diff --git a/services/web/app/src/Features/LinkedFiles/ProjectFileAgent.js b/services/web/app/src/Features/LinkedFiles/ProjectFileAgent.js
index 3c0272da7b..d594153adf 100644
--- a/services/web/app/src/Features/LinkedFiles/ProjectFileAgent.js
+++ b/services/web/app/src/Features/LinkedFiles/ProjectFileAgent.js
@@ -1,7 +1,6 @@
 /* eslint-disable
     n/handle-callback-err,
     max-len,
-    no-unused-vars,
 */
 // TODO: This file was created by bulk-decaffeinate.
 // Fix any style issues and re-enable lint.
@@ -14,21 +13,18 @@
 let ProjectFileAgent
 const AuthorizationManager = require('../Authorization/AuthorizationManager')
 const ProjectLocator = require('../Project/ProjectLocator')
-const ProjectGetter = require('../Project/ProjectGetter')
 const DocstoreManager = require('../Docstore/DocstoreManager')
 const DocumentUpdaterHandler = require('../DocumentUpdater/DocumentUpdaterHandler')
 const FileStoreHandler = require('../FileStore/FileStoreHandler')
 const _ = require('lodash')
-const Settings = require('@overleaf/settings')
 const LinkedFilesHandler = require('./LinkedFilesHandler')
 const {
   BadDataError,
   AccessDeniedError,
   BadEntityTypeError,
   SourceFileNotFoundError,
-  ProjectNotFoundError,
-  V1ProjectNotFoundError,
 } = require('./LinkedFilesErrors')
+const { promisify } = require('@overleaf/promise-utils')
 
 module.exports = ProjectFileAgent = {
   createLinkedFile(
@@ -39,10 +35,10 @@ module.exports = ProjectFileAgent = {
     userId,
     callback
   ) {
-    if (!this._canCreate(linkedFileData)) {
+    if (!ProjectFileAgent._canCreate(linkedFileData)) {
       return callback(new AccessDeniedError())
     }
-    return this._go(
+    return ProjectFileAgent._go(
       projectId,
       linkedFileData,
       name,
@@ -60,7 +56,7 @@ module.exports = ProjectFileAgent = {
     userId,
     callback
   ) {
-    return this._go(
+    return ProjectFileAgent._go(
       projectId,
       linkedFileData,
       name,
@@ -74,7 +70,7 @@ module.exports = ProjectFileAgent = {
     if (callback == null) {
       callback = function () {}
     }
-    return this._checkAuth(
+    return ProjectFileAgent._checkAuth(
       projectId,
       linkedFileData,
       userId,
@@ -85,7 +81,7 @@ module.exports = ProjectFileAgent = {
         if (!allowed) {
           return callback(new AccessDeniedError())
         }
-        if (!this._validate(linkedFileData)) {
+        if (!ProjectFileAgent._validate(linkedFileData)) {
           return callback(new BadDataError())
         }
         return callback(null, linkedFileData)
@@ -94,8 +90,8 @@ module.exports = ProjectFileAgent = {
   },
 
   _go(projectId, linkedFileData, name, parentFolderId, userId, callback) {
-    linkedFileData = this._sanitizeData(linkedFileData)
-    return this._prepare(
+    linkedFileData = ProjectFileAgent._sanitizeData(linkedFileData)
+    return ProjectFileAgent._prepare(
       projectId,
       linkedFileData,
       userId,
@@ -103,10 +99,10 @@ module.exports = ProjectFileAgent = {
         if (err != null) {
           return callback(err)
         }
-        if (!this._validate(linkedFileData)) {
+        if (!ProjectFileAgent._validate(linkedFileData)) {
           return callback(new BadDataError())
         }
-        return this._getEntity(
+        return ProjectFileAgent._getEntity(
           linkedFileData,
           userId,
           (err, sourceProject, entity, type) => {
@@ -177,36 +173,39 @@ module.exports = ProjectFileAgent = {
     }
     callback = _.once(callback)
     const { source_entity_path: sourceEntityPath } = linkedFileData
-    return this._getSourceProject(linkedFileData, function (err, project) {
-      if (err != null) {
-        return callback(err)
-      }
-      const sourceProjectId = project._id
-      return DocumentUpdaterHandler.flushProjectToMongo(
-        sourceProjectId,
-        function (err) {
-          if (err != null) {
-            return callback(err)
-          }
-          return ProjectLocator.findElementByPath(
-            {
-              project_id: sourceProjectId,
-              path: sourceEntityPath,
-              exactCaseMatch: true,
-            },
-            function (err, entity, type) {
-              if (err != null) {
-                if (/^not found.*/.test(err.message)) {
-                  err = new SourceFileNotFoundError()
-                }
-                return callback(err)
-              }
-              return callback(null, project, entity, type)
-            }
-          )
+    return ProjectFileAgent._getSourceProject(
+      linkedFileData,
+      function (err, project) {
+        if (err != null) {
+          return callback(err)
         }
-      )
-    })
+        const sourceProjectId = project._id
+        return DocumentUpdaterHandler.flushProjectToMongo(
+          sourceProjectId,
+          function (err) {
+            if (err != null) {
+              return callback(err)
+            }
+            return ProjectLocator.findElementByPath(
+              {
+                project_id: sourceProjectId,
+                path: sourceEntityPath,
+                exactCaseMatch: true,
+              },
+              function (err, entity, type) {
+                if (err != null) {
+                  if (/^not found.*/.test(err.message)) {
+                    err = new SourceFileNotFoundError()
+                  }
+                  return callback(err)
+                }
+                return callback(null, project, entity, type)
+              }
+            )
+          }
+        )
+      }
+    )
   },
 
   _sanitizeData(data) {
@@ -242,7 +241,7 @@ module.exports = ProjectFileAgent = {
     if (!ProjectFileAgent._validate(data)) {
       return callback(new BadDataError())
     }
-    return this._getSourceProject(data, function (err, project) {
+    return ProjectFileAgent._getSourceProject(data, function (err, project) {
       if (err != null) {
         return callback(err)
       }
@@ -260,3 +259,8 @@ module.exports = ProjectFileAgent = {
     })
   },
 }
+
+ProjectFileAgent.promises = {
+  createLinkedFile: promisify(ProjectFileAgent.createLinkedFile),
+  refreshLinkedFile: promisify(ProjectFileAgent.refreshLinkedFile),
+}
diff --git a/services/web/app/src/Features/LinkedFiles/ProjectOutputFileAgent.js b/services/web/app/src/Features/LinkedFiles/ProjectOutputFileAgent.js
index c6533b916f..c1141efc7e 100644
--- a/services/web/app/src/Features/LinkedFiles/ProjectOutputFileAgent.js
+++ b/services/web/app/src/Features/LinkedFiles/ProjectOutputFileAgent.js
@@ -10,6 +10,7 @@ const {
 } = require('./LinkedFilesErrors')
 const { OutputFileFetchFailedError } = require('../Errors/Errors')
 const LinkedFilesHandler = require('./LinkedFilesHandler')
+const { promisify } = require('@overleaf/promise-utils')
 
 function _prepare(projectId, linkedFileData, userId, callback) {
   _checkAuth(projectId, linkedFileData, userId, (err, allowed) => {
@@ -225,4 +226,11 @@ function _compileAndGetFileStream(linkedFileData, userId, callback) {
   })
 }
 
-module.exports = { createLinkedFile, refreshLinkedFile }
+module.exports = {
+  createLinkedFile,
+  refreshLinkedFile,
+  promises: {
+    createLinkedFile: promisify(createLinkedFile),
+    refreshLinkedFile: promisify(refreshLinkedFile),
+  },
+}
diff --git a/services/web/app/src/Features/References/ReferencesHandler.js b/services/web/app/src/Features/References/ReferencesHandler.js
index b80403dfa9..1ad2d77c86 100644
--- a/services/web/app/src/Features/References/ReferencesHandler.js
+++ b/services/web/app/src/Features/References/ReferencesHandler.js
@@ -24,6 +24,7 @@ const DocumentUpdaterHandler = require('../DocumentUpdater/DocumentUpdaterHandle
 const _ = require('lodash')
 const Async = require('async')
 const Errors = require('../Errors/Errors')
+const { promisify } = require('@overleaf/promise-utils')
 
 if (!Features.hasFeature('references')) {
   logger.debug('references search not enabled')
@@ -196,6 +197,10 @@ module.exports = ReferencesHandler = {
   },
 }
 
+ReferencesHandler.promises = {
+  indexAll: promisify(ReferencesHandler.indexAll),
+}
+
 function __guard__(value, transform) {
   return typeof value !== 'undefined' && value !== null
     ? transform(value)
diff --git a/services/web/test/unit/src/LinkedFiles/LinkedFilesControllerTests.js b/services/web/test/unit/src/LinkedFiles/LinkedFilesControllerTests.js
index f1f31b8757..a0a08be251 100644
--- a/services/web/test/unit/src/LinkedFiles/LinkedFilesControllerTests.js
+++ b/services/web/test/unit/src/LinkedFiles/LinkedFilesControllerTests.js
@@ -17,15 +17,19 @@ describe('LinkedFilesController', function () {
   beforeEach(function () {
     this.userId = 'user-id'
     this.Agent = {
-      createLinkedFile: sinon.stub().yields(),
-      refreshLinkedFile: sinon.stub().yields(),
+      promises: {
+        createLinkedFile: sinon.stub().resolves(),
+        refreshLinkedFile: sinon.stub().resolves(),
+      },
     }
     this.projectId = 'projectId'
     this.provider = 'provider'
     this.name = 'linked-file-name'
     this.data = { customAgentData: 'foo' }
     this.LinkedFilesHandler = {
-      getFileById: sinon.stub(),
+      promises: {
+        getFileById: sinon.stub(),
+      },
     }
     this.AnalyticsManager = {}
     this.SessionManager = {
@@ -77,7 +81,7 @@ describe('LinkedFilesController', function () {
       this.next = sinon.stub().callsFake(() => done('unexpected error'))
       this.res = {
         json: () => {
-          expect(this.Agent.createLinkedFile).to.have.been.calledWith(
+          expect(this.Agent.promises.createLinkedFile).to.have.been.calledWith(
             this.projectId,
             { ...this.data, importedAt: this.fakeTime.toISOString() },
             this.name,
@@ -100,10 +104,14 @@ describe('LinkedFilesController', function () {
           importedAt: new Date(2020, 1, 1).toISOString(),
         },
       }
-      this.LinkedFilesHandler.getFileById
+      this.LinkedFilesHandler.promises.getFileById
         .withArgs(this.projectId, 'file-id')
-        .yields(null, this.file, 'fake-path', {
-          _id: 'parent-folder-id',
+        .resolves({
+          file: this.file,
+          path: 'fake-path',
+          parentFolder: {
+            _id: 'parent-folder-id',
+          },
         })
       this.req = {
         params: { project_id: this.projectId, file_id: 'file-id' },
@@ -116,7 +124,7 @@ describe('LinkedFilesController', function () {
       this.next = sinon.stub().callsFake(() => done('unexpected error'))
       this.res = {
         json: () => {
-          expect(this.Agent.refreshLinkedFile).to.have.been.calledWith(
+          expect(this.Agent.promises.refreshLinkedFile).to.have.been.calledWith(
             this.projectId,
             {
               ...this.data,