diff --git a/cmd/tailscale/cli/cli_test.go b/cmd/tailscale/cli/cli_test.go
index 36cffa8ab..6ad7e0888 100644
--- a/cmd/tailscale/cli/cli_test.go
+++ b/cmd/tailscale/cli/cli_test.go
@@ -1016,9 +1016,6 @@ func TestPrefFlagMapping(t *testing.T) {
 			continue
 		}
 		switch prefName {
-		case "AllowSingleHosts":
-			// Fake pref for downgrade compat. See #12058.
-			continue
 		case "WantRunning", "Persist", "LoggedOut":
 			// All explicitly handled (ignored) by checkForAccidentalSettingReverts.
 			continue
diff --git a/ipn/ipn_clone.go b/ipn/ipn_clone.go
index e179438cd..773167a0d 100644
--- a/ipn/ipn_clone.go
+++ b/ipn/ipn_clone.go
@@ -104,7 +104,6 @@ func (src *Prefs) Clone() *Prefs {
 	DriveShares                []*drive.Share
 	RelayServerPort            *uint16
 	RelayServerStaticEndpoints []netip.AddrPort
-	AllowSingleHosts           marshalAsTrueInJSON
 	Persist                    *persist.Persist
 }{})
 
diff --git a/ipn/ipn_view.go b/ipn/ipn_view.go
index 4e9d46bda..31c3dff2f 100644
--- a/ipn/ipn_view.go
+++ b/ipn/ipn_view.go
@@ -453,16 +453,6 @@ func (v PrefsView) RelayServerStaticEndpoints() views.Slice[netip.AddrPort] {
 	return views.SliceOf(v.ж.RelayServerStaticEndpoints)
 }
 
-// AllowSingleHosts was a legacy field that was always true
-// for the past 4.5 years. It controlled whether Tailscale
-// peers got /32 or /128 routes for each other.
-// As of 2024-05-17 we're starting to ignore it, but to let
-// people still downgrade Tailscale versions and not break
-// all peer-to-peer networking we still write it to disk (as JSON)
-// so it can be loaded back by old versions.
-// TODO(bradfitz): delete this in 2025 sometime. See #12058.
-func (v PrefsView) AllowSingleHosts() marshalAsTrueInJSON { return v.ж.AllowSingleHosts }
-
 // The Persist field is named 'Config' in the file for backward
 // compatibility with earlier versions.
 // TODO(apenwarr): We should move this out of here, it's not a pref.
@@ -506,7 +496,6 @@ func (v PrefsView) Persist() persist.PersistView { return v.ж.Persist.View() }
 	DriveShares                []*drive.Share
 	RelayServerPort            *uint16
 	RelayServerStaticEndpoints []netip.AddrPort
-	AllowSingleHosts           marshalAsTrueInJSON
 	Persist                    *persist.Persist
 }{})
 
diff --git a/ipn/prefs.go b/ipn/prefs.go
index e54086b61..01c8bc5f8 100644
--- a/ipn/prefs.go
+++ b/ipn/prefs.go
@@ -291,16 +291,6 @@ type Prefs struct {
 	// non-nil.
 	RelayServerStaticEndpoints []netip.AddrPort `json:",omitempty"`
 
-	// AllowSingleHosts was a legacy field that was always true
-	// for the past 4.5 years. It controlled whether Tailscale
-	// peers got /32 or /128 routes for each other.
-	// As of 2024-05-17 we're starting to ignore it, but to let
-	// people still downgrade Tailscale versions and not break
-	// all peer-to-peer networking we still write it to disk (as JSON)
-	// so it can be loaded back by old versions.
-	// TODO(bradfitz): delete this in 2025 sometime. See #12058.
-	AllowSingleHosts marshalAsTrueInJSON
-
 	// The Persist field is named 'Config' in the file for backward
 	// compatibility with earlier versions.
 	// TODO(apenwarr): We should move this out of here, it's not a pref.
@@ -331,13 +321,6 @@ func (au1 AutoUpdatePrefs) Equals(au2 AutoUpdatePrefs) bool {
 		ok1 == ok2
 }
 
-type marshalAsTrueInJSON struct{}
-
-var trueJSON = []byte("true")
-
-func (marshalAsTrueInJSON) MarshalJSON() ([]byte, error) { return trueJSON, nil }
-func (*marshalAsTrueInJSON) UnmarshalJSON([]byte) error  { return nil }
-
 // AppConnectorPrefs are the app connector settings for the node agent.
 type AppConnectorPrefs struct {
 	// Advertise specifies whether the app connector subsystem is advertising
diff --git a/ipn/prefs_test.go b/ipn/prefs_test.go
index c20de0c00..97ed33c23 100644
--- a/ipn/prefs_test.go
+++ b/ipn/prefs_test.go
@@ -70,7 +70,6 @@ func TestPrefsEqual(t *testing.T) {
 		"DriveShares",
 		"RelayServerPort",
 		"RelayServerStaticEndpoints",
-		"AllowSingleHosts",
 		"Persist",
 	}
 	if have := fieldsOf(reflect.TypeFor[Prefs]()); !reflect.DeepEqual(have, prefsHandles) {
@@ -714,7 +713,7 @@ func TestMaskedPrefsFields(t *testing.T) {
 	have := map[string]bool{}
 	for _, f := range fieldsOf(reflect.TypeFor[Prefs]()) {
 		switch f {
-		case "Persist", "AllowSingleHosts":
+		case "Persist":
 			// These can't be edited.
 			continue
 		}
@@ -1222,27 +1221,6 @@ func TestNotifyPrefsJSONRoundtrip(t *testing.T) {
 	}
 }
 
-// Verify that our Prefs type writes out an AllowSingleHosts field so we can
-// downgrade to older versions that require it.
-func TestPrefsDowngrade(t *testing.T) {
-	var p Prefs
-	j, err := json.Marshal(p)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	type oldPrefs struct {
-		AllowSingleHosts bool
-	}
-	var op oldPrefs
-	if err := json.Unmarshal(j, &op); err != nil {
-		t.Fatal(err)
-	}
-	if !op.AllowSingleHosts {
-		t.Fatal("AllowSingleHosts should be true")
-	}
-}
-
 func TestParseAutoExitNodeString(t *testing.T) {
 	tests := []struct {
 		name       string
diff --git a/types/prefs/prefs_example/prefs_example_clone.go b/types/prefs/prefs_example/prefs_example_clone.go
index c5fdc49fc..9d43fb250 100644
--- a/types/prefs/prefs_example/prefs_example_clone.go
+++ b/types/prefs/prefs_example/prefs_example_clone.go
@@ -61,7 +61,6 @@ func (src *Prefs) Clone() *Prefs {
 	PostureChecking        prefs.Item[bool]
 	NetfilterKind          prefs.Item[string]
 	DriveShares            prefs.StructList[*drive.Share]
-	AllowSingleHosts       prefs.Item[marshalAsTrueInJSON]
 	Persist                *persist.Persist
 }{})
 
diff --git a/types/prefs/prefs_example/prefs_example_view.go b/types/prefs/prefs_example/prefs_example_view.go
index 67a284bb5..aa71c1a89 100644
--- a/types/prefs/prefs_example/prefs_example_view.go
+++ b/types/prefs/prefs_example/prefs_example_view.go
@@ -145,7 +145,6 @@ func (v PrefsView) NetfilterKind() prefs.Item[string] { return v.ж.NetfilterKin
 func (v PrefsView) DriveShares() prefs.StructListView[*drive.Share, drive.ShareView] {
 	return prefs.StructListViewOf(&v.ж.DriveShares)
 }
-func (v PrefsView) AllowSingleHosts() prefs.Item[marshalAsTrueInJSON] { return v.ж.AllowSingleHosts }
 
 // Persist is an internal state rather than a preference.
 // It can be kept in the Prefs structure but should not be wrapped
@@ -182,7 +181,6 @@ func (v PrefsView) Persist() persist.PersistView { return v.ж.Persist.View() }
 	PostureChecking        prefs.Item[bool]
 	NetfilterKind          prefs.Item[string]
 	DriveShares            prefs.StructList[*drive.Share]
-	AllowSingleHosts       prefs.Item[marshalAsTrueInJSON]
 	Persist                *persist.Persist
 }{})
 
diff --git a/types/prefs/prefs_example/prefs_types.go b/types/prefs/prefs_example/prefs_types.go
index d0764c64b..e704e6bef 100644
--- a/types/prefs/prefs_example/prefs_types.go
+++ b/types/prefs/prefs_example/prefs_types.go
@@ -106,8 +106,7 @@ type Prefs struct {
 	// not be modified after the preference is set.
 	// Since the item type (*drive.Share) is mutable and implements [views.ViewCloner],
 	// we need to use [prefs.StructList] instead of [prefs.List].
-	DriveShares      prefs.StructList[*drive.Share]  `json:",omitzero"`
-	AllowSingleHosts prefs.Item[marshalAsTrueInJSON] `json:",omitzero"`
+	DriveShares prefs.StructList[*drive.Share] `json:",omitzero"`
 
 	// Persist is an internal state rather than a preference.
 	// It can be kept in the Prefs structure but should not be wrapped
@@ -162,10 +161,3 @@ func (p Prefs) MarshalJSON() ([]byte, error) {
 func (p *Prefs) UnmarshalJSON(b []byte) error {
 	return jsonv2.Unmarshal(b, p) // uses UnmarshalJSONFrom
 }
-
-type marshalAsTrueInJSON struct{}
-
-var trueJSON = []byte("true")
-
-func (marshalAsTrueInJSON) MarshalJSON() ([]byte, error) { return trueJSON, nil }
-func (*marshalAsTrueInJSON) UnmarshalJSON([]byte) error  { return nil }