diff --git a/src/core/post-process.js b/src/core/post-process.js
index 22ec19690a..ad4a4ae338 100644
--- a/src/core/post-process.js
+++ b/src/core/post-process.js
@@ -9,7 +9,7 @@
  *      want to be using a new module with your own profile.
  *  - afterEnd: final thing that is called.
  */
-import { showError } from "./utils.js";
+import { makePluginUtils, showError } from "./utils.js";
 
 export const name = "core/post-process";
 
@@ -24,9 +24,11 @@ export async function run(config) {
         }
         return isFunction;
       })
-      .map(async f => {
+      .map(async (f, i) => {
+        const fnName = `${name}/${f.name || `[${i}]`}`;
+        const utils = makePluginUtils(fnName);
         try {
-          return await f(config, document);
+          return await f(config, document, utils);
         } catch (err) {
           const msg = `Function ${f.name} threw an error during \`postProcess\`.`;
           const hint = "See developer console.";
diff --git a/src/core/pre-process.js b/src/core/pre-process.js
index d55701160e..5eb830a721 100644
--- a/src/core/pre-process.js
+++ b/src/core/pre-process.js
@@ -8,7 +8,7 @@
  *      tested. Use with care, if you know what you're doing. Chances are you really
  *      want to be using a new module with your own profile
  */
-import { showError } from "./utils.js";
+import { makePluginUtils, showError } from "./utils.js";
 
 export const name = "core/pre-process";
 
@@ -23,9 +23,11 @@ export async function run(config) {
         }
         return isFunction;
       })
-      .map(async f => {
+      .map(async (f, i) => {
+        const fnName = `${name}/${f.name || `[${i}]`}`;
+        const utils = makePluginUtils(fnName);
         try {
-          return await f(config, document);
+          return await f(config, document, utils);
         } catch (err) {
           const msg = `Function ${f.name} threw an error during \`preProcess\`.`;
           const hint = "See developer console.";
diff --git a/src/core/utils.js b/src/core/utils.js
index da6f86994f..373e7fc66b 100644
--- a/src/core/utils.js
+++ b/src/core/utils.js
@@ -896,6 +896,21 @@ export function showWarning(message, pluginName, options = {}) {
   pub("warn", new RespecError(message, pluginName, opts));
 }
 
+/**
+ * Creates showError, showWarning utilities for use in custom pre-process and
+ * post-process plugins.
+ * @param {string} pluginName
+ */
+export function makePluginUtils(pluginName) {
+  /** @typedef {Parameters<typeof showError>[2]} Options */
+  return {
+    /** @type {(message: string, options?: Options) => void} */
+    showError: (msg, options) => showError(msg, pluginName, options),
+    /** @type {(message: string, options?: Options) => void} */
+    showWarning: (msg, options) => showWarning(msg, pluginName, options),
+  };
+}
+
 /**
  * Makes a string `coded`.
  *
diff --git a/tests/spec/core/pre-process-spec.html b/tests/spec/core/pre-process-spec.html
index 16724fd35f..f08ca1a7a5 100644
--- a/tests/spec/core/pre-process-spec.html
+++ b/tests/spec/core/pre-process-spec.html
@@ -15,6 +15,11 @@
   });
 }
 
+function preWithWarning(_conf, _doc, utils) {
+  document.getElementById("pre-warning").innerHTML = "pass";
+  utils.showWarning("This is a warning");
+}
+
 function postSyncFunc() {
   document.getElementById("post-sync").innerHTML = "pass";
 }
@@ -28,6 +33,17 @@
   });
 }
 
+function postWithDetailedError(_conf, _doc, utils) {
+  const el = document.getElementById("post-error");
+  el.innerHTML = "pass";
+  utils.showError("This is an error", {
+    hint: "This is a hint",
+    title: "This is a title",
+    details: "This is a detailed error message",
+    elements: [el],
+  });
+}
+
 function afterEnd() {
   return new Promise(resolve => {
     setTimeout(() => {
@@ -50,11 +66,13 @@
   preSyncFunc,
   preAsyncFunc,
   noOp, {},
+  preWithWarning
 ];
 
 respecConfig.postProcess = [
   postSyncFunc,
   postAsyncFunc,
+  postWithDetailedError,
   noOp, {},
 ];
 respecConfig.afterEnd = afterEnd;
@@ -72,7 +90,9 @@
 <section>
   <p id="pre-sync">FAIL</p>
   <p id="pre-async">FAIL</p>
+  <p id="pre-warning">FAIL</p>
   <p id="post-sync">FAIL</p>
+  <p id="post-error">FAIL</p>
   <p id="post-async">FAIL</p>
   <p id="afterend">FAIL</p>
 </section>
diff --git a/tests/spec/core/pre-process-spec.js b/tests/spec/core/pre-process-spec.js
index 5150c844c7..f0e091ca70 100644
--- a/tests/spec/core/pre-process-spec.js
+++ b/tests/spec/core/pre-process-spec.js
@@ -16,6 +16,35 @@ describe("Core - preProcess, postProcess, afterEnd", () => {
     expect(doc.getElementById("pre-async").innerHTML).toBe("pass");
     expect(doc.getElementById("post-sync").innerHTML).toBe("pass");
     expect(doc.getElementById("post-async").innerHTML).toBe("pass");
+    expect(doc.getElementById("pre-warning").innerHTML).toBe("pass");
+    expect(doc.getElementById("post-error").innerHTML).toBe("pass");
+  });
+
+  it("can show warnings and errors", () => {
+    const warnings = doc.respec.warnings.filter(warn =>
+      warn.plugin.startsWith("core/pre-process")
+    );
+    expect(warnings).toHaveSize(1);
+    expect(warnings[0].plugin).toBe("core/pre-process/preWithWarning");
+    expect(warnings[0].message).toBe("This is a warning");
+
+    const errors = doc.respec.errors.filter(
+      err =>
+        err.plugin.startsWith("core/post-process") &&
+        !err.message.startsWith("Every item")
+    );
+    expect(errors).toHaveSize(1);
+    expect(errors[0]).toEqual(
+      jasmine.objectContaining({
+        plugin: "core/post-process/postWithDetailedError",
+        message: "This is an error",
+        details: "This is a detailed error message",
+        hint: "This is a hint",
+        title: "This is a title",
+        name: "ReSpecError",
+        elements: [doc.getElementById("post-error")],
+      })
+    );
   });
 
   it("runs afterEnd method", () => {