diff --git a/toolkit/components/extensions/ConduitsChild.jsm b/toolkit/components/extensions/ConduitsChild.jsm
index 80db2d1253ab..5abb02daebfc 100644
--- a/toolkit/components/extensions/ConduitsChild.jsm
+++ b/toolkit/components/extensions/ConduitsChild.jsm
@@ -7,6 +7,12 @@
  * This @file implements the child side of Conduits, an abstraction over
  * Fission IPC for extension API subject.  See {@link ConduitsParent.jsm}
  * for more details about the overall design.
+ *
+ * @typedef {object} MessageData
+ * @prop {ConduitID} [target]
+ * @prop {ConduitID} [sender]
+ * @prop {boolean} query
+ * @prop {object} arg
  */
 
 const EXPORTED_SYMBOLS = ["BaseConduit", "ConduitsChild"];
@@ -47,7 +53,7 @@ class BaseConduit {
    * @param {string} method
    * @param {boolean} query Flag indicating a response is expected.
    * @param {JSWindowActor} actor
-   * @param {{arg: object, sender: ConduitID}} data
+   * @param {MessageData} data
    * @returns {Promise?}
    */
   _send(method, query, actor, data) {
@@ -144,9 +150,18 @@ class ConduitsChild extends JSWindowActorChild {
 
   /**
    * JSWindowActor method, routes the message to the target subject.
+   * @param {string} name
+   * @param {MessageData|MessageData[]} data
    * @returns {Promise?}
    */
-  receiveMessage({ name, data: { target, arg, query, sender } }) {
+  receiveMessage({ name, data }) {
+    // Batch of webRequest events, run each and return results, ignoring errors.
+    if (Array.isArray(data)) {
+      let run = data => this.receiveMessage({ name, data });
+      return Promise.all(data.map(data => run(data).catch(Cu.reportError)));
+    }
+
+    let { target, arg, query, sender } = data;
     let conduit = this.conduits.get(target);
     if (!conduit) {
       throw new Error(`${name} for closed conduit ${target}: ${uneval(arg)}`);
diff --git a/toolkit/components/extensions/ConduitsParent.jsm b/toolkit/components/extensions/ConduitsParent.jsm
index 274b0ee266d5..a841e2ffb5ab 100644
--- a/toolkit/components/extensions/ConduitsParent.jsm
+++ b/toolkit/components/extensions/ConduitsParent.jsm
@@ -52,6 +52,8 @@ const { BaseConduit } = ChromeUtils.import(
   "resource://gre/modules/ConduitsChild.jsm"
 );
 
+const BATCH_TIMEOUT_MS = 250;
+
 /**
  * Internal, keeps track of all parent and remote (child) conduits.
  */
@@ -162,8 +164,13 @@ class BroadcastConduit extends BaseConduit {
     if (!this.open) {
       throw new Error(`send${method} on closed conduit ${this.id}`);
     }
-    let sender = this.address;
+
+    let sender = this.id;
     let { actor } = Hub.remotes.get(target);
+
+    if (method === "RunListener" && arg.path.startsWith("webRequest.")) {
+      return actor.batch(method, { target, arg, query, sender });
+    }
     return super._send(method, query, actor, { target, arg, query, sender });
   }
 
@@ -188,10 +195,38 @@ class BroadcastConduit extends BaseConduit {
 class ConduitsParent extends JSWindowActorParent {
   constructor() {
     super();
+    this.batchData = [];
+    this.batchPromise = null;
+  }
+
+  /**
+   * Group webRequest events to send them as a batch, reducing IPC overhead.
+   * @param {string} name
+   * @param {MessageData} data
+   */
+  async batch(name, data) {
+    let num = this.batchData.length;
+    this.batchData.push(data);
+
+    if (!num) {
+      let resolve;
+      this.batchPromise = new Promise(r => (resolve = r));
+
+      let send = () => {
+        resolve(this.manager && this.sendQuery(name, this.batchData));
+        this.batchData = [];
+      };
+      ChromeUtils.idleDispatch(send, { timeout: BATCH_TIMEOUT_MS });
+    }
+
+    let results = await this.batchPromise;
+    return results && results[num];
   }
 
   /**
    * JSWindowActor method, routes the message to the target subject.
+   * @param {string} name
+   * @param {MessageData} data
    * @returns {Promise?}
    */
   receiveMessage({ name, data: { arg, query, sender } }) {
diff --git a/toolkit/components/extensions/ExtensionParent.jsm b/toolkit/components/extensions/ExtensionParent.jsm
index b2723ed70dd1..9773cf0fad1b 100644
--- a/toolkit/components/extensions/ExtensionParent.jsm
+++ b/toolkit/components/extensions/ExtensionParent.jsm
@@ -1134,9 +1134,6 @@ ParentAPIManager = {
     let { childId } = data;
     let handlingUserInput = false;
 
-    // TODO: Bug 1587058 - Redesign webRequest event coelescing.
-    // let lowPriority = data.path.startsWith("webRequest.");
-
     let listener = async (...listenerArgs) => {
       let result = await this.conduit.queryRunListener(childId, {
         childId,