diff --git a/doc/devmeta/track-comments.md b/doc/devmeta/track-comments.md
index 916d4581..91e43bf6 100644
--- a/doc/devmeta/track-comments.md
+++ b/doc/devmeta/track-comments.md
@@ -34,3 +34,15 @@ Comments beginning with `// track:`. See
   or there's a common behavior that should happen
   in between. The Sequence class is good for this so
   it might be a worthy migration.
+- `track: opposite condition of sibling`
+  A sibling class, function, method, or other construct of
+  source code has a boolean expression which always evaluates
+  to the opposite of the one below this track comment.
+- `track: null check before processing`
+  An object could be undefined or null, additional processing
+  occurs after a null check, and the unprocessed object is not
+  relevant to the rest of the code. If the code for obtaining
+  the object and processing it is moved to a function outside,
+  then the null check should result in a early return of null;
+  this code with the track comment may have additional logic
+  for the null/undefined case.
diff --git a/packages/backend/src/api/APIError.js b/packages/backend/src/api/APIError.js
index 20abbeee..c546f456 100644
--- a/packages/backend/src/api/APIError.js
+++ b/packages/backend/src/api/APIError.js
@@ -462,6 +462,11 @@ module.exports = class APIError {
             status: 422,
             message: 'Email must be confirmed to apply a share.',
         },
+        'no_need_to_request': {
+            status: 422,
+            message: 'This share is already valid for this user; ' +
+                'POST to /apply for access.'
+        },
         'can_not_apply_to_this_user': {
             status: 422,
             message: 'This share can not be applied to this user.',
diff --git a/packages/backend/src/services/ShareService.js b/packages/backend/src/services/ShareService.js
index 6caaee6f..f7b6a6b9 100644
--- a/packages/backend/src/services/ShareService.js
+++ b/packages/backend/src/services/ShareService.js
@@ -6,6 +6,7 @@ const { whatis } = require("../util/langutil");
 const { Actor, UserActorType } = require("./auth/Actor");
 const BaseService = require("./BaseService");
 const { DB_WRITE } = require("./database/consts");
+const { UsernameNotifSelector } = require("./NotificationService");
 
 class ShareService extends BaseService {
     static MODULES = {
@@ -85,16 +86,16 @@ class ShareService extends BaseService {
                     uid: share_uid,
                 });
                 
+                if ( ! share ) {
+                    throw APIError.create('share_expired');
+                }
+                
                 share.data = this.db.case({
                     mysql: () => share.data,
                     otherwise: () =>
                         JSON.parse(share.data ?? '{}'),
                 })();
                 
-                if ( ! share ) {
-                    throw APIError.create('share_expired');
-                }
-                
                 const actor = Actor.adapt(req.actor ?? req.user);
                 if ( ! actor ) {
                     // this shouldn't happen; auth should catch it
@@ -137,6 +138,74 @@ class ShareService extends BaseService {
                 });
             }
         }).attach(router);
+
+        Endpoint({
+            route: '/request',
+            methods: ['POST'],
+            mw: [configurable_auth()],
+            handler: async (req, res) => {
+                const share_uid = req.body.uid;
+                
+                const share = await svc_share.get_share({
+                    uid: share_uid,
+                });
+                
+                // track: null check before processing
+                if ( ! share ) {
+                    throw APIError.create('share_expired');
+                }
+                
+                share.data = this.db.case({
+                    mysql: () => share.data,
+                    otherwise: () =>
+                        JSON.parse(share.data ?? '{}'),
+                })();
+                
+                const actor = Actor.adapt(req.actor ?? req.user);
+                if ( ! actor ) {
+                    // this shouldn't happen; auth should catch it
+                    throw new Error('actor missing');
+                }
+                
+                // track: opposite condition of sibling
+                // :: sibling: /apply endpoint
+                if (
+                    actor.type.user.email_confirmed &&
+                    actor.type.user.email === share.recipient_email
+                ) {
+                    throw APIError.create('no_need_to_request');
+                }
+                
+                const issuer_user = await get_user({
+                    id: share.issuer_user_id,
+                });
+
+                if ( ! issuer_user ) {
+                    throw APIError.create('share_expired');
+                }
+                
+                const svc_notification = this.services.get('notification');
+                svc_notification.notify(
+                    UsernameNotifSelector(issuer_user.username),
+                    {
+                        source: 'sharing',
+                        title: `User ${actor.type.user.username} is ` +
+                            `trying to open a share you sent to ` +
+                            share.recipient_email,
+                        template: 'user-requesting-share',
+                        fields: {
+                            username: actor.type.user.username,
+                            intended_recipient: share.recipient_email,
+                            permissions: share.data.permissions,
+                        },
+                    }
+                );
+                res.json({
+                    $: 'api:status-report',
+                    status: 'success',
+                });
+            }
+        }).attach(router);
     }
     
     async get_share ({ uid }) {
diff --git a/packages/backend/src/services/drivers/DriverService.js b/packages/backend/src/services/drivers/DriverService.js
index 70b60deb..8dbd898e 100644
--- a/packages/backend/src/services/drivers/DriverService.js
+++ b/packages/backend/src/services/drivers/DriverService.js
@@ -34,6 +34,11 @@ class DriverService extends BaseService {
         this.interfaces = require('./interfaces');
         this.interface_to_implementation = {};
     }
+    
+    _init () {
+        const svc_registry = this.services.get('registry');
+        svc_registry.register_collection('');
+    }
 
     register_driver (interface_name, implementation) {
         this.interface_to_implementation[interface_name] = implementation;