diff --git a/apps/gittensory-miner-extension/icons/icon-128.png b/apps/gittensory-miner-extension/icons/icon-128.png
new file mode 100644
index 000000000..acc7ab28e
Binary files /dev/null and b/apps/gittensory-miner-extension/icons/icon-128.png differ
diff --git a/apps/gittensory-miner-extension/icons/icon-16.png b/apps/gittensory-miner-extension/icons/icon-16.png
new file mode 100644
index 000000000..ef4576ea8
Binary files /dev/null and b/apps/gittensory-miner-extension/icons/icon-16.png differ
diff --git a/apps/gittensory-miner-extension/icons/icon-32.png b/apps/gittensory-miner-extension/icons/icon-32.png
new file mode 100644
index 000000000..cb37b26ae
Binary files /dev/null and b/apps/gittensory-miner-extension/icons/icon-32.png differ
diff --git a/apps/gittensory-miner-extension/icons/icon-48.png b/apps/gittensory-miner-extension/icons/icon-48.png
new file mode 100644
index 000000000..ccaf2d2be
Binary files /dev/null and b/apps/gittensory-miner-extension/icons/icon-48.png differ
diff --git a/apps/gittensory-miner-extension/manifest.json b/apps/gittensory-miner-extension/manifest.json
index f27558bd7..a43eb2d15 100644
--- a/apps/gittensory-miner-extension/manifest.json
+++ b/apps/gittensory-miner-extension/manifest.json
@@ -3,6 +3,12 @@
   "name": "LoopOver Miner Opportunity",
   "description": "Contributor-facing GitHub issue opportunity signals from a locally configured miner plane.",
   "version": "0.1.0",
+  "icons": {
+    "16": "icons/icon-16.png",
+    "32": "icons/icon-32.png",
+    "48": "icons/icon-48.png",
+    "128": "icons/icon-128.png"
+  },
   "permissions": ["storage"],
   "host_permissions": ["https://github.com/*", "http://localhost/*", "http://127.0.0.1/*"],
   "background": {
@@ -19,6 +25,11 @@
   ],
   "options_page": "options.html",
   "action": {
-    "default_title": "LoopOver Miner"
+    "default_title": "LoopOver Miner",
+    "default_icon": {
+      "16": "icons/icon-16.png",
+      "32": "icons/icon-32.png",
+      "48": "icons/icon-48.png"
+    }
   }
 }
diff --git a/scripts/build-miner-extension.mjs b/scripts/build-miner-extension.mjs
index 67d4a4fd4..d22e73a73 100644
--- a/scripts/build-miner-extension.mjs
+++ b/scripts/build-miner-extension.mjs
@@ -22,13 +22,19 @@ const PACKAGE_FILES = [
   "options.js",
   "styles.css",
   "toolbar-badge.js",
+  "icons/icon-16.png",
+  "icons/icon-32.png",
+  "icons/icon-48.png",
+  "icons/icon-128.png",
 ];
 
 rmSync(outDir, { recursive: true, force: true });
 mkdirSync(outDir, { recursive: true });
 
 for (const file of PACKAGE_FILES) {
-  cpSync(resolve(source, file), resolve(outDir, file));
+  const dest = resolve(outDir, file);
+  mkdirSync(dirname(dest), { recursive: true }); // create nested dirs (e.g. icons/) before copying
+  cpSync(resolve(source, file), dest);
 }
 
 const zipPath = resolve(source, "dist/loopover-miner-extension.zip");
diff --git a/test/unit/miner-extension-icons.test.ts b/test/unit/miner-extension-icons.test.ts
new file mode 100644
index 000000000..d9230bc07
--- /dev/null
+++ b/test/unit/miner-extension-icons.test.ts
@@ -0,0 +1,56 @@
+import { existsSync, readFileSync } from "node:fs";
+
+import { describe, expect, it } from "vitest";
+
+const EXT = "apps/gittensory-miner-extension";
+const manifest = JSON.parse(readFileSync(`${EXT}/manifest.json`, "utf8"));
+
+/** Parse a PNG's signature + IHDR (width/height/colorType) — enough to assert a real image of the expected size. */
+function readPng(path: string): {
+  valid: boolean;
+  width: number;
+  height: number;
+  colorType: number;
+} {
+  const buf = readFileSync(path);
+  const valid =
+    buf.subarray(0, 8).toString("hex") === "89504e470d0a1a0a" &&
+    buf.subarray(12, 16).toString("ascii") === "IHDR";
+  return {
+    valid,
+    width: buf.readUInt32BE(16),
+    height: buf.readUInt32BE(20),
+    colorType: buf[25] ?? 0,
+  };
+}
+
+describe("miner extension icons (#4862)", () => {
+  const SIZES = [16, 32, 48, 128] as const;
+
+  it("declares an icon set at the standard sizes in the manifest", () => {
+    for (const size of SIZES) {
+      expect(manifest.icons[String(size)]).toBe(`icons/icon-${size}.png`);
+    }
+  });
+
+  it("wires the toolbar action's default_icon at 16/32/48", () => {
+    for (const size of [16, 32, 48] as const) {
+      expect(manifest.action.default_icon[String(size)]).toBe(
+        `icons/icon-${size}.png`,
+      );
+    }
+  });
+
+  it("ships every declared icon as a real RGBA PNG whose dimensions match its declared size", () => {
+    for (const size of SIZES) {
+      const rel = manifest.icons[String(size)] as string;
+      const path = `${EXT}/${rel}`;
+      expect(existsSync(path), `${rel} exists`).toBe(true);
+      const png = readPng(path);
+      expect(png.valid, `${rel} is a valid PNG`).toBe(true);
+      expect(png.width).toBe(size);
+      expect(png.height).toBe(size);
+      expect(png.colorType).toBe(6); // 6 = truecolor + alpha (RGBA)
+    }
+  });
+});