diff --git a/lib/shared/typeahead-utils.js b/lib/shared/typeahead-utils.js
new file mode 100644
--- /dev/null
+++ b/lib/shared/typeahead-utils.js
@@ -0,0 +1,26 @@
+// @flow
+
+import type { RelativeMemberInfo } from '../types/thread-types';
+import SearchIndex from './search-index';
+import { threadOtherMembers } from './thread-utils';
+import { stringForUserExplicit } from './user-utils';
+
+function getTypeaheadUserSuggestions(
+  userSearchIndex: SearchIndex,
+  threadMembers: $ReadOnlyArray<RelativeMemberInfo>,
+  viewerID: ?string,
+  typedUsernamePrefix: string,
+): $ReadOnlyArray<RelativeMemberInfo> {
+  const userIDs = userSearchIndex.getSearchResults(typedUsernamePrefix);
+  const usersInThread = threadOtherMembers(threadMembers, viewerID);
+
+  return usersInThread
+    .filter(
+      user => typedUsernamePrefix.length === 0 || userIDs.includes(user.id),
+    )
+    .sort((userA, userB) =>
+      stringForUserExplicit(userA).localeCompare(stringForUserExplicit(userB)),
+    );
+}
+
+export { getTypeaheadUserSuggestions };
diff --git a/web/chat/chat-input-bar.react.js b/web/chat/chat-input-bar.react.js
--- a/web/chat/chat-input-bar.react.js
+++ b/web/chat/chat-input-bar.react.js
@@ -51,9 +51,10 @@
 import { useSelector } from '../redux/redux-utils';
 import { nonThreadCalendarQuery } from '../selectors/nav-selectors';
 import SWMansionIcon from '../SWMansionIcon.react';
+import { webTypeaheadRegex } from '../utils/typeahead-utils';
 import css from './chat-input-bar.css';
 import TypeaheadTooltip from './typeahead-tooltip.react';
-import { typeaheadRegex } from './typeahead-utils';
+
 type BaseProps = {
   +threadInfo: ThreadInfo,
   +inputState: InputState,
@@ -77,7 +78,6 @@
   +typeaheadMatchedStrings: ?TypeaheadMatchedStrings,
 };
 export type TypeaheadMatchedStrings = {
-  +entireText: string,
   +textBeforeAtSymbol: string,
   +usernamePrefix: string,
 };
@@ -573,7 +573,7 @@
       () =>
         inputSliceEndingAtCursor.length === props.inputState.draft.length ||
         /\s/.test(props.inputState.draft[props.inputState.textCursorPosition])
-          ? inputSliceEndingAtCursor.match(typeaheadRegex)
+          ? inputSliceEndingAtCursor.match(webTypeaheadRegex)
           : null,
       [
         inputSliceEndingAtCursor,
@@ -586,9 +586,9 @@
       () =>
         typeaheadRegexMatches !== null
           ? {
-              entireText: typeaheadRegexMatches[0],
-              textBeforeAtSymbol: typeaheadRegexMatches[1],
-              usernamePrefix: typeaheadRegexMatches[2],
+              textBeforeAtSymbol:
+                typeaheadRegexMatches.groups?.textPrefix ?? '',
+              usernamePrefix: typeaheadRegexMatches.groups?.username ?? '',
             }
           : null,
       [typeaheadRegexMatches],
diff --git a/web/chat/typeahead-tooltip.react.js b/web/chat/typeahead-tooltip.react.js
--- a/web/chat/typeahead-tooltip.react.js
+++ b/web/chat/typeahead-tooltip.react.js
@@ -4,20 +4,19 @@
 import * as React from 'react';
 
 import SearchIndex from 'lib/shared/search-index';
-import { threadOtherMembers } from 'lib/shared/thread-utils';
+import { getTypeaheadUserSuggestions } from 'lib/shared/typeahead-utils';
 import type { RelativeMemberInfo } from 'lib/types/thread-types';
 
 import type { InputState } from '../input/input-state';
-import { type TypeaheadMatchedStrings } from './chat-input-bar.react';
-import css from './typeahead-tooltip.css';
 import {
   getTypeaheadOverlayScroll,
   getTypeaheadTooltipActions,
   getTypeaheadTooltipButtons,
   getTypeaheadTooltipPosition,
-  getTypeaheadUserSuggestions,
   getTypeaheadChosenActionPosition,
-} from './typeahead-utils';
+} from '../utils/typeahead-utils';
+import { type TypeaheadMatchedStrings } from './chat-input-bar.react';
+import css from './typeahead-tooltip.css';
 
 export type TypeaheadTooltipProps = {
   +inputState: InputState,
@@ -38,13 +37,9 @@
     matchedStrings,
   } = props;
 
-  const {
-    entireText: matchedText,
-    textBeforeAtSymbol: matchedTextBeforeAtSymbol,
-    usernamePrefix: matchedUsernamePrefix,
-  } = matchedStrings;
+  const { textBeforeAtSymbol, usernamePrefix } = matchedStrings;
 
-  const typedPrefix = matchedUsernamePrefix ?? '';
+  const typedUsernamePrefix = usernamePrefix ?? '';
 
   const [isAnimation, setIsAnimation] = React.useState(false);
   const overlayRef = React.useRef<?HTMLDivElement>();
@@ -59,10 +54,11 @@
     () =>
       getTypeaheadUserSuggestions(
         userSearchIndex,
-        threadOtherMembers(threadMembers, viewerID),
-        typedPrefix,
+        threadMembers,
+        viewerID,
+        typedUsernamePrefix,
       ),
-    [userSearchIndex, threadMembers, viewerID, typedPrefix],
+    [userSearchIndex, threadMembers, viewerID, typedUsernamePrefix],
   );
 
   const actions = React.useMemo(
@@ -72,27 +68,23 @@
         inputStateSetDraft: inputState.setDraft,
         inputStateSetTextCursorPosition: inputState.setTextCursorPosition,
         suggestedUsers,
-        matchedTextBeforeAtSymbol,
-        matchedText,
+        textBeforeAtSymbol,
+        typedUsernamePrefix,
       }),
     [
       inputState.draft,
       inputState.setDraft,
       inputState.setTextCursorPosition,
       suggestedUsers,
-      matchedTextBeforeAtSymbol,
-      matchedText,
+      textBeforeAtSymbol,
+      typedUsernamePrefix,
     ],
   );
 
   const tooltipPosition = React.useMemo(
     () =>
-      getTypeaheadTooltipPosition(
-        textarea,
-        actions.length,
-        matchedTextBeforeAtSymbol,
-      ),
-    [textarea, actions.length, matchedTextBeforeAtSymbol],
+      getTypeaheadTooltipPosition(textarea, actions.length, textBeforeAtSymbol),
+    [textarea, actions.length, textBeforeAtSymbol],
   );
 
   const tooltipPositionStyle = React.useMemo(
diff --git a/web/chat/typeahead-utils.js b/web/utils/typeahead-utils.js
rename from web/chat/typeahead-utils.js
rename to web/utils/typeahead-utils.js
--- a/web/chat/typeahead-utils.js
+++ b/web/utils/typeahead-utils.js
@@ -4,16 +4,15 @@
 import * as React from 'react';
 
 import { oldValidUsernameRegexString } from 'lib/shared/account-utils';
-import SearchIndex from 'lib/shared/search-index';
 import { stringForUserExplicit } from 'lib/shared/user-utils';
 import type { RelativeMemberInfo } from 'lib/types/thread-types';
 
+import { typeaheadStyle } from '../chat/chat-constants';
+import css from '../chat/typeahead-tooltip.css';
 import Button from '../components/button.react';
 import type { TypeaheadState } from '../input/input-state';
-import { typeaheadStyle } from './chat-constants';
-import css from './typeahead-tooltip.css';
 
-const typeaheadRegex: RegExp = new RegExp(
+const webTypeaheadRegex: RegExp = new RegExp(
   `(?<textPrefix>(?:^(?:.|\n)*\\s+)|^)@(?<username>${oldValidUsernameRegexString})?$`,
 );
 
@@ -28,20 +27,6 @@
   +left: number,
 };
 
-function getTypeaheadUserSuggestions(
-  userSearchIndex: SearchIndex,
-  usersInThread: $ReadOnlyArray<RelativeMemberInfo>,
-  typedPrefix: string,
-): $ReadOnlyArray<RelativeMemberInfo> {
-  const userIDs = userSearchIndex.getSearchResults(typedPrefix);
-
-  return usersInThread
-    .filter(user => typedPrefix.length === 0 || userIDs.includes(user.id))
-    .sort((userA, userB) =>
-      stringForUserExplicit(userA).localeCompare(stringForUserExplicit(userB)),
-    );
-}
-
 function getCaretOffsets(
   textarea: HTMLTextAreaElement,
   text: string,
@@ -94,8 +79,8 @@
   inputStateSetDraft: (draft: string) => void,
   inputStateSetTextCursorPosition: (newPosition: number) => void,
   suggestedUsers: $ReadOnlyArray<RelativeMemberInfo>,
-  matchedTextBeforeAtSymbol: string,
-  matchedText: string,
+  textBeforeAtSymbol: string,
+  typedUsernamePrefix: string,
 };
 
 function getTypeaheadTooltipActions(
@@ -106,8 +91,8 @@
     inputStateSetDraft,
     inputStateSetTextCursorPosition,
     suggestedUsers,
-    matchedTextBeforeAtSymbol,
-    matchedText,
+    textBeforeAtSymbol,
+    typedUsernamePrefix,
   } = params;
   return suggestedUsers
     .filter(
@@ -116,9 +101,12 @@
     .map(suggestedUser => ({
       key: suggestedUser.id,
       onClick: () => {
-        const newPrefixText = matchedTextBeforeAtSymbol;
+        const newPrefixText = textBeforeAtSymbol;
+
+        const totalMatchLength =
+          textBeforeAtSymbol.length + typedUsernamePrefix.length + 1; // 1 for @ char
 
-        let newSuffixText = inputStateDraft.slice(matchedText.length);
+        let newSuffixText = inputStateDraft.slice(totalMatchLength);
         newSuffixText = (newSuffixText[0] !== ' ' ? ' ' : '') + newSuffixText;
 
         const newText =
@@ -195,11 +183,11 @@
 function getTypeaheadTooltipPosition(
   textarea: HTMLTextAreaElement,
   actionsLength: number,
-  matchedTextBefore: string,
+  textBeforeAtSymbol: string,
 ): TooltipPosition {
   const { caretTopOffset, caretLeftOffset } = getCaretOffsets(
     textarea,
-    matchedTextBefore,
+    textBeforeAtSymbol,
   );
 
   const textareaBoundingClientRect = textarea.getBoundingClientRect();
@@ -234,8 +222,7 @@
 }
 
 export {
-  typeaheadRegex,
-  getTypeaheadUserSuggestions,
+  webTypeaheadRegex,
   getCaretOffsets,
   getTypeaheadTooltipActions,
   getTypeaheadTooltipButtons,