diff --git a/src/internal/kopia/backup_bases.go b/src/internal/kopia/backup_bases.go
index 4c2c95fb7..be94c6167 100644
--- a/src/internal/kopia/backup_bases.go
+++ b/src/internal/kopia/backup_bases.go
@@ -8,7 +8,6 @@ import (
 	"golang.org/x/exp/slices"
 
 	"github.com/alcionai/corso/src/internal/version"
-	"github.com/alcionai/corso/src/pkg/backup/identity"
 	"github.com/alcionai/corso/src/pkg/logger"
 )
 
@@ -23,11 +22,6 @@ type BackupBases interface {
 	ClearMergeBases()
 	AssistBases() []ManifestEntry
 	ClearAssistBases()
-	MergeBackupBases(
-		ctx context.Context,
-		other BackupBases,
-		reasonToKey func(identity.Reasoner) string,
-	) BackupBases
 }
 
 type backupBases struct {
@@ -111,119 +105,6 @@ func (bb *backupBases) ClearAssistBases() {
 	bb.assistBases = nil
 }
 
-// MergeBackupBases reduces the two BackupBases into a single BackupBase.
-// Assumes the passed in BackupBases represents a prior backup version (across
-// some migration that disrupts lookup), and that the BackupBases used to call
-// this function contains the current version.
-//
-// reasonToKey should be a function that, given a Reasoner, will produce some
-// string that represents Reasoner in the context of the merge operation. For
-// example, to merge BackupBases across a ProtectedResource migration, the
-// Reasoner's service and category can be used as the key.
-//
-// Selection priority, for each reason key generated by reasonsToKey, follows
-// these rules:
-//  1. If the called BackupBases has an entry for a given reason, ignore the
-//     other BackupBases matching that reason.
-//  2. If the called BackupBases has only AssistBases, look for a matching
-//     MergeBase manifest in the other BackupBases.
-//  3. If the called BackupBases has no entry for a reason, look for a matching
-//     MergeBase in the other BackupBases.
-func (bb *backupBases) MergeBackupBases(
-	ctx context.Context,
-	other BackupBases,
-	reasonToKey func(reason identity.Reasoner) string,
-) BackupBases {
-	if other == nil || (len(other.MergeBases()) == 0 && len(other.AssistBases()) == 0) {
-		return bb
-	}
-
-	if bb == nil || (len(bb.MergeBases()) == 0 && len(bb.AssistBases()) == 0) {
-		return other
-	}
-
-	toMerge := map[string]struct{}{}
-	assist := map[string]struct{}{}
-
-	// Track the bases in bb.
-	for _, m := range bb.mergeBases {
-		for _, r := range m.Reasons {
-			k := reasonToKey(r)
-
-			toMerge[k] = struct{}{}
-			assist[k] = struct{}{}
-		}
-	}
-
-	for _, m := range bb.assistBases {
-		for _, r := range m.Reasons {
-			k := reasonToKey(r)
-			assist[k] = struct{}{}
-		}
-	}
-
-	var toAdd []ManifestEntry
-
-	// Calculate the set of mergeBases to pull from other into this one.
-	for _, m := range other.MergeBases() {
-		useReasons := []identity.Reasoner{}
-
-		for _, r := range m.Reasons {
-			k := reasonToKey(r)
-			if _, ok := toMerge[k]; ok {
-				// Assume other contains prior manifest versions.
-				// We don't want to stack a prior version incomplete onto
-				// a current version's complete snapshot.
-				continue
-			}
-
-			useReasons = append(useReasons, r)
-		}
-
-		if len(useReasons) > 0 {
-			m.Reasons = useReasons
-			toAdd = append(toAdd, m)
-		}
-	}
-
-	res := &backupBases{
-		backups:     bb.Backups(),
-		mergeBases:  bb.MergeBases(),
-		assistBases: bb.AssistBases(),
-		// Note that assistBackups are a new feature and don't exist
-		// in prior versions where we were using UPN based reasons i.e.
-		// other won't have any assistBackups.
-		assistBackups: bb.AssistBackups(),
-	}
-
-	// Add new mergeBases and backups.
-	for _, man := range toAdd {
-		// Will get empty string if not found which is fine, it'll fail one of the
-		// other checks.
-		bID, _ := man.GetTag(TagBackupID)
-
-		bup, ok := getBackupByID(other.Backups(), bID)
-		if !ok {
-			logger.Ctx(ctx).Infow(
-				"not unioning snapshot missing backup",
-				"other_manifest_id", man.ID,
-				"other_backup_id", bID)
-
-			continue
-		}
-
-		bup.Reasons = man.Reasons
-
-		res.backups = append(res.backups, bup)
-		res.mergeBases = append(res.mergeBases, man)
-		// TODO(pandeyabs): Remove this once we remove overlap between
-		// between merge and assist bases as part of #3943.
-		res.assistBases = append(res.assistBases, man)
-	}
-
-	return res
-}
-
 func findNonUniqueManifests(
 	ctx context.Context,
 	manifests []ManifestEntry,
diff --git a/src/internal/kopia/backup_bases_test.go b/src/internal/kopia/backup_bases_test.go
index faa402162..3b0fc91cc 100644
--- a/src/internal/kopia/backup_bases_test.go
+++ b/src/internal/kopia/backup_bases_test.go
@@ -1,7 +1,6 @@
 package kopia
 
 import (
-	"fmt"
 	"testing"
 
 	"github.com/kopia/kopia/repo/manifest"
@@ -203,279 +202,6 @@ func (suite *BackupBasesUnitSuite) TestClearAssistBases() {
 	assert.Empty(suite.T(), bb.AssistBases())
 }
 
-func (suite *BackupBasesUnitSuite) TestMergeBackupBases() {
-	ro := "resource_owner"
-
-	type testInput struct {
-		id  int
-		cat []path.CategoryType
-	}
-
-	// Make a function so tests can modify things without messing with each other.
-	makeBackupBases := func(mergeInputs []testInput, assistInputs []testInput) *backupBases {
-		res := &backupBases{}
-
-		for _, i := range mergeInputs {
-			baseID := fmt.Sprintf("id%d", i.id)
-			reasons := make([]identity.Reasoner, 0, len(i.cat))
-
-			for _, c := range i.cat {
-				reasons = append(reasons, NewReason("", ro, path.ExchangeService, c))
-			}
-
-			m := makeManifest(baseID, "", "b"+baseID, reasons...)
-			res.assistBases = append(res.assistBases, m)
-
-			b := BackupEntry{
-				Backup: &backup.Backup{
-					BaseModel:     model.BaseModel{ID: model.StableID("b" + baseID)},
-					SnapshotID:    baseID,
-					StreamStoreID: "ss" + baseID,
-				},
-				Reasons: reasons,
-			}
-
-			res.backups = append(res.backups, b)
-			res.mergeBases = append(res.mergeBases, m)
-		}
-
-		for _, i := range assistInputs {
-			baseID := fmt.Sprintf("id%d", i.id)
-
-			reasons := make([]identity.Reasoner, 0, len(i.cat))
-
-			for _, c := range i.cat {
-				reasons = append(reasons, NewReason("", ro, path.ExchangeService, c))
-			}
-
-			m := makeManifest(baseID, "", "a"+baseID, reasons...)
-
-			b := BackupEntry{
-				Backup: &backup.Backup{
-					BaseModel: model.BaseModel{
-						ID:   model.StableID("a" + baseID),
-						Tags: map[string]string{model.BackupTypeTag: model.AssistBackup},
-					},
-					SnapshotID:    baseID,
-					StreamStoreID: "ss" + baseID,
-				},
-				Reasons: reasons,
-			}
-
-			res.assistBackups = append(res.assistBackups, b)
-			res.assistBases = append(res.assistBases, m)
-		}
-
-		return res
-	}
-
-	table := []struct {
-		name        string
-		merge       []testInput
-		assist      []testInput
-		otherMerge  []testInput
-		otherAssist []testInput
-		expect      func() *backupBases
-	}{
-		{
-			name: "Other Empty",
-			merge: []testInput{
-				{cat: []path.CategoryType{path.EmailCategory}},
-			},
-			assist: []testInput{
-				{cat: []path.CategoryType{path.EmailCategory}},
-			},
-			expect: func() *backupBases {
-				bs := makeBackupBases([]testInput{
-					{cat: []path.CategoryType{path.EmailCategory}},
-				}, []testInput{
-					{cat: []path.CategoryType{path.EmailCategory}},
-				})
-
-				return bs
-			},
-		},
-		{
-			name: "current Empty",
-			otherMerge: []testInput{
-				{cat: []path.CategoryType{path.EmailCategory}},
-			},
-			otherAssist: []testInput{
-				{cat: []path.CategoryType{path.EmailCategory}},
-			},
-			expect: func() *backupBases {
-				bs := makeBackupBases([]testInput{
-					{cat: []path.CategoryType{path.EmailCategory}},
-				}, []testInput{
-					{cat: []path.CategoryType{path.EmailCategory}},
-				})
-
-				return bs
-			},
-		},
-		{
-			name: "Other overlaps merge and assist",
-			merge: []testInput{
-				{
-					id:  1,
-					cat: []path.CategoryType{path.EmailCategory},
-				},
-			},
-			assist: []testInput{
-				{
-					id:  4,
-					cat: []path.CategoryType{path.EmailCategory},
-				},
-			},
-			otherMerge: []testInput{
-				{
-					id:  2,
-					cat: []path.CategoryType{path.EmailCategory},
-				},
-				{
-					id:  3,
-					cat: []path.CategoryType{path.EmailCategory},
-				},
-			},
-			otherAssist: []testInput{
-				{
-					id:  5,
-					cat: []path.CategoryType{path.EmailCategory},
-				},
-			},
-			expect: func() *backupBases {
-				bs := makeBackupBases([]testInput{
-					{
-						id:  1,
-						cat: []path.CategoryType{path.EmailCategory},
-					},
-				}, []testInput{
-					{
-						id:  4,
-						cat: []path.CategoryType{path.EmailCategory},
-					},
-				})
-
-				return bs
-			},
-		},
-		{
-			name: "Other overlaps merge",
-			merge: []testInput{
-				{
-					id:  1,
-					cat: []path.CategoryType{path.EmailCategory},
-				},
-			},
-			otherMerge: []testInput{
-				{
-					id:  2,
-					cat: []path.CategoryType{path.EmailCategory},
-				},
-			},
-			expect: func() *backupBases {
-				bs := makeBackupBases([]testInput{
-					{
-						id:  1,
-						cat: []path.CategoryType{path.EmailCategory},
-					},
-				}, nil)
-
-				return bs
-			},
-		},
-		{
-			name: "Current assist overlaps with Other merge",
-			assist: []testInput{
-				{
-					id:  3,
-					cat: []path.CategoryType{path.EmailCategory},
-				},
-			},
-			otherMerge: []testInput{
-				{
-					id:  1,
-					cat: []path.CategoryType{path.EmailCategory},
-				},
-			},
-			otherAssist: []testInput{
-				{
-					id:  2,
-					cat: []path.CategoryType{path.EmailCategory},
-				},
-			},
-
-			expect: func() *backupBases {
-				bs := makeBackupBases([]testInput{
-					{
-						id:  1,
-						cat: []path.CategoryType{path.EmailCategory},
-					},
-				}, []testInput{
-					{
-						id:  3,
-						cat: []path.CategoryType{path.EmailCategory},
-					},
-				})
-
-				return bs
-			},
-		},
-		{
-			name: "Other Disjoint",
-			merge: []testInput{
-				{cat: []path.CategoryType{path.EmailCategory}},
-				{
-					id:  1,
-					cat: []path.CategoryType{path.EmailCategory},
-				},
-			},
-			otherMerge: []testInput{
-				{
-					id:  2,
-					cat: []path.CategoryType{path.ContactsCategory},
-				},
-			},
-			expect: func() *backupBases {
-				bs := makeBackupBases([]testInput{
-					{cat: []path.CategoryType{path.EmailCategory}},
-					{
-						id:  1,
-						cat: []path.CategoryType{path.EmailCategory},
-					},
-					{
-						id:  2,
-						cat: []path.CategoryType{path.ContactsCategory},
-					},
-				}, nil)
-
-				return bs
-			},
-		},
-	}
-
-	for _, test := range table {
-		suite.Run(test.name, func() {
-			t := suite.T()
-
-			bb := makeBackupBases(test.merge, test.assist)
-			other := makeBackupBases(test.otherMerge, test.otherAssist)
-			expected := test.expect()
-
-			ctx, flush := tester.NewContext(t)
-			defer flush()
-
-			got := bb.MergeBackupBases(
-				ctx,
-				other,
-				func(r identity.Reasoner) string {
-					return r.Service().String() + r.Category().String()
-				})
-			AssertBackupBasesEqual(t, expected, got)
-		})
-	}
-}
-
 func (suite *BackupBasesUnitSuite) TestFixupAndVerify() {
 	ro := "resource_owner"
 
diff --git a/src/internal/operations/backup.go b/src/internal/operations/backup.go
index d3d4f0a9f..5cf810066 100644
--- a/src/internal/operations/backup.go
+++ b/src/internal/operations/backup.go
@@ -333,11 +333,6 @@ func (op *BackupOperation) do(
 		return nil, clues.Wrap(err, "getting reasons")
 	}
 
-	fallbackReasons, err := makeFallbackReasons(op.account.ID(), op.Selectors)
-	if err != nil {
-		return nil, clues.Wrap(err, "getting fallback reasons")
-	}
-
 	logger.Ctx(ctx).With(
 		"control_options", op.Options,
 		"selectors", op.Selectors).
@@ -355,7 +350,7 @@ func (op *BackupOperation) do(
 		ctx,
 		kbf,
 		op.kopia,
-		reasons, fallbackReasons,
+		reasons,
 		op.account.ID(),
 		op.incremental,
 		op.disableAssistBackup)
@@ -430,16 +425,6 @@ func (op *BackupOperation) do(
 	return deets, nil
 }
 
-func makeFallbackReasons(tenant string, sel selectors.Selector) ([]identity.Reasoner, error) {
-	if sel.PathService() != path.SharePointService &&
-		sel.DiscreteOwner != sel.DiscreteOwnerName {
-		return sel.Reasons(tenant, true)
-	}
-
-	// return nil for fallback reasons since a nil value will no-op.
-	return nil, nil
-}
-
 // checker to see if conditions are correct for incremental backup behavior such as
 // retrieving metadata like delta tokens and previous paths.
 func useIncrementalBackup(sel selectors.Selector, opts control.Options) bool {
diff --git a/src/internal/operations/manifests.go b/src/internal/operations/manifests.go
index 95b313adc..060e7aab5 100644
--- a/src/internal/operations/manifests.go
+++ b/src/internal/operations/manifests.go
@@ -20,7 +20,7 @@ func produceManifestsAndMetadata(
 	ctx context.Context,
 	bf inject.BaseFinder,
 	rp inject.RestoreProducer,
-	reasons, fallbackReasons []identity.Reasoner,
+	reasons []identity.Reasoner,
 	tenantID string,
 	getMetadata, dropAssistBases bool,
 ) (kopia.BackupBases, []data.RestoreCollection, bool, error) {
@@ -29,7 +29,6 @@ func produceManifestsAndMetadata(
 		bf,
 		rp,
 		reasons,
-		fallbackReasons,
 		tenantID,
 		getMetadata)
 	if err != nil {
@@ -57,7 +56,7 @@ func getManifestsAndMetadata(
 	ctx context.Context,
 	bf inject.BaseFinder,
 	rp inject.RestoreProducer,
-	reasons, fallbackReasons []identity.Reasoner,
+	reasons []identity.Reasoner,
 	tenantID string,
 	getMetadata bool,
 ) (kopia.BackupBases, []data.RestoreCollection, bool, error) {
@@ -68,24 +67,6 @@ func getManifestsAndMetadata(
 	)
 
 	bb := bf.FindBases(ctx, reasons, tags)
-	// TODO(ashmrtn): Only fetch these if we haven't already covered all the
-	// reasons for this backup.
-	fbb := bf.FindBases(ctx, fallbackReasons, tags)
-
-	// one of three cases can occur when retrieving backups across reason migrations:
-	// 1. the current reasons don't match any manifests, and we use the fallback to
-	// look up the previous reason version.
-	// 2. the current reasons only contain an incomplete manifest, and the fallback
-	// can find a complete manifest.
-	// 3. the current reasons contain all the necessary manifests.
-	// Note: This is not relevant for assist backups, since they are newly introduced
-	// and they don't exist with fallback reasons.
-	bb = bb.MergeBackupBases(
-		ctx,
-		fbb,
-		func(r identity.Reasoner) string {
-			return r.Service().String() + r.Category().String()
-		})
 
 	if !getMetadata {
 		return bb, nil, false, nil
diff --git a/src/internal/operations/manifests_test.go b/src/internal/operations/manifests_test.go
index d6e284750..fd3298e20 100644
--- a/src/internal/operations/manifests_test.go
+++ b/src/internal/operations/manifests_test.go
@@ -12,9 +12,7 @@ import (
 
 	"github.com/alcionai/corso/src/internal/data"
 	"github.com/alcionai/corso/src/internal/kopia"
-	"github.com/alcionai/corso/src/internal/model"
 	"github.com/alcionai/corso/src/internal/tester"
-	"github.com/alcionai/corso/src/pkg/backup"
 	"github.com/alcionai/corso/src/pkg/backup/identity"
 	"github.com/alcionai/corso/src/pkg/fault"
 	"github.com/alcionai/corso/src/pkg/path"
@@ -482,7 +480,7 @@ func (suite *OperationsManifestsUnitSuite) TestProduceManifestsAndMetadata() {
 				ctx,
 				test.bf,
 				&test.rp,
-				test.reasons, nil,
+				test.reasons,
 				tid,
 				test.getMeta,
 				test.dropAssist)
@@ -532,499 +530,3 @@ func (suite *OperationsManifestsUnitSuite) TestProduceManifestsAndMetadata() {
 		})
 	}
 }
-
-func (suite *OperationsManifestsUnitSuite) TestProduceManifestsAndMetadata_FallbackReasons() {
-	const (
-		ro   = "resourceowner"
-		fbro = "fb_resourceowner"
-		tid  = "tenantid"
-		did  = "detailsid"
-	)
-
-	makeMan := func(ro, id, incmpl string, cats ...path.CategoryType) kopia.ManifestEntry {
-		return kopia.ManifestEntry{
-			Manifest: &snapshot.Manifest{
-				ID:               manifest.ID(id),
-				IncompleteReason: incmpl,
-				Tags:             map[string]string{"tag:" + kopia.TagBackupID: id + "bup"},
-			},
-			Reasons: buildReasons(ro, path.ExchangeService, cats...),
-		}
-	}
-
-	makeBackup := func(ro, snapID string, cats ...path.CategoryType) kopia.BackupEntry {
-		return kopia.BackupEntry{
-			Backup: &backup.Backup{
-				BaseModel: model.BaseModel{
-					ID: model.StableID(snapID + "bup"),
-				},
-				SnapshotID:    snapID,
-				StreamStoreID: snapID + "store",
-			},
-			Reasons: buildReasons(ro, path.ExchangeService, cats...),
-		}
-	}
-
-	emailReason := kopia.NewReason(
-		"",
-		ro,
-		path.ExchangeService,
-		path.EmailCategory)
-
-	fbEmailReason := kopia.NewReason(
-		"",
-		fbro,
-		path.ExchangeService,
-		path.EmailCategory)
-
-	table := []struct {
-		name            string
-		bf              *mockBackupFinder
-		rp              mockRestoreProducer
-		reasons         []identity.Reasoner
-		fallbackReasons []identity.Reasoner
-		getMeta         bool
-		dropAssist      bool
-		assertErr       assert.ErrorAssertionFunc
-		assertB         assert.BoolAssertionFunc
-		expectDCS       []mockColl
-		expectMans      kopia.BackupBases
-	}{
-		{
-			name: "don't get metadata, only fallbacks",
-			bf: &mockBackupFinder{
-				data: map[string]kopia.BackupBases{
-					fbro: kopia.NewMockBackupBases().WithMergeBases(
-						makeMan(fbro, "fb_id1", "", path.EmailCategory),
-					).WithBackups(
-						makeBackup(fbro, "fb_id1", path.EmailCategory),
-					),
-				},
-			},
-			rp:              mockRestoreProducer{},
-			fallbackReasons: []identity.Reasoner{fbEmailReason},
-			getMeta:         false,
-			assertErr:       assert.NoError,
-			assertB:         assert.False,
-			expectDCS:       nil,
-			expectMans: kopia.NewMockBackupBases().WithAssistBases(
-				makeMan(fbro, "fb_id1", "", path.EmailCategory),
-			),
-		},
-		{
-			name: "only fallbacks",
-			bf: &mockBackupFinder{
-				data: map[string]kopia.BackupBases{
-					fbro: kopia.NewMockBackupBases().WithMergeBases(
-						makeMan(fbro, "fb_id1", "", path.EmailCategory),
-					).WithBackups(
-						makeBackup(fbro, "fb_id1", path.EmailCategory),
-					),
-				},
-			},
-			rp: mockRestoreProducer{
-				collsByID: map[string][]data.RestoreCollection{
-					"fb_id1": {data.NoFetchRestoreCollection{Collection: mockColl{id: "fb_id1"}}},
-				},
-			},
-			fallbackReasons: []identity.Reasoner{fbEmailReason},
-			getMeta:         true,
-			assertErr:       assert.NoError,
-			assertB:         assert.True,
-			expectDCS:       []mockColl{{id: "fb_id1"}},
-			expectMans: kopia.NewMockBackupBases().WithMergeBases(
-				makeMan(fbro, "fb_id1", "", path.EmailCategory),
-			).WithBackups(
-				makeBackup(fbro, "fb_id1", path.EmailCategory),
-			),
-		},
-		{
-			name: "only fallbacks, no assist",
-			bf: &mockBackupFinder{
-				data: map[string]kopia.BackupBases{
-					fbro: kopia.NewMockBackupBases().WithMergeBases(
-						makeMan(fbro, "fb_id1", "", path.EmailCategory),
-					).WithBackups(
-						makeBackup(fbro, "fb_id1", path.EmailCategory),
-					),
-				},
-			},
-			rp: mockRestoreProducer{
-				collsByID: map[string][]data.RestoreCollection{
-					"fb_id1": {data.NoFetchRestoreCollection{Collection: mockColl{id: "fb_id1"}}},
-				},
-			},
-			fallbackReasons: []identity.Reasoner{fbEmailReason},
-			getMeta:         true,
-			dropAssist:      true,
-			assertErr:       assert.NoError,
-			assertB:         assert.True,
-			expectDCS:       []mockColl{{id: "fb_id1"}},
-			expectMans: kopia.NewMockBackupBases().WithMergeBases(
-				makeMan(fbro, "fb_id1", "", path.EmailCategory),
-			).WithBackups(
-				makeBackup(fbro, "fb_id1", path.EmailCategory),
-			).
-				ClearMockAssistBases(),
-		},
-		{
-			name: "complete mans and fallbacks",
-			bf: &mockBackupFinder{
-				data: map[string]kopia.BackupBases{
-					ro: kopia.NewMockBackupBases().WithMergeBases(
-						makeMan(ro, "id1", "", path.EmailCategory),
-					),
-					fbro: kopia.NewMockBackupBases().WithMergeBases(
-						makeMan(fbro, "fb_id1", "", path.EmailCategory),
-					).WithBackups(
-						makeBackup(fbro, "fb_id1", path.EmailCategory),
-					),
-				},
-			},
-			rp: mockRestoreProducer{
-				collsByID: map[string][]data.RestoreCollection{
-					"id1":    {data.NoFetchRestoreCollection{Collection: mockColl{id: "id1"}}},
-					"fb_id1": {data.NoFetchRestoreCollection{Collection: mockColl{id: "fb_id1"}}},
-				},
-			},
-			reasons:         []identity.Reasoner{emailReason},
-			fallbackReasons: []identity.Reasoner{fbEmailReason},
-			getMeta:         true,
-			assertErr:       assert.NoError,
-			assertB:         assert.True,
-			expectDCS:       []mockColl{{id: "id1"}},
-			expectMans: kopia.NewMockBackupBases().WithMergeBases(
-				makeMan(ro, "id1", "", path.EmailCategory),
-			),
-		},
-		{
-			name: "incomplete mans and fallbacks",
-			bf: &mockBackupFinder{
-				data: map[string]kopia.BackupBases{
-					ro: kopia.NewMockBackupBases().WithAssistBases(
-						makeMan(ro, "id2", "checkpoint", path.EmailCategory),
-					),
-					fbro: kopia.NewMockBackupBases().WithAssistBases(
-						makeMan(fbro, "fb_id2", "checkpoint", path.EmailCategory),
-					),
-				},
-			},
-			rp: mockRestoreProducer{
-				collsByID: map[string][]data.RestoreCollection{
-					"id2":    {data.NoFetchRestoreCollection{Collection: mockColl{id: "id2"}}},
-					"fb_id2": {data.NoFetchRestoreCollection{Collection: mockColl{id: "fb_id2"}}},
-				},
-			},
-			reasons:         []identity.Reasoner{emailReason},
-			fallbackReasons: []identity.Reasoner{fbEmailReason},
-			getMeta:         true,
-			assertErr:       assert.NoError,
-			assertB:         assert.True,
-			expectDCS:       nil,
-			expectMans: kopia.NewMockBackupBases().WithAssistBases(
-				makeMan(ro, "id2", "checkpoint", path.EmailCategory),
-			),
-		},
-		{
-			name: "complete and incomplete mans and fallbacks",
-			bf: &mockBackupFinder{
-				data: map[string]kopia.BackupBases{
-					ro: kopia.NewMockBackupBases().WithMergeBases(
-						makeMan(ro, "id1", "", path.EmailCategory),
-					).WithAssistBases(
-						makeMan(ro, "id2", "checkpoint", path.EmailCategory),
-					),
-					fbro: kopia.NewMockBackupBases().WithMergeBases(
-						makeMan(fbro, "fb_id1", "", path.EmailCategory),
-					).WithBackups(
-						makeBackup(fbro, "fb_id1", path.EmailCategory),
-					).WithAssistBases(
-						makeMan(fbro, "fb_id2", "checkpoint", path.EmailCategory),
-					),
-				},
-			},
-			rp: mockRestoreProducer{
-				collsByID: map[string][]data.RestoreCollection{
-					"id1":    {data.NoFetchRestoreCollection{Collection: mockColl{id: "id1"}}},
-					"id2":    {data.NoFetchRestoreCollection{Collection: mockColl{id: "id2"}}},
-					"fb_id1": {data.NoFetchRestoreCollection{Collection: mockColl{id: "fb_id1"}}},
-					"fb_id2": {data.NoFetchRestoreCollection{Collection: mockColl{id: "fb_id2"}}},
-				},
-			},
-			reasons:         []identity.Reasoner{emailReason},
-			fallbackReasons: []identity.Reasoner{fbEmailReason},
-			getMeta:         true,
-			assertErr:       assert.NoError,
-			assertB:         assert.True,
-			expectDCS:       []mockColl{{id: "id1"}},
-			expectMans: kopia.NewMockBackupBases().WithMergeBases(
-				makeMan(ro, "id1", "", path.EmailCategory),
-			).WithAssistBases(
-				makeMan(ro, "id2", "checkpoint", path.EmailCategory),
-			),
-		},
-		{
-			name: "incomplete mans and complete fallbacks",
-			bf: &mockBackupFinder{
-				data: map[string]kopia.BackupBases{
-					ro: kopia.NewMockBackupBases().WithAssistBases(
-						makeMan(ro, "id2", "checkpoint", path.EmailCategory),
-					),
-					fbro: kopia.NewMockBackupBases().WithMergeBases(
-						makeMan(fbro, "fb_id1", "", path.EmailCategory),
-					).WithBackups(
-						makeBackup(fbro, "fb_id1", path.EmailCategory),
-					),
-				},
-			},
-			rp: mockRestoreProducer{
-				collsByID: map[string][]data.RestoreCollection{
-					"id2":    {data.NoFetchRestoreCollection{Collection: mockColl{id: "id2"}}},
-					"fb_id1": {data.NoFetchRestoreCollection{Collection: mockColl{id: "fb_id1"}}},
-				},
-			},
-			reasons:         []identity.Reasoner{emailReason},
-			fallbackReasons: []identity.Reasoner{fbEmailReason},
-			getMeta:         true,
-			assertErr:       assert.NoError,
-			assertB:         assert.True,
-			expectDCS:       []mockColl{{id: "fb_id1"}},
-			expectMans: kopia.NewMockBackupBases().WithMergeBases(
-				makeMan(fbro, "fb_id1", "", path.EmailCategory),
-			).WithBackups(
-				makeBackup(fbro, "fb_id1", path.EmailCategory),
-			).WithAssistBases(
-				makeMan(ro, "id2", "checkpoint", path.EmailCategory),
-			),
-		},
-		{
-			name: "incomplete mans and complete fallbacks, no assist bases",
-			bf: &mockBackupFinder{
-				data: map[string]kopia.BackupBases{
-					ro: kopia.NewMockBackupBases().WithAssistBases(
-						makeMan(ro, "id2", "checkpoint", path.EmailCategory),
-					),
-					fbro: kopia.NewMockBackupBases().WithMergeBases(
-						makeMan(fbro, "fb_id1", "", path.EmailCategory),
-					).WithBackups(
-						makeBackup(fbro, "fb_id1", path.EmailCategory),
-					),
-				},
-			},
-			rp: mockRestoreProducer{
-				collsByID: map[string][]data.RestoreCollection{
-					"id2":    {data.NoFetchRestoreCollection{Collection: mockColl{id: "id2"}}},
-					"fb_id1": {data.NoFetchRestoreCollection{Collection: mockColl{id: "fb_id1"}}},
-				},
-			},
-			reasons:         []identity.Reasoner{emailReason},
-			fallbackReasons: []identity.Reasoner{fbEmailReason},
-			getMeta:         true,
-			dropAssist:      true,
-			assertErr:       assert.NoError,
-			assertB:         assert.True,
-			expectDCS:       []mockColl{{id: "fb_id1"}},
-			expectMans: kopia.NewMockBackupBases().WithMergeBases(
-				makeMan(fbro, "fb_id1", "", path.EmailCategory),
-			).WithBackups(
-				makeBackup(fbro, "fb_id1", path.EmailCategory),
-			).
-				ClearMockAssistBases(),
-		},
-		{
-			name: "complete mans and incomplete fallbacks",
-			bf: &mockBackupFinder{
-				data: map[string]kopia.BackupBases{
-					ro: kopia.NewMockBackupBases().WithMergeBases(
-						makeMan(ro, "id1", "", path.EmailCategory),
-					),
-					fbro: kopia.NewMockBackupBases().WithAssistBases(
-						makeMan(fbro, "fb_id2", "checkpoint", path.EmailCategory),
-					),
-				},
-			},
-			rp: mockRestoreProducer{
-				collsByID: map[string][]data.RestoreCollection{
-					"id1":    {data.NoFetchRestoreCollection{Collection: mockColl{id: "id1"}}},
-					"fb_id2": {data.NoFetchRestoreCollection{Collection: mockColl{id: "fb_id2"}}},
-				},
-			},
-			reasons:         []identity.Reasoner{emailReason},
-			fallbackReasons: []identity.Reasoner{fbEmailReason},
-			getMeta:         true,
-			assertErr:       assert.NoError,
-			assertB:         assert.True,
-			expectDCS:       []mockColl{{id: "id1"}},
-			expectMans: kopia.NewMockBackupBases().WithMergeBases(
-				makeMan(ro, "id1", "", path.EmailCategory),
-			),
-		},
-		{
-			name: "complete mans and complete fallbacks, multiple reasons",
-			bf: &mockBackupFinder{
-				data: map[string]kopia.BackupBases{
-					ro: kopia.NewMockBackupBases().WithMergeBases(
-						makeMan(ro, "id1", "", path.EmailCategory, path.ContactsCategory),
-					),
-					fbro: kopia.NewMockBackupBases().WithMergeBases(
-						makeMan(fbro, "fb_id1", "", path.EmailCategory, path.ContactsCategory),
-					).WithBackups(
-						makeBackup(fbro, "fb_id1", path.EmailCategory, path.ContactsCategory),
-					),
-				},
-			},
-			rp: mockRestoreProducer{
-				collsByID: map[string][]data.RestoreCollection{
-					"id1":    {data.NoFetchRestoreCollection{Collection: mockColl{id: "id1"}}},
-					"fb_id1": {data.NoFetchRestoreCollection{Collection: mockColl{id: "fb_id1"}}},
-				},
-			},
-			reasons: []identity.Reasoner{
-				emailReason,
-				kopia.NewReason("", ro, path.ExchangeService, path.ContactsCategory),
-			},
-			fallbackReasons: []identity.Reasoner{
-				fbEmailReason,
-				kopia.NewReason("", fbro, path.ExchangeService, path.ContactsCategory),
-			},
-			getMeta:   true,
-			assertErr: assert.NoError,
-			assertB:   assert.True,
-			expectDCS: []mockColl{{id: "id1"}},
-			expectMans: kopia.NewMockBackupBases().WithMergeBases(
-				makeMan(ro, "id1", "", path.EmailCategory, path.ContactsCategory),
-			),
-		},
-		{
-			name: "complete mans and complete fallbacks, distinct reasons",
-			bf: &mockBackupFinder{
-				data: map[string]kopia.BackupBases{
-					ro: kopia.NewMockBackupBases().WithMergeBases(
-						makeMan(ro, "id1", "", path.EmailCategory),
-					),
-					fbro: kopia.NewMockBackupBases().WithMergeBases(
-						makeMan(fbro, "fb_id1", "", path.ContactsCategory),
-					).WithBackups(
-						makeBackup(fbro, "fb_id1", path.ContactsCategory),
-					),
-				},
-			},
-			rp: mockRestoreProducer{
-				collsByID: map[string][]data.RestoreCollection{
-					"id1":    {data.NoFetchRestoreCollection{Collection: mockColl{id: "id1"}}},
-					"fb_id1": {data.NoFetchRestoreCollection{Collection: mockColl{id: "fb_id1"}}},
-				},
-			},
-			reasons: []identity.Reasoner{emailReason},
-			fallbackReasons: []identity.Reasoner{
-				kopia.NewReason("", fbro, path.ExchangeService, path.ContactsCategory),
-			},
-			getMeta:   true,
-			assertErr: assert.NoError,
-			assertB:   assert.True,
-			expectDCS: []mockColl{{id: "id1"}, {id: "fb_id1"}},
-			expectMans: kopia.NewMockBackupBases().WithMergeBases(
-				makeMan(ro, "id1", "", path.EmailCategory),
-				makeMan(fbro, "fb_id1", "", path.ContactsCategory),
-			).WithBackups(
-				makeBackup(fbro, "fb_id1", path.ContactsCategory),
-			),
-		},
-		{
-			name: "complete mans and complete fallbacks, fallback has superset of reasons",
-			bf: &mockBackupFinder{
-				data: map[string]kopia.BackupBases{
-					ro: kopia.NewMockBackupBases().WithMergeBases(
-						makeMan(ro, "id1", "", path.EmailCategory),
-					),
-					fbro: kopia.NewMockBackupBases().WithMergeBases(
-						makeMan(fbro, "fb_id1", "", path.EmailCategory, path.ContactsCategory),
-					).WithBackups(
-						makeBackup(fbro, "fb_id1", path.EmailCategory, path.ContactsCategory),
-					),
-				},
-			},
-			rp: mockRestoreProducer{
-				collsByID: map[string][]data.RestoreCollection{
-					"id1":    {data.NoFetchRestoreCollection{Collection: mockColl{id: "id1"}}},
-					"fb_id1": {data.NoFetchRestoreCollection{Collection: mockColl{id: "fb_id1"}}},
-				},
-			},
-			reasons: []identity.Reasoner{
-				emailReason,
-				kopia.NewReason("", ro, path.ExchangeService, path.ContactsCategory),
-			},
-			fallbackReasons: []identity.Reasoner{
-				fbEmailReason,
-				kopia.NewReason("", fbro, path.ExchangeService, path.ContactsCategory),
-			},
-			getMeta:   true,
-			assertErr: assert.NoError,
-			assertB:   assert.True,
-			expectDCS: []mockColl{{id: "id1"}, {id: "fb_id1"}},
-			expectMans: kopia.NewMockBackupBases().WithMergeBases(
-				makeMan(ro, "id1", "", path.EmailCategory),
-				makeMan(fbro, "fb_id1", "", path.ContactsCategory),
-			).WithBackups(
-				makeBackup(fbro, "fb_id1", path.ContactsCategory),
-			),
-		},
-	}
-
-	for _, test := range table {
-		suite.Run(test.name, func() {
-			t := suite.T()
-
-			ctx, flush := tester.NewContext(t)
-			defer flush()
-
-			mans, dcs, b, err := produceManifestsAndMetadata(
-				ctx,
-				test.bf,
-				&test.rp,
-				test.reasons, test.fallbackReasons,
-				tid,
-				test.getMeta,
-				test.dropAssist)
-			test.assertErr(t, err, clues.ToCore(err))
-			test.assertB(t, b)
-
-			kopia.AssertBackupBasesEqual(t, test.expectMans, mans)
-
-			expect, got := []string{}, []string{}
-
-			for _, dc := range test.expectDCS {
-				expect = append(expect, dc.id)
-			}
-
-			for _, dc := range dcs {
-				if !assert.IsTypef(
-					t,
-					data.NoFetchRestoreCollection{},
-					dc,
-					"unexpected type returned [%T]",
-					dc,
-				) {
-					continue
-				}
-
-				tmp := dc.(data.NoFetchRestoreCollection)
-
-				if !assert.IsTypef(
-					t,
-					mockColl{},
-					tmp.Collection,
-					"unexpected type returned [%T]",
-					tmp.Collection,
-				) {
-					continue
-				}
-
-				mc := tmp.Collection.(mockColl)
-				got = append(got, mc.id)
-			}
-
-			assert.ElementsMatch(t, expect, got, "expected collections are present")
-		})
-	}
-}