feat: Add agent capacity controllers (#12200)

## Linear reference:
https://linear.app/chatwoot/issue/CW-4649/re-imagine-assignments

## Description
This PR introduces the foundation for Assignment V2 system by
implementing agent_capacity and their association with inboxes and
users.

## Type of change

- [ ] New feature (non-breaking change which adds functionality)

## How Has This Been Tested?

Test Coverage:
-  Controller specs for assignment policies CRUD operations
-  Enterprise-specific specs for balanced assignment order
-  Model specs for community/enterprise separation

## Checklist:

- [ ] My code follows the style guidelines of this project
- [ ] I have performed a self-review of my code
- [ ] I have commented on my code, particularly in hard-to-understand
areas
- [ ] I have made corresponding changes to the documentation
- [ ] My changes generate no new warnings
- [ ] I have added tests that prove my fix is effective or that my
feature works
- [ ] New and existing unit tests pass locally with my changes
- [ ] Any dependent changes have been merged and published in downstream
modules

---------

Co-authored-by: Pranav <pranav@chatwoot.com>

config/locales/en.yml

@@ -372,6 +372,8 @@ en:
 
       Transcript:
       %{format_messages}
+  agent_capacity_policy:
+    inbox_already_assigned: 'Inbox has already been assigned to this policy'
   portals:
     send_instructions:
       email_required: 'Email is required'

config/routes.rb

@@ -97,6 +97,12 @@ Rails.application.routes.draw do
           end
           resources :sla_policies, only: [:index, :create, :show, :update, :destroy]
           resources :custom_roles, only: [:index, :create, :show, :update, :destroy]
+          resources :agent_capacity_policies, only: [:index, :create, :show, :update, :destroy] do
+            scope module: :agent_capacity_policies do
+              resources :users, only: [:index, :create, :destroy]
+              resources :inbox_limits, only: [:create, :update, :destroy]
+            end
+          end
           resources :campaigns, only: [:index, :create, :show, :update, :destroy]
           resources :dashboard_apps, only: [:index, :show, :create, :update, :destroy]
           namespace :channels do

enterprise/app/controllers/api/v1/accounts/agent_capacity_policies/inbox_limits_controller.rb

@@ -0,0 +1,47 @@
+class Api::V1::Accounts::AgentCapacityPolicies::InboxLimitsController < Api::V1::Accounts::EnterpriseAccountsController
+  before_action -> { check_authorization(AgentCapacityPolicy) }
+  before_action :fetch_policy
+  before_action :fetch_inbox, only: [:create]
+  before_action :fetch_inbox_limit, only: [:update, :destroy]
+  before_action :validate_no_duplicate, only: [:create]
+
+  def create
+    @inbox_limit = @agent_capacity_policy.inbox_capacity_limits.create!(
+      inbox: @inbox,
+      conversation_limit: permitted_params[:conversation_limit]
+    )
+  end
+
+  def update
+    @inbox_limit.update!(conversation_limit: permitted_params[:conversation_limit])
+  end
+
+  def destroy
+    @inbox_limit.destroy!
+    head :no_content
+  end
+
+  private
+
+  def fetch_policy
+    @agent_capacity_policy = Current.account.agent_capacity_policies.find(params[:agent_capacity_policy_id])
+  end
+
+  def fetch_inbox
+    @inbox = Current.account.inboxes.find(permitted_params[:inbox_id])
+  end
+
+  def fetch_inbox_limit
+    @inbox_limit = @agent_capacity_policy.inbox_capacity_limits.find(params[:id])
+  end
+
+  def validate_no_duplicate
+    return unless @agent_capacity_policy.inbox_capacity_limits.exists?(inbox: @inbox)
+
+    render_could_not_create_error(I18n.t('agent_capacity_policy.inbox_already_assigned'))
+  end
+
+  def permitted_params
+    params.permit(:inbox_id, :conversation_limit)
+  end
+end

enterprise/app/controllers/api/v1/accounts/agent_capacity_policies/users_controller.rb

@@ -0,0 +1,35 @@
+class Api::V1::Accounts::AgentCapacityPolicies::UsersController < Api::V1::Accounts::EnterpriseAccountsController
+  before_action -> { check_authorization(AgentCapacityPolicy) }
+  before_action :fetch_policy
+  before_action :fetch_user, only: [:destroy]
+
+  def index
+    @users = Current.account.users.joins(:account_users)
+                    .where(account_users: { agent_capacity_policy_id: @agent_capacity_policy.id })
+  end
+
+  def create
+    @account_user = Current.account.account_users.find_by!(user_id: permitted_params[:user_id])
+    @account_user.update!(agent_capacity_policy: @agent_capacity_policy)
+    @user = @account_user.user
+  end
+
+  def destroy
+    @account_user.update!(agent_capacity_policy: nil)
+    head :ok
+  end
+
+  private
+
+  def fetch_policy
+    @agent_capacity_policy = Current.account.agent_capacity_policies.find(params[:agent_capacity_policy_id])
+  end
+
+  def fetch_user
+    @account_user = Current.account.account_users.find_by!(user_id: params[:id])
+  end
+
+  def permitted_params
+    params.permit(:user_id)
+  end
+end

enterprise/app/controllers/api/v1/accounts/agent_capacity_policies_controller.rb

@@ -0,0 +1,37 @@
+class Api::V1::Accounts::AgentCapacityPoliciesController < Api::V1::Accounts::EnterpriseAccountsController
+  before_action :check_authorization
+  before_action :fetch_policy, only: [:show, :update, :destroy]
+
+  def index
+    @agent_capacity_policies = Current.account.agent_capacity_policies
+  end
+
+  def show; end
+
+  def create
+    @agent_capacity_policy = Current.account.agent_capacity_policies.create!(permitted_params)
+  end
+
+  def update
+    @agent_capacity_policy.update!(permitted_params)
+  end
+
+  def destroy
+    @agent_capacity_policy.destroy!
+    head :ok
+  end
+
+  private
+
+  def permitted_params
+    params.require(:agent_capacity_policy).permit(
+      :name,
+      :description,
+      exclusion_rules: [:overall_capacity, { hours: [], days: [] }]
+    )
+  end
+
+  def fetch_policy
+    @agent_capacity_policy = Current.account.agent_capacity_policies.find(params[:id])
+  end
+end

enterprise/app/models/agent_capacity_policy.rb

@@ -0,0 +1,27 @@
+# == Schema Information
+#
+# Table name: agent_capacity_policies
+#
+#  id              :bigint           not null, primary key
+#  description     :text
+#  exclusion_rules :jsonb            not null
+#  name            :string(255)      not null
+#  created_at      :datetime         not null
+#  updated_at      :datetime         not null
+#  account_id      :bigint           not null
+#
+# Indexes
+#
+#  index_agent_capacity_policies_on_account_id  (account_id)
+#
+class AgentCapacityPolicy < ApplicationRecord
+  MAX_NAME_LENGTH = 255
+
+  belongs_to :account
+  has_many :inbox_capacity_limits, dependent: :destroy
+  has_many :inboxes, through: :inbox_capacity_limits
+  has_many :account_users, dependent: :nullify
+
+  validates :name, presence: true, length: { maximum: MAX_NAME_LENGTH }
+  validates :account, presence: true
+end

enterprise/app/models/enterprise/concerns/account.rb

@@ -5,6 +5,7 @@ module Enterprise::Concerns::Account
     has_many :sla_policies, dependent: :destroy_async
     has_many :applied_slas, dependent: :destroy_async
     has_many :custom_roles, dependent: :destroy_async
+    has_many :agent_capacity_policies, dependent: :destroy_async
 
     has_many :captain_assistants, dependent: :destroy_async, class_name: 'Captain::Assistant'
     has_many :captain_assistant_responses, dependent: :destroy_async, class_name: 'Captain::AssistantResponse'

enterprise/app/models/enterprise/concerns/account_user.rb

@@ -3,5 +3,6 @@ module Enterprise::Concerns::AccountUser
 
   included do
     belongs_to :custom_role, optional: true
+    belongs_to :agent_capacity_policy, optional: true
   end
 end

enterprise/app/models/inbox_capacity_limit.rb

@@ -0,0 +1,24 @@
+# == Schema Information
+#
+# Table name: inbox_capacity_limits
+#
+#  id                       :bigint           not null, primary key
+#  conversation_limit       :integer          not null
+#  created_at               :datetime         not null
+#  updated_at               :datetime         not null
+#  agent_capacity_policy_id :bigint           not null
+#  inbox_id                 :bigint           not null
+#
+# Indexes
+#
+#  idx_on_agent_capacity_policy_id_inbox_id_71c7ec4caf      (agent_capacity_policy_id,inbox_id) UNIQUE
+#  index_inbox_capacity_limits_on_agent_capacity_policy_id  (agent_capacity_policy_id)
+#  index_inbox_capacity_limits_on_inbox_id                  (inbox_id)
+#
+class InboxCapacityLimit < ApplicationRecord
+  belongs_to :agent_capacity_policy
+  belongs_to :inbox
+
+  validates :conversation_limit, presence: true, numericality: { greater_than: 0, only_integer: true }
+  validates :inbox_id, uniqueness: { scope: :agent_capacity_policy_id }
+end

enterprise/app/policies/agent_capacity_policy_policy.rb

@@ -0,0 +1,21 @@
+class AgentCapacityPolicyPolicy < ApplicationPolicy
+  def index?
+    @account_user.administrator?
+  end
+
+  def create?
+    @account_user.administrator?
+  end
+
+  def show?
+    @account_user.administrator?
+  end
+
+  def update?
+    @account_user.administrator?
+  end
+
+  def destroy?
+    @account_user.administrator?
+  end
+end

enterprise/app/views/api/v1/accounts/agent_capacity_policies/create.json.jbuilder

@@ -0,0 +1,2 @@
+json.partial! 'api/v1/models/agent_capacity_policy', formats: [:json],
+                                                     agent_capacity_policy: @agent_capacity_policy

enterprise/app/views/api/v1/accounts/agent_capacity_policies/inbox_limits/create.json.jbuilder

@@ -0,0 +1,6 @@
+json.id @inbox_limit.id
+json.inbox_id @inbox_limit.inbox_id
+json.agent_capacity_policy_id @inbox_limit.agent_capacity_policy_id
+json.conversation_limit @inbox_limit.conversation_limit
+json.created_at @inbox_limit.created_at.to_i
+json.updated_at @inbox_limit.updated_at.to_i

enterprise/app/views/api/v1/accounts/agent_capacity_policies/inbox_limits/update.json.jbuilder

@@ -0,0 +1,7 @@
+json.id @inbox_limit.id
+json.inbox_id @inbox_limit.inbox_id
+json.inbox_name @inbox_limit.inbox.name
+json.agent_capacity_policy_id @agent_capacity_policy.id
+json.conversation_limit @inbox_limit.conversation_limit
+json.created_at @inbox_limit.created_at.to_i
+json.updated_at @inbox_limit.updated_at.to_i

enterprise/app/views/api/v1/accounts/agent_capacity_policies/index.json.jbuilder

@@ -0,0 +1,4 @@
+json.array! @agent_capacity_policies do |policy|
+  json.partial! 'api/v1/models/agent_capacity_policy', formats: [:json],
+                                                       agent_capacity_policy: policy
+end

enterprise/app/views/api/v1/accounts/agent_capacity_policies/show.json.jbuilder

@@ -0,0 +1,2 @@
+json.partial! 'api/v1/models/agent_capacity_policy', formats: [:json],
+                                                     agent_capacity_policy: @agent_capacity_policy

enterprise/app/views/api/v1/accounts/agent_capacity_policies/update.json.jbuilder

@@ -0,0 +1,2 @@
+json.partial! 'api/v1/models/agent_capacity_policy', formats: [:json],
+                                                     agent_capacity_policy: @agent_capacity_policy

enterprise/app/views/api/v1/accounts/agent_capacity_policies/users/create.json.jbuilder

@@ -0,0 +1 @@
+json.partial! 'api/v1/models/user', resource: @user

enterprise/app/views/api/v1/accounts/agent_capacity_policies/users/index.json.jbuilder

@@ -0,0 +1,3 @@
+json.array! @users do |user|
+  json.partial! 'api/v1/models/user', resource: user
+end

enterprise/app/views/api/v1/models/_agent_capacity_policy.json.jbuilder

@@ -0,0 +1,13 @@
+json.id agent_capacity_policy.id
+json.name agent_capacity_policy.name
+json.description agent_capacity_policy.description
+json.exclusion_rules agent_capacity_policy.exclusion_rules
+json.created_at agent_capacity_policy.created_at.to_i
+json.updated_at agent_capacity_policy.updated_at.to_i
+json.account_id agent_capacity_policy.account_id
+
+json.inbox_capacity_limits agent_capacity_policy.inbox_capacity_limits do |limit|
+  json.id limit.id
+  json.inbox_id limit.inbox_id
+  json.conversation_limit limit.conversation_limit
+end

spec/enterprise/controllers/api/v1/accounts/agent_capacity_policies/inbox_limits_controller_spec.rb

@@ -0,0 +1,80 @@
+require 'rails_helper'
+
+RSpec.describe 'Agent Capacity Policy Inbox Limits API', type: :request do
+  let(:account) { create(:account) }
+  let!(:agent_capacity_policy) { create(:agent_capacity_policy, account: account) }
+  let!(:inbox) { create(:inbox, account: account) }
+  let(:administrator) { create(:user, account: account, role: :administrator) }
+  let(:agent) { create(:user, account: account, role: :agent) }
+
+  describe 'POST /api/v1/accounts/{account.id}/agent_capacity_policies/{policy_id}/inbox_limits' do
+    context 'when not admin' do
+      it 'requires admin role' do
+        post "/api/v1/accounts/#{account.id}/agent_capacity_policies/#{agent_capacity_policy.id}/inbox_limits",
+             params: { inbox_id: inbox.id, conversation_limit: 10 },
+             headers: agent.create_new_auth_token,
+             as: :json
+
+        expect(response).to have_http_status(:unauthorized)
+      end
+    end
+
+    context 'when admin' do
+      it 'creates an inbox limit' do
+        post "/api/v1/accounts/#{account.id}/agent_capacity_policies/#{agent_capacity_policy.id}/inbox_limits",
+             params: { inbox_id: inbox.id, conversation_limit: 10 },
+             headers: administrator.create_new_auth_token,
+             as: :json
+
+        expect(response).to have_http_status(:success)
+        json_response = response.parsed_body
+        expect(json_response['conversation_limit']).to eq(10)
+        expect(json_response['inbox_id']).to eq(inbox.id)
+      end
+
+      it 'prevents duplicate inbox assignments' do
+        create(:inbox_capacity_limit, agent_capacity_policy: agent_capacity_policy, inbox: inbox)
+
+        post "/api/v1/accounts/#{account.id}/agent_capacity_policies/#{agent_capacity_policy.id}/inbox_limits",
+             params: { inbox_id: inbox.id, conversation_limit: 10 },
+             headers: administrator.create_new_auth_token,
+             as: :json
+
+        expect(response).to have_http_status(:unprocessable_entity)
+        expect(response.parsed_body['error']).to eq(I18n.t('agent_capacity_policy.inbox_already_assigned'))
+      end
+    end
+  end
+
+  describe 'PUT /api/v1/accounts/{account.id}/agent_capacity_policies/{policy_id}/inbox_limits/{id}' do
+    let!(:inbox_limit) { create(:inbox_capacity_limit, agent_capacity_policy: agent_capacity_policy, inbox: inbox, conversation_limit: 5) }
+
+    context 'when admin' do
+      it 'updates the inbox limit' do
+        put "/api/v1/accounts/#{account.id}/agent_capacity_policies/#{agent_capacity_policy.id}/inbox_limits/#{inbox_limit.id}",
+            params: { conversation_limit: 15 },
+            headers: administrator.create_new_auth_token,
+            as: :json
+
+        expect(response).to have_http_status(:success)
+        expect(response.parsed_body['conversation_limit']).to eq(15)
+        expect(inbox_limit.reload.conversation_limit).to eq(15)
+      end
+    end
+  end
+
+  describe 'DELETE /api/v1/accounts/{account.id}/agent_capacity_policies/{policy_id}/inbox_limits/{id}' do
+    let!(:inbox_limit) { create(:inbox_capacity_limit, agent_capacity_policy: agent_capacity_policy, inbox: inbox) }
+
+    context 'when admin' do
+      it 'removes the inbox limit' do
+        delete "/api/v1/accounts/#{account.id}/agent_capacity_policies/#{agent_capacity_policy.id}/inbox_limits/#{inbox_limit.id}",
+               headers: administrator.create_new_auth_token,
+               as: :json
+
+        expect(response).to have_http_status(:no_content)
+        expect(agent_capacity_policy.inbox_capacity_limits.find_by(id: inbox_limit.id)).to be_nil
+      end
+    end
+  end
+end

spec/enterprise/controllers/api/v1/accounts/agent_capacity_policies/users_controller_spec.rb

@@ -0,0 +1,66 @@
+require 'rails_helper'
+
+RSpec.describe 'Agent Capacity Policy Users API', type: :request do
+  let(:account) { create(:account) }
+  let!(:agent_capacity_policy) { create(:agent_capacity_policy, account: account) }
+  let!(:user) { create(:user, account: account, role: :agent) }
+  let(:administrator) { create(:user, account: account, role: :administrator) }
+  let(:agent) { create(:user, account: account, role: :agent) }
+
+  describe 'GET /api/v1/accounts/{account.id}/agent_capacity_policies/{policy_id}/users' do
+    context 'when admin' do
+      it 'returns assigned users' do
+        user.account_users.first.update!(agent_capacity_policy: agent_capacity_policy)
+
+        get "/api/v1/accounts/#{account.id}/agent_capacity_policies/#{agent_capacity_policy.id}/users",
+            headers: administrator.create_new_auth_token,
+            as: :json
+
+        expect(response).to have_http_status(:success)
+        expect(response.parsed_body.first['id']).to eq(user.id)
+      end
+    end
+  end
+
+  describe 'POST /api/v1/accounts/{account.id}/agent_capacity_policies/{policy_id}/users' do
+    context 'when not admin' do
+      it 'requires admin role' do
+        post "/api/v1/accounts/#{account.id}/agent_capacity_policies/#{agent_capacity_policy.id}/users",
+             params: { user_id: user.id },
+             headers: agent.create_new_auth_token,
+             as: :json
+
+        expect(response).to have_http_status(:unauthorized)
+      end
+    end
+
+    context 'when admin' do
+      it 'assigns user to the policy' do
+        post "/api/v1/accounts/#{account.id}/agent_capacity_policies/#{agent_capacity_policy.id}/users",
+             params: { user_id: user.id },
+             headers: administrator.create_new_auth_token,
+             as: :json
+
+        expect(response).to have_http_status(:success)
+        expect(user.account_users.first.reload.agent_capacity_policy).to eq(agent_capacity_policy)
+      end
+    end
+  end
+
+  describe 'DELETE /api/v1/accounts/{account.id}/agent_capacity_policies/{policy_id}/users/{id}' do
+    context 'when admin' do
+      before do
+        user.account_users.first.update!(agent_capacity_policy: agent_capacity_policy)
+      end
+
+      it 'removes user from the policy' do
+        delete "/api/v1/accounts/#{account.id}/agent_capacity_policies/#{agent_capacity_policy.id}/users/#{user.id}",
+               headers: administrator.create_new_auth_token,
+               as: :json
+
+        expect(response).to have_http_status(:ok)
+        expect(user.account_users.first.reload.agent_capacity_policy).to be_nil
+      end
+    end
+  end
+end

spec/enterprise/controllers/api/v1/accounts/agent_capacity_policies_controller_spec.rb

@@ -0,0 +1,202 @@
+require 'rails_helper'
+
+RSpec.describe 'Agent Capacity Policies API', type: :request do
+  let(:account) { create(:account) }
+  let!(:agent_capacity_policy) { create(:agent_capacity_policy, account: account) }
+
+  describe 'GET /api/v1/accounts/{account.id}/agent_capacity_policies' do
+    context 'when it is an unauthenticated user' do
+      it 'returns unauthorized' do
+        get "/api/v1/accounts/#{account.id}/agent_capacity_policies"
+
+        expect(response).to have_http_status(:unauthorized)
+      end
+    end
+
+    context 'when it is an authenticated agent' do
+      let(:agent) { create(:user, account: account, role: :agent) }
+
+      it 'returns unauthorized for agent' do
+        get "/api/v1/accounts/#{account.id}/agent_capacity_policies",
+            headers: agent.create_new_auth_token,
+            as: :json
+
+        expect(response).to have_http_status(:unauthorized)
+      end
+    end
+
+    context 'when it is an administrator' do
+      let(:administrator) { create(:user, account: account, role: :administrator) }
+
+      it 'returns all agent capacity policies' do
+        get "/api/v1/accounts/#{account.id}/agent_capacity_policies",
+            headers: administrator.create_new_auth_token,
+            as: :json
+
+        expect(response).to have_http_status(:success)
+        expect(response.parsed_body.first['id']).to eq(agent_capacity_policy.id)
+      end
+    end
+  end
+
+  describe 'GET /api/v1/accounts/{account.id}/agent_capacity_policies/{id}' do
+    context 'when it is an unauthenticated user' do
+      it 'returns unauthorized' do
+        get "/api/v1/accounts/#{account.id}/agent_capacity_policies/#{agent_capacity_policy.id}"
+
+        expect(response).to have_http_status(:unauthorized)
+      end
+    end
+
+    context 'when it is an authenticated agent' do
+      let(:agent) { create(:user, account: account, role: :agent) }
+
+      it 'returns unauthorized for agent' do
+        get "/api/v1/accounts/#{account.id}/agent_capacity_policies/#{agent_capacity_policy.id}",
+            headers: agent.create_new_auth_token,
+            as: :json
+
+        expect(response).to have_http_status(:unauthorized)
+      end
+    end
+
+    context 'when it is an administrator' do
+      let(:administrator) { create(:user, account: account, role: :administrator) }
+
+      it 'returns the agent capacity policy' do
+        get "/api/v1/accounts/#{account.id}/agent_capacity_policies/#{agent_capacity_policy.id}",
+            headers: administrator.create_new_auth_token,
+            as: :json
+
+        expect(response).to have_http_status(:success)
+        expect(response.parsed_body['id']).to eq(agent_capacity_policy.id)
+      end
+    end
+  end
+
+  describe 'POST /api/v1/accounts/{account.id}/agent_capacity_policies' do
+    context 'when it is an unauthenticated user' do
+      it 'returns unauthorized' do
+        post "/api/v1/accounts/#{account.id}/agent_capacity_policies"
+
+        expect(response).to have_http_status(:unauthorized)
+      end
+    end
+
+    context 'when it is an authenticated user' do
+      let(:agent) { create(:user, account: account, role: :agent) }
+      let(:administrator) { create(:user, account: account, role: :administrator) }
+
+      it 'returns unauthorized for agent' do
+        params = { agent_capacity_policy: { name: 'Test Policy' } }
+
+        post "/api/v1/accounts/#{account.id}/agent_capacity_policies",
+             params: params,
+             headers: agent.create_new_auth_token,
+             as: :json
+
+        expect(response).to have_http_status(:unauthorized)
+      end
+
+      it 'creates a new agent capacity policy when administrator' do
+        params = {
+          agent_capacity_policy: {
+            name: 'Test Policy',
+            description: 'Test Description',
+            exclusion_rules: { overall_capacity: 10 }
+          }
+        }
+
+        post "/api/v1/accounts/#{account.id}/agent_capacity_policies",
+             params: params,
+             headers: administrator.create_new_auth_token,
+             as: :json
+
+        expect(response).to have_http_status(:success)
+        expect(response.parsed_body['name']).to eq('Test Policy')
+        expect(response.parsed_body['description']).to eq('Test Description')
+      end
+
+      it 'returns validation errors for invalid data' do
+        params = { agent_capacity_policy: { name: '' } }
+
+        post "/api/v1/accounts/#{account.id}/agent_capacity_policies",
+             params: params,
+             headers: administrator.create_new_auth_token,
+             as: :json
+
+        expect(response).to have_http_status(:unprocessable_entity)
+      end
+    end
+  end
+
+  describe 'PUT /api/v1/accounts/{account.id}/agent_capacity_policies/{id}' do
+    context 'when it is an unauthenticated user' do
+      it 'returns unauthorized' do
+        put "/api/v1/accounts/#{account.id}/agent_capacity_policies/#{agent_capacity_policy.id}"
+
+        expect(response).to have_http_status(:unauthorized)
+      end
+    end
+
+    context 'when it is an authenticated user' do
+      let(:agent) { create(:user, account: account, role: :agent) }
+      let(:administrator) { create(:user, account: account, role: :administrator) }
+
+      it 'returns unauthorized for agent' do
+        params = { agent_capacity_policy: { name: 'Updated Policy' } }
+
+        put "/api/v1/accounts/#{account.id}/agent_capacity_policies/#{agent_capacity_policy.id}",
+            params: params,
+            headers: agent.create_new_auth_token,
+            as: :json
+
+        expect(response).to have_http_status(:unauthorized)
+      end
+
+      it 'updates the agent capacity policy when administrator' do
+        params = { agent_capacity_policy: { name: 'Updated Policy' } }
+
+        put "/api/v1/accounts/#{account.id}/agent_capacity_policies/#{agent_capacity_policy.id}",
+            params: params,
+            headers: administrator.create_new_auth_token,
+            as: :json
+
+        expect(response).to have_http_status(:success)
+        expect(response.parsed_body['name']).to eq('Updated Policy')
+      end
+    end
+  end
+
+  describe 'DELETE /api/v1/accounts/{account.id}/agent_capacity_policies/{id}' do
+    context 'when it is an unauthenticated user' do
+      it 'returns unauthorized' do
+        delete "/api/v1/accounts/#{account.id}/agent_capacity_policies/#{agent_capacity_policy.id}"
+
+        expect(response).to have_http_status(:unauthorized)
+      end
+    end
+
+    context 'when it is an authenticated user' do
+      let(:agent) { create(:user, account: account, role: :agent) }
+      let(:administrator) { create(:user, account: account, role: :administrator) }
+
+      it 'returns unauthorized for agent' do
+        delete "/api/v1/accounts/#{account.id}/agent_capacity_policies/#{agent_capacity_policy.id}",
+               headers: agent.create_new_auth_token,
+               as: :json
+
+        expect(response).to have_http_status(:unauthorized)
+      end
+
+      it 'deletes the agent capacity policy when administrator' do
+        delete "/api/v1/accounts/#{account.id}/agent_capacity_policies/#{agent_capacity_policy.id}",
+               headers: administrator.create_new_auth_token,
+               as: :json
+
+        expect(response).to have_http_status(:ok)
+        expect { agent_capacity_policy.reload }.to raise_error(ActiveRecord::RecordNotFound)
+      end
+    end
+  end
+end

spec/enterprise/models/agent_capacity_policy_spec.rb

@@ -0,0 +1,29 @@
+require 'rails_helper'
+
+RSpec.describe AgentCapacityPolicy, type: :model do
+  let(:account) { create(:account) }
+
+  describe 'validations' do
+    it { is_expected.to validate_presence_of(:name) }
+    it { is_expected.to validate_length_of(:name).is_at_most(255) }
+  end
+
+  describe 'destruction' do
+    let(:policy) { create(:agent_capacity_policy, account: account) }
+    let(:user) { create(:user, account: account) }
+    let(:inbox) { create(:inbox, account: account) }
+
+    it 'destroys associated inbox capacity limits' do
+      create(:inbox_capacity_limit, agent_capacity_policy: policy, inbox: inbox)
+      expect { policy.destroy }.to change(InboxCapacityLimit, :count).by(-1)
+    end
+
+    it 'nullifies associated account users' do
+      account_user = user.account_users.first
+      account_user.update!(agent_capacity_policy: policy)
+
+      policy.destroy
+      expect(account_user.reload.agent_capacity_policy).to be_nil
+    end
+  end
+end

spec/enterprise/models/inbox_capacity_limit_spec.rb

@@ -0,0 +1,33 @@
+require 'rails_helper'
+
+RSpec.describe InboxCapacityLimit, type: :model do
+  let(:account) { create(:account) }
+  let(:policy) { create(:agent_capacity_policy, account: account) }
+  let(:inbox) { create(:inbox, account: account) }
+
+  describe 'validations' do
+    subject { create(:inbox_capacity_limit, agent_capacity_policy: policy, inbox: inbox) }
+
+    it { is_expected.to validate_presence_of(:conversation_limit) }
+    it { is_expected.to validate_numericality_of(:conversation_limit).is_greater_than(0).only_integer }
+    it { is_expected.to validate_uniqueness_of(:inbox_id).scoped_to(:agent_capacity_policy_id) }
+  end
+
+  describe 'uniqueness constraint' do
+    it 'prevents duplicate inbox limits for the same policy' do
+      create(:inbox_capacity_limit, agent_capacity_policy: policy, inbox: inbox)
+      duplicate = build(:inbox_capacity_limit, agent_capacity_policy: policy, inbox: inbox)
+
+      expect(duplicate).not_to be_valid
+      expect(duplicate.errors[:inbox_id]).to include('has already been taken')
+    end
+
+    it 'allows the same inbox in different policies' do
+      other_policy = create(:agent_capacity_policy, account: account)
+      create(:inbox_capacity_limit, agent_capacity_policy: policy, inbox: inbox)
+
+      different_policy_limit = build(:inbox_capacity_limit, agent_capacity_policy: other_policy, inbox: inbox)
+      expect(different_policy_limit).to be_valid
+    end
+  end
+end

spec/factories/agent_capacity_policies.rb

@@ -0,0 +1,21 @@
+FactoryBot.define do
+  factory :agent_capacity_policy do
+    account
+    sequence(:name) { |n| "Agent Capacity Policy #{n}" }
+    description { 'Test agent capacity policy' }
+    exclusion_rules { {} }
+
+    trait :with_overall_capacity do
+      exclusion_rules { { 'overall_capacity' => 10 } }
+    end
+
+    trait :with_time_exclusions do
+      exclusion_rules do
+        {
+          'hours' => [0, 1, 2, 3, 4, 5],
+          'days' => %w[saturday sunday]
+        }
+      end
+    end
+  end
+end

spec/factories/inbox_capacity_limits.rb

@@ -0,0 +1,7 @@
+FactoryBot.define do
+  factory :inbox_capacity_limit do
+    association :agent_capacity_policy, factory: :agent_capacity_policy
+    inbox
+    conversation_limit { 5 }
+  end
+end