diff --git a/dist/index.d.ts b/dist/index.d.ts
index d0d893ea0caffb6c1c70c5f95aed8ca49bc74701..738c53fe71b5cde39d288b11481da83eef380f04 100644
--- a/dist/index.d.ts
+++ b/dist/index.d.ts
@@ -14,7 +14,7 @@ declare type AddSuffix<Obj extends Record<string, any>, Suffix extends string> =
     [Key in keyof Obj as `${string & Key}${Suffix}`]: Obj[Key];
 };
 
-export declare function GraphiQL({ dangerouslyAssumeSchemaIsValid, confirmCloseTab, defaultQuery, defaultTabs, externalFragments, fetcher, getDefaultFieldNames, headers, inputValueDeprecation, introspectionQueryName, maxHistoryLength, onEditOperationName, onSchemaChange, onTabChange, onTogglePluginVisibility, operationName, plugins, query, response, schema, schemaDescription, shouldPersistHeaders, storage, validationRules, variables, visiblePlugin, defaultHeaders, ...props }: GraphiQLProps): JSX_2.Element;
+export declare function GraphiQL({ dangerouslyAssumeSchemaIsValid, confirmCloseTab, defaultQuery, defaultTabs, externalFragments, fetcher, getDefaultFieldNames, headers, inputValueDeprecation, introspectionQueryName, maxHistoryLength, onEditOperationName, onSchemaChange, onTabChange, onTogglePluginVisibility, operationName, plugins, query, response, schema, schemaDescription, shouldPersistHeaders, storage, validationRules, variables, visiblePlugin, defaultHeaders, onModifyHeaders, ...props }: GraphiQLProps): JSX_2.Element;
 
 export declare namespace GraphiQL {
     var Logo: typeof GraphiQLLogo;
diff --git a/dist/index.js b/dist/index.js
index 8658855e3697ce1f5e8bd83afc2beecade922288..d94624983c04ef8efccf5b7fe0dd436ad5762136 100644
--- a/dist/index.js
+++ b/dist/index.js
@@ -392,7 +392,7 @@ function GraphiQLInterface(props) {
         },
         tab.title
       ),
-      tabs.length > 1 && /* @__PURE__ */ React.createElement(react.Tab.Close, { onClick: handleTabClose })
+      /* @__PURE__ */ React.createElement(react.Tab.Close, { onClick: handleTabClose })
     ))
   ), /* @__PURE__ */ React.createElement(react.Tooltip, { label: "New tab" }, /* @__PURE__ */ React.createElement(
     react.UnStyledButton,
diff --git a/dist/index.mjs b/dist/index.mjs
index cf1a9036b4b35b7918da09ead6977e1e77724b8a..970cc4cda25ff74c49e542db51af558d7e0d277a 100644
--- a/dist/index.mjs
+++ b/dist/index.mjs
@@ -1,4 +1,4 @@
-import { GraphiQLProvider, useEditorContext, useExecutionContext, useSchemaContext, useStorageContext, usePluginContext, useTheme, useDragResize, Tooltip, UnStyledButton, ReloadIcon, KeyboardShortcutIcon, SettingsIcon, Tabs, Tab, PlusIcon, QueryEditor, ExecuteButton, ChevronUpIcon, ChevronDownIcon, VariableEditor, HeaderEditor, Spinner, ResponseEditor, Dialog, ButtonGroup, Button, useCopyQuery, useMergeQuery, usePrettifyEditors, ToolbarButton, PrettifyIcon, MergeIcon, CopyIcon } from "@graphiql/react";
+import { GraphiQLProvider, useEditorContext, useExecutionContext, useSchemaContext, useStorageContext, usePluginContext, useTheme, useDragResize, Tooltip, UnStyledButton, ReloadIcon, KeyboardShortcutIcon, SettingsIcon, Tabs, Tab, PlusIcon, QueryEditor, ExecuteButton, ChevronUpIcon, ChevronDownIcon, VariableEditor, HeaderEditor, Spinner, ResponseEditor, Dialog, ButtonGroup, Button, useCopyQuery, useMergeQuery, usePrettifyEditors, ToolbarButton, PrettifyIcon, MergeIcon, CopyIcon, isMacOs } from "@graphiql/react";
 import { GraphiQLProvider as GraphiQLProvider2 } from "@graphiql/react";
 import React, { version, useMemo, useEffect, useState, Children, cloneElement, useCallback, Fragment } from "react";
 const majorVersion = parseInt(version.slice(0, 2), 10);
@@ -39,6 +39,7 @@ function GraphiQL({
   variables,
   visiblePlugin,
   defaultHeaders,
+  onModifyHeaders,
   ...props
 }) {
   var _a, _b;
@@ -85,7 +86,8 @@ function GraphiQL({
       shouldPersistHeaders,
       storage,
       validationRules,
-      variables
+      variables,
+      onModifyHeaders
     },
     /* @__PURE__ */ React.createElement(
       GraphiQLInterface,
@@ -391,14 +393,14 @@ function GraphiQLInterface(props) {
         },
         tab.title
       ),
-      tabs.length > 1 && /* @__PURE__ */ React.createElement(Tab.Close, { onClick: handleTabClose })
+      /* @__PURE__ */ React.createElement(Tab.Close, { onClick: handleTabClose })
     ))
   ), /* @__PURE__ */ React.createElement(Tooltip, { label: "New tab" }, /* @__PURE__ */ React.createElement(
     UnStyledButton,
     {
       type: "button",
       className: "graphiql-tab-add",
-      onClick: handleAddTab,
+      onClick: () => handleAddTab(),
       "aria-label": "New tab"
     },
     /* @__PURE__ */ React.createElement(PlusIcon, { "aria-hidden": "true" })
@@ -602,7 +604,7 @@ function GraphiQLInterface(props) {
     )) : null
   )));
 }
-const modifier = typeof navigator !== "undefined" && navigator.platform.toLowerCase().indexOf("mac") === 0 ? "Cmd" : "Ctrl";
+const modifier = isMacOs ? "⌘" : "Ctrl";
 const SHORT_KEYS = Object.entries({
   "Search in editor": [modifier, "F"],
   "Search in documentation": [modifier, "K"],