From 5ebb2eeebf6688087f850b3ce193a39550898b6c Mon Sep 17 00:00:00 2001
From: Alex Donesky <adonesky@gmail.com>
Date: Wed, 2 Sep 2026 21:37:30 -0500
Subject: [PATCH 1/3] fix: emit ESM-compatible wordlist import

Use a namespace import so the generated ESM bundle remains compatible with strict bundlers and add an artifact regression check.
---
 .github/workflows/build-lint-test.yml |  1 +
 package.json                          |  1 +
 scripts/test-esm-build.js             | 14 ++++++++++++++
 src/mnemonic.ts                       |  4 +++-
 4 files changed, 19 insertions(+), 1 deletion(-)
 create mode 100644 scripts/test-esm-build.js

diff --git a/.github/workflows/build-lint-test.yml b/.github/workflows/build-lint-test.yml
index 6ff43e28e..7fdcdd02f 100644
--- a/.github/workflows/build-lint-test.yml
+++ b/.github/workflows/build-lint-test.yml
@@ -32,6 +32,7 @@ jobs:
           is-high-risk-environment: false
           node-version: ${{ matrix.node-version }}
       - run: yarn build
+      - run: yarn test:build
       # This step is dependent on the TypeScript build output, so it's run
       # here, rather than in the test job.
       - run: yarn test:types
diff --git a/package.json b/package.json
index 1206bd23c..4457ac61b 100644
--- a/package.json
+++ b/package.json
@@ -53,6 +53,7 @@
     "lint:misc": "prettier '**/*.json' '**/*.md' '!CHANGELOG.md' '**/*.yml' '!.yarnrc.yml' --ignore-path .gitignore --no-error-on-unmatched-pattern",
     "prepack": "./scripts/prepack.sh",
     "test": "yarn test:source && yarn test:types",
+    "test:build": "node ./scripts/test-esm-build.js",
     "test:source": "jest && jest-it-up",
     "test:types": "tsd",
     "test:watch": "jest --watch"
diff --git a/scripts/test-esm-build.js b/scripts/test-esm-build.js
new file mode 100644
index 000000000..90df0a3dd
--- /dev/null
+++ b/scripts/test-esm-build.js
@@ -0,0 +1,14 @@
+const assert = require('node:assert/strict');
+const { readFileSync } = require('node:fs');
+const path = require('node:path');
+
+const mnemonicModule = readFileSync(
+  path.resolve(__dirname, '../dist/mnemonic.mjs'),
+  'utf8',
+);
+
+assert.match(
+  mnemonicModule,
+  /^import \* as \w+ from "@metamask\/scure-bip39\/dist\/wordlists\/english\.js";$/mu,
+  'The ESM build must use a namespace import for the CommonJS wordlist module',
+);
diff --git a/src/mnemonic.ts b/src/mnemonic.ts
index 16815344f..ea462964b 100644
--- a/src/mnemonic.ts
+++ b/src/mnemonic.ts
@@ -1,4 +1,6 @@
-import { wordlist } from '@metamask/scure-bip39/dist/wordlists/english';
+import * as englishWordlist from '@metamask/scure-bip39/dist/wordlists/english';
+
+const { wordlist } = englishWordlist;
 
 /**
  * Transform a typed array containing mnemonic data to the seed phrase.

From e1e514913c43f13233f4224c852411a96959d30e Mon Sep 17 00:00:00 2001
From: Alex Donesky <adonesky@gmail.com>
Date: Wed, 2 Sep 2026 21:38:28 -0500
Subject: [PATCH 2/3] chore: document ESM wordlist fix

---
 CHANGELOG.md | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index db8f785c2..02a3c7a15 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Fixed
+
+- Fix ESM compatibility for the BIP-39 mnemonic utilities ([#309](https://github.com/MetaMask/utils/pull/309))
+
 ## [11.12.0]
 
 ### Added

From b7f81f2fb625066fd52038c7ce45bcc7c6f05627 Mon Sep 17 00:00:00 2001
From: Alex Donesky <adonesky@gmail.com>
Date: Thu, 3 Sep 2026 09:23:18 -0500
Subject: [PATCH 3/3] test: remove ESM artifact check

---
 .github/workflows/build-lint-test.yml |  1 -
 package.json                          |  1 -
 scripts/test-esm-build.js             | 14 --------------
 3 files changed, 16 deletions(-)
 delete mode 100644 scripts/test-esm-build.js

diff --git a/.github/workflows/build-lint-test.yml b/.github/workflows/build-lint-test.yml
index 7fdcdd02f..6ff43e28e 100644
--- a/.github/workflows/build-lint-test.yml
+++ b/.github/workflows/build-lint-test.yml
@@ -32,7 +32,6 @@ jobs:
           is-high-risk-environment: false
           node-version: ${{ matrix.node-version }}
       - run: yarn build
-      - run: yarn test:build
       # This step is dependent on the TypeScript build output, so it's run
       # here, rather than in the test job.
       - run: yarn test:types
diff --git a/package.json b/package.json
index 4457ac61b..1206bd23c 100644
--- a/package.json
+++ b/package.json
@@ -53,7 +53,6 @@
     "lint:misc": "prettier '**/*.json' '**/*.md' '!CHANGELOG.md' '**/*.yml' '!.yarnrc.yml' --ignore-path .gitignore --no-error-on-unmatched-pattern",
     "prepack": "./scripts/prepack.sh",
     "test": "yarn test:source && yarn test:types",
-    "test:build": "node ./scripts/test-esm-build.js",
     "test:source": "jest && jest-it-up",
     "test:types": "tsd",
     "test:watch": "jest --watch"
diff --git a/scripts/test-esm-build.js b/scripts/test-esm-build.js
deleted file mode 100644
index 90df0a3dd..000000000
--- a/scripts/test-esm-build.js
+++ /dev/null
@@ -1,14 +0,0 @@
-const assert = require('node:assert/strict');
-const { readFileSync } = require('node:fs');
-const path = require('node:path');
-
-const mnemonicModule = readFileSync(
-  path.resolve(__dirname, '../dist/mnemonic.mjs'),
-  'utf8',
-);
-
-assert.match(
-  mnemonicModule,
-  /^import \* as \w+ from "@metamask\/scure-bip39\/dist\/wordlists\/english\.js";$/mu,
-  'The ESM build must use a namespace import for the CommonJS wordlist module',
-);