Hi,

Please refer to the code below:

Model:crm.lead

from odoo import models, fields, api
from odoo.exceptions import ValidationError

class CrmLead(models.Model):
    _inherit = 'crm.lead'

    linked_user_ids = fields.One2many(
        'crm.deal.value',
        'lead_id',
        string='Consultants',
        index=True,
        tracking=True
    )

    total_value = fields.Monetary(
        string='Total Value',
        currency_field='company_currency',
        compute='_compute_total_value',
        store=True,
        tracking=True
    )

    @api.depends('linked_user_ids', 'linked_user_ids.value')
    def _compute_total_value(self):
        for lead in self:
            lead.total_value = sum(
                user.value or 0.0 for user in lead.linked_user_ids) or 0.0

    @api.constrains('linked_user_ids', 'linked_user_ids.value',
                    'expected_revenue')
    def _check_total_value(self):
        """
            Ensure that the sum of all linked deal values matches the opportunity's expected revenue.

            This constraint validates that the combined `value` of all records in `linked_user_ids`
            (i.e., all `crm.deal.value` entries linked to the lead) is exactly equal to
            the lead's `expected_revenue`.

            Why the total is calculated inline:
                - Using the stored computed field `total_value` can lead to stale values during
                  simultaneous create/update/delete operations because Odoo's ORM recomputes
                  stored fields only after flushing changes to the database.
                - By directly summing `linked_user_ids.value`, this method uses the in-memory
                  state of the recordset, ensuring correctness even when deletions and updates
                  happen in the same transaction.

            Raises:
                ValidationError: If the sum of all contributions does not match `expected_revenue`.
            """
        for lead in self:
            total = sum(user.value or 0.0 for user in lead.linked_user_ids)
            if total != lead.expected_revenue:
                raise ValidationError(
                    "Total contribution value should be equal to the opportunity's expected revenue."
                )

Hope it helps.