diff --git a/api/dataservices/source/access_rules.go b/api/dataservices/source/access_rules.go
index e2f29f3d7a..d36a186006 100644
--- a/api/dataservices/source/access_rules.go
+++ b/api/dataservices/source/access_rules.go
@@ -76,17 +76,14 @@ func userCanReadSource(source *portainer.Source, context UserContext) bool {
 		return true
 	}
 
-	// An explicit user grant wins over AdministratorsOnly: sanitizeAccesses clears
-	// UserAccesses whenever an admin marks a source admins-only, so an entry here
-	// can only come from the deliberate auto-grant in FindOrCreateGitSource.
-	if slices.Contains(source.UserAccesses, context.ID()) {
-		return true
-	}
-
 	if source.AdministratorsOnly {
 		return false
 	}
 
+	if slices.Contains(source.UserAccesses, context.ID()) {
+		return true
+	}
+
 	if len(userTeams) == 0 || len(source.TeamAccesses) == 0 {
 		return false
 	}
diff --git a/api/dataservices/source/access_rules_test.go b/api/dataservices/source/access_rules_test.go
index 71b7347c90..fe1c2c86e7 100644
--- a/api/dataservices/source/access_rules_test.go
+++ b/api/dataservices/source/access_rules_test.go
@@ -15,13 +15,12 @@ func Test_UserCanReadSource_AdministratorsOnly(t *testing.T) {
 	adminOnly := &portainer.Source{AdministratorsOnly: true}
 	require.False(t, userCanReadSource(adminOnly, standardUser))
 
-	// An explicit UserAccesses entry (the FindOrCreateGitSource auto-grant) wins
-	// over AdministratorsOnly.
+	// AdministratorsOnly is a hard enforcement: no user or team access overrides
+	// it. Sharing a source with a non-admin requires demoting the flag, as the
+	// FindOrCreateGitSource auto-grant does.
 	granted := &portainer.Source{AdministratorsOnly: true, UserAccesses: []portainer.UserID{2}}
-	require.True(t, userCanReadSource(granted, standardUser))
-	require.False(t, userCanReadSource(granted, teamMember))
+	require.False(t, userCanReadSource(granted, standardUser))
 
-	// Team accesses do not override AdministratorsOnly — only user grants do.
 	teamGranted := &portainer.Source{AdministratorsOnly: true, TeamAccesses: []portainer.TeamID{7}}
 	require.False(t, userCanReadSource(teamGranted, teamMember))
 }
diff --git a/api/dataservices/source/tx.go b/api/dataservices/source/tx.go
index 864e86ebba..de8f8589db 100644
--- a/api/dataservices/source/tx.go
+++ b/api/dataservices/source/tx.go
@@ -1,6 +1,8 @@
 package source
 
 import (
+	"slices"
+
 	portainer "github.com/portainer/portainer/api"
 	"github.com/portainer/portainer/api/dataservices"
 	gittypes "github.com/portainer/portainer/api/git/types"
@@ -174,7 +176,12 @@ func (service ServiceTx) FindOrCreateGitSource(context UserContext, src *portain
 
 		// give user access to the first source if he doesn't have access
 		// to any of the sources that have the same url+auth
-		existing[0].UserAccesses = append(existing[0].UserAccesses, context.ID())
+		if !slices.Contains(existing[0].UserAccesses, context.ID()) {
+			existing[0].UserAccesses = append(existing[0].UserAccesses, context.ID())
+		}
+		// AdministratorsOnly is a hard enforcement that would defeat the grant, and
+		// a source shared with a non-admin is factually no longer admins-only.
+		existing[0].AdministratorsOnly = false
 		if err := service.base.Update(existing[0].ID, &existing[0]); err != nil {
 			return nil, err
 		}
diff --git a/api/gitops/workflows/source_artifact_test.go b/api/gitops/workflows/source_artifact_test.go
index 6835148d6c..1cbdc8e136 100644
--- a/api/gitops/workflows/source_artifact_test.go
+++ b/api/gitops/workflows/source_artifact_test.go
@@ -487,7 +487,9 @@ func TestFindOrCreateGitSource_AutoGrantLetsStandardUserReadAdminOnlySource(t *t
 
 	// A standard user supplying the same URL+auth is auto-granted access to the
 	// existing source and must be able to read it afterwards (the stack builder
-	// reads it back in the same transaction to persist sync status).
+	// reads it back in the same transaction to persist sync status). The grant
+	// demotes AdministratorsOnly, which is a hard enforcement and would
+	// otherwise defeat the granted access.
 	err = store.UpdateTx(func(tx dataservices.DataStoreTx) error {
 		s, err := makeSource(standardUserContext)(tx)
 		if err != nil {
@@ -500,6 +502,11 @@ func TestFindOrCreateGitSource_AutoGrantLetsStandardUserReadAdminOnlySource(t *t
 		return err
 	})
 	require.NoError(t, err)
+
+	shared, err := store.Source().Read(standardUserContext, sourceID)
+	require.NoError(t, err)
+	require.False(t, shared.AdministratorsOnly)
+	require.Equal(t, []portainer.UserID{2}, shared.UserAccesses)
 }
 
 func TestSaveWorkflowGitConfig_UpdatesFileAndSourceWhenURLUnchanged(t *testing.T) {