From dd3d3e4b5f76e71bcf5cf53dd2097a58e416a6af Mon Sep 17 00:00:00 2001
From: Emma Jamieson-Hoare <ejamieson19@gmail.com>
Date: Tue, 2 Jun 2026 14:07:47 +0200
Subject: [PATCH 1/2] test: add ES2020 challenge typecheck fixture

---
 examples/charge-wagmi/src/mppx-es2020-compat.ts | 13 +++++++++++++
 1 file changed, 13 insertions(+)
 create mode 100644 examples/charge-wagmi/src/mppx-es2020-compat.ts

diff --git a/examples/charge-wagmi/src/mppx-es2020-compat.ts b/examples/charge-wagmi/src/mppx-es2020-compat.ts
new file mode 100644
index 00000000..665cc19c
--- /dev/null
+++ b/examples/charge-wagmi/src/mppx-es2020-compat.ts
@@ -0,0 +1,13 @@
+import { Challenge } from 'mppx'
+
+// Included by the ES2020 example tsconfig to catch library APIs that require newer libs.
+export const serializedChallenge = Challenge.serialize(
+  Challenge.from({
+    id: 'abc123',
+    realm: 'api.example.com',
+    method: 'tempo',
+    intent: 'charge',
+    request: { amount: '1000000', currency: 'USD' },
+    description: 'Pay "premium" path C:\\tempo\\api',
+  }),
+)

From 5298d2a24a6494001d41f2298cbfae16d00cbb68 Mon Sep 17 00:00:00 2001
From: Emma Jamieson-Hoare <ejamieson19@gmail.com>
Date: Tue, 2 Jun 2026 14:34:52 +0200
Subject: [PATCH 2/2] test: expand challenge quoted-string escaping cases

---
 src/Challenge.test.ts | 34 ++++++++++++++++++++++++++++++----
 1 file changed, 30 insertions(+), 4 deletions(-)

diff --git a/src/Challenge.test.ts b/src/Challenge.test.ts
index 357e0b27..b1226130 100644
--- a/src/Challenge.test.ts
+++ b/src/Challenge.test.ts
@@ -454,19 +454,45 @@ describe('serialize', () => {
     expect(header).toContain('expires="2025-01-06T12:00:00Z"')
   })
 
-  test('behavior: escapes quoted-string values', () => {
+  test.each([
+    {
+      description: 'Plain payment description',
+      escaped: 'Plain payment description',
+      label: 'plain values',
+    },
+    {
+      description: 'Pay "premium"',
+      escaped: 'Pay \\"premium\\"',
+      label: 'double quotes',
+    },
+    {
+      description: 'Path C:\\tempo\\api',
+      escaped: 'Path C:\\\\tempo\\\\api',
+      label: 'backslashes',
+    },
+    {
+      description: 'Pay "premium" path C:\\tempo\\api',
+      escaped: 'Pay \\"premium\\" path C:\\\\tempo\\\\api',
+      label: 'mixed quotes and backslashes',
+    },
+    {
+      description: 'Ends with slash \\',
+      escaped: 'Ends with slash \\\\',
+      label: 'trailing backslash',
+    },
+  ])('behavior: escapes quoted-string values: $label', ({ description, escaped }) => {
     const challenge = Challenge.from({
       id: 'abc123',
       realm: 'api.example.com',
       method: 'tempo',
       intent: 'charge',
       request: { amount: '1000000' },
-      description: 'Pay "premium" path C:\\tempo\\api',
+      description,
     })
 
     const header = Challenge.serialize(challenge)
-    expect(header).toContain('description="Pay \\"premium\\" path C:\\\\tempo\\\\api"')
-    expect(Challenge.deserialize(header).description).toBe('Pay "premium" path C:\\tempo\\api')
+    expect(header).toContain(`description="${escaped}"`)
+    expect(Challenge.deserialize(header).description).toBe(description)
   })
 
   test('error: rejects CRLF in quoted-string values', () => {