diff --git a/config/import.go b/config/import.go
index 6ea4d060f..21bf232c1 100644
--- a/config/import.go
+++ b/config/import.go
@@ -1,11 +1,18 @@
 package config
 
+import (
+	"github.com/ipfs/boxo/ipld/unixfs/importer/helpers"
+	"github.com/ipfs/boxo/ipld/unixfs/io"
+)
+
 const (
 	DefaultCidVersion      = 0
 	DefaultUnixFSRawLeaves = false
 	DefaultUnixFSChunker   = "size-262144"
 	DefaultHashFunction    = "sha2-256"
 
+	DefaultUnixFSHAMTDirectorySizeThreshold = "256KiB" // https://github.com/ipfs/boxo/blob/6c5a07602aed248acc86598f30ab61923a54a83e/ipld/unixfs/io/directory.go#L26
+
 	// DefaultBatchMaxNodes controls the maximum number of nodes in a
 	// write-batch. The total size of the batch is limited by
 	// BatchMaxnodes and BatchMaxSize.
@@ -14,15 +21,26 @@ const (
 	// write-batch. The total size of the batch is limited by
 	// BatchMaxnodes and BatchMaxSize.
 	DefaultBatchMaxSize = 100 << 20 // 20MiB
+
+)
+
+var (
+	DefaultUnixFSFileMaxLinks           = int64(helpers.DefaultLinksPerBlock)
+	DefaultUnixFSDirectoryMaxLinks      = int64(0)
+	DefaultUnixFSHAMTDirectoryMaxFanout = int64(io.DefaultShardWidth)
 )
 
 // Import configures the default options for ingesting data. This affects commands
 // that ingest data, such as 'ipfs add', 'ipfs dag put, 'ipfs block put', 'ipfs files write'.
 type Import struct {
-	CidVersion      OptionalInteger
-	UnixFSRawLeaves Flag
-	UnixFSChunker   OptionalString
-	HashFunction    OptionalString
-	BatchMaxNodes   OptionalInteger
-	BatchMaxSize    OptionalInteger
+	CidVersion                       OptionalInteger
+	UnixFSRawLeaves                  Flag
+	UnixFSChunker                    OptionalString
+	HashFunction                     OptionalString
+	UnixFSFileMaxLinks               OptionalInteger
+	UnixFSDirectoryMaxLinks          OptionalInteger
+	UnixFSHAMTDirectoryMaxFanout     OptionalInteger
+	UnixFSHAMTDirectorySizeThreshold OptionalString
+	BatchMaxNodes                    OptionalInteger
+	BatchMaxSize                     OptionalInteger
 }
diff --git a/config/internal.go b/config/internal.go
index fe7e84320..f8300f540 100644
--- a/config/internal.go
+++ b/config/internal.go
@@ -3,7 +3,7 @@ package config
 type Internal struct {
 	// All marked as omitempty since we are expecting to make changes to all subcomponents of Internal
 	Bitswap                     *InternalBitswap  `json:",omitempty"`
-	UnixFSShardingSizeThreshold *OptionalString   `json:",omitempty"`
+	UnixFSShardingSizeThreshold *OptionalString   `json:",omitempty"` // moved to Import.UnixFSHAMTDirectorySizeThreshold
 	Libp2pForceReachability     *OptionalString   `json:",omitempty"`
 	BackupBootstrapInterval     *OptionalDuration `json:",omitempty"`
 }
diff --git a/config/profile.go b/config/profile.go
index 69aaf66dc..a26d74f99 100644
--- a/config/profile.go
+++ b/config/profile.go
@@ -266,24 +266,44 @@ fetching may be degraded.
 		},
 	},
 	"legacy-cid-v0": {
-		Description: `Makes UnixFS import produce legacy CIDv0 with no raw leaves, sha2-256 and 256 KiB chunks.`,
-
+		Description: `Makes UnixFS import produce legacy CIDv0 with no raw leaves, sha2-256 and 256 KiB chunks. This is likely the least optimal preset, use only if legacy behavior is required.`,
 		Transform: func(c *Config) error {
 			c.Import.CidVersion = *NewOptionalInteger(0)
 			c.Import.UnixFSRawLeaves = False
 			c.Import.UnixFSChunker = *NewOptionalString("size-262144")
 			c.Import.HashFunction = *NewOptionalString("sha2-256")
+			c.Import.UnixFSFileMaxLinks = *NewOptionalInteger(174)
+			c.Import.UnixFSDirectoryMaxLinks = *NewOptionalInteger(0)
+			c.Import.UnixFSHAMTDirectoryMaxFanout = *NewOptionalInteger(256)
+			c.Import.UnixFSHAMTDirectorySizeThreshold = *NewOptionalString("256KiB")
 			return nil
 		},
 	},
 	"test-cid-v1": {
-		Description: `Makes UnixFS import produce modern CIDv1 with raw leaves, sha2-256 and 1 MiB chunks.`,
-
+		Description: `Makes UnixFS import produce CIDv1 with raw leaves, sha2-256 and 1 MiB chunks (max 174 links per file, 256 per HAMT node, switch dir to HAMT above 256KiB).`,
 		Transform: func(c *Config) error {
 			c.Import.CidVersion = *NewOptionalInteger(1)
 			c.Import.UnixFSRawLeaves = True
 			c.Import.UnixFSChunker = *NewOptionalString("size-1048576")
 			c.Import.HashFunction = *NewOptionalString("sha2-256")
+			c.Import.UnixFSFileMaxLinks = *NewOptionalInteger(174)
+			c.Import.UnixFSDirectoryMaxLinks = *NewOptionalInteger(0)
+			c.Import.UnixFSHAMTDirectoryMaxFanout = *NewOptionalInteger(256)
+			c.Import.UnixFSHAMTDirectorySizeThreshold = *NewOptionalString("256KiB")
+			return nil
+		},
+	},
+	"test-cid-v1-wide": {
+		Description: `Makes UnixFS import produce CIDv1 with raw leaves, sha2-256 and 1MiB chunks and wider file DAGs (max 1024 links per every node type, switch dir to HAMT above 1MiB).`,
+		Transform: func(c *Config) error {
+			c.Import.CidVersion = *NewOptionalInteger(1)
+			c.Import.UnixFSRawLeaves = True
+			c.Import.UnixFSChunker = *NewOptionalString("size-1048576") // 1MiB
+			c.Import.HashFunction = *NewOptionalString("sha2-256")
+			c.Import.UnixFSFileMaxLinks = *NewOptionalInteger(1024)
+			c.Import.UnixFSDirectoryMaxLinks = *NewOptionalInteger(0) // no limit here, use size-based Import.UnixFSHAMTDirectorySizeThreshold instead
+			c.Import.UnixFSHAMTDirectoryMaxFanout = *NewOptionalInteger(1024)
+			c.Import.UnixFSHAMTDirectorySizeThreshold = *NewOptionalString("1MiB") // 1MiB
 			return nil
 		},
 	},
diff --git a/core/commands/add.go b/core/commands/add.go
index a1642f127..f800e4f42 100644
--- a/core/commands/add.go
+++ b/core/commands/add.go
@@ -37,23 +37,26 @@ type AddEvent struct {
 }
 
 const (
-	quietOptionName       = "quiet"
-	quieterOptionName     = "quieter"
-	silentOptionName      = "silent"
-	progressOptionName    = "progress"
-	trickleOptionName     = "trickle"
-	wrapOptionName        = "wrap-with-directory"
-	onlyHashOptionName    = "only-hash"
-	chunkerOptionName     = "chunker"
-	pinOptionName         = "pin"
-	rawLeavesOptionName   = "raw-leaves"
-	noCopyOptionName      = "nocopy"
-	fstoreCacheOptionName = "fscache"
-	cidVersionOptionName  = "cid-version"
-	hashOptionName        = "hash"
-	inlineOptionName      = "inline"
-	inlineLimitOptionName = "inline-limit"
-	toFilesOptionName     = "to-files"
+	quietOptionName             = "quiet"
+	quieterOptionName           = "quieter"
+	silentOptionName            = "silent"
+	progressOptionName          = "progress"
+	trickleOptionName           = "trickle"
+	wrapOptionName              = "wrap-with-directory"
+	onlyHashOptionName          = "only-hash"
+	chunkerOptionName           = "chunker"
+	pinOptionName               = "pin"
+	rawLeavesOptionName         = "raw-leaves"
+	maxFileLinksOptionName      = "max-file-links"
+	maxDirectoryLinksOptionName = "max-directory-links"
+	maxHAMTFanoutOptionName     = "max-hamt-fanout"
+	noCopyOptionName            = "nocopy"
+	fstoreCacheOptionName       = "fscache"
+	cidVersionOptionName        = "cid-version"
+	hashOptionName              = "hash"
+	inlineOptionName            = "inline"
+	inlineLimitOptionName       = "inline-limit"
+	toFilesOptionName           = "to-files"
 
 	preserveModeOptionName  = "preserve-mode"
 	preserveMtimeOptionName = "preserve-mtime"
@@ -143,6 +146,9 @@ new flags may be added in the future. It is not guaranteed for the implicit
 defaults of 'ipfs add' to remain the same in future Kubo releases, or for other
 IPFS software to use the same import parameters as Kubo.
 
+Use Import.* configuration options to override global implicit defaults:
+https://github.com/ipfs/kubo/blob/master/docs/config.md#import
+
 If you need to back up or transport content-addressed data using a non-IPFS
 medium, CID can be preserved with CAR files.
 See 'dag export' and 'dag import' for more information.
@@ -166,12 +172,15 @@ See 'dag export' and 'dag import' for more information.
 		cmds.BoolOption(trickleOptionName, "t", "Use trickle-dag format for dag generation."),
 		cmds.BoolOption(onlyHashOptionName, "n", "Only chunk and hash - do not write to disk."),
 		cmds.BoolOption(wrapOptionName, "w", "Wrap files with a directory object."),
-		cmds.StringOption(chunkerOptionName, "s", "Chunking algorithm, size-[bytes], rabin-[min]-[avg]-[max] or buzhash"),
-		cmds.BoolOption(rawLeavesOptionName, "Use raw blocks for leaf nodes."),
+		cmds.StringOption(chunkerOptionName, "s", "Chunking algorithm, size-[bytes], rabin-[min]-[avg]-[max] or buzhash. Default: Import.UnixFSChunker"),
+		cmds.BoolOption(rawLeavesOptionName, "Use raw blocks for leaf nodes. Default: Import.UnixFSRawLeaves"),
+		cmds.IntOption(maxFileLinksOptionName, "Limit the maximum number of links in UnixFS file nodes to this value. (experimental) Default: Import.UnixFSFileMaxLinks"),
+		cmds.IntOption(maxDirectoryLinksOptionName, "Limit the maximum number of links in UnixFS basic directory nodes to this value. Default: Import.UnixFSDirectoryMaxLinks. WARNING: experimental, Import.UnixFSHAMTThreshold is a safer alternative."),
+		cmds.IntOption(maxHAMTFanoutOptionName, "Limit the maximum number of links of a UnixFS HAMT directory node to this (power of 2, multiple of 8). Default: Import.UnixFSHAMTDirectoryMaxFanout WARNING: experimental, see Import.UnixFSHAMTDirectorySizeThreshold as well."),
 		cmds.BoolOption(noCopyOptionName, "Add the file using filestore. Implies raw-leaves. (experimental)"),
 		cmds.BoolOption(fstoreCacheOptionName, "Check the filestore for pre-existing blocks. (experimental)"),
-		cmds.IntOption(cidVersionOptionName, "CID version. Defaults to 0 unless an option that depends on CIDv1 is passed. Passing version 1 will cause the raw-leaves option to default to true."),
-		cmds.StringOption(hashOptionName, "Hash function to use. Implies CIDv1 if not sha2-256. (experimental)"),
+		cmds.IntOption(cidVersionOptionName, "CID version. Defaults to 0 unless an option that depends on CIDv1 is passed. Passing version 1 will cause the raw-leaves option to default to true. Default: Import.CidVersion"),
+		cmds.StringOption(hashOptionName, "Hash function to use. Implies CIDv1 if not sha2-256. Default: Import.HashFunction"),
 		cmds.BoolOption(inlineOptionName, "Inline small blocks into CIDs. (experimental)"),
 		cmds.IntOption(inlineLimitOptionName, "Maximum block size to inline. (experimental)").WithDefault(32),
 		cmds.BoolOption(pinOptionName, "Pin locally to protect added files from garbage collection.").WithDefault(true),
@@ -222,6 +231,9 @@ See 'dag export' and 'dag import' for more information.
 		chunker, _ := req.Options[chunkerOptionName].(string)
 		dopin, _ := req.Options[pinOptionName].(bool)
 		rawblks, rbset := req.Options[rawLeavesOptionName].(bool)
+		maxFileLinks, maxFileLinksSet := req.Options[maxFileLinksOptionName].(int)
+		maxDirectoryLinks, maxDirectoryLinksSet := req.Options[maxDirectoryLinksOptionName].(int)
+		maxHAMTFanout, maxHAMTFanoutSet := req.Options[maxHAMTFanoutOptionName].(int)
 		nocopy, _ := req.Options[noCopyOptionName].(bool)
 		fscache, _ := req.Options[fstoreCacheOptionName].(bool)
 		cidVer, cidVerSet := req.Options[cidVersionOptionName].(int)
@@ -253,6 +265,21 @@ See 'dag export' and 'dag import' for more information.
 			rawblks = cfg.Import.UnixFSRawLeaves.WithDefault(config.DefaultUnixFSRawLeaves)
 		}
 
+		if !maxFileLinksSet && !cfg.Import.UnixFSFileMaxLinks.IsDefault() {
+			maxFileLinksSet = true
+			maxFileLinks = int(cfg.Import.UnixFSFileMaxLinks.WithDefault(config.DefaultUnixFSFileMaxLinks))
+		}
+
+		if !maxDirectoryLinksSet && !cfg.Import.UnixFSDirectoryMaxLinks.IsDefault() {
+			maxDirectoryLinksSet = true
+			maxDirectoryLinks = int(cfg.Import.UnixFSDirectoryMaxLinks.WithDefault(config.DefaultUnixFSDirectoryMaxLinks))
+		}
+
+		if !maxHAMTFanoutSet && !cfg.Import.UnixFSHAMTDirectoryMaxFanout.IsDefault() {
+			maxHAMTFanoutSet = true
+			maxHAMTFanout = int(cfg.Import.UnixFSHAMTDirectoryMaxFanout.WithDefault(config.DefaultUnixFSHAMTDirectoryMaxFanout))
+		}
+
 		// Storing optional mode or mtime (UnixFS 1.5) requires root block
 		// to always be 'dag-pb' and not 'raw'. Below adjusts raw-leaves setting, if possible.
 		if preserveMode || preserveMtime || mode != 0 || mtime != 0 {
@@ -329,6 +356,18 @@ See 'dag export' and 'dag import' for more information.
 			opts = append(opts, options.Unixfs.RawLeaves(rawblks))
 		}
 
+		if maxFileLinksSet {
+			opts = append(opts, options.Unixfs.MaxFileLinks(maxFileLinks))
+		}
+
+		if maxDirectoryLinksSet {
+			opts = append(opts, options.Unixfs.MaxDirectoryLinks(maxDirectoryLinks))
+		}
+
+		if maxHAMTFanoutSet {
+			opts = append(opts, options.Unixfs.MaxHAMTFanout(maxHAMTFanout))
+		}
+
 		if trickle {
 			opts = append(opts, options.Unixfs.Layout(options.TrickleLayout))
 		}
diff --git a/core/coreapi/unixfs.go b/core/coreapi/unixfs.go
index 3a74d3046..eece797a5 100644
--- a/core/coreapi/unixfs.go
+++ b/core/coreapi/unixfs.go
@@ -50,6 +50,12 @@ func (api *UnixfsAPI) Add(ctx context.Context, files files.Node, opts ...options
 		attribute.Int("inlinelimit", settings.InlineLimit),
 		attribute.Bool("rawleaves", settings.RawLeaves),
 		attribute.Bool("rawleavesset", settings.RawLeavesSet),
+		attribute.Int("maxfilelinks", settings.MaxFileLinks),
+		attribute.Bool("maxfilelinksset", settings.MaxFileLinksSet),
+		attribute.Int("maxdirectorylinks", settings.MaxDirectoryLinks),
+		attribute.Bool("maxdirectorylinksset", settings.MaxDirectoryLinksSet),
+		attribute.Int("maxhamtfanout", settings.MaxHAMTFanout),
+		attribute.Bool("maxhamtfanoutset", settings.MaxHAMTFanoutSet),
 		attribute.Int("layout", int(settings.Layout)),
 		attribute.Bool("pin", settings.Pin),
 		attribute.Bool("onlyhash", settings.OnlyHash),
@@ -132,6 +138,16 @@ func (api *UnixfsAPI) Add(ctx context.Context, files files.Node, opts ...options
 	fileAdder.Pin = settings.Pin && !settings.OnlyHash
 	fileAdder.Silent = settings.Silent
 	fileAdder.RawLeaves = settings.RawLeaves
+	if settings.MaxFileLinksSet {
+		fileAdder.MaxLinks = settings.MaxFileLinks
+	}
+	if settings.MaxDirectoryLinksSet {
+		fileAdder.MaxDirectoryLinks = settings.MaxDirectoryLinks
+	}
+
+	if settings.MaxHAMTFanoutSet {
+		fileAdder.MaxHAMTFanout = settings.MaxHAMTFanout
+	}
 	fileAdder.NoCopy = settings.NoCopy
 	fileAdder.CidBuilder = prefix
 	fileAdder.PreserveMode = settings.PreserveMode
diff --git a/core/coreiface/options/unixfs.go b/core/coreiface/options/unixfs.go
index c837ec1b2..20f18d1e0 100644
--- a/core/coreiface/options/unixfs.go
+++ b/core/coreiface/options/unixfs.go
@@ -7,6 +7,8 @@ import (
 	"time"
 
 	dag "github.com/ipfs/boxo/ipld/merkledag"
+	"github.com/ipfs/boxo/ipld/unixfs/importer/helpers"
+	"github.com/ipfs/boxo/ipld/unixfs/io"
 	cid "github.com/ipfs/go-cid"
 	mh "github.com/multiformats/go-multihash"
 )
@@ -22,10 +24,16 @@ type UnixfsAddSettings struct {
 	CidVersion int
 	MhType     uint64
 
-	Inline       bool
-	InlineLimit  int
-	RawLeaves    bool
-	RawLeavesSet bool
+	Inline               bool
+	InlineLimit          int
+	RawLeaves            bool
+	RawLeavesSet         bool
+	MaxFileLinks         int
+	MaxFileLinksSet      bool
+	MaxDirectoryLinks    int
+	MaxDirectoryLinksSet bool
+	MaxHAMTFanout        int
+	MaxHAMTFanoutSet     bool
 
 	Chunker string
 	Layout  Layout
@@ -60,10 +68,16 @@ func UnixfsAddOptions(opts ...UnixfsAddOption) (*UnixfsAddSettings, cid.Prefix,
 		CidVersion: -1,
 		MhType:     mh.SHA2_256,
 
-		Inline:       false,
-		InlineLimit:  32,
-		RawLeaves:    false,
-		RawLeavesSet: false,
+		Inline:               false,
+		InlineLimit:          32,
+		RawLeaves:            false,
+		RawLeavesSet:         false,
+		MaxFileLinks:         helpers.DefaultLinksPerBlock,
+		MaxFileLinksSet:      false,
+		MaxDirectoryLinks:    0,
+		MaxDirectoryLinksSet: false,
+		MaxHAMTFanout:        io.DefaultShardWidth,
+		MaxHAMTFanoutSet:     false,
 
 		Chunker: "size-262144",
 		Layout:  BalancedLayout,
@@ -190,6 +204,35 @@ func (unixfsOpts) RawLeaves(enable bool) UnixfsAddOption {
 	}
 }
 
+// MaxFileLinks specifies the maximum number of children for UnixFS file
+// nodes.
+func (unixfsOpts) MaxFileLinks(n int) UnixfsAddOption {
+	return func(settings *UnixfsAddSettings) error {
+		settings.MaxFileLinks = n
+		settings.MaxFileLinksSet = true
+		return nil
+	}
+}
+
+// MaxDirectoryLinks specifies the maximum number of children for UnixFS basic
+// directory nodes.
+func (unixfsOpts) MaxDirectoryLinks(n int) UnixfsAddOption {
+	return func(settings *UnixfsAddSettings) error {
+		settings.MaxDirectoryLinks = n
+		settings.MaxDirectoryLinksSet = true
+		return nil
+	}
+}
+
+// MaxHAMTFanout specifies the maximum width of the HAMT directory shards.
+func (unixfsOpts) MaxHAMTFanout(n int) UnixfsAddOption {
+	return func(settings *UnixfsAddSettings) error {
+		settings.MaxHAMTFanout = n
+		settings.MaxHAMTFanoutSet = true
+		return nil
+	}
+}
+
 // Inline tells the adder to inline small blocks into CIDs
 func (unixfsOpts) Inline(enable bool) UnixfsAddOption {
 	return func(settings *UnixfsAddSettings) error {
diff --git a/core/coreunix/add.go b/core/coreunix/add.go
index 5f7cbb610..d9dc555d2 100644
--- a/core/coreunix/add.go
+++ b/core/coreunix/add.go
@@ -19,6 +19,7 @@ import (
 	"github.com/ipfs/boxo/ipld/unixfs/importer/balanced"
 	ihelper "github.com/ipfs/boxo/ipld/unixfs/importer/helpers"
 	"github.com/ipfs/boxo/ipld/unixfs/importer/trickle"
+	uio "github.com/ipfs/boxo/ipld/unixfs/io"
 	"github.com/ipfs/boxo/mfs"
 	"github.com/ipfs/boxo/path"
 	pin "github.com/ipfs/boxo/pinning/pinner"
@@ -51,38 +52,43 @@ func NewAdder(ctx context.Context, p pin.Pinner, bs bstore.GCLocker, ds ipld.DAG
 	bufferedDS := ipld.NewBufferedDAG(ctx, ds)
 
 	return &Adder{
-		ctx:        ctx,
-		pinning:    p,
-		gcLocker:   bs,
-		dagService: ds,
-		bufferedDS: bufferedDS,
-		Progress:   false,
-		Pin:        true,
-		Trickle:    false,
-		Chunker:    "",
+		ctx:           ctx,
+		pinning:       p,
+		gcLocker:      bs,
+		dagService:    ds,
+		bufferedDS:    bufferedDS,
+		Progress:      false,
+		Pin:           true,
+		Trickle:       false,
+		MaxLinks:      ihelper.DefaultLinksPerBlock,
+		MaxHAMTFanout: uio.DefaultShardWidth,
+		Chunker:       "",
 	}, nil
 }
 
 // Adder holds the switches passed to the `add` command.
 type Adder struct {
-	ctx        context.Context
-	pinning    pin.Pinner
-	gcLocker   bstore.GCLocker
-	dagService ipld.DAGService
-	bufferedDS *ipld.BufferedDAG
-	Out        chan<- interface{}
-	Progress   bool
-	Pin        bool
-	Trickle    bool
-	RawLeaves  bool
-	Silent     bool
-	NoCopy     bool
-	Chunker    string
-	mroot      *mfs.Root
-	unlocker   bstore.Unlocker
-	tempRoot   cid.Cid
-	CidBuilder cid.Builder
-	liveNodes  uint64
+	ctx               context.Context
+	pinning           pin.Pinner
+	gcLocker          bstore.GCLocker
+	dagService        ipld.DAGService
+	bufferedDS        *ipld.BufferedDAG
+	Out               chan<- interface{}
+	Progress          bool
+	Pin               bool
+	Trickle           bool
+	RawLeaves         bool
+	MaxLinks          int
+	MaxDirectoryLinks int
+	MaxHAMTFanout     int
+	Silent            bool
+	NoCopy            bool
+	Chunker           string
+	mroot             *mfs.Root
+	unlocker          bstore.Unlocker
+	tempRoot          cid.Cid
+	CidBuilder        cid.Builder
+	liveNodes         uint64
 
 	PreserveMode  bool
 	PreserveMtime bool
@@ -94,12 +100,13 @@ func (adder *Adder) mfsRoot() (*mfs.Root, error) {
 	if adder.mroot != nil {
 		return adder.mroot, nil
 	}
-	rnode := unixfs.EmptyDirNode()
-	err := rnode.SetCidBuilder(adder.CidBuilder)
-	if err != nil {
-		return nil, err
-	}
-	mr, err := mfs.NewRoot(adder.ctx, adder.dagService, rnode, nil)
+
+	// Note, this adds it to DAGService already.
+	mr, err := mfs.NewEmptyRoot(adder.ctx, adder.dagService, nil, mfs.MkdirOpts{
+		CidBuilder:    adder.CidBuilder,
+		MaxLinks:      adder.MaxDirectoryLinks,
+		MaxHAMTFanout: adder.MaxHAMTFanout,
+	})
 	if err != nil {
 		return nil, err
 	}
@@ -119,10 +126,15 @@ func (adder *Adder) add(reader io.Reader) (ipld.Node, error) {
 		return nil, err
 	}
 
+	maxLinks := ihelper.DefaultLinksPerBlock
+	if adder.MaxLinks > 0 {
+		maxLinks = adder.MaxLinks
+	}
+
 	params := ihelper.DagBuilderParams{
 		Dagserv:     adder.bufferedDS,
 		RawLeaves:   adder.RawLeaves,
-		Maxlinks:    ihelper.DefaultLinksPerBlock,
+		Maxlinks:    maxLinks,
 		NoCopy:      adder.NoCopy,
 		CidBuilder:  adder.CidBuilder,
 		FileMode:    adder.FileMode,
@@ -252,12 +264,15 @@ func (adder *Adder) addNode(node ipld.Node, path string) error {
 	if err != nil {
 		return err
 	}
+
 	dir := gopath.Dir(path)
 	if dir != "." {
 		opts := mfs.MkdirOpts{
-			Mkparents:  true,
-			Flush:      false,
-			CidBuilder: adder.CidBuilder,
+			Mkparents:     true,
+			Flush:         false,
+			CidBuilder:    adder.CidBuilder,
+			MaxLinks:      adder.MaxDirectoryLinks,
+			MaxHAMTFanout: adder.MaxHAMTFanout,
 		}
 		if err := mfs.Mkdir(mr, dir, opts); err != nil {
 			return err
@@ -460,12 +475,14 @@ func (adder *Adder) addDir(ctx context.Context, path string, dir files.Directory
 
 	// if we need to store mode or modification time then create a new root which includes that data
 	if toplevel && (adder.FileMode != 0 || !adder.FileMtime.IsZero()) {
-		nd := unixfs.EmptyDirNodeWithStat(adder.FileMode, adder.FileMtime)
-		err := nd.SetCidBuilder(adder.CidBuilder)
-		if err != nil {
-			return err
-		}
-		mr, err := mfs.NewRoot(ctx, adder.dagService, nd, nil)
+		mr, err := mfs.NewEmptyRoot(ctx, adder.dagService, nil,
+			mfs.MkdirOpts{
+				CidBuilder:    adder.CidBuilder,
+				MaxLinks:      adder.MaxDirectoryLinks,
+				MaxHAMTFanout: adder.MaxHAMTFanout,
+				ModTime:       adder.FileMtime,
+				Mode:          adder.FileMode,
+			})
 		if err != nil {
 			return err
 		}
@@ -478,11 +495,13 @@ func (adder *Adder) addDir(ctx context.Context, path string, dir files.Directory
 			return err
 		}
 		err = mfs.Mkdir(mr, path, mfs.MkdirOpts{
-			Mkparents:  true,
-			Flush:      false,
-			CidBuilder: adder.CidBuilder,
-			Mode:       adder.FileMode,
-			ModTime:    adder.FileMtime,
+			Mkparents:     true,
+			Flush:         false,
+			CidBuilder:    adder.CidBuilder,
+			Mode:          adder.FileMode,
+			ModTime:       adder.FileMtime,
+			MaxLinks:      adder.MaxDirectoryLinks,
+			MaxHAMTFanout: adder.MaxHAMTFanout,
 		})
 		if err != nil {
 			return err
diff --git a/core/node/groups.go b/core/node/groups.go
index e8f9739c3..4a471f170 100644
--- a/core/node/groups.go
+++ b/core/node/groups.go
@@ -408,20 +408,29 @@ func IPFS(ctx context.Context, bcfg *BuildCfg) fx.Option {
 		return fx.Error(err)
 	}
 
+	// Migrate users of deprecated Experimental.ShardingEnabled flag
+	if cfg.Experimental.ShardingEnabled {
+		logger.Fatal("The `Experimental.ShardingEnabled` field is no longer used, please remove it from the config. Use Import.UnixFSHAMTDirectorySizeThreshold instead.")
+	}
+	if !cfg.Internal.UnixFSShardingSizeThreshold.IsDefault() {
+		msg := "The `Internal.UnixFSShardingSizeThreshold` field was renamed to `Import.UnixFSHAMTDirectorySizeThreshold`. Please update your config.\n"
+		if !cfg.Import.UnixFSHAMTDirectorySizeThreshold.IsDefault() {
+			logger.Fatal(msg) // conflicting values, hard fail
+		}
+		logger.Error(msg)
+		cfg.Import.UnixFSHAMTDirectorySizeThreshold = *cfg.Internal.UnixFSShardingSizeThreshold
+	}
+
 	// Auto-sharding settings
-	shardSizeString := cfg.Internal.UnixFSShardingSizeThreshold.WithDefault("256kiB")
-	shardSizeInt, err := humanize.ParseBytes(shardSizeString)
+	shardingThresholdString := cfg.Import.UnixFSHAMTDirectorySizeThreshold.WithDefault(config.DefaultUnixFSHAMTDirectorySizeThreshold)
+	shardSingThresholdInt, err := humanize.ParseBytes(shardingThresholdString)
 	if err != nil {
 		return fx.Error(err)
 	}
-	uio.HAMTShardingSize = int(shardSizeInt)
-
-	// Migrate users of deprecated Experimental.ShardingEnabled flag
-	if cfg.Experimental.ShardingEnabled {
-		logger.Fatal("The `Experimental.ShardingEnabled` field is no longer used, please remove it from the config.\n" +
-			"go-ipfs now automatically shards when directory block is bigger than  `" + shardSizeString + "`.\n" +
-			"If you need to restore the old behavior (sharding everything) set `Internal.UnixFSShardingSizeThreshold` to `1B`.\n")
-	}
+	shardMaxFanout := cfg.Import.UnixFSHAMTDirectoryMaxFanout.WithDefault(config.DefaultUnixFSHAMTDirectoryMaxFanout)
+	// TODO: avoid overriding this globally, see if we can extend Directory interface like Get/SetMaxLinks from https://github.com/ipfs/boxo/pull/906
+	uio.HAMTShardingSize = int(shardSingThresholdInt)
+	uio.DefaultShardWidth = int(shardMaxFanout)
 
 	return fx.Options(
 		bcfgOpts,
diff --git a/docs/changelogs/v0.35.md b/docs/changelogs/v0.35.md
index e9daf0d51..bc3a857f8 100644
--- a/docs/changelogs/v0.35.md
+++ b/docs/changelogs/v0.35.md
@@ -13,6 +13,10 @@ This release  was brought to you by the [Shipyard](http://ipshipyard.com/) team.
   - [Dedicated `Reprovider.Strategy` for MFS](#dedicated-reproviderstrategy-for-mfs)
   - [Additional new configuration options](#additional-new-configuration-options)
   - [Grid view in WebUI](#grid-view-in-webui)
+  - [Enhanced DAG-Shaping Controls for `ipfs add`](#enhanced-dag-shaping-controls-for-ipfs-add)
+    - [New `ipfs add` Options](#new-ipfs-add-options)
+    - [Persistent `Import.*` Configuration](#persistent-import-configuration)
+    - [Updated Configuration Profiles](#updated-configuration-profiles)
   - [📦️ Important dependency updates](#-important-dependency-updates)
 - [📝 Changelog](#-changelog)
 - [👨‍👩‍👧‍👦 Contributors](#-contributors)
@@ -42,6 +46,41 @@ The WebUI, accessible at http://127.0.0.1:5001/webui/, now includes support for
 
 > ![image](https://github.com/user-attachments/assets/80dcf0d0-8103-426f-ae91-416fb25d32b6)
 
+#### Enhanced DAG-Shaping Controls for `ipfs add`
+
+This release advances CIDv1 support by introducing fine-grained control over UnixFS DAG shaping during data ingestion with the `ipfs add` command.
+
+Wider DAG trees (more links per node, higher fanout, larger thresholds) are beneficial for large files and directories with many files, reducing tree depth and lookup latency in high-latency networks, but they increase node size, straining memory and CPU on resource-constrained devices. Narrower trees (lower link count, lower fanout, smaller thresholds) are preferable for smaller directories, frequent updates, or low-power clients, minimizing overhead and ensuring compatibility, though they may increase traversal steps for very large datasets.
+
+Kubo now allows users to act on these tradeoffs and customize the width of the DAG created by `ipfs add` command.
+
+##### New `ipfs add` Options
+
+Three new options allow you to override default settings for specific import operations:
+
+- `--max-file-links`: Sets the maximum number of child links for a single file chunk.
+- `--max-directory-links`: Defines the maximum number of child entries in a "basic" (single-chunk) directory.
+  - Note: Directories exceeding this limit or the `Import.UnixFSHAMTDirectorySizeThreshold` are converted to HAMT-based (sharded across multiple blocks) structures.
+- `--max-hamt-fanout`: Specifies the maximum number of child nodes for HAMT internal structures.
+
+##### Persistent `Import.*` Configuration
+
+You can set default values for these options using the following configuration settings:
+- [`Import.UnixFSFileMaxLinks`](https://github.com/ipfs/kubo/blob/master/docs/config.md#importunixfsfilemaxlinks)
+- [`Import.UnixFSDirectoryMaxLinks`](https://github.com/ipfs/kubo/blob/master/docs/config.md#importunixfsdirectorymaxlinks)
+- [`Import.UnixFSHAMTDirectoryMaxFanout`](https://github.com/ipfs/kubo/blob/master/docs/config.md#importunixfshamtdirectorymaxfanout)
+- [`Import.UnixFSHAMTDirectorySizeThreshold`](https://github.com/ipfs/kubo/blob/master/docs/config.md#importunixfshamtdirectorysizethreshold)
+
+##### Updated Configuration Profiles
+
+The release updated configuration [profiles](https://github.com/ipfs/kubo/blob/master/docs/config.md#profiles) to incorporate these new `Import.*` settings:
+- Updated Profile: `test-cid-v1` now includes current defaults as explicit `Import.UnixFSFileMaxLinks=174`, `Import.UnixFSDirectoryMaxLinks=0`, `Import.UnixFSHAMTDirectoryMaxFanout=256` and `Import.UnixFSHAMTDirectorySizeThreshold=256KiB`
+- New Profile: `test-cid-v1-wide` adopts experimental directory DAG-shaping defaults, increasing the maximum file DAG width from 174 to 1024, HAMT fanout from 256 to 1024, and raising the HAMT directory sharding threshold from 256KiB to 1MiB, aligning with 1MiB file chunks.
+  - Feedback: Try it out and share your thoughts at [discuss.ipfs.tech/t/should-we-profile-cids](https://discuss.ipfs.tech/t/should-we-profile-cids/18507) or [ipfs/specs#499](https://github.com/ipfs/specs/pull/499).
+
+> [!TIP]
+> Apply one of CIDv1 test [profiles](https://github.com/ipfs/kubo/blob/master/docs/config.md#profiles) with `ipfs config profile apply test-cid-v1[-wide]`.
+
 #### 📦️ Important dependency updates
 
 - update `ipfs-webui` to [v4.7.0](https://github.com/ipfs/ipfs-webui/releases/tag/v4.7.0)
diff --git a/docs/config.md b/docs/config.md
index 367fffb83..1ec5677db 100644
--- a/docs/config.md
+++ b/docs/config.md
@@ -185,6 +185,10 @@ config file at runtime.
     - [`Import.HashFunction`](#importhashfunction)
     - [`Import.BatchMaxNodes`](#importbatchmaxnodes)
     - [`Import.BatchMaxSize`](#importbatchmaxsize)
+    - [`Import.UnixFSFileMaxLinks`](#importunixfsfilemaxlinks)
+    - [`Import.UnixFSDirectoryMaxLinks`](#importunixfsdirectorymaxlinks)
+    - [`Import.UnixFSHAMTDirectoryMaxFanout`](#importunixfshamtdirectorymaxfanout)
+    - [`Import.UnixFSHAMTDirectorySizeThreshold`](#importunixfshamtdirectorysizethreshold)
   - [`Version`](#version)
     - [`Version.AgentSuffix`](#versionagentsuffix)
     - [`Version.SwarmCheckEnabled`](#versionswarmcheckenabled)
@@ -1199,15 +1203,7 @@ Type: `optionalInteger` (`null` means default which is 10)
 
 ### `Internal.UnixFSShardingSizeThreshold`
 
-The sharding threshold used internally to decide whether a UnixFS directory should be sharded or not.
-This value is not strictly related to the size of the UnixFS directory block and any increases in
-the threshold should come with being careful that block sizes stay under 2MiB in order for them to be
-reliably transferable through the networking stack (IPFS peers on the public swarm tend to ignore requests for blocks bigger than 2MiB).
-
-Decreasing this value to 1B is functionally equivalent to the previous experimental sharding option to
-shard all directories.
-
-Type: `optionalBytes` (`null` means default which is 256KiB)
+**MOVED:** see [`Import.UnixFSHAMTDirectorySizeThreshold`](#importunixfshamtdirectorysizethreshold)
 
 ## `Ipns`
 
@@ -2560,6 +2556,80 @@ Default: `20971520` (20MiB)
 
 Type: `optionalInteger`
 
+### `Import.UnixFSFileMaxLinks`
+
+The maximum number of links that a node part of a UnixFS File can have
+when building the DAG while importing.
+
+This setting controls both the fanout in files that are chunked into several
+blocks and grouped as a Unixfs (dag-pb) DAG.
+
+Default: `174`
+
+Type: `optionalInteger`
+
+### `Import.UnixFSDirectoryMaxLinks`
+
+The maximum number of links that a node part of a UnixFS basic directory can
+have when building the DAG while importing.
+
+This setting controls both the fanout for basic, non-HAMT folder nodes. It
+sets a limit after which directories are converted to a HAMT-based structure.
+
+When unset (0), no limit exists for chilcren. Directories will be converted to
+HAMTs based on their estimated size only.
+
+This setting will cause basic directories to be converted to HAMTs when they
+exceed the maximum number of children. This happens transparently during the
+add process. The fanout of HAMT nodes is controlled by `MaxHAMTFanout`.
+
+Commands affected: `ipfs add`
+
+Default: `0` (no limit, because [`Import.UnixFSHAMTDirectorySizeThreshold`](#importunixfshamtdirectorysizethreshold) triggers controls when to switch to HAMT sharding when a directory grows too big)
+
+Type: `optionalInteger`
+
+### `Import.UnixFSHAMTDirectoryMaxFanout`
+
+The maximum number of children that a node part of a Unixfs HAMT directory
+(aka sharded directory) can have.
+
+HAMT directory have unlimited children and are used when basic directories
+become too big or reach `MaxLinks`. A HAMT is an structure made of unixfs
+nodes that store the list of elements in the folder. This option controls the
+maximum number of children that the HAMT nodes can have.
+
+Needs to be a power of two (shard entry size) and multiple of 8 (bitfield size).
+
+Commands affected: `ipfs add`, `ipfs daemon` (globally overrides [`boxo/ipld/unixfs/io.DefaultShardWidth`](https://github.com/ipfs/boxo/blob/6c5a07602aed248acc86598f30ab61923a54a83e/ipld/unixfs/io/directory.go#L30C5-L30C22))
+
+Default: `256`
+
+Type: `optionalInteger`
+
+### `Import.UnixFSHAMTDirectorySizeThreshold`
+
+The sharding threshold to decide whether a basic UnixFS directory
+should be sharded (converted into HAMT Directory) or not.
+
+This value is not strictly related to the size of the UnixFS directory block
+and any increases in the threshold should come with being careful that block
+sizes stay under 2MiB in order for them to be reliably transferable through the
+networking stack. At the time of writing this, IPFS peers on the public swarm
+tend to ignore requests for blocks bigger than 2MiB.
+
+Uses implementation from `boxo/ipld/unixfs/io/directory`, where the size is not
+the *exact* block size of the encoded directory but just the estimated size
+based byte length of DAG-PB Links names and CIDs.
+
+Setting to `1B` is functionally equivalent to always using HAMT (useful in testing).
+
+Commands affected: `ipfs add`, `ipfs daemon` (globally overrides [`boxo/ipld/unixfs/io.HAMTShardingSize`](https://github.com/ipfs/boxo/blob/6c5a07602aed248acc86598f30ab61923a54a83e/ipld/unixfs/io/directory.go#L26))
+
+Default: `256KiB` (may change, inspect `DefaultUnixFSHAMTDirectorySizeThreshold` to confirm)
+
+Type: `optionalBytes`
+
 ## `Version`
 
 Options to configure agent version announced to the swarm, and leveraging
@@ -2742,16 +2812,38 @@ Disables [Reprovider](#reprovider) system (and announcing to Amino DHT).
 
 Makes UnixFS import (`ipfs add`) produce legacy CIDv0 with no raw leaves, sha2-256 and 256 KiB chunks.
 
+See <https://github.com/ipfs/kubo/blob/master/config/profile.go> for exact [`Import.*`](#import) settings.
+
 > [!NOTE]
 > This profile is provided for legacy users and should not be used for new projects.
 
 ### `test-cid-v1` profile
 
-Makes UnixFS import (`ipfs add`) produce modern CIDv1 with raw leaves, sha2-256 and 1 MiB chunks.
+Makes UnixFS import (`ipfs add`) produce modern CIDv1 with raw leaves, sha2-256
+and 1 MiB chunks (max 174 links per file, 256 per HAMT node, switch dir to HAMT
+above 256KiB).
+
+See <https://github.com/ipfs/kubo/blob/master/config/profile.go> for exact [`Import.*`](#import) settings.
 
 > [!NOTE]
-> This profile will become the new implicit default, provided for testing purposes.
-> Follow [kubo#4143](https://github.com/ipfs/kubo/issues/4143) for more details.
+> [`Import.*`](#import) settings applied by this profile MAY change in future release. Provided for testing purposes.
+>
+> Follow [kubo#4143](https://github.com/ipfs/kubo/issues/4143) for more details,
+> and provide feedback in [discuss.ipfs.tech/t/should-we-profile-cids](https://discuss.ipfs.tech/t/should-we-profile-cids/18507) or [ipfs/specs#499](https://github.com/ipfs/specs/pull/499).
+
+### `test-cid-v1-wide` profile
+
+Makes UnixFS import (`ipfs add`) produce modern CIDv1 with raw leaves, sha2-256
+and 1 MiB chunks and wider file DAGs (max 1024 links per every node type,
+switch dir to HAMT above 1MiB).
+
+See <https://github.com/ipfs/kubo/blob/master/config/profile.go> for exact [`Import.*`](#import) settings.
+
+> [!NOTE]
+> [`Import.*`](#import) settings applied by this profile MAY change in future release. Provided for testing purposes.
+>
+> Follow [kubo#4143](https://github.com/ipfs/kubo/issues/4143) for more details,
+> and provide feedback in [discuss.ipfs.tech/t/should-we-profile-cids](https://discuss.ipfs.tech/t/should-we-profile-cids/18507) or [ipfs/specs#499](https://github.com/ipfs/specs/pull/499).
 
 ## Types
 
diff --git a/docs/examples/kubo-as-a-library/go.mod b/docs/examples/kubo-as-a-library/go.mod
index bfaa528c9..7adc7c80a 100644
--- a/docs/examples/kubo-as-a-library/go.mod
+++ b/docs/examples/kubo-as-a-library/go.mod
@@ -7,7 +7,7 @@ go 1.24
 replace github.com/ipfs/kubo => ./../../..
 
 require (
-	github.com/ipfs/boxo v0.29.2-0.20250409154342-bbaf2e146dfb
+	github.com/ipfs/boxo v0.29.2-0.20250415191135-dc60fe747c37
 	github.com/ipfs/kubo v0.0.0-00010101000000-000000000000
 	github.com/libp2p/go-libp2p v0.41.1
 	github.com/multiformats/go-multiaddr v0.15.0
diff --git a/docs/examples/kubo-as-a-library/go.sum b/docs/examples/kubo-as-a-library/go.sum
index eb2997529..5e2f686a0 100644
--- a/docs/examples/kubo-as-a-library/go.sum
+++ b/docs/examples/kubo-as-a-library/go.sum
@@ -298,8 +298,8 @@ github.com/ipfs-shipyard/nopfs/ipfs v0.25.0 h1:OqNqsGZPX8zh3eFMO8Lf8EHRRnSGBMqcd
 github.com/ipfs-shipyard/nopfs/ipfs v0.25.0/go.mod h1:BxhUdtBgOXg1B+gAPEplkg/GpyTZY+kCMSfsJvvydqU=
 github.com/ipfs/bbloom v0.0.4 h1:Gi+8EGJ2y5qiD5FbsbpX/TMNcJw8gSqr7eyjHa4Fhvs=
 github.com/ipfs/bbloom v0.0.4/go.mod h1:cS9YprKXpoZ9lT0n/Mw/a6/aFV6DTjTLYHeA+gyqMG0=
-github.com/ipfs/boxo v0.29.2-0.20250409154342-bbaf2e146dfb h1:kA7c3CF6/d8tUwGJR/SwIfaRz7Xk7Fbyoh2ePZAFMlw=
-github.com/ipfs/boxo v0.29.2-0.20250409154342-bbaf2e146dfb/go.mod h1:omQZmLS7LegSpBy3m4CrAB9/SO7Fq3pfv+5y1FOd+gI=
+github.com/ipfs/boxo v0.29.2-0.20250415191135-dc60fe747c37 h1:q3a+2FIbWzZbx/yUqpuG4jLVSa6GvxtRfx9TU5GLiN0=
+github.com/ipfs/boxo v0.29.2-0.20250415191135-dc60fe747c37/go.mod h1:omQZmLS7LegSpBy3m4CrAB9/SO7Fq3pfv+5y1FOd+gI=
 github.com/ipfs/go-bitfield v1.1.0 h1:fh7FIo8bSwaJEh6DdTWbCeZ1eqOaOkKFI74SCnsWbGA=
 github.com/ipfs/go-bitfield v1.1.0/go.mod h1:paqf1wjq/D2BBmzfTVFlJQ9IlFOZpg422HL0HqsGWHU=
 github.com/ipfs/go-bitswap v0.11.0 h1:j1WVvhDX1yhG32NTC9xfxnqycqYIlhzEzLXG/cU1HyQ=
diff --git a/fuse/readonly/ipfs_test.go b/fuse/readonly/ipfs_test.go
index 6d667843c..e7dfbcb2a 100644
--- a/fuse/readonly/ipfs_test.go
+++ b/fuse/readonly/ipfs_test.go
@@ -150,7 +150,10 @@ func TestIpfsStressRead(t *testing.T) {
 
 	// Now make a bunch of dirs
 	for i := 0; i < ndiriter; i++ {
-		db := uio.NewDirectory(nd.DAG)
+		db, err := uio.NewDirectory(nd.DAG)
+		if err != nil {
+			t.Fatal(err)
+		}
 		for j := 0; j < 1+rand.Intn(10); j++ {
 			name := fmt.Sprintf("child%d", j)
 
@@ -245,8 +248,11 @@ func TestIpfsBasicDirRead(t *testing.T) {
 	fi, data := randObj(t, nd, 10000)
 
 	// Make a directory and put that file in it
-	db := uio.NewDirectory(nd.DAG)
-	err := db.AddChild(nd.Context(), "actual", fi)
+	db, err := uio.NewDirectory(nd.DAG)
+	if err != nil {
+		t.Fatal(err)
+	}
+	err = db.AddChild(nd.Context(), "actual", fi)
 	if err != nil {
 		t.Fatal(err)
 	}
diff --git a/go.mod b/go.mod
index 8975eb210..68e8c7a3f 100644
--- a/go.mod
+++ b/go.mod
@@ -21,7 +21,7 @@ require (
 	github.com/hashicorp/go-version v1.7.0
 	github.com/ipfs-shipyard/nopfs v0.0.14
 	github.com/ipfs-shipyard/nopfs/ipfs v0.25.0
-	github.com/ipfs/boxo v0.29.2-0.20250409154342-bbaf2e146dfb
+	github.com/ipfs/boxo v0.29.2-0.20250415191135-dc60fe747c37
 	github.com/ipfs/go-block-format v0.2.0
 	github.com/ipfs/go-cid v0.5.0
 	github.com/ipfs/go-cidutil v0.1.0
diff --git a/go.sum b/go.sum
index e926a4596..cf9c33444 100644
--- a/go.sum
+++ b/go.sum
@@ -362,8 +362,8 @@ github.com/ipfs-shipyard/nopfs/ipfs v0.25.0 h1:OqNqsGZPX8zh3eFMO8Lf8EHRRnSGBMqcd
 github.com/ipfs-shipyard/nopfs/ipfs v0.25.0/go.mod h1:BxhUdtBgOXg1B+gAPEplkg/GpyTZY+kCMSfsJvvydqU=
 github.com/ipfs/bbloom v0.0.4 h1:Gi+8EGJ2y5qiD5FbsbpX/TMNcJw8gSqr7eyjHa4Fhvs=
 github.com/ipfs/bbloom v0.0.4/go.mod h1:cS9YprKXpoZ9lT0n/Mw/a6/aFV6DTjTLYHeA+gyqMG0=
-github.com/ipfs/boxo v0.29.2-0.20250409154342-bbaf2e146dfb h1:kA7c3CF6/d8tUwGJR/SwIfaRz7Xk7Fbyoh2ePZAFMlw=
-github.com/ipfs/boxo v0.29.2-0.20250409154342-bbaf2e146dfb/go.mod h1:omQZmLS7LegSpBy3m4CrAB9/SO7Fq3pfv+5y1FOd+gI=
+github.com/ipfs/boxo v0.29.2-0.20250415191135-dc60fe747c37 h1:q3a+2FIbWzZbx/yUqpuG4jLVSa6GvxtRfx9TU5GLiN0=
+github.com/ipfs/boxo v0.29.2-0.20250415191135-dc60fe747c37/go.mod h1:omQZmLS7LegSpBy3m4CrAB9/SO7Fq3pfv+5y1FOd+gI=
 github.com/ipfs/go-bitfield v1.1.0 h1:fh7FIo8bSwaJEh6DdTWbCeZ1eqOaOkKFI74SCnsWbGA=
 github.com/ipfs/go-bitfield v1.1.0/go.mod h1:paqf1wjq/D2BBmzfTVFlJQ9IlFOZpg422HL0HqsGWHU=
 github.com/ipfs/go-bitswap v0.11.0 h1:j1WVvhDX1yhG32NTC9xfxnqycqYIlhzEzLXG/cU1HyQ=
diff --git a/test/cli/add_test.go b/test/cli/add_test.go
index ae652989a..775a6063b 100644
--- a/test/cli/add_test.go
+++ b/test/cli/add_test.go
@@ -1,10 +1,17 @@
 package cli
 
 import (
+	"io"
+	"os"
+	"path/filepath"
+	"strings"
 	"testing"
 
+	"github.com/dustin/go-humanize"
 	"github.com/ipfs/kubo/config"
 	"github.com/ipfs/kubo/test/cli/harness"
+	"github.com/ipfs/kubo/test/cli/testutils"
+	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
 
@@ -19,6 +26,11 @@ func TestAdd(t *testing.T) {
 		shortStringCidV1Sha512      = "bafkrgqbqt3gerhas23vuzrapkdeqf4vu2dwxp3srdj6hvg6nhsug2tgyn6mj3u23yx7utftq3i2ckw2fwdh5qmhid5qf3t35yvkc5e5ottlw6"
 	)
 
+	const (
+		cidV0Length = 34 // cidv0 sha2-256
+		cidV1Length = 36 // cidv1 sha2-256
+	)
+
 	t.Run("produced cid version: implicit default (CIDv0)", func(t *testing.T) {
 		t.Parallel()
 		node := harness.NewT(t).NewNode().Init().StartDaemon()
@@ -96,6 +108,33 @@ func TestAdd(t *testing.T) {
 		require.Equal(t, shortStringCidV1NoRawLeaves, cidStr)
 	})
 
+	t.Run("produced unixfs max file links: command flag --max-file-links overrides configuration in Import.UnixFSFileMaxLinks", func(t *testing.T) {
+		t.Parallel()
+
+		//
+		// UnixFSChunker=size-262144 (256KiB)
+		// Import.UnixFSFileMaxLinks=174
+		node := harness.NewT(t).NewNode().Init("--profile=legacy-cid-v0") // legacy-cid-v0 for determinism across all params
+		node.UpdateConfig(func(cfg *config.Config) {
+			cfg.Import.UnixFSChunker = *config.NewOptionalString("size-262144") // 256 KiB chunks
+			cfg.Import.UnixFSFileMaxLinks = *config.NewOptionalInteger(174)     // max 174 per level
+		})
+		node.StartDaemon()
+		defer node.StopDaemon()
+
+		// Add 174MiB file:
+		// 1024 * 256KiB should fit in single layer
+		seed := shortString
+		cidStr := node.IPFSAddDeterministic("262144KiB", seed, "--max-file-links", "1024")
+		root, err := node.InspectPBNode(cidStr)
+		assert.NoError(t, err)
+
+		// Expect 1024 links due to cli parameter raising link limit from 174 to 1024
+		require.Equal(t, 1024, len(root.Links))
+		// expect same CID every time
+		require.Equal(t, "QmbBftNHWmjSWKLC49dMVrfnY8pjrJYntiAXirFJ7oJrNk", cidStr)
+	})
+
 	t.Run("ipfs init --profile=legacy-cid-v0 sets config that produces legacy CIDv0", func(t *testing.T) {
 		t.Parallel()
 		node := harness.NewT(t).NewNode().Init("--profile=legacy-cid-v0")
@@ -106,13 +145,307 @@ func TestAdd(t *testing.T) {
 		require.Equal(t, shortStringCidV0, cidStr)
 	})
 
-	t.Run("ipfs init --profile=test-cid-v1 produces modern CIDv1", func(t *testing.T) {
+	t.Run("ipfs init --profile=legacy-cid-v0 applies UnixFSChunker=size-262144 and UnixFSFileMaxLinks", func(t *testing.T) {
+		t.Parallel()
+		seed := "v0-seed"
+		profile := "--profile=legacy-cid-v0"
+
+		t.Run("under UnixFSFileMaxLinks=174", func(t *testing.T) {
+			t.Parallel()
+			node := harness.NewT(t).NewNode().Init(profile)
+			node.StartDaemon()
+			defer node.StopDaemon()
+			// Add 44544KiB file:
+			// 174 * 256KiB should fit in single DAG layer
+			cidStr := node.IPFSAddDeterministic("44544KiB", seed)
+			root, err := node.InspectPBNode(cidStr)
+			assert.NoError(t, err)
+			require.Equal(t, 174, len(root.Links))
+			// expect same CID every time
+			require.Equal(t, "QmUbBALi174SnogsUzLpYbD4xPiBSFANF4iztWCsHbMKh2", cidStr)
+		})
+
+		t.Run("above UnixFSFileMaxLinks=174", func(t *testing.T) {
+			t.Parallel()
+			node := harness.NewT(t).NewNode().Init(profile)
+			node.StartDaemon()
+			defer node.StopDaemon()
+			// add 256KiB (one more block), it should force rebalancing DAG and moving most to second layer
+			cidStr := node.IPFSAddDeterministic("44800KiB", seed)
+			root, err := node.InspectPBNode(cidStr)
+			assert.NoError(t, err)
+			require.Equal(t, 2, len(root.Links))
+			// expect same CID every time
+			require.Equal(t, "QmepeWtdmS1hHXx1oZXsPUv6bMrfRRKfZcoPPU4eEfjnbf", cidStr)
+		})
+	})
+
+	t.Run("ipfs init --profile=legacy-cid-v0 applies UnixFSHAMTDirectoryMaxFanout=256 and UnixFSHAMTDirectorySizeThreshold=256KiB", func(t *testing.T) {
+		t.Parallel()
+		seed := "hamt-legacy-cid-v0"
+		profile := "--profile=legacy-cid-v0"
+
+		t.Run("under UnixFSHAMTDirectorySizeThreshold=256KiB", func(t *testing.T) {
+			t.Parallel()
+			node := harness.NewT(t).NewNode().Init(profile)
+			node.StartDaemon()
+			defer node.StopDaemon()
+
+			randDir, err := os.MkdirTemp(node.Dir, seed)
+			require.NoError(t, err)
+
+			// Create directory with a lot of files that have filenames which together take close to UnixFSHAMTDirectorySizeThreshold in total
+			err = createDirectoryForHAMT(randDir, cidV0Length, "255KiB", seed)
+			require.NoError(t, err)
+			cidStr := node.IPFS("add", "-r", "-Q", randDir).Stdout.Trimmed()
+
+			// Confirm the number of links is more than UnixFSHAMTDirectorySizeThreshold (indicating regular "basic" directory"
+			root, err := node.InspectPBNode(cidStr)
+			assert.NoError(t, err)
+			require.Equal(t, 903, len(root.Links))
+		})
+
+		t.Run("above UnixFSHAMTDirectorySizeThreshold=256KiB", func(t *testing.T) {
+			t.Parallel()
+			node := harness.NewT(t).NewNode().Init(profile)
+			node.StartDaemon()
+			defer node.StopDaemon()
+
+			randDir, err := os.MkdirTemp(node.Dir, seed)
+			require.NoError(t, err)
+
+			// Create directory with a lot of files that have filenames which together take close to UnixFSHAMTDirectorySizeThreshold in total
+			err = createDirectoryForHAMT(randDir, cidV0Length, "257KiB", seed)
+			require.NoError(t, err)
+			cidStr := node.IPFS("add", "-r", "-Q", randDir).Stdout.Trimmed()
+
+			// Confirm this time, the number of links is less than UnixFSHAMTDirectorySizeThreshold
+			root, err := node.InspectPBNode(cidStr)
+			assert.NoError(t, err)
+			require.Equal(t, 252, len(root.Links))
+		})
+	})
+
+	t.Run("ipfs init --profile=test-cid-v1 produces CIDv1 with raw leaves", func(t *testing.T) {
 		t.Parallel()
 		node := harness.NewT(t).NewNode().Init("--profile=test-cid-v1")
 		node.StartDaemon()
 		defer node.StopDaemon()
 
 		cidStr := node.IPFSAddStr(shortString)
-		require.Equal(t, shortStringCidV1, cidStr)
+		require.Equal(t, shortStringCidV1, cidStr) // raw leaf
 	})
+
+	t.Run("ipfs init --profile=test-cid-v1 applies UnixFSChunker=size-1048576", func(t *testing.T) {
+		t.Parallel()
+		seed := "v1-seed"
+		profile := "--profile=test-cid-v1"
+
+		t.Run("under UnixFSFileMaxLinks=174", func(t *testing.T) {
+			t.Parallel()
+			node := harness.NewT(t).NewNode().Init(profile)
+			node.StartDaemon()
+			defer node.StopDaemon()
+			// Add 174MiB file:
+			// 174 * 1MiB should fit in single layer
+			cidStr := node.IPFSAddDeterministic("174MiB", seed)
+			root, err := node.InspectPBNode(cidStr)
+			assert.NoError(t, err)
+			require.Equal(t, 174, len(root.Links))
+			// expect same CID every time
+			require.Equal(t, "bafybeigwduxcf2aawppv3isnfeshnimkyplvw3hthxjhr2bdeje4tdaicu", cidStr)
+		})
+
+		t.Run("above UnixFSFileMaxLinks=174", func(t *testing.T) {
+			t.Parallel()
+			node := harness.NewT(t).NewNode().Init(profile)
+			node.StartDaemon()
+			defer node.StopDaemon()
+			// add +1MiB (one more block), it should force rebalancing DAG and moving most to second layer
+			cidStr := node.IPFSAddDeterministic("175MiB", seed)
+			root, err := node.InspectPBNode(cidStr)
+			assert.NoError(t, err)
+			require.Equal(t, 2, len(root.Links))
+			// expect same CID every time
+			require.Equal(t, "bafybeidhd7lo2n2v7lta5yamob3xwhbxcczmmtmhquwhjesi35jntf7mpu", cidStr)
+		})
+	})
+
+	t.Run("ipfs init --profile=test-cid-v1 applies UnixFSHAMTDirectoryMaxFanout=256 and UnixFSHAMTDirectorySizeThreshold=256KiB", func(t *testing.T) {
+		t.Parallel()
+		seed := "hamt-cid-v1"
+		profile := "--profile=test-cid-v1"
+
+		t.Run("under UnixFSHAMTDirectorySizeThreshold=256KiB", func(t *testing.T) {
+			t.Parallel()
+			node := harness.NewT(t).NewNode().Init(profile)
+			node.StartDaemon()
+			defer node.StopDaemon()
+
+			randDir, err := os.MkdirTemp(node.Dir, seed)
+			require.NoError(t, err)
+
+			// Create directory with a lot of files that have filenames which together take close to UnixFSHAMTDirectorySizeThreshold in total
+			err = createDirectoryForHAMT(randDir, cidV1Length, "255KiB", seed)
+			require.NoError(t, err)
+			cidStr := node.IPFS("add", "-r", "-Q", randDir).Stdout.Trimmed()
+
+			// Confirm the number of links is more than UnixFSHAMTDirectoryMaxFanout (indicating regular "basic" directory"
+			root, err := node.InspectPBNode(cidStr)
+			assert.NoError(t, err)
+			require.Equal(t, 897, len(root.Links))
+		})
+
+		t.Run("above UnixFSHAMTDirectorySizeThreshold=256KiB", func(t *testing.T) {
+			t.Parallel()
+			node := harness.NewT(t).NewNode().Init(profile)
+			node.StartDaemon()
+			defer node.StopDaemon()
+
+			randDir, err := os.MkdirTemp(node.Dir, seed)
+			require.NoError(t, err)
+
+			// Create directory with a lot of files that have filenames which together take close to UnixFSHAMTDirectorySizeThreshold in total
+			err = createDirectoryForHAMT(randDir, cidV1Length, "257KiB", seed)
+			require.NoError(t, err)
+			cidStr := node.IPFS("add", "-r", "-Q", randDir).Stdout.Trimmed()
+
+			// Confirm this time, the number of links is less than UnixFSHAMTDirectoryMaxFanout
+			root, err := node.InspectPBNode(cidStr)
+			assert.NoError(t, err)
+			require.Equal(t, 252, len(root.Links))
+		})
+	})
+
+	t.Run("ipfs init --profile=test-cid-v1-wide applies UnixFSChunker=size-1048576 and UnixFSFileMaxLinks=1024", func(t *testing.T) {
+		t.Parallel()
+		seed := "v1-seed-1024"
+		profile := "--profile=test-cid-v1-wide"
+
+		t.Run("under UnixFSFileMaxLinks=1024", func(t *testing.T) {
+			t.Parallel()
+			node := harness.NewT(t).NewNode().Init(profile)
+			node.StartDaemon()
+			defer node.StopDaemon()
+			// Add 174MiB file:
+			// 1024 * 1MiB should fit in single layer
+			cidStr := node.IPFSAddDeterministic("1024MiB", seed)
+			root, err := node.InspectPBNode(cidStr)
+			assert.NoError(t, err)
+			require.Equal(t, 1024, len(root.Links))
+			// expect same CID every time
+			require.Equal(t, "bafybeiej5w63ir64oxgkr5htqmlerh5k2rqflurn2howimexrlkae64xru", cidStr)
+		})
+
+		t.Run("above UnixFSFileMaxLinks=1024", func(t *testing.T) {
+			t.Parallel()
+			node := harness.NewT(t).NewNode().Init(profile)
+			node.StartDaemon()
+			defer node.StopDaemon()
+			// add +1MiB (one more block), it should force rebalancing DAG and moving most to second layer
+			cidStr := node.IPFSAddDeterministic("1025MiB", seed)
+			root, err := node.InspectPBNode(cidStr)
+			assert.NoError(t, err)
+			require.Equal(t, 2, len(root.Links))
+			// expect same CID every time
+			require.Equal(t, "bafybeieilp2qx24pe76hxrxe6bpef5meuxto3kj5dd6mhb5kplfeglskdm", cidStr)
+		})
+	})
+
+	t.Run("ipfs init --profile=test-cid-v1-wide applies UnixFSHAMTDirectoryMaxFanout=256 and UnixFSHAMTDirectorySizeThreshold=1MiB", func(t *testing.T) {
+		t.Parallel()
+		seed := "hamt-cid-v1"
+		profile := "--profile=test-cid-v1-wide"
+
+		t.Run("under UnixFSHAMTDirectorySizeThreshold=1MiB", func(t *testing.T) {
+			t.Parallel()
+			node := harness.NewT(t).NewNode().Init(profile)
+			node.StartDaemon()
+			defer node.StopDaemon()
+
+			randDir, err := os.MkdirTemp(node.Dir, seed)
+			require.NoError(t, err)
+
+			// Create directory with a lot of files that have filenames which together take close to UnixFSHAMTDirectorySizeThreshold in total
+			err = createDirectoryForHAMT(randDir, cidV1Length, "1023KiB", seed)
+			require.NoError(t, err)
+			cidStr := node.IPFS("add", "-r", "-Q", randDir).Stdout.Trimmed()
+
+			// Confirm the number of links is more than UnixFSHAMTDirectoryMaxFanout (indicating regular "basic" directory"
+			root, err := node.InspectPBNode(cidStr)
+			assert.NoError(t, err)
+			require.Equal(t, 3599, len(root.Links))
+		})
+
+		t.Run("above UnixFSHAMTDirectorySizeThreshold=1MiB", func(t *testing.T) {
+			t.Parallel()
+			node := harness.NewT(t).NewNode().Init(profile)
+			node.StartDaemon()
+			defer node.StopDaemon()
+
+			randDir, err := os.MkdirTemp(node.Dir, seed)
+			require.NoError(t, err)
+
+			// Create directory with a lot of files that have filenames which together take close to UnixFSHAMTDirectorySizeThreshold in total
+			err = createDirectoryForHAMT(randDir, cidV1Length, "1025KiB", seed)
+			require.NoError(t, err)
+			cidStr := node.IPFS("add", "-r", "-Q", randDir).Stdout.Trimmed()
+
+			// Confirm this time, the number of links is less than UnixFSHAMTDirectoryMaxFanout
+			root, err := node.InspectPBNode(cidStr)
+			assert.NoError(t, err)
+			require.Equal(t, 992, len(root.Links))
+		})
+	})
+
+}
+
+// createDirectoryForHAMT aims to create enough files with long names for the directory block to be close to the UnixFSHAMTDirectorySizeThreshold.
+// The calculation is based on boxo's HAMTShardingSize and sizeBelowThreshold which calculates ballpark size of the block
+// by adding length of link names and the binary cid length.
+// See https://github.com/ipfs/boxo/blob/6c5a07602aed248acc86598f30ab61923a54a83e/ipld/unixfs/io/directory.go#L491
+func createDirectoryForHAMT(dirPath string, cidLength int, unixfsNodeSizeTarget, seed string) error {
+	hamtThreshold, err := humanize.ParseBytes(unixfsNodeSizeTarget)
+	if err != nil {
+		return err
+	}
+
+	// Calculate how many files with long filenames are needed to hit UnixFSHAMTDirectorySizeThreshold
+	nameLen := 255 // max that works across windows/macos/linux
+	alphabetLen := len(testutils.AlphabetEasy)
+	numFiles := int(hamtThreshold) / (nameLen + cidLength)
+
+	// Deterministic pseudo-random bytes for static CID
+	drand, err := testutils.DeterministicRandomReader(unixfsNodeSizeTarget, seed)
+	if err != nil {
+		return err
+	}
+
+	// Create necessary files in a single, flat directory
+	for i := 0; i < numFiles; i++ {
+		buf := make([]byte, nameLen)
+		_, err := io.ReadFull(drand, buf)
+		if err != nil {
+			return err
+		}
+
+		// Convert deterministic pseudo-random bytes to ASCII
+		var sb strings.Builder
+
+		for _, b := range buf {
+			// Map byte to printable ASCII range (33-126)
+			char := testutils.AlphabetEasy[int(b)%alphabetLen]
+			sb.WriteRune(char)
+		}
+		filename := sb.String()[:nameLen]
+		filePath := filepath.Join(dirPath, filename)
+
+		// Create empty file
+		f, err := os.Create(filePath)
+		if err != nil {
+			return err
+		}
+		f.Close()
+	}
+	return nil
 }
diff --git a/test/cli/harness/ipfs.go b/test/cli/harness/ipfs.go
index 8537e2aa2..0842d3627 100644
--- a/test/cli/harness/ipfs.go
+++ b/test/cli/harness/ipfs.go
@@ -76,6 +76,17 @@ func (n *Node) IPFSAddStr(content string, args ...string) string {
 	return n.IPFSAdd(strings.NewReader(content), args...)
 }
 
+// IPFSAddDeterministic produces a CID of a file of a certain size, filled with deterministically generated bytes based  on some seed.
+// This ensures deterministic CID on the other end, that can be used in tests.
+func (n *Node) IPFSAddDeterministic(size string, seed string, args ...string) string {
+	log.Debugf("node %d adding %s of deterministic pseudo-random data with seed %q and args: %v", n.ID, size, seed, args)
+	reader, err := DeterministicRandomReader(size, seed)
+	if err != nil {
+		panic(err)
+	}
+	return n.IPFSAdd(reader, args...)
+}
+
 func (n *Node) IPFSAdd(content io.Reader, args ...string) string {
 	log.Debugf("node %d adding with args: %v", n.ID, args)
 	fullArgs := []string{"add", "-q"}
@@ -108,3 +119,15 @@ func (n *Node) IPFSDagImport(content io.Reader, cid string, args ...string) erro
 	})
 	return res.Err
 }
+
+/*
+func (n *Node) IPFSDagExport(cid string, car *os.File) error {
+	log.Debugf("node %d dag export of %s to %q with args: %v", n.ID, cid, car.Name())
+	res := n.Runner.MustRun(RunRequest{
+		Path:    n.IPFSBin,
+		Args:    []string{"dag", "export", cid},
+		CmdOpts: []CmdOpt{RunWithStdout(car)},
+	})
+	return res.Err
+}
+*/
diff --git a/test/cli/harness/pbinspect.go b/test/cli/harness/pbinspect.go
new file mode 100644
index 000000000..6abddb61f
--- /dev/null
+++ b/test/cli/harness/pbinspect.go
@@ -0,0 +1,54 @@
+package harness
+
+import (
+	"bytes"
+	"encoding/json"
+)
+
+// InspectPBNode uses dag-json output of 'ipfs dag get' to inspect
+// "Logical Format" of DAG-PB as defined in
+// https://web.archive.org/web/20250403194752/https://ipld.io/specs/codecs/dag-pb/spec/#logical-format
+// (mainly used for inspecting Links without depending on any libraries)
+func (n *Node) InspectPBNode(cid string) (PBNode, error) {
+	log.Debugf("node %d dag get %s as dag-json", n.ID, cid)
+
+	var root PBNode
+	var dagJsonOutput bytes.Buffer
+	res := n.Runner.MustRun(RunRequest{
+		Path:    n.IPFSBin,
+		Args:    []string{"dag", "get", "--output-codec=dag-json", cid},
+		CmdOpts: []CmdOpt{RunWithStdout(&dagJsonOutput)},
+	})
+	if res.Err != nil {
+		return root, res.Err
+	}
+
+	err := json.Unmarshal(dagJsonOutput.Bytes(), &root)
+	if err != nil {
+		return root, err
+	}
+	return root, nil
+
+}
+
+// Define structs to match the JSON for
+type PBHash struct {
+	Slash string `json:"/"`
+}
+
+type PBLink struct {
+	Hash  PBHash `json:"Hash"`
+	Name  string `json:"Name"`
+	Tsize int    `json:"Tsize"`
+}
+
+type PBData struct {
+	Slash struct {
+		Bytes string `json:"bytes"`
+	} `json:"/"`
+}
+
+type PBNode struct {
+	Data  PBData   `json:"Data"`
+	Links []PBLink `json:"Links"`
+}
diff --git a/test/cli/testutils/random_deterministic.go b/test/cli/testutils/random_deterministic.go
new file mode 100644
index 000000000..e55404168
--- /dev/null
+++ b/test/cli/testutils/random_deterministic.go
@@ -0,0 +1,46 @@
+package testutils
+
+import (
+	"crypto/sha256"
+	"io"
+
+	"github.com/dustin/go-humanize"
+	"golang.org/x/crypto/chacha20"
+)
+
+type randomReader struct {
+	cipher    *chacha20.Cipher
+	remaining int64
+}
+
+func (r *randomReader) Read(p []byte) (int, error) {
+	if r.remaining <= 0 {
+		return 0, io.EOF
+	}
+	n := int64(len(p))
+	if n > r.remaining {
+		n = r.remaining
+	}
+	// Generate random bytes directly into the provided buffer
+	r.cipher.XORKeyStream(p[:n], make([]byte, n))
+	r.remaining -= n
+	return int(n), nil
+}
+
+// createRandomReader produces specified number of pseudo-random bytes
+// from a seed.
+func DeterministicRandomReader(sizeStr string, seed string) (io.Reader, error) {
+	size, err := humanize.ParseBytes(sizeStr)
+	if err != nil {
+		return nil, err
+	}
+	// Hash the seed string to a 32-byte key for ChaCha20
+	key := sha256.Sum256([]byte(seed))
+	// Use ChaCha20 for deterministic random bytes
+	var nonce [chacha20.NonceSize]byte // Zero nonce for simplicity
+	cipher, err := chacha20.NewUnauthenticatedCipher(key[:chacha20.KeySize], nonce[:])
+	if err != nil {
+		return nil, err
+	}
+	return &randomReader{cipher: cipher, remaining: int64(size)}, nil
+}
diff --git a/test/cli/testutils/random_files.go b/test/cli/testutils/random_files.go
index c7dca10d6..7991cad83 100644
--- a/test/cli/testutils/random_files.go
+++ b/test/cli/testutils/random_files.go
@@ -24,20 +24,22 @@ type RandFiles struct {
 	FanoutFiles int // how many files per dir
 	FanoutDirs  int // how many dirs per dir
 
-	RandomSize   bool // randomize file sizes
-	RandomFanout bool // randomize fanout numbers
+	RandomSize     bool // randomize file sizes
+	RandomNameSize bool // randomize filename lengths
+	RandomFanout   bool // randomize fanout numbers
 }
 
 func NewRandFiles() *RandFiles {
 	return &RandFiles{
-		Rand:         rand.New(rand.NewSource(time.Now().UnixNano())),
-		FileSize:     4096,
-		FilenameSize: 16,
-		Alphabet:     AlphabetEasy,
-		FanoutDepth:  2,
-		FanoutDirs:   5,
-		FanoutFiles:  10,
-		RandomSize:   true,
+		Rand:           rand.New(rand.NewSource(time.Now().UnixNano())),
+		FileSize:       4096,
+		FilenameSize:   16,
+		Alphabet:       AlphabetEasy,
+		FanoutDepth:    2,
+		FanoutDirs:     5,
+		FanoutFiles:    10,
+		RandomSize:     true,
+		RandomNameSize: true,
 	}
 }
 
@@ -83,7 +85,10 @@ func (r *RandFiles) WriteRandomFile(root string) error {
 		filesize = r.Rand.Int63n(filesize) + 1
 	}
 
-	n := rand.Intn(r.FilenameSize-4) + 4
+	n := r.FilenameSize
+	if r.RandomNameSize {
+		n = rand.Intn(r.FilenameSize-4) + 4
+	}
 	name := r.RandomFilename(n)
 	filepath := path.Join(root, name)
 	f, err := os.Create(filepath)
diff --git a/test/dependencies/go.mod b/test/dependencies/go.mod
index 0cf72f9ca..fef506300 100644
--- a/test/dependencies/go.mod
+++ b/test/dependencies/go.mod
@@ -33,6 +33,7 @@ require (
 	github.com/Masterminds/semver/v3 v3.2.1 // indirect
 	github.com/OpenPeeDeeP/depguard/v2 v2.2.0 // indirect
 	github.com/alecthomas/go-check-sumtype v0.1.4 // indirect
+	github.com/alecthomas/units v0.0.0-20240927000941-0f3dac36c52b // indirect
 	github.com/alexkohler/nakedret/v2 v2.0.4 // indirect
 	github.com/alexkohler/prealloc v1.0.0 // indirect
 	github.com/alingse/asasalint v0.0.11 // indirect
@@ -57,6 +58,7 @@ require (
 	github.com/chavacava/garif v0.1.0 // indirect
 	github.com/ckaznocha/intrange v0.1.2 // indirect
 	github.com/cpuguy83/go-md2man/v2 v2.0.5 // indirect
+	github.com/crackcomm/go-gitignore v0.0.0-20241020182519-7843d2ba8fdf // indirect
 	github.com/curioswitch/go-reassign v0.2.0 // indirect
 	github.com/daixiang0/gci v0.13.4 // indirect
 	github.com/davecgh/go-spew v1.1.2-0.20180830191138-d8f796af33cc // indirect
@@ -116,7 +118,8 @@ require (
 	github.com/huin/goupnp v1.3.0 // indirect
 	github.com/inconshreveable/mousetrap v1.1.0 // indirect
 	github.com/ipfs/bbloom v0.0.4 // indirect
-	github.com/ipfs/boxo v0.29.2-0.20250409154342-bbaf2e146dfb // indirect
+	github.com/ipfs/boxo v0.29.2-0.20250415191135-dc60fe747c37 // indirect
+	github.com/ipfs/go-bitfield v1.1.0 // indirect
 	github.com/ipfs/go-block-format v0.2.0 // indirect
 	github.com/ipfs/go-cid v0.5.0 // indirect
 	github.com/ipfs/go-datastore v0.8.2 // indirect
@@ -273,6 +276,7 @@ require (
 	github.com/urfave/cli v1.22.16 // indirect
 	github.com/uudashr/gocognit v1.1.3 // indirect
 	github.com/whyrusleeping/base32 v0.0.0-20170828182744-c30ac30633cc // indirect
+	github.com/whyrusleeping/chunker v0.0.0-20181014151217-fe64bd25879f // indirect
 	github.com/whyrusleeping/go-keyspace v0.0.0-20160322163242-5b898ac5add1 // indirect
 	github.com/wlynxg/anet v0.0.5 // indirect
 	github.com/xen0n/gosmopolitan v1.2.2 // indirect
diff --git a/test/dependencies/go.sum b/test/dependencies/go.sum
index 4fef97504..a0be36844 100644
--- a/test/dependencies/go.sum
+++ b/test/dependencies/go.sum
@@ -43,6 +43,8 @@ github.com/alecthomas/go-check-sumtype v0.1.4 h1:WCvlB3l5Vq5dZQTFmodqL2g68uHiSww
 github.com/alecthomas/go-check-sumtype v0.1.4/go.mod h1:WyYPfhfkdhyrdaligV6svFopZV8Lqdzn5pyVBaV6jhQ=
 github.com/alecthomas/repr v0.2.0 h1:HAzS41CIzNW5syS8Mf9UwXhNH1J9aix/BvDRf1Ml2Yk=
 github.com/alecthomas/repr v0.2.0/go.mod h1:Fr0507jx4eOXV7AlPV6AVZLYrLIuIeSOWtW57eE/O/4=
+github.com/alecthomas/units v0.0.0-20240927000941-0f3dac36c52b h1:mimo19zliBX/vSQ6PWWSL9lK8qwHozUj03+zLoEB8O0=
+github.com/alecthomas/units v0.0.0-20240927000941-0f3dac36c52b/go.mod h1:fvzegU4vN3H1qMT+8wDmzjAcDONcgo2/SZ/TyfdUOFs=
 github.com/alexkohler/nakedret/v2 v2.0.4 h1:yZuKmjqGi0pSmjGpOC016LtPJysIL0WEUiaXW5SUnNg=
 github.com/alexkohler/nakedret/v2 v2.0.4/go.mod h1:bF5i0zF2Wo2o4X4USt9ntUWve6JbFv02Ff4vlkmS/VU=
 github.com/alexkohler/prealloc v1.0.0 h1:Hbq0/3fJPQhNkN0dR95AVrr6R7tou91y0uHG5pOcUuw=
@@ -105,6 +107,8 @@ github.com/cpuguy83/go-md2man/v2 v2.0.0-20190314233015-f79a8a8ca69d/go.mod h1:ma
 github.com/cpuguy83/go-md2man/v2 v2.0.4/go.mod h1:tgQtvFlXSQOSOSIRvRPT7W67SCa46tRHOmNcaadrF8o=
 github.com/cpuguy83/go-md2man/v2 v2.0.5 h1:ZtcqGrnekaHpVLArFSe4HK5DoKx1T0rq2DwVB0alcyc=
 github.com/cpuguy83/go-md2man/v2 v2.0.5/go.mod h1:tgQtvFlXSQOSOSIRvRPT7W67SCa46tRHOmNcaadrF8o=
+github.com/crackcomm/go-gitignore v0.0.0-20241020182519-7843d2ba8fdf h1:dwGgBWn84wUS1pVikGiruW+x5XM4amhjaZO20vCjay4=
+github.com/crackcomm/go-gitignore v0.0.0-20241020182519-7843d2ba8fdf/go.mod h1:p1d6YEZWvFzEh4KLyvBcVSnrfNDDvK2zfK/4x2v/4pE=
 github.com/cskr/pubsub v1.0.2 h1:vlOzMhl6PFn60gRlTQQsIfVwaPB/B/8MziK8FhEPt/0=
 github.com/cskr/pubsub v1.0.2/go.mod h1:/8MzYXk/NJAz782G8RPkFzXTZVu63VotefPnR9TIRis=
 github.com/curioswitch/go-reassign v0.2.0 h1:G9UZyOcpk/d7Gd6mqYgd8XYWFMw/znxwGDUstnC9DIo=
@@ -294,8 +298,10 @@ github.com/inconshreveable/mousetrap v1.1.0 h1:wN+x4NVGpMsO7ErUn/mUI3vEoE6Jt13X2
 github.com/inconshreveable/mousetrap v1.1.0/go.mod h1:vpF70FUmC8bwa3OWnCshd2FqLfsEA9PFc4w1p2J65bw=
 github.com/ipfs/bbloom v0.0.4 h1:Gi+8EGJ2y5qiD5FbsbpX/TMNcJw8gSqr7eyjHa4Fhvs=
 github.com/ipfs/bbloom v0.0.4/go.mod h1:cS9YprKXpoZ9lT0n/Mw/a6/aFV6DTjTLYHeA+gyqMG0=
-github.com/ipfs/boxo v0.29.2-0.20250409154342-bbaf2e146dfb h1:kA7c3CF6/d8tUwGJR/SwIfaRz7Xk7Fbyoh2ePZAFMlw=
-github.com/ipfs/boxo v0.29.2-0.20250409154342-bbaf2e146dfb/go.mod h1:omQZmLS7LegSpBy3m4CrAB9/SO7Fq3pfv+5y1FOd+gI=
+github.com/ipfs/boxo v0.29.2-0.20250415191135-dc60fe747c37 h1:q3a+2FIbWzZbx/yUqpuG4jLVSa6GvxtRfx9TU5GLiN0=
+github.com/ipfs/boxo v0.29.2-0.20250415191135-dc60fe747c37/go.mod h1:omQZmLS7LegSpBy3m4CrAB9/SO7Fq3pfv+5y1FOd+gI=
+github.com/ipfs/go-bitfield v1.1.0 h1:fh7FIo8bSwaJEh6DdTWbCeZ1eqOaOkKFI74SCnsWbGA=
+github.com/ipfs/go-bitfield v1.1.0/go.mod h1:paqf1wjq/D2BBmzfTVFlJQ9IlFOZpg422HL0HqsGWHU=
 github.com/ipfs/go-block-format v0.2.0 h1:ZqrkxBA2ICbDRbK8KJs/u0O3dlp6gmAuuXUJNiW1Ycs=
 github.com/ipfs/go-block-format v0.2.0/go.mod h1:+jpL11nFx5A/SPpsoBn6Bzkra/zaArfSmsknbPMYgzM=
 github.com/ipfs/go-cid v0.5.0 h1:goEKKhaGm0ul11IHA7I6p1GmKz8kEYniqFopaB5Otwg=
@@ -767,6 +773,8 @@ github.com/warpfork/go-wish v0.0.0-20220906213052-39a1cc7a02d0 h1:GDDkbFiaK8jsSD
 github.com/warpfork/go-wish v0.0.0-20220906213052-39a1cc7a02d0/go.mod h1:x6AKhvSSexNrVSrViXSHUEbICjmGXhtgABaHIySUSGw=
 github.com/whyrusleeping/base32 v0.0.0-20170828182744-c30ac30633cc h1:BCPnHtcboadS0DvysUuJXZ4lWVv5Bh5i7+tbIyi+ck4=
 github.com/whyrusleeping/base32 v0.0.0-20170828182744-c30ac30633cc/go.mod h1:r45hJU7yEoA81k6MWNhpMj/kms0n14dkzkxYHoB96UM=
+github.com/whyrusleeping/chunker v0.0.0-20181014151217-fe64bd25879f h1:jQa4QT2UP9WYv2nzyawpKMOCl+Z/jW7djv2/J50lj9E=
+github.com/whyrusleeping/chunker v0.0.0-20181014151217-fe64bd25879f/go.mod h1:p9UJB6dDgdPgMJZs7UjUOdulKyRr9fqkS+6JKAInPy8=
 github.com/whyrusleeping/go-keyspace v0.0.0-20160322163242-5b898ac5add1 h1:EKhdznlJHPMoKr0XTrX+IlJs1LH3lyx2nfr1dOlZ79k=
 github.com/whyrusleeping/go-keyspace v0.0.0-20160322163242-5b898ac5add1/go.mod h1:8UvriyWtv5Q5EOgjHaSseUEdkQfvwFv1I/In/O2M9gc=
 github.com/wlynxg/anet v0.0.3/go.mod h1:eay5PRQr7fIVAMbTbchTnO9gG65Hg/uYGdc7mguHxoA=
diff --git a/test/sharness/t0032-mount-sharded.sh b/test/sharness/t0032-mount-sharded.sh
index 10ba421a2..7a3e51858 100755
--- a/test/sharness/t0032-mount-sharded.sh
+++ b/test/sharness/t0032-mount-sharded.sh
@@ -16,7 +16,7 @@ fi
 test_init_ipfs
 
 test_expect_success 'force sharding' '
-  ipfs config --json Internal.UnixFSShardingSizeThreshold "\"1B\""
+  ipfs config --json Import.UnixFSHAMTDirectorySizeThreshold "\"1B\""
 '
 
 test_launch_ipfs_daemon
diff --git a/test/sharness/t0250-files-api.sh b/test/sharness/t0250-files-api.sh
index 9c01a5bcf..63dacf7d4 100755
--- a/test/sharness/t0250-files-api.sh
+++ b/test/sharness/t0250-files-api.sh
@@ -849,7 +849,7 @@ tests_for_files_api "with-daemon"
 test_kill_ipfs_daemon
 
 test_expect_success "enable sharding in config" '
-  ipfs config --json Internal.UnixFSShardingSizeThreshold "\"1B\""
+  ipfs config --json Import.UnixFSHAMTDirectorySizeThreshold "\"1B\""
 '
 
 test_launch_ipfs_daemon_without_network
@@ -880,7 +880,7 @@ test_expect_success "set up automatic sharding/unsharding data" '
 '
 
 test_expect_success "reset automatic sharding" '
-  ipfs config --json Internal.UnixFSShardingSizeThreshold null
+  ipfs config --json Import.UnixFSHAMTDirectorySizeThreshold null
 '
 
 test_launch_ipfs_daemon_without_network
diff --git a/test/sharness/t0260-sharding.sh b/test/sharness/t0260-sharding.sh
index 85e4a7ca7..7b0094fd4 100755
--- a/test/sharness/t0260-sharding.sh
+++ b/test/sharness/t0260-sharding.sh
@@ -34,7 +34,7 @@ test_init_ipfs
 UNSHARDED="QmavrTrQG4VhoJmantURAYuw3bowq3E2WcvP36NRQDAC1N"
 
 test_expect_success "force sharding off" '
-ipfs config --json Internal.UnixFSShardingSizeThreshold "\"1G\""
+ipfs config --json Import.UnixFSHAMTDirectorySizeThreshold "\"1G\""
 '
 
 test_add_dir "$UNSHARDED"
@@ -46,7 +46,7 @@ test_add_dir "$UNSHARDED"
 test_kill_ipfs_daemon
 
 test_expect_success "force sharding on" '
-  ipfs config --json Internal.UnixFSShardingSizeThreshold "\"1B\""
+  ipfs config --json Import.UnixFSHAMTDirectorySizeThreshold "\"1B\""
 '
 
 SHARDED="QmSCJD1KYLhVVHqBK3YyXuoEqHt7vggyJhzoFYbT8v1XYL"