when i try the code in database the record is created but i am not getting any chatter message(FYI i have notifications enabled). And when i reverse to my code it sends the message

Hi,

-Safe HTML escaping so links render properly in all browsers.

-One-to-many group messaging so you can post to multiple people in a single channel instead of looping per partner.

Try the following code,

    def trigger_test_notif(self):

        self.ensure_one()

        partner_ids = None

        message = 'TEST MESSAGE'

        message_type = 'with_link'

        user_ids = None

        if user_ids is None and partner_ids is None:

            user_ids = [2, 6, 186]

        return self.send_chatter_message(user_ids, partner_ids, message, message_type)

    # ---------------------------

    # Send message to partners

    # ---------------------------

    def send_chatter_message(self, user_ids, partner_ids, message, message_type):

        self.ensure_one()

        # Resolve partner_ids from input

        if partner_ids:

            if hasattr(partner_ids, 'ids'):

                partners = partner_ids

            elif isinstance(partner_ids, (list, tuple, set)):

                flat = []

                for p in partner_ids:

                    if isinstance(p, (list, tuple, set)):

                        flat.extend(p)

                    else:

                        flat.append(p)

                partners = self.env['res.partner'].browse([int(x) for x in flat if x])

            else:

                partners = self.env['res.partner'].browse([int(partner_ids)])

        else:

            # Resolve users → partners

            if user_ids:

                if isinstance(user_ids, (list, tuple, set)):

                    u_ids = [int(u) for u in user_ids if u]

                else:

                    u_ids = [int(user_ids)]

            else:

                u_ids = []

            users = self.env['res.users'].browse(u_ids)

            partners = users.mapped('partner_id')

        if not partners:

            return False

        sender_pid = int(self.env.user.partner_id.id)

        recipients = partners.filtered(lambda p: p.id != sender_pid)

        if not recipients:

            return False

        # Build message body safely

        text = (message or "").strip()

        model_name = self._name

        record_link = f"/web#id={self.id}&model={model_name}&view_type=form"

        base_url = self.env['ir.config_parameter'].sudo().get_param('web.base.url') or ''

        if base_url.endswith('/'):

            base_url = base_url.rstrip('/')

        full_record_url = base_url + record_link if base_url else record_link

        if message_type == 'with_link':

            display = html_escape(text or "This is a chat message")

            safe_href = html_escape(full_record_url)

            body = f"""

                <p>{display}</p>

                <p><a href="{safe_href}" target="_blank" rel="noopener">Open record</a></p>

            """

        else:

            display = html_escape(text or "This is a chat message")

            body = f"<p>{display}</p>"

        # Create or reuse a group chat channel with recipients

        channel_obj = self.env['discuss.channel'].sudo()

        recipient_ids = recipients.ids + [sender_pid]

        # Try to find an existing channel with exactly this set of partners

        channel = channel_obj.search([

            ('channel_partner_ids', 'in', recipient_ids),

        ], limit=1)

        if not channel:

            vals = {

                'channel_type': 'chat',

                'name': ', '.join(recipients.mapped('name')) + ', ' + self.env.user.name,

                'channel_partner_ids': [(4, pid) for pid in recipient_ids],

            }

            channel = channel_obj.create(vals)

        # Post message once for all

        posted = channel.with_context(mail_create_nosubscribe=True).message_post(

            body=body,

            message_type='comment',

            subtype_xmlid='mail.mt_comment',

            author_id=sender_pid,

        )

        try:

            msg = self.env['mail.message'].sudo().browse(posted.id)

            msg.write({'body': body})  # enforce consistent body formatting

        except Exception as e:

            _logger.warning("Failed to overwrite mail.message body id=%s: %s", getattr(posted, 'id', None), e)

        return True

    Used html_escape so links always render clickable in Safari, Firefox, IE, Chrome.

    Built a group channel once with all recipients, so you don’t loop user by user.

    Kept compatibility with both user_ids and partner_ids inputs.

Hope it helps