diff --git a/api/auth_middleware_test.go b/api/auth_middleware_test.go
index 98d8d651..d7edebe7 100644
--- a/api/auth_middleware_test.go
+++ b/api/auth_middleware_test.go
@@ -315,6 +315,50 @@ func TestGetApiSignerWithApiAccessKey(t *testing.T) {
 		"body %s should contain address %s", string(body), parentApiKey)
 }
 
+func TestRequireWriteScope(t *testing.T) {
+	// requireWriteScope only reads c.Locals("oauthScope"), so no DB is needed.
+	app := &ApiServer{}
+
+	// Create a dummy write route that chains requireWriteScope after a scope-setting middleware
+	testApp := fiber.New()
+	testApp.Post("/write", func(c *fiber.Ctx) error {
+		// Simulate what authMiddleware does: set oauthScope if a PKCE token was used
+		scope := c.Get("X-Test-Oauth-Scope")
+		if scope != "" {
+			c.Locals("oauthScope", scope)
+		}
+		return c.Next()
+	}, app.requireWriteScope, func(c *fiber.Ctx) error {
+		return c.SendStatus(fiber.StatusOK)
+	})
+
+	// PKCE token with scope=read should be rejected (403)
+	t.Run("read scope rejected", func(t *testing.T) {
+		req := httptest.NewRequest("POST", "/write", nil)
+		req.Header.Set("X-Test-Oauth-Scope", "read")
+		res, err := testApp.Test(req, -1)
+		assert.NoError(t, err)
+		assert.Equal(t, fiber.StatusForbidden, res.StatusCode)
+	})
+
+	// PKCE token with scope=write should be allowed (200)
+	t.Run("write scope allowed", func(t *testing.T) {
+		req := httptest.NewRequest("POST", "/write", nil)
+		req.Header.Set("X-Test-Oauth-Scope", "write")
+		res, err := testApp.Test(req, -1)
+		assert.NoError(t, err)
+		assert.Equal(t, fiber.StatusOK, res.StatusCode)
+	})
+
+	// Non-OAuth auth (no oauthScope set) should pass through (200)
+	t.Run("non-oauth auth passes through", func(t *testing.T) {
+		req := httptest.NewRequest("POST", "/write", nil)
+		res, err := testApp.Test(req, -1)
+		assert.NoError(t, err)
+		assert.Equal(t, fiber.StatusOK, res.StatusCode)
+	})
+}
+
 // ensureApiKeysTables creates api_keys and api_access_keys if they do not exist.
 func ensureApiKeysTables(t *testing.T, app *ApiServer, ctx context.Context) {
 	t.Helper()