diff --git a/changelog/29325.txt b/changelog/29325.txt
new file mode 100644
index 0000000000..5c213fea0a
--- /dev/null
+++ b/changelog/29325.txt
@@ -0,0 +1,4 @@
+```release-note:improvement
+identity: Added reporting in Vault logs during unseal to help identify any
+duplicate identify resources in storage.
+```
diff --git a/vault/identity_store_conflicts.go b/vault/identity_store_conflicts.go
index 8495af1a25..23cabcf10e 100644
--- a/vault/identity_store_conflicts.go
+++ b/vault/identity_store_conflicts.go
@@ -6,7 +6,11 @@ package vault
 import (
 	"context"
 	"errors"
+	"fmt"
+	"sort"
+	"strings"
 
+	"github.com/hashicorp/go-hclog"
 	log "github.com/hashicorp/go-hclog"
 	"github.com/hashicorp/vault/helper/identity"
 )
@@ -83,3 +87,277 @@ func (r *errorResolver) ResolveAliases(ctx context.Context, parent *identity.Ent
 
 	return errDuplicateIdentityName
 }
+
+// duplicateReportingErrorResolver collects duplicate information and optionally
+// logs a report on all the duplicates. We don't embed an errorResolver here
+// because we _don't_ want it's side effect of warning on just some duplicates
+// as we go as that's confusing when we have a more comprehensive report. The
+// only other behavior it has is to return a constant error which we can just do
+// ourselves.
+type duplicateReportingErrorResolver struct {
+	// seen* track the unique factors for each identity artifact, so
+	// that we can report on any duplication including different-case duplicates
+	// when in case-sensitive mode.
+	//
+	// Since this is only ever called from `load*` methods on IdentityStore during
+	// an unseal we can assume that it's all from a single goroutine and does'nt
+	// need locking.
+	seenEntities     map[string][]*identity.Entity
+	seenGroups       map[string][]*identity.Group
+	seenAliases      map[string][]*identity.Alias
+	seenLocalAliases map[string][]*identity.Alias
+	logger           hclog.Logger
+}
+
+func newDuplicateReportingErrorResolver(logger hclog.Logger) *duplicateReportingErrorResolver {
+	return &duplicateReportingErrorResolver{
+		seenEntities:     make(map[string][]*identity.Entity),
+		seenGroups:       make(map[string][]*identity.Group),
+		seenAliases:      make(map[string][]*identity.Alias),
+		seenLocalAliases: make(map[string][]*identity.Alias),
+		logger:           logger,
+	}
+}
+
+func (r *duplicateReportingErrorResolver) ResolveEntities(ctx context.Context, existing, duplicate *identity.Entity) error {
+	entityKey := fmt.Sprintf("%s/%s", duplicate.NamespaceID, strings.ToLower(duplicate.Name))
+	r.seenEntities[entityKey] = append(r.seenEntities[entityKey], duplicate)
+	return errDuplicateIdentityName
+}
+
+func (r *duplicateReportingErrorResolver) ResolveGroups(ctx context.Context, existing, duplicate *identity.Group) error {
+	groupKey := fmt.Sprintf("%s/%s", duplicate.NamespaceID, strings.ToLower(duplicate.Name))
+	r.seenGroups[groupKey] = append(r.seenGroups[groupKey], duplicate)
+	return errDuplicateIdentityName
+}
+
+func (r *duplicateReportingErrorResolver) ResolveAliases(ctx context.Context, parent *identity.Entity, existing, duplicate *identity.Alias) error {
+	aliasKey := fmt.Sprintf("%s/%s", duplicate.MountAccessor, strings.ToLower(duplicate.Name))
+	if duplicate.Local {
+		r.seenLocalAliases[aliasKey] = append(r.seenLocalAliases[aliasKey], duplicate)
+	} else {
+		r.seenAliases[aliasKey] = append(r.seenAliases[aliasKey], duplicate)
+	}
+	return errDuplicateIdentityName
+}
+
+type identityDuplicateReportEntry struct {
+	artifactType   string
+	scope          string
+	name           string
+	id             string
+	canonicalID    string
+	resolutionHint string
+	index          int // we care about preserving load order in reporting
+	numOthers      int
+}
+
+type identityDuplicateReport struct {
+	entities                []identityDuplicateReportEntry
+	groups                  []identityDuplicateReportEntry
+	aliases                 []identityDuplicateReportEntry
+	localAliases            []identityDuplicateReportEntry
+	numEntityDuplicates     int
+	numGroupDuplicates      int
+	numAliasDuplicates      int
+	numLocalAliasDuplicates int
+}
+
+func (r *identityDuplicateReportEntry) Description() string {
+	scopeField := "namespace ID"
+	if r.artifactType == "entity-alias" || r.artifactType == "local entity-alias" {
+		scopeField = "mount accessor"
+	}
+	return fmt.Sprintf("%s %q with %s %q duplicates %d others",
+		r.artifactType, r.name, scopeField, r.scope, r.numOthers)
+}
+
+// Labels returns metadata pairs suitable for passing to a logger each slice
+// element corresponds alternately to a key and then a value.
+func (r *identityDuplicateReportEntry) Labels() []interface{} {
+	args := []interface{}{"id", r.id}
+	if r.canonicalID != "" {
+		args = append(args, "canonical_id")
+		args = append(args, r.canonicalID)
+	}
+	if r.resolutionHint != "" {
+		args = append(args, "force_deduplication")
+		args = append(args, r.resolutionHint)
+	}
+	return args
+}
+
+func (r *duplicateReportingErrorResolver) Report() identityDuplicateReport {
+	var report identityDuplicateReport
+
+	for _, entities := range r.seenEntities {
+		if len(entities) <= 1 {
+			// Fast path, skip non-duplicates
+			continue
+		}
+		report.numEntityDuplicates++
+		// We don't care if it's an exact match or not for entities since we'll
+		// rename in either case when we force a de-dupe.
+		for idx, entity := range entities {
+			r := identityDuplicateReportEntry{
+				artifactType: "entity",
+				scope:        entity.NamespaceID,
+				name:         entity.Name,
+				id:           entity.ID,
+				index:        idx,
+				numOthers:    len(entities) - 1,
+			}
+			if idx < len(entities)-1 {
+				r.resolutionHint = fmt.Sprintf("would rename to %s-%s", entity.Name, entity.ID)
+			} else {
+				r.resolutionHint = "would not rename"
+			}
+			report.entities = append(report.entities, r)
+		}
+	}
+	sortReportEntries(report.entities)
+
+	for _, groups := range r.seenGroups {
+		if len(groups) <= 1 {
+			// Fast path, skip non-duplicates
+			continue
+		}
+		report.numGroupDuplicates++
+		// We don't care if it's an exact match or not for groups since we'll
+		// rename in either case when we force a de-dupe.
+		for idx, group := range groups {
+			r := identityDuplicateReportEntry{
+				artifactType: "group",
+				scope:        group.NamespaceID,
+				name:         group.Name,
+				id:           group.ID,
+				index:        idx,
+				numOthers:    len(groups) - 1,
+			}
+			if idx < len(groups)-1 {
+				r.resolutionHint = fmt.Sprintf("would rename to %s-%s", group.Name, group.ID)
+			} else {
+				r.resolutionHint = "would not rename"
+			}
+			report.groups = append(report.groups, r)
+		}
+	}
+	sortReportEntries(report.groups)
+
+	reportAliases(&report, r.seenAliases, false)
+	reportAliases(&report, r.seenLocalAliases, true)
+
+	return report
+}
+
+func reportAliases(report *identityDuplicateReport, seen map[string][]*identity.Alias, local bool) {
+	artType := "entity-alias"
+	if local {
+		artType = "local entity-alias"
+	}
+	for _, aliases := range seen {
+		if len(aliases) <= 1 {
+			// Fast path, skip non-duplicates
+			continue
+		}
+		if local {
+			report.numLocalAliasDuplicates++
+		} else {
+			report.numAliasDuplicates++
+		}
+		// We can't have exact match duplicated for aliases at this point because
+		// the would have been merged during load. These are different-case
+		// duplicates that must be handled.
+		for idx, alias := range aliases {
+			r := identityDuplicateReportEntry{
+				artifactType: artType,
+				scope:        alias.MountAccessor,
+				name:         alias.Name,
+				id:           alias.ID,
+				canonicalID:  alias.CanonicalID,
+				index:        idx,
+				numOthers:    len(aliases) - 1,
+			}
+			if idx < len(aliases)-1 {
+				r.resolutionHint = fmt.Sprintf("would merge into entity %s", aliases[len(aliases)-1].CanonicalID)
+			} else {
+				r.resolutionHint = "would merge others into this entity"
+			}
+			if local {
+				report.localAliases = append(report.localAliases, r)
+			} else {
+				report.aliases = append(report.aliases, r)
+			}
+		}
+	}
+	sortReportEntries(report.aliases)
+}
+
+func sortReportEntries(es []identityDuplicateReportEntry) {
+	sort.Slice(es, func(i, j int) bool {
+		a, b := es[i], es[j]
+		if a.scope != b.scope {
+			return a.scope < b.scope
+		}
+		aName, bName := strings.ToLower(a.name), strings.ToLower(b.name)
+		if aName != bName {
+			return aName < bName
+		}
+		return a.index < b.index
+	})
+}
+
+// Warner is a subset of hclog.Logger that only has the Warn method to make
+// testing simpler.
+type Warner interface {
+	Warn(msg string, args ...interface{})
+}
+
+// TODO set this correctly.
+const identityDuplicateReportUrl = "https://developer.hashicorp.com/vault/docs/upgrading/identity-deduplication"
+
+func (r *duplicateReportingErrorResolver) LogReport(log Warner) {
+	report := r.Report()
+
+	if report.numEntityDuplicates == 0 && report.numGroupDuplicates == 0 && report.numAliasDuplicates == 0 {
+		return
+	}
+
+	log.Warn("DUPLICATES DETECTED, see following logs for details and refer to " +
+		identityDuplicateReportUrl + " for resolution.")
+
+	// Aliases first since they are most critical to resolve. Local first because
+	// all the rest can be ignored on a perf secondary.
+	if len(report.localAliases) > 0 {
+		log.Warn(fmt.Sprintf("%d different-case local entity alias duplicates found (potential security risk)", report.numLocalAliasDuplicates))
+		for _, e := range report.localAliases {
+			log.Warn(e.Description(), e.Labels()...)
+		}
+		log.Warn("end of different-case local entity-alias duplicates")
+	}
+	if len(report.aliases) > 0 {
+		log.Warn(fmt.Sprintf("%d different-case entity alias duplicates found (potential security risk)", report.numAliasDuplicates))
+		for _, e := range report.aliases {
+			log.Warn(e.Description(), e.Labels()...)
+		}
+		log.Warn("end of different-case entity-alias duplicates")
+	}
+
+	if len(report.entities) > 0 {
+		log.Warn(fmt.Sprintf("%d entity duplicates found", report.numEntityDuplicates))
+		for _, e := range report.entities {
+			log.Warn(e.Description(), e.Labels()...)
+		}
+		log.Warn("end of entity duplicates")
+	}
+
+	if len(report.groups) > 0 {
+		log.Warn(fmt.Sprintf("%d group duplicates found", report.numGroupDuplicates))
+		for _, e := range report.groups {
+			log.Warn(e.Description(), e.Labels()...)
+		}
+		log.Warn("end of group duplicates")
+	}
+	log.Warn("end of identity duplicate report, refer to " +
+		identityDuplicateReportUrl + " for resolution.")
+}
diff --git a/vault/identity_store_conflicts_test.go b/vault/identity_store_conflicts_test.go
new file mode 100644
index 0000000000..ac757ec950
--- /dev/null
+++ b/vault/identity_store_conflicts_test.go
@@ -0,0 +1,180 @@
+// Copyright (c) HashiCorp, Inc.
+// SPDX-License-Identifier: BUSL-1.1
+
+package vault
+
+import (
+	"bytes"
+	"context"
+	"fmt"
+	"strings"
+	"testing"
+
+	log "github.com/hashicorp/go-hclog"
+	"github.com/hashicorp/vault/helper/identity"
+	"github.com/stretchr/testify/require"
+)
+
+// TestDuplicateReportingErrorResolver tests that the reporting error resolver
+// correctly records, identifies, sorts and outputs information about duplicate
+// entities.
+func TestDuplicateReportingErrorResolver(t *testing.T) {
+	t.Parallel()
+
+	entities := [][]string{
+		// Some unduplicated entities in a different namespaces
+		{"root", "foo"},
+		{"root", "bar"},
+		{"admin", "foo"},
+		{"developers", "BAR"},
+
+		// Some exact-match duplicates in different namespaces
+		{"root", "exact-dupe-1"},
+		{"root", "exact-dupe-1"},
+		{"admin", "exact-dupe-1"},
+		{"admin", "exact-dupe-1"},
+
+		// Some different-case duplicates in different namespaces
+		{"root", "different-case-dupe-1"},
+		{"root", "DIFFERENT-CASE-DUPE-1"},
+		{"admin", "different-case-dupe-1"},
+		{"admin", "DIFFERENT-case-DUPE-1"},
+		{"admin", "different-case-DUPE-1"},
+	}
+
+	// Note that `local-` prefix here is used to define a mount as local as well
+	// as used in it's name.
+	aliases := [][]string{
+		// Unduplicated aliases on different mounts
+		{"mount1", "alias1"},
+		{"mount2", "alias1"},
+		{"mount2", "alias2"},
+		{"local-mount", "alias1"},
+
+		// We don't bother testing exact-match aliases since they will have been
+		// merged by the time they are reported)
+
+		// Different-case aliases on different mounts (some local)
+		{"mount1", "different-case-alias-1"},
+		{"mount1", "DIFFERENT-CASE-ALIAS-1"},
+		{"mount2", "different-case-alias-1"},
+		{"mount2", "DIFFERENT-CASE-ALIAS-1"},
+		{"mount2", "different-CASE-ALIAS-1"},
+		{"local-mount", "DIFFERENT-CASE-ALIAS-1"},
+		{"local-mount", "different-CASE-ALIAS-1"},
+	}
+
+	expectReport := `
+DUPLICATES DETECTED, see following logs for details and refer to https://developer.hashicorp.com/vault/docs/upgrading/identity-deduplication for resolution.:
+1 different-case local entity alias duplicates found (potential security risk):
+local entity-alias "DIFFERENT-CASE-ALIAS-1" with mount accessor "local-mount" duplicates 1 others: id="00000000-0000-0000-0000-000000000009" canonical_id="11111111-0000-0000-0000-000000000009" force_deduplication="would merge into entity 11111111-0000-0000-0000-000000000010"
+local entity-alias "different-CASE-ALIAS-1" with mount accessor "local-mount" duplicates 1 others: id="00000000-0000-0000-0000-000000000010" canonical_id="11111111-0000-0000-0000-000000000010" force_deduplication="would merge others into this entity"
+end of different-case local entity-alias duplicates:
+2 different-case entity alias duplicates found (potential security risk):
+entity-alias "different-case-alias-1" with mount accessor "mount1" duplicates 1 others: id="00000000-0000-0000-0000-000000000004" canonical_id="11111111-0000-0000-0000-000000000004" force_deduplication="would merge into entity 11111111-0000-0000-0000-000000000005"
+entity-alias "DIFFERENT-CASE-ALIAS-1" with mount accessor "mount1" duplicates 1 others: id="00000000-0000-0000-0000-000000000005" canonical_id="11111111-0000-0000-0000-000000000005" force_deduplication="would merge others into this entity"
+entity-alias "different-case-alias-1" with mount accessor "mount2" duplicates 2 others: id="00000000-0000-0000-0000-000000000006" canonical_id="11111111-0000-0000-0000-000000000006" force_deduplication="would merge into entity 11111111-0000-0000-0000-000000000008"
+entity-alias "DIFFERENT-CASE-ALIAS-1" with mount accessor "mount2" duplicates 2 others: id="00000000-0000-0000-0000-000000000007" canonical_id="11111111-0000-0000-0000-000000000007" force_deduplication="would merge into entity 11111111-0000-0000-0000-000000000008"
+entity-alias "different-CASE-ALIAS-1" with mount accessor "mount2" duplicates 2 others: id="00000000-0000-0000-0000-000000000008" canonical_id="11111111-0000-0000-0000-000000000008" force_deduplication="would merge others into this entity"
+end of different-case entity-alias duplicates:
+4 entity duplicates found:
+entity "different-case-dupe-1" with namespace ID "admin" duplicates 2 others: id="00000000-0000-0000-0000-000000000010" force_deduplication="would rename to different-case-dupe-1-00000000-0000-0000-0000-000000000010"
+entity "DIFFERENT-case-DUPE-1" with namespace ID "admin" duplicates 2 others: id="00000000-0000-0000-0000-000000000011" force_deduplication="would rename to DIFFERENT-case-DUPE-1-00000000-0000-0000-0000-000000000011"
+entity "different-case-DUPE-1" with namespace ID "admin" duplicates 2 others: id="00000000-0000-0000-0000-000000000012" force_deduplication="would not rename"
+entity "exact-dupe-1" with namespace ID "admin" duplicates 1 others: id="00000000-0000-0000-0000-000000000006" force_deduplication="would rename to exact-dupe-1-00000000-0000-0000-0000-000000000006"
+entity "exact-dupe-1" with namespace ID "admin" duplicates 1 others: id="00000000-0000-0000-0000-000000000007" force_deduplication="would not rename"
+entity "different-case-dupe-1" with namespace ID "root" duplicates 1 others: id="00000000-0000-0000-0000-000000000008" force_deduplication="would rename to different-case-dupe-1-00000000-0000-0000-0000-000000000008"
+entity "DIFFERENT-CASE-DUPE-1" with namespace ID "root" duplicates 1 others: id="00000000-0000-0000-0000-000000000009" force_deduplication="would not rename"
+entity "exact-dupe-1" with namespace ID "root" duplicates 1 others: id="00000000-0000-0000-0000-000000000004" force_deduplication="would rename to exact-dupe-1-00000000-0000-0000-0000-000000000004"
+entity "exact-dupe-1" with namespace ID "root" duplicates 1 others: id="00000000-0000-0000-0000-000000000005" force_deduplication="would not rename"
+end of entity duplicates:
+4 group duplicates found:
+group "different-case-dupe-1" with namespace ID "admin" duplicates 2 others: id="00000000-0000-0000-0000-000000000010" force_deduplication="would rename to different-case-dupe-1-00000000-0000-0000-0000-000000000010"
+group "DIFFERENT-case-DUPE-1" with namespace ID "admin" duplicates 2 others: id="00000000-0000-0000-0000-000000000011" force_deduplication="would rename to DIFFERENT-case-DUPE-1-00000000-0000-0000-0000-000000000011"
+group "different-case-DUPE-1" with namespace ID "admin" duplicates 2 others: id="00000000-0000-0000-0000-000000000012" force_deduplication="would not rename"
+group "exact-dupe-1" with namespace ID "admin" duplicates 1 others: id="00000000-0000-0000-0000-000000000006" force_deduplication="would rename to exact-dupe-1-00000000-0000-0000-0000-000000000006"
+group "exact-dupe-1" with namespace ID "admin" duplicates 1 others: id="00000000-0000-0000-0000-000000000007" force_deduplication="would not rename"
+group "different-case-dupe-1" with namespace ID "root" duplicates 1 others: id="00000000-0000-0000-0000-000000000008" force_deduplication="would rename to different-case-dupe-1-00000000-0000-0000-0000-000000000008"
+group "DIFFERENT-CASE-DUPE-1" with namespace ID "root" duplicates 1 others: id="00000000-0000-0000-0000-000000000009" force_deduplication="would not rename"
+group "exact-dupe-1" with namespace ID "root" duplicates 1 others: id="00000000-0000-0000-0000-000000000004" force_deduplication="would rename to exact-dupe-1-00000000-0000-0000-0000-000000000004"
+group "exact-dupe-1" with namespace ID "root" duplicates 1 others: id="00000000-0000-0000-0000-000000000005" force_deduplication="would not rename"
+end of group duplicates:
+end of identity duplicate report, refer to https://developer.hashicorp.com/vault/docs/upgrading/identity-deduplication for resolution.:
+`
+
+	// Create a new errorResolver
+	r := newDuplicateReportingErrorResolver(log.NewNullLogger())
+
+	for i, pair := range entities {
+		// Create a fake UUID based on the index this makes sure sort order is
+		// preserved when eyeballing the expected report.
+		id := fmt.Sprintf("00000000-0000-0000-0000-%012d", i)
+		// Create a new entity with the pair
+		entity := &identity.Entity{
+			ID:          id,
+			Name:        pair[1],
+			NamespaceID: pair[0],
+		}
+
+		// Call ResolveEntities, assume existing is nil for now. In real life we
+		// should be passed the existing entity for the exact match dupes but we
+		// don't depend on that so it's fine to omit.
+		_ = r.ResolveEntities(context.Background(), nil, entity)
+		// Don't care about the actual error here since it would be ignored in
+		// case-sensitive mode anyway.
+
+		// Also, since the data model is the same, pretend these are groups too
+		group := &identity.Group{
+			ID:          id,
+			Name:        pair[1],
+			NamespaceID: pair[0],
+		}
+		_ = r.ResolveGroups(context.Background(), nil, group)
+	}
+
+	// Load aliases second because that is realistic and yet we want to report on
+	// them first.
+	for i, pair := range aliases {
+		entity := &identity.Entity{
+			ID:          fmt.Sprintf("11111111-0000-0000-0000-%012d", i),
+			Name:        pair[1] + "-entity",
+			NamespaceID: "root",
+		}
+		alias := &identity.Alias{
+			ID:            fmt.Sprintf("00000000-0000-0000-0000-%012d", i),
+			CanonicalID:   entity.ID,
+			Name:          pair[1],
+			MountAccessor: pair[0],
+			// Parse our hacky DSL to define some alias mounts as local
+			Local: strings.HasPrefix(pair[0], "local-"),
+		}
+		_ = r.ResolveAliases(context.Background(), entity, nil, alias)
+	}
+
+	// "log" the report and check it matches expected report below.
+	var testLog identityTestWarnLogger
+	r.LogReport(&testLog)
+
+	// Dump the raw report to make it easier to copy paste/read
+	t.Log("\n\n" + testLog.buf.String())
+
+	require.Equal(t,
+		strings.TrimSpace(expectReport),
+		strings.TrimSpace(testLog.buf.String()),
+	)
+}
+
+type identityTestWarnLogger struct {
+	buf bytes.Buffer
+}
+
+func (l *identityTestWarnLogger) Warn(msg string, args ...interface{}) {
+	l.buf.WriteString(msg + ":")
+	if len(args)%2 != 0 {
+		panic("args must be key-value pairs")
+	}
+	for i := 0; i < len(args); i += 2 {
+		l.buf.WriteString(fmt.Sprintf(" %s=%q", args[i], args[i+1]))
+	}
+	l.buf.WriteString("\n")
+}
diff --git a/vault/identity_store_test.go b/vault/identity_store_test.go
index cce4da413c..7ad41261ed 100644
--- a/vault/identity_store_test.go
+++ b/vault/identity_store_test.go
@@ -7,12 +7,16 @@ import (
 	"context"
 	"fmt"
 	"math/rand"
+	"regexp"
+	"slices"
+	"strconv"
 	"strings"
 	"testing"
 	"time"
 
 	"github.com/armon/go-metrics"
 	"github.com/go-test/deep"
+	"github.com/hashicorp/go-hclog"
 	uuid "github.com/hashicorp/go-uuid"
 	credGithub "github.com/hashicorp/vault/builtin/credential/github"
 	"github.com/hashicorp/vault/builtin/credential/userpass"
@@ -1457,10 +1461,10 @@ func TestEntityStoreLoadingIsDeterministic(t *testing.T) {
 	// probability that is unrealistic but ensures we have duplicates on every
 	// test run with high probability and more than 1 duplicate often.
 	for i := 0; i <= 100; i++ {
-		id := fmt.Sprintf("entity-%d", i)
+		name := fmt.Sprintf("entity-%d", i)
 		alias := fmt.Sprintf("alias-%d", i)
 		localAlias := fmt.Sprintf("localalias-%d", i)
-		e := makeEntityForPacker(t, id, c.identityStore.entityPacker)
+		e := makeEntityForPacker(t, name, c.identityStore.entityPacker)
 		attachAlias(t, e, alias, upme)
 		attachAlias(t, e, localAlias, localMe)
 		err = TestHelperWriteToStoragePacker(ctx, c.identityStore.entityPacker, e.ID, e)
@@ -1493,6 +1497,14 @@ func TestEntityStoreLoadingIsDeterministic(t *testing.T) {
 			rnd = rand.Float64()
 			dupeNum++
 		}
+		// See if we should add entity _name_ duplicates too (with no aliases)
+		rnd = rand.Float64()
+		for rnd < pDup {
+			e := makeEntityForPacker(t, name, c.identityStore.entityPacker)
+			err = TestHelperWriteToStoragePacker(ctx, c.identityStore.entityPacker, e.ID, e)
+			require.NoError(t, err)
+			rnd = rand.Float64()
+		}
 		// One more edge case is that it's currently possible as of the time of
 		// writing for a failure during entity invalidation to result in a permanent
 		// "cached" entity in the local alias packer even though we do have the
@@ -1511,23 +1523,27 @@ func TestEntityStoreLoadingIsDeterministic(t *testing.T) {
 
 	// Create some groups
 	for i := 0; i <= 100; i++ {
-		id := fmt.Sprintf("group-%d", i)
-		bucketKey := c.identityStore.groupPacker.BucketKey(id)
+		name := fmt.Sprintf("group-%d", i)
 		// Add an alias to every other group
 		alias := ""
 		if i%2 == 0 {
 			alias = fmt.Sprintf("groupalias-%d", i)
 		}
-		e := makeGroupWithIDAndAlias(t, id, alias, bucketKey, upme)
+		e := makeGroupWithNameAndAlias(t, name, alias, c.identityStore.groupPacker, upme)
 		err = TestHelperWriteToStoragePacker(ctx, c.identityStore.groupPacker, e.ID, e)
 		require.NoError(t, err)
 	}
 	// Now add 10 groups with the same alias to ensure duplicates don't cause
 	// non-deterministic behavior.
 	for i := 0; i <= 10; i++ {
-		id := fmt.Sprintf("group-dup-%d", i)
-		bucketKey := c.identityStore.groupPacker.BucketKey(id)
-		e := makeGroupWithIDAndAlias(t, id, "groupalias-dup", bucketKey, upme)
+		name := fmt.Sprintf("group-dup-%d", i)
+		e := makeGroupWithNameAndAlias(t, name, "groupalias-dup", c.identityStore.groupPacker, upme)
+		err = TestHelperWriteToStoragePacker(ctx, c.identityStore.groupPacker, e.ID, e)
+		require.NoError(t, err)
+	}
+	// Add a second and third groups with duplicate names too.
+	for _, name := range []string{"group-0", "group-1", "group-1"} {
+		e := makeGroupWithNameAndAlias(t, name, "", c.identityStore.groupPacker, upme)
 		err = TestHelperWriteToStoragePacker(ctx, c.identityStore.groupPacker, e.ID, e)
 		require.NoError(t, err)
 	}
@@ -1539,14 +1555,14 @@ func TestEntityStoreLoadingIsDeterministic(t *testing.T) {
 	// To test that this is deterministic we need to load from storage a bunch of
 	// times and make sure we get the same result. For easier debugging we'll
 	// build a list of human readable ids that we can compare.
-	lastIDs := []string{}
+	prevLoadedNames := []string{}
 	for i := 0; i < 10; i++ {
 		// Seal and unseal to reload the identity store
 		require.NoError(t, c.Seal(rootToken))
 		require.True(t, c.Sealed())
 		for _, key := range sealKeys {
 			unsealed, err := c.Unseal(key)
-			require.NoError(t, err)
+			require.NoError(t, err, "failed unseal on attempt %d", i)
 			if unsealed {
 				break
 			}
@@ -1554,7 +1570,7 @@ func TestEntityStoreLoadingIsDeterministic(t *testing.T) {
 		require.False(t, c.Sealed())
 
 		// Identity store should be loaded now. Check it's contents.
-		loadedIDs := []string{}
+		loadedNames := []string{}
 
 		tx := c.identityStore.db.Txn(false)
 
@@ -1562,73 +1578,143 @@ func TestEntityStoreLoadingIsDeterministic(t *testing.T) {
 		iter, err := tx.LowerBound(entitiesTable, "id", "")
 		require.NoError(t, err)
 		for item := iter.Next(); item != nil; item = iter.Next() {
-			// We already added "type" prefixes to the IDs when creating them so just
-			// append here.
 			e := item.(*identity.Entity)
-			loadedIDs = append(loadedIDs, e.ID)
+			loadedNames = append(loadedNames, e.Name)
 			for _, a := range e.Aliases {
-				loadedIDs = append(loadedIDs, a.ID)
+				loadedNames = append(loadedNames, a.Name)
 			}
 		}
 		// This is a non-triviality check to make sure we actually loaded stuff and
 		// are not just passing because of a bug in the test.
-		numLoaded := len(loadedIDs)
+		numLoaded := len(loadedNames)
 		require.Greater(t, numLoaded, 300, "not enough entities and aliases loaded on attempt %d", i)
 
+		// Standalone alias query
+		iter, err = tx.LowerBound(entityAliasesTable, "id", "")
+		require.NoError(t, err)
+		for item := iter.Next(); item != nil; item = iter.Next() {
+			a := item.(*identity.Alias)
+			loadedNames = append(loadedNames, a.Name)
+		}
+
 		// Groups
 		iter, err = tx.LowerBound(groupsTable, "id", "")
 		require.NoError(t, err)
 		for item := iter.Next(); item != nil; item = iter.Next() {
 			g := item.(*identity.Group)
-			loadedIDs = append(loadedIDs, g.ID)
+			loadedNames = append(loadedNames, g.Name)
 			if g.Alias != nil {
-				loadedIDs = append(loadedIDs, g.Alias.ID)
+				loadedNames = append(loadedNames, g.Alias.Name)
 			}
 		}
 		// This is a non-triviality check to make sure we actually loaded stuff and
 		// are not just passing because of a bug in the test.
-		groupsLoaded := len(loadedIDs) - numLoaded
+		groupsLoaded := len(loadedNames) - numLoaded
 		require.Greater(t, groupsLoaded, 140, "not enough groups and aliases loaded on attempt %d", i)
 
-		entIdentityStoreDeterminismAssert(t, i, loadedIDs, lastIDs)
+		// note `lastIDs` argument is not needed any more but we can't change the
+		// signature without breaking enterprise. It's simpler to keep it unused for
+		// now until both parts of this merge.
+		entIdentityStoreDeterminismAssert(t, i, loadedNames, nil)
 
 		if i > 0 {
 			// Should be in the same order if we are deterministic since MemDB has strong ordering.
-			require.Equal(t, lastIDs, loadedIDs, "different result on attempt %d", i)
+			require.Equal(t, prevLoadedNames, loadedNames, "different result on attempt %d", i)
 		}
-		lastIDs = loadedIDs
+
+		prevLoadedNames = loadedNames
 	}
 }
 
-func makeGroupWithIDAndAlias(t *testing.T, id, alias, bucketKey string, me *MountEntry) *identity.Group {
-	g := &identity.Group{
-		ID:          id,
-		Name:        id,
-		NamespaceID: namespace.RootNamespaceID,
-		BucketKey:   bucketKey,
-	}
-	if alias != "" {
-		g.Alias = &identity.Alias{
-			ID:            id,
-			Name:          alias,
-			CanonicalID:   id,
-			MountType:     me.Type,
-			MountAccessor: me.Accessor,
-		}
-	}
-	return g
-}
+// TestEntityStoreLoadingDuplicateReporting tests the reporting of different
+// types of duplicates during unseal when in case-sensitive mode.
+func TestEntityStoreLoadingDuplicateReporting(t *testing.T) {
+	logger := corehelpers.NewTestLogger(t)
+	ims, err := inmem.NewTransactionalInmemHA(nil, logger)
+	require.NoError(t, err)
 
-func makeLocalAliasWithID(t *testing.T, id, entityID string, bucketKey string, me *MountEntry) *identity.LocalAliases {
-	return &identity.LocalAliases{
-		Aliases: []*identity.Alias{
-			{
-				ID:            id,
-				Name:          id,
-				CanonicalID:   entityID,
-				MountType:     me.Type,
-				MountAccessor: me.Accessor,
-			},
+	cfg := &CoreConfig{
+		Physical:        ims,
+		HAPhysical:      ims.(physical.HABackend),
+		Logger:          logger,
+		BuiltinRegistry: corehelpers.NewMockBuiltinRegistry(),
+		CredentialBackends: map[string]logical.Factory{
+			"userpass": userpass.Factory,
 		},
 	}
+
+	c, sealKeys, rootToken := TestCoreUnsealedWithConfig(t, cfg)
+
+	// Inject values into storage
+	upme, err := TestUserpassMount(c, false)
+	require.NoError(t, err)
+	localMe, err := TestUserpassMount(c, true)
+	require.NoError(t, err)
+
+	ctx := namespace.RootContext(nil)
+
+	identityCreateCaseDuplicates(t, ctx, c, upme, localMe)
+
+	entIdentityStoreDuplicateReportTestSetup(t, ctx, c, rootToken)
+
+	// Storage is now primed for the test.
+
+	// Seal and unseal to reload the identity store
+	require.NoError(t, c.Seal(rootToken))
+	require.True(t, c.Sealed())
+
+	// Setup a logger we can use to capture unseal logs
+	var unsealLogs []string
+	unsealLogger := &logFn{
+		fn: func(msg string, args []interface{}) {
+			pairs := make([]string, 0, len(args)/2)
+			for pair := range slices.Chunk(args, 2) {
+				// Yes this will panic if we didn't log an even number of args but thats
+				// OK because that's a bug!
+				pairs = append(pairs, fmt.Sprintf("%s=%s", pair[0], pair[1]))
+			}
+			unsealLogs = append(unsealLogs, fmt.Sprintf("%s: %s", msg, strings.Join(pairs, " ")))
+		},
+	}
+	logger.RegisterSink(unsealLogger)
+
+	for _, key := range sealKeys {
+		unsealed, err := c.Unseal(key)
+		require.NoError(t, err)
+		if unsealed {
+			break
+		}
+	}
+	require.False(t, c.Sealed())
+	logger.DeregisterSink(unsealLogger)
+
+	// Identity store should be loaded now. Check it's contents.
+
+	// We don't expect any actual behavior change just logs reporting duplicates.
+	// We could assert the current "expected" behavior but it's actually broken in
+	// many of these cases and seems strange to encode in a test that we want
+	// broken behavior!
+	numDupes := make(map[string]int)
+	duplicateCountRe := regexp.MustCompile(`(\d+) (different-case( local)? entity alias|entity|group) duplicates found`)
+	for _, log := range unsealLogs {
+		if matches := duplicateCountRe.FindStringSubmatch(log); len(matches) >= 3 {
+			num, _ := strconv.Atoi(matches[1])
+			numDupes[matches[2]] = num
+		}
+	}
+	t.Logf("numDupes: %v", numDupes)
+	wantAliases, wantLocalAliases, wantEntities, wantGroups := identityStoreDuplicateReportTestWantDuplicateCounts()
+	require.Equal(t, wantLocalAliases, numDupes["different-case local entity alias"])
+	require.Equal(t, wantAliases, numDupes["different-case entity alias"])
+	require.Equal(t, wantEntities, numDupes["entity"])
+	require.Equal(t, wantGroups, numDupes["group"])
+}
+
+type logFn struct {
+	fn func(msg string, args []interface{})
+}
+
+// Accept implements hclog.SinkAdapter
+func (f *logFn) Accept(name string, level hclog.Level, msg string, args ...interface{}) {
+	f.fn(msg, args)
 }
diff --git a/vault/identity_store_test_stubs_oss.go b/vault/identity_store_test_stubs_oss.go
index e3a5703885..821b62428c 100644
--- a/vault/identity_store_test_stubs_oss.go
+++ b/vault/identity_store_test_stubs_oss.go
@@ -12,10 +12,25 @@ import (
 
 //go:generate go run github.com/hashicorp/vault/tools/stubmaker
 
-func entIdentityStoreDeterminismTestSetup(t *testing.T, ctx context.Context, c *Core, upme, localme *MountEntry) {
+func entIdentityStoreDeterminismTestSetup(t *testing.T, ctx context.Context, c *Core, me, localme *MountEntry) {
 	// no op
 }
 
 func entIdentityStoreDeterminismAssert(t *testing.T, i int, loadedIDs, lastIDs []string) {
 	// no op
 }
+
+func entIdentityStoreDuplicateReportTestSetup(t *testing.T, ctx context.Context, c *Core, rootToken string) {
+	// no op
+}
+
+func identityStoreDuplicateReportTestWantDuplicateCounts() (int, int, int, int) {
+	// Note that the second count is for local aliases. CE Vault doesn't really
+	// distinguish between local and non-local aliases because it doesn't have any
+	// support for Performance Replication. But it's possible in code at least to
+	// set the local flag on a mount or alias during creation so we might as well
+	// test it behaves as expected in the CE code. It's maybe just about possible
+	// that this could happen in real life too because of a downgrade from
+	// Enterprise.
+	return 1, 1, 1, 1
+}
diff --git a/vault/identity_store_util.go b/vault/identity_store_util.go
index 845b0672d1..602f34016e 100644
--- a/vault/identity_store_util.go
+++ b/vault/identity_store_util.go
@@ -23,6 +23,7 @@ import (
 	"github.com/hashicorp/vault/helper/storagepacker"
 	"github.com/hashicorp/vault/sdk/helper/consts"
 	"github.com/hashicorp/vault/sdk/logical"
+	"github.com/stretchr/testify/require"
 	"google.golang.org/protobuf/types/known/anypb"
 	"google.golang.org/protobuf/types/known/timestamppb"
 )
@@ -83,9 +84,19 @@ func (c *Core) loadIdentityStoreArtifacts(ctx context.Context) error {
 		return err
 	}
 
+	// Also reset the conflict resolver so that we report potential duplicates to
+	// be resolved before it's safe to return to case-insensitive mode.
+	reporterResolver := newDuplicateReportingErrorResolver(c.identityStore.logger)
+	c.identityStore.conflictResolver = reporterResolver
+
 	// Attempt to load identity artifacts once more after memdb is reset to
 	// accept case sensitive names
-	return loadFunc(ctx)
+	err = loadFunc(ctx)
+
+	// Log reported duplicates if any found whether or not we end up erroring.
+	reporterResolver.LogReport(c.identityStore.logger)
+
+	return err
 }
 
 func (i *IdentityStore) sanitizeName(name string) string {
@@ -623,8 +634,8 @@ func (i *IdentityStore) upsertEntityInTxn(ctx context.Context, txn *memdb.Txn, e
 		default:
 			// Though this is technically a conflict that should be resolved by the
 			// ConflictResolver implementation, the behavior here is a bit nuanced.
-			// Rather than introduce a behavior change, handle this case directly as
-			// before by merging.
+			// Rather than introduce a behavior change, we handle this case directly
+			// as before by merging.
 			i.logger.Warn("alias is already tied to a different entity; these entities are being merged",
 				"alias_id", alias.ID,
 				"other_entity_id", aliasByFactors.CanonicalID,
@@ -644,10 +655,34 @@ func (i *IdentityStore) upsertEntityInTxn(ctx context.Context, txn *memdb.Txn, e
 			return nil
 		}
 
-		if strutil.StrListContains(aliasFactors, i.sanitizeName(alias.Name)+alias.MountAccessor) {
-			if err := i.conflictResolver.ResolveAliases(ctx, entity, aliasByFactors, alias); err != nil && !i.disableLowerCasedNames {
-				return err
-			}
+		// This is subtle. We want to call `ResolveAliases` so that the resolver can
+		// get full insight into all the aliases loaded and generate useful reports
+		// about duplicates. However, we don't want to actually change the error
+		// handling behavior from before which would only return an error in a very
+		// specific case (when the alias being added is a duplicate of one for the
+		// same entity and we are not in case-sensitive mode). So we call the method
+		// here unconditionally, but then only handle the resultant error in the
+		// specific case we care about. Note that we choose not to call it `err` to
+		// avoid it being left non-nil in some cases and tripping up later error
+		// handling code, and to signal something different is happening here. Note
+		// that we explicitly _want_ this to be here an not before we merge
+		// duplicates above, because duplicates that have always merged are not a
+		// problem to the user and are already logged. We care about different-case
+		// duplicates that are not being considered duplicates right now because we
+		// are in case-sensitive mode so we can report these to the operator ahead
+		// of them disabling case-sensitive mode.
+		conflictErr := i.conflictResolver.ResolveAliases(ctx, entity, aliasByFactors, alias)
+
+		// This appears to be accounting for any duplicate aliases for the same
+		// Entity. In that case we would have skipped over the merge above in the
+		// `aliasByFactors.CanonicalID == entity.ID` case and made it here. Now we
+		// are here, duplicates are reported and may cause an insert error but only
+		// if we are in default case-insensitive mode. Once we are in case-sensitive
+		// mode we'll happily ignore duplicates of any case! This doesn't seem
+		// especially desirable to me, but we'd rather not change behavior for now.
+		if strutil.StrListContains(aliasFactors, i.sanitizeName(alias.Name)+alias.MountAccessor) &&
+			conflictErr != nil && !i.disableLowerCasedNames {
+			return conflictErr
 		}
 
 		// Insert or update alias in MemDB using the transaction created above
@@ -2636,24 +2671,113 @@ func (i *IdentityStore) countEntitiesByMountAccessor(ctx context.Context) (map[s
 	return byMountAccessor, nil
 }
 
-func makeEntityForPacker(_t *testing.T, id string, p *storagepacker.StoragePacker) *identity.Entity {
+func makeEntityForPacker(t *testing.T, name string, p *storagepacker.StoragePacker) *identity.Entity {
+	t.Helper()
+	return makeEntityForPackerWithNamespace(t, namespace.RootNamespaceID, name, p)
+}
+
+func makeEntityForPackerWithNamespace(t *testing.T, namespaceID, name string, p *storagepacker.StoragePacker) *identity.Entity {
+	t.Helper()
+	id, err := uuid.GenerateUUID()
+	require.NoError(t, err)
 	return &identity.Entity{
 		ID:          id,
-		Name:        id,
-		NamespaceID: namespace.RootNamespaceID,
+		Name:        name,
+		NamespaceID: namespaceID,
 		BucketKey:   p.BucketKey(id),
 	}
 }
 
 func attachAlias(t *testing.T, e *identity.Entity, name string, me *MountEntry) *identity.Alias {
 	t.Helper()
+	id, err := uuid.GenerateUUID()
+	require.NoError(t, err)
+	if e.NamespaceID != me.NamespaceID {
+		panic("mount and entity in different namespaces")
+	}
 	a := &identity.Alias{
-		ID:            name,
+		ID:            id,
 		Name:          name,
+		NamespaceID:   me.NamespaceID,
 		CanonicalID:   e.ID,
 		MountType:     me.Type,
 		MountAccessor: me.Accessor,
+		Local:         me.Local,
 	}
 	e.UpsertAlias(a)
 	return a
 }
+
+func identityCreateCaseDuplicates(t *testing.T, ctx context.Context, c *Core, upme, localme *MountEntry) {
+	t.Helper()
+
+	if upme.NamespaceID != localme.NamespaceID {
+		panic("both replicated and local auth mounts must be in the same namespace")
+	}
+
+	// Create entities with both case-sensitive and case-insensitive duplicate
+	// suffixes.
+	for i, suffix := range []string{"-case", "-case", "-cAsE"} {
+		// Entity duplicated by name
+		e := makeEntityForPackerWithNamespace(t, upme.NamespaceID, "entity"+suffix, c.identityStore.entityPacker)
+		err := TestHelperWriteToStoragePacker(ctx, c.identityStore.entityPacker, e.ID, e)
+		require.NoError(t, err)
+
+		// Entity that isn't a dupe itself but has duplicated aliases
+		e2 := makeEntityForPackerWithNamespace(t, upme.NamespaceID, fmt.Sprintf("entity-%d", i), c.identityStore.entityPacker)
+		// Add local and non-local aliases for this entity (which will also be
+		// duplicated)
+		attachAlias(t, e2, "alias"+suffix, upme)
+		attachAlias(t, e2, "local-alias"+suffix, localme)
+		err = TestHelperWriteToStoragePacker(ctx, c.identityStore.entityPacker, e2.ID, e2)
+		require.NoError(t, err)
+
+		// Group duplicated by name
+		g := makeGroupWithNameAndAlias(t, "group"+suffix, "", c.identityStore.groupPacker, upme)
+		err = TestHelperWriteToStoragePacker(ctx, c.identityStore.groupPacker, g.ID, g)
+		require.NoError(t, err)
+	}
+}
+
+func makeGroupWithNameAndAlias(t *testing.T, name, alias string, p *storagepacker.StoragePacker, me *MountEntry) *identity.Group {
+	t.Helper()
+	id, err := uuid.GenerateUUID()
+	require.NoError(t, err)
+	id2, err := uuid.GenerateUUID()
+	require.NoError(t, err)
+	g := &identity.Group{
+		ID:          id,
+		Name:        name,
+		NamespaceID: me.NamespaceID,
+		BucketKey:   p.BucketKey(id),
+	}
+	if alias != "" {
+		g.Alias = &identity.Alias{
+			ID:            id2,
+			Name:          alias,
+			CanonicalID:   id,
+			MountType:     me.Type,
+			MountAccessor: me.Accessor,
+			NamespaceID:   me.NamespaceID,
+		}
+	}
+	return g
+}
+
+func makeLocalAliasWithName(t *testing.T, name, entityID string, bucketKey string, me *MountEntry) *identity.LocalAliases {
+	t.Helper()
+	id, err := uuid.GenerateUUID()
+	require.NoError(t, err)
+	return &identity.LocalAliases{
+		Aliases: []*identity.Alias{
+			{
+				ID:            id,
+				Name:          name,
+				CanonicalID:   entityID,
+				MountType:     me.Type,
+				MountAccessor: me.Accessor,
+				NamespaceID:   me.NamespaceID,
+			},
+		},
+	}
+}
diff --git a/vault/testing.go b/vault/testing.go
index bd5c6d0fca..30575029cc 100644
--- a/vault/testing.go
+++ b/vault/testing.go
@@ -2225,6 +2225,10 @@ var (
 )
 
 func TestUserpassMount(c *Core, local bool) (*MountEntry, error) {
+	return TestUserpassMountContext(namespace.RootContext(nil), c, local)
+}
+
+func TestUserpassMountContext(ctx context.Context, c *Core, local bool) (*MountEntry, error) {
 	name := "userpass"
 	if local {
 		name += "-local"
@@ -2234,10 +2238,12 @@ func TestUserpassMount(c *Core, local bool) (*MountEntry, error) {
 		Path:        name + "/",
 		Type:        "userpass",
 		Description: name,
-		Accessor:    name,
-		Local:       local,
+		// Don't specify an accessor so we use a random one otherwise we will cause
+		// horrible issues when we try to create a new mount on a different
+		// namespace but they have the same accessor!
+		Local: local,
 	}
-	if err := c.enableCredential(namespace.RootContext(nil), userpassMe); err != nil {
+	if err := c.enableCredential(ctx, userpassMe); err != nil {
 		return nil, err
 	}
 	return userpassMe, nil