diff --git a/app/corpora/cqi_over_sio/cqi.py b/app/corpora/cqi_over_sio/cqi.py
index 62a7f63b..2e483b21 100644
--- a/app/corpora/cqi_over_sio/cqi.py
+++ b/app/corpora/cqi_over_sio/cqi.py
@@ -62,13 +62,7 @@ CQI_FUNCTION_NAMES: List[str] = [
 
 @socketio.on('cqi', namespace=ns)
 @socketio_login_required
-def cqi_over_sio(fn_data):
-    try:
-        fn_name: str = fn_data['fn_name']
-    except KeyError:
-        return {'code': 400, 'msg': 'Bad Request'}
-    fn_name: str = fn_data['fn_name']
-    fn_args: Dict = fn_data.get('fn_args', {})
+def cqi_over_sio(fn_name: str, fn_args: Dict = {}):
     try:
         cqi_client: CQiClient = session['cqi_over_sio']['cqi_client']
         cqi_client_lock: Lock = session['cqi_over_sio']['cqi_client_lock']
@@ -77,7 +71,6 @@ def cqi_over_sio(fn_data):
     if fn_name in CQI_FUNCTION_NAMES:
         fn: Callable = getattr(cqi_client.api, fn_name)
     elif fn_name in CQI_EXTENSION_FUNCTION_NAMES:
-        fn_args['cqi_client'] = cqi_client
         fn: Callable = getattr(extensions_module, fn_name)
     else:
         return {'code': 400, 'msg': 'Bad Request'}
@@ -92,14 +85,14 @@ def cqi_over_sio(fn_data):
             return {'code': 400, 'msg': 'Bad Request'}
     cqi_client_lock.acquire()
     try:
-        return_value = fn(**fn_args)
+        fn_return_value = fn(**fn_args)
     except BrokenPipeError:
-        return_value = {
+        fn_return_value = {
             'code': 500,
             'msg': 'Internal Server Error'
         }
     except CQiException as e:
-        return_value = {
+        return {
             'code': 502,
             'msg': 'Bad Gateway',
             'payload': {
@@ -110,11 +103,11 @@ def cqi_over_sio(fn_data):
         }
     finally:
         cqi_client_lock.release()
-    if isinstance(return_value, CQiStatus):
+    if isinstance(fn_return_value, CQiStatus):
         payload = {
-            'code': return_value.code,
-            'msg': return_value.__class__.__name__
+            'code': fn_return_value.code,
+            'msg': fn_return_value.__class__.__name__
         }
     else:
-        payload = return_value
+        payload = fn_return_value
     return {'code': 200, 'msg': 'OK', 'payload': payload}
diff --git a/app/corpora/cqi_over_sio/extensions.py b/app/corpora/cqi_over_sio/extensions.py
index 33e00bc0..d92b6d5e 100644
--- a/app/corpora/cqi_over_sio/extensions.py
+++ b/app/corpora/cqi_over_sio/extensions.py
@@ -22,20 +22,22 @@ CQI_EXTENSION_FUNCTION_NAMES: List[str] = [
 ]
 
 
-def ext_corpus_update_db(cqi_client: CQiClient, corpus: str):
+def ext_corpus_update_db(corpus: str):
     db_corpus = Corpus.query.get(session['cqi_over_sio']['corpus_id'])
+    cqi_client: CQiClient = session['cqi_over_sio']['cqi_client']
     cqi_corpus = cqi_client.corpora.get(corpus)
     db_corpus.num_tokens = cqi_corpus.size
     db.session.commit()
     return StatusOk()
 
 
-def ext_corpus_static_data(cqi_client: CQiClient, corpus: str) -> Dict:
+def ext_corpus_static_data(corpus: str) -> Dict:
     db_corpus = Corpus.query.get(session['cqi_over_sio']['corpus_id'])
     static_corpus_data_file = os.path.join(db_corpus.path, 'cwb', 'static.json')
     if os.path.exists(static_corpus_data_file):
         with open(static_corpus_data_file, 'r') as f:
             return json.load(f)
+    cqi_client: CQiClient = session['cqi_over_sio']['cqi_client']
     cqi_corpus = cqi_client.corpora.get(corpus)
     ##########################################################################
     # A faster way to get cpos boundaries for smaller s_attrs                #
@@ -137,11 +139,11 @@ def ext_corpus_static_data(cqi_client: CQiClient, corpus: str) -> Dict:
 
 
 def ext_corpus_paginate_corpus(
-    cqi_client: CQiClient,
     corpus: str,
     page: int = 1,
     per_page: int = 20
 ) -> Dict:
+    cqi_client: CQiClient = session['cqi_over_sio']['cqi_client']
     cqi_corpus = cqi_client.corpora.get(corpus)
     # Sanity checks
     if (
@@ -182,13 +184,13 @@ def ext_corpus_paginate_corpus(
 
 
 def ext_cqp_paginate_subcorpus(
-    cqi_client: CQiClient,
     subcorpus: str,
     context: int = 50,
     page: int = 1,
     per_page: int = 20
 ) -> Dict:
     corpus_name, subcorpus_name = subcorpus.split(':', 1)
+    cqi_client: CQiClient = session['cqi_over_sio']['cqi_client']
     cqi_corpus = cqi_client.corpora.get(corpus_name)
     cqi_subcorpus = cqi_corpus.subcorpora.get(subcorpus_name)
     # Sanity checks
@@ -230,12 +232,12 @@ def ext_cqp_paginate_subcorpus(
 
 
 def ext_cqp_partial_export_subcorpus(
-    cqi_client: CQiClient,
     subcorpus: str,
     match_id_list: list,
     context: int = 50
 ) -> Dict:
     corpus_name, subcorpus_name = subcorpus.split(':', 1)
+    cqi_client: CQiClient = session['cqi_over_sio']['cqi_client']
     cqi_corpus = cqi_client.corpora.get(corpus_name)
     cqi_subcorpus = cqi_corpus.subcorpora.get(subcorpus_name)
     cqi_subcorpus_partial_export = partial_export_subcorpus(cqi_subcorpus, match_id_list, context=context)
@@ -243,11 +245,11 @@ def ext_cqp_partial_export_subcorpus(
 
 
 def ext_cqp_export_subcorpus(
-    cqi_client: CQiClient,
     subcorpus: str,
     context: int = 50
 ) -> Dict:
     corpus_name, subcorpus_name = subcorpus.split(':', 1)
+    cqi_client: CQiClient = session['cqi_over_sio']['cqi_client']
     cqi_corpus = cqi_client.corpora.get(corpus_name)
     cqi_subcorpus = cqi_corpus.subcorpora.get(subcorpus_name)
     cqi_subcorpus_export = export_subcorpus(cqi_subcorpus, context=context)
diff --git a/app/static/js/CorpusAnalysis/CorpusAnalysisApp.js b/app/static/js/CorpusAnalysis/CorpusAnalysisApp.js
index c3adcc7f..8af82e8d 100644
--- a/app/static/js/CorpusAnalysis/CorpusAnalysisApp.js
+++ b/app/static/js/CorpusAnalysis/CorpusAnalysisApp.js
@@ -100,14 +100,13 @@ class CorpusAnalysisApp {
           this.elements.m.initModal.close();
         },
         (cqiError) => {
+          let errorString = `${cqiError.code}: ${cqiError.constructor.name}`;
           let errorsElement = this.elements.initModal.querySelector('.errors');
           let progressElement = this.elements.initModal.querySelector('.progress');
-          errorsElement.innerText = JSON.stringify(cqiError);
+          errorsElement.innerText = errorString;
           errorsElement.classList.remove('hide');
+          app.flash(errorString, 'error');
           progressElement.classList.add('hide');
-          if ('payload' in cqiError && 'code' in cqiError.payload && 'msg' in cqiError.payload) {
-            app.flash(`${cqiError.payload.code}: ${cqiError.payload.msg}`, 'error');
-          }
         }
       );
 
diff --git a/app/static/js/CorpusAnalysis/CorpusAnalysisConcordance.js b/app/static/js/CorpusAnalysis/CorpusAnalysisConcordance.js
index dc1ee3a2..e6c00e73 100644
--- a/app/static/js/CorpusAnalysis/CorpusAnalysisConcordance.js
+++ b/app/static/js/CorpusAnalysis/CorpusAnalysisConcordance.js
@@ -68,13 +68,11 @@ class CorpusAnalysisConcordance {
             this.elements.progress.classList.add('hide');
             this.app.enableActionElements();
           },
-          (cqiStatus) => {
-            // TODDO: CHECK THIS!
-            this.elements.error.innerText = JSON.stringify(cqiStatus);
+          (cqiError) => {
+            let errorString = `${cqiError.code}: ${cqiError.constructor.name}`;
+            this.elements.error.innerText = errorString;
             this.elements.error.classList.remove('hide');
-            if ('payload' in cqiStatus && 'code' in cqiStatus.payload && 'msg' in cqiStatus.payload) {
-              app.flash(`${cqiStatus.payload.code}: ${cqiStatus.payload.msg}`, 'error');
-            }
+            app.flash(errorString, 'error');
             this.elements.progress.classList.add('hide');
             this.app.enableActionElements();
           }
@@ -313,8 +311,9 @@ class CorpusAnalysisConcordance {
             this.clearSubcorpusPagination();
           }
         },
-        (cQiError) => {
-          app.flash(`${cQiError.payload.code}: ${cQiError.payload.msg}`, 'error');
+        (cqiError) => {
+          let errorString = `${cqiError.code}: ${cqiError.constructor.name}`;
+          app.flash(errorString, 'error');
         }
       );
     });
diff --git a/app/static/js/CorpusAnalysis/CorpusAnalysisReader.js b/app/static/js/CorpusAnalysis/CorpusAnalysisReader.js
index 33dd6f47..d6c99926 100644
--- a/app/static/js/CorpusAnalysis/CorpusAnalysisReader.js
+++ b/app/static/js/CorpusAnalysis/CorpusAnalysisReader.js
@@ -45,11 +45,10 @@ class CorpusAnalysisReader {
             this.app.enableActionElements();
           },
           (cqiError) => {
-            this.elements.error.innerText = JSON.stringify(error);
+            let errorString = `${cqiError.code}: ${cqiError.constructor.name}`;
+            this.elements.error.innerText = errorString;
             this.elements.error.classList.remove('hide');
-            if ('payload' in error && 'code' in error.payload && 'msg' in error.payload) {
-              app.flash(`${error.payload.code}: ${error.payload.msg}`, 'error');
-            }
+            app.flash(errorString, 'error');
             this.elements.progress.classList.add('hide');
             this.app.enableActionElements();
           }
diff --git a/app/static/js/cqi/api/client.js b/app/static/js/cqi/api/client.js
index c6c7e5b9..daf2a401 100644
--- a/app/static/js/cqi/api/client.js
+++ b/app/static/js/cqi/api/client.js
@@ -30,14 +30,12 @@ cqi.api.APIClient = class APIClient {
       //   if (timeoutError) {
       //     reject(timeoutError);
       //   }
-      this.socket.emit('cqi', {fn_name: fn_name, fn_args: fn_args}, (response) => {
+      this.socket.emit('cqi', fn_name, fn_args, (response) => {
         if (response.code === 200) {
           resolve(response.payload);
-        }
-        if (response.code === 500) {
+        } else if (response.code === 500) {
           reject(new Error(`[${response.code}] ${response.msg}`));
-        }
-        if (response.code === 502) {
+        } else if (response.code === 502) {
           reject(new cqi.errors.lookup[response.payload.code]());
         }
       });