossdk.io/x/tx/signing"

	autocliv1 "cosmossdk.io/api/cosmos/autocli/v1"
	reflectionv1 "cosmossdk.io/api/cosmos/reflection/v1"
    "cosmossdk.io/client/v2/autocli"
    "cosmossdk.io/core/appmodule"
    "github.com/cosmos/cosmos-sdk/codec/address"

	authcodec "github.com/cosmos/cosmos-sdk/x/auth/codec"
    "github.com/cosmos/cosmos-sdk/x/auth/tx"

	abci "github.com/cometbft/cometbft/abci/types"
	dbm "github.com/cosmos/cosmos-db"
    "github.com/cosmos/gogoproto/proto"
    "github.com/spf13/cast"

	storetypes "cosmossdk.io/store/types"
    "cosmossdk.io/x/evidence"
	evidencekeeper "cosmossdk.io/x/evidence/keeper"
	evidencetypes "cosmossdk.io/x/evidence/types"
    "cosmossdk.io/x/feegrant"
	feegrantkeeper "cosmossdk.io/x/feegrant/keeper"
	feegrantmodule "cosmossdk.io/x/feegrant/module"
    "cosmossdk.io/x/nft"
	nftkeeper "cosmossdk.io/x/nft/keeper"
	nftmodule "cosmossdk.io/x/nft/module"
    "cosmossdk.io/x/upgrade"
	upgradekeeper "cosmossdk.io/x/upgrade/keeper"
	upgradetypes "cosmossdk.io/x/upgrade/types"
    "cosmossdk.io/x/circuit"
	circuitkeeper "cosmossdk.io/x/circuit/keeper"
	circuittypes "cosmossdk.io/x/circuit/types"
    "github.com/cosmos/cosmos-sdk/baseapp"
    "github.com/cosmos/cosmos-sdk/client"
    "github.com/cosmos/cosmos-sdk/client/flags"
    "github.com/cosmos/cosmos-sdk/client/grpc/cmtservice"
	nodeservice "github.com/cosmos/cosmos-sdk/client/grpc/node"
    "github.com/cosmos/cosmos-sdk/codec"
    "github.com/cosmos/cosmos-sdk/codec/types"
    "github.com/cosmos/cosmos-sdk/runtime"
	runtimeservices "github.com/cosmos/cosmos-sdk/runtime/services"
    "github.com/cosmos/cosmos-sdk/server"
    "github.com/cosmos/cosmos-sdk/server/api"
    "github.com/cosmos/cosmos-sdk/server/config"
	servertypes "github.com/cosmos/cosmos-sdk/server/types"
    "github.com/cosmos/cosmos-sdk/std"
	testdata_pulsar "github.com/cosmos/cosmos-sdk/testutil/testdata/testpb"
	sdk "github.com/cosmos/cosmos-sdk/types"
    "github.com/cosmos/cosmos-sdk/types/module"
    "github.com/cosmos/cosmos-sdk/types/msgservice"
    "github.com/cosmos/cosmos-sdk/version"
    "github.com/cosmos/cosmos-sdk/x/auth"
    "github.com/cosmos/cosmos-sdk/x/auth/ante"
	authkeeper "github.com/cosmos/cosmos-sdk/x/auth/keeper"
    "github.com/cosmos/cosmos-sdk/x/auth/posthandler"
	authsims "github.com/cosmos/cosmos-sdk/x/auth/simulation"
	authtx "github.com/cosmos/cosmos-sdk/x/auth/tx"
	authtypes "github.com/cosmos/cosmos-sdk/x/auth/types"
    "github.com/cosmos/cosmos-sdk/x/auth/vesting"
	vestingtypes "github.com/cosmos/cosmos-sdk/x/auth/vesting/types"
    "github.com/cosmos/cosmos-sdk/x/authz"
	authzkeeper "github.com/cosmos/cosmos-sdk/x/authz/keeper"
	authzmodule "github.com/cosmos/cosmos-sdk/x/authz/module"
    "github.com/cosmos/cosmos-sdk/x/bank"
	bankkeeper "github.com/cosmos/cosmos-sdk/x/bank/keeper"
	banktypes "github.com/cosmos/cosmos-sdk/x/bank/types"
	consensus "github.com/cosmos/cosmos-sdk/x/consensus"
	consensusparamkeeper "github.com/cosmos/cosmos-sdk/x/consensus/keeper"
	consensusparamtypes "github.com/cosmos/cosmos-sdk/x/consensus/types"
    "github.com/cosmos/cosmos-sdk/x/crisis"
	crisiskeeper "github.com/cosmos/cosmos-sdk/x/crisis/keeper"
	crisistypes "github.com/cosmos/cosmos-sdk/x/crisis/types"
	distr "github.com/cosmos/cosmos-sdk/x/distribution"
	distrkeeper "github.com/cosmos/cosmos-sdk/x/distribution/keeper"
	distrtypes "github.com/cosmos/cosmos-sdk/x/distribution/types"
    "github.com/cosmos/cosmos-sdk/x/genutil"
	genutiltypes "github.com/cosmos/cosmos-sdk/x/genutil/types"
    "github.com/cosmos/cosmos-sdk/x/gov"
	govclient "github.com/cosmos/cosmos-sdk/x/gov/client"
	govkeeper "github.com/cosmos/cosmos-sdk/x/gov/keeper"
	govtypes "github.com/cosmos/cosmos-sdk/x/gov/types"
	govv1beta1 "github.com/cosmos/cosmos-sdk/x/gov/types/v1beta1"
    "github.com/cosmos/cosmos-sdk/x/group"
	groupkeeper "github.com/cosmos/cosmos-sdk/x/group/keeper"
	groupmodule "github.com/cosmos/cosmos-sdk/x/group/module"
    "github.com/cosmos/cosmos-sdk/x/mint"
	mintkeeper "github.com/cosmos/cosmos-sdk/x/mint/keeper"
	minttypes "github.com/cosmos/cosmos-sdk/x/mint/types"
    "github.com/cosmos/cosmos-sdk/x/params"
	paramsclient "github.com/cosmos/cosmos-sdk/x/params/client"
	paramskeeper "github.com/cosmos/cosmos-sdk/x/params/keeper"
	paramstypes "github.com/cosmos/cosmos-sdk/x/params/types"
	paramproposal "github.com/cosmos/cosmos-sdk/x/params/types/proposal"
    "github.com/cosmos/cosmos-sdk/x/slashing"
	slashingkeeper "github.com/cosmos/cosmos-sdk/x/slashing/keeper"
	slashingtypes "github.com/cosmos/cosmos-sdk/x/slashing/types"
    "github.com/cosmos/cosmos-sdk/x/staking"
	stakingkeeper "github.com/cosmos/cosmos-sdk/x/staking/keeper"
	stakingtypes "github.com/cosmos/cosmos-sdk/x/staking/types"
)

const appName = "SimApp"

var (
	// DefaultNodeHome default home directories for the application daemon
	DefaultNodeHome string

	// module account permissions
	maccPerms = map[string][]string{
    authtypes.FeeCollectorName:     nil,
		distrtypes.ModuleName:          nil,
		minttypes.ModuleName:           {
    authtypes.Minter
},
		stakingtypes.BondedPoolName:    {
    authtypes.Burner, authtypes.Staking
},
		stakingtypes.NotBondedPoolName: {
    authtypes.Burner, authtypes.Staking
},
		govtypes.ModuleName:            {
    authtypes.Burner
},
		nft.ModuleName:                 nil,
}
)

var (
	_ runtime.AppI            = (*SimApp)(nil)
	_ servertypes.Application = (*SimApp)(nil)
)

// stdAccAddressCodec is a temporary address codec that we will use until we
// can populate it with the correct bech32 prefixes without depending on the global.
type stdAccAddressCodec struct{
}

func (g stdAccAddressCodec)

StringToBytes(text string) ([]byte, error) {
    if text == "" {
    return nil, nil
}

return sdk.AccAddressFromBech32(text)
}

func (g stdAccAddressCodec)

BytesToString(bz []byte) (string, error) {
    if bz == nil {
    return "", nil
}

return sdk.AccAddress(bz).String(), nil
}

// stdValAddressCodec is a temporary address codec that we will use until we
// can populate it with the correct bech32 prefixes without depending on the global.
type stdValAddressCodec struct{
}

func (g stdValAddressCodec)

StringToBytes(text string) ([]byte, error) {
    return sdk.ValAddressFromBech32(text)
}

func (g stdValAddressCodec)

BytesToString(bz []byte) (string, error) {
    return sdk.ValAddress(bz).String(), nil
}

// SimApp extends an ABCI application, but with most of its parameters exported.
// They are exported for convenience in creating helper functions, as object
// capabilities aren't needed for testing.
type SimApp struct {
	*baseapp.BaseApp
	legacyAmino       *codec.LegacyAmino
	appCodec          codec.Codec
	txConfig          client.TxConfig
	interfaceRegistry types.InterfaceRegistry

	// keys to access the substores
	keys  map[string]*storetypes.KVStoreKey
	tkeys map[string]*storetypes.TransientStoreKey

	// keepers
	AccountKeeper         authkeeper.AccountKeeper
	BankKeeper            bankkeeper.Keeper
	StakingKeeper         *stakingkeeper.Keeper
	SlashingKeeper        slashingkeeper.Keeper
	MintKeeper            mintkeeper.Keeper
	DistrKeeper           distrkeeper.Keeper
	GovKeeper             govkeeper.Keeper
	CrisisKeeper          *crisiskeeper.Keeper
	UpgradeKeeper         *upgradekeeper.Keeper
	ParamsKeeper          paramskeeper.Keeper
	AuthzKeeper           authzkeeper.Keeper
	EvidenceKeeper        evidencekeeper.Keeper
	FeeGrantKeeper        feegrantkeeper.Keeper
	GroupKeeper           groupkeeper.Keeper
	NFTKeeper             nftkeeper.Keeper
	ConsensusParamsKeeper consensusparamkeeper.Keeper
	CircuitKeeper         circuitkeeper.Keeper

	// the module manager
	ModuleManager      *module.Manager
	BasicModuleManager module.BasicManager

	// simulation manager
	sm *module.SimulationManager

	// module configurator
	configurator module.Configurator
}

func init() {
    userHomeDir, err := os.UserHomeDir()
    if err != nil {
    panic(err)
}

DefaultNodeHome = filepath.Join(userHomeDir, ".simapp")
}

// NewSimApp returns a reference to an initialized SimApp.
func NewSimApp(
	logger log.Logger,
	db dbm.DB,
	traceStore io.Writer,
	loadLatest bool,
	appOpts servertypes.AppOptions,
	baseAppOptions ...func(*baseapp.BaseApp),
) *SimApp {
    interfaceRegistry, _ := types.NewInterfaceRegistryWithOptions(types.InterfaceRegistryOptions{
    ProtoFiles: proto.HybridResolver,
    SigningOptions: signing.Options{
    AddressCodec: address.Bech32Codec{
    Bech32Prefix: sdk.GetConfig().GetBech32AccountAddrPrefix(),
},
    ValidatorAddressCodec: address.Bech32Codec{
    Bech32Prefix: sdk.GetConfig().GetBech32ValidatorAddrPrefix(),
},
},
})
    appCodec := codec.NewProtoCodec(interfaceRegistry)
    legacyAmino := codec.NewLegacyAmino()
    txConfig := tx.NewTxConfig(appCodec, tx.DefaultSignModes)

std.RegisterLegacyAminoCodec(legacyAmino)

std.RegisterInterfaces(interfaceRegistry)

	// Below we could construct and set an application specific mempool and
	// ABCI 1.0 PrepareProposal and ProcessProposal handlers. These defaults are
	// already set in the SDK's BaseApp, this shows an example of how to override
	// them.
	//
	// Example:
	//
	// bApp := baseapp.NewBaseApp(...)
	// nonceMempool := mempool.NewSenderNonceMempool()
	// abciPropHandler := NewDefaultProposalHandler(nonceMempool, bApp)
	//
	// bApp.SetMempool(nonceMempool)
	// bApp.SetPrepareProposal(abciPropHandler.PrepareProposalHandler())
	// bApp.SetProcessProposal(abciPropHandler.ProcessProposalHandler())
	//
	// Alternatively, you can construct BaseApp options, append those to
	// baseAppOptions and pass them to NewBaseApp.
	//
	// Example:
	//
	// prepareOpt = func(app *baseapp.BaseApp) {
	// 	abciPropHandler := baseapp.NewDefaultProposalHandler(nonceMempool, app)
	// 	app.SetPrepareProposal(abciPropHandler.PrepareProposalHandler())
	//
}
	// baseAppOptions = append(baseAppOptions, prepareOpt)
    bApp := baseapp.NewBaseApp(appName, logger, db, txConfig.TxDecoder(), baseAppOptions...)

bApp.SetCommitMultiStoreTracer(traceStore)

bApp.SetVersion(version.Version)

bApp.SetInterfaceRegistry(interfaceRegistry)

bApp.SetTxEncoder(txConfig.TxEncoder())
    keys := storetypes.NewKVStoreKeys(
		authtypes.StoreKey, banktypes.StoreKey, stakingtypes.StoreKey, crisistypes.StoreKey,
		minttypes.StoreKey, distrtypes.StoreKey, slashingtypes.StoreKey,
		govtypes.StoreKey, paramstypes.StoreKey, consensusparamtypes.StoreKey, upgradetypes.StoreKey, feegrant.StoreKey,
		evidencetypes.StoreKey, circuittypes.StoreKey,
		authzkeeper.StoreKey, nftkeeper.StoreKey, group.StoreKey,
	)

	// register streaming services
    if err := bApp.RegisterStreamingServices(appOpts, keys); err != nil {
    panic(err)
}
    tkeys := storetypes.NewTransientStoreKeys(paramstypes.TStoreKey)
    app := &SimApp{
    BaseApp:           bApp,
		legacyAmino:       legacyAmino,
		appCodec:          appCodec,
		txConfig:          txConfig,
		interfaceRegistry: interfaceRegistry,
		keys:              keys,
		tkeys:             tkeys,
}

app.ParamsKeeper = initParamsKeeper(appCodec, legacyAmino, keys[paramstypes.StoreKey], tkeys[paramstypes.TStoreKey])

	// set the BaseApp's parameter store
	app.ConsensusParamsKeeper = consensusparamkeeper.NewKeeper(appCodec, runtime.NewKVStoreService(keys[consensusparamtypes.StoreKey]), authtypes.NewModuleAddress(govtypes.ModuleName).String(), runtime.EventService{
})

bApp.SetParamStore(app.ConsensusParamsKeeper.ParamsStore)

	// add keepers
	app.AccountKeeper = authkeeper.NewAccountKeeper(appCodec, runtime.NewKVStoreService(keys[authtypes.StoreKey]), authtypes.ProtoBaseAccount, maccPerms, sdk.Bech32MainPrefix, authtypes.NewModuleAddress(govtypes.ModuleName).String())

app.BankKeeper = bankkeeper.NewBaseKeeper(
		appCodec,
		runtime.NewKVStoreService(keys[banktypes.StoreKey]),
		app.AccountKeeper,
		BlockedAddresses(),
		authtypes.NewModuleAddress(govtypes.ModuleName).String(),
		logger,
	)

app.StakingKeeper = stakingkeeper.NewKeeper(
		appCodec, keys[stakingtypes.StoreKey], app.AccountKeeper, app.BankKeeper, authtypes.NewModuleAddress(govtypes.ModuleName).String(),
	)

app.MintKeeper = mintkeeper.NewKeeper(appCodec, runtime.NewKVStoreService(keys[minttypes.StoreKey]), app.StakingKeeper, app.AccountKeeper, app.BankKeeper, authtypes.FeeCollectorName, authtypes.NewModuleAddress(govtypes.ModuleName).String())

app.DistrKeeper = distrkeeper.NewKeeper(appCodec, runtime.NewKVStoreService(keys[distrtypes.StoreKey]), app.AccountKeeper, app.BankKeeper, app.StakingKeeper, authtypes.FeeCollectorName, authtypes.NewModuleAddress(govtypes.ModuleName).String())

app.SlashingKeeper = slashingkeeper.NewKeeper(
		appCodec, legacyAmino, runtime.NewKVStoreService(keys[slashingtypes.StoreKey]), app.StakingKeeper, authtypes.NewModuleAddress(govtypes.ModuleName).String(),
	)
    invCheckPeriod := cast.ToUint(appOpts.Get(server.FlagInvCheckPeriod))

app.CrisisKeeper = crisiskeeper.NewKeeper(appCodec, runtime.NewKVStoreService(keys[crisistypes.StoreKey]), invCheckPeriod,
		app.BankKeeper, authtypes.FeeCollectorName, authtypes.NewModuleAddress(govtypes.ModuleName).String(), app.AccountKeeper.AddressCodec())

app.FeeGrantKeeper = feegrantkeeper.NewKeeper(appCodec, runtime.NewKVStoreService(keys[feegrant.StoreKey]), app.AccountKeeper)

	// register the staking hooks
	// NOTE: stakingKeeper above is passed by reference, so that it will contain these hooks
	app.StakingKeeper.SetHooks(
		stakingtypes.NewMultiStakingHooks(app.DistrKeeper.Hooks(), app.SlashingKeeper.Hooks()),
	)

app.CircuitKeeper = circuitkeeper.NewKeeper(appCodec, runtime.NewKVStoreService(keys[circuittypes.StoreKey]), authtypes.NewModuleAddress(govtypes.ModuleName).String(), app.AccountKeeper.AddressCodec())

app.BaseApp.SetCircuitBreaker(&app.CircuitKeeper)

app.AuthzKeeper = authzkeeper.NewKeeper(runtime.NewKVStoreService(keys[authzkeeper.StoreKey]), appCodec, app.MsgServiceRouter(), app.AccountKeeper)
    groupConfig := group.DefaultConfig()
	/*
		Example of setting group params:
		groupConfig.MaxMetadataLen = 1000
	*/
	app.GroupKeeper = groupkeeper.NewKeeper(keys[group.StoreKey], appCodec, app.MsgServiceRouter(), app.AccountKeeper, groupConfig)

	// get skipUpgradeHeights from the app options
    skipUpgradeHeights := map[int64]bool{
}
    for _, h := range cast.ToIntSlice(appOpts.Get(server.FlagUnsafeSkipUpgrades)) {
    skipUpgradeHeights[int64(h)] = true
}
    homePath := cast.ToString(appOpts.Get(flags.FlagHome))
	// set the governance module account as the authority for conducting upgrades
	app.UpgradeKeeper = upgradekeeper.NewKeeper(skipUpgradeHeights, runtime.NewKVStoreService(keys[upgradetypes.StoreKey]), appCodec, homePath, app.BaseApp, authtypes.NewModuleAddress(govtypes.ModuleName).String())

	// Register the proposal types
	// Deprecated: Avoid adding new handlers, instead use the new proposal flow
	// by granting the governance module the right to execute the message.
	// See: /sdk/v0.53/build/modules/gov#proposal-messages
    govRouter := govv1beta1.NewRouter()

govRouter.AddRoute(govtypes.RouterKey, govv1beta1.ProposalHandler).
		AddRoute(paramproposal.RouterKey, params.NewParamChangeProposalHandler(app.ParamsKeeper)).
		AddRoute(upgradetypes.RouterKey, upgrade.NewSoftwareUpgradeProposalHandler(app.UpgradeKeeper))
    govConfig := govtypes.DefaultConfig()
	/*
		Example of setting gov params:
		govConfig.MaxMetadataLen = 10000
	*/
    govKeeper := govkeeper.NewKeeper(
		appCodec, runtime.NewKVStoreService(keys[govtypes.StoreKey]), app.AccountKeeper, app.BankKeeper,
		app.StakingKeeper, app.DistrKeeper, app.MsgServiceRouter(), govConfig, authtypes.NewModuleAddress(govtypes.ModuleName).String(),
	)

	// Set legacy router for backwards compatibility with gov v1beta1
	govKeeper.SetLegacyRouter(govRouter)

app.GovKeeper = *govKeeper.SetHooks(
		govtypes.NewMultiGovHooks(
		// register the governance hooks
		),
	)

app.NFTKeeper = nftkeeper.NewKeeper(runtime.NewKVStoreService(keys[nftkeeper.StoreKey]), appCodec, app.AccountKeeper, app.BankKeeper)

	// create evidence keeper with router
    evidenceKeeper := evidencekeeper.NewKeeper(
		appCodec, runtime.NewKVStoreService(keys[evidencetypes.StoreKey]), app.StakingKeeper, app.SlashingKeeper, app.AccountKeeper.AddressCodec(), runtime.ProvideCometInfoService(),
	)
	// If evidence needs to be handled for the app, set routes in router here and seal
	app.EvidenceKeeper = *evidenceKeeper

	/****  Module Options ****/

	// NOTE: we may consider parsing `appOpts` inside module constructors. For the moment
	// we prefer to be more strict in what arguments the modules expect.
    skipGenesisInvariants := cast.ToBool(appOpts.Get(crisis.FlagSkipGenesisInvariants))

	// NOTE: Any module instantiated in the module manager that is later modified
	// must be passed by reference here.
	app.ModuleManager = module.NewManager(
		genutil.NewAppModule(
			app.AccountKeeper, app.StakingKeeper, app,
			txConfig,
		),
		auth.NewAppModule(appCodec, app.AccountKeeper, authsims.RandomGenesisAccounts, app.GetSubspace(authtypes.ModuleName)),
		vesting.NewAppModule(app.AccountKeeper, app.BankKeeper),
		bank.NewAppModule(appCodec, app.BankKeeper, app.AccountKeeper, app.GetSubspace(banktypes.ModuleName)),
		crisis.NewAppModule(app.CrisisKeeper, skipGenesisInvariants, app.GetSubspace(crisistypes.ModuleName)),
		feegrantmodule.NewAppModule(appCodec, app.AccountKeeper, app.BankKeeper, app.FeeGrantKeeper, app.interfaceRegistry),
		gov.NewAppModule(appCodec, &app.GovKeeper, app.AccountKeeper, app.BankKeeper, app.GetSubspace(govtypes.ModuleName)),
		mint.NewAppModule(appCodec, app.MintKeeper, app.AccountKeeper, nil, app.GetSubspace(minttypes.ModuleName)),
		slashing.NewAppModule(appCodec, app.SlashingKeeper, app.AccountKeeper, app.BankKeeper, app.StakingKeeper, app.GetSubspace(slashingtypes.ModuleName), app.interfaceRegistry),
		distr.NewAppModule(appCodec, app.DistrKeeper, app.AccountKeeper, app.BankKeeper, app.StakingKeeper, app.GetSubspace(distrtypes.ModuleName)),
		staking.NewAppModule(appCodec, app.StakingKeeper, app.AccountKeeper, app.BankKeeper, app.GetSubspace(stakingtypes.ModuleName)),
		upgrade.NewAppModule(app.UpgradeKeeper, app.AccountKeeper.AddressCodec()),
		evidence.NewAppModule(app.EvidenceKeeper),
		params.NewAppModule(app.ParamsKeeper),
		authzmodule.NewAppModule(appCodec, app.AuthzKeeper, app.AccountKeeper, app.BankKeeper, app.interfaceRegistry),
		groupmodule.NewAppModule(appCodec, app.GroupKeeper, app.AccountKeeper, app.BankKeeper, app.interfaceRegistry),
		nftmodule.NewAppModule(appCodec, app.NFTKeeper, app.AccountKeeper, app.BankKeeper, app.interfaceRegistry),
		consensus.NewAppModule(appCodec, app.ConsensusParamsKeeper),
		circuit.NewAppModule(appCodec, app.CircuitKeeper),
	)

	// BasicModuleManager defines the module BasicManager is in charge of setting up basic,
	// non-dependant module elements, such as codec registration and genesis verification.
	// By default it is composed of all the module from the module manager.
	// Additionally, app module basics can be overwritten by passing them as argument.
	app.BasicModuleManager = module.NewBasicManagerFromManager(
		app.ModuleManager,
		map[string]module.AppModuleBasic{
    genutiltypes.ModuleName: genutil.NewAppModuleBasic(genutiltypes.DefaultMessageValidator),
			govtypes.ModuleName: gov.NewAppModuleBasic(
				[]govclient.ProposalHandler{
    paramsclient.ProposalHandler,
},
			),
})

app.BasicModuleManager.RegisterLegacyAminoCodec(legacyAmino)

app.BasicModuleManager.RegisterInterfaces(interfaceRegistry)

	// During begin block slashing happens after distr.BeginBlocker so that
	// there is nothing left over in the validator fee pool, so as to keep the
	// CanWithdrawInvariant invariant.
	// NOTE: staking module is required if HistoricalEntries param > 0
	app.ModuleManager.SetOrderBeginBlockers(
		upgradetypes.ModuleName,
		minttypes.ModuleName,
		distrtypes.ModuleName,
		slashingtypes.ModuleName,
		evidencetypes.ModuleName,
		stakingtypes.ModuleName,
		genutiltypes.ModuleName,
		authz.ModuleName,
	)

app.ModuleManager.SetOrderEndBlockers(
		crisistypes.ModuleName,
		govtypes.ModuleName,
		stakingtypes.ModuleName,
		genutiltypes.ModuleName,
		feegrant.ModuleName,
		group.ModuleName,
	)

	// NOTE: The genutils module must occur after staking so that pools are
	// properly initialized with tokens from genesis accounts.
	// NOTE: The genutils module must also occur after auth so that it can access the params from auth.
    genesisModuleOrder := []string{
    authtypes.ModuleName, banktypes.ModuleName,
		distrtypes.ModuleName, stakingtypes.ModuleName, slashingtypes.ModuleName, govtypes.ModuleName,
		minttypes.ModuleName, crisistypes.ModuleName, genutiltypes.ModuleName, evidencetypes.ModuleName, authz.ModuleName,
		feegrant.ModuleName, nft.ModuleName, group.ModuleName, paramstypes.ModuleName, upgradetypes.ModuleName,
		vestingtypes.ModuleName, consensusparamtypes.ModuleName, circuittypes.ModuleName,
}

app.ModuleManager.SetOrderInitGenesis(genesisModuleOrder...)

app.ModuleManager.SetOrderExportGenesis(genesisModuleOrder...)

	// Uncomment if you want to set a custom migration order here.
	// app.ModuleManager.SetOrderMigrations(custom order)

app.ModuleManager.RegisterInvariants(app.CrisisKeeper)

app.configurator = module.NewConfigurator(app.appCodec, app.MsgServiceRouter(), app.GRPCQueryRouter())
    err := app.ModuleManager.RegisterServices(app.configurator)
    if err != nil {
    panic(err)
}

	// RegisterUpgradeHandlers is used for registering any on-chain upgrades.
	// Make sure it's called after `app.ModuleManager` and `app.configurator` are set.
	app.RegisterUpgradeHandlers()

autocliv1.RegisterQueryServer(app.GRPCQueryRouter(), runtimeservices.NewAutoCLIQueryService(app.ModuleManager.Modules))

reflectionSvc, err := runtimeservices.NewReflectionService()
    if err != nil {
    panic(err)
}

reflectionv1.RegisterReflectionServiceServer(app.GRPCQueryRouter(), reflectionSvc)

	// add test gRPC service for testing gRPC queries in isolation
	testdata_pulsar.RegisterQueryServer(app.GRPCQueryRouter(), testdata_pulsar.QueryImpl{
})

	// create the simulation manager and define the order of the modules for deterministic simulations
	//
	// NOTE: this is not required apps that don't use the simulator for fuzz testing
	// transactions
    overrideModules := map[string]module.AppModuleSimulation{
    authtypes.ModuleName: auth.NewAppModule(app.appCodec, app.AccountKeeper, authsims.RandomGenesisAccounts, app.GetSubspace(authtypes.ModuleName)),
}

app.sm = module.NewSimulationManagerFromAppModules(app.ModuleManager.Modules, overrideModules)

app.sm.RegisterStoreDecoders()

	// initialize stores
	app.MountKVStores(keys)

app.MountTransientStores(tkeys)

	// initialize BaseApp
	app.SetInitChainer(app.InitChainer)

app.SetBeginBlocker(app.BeginBlocker)

app.SetEndBlocker(app.EndBlocker)

app.setAnteHandler(txConfig)

	// In v0.46, the SDK introduces _postHandlers_. PostHandlers are like
	// antehandlers, but are run _after_ the `runMsgs` execution. They are also
	// defined as a chain, and have the same signature as antehandlers.
	//
	// In baseapp, postHandlers are run in the same store branch as `runMsgs`,
	// meaning that both `runMsgs` and `postHandler` state will be committed if
	// both are successful, and both will be reverted if any of the two fails.
	//
	// The SDK exposes a default postHandlers chain, which comprises of only
	// one decorator: the Transaction Tips decorator. However, some chains do
	// not need it by default, so feel free to comment the next line if you do
	// not need tips.
	// To read more about tips:
	// /sdk/v0.53/build/modules/auth/auth
	//
	// Please note that changing any of the anteHandler or postHandler chain is
	// likely to be a state-machine breaking change, which needs a coordinated
	// upgrade.
	app.setPostHandler()

	// At startup, after all modules have been registered, check that all prot
	// annotations are correct.
	protoFiles, err := proto.MergedRegistry()
    if err != nil {
    panic(err)
}

err = msgservice.ValidateProtoAnnotations(protoFiles)
    if err != nil {
		// Once we switch to using protoreflect-based antehandlers, we might
		// want to panic here instead of logging a warning.
		fmt.Fprintln(os.Stderr, err.Error())
}
    if loadLatest {
    if err := app.LoadLatestVersion(); err != nil {
    panic(fmt.Errorf("error loading last version: %w", err))
}
	
}

return app
}

func (app *SimApp)

setAnteHandler(txConfig client.TxConfig) {
    anteHandler, err := NewAnteHandler(
		HandlerOptions{
    ante.HandlerOptions{
    AccountKeeper:   app.AccountKeeper,
    BankKeeper:      app.BankKeeper,
    SignModeHandler: txConfig.SignModeHandler(),
    FeegrantKeeper:  app.FeeGrantKeeper,
    SigGasConsumer:  ante.DefaultSigVerificationGasConsumer,
},
			&app.CircuitKeeper,
},
	)
    if err != nil {
    panic(err)
}

	// Set the AnteHandler for the app
	app.SetAnteHandler(anteHandler)
}

func (app *SimApp)

setPostHandler() {
    postHandler, err := posthandler.NewPostHandler(
		posthandler.HandlerOptions{
},
	)
    if err != nil {
    panic(err)
}

app.SetPostHandler(postHandler)
}

// Name returns the name of the App
func (app *SimApp)

Name()

string {
    return app.BaseApp.Name()
}

// BeginBlocker application updates every begin block
func (app *SimApp)

BeginBlocker(ctx sdk.Context) (sdk.BeginBlock, error) {
    return app.ModuleManager.BeginBlock(ctx)
}

// EndBlocker application updates every end block
func (app *SimApp)

EndBlocker(ctx sdk.Context) (sdk.EndBlock, error) {
    return app.ModuleManager.EndBlock(ctx)
}

func (a *SimApp)

Configurator()

module.Configurator {
    return a.configurator
}

// InitChainer application update at chain initialization
func (app *SimApp)

InitChainer(ctx sdk.Context, req *abci.RequestInitChain) (*abci.ResponseInitChain, error) {
    var genesisState GenesisState
    if err := json.Unmarshal(req.AppStateBytes, &genesisState); err != nil {
    panic(err)
}

app.UpgradeKeeper.SetModuleVersionMap(ctx, app.ModuleManager.GetVersionMap())

return app.ModuleManager.InitGenesis(ctx, app.appCodec, genesisState)
}

// LoadHeight loads a particular height
func (app *SimApp)

LoadHeight(height int64)

error {
    return app.LoadVersion(height)
}

// LegacyAmino returns SimApp's amino codec.
//
// NOTE: This is solely to be used for testing purposes as it may be desirable
// for modules to register their own custom testing types.
func (app *SimApp)

LegacyAmino() *codec.LegacyAmino {
    return app.legacyAmino
}

// AppCodec returns SimApp's app codec.
//
// NOTE: This is solely to be used for testing purposes as it may be desirable
// for modules to register their own custom testing types.
func (app *SimApp)

AppCodec()

codec.Codec {
    return app.appCodec
}

// InterfaceRegistry returns SimApp's InterfaceRegistry
func (app *SimApp)

InterfaceRegistry()

types.InterfaceRegistry {
    return app.interfaceRegistry
}

// TxConfig returns SimApp's TxConfig
func (app *SimApp)

TxConfig()

client.TxConfig {
    return app.txConfig
}

// AutoCliOpts returns the autocli options for the app.
func (app *SimApp)

AutoCliOpts()

autocli.AppOptions {
    modules := make(map[string]appmodule.AppModule, 0)
    for _, m := range app.ModuleManager.Modules {
    if moduleWithName, ok := m.(module.HasName); ok {
    moduleName := moduleWithName.Name()
    if appModule, ok := moduleWithName.(appmodule.AppModule); ok {
    modules[moduleName] = appModule
}
	
}
	
}

return autocli.AppOptions{
    Modules:      modules,
    AddressCodec: authcodec.NewBech32Codec(sdk.GetConfig().GetBech32AccountAddrPrefix()),
}
}

// DefaultGenesis returns a default genesis from the registered AppModuleBasic's.
func (a *SimApp)

DefaultGenesis()

map[string]json.RawMessage {
    return a.BasicModuleManager.DefaultGenesis(a.appCodec)
}

// GetKey returns the KVStoreKey for the provided store key.
//
// NOTE: This is solely to be used for testing purposes.
func (app *SimApp)

GetKey(storeKey string) *storetypes.KVStoreKey {
    return app.keys[storeKey]
}

// GetStoreKeys returns all the stored store keys.
func (app *SimApp)

GetStoreKeys() []storetypes.StoreKey {
    keys := make([]storetypes.StoreKey, len(app.keys))
    for _, key := range app.keys {
    keys = append(keys, key)
}

return keys
}

// GetSubspace returns a param subspace for a given module name.
//
// NOTE: This is solely to be used for testing purposes.
func (app *SimApp)

GetSubspace(moduleName string)

paramstypes.Subspace {
    subspace, _ := app.ParamsKeeper.GetSubspace(moduleName)

return subspace
}

// SimulationManager implements the SimulationApp interface
func (app *SimApp)

SimulationManager() *module.SimulationManager {
    return app.sm
}

// RegisterAPIRoutes registers all application module routes with the provided
// API server.
func (app *SimApp)

RegisterAPIRoutes(apiSvr *api.Server, apiConfig config.APIConfig) {
    clientCtx := apiSvr.ClientCtx
	// Register new tx routes from grpc-gateway.
	authtx.RegisterGRPCGatewayRoutes(clientCtx, apiSvr.GRPCGatewayRouter)

	// Register new CometBFT queries routes from grpc-gateway.
	cmtservice.RegisterGRPCGatewayRoutes(clientCtx, apiSvr.GRPCGatewayRouter)

	// Register node gRPC service for grpc-gateway.
	nodeservice.RegisterGRPCGatewayRoutes(clientCtx, apiSvr.GRPCGatewayRouter)

	// Register grpc-gateway routes for all modules.
	app.BasicModuleManager.RegisterGRPCGatewayRoutes(clientCtx, apiSvr.GRPCGatewayRouter)

	// register swagger API from root so that other applications can override easily
    if err := server.RegisterSwaggerAPI(apiSvr.ClientCtx, apiSvr.Router, apiConfig.Swagger); err != nil {
    panic(err)
}
}

// RegisterTxService implements the Application.RegisterTxService method.
func (app *SimApp)

RegisterTxService(clientCtx client.Context) {
    authtx.RegisterTxService(app.BaseApp.GRPCQueryRouter(), clientCtx, app.BaseApp.Simulate, app.interfaceRegistry)
}

// RegisterTendermintService implements the Application.RegisterTendermintService method.
func (app *SimApp)

RegisterTendermintService(clientCtx client.Context) {
    cmtApp := server.NewCometABCIWrapper(app)

cmtservice.RegisterTendermintService(
		clientCtx,
		app.BaseApp.GRPCQueryRouter(),
		app.interfaceRegistry,
		cmtApp.Query,
	)
}

func (app *SimApp)

RegisterNodeService(clientCtx client.Context, cfg config.Config) {
    nodeservice.RegisterNodeService(clientCtx, app.GRPCQueryRouter(), cfg)
}

// GetMaccPerms returns a copy of the module account permissions
//
// NOTE: This is solely to be used for testing purposes.
func GetMaccPerms()

map[string][]string {
    dupMaccPerms := make(map[string][]string)
    for k, v := range maccPerms {
    dupMaccPerms[k] = v
}

return dupMaccPerms
}

// BlockedAddresses returns all the app's blocked account addresses.
func BlockedAddresses()

map[string]bool {
    modAccAddrs := make(map[string]bool)
    for acc := range GetMaccPerms() {
    modAccAddrs[authtypes.NewModuleAddress(acc).String()] = true
}

	// allow the following addresses to receive funds
	delete(modAccAddrs, authtypes.NewModuleAddress(govtypes.ModuleName).String())

return modAccAddrs
}

// initParamsKeeper init params keeper and its subspaces
func initParamsKeeper(appCodec codec.BinaryCodec, legacyAmino *codec.LegacyAmino, key, tkey storetypes.StoreKey)

paramskeeper.Keeper {
    paramsKeeper := paramskeeper.NewKeeper(appCodec, legacyAmino, key, tkey)

paramsKeeper.Subspace(authtypes.ModuleName)

paramsKeeper.Subspace(banktypes.ModuleName)

paramsKeeper.Subspace(stakingtypes.ModuleName)

paramsKeeper.Subspace(minttypes.ModuleName)

paramsKeeper.Subspace(distrtypes.ModuleName)

paramsKeeper.Subspace(slashingtypes.ModuleName)

paramsKeeper.Subspace(govtypes.ModuleName)

paramsKeeper.Subspace(crisistypes.ModuleName)

return paramsKeeper
}

Learn

Building a Chain

Building a Module

Run a Node

How-to Guides

Tooling

Reference

What is app.go?

Core Components

SimApp Struct

Key Initialization Steps

1. Codec Setup

2. BaseApp Creation

3. Store Keys Registration

4. Keeper Initialization

5. Module Manager Setup

Module Account Permissions

Execution Order

Begin Block Order

End Block Order

Genesis Order

ABCI Lifecycle Methods

InitChainer

BeginBlocker & EndBlocker

Ante and Post Handlers

AnteHandler

PostHandler

API and Service Registration

Building Your Own Application

Additional Resources

Complete `app.go`

Learn

Building a Chain

Building a Module

Run a Node

How-to Guides

Tooling

Reference

​What is app.go?

​Core Components

​SimApp Struct

​Key Initialization Steps

​1. Codec Setup

​2. BaseApp Creation

​3. Store Keys Registration

​4. Keeper Initialization

​5. Module Manager Setup

​Module Account Permissions

​Execution Order

​Begin Block Order

​End Block Order

​Genesis Order

​ABCI Lifecycle Methods

​InitChainer

​BeginBlocker & EndBlocker

​Ante and Post Handlers

​AnteHandler

​PostHandler

​API and Service Registration

​Building Your Own Application

​Additional Resources

​Complete app.go

What is app.go?

Core Components

SimApp Struct

Key Initialization Steps

1. Codec Setup

2. BaseApp Creation

3. Store Keys Registration

4. Keeper Initialization

5. Module Manager Setup

Module Account Permissions

Execution Order

Begin Block Order

End Block Order

Genesis Order

ABCI Lifecycle Methods

InitChainer

BeginBlocker & EndBlocker

Ante and Post Handlers

AnteHandler

PostHandler

API and Service Registration

Building Your Own Application

Additional Resources

Complete `app.go`