Add hashtag link detection. Closes #134.

frontend/src/test/messageList.test.tsx

@@ -140,6 +140,59 @@ describe('MessageList channel sender rendering', () => {
     expect(screen.getByRole('button', { name: 'View info for Alice' })).toBeInTheDocument();
   });
 
+  it('renders valid channel references as clickable links and ignores invalid ones', async () => {
+    const user = userEvent.setup();
+    const onChannelReferenceClick = vi.fn();
+
+    render(
+      <MessageList
+        messages={[
+          createMessage({
+            text: 'Alice: Join #mesh-room now skip #bad--room and visit https://example.com/#also-skip',
+          }),
+        ]}
+        contacts={[]}
+        loading={false}
+        onChannelReferenceClick={onChannelReferenceClick}
+      />
+    );
+
+    const linkedChannel = screen.getByRole('button', { name: '#mesh-room' });
+    expect(linkedChannel).toBeInTheDocument();
+    expect(screen.queryByRole('button', { name: '#bad--room' })).not.toBeInTheDocument();
+    expect(
+      screen.getByRole('link', { name: 'https://example.com/#also-skip' })
+    ).toBeInTheDocument();
+
+    await user.click(linkedChannel);
+
+    expect(onChannelReferenceClick).toHaveBeenCalledWith('#mesh-room');
+  });
+
+  it('links valid channel references in direct messages too', async () => {
+    const user = userEvent.setup();
+    const onChannelReferenceClick = vi.fn();
+
+    render(
+      <MessageList
+        messages={[
+          createMessage({
+            type: 'PRIV',
+            text: 'check #ops-room',
+            conversation_key: 'ab'.repeat(32),
+          }),
+        ]}
+        contacts={[]}
+        loading={false}
+        onChannelReferenceClick={onChannelReferenceClick}
+      />
+    );
+
+    await user.click(screen.getByRole('button', { name: '#ops-room' }));
+
+    expect(onChannelReferenceClick).toHaveBeenCalledWith('#ops-room');
+  });
+
   it('renders and dismisses an unread marker at the first unread message boundary', async () => {
     const user = userEvent.setup();
     const messages = [

frontend/src/test/messageParser.test.ts

@@ -6,7 +6,12 @@
  */
 
 import { describe, it, expect } from 'vitest';
-import { parseSenderFromText, formatTime } from '../utils/messageParser';
+import {
+  findLinkedChannelReferences,
+  formatTime,
+  isValidLinkedChannelName,
+  parseSenderFromText,
+} from '../utils/messageParser';
 
 describe('parseSenderFromText', () => {
   it('extracts sender and content from "sender: message" format', () => {
@@ -95,3 +100,31 @@ describe('formatTime', () => {
     expect(result).toMatch(/\d{1,2}:\d{2}/); // time portion
   });
 });
+
+describe('linked channel references', () => {
+  it('accepts lowercase alphanumeric names with single dashes', () => {
+    expect(isValidLinkedChannelName('ops')).toBe(true);
+    expect(isValidLinkedChannelName('ops-1')).toBe(true);
+    expect(isValidLinkedChannelName('1-2-3')).toBe(true);
+  });
+
+  it('rejects uppercase, leading or trailing dashes, and repeated dashes', () => {
+    expect(isValidLinkedChannelName('Ops')).toBe(false);
+    expect(isValidLinkedChannelName('-ops')).toBe(false);
+    expect(isValidLinkedChannelName('ops-')).toBe(false);
+    expect(isValidLinkedChannelName('ops--room')).toBe(false);
+  });
+
+  it('finds standalone linked channel references in message text', () => {
+    expect(findLinkedChannelReferences('Join #mesh-room then say hi in #ops2')).toEqual([
+      { label: '#mesh-room', start: 5, end: 15 },
+      { label: '#ops2', start: 31, end: 36 },
+    ]);
+  });
+
+  it('ignores invalid or embedded channel-like text', () => {
+    expect(
+      findLinkedChannelReferences('skip #Bad #bad--name abc#ops #ops- #opsRoom #ops_room #good-room,')
+    ).toEqual([]);
+  });
+});

frontend/src/test/newMessageModal.test.tsx

@@ -32,7 +32,10 @@ describe('NewMessageModal form reset', () => {
     vi.clearAllMocks();
   });
 
-  function renderModal(open = true) {
+  function renderModal(
+    open = true,
+    overrides: Partial<Parameters<typeof NewMessageModal>[0]> = {}
+  ) {
     return render(
       <NewMessageModal
         open={open}
@@ -41,6 +44,7 @@ describe('NewMessageModal form reset', () => {
         onCreateContact={onCreateContact}
         onCreateChannel={onCreateChannel}
         onCreateHashtagChannel={onCreateHashtagChannel}
+        {...overrides}
       />
     );
   }
@@ -50,6 +54,26 @@ describe('NewMessageModal form reset', () => {
   }
 
   describe('hashtag tab', () => {
+    it('prefills the hashtag tab from a linked channel request', async () => {
+      renderModal(true, {
+        prefillRequest: {
+          tab: 'hashtag',
+          hashtagName: 'mesh-room',
+          nonce: 1,
+        },
+      });
+
+      await waitFor(() => {
+        expect(screen.getByRole('tab', { name: 'Hashtag Channel' })).toHaveAttribute(
+          'data-state',
+          'active'
+        );
+      });
+      expect((screen.getByPlaceholderText('channel-name') as HTMLInputElement).value).toBe(
+        'mesh-room'
+      );
+    });
+
     it('clears name after successful Create', async () => {
       const user = userEvent.setup();
       const { unmount } = renderModal();