diff --git a/package-lock.json b/package-lock.json
index 636a455..d2609f1 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,12 +1,12 @@
 {
     "name": "@accordproject/template-engine",
-    "version": "2.5.11",
+    "version": "2.5.12",
     "lockfileVersion": 3,
     "requires": true,
     "packages": {
         "": {
             "name": "@accordproject/template-engine",
-            "version": "2.5.11",
+            "version": "2.5.12",
             "license": "Apache-2.0",
             "dependencies": {
                 "@accordproject/concerto-codegen": "3.23.1-20240509154651",
@@ -15,6 +15,7 @@
                 "@accordproject/markdown-common": "^0.16.22",
                 "@accordproject/markdown-template": "^0.16.22",
                 "@typescript/twoslash": "^3.2.4",
+                "browser-or-node": "^3.0.0",
                 "dayjs": "1.11.10",
                 "jsonpath": "^1.1.1",
                 "tar": "^6.2.0",
@@ -3035,6 +3036,11 @@
                 "node": ">=8"
             }
         },
+        "node_modules/browser-or-node": {
+            "version": "3.0.0",
+            "resolved": "https://registry.npmjs.org/browser-or-node/-/browser-or-node-3.0.0.tgz",
+            "integrity": "sha512-iczIdVJzGEYhP5DqQxYM9Hh7Ztpqqi+CXZpSmX8ALFs9ecXkQIeqRyM6TfxEfMVpwhl3dSuDvxdzzo9sUOIVBQ=="
+        },
         "node_modules/browser-process-hrtime": {
             "version": "1.0.0",
             "resolved": "https://registry.npmjs.org/browser-process-hrtime/-/browser-process-hrtime-1.0.0.tgz",
diff --git a/package.json b/package.json
index 13b6e0a..251ac04 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
     "name": "@accordproject/template-engine",
-    "version": "2.5.11",
+    "version": "2.5.12",
     "description": "Generation of AgreementMark from TemplateMark + JSON Data",
     "homepage": "https://github.com/accordproject",
     "engines": {
@@ -46,6 +46,7 @@
         "@accordproject/markdown-common": "^0.16.22",
         "@accordproject/markdown-template": "^0.16.22",
         "@typescript/twoslash": "^3.2.4",
+        "browser-or-node": "^3.0.0",
         "dayjs": "1.11.10",
         "jsonpath": "^1.1.1",
         "tar": "^6.2.0",
diff --git a/src/JavaScriptEvaluator.ts b/src/JavaScriptEvaluator.ts
index 4a2cf12..783d1db 100644
--- a/src/JavaScriptEvaluator.ts
+++ b/src/JavaScriptEvaluator.ts
@@ -74,7 +74,7 @@ export class JavaScriptEvaluator {
     workers: Array<ChildProcess>; // child processes
     queue: Array<WorkItem>; // queue of work to do
 
-    constructor(options: JavaScriptEvaluatorOptions) {
+    constructor(options: JavaScriptEvaluatorOptions = {waitInterval: 50, maxWorkers: 8, maxQueueDepth: 1000}) {
         this.options = options;
         this.workers = [];
         this.queue = [];
diff --git a/src/TemplateMarkInterpreter.ts b/src/TemplateMarkInterpreter.ts
index 5f705fb..60fecc2 100644
--- a/src/TemplateMarkInterpreter.ts
+++ b/src/TemplateMarkInterpreter.ts
@@ -14,6 +14,7 @@
 
 import jp from 'jsonpath';
 import traverse from 'traverse';
+import { isBrowser } from 'browser-or-node';
 import os from 'os';
 
 import { ClassDeclaration, Factory, Introspector, ModelManager, Serializer } from '@accordproject/concerto-core';
@@ -51,9 +52,8 @@ function checkCode(code:ICode) {
 
 // this is a global because we don't want the user
 // to configure child processes at the TemplateMarkInterpreter instance level
-const availableProcessors = process.env.MAX_WORKERS ? Number.parseInt(process.env.MAX_WORKERS) : os.availableParallelism();
-const javaScriptEvaluator = new JavaScriptEvaluator({
-    maxWorkers: availableProcessors, // how many child processes
+const javaScriptEvaluator = isBrowser ? new JavaScriptEvaluator() : new JavaScriptEvaluator({
+    maxWorkers: process.env.MAX_WORKERS ? Number.parseInt(process.env.MAX_WORKERS) : os.availableParallelism(), // how many child processes
     waitInterval: process.env.WAIT_INTERVAL ? Number.parseInt(process.env.WAIT_INTERVAL) : 50, // how long to wait before rescheduling work
     maxQueueDepth: process.env.MAX_QUEUE_DEPTH ? Number.parseInt(process.env.MAX_QUEUE_DEPTH) : 1000 // max requests to queue
 });
@@ -91,6 +91,9 @@ async function evaluateJavaScript(clauseLibrary:object, data: TemplateData, fn:
     try {
         const request = {code: expression, argumentNames: functionArgNames, arguments: functionArgValues};
         if(options?.childProcessJavaScriptEvaluation) {
+            if(isBrowser) {
+                throw new Error('Child process evaluation is not supported inside web browser');
+            }
             const evalOptions = options?.timeout ? {timeout: options.timeout} : undefined;
             const r = await javaScriptEvaluator.evalChildProcess(request, evalOptions);
             return (typeof r.result === 'object') ? JSON.stringify(r.result) : r.result.toString();