diff --git a/config/initializers/ai_agents.rb b/config/initializers/ai_agents.rb
index be8a8a9cc..5255ae69b 100644
--- a/config/initializers/ai_agents.rb
+++ b/config/initializers/ai_agents.rb
@@ -3,20 +3,14 @@
 require 'agents'
 
 Rails.application.config.after_initialize do
-  api_key = InstallationConfig.find_by(name: 'CAPTAIN_OPEN_AI_API_KEY')&.value
-  model = InstallationConfig.find_by(name: 'CAPTAIN_OPEN_AI_MODEL')&.value.presence || LlmConstants::DEFAULT_MODEL
-  api_endpoint = InstallationConfig.find_by(name: 'CAPTAIN_OPEN_AI_ENDPOINT')&.value || LlmConstants::OPENAI_API_ENDPOINT
+  settings = Captain::Llm::ProviderConfig.settings
+  next if settings[:api_key].blank?
 
-  if api_key.present?
-    Agents.configure do |config|
-      config.openai_api_key = api_key
-      if api_endpoint.present?
-        api_base = "#{api_endpoint.chomp('/')}/v1"
-        config.openai_api_base = api_base
-      end
-      config.default_model = model
-      config.debug = false
-    end
+  Agents.configure do |config|
+    config.openai_api_key = settings[:api_key]
+    config.openai_api_base = "#{settings[:api_base]}/v1" if settings[:api_base].present?
+    config.default_model = settings[:model]
+    config.debug = false
   end
 rescue StandardError => e
   Rails.logger.error "Failed to configure AI Agents SDK: #{e.message}"
diff --git a/config/installation_config.yml b/config/installation_config.yml
index 34cb736bf..1d02405d2 100644
--- a/config/installation_config.yml
+++ b/config/installation_config.yml
@@ -182,6 +182,16 @@
 # End of Microsoft Email Channel Config
 
 # MARK: Captain Config
+- name: CAPTAIN_LLM_PROVIDER
+  display_title: 'Captain LLM Provider'
+  description: 'Qual provider o Captain usa: openai_api (padrão, API key tradicional) ou openai_codex_oauth (assinatura ChatGPT Plus via proxy interno).'
+  value: 'openai_api'
+  locked: false
+- name: CAPTAIN_CODEX_PROXY_URL
+  display_title: 'Captain Codex Proxy URL'
+  description: 'URL base do proxy Codex interno quando CAPTAIN_LLM_PROVIDER=openai_codex_oauth. Default: http://localhost:3000/codex'
+  value: 'http://localhost:3000/codex'
+  locked: false
 - name: CAPTAIN_OPEN_AI_API_KEY
   display_title: 'OpenAI API Key'
   description: 'The API key used to authenticate requests to OpenAI services for Captain AI.'
diff --git a/enterprise/app/services/captain/llm/provider_config.rb b/enterprise/app/services/captain/llm/provider_config.rb
new file mode 100644
index 000000000..5cf1fdbda
--- /dev/null
+++ b/enterprise/app/services/captain/llm/provider_config.rb
@@ -0,0 +1,78 @@
+# Single source of truth para a configuração do provider LLM do Captain.
+#
+# Lê CAPTAIN_LLM_PROVIDER e retorna a combinação certa de (api_key, api_base, model):
+#
+# - openai_api (padrão): usa CAPTAIN_OPEN_AI_API_KEY + CAPTAIN_OPEN_AI_ENDPOINT.
+#   Mesmo comportamento legado.
+#
+# - openai_codex_oauth: aponta para o proxy interno
+#   (CAPTAIN_CODEX_PROXY_URL, default http://localhost:3000/codex) e usa uma
+#   api_key dummy — o proxy ignora o Authorization header e usa OAuth interno.
+#
+# O "legacy" ruby-openai usado para PDF/Files API NÃO deve usar esse módulo:
+# o endpoint Codex não expõe Files API, então esses serviços continuam
+# apontando sempre para OpenAI tradicional.
+class Captain::Llm::ProviderConfig
+  DEFAULT_MODEL = 'gpt-4.1-mini'.freeze
+  DEFAULT_OPENAI_ENDPOINT = 'https://api.openai.com'.freeze
+  DEFAULT_CODEX_PROXY_URL = 'http://localhost:3000/codex'.freeze
+  DUMMY_API_KEY = 'codex-oauth'.freeze
+
+  class << self
+    def provider
+      cfg('CAPTAIN_LLM_PROVIDER').presence || 'openai_api'
+    end
+
+    def codex_oauth?
+      provider == 'openai_codex_oauth'
+    end
+
+    # Retorna { api_key:, api_base:, model: } para RubyLLM/Agents.
+    def settings
+      if codex_oauth?
+        codex_settings
+      else
+        openai_api_settings
+      end
+    end
+
+    def api_key
+      settings[:api_key]
+    end
+
+    # Base URL "crua", sem /v1. O cliente (ai_agents.rb) adiciona /v1.
+    def api_base
+      settings[:api_base]
+    end
+
+    def model
+      settings[:model]
+    end
+
+    private
+
+    def codex_settings
+      {
+        api_key: DUMMY_API_KEY,
+        api_base: (cfg('CAPTAIN_CODEX_PROXY_URL').presence || DEFAULT_CODEX_PROXY_URL).chomp('/'),
+        model: cfg('CAPTAIN_OPEN_AI_MODEL').presence || default_codex_model
+      }
+    end
+
+    def openai_api_settings
+      {
+        api_key: cfg('CAPTAIN_OPEN_AI_API_KEY'),
+        api_base: (cfg('CAPTAIN_OPEN_AI_ENDPOINT').presence || DEFAULT_OPENAI_ENDPOINT).chomp('/'),
+        model: cfg('CAPTAIN_OPEN_AI_MODEL').presence || DEFAULT_MODEL
+      }
+    end
+
+    def default_codex_model
+      'gpt-5.4'
+    end
+
+    def cfg(name)
+      InstallationConfig.find_by(name: name)&.value
+    end
+  end
+end
diff --git a/lib/llm/config.rb b/lib/llm/config.rb
index 48de51022..dc4e1691e 100644
--- a/lib/llm/config.rb
+++ b/lib/llm/config.rb
@@ -1,7 +1,7 @@
 require 'ruby_llm'
 
 module Llm::Config
-  DEFAULT_MODEL = 'gpt-4.1-mini'.freeze
+  DEFAULT_MODEL = Captain::Llm::ProviderConfig::DEFAULT_MODEL
 
   class << self
     def initialized?
@@ -31,19 +31,13 @@ module Llm::Config
     private
 
     def configure_ruby_llm
+      settings = Captain::Llm::ProviderConfig.settings
+
       RubyLLM.configure do |config|
-        config.openai_api_key = system_api_key if system_api_key.present?
-        config.openai_api_base = openai_endpoint.chomp('/') if openai_endpoint.present?
+        config.openai_api_key = settings[:api_key] if settings[:api_key].present?
+        config.openai_api_base = "#{settings[:api_base]}/v1" if settings[:api_base].present?
         config.logger = Rails.logger
       end
     end
-
-    def system_api_key
-      InstallationConfig.find_by(name: 'CAPTAIN_OPEN_AI_API_KEY')&.value
-    end
-
-    def openai_endpoint
-      InstallationConfig.find_by(name: 'CAPTAIN_OPEN_AI_ENDPOINT')&.value
-    end
   end
 end
diff --git a/spec/enterprise/services/captain/llm/provider_config_spec.rb b/spec/enterprise/services/captain/llm/provider_config_spec.rb
new file mode 100644
index 000000000..7235a21dc
--- /dev/null
+++ b/spec/enterprise/services/captain/llm/provider_config_spec.rb
@@ -0,0 +1,67 @@
+require 'rails_helper'
+
+RSpec.describe Captain::Llm::ProviderConfig do
+  before do
+    InstallationConfig.delete_all
+  end
+
+  describe '.settings' do
+    context 'when provider is openai_api (default)' do
+      before do
+        InstallationConfig.create!(name: 'CAPTAIN_OPEN_AI_API_KEY', value: 'sk-real')
+        InstallationConfig.create!(name: 'CAPTAIN_OPEN_AI_ENDPOINT', value: 'https://api.openai.com')
+        InstallationConfig.create!(name: 'CAPTAIN_OPEN_AI_MODEL', value: 'gpt-4o-mini')
+      end
+
+      it 'returns the traditional OpenAI API settings' do
+        settings = described_class.settings
+        expect(settings[:api_key]).to eq('sk-real')
+        expect(settings[:api_base]).to eq('https://api.openai.com')
+        expect(settings[:model]).to eq('gpt-4o-mini')
+      end
+
+      it 'reports codex_oauth? as false' do
+        expect(described_class.codex_oauth?).to be false
+      end
+    end
+
+    context 'when provider is openai_codex_oauth' do
+      before do
+        InstallationConfig.create!(name: 'CAPTAIN_LLM_PROVIDER', value: 'openai_codex_oauth')
+        InstallationConfig.create!(name: 'CAPTAIN_CODEX_PROXY_URL', value: 'http://localhost:3000/codex')
+      end
+
+      it 'returns the proxy settings with a dummy key' do
+        settings = described_class.settings
+        expect(settings[:api_key]).to eq(described_class::DUMMY_API_KEY)
+        expect(settings[:api_base]).to eq('http://localhost:3000/codex')
+      end
+
+      it 'falls back to default gpt-5.4 model when no custom model is set' do
+        expect(described_class.settings[:model]).to eq('gpt-5.4')
+      end
+
+      it 'honors CAPTAIN_OPEN_AI_MODEL override even with Codex OAuth' do
+        InstallationConfig.create!(name: 'CAPTAIN_OPEN_AI_MODEL', value: 'gpt-5.4-mini')
+        expect(described_class.settings[:model]).to eq('gpt-5.4-mini')
+      end
+
+      it 'reports codex_oauth? as true' do
+        expect(described_class.codex_oauth?).to be true
+      end
+
+      it 'strips trailing slash from proxy URL' do
+        InstallationConfig.find_by!(name: 'CAPTAIN_CODEX_PROXY_URL').update!(value: 'http://localhost:3000/codex/')
+        expect(described_class.settings[:api_base]).to eq('http://localhost:3000/codex')
+      end
+    end
+
+    context 'when CAPTAIN_CODEX_PROXY_URL is missing' do
+      before { InstallationConfig.create!(name: 'CAPTAIN_LLM_PROVIDER', value: 'openai_codex_oauth') }
+
+      it 'falls back to the default localhost URL' do
+        expect(described_class.settings[:api_base]).to eq(described_class::DEFAULT_CODEX_PROXY_URL)
+      end
+    end
+  end
+end