diff --git a/services/web/app/src/Features/Compile/ClsiCookieManager.js b/services/web/app/src/Features/Compile/ClsiCookieManager.js
index 8fdb45b40b..6f45a7fa5f 100644
--- a/services/web/app/src/Features/Compile/ClsiCookieManager.js
+++ b/services/web/app/src/Features/Compile/ClsiCookieManager.js
@@ -33,6 +33,9 @@ module.exports = function (backendGroup) {
       compileBackendClass,
       callback
     ) {
+      if (!clsiCookiesEnabled) {
+        return callback()
+      }
       rclient.get(this.buildKey(projectId, userId), (err, serverId) => {
         if (err) {
           return callback(err)
diff --git a/services/web/app/src/Features/Compile/CompileController.js b/services/web/app/src/Features/Compile/CompileController.js
index 57481389ab..67d018b485 100644
--- a/services/web/app/src/Features/Compile/CompileController.js
+++ b/services/web/app/src/Features/Compile/CompileController.js
@@ -1,12 +1,13 @@
 let CompileController
-const { URL } = require('url')
+const { URL, URLSearchParams } = require('url')
+const { pipeline } = require('stream/promises')
+const { Cookie } = require('tough-cookie')
 const OError = require('@overleaf/o-error')
 const Metrics = require('@overleaf/metrics')
 const ProjectGetter = require('../Project/ProjectGetter')
 const CompileManager = require('./CompileManager')
 const ClsiManager = require('./ClsiManager')
 const logger = require('@overleaf/logger')
-const request = require('request')
 const Settings = require('@overleaf/settings')
 const SessionManager = require('../Authentication/SessionManager')
 const { RateLimiter } = require('../../infrastructure/RateLimiter')
@@ -17,6 +18,10 @@ const Path = require('path')
 const AnalyticsManager = require('../Analytics/AnalyticsManager')
 const SplitTestHandler = require('../SplitTests/SplitTestHandler')
 const { callbackify } = require('../../util/promises')
+const {
+  fetchStreamWithResponse,
+  RequestFailedError,
+} = require('@overleaf/fetch-utils')
 
 const COMPILE_TIMEOUT_MS = 10 * 60 * 1000
 
@@ -274,24 +279,19 @@ module.exports = CompileController = {
   downloadPdf(req, res, next) {
     Metrics.inc('pdf-downloads')
     const projectId = req.params.Project_id
-    const isPdfjsPartialDownload = req.query?.pdfng
     const rateLimit = function (callback) {
-      if (isPdfjsPartialDownload) {
-        callback(null, true)
-      } else {
-        pdfDownloadRateLimiter
-          .consume(req.ip)
-          .then(() => {
-            callback(null, true)
-          })
-          .catch(err => {
-            if (err instanceof Error) {
-              callback(err)
-            } else {
-              callback(null, false)
-            }
-          })
-      }
+      pdfDownloadRateLimiter
+        .consume(req.ip)
+        .then(() => {
+          callback(null, true)
+        })
+        .catch(err => {
+          if (err instanceof Error) {
+            callback(err)
+          } else {
+            callback(null, false)
+          }
+        })
     }
 
     ProjectGetter.getProject(projectId, { name: 1 }, function (err, project) {
@@ -328,7 +328,7 @@ module.exports = CompileController = {
               req.params.build_id,
               'output.pdf'
             )
-            CompileController.proxyToClsi(projectId, url, req, res, next)
+            CompileController.proxyToClsi(projectId, url, {}, req, res, next)
           })
         }
       })
@@ -374,7 +374,7 @@ module.exports = CompileController = {
         return
       }
       const url = `/project/${projectId}/output/output.pdf`
-      CompileController.proxyToClsi(projectId, url, req, res, next)
+      CompileController.proxyToClsi(projectId, url, {}, req, res, next)
     })
   },
 
@@ -390,7 +390,7 @@ module.exports = CompileController = {
         req.params.build_id,
         req.params.file
       )
-      CompileController.proxyToClsi(projectId, url, req, res, next)
+      CompileController.proxyToClsi(projectId, url, {}, req, res, next)
     })
   },
 
@@ -412,6 +412,7 @@ module.exports = CompileController = {
     CompileController.proxyToClsiWithLimits(
       submissionId,
       url,
+      {},
       limits,
       req,
       res,
@@ -464,8 +465,14 @@ module.exports = CompileController = {
         if (error) return next(error)
 
         const url = CompileController._getUrl(projectId, userId, 'sync/pdf')
-        const destination = { url, qs: { page, h, v, imageName } }
-        CompileController.proxyToClsi(projectId, destination, req, res, next)
+        CompileController.proxyToClsi(
+          projectId,
+          url,
+          { page, h, v, imageName },
+          req,
+          res,
+          next
+        )
       })
     })
   },
@@ -499,13 +506,19 @@ module.exports = CompileController = {
         if (error) return next(error)
 
         const url = CompileController._getUrl(projectId, userId, 'sync/code')
-        const destination = { url, qs: { file, line, column, imageName } }
-        CompileController.proxyToClsi(projectId, destination, req, res, next)
+        CompileController.proxyToClsi(
+          projectId,
+          url,
+          { file, line, column, imageName },
+          req,
+          res,
+          next
+        )
       })
     })
   },
 
-  proxyToClsi(projectId, url, req, res, next) {
+  proxyToClsi(projectId, url, qs, req, res, next) {
     CompileManager.getProjectCompileLimits(projectId, function (error, limits) {
       if (error) {
         return next(error)
@@ -513,6 +526,7 @@ module.exports = CompileController = {
       CompileController.proxyToClsiWithLimits(
         projectId,
         url,
+        qs,
         limits,
         req,
         res,
@@ -521,60 +535,44 @@ module.exports = CompileController = {
     })
   },
 
-  proxyToClsiWithLimits(projectId, url, limits, req, res, next) {
+  proxyToClsiWithLimits(projectId, url, qs, limits, req, res, next) {
     _getPersistenceOptions(
       req,
       projectId,
       limits.compileGroup,
       limits.compileBackendClass,
       (err, persistenceOptions) => {
-        let qs
         if (err) {
           OError.tag(err, 'error getting cookie jar for clsi request')
           return next(err)
         }
-        // expand any url parameter passed in as {url:..., qs:...}
-        if (typeof url === 'object') {
-          ;({ url, qs } = url)
-        }
-        const compilerUrl = Settings.apis.clsi.url
-        url = `${compilerUrl}${url}`
-        const oneMinute = 60 * 1000
-        // the base request
-        const options = {
-          url,
+        url = new URL(`${Settings.apis.clsi.url}${url}`)
+        url.search = new URLSearchParams({
+          ...persistenceOptions.qs,
+          ...qs,
+        }).toString()
+        fetchStreamWithResponse(url.href, {
           method: req.method,
-          timeout: oneMinute,
-          ...persistenceOptions,
-        }
-        // add any provided query string
-        if (qs != null) {
-          options.qs = Object.assign(options.qs || {}, qs)
-        }
-        // if we have a build parameter, pass it through to the clsi
-        if (req.query?.pdfng && req.query?.build != null) {
-          // only for new pdf viewer
-          if (options.qs == null) {
-            options.qs = {}
-          }
-          options.qs.build = req.query.build
-        }
-        // if we are byte serving pdfs, pass through If-* and Range headers
-        // do not send any others, there's a proxying loop if Host: is passed!
-        if (req.query?.pdfng) {
-          const newHeaders = {}
-          for (const h in req.headers) {
-            if (/^(If-|Range)/i.test(h)) {
-              newHeaders[h] = req.headers[h]
+          signal: AbortSignal.timeout(60 * 1000),
+          headers: persistenceOptions.headers,
+        })
+          .then(({ stream, response }) => {
+            for (const key of ['Content-Length', 'Content-Type']) {
+              res.setHeader(key, response.headers.get(key))
             }
-          }
-          options.headers = newHeaders
-        }
-        const proxy = request(options)
-        proxy.pipe(res)
-        proxy.on('error', error =>
-          logger.warn({ err: error, url }, 'CLSI proxy error')
-        )
+            res.writeHead(response.status)
+            return pipeline(stream, res)
+          })
+          .catch(err => {
+            if (!res.headersSent) {
+              if (err instanceof RequestFailedError) {
+                res.sendStatus(err.response.status)
+              } else {
+                res.sendStatus(500)
+              }
+            }
+            logger.warn({ err, projectId, url }, 'CLSI proxy error')
+          })
       }
     )
   },
@@ -613,15 +611,29 @@ function _getPersistenceOptions(
   const { clsiserverid } = req.query
   const userId = SessionManager.getLoggedInUserId(req)
   if (clsiserverid && typeof clsiserverid === 'string') {
-    callback(null, { qs: { clsiserverid, compileGroup, compileBackendClass } })
+    callback(null, {
+      qs: { clsiserverid, compileGroup, compileBackendClass },
+      headers: {},
+    })
   } else {
-    ClsiCookieManager.getCookieJar(
+    ClsiCookieManager.getServerId(
       projectId,
       userId,
       compileGroup,
       compileBackendClass,
-      (err, jar) => {
-        callback(err, { jar, qs: { compileGroup, compileBackendClass } })
+      (err, clsiServerId) => {
+        if (err) return callback(err)
+        callback(null, {
+          qs: { compileGroup, compileBackendClass },
+          headers: clsiServerId
+            ? {
+                Cookie: new Cookie({
+                  key: Settings.clsiCookie.key,
+                  value: clsiServerId,
+                }).cookieString(),
+              }
+            : {},
+        })
       }
     )
   }
diff --git a/services/web/app/src/Features/User/UserCreator.js b/services/web/app/src/Features/User/UserCreator.js
index 8e2ef7e9cd..226b0a7826 100644
--- a/services/web/app/src/Features/User/UserCreator.js
+++ b/services/web/app/src/Features/User/UserCreator.js
@@ -59,9 +59,6 @@ async function createNewUser(attributes, options = {}) {
   Object.assign(user, attributes)
 
   user.ace.syntaxValidation = true
-  if (user.featureSwitches != null) {
-    user.featureSwitches.pdfng = true
-  }
 
   const reversedHostname = user.email.split('@')[1].split('').reverse().join('')
 
diff --git a/services/web/frontend/js/infrastructure/error-reporter.js b/services/web/frontend/js/infrastructure/error-reporter.js
index 08745f0cd1..878a92b6b8 100644
--- a/services/web/frontend/js/infrastructure/error-reporter.js
+++ b/services/web/frontend/js/infrastructure/error-reporter.js
@@ -29,7 +29,6 @@ function sentryReporter() {
             'SecurityError: Permission denied to access property "pathname" on cross-origin object',
             // Ignore unhandled error that is "expected" - see https://github.com/overleaf/issues/issues/3321
             /^Missing PDF/,
-            /^pdfng error Error: MissingPDFException/,
             // Ignore "expected" error from aborted fetch - see https://github.com/overleaf/issues/issues/3321
             /^AbortError/,
             // Ignore spurious error from Ace internals - see https://github.com/overleaf/issues/issues/3321
diff --git a/services/web/package.json b/services/web/package.json
index 2b8b15ea97..e3cf26d22b 100644
--- a/services/web/package.json
+++ b/services/web/package.json
@@ -260,6 +260,7 @@
     "@babel/register": "^7.21.0",
     "@juggle/resize-observer": "^3.3.1",
     "@lezer/generator": "^1.3.0",
+    "@overleaf/stream-utils": "*",
     "@testing-library/cypress": "^9.0.0",
     "@testing-library/dom": "^9.3.0",
     "@testing-library/react": "^12.1.5",
diff --git a/services/web/test/unit/src/Compile/CompileControllerTests.js b/services/web/test/unit/src/Compile/CompileControllerTests.js
index 45e8da9450..11529ea10c 100644
--- a/services/web/test/unit/src/Compile/CompileControllerTests.js
+++ b/services/web/test/unit/src/Compile/CompileControllerTests.js
@@ -5,6 +5,8 @@ const modulePath = '../../../../app/src/Features/Compile/CompileController.js'
 const SandboxedModule = require('sandboxed-module')
 const MockRequest = require('../helpers/MockRequest')
 const MockResponse = require('../helpers/MockResponse')
+const { Headers } = require('node-fetch')
+const { ReadableString } = require('@overleaf/stream-utils')
 
 describe('CompileController', function () {
   beforeEach(function () {
@@ -29,21 +31,23 @@ describe('CompileController', function () {
     this.settings = {
       apis: {
         clsi: {
-          url: 'clsi.example.com',
+          url: 'http://clsi.example.com',
           defaultBackendClass: 'e2',
         },
         clsi_priority: {
-          url: 'clsi-priority.example.com',
+          url: 'http://clsi-priority.example.com',
         },
       },
       defaultFeatures: {
         compileGroup: 'standard',
         compileTimeout: 60,
       },
+      clsiCookie: {
+        key: 'cookie-key',
+      },
     }
-    this.jar = { cookie: 'stuff' }
     this.ClsiCookieManager = {
-      getCookieJar: sinon.stub().yields(null, this.jar),
+      getServerId: sinon.stub().yields(null, 'clsi-server-id-from-redis'),
     }
     this.SessionManager = {
       getLoggedInUser: sinon.stub().callsArgWith(1, null, this.user),
@@ -51,9 +55,27 @@ describe('CompileController', function () {
       getSessionUser: sinon.stub().returns(this.user),
       isUserLoggedIn: sinon.stub().returns(true),
     }
+    this.pipeline = sinon.stub().callsFake(async (stream, res) => {
+      if (res.callback) res.callback()
+    })
+    this.clsiStream = new ReadableString('{}')
+    this.clsiResponse = {
+      headers: new Headers({
+        'Content-Length': '2',
+        'Content-Type': 'application/json',
+      }),
+    }
+    this.fetchUtils = {
+      fetchStreamWithResponse: sinon.stub().resolves({
+        stream: this.clsiStream,
+        response: this.clsiResponse,
+      }),
+    }
     this.CompileController = SandboxedModule.require(modulePath, {
       requires: {
+        'stream/promises': { pipeline: this.pipeline },
         '@overleaf/settings': this.settings,
+        '@overleaf/fetch-utils': this.fetchUtils,
         request: (this.request = sinon.stub()),
         '../Project/ProjectGetter': (this.ProjectGetter = {}),
         '@overleaf/metrics': (this.Metrics = { inc: sinon.stub() }),
@@ -349,7 +371,6 @@ describe('CompileController', function () {
     beforeEach(function () {
       this.req.params = { Project_id: this.projectId }
 
-      this.req.query = { pdfng: true }
       this.project = { name: 'test namè; 1' }
       this.ProjectGetter.getProject = sinon
         .stub()
@@ -357,8 +378,10 @@ describe('CompileController', function () {
     })
 
     describe('when downloading for embedding', function () {
-      beforeEach(function () {
-        this.CompileController.proxyToClsi = sinon.stub()
+      beforeEach(function (done) {
+        this.CompileController.proxyToClsi = sinon
+          .stub()
+          .callsFake(() => done())
         this.CompileController.downloadPdf(this.req, this.res, this.next)
       })
 
@@ -387,6 +410,7 @@ describe('CompileController', function () {
           .calledWith(
             this.projectId,
             `/project/${this.projectId}/user/${this.user_id}/output/output.pdf`,
+            {},
             this.req,
             this.res,
             this.next
@@ -396,9 +420,11 @@ describe('CompileController', function () {
     })
 
     describe('when the a build-id is provided', function () {
-      beforeEach(function () {
+      beforeEach(function (done) {
         this.req.params.build_id = this.buildId = '1234-5678'
-        this.CompileController.proxyToClsi = sinon.stub()
+        this.CompileController.proxyToClsi = sinon
+          .stub()
+          .callsFake(() => done())
         this.CompileController.downloadPdf(this.req, this.res, this.next)
       })
 
@@ -407,6 +433,7 @@ describe('CompileController', function () {
           .calledWith(
             this.projectId,
             `/project/${this.projectId}/user/${this.user_id}/build/${this.buildId}/output/output.pdf`,
+            {},
             this.req,
             this.res,
             this.next
@@ -414,26 +441,6 @@ describe('CompileController', function () {
           .should.equal(true)
       })
     })
-
-    describe('when the pdf is not going to be used in pdfjs viewer', function () {
-      it('should check the rate limiter when pdfng is not set', function (done) {
-        this.req.query = {}
-        this.CompileController.proxyToClsi = (projectId, url) => {
-          expect(this.rateLimiter.consume).to.have.been.called
-          done()
-        }
-        this.CompileController.downloadPdf(this.req, this.res)
-      })
-
-      it('should check the rate limiter when pdfng is false', function (done) {
-        this.req.query = { pdfng: false }
-        this.CompileController.proxyToClsi = (projectId, url) => {
-          expect(this.rateLimiter.consume).to.have.been.called
-          done()
-        }
-        this.CompileController.downloadPdf(this.req, this.res)
-      })
-    })
   })
 
   describe('getFileFromClsiWithoutUser', function () {
@@ -464,6 +471,7 @@ describe('CompileController', function () {
         this.CompileController.proxyToClsiWithLimits.should.have.been.calledWith(
           this.submission_id,
           this.expected_url,
+          {},
           {
             compileGroup: 'standard',
             compileBackendClass: 'e2',
@@ -486,6 +494,7 @@ describe('CompileController', function () {
         this.CompileController.proxyToClsiWithLimits.should.have.been.calledWith(
           this.submission_id,
           this.expected_url,
+          {},
           {
             compileGroup: 'special',
             compileBackendClass: 'e2',
@@ -517,10 +526,8 @@ describe('CompileController', function () {
     it('should proxy the request with an imageName', function () {
       expect(this.CompileController.proxyToClsi).to.have.been.calledWith(
         this.projectId,
-        {
-          url: `/project/${this.projectId}/user/${this.user_id}/sync/code`,
-          qs: { file, line, column, imageName },
-        },
+        `/project/${this.projectId}/user/${this.user_id}/sync/code`,
+        { file, line, column, imageName },
         this.req,
         this.res,
         this.next
@@ -551,10 +558,8 @@ describe('CompileController', function () {
     it('should proxy the request with an imageName', function () {
       expect(this.CompileController.proxyToClsi).to.have.been.calledWith(
         this.projectId,
-        {
-          url: `/project/${this.projectId}/user/${this.user_id}/sync/pdf`,
-          qs: { page, h, v, imageName },
-        },
+        `/project/${this.projectId}/user/${this.user_id}/sync/pdf`,
+        { page, h, v, imageName },
         this.req,
         this.res,
         this.next
@@ -564,16 +569,6 @@ describe('CompileController', function () {
 
   describe('proxyToClsi', function () {
     beforeEach(function () {
-      this.request.returns(
-        (this.proxy = {
-          pipe: sinon.stub(),
-          on: sinon.stub(),
-        })
-      )
-      this.upstream = {
-        statusCode: 204,
-        headers: { mock: 'header' },
-      }
       this.req.method = 'mock-method'
       this.req.headers = {
         Mock: 'Headers',
@@ -585,7 +580,8 @@ describe('CompileController', function () {
 
     describe('old pdf viewer', function () {
       describe('user with standard priority', function () {
-        beforeEach(function () {
+        beforeEach(function (done) {
+          this.res.callback = done
           this.CompileManager.getProjectCompileLimits = sinon
             .stub()
             .callsArgWith(1, null, {
@@ -595,6 +591,7 @@ describe('CompileController', function () {
           this.CompileController.proxyToClsi(
             this.projectId,
             (this.url = '/test'),
+            { query: 'foo' },
             this.req,
             this.res,
             this.next
@@ -602,43 +599,45 @@ describe('CompileController', function () {
         })
 
         it('should open a request to the CLSI', function () {
-          this.request
-            .calledWith({
-              jar: this.jar,
-              qs: { compileGroup: 'standard', compileBackendClass: 'e2' },
-              method: this.req.method,
-              url: `${this.settings.apis.clsi.url}${this.url}`,
-              timeout: 60 * 1000,
-            })
-            .should.equal(true)
+          this.fetchUtils.fetchStreamWithResponse.should.have.been.calledWith(
+            `${this.settings.apis.clsi.url}${this.url}?compileGroup=standard&compileBackendClass=e2&query=foo`
+          )
         })
 
         it('should pass the request on to the client', function () {
-          this.proxy.pipe.calledWith(this.res).should.equal(true)
-        })
-
-        it('should bind an error handle to the request proxy', function () {
-          this.proxy.on.calledWith('error').should.equal(true)
+          this.pipeline.should.have.been.calledWith(this.clsiStream, this.res)
         })
       })
 
       describe('user with priority compile', function () {
-        beforeEach(function () {
+        beforeEach(function (done) {
+          this.res.callback = done
           this.CompileManager.getProjectCompileLimits = sinon
             .stub()
-            .callsArgWith(1, null, { compileGroup: 'priority' })
+            .callsArgWith(1, null, {
+              compileGroup: 'priority',
+              compileBackendClass: 'c2d',
+            })
           this.CompileController.proxyToClsi(
             this.projectId,
             (this.url = '/test'),
+            {},
             this.req,
             this.res,
             this.next
           )
         })
+
+        it('should open a request to the CLSI', function () {
+          this.fetchUtils.fetchStreamWithResponse.should.have.been.calledWith(
+            `${this.settings.apis.clsi.url}${this.url}?compileGroup=priority&compileBackendClass=c2d`
+          )
+        })
       })
 
       describe('user with standard priority via query string', function () {
-        beforeEach(function () {
+        beforeEach(function (done) {
+          this.res.callback = done
           this.req.query = { compileGroup: 'standard' }
           this.CompileManager.getProjectCompileLimits = sinon
             .stub()
@@ -649,6 +648,7 @@ describe('CompileController', function () {
           this.CompileController.proxyToClsi(
             this.projectId,
             (this.url = '/test'),
+            {},
             this.req,
             this.res,
             this.next
@@ -656,28 +656,19 @@ describe('CompileController', function () {
         })
 
         it('should open a request to the CLSI', function () {
-          this.request
-            .calledWith({
-              jar: this.jar,
-              qs: { compileGroup: 'standard', compileBackendClass: 'e2' },
-              method: this.req.method,
-              url: `${this.settings.apis.clsi.url}${this.url}`,
-              timeout: 60 * 1000,
-            })
-            .should.equal(true)
+          this.fetchUtils.fetchStreamWithResponse.should.have.been.calledWith(
+            `${this.settings.apis.clsi.url}${this.url}?compileGroup=standard&compileBackendClass=e2`
+          )
         })
 
         it('should pass the request on to the client', function () {
-          this.proxy.pipe.calledWith(this.res).should.equal(true)
-        })
-
-        it('should bind an error handle to the request proxy', function () {
-          this.proxy.on.calledWith('error').should.equal(true)
+          this.pipeline.should.have.been.calledWith(this.clsiStream, this.res)
         })
       })
 
       describe('user with non-existent priority via query string', function () {
-        beforeEach(function () {
+        beforeEach(function (done) {
+          this.res.callback = done
           this.req.query = { compileGroup: 'foobar' }
           this.CompileManager.getProjectCompileLimits = sinon
             .stub()
@@ -688,6 +679,7 @@ describe('CompileController', function () {
           this.CompileController.proxyToClsi(
             this.projectId,
             (this.url = '/test'),
+            {},
             this.req,
             this.res,
             this.next
@@ -695,20 +687,15 @@ describe('CompileController', function () {
         })
 
         it('should proxy to the standard url', function () {
-          this.request
-            .calledWith({
-              jar: this.jar,
-              qs: { compileGroup: 'standard', compileBackendClass: 'e2' },
-              method: this.req.method,
-              url: `${this.settings.apis.clsi.url}${this.url}`,
-              timeout: 60 * 1000,
-            })
-            .should.equal(true)
+          this.fetchUtils.fetchStreamWithResponse.should.have.been.calledWith(
+            `${this.settings.apis.clsi.url}${this.url}?compileGroup=standard&compileBackendClass=e2`
+          )
         })
       })
 
       describe('user with build parameter via query string', function () {
-        beforeEach(function () {
+        beforeEach(function (done) {
+          this.res.callback = done
           this.CompileManager.getProjectCompileLimits = sinon
             .stub()
             .callsArgWith(1, null, {
@@ -719,6 +706,7 @@ describe('CompileController', function () {
           this.CompileController.proxyToClsi(
             this.projectId,
             (this.url = '/test'),
+            {},
             this.req,
             this.res,
             this.next
@@ -726,104 +714,10 @@ describe('CompileController', function () {
         })
 
         it('should proxy to the standard url without the build parameter', function () {
-          this.request
-            .calledWith({
-              jar: this.jar,
-              qs: { compileGroup: 'standard', compileBackendClass: 'e2' },
-              method: this.req.method,
-              url: `${this.settings.apis.clsi.url}${this.url}`,
-              timeout: 60 * 1000,
-            })
-            .should.equal(true)
-        })
-      })
-    })
-
-    describe('new pdf viewer', function () {
-      beforeEach(function () {
-        this.req.query = { pdfng: true }
-      })
-      describe('user with standard priority', function () {
-        beforeEach(function () {
-          this.CompileManager.getProjectCompileLimits = sinon
-            .stub()
-            .callsArgWith(1, null, {
-              compileGroup: 'standard',
-              compileBackendClass: 'e2',
-            })
-          this.CompileController.proxyToClsi(
-            this.projectId,
-            (this.url = '/test'),
-            this.req,
-            this.res,
-            this.next
+          this.fetchUtils.fetchStreamWithResponse.should.have.been.calledWith(
+            `${this.settings.apis.clsi.url}${this.url}?compileGroup=standard&compileBackendClass=e2`
           )
         })
-
-        it('should open a request to the CLSI', function () {
-          this.request
-            .calledWith({
-              jar: this.jar,
-              qs: { compileGroup: 'standard', compileBackendClass: 'e2' },
-              method: this.req.method,
-              url: `${this.settings.apis.clsi.url}${this.url}`,
-              timeout: 60 * 1000,
-              headers: {
-                Range: '123-456',
-                'If-Range': 'abcdef',
-                'If-Modified-Since': 'Mon, 15 Dec 2014 15:23:56 GMT',
-              },
-            })
-            .should.equal(true)
-        })
-
-        it('should pass the request on to the client', function () {
-          this.proxy.pipe.calledWith(this.res).should.equal(true)
-        })
-
-        it('should bind an error handle to the request proxy', function () {
-          this.proxy.on.calledWith('error').should.equal(true)
-        })
-      })
-
-      describe('user with build parameter via query string', function () {
-        beforeEach(function () {
-          this.CompileManager.getProjectCompileLimits = sinon
-            .stub()
-            .callsArgWith(1, null, {
-              compileGroup: 'standard',
-              compileBackendClass: 'e2',
-            })
-          this.req.query = { build: 1234, pdfng: true }
-          this.CompileController.proxyToClsi(
-            this.projectId,
-            (this.url = '/test'),
-            this.req,
-            this.res,
-            this.next
-          )
-        })
-
-        it('should proxy to the standard url with the build parameter', function () {
-          this.request
-            .calledWith({
-              jar: this.jar,
-              method: this.req.method,
-              qs: {
-                build: 1234,
-                compileGroup: 'standard',
-                compileBackendClass: 'e2',
-              },
-              url: `${this.settings.apis.clsi.url}${this.url}`,
-              timeout: 60 * 1000,
-              headers: {
-                Range: '123-456',
-                'If-Range': 'abcdef',
-                'If-Modified-Since': 'Mon, 15 Dec 2014 15:23:56 GMT',
-              },
-            })
-            .should.equal(true)
-        })
       })
     })
   })
@@ -872,6 +766,7 @@ describe('CompileController', function () {
         this.CompileController.proxyToClsi,
         this.projectId,
         `/project/${this.projectId}/output/output.pdf`,
+        {},
         this.req,
         this.res
       )
@@ -880,6 +775,7 @@ describe('CompileController', function () {
         .calledWith(
           this.projectId,
           `/project/${this.projectId}/output/output.pdf`,
+          {},
           this.req,
           this.res
         )
diff --git a/services/web/test/unit/src/helpers/MockResponse.js b/services/web/test/unit/src/helpers/MockResponse.js
index 4b43c46fd1..6ade53e06b 100644
--- a/services/web/test/unit/src/helpers/MockResponse.js
+++ b/services/web/test/unit/src/helpers/MockResponse.js
@@ -81,6 +81,10 @@ class MockResponse {
     }
   }
 
+  writeHead(status) {
+    this.statusCode = status
+  }
+
   send(status, body) {
     if (arguments.length < 2) {
       if (typeof status !== 'number') {