diff --git a/packages/api/src/routes/auth/callbacks/createSessionCallback.js b/packages/api/src/routes/auth/callbacks/createSessionCallback.js
index 3edbbdf6d..ece123f2d 100644
--- a/packages/api/src/routes/auth/callbacks/createSessionCallback.js
+++ b/packages/api/src/routes/auth/callbacks/createSessionCallback.js
@@ -24,7 +24,6 @@ function createSessionCallback({ authConfig, plugins }) {
   });
 
   async function sessionCallback({ session, token, user }) {
-    // console.log({ session, token, user });
     if (token) {
       const {
         sub,
@@ -74,6 +73,7 @@ function createSessionCallback({ authConfig, plugins }) {
     }
 
     for (const plugin of sessionCallbackPlugins) {
+      // eslint-disable-next-line no-param-reassign
       session = await plugin.fn({
         properties: plugin.properties ?? {},
         session,
diff --git a/packages/build/src/build/buildRefs/buildRefs.js b/packages/build/src/build/buildRefs/buildRefs.js
index ad5b8d89e..2a95405f7 100644
--- a/packages/build/src/build/buildRefs/buildRefs.js
+++ b/packages/build/src/build/buildRefs/buildRefs.js
@@ -16,14 +16,21 @@
 
 import recursiveBuild from './recursiveBuild.js';
 import makeRefDefinition from './makeRefDefinition.js';
-// TODO: build operators aren't evaluated in lowdefy.yaml file. Move recursive call up a layer or something.
+import evaluateBuildOperators from './evaluateBuildOperators.js';
+
 async function buildRefs({ context }) {
-  const components = await recursiveBuild({
+  const refDef = makeRefDefinition('lowdefy.yaml');
+  let components = await recursiveBuild({
     context,
-    refDef: makeRefDefinition('lowdefy.yaml'),
+    refDef,
     count: 0,
   });
-  return components || {};
+  components = await evaluateBuildOperators({
+    context,
+    input: components,
+    refDef,
+  });
+  return components ?? {};
 }
 
 export default buildRefs;
diff --git a/packages/build/src/build/buildRefs/buildRefs.test.js b/packages/build/src/build/buildRefs/buildRefs.test.js
index ff66c1ce4..a20881851 100644
--- a/packages/build/src/build/buildRefs/buildRefs.test.js
+++ b/packages/build/src/build/buildRefs/buildRefs.test.js
@@ -19,6 +19,12 @@ import { jest } from '@jest/globals';
 import buildRefs from './buildRefs.js';
 import testContext from '../../test/testContext.js';
 
+const mockLogWarn = jest.fn();
+
+const logger = {
+  warn: mockLogWarn,
+};
+
 const readConfigFileMockImplementation = (files) => {
   const mockImp = (filePath) => {
     const file = files.find((file) => file.path === filePath);
@@ -33,6 +39,7 @@ const readConfigFileMockImplementation = (files) => {
 const mockReadConfigFile = jest.fn();
 
 const context = testContext({
+  logger,
   readConfigFile: mockReadConfigFile,
 });
 
@@ -1047,3 +1054,91 @@ _ref: target`,
     });
   });
 });
+
+describe('Evaluate build time operators', () => {
+  test('Evaluate build time operators in lowdefy.yaml', async () => {
+    const files = [
+      {
+        path: 'lowdefy.yaml',
+        content: `
+answer:
+  _build.sum:
+    - 1
+    - 1`,
+      },
+    ];
+    mockReadConfigFile.mockImplementation(readConfigFileMockImplementation(files));
+    const res = await buildRefs({ context });
+    expect(res).toEqual({
+      answer: 2,
+    });
+  });
+
+  test('Evaluate build time operators in referenced file', async () => {
+    const files = [
+      {
+        path: 'lowdefy.yaml',
+        content: `
+answer:
+  _ref: file.yaml`,
+      },
+      {
+        path: 'file.yaml',
+        content: `
+_build.sum:
+  - 1
+  - 1`,
+      },
+    ];
+    mockReadConfigFile.mockImplementation(readConfigFileMockImplementation(files));
+    const res = await buildRefs({ context });
+    expect(res).toEqual({
+      answer: 2,
+    });
+  });
+
+  test('Build time operator error in lowdefy.yaml', async () => {
+    const files = [
+      {
+        path: 'lowdefy.yaml',
+        content: `
+answer:
+  _build.sum: A`,
+      },
+    ];
+    mockReadConfigFile.mockImplementation(readConfigFileMockImplementation(files));
+    const res = await buildRefs({ context });
+    expect(res).toEqual({
+      answer: null,
+    });
+    expect(mockLogWarn.mock.calls).toEqual([
+      ['Build operator errors.'],
+      ['Operator Error: _sum takes an array type as input. Received: "A" at lowdefy.yaml.'],
+    ]);
+  });
+
+  test('Build time operator error in referenced file', async () => {
+    const files = [
+      {
+        path: 'lowdefy.yaml',
+        content: `
+answer:
+  _ref: file.yaml`,
+      },
+      {
+        path: 'file.yaml',
+        content: `
+_build.sum: A`,
+      },
+    ];
+    mockReadConfigFile.mockImplementation(readConfigFileMockImplementation(files));
+    const res = await buildRefs({ context });
+    expect(res).toEqual({
+      answer: null,
+    });
+    expect(mockLogWarn.mock.calls).toEqual([
+      ['Build operator errors.'],
+      ['Operator Error: _sum takes an array type as input. Received: "A" at file.yaml.'],
+    ]);
+  });
+});
diff --git a/packages/build/src/build/buildRefs/recursiveBuild.js b/packages/build/src/build/buildRefs/recursiveBuild.js
index 012044299..df8aa20b6 100644
--- a/packages/build/src/build/buildRefs/recursiveBuild.js
+++ b/packages/build/src/build/buildRefs/recursiveBuild.js
@@ -25,12 +25,8 @@ async function recursiveParseFile({ context, refDef, count, referencedFrom }) {
     throw new Error(`Maximum recursion depth of references exceeded.`);
   }
   let fileContent = await getRefContent({ context, refDef, referencedFrom });
-  const parsedFileContent = await evaluateBuildOperators({
-    context,
-    input: fileContent,
-    refDef: { path: 'lowdefy.yaml' },
-  });
-  const { foundRefs, fileContentBuiltRefs } = getRefsFromFile(parsedFileContent);
+
+  const { foundRefs, fileContentBuiltRefs } = getRefsFromFile(fileContent);
 
   const parsedFiles = {};
 
@@ -39,7 +35,6 @@ async function recursiveParseFile({ context, refDef, count, referencedFrom }) {
   // To do this, since foundRefs is an array of ref definitions that are in order of the
   // deepest nodes first we for loop over over foundRefs one by one, awaiting each result.
 
-  // eslint-disable-next-line no-restricted-syntax
   for (const newRefDef of foundRefs.values()) {
     // Parse vars and path before passing down to parse new file
     const parsedRefDef = populateRefs({
@@ -55,19 +50,20 @@ async function recursiveParseFile({ context, refDef, count, referencedFrom }) {
       referencedFrom: refDef.path,
     });
 
-    const evaluatedOperators = await evaluateBuildOperators({
+    const transformedFile = await runTransformer({
       context,
       input: parsedFile,
       refDef: parsedRefDef,
     });
 
-    const transformedFile = await runTransformer({
+    // Evaluated in recursive loop for better error messages
+    const evaluatedOperators = await evaluateBuildOperators({
       context,
-      input: evaluatedOperators,
+      input: transformedFile,
       refDef: parsedRefDef,
     });
 
-    parsedFiles[newRefDef.id] = transformedFile;
+    parsedFiles[newRefDef.id] = evaluatedOperators;
   }
   return populateRefs({
     toPopulate: fileContentBuiltRefs,
diff --git a/packages/operators/src/nodeParser.js b/packages/operators/src/nodeParser.js
index 69c973cf9..2c9fded44 100644
--- a/packages/operators/src/nodeParser.js
+++ b/packages/operators/src/nodeParser.js
@@ -17,15 +17,18 @@
 import { serializer, type } from '@lowdefy/helpers';
 
 class NodeParser {
-  constructor({ env, payload, secrets, user, operators }) {
+  constructor({ env, payload, secrets, user, operators, verbose }) {
     this.env = env;
     this.operators = operators;
     this.payload = payload;
     this.secrets = secrets;
     this.user = user;
     this.parse = this.parse.bind(this);
+    this.verbose;
   }
 
+  // TODO: Look at logging here
+  // TODO: Remove console.error = () => {}; from tests
   parse({ args, input, location, operatorPrefix = '_' }) {
     if (type.isUndefined(input)) {
       return { output: input, errors: [] };
@@ -63,7 +66,9 @@ class NodeParser {
         return res;
       } catch (e) {
         errors.push(e);
-        console.error(e);
+        if (this.verbose) {
+          console.error(e);
+        }
         return null;
       }
     };
diff --git a/packages/operators/src/nodeParser.test.js b/packages/operators/src/nodeParser.test.js
index 5e0ca9aa8..5d96053da 100644
--- a/packages/operators/src/nodeParser.test.js
+++ b/packages/operators/src/nodeParser.test.js
@@ -17,8 +17,6 @@
 /* eslint-disable max-classes-per-file */
 import NodeParser from './nodeParser.js';
 
-console.error = () => {};
-
 const args = [{ args: true }];
 
 const operators = {